8     	160317	                  EPA-340/1-84-019a


Wet Scrubber  Inspection
  Procedures Workshop
               Prepared by:
             JACA Corporation
             550 Pinetown Road
       Fort Washington, Pennsylvania 19034
            Richards Engineering
            2605 Tanglewood Road
         Durham, North Carolina 27705
           Contract No: 68-02-3962
         EPA Project Officer: John Busik
         EPA Task Manager: Kirk Foster
              Submitted to:
      Stationary Source Compliance Division
    Office of Air Quality Planning and Standards
             401 M Street, S.W.
           Washington, D.C. 20460

             September 1984


     This manual was prepared by JACA Corporation and Richards Engineering for
the Stationary Source Compliance Division of the U.S. Environmental Protection
Agency in partial fulfillment of Contract No. 68-02-3962,  Task 1-14.  The con-
tents of this report are reproduced herein as received from the contractors.
The opinions, findings and conclusions expressed are those of the authors and
not necessarily those of the U.S. Environmental Protection Agency.  Any mention
of product names does not constitute endorsement by the U.S. Environmental
Protection Agency.

     The safety precautions set forth in this manual and presented at any
training or orientation session, seminar, or other presentation using this
manual are general in nature.  The precise safety precautions required for any
given situation depend upon and must be tailored to the specific circumstances.
JACA Corporation and Richards Engineering expressly disclaim any liability for
any personal injuries, death, property damage, or economic loss arising from
any actions taken in reliance upon this manual or any training or orientation
session, seminar, or other presentations based upon this manual.


     JACA Corporation and Richards Engineering would like to thank Mr.  Kirk
Foster of the U.S. Environmental Protection Agency for his assistance during
this project.  Subcontractors assisting with this project included Mr.  Kenneth
Schifftner, P.E. of Schifftner & Associates, Mr. Raymond Richards, P.E. of
Richards Technical Services and Mr. Larry Hill, P.E. of EST Corporation.  The
technical information and assistance they provided is gratefully achknowledged.
The project director was Mr. Uday Patankar, P.E. of JACA Corporation.  He was
assisted by Mr. Robert Schlosser, P.E.  The project manager at Richards
Engineering was Mr. John Richards, Ph.D., P.E.


                               TABLE OF CONTENTS


Introduction to the Use of the Manual                        1

Lecture 1.  Introduction to Wet Scrubber Systems            11

Lecture 2.  Baseline Inspection Technique                   51

Lecture 3.  Visible Emission Observation of Wet Scrubber
            Systems                                         73

Lecture 4.  Evaluation of On-Site Gauges and Use of
            Portable Instruments                            83

Lecture 5.  Evaluation of Wet Scrubber System Components   135

Lecture 6.  Liquor Analyses                                213

Lecture 7.  Evaluation of Particulate Wet Scrubbers        227

Lecture 8.  Evaluation of Gaseous Absorbers                271

Lecture 9.  Inspection Safety                              301

Appendix A  Bibliography                                   339

Appendix B  Workshop Forms                                 351


     The Stationary Source Compliance Division of the U.S.  Environmental Pro-
tection Agency has sponsored the development of this manual which is intended
to assist regulatory agencies in performing detailed inspections of wet scrubber
systems.  These inspections are conducted to determine if the air pollution
control equipment is operating in compliance with applicable regulations and to
determine if the corrective actions proposed by source owners have a reasonable
chance to successfully rectify chronic excess emission problems.  The technical
information will also help equipment operators to monitor the performance of
their scrubber systems.  The evaluation procedures are intended to identify
operating problems at an early stage so that excess emission problems can be
avoided and so that any necessary equipment repairs can be made quickly and

     The workshop program addresses both particulate and gaseous scrubbers.
Common modes of failure of these systems are discussed to illustrate the
importance of the various inspection activities.  Emphasis is placed on the
evaluation of wet scrubber components such as pumps, nozzles, demisters, and
piping.  There is also considerable information concerning the critical eval-
uation of on-site gauges and the use of portable instruments when necessary.
Inspection safety is also emphasized.

1.0 Use of This Manual

     The materials have been prepared so that it is possible to use the manuals
either in workshops or as self instructional guides.  Both the Lecturer's Manual
and the General Manual are used for workshops.  The General Manual includes black
and white reproductions of all the visual aids used in the workshop program.
Detailed lecture notes are included with each of the slides so that all of the
attendees can review the technical information at a later date.  The presence
of the lecture notes also allows the attendees to concentrate on listening to the
workshop coordinator rather than attempting to compile a complete set of notes.
The general manual also includes a set of review problems and questions at the
end of each lecture.  These can be answered either individually or in small
working groups.

     The Lecturer's Manual is identical to the General Manual with the addition
of suggestions of various options for presenting the technical material.  This
is very important since most audiences are comprised of attendees with very
diverse backgrounds with respect to wet scrubber systems.  It is common to have
persons with no experience at all in the same audience with engineers having
more than 10 years of practical field experience.   The program must be adjusted
to the attendees' level of experience.  The Lecturer's Manual also includes a
detailed discussion of each review problem and question.  The additional
material in the Lecturer's Manual is arranged so that the workshop coordinator
is always on the same page as the attendees who are using the General Manual.

     The Lecturer's Manual can be used as a self-instruction manual by persons
who want to review material discussed during a previous workshop or by persons
who were unable to attend a full workshop.  The lecturer's notes will be help-
ful in determining what material should be studied.   The answers to the review
problems and questions will be helpful in reviewing  the lectures.

2.0  Presentation of Workshops

     Workshops are intended to be valuable learning  experiences for all of the
participants, including the workshop coordinator. To achieve this goal, a con-
siderable amount of preparation work is necessary.  This section addresses some
of this initial effort required to structure a successful program

2.1  Know Your Audience - This is the most important step in preparing for
a workshop program.  The range of experience with wet scrubber systems should
be determined since it is important to orient the technical information to the
backgrounds of the participants.  It is easy to bore the highly experienced
individuals and to overwhelm those with no prior experience with wet scrubbers.
If the range of experience is very large, it may be  wise to split the group
into more homogeneous groups so that the material of interest to each can be
properly presented.

     People learn in different ways.  Some can effectively learn during formal
lectures while others retain more when solving problems or discussing questions
in small groups.  Others retain the concepts only after they have had an oppor-
tunity to try them in the field.  To the extent possible, the workshop should
include all three major elements: (1) formal lecture, (2) problem sessions, and
(3) field demonstrations.  Obviously, this manual can only address the first
two.  Nevertheless, the value of field demonstrations should not be underesti-
mated.  They should be conducted soon after the workshop program.   The mix of
lecture material and problem sessions used in the workshop must be chosen by
the workshop coordinator based on the perceived interests of the participants.
Within the time frame allowed by the typical workshop agenda, there is insuffi-
cient time for both as presented in this manual.  This means that the workshop
coordinator must carefully review this manual and decide what technical inform-
ation is relevant and what portion of the time should be devoted to the problem

     It is equally important to know the types of wet scrubbers of concern.
The workshop materials are intended for an entirely different purpose than
college level engineering courses and the U.S. Environmental Protection Agency
Air Pollution Training Institute courses.  These formalized educational programs
are designed to provide a sound foundation in fundamental principles and calcu-
lation techniques.  As such they are invaluable pre-requistes to the material
presented in this workshop.  Here the primary objective is to present very
practical information on what the field inspector should do "tomorrow" on the
specific scrubber systems within his or her jurisdication.  For this reason, it
is necessary to emphasize the material concerning the specific scrubbers that
are of concern to the participants.  Regulatory agency inspectors are usually
too busy to enjoy discussing topics which do not appear to have a practical
application in their areas.

     If the interests and background of the participants are not known prior to
the workshop, the coordinator should make a survey at the very beginning of the
program.  The material should then be adjusted to the extent possible.  It is

better to preregister all participants so that there is more lead time to
tailor the program to the group.  Appendix B includes a sample card that can
be distributed in advance or used at the beginning of the workshop.  This card
provides the necessary information on the backgrounds of the attendees and
also provides a permanent record of their participation.

2.2  Use an Adequate Meeting Room - Most of the participants attending the
program will be accustomed to field work.  They are especially intolerate of
inadequate meeting rooms.  The room should have the following features:

     0 The chairs should be comfortable.

     0 The room should be large enough to accomodate the group without taxing
       the heating and air conditioning system.

     0 There should be tables for all participants to facilitate note taking
       and problem solving.

     0 There should be a way to show the 35 mm slides without darkening the
       entire meeting room.

     0 The room should be reasonably quiet.

     0 There should be an area to display portable inspection equipment
       and safety equipment.

     Overall, the room must be conducive to an intense learning exercise.
It is unfortunate that many of the meeting rooms available in agency office
buildings are not good for workshops.  Hard chairs are common since the rooms
were intended only for short meetings, not two or three day programs.  It is
often impossible to dim the lights without incurring the wrath of other agency
personnel in adjacent offices.  Also, the rooms are often so small that it is
difficult to use the visual aids without the attendees feeling the hot exhaust
of the projector.  Long programs in inadequate meeting rooms are a form of
cruel and unusual punishment.  It should be remembered that the cost of a good
meeting room is often a small fraction of the transportation costs incurred in
bringing field inspectors in to a central location from the various district

2.3  Prepare for the Program - There are a number of preliminary activities
which are necessary to ensure that the program runs smoothly.  The most impor-
tant of these is for the workshop coordinator to read the manual thoroughly and
decide what portions are relevant.  It is also helpful to distribute copies of
the general manual to the preregistered attendees so they have an opportunity to
review the material before the program.  More detailed and interesting questions
are asked when the manuals are distributed before program.

     The room should be completely set up prior to the arrival of the
attendees.  The visual aid equipment should be set up and checked out so that
there is no question that it is working properly.  It is almost always wise to
have spare projection bulbs for the visual aid equipment.  The slides should be
tried on the screen to confirm that the screen is placed properly and that the
entire slide is visible.  If not, the projector and/or the screen should be
repositioned.  All of the slides should be loaded and checked on the screen.

One of the most embarrasing and distracting events in a workshop is the
occassional backwards and upside down slide.  This is entirely avoidable!

    The tables should be arranged so that there are enough seats and that
everyone has an adequate view of the screen.   Handouts and forms should be
distributed to each seat to save time at the beginning of the workshop and
to ensure that there is no question that there are sufficent copies for

     The locations of rest rooms and fire escapes should be noted so that  the
attendees can be advised at the beginning of the workshop.  It is also helpful
to identify a phone which can be used for messages.

2.4 Conducting the Workshop - The workshop coordinator sets the tone for
the workshop in the initial remarks.  The participation of all the attendees
should be encouraged since often they have valuable experience with is relevant
to the specific plants in the area.  Their comments liven up the program and
supplement the technical material in this manual.  An informal attitude is gen-
erally effective in encouraging active participation.

     Under no circumstances should the information simply be read from the
manual.  This defeats the basic objective of this manual which is to free both
the speaker and the attendees from having to cover each detailed point.  Any
attendee who is truly interested in the topic can read the manual carefully
after (or before) the program.  This manual simply provides a skeleton over
which the speaker and attendees can discuss issues relevent to their area.

     Occassional breaks are built into the program.  These are necessary to
allow everyone to stretch and to allow the speaker's voice to rest briefly.
Also, these periods provide some of the most useful informal discussions
concerning the lecture material.

     At the end of the workshop, a critique form should be handed out to all of
the participants (including the coordinator).  It should be filled out before
everyone leaves since few will ever return it otherwise.  The coordinator should
carefully review the comments to determine ways to improve future programs and
ways to assist the participants in getting the resources necessary to implement
the techniques discussed.  The latter point is especially important since the
In many cases, they will not have the time or equipment necessary to perform
these inspections.  Presumably, they will be receiving these soon or there was
no sense in presenting the program in the first place!  The critiques help to
determine just what is necessary to begin implementing the program.  A sample
critique form is included in Appendix B.

     One conunon misunderstanding regarding critiques is that they are intended
to rate the capability of the speaker or to rate the value of the program.
Actually, the value of the program can not be judged until the participants
have had an opportunity to try the techniques in the field for six months to a
year.  The speaker's performance should be just one element of a successful
workshop.  The very successful workshops are those in which the speaker simply
guides the discussion.  The attendees should do most of the talking. Remember,
this is not a training course!  A workshop is a meeting of professionals
discussing and refining their technical procedures.

3.0 Typical Agenda

     A typical agenda for a two-day program is presented on the next two pages.
As discussed above, this should be used as a starting point in the development
of a program for the specific audience.  A copy of the program agenda to be
used should be given to all participants before the start of the program.



                                Sample Agenda
Time          Lecture

8:30 a.m.     Welcome and Introduction

8:45 a.m.     1.  Introduction to Wet Scrubber Systems
                  A.  System Components
                  B.  Flowcharting Techniques
                  C.  Review Problems and Questions

10:15         Break

10:30         2.  Baseline Inspection Techniques
                  A.  Basic Principles
                  B.  Comparison of Baseline Data with Inspection Data
                  C.  Review Problems and Questions

12:00         Lunch

1:00          3.  Visible Emission Observation
                  A.  Expanded Method 9 Procedures
                  B.  Reentrainment
                  C.  Odor Surveys
                  D.  Review Problems and Questions

1:45          4.  Evaluation of On-Site Instruments and Use of Portable Gauges
                  A.  Static Pressure Gauges
             ,     B.  Temperature Monitors

2:30          Break

2:45          4.  (Continued)
                  C.  Oxygen and Carbon Dioxide Analyzers
                  D.  pH Meters and Indicator Paper
                  E.  Gas Flow Measurement
                  F.  Fan Speed and Motor Currents
                  G.  Pump Motor Currents
                  H.  Liquid Pressures
                  I.  Liquid Flow Rates
                  J.  Other Instruments
                  K.  Recommended Port Designs

4:30         Adjourn



                          Sample Agenda (Continued)

Day 2

Time          Lecture

8:30          5. Evaluation of Wet Scrubber System Components
                 A.  Demisters
                 B.  Pumps
                 C.  Piping
                 D.  Nozzles
                 E.  Fans
                 F.  Materials of Construction
                 G.  Review Problems and Questions

10:30         Break

10:45         6.  Liquor Analyses

11:15         7.  Particulate Wet Scrubbers
                  A.  Particle Size
                  B.  Pressure Drop

12:00         Lunch

 1:00         7.  (Continued)
                 C.  Spray Tower Scrubbers
                 D.  Packed Tower Scrubbers
                 E.  Moving Bed Scrubbers
                 F.  Tray Scrubbers
                 G.  Mechanically Aided Scrubbers
                 H.  Venturi and Other Gas-Atomized Scrubbers
                 I.  Review Problems and Questions

 2:00        . Break

 2:15         8.  Gas and Odor Scrubbers
                 A.  HC1 and Chlorine Scrubbers
                 B.  Fluoride and SiF4 Scrubbers
                 C.  Hypochorite and Permanganate Odor Scrubbers

 3:15         9. Inspection Safety
                 A.  Walking and Climbing Hazards
                 B.  Explosion Hazards
                 C.  Burn Hazards
                 D.  Eye Hazards
                 E.  Heat and Cold Stress
                 F.  Inhalation Hazards
                 G.  Review Problems and Questions

 4:15         Summary and Critique

 4:30         Adjourn


                             WET SCRUBER SYSTEM
           INSPECTION OF
                                      This workshop concerns particulate and
                                      gaseous scrubbers.  The program begins
                                      with a summary of the major differences
                                      between wet scrubber systems and other
                                      types of control devices.  Some of the
                                      common components are introduced and all
                                      major definitions are presented.

                                      The lecture which follows concerns the
                                      Baseline Inspection Technique.  The
                                      approach for wet scrubber systems is
                                      conceptually similar to that for other
                                      control devices.  However, there are
                                      some important differences in emphasis.

     There are certain inspection procedures common to all types of scrubber
systems.  These common operations are  grouped together in one major lecture
which includes: the use of portable instrumentation, the evaluation of visible
emissions, the evaluation of reentrainment, the inspection of pumps, nozzle
inspection, and the evaluation of the  piping system.

     Specific inspection procedures are  presented for each major class of
particulate and gaseous scrubbers.  This material emphasizes the problems which
are most common for these types of units.

Lecturer's Notes
     This slide and written material is  intended to provide a brief overview
of the workshop.  It is important at this stage of the program to survey the
experience of the audience and adjust  the level of the technical discussions
accordingly.  The initial lecture is for persons with only limited experience
with scrubber systems.  Some of the material concerning portable instrumenta-
tion and scrubber evaluations is intended primarily for experienced personnel.
The safety considerations are very important for all attendees, and should not
be abbreviated under any circumstances.


         Gas Cooler
         Scrubber Vessel
         Recirculation Tank
         Recirculation Pump
         Bypass Ducts and Dampers
         Alkaline Additive System
         Purge and Make-up Systems
         Scrubber Instruments
                                       A  scrubber  is not an isolated piece of
                                       equipment.   It is a SYSTEM comprised of
                                       a  large  number of individual components.
                                       This  single point is the most important
                                       fact  to  be  presented in this first
                                       lecture.  It distinguishes scrubbers
                                       from  other  types of air pollution con-
                                       trol  devices.

                                       Many  of  the scrubber performance prob-
                                       lems  originate with deficiencies with
                                       the components rather than errors in the
                                       design and  operation of the scrubber
                                       vessel itself.  This means that the
                                       operation of each system component must
                                       be understood and that each inspection
                                       will  involve a number of inspection
                    union *nnc ntEsaxc  o'
                                        A logical starting, point in the
                                        evaluation of a wet scrubber SYSTEM
                                        is to determine the orientation of
                                        the scrubber vessel with respect to
                                        the fan which moves the gas stream.

                                        If the fan is downstream from the
                                        scrubber vessel, the ductwork leading
                                        to the scrubber and the scrubber vessel
                                        itself are under negative pressure.
                                        This simply means that the gas pressure
                                        inside is lower than the atmospheric
                                        pressure.  The small circles contain
                                        typical static pressures at the scrubber
                                        outlet and the beginning of the duct-
                                        work.  The static pressures become more
                                        negative as the gas approaches the fan.

     Wet scrubber systems  operate at much greater negative pressures than any
other type of air pollution  control system.  It is common for the scrubber
outlet static pressure  to  be in  the range of -25 to -60 inches of water. There
are a few units operating  in the range of -100 to -150 inches of water.

Lecturer's Notes
     The term "static pressure"  may be unfamiliar to some of the attendees.  If
so, it should be stated that this is simply the pressure of the gas at rest or
measured in a direction normal  to the flow direction.  It may also be necessary
to compare "inches  of water" to  "pounds per square inch".  One pound per square
inch (psi) equals approximately  27.7 inches of water.
     The concept of "negative pressure" is very difficult for some who see this
as a contradiction  in terms. It should be stressed that negative pressures are
lower than ambient  pressure  but  nevertheless real gas pressures.

                       COLD STACK
When the static pressure in the scrubber
system is negative, there is a tendency
for air to infiltrate the system.  This
can reduce the amount of gas pulled from
the process source and can cause local-
ized gas-liquor distribution problems in
the scrubber.  Both conditions can lead
to significantly increased emissions
from the system.

Points of entry are shown on this slide.
Since the static pressures are more
negative on the discharge side of the
scrubber and at the fan inlet, these
areas are common sites of infiltration.
It is also important to maintain a
water seal at the scrubber sump equal
to or greater than the static pressure
to prevent air infiltration here.
                                       The fan can be located upstream of the
                                       scrubber vessel,  thereby placing the
                                       entire scrubber and connecting ductwork
                                       under positive pressure.  Typical
                                       static pressure values are shown on
                                       this slide.  Note that the static
                                       pressures become progressively smaller
                                       as the gas passes through the scrubber
                                       vessel and out the ductwork to the

              (                         Since the gas pressures inside are
                                       higher than ambient pressures, there is
                                       a tendency for gas to leak out.  These
                                       gases can be quite dangerous if there
                                       are poorly ventilated areas around the
                                       scrubber and ductwork.

     The health hazards which can exist around positive pressure scrubber
systems should not be underestimated.  Wet scrubber systems tend to operate at
higher positive pressures than any other type of control system.  This combined
with corrosion and erosion problems makes gas leakage very possible.  Often
wet scrubbers are placed indoors to minimize freezing problems, and this con-
tainment structure reduces natural ventilation.  Field inspectors should have
proper safety equipment and should not enter areas with anticipated high
pollutant concentrations.

Lecturer's Notes
     The gas leakage problem should be stressed here and be reiterated during
the safety lecture.  It may be useful to point out that some scrubbers handling
toxic gases can operate as high as +200 inches of water!

Another gas flow arrangement has fans
both before and after the scrubber
vessel.  This is termed a "push-pull"

This type of system usually results
from the upgrading of a scrubber
beyond the capability of an existing
fan.  The additional fan provides
greater static pressures for the
modified system.

As before, the static pressures decrease
progressively from the discharge of the
one fan to the inlet of the other.  This
arrangement has no adverse impact on the
scrubber performance.
                                       It is common to include a bypass stack
                                       ahead of the scrubber vessel.  This can
                                       be opened in the event of a sudden
                                       process upset or the need for scrubber
                                       maintenance while the process remains
                                       in operation.

                                       The draft created by the stack is
                                       usually sufficient to exhaust the
                                       process equipment during the interim.
                                       Therefore, it is rare to have a fan on
                                       the bypass stack.

                                       Corrosion of the bypass damper can lead
                                       to some unintentional leakage of un-
                                       treated gas out the bypass stack.  This
                                       will not have the characteristic steam
                                       plume since the water vapor content at
                                       this point of the system is low.

     On negative pressure systems as shown here, there can be some infiltration
of ambient air down the bypass stack if  (1) the negative pressure in the duct
is lower than the draft created by the stack, and (2) there is leakage of the
bypass damper.  Methods of checking for  both untreated gas release and air
infiltration are included in the inspection procedures discussed later.

                                       Many sources served by wet scrubbers
                                       have very hot gas temperatures.  It
                                       is not prudent to expose the scrubber
                                       vessel itself to these temperatures
                                       since this could damage the protective
                                       liners on the scrubber walls. The evap-
                                       oration of droplets exposed to high
                                       temperature also makes the droplet less
                                       likely to capture a particle.  Therefore,
                                       scrubber performance is reduced.

                                       Cooling of high temperature gas streams
                                       is done almost exclusively by spraying
                                       water into the gas stream.  Unlike
                                       fabric filters, dilution and radiant
                                       cooling tubes are not common.

     The gas cooling can be done in a specially designed evaporative cooler or
in a small presaturator attached to the scrubber vessel.  This slide shows a
small presaturator ahead of the scrubber.  Note that separate liquor lines are
shown for the scrubber and the presaturator since the source of liquor is often

SLIDE 1-9                              An evaporative cooler is shown in this
                                       slide.  It can be a simple spray cham-
                                       ber with low pressure nozzles or a
                                       large cylindrical chamber having a set
                                       of high pressure nozzles near the top.
                                       Some of the water sprayed into the cham-
                                       ber evaporates, thereby cooling the gas
                                       stream.  The remainder of the water
                                       drains from the bottom.  Specially de-
                                       signed evaporative coolers with high
                                       pressure nozzles often achieve 70 to 95%
                                       water evaporation.

                                       The quality of water used in gas coolers
                                       is critical to both the evaporative
                                       cooler and to the overall scrubber sys-
                                       tem.  This is an important inspection

     Once the gas stream temperature has been reduced, material which has been
in the vapor state begins to condense to form particulate matter.  The particle
size range of the resulting material depends on the quantity of material con-
densed and on the manner of condensation.  The water vapor injected into the
gas stream may also begin to condense on the surfaces of particles in the gas
stream.  Both of these phenomenon favor improved collection efficiency.

Lecturer's Notes
     One of the major differences between wet scrubber systems and other types
of air pollution control systems is that the particulate matter characteristics
can change drastically while passing through the system.  Such changes have a
large effect on pollutant removal efficiencies.


SLIDE 1-10
                                       Centrifugal fans are used to move the
                                       gas stream through the wet scrubber
                                       system.   There are two major types in
                                       service:  (1) radial blade fans,  and
                                       (2) backward curved fans.  The latter
                                       are more  prone to build-up of solids on
                                       the blades and, therefore, require more

                                       The inspection procedures will use some
                                       of the fan operating data such as the
                                       fan motor currents.  For this reason, it
                                       will be important to have a general
                                       understanding of fan curves and system
                                       resistance curves.  It will become
                                       apparent  that fan curves have similar-
                                       ites with centrifugal pump curves.

     The gas flow rate delivered by the fan is primarily controlled by the
dampers before or after the fan.  During start-up it is common practice to keep
the dampers partially closed to minimize the initial fan motor load.
SLIDE 1-11
                                       The last major component of the gas
                                       handling equipment is the stack.  Unlike
                                       large fabric filter and electrostatic
                                       precipitator systems, there are no
                                       transmissometers used on wet scrubber
                                       stacks.  This is because the water
                                       droplets which invariably condense in
                                       the gas stream scatter light very
                                       effectively.  Transmissometers can not
                                       distinguish between the scattering due
                                       to particles and that due to droplets.

                                       The only visible emissions data which
                                       can be used in the inspection technique
                                       is that which is obtained by stack ob-
                                       servation.  No continuously recorded
                                       data is available.

     The water droplets which preclude the use of transmissometers also can
complicate the manual observations.  Field inspectors must be trained in the
proper procedures for observing wet scrubber plumes.  Some of the important
points are summarized in a later lecture.

Lecturer's Notes
     The frequent lack of adequate visible emissions data forces greater
emphasis on measurable scrubber operating parameters.  This is one of the major
differences between wet scrubber inspections and the inspection of other air
pollution control systems.

                  f MS, 50,000 ACFM
SLIDE 1-12
                                        The  next  set of slides concerns the
                                        liquor  recirculation system. There are
                                        two  basic arrangements: (1) the once
           9invi   ^^^                   through system, and (2) the recircula-
                                        tion system.  Obviously, the once
                                        through system is easier to inspect due
                                        to the  relative simplicity of the flow

                                        This slide illustrates the once through
                                        flow arrangement.  The scrubber liquor
                                        is drawn  from a process water source or
                                        municipal supply.  It is drained into a
                                        sewer or  other treatment unit for final

     The main advantage of this  approach is that solids and corrosive materials
do not gradually accumulate  to harmful  levels.  This reduces the pump, nozzle
and scrubber vessel erosion  and  corrosion problems.  Absorption of some gases
is also favored.  However, the large  majority  of these systems have been con-
verted to recirculation systems  to  reduce water  useage and to reduce waste-
water treatment costs.
               LIOUOH TO
              TRCTUNT AND
   SAS f	'
30,000 ACFM
                                       .'he heart of the recirculation system
                                       .3 the recirculation pump.   Centrifugal
                                       pumps are used exclusively  for this
                                       service because they are capable of
                                       of supplying high liquor flow rates at
                                       moderate to high pressures.   The pump
                                       must not only provide the necessary
                                       liquor pressures at the scrubber inlet;
                                       it must also lift the liquor back up to
                                       the elevation of the inlet.

                                       The pump must be carefully  chosen to
                                       provide desired flow rates  and pressures
                                       for the actual system present.

     During the inspection, the pump operating data will provide indirect
indications of the liquor flow rate.  This is important since the  flow rate
monitors are rarely present.  The operating condition of the pump  should be
observed briefly to confirm that there are no emerging problems.
SLIDE 1-15
                                       There is more to the wet scrubber
                                       piping system than simply connecting
                                       point A to point B.   The pipe must be
                                       sized properly to get the desired system
                                       resistance.  The materials of construc-
                                       tion should be selected so that the
                                       pipes will withstand the corrosive,
                                       erosive and settling characteristics of
                                       the liquor.

                                       The piping arrangement must allow for
                                       complete draining of the lines during
                                       off-line winter conditions.  There must
                                       also be provisions for the flushing of
                                       solids from the pipes on a routine

     The pipes must be supported in a manner that places no loads on the
recirculation pump.  The valves should be selected so that  water hammer is
also not transmitted back to the pump.  The pump suction line should be sloped
to prevent gas pockets and to provide adequate suction head at the pump.  In
short, the piping should not be an afterthought in the design and installation
of a scrubber system.

SLIDE 1-16
                                       Any scrubber composed of carbon steel
                                       must operate at pH levels above 5 and
                                       preferably above 5.5.  Scrubbers being
                                       used for odor control often operate
                                       between ph levels of 8 to 10 in order to
                                       maximize absorption.

                                       To maintain the pH in the desired range,
                                       it is necessary to add a neutralizing
                                       agent.  Materials in common use include
                                       soda ash, lime, and limestone.  These
                                       can be added either on an intermittant
                                       basis by dumping bags into the recircu-
                                       lation tank, or on a continuous basis as
                                       shown in the slide.
     The continuous addition systems are more complicated.  However, they do
not suffer the frequent large swings in pH common to those  with intermittant
addition.  The rate of addition is generally controlled by  a pH meter located
in the recirculation tank or similar location.

Lecturer's Notes
     Obviously when evaluating the liquor pH, it is important to know both
where the sample was taken and when it was taken.  The pH can be a highly
variable parameter in wet scrubber systems.  The importance of documenting
time and location will be a common theme of later discussions of wet scrubber
operating parameters.
SLIDE 1-17
                                       ,.-e nozzles and liquor distribution
                                       headers are critical to all scrubber
                                       designs.  Pluggage of even a small
                                       fraction of the nozzles leads to very
                                       poor gas-liquor distribution.

                                       There are a wide variety of commercially
                                       available nozzles.  The nozzle model
                                       must first match the suspended solids
                                       levels expected in the scrubber system.
                                       Certain types are appropriate only for
                                       clean liquors.

                 ""*'                    The arrangement of nozzles must take
                                       Into account the spray angle and spray
                                       uattern of the specific nozzle.

     While the nozzles are the sme.ll.-=" individual component used in a wet
scrubber system, they are normally responsible for a large share of the
unscheduled maintenance effort.   The small clearances through many nozzle
designs makes then especially prone to pluggage even at solids levels which
do not affect control valves and pipes.  The high velocities at the nozzle
orifice can result in rapid erosion.

         Clarifiers with Vacuum Filters
             Settling Ponds
SLIDE 1-18
                                       Wastewater treatment facilities range
                                       from very simple ponds to elaborate
                                       clarifier-vacumn filtration plants.
                                       Obviously, only the very large scrubber
                                       systems have the latter type of fac-
                                       ilities.  All of these, however, share
                                       the common purpose of reduction in the
                                       liquor solids content.

                                       The clarifier (sometimes called a sed-
                                       imentation tank) is simply a large tank
                                       where the suspended solids can settle
                                       to the bottom.  The accumulated sludge
                                       is continuously removed from the bottom.
                                       A rotary vacuum filter is used to remove
                                       the suspended solids from the calrifer
                                       underflow.  The clarified effluent is
                                       removed from the top of the clarifier.

     Often the settling characteristics of the suspended solids can be improv-
ed by the addition of flocculation agents.  These cause the fine particles to
agglomerate together and thus increase the settling rate.  Unfortunately, the
flocculants may have an adverse impact on the liquor surface tension.

Lecturer's Notes
      It is an unfortunate fact that steps taken to optimize the performance
of one of the wet scrubber system components can have an harmful affect on
another component.  In this case, the increased surface tension with certain
flocculants can change spray droplet size and decrease particle capture for a
given size droplet.  Both changes can affect particulate removal.  A number of
trade-offs must be made by a well informed operator in order to achieve
optimum performance of the overall system.
SLIDE 1-19
                                       Ponds are the simplest type of liquor
                                       treatment system.  They can range from
                                       very small, single zone ponds to quite
                                       large, multi-zoned settling basins.

                                       The test of pond performance is the
                                       ability to deliver relatively clean
                                       liquor back to the scrubber system over
                                       a long time period.  One means to im-
                                       prove performance is the use of several
                                       zones each separated by an overflow
                                       weir.  There should also be an easy way
                                       to remove the solids from the first and
                                       second zones on a regular basis.


        A. Thermocouples
        B. Pressure Drop Gauges
        C. Fan Motor Current

        A. pH Meters
        B. Pump Discharge Pressure
        C. Pump Motor Current
        D. Pipe Pressures
        E. Flow Rate Monitors
SLIDE 1-20                             This slide  lists  the  types  of instrumen-
                                       tation available  on wet  scrubber systems.
                                       Some of these are used to control system
                                       operation and some are intended to pro-
                                       vide general indications of performance
                                       for the operator.

                                       All instruments used  on  wet scrubber
                                       systems are subject to pluggage,
      2. LIQUID STREAM MONITORS            erosion and corrosion.   Conscientious
                                       maintenance is often  not sufficient to
                                       keep all instruments  in  proper working
                                       order.  Therefore, the process control
                                       instruments should always be included
                                       on an initial list of possible culprits
                                       responsible for performance problems.
                                       Also, the indicated data for scrubber
                                       instruments always deserves scrutiny.

     The more advanced forms of the inspection procedures will  utilize some
portable instruments.  They are necessary to overcome the limitations of the
permanently mounted instruments and they are also  helpful when  the necessary
gauges are not available.  Measurement ports are necessary.

Lecturer's Notes
     The attendees need to understand that it is very difficult to keep wet
scrubber instrumentation working and they should not be  too  quick  in accusing
plant operators of inadequate maintenance of the instruments.   While this may
sometimes be the case, more often it is due simply to the tendencies for
pluggage, erosion and corrosion.  In other words,  field  inspectors need to be
sympathetic to occassional instrument malfunctions.  Material presented later
will address some of the steps which can be taken  to minimize failure.
SLIDE 1-21
       Source:  Air  Pollution
               Training Institute
                                       There are  several  distinct types of
                                       demisters  in  common service.   All of
                                       these are  intended to remove  the very
                                       large (100 to 800  micron diameter)
                                       droplets formed  in the scrubber.

                                       The type shown in  this slide  can be
                                       placed  in  the upper sections  of
                                       cylindrical scrubbers.  The gas stream
                                       passes  through the demister at super-
                                       ficial  velocities  in the range of 5 to
                                       20 feet per second.  The droplets which
                                       impact  on  the demisters simply drain
                                       back into  the scrubber.
     The chevron demisters force  the  gas  stream  to  make  several quick turns
which the large droplets can not  negotiate.  These  come  in  numerous blade
designs and with 2, 3, and 4 passes.  Mesh pads  (not  shown)  operate in the same
manner as household furnace filters with  the fibers serving  as impaction targets.
Both styles of demisters must be  cleaned  regularily to prevent the accumulation
of solids on the surfaces.

SLIDE 1-22
                                       Other styles of demisters are shown in
                                       this slide.  Both of these take advan-
   SIOE ELEVATION  =_ ^^      PLAN VIEW         tage of a spinning gas stream which
           x   \    x~~"\           results in the impaction of the large
                             'ouacr     droplets on the demister wall.  These
                                       types of units are commonly included
                                       with venturi scrubbers.

                                       On positive pressure units, the stack
                                       sampling ports are directly above this
                                       demister.  Provisions must be made to
                                       eliminate the cyclonic flow in the
                                       stack so that pitot traverses and stack
                                       sampling procedures can be conducted.

     Generally the type of demister used is determined by the configuration of
the scrubber vessel.  The demisters shown in the last two slides serve differ-
ent applications and are not competitive approaches.

Lecturer's Notes
     The removal of 100 to 800 micron droplets may seem simple.  However, this
is one of the most common sources of trouble in some systems.  The consequences
of improper demister performance include rainout of particulate laden droplets
close to the stack and the accumulation of material on downstream fans.
SLIDE 1-23
                                      The most common scrubber designs will
                                       be addressed in the program.  It is
                                       important to be able to recognize the
     TYPE OF SCRUBBER VESSELS          advantages and limitations of each
                                       during the inspection.  Specific in-
        p'  DA^I7^/ERS                  spection procedures have been prepared
        D.  HACKED BEOS                   j_       .      ._i_     ._          j     r
        C  MOVING BEDS                       ocus in on the most common modes of
        D.  MECHANICALLY AIDED              failure of each type.
        E.  ORIFICE
        F.  VENTURI                       The list provided is far from complete.
        G.  TRAY TOWER                    There are a number of innovative
                                       designs which have been commercially
                                       introduced in the last five years.
                                       There are also a number of variations
                                       of the listed types, each having unique
                                       design features. The inspection techni-
                                       ques for these modified and new designs
                                       will have to be developed by each in-
                                       spector based partially on the proced-
                                       ures presented in this program.
Lecturer's Notes
     The terminology in the wet scrubber industry is not standardized.  These
titles could differ from those familiar to some of the attendees.  Also, the
manner in which scrubbers are grouped can vary.  These categories are conven-
ient for this program since the inspection procedures are distinctly different
for each of the categories listed.


Clean gas
SLIDE 1-24
                                       A spray tower scrubber is illustrated
                                       in this slide.  This is the simplest
                                       type of unit and it has only a limited
                                       particulate removal capability.  It is
                                       selected for applications where there is
                                       not much particulate matter smaller than
                                       5 microns.  It can also be used in some
                                       gas absorption systems.

                                       The gas stream enters near the bottom
                                       and flows upward at velocities between
                                       2 and 5 feet per second.  The liquor
                                       enters at the top.  Therefore, the flow
                                       is in the countercurrent direction
                                       relative to the gas stream.  Liquor
                                       distribution is entirely controlled by
                                       the types of nozzles, the nozzle spray
                                       angle, the nozzle placements and the
                                       liquor pressure.

     Most of these systems are relatively simple.  However, alkaline addition
equipment is sometimes necessary.  The instrumentation is usually very limited
and this complicates the inspection procedures.
  MiK eliminator
SLIDE 1-25
                                       Packed bed scrubbers are primarily in-
                                       tended for gas absorption.  The large
                                       liquor surface area created as the
                                       liquor gradually passes over the pack-
                                       ing material favors gas diffusion and
                                       absorption.  These are not effective
                                       for particulate removal since the low
                                       gas velocities do not result in much
                                       paticulate impaction on water droplets.

                                       The gas stream again enters from the
                                       bottom and passes upward through one or
                                       more beds.  The liquor is sprayed on
                                       the top and flows downward.  Liquor
                                       distribution is important for high
                                       efficiency removal of gases.

     One of the major problems with these scrubbers is the accumulation of
solids at the entry to the bottom bed and within the beds.  The dissolved
soilds and suspended solids levels in the liquor must be monitored carefully.
It is difficult to routinely remove these solids due to the characteristics of
the packing materials.
    !'.* Dirty gu

SLIBF 1-26
           Clean ga*
                     Mist eliminator
                          Dirty gu
                                       Moving beds have entirely different
                                       characteristics than packed beds.
                                       They have moderate to high particulate
                                       removal capability due to the formation
                                       of fine droplets within each bed and
                                       the relatively high gas velocities.
                                       Both of these factors favor particle
                                       impaction.  The high liquor surface
                                       area created also makes these units
                                       acceptable for gas absorption.  The
                                       turbulent action of the packing pro-
                                       vides a self cleaning characteristic.
                                       Therefore, pluggage is not an issue.
                                       These were originally developed by the
                                       primary aluminum industry which needed
                                       to remove sticky organic particles and
                                       hydrogen fluoride gas.

The most common version of moving bed scrubbers has several "beds" partially
full of hollow balls which closely resemble ping pong balls.  The packing
moves violently due to the combined action of the rising gas stream and the
falling liquid.  Water droplets formed in the turbulent bed serve as the
particle impaction targets and as the gas absorption surface.

Lecturer's Notes
     One common trade name for this style of scrubber is the Turbulent Contact
Absorber, or TCA for short.  It is also called simply a "Ping Pong Ball Scrub-
ber."  Marble bed scrubbers are sometimes classified as a moving bed since the
packing is free to move.  However, the performance characteristics are more
like the packed bed than the TCA shown above.
SLIDE 1-27
   Source: Air Pollution
           Training Institut
                                       One common type of mechanically aided
                                       scrubber is illustrated in this slide.
                                       The gas stream enters axially and is
                                       spun outward due to the rapid rotation
                                       of the scrubber fan blade.  Liquor is
                                       sprayed in the inlet duct.  Impaction
                                       of particles occurs on the initially
                                       slow moving droplets.

                                       Unlike all other types of scrubbers,
                                       this particular design does not have a
                                       "pressure drop".  The mechanical energy
                                       provided by the shaft achieves the
                                       scrubbing action and moves the gas
                                       stream through the ductwork.  There is a
                                       static pressure rise across this type of
     These scrubbers are used only for relatively small systems having gas
flows less than 10,000 ACFM.  The scrubber systems are relatively simple.
However, it is important to have high quality liquor so that erosion and build-
up on the fan blades is minimized.  Obviously, no fans are necessary with this
type of system.

MUt eliminator

Liquid inlet

Plate or try
SLIDE 1-28
                                       A tray tower scrubber can be used for
                                       both particulate and gaseous removal.
                                       However, the most common applications
                                       are for particulate control.  It con-
                                       sists of a series of trays with holes.
                                       The gas stream enters from the bottom
                                       and passes upward through the holes.
                                       Liquor enters from the top and passes
                                       across each tray as it goes downward.
                                       Downcomers are used for moving the
                                       liquor from one tray to another.

                                       A chevron or mesh pad demister is placed
                                       above the elevation of the liquor inlet.
                                       This collects any droplets entrained
                                       from the top tray of the scrubber.

                                       Two of the major tray designs are
                                       shown in this slide.  The sieve plate
                                       has relatively large holes compared with
                                       the impingement tray.  The latter has
                                       high velocities through the holes and a
                                       target directly above the holes.

     One of the main advantages of this style is that there are several opport-
unities to collect pollutants.  Slight gas-liquor distribution problems on one
tray can be tolerated since the material can be caught on subsequent trays.
The liquor quality is again important since it is easy for the holes to plug.
BLIDE 1-29
                                       The orifice scrubber is one of a large
                                       number of units which is classified as a
                                       gas atomized scrubber.  This means that
                                       the droplets which serve as impaction
                                       targets are formed in high velocity gas

                                       In this case, the gas enters the vert-
                                       ical tube and makes a 180 turn just
                                       above the surface of the liquor.  The
                                       action of the gas stream atomizes the
                                       liquor which was entrained by the
                                       passing gas stream.  Baffles included in
                                       the scrubber "box" knock down any drops
                                       which remain suspended in the gas.

      They are usually very small scrubbers.  The system can be exceedingly
simple since it is not absolutely necessary to have a recirculation pump and
piping system.  In a sense, everything is self contained in the scrubber vessel.
The inspection of these units is often complicated by the almost complete lack
of instrumentation.

SLIDE 1-30                             A classic style of a venturi scrubber
                                       is shown here.  The gas stream enters
                                       the converging section and is acceler-
                                       ated by approximately a factor of ten
                                       above normal duct velocities. The liquor
                                       is injected just above the throat.
                                       Droplets form due to the shearing
                                       action of the high gas velocities.

                                       Impaction of particles occurs on the
                                       droplets which are initially moving
                                       slower than the gas stream.  The high
                                       liquor surface area also allows for
                                       some gas absorption.

     The gas stream is decelerated in the diverging section.  In early designs,
the diverging section was long and had a small angle in order to reconvert some
of the gas stream kinetic energy back to potential energy (pressure recovery).
Most of the units in present use have a very short diverging section and angles
approaching 25.  There is only limited pressure recovery with these units.

     After the venturi section, the gas stream turns 90 and passes into the
demister chamber.  The venturi scrubbers usually are part of a large and
relatively complex scrubber system.  Waste water treatment systems, alkaline
addition equipment and presaturators are common.

Lecturer's Notes
     The feature which makes the venturi so effective is also its Achilles
Heel.  The very high gas velocities of 20,000 to 40,000 feet per minute at the
throat entry provide excellent impaction conditions.  However, the gas stream
quickly exits the throat and decelerates.  Very little particle removal occurs
after the gas stream leaves the throat.  If the gas-liquor distribution is not
proper at the throat entry, the scrubber effectiveness will be compromised.
SLIDE 1-31
There are a large number of variations
to the standard venturi configuration.
This slide shows dampers mounted on both
sides of a rectangular throat.  These
can be partially closed to reduce the
throat area.  At a constant gas flow
rate, the reduced throat area results in
higher gas velocities.  The improved
particulate removal efficiency is
obtained at the expense of higher static
pressure drops across the throat.

The position and physical condition of
the dampers can not generally be con-
firmed by external checks and there is
no way to see inside while the unit is
operating.  These must be checked when
the unit is down, however, since the
dampers are subject to extreme abrasion.

    Source: Air Pollution
            Training Institute
Another common style of venturi scrubber
is shown in this slide.  Instead of a
"venturi" assembly, this scrubber uses a
horizontal deck of rods.  The restricted
area between the rods accelerates the
gas stream and provides a zone for drop-
let atomization.  The "throat" has
almost negligible length.  The numbers
or diameters of the rods can be varied
as necessary to achieve the desired gas

The inspection procedure for this style
of scrubber is very similar to that for
the classical venturi units.  The only
difference is that there is concern with
rod erosion and corrosion in this design.
     Unlike classicl venturi scrubbers, these units can be arranged to have
several decks in series.  This multiple deck arrangement is used most commonly
when the scrubber's primary purpose is gas absorption rather than particulate
control.  In gas absorption units, the gas velocities between the rods is lower
than it is in particulate scrubbers.

Lecturer's Notes
     These "Rod Deck" scrubbers are mentioned because of the growing use for
both particulate and gaseous control applications.  Some of the particulate
systems can be quite small and serve applications in which historically the
"venturi" has not been competitive.  Large units are used for utility scale
flue gas desulfurization.
SLIDE 1-33                             The first portion of this lecture has
                                       concerned the typical components of a
                                       wet scrubber system and a brief intro-
                                       duction to the most common types of
     TERMS AND DEFINITIONS         scrubber vessels.  Basic functions of
                                       each of these must be understood before
                                       proceeding with this program.

                                       It is equally important that all of
                                       major terms used in the program are
                                       defined.  Unfortunately, there is some
                                       inconsistency in the wet scrubber lit-
                                       erature terminology.  The next set of
                                       slides discusses these terms.

Lecturer's Notes
     Up to this point, the material has been introductory in nature and could
be skipped when the attendees are experienced with scrubber systems.   It is
advisable, however, to go over the next few slides so that everyone will under-
stand the meaning of the terms used later in the program manual.  It  should be
noted that the definitions used here are not represented as being the best or
most commonly used definitions.   They are simply the meanings intended by the
author of this manual.

SLIDE 1-34
Pressure drop is sometimes used as a
measure of the amount of energy consumed
in the scrubber.  This is supposedly
related to the overall effectiveness of
the scrubber for particulate removal.
     The fact that the correlation seems to make sense  sometimes  does  not  alter
the fact that pressure drop versus collection efficiency alone  is not  a  measure
of energy use.  In fact,  the energy consumption is  related  to the TOTAL  PRESSURE
what is implicitly meant by "pressure drop") is just one component of  the  TOTAL
PRESSURE.  The other is the VELOCITY PRESSURE.  It  is also  important to  specify
the locations between which the pressure drop is measured.   In  this report the
term "pressure drop" will mean the difference in static pressures measured at
two specified locations.

Lecturer's Notes
     The sloppy use of the term "pressure drop" can be  a serious  problem.   If
there is some confusion on the part of the attendees, the definitions  of static,
velocity, and total pressure should be provided.  It may also be  helpful to
introduce Bernoulli's Equation at this time for the more experienced groups.
This will be used later in the program.
SLIDE 1-35
                                       A term as simple as particle diameter
                                       can be confusing.  The meaning of the
          PARTICLE SIZE              term depends on the way in which the
                                       material was obtained and anaylzed.

              ,                         In this manual, the diameter specified
                                       is the aerodynamic diameter.  This is
                                       the diameter of a unit density (same
                                       specific gravity as water) sphere having
                                       the same aerodynamic properties as an
                                       actual particle.

     What this means is that the actual particle behaved in a sampling device
in a manner which is identical to a known size test aerosol.  The factors which
affect the motion of a particle in a gas stream also affect the aerodynamic
diameter. They include actual diameter, actual density, and particle shape.

Lecturer's Notes
     It should be noted that the particle size distribution that would be
derived from microscopic analyses may differ from that determined from a
cascade impactor.  Since almost all size data is obtained by cascade
impactors, and since this directly yields an aerodynamic diameter, this term is
the easiest to use despite the cumbersome units.

SLIDE 1-36
   A, 6PM
                  OUTLET LIQUOR
                  B, GPM
The liquid-to gas ratio is illustrated
here.  In this manual,  the term means
the total gas flow rate in actual cubic
feet per minute divided by the liquor
flow rate introduced at the scrubber
vessel only.  It does not include liquor
or make up water sprayed in evaporative
coolers, or water use to flush

The outlet gas flow rate is used as the
basis for the definition since this is
the easiest to measure.  Stack sampling
ports are usually available for this
purpose.  Also, the outlet gas flow rate
is less subject to change due to temp-
erature fluctuations.
SLIDE 1-37
                                       Erosion is the physical removal of a
                                       surface caused by impacting particles.
                                       Corrosion is the chemical and electro-
       __                            chemical removal of surfaces.
                                       While these are distinctly different
                                       phenomenon, there is some interaction
                                       between the two.  Surfaces which have
                                       been eroded are more susceptible to
                                       corrosion.  Surfaces which have corrod-
                                       ed are more susceptible to erosion.  The
                                       term "erosion/corrosion" is used fre-
                                       quently to refer to the combined action
                                       of both.  This is a logical approach
                                       since it is often impossible to deter-
                                       mine which is most significant or which
                                       occurred first.

     Erosion and corrosion present more problems for wet scrubber systems than
for any other type of air pollution control system.  One of the reasons is that
there are a number of localized areas in the wet scrubber system which have
high liquor and gas velocities.  The suspended particulate in both streams
becomes highly erosive at high velocities.  Corrosion is promoted by the moist


                       cw V
                                                VENTURI SCRUBBER
                                                WITH CYCLONIC
SLIDE 1-38
                                       Flowcharts are absolutely necessary for
                                       a  detailed and effective inspection of
                                       a  wet  scrubber system.

                                       The  locations of all measurement ports
                                       and  instruments should be shown along
                                       with the  sources of all liquid streams.
                                       Bypass vents and stacks should also be

     The flowchart should not  be cluttered  with  unnecessary detail.  Also, it
should be remembered that a flowchart  is  not  judged on the basis of artistic
merit, but rather the insight  it provides to  an  inspector trying to evaluate a
change in system operating conditions.

     Symbols and drawing conventions presented in the next set of slides have
been taken from the Chemical Engineering  literature and from standards pre-
sented by the Instrument Society of America.   However, some license has been
taken in order to compile a set  of symbols  specifically for inspectors of air
pollution control equipment.  Each field  inspector is invited to make further
changes as they see fit.


                         MESH PAD DEMISTER
                          CHEVRON DEMISTER

SLIDE 1-39
                                       The first step in the procedure is to
                        	"       adopt a convention for liquid and
                                       gaseous streams.   The line types shown
                                       in this slide have been arbitrarily
                                       chosen for this purpose.

                                       Note that the pipe sizes can be easily
                                       shown on the solid lines.  The size
                                       data shown is the actual diameter
                                       (approximate data is sufficient) rather
                                       than the specific pipe size. The dotted
                                       lines for the pollutant laden gas
                                       streams can also be interrupted to show
                                       the approximate size of the ducts. This
                                       data helps to identify ducts and pipes
                                       while comparing the flowchart to the
                                       actual system.

     It is usually best not to show steam lines and other material transfer
lines not directly related to the scrubber operation.  It is difficult enough
simply trying to understand some of the complicated and often modified
systems.  Extraneous material is not helpful.
SLIDE 1-40
                                       The type of scrubber vessel and
                   	^_              demister should be indicated using the
                                       figures on the opposite and next pages.
                                       Note that these provide just enough
                                       information to indicate the type of unit
                                       but do not require extensive drawing.

                                       The points at which the various gas and
                                       liquid streams enter and exit the unit
                                       should be shown.  The directions of
                                       flow are indicated by arrows.

                                       With this part of" the flowchart, it
                                       should be possible to get a conceptual
                                       idea of how the unit is working.

     With the number of innovative systems now entering the v/et scrubber
market, there will soon be a need to develop additional symbols.  Remember that
consistency and logic are necessary when it comes to flowcharts.

         0 O

SLIDE 1-41
                                       This is an  example  of  a  wet scrubber
                                       system based  on  the symbols presented.
                                       The scrubber  vessel is an impingment
                                       type tray scrubber  and there is a
                                       chevron demister at the  top of the unit.
                                       The liquor  enters from the top and flows
                                       down to a sump at the  bottom of the unit.
                                       While most  of the liquor is recirculated,
                                       a  purge stream (number 3) is drawn off
                                       for treatment.   Fresh  water is used for
                                       occassional cleaning of  the demister.

                                       The fan is  upstream of the scrubber.
                                       Therefore the scrubber vessel and
                                       ductwork from the source are under
                                       positive pressure.

    Note that the stack is numbered.   It  is best to  have a consistent number-
ing scheme for each stack and vent rather than relying  on  the identification
system used at the plant.  These are  subject to change  over time.  When making
visible emission observations, the number of the stack  specified on this flow-
chart should be recorded along with other identification information.
                       FROM WASTEWATER
                      TO WASTEWATER
SLIDE 1-42
                    I	 GAS STF
         INLET GAS
                                       The symbols  for  process water,  city
                                       water,  compressed  air and  other system
                                       utilities are  shown  in the list below.
                                       The figure to  the  left shows how these
                                       can be  used  in a flowchart.  Use of
                                       these symbols  helps  to unclutter the
                                       A  - Plant  compressed  air
                                       IA - Plant  instrument  quality air
                                       CW - City water
                                       PW - Water  from  process equipment
                                       BW - Boiler feed water
                                       DW - Distilled water
                                       FG - Fuel gas
                                       FO - Oil
                                       FC - Coal
                                       FW - Wood fuel
                                       HM - Heating medium
                                       HS - High pressure  steam
                                       LS - Low pressure steam
                                       SC - Steam  condensate
                                       E  - Electrically controlled

     It should be noted that some of these symbols differ  from conventional
flowchart practice.  The symbol CW, for example, often  stands for cooling
water rather than for city water.

SLIDE 1-43
                     STATIC PRESSURE -17'
                     TEMPERATURE 134-F
                     FLOW RATE 32.OOO ACFM
In some cases, it may  be  helpful to put
some of the typical  operating data on
the flowchart itself.  There  are two
ways this can be done  easily.

The figure to the left shows  the data
contained in blocks.   A thin  indicator
line is used to connect this  block to
the appropriate stream line.

This is an adequate  approach  as long as
the system is relatively  simple and the
amount of data listed  in  small.  For
large scrubber systems, this  can become
cumbersome and confusing.   The approach
shown on the next slide is  appropriate
for such systems.
  IDE 1-44
IN. W.C.
                  The liquid and gas streams  in  this
                  flowchart have been assigned numbers
                  which are enclosed in diamond  shaped
                  boxes.  These are connected to the
                  appropriate streams by thin indicator

                  The applicable data for the stream  num-
                  ber is shown below the flowchart  in a
                  tabular format.  Considerably  more  data
                  can fit into this table than could  be
                  put into the individual data boxes
                  shown in the previous slide.

SLIDE 1-45
                                       Notation for the process and wet
                                       scrubber system instrumentation has
                                       been patterned after standard chemical
                                       enginering symbols.  Several additions
                                       and changes were necessary to include
                                       features of importance to scrubber

                                       The presence of an instrument or an
                                       accessible measurement tap are shown
                                       as a circle.  A thin indicator line is
                                       used to connect this symbol to the
                                       appropriate location of the system.
                                       The notation inside presents informa-
                                       tion on the type of instrument.

     There are 3 distinct types of codes: those ending in "I" specify that
the unit is an indicating gauge only, those ending in "R" are equipped with
a recorder, and those ending in "T" are simply accessible measurement ports.
The recommended symbols are listed on the opposite page.

     The operating range of the instrument can be specified in the indicator
circle along with the instrument symbol.  For ports, the inside diameter is
useful information since it determines the type of equipment which is necessary
to seal the port during measurements.
SLIDE 1-46

The use of a line across the diameter of
the instrumentation circle indicates
that the instrument is panel mounted.

The slide to the left has three differ-
ent symbols to illustrate how the line
can be helpful.  The first (l-46a) means
that there is a differential pressure
indicator on the the system itself.  The
second (l-46b) means that a differential
pressure indicator gauge is on a control
panel somewhere.  The third (l-49c) is
more explicit in that the location of
the gauge is stated to be the control
room symbol.  CR is a useful symbol for

 1.   TI   - Temperature indicator
 2.   TR   - Temperature recorder

 3.   DPI  - Gas stream static pressure drop indicator
 4.   DRP  - Gas stream static pressure drop recorder
            (Both upstream and downstream measurement
            locations must be indicated for differential
            pressure instruments)

 5.   SPI  - Gas stream static pressure indicator
 6.   SPR  - Gas stream static pressure recorder
 7.   GFI  - Gas flow rate indicator
 8.   GFR  - Gas flow rate recorder

 9.   LFI  - Liquid flow rate indicator
10.   LFR  - Liquid flow rate recorder
11.   PI   - Liquid pressure indicator
12.   PR   - Liquid pressure recorder
13.   LCI  - Liquid level control indicator
14.   pH   - pH meter
15.   RHO  - Liquid density meter

16.   PWI  - Power on indicator liqht
17.   MCI  - Motor'current indicator
18.   MWI  - Motor wattage indicator
19.   VI   - Voltage indicator
20.   AI   - Current indicator
21.   PVI  - Primary voltage
22.   PCI  - Primary current
23.   SVI  - Secondary voltage
2'4.   SCI  - Secondary current
25.   SPI  - Spark rate

26.   02R  - Gas stream oxygen recorder
27.   COR  - Gas stream carbon monoxide recorder
28.   GBR  - Gas stream combustibles recorder
29.   S02R - Gas stream sulfur dioxide recorder
30.   OPR  - Gas stream opacity recorder

31.   AT   - Accessible measurement tap
32.   ST   - Stack sampling ports

33.   API  - Compressed air pressure indicator
34.   IAPI - Instrument air pressure indicator

SLIDE 1-47
           GAS STREAM
              IN SITU INSTRUMENT
For the few wet scrubber systems having
continuous emission monitors, it is
useful to specify the general type of
instrument.  Extractive instruments are
shown as a box removed from the gas
stream and connected by a short dotted
line.  The in-situ instruments are
shown straddling the gas stream line.
SLIDE 1-48
   4 C5-40
                  -4- C5-IO-RUBBER

Some of the main causes of wet scrubber
system failure are corrosion and ero-
sion.  If these problems are likely,
the materials of construction can be
noted on the flowchart.

A four part coding system is proposed
here for identification of the materials
of construction.  The first part is the
pipe or duct size in inches.  The second
is the basic material.  The third is the
thickness (or schedule number in the
case of pipes) and the fourth i,s the
type of coating or liner.  Material
codes are presented below and use of
the entire code is illustrated in the
adjacent figure.
     CS  - Carbon steel (Specify AISI number if known)
     SS  - Stainless steel (Specify AISI number if known)
     FRP - Fiberglass reinforced plastic
     PVC - Polyvinyl chloride (Specify type if known)
     NAS - Nickel alloy stainless steel (Specify trade name or AISI number)
     W   - Wood

     There are no abbreviations suggested for the liner.  The type should
simply be spelled out.  The material codes listed above are similar to the
standard chemical engineering symbols.  However, some changes have been made,


SLIDE 1-49
A complete flowchart for a wet scrubber
system is shown in this slide.
It incorporates every major feature
discussed in this section.

Flowcharts similar to that shown are
invaluable when attempting to diagnose
operating problems with a system.
They also help to determine the most
appropriate measurement locations.

Measurement errors and system gauges
which are indicating incorrectly can
often be identified using the

      It should be clear that the figure represents a tray type scrubber with
      a chevron demister.  The liquor is recirculated.  For simplicity,  the
      entire scrubber system has not been shown.

1-1.  The correct answer to this problem is that the static pressure drop can
      not be calculated from the present set of data which is obviously in
      error.  There is no way the static pressure at point #3 could be higher
      than the static pressure at point #2.

      If a number of the attendees answered either 3 inches (point 3 minus
      point 2) or 12 inches (point 3 minus point 1), that indicates a lack of
      understanding about the way static pressures vary while gas streams pass
      through control devices.  It increases only when going past a fan.

1-2.  Now that we have what appears to be sensible data, the scrubber pressure
      drop can be calculated as the value at point 3 minus the value at point
      2, which is simply 7 inches.  PLEASE STRESS THAT THE LOCATIONS OF THE
      ANSWER IS: 7 INCHES FROM POINTS 2 TO 3.  Note that this now includes the
      demister's contribution to the overall scrubber pressure drop.  It would
      have been preferable to use data from point 4 had this been available.

1-3.  In this particular case there is sufficient information about the
      liquor flow rates and it possible to calculate the purge stream flow rate
      from a simple material balance.  The answer is 15 gallons per minute.
      There are times when an approximate material -balance can be very useful
      and the attendees will occassionally be reminded of these in the program.
      Usually, it is easier to do this with the gas streams than the liquor
      streams because in the large majority of cases, the flow rates of most
      streams will not be known.  We can measure the flow rates of the gas
      streams easily.  To answer this question correctly, the attendees will
      also haye to be able to recognize which stream is the purge stream.

1-4.  The concepts of positive and negative pressure are reviewed in this
      question.  Since the hole in the scrubber wall is downstream of the fan,
      the chances are very high that there will be gas flow out rather than
      air infiltration inward.  If the gas is highly toxic and ventilation in
      the area of the hole is poor, this could represent a dangerous situation.
      One of the first steps in any inspection is the recognition of areas
      where gas leakage and accumulation is possible.

                                                    TO STACK 101
                                                    FROM  WASTEWATER
                            Sample  Flowchart #1
1-1.  What is  the scrubber pressure  drop when the static  pressures are as
      follows:  SPI 1 = -6 inches,  SPI 2 = + 3 inches,  and SPI 3 = + 6 inches.

1-2.  What is  the scrubber pressure  drop and the demister pressure drop when
      the following static pressures are measured: SPI 1= -3 inches,
      SPI 2 =  +8 inches, and SPI 3 = +1 inches.

1-3.  What is  the approximate purge  stream flow rate if the liquid flow rates
      are as follows: Stream #1  - unknown, Stream #2 - 210 gpm, Stream #3 -
      unknown,  Stream 14 - 50 gpm, Stream #5-0 gpm,  Stream #6 - 175 gpm.

1-4.  There is a small hole in the scrubber vessel wall,  directly below one of
      the trays.  Is air infiltration likely?


      This is again a tray tower scrubber.  However,  this time the unit is
      under negative pressure.   None of the liquid flow lines have been shown
      since none of the questions involve this part of the system.

1-5.  Assuming that the static pressure measurements at points #1 and #3 have
      been made carefully, the on-site gauge is definitely wrong.  Based on
      the measurements, the maximum static pressure drop is 8 inches and this
      includes the demister which normally contributes about 1 inch.  The
      preferred locations for the static pressure drop measurements would be
      locations AT #1 and AT #2.

1-6.  There is no reason to believe that a measurement error has occurred
      based only on the data provided.  It is very possible that some of the
      oxygen has been absorbed in the scrubber, therefore, reducing the levels
      in stream.  Some air infiltration is always possible, especially at the
      fan itself, and this could increase the oxygen levels in stream #3.  The
      fact that both streams #1 and #3 are at 8% is a coincidence presented
      here to confuse the unwary.  The point of this question is that oxygen
      changes before and after a scrubber are not very useful in attempting to
      diagnose and quantify air infiltration.

1-7.  The liquid-to-gas ratio is approximately 11.45 gallons per thousand ACF.

1-8.  This is probably not a measurement error.  There is some temperature
      gain across most fans due to the conversion of some mechanical energy
      to heat.  This was not discussed as yet in the program.  Through out the
      workshop program these questions and problems will be used not just for
      review but also to introduce some useful information which can not be
      conveniently discussed in the slide-lecture note format.  This is the
      first of these points.

                             Example Flowchart #2
1-5.  The static pressure drop gauge on this system is indicating 12 inches
      of water.  The static pressures measured at points AT #1 is -12 inches
      and at point AT #3 is -20 inches.  Is there any reason to suspect the
      accuracy of the permanently mounted static pressure drop gauge?

1-6.  The measured flue gas oxygen content in stream #1 is 8%, in stream #2 is
      5% and in stream #3 is 8%.  Does this show that the inspector has made
      incorrect oxygen measurements?

1-7.  What is the liquid-to-gas ratio for this system if the total liquor flow
      rate is 200 gpm, the gas flow rate of stream #1 is 20,500 ACFM, and the
      gas flow rate of stream #2 is 17,500 acfm?

1-8.  The gas temperature in stream #2 is measured at 109 F and the tempera-
      ture in stream #3 is measured at 118 F.  Has a measurement error been


      This system has a rod deck type gas-atomized scrubber and a cyclonic
      demister.  A calcium hydroxide solution is being added to the recirc-
      ulation tank to maintain the liquor pH in an acceptable range.  Not
      shown in the figure is a clarifier and vacumn filter system which are
      necessary to maintain an acceptable solids content in the liquor. A
      bypass stack with butterfly dampers is included.  The damper on the
      stack is normally closed and the one on the gas stream to the scrubber
      is normally open.  The scrubber and demister are rubber lined carbon
      steel.  Everyone should have been able to describe this system using
      the flowchart symbols.

1-11. Yes, there is a slight possibility that untreated gas could be going up
      the bypass stack.  Note that the static pressure in stream #3 is more
      negative than it is in stream #2 due to the draft created by the stack above
      point #3.  If the damper is not seated properly this will cause some

1-12. It is clear from the flowchart that the liquor sample has been withdrawn
      from the area which should have the highest ph since it is downstream
      from the location of the calcium hydroxide addition.  The liquor pH will
      be lower after the scrubber throat and in the scrubber sump due to the
      absorption of acidic gases such as S02 and C02.

1-13. If things work as they should, the bypass damper should open quickly
      to vent the hot, untreated gas directly to the atmosphere.  If the
      dampers don't work properly, hot gas will destroy the rubber liner,
      leading to major damage and perhaps a prolonged outage.  This question
      is intended to illustrate the usefulness of placing materials informtion
      on the  flowchart.  If this information were not here, it would be easy to
      forget  that the scrubber is extremely vulnerable to temperature spikes.

1-14. Air infiltration is most likely in areas of the maximum negative static
      pressure.  This means any area downstream of the rod deck in this case.
      Upstream, the static pressures would be quite low.

                                                       FROM LIME
                                              TO CLARIFIER
                             Example Flowchart #3
1-9.   The static pressures in stream #1 is -1 inch,  in  stream #2  is -1  inch,
       and in stream #3 is -2 inches.  Is there any possibility for  loss of
       untreated gas up through the bypass duct?

1-10.  The pH of the recirculation liquor is measured using  a  sample obtained
       at the recirculation pump discharge.  If the measured pH is 7 and
       corrosion is only a problem when the pH is  below  5.5, is there any
       reason to worry about corrosion?

1-11.  Due to a sudden failure of the recirculation pump,  all  liquor flow to
       the inlet of the scrubber is lost for a period of 20  minutes.  What
       will be the result this problem?

1-12.  If air infiltration is suspected due to very poor capture of
       particulate at the process hoods, where are the logical places to begin
       searching for the infiltration points?


                                  LECTURE 2

                        WET SCRUBBER SYSTEM  EVALUATION
SLIDE 2-1                              This  lecture  concerns  the application
                                       of  the  Baseline  Inspection Technique
                                       to  wet  scrubber  systems.  The procedure
   BASELINE INSPECTION PROCEDURES     is  designed to help regulatory agency
                 FOR                   inspectors and source  operators to
   vET SCRUBBER SYSTEM EVALUATION     identify  performance problems at the
                                       earliest  possible  stage.  Determination
                                       of  the  possible  causes of observed
                                       problems  is another important aspect
                                       of  the  Baseline  Technique.

     The inspection procedure is limited to  the  full identification and eval-
uation of problems and  does not address specific correction actions.  The
latter would infringe on the perogatives of  the  source  management.  The role
of the inspector  is limited to determining if  the actions proposed by the
source have a reasonable possibility of success  and  would abate the excessive
emission conditions in  a timely manner. The data and observations made during
the baseline inspection enable the regulatory  agency to evaluate these pro-
posed actions very effectively.  If the plant  management  actions appear to be
unsatisfactory,  the baseline inspection data can also be  used to support
enforcement actions.

     The slides which follow present some  of the basic  principles of the Base-
line Inspection Technique.   The concept of inspection levels  is also defined.
The latter is intended  to provide flexibility  to regulatory agencies in the
amount of time invested in  each wet scrubber system  inspection.


           TO EVALUATE
                                       EACH WET SCRUBBER SYSTEM SHOULD BE
                                       APPROACHED INITIALLY AS IF IT PERFORMS
                                       IN A DIFFERENT MANNER THAN ALL OTHER
                                       SIMILAR WET SCRUBBERS ON SUPPOSEDLY
                                       SIMILAR SOURCES.  In other words, the
                                       performance of one unit should not be
                                       compared with the performance of an-
                                       other, unless data gathered over a long
                                       time period shows these two to be
                                       similar.  In the case of wet scrubber
                                       systems, there are numerous reasons why
                                       significant performance differences occur
                                       in two systems which appear similar.

     Unlike some control systems, the particle size distributions in the gas
streams entering and leaving wet scrubbers are subject to subtle but signifi-
cant changes.  Some of the phenomenon which can affect particle size include
heterogenous condensation, agglomerate shattering, and particulate regenera-
tion.  Since performance is highly sensitive to particle size, these affect the
overall performance.  Another major reason for unit to unit differences is the
gas-liquor distribution.  Subtle changes in this distribution have a major
impact on the overall particulate and gaseous control efficiencies.  The varia-
tion in system components also contribute to the site-to-site differences.
Normal Value
of Parameter
for This Unit
                           Present Value
                           of Parameter
                           for This Unit
Instead of using literature data or the
performance data from other systems as
the yardstick of performance, the Base-
line Inspection Technique uses data from
the specific unit.  This data is more
easily accessible and is more accurate
since there is no question about its

During the inspection of wet scrubbers,
the present operating conditions are
compared with conditions some time in
the past when the unit was believed to
be working properly.  A shift in the
a parameter is a symptom of a problem.
Lecturer's Notes
     The importance of evaluating scrubbers using unit-specific data can not be
overemphasized.  One cupola venturi scrubber operating at a 25 inch static
pressure drop can have better performance than an adjacent unit operating at 50
inches.  Inspectors must avoid the simplistic conclusions which can result
from comparing one unit to another.  Such comparisons can only be done after
it has been demonstrated that the units are in fact similar.
     The acquistion of baseline data is discussed in later slides.  Questions
concerning baseline data should be reserved for later.

           AS POSSIBLE
Sometimes it is possible to identify
a wet scrubber performance problem by
examining the shift in one parameter.
For example, a 50% drop in liquor  flow
rate indicates serious trouble for
almost all types of scrubbers.

In most cases, however, it necessary  to
look at as much data as possible in
order to figure out the likely fundamen-
tal problem.  Small shifts in a number
of parameters are also useful for  the
early identification of problems.   For
these reasons, the inspection procedures
used in this workshop deal with sets of
            ARE OFTEN
It is not easy to maintain instruments
on wet scrubbers systems.   The probes
are subject to pluggage, corrosion,  and
erosion.  Even well maintained instru-
ments can be incorrect some of time.

There is a general correlation between
the level of performance of the wet
scrubber system and the accuracy and
availability of the instruments.  Those
units which seem to be performing very
well usually have monitoring instruments
which work at least most of the time.
The units with chronic compliance pro-
blems frequently seem to have instru-
ments out of service or no instruments
at all.  It is obviously the latter
group which is of most interest to regu-
latory agency inspectors.   Therefore, it
is good practice to question the accur-
acy of the gauges.


  Primary   1. Safety Equipment
  Equipment 2. Static Pressure Gauge
          3. Temperature
          4. Oj/COj Analyzer
          5. Flashlight
          6. pH Meter or pH Paper
  Secondary 1. PitotTube  _
  Equipment 2. Tachometer
          3. Velorneter
                                       The types of portable instrumentation
                                       used in the inspection of wet scrubbers
                                       are listed in this slide.  The list is
                                       divided into a primary set which is used
                                       very frequently and a secondary set
                                       which is rarely used.

                                       All of this equipment is relatively
                                       inexpensive and easy to use.  The gauges
                                       needed for a given inspection can usual-
                                       ly be carried in a tool pouch or small
                                       tool case.  Instrument calibrations are
                                       simple except for thermocouples.
     There are several approaches to the use of portable instruments.   In
plants which have union agreements regarding instrumentation,  the  gauges should
be given to the appropriate plant personnel to conduct the measurements while
the inspector observes.  In other cases, the plant management  may  perfer that
the agency inspector make the measurements.  If the regulatory agency  does not
presently have the necessary instruments, the inspector can  request  that plant
personnel conduct the measurements using their own gauges  (most  plants have the
items listed above).  In any case, the objective is to make  sure that  accurate
and complete data has been gathered during the inspection.

Lecturer_' s Notes
     It should be noted that portable instruments are used only  on detailed
inspections.  On most occassions, the accuracy of on-site gauges will  be eval-
uated visually with no attempt to measure any operating conditions.  Anyone
using portable instruments must adhere to the general safety procedures covered
later in the workshop and any specific policies at the plant being inspected.
                                       Field inspections should  be conducted  in
                                       a methodical order.  The  initial  data
                                       should be reviewed during the  inspection
                                       so that the remainder of  the effort can
                                       be focused on any suspected problems.
                                       If the initial data suggests that system
                                       performance is similar  to baseline per-
                                       iods then the inspection  is terminated.

                                       The approach recommended  in the program
                                       is termed the "Counterflow" procedure.
                                       The inspection starts with a careful
                                       evaluation of stack visible emissions
                                       and then proceeds in a  countercurrent
                                       direction relative to the gas  stream.

     Emphasis is given to evaluation of scrubber vessel and liquor recircula-
tion system operating parameters.  The process equipment is evaluated only
when (1) there are indications of an emissions problem, and (2)  the data and
observations made of the stack and wet scrubber system suggests  that  the fun-
damental cause of the condition is a change in process operation. This  does
not mean that process conditions are not important, but this time consuming
part of the inspection should be done only when there is a clear need to do so.

SLIDE 2-8                              Two  key  words  necessary  in wet  scrubber
                                       system inspections are flexibility and

          FLEXIBILITY                 Due  to the  extreme diversity  of system
          JUDGEMENT                 designs, it is difficult to develop an
                                       inspection  scheme which  is appropriate
                                       for  each one.   In some cases, it will be
                                       necessary to go beyond the observations
                                       and  data discussed in the workshop in
                                       order to evaluate conditions.   In other
                                       cases, strict  adherence  to all  the steps
                                       mentioned would represent overkill. Each
                                       field inspector must understand the in-
                                       spection procedures and  control system
                                       operating principles well enough to
                                       tailor the  inspection to the  system. In
                                       other words, the inspection procedure
                                       must be  moderately flexible.

     The field inspection,  in conjunction with  his or her supervisor must make
certain judgements regarding the amount of  effort  warranted for the  specific
inspection.  The material presented for each scrubber type is divided  into
several distinct levels.  The most detailed inspections are done on  sources
with chronic compliance problems or on those at which a problem is now suspect-
ted.  There must also be some judgements regarding any potential health and
safety problems.  Obviously, a field inspector  should not do anything  that in
his or her judgement would present a safety problem or which could harm the
plant equipment.
SLIDE 2-9                              The inspection procedures are  divided
                                       into distinct levels.   Level  1 inspec-
                                       tions are done mainly  from the plant
                                       boundry and consist  of an observation  of
                                       the visible emissions  and any  fugitive
                    BEVELS OF        emissions from plant facilities.
                                       \Level 2 inspections  are walk  through
                                       inspections of the control system and
                                       the process equipment.  These  are
                                       routine inspections  which are  conducted
                                       on sources believed  to be in  compliance.
                                       The emphasis here is on identification of
                                       any problems which could lead  to  excess
                                       emissions in the near  future.
     The most detailed form of the inspection procedure is Level 3.   This
involves the use of portable instruments so that all possible parameters
relevant to the suspected problem(s) are measured and evaluated.  The data and
observations are shared with plant personnel to see if agreement can be reach-
ed concerning the types of problems which exist.  The actions proposed by plant
personnel to correct or prevent the problem should be evaluated by the field
inspector and supervisory agency personnel.


Stream 1 Static Pressure
Stream 2 Static Pressure

Stream 1 Gas Temperature
Stream 2 Gas Temperature

Stream 4 Liquor Flow
                                 Inspection Number
    Comparison of Present Data with
    Inspection 1 Data Only
    AP(insp 1)
43 inches
46 inches
     T2(present) = 129
     T2(insp 1)  = 136
     Conclusion: Minor Variation
      Comparison of Present Data with
      All Four Previous Inspections

      AP(present) = 43 inches
      A.P(mean, 1-4) = 45 inches
                                1-4) =
                          T2(present) = 129 F
                          T2(mean, 1-4) = 134 F
                          T2U ,  1-4) =

                          Conclusion: Student's t Test
                          indicates >95% probability that
                          present pressure drop is low and
                          a >98% probability that the gas
                          temperature of stream 2 is low.
                          Air infiltration likely.

SLIDE 2-10
The baseline data should not be regarded
as some mystical, unchanging yardstick
with which scrubber performance can
always be measured.  It should, instead,
be a constantly growing data set which
is supplemented by the results of each

For example, The inspection data from
plant A is a hypothetical level 3
inspection.  Inspections B and C are
level 2 inspections during which the
plant instruments appeared to be
working.  A comparison of the present
data with the range of data in all three
previous inspections clearly shows that
there has been a change in the operating
conditions.  If only the data from in-
spection A were available, it would have
been hard to determine if the differ-
ences were due to a change or just to
normal variability. When combining data
from several inspections it is neces-
sary to confirm that there have been no
major process changes.




Regulatory Limit
              400     800    1200   1600  2000


            To calculate corrected pressure drop from
            data in  units of inches of water,
                Inches W.G.* (5.2 Lbf/ft2/inch WG) =
                M/(Gas Density, Lbm/ft3) =
                      C, (Lbf-Ft/Lbm)

SLIDE 2-11                             In most  cases,  scrubber  performance is
                                       evaluated  by  comparing present condi-
                                       itions to  the general operating range.
      -.T-.^T-,^...  ,AI w*ir-         This was illustrated in  the previous
      STATISTICAL ANALYSES         slide    In some cases> however, it is
                                       useful to  apply some basic statistical
                                       tests to gain some  insight regarding the
                                       significance  of shifts in the operating
                                       parameters.   The example on the oppos-
                                       ite page provides the data used here.

     With only one inspection serving as the baseline,  the shifts in static
pressure drop and gas temperature are difficult to evaluate.  With data from
several inspections, the normal variability can be reviewed and the Student's
t test can be used to evaluate the significance of the shifts.  Both the gas
temperature and the pressure drop have apparently changed  substantially.  In
this case, it is very possible that the scrubber  vessel is experiencing some
air infiltration and this is reducing the quantity of  gas  pulled from the
process source.  The remainder of the present inspection concentrates on air
infiltration issues.  The sites of air infiltration  are be checked and pitot
traverses are conducted before and after the scrubber  vessel.

Lecturer's Notes
     The purpose of this example is to show how the  baseline data expands over
time and how the basic statistic analyses can be  applied.  This procedure is
one step beyond simple comparison of conditions against a  range of values as
illustrated in the previous example. . The next  step  goes one step further by
using a performance correlation.

 SLIDE 2-12
    Test       P "x"      Emissions "y"
A useful correlation for certain wet
scrubber systems can sometimes be pre-
pared when several stack tests have
been conducted at different operating

The hypothetical set of data provided
on the opposite page has been used to
illustrate how the confidence interval
on the correlation changes as more
data is obtained. The 90% confidence
interval using tests 1 and 2 can be
compared with the interval using all
five tests.
     As a starting point, it is helpful to transform this data to a form which
is easier to use.  The data taken from the opposite page has been converted in
the form shown in this slide.  The natural log of the emissions data has been
used since the "eyeball" curve seems to be exponential in nature.  Multiplica-
tion of the number by 100 avoids the necessity of handling negative logarithms.
The pressure data has been converted from the familar inches of water format to
the corrected pressure drop form.  The general procedures are illustrated at
the bottom of the opposite page (the corrected pressure drop term will be
introduced later).  The corrected pressure drops have then been divided by 100
so it will not be necessary to manipulate large numbers.
SLIDE 2-13

 = 020
  0 IS
g 0.05
7, 004
I 0.03

  0.01 >-
                   10    15
                   P, INCHES.wc.
           The  statistical  procedures  summarized
           at the end  of  this  lecture  have  been
           applied  to  the data shown in  the above
           slide.   The curve shown  in  this  slide is
           the  result  of  including  all five of  the

           The  solid line in the  middle  is  the
           linear regression line.  The  curved
           lines above and  below  this  are the 90%
           confidence  intervals.

           If the measured  pressure drop is so  low
           that the lower confidence interval is
           above the regulatory limit, then there
           is a 90% probability,  based on this  one
           correlation, that the  unit  is now out
           of compliance.
     The circle on the right indicates the average corrected pressure drop
which is necessary to remain below the regulatory limit.  If there is a correc-
ted pressure drop of 11 inches of water (see circle to the left), then there
is a good possibility that emissions are now greater than the 0.10 pounds per
million BTU imput.

SLIDE 2-14
This is a graph of the correlation using
only tests 1, 3 and 4.  The confidence
interval now looks much larger.  This
indicates that less is known about the
variability of the emissions-corrected
pressure drop data.

In this case, the corrected pressure
drop must decrease below 9 inches before
there is reasonable confidence that
excess emissions are occurring.  In the
earlier example, a decrease to 11 inches
would have indicated this clearly.
      These curves are intended to illustrate simply that the more data
available, the more sensitive the baseline analyses can be.   Each set of data
helps to further define the normal variability so that abnormal conditions are
easier to spot.  It should be noted that the data used in this hypothetical
example was specifically chosen so that there would be very  little variability.
This inherently reduces the width of the two confidence intervals.  In some
cases, the plotted confidence intervals with just three data points could be
so large as to render the entire procedure meaningless.  The factor which
determines the number of data points necessary for a good correlation is the
variability of the system itself and the choice of an operating parameter used
in the correlation.

SLIDE 2-15
                                       For  some wet  scrubber systems, the
                                       performance correlations using the
                                       baseline data can be very useful in
             SUMMARY                estimating the  potential for excess
  PERFORMANCE CORRELATIONS     emissions.  It  should be remembered,
                                       however, that these are not sufficient-
                                       ly accurate to  serve as a basis for a
                                       notice of violation.  That can only be
                                       done by a reference method test speci-
                                       fied in the applicable regulations.
                                       These correlations are only intended as
                                       an aid to the agency inspector or source
                                       operator attempting to determine if a
                                       shift in conditions is significant.
     One common problem with wet scrubber correlations  is  that  there are a
number of conditions which can invalidate a  usually  accurate  relationship.  The
most common of these are sudden shifts in the inlet  gas stream  particle size
distribution.  These changes will be examined in  some detail  in later  sections
of the workshop.

Lecturer's Notes
     The use of correlations should not be overemphasized.  The simple com-
parisons of present conditions to several previous sets of  inspection  data are
usually more than sufficient.  It is conceivable  that some  of the  attendees
will spend too much time compiling performance correlations.  Sometimes these
are worthwhile, sometimes they are not.

SLIDE 2-16                             One way to compile  a baseline data set
                                       is to extract data  from  wet scrubber
                                       system operating logs.  The main risk
                                       with  this  approach  is  that  data from
   OPERATING LOGS AND RECORDS  *alfunctionin instrumentation  will be
                                       used.  Nevertheless, this is the only
                                       approach possible when the  unit has not
                                       been  stack tested and  detailed  inspec-
                                       tions have never been  conducted.  Once
                                       better data becomes available,  the in-
                                       formation  retrived  from  old files can be

     The data which is most useful includes  gas temperatures, static pressure
drops, liquor flow rates, liquor pH levels,  and nozzle  header pressures.  Only
rarely will data other than that listed above be  found.

     As much information as possible on the  process  operating rate and condi-
tions should also be pulled from the files.   This information is almost always
recorded on other operating logs.  Therefore, additional "digging" is  in  order.
Unfortunately, some plants discard operating records after 3  months.   This
practice may preclude any access to data which predates the apparent problems
with the wet scrubber system.


SLIDE 2-17
                                       There are several ways to evaluate the
                                       present data against a set of data
                                       retrived from the files.  This slide
                                       presents data showing how the Student's
                                       t test can be applied to several sets
                                       of scrubber system operating data.

                                       In this case, all three parameters
                                       appear to be significantly different
                                       from the data taken from the records.
                                       The manner in which the present data
                                       deviates from the recorded values
                                       indicates a sudden drop in liquor flow
                                       rate to the inlet of the scrubber.  The
                                       diagnosis of problems is discussed in
                                       some detail later in the program.

     The Student's t test indicates that there is a 90% probability that the
pressure drop is lower than normal, there is an 80% probability that the outlet
gas temperature is higher, and a 95% probability that the nozzle header pres-
sure has decreased.  All of these indicate a reduction in the liquor flow to
the scrubber.  One possible explanation is a change in the recirculation pump
impeller.  It is often the simultaneous changes in several parameters that are
most useful for pinpointing possible problem areas.  The use of several para-
meters is especially important when using data from operating logs where the
accuracy of the data can not be easily confirmed.









Gas Temp










SLIDE 2-18
                                       In summary, the baseline data provides
                                       a means to measure present operating
                                       conditions.  Shifts in the values of
                                       key operating parameters can be
                                       evaluated simply by inspection or
                                       through basic statistical techniques.

                                       There are distinct levels of effort
                                       used for different circumstances.
                                       Plant boundry inspections consist only
                                       of visible emission observation.  The
                                       regularily scheduled walk through
                                       inspecton involves both visible
                                       emissions observations and the eval-
                                       uation of operating conditions indic-
                                       ated by on-site gauges

      When a wet scrubber system has a history of excess emission problems or
the data gained in the level 1 or 2 inspections suggests potential scrubber
performance problems, a detailed inspection is conducted.  This involves the
use of portable instruments as necessary and a more comprehensive check of
system conditions.  Regardless of the level of the inspection, the performance
is always evaluated by the comparison of present conditions against site-
specific baseline data.


2-1.  Yes, a more detailed inspection is necessary as soon as possible to
      determine if the unit is now or soon will be out of compliance.   An
      increase of this magnitude is a very bad sign even though the unit is
      not out of compliance based on the visible emission observation.

2-2.  No, each field inspector, with the assistance of his or her supervisor,
      decides what is the most effective and safe procedure for conducting an
      inspection of a given facility.  A certain amount of professional judge-
      ment is required for all field inspections.

2-3.  The answer is simple, the inspector should NOT enter the unit under any
      circumstances.  While most plant personnel are well trained and  aware of
      safety hazards, there are always a few that are not.  There could be
      pockets of toxic gas and inadequate oxygen inside a unit that is out-of-
      service.  It is also possible that the unit is not properly locked off
      line.  Everything a regulatory agency inspector needs to see can be seen
      very well from an acces hatch. There is NEVER ANY REASON TO ENTER.

2-4.  The only correct answer is c, a general assessment of the performance
      of the wet scrubber.  It is very presumptous to think that anyone can
      go into a plant and in a matter of several hours completely judge the
      adequacy of their maintenance procedures.  Furthermore, no inspection
      procedure can ever substitute for a reference stack test method, which is
      the only way to determine compliance with mass emission requirements.
      To compile and present a list of demanded repairs and modifications is
      both unwise and wrong.  First of all, the agency takes on some of the
      liability for systems specifically demanded.  Furthermore, this  approach
      preempts their ligitimate options for running the plant.  The inspection
      simply results in a list of probable problems so that the inspector can
      determine if the corrective actions planned by the source have a reason-
      able chance of minimizing the problem in a timely manner.  If there is
      disagreement between the plant and the agency, legal action is the
      appropriate next step.

2-5.  There is no reason to stack test either unit based on the information
      presented. Answer c is correct.  The fact that two identical scrubbers
      on two supposedly identical asphalt plants are running at different
      pressure drops is not significant.   What would be significant is a
      decrease in the pressure drop for the specific unit.  It should  also be
      noted that supposedly identical plants can have remarkably different
      particle size distributions and therefore require different pressure
      drops.  In this case, slight movement of the asphalt injection pipe or
      a slight change in the mix temperature could create drastic differences
      in the particle size distributions from the two "identical" plants.

2-1.   During a routine plant boundry observation of the visible emissions  from
      a cupola wet scrubber system,  the inspector notices that the residual
      opacity has increased from the normal 5% to a level between 10 and 15%.
      The regulatory limit is 20%.  Is a more detailed inspection of the
      system necessary at this time?

          a.  Yes
          b.  No
          c.  Maybe

2-2.   Is it mandatory to conduct the inspection in a counterflow manner when
      performing a Baseline Inspection?

          a.  Yes
          b.  No
          c.  Sometimes

2-3.   During a level 3 inspection, the plant personnel invite the agency
      inspector to enter the cyclonic demister to observe a scaling problem
      which has developed recently.   What safety procedures are appropriate
      in this situation?
2-4.  Which of the following is achieved during a Baseline Inspection of
      a wet scrubber system?

      a.  An accurate and complete determination of compliance with the
          regulatory requirements
      b.  A general evaluation of control system performance
      c.  An assessment of the adequacy of the plant maintenance procedures
      d.  Compilation of a list of needed modifications and repairs
      e.  All of the above

2-5.  There are two Model SX-68-7 fixed throat venturi scrubbers serving two
      identical drum mix asphalt plants.  One of these is operating at a
      pressure drop of 19 inches W.C.  and an inlet gas temperature of 264 F.
      The other is operating at 14 inches W.C with an inlet gas temperture of
      270 F.  Does this data demonstrate the need to stack test either one or
      both of the scrubbers?

      a.  The one with the low pressure drop should be tested
      b.  Both should be tested
      c.  None of the above


2-6.  No, it is not significant at the 90% level.   Those who feel  it  is
      significant have probably used the wrong degrees of freedom  when using
      the t Tables.

2-7.  Comparison of conditions at one unit with data from others should  be
      done only as a last resort and only if it can be demonstrated that the
      process and control systems are very similar.  No statistical test is
      appropriate at this time.

2-8.  The correct answer is that the inspector should recommend that  the
      agency conduct a stack test based on whatever observations and  data
      could be obtained.  Concerning the plant's refusal to install ports,
      they could well have valid legal, technical  and/or safety reasons  for
      taking this position.  The agency can not demand measurement ports.
      It is equally inappropriate to wait until a  level three inspection can
      be done.  Again, the main purpose of inspections is to minimize air
      pollution and not to complete some arbitrary sequence of inspections.
      In other words, it is not necessary to complete a level 3 inspection
      before requesting a stack test or before discussing the potential
      problems with source management personnel.

2-9.  "Maybe" is the best answer.  The point of this question is that inspectors
      should not let themselves be boxed in by any statistical analyses.  Just
      because the changes are not significant at the 90% level does not  mean
      that they are not real.  In fact, excess emissions may have  already
      resulted.  The inspection should continue until all of the potentially
      relevant information regarding possible problems has been obtained.  The
      inspector should base his or her conclusion  on all the data  and observa-
      tions made and not just on the few items for which the statistical tests
      can be applied.   Subjective judgements also have a legitimate  role in
      reaching a position regarding the source's compliance status.

2-10  The correct answer is "b", the measurement should be forgotten.  In many
      cases, "all reasonable precautions" may not  be enough and the inspector
      can be overcome.  Now plant personnel may be tempted to place themselves
      at risk to remove the inspector from a location where he or  she should
      not have gone in the first place.  The other three answers listed  are
      also poor.  Guesses should never be used just because a measurement was
      not possible.  Sometimes no information is better than incorrect inform-
      ation.  Calling supervisory personnel for advice may sound good, but how
      can this individual fully appreciate the exact conditions facing the
      inspector?  It is also possible that during the call, the inspector will
      not completely describe the situation.  Requesting the plant personnel to
      enter an area that you are not willing to enter is not appropriate.  It
      is the inspector's job to perform the inspection and plant personnel (no
      matter how willing) should not have to take unreasonable risks  to  obtain
      necessary data.  Forget the measurement!


2-6.  During the previous three inspections the gas outlet temperature from
      the scrubber demister has been 126 F, 134 F, and 132 F.   Now the
      demister outlet temperature is 137 F.  Using the Student's t Test, is
      the increase significant at the 90% level?

2-7.  Data concerning three venturi scrubbers on grey iron cupolas has been
      published in a recent publication of the U.S. Environmental Protection
      Agency.  This indicates that these operate at pressure drops of 36, 42,
      and 43 inches W.C.  A similar cupola venturi scrubber being inspected
      has a pressure drop of 34 inches W.C.  What statistical test should be
      used to determine if there is a potential scrubber operating problem?

2-9.  During a level 2 inspection, the data and observations made by the
      inspector strongly indicate that the unit is out of compliance with
      the mass emission limits.  There are no presently available ports to
      confirm the on-site instrumentation and the plant management refuses
      to install these ports so that a more detailed inspection can be
      conducted in the near future.  What course of action should the
      inspector take?

          a.  Issue a Notice of Violation to the plant due to the
              lack of measurement ports.
          b.  Recommend that the agency request a stack test under the
              conditions representive of present performance.
          c.  Wait until a level 3 inspection can be completed, and then
              determine if enforcement action is necessary.
2-9.   The comparison of present scrubber conditions against the available
       baseline data indicates decreases in the static pressure drop and the
       liquor flow rate, but an increase in the nozzle header pressure.   The
       statistical evaluations indicate that none of the changes are signifi-
       cant at the 90% level.  Does this demonstrate that the unit is working

           a.  Yes
           b.  No
           c.  Maybe

2-10.  During a level 3 inspection, it is noticed that there is only limited
       ventilation around one measurement port  of a positive pressure unit.
       If the measurement is not obtained,  it may be impossible to fully
       evaluate the operating conditions.  What should the inspector do?

           a.  Using all possible precautions,  make the measurement.
           b.  Forget the measurement.
           c.  Make a reasonable estimate.
           d.  Call supervisory personnel back  at the office for advice.
           e.  Ask plant personnel to make  the  measurement.


                                  LECTURE 3

                        PLANT BOUNDRY LINE INSPECTIONS

                                       A Level 1 inspection of any wet
                                       scrubber system consists  simply  of  an
                                       evaluation of the scrubber plume and
   PLANT BOUNDRY LINE INSPECTIONS     any bypass stacks plumes.  ^ese in_
        1. Visible Emissions Observations          spections are normally conducted from
        2. Scrubber Reentrainment              the plant boundry .
        3. Odor Surveys
                                       The primary purpose is to determine if
                                       the unit is in compliance with visible
                                       emission regulations (particulate wet
                                       scrubbers) or with odor requirements
                                       (gaseous scrubbers).  More detailed
                                       Level 2 or Level 3 inspections are  con-
                                       ducted if symptoms of problems exist.

     This lecture briefly reviews important points concerning visible emission
and odor observations conducted from plant boundries.  This material goes  be-
yond simply determining that there is a problem.  A number of observations are
discussed which help determine the nature of the problem and which aid  in  the
preparations for the more detailed inspections.

Lecturer's Notes
     The plant boundry inspection can be quite beneficial if a modest amount
of time is invested by the inspector.  It will become obvious that this mat-
erial is not a rehash of lectures presented in the "smoke schools"  or  other
similar programs.


                                       Before leaving for  a Level  1  inspection
                                       of a wet scrubber system, the general
                                       weather conditions  should be  noted.
                                       Days similar to the one shown in this
                                       slide are obviously not conducive to
                                       visible emissions observations.   It  may
                                       be possible to conduct a meaningful
                                       odor survey.  However, even this is
                                       doubtful under the  conditions shown.

                                       In these circumstances, it  may be more
                                       appropriate to conduct a Level 2 inspec-
                                       tion of the wet scrubber system.  On
                                       the other hand there is always some
                                       paper work to catch up on.
                                       The initial task during a boundry line
                                       inspection is to make a presurvey of
                                       available observation sites.   The
                                       hypothetical plant layout shown  in this
                                       slide is used as an example of such a

                                       The purpose of the initial survey is  to
                                       determine the optimum location for a
                                       visible emission observation  for the
                                       stack or stacks of interest.   This goes
                                       beyond just concern over sun  angle and
                                       the direct of plume travel.  The in-
                                       spector should note any activity which
                                       could lead to multiple plumes along the
                                       line of sight.  This could be caused  by
                                       several stacks grouped closely together
                                       or due to fugitive emissons close to
                                       the stack of interest.  The reasons for
                                       selecting the observation point  should
                                       be briefly documented in the  inspection

     During the presurvey, the inspector should make both upwind and downwind
odor surveys.  This should be done before any visible emission observations,
since olefactory fatigue can reduce the sensitivity to odors after prolonged
periods of time.  The wind direction at times that odors are apparent should be
observed and noted.  Trees, flags, and plume travel directions usually  provide
sufficient indicators of wind direction.

If odors are detected, the  "character"
of the odor should be described  using
some accepted descriptive terms.   The
list provided in this slide can  be used
as is or can be modified for common
odors near the source.  In  any case, it
is helpful if the regulatory agency
inspector, the plant personnel and the
residents of community agree on  a  rea-
sonably concise set of terms.  This
will facilitate comparison  of the
records kept by everyone concerned.
     The time of day that any odors are  noticed should be carefully recorded
in the inspection notes.  The meteorological  conditions are also of interest.
This data will be helpful later  in tracking down the source(s) of odors and in
comparing the inspector's observations with those of the residents and plant
                                        One of the main questions faced in the
                                        visible emissions observations of wet
                                        scrubber systems is whether or not the
                                        observed plume is composed of real
                                        particulate or just condensed water
                                        droplets.  It is a legitimate question
                                        since water droplets scatter light as
                                        well as particles.

                                        There are several ways to distinguish
                                        the condensed water droplets (sometimes
                                        called the "steam" plume) from the true
                                        particulate matter in the plume.
                                        This photograph shows the plume from a
                                        series of spray scrubbers serving
                                        fiberglass forming lines.  The point at
                                        which the condensed water droplets re-
                                        vaporize is marked with arrow #1.  It
                                        is not difficult to identify this point
                                        of the plume and to see that there is
                                        considerable residual aerosol left in
                                        the plume after the water droplets
                                        cease to exist.

                                      The residual plume from this scrubber
                                      stack is apparent downwind from the
                                      point marked as arrow #1.   This has a
                                      distinct bluish white color (which is
                                      not readily apparent in the black and
                                      white reproduction).  This color is the
                                      result of the scattering of blue light
                                      by submicron aerosols.  Particles in
                                      this very small size range scatter blue
                                      light efficiently since the particle
                                      diameter is close to the wavelength of
                                      blue light.

                                      Any time that a bluish white color is
                                      noted, it is clear that significant
                                      quantities of particulate matter is

     The color of the plume  should be carefully described in the inspection
notes.  The location in  the  plume at which it becomes visible and the color
itself should be described.   The bluish white plumes often indicated inade-
quate collection of fine particulate (less than 2 microns), condensation of
vapors in the scrubber,  or regeneration of particles due to droplet evapor-
ation.  Brownish-white plumes often indicate poor collection of moderate and
large size particulate.   Combustion problems in fossil-fuel fired sources can
generate a black residual plume.
In addition,  inspectors should  observe
any steam vents in the general  vicinity
of the scrubber system or  adjacent
plants.  The time it takes for  these
to disperse should be noted.

There should be a noticeable  difference
between the steam plume dissipation and
the persistence of the scrubber plume.
There should also be a very distinctive
color difference.

In a sense, the use of known  steam  vent
plume descriptions provides an  "inter-
nal standard" regarding the behavior
of condensed water droplets under the
present meteorological conditions.

                                       For compliance determinations,  the
                                       visible emissions must be observed at
                                       the point of maximum opacity either
                                       before the water droplets begin to
                                       condense (see arrow #1) or at a point
                                       after they have re-vaporized (see arrow
                                       #2).   Since a baseline inspection in-
                                       cludes a reference method stack test,
                                       such  an observation should be made.

                                       However, for diagnostic purposes, the
                                       opacity should be observed directly
                                       above the stack whenever conditions
                                       permit (no water droplets).  At the
                                       stack there is a constant path length
                                       and the opacity readings can be com-
                                       pared with baseline levels.

     The path length through the residual plume varies with the weather
conditons.  Due to this factor it is difficult to compare present conditions
against baseline conditions.  Also, the residual plume is generally highly
diluted and is not a very sensitive indicator of scrubber performance.  There
could be substantally increased emissions without a noticeable increase in the
residual plume.
The elevation angle of the visible
emission observation is illustrated in
this slide.  Stack observations made
strictly for diagnostic purposes should
be corrected for the difference in the
path length between the actual line of
sight versus the actual plume diameter.

The equation for correcting the opacity
value is shown at the bottom of the
slide.  The angle of observation can be
calculated by knowing the stack height
(check file data) and by estimating the
distance to the stack.  The latter can
be accurately estimated from a plot plan
of the facility.  If the plot plan is
not available, a range finder can be
used to estimate distance accurately.

SLIDE 3-10                             During the visible emission observation,
                                       the presence of a condensing plume or
                                       reacting plume should be noted.   As
                                       shown in this slide,  the plume has a
                                       gradually increasing  opacity as  it
                                       travels downwind.

                                       This characteristic is opposite  to what
                                       is normally expected. It is caused by
                                       the formation of particulate from gases
                                       reacting in the plume.  In some  cases,
                                       it could be caused by the condensation
                                       of vapor phase material in the plume.
                                       However, the latter mechanism would
                                       probably be completed in the scrubber
                                       vessel and would not  be noticed  in the
                                       plume .

     The presence of a plume of increasing opacity is generally caused  by
material which passes through the scrubber system as a gas or a vapor.   This
may indicate inadquate collection efficiency for these materials, improper
conditioning of the gas stream before scrubber entry, or a change in the
process operation which results in the generation of pollutants which can not
be properly treated in this scrubber system.  In any case, a more detailed
inspection is necessary.
SLIDE 3-11                             The presence of a layer of mud at the
                                       stack discharge is an indication of
                                       iroplet reentrainment.  Another common
                                       symptom is a discolored area caused by
                                     ;  che drainage of scrubber liquor down
                                     :  the outside of the stack.  When these
                                       are noticed, there is often rainout of
                                       small liquor droplets in the general
                                       vicinity of the stack.

                                       If these small droplets are falling
                                     k  outside the plant boundry line, local
                                     *  residents may complain of damage to car
                                     ,  finishes, house paints and gardens.
                                       During the follow-up level 2 or level 3
                                       inspection, the operation of the scrub-
                                       ber demister should be checked in some
                                       detail.  Such problems are almost always
                                       correctable in a short amount of time.

      To determine if the reentrainment conditions still persist, a general
survey of the area outside the plant boundry should be made.  Obvious spotting
of car finishes usually provides a good indication of recent droplet carry-
over into neighborhood areas.  Spotting and discoloration of house finishes
are less reliable indicators since this could have occurred some time in the
past and the owners have just not had the opportunity to repaint.

SLIDE 3-12                             After completing the scrubber stack
                                       visible emission observation, a second
                                       trip around the facility should be
                                       made.  During this survey,  anything
                                       which may have interferred  with the
                                       stack observation should be noted.
                                       Possible situations include fugitive
                                       emissions from vehicle movement or from
                                       storage piles, and the start-up of an-
                                       other source along the line of site.
                                       The absence of any of these conditions
                                       confirms that only the scrubber stack
                                       was observed.

                                       Steam vent dissipation characteristics
                                       should also be described.  This helps to
                                       demonstrate that the material observed
                                       was in fact particulate and not steam.

     The second survey around the facility also provides a good time to select
the best observation point for checking bypass stack emissions and fugitive
emissions from the process equipment served by the scrubber.  Standard Method
9 procedures should be used in observing these possible emission sources.

     During the second survey, any odors should again be noted.  The intensity
and characteristics should be described so that the source(s) can  eventually
be identified.

3-1.   There is reason for concern.   Two 20% opacity plumes in series would
       result in an opacity of approximately 36%.   The observed value is in
       excess of this level.  Attendees who were incorrect probably assumed
       that opacities are additive.   A review of the basic principles of
       transmittance quickly indicates that opacity is an exponential

3-2.   The observations should be repeated for each stack.

3-3.   Answer c is the correct answer, assuming that the inspector is
       qualified to conduct level 2  or level 3 inspections of scrubber
       systems.  The key point is that there is a very significant excess
       emissions problem at the present time which can not be ignored.
       The unit is definitely out of compliance with the visible emissions

3-4    Yes, the 45 angle results in a true 20% opacity plume equivalent
       27% opacity.

3-5.   Answer b is correct.  In this case, it is probable that there is severe
       air infiltration into the unit or a similar problem which reduces the
       capture of pollutants at the  process area.


3-1.  During the second survey of the facility, it is discovered that a second
      scrubber system has started since the beginning of the visible emission
      observation.  The plume from this second system is in the same line of
      sight as the observed plume.  If the average opacity of the observation
      just completed was 39%, is there any reason to believe that either of the
      scrubber systems is out of compliance with a 20% opacity regulation?
      (Additional Notes: It lasted more than 6 minutes, and the observation
      point did not include steam from either scrubber).

3-2.  In the situation described in problem 3-1, a second source along the line
      of site starts operating at sometime during the observation.  This is not
      discovered until after the observation is concluded.  What should be done?

3-3.  During a properly conducted observation of a scrubber stack, the opacity
      pattern has regularly occurring spikes of 70 to 90% opacity lasting from
      30 seconds to 90 seconds.  These occur approximately every 4 minutes.
      The reminder of the time the opacity is in the range of 10 to 15% opacity.
      The baseline opacity data for this facility indicates an average of 10 to
      15% without any spiking.  The visible emissions limit is 20%.  What should
      be done?

           a.  Nothing, there has been no shift in the baseline opacity levels
               and the unit is in compliance with the 20% regulation.

           b.  The next regularly scheduled inspection of this facility should
               be either a Level 2 or Level 3 inspection rather than a Level 1

           c.  A Level 2 or Level 3 inspection should be conducted immediately
               to determine the cause of the spiking and to determine the
               corrective actions that the source intends to take.

3-4.  During a presurvey of a plant, the best observation point is a small hill
      overlooking the scrubber stack.  The angle down through the plume is 45.
      If the observed opacity is 27%, is the unit in compliance with a 20%
      opacity standard?

3-5.  The residual plume from a scrubber system has an average opacity of less
      than 5%.  There are fugitive emissions from the roof monitor above the
      process equipment served by the scrubber.  However, these fugitive
      emissions are not noticeable at the plant boundry line.  What should be

           a.  Nothing

           b.  A Level 2 or Level 3 inspection should be performed as soon as

           c.  The observations should be repeated during some period when
               there are no condensed water droplets anywhere in the plume.


                                  LECTURE 4


           Static Pressures
           Flow Rates
           Oxygen Concentrations

           Flow Rates
                                       This lecture concerns  data.   The para-
                                       meters which are important  in most wet
                                       scrubber system inspections are listed
                                       in the adjacent slide.

                                       In level 2  inspections it is important
                                       to confirm  that the  permanently mounted
                                       on-site instruments  are working proper-
                                       ly.  Some of the common symptoms of
                                       gauge malfunction are  discussed.  While
                                       it will not be  possible to  make a com-
                                       prehensive  evaluation  of instrument
                                       performance, these procedures will at
                                       least help  identify  gauges  suffering
                                       from the most common failures.

     In level 3 and 4 inspections, both the on-site gauges  and some portable
instruments may be used.  Procedures for using the portable instrumets to
evaluate wet scrubber systems are discussed in this lecture.   They include
basic calibration checks and ways to avoid measurement errors.  Safety consid-
erations are an important part of this material.

     Measurement ports are necessary for the portable  instruments.   The proper
sizes and locations of measurement ports on common types of wet scrubbers are
discussed in this lecture.



   1. Ports should be >V4" and <2" diameter.
   2. There should be safe access to the port
     to facilitate rod out prior to the measure-
   3. Never  use ports connected to D/P
   4. Never have measurement ports installed
     while the system is running.
                                   Before beginning  the  discussions of
                                   each type of  instrument,  basic common
                                   sense facts deserve some  attention.

                                   There are a large number  of on-site
                                   gauges and measurement ports located in
                                   strange and obscure locations around
                                   wet scrubber  systems.  HEROIC MEASURES
                                   SHOULD NOT BE TAKEN TO REACH THESE
                                   IMPROPERLY LOCATED GAUGES OR PORTS.
                                   This means that the inspection will not
                                   be as thorough as it  might otherwise be,
                                   However, this is  preferable to an
     Only the data necessary  to  confirm compliance or to determine the general
types of problems which exist should be obtained.   Extensive time should not
be devoted to the inspection  just  so that the inspection is "complete" or so
some inspection report form can  be filled out.  The art of field inspection is
determining which measurements are relevant for the particular system at the
specific time.  Anything  beyond  these measurements is a waste of the inspect-
or's time and an inconvenience to  source personnel who must accompany the

Lecturer's Notes
     There is a tendency  of some inspectors to try to become the "consultant"
of the source.  This is not an appropriate use of time.  The job of the in-
spector is only to determine  if  there is a problem and if the source has made a
reasonable response to correct and minimize this condition in the near future.
It is the job of the plant personnel to make whatever supplemental measure-
ments and observations necessary to evaluate the exact nature of the problem
and to recommend the design and/or operational changes.
SLIDE 4-3.
        1. Manometers
        2. Diaphragm Gauges
                                        There are two main options available
                                        for the measurement of static  pressure:
                                            manometers, (2) diaphragm  gauges.
                                        The manometer  wnich can be  filled  with
                                         . _,     . ,   '        ,            ,
                                        either oil or water, does not  need  to
                                        be calibrated.  It is a relatively
                                        simple instrument and is not very vul-
                                        nerable to malfunctions.  Low  range
                                        manometers can be mounted on the
                                        scrubber vessel permanently  and slack
                                        tube manometers can be used  as a
                                        portable instrument.

    The diaphragm  gauge can also be used as a permanently mounted unit or  as a
portable  instrument.   These are made in a number of ranges from 0 to  2 inches
W.C. to as high  as 0  to 150 inches.  At the higher static pressures ( >36
inches W.C.)  these diaphragm gauges are the only practical approach since  the
manometers would be too long.

 SLIDE 4-4
                                        A manometer  is  simply  a  U-shaped  tube
                                        filled  with  a fluid.   When  unequal
                                        pressures  exist at  the tops of  the  two
                                        ends, the  fluid moves  to equalize the
                                        pressure difference.

                                        The  difference  in the  heights of  fluid
                                        in the  two sides is a  measure of  the
                                        pressure difference.   In the sketch
                                        shown here there is a  difference of 20
                                        inches. Therefore,  the pressure is  20
                                        inches  of  water.

                                        It should  be noted  that  the specific
                                        gravity of the  fluid is  important.  For
                                        example, if mercury was  placed in the
                                        manometer  shown to  the left, it would
                                        show a  difference of only 1.5 inches
                                        since it has a  specific  gravity of
                                        13.6.  Most scales  used  on  manometers
                                        assume  a specific gravity of 1 (for
                                       The diaphragm gauge is shown in this
                                       photograph. Near the back of the instru-
                                       ment are two chambers separated by a
                                       flexible diaphragm.  This moves when
                                       unequal pressures exist in the two
                                       chambers.  The degree of movement is
                                       proportional to the static pressure

                                       Diaphragm movement is sensed by a helic
                                       coil.  The move of this coil is trans-
                                       mitted mechanically to the indicator
                                       needle on the face plate.  The unit
                                       does not need electrical power
     There is no gas flow through the two chambers.   These actually are like
dead end streets to the lines coming from the scrubber to the instrument.
This feature minimizes the accumulation of material  in the chambers and the
chemical attack of the diaphragm.  As with any resilent synthetic material,
the diaphragm does have temperature sensitivities.   Due to these limits,  the
gauge is subject to problems when the diaphragm temperature is lower than  20
F and higher than 140 F.

                                       A small  water  filled manometer  is  shown
                                       on the downstream side  of a  rod  deck
                                       gas-atomized scrubber.  While this is  a
                                       relatively  cold  location, the gas  temp-
                                       erature  going  through this part of the
                                       scrubber vessel  is still 125 F.   This
                                       is a very typical temperature for  ex-
                                       haust streams  from wet  scrubbers.

                                       Since the manometer is  in direct con-
                                       tact with the  wall, the manometer  fluid
                                       is constantly  heated.   The vaporization
                                       will gradually reduce the amount of
                                       fluid in the manometer. If  the fluid
                                       level is so low that a  measurement can
                                       not be obtained, plant  personnel can be
                                       asked to refill  the manometer during
                                       the inspection.

     It should be noted that there is nothing to stop fluid vaporization  from
a manometer regardless of how it is connected.   When  it is being used  to
measure static pressure, one side is open to the atmosphere.   When  it  is  being
used to measure static pressure drop, both sides are  open to areas  with moving
gas streams.
                                       Pluggage of a portion of the manometer
                                       can occur due to the gradual diffusion
                                       of particulate matter down one of the
                                       lines.  The accumulated material blocks
                                       the movement of the fluid and can lead
                                       to erroneous readings.  Occassionally
                                       there may be a need to remove the mano-
                                       meter and clean it out.

                                       These deposits are easy to spot.  Plant
                                       personnel should be able to correct
                                       this during the inspection.

 SLIDE 4-8
                                        A .T.cre common site of pluggage is at
                                        the port itself.  Solids or sludge can
                                        quickly accumulate in the fitting used
                                        to connect the manometer (or diaphragm
                                        gauge) lines to the port.  This is more
                                        difficult to identify.

                                        On negative pressure units, the lines
                                        can be disconnected at the instrument
                                        (by plant personnel) and a very small
                                        scrap of paper placed against the line
                                        opening.  If the line is open the scrap
                                        will be held firmly on the line.   This
                                        works even when the static pressure is
                                        as low as -1 inch W.C.  On positive
                                        pressure lines, it should be possible
                                        to feel slight flow out of the dis-
                                        connected line onto the back of the
                                        hand.   This is not quite as sensitive
                                        as the negative pressure test.

      Some people attempt to feel the slight gas flows by placing the line
 against  their face.   While this may  be more sensitive for low positive pres-
 sure conditions, it  places the  potentially  toxic gas stream near the nose.
 SLIDE 4-9
                                       A manometer or diaphragm gauge used for
                                       static  pressure measurements should in-
                                       dicate  zero when the single line is
                                       disconnected.  This is indicated in the
                                       slide to the left.

                                       If a manometer fails to indicate zero
                                       there is probably an obstruction in one
                                       or both of the lines.  Another possible
                                       explanation is freezing of the fluid.

                                       An attempt should be made to re-zero
                                       diaphragm gauges which do not return to
                                       zero when the static pressure line is
                                       disconnected.  If it can not be zeroed
                                       it is definitely bad.   Even if it can
                                       be zeroed there still remains the
                                       chance that it is defective.

      A small section of 1/4" O.D. tubing can be connected to the instrument
(.with the plant representative's approval)  and the response of the diaphragm
checked by applying slight positive and negative pressures.  A squeeze bulb
with two check valves is useful for this purpose (one of these is present with
the oxygen analyzer to be discussed later).  If the gauge responds in the
proper directions, it probably is operational.

 SLIDE  4-10
                                       "luggage of the port and/or the line
                                       leading to the static pressure gauges
                                       can be expected whenever a situation as
                                       shown here exists.  These are 1/4" O.D.
                                       copper tubes leading from a number of
                                       ports down to static pressure gauges in
                                       the control room.  It doesn't take much
                                       solids to close off a tube this small.

                                       The lines should be as short as possi-
                                       ble and as large as possible.  It is
                                       not unusual to find plants which have
                                       ripped out lines like this and put in
                                       1/2" to 2" lines in order to minimize
                                       the pluggage problem,
SLIDE 4-11
                                       Another  feature which is prone to
                                       pluggage is  the use of an elbow fitting
                                       close  to the port.  This is an ideal
                                       site for solids build-up.  As a com-
                                       plicating matter, the small pipe ahead
                                       of  the elbow fitting is horizontal and
                                       fluid may not flow out easily.

SLIDE 4-i;
                                       One way to minimize pluggage problems
                                       is to use a differential pressure
                                       transmitter close to the port.   This
                                       converts the static pressure to an
                                       electrical value which is then
                                       displayed on a control room gauge.

                                       Note that the pipe coming from  the
                                       scrubber wall is a 1" pipe.  This will
                                       plug less frequently than 1/4"  ports
                                       which are commonly used.
SLIDE 4-13

                                       Liaphragm gauges which are attached
                                       iirectly to the scrubber vessel wall
                                       _^r. be adversely affected by the
                                       internal gas temperatures.  The exit
                                       gas temperatures of the scrubber are
                                       often quite close to the maximum
                                       allowable temperature of the diaphragm
                                       between the two chambers.  Due to the
                                       ease of heat conduct between the wall
                                       of the scrubber and the gauge body, the
                                       diaphragm could exceed recommended
                                       temperatures.  It should be remembered
                                       "hat the diaphragm is in the back of
                                       the instrument and therefore is quite
                                       -lose to the scrubber wall.

     One way to minimize this problem is  to mount the gauge on a small
stand-off so that there is an inch of more of clearance between the back of
the gauge and the scrubber wall.   This reduces heat transfer by direct con-
duction to relatively low rates.

 SLIDE 4-14
                                        On-site  gauges which  are  partially  or
                                        completely  full  of  liquid are  probably
                                        not working properly.   It is easy for
                                        this  liquid to accumulate even though
                                        there is no gas  flow  through the in-
                                        strument.   Diffusion  of moisture (and
                                        some  corrosive materials) can  occur
                                        down  one or both of the connecting
                                        lines.  Condensation  can  occur in the
                                        gauge itself or  in  the connecting
                                        tubing.  The orientation  of many gauges
                                        ensures that any condensation  in the
                                        tubing drains down  to the gauge itself.
SLIDE 4-15


Prior to accepting data from the on-
site gauges, the condition of the
connecting lines should be briefly

Tubing composed of polypropylene and
polyethylene can be common brittle and
break.  This means that the part of the
gauge is actually sensing atmospheric
pressure rather than the scrubber sys-
tem static pressure.  The error will
not always be apparent from the gauge
     Tubing composed of a soft plastic (e.g. Tygon) can be inadvertently
crimped.  If it drapes over a hot surface part of the tube may have collasped.

     If problems with the guage connecting lines are chronic or severe, it may
be advisable to replace these with copper tubing.  This is less susceptible to
crimping and can withstand surface temperatures up to 800 F.  It is the most
rigorous material for small diameter gauge connection lines.

SLIDE 4-16

                                       During level 3  inspections  of  wet
                                       scrubber systems,  portable  instruments
                                       should be used  when there are  questions
                                       regarding the performance of the on-
                                       site gauges. The  portable  instruments
                                       for measuring static pressure  are  the
                                       same as those used for  on-site gauges.

                                       This slide shows a slack tube  manomet-
                                       er.  It rolls up to facilitate moving
                                       from place to place. Magnets  at the
                                       top and bottom  (see arrows  #1  and  #2)
                                       are used to hang the instrument.   Screw
                                       in caps (see arrows #3  and  #4) seal the
                                       instrument when not in  use.

     It is obviously important to remember to close the end caps before
rolling up the unit and moving on.  The fluid will run all over the careless
inspector.  The manometer should not be used at locations which exceed the
limits of the unit.  For example connecting a 36" slack tube to a  port where
the static pressure is -50 inches will result in the quick loss of some of the
fluid into the duct.
SLIDE 4-17                             Both the standard size and minature
                                       size diaphragm gauges are shown in this
                                       photograph. The small sized unit fits
                                       in a pocket and is therefore easy to
                                       carry around.   It has an accuracy of
                                       plus or minus  5% while the standard
                                       sized unit is  plus or minus 3% accuracy.

                                       Both instruments are relatively insen-
                                       sitive to vibration and shock.  If the
                                       static pressures measured are above or
                                       below the range of the instrument, it
                                       simply pegs.  This does not hurt the
                                       unit or throw  it out of calibration.

     Before use, the instrument is zeroed using the small set screws at the
front of each gauge.  When used to measure static pressure one of the taps is
connected to the wet scrubber system and the other is left open to the atmos-
phere.  When used to measure static pressure drop directly, both taps are
connected to ports on the scrubber system.

     They are obviously subject to the same temperature limitations as gauges
mounted permanently on control systems.  When used as portable instruments,
however, it is unlikely that they will be exposed to  the extreme temperatures
for more than several minutes at a time before being  put back into a protected
area.  There is also little time available for diffusion of corrosive gases
down into the chambers.  In other words, these work better when used as
portable instruments than when used into full time service as permanently
mounted gauges.


SLIDE 4-18                             Prior to starting the field work,  the
                                       diaphragm gauges should be calibrated
                                       against a manometer.   The apparatus for
                                       doing this calibration is simple as
                                       illustrated in the adjacent sketch.

                                       Both the diaphragm gauge and a mano-
                                       meter are connected to a tee fitting,
                                       which in turn leads to some source of
                                       positive and negative pressure.  The
                                       squeeze bulb with check valves is a
                                       convenient source of positive or neg-
                                       ative pressure since it is possible to
                                       hold the pressure for a few moments.

     The squeeze bulb supplied with the oxygen/carbon dioxide analyzer can be
used for this service.  This has a range of -40 inches W.C.  to + 40 inches
W.C. which is adequate for most situations.  The complete calibration takes
about 5 minutes as long as the slack tube manometer can be left set up in some
out of the way location.

     One of the basic requirements involved in the use of any portable instru-
ment is that the unit should be checked out and calibrated before leaving
the office for field work.
SLIDE 4-19
                                       The diaphragm gauge calibration curve
         ^                             should look like the graph shown here.
                                       The data should fall close to a 45
                                       line.  If the unit fails to remain
                                       within the error band or if the plotted
                                       data is non-linear, then the gauge
                                       should be repaired or replaced.

                                       The calibration data should be main-
                                       tained in a convenient file at the
                          "i            office and should not be taken to the
                                       field.  This data can be used later to
                                       demonstrate that the measurements taken
                                       in the field were accurate.

     The same procedure discussed in the last two slides can be used to
calibrate a permanently mounted diaphragm gauge at the plant being inspected.
The connecting tubes are simply disconnected, and a slack tube manometer used
as the primary standard.  It is not unusual to find that the various insults
suffered by the permanently mounted gauge has thrown it well out of

SLIDE 4-20            jr                One of the wet scrubber  operating para-
                                       meters of most interest  is the static
                                       pressure drop.  It  is  usually not
                                       advisable to try to measure this dir-
                                       ectly even though this can be done by
                                       connecting the "hi" and  "low" ports to
                                       different parts of  the system as shown
                                       in the top portion  of  this slide.

                                       With this approach, a  large quantity of
                                       flexible tubing is  required and this
                                       can become crimped  during the measure-
                                       ment.  There is also a chance that one
                                       of the ports will plug during the

     It is preferable to make the static pressure measurements  one at a time.
The pressure drop is then calculated by subtracting one value from the other.
This approach is easier and less subject to measurement error.   Less tubing is
also required since a maximum of 3 feet is normally required  for static pres-
sure measurements.
SLIDE 4-21
For locations which have high negative
static pressures, it is very important
to completely seal the port to prevent
aspiration effect error.  With the
condition shown in this slide, the
localized static pressure at the tip of
the copper probe can be more negative
than the true negative static pres-
sure.  This is due to the additional
suction effect caused by the high
velocity ambient air rushing in around
the probe.  The threshold of this
effect is around -10 inches W.C. and it
becomes progressively more significant
as the pressures decrease (at -50 inches
it is worse than at -10 inches W.C.).
      For example, it is possible to "measure" a static pressure of -25 inches
W.C. when the true static pressure is -20 inches W.C.  At higher negative
static pressures, it is possible to "measure" a static pressure of -150 inches
W.C. when the true static pressure is -100 inches W.C.  Sealing the port
tightly eliminates the problem immediately.  Movement of the probe well into
the gas stream and away from the area of the infiltration also totally elimi-
nates the problem.

Lecturer's Notes
     In practically every measurement discussed in the workshop, it will be
possible to enhance measurement accuracy by moving the probe into the gas
stream and away from the duct wall.
     This problem is not unique to portable gauges.  A permanently mounted
gauge with a crack in the weld of the port will suffer the same effect.

      1. Hand
      2. Glove or Fabric Piece
      3. Rubber Stopper
      4. Sanding Disk with Rubber Stopper
SLIDE 4-22
                                       Options for sealing of ports are  listed
                                       in this slide.  The hand is never a
                                       good choice since a tight  seal  is
                                       almost impossible to achieve.   Also,
                                       the metal surfaces are usually  hot and
                                       may be covered with deposits of toxic

                                       A glove is also not appropriate.   At
                                       very high static pressures there  can be
                                       5 to 10 pound of force across the small
                                       open areas of ports.  The  unwary  person
                                       will lose the glove to the equipment.
                                       Inside, the glove will not be benefic-
                                       ial for the system, regardless  of where
                                       it comes to rest.

     The rubber stopper or the sanding disk with rubber stopper are more use-
ful since it is possible to get a good seal.  The rubber stoppers main func-
tion is to maintain a tight hold on the probe so it is not lost.  These  two
approaches are useful as long as the port surface temperature is  not too high.
SLIDE 4-23
                    SANDING DISK

                     COPPER TUBE
                      RUBBER STOPPER
                                       The sanding disk with  rubber stopper
                                       approach  is illustrated  here.  The
                                       sanding disk must  be a least 1" larger
                                       in diameter than the outer diameter of
                                       the port.  It  is the sanding disk which
                                       provides  the main  seal against air in-
                                       filtration.  The rubber  stopper behind
                                       the sanding disk is drilled slightly
                                       small  so  that  the  1/4" copper tube is
                                       firmly held.   This apparatus is extreme-
                                       ly cheap  to assemble and is easy to use.
         -DUCT WALL

SLIDE 4-25
 SLIDE 4-24                             Another problem that can occur during
                                       static pressure measurement does not
                                       affect the accuracy but instead in-
                                       volves a potential safety hazard.  As
                                       illustrated in this slide, any probe in
                                       a rapidly moving gas stream will have
                                       particles frequently colliding with the
                                       probe surface.  The rubbing action will
                                       cause static electrical charges to
                                       accumulate on the probe surface.  It is
                                       conceivable in certain situations that
                                       the charges could reach a high enough
                                       voltage to cause an arc from the probe
                                       to the grounded duct wall.  This would
                                       initiate a primary explosion in the
                                       duct with the possibility for more vio-
                                       lent secondary explosions as the duct
                                       ruptures.  The factors which favor this
                                       condition include: (1) an electrically
                                       isolated probe, (2) low relative
                                       humidity in the duct, and (3) high
                                       particulate mass concentration.

                                       One way to avoid any static charge
                                       build-up on the probe is to use a
                                       grounding/bonding cable similar to that
                                       shown in this slide.  On one end is a
                                       standard household type clamp which can
                                       be firmly attached to the metallic probe,
                                       The other end is a jaw type clamp which
                                       attaches to any grounded item outside of
                                       the port.  Since the cable does not have
                                       any insulation, it is easy to confirm
                                       that there are no breaks.

                                       The grounding/bonding cable should be
                                       visually inspected prior to use and all
                                       connections should be made before the
                                       probe is inserted into the gas stream.

     The grounding/bonding cable allows the continual dissipation of the
electrical charges.  The duct wall and the probe remain at the same voltage
potential.  Therefore an arc can not occur.

     If there is any question at all concerning the need for a grounding/bond-
ing cabe, it should be used.  Obviously the clamp should not be attached to
any electrical line or conduit in the vicinity of the port.

     One of the reasons this subject is emphasized in this workshop is that
wet scrubbers are often used to remove pollutants from gas streams which are
potentially explosive.  All other particulate control systems have components
which could detonate the gases components,  thus leaving wet scrubbers as the
only alternative.  It is particularly important at the inlet of scrubbers to
avoid any possibility of static arcs.  Downstream there usually (but not
always) is enough moisture to dissipate the static without the cable.

SLIDE 4-26
                                       Static  pressure data is an important
                                       part  of all  level  2 and level 3 wet
                                       scrubber system inspections.
 STATIC PRESSURE MEASUREMENTS     In  the  level 2 inspections, the on-site
                                       guages  should be checked  to the extent
                                       possible before the data  is recorded in
                                       the inspection notes.  With the plant
                                       management's permission,  the lines to
                                       gauge should be disconnected to check
                                       the meter response and to determine if
                                       the lines are plugged.

     Obvious problems should also be noted,  such as freezing of  manometer
fluid, use of improper fluid for  manometer scale, excessive temperatures on
diaphragm gauges,  and water in diaphragm gauges.

     The portable  gauges used in  level 3 inspections should be checked and
calibrated before  use.  Air infiltration around the port  should  be prevented
during the measurement by a seal  which can not be sucked  into the duct.  The
probes should be grounded to prevent static  accumulation.
SLIDE 4-27
                                       The four types  of  instruments  that  can
                                       be used  to measure gas  stream  and
            TECHNIQUES                liquid stream temperatures  are listed
              FOR THE                  ^n this  slide.   Of these, the  mercury
   MEASUREMENT OF TEMPERATURE       thermometer is  definitely not  desirable
       1. Mercury Thermometer               since it is easily broken.
       2. Dial-Type Thermometer
       3. Thermistor                       The thermister  is  often readily avail-
                                       able from the control agency lab. This
                                       however, is limited to  a maximum temp-
                                       erature  of approximately 150 F.  It is
                                       useful primarily for the measurement of
                                       liquid temperatures and possibly the
                                       measurement of  pipe skin temperatures.

     The dial type thermometer is attractive to control agencies since it  is
relatively inexpensive.  The limited reach of this instrument  can  lead to
measurement errors.

   The most versatile instrument is the thermocouple.   It operates over the
widest temperature range of any temperature monitor and the probes are easier
to use.  The main disadvantage is the relatively high  cost. Like  all battery
powered instruments,  the thermocouple should not be taken into potentially
hazardous locations.

SLIDE 4-28
                      DIAL TYPE
                DUCT WALL
                                       One disadvantage of the dial-type
                                       thermometers is the very limited reach
                                       possible with the 9 to 12 inch stems.
                                       As shown in the adjacent sketch, the
                                       temperatures of the gas streams close to
                                       the wall may be lower than those out in
                                       the main part of the duct.

                                       In some common ports, the pipe nipple
                                       extends out from the duct wall 4 to 8
                                       inches.  With these ports, the sensor
                                       part of the instrument may only barely
                                       be in the gas stream at all.

     It is not wise to attempt to use the dial-type thermometers in any duct
in which there is a strong gas temperature gradiant.  This situation should be
suspected whenever the port is close to flow disturbances such as elbows,
and access hatches.

     This same problem can affect the accuracy of thermocouple mounted in
permanent thermowells.  If they do not extend far enough into the gas stream,
they may also indicate lower than actual gas temperatures.  There is no way
to tell from the outside of the thermowell just how far it does extend inward.
However, the plant instrumentation group should be able to supply this inform-
ation and explain the rationale for the specific thermowell length and
SLIDE 4-29
                                       If condensed water (or any other fluid)
                                       is visible in the dial-type thermometer
                                       the gauge is no longer working.  It is
                                       supposed to be a totally enclosed gauge,
                                       so the presence of liquids demonstrates
                                       that part of the stem has corroded or
                                       eroded away.

                                        This is a photograph showing the
                                        connection heads for two thermocouples.
                                        Just by locating these heads it is
                                        possible to determine the locations of
                                        any  thermocouples along the gas stream

                                        There  is very little that happens to
                                        these  instruments that does not com-
                                        pletely shut them down.  If the  unit
                                        is providing a read-out at all, it is
                                        probably working adequately.  Of,
                                        course it is always prudent to check
                                        if the indicated temperature is logical,

     All thermocouple data must be obtained in the control room for the
process or wet scrubber system.  One of the most common errors in recording
this data is misassigned location I.D.s on  the strip chart recorder or plant
data acquistion system.  The best way to screen out these inadvertent errors
is to check the changes in temperature  as the gas stream passes through the
wet scrubber system.  Usually it gets colder  until it reaches a gas reheater
(if used in the system).  This is one of the  reasons that it is helpful to
have a flowchart handy so the locations of  the thermocouples can be clearly
SLIDE 4-31
   1. Calibrate probe and meter against a NBS
     traceable thermocouple.
   2. Check ice point and boiling point values
     prior to each day.
                                       When  conducting level 3 inspections,
                                       there is  often  the  need to supplement
                                       the available temperature data supplied
                                       by on-site monitors.   The instruments
                                       commonly  used for this purpose include
                                       the dial-type thermometer and the

                                       Before starting any field work each
                                       day,  both should be checked in boiling
                                       water and in finely crushed ice.   This
                                       two point check is  not a full calibra-
                                       tion  but  it does increase confidence in
                                       the performance of  either instrument.

     On a regular basis, the units should be calibrated at a certified lab.
In the case of the thermocouple, it should be compared against an NBS
traceable probe and instrument.  The cost for these semi-annual or annual
calibrations is nominal.

SLIDE 4-32

      1. Unrepresentative Measurement
      2. Cooling of the Probe Due to Air
        Infiltration Through the Port
      3. Impaction of Water Droplets
                                        This  list summarizes the three most
                                        common errors in the measurement of gas
                                        stream temperatures with portable

                                        To  avoid the problems of unrepresent-
                                        ative measurement locations, the port
                                        location should be carefully chosen.
                                        Again ports downstream of large access
                                        hatches, or in bends in the duct work
                                        are not the optimal locations.  Also,
                                        it  is important to measure the gas
                                        streams in the main flow of the duct
                                        and not just at the wall.

     The problem with air infiltration  should be solved with the same basic
approach discussed with respect  to  the  aspiration error in static pressure
measurements.  The port should be completely sealed using a rubber stopper or
a sanding disk and rubber stopper.
SLIDE 4-33
                                       Two ways to  position the thermocouple
                                       probe at the desired location well
                                       inside a duct are shown in the photo-
                                       graph to the left.   The one on the left
                                       of the slide is  the tip of a S-Type
                                       pitot tube.   A flexible thermocouple
                                       probe without a  protective sheath has
                                       been attached to the pitot tube.  The
                                       thermocouple bead is approximately 1"
                                       behind the end of the pitot.

                                       The equipment to the right of the slide
                                       is a standard 1/4"  O.D. copper tube
                                       through the  sanding disk seal.  The
                                       flexible thermocouple probe has been
                                       threaded through the copper tube and
                                       terminates at the end of the copper

 SLID?  4-34
                                       Erratic temperature measurements can
                                       occur immediately downstream from wet
                                       scrubbers and evaporative coolers.
                                       Liquor droplets in the gas stream
                                       impact on the temperature probe and
                                       briefly reduce the temperature from the
                                       dry bulb to the wet bulb levels.  The
                                       observed temperature is characterized
                                       by sudden drops in the values followed
                                       by slow climbs back to steady state
                                       values.  This, of course, is only a
                                       problem when the gas stream is not
                                       fully saturated and there is a differ-
                                       ence between the wet bulb and dry bulb

     In some cases, it is possible to shield the thermocouple probe so that
 there  is no impaction on the probe itself.  Also, a sample can be extracted
 through a trap to remove the droplets prior to the monitor.  The latter is
 done at the risk of cooling the gas stream as it passes through the trap and
 sample delivery lines.  The preferred approach is to find another location
 where  the dry bulb temperature can be measured accurately.

     When evaluating gas-liquor maldistribution, it is sometimes useful to use
 ports where some liquor droplet entrainment remains.   Gas streams from wet
 scrubbers should usually be saturated and the presence of this measurement
 problem is a sign of poor distribution.  Wet bulb measurements can also be
 made by wetting a sleeve around the thermocouple probe.
SLIDE 4-35
                                       The liquor temperatures can be measured
                                       by obtaining a small sample and then
                                       using a dial-type thermometer, a therm-
                                       ister, or a thermocouple.  The probe
                                       should be washed and dried after each
                                       measurement to remove corrosive materials,

                                       Frequently, it is necessary to estimate
                                       the liquor temperatures at locations
                                       where it is inconvenient to obtain a
                                       sample.  One example is the various
                                       headers leading to nozzles on the inlet
                                       of a venturi scrubber.   For these sit-
                                       uations, the pipe skin  temperature can
                                       be measured using either a thermocouple
                                       or a thermister.

     The pipe skin temperature is always slightly lower than the actual liquor
temperatures. However, it is proportional to the liquor temperatures.  One of
the advantages of the baseline approach is that a shift in the pipe skin
temperatures becomes a meaningful parameter.  It is not absolutely necessary
to know the actual values.

 SLIDE 4-36
                                       When making temperature measurements
                                       one of the main requirements is to
                                       ensure that a representative location
                                       is chosen.  This applies to both on-
             SUMMARY                site instruments and to portable units.
GAS TEMPERATURE MEASUREMENT   .,,.,      , ,,  .   .     .-,..
                                       With the portable instruments it is
                                       possible to locate the probe well
                                       inside the duct or even to perform a
                                       complete traverse.  This is useful when
                                       a strong temperature gradient exists
                                       across the duct.

                                       Before using any portable instruments,
                                       a two point (zero and 100 C) calibration
                                       should be made.  The units,should be sent
                                       out for calibration every six to twelve

     For liquid stream lines, the temperature of a small sample is measured.
 In locations where it is impractical to get a sample, the pipe skin tempera-
 ture should be measured.
 SLIDE 4-37
                                       The oxygen concentration of the inlet
                                       gas stream is useful for evaluating the
                                       combustion conditions at the boiler and
     OXYGEN MEASUREMENT INSTRUMENTS      for evaluating air infiltration up-
                                       stream of the wet scrubber system.
             1. ORSAT Analyzer
             3. S^SSU             * instruments generally used for this
                                       purpose are listed in the adjacent
                                       slide.  All permanently mounted units
                                       are electroconductivity sensors.  These
                                       extract a small gas sample continuously.
                                       They are normally installed directly
                                       behind the boiler and next to any
                                       continuous monitors for sulfur dioxide.

     The ORSAT is a manual, wet chemical method which simultaneously yields
 data concerning oxygen, carbon dioxide and carbon monoxide.  The ORSAT
 apparatus is relatively inexpensive.  However, the measurement is time consum-
 ing.  The gas absorption instruments utilize the same techniques as the ORSAT.
 The main difference is that each unit will only measure one compound.  Also,
 there is no  gas absorption unit for carbon monoxide.  The gas absorption units
 are easy to  carry around during an inspection.

SLIDE 4-38

     1. Unrepresentative Measurement Location
     2. Air Infiltration into Sample Line
     3. Defective Electroconductivity Cell
     4. Pump Failure
                                       The most frequent problems with  the
                                       electroconductivity instruments  are
                                       listed in this slide.

                                       Unrepresentative locations can be
                                       avoided by pulling the sample from well
                                       inside the gas stream.  It should not
                                       be extracted close to the duct wall.

                                       All of the other problems can be identi-
                                       fied by the attempted calibration.   All
                                       permanently mounted units should have  a
                                       calibration cylinder having  a known
                                       oxygen concentration close to the con-
                                       centration expected in the duct.

     The calibration gas should be connected to the sample line through a
three-way valve which shuts off the duct line when the cal gas line is  open.
The cal gas should enter the line very close to the duct wall so that leaks
along the sample line to the instrument can be found.  Air infiltration along
the line leads to higher than expected oxygen concentrations while  electrocon-
ductivity cell problems usually gives low readings.
SLIDE 4-39

                                       The ORSAT analyzer  is  shown here.   It
                                       consists of  three liquid  reserviors
                                       and a sample reservior.   A  gas sample
                                       is drawn into  the instruments and
                                       sequentially mixed  with all three
                                       liquids, each  of which removes one of
                                       the gas sample components.   The oxygen,
                                       carbon dioxide and  carbon monoxide
                                       concentrations are  determined by the
                                       height of a  column  of  liquid displaced
                                       by the gas sample.   This  decreases as
                                       each component is removed.   The unit
                                       has an accuracy of  plus or  minus 1/2%
                                       for each gas compound.

     The gas sample is drawn from the measurement port using  a pump and a
Mylar or Tedlar sample bag.  A portion of this sample is then pumped into the
ORSAT instrument.  Care is necessary to avoid dilution of  the sample during
pumping from the duct, during storage in the bag, and during  pumping to the
instrument.  This will obviously lead to high oxygen  levels and  lower than
actual carbon dioxide and carbon monoxide values.   Another potential error
results from the use of exhausted absorption chemicals.

SLIDE 4-40
                                       A common type of gas absorption unit is
                                       shown in this photograph.  The absorb-
                                       ing solution is similar to that used in
                                       the ORSAT with the exception that there
                                       are separate units for oxygen and car-
                                       bon dioxide.

                                       The types of solutions used in the car-
                                       bon dioxide unit is potassium hydroxide
                                       and in the oxygen unit is a combination
                                       of zinc chloride, cuprous chloride and
                                       hyrdochloric acid.  Both solutions are
                                       highly corrosive and should be handled
                                       with care.  If used improperly, it is
                                       possible to get these materials on the
     As with the ORSATs, it is necessary to change the fluids on a regular
basis.  The oxygen solutions last for 50 to 100 measurements while the carbon
dioxide solutions last for 200 to 400 measurements.  The actual fluid life
depends partially on the concentrations of gases measured.
SLIDE 4-41
                                       This slide presents a cutaway sketch of
                                       the Fyrite analyzer.  The gas sample
                                       is pumped into the top reservior using
                                       a squeeze bulb (not shown).  The double
                                       seated plunger valve is manually closed
                                       when sampling is done. The entire unit
                                       is then inverted several times  (between
                                       two and four times) to completely mix
                                       the gas sample and the fluid.   The ab-
                                       sorption of the specific gas compound
                                       reduces the overall gas pressure inside
                                       the unit, thereby causing the flexible
                                       diaphragm at the bottom to rise.  This
                                       lifts the column of fluid up the small
                                       center tube.  The rise in the height of
                                       the fluid is proportional to the amount
                                       of gas absorbed.

     The absorption of any gas is a temperature dependent process.  If the
fluid is too hot, the indicated reading can be low and if the fluid is chilled
(during winter inspections) the indicated readings can be high.

     Pumping gas through the reservior too long before closing the top valve
can give lower than actual readings.  This is due to slow diffusion of the gas
down to the fluid surface resulting in depletion of part absorbable component
in the gas sample.

SLIDE 4-42

        1. Unrepresentative Location
        2. Air Infiltration Through
          Measurement Port
        3. Air Infiltration Into
          Sampling Line
        4. Exhausted Chemicals
The four most common  errors  in the
use of gas absorption instruments and
ORSAT instruments are listed in this

In selecting a location to make the
measurement, it is wise to avoid the
areas adjacent to potential  air in-
filtration sources.   These include
access hatches, expansion joints, duct
flanges, and dust drop out hoppers.

If stratification of  the gases in the
flowing gas are anticipated, it will be
necessary to make the measurements at a
number of locations across'the duct.
The pitot tube provides a convenient
means to "traverse" the gas  stream for
this purpose.
SLIDE 4-43
                            TO GAUGE
When using  a  1/4" O.D. copper tube as
the sampling  line,  it should extend a
foot or  two into the gas stream.  It
should also be bent in an upstream
direction  so  that any air infiltrating
through  the port is not pulled into the
instrument  sample line.

As with  all metallic probes in rapidly
moving gas  streams, a grounding/bond-
ing rod  should be attached to the tube
before it  is  used.

SLIDE 4-44
                                       A typical sampling line for the gas
                                       absorber is shown here.  Item #1 is a
                                       humidification tube which is needed only
                                       during the calibration.  The friction
                                       seals on either side of the tube can
                                       leak and it is helpful to use a line
                                       without one of these for the field

                                       The items marked as #2 and #3 are the
                                       inlet and outlet check valves.  Air
                                       infiltration can occur on the inlet
                                       check valve if it does not seat
                                       properly in the squeeze bulb or if the
                                       check valve has cracked.  Both problems
                                       are common.  Before using the sampling
                                       line, its integrity should'be checked.

     This is done by crimping the flexible tubing near the metallic probe and
squeezing the bulb.  It should not reinflate while this line is crimped.  If
it does, one of the check valves is not adequate.  The fitting on the end of
the sampling line (marked with arrow #4) should then be blocked with a thumb.
It should be impossible to pump  the squeeze bulb if the check valves are in
good shape.  If the sampling line does not pass these two tests, then it
should be replaced before attempting any measurements.
SLIDE 4-45
          CHECKING 02 AND C02

 Natural Gas
 #2 Oil
 #6 Oil
 Bituminous Coal
 Anthracite Coal
To check the accuracy of either the gas
absorber instruments or the ORSAT the
sum of the oxygen and carbon dioxide
measurements should be checked against
the ranges shown in this slide.

If the sum of the two measurements does
not fall within this range, then there
has been a measurement mistake or the
chemicals are exhausted.  In either
case the data is not good and should
not be used.  These ranges take normal
instrument error into account.
Lecturer's Notes
     A demonstration of the gas absorbers (or ORSAT) is often useful to
further explain how to check the accuracy of the measurements.  A small mylar
bag should be filled with your exhausted breath to be used as "typical flue
gas"  Measurements of the oxygen concentration should be approximately 15 to
16% and the carbon dioxide concentration should be approximately 4 to 5%.  The
sum falls into the range for bituminous coal and for wood.

 SLIDF 4-46

       1. Gas Cylinders containing known
         concentrations of oxygen and
         carbon dioxide
       2. Ambient Air for 02 instrument;
         Exhaled Breath for CO: instrument
                          The two options for calibrating any
                          oxygen analyzer are listed in this
                          slide.  Obviously the gas cylinders
                          containing known concentrations of
                          oxygen and carbon dioxide are the
                          preferred approach.  This is the way
                          the electroconductivity instruments
                          should be calibrated.  Records con-
                          cerning the frequency and method of
                          calibration should be on file at the

                          Agency inspectors using the ORSATs and
                          the gas absorption units should also
                          use gas cylinders if they are afford-
                          able.  Alternatively, these can be
                          calibrated using ambient air and ex-
                          haled breath.
 SLIDE 4-47
                                        During level 2 inspections it  is  useful
                                        to mark the locations of any oxygen
                                        analyzers on the system flowchart and
                                        electroconductivity instruments  should
                                        be checked briefly.  The condition  of
                                        the sample delivery line should  be
                                        checked for possible leaks.   If  there
                                        are any questions about the  data, the
                                        plant personnel should be asked  to
                                        repeat the calibration (single point is
                                        adequate) during the inspection.

                                        If plant personnel are using the ORSAT
                                        or the gas absorbers, the inspector
                                        should confirm that the sum  of the
                                        values makes sense and that  the  probe
                                        or bag is not leaking.

      The gas sample should always be taken at a location well within the duct
 to avoid ambient air infiltration.  In some cases, multiple measurements
 across the duct may be necessary if the gas stream is stratified.

      As with any probe used in the rapidly moving gas stream, it is important
 to use the grounding/bonding cable to prevent static accumulation.   Both the
 ORSAT and the gas absorption instruments use highly corrosive liquids and  care
 in handling is necessary.  If some is spilled it is important to wash it off
 the skin prompty and keep the liquid away from the eyes.

              FOR THE
        1. Indicator Paper
        2. pH Meter (Battery Powered)
SLIDE 4-48                             pH instruments are used in wet scrubber
                                       systems to control the addition rate of
                                       alkaline materials.  They enhance the
                                       absorption of some gases, ensure that
                                       oxidizing chemicals are in the active
                                       chemical form, and reduce the chances
                                       of corrosion.

                                       The only way to check the on-site pH
                                       meter accuracy is to obtain a liquor
                                       sample FROM THE SAME LOCATION AS THE
                                       METER PROBE and repeat the measurement
                                       with another meter.  On level 2 in-
                                       spections this is not possible since a
                                       meter is not brought to the plant.  It
                                       would be possible to take a sample back
                                       to the agency lab.  However, there is
                                       always a question about the stability of
                                       the pH as the sample ages.

      On level 3 inspections, it is possible to use either indicator paper or a
battery powered pH meter.  The measurement should be made soon after the sample
has been obtained.

         2. Oxidizing Solutions
         3. High Suspended Solids Levels
SLIDE 4-49                             The inherent limitations of pH indica-
                                       tor paper are listed here.  These are
                                       most common when inspecting odor con-
                                       trol scrubbers using hypochlorite
                                       solutions or permanganate solutions.

                                       As long as the listed conditions are
                                       not present, the pH paper has an accur-
                                       acy in the range of plus or minus one
                                       full pH unit.  This may not seem to be
                                       very accurate, but highly accurate pH
                                       data is not needed in all inspections.

     In many situations, it is only necessary to know that the pH is not much
below 6 or much above 11.  The pH paper provides sufficient accuracy to
support this conclusion.  Therefore, it is acceptable for a large portion of
the particulate wet scrubbers.

   rr .use
       Use Fresh Buffer Solutions to
       Calibrate Battery Powered pH
       Meter or to Check Indicator
                                       Prior to any pH measurement, the meter
                                       should be checked against buffer
                                       solutions of approximately 4, 7 and 10
                                       pH units.  Reasonably fresh buffers
                                       should be used since they have a ten-
                                       dency to age.

                                       Although it is not usually done, it is
                                       also a good practice to check the
                                       indicator paper against a least one of
                                       the buffers within the measurement range
                                       of the paper.  If the paper has aged, it
                                       will not indicate properly.

Lecturer's Notes
     If there are any questions concerning how to use a pH meter,'it should be
demonstrated using the coffee, soft drink and limestone slurry solutions.  The
latter is used to illustrate how the pH can change over time as alkaline mat-
erial slowly dissolves.  Most of the attendees are experienced with these in-
struments.  Therefore, these demonstrations can often be skipped
SLIDE 4-51
                                       The pitot traverse is conducted when
                                       there is a need to determine the gas
                                       flow rate.  These is done (1) to eval-
                                       uate the amount of gas pulled from
                                       process hoods and equipment, (2) to
                                       evaluate increases in static pressure
                                       drop across scrubbers, and (3) to quan-
                                       tify air infiltration into scrubbers.

                                       This is a time consuming measurement
                                       that is not done routinely by plant
                                       personnel or agency inspectors.  For
                                       these reasons, this is not part of a
                                       normal level 2 inspection.  It is
                                       necessary in only a fraction of the
                                       level 3 inspections.

 SLIDE 4-52                             There are two types of pitot tubes: the
                                        standard pitot and the S-type pitot.
                                        The standard pitot is two concentric
                                        tubes shaped like an "L".  The center
                                        tube is open to the gas flow and
                                        measures the total pressure of the gas
                                        stream (velocity pressure plus the
                                        static pressure).  The outer tube has
                                        a number of  small holes around the
                                        circumference.  When the standard pitot
                                        tube is in the proper orientation,
                                        these small  holes are pointed normal to
                                        the gas flow direction.   They measure
                                        only the static pressure.  When both
                                        pitot tubes  are connected across the
                                        differential pressure gauge,  the vel-
                                        ocity pressure is read directly.
      The S-type pitot tube is  shown on  the left center of the photograph.
 It consists of two parallel tubes bent  in  opposite  directions.   The  one
 facing the gas stream measures the total pressure and the one pointed away
 from  the gas stream measures the static  pressure.   The velocity  pressure is
 measured as the difference between these two pressures.

      The S-type pitot tube is preferred for  equipment  inspection since  it  is
 less  prone to pluggage when used in areas  with  high particulate  mass  levels or
 with  entrained water droplets.  The main disadvantage  of  the  S-type is  that it
 must  be calibrated.

 Lecturer's Notes
      Both types of pitot tubes should be on  display during breaks during  the
 lecture.   It is also helpful to have an inclined manometer or a  low range
 diaphragm gauge available to illustrate how  the velocity  pressure is measured.
 It is not wise to pass the large 6 foot long pitot tubes  around  the room
 during the lecture for obvious reasons.
SLIDE 4-53
       0-10" Inclined Manometer
       O-2" Differential Pressure Gauge
The two instruments available  for  the
measurement of velocity pressure are
listed in this slide  The type used in
stack tests is the inclined manometer
(either 0 to 5 inch or 0 to 10 inch
units are available).  It provides high
accuracy in the 0 to 1 inch velocity
pressure range which is the most commonly
encountered range.  It is somewhat bulky
to carry around and difficult  to level.

As an alternative to the inclined man-
ometer, the low range diaphragm gauge
can be used.  This one has a "D" ring
taped to the top so it can be hung from
a magnet.   It is slightly less
accurate but easier to use.




1 Pitot-/
                        PLAN VIEW
                        (Gal flow upword
                        "out of pog")
                       Duct Wall
                        SIDE VIEW
                                       A check for  cyclonic  flow should be made
                                       before beginning  the  pitot traverse or
                                       any of the preliminary  work in deter-
                                       mining the number of  traverse points
                                       required.  Cyclonic flow is very common
                                       down  stream  of wet scrubber denisters
                                       and certain  fans.

                                       As shown  in  the adjacent slide, the
                                       pitot tube is inserted  with the nozzles
                                       oriented  perpendicular  to the direc-
                                       tion  of gas  flow. Since both nozzles
                                       should be sensing the static pressure,
                                       the differential  pressure indicated on
                                       the gauge should  be zero.

     The pitot tube should be rotated  10 to  20  in  both  directions in an
attempt to "null" the readings.  If measurable velocity  pressures persist even
with this slight twist, then the flow  has too much  cyclonic  character to con-
duct a pitot travers.

Lecturer's Notes
     It is important that this check be done first. There is  no sense making
all the traverse point calculations and marking  the probe if the location is
not acceptable due to cyclonic flow.   Inspectors should  not  ignore this test
even though cyclonic flow appears unlikely.  The angular momentum of cyclonic
flow can persist for long distances.   Therefore, the origin  of the gas spin
may not be so obvious.
SLIDE 4-55
          PLUG FLOW
Conducting a pitot traver in accordance
with EPA Reference Method 2 can  be  very
time consuming.  In some cases,  the
inspector may be able to make a  single
point velocity pressure measurement
rather than a full traverse.  This  is
appropriate when only an approximate
estimate of flow rate is sufficient.

A quick check of the velocity pressures
across the duct should be made to deter-
mine if a single point traverse  is
possible.  If the distributions  are
similar to either of those shown on this
slide, a single point measurement is
     In the case of the parabolic distribution,  the  velocity pressure should
be measured at the peak of the curve.  The average velocity is related to the
peak velocity multiplied by 0.81.  In the case of the  plug flow distribution,
the average velocity is equal to the measured value  near  the center.

SLIDE 4-56
If a complete traverse is necessary, the
procedures stated in EPA Method 2 should
be followed.  The distances to the
upstream and downstream flow disturb-
ances are measured and the number of
traverse points are determined from the
Method 2 figure..  The next step is to
measure the diameter of the stack or
duct.  The diameter can be measured by
placing the pitot tube across the duct.
However, this risks damage to the sensor
tips of the pitot.  It is also possible
to jam solids into the pitot tube if the
opposite wall has thick deposits.  A
better approach for measuring the dia-
meter is to measure the circumference
and divide by 3.14 (assuming it is
SLIDE 4-57
Source:  Air Pollution
        Training Institute
One of the most common errors made
during a pitot traverse is the rotation
of the tube away from the direction of
the flow.  When this occurs in the manner
shown in this slide, it is termed the
"Yaw" error.

With slight rotation, there tends to be
higher than actual velocity pressures
measured.  Additional rotation results
in readings far below the actual values.

This type of error is generally due to
lack of concentration on the part of the
inspector.  It is important to keep the
two parallel tubes which comprise a
S-type pitot tube constantly lined up
in the direction of gas flow.

SLIDE 4-58
Source:  Air Pollution
         Training Institute
j.'he second form of alignment error is
the "Pitch" angle.  As the pitot tube
moves at an angle to the gas flow
direction, the value of the observed
velocity pressure drops rapidly.

This error is particularity difficult
to prevent on large ducts when the
pitot tube may be extended as much as 6
feet into the gas stream.  The inspect-
or is then holding only a small portion
of the pitot and has very little lever-
age.  Compounding the problem is the
tendency for the pitot tube to "sail"
in high velocity gas streams.
      Every attempt should be made  to  minimize  this error by watching the
angle of the pitot tube relative  to the  duct  or stack.  The measurements
should be repeated several times  if there  is  any question concerning the
quality of the data.

     As with any probe in a moving  gas stream,  a grounding/bonding cable
should be attached to the pitot tube prior to conducting the measurement. It
is also important to seal the port  to  prevent air  infitration related errors
on points close to the port and to  prevent exposure to toxic particulate and
gases coming out of the duct.

Lecturer's Notes
     Several of the.port designs  shown later  in this  lecture have been
specifically designed to minimize yaw  and  pitch error while conducting pitot
traverses.  These designs also seal the  port  so there is less chance of
exposure to toxic gases and particulate  during  the measurement.
SLIDE 4-59
In summary, an S-type pitot tube is
normally used for gas flow measurements
since it is less prone to pluggage
than the standard pitot tube.  Before
conducting the full traverse, it is
necessary to check for cyclonic flow.
A pitot traverse should not be done in
any location where cyclonic flow is
significant.  The velocity pressure
distribution should also be checked
before beginning the calculations for
the traverse.  If it is parabolic or
very uniform, a single point traverse
may be possible.

Whenever conducting a pitot traverse
the grounding/bonding cable should be
attached.  The port should be sealed
to prevent exposure to toxic pollutants
and to prevent measurement errors.

             Rotational Speed
            System Resistance
SLIDE 4-60
                                       The gas flow rate through a wet scrub-
                                       ber system is partially controlled by
                                       the fan rotational speed and the fan
                                       damper settings.  The fan operation
                                       should be checked whenever gas flow
                                       changes have been shown by pitot trav-
                                       erses or are suspected based on the
                                       scrubber operating conditions.

                                       One of the best indicators of fan op-
                                       erating conditions is the fan motor
                                       current. AN INCREASE IN THE CURRENT
                                       MEANS AN INCREASE IN THE TOTAL MASS OF
                                       GAS MOVED BY THE FAN.  By adjusting for
                                       changes in gas density, it is possible
                                       to QUALITATIVELY evaluate changes in
                                       the gas flow rate.

     There is no practical means to check the accuracy of on-site fan current
meters using inspector supplied portable instruments.  Inspectors should re-
quest that the plant representative arrange for the current to be measured
using an inductance ammeter if there is any question concerning the indicated
value.  This can also be done if the fan motor current is not monitored.  Under
no circumstances should the inspector attempt to make this measurement!  Only a
qualified electrician should open electrical cabinets and make current mea-
SLIDE 4-61
         1. Manual Tachometer
         2. Phototachometer
         3. Strobetachometer
         4. Sheeve Ratio Calculation
                                       The gas flow through an air  pollution
                                       control system is proportional  to  the
                                       fan rotational speed.  In a  sense,  the
                                       fan works like a shovel and  the faster
                                       it moves, the more gas is moved.

                                       On direct drive fans, the speed can be
                                       changed only by changing the motor.
                                       The speed can be read directly  from the
                                       nameplate of the motor.  On  belt driven
                                       fans, the most common type on wet
                                       scrubber systems, it is easy to modify
                                       the fan speed simply be changing the

     There are rarely monitors for the fan speed.  Whenever the fan speed  data
is needed, it is measured by plant personnel using one of the instruments  listed
above.  The same instruments can be used by agency inspectors.  The manual
tachometer is inexpensive and easy to use.  There must be good access  to  the
end of the fan shaft, but this is often blocked by belt guards.  Phototachometers
and strobotachometers do not require direct access to the rotating  equipment.
However, these are more expensive and difficult to use.  In the case of the
phototachometer, a piece of reflective tape must be placed on the fan  shaft
(when the unit is down) to serve as a light reflector.

SLIDE 4-62
                                       One way to estimate the fan speed is to
                                       ::easure the fan sheaves.   The fan speed
                                       is the ratio of the fan sheaves times
                                       the fan motor rotational  speed.  The
                                       latter can read directly  from the name-
                                       plate of the motor.

                                       This photograph illustrates the mea-
                                       surement of the sheave on the fan.  In
                                       this case, it is easy to  see the sheave
                                       and to make a reasonable  measurement of
                                       the diamter.  Some fans come with a
                                       sheet metal belt cover rather than the
                                       expanded metal cover shown here.  With
                                       the sheet metal covers, it is impossible
                                       to estimate the sheave diameter and this
                                       approach is not possible. 'THE BELT COVER
                                       SHOULD NEVER BE REMOVED.   ALSO, THE FAN
                                       SHOULD NOT BE OPERATING WHEN THE SHEAVE
                                       DIMETER IS BEING MEASURED.
    Fan RPM  = (MRPM)[MD/FD]

        MRPM = Motor Speed
        MD   = Motor Sheave Diameter
        FD   = Fan Sheave Diameter
                                       It could be argued  that  this is not an
                                       accurate enough measurement.  However,
                                       it clearly indicates when an inten-
                                       tional change in fan speed has been
                                       made.   This fact is more important than
                                       the actual fan rotational speed value
                                       at the present time.
            1. Severe Vibration
            2. Belt Squeal
SLIDE 4-63

                                       The presence of fan vibration and/or
                                       belt squeal should be noted.Severe fan
                                       vibration can occur due to build-up of
                                       material on the fan wheel or  due to
                                       erosion of the fan wheel.  Bearing wear
                                       is another common cause of this conditions,
                                       IF THERE IS SEVERE VIBRATION, THE
                                       INSPECTOR SHOULD LEAVE THE AREA
                                       IMMEDIATELY!  THE FAN CAN DISINTEGRATE
                                       SUDDENLY!  It can occur during start-up
                                       and during sudden changes in  routine

     Belt squeal is due to the slippage of the drive belts in the fan and/or
motor sheaves.  This results in a modest fan rotational speed reduction, often
in the range of 100 to 200 rpm.  It is hard not to notice the highly irritat-
ing belt squeal.


            1.  Damper Settings
            2.  Gas Flow Rates
SLIDE 4-64                             There  are  two  things  that  can  not  be
                                       determined by  evaluating fan operating
                                       parameters or  by  checking  fan  condi-
                                       tions .   These  practical limits to  fan
                                       evaluation are listed in this  slide.

                                       It is  usually  impossible for an agency
                                       inspector  to check the damper  position
                                       from the position of  damper activators
                                       outside the duct.  A  change in the gas
                                       flow rate  can  be  made by changing  the
                                       damper position without any change in
                                       the rotational speed. The only in-
                                       dication of this  is a change in the
                                       motor  current  and the latter is af-
                                       fected by  a number of conditions,  not
                                       just damper position.

     It is also extremely difficult to estimate the gas  flow rate through the
fan based on fan operating parameters such as static  pressure rise, motor
current, rotational speed and gas temperature. The fan  performance curves are
expressed in terms of the brake horsepower which  is related  to the motor
current.  Unfortunately the brake horsepower  is also  affected by  the  motor
load factor for common three phase motors as  indicated in the equation below.
                Where:  B.H.P.   =  Brake Horsepower,  Watts
                            A   =  Motor Current,  Amps A.C.
                            V   =  Motor Voltage,  Volts A.C.
                            L   =  Motor Load Factor, dimensionless

     The load factor is the difference in the phase angles of  the voltages  and
currents in the alternating current line.  This is not a constant value  at  a
given site over time.  For example, this will vary significantly as the  over
load of the motor is varied.  Also, other electrical equipment at the plant
can influence the load factor for the motor serving the wet  scrubber fan.   The
only way to measure this value is to place wattmeters on two of the three lines
of the three phase motor.  This degree of effort goes beyond that reasonable
for field inspectors especially considering that the pitot traverse is both
easier and more accurate.
SLIDE 4-65
                                       During level  2  inspections  the  fan
                                       motor  current should  be  noted from  the
                                       on-site meters.   If there is any  question
                                       about  the  data,  the inspector should
                                       request that  plant personnel remeasure
                                       the  motor  currents using an inductance
                                       meter.  In some cases, the  fan  speed  can
                                       be estimated  by using the sheave  ratio
                                       method. The  nameplate rpm  ratings  of
                                       the  fan motors  should be noted  in every
                                       case.   During level 3 inspections,  the
                                       fan  speed  should be measured when gas
                                       flow changes  are suspected.


          1. MOTOR CURRENT

SLIDE 4-66                             The data concerning pump performance is
                                       similar to that for analyzing fan op-
                                       eration.  The pump motor current is
                                       proportional to the quantity of liquid
                                       delivered.  If this is not measured
                                       continuosly, it can be measured during
                                       the inspection by plant personnel using
                                       an inductance ammeter.  Like the fan
                                       gas flow rates, it is not possible to
                                       quantify the liquid flow rate using the
                                       motor currents.

                                       The second operating parameter of in-
                                       terest is the pump discharge pressure.
                                       This is normally monitored by a gauge
                                       mounted immediately downstream of the
                                       main control valve on the discharge

      It should be obvious that there are no "portable" gauges which can be
used to measure the pressure in a pipe.  If there is no gauge or not a fitting
which would accept a gauge, it is impossible to determine the pressure.  When
there is some question concerning an existing gauge, it is sometimes possible
to temporarily substitute a new unit for the present gauge.  There must be a
valve isolating the gauge if this is done while the pump is operating.  It is
conceivable that a regulatory agency inspector could bring a gauge for this
purpose.  However, a pipe fitter would be needed to connect the gauge to the
specific valve fittings.
SLIDE 4-67                             The most common type of liquid pressure
                                       gauge is a bourdon tube.  This has a
                                       metallic element which bends slighlty
                                       when exposed to pressure.   The movement
                                       of the bourdon tube in response to the
                                       pressure is transmitted mechanically to
                                       the indicator needle.

                                       Pressure gauges of this type are vul-
                                       nerable to pluggage within the tube
                                       itself and in the gauge inlet.  The
                                       indicated value on the gauge is no
                                       longer valid when it is plugged.  As
                                       with all pressure gauges,  there is no
                                       flow through the gauge to  purge it of
                                       accumulated solids.  To minimize the
                                       problem, the gauges should be mounted
                                       above the pipe to facilitate drainage.

     Excessive vibration can also lead to the early demise of bourdon gauge.
Constant vibration, especially on the pump discharge, leads to the eventual
failure of the mechanical linkage between the bourdon tube and the indicator
needle.   Vibration can be minimized by mounting the pressure gauge on a short
coil of pipe or tubing which dampens the vibration intensity.


            1. Rotameters
            2. Orifice Plates
            3. Paddle Wheel Gauges
            4 Vane Type Gauges
            5. Magnetic Flow Meters
            6. Doppler Gauges
SLIDE 4-68                              There  are  a  number of  instruments in
                                        use  for  measuring the  liquid flow
                                        rates.   All  but  one of these must be
                                        permanently  installed  on  the pipe.

                                        While  the  doppler instrument could  be
                                        used as  a  portable inspection tool,  its
                                        use  has  been limited due  to its high
                                        cost.    This means that there is no
                                        portable instrument available to check
                                        the  accuracy of  the on-site permanent
                                        instruments.  This fact increases the
                                        importance of checking the  meter op-
                                        eration  to the extent  possible.

     All of the liquid flow meters can  suffer performance problems when
exposed to high suspended solids liquor streams and to  corrosive liquids   The
degree of vulnerability varies roughly with the cost and sophistication of  the
instrument .

Lecturer's Notes
         large majority of wet scrubber  systems  do  not  have flow meters   This
is especially common on the medium to  small  systems.  Due to the lack of port-
able instruments, there is no way to estimate  liquid  flow rate in such
systems.  This is particularly unfortunate  since a number of scrubber
problems include a reduction in liquid flow  and  the availability of this data
would aid in the early detection of the  problems.   Some inspectors have at-
temped to overcome this deficiency of data by  attempting to measure the flow
from the scrubber sump using a bucket and stopwatch.  This is not advisable
since many of the scrubber effluent liquors  have irritant characteristics and
a few have pathogenic organisms.

SLIDE 4-69
                                       This is a photograph of an orifice
                                       meter on a sewage sludge incinerator
                                       scrubber.  The orifice plate is in  the
                                       middle of the flange.  Taps before  and
                                       after the flange are connected to a
                                       mercury filled manometer to measure the
                                       differential pressure across the plate.
                                       This pressure is proportional to the
                                       liquid flow rate through the orifice.

                                       Gradual erosion and corrosion of the
                                       sharp edge orifice plate will cause the
                                       gauge to read less than the actual  flow
                                       rate.  Unfortunately, there is no easy
                                       way to confirm that the orifice plate
                                       has been damaged until the pipe can be
                                       isolated or the system shut down.
                                       These must be inspected frequently  due
                                       to the susceptibility to v/ear.


                I   Venturi
SLIDE 4-70
                                       A  venturi  meter works  in a  similar manner
                                       to the  orifice plate.  Here, the liquid
                                       is accelerated as  it enters the converg-
                                       ing section  and it decelerates as it
                               &f      leaves  through the diverging section.
                                 ^     Pressure lines before  and after the
                                       venturi throat are connected to a mer-
                                       cury filled  manometer.  The liquor flow
                                       is proportional to the differential
                                       pressure.  Unlike  the  orifice plate,
                                       this instrument does not have a compon-
                                       ent in  the direct  path of the abrasive
                                       liquid  stream.

                                       The main disadvantage  of the venturi
                                       meter is the space requirement. It is
                                       also much  more expensive than the
                                       orifice plate.

     One of the few problems which can affect  the accuracy of this type of
flow monitor is pluggage of one or both of the manometer  leads.  It may be
possible to see these deposits.
SLIDE 4-71
                                       A sketch of a swinging vane liquid
                                       flow meter is shown in this slide.
                                       This instrument is mounted in line with
                                       the piping.  The deflection of the vane
                                       is proportional to the liquid velocity.
                                       This deflection can be seen through
                                       the transparent portion of the unit.

                                       Like most other styles of flow meters,
                                       these are vulnerable to error when used
                                       in high suspended solids streams.   The
                                       accumulation of solids on the vane
                                       changes the weight and therefore
                                       affects the amount of vane movement at
                                       a given liquid velocity.  The solids
                                       can accumulate to the point that the
                                       vane is unmoveable.

 SLIDE 4-72
    Magnetic  Flowmeter
                                       A magnetic flowmeter is less susceptible
                                       to measurements problems in liquid
                                       streams with high solids levels.  It is
                                       considerably more expensive than other
                                       flow monitors discussed so far.

                                       A magnetic field is established at right
                                       angles to the flow through the instrument,
                                       Since water is an electrical conducter,
                                       a current is induced as the water cuts
                                       the magnetic field lines.  The inducted
                                       current is measured by electrodes on both
                                       sides of the instrument.  This current is
                                       proportional to the liquid velocity. The
                                       flow rate is calculated as the cross
                                       sectional area of the pipe times the
                                       average velocity.
     Since the sensor portion of the instrument is not in the direct path of
the liquid, there is only minimal abrasion.   The only components which are
vulnerable are the two electrodes and the lining of the flow tube.   The latter
is normally lined with an abrasion resistant material such as polyurethane.

     The instrument can be calibrated using  actual liquid streams in a cal-
ibration rig.  A simplier and more common technique is an electronic calibra-
tion of the instrument circuits.  The latter is normally adquate for use
with wet scrubber systems.
 SLIDE  4-73                             The doppler liquid flow monitors use
                                       ultrasonic noise to sense the velocity
                                       of solids and bubbles entrained in the
                                       liquid stream.  These can be installed
                                       as permanent instruments or used as
                                       small portable gauges.  The permanent
                                       instruments generally have a sensor
                                       that is exposed to the liquid stream
                                       while the portable units simply clamp to
                                       the outside of the pipes.

                                       The transmitting element sends an ultra-
                                       sonic sound wave diagonally into the
                                       liquid stream.  The rapidly moving par-
                                       ticles or bubbles reflect this wave back
                                       at a frequency slightly higher than the
                                       transmission signal.   The difference in
                                       frequencies is proportional to the
                                       velocity of the liquid stream.

     To use this portable instrument,  it  is necessary to carefully clamp the
sensor to the pipe wall.   An acoustic  pad supports the sensor and special
petroleum is used on the  pipe wall.  This is necessary to optimize the
transmission of the sound waves in and out of the pipes.   The "wetted" sensor
used for permanent installations is more  sensitive since  there is no  pipe  wall
to attenuate the signal and to cause "ringing" of the sound.

   Source  MAPCO Controls Co.


   1. Bubbles or Paniculate Necessary
   2. Velocities Must Be Greater Than
    One Foot Per Second
   3. Pluggage of Element Port Possible
SLIDE 4-74                              The major limitation of this approach
                                        is the need for an adequate concentra-
                                        tion of bubbles and/or particles in  the
                                        liquid stream.  This technique will  not
                                        work for clean liquids.

                                        As with any sensor exposed to the
                                        liquid stream there is always the
                                        potential for pluggage over the sensor.
                                        This could act to reduce the sensit-
                                        ivity of the instrument.  Corrosion  of
                                        the ultrasonic elements is also
                                        possible in some cases.

      This can not be used  at  all  below liquid velocities of 1 foot per second
and has limited sensitivity below  3 and 1/2 feet per second.  Neither of  these
limits presents serious problems,  however, since most liquid streams are  in
the range of 5 to 12 feet per  second.

         1. BuMMLml
         2. FitMTKOP*
         3. Sling Psychromettr
         4. Nvptil4onMlflr

         6. ExotMion Proof Flashlight
         7. Range Finoef
 SLIDE 4_75                             Other instruments potentially useful
                                        for wet scrubber system inspection  are
                                        listed here.

                                        A small level is used to determine  if
                                        the piping is sloped properly.   The
                                        suction line should be sloped as least
                                        1 to prevent the accumulation  of air
                                        pockets.  The recirculation lines
                                        should be sloped to faciliate draining
                                        and to faciliate solids flushing.

                                        Fiberscopes have the potential  to allow
                                        close-up inspection of nozzles  mounted
                                        inside hard-to-reach scrubber internal
                                        areas.  Commercially available  models
                                        include a battery powered  light source
                                        and a 6 foot long rigid probe which
                                        rotates.  The probes are normally 1/4"
                                        diameter.  Therefore, these would fit
                                        through common static pressure  measure-
                                        ment ports.

     The sling  psychrometer is often useful for measuring the ambient  relative
humidity during visible  emission observations.  The wet bulb and  dry bulb
temperatures are measured simultaneously with this instrument and the  relative
humidity is determined by plotting the data on a psychometric chart.

     Nephleometers  have  been suggested for use as portable opacity monitors
for wet scrubber systems.  These are not vulnerable to water droplet inter-
ference problems which to date have precluded use of transmissometers.  They
operate as extractive instruments.  Therefore, only a small port  is

                                      The next set of slides concerns
                                      measurement ports.  It is important
                                      to select the appropriately sized and
           SELECTION OF            located ports in order to avoid the
       MEASUREMENT PORTS        measurement problems discussed so far
                                      in this lecture.

                                      Unfortunatly, a large number of exist-
                                      ing wet scrubber systems have no ports
                                      at all or have ports in inaccessible
                                      locations.  HEROIC EFFORTS SHOULD NOT
                                      BE MADE TO REACH IMPROPERLY LOCATED
     Hopefully,  in the next  several  years, regulatory agencies will encourage
source operators to install  the  proper  ports  so  that both the operators and the
inspectors can adequately evaluate performance of wet scrubber systems.  Some
port designs are recommended in  this section.  Locations for measurement ports
are discussed in the lecture concerning each  specific type of scrubber vessel.
SLIDE 4-77
                                       The only ports  available  on  some  units
                                       are the  stack sampling  ports downstream
                                       of the scrubber.   These are  usually
                                       four inches  in  diameter.

                                       If the gas stream is  slightly positive,
                                       the pollutant laden gas will flow out
                                       rapidly  and  accumulate  in the breathing
                                       zone of  the  person making the measure-
                                       ment. If the port is under  negative
                                       pressure, ambient air will rush through
                                       the port and cause errors.  These ports
                                       are difficult to  work with.
     An additional problem with large ports is the removal of the pipe caps or
plugs used to seal the ports when not in use.   This can take several hours.

SLIDE 4-73
                                       This photograph illustrates the ideal
                                       size for a measurement port on a wet
                                       scrubber vessel.  It should be in the
                                       range of 1/4" diameter to 1" diameter.
                                       This minimizes the potential for
                                       fumigation in positive pressure systems
                                       and reduces the ambient air infiltration
                                       problems in negative pressure units.
                                       The small plug is also much easier to
                                       remove than large ports.

                                       On gas handling ducts, a larger port is
                                       necessary to permit the use of an S-type
                                       pitot tube. It should be at least 1 and
                                       1/2" in diameter but smaller than
                                       2" diameter.
SLIDE 4-79
                                       There  must  be  convenient  and  safe
                                       access to the  port  itself.  Running
                                       small  diameter tubing  down  from  an
                                       inaccessible ports  is  not sufficient.
                                       It  is  difficult to  clean  out  a plugged
                                       port with this arrangement.   It  is
                                       impossible  to  measure  the gas tempera-
                                       ture even if a pump were  used to pull a
                                       gas sample.  The temperature  would drop
                                       close  to ambient levels while passing
                                       down the tubing.  Even the measurement
                                       of  gas stream  oxygen and  carbon  dioxide
                                       concentrations is difficult under these

                                         This is a photograph of a clean out
                                         port (marked as  arrow #1) with a dif-
                                         ferential pressure transducer (marked
                                         as arrow #2).  The purpose of this port
                                         is to permit removal of accumulated
                                         solids from  the  port while the D/P
                                         transducer is  off-line.  OPENING THIS
                                         PORT WHILE THE INSTRUMENT IS OPERATING
                                         WILL RESULT  IN AN  ERRONEOUS SIGNAL
                                         BEING SENT TO  THE  PLANT PROCESS CONTROL
                                         SYSTEM.  THE PROCESS WILL BE TRIPPED
                                         OFF-LINE.  Do  not  open these clean out

                                         A small inspection port installed at
                                         least several  feet from the instrument
                                         port could be  opened without causing
                                         this problem.
Lecturer's Notes
     This is  a  good time in the  lecture to make the point that specific  ports
are needed to faciliate wet scrubber inspection.  Ports  installed for  stack
sampling or for routine system monitors are rarely the correct size or at  the
correct location.   Specific ports  should be installed to faciliate the use of
portable inspection instruments!
SLTDE 4-81
                SiGEU PLUG  SS-00-,
            WRKER 0-RING
            SIZE 2-202
            MttGELOK NUT
                     Fi|ur. 3-3b. I/A" Port With
                           SuMt'd Flu|
         55 FLAT HEAD RIVET
         !/ X 1 S/'
    Fiturt 3-Jt.  1/A" Pen wi
          Sl hi! O
                        SWAGELOK MALE CONNECTOR
       J-Jc. 1M* fort With
   Sut Typ. Up
A sketch of  a 1/4" inspection  port is
shown in this slide.  This port  is made
from a standard Swagelock fitting which
is welded  to the side of the duct or wet
scrubber wall.   An 0-ring seal prevents
any gas leakage outward or ambient air

For areas  where accumulation of  solids
or sludge  is likely, the port  can be
inclined 30 to permit drainage.

The port is  sealed with a cap  with a
small rod  attached.  This fills  the port
recess when  not in use.  A simple cap
plug could be used in situations  where
rodding out  the port is not difficult.

S'.JDE 4-82
   0-fiir.G ' n/16 CC * ' 5/16 1C X 3/)t DIA
                 /-l/4"-20 THUMB SCREW X !'LG
                  1 S/1' WOBE SHELL
                                SCORE CO_A
            LD UJI
       -S5P1PE-1 1/4-| I
            .MO WALL
                  (2) 3/8 HEX HS BOLT X 1' LG
                    WITH HEX NUT
                                        A  Dort  useful for ductwork  ahead of and
                                        following the wet scrubber  vessel is
                                        shown here.  This consists  of a 1 and
                                        5/16  inch diameter pipe welded to a
                                        flange.  There is also a  gas tight weld
                                        to the  side of the duct.

                                        This  port serves as a support and
                                        alignment mechanism for a pitot tube.
                                        An outer flange allows rotation 10 to
                                        20 in  either direction to  correct for
                                        minor cyclonic flow.  An  0-ring on the
                                        shoulder of the inner flange fits
                                        around the pitot tube to  provide a gas
                                        tight seal.  This again protects the
                                        inspector during the measurements and
                                        also prevents air infiltration on
                                        negative systems.

     It should  be noted that the hole  in  the duct v/all is only  1 and 1/4
inches which  is considerably smaller than the 4 inch holes common to stack
sampling ports.  While opening the  port  to put the pitot tube  in or to pull it
out, the inspector is subject to fumigation in positive pressure ports.  With
the smaller ports, the flow is only appoximately 10% that of  the large ports.
xi ^1

t? i =

.^U BAR-I S/lCDiA X 4 1/2' LG

"^k *^Lt
                     lA'OROX 3 Ot)
                 NOTE: vi6  i s/n SLEEVES
                 ADO I LB/FT OFLGTn
    SS TUBE !/!' 0.0 X .Oil' WALL'
SS TUBE I US' 0.0 X 0<9* WALI
SLIDE 4-83
                                         The pitot tube must have some minor
                                         modifications for use in the port
	T                                      described in the  previous slide. These
                                         modifications are inexpensive and  can be
                                    ^   made to existing  pitot tubes.

                                         As shown here, the pitot tube has  been
                                         encased in a 1" tube with gas tight
                                         seals at either end.  There is also  a
                                         bulkhead support  at the middle of  the
                                         tube.  This converts the pitot tube  into
                                         a round assembly  which can be easily
                                         sealed with an 0-ring.

                                         The tube and seals add only about  4  to
                                         5 pounds to the total weight of  the
                                         pitot tube.  This is a small price to
                                         pay for improved  security against  toxic
                                         gas and particulate fumigation.   It
                                         also prevents  yaw and pitch error.

      Static grounding occurs inherently due to the direct contact between the
pitot tube assembly and  the  port on the duct wall.  Nevertheless, the grounding
cable should be attached.
   VltW I-I        SECTION a-g     ULHtAD DETAIL


   E: s/is" a i s/ie" O.D. SLEEVES ADD LESS THAN i/rr OF ITO-

SLIDE 4-84
                                           inspection ports of  the type shown
                                             or any other type  can only be
                                       installed when the system  is off-line
                                       and the immediate area has been purged
                                       af explosive dusts or vapors.

                                       INSPECTORS SHOULD NEVER  REQUEST THAT
                                       THESE PORTS BE INSTALLED WHILE THE
                                       EQUIPMENT IS OPERATING OR  BEFORE THE
                                       AREA HAS BEEN PROPERLY PREPARED.

                                       Drilling or cutting  could  easily result
                                       in an explosion.  In particulate control
                                       systems, a light layer of  dust is common
                                       on the bottom of the ducts.  Even a 1/16"
                                       layer can lead to a  devastating explosion,

     Many of the gaseous control  systems can have pockets of explosive gases
including but not limited to ammonia and carbon monoxide.   The  unit must be
purged of these gases before hot  work  is begun.
SLIDE 4-85

     i Ports should be >V4" and <2" diameter.
     2. There should be safe access to the port
      to facilitate rod out prior to the measure-
     3. Never use ports connected to  D/P
     i Never have measurement ports instance
      wnile the system is running.
                                        This  slide summarizes some of the
                                        important points regarding the use of
                                        measurement ports in level 3 and level
                                        4  inspections.   Safety is the prime
                                        consideration.   If significant climbing
                                        or inhalation risks are involved in
                                        making the measurement, it should not
                                        be attempted.  All probes inserted into
                                        rapidly moving gas streams should be
                                        bonded to the duct using the grounding
                                        and bonding cable.

                                        The port must be sealed well enough to
                                        prevent air infiltration related errors
                                        and to preclude loss of the probe into
                                        the duct.

     When making measurements in ductwork, it is important to choose a repre-
sentative location.  Whenever possible, the measurements should be repeated at
several locations as the  probe traverses  the gas stream.  Single point measure-
ments taken close to the  wall should to be avoided to the extent possible.

     In the slow moving gas  streams found on the walls of scrubber vessels and
demisters, the measurements  must inherently be taken close to the wall surface.
This is not a serious  problem since there are lower temperature and static
pressure gradiants across these areas.

Lecturer's Notes
     The safety guidelines should be emphasized in the summary of this lecture.
It should be noted that attendees should avoid the level 3 and 4 inspections
until they are fully qualified.  There is no need to rush into the use of
portable instruments.  However, once the use of these has been mastered and
they are able to easily evaluate on-site instrumentation data, the speed and
accuracy of their inspections will improve significantly.


4-1.  Any or all of the first three (a,b,and c) could cause this increase in
      the measured oxygen concentration.   Answer d is very improbable since
      there would not be enough dissolved oxygen in the liquor to cause this
      increase in gas stream oxygen levels.   The point of this question is
      that the oxygen concentration of the effluent gas stream is influenced
      by both infiltration and absorption.  Therefore, it is rarely measured.

4-2   Answers c and d are correct.  The fan calculations are theoretically
      possible but prohibitively difficult due to the need to know the motor
      load factor.  Also, the accuracy of the published fan curves for a
      specific unit can always be questioned.  Answer b is for those who had a
      stack sampling course 6 years ago and forget that they talked about F
      Factors for estimating gas flow rates from combustion sources.  Some may
      cry foul concerning tracer tests.  These were not discussed.  However,
      they are very effective for determining the gas flow rates in low
      velocity gas streams.  As they should remember, a pitot tube is not
      effective below 600 feet per minute.  You should point out that some new
      material is intentional being introduced in these sets of review
      problems and questions.

4-3.  The gauge is certainly not in the best of shape and should be discarded
      if others are available.  However,  if this is the only one available, it
      is possible to struggle through by calibrating immediately before and
      after the inspection.  As long as the two calibrations are similar, the
      curves can be used to correct the data.  If there is a shift in the
      curves, the static pressure measurements are not good.

      Attendees who are alert may question why the static pressure gauge should
      be used at all.  The slack tube manometer must be available, otherwise
      how could this curve be generated?  Good point!  However, the slack tubes
      are miserable when some climbing is involved in reaching the various
      static pressure measurement ports.

4-4.  Answers c and d are correct.  The measurements should be taken.  However,
      the calibration should be rechecked at the earliest opportunity.  Those
      who have mastered the art of multiple choice questions should have been
      able to guess this just from problem 4-3.

4-1.  The oxygen concentration in the scrubber inlet is 8.5% and at the outlet
      is 10.8%.  What are the possible explanations for this increase?

      a.  Severe air infiltration into the scrubber vessel
      b.  Absorption of some of the gas stream components
      c.  Measurement error
      d.  Stripping of oxygen from the liquor
      e.  None of the above

4-2.  Gas flow rate can be accurately measured using which of the following

      a.  Fan calculations based on published fan curves
      b.  E factors
      c.  Pitot traverses
      d.  Tracer tests

4-3.  During a routine calibration of a diaphragm valve the data plotted below
      is obtained.  Is it possible to conduct an inspection using this gauge?
4-4.  During an inspection, a diaphragm gauge is accidently dropped about ten
      feet to a hard surface.  Upon reaching the unit it is noticed that the
      zero is no longer correct. However, it can be reset using the set screw
      on the front of the gauge.  What should be done now?

      a.  The guage should be discarded.
      b.  The gauge should be used in the reminder of the inspection if
          no other operational gauge is available.
      c.  The gauge should be calibrated at the site, if possible.  If this
          is not possible, it should be calibrated immediatly on return to the
      d.  The gauge is resistant to vibration and shock.  Therefore it is
          not affected by this accident.


4-5.  The static pressure drop across the scrubber vessel and the demister can
      not be determined from the data shown.   It is necessary to know the
      static pressure in stream #3 and in stream #2 to calculate the static
      pressure drop.

4-6.  The most likely explanation is aspiration effect error during the mea-
      surement in stream #1.  Another explanation would be an increase in the
      liquor flow rate which was not indicated properly by the liquid flow

4-7.  No.  Actually all of the data seems to be indicating a flow rate increase.
      Also, these instruments have a tendency to give a low reading if the
      suspended solids and/or low pH conditions have damaged the orifice plate.
      One way to check the liquor flow rate data is to determine if there has
      been an increase in the scrubber static pressure drop.  Most, but not all,
      scrubbers have an increase in static pressure drop if the liquor flow
      rate increases while the gas flow rate remains constant.  The latter is
      indirectly indicated by stable fan motor currents.

4-8.  No.  The data could be correct.  This answer may catch those who try to
      answer to quickly.  Without any information concerning the gas handling
      system preceeding the portion shown on the flowchart, there is no way to
      tell if there is also a fan ahead of the scrubber.  It is not uncommon
      to find just such a "push-pull" arrangement with fans ahead of and fol-
      lowing the scrubber vessel.

      Opening a large port on stream #1 on the assumption that the port is at
      negative pressure could lead to fumigation of the inspector.  The
      complete system flowchart should be reviewed and a check should be made
      of the actual gas handling system.  All fans must be located so that a
      reasonable estimate of the static pressure drop at any location can be
      made before opening the port.  This question again illustrates the value
      of system flowcharts during the inspection.

4-5.   In the wet scrubber system above, what is the pressure drop across
       the scrubber vessel and demister if the static pressure in stream #1
       is -16 inches and the static pressure in line #4 is -1/2 inch?

4-6.   During an inspection of the scrubber system above, the static pressure in
       stream #1 is measured at -34 inches and the static pressure in stream #3
       is measured at -5 inches.  The fan motor current is close to typical
       values and the liquid flow rate monitor on stream 2 indicates close to
       baseline flow rates.  What is one logical explanation for the increase
       in static pressure drop from baseline levels of 24 inches to the present
       29 inches?

4-7.   There is an orifice plate liquor flow meter in stream 2, downstream from
       the recirculation pump.  The liquor has a suspended solids concentration
       of approximately 5% (by weight) and the pH is 5.1.  The pump discharge
       pressure is lower but the motor current is slightly higher.  The nozzle
       pressure has increased slightly.  The liquid flow meter is indicating
       15% higher liquid flows than normal.  Can this liquid flow rate data be
       dismissed as being obviously in error?  What can be done to check it

4-8.   A static pressure measurement made at in stream #1 indicated a value of
       +4 inches W.C.  Can this be dismissed as being obviously in error?


4-9.  The correct answers are a and c.   The entrained water droplets cause the
      meter to flucuate between the wet bulb and dry bulb temperatures.   A
      short in the thermocouple probe would cause a similar problem.  However,
      the flucuations would be even more intense and rapid.  Answer b is very
      improbable.  There may be a rapid step change in the gas temperature but
      there is rarely a series of rapid flucuations.  The scrubber would tend
      to dampen any such flucuations thereby making these even less plausible.
      The inner surface of the duct wall would be slighly cooler than the gas
      stream but occassional touching of this wall with the probe would  not
      cause rapid flucuations.

4-10. Only the battery powered pH meter should be used.  The hypochlorite
      solution would attack the dye in the pH indicator paper.

4-11. Only answer e is correct.  Answer d may make sense.  However, it is hard
      to find a rubber stopper that large.  Answer f has some elements of truth.
      However, sometimes it is necessary to use less than optimum ports.
      Answer f would be correct only if there were significant safety problems
      with the port also.

4-12. Nothing can be done except to go back to get it before starting any
      measurements.  A grounding/bonding cable is necessary whenever a
      probe is used in any duct where static accumulation is conceivable.
      Inlet gas streams of scrubbers could have static accumulation.

4-13. Answer b is correct, the oxygen concentration remains 20.9%.  Anyone
      answering c has a nasty habit of guessing and is very weak in

4-14. Of the answers listed, only b makes sense.  Answers a and c are done
      at the risk of a serious explosion.


4-9.  An erratic reading is noted while making a temperature measurement
      downstream from a scrubber.  Why?

      a.  The gas stream is not saturated and there are entrained droplets.
      b.  There are very rapid flucuations in the inlet gas temperature
          to the scrubber.
      c.  The probe is damaged.
      d.  The probe is occassionally touching the inner wall of the duct.

4-10. There is some apparent corrosion in a recirculation tank in a odor
      scrubber.  The suspended solids level is less than 3% and the liquor
      temperature is 105 F.  The liquor being used is a hypochlorite sol-
      ution.  What should be done to evaluate the liquor pH.

      a.  Measure the pH using a battery powered pH meter.
      b.  Measure the pH using pH indicator paper.
      c.  Either a or b

4-11. A 4 inch diameter stack sampling port is to used to measure the gas
      stream temperature and static pressure.  The static pressure is
      believed to be between -2 inches and -5 inches W.C.  What can be used
      to seal the port at these static pressure levels?

      a.  Nothing is necessary at these low static pressures.
      b.  A hand
      c.  A glove
      d.  A rubber stopper having a diameter greater than 4 inches
      e.  A sanding disk having a diameter greater than 5 inches with
          a rubber stopper behind the sanding disk
      f.  A port this large should never be used under any circumstances.

4-12. During an inspection it is necessary to conduct a pitot traverse ahead
      of the scrubber to confirm a severe inleakage problem with the scrubber
      vessel.  What can be done if you forgot to bring the grounding/bonding

4-13. When calibrating the gas absorber type oxygen instrument, what oxygen
      value should the unit indicate when using ambient air?

      a.  21.9% in the winter, 20.9% in the summer.
      b.  20.9% in the summer, 20.9% in the winter
      c.  19.9% north of the 20 longitude, 19.7% south of 20 longitude
      d.  21.9% everywhere, all the time

4-14. A wet scrubber is strongly suspected to be out of compliance due to
      a large residual plume from the stack.  There are no instruments on
      the unit and no measurement taps safely available.  What should be done?

      a.  Demand ports be installed immediately so the inspection can be done.
      b.  Recommend to agency supervisors that the operators be requested
          to perform a stack test as soon as possible.
      c.  Offer to drill a 1/4" hole to facilitate the present inspection and
          request permanent ports for future inspections.



                                  LECTURE 5

              1. Demisters
              2. Pumps
              3. Piping
              4. Nozzles
              5. Fans and
                                       This lecture addresses some of the
                                       components used in most wet scrubbers.
                                       Evaluation of these compontents is a
                                       necessary part of most level 2 and
                                       level 3 inspections.

                                       Demisters remove large droplets formed
                                       during the passage of the gas stream
                                       through the wet scrubber vessel.  The
                                       removal of the droplets is necessary to
                                       protect the downstream fans.  Failure
                                       of the demisters can also result in
                                       localized nuisance problems due to
                                       droplet rainout.

                                       Pumps and fan problems can have a
                                       severe impact on the overall perform-
                                       ance of the scrubber.  The purpose of
                                       the inspection is to qualitatively
                                       estimate changes in liquid and gas
                                       stream flow rates.

     Proper liquid-gas distribution can be achieved only when the proper
nozzles are selected and when they are operating properly.  Unfortunately,
they are very susceptible to pluggage and erosion problems when there are
high suspended solids in the recirculation liquor.

     System piping is inspected to evaluate the potential for pluggage of
lines and freezing of lines in the vicinity of the scrubber vessel.  Problems
with the pumps can also occur due to improper piping.


       1.  Prevent Stack Rainout

       2.  Protect Downstream Equipment
         a. Fans
         b. In-Line Reheaters
         c. Stack Liners
         d. Ductwork
SLIDE 5-2                              One of the main functions of demisters
                                       is to prevent the rainout of liquor
                                       droplets from the scrubber system
                                       plume.  At the very least, the deposited
                                       droplets are a nuisance to the general
                                       community near the plant boundry line.
                                       In some cases, damage to automobile
                                       finishes and house paints can occur.

                                       An equally important function of de-
                                       misters is to protect the downstream
                                       scrubber components listed in this
                                       slide.  The gradual accumulation of
                                       solids on fan blades can result in
                                       corrosion or fan balance problems.  The
                                       bypass stack for the system may have  to
                                       be used while repairs to the fan are

     The demisters are not part of the routine scrubber system inspection
agenda.  They are added only when the symptoms of demister problems are ob-
served during initial phases of the inspection.  Some of these include obvious
rainout of droplets close to the stack, the presence of a mud "lip" at the
stack discharge, the presence of a discolored area near the stack discharge,
and/or moderate fan vibration.  During level 2 inspections, the demister
evaluation is limited to a review of demister cleaning system characteris-
tics.  Measurements can be performed in a level 3 inspection to isolate some
of the common demister problems.
SLICE 5-3                              The droplets which must be removed from
                                       the gas stream by demisters are large
                                       in comparison to typical particles.  It
                                       is common for these droplets to be in
                                       the 100 to 500 micron range.  The largest
                                       of these has a mass which is more than
                                       100,000 times that of a 1 micron duct
                                       particle.  The projected areas shown
                                       in this slide illustrate the typical
                                    t   size distribution of entrained droplets.

                                       Due to the large droplet sizes, all
                                       commercially available demisters use
                                       impaction to separate entrained droplets
                                       from the gas stream.  The effectiveness
                                       of impaction is proportional to the gas
                                       stream velocity and to the square of of
                                       the droplet diameter.

     Considering the large size of the droplets, they should be easy to
collect.  In fact, most demisters have very high removal efficiencies unless
the gas velocities drop far below normal design ranges.  The problems which
are most common have nothing to do with initial capture of the droplets, but
rather with what happens afterwards to the liquid on the demister.

0. O
i Microns

                                       Excessive gas velocities through the
             '.   '                    demister can lead to formation of
                                       droplets from the surfaces of the
                                       demisters.  A common mechanism for
                                       droplet formation is shown on this

                                       While gas velocity is the dominant
                                       factor, the configuration of the
                                       demister obviously plays a role in the
                                       tendency for reentrainment.  Sharp
                                       edges on the downstream side of the
                                       demister favor droplet formation.  The
                                       surface tension of the liquid is also
                                       important.  As this decreases, the
                                       tendency for reentrainment increases.

Lecturer's Notes
     This is one of the first times that the surface tension is mentioned as
an important operating variable.  It will be discussed later in the section
concerning spray tower scrubbers and venturi scrubbers.  It is also discussed
with respect to nozzle performance.  Unfortunately, there is rarely any data
on surface tension.
     If any of the attendees do not understand the meaning of surface tension,
it should be discussed at this time.
 ?LIDE 5-5
                                       High gas velocities can occur on
   \ . '          <'  '  .'                 demisters due to pluggage and scaling.
    '. *       , .            '.         Pluggage is the accumulation of
                                       suspended solids on the demister
                                       elements.  Scaling is the precipitation
                                       of soluble materials out of solution
                                       onto the demister elements.

                                       Regardless of the mechanism of solids
                                       accumulation, the area available for
                                       gas passage is drastically reduced.
                                       This leads to increased gas velocities
                                       through at least a portion of the de-
                                       mister.  Reentrainment occurs in these
                                       areas due to the mechanisms presented
                                       in the previous slide.

     In the previous slide, the reentrainment problem is due to the excessive
design gas velocities for the demister.  The solids accumulation related pro-
blems are due to  inadequate demister cleaning, to excessive solids in the
liquor droplets or  to improper demister location.

          1. Cyclonic Demisters
            a. Standard Flow
            b. Reverse Flow
            c. Rotary Vane

          2. Impaction Target Demisters
            a. Chevrons
            b. Baffles
            c. Mesh Pads
            d. Tube Banks

          3. Dry Stages
            a. Trays
            b. Moving Beds
These are the most common types  of
demisters.  They differ with regard  to
the tendency to plug and the velocities
at which reentrainment becomes serious.

The standard flow and reverse flow
cyclonic demisters are used primarily
behind gas-atomized scrubbers, such  as
venturi scrubbers.  All of the other
styles primarily serve scrubbers having
vertical cylindrical scrubber vessels.
The latter includes tray towers, packed
beds, moving beds and spray towers.
Many of these can be installed in either
a vertical or horizontal orientation.
The latter has better liquid drainage
and is less prone to reentrainment.
     The dry stages can be used on moving  bed  and  tray  tower scrubbers which
can achieve the necessary pollutant removal  efficiencies without using all of
the stages.  The liquor inlet is moved to  one  of the  lower stages and the top
stage is operated dry.  The droplets which are captured simply drain back
down into the scrubber.  This type of demister is  rarely used on a new system.
It has been used infrequently for some existing systems.
Source:  Air Pollution
         Training Institute
This is a sketch of a  standard cyclonic
demister.  Its most common  application
is downstream of a venturi  or rod deck
scrubber.  Its effectiveness  improves
with increasing gas velocities due to
the improved centrifugal  forces on the

There is obviously nothing  in this unit
which can plug.  Scaling  can  occur in
the lower areas (the sump), but this
does not lead directly to droplet re-

There is very little to inspect on one
of these units.  They  either  work or
they don't work.  On level  3  inspec-
tions, it may be helpful  to measure the
outlet gas flow.
Lecturer's Notes
     The measurement  of gas  flow is  often complicated by the persistence of
cyclonic flow in the  stack.  This is especially common on positive pressure
units in which the cyclonic  chamber  outlet duct serves as the stack.

                          PLAN VIEW
At high gas flow rates, the liquid
which impacts on the inner wall of the
cyclonic demister can spiral up the
side and enter the stack area.  This
path is illustrated in this slide using
a heavy dotted line.  The point of
reentrainment is the outlet of the
demister (arrow #1).

Reentrainment can also occur as the
spiraling liquid stream returns to the
upper portion of the inlet gas duct.
Here the liquid is sheared off the sharp
edge by the high velocity gas stream.
The location where most of the reentrain-
occurs is shown by arrow #2.
                                       One  simple procedure  for  eliminating
                                       reentrainment  on  the  gas  inlet  duct
                                       (arrow  #2, Slide  5-8)   has  been suc-
                                       cessfully demonstrated  at a grey iron
                                       frtoundry.   As shown  in this slide, a
                                       small section  of  angle  iron was been
                                       welded  along the  gas  inlet  duct.  This
                                       serves  as a  scalper for the liquid
                                       spiraling around  the  demister.   The
                                       liquid  is directed down to  the  sump and
                                       away from the  high velocity gas stream.

                                       A similar approach may  help reduce the
                                       spiraling stream  passing  up to  the de-
                                       mister  outlet  duct.   However, a long
                                       section of angle  iron or  similar mat-
                                       erial may also disrupt  the  vortex
                                       necessary for  proper  droplet capture.

SLKE 5-10
This is a reverse flow type cyclonic
demister.  The gas stream enters near
the bottom and flows upward in the
outer annular area.  A 180 turn is
made as the gas stream enters the down-
ward point outlet duct.  The bottom of
the demister is sloped to facilitate

Removal of entrained droplets occurs
due to both the cyclonic action and the
sharp gas stream turn.  These units are
not prone to reentrainment.  However,
it is still possible to have some drop-
let formation at the lip of the inlet
duct.  With this style, it is especially
important to keep the drain open so
that the liquid level does not rise.
Lecturer's Notes
     Inspectors who are not experienced with wet scrubbers may not be able to
identify these initially during an inspection.  There is a natural expectation
to have the gas stream exit from the top of scrubbers and demisters and this
leads to the confusion.
SLIDE 5-11
Source:  Air Pollution
         Training Institute
This is a sketch of a mesh pad demist-
er .  Collection of droplets occurs due
to impaction on the filaments of the
mesh pad.  These are oriented horizon-
tally and the liquid simply drains back
down into the scrubber.

To prevent flooding (excessive liquid
hold-up), some units are inclined
slightly to improve the drainage.
Also, it is possible to install a
standpipe and trap to drain the liquid
above the pad.

It is important that the mesh pads be
installed tightly against the wall.
There should be no obvious voids which
gas could pass through.  All of the
individual sections should be wired
together and to the retainer supports.
It should not be possible to manually
move the mesh pad sections if they are
installed properly.

SLIDE 5-12
          max  =
                                       Mesh pad pluggage and reentrainment
                                       are minimized by properly gas vel-
                                       ocities.  As a general guideline,  the
                                       velocity should not exceed the value
                                       indicated by the equation in the slide.

                                       The face velocity is simply the actual
                                       gas flow rate (ACFM) divided by the
                                       total open area of the demister.  The
                                       latter is calculated by subtracting the
                                       area of supports, grids and retainers
                                       from the demister total area.
     The empirical "K" factor for metallic meshes having densities of 5 to 9
pounds per cubic feet is 0.4, and for metallic meshes having densities of  more
than 9 but less than 12 pounds per cubic feet is 0.35.   For mesh pads composed
of Teflon, Polypropylene or Kynar use a "K" factor of 0.3.   The equation yields
velocity in feet per second.

Lecturer's Notes
     For a rough approximation, the density of the liquor can be taken as  62.4
pound per cubic foot and the density of the gas can be taken as 0.06 pounds
per cubic foot (-10 inches static pressure, 130 F).   This makes the square
root term equal to 32.25.
SLIDE 5-13
            1. Use Coarser Mesh

            2. Flush With Clean
                                       For mesh pads having chronic pluggage
                                       conditions,  the alternatives listed
                                       here may be  of use.

                                       Mesh pads are especially prone to plug-
                                       gage due to  the low open area and the
                                       difficult drainage path.  A coarser
                                       mesh partially alleviates these
                                       problems. This will also lead to a
                                       slightly lower pressure drop.  However,
                                       this is done at the risk of lower drop-
                                       let capture  effectiveness in the
                                       coarser mesh pad.

     Sprays should generally be used whenever there is appreciable solids
levels in the scrubber liquor.  With mesh pads, it  is important that these
sprays be pointed downward.  Upward sprays can drive the  solids deeply into
the mesh pad and partially blind the demister.   Demisters with high solids
deposits can suffer reentrainment and high static pressure drop.  If the
conditions are sufficiently severe, the entire demister can be ripped from its
supports and sucked into downstream I.D. Fans.  For example a completed
blinded demister 8 feet in diameter with a 10 inches W.C. static pressure on
the downstream side is subjected to a force of over 2500  pounds!

     The initial sign of mesh pad pluggage is an increase in the static
pressure drop at a given gas flow rate.  Baseline data is helpful for
identifying the onset of pluggage.  In any case, a  static pressure drop over
0.5 inches W.C. is a sign of trouble.

                2 PASS

       Source:  Electric  Power
               Research  Institute
                                       This is a side view of a two pass
                                       chevron demister.  The gas stream enters
                                       from the bottom and must pass up through
                                       the twisted passages.  Droplets impact
                                       on the blades and drain down.

                                       These are available in two, three and
                                       four pass designs with the capture im-
                                       proving with the number of passes.  The
                                       inside angles of the chevrons vary from
                                       a low of 60 to maximum of 120.  Drop-
                                       let collection improves with increasing
     Various blade designs are available to reduce reentrainment tendencies.
These involve small channels and scalpers to aid the liquid drain downward
without any wave action which could result in droplet formation. 'These also
prevent liquid from reaching the downstream edge of the blades where the
liquid could be sheared off by the gas stream passing out of the demister.
The main disadvantage of these pockets and channels is the tendency to plug
when high suspended solids are collected.  This can accelerate pluggage of the
entire demister since washing is inhibited.  These special blade designs are
used most frequently on demisters in which the chevrons are mounted vertically
and the gas flow is horizontal.  These demisters have inherently improved
drainage so the pluggage is less of a problem.
             FOR CHEVRONS
              Vertical Gas Flow
            5 to 15 Feet Per Second

             Horizontal Gas Flow
            7 to 25 Feet Per Second
SLIDE 5-15
                                       Chevron demisters are subject to drop-
                                       let reentrainment at high gas velocities
                                       as indicated in the equation shown in
                                       slide 5-12.  The "K" factors for a
                                       typical 3 pass chevron with vertical gas
                                       flow is 0.2 to 0.5.  The value of the
                                       constant for the same 3 pass unit having
                                       horizontal gas flow is 0.2 to 0.8.  The
                                       large range is needed due to differences
                                       in the blade angles, blade geometry, and
                                       liquor surface tension.  At typical
                                       liquid and gas stream densities, this
                                       equation indicates that the superficial
                                       velocities should be between the values
                                       shown in this slide.

     Most chevrons are designed for a gas velocity between 10 and 20 feet per
second, depending on the specific characteristics of the application.  The
accumulation of solids can result in an unintentional increase in the gas vel-
ocities and increased reentrainment.  To minimize solids build-up, it is common
practice to spray the demister sections on a regular basis.  The sprays can be
either above or below the demisters.

SLIDE 5-16
                                       To  facilitate  early  identification  of
                                       the solids  accumulation  on. chevron  de-
                                       mister  sections,  there should  be  static
                                       pressure  measurement taps  before  and
                                       after the demister .   An  increase  in the
                                       pressure  drop  at  a constant flow  rate is
                                       a clear sign of emerging pluggage (and
                                       reentrainment) .   The static pressure
                                       drop should be measured  during the
                                       baseline  period to serve as a  compar-
                                       ison when problems are suspected  later.

                                       There should also be a viewing port or
                                       hatch in  the demister area so  that  the
                                       conditions  can be evaluated when  the
                                       scrubber  is down  for service.

     When comparing against baseline pressure  drops,  it  is  necessary  to  correct
for differences in the gas flow rates.   The equation  shown  below  can  be  used
to make this correction.   This is intended only  as a  rough  approximation and
is based on the fact that pressure drop is related to the square  of the  gas
flow rate.  Production data can sometimes  be used  as  a rough indicator of  the
gas flow rate.
                AP   =   AP
                      Where:  AP
                                    Corrected Pressure Drop
                                    Observed Pressure Drop
                                    Baseline Gas Flow Rate
                                    Present Gas Flow Rate
SLIDE 5-17
Source:  Air Pollution
         Training Institute
                                       A radial vane type demister is shown
                                       here.   There are curved baffle vanes
                                       which  are attached to the hub and to
                                       the outer spool.  As the gas stream
                                       passes around the curved vanes, it is
                                       accelerated and spun.  Droplets impact
                                       the wall of the scrubber vessel due to
                                       centrifugal force.  The accumulated
                                       liquid is continuously drained from the
                                       annular area between the scrubber wall
                                       and the radial vane demister.

                                       For adequate performance, it is import-
                                       ant that there is some clearance above
                                       the demister for the spinning gas
                                       stream.  A minimum clearance of one-half
                                       the scrubber diameter is necessary to
                                       complete droplet removal.
     As with any demister, solids accumulation must be removed frequently.
This can be done with sprays either above or below the demister.  It is also
necessary to keep the drain line open.  It can plug at the entry point or at
the discharge point

SLIDE 5-18
                                       This is  the  downstream side  of  a  radial
                                       vane demister.   Note  the  heavy  deposits
                                       on the blades and  the restricted  gas
                                       passages between the  blades.  A unit  in
                                       this condition  is  prone to reentrain-
                                       ment.  The solids  accumulated on  this
                                       demister primarily because it had to  be
                                       cleaned  manually and  this was done on a
                                       once per week basis.
SLIDE 5-19
            EVALUATION OF
During Level 3 inspections of the radial
vane demisters, the static pressure drop
should be checked.  Increases over base-
line levels (after correction for gas
flow rate changes) indicate the accumu-
lation of solids.   Any pressure drop in
excess of 2 inches W.C. is a possible
indication of pluggage.


           1. Liquor Turbidity
           2. Liquor pH
           3. Liquor Pressure
           4. Operating Frequency
           5. On-Time
SLIDE 5-20
                                       During all inspections  of  demisters,  the
                                       washing system layout and  operation
                                       should be checked.   Some of  the import-
                                       ant points are listed on this  slide.
                                       However, some of this operating data  is
                                       often unavailable.

                                       The cleaning system  must be  run often
                                       enough and at high enough  pressure to
                                       remove the solids which accumulate.  The
                                       nozzle type and spray angle  must ensure
                                       complete coverage of the demister.

                                       If possible, a sample of the liquid used
                                       as demister wash should be checked.
                                       This should be low in total  solids so
                                       that the wash water  does nbt contribute
                                       to a scaling and/or  pluggage condition.
                                       The pH should also not  be  so high that
                                       scaling is inevitable.

     In some scrubber systems, the demister wash system is  used as  the scrubber
system make-up water line.  This is a good practice since the  make-up water
supply is normally clean and close to a neutral pH.
SLIDE 5-21
  UoU. p^ta.
                                       Another factor of  importance  is the
                                       distance between the  top  stage  of the
                                       scrubber and the and  the  bottom of the
                                       demister (see distance  from #1  to #2).
                                       This is termed the "freeboard"  distance.

                                       The demister must  be  high enough above
                                       the last scrubber  tray  so that  it is
                                       not subject to the very high  liquor
                                       loadings close to  the trays (or beds).
                                       There must be a sufficient distance for
                                       large settleable drops  and liquid jets
                                       to fall back to the tray  without hit-
                                       ting the demister.

                                       Excessive freeboard distance  does not
                                       affect demister performance.  However,
                                       this does add to the  scrubber vessel
                                       height and cost.


        1. Wash Water Quality
        2. Cleaning Operating Times
        3. Liquid Pressures
        4. Static Pressure Drop
        5. Gas Flow Rate
                                      This is a brief summary  of  the  common
                                      inspection points for  suspected de-
                                      mister problems.  The  presence  of a
                                      water wash system and  the quality of
                                      wash water should be checked during all
                                      inspections.   The distance  of the de-
                                      mister from the top of active trays or
                                      beds should also be checked, especially
                                      when gas  velocities through the unit
                                      are high.

                                      On Level  3 inspections, the pressure
                                      drop should  be compared against the
                                      baseline  values.   Even slight shifts
                                      after  correction  for  gas flow changes
                                      indicates the onset of pluggage.  The
                                      ceiling value pressure drop's listed
                                      earlier should generally not be  ex-
                                       ceeded.   The gas flow rate  can be
                                       measured to determine if the capacity
                                       of the demister has been exceeded.

     On scrubber systems that are down,  an internal check should  be made  for
deposits on the demister and for the condition of the washing  system  spray
nozzles.  Under no circumstances should the inspector enter  the scrubber
vessel since there could be toxic gases trapped in portions  of the off-line
scrubber system.  It is also possible to  crush fragile chevron blades and
rotary spin vanes which are often made of plastic.
SLIDE 5-23
         1/2 Tube ,
 Source:  Shifftner
                                        When symptoms of demister problems are
                                        noted during Level 3 inspections, the
                                        probe shown in this sketch can help to
                                        determine the source of the liquor
                                        droplets observed.  This is a section
                                        of 1/2 inch O.B. copper tube with a
                                        slot cut out near the top.  The tube is
                                        sealed with an end cap and the other
                                        end includes fitting which reduce down
                                        to a nipple.  A flexible piece of
                                        tubing leads from the probe nipple down
                                        to a sample bottle.

                                        The probe is inserted into the stack to
                                        determine if there are droplets  in the
                                        gas stream.  Checks are  also made to
                                        determine if liquor is moving up or down
                                        the scrubber stack.

SLIDE 5-24
          A     A
The rate of liquor capture should be
noted when the probe is placed near the
center of the stack. Droplets in this
portion of the stack clearly indicate
that there is excessive liquid carry-
over from the scrubber vessel.  The
demister should be inspected in detail.

Anything that would contribute to drop-
let reentraimnent should be removed
from the stack and placed elsewhere in
the system, if possible.
SLIDE 5-25
                                       When the probe is placed in the
                                       position shown here, the presence of
                                       ascending wall flow can be determined.
                                       The liquor moving up the interior wall
                                       can be due to demister failure or
                                       simply to the condensation of water
                                       vapor in the cold stack.  The latter is
                                       possible when ambient temperatures are
                                       low.  Normally, the stack velocity must
                                       be more than 35 feet per second to push
                                       the liquor up the wall.

                                       This is one possible explanation for
                                       slight rainout conditions in the
                                       absence of any demister malfunctions.

SLIDE 5-26
                 PLUME OBSERVATIONS
                BYPASS_	T
                                                          PLUME OBSERVATIONS
                                                                * 1
                                                         COLD STACK
                                                               SJgg UME
     This flowchart shows the typical locations of pumps in a wet scrubber
system.  The recirculation pump is the one that most directly affects the
performance of the wet scrubber and is, therefore, the one of most interest to
control agency inspectors.  This pump must be capable of delivering the liquor
at the design flow rates and pressures at the inlet to the scrubber.  It
must be able to withstand the suspended solids and corrosive materials which
accumulate in the recirculation liquor.

     To maintain the suspended solids and corrosive materials at an acceptable
maximum concentration, some of the liquor is either purged from the system or
sent to a liquor treatment circuit.  This purge line pump handles only 5 to 20%
of the capacity of the recirculation pump.  However, it is subject to the same
liquor quality.   The make-up pump delivers relatively clean process water or
liquor to replace that lost due to evaporation, lost in the sludge removed, and
lost as stack reentrainment.  This pump usually has a capacity similar to the
purge pump.

     Other pumps are used for alkaline supply and for metering in additives
for foam suppression, odor control, surface tension control, and solids
settling.  Sludge pumps may be used under clarifers for removal of high solids
liquid streams.


SLIDE 5-27

           1. Continuous Delivery
             of Liquor at Desired
             Flow Rate

           2. Delivery of Liquor at
             Necessary Pressure
                                       A failure of any one of the main  pumps
                                       could result in temporary outage  of  the
                                       scrubber and the bypassing of  the ef-
                                       fluent gas stream.  The recirculation
                                       pumps and the purge line pumps are most
                                       susceptible to these sudden problems due
                                       to the characteristics of the  liquor
                                       often handled.  However, the loss of the
                                       alkaline supply pump or additive  supply
                                       pump could lead to serious corrosion
                                       conditions which demand immediate correc-
                                       tive actions.

     The recirculation pump operating data can provide a useful, indirect
measurement of the liquor flow rate.  Comparison of the discharge pressures and
pump motor currents with baseline values can indicate if the liquor flow rate
has probably increased or decreased significantly since the baseline  period.
The pump discharge pressure and the general operating conditions can  help
determine if the pump is the cause for decreases in either the liquor flow
rates or the pressures at the scrubber inlet.
          1. Centrifugal
          2. Positive Displacement
          3. Progressing Cavity
SLIDE 5-28
                                       There are numerous  pump  designs.   How-
                                       ever, for wet  scrubber applications  the
                                       pump types listed in  this  slide are  the
                                       most common.   The centrifugal  pumps  are
                                       used most frequently  for liquor recir-
                                       culation and liquor purge  since they can
                                       handle large quantities  of liquor  which
                                       are abrasive and corrosive.  The centrif-
                                       ugal pumps usually  operate at  400  to 900
                                       rpm and deliver liquor at  40 to 200  psig.
                                       These are relatively  modest demands  com-
                                       pared to the requirements  for  centrifugal
                                       pumps in other applications.

     The types of centrifugal pumps can be further divided into a number  of
individual categories which are primarily based on the pump  impeller  design.
These different types are discussed in more detail in later  slides.

     The diaphragm pump is a type of positive displacement pump (one  of the
major categories of pumps) which is used almost exclusively  for the movement
of very high solids content slurries.  These are most common on the clarifier
and thickener underflows.  The progressing cavity pumps are  useful  for the
movement of high solids, large suspended particles and/or  potentially clogging
type solids.

SLIDE 5-29
                       Radial force
    Source: Chemical Engineering
           June, 1972
The radial flow centrifugal  pump  is the
most common type of pump used  for wet
scrubbers.  The liquor enters  the pump
axially and is accelerated by  the
rotating impeller.   The flow from the
impeller into the casing area  is  radial
with respect to the impeller.

As the liquor leaves the impeller, it
decelerates somewhat which results in
the conversion of some of the  velocity
head to pressure head.   The  general
relationship between the two is pro-
vided in the equation below:
      => x (GH)
Velocity,  V,is in  feet per second, G
gravitation acceleration in feet per
second squared,  and  pressure head, H,
in feet.
SLIDE 5-30
                                      The centrifugal pumps can either be
                                      oriented  in  the vertical or horizonal
                                      directions.  The most common is the
                                      horizontal arrangement shown in the top
                                      portion of the slide.

                                      A vertical arrangement is useful to
                                      obtain greater suction head (a very
                                      important operating requirement to be
                                      discussed later) and to minimize the
                                      required  floor space.

                                      The pump  body configurations in the
                                      vertical  and horizontal orientations
                                      are somewhat different.  However, the
                                      differences do not change the way in
                                      which  pump performance is analyzed, and
                                      it does not significantly change the
                                      types  of  problems which are most

SLIDE 5-31                             The components  of  a  pumping  system  in-
                                       clude  the  suction  pipe,  strainer,
                                       suction side check valve (termed foot
                                       valve  in slide), discharge check valve,
                                       and discharge valve.   The latter is
                                       termed a gate valve  (a specific type of
                                       control valve).  Not all of  these are
                                       necessary  for each system.

                                       The strainer removes tramp iron and
                                       large  particulate  which would damage
                                       the pump impeller  and/or liner.  The
                                       strainer is usually  used on  all new
                                       systems but is  sometimes removed when
                                       there  is a tendency  for the  liquor  to
                                       blind  the  strainer.   This would cause
                                       serious pump damage.

     The foot valve (or check valve) prevents air infiltration into the suction
side of the pump during outages.  If air enters the pump  it must be primed and
there is a risk of cavitation (a serious operating problem).  The eccentric
reducer on the suction line allows connection of  the suction line to the pump
flange without the creation of air pockets which  can also cause cavitation
under some operating conditions.  The suction line is  angled downward to also
prevent air pockets.

     The flow of liquid out of the pump is controlled  by  the discharge line
valve.  This is normally a gate valve (valve  designs are  discussed  in a later
part of the lecture).  Although not shown, there  is often a discharge line
pressure gauge on the line before the discharge valve.
SLIDE 5-32
       (il ara IWELUBS
                                       Several examples of the large number  of
                                       available impeller designs are shown  in
                                       this slide.   The open and semi-open
                                       impellers are often used on heavy
                                       slurries and other abrasive liquors.
                                       The nonclogging impeller is useful  for
                                       heavy slurries including stringy

                                       The closed impeller design is suitable
                                       for relatively clean liquors with
                                       little or no solids.  This design
                                       provides higher efficiency.
     The quantity of liquor and the pressure of  the liquor  supplied  by  the
pump depend on the impeller configuration and the  impeller   iameter.  When
impellers are replaced,  identical units should be  reinstalled.   The  use of
smaller diameter impellers with or without the identical  configuration  can
result in less than the  desired pump performance.

SLIDE 5-33



fcj  40

LL!  20


g  80

           200  400   600   800  1000
          200  400  600   800
           CAPACITY, GPM*-
           The characteristic curve of a centri-
           fugal pump is shown.  As the quantity
           of liquid delivered increases, the head
           developed decreases slightly.

           The position and shape of this curve is
           determined by a number of design
           factorsincluding: (1) impeller shape,
           (2) impeller diameter, (3) casing
           shape, and (4) pump rotational speed.

           Under normal conditions, the pump will
           perform on this curve at a position
           determined by the piping system re-
           sistance.  However, problems such as
           cavitation and impeller wear can cause
           reductions in both flow rate and head.
     Field inspectors and maintanence personnel will rarely have these curves
for use in evaluating pump performance.  The curves are used simply to
illustrate the meanings of the pump instrumentation such as the discharge
pressure gauge and the pump motor ammeter.
SLIDE 5-34


u  140
o"  120

           200  400  600   800   1000
                                       The  system resistance curve is shown in
                                       this graph along with the pump curve
                                       introduced in the previous slide.  At
                                       the  origin,  the system resistance is
                                       equal to  the discharge head, which is
                                       equivalent to the vertical distance that
                                       the  liquor is being lifted.  The system
                                       resistance increases with the square of
                                       the  flow  rate due to frictional losses
                                       in the pipes and valves.

                                       The  system resistance curve is cal-
                                       culated for  a new system based on the
                                 IOOO  piping layout, liquor velocities and
                                       the  pipe  characteristics.  The intersec-
                                       tion of the  pump curve with the system
                                       curve defines the intended operating
                                       point (point A on this graph) of the
                                       overall system.

     Unfortunately,  several  factors  can lead to  a change in the position of
the system resistance curve.   Some designers may assume higher estimated
resistances than actually exist  in order to provide a "safety factor".  This
can lead to lower resistance than intended.   There  can also be pluggage of
control valves,  nozzles and  piping which leads to higher resistance than
desired.  In either  case, the pump selected may  not be appropriate for the
actual conditions which exist.
           200  400  600
              CAPACITY, GPM

SLIDE 5-35
              ZOO 4OO 60O 80O  K5OO
       u 160
       o 140
       u 120



         Hp =
              200  4OO 60O  800 IOOO

                 CAPACITY. 6PM 
                   x V x C x P.F.
The brake horsepower curve is now added
to the pump and system curves discussed
in the last two slides.  The horsepower
rises as the quantity of liquor pumped

The brake horsepower is the total
energy being used by the pump motor.
It includes the energy imparted to  the
liquid stream and the portion of the
energy which is wasted and dissipated
as heat in the pump motor.  It is
related to the motor current by the
relationship shown in the equation
                     Hp = Total Horsepower
                      V = Volts, A.C.
                      C = Current, A.C.
                    P.F.= Power Factor, dimensionless

     While there is obviously a direct proportionality between the motor
current and the horsepower, it is not possible to calculate the present horse-
power from the motor current and operating voltages.  The power factor is not
generally known, is not generally constant, and is difficult to measure.  For
this reason, it is not possible to use a pump curve to calculate the  flow rate
from the motor currents and voltages.  Variable liquor characteristics and
pump impeller wear also make this impossible.  However, a decrease in the motor
current usually means that the liquor flow rate has decreased from baseline

    The total pressure head (see vertical axis) is the total of the liquor
velocity pressure  and the absolute liquid pressure.  These two components of
the total pressure head are convertible from one form to the other and are
related by the equation shown below.  Application of this equation for typical
pipe velocities will illustrate that the velocity head is much smaller than
the absolute pressure component.

                     x G x H

           Where:  V = velocity of liquor in feet per second
                   G = gravitational acceleration, in feet per second squared
                   H = liquid pressure, in feet

     While the measured pressure will depend on the velocity of the liquor at
the point of measurement, the discharge pressure does provide a general
indicator of the overall pressure head being supplied by the pump.  Many pump
operating problems result in a significant reduction in the pressure  head.

     One complicating factor in the use of the discharge pressure, is the
pluggage of downstream valves and nozzles.  This can increase the measured
discharge pressure slightly, while reducing the flow.

SLIDE 5-36
                                       There are many common operating problems
                                       of wet scrubber system pumps.  Most of
                                       these have a direct impact on the per-

    PUMP OPERATING PROBLEMS     quantity" of
                                       pressure of the liquor.

                                       In the slides that follow, some of the
                                       possible reasons for these problems will
                                       be presented to help inspectors determine
                                       if the corrective actions planned have a
                                       reasonable chance of success.  However,
                                       it is usually not possible for an
                                       inspector to determine the exact cause
                                       of the problem

     There are more than 90 commonly reported causes of pump failure due to
both mechanical and hydraulic factors.  Some of these can be identified by
observing pump operation and some can be identified when the pump is torn down
for maintenance.  The reasons for repeat failures of certain components,
however, can be a complicated issue best left to pump specialists.

     The inspector's role is to confirm: (1) that the operators are aware of
a change in pump performance which may be an emerging scrubber problem, that
(2) the operator's corrective actions will probably prevent or minimize the
condition, and that (3) the operator is not tolerating frequent pump problems
without attacking the fundamental cause(s).
SLIDE 5-37
                                       The lack of liquor flow can be due to a
                                       number of pump problems, all major.
                                       Most of these listed on the slide result
      LOW LIQUOR FLOW RATE       in burnout of the PumP motor-

     1. CAVITATION                        Other possible causes for the lack of
     a PLUGGEDPSTE^.NER                   lic*uor flow include a closed discharge
     4. IMPELLER EROSION                   line valve and pluggage along the
     s: PLUGGED PIPES OR NOZZLES            discharge line and/or nozzles.
     7. SOLIDS ACCUMULATION IN CASING         j^ SQUrce of the problem can rapidly
                                       be identified by checking the pump
                                       operation.  If the drive shaft is still
                                       spinning, the problem is in the
                                       discharge valve or piping.  The  pump
                                       should be shut down immediately.

     If the shaft is not spinning, the pump is either already shut off  or has
bound up.  Before starting up the pump again or starting up a spare pump, the
condition of  the nozzles and other potential areas for line pluggage should be
checked.  Loads placed  on the pump by the piping should also be visually


                                       One cause of the no flow condition is
                                       the freezing of exposed piping from the
                                       pump discharge to the top portion of
                                       the scrubber vessel.   Ways to minimize
                                       line freezing include:

                                           1.   Maintaining flow through lines
                                               even when scrubber is down.

                                           2.   Insulating lines.

                                           3.   Draining and flushing lines
                                               during outages.

                                           4.   Placing pumps in heated and/or
                                               sheltered pump house

     The last two steps are common during operation in cold climates.  Main-
taining flow during all periods can also help  prevent the settling of solids
in the piping.  Insulation of lines will be of help for short periods but will
not prevent freezing when systems are shut down for weekends or other extended
SLIDE 5-39
                                       This is a view of a recirculation pump
                                       within the pump house.   The heated area
                                       protects the pump from freezing
                                       conditions during extreme weather and
                                       during outages.

                                       The suction line of a pump must be kept
                                       full of liquid so that the pump will
                                       not cavitate (problem defined in a
                                       later slide) during start-up.  Since
                                       the line can not be drained,  the pump
                                       must be kept in a heated area.

                                       Freezing of the seal water line or the
                                       packing material could also lead to
                                       pump damage.


SLIDE 5-40
                                       Impeller wear and damage can be caused
                                       by the problems listed in this slide.
                                       Corrosion occurs when the liquor com-
                                       position and/or pH is not compatible
                                       with the impeller materials of con-
                                       struction.  The pH measurement provides
                                       one indication of impending corrosion
                                       problems.  The condition of the casing
                                       can also provide some warning.

                                       Cavitation conditions usually result in
                                       pump vibration and high noise levels.
                                       Rapid corrective action is necessary in
                                       this case.

                                       Abrasion occurs due to high suspended
                                       solids levels and large particle sizes
                                       of the suspended materials.  Low pump
                                       speeds can minimize this problem.

     The consequences of impeller wear include reduced liquor flow rate and
reduced discharge line pressures.  The pressure gauge will provide one
indication of this problem. However, there are a number of conditions which
can reduce the pressures.
SLIDE 5-41
                         Impeller Vane
                      Shaft with
                      Key Insert
      Source: Plant Engineering
              October 3, 1974
                                       Cavitation is a serious  operating
                                       problem which occurs when  a  portion of
                                       the liquor being handled in  the  pump
                                       vaporizes while passing  over the
                                       impeller blades.  This slide illus-
                                       trates the location of the bubble
                                       formation on the impeller  surfaces.

                                       As the liquor proceeds outward,  the
                                       pressures increase and the bubble
                                       implodes.  The energy released during
                                       this action can destroy  protective
                                       liners on the impeller and can even
                                       remove metal from the impeller itself.
                                       The imploding bubbles also result in
                                       noise and pump vibration.
     Due to the rapid damage to the impeller and the casing liners  (if
present), cavitating pumps should be shut down as soon as possible.   The
source of the cavitation should be corrected before returning the pump  to
service.  Some of the most common causes of this condition include,  air
infiltration, inadequate net positive suction head, and gas pockets  in  the
suction line.  These problems are discussed in the next set of  slides.

 SLIDE 5-42
 (NPSH)a  =  (H - Pv)/    - hf - he
  H  =  Absolute  suction  pressure
        at  the  pump  inlet
Pv  =  Vapor pressure of the liquid
        at  the  given temperature
  8  =  Specific  weight of liquor
hf  =  Frictional lossed in  suction
he  =  Entry losses
           The  available  net  positive suction head
           is the  difference  between the existing
           absolute  suction head  and the vapor
           pressure  of  the liquor at the operating
           temperature  of the pump.   This is a
           characteristic of  the  system in that it
           is determined  by:  (1)  the liquor com-
           position,  (2)  the  elevation of the
           suction point  relative to the pump,  and
           (3)  the frictional losses in the suction
           line.  The procedure for  calculating the
           available net  positive suction head
           (NSPH)a is shown in the equation.
     It is apparent that the available  net  positive  suction head depends on the
elevation of the reservoir supplying  the  pump  (or  the depth of the suction line
in a pond).  Another important factor is  the flow  rate of the liquor since this
determines the magnitudes of both the frictional losses and the suction pipe
entry losses.

     The required net positive suction  head is a function of both the pump
design and the liquor flow rate.  It  must be specified by the manufacturer of
the pump.  Selecting the appropriate  pump for the  system available net
positive suction head is the responsibility of the system operator.

     Inadequate net positive suction  head is reported to be one of the most
common reasons for inadequate pump performance.
SLIDE 5-43
     , zoo

     !r I8
     w 160
     o I4O
     u 120
           200  400 coo aoo  1000
  yj Ul C
The net positive suction head required
for a given pump, along with the  system
resistance curve and the pump character-
istic curve are shown in this slide.

This data is always presented for liquid
liquid at standard temperatures and
specific weights.  It should be corrected
for temperature and solids content for
the actual system before the pump is
           20O  400 60O  800 IOOC

              CAPACITY. 6PM
            Plant Engineering
            August 8, 1974

SLIDE 5-44

         INTAKE PIPE
If the pump is subject to cavitation,
problems, one or more of the  following
steps could be taken to prevent  the

Raising the height of the recirculation
tank and/or the scrubber sump is often
uneconomical.  Lowering the intake
point of the suction line is  more
practical.  Converting to a vertical
pump can also be done with a  minimum of
system modification.

Operation at lower flows can  have some
beneficial impact for the pump,  but
adversely affect scrubber operation.
Also, the required net positive  suction
head increases slightly at very  low
flows, as indicated on the earlier slide.
SLIDE 5-45
Another source of  cavitation is the
presense of gas  pockets  in the suction
line of the pump.   Three ways to avoid
gas pockets are  shown  in the slides
which follow.

The suction pipe leading to the pump
slopes upward a  minimum  of 1 so that
gas pockets can  not occur in a high
point of this piping.
Source:  Machine  Design
         May  8, 1980

SLIDE 5-46
 Bleed valve permits
  air removal
Hole allows air to escape
 from pump casing
                          -Tongue blocks air escape
                           through discharge port
The volute casing  of the pump  may
accumulate some air  at a high  point of
the casing behind  the tongue.   A vent
at this  point allows bleeding  off of
any air  trapped in this area during
start-up of the pump.
Source:   Machine  Design
          May 8, 1980
SLIDE 5-47
        Trapped  Standard
          Straight section
          realigns flow-j
  Eccentric Reducerj   f
Eccentric reducers should  be used to
connect the suction line to  the pump
itself.  In this  way, gas  pockets can
not  develop.

Any  flange gaskets should  be cut with
an oversize opening so that  a portion
of the flange does not extend into the
liquid stream as  shown.
Source:   Machine  Design
          May 8, 1980

SLIDE 5-48
A foot valve is advisable when the
suction line is drawing liquor up out
of a tank or pond.  This acts as a float
type check valve which closes off the
suction line if the liquid level drops.

This type of check valve is not necessary
when there is a flooded suction line.
Systems in which the pump pulls from the
scrubber sump generally have flooded
suction.  It is important to fill the
sump (necessary as a water seal anyway)
before starting the pump.
Source:  Plant Engineering
         July 6, 1978
SLIDE 5-49
         PUMf INTAKE
When the pump pulls from a tank, it is
important to place the intake line(s) at
the proper position to avoid vortices.
Air can be drawn into the line  if  the
pick up point is too close to these vor-

There are published guidelines .on  the
minimum depth of the suction line  for
the size of the suction pipes.  Also,
information is available to design the
tank to prevent air pick-up.

SLIDE 5-50

                                       Typical materials used in pumps are
                                       listed here.   The carbon steels are
                                       adequate for  general service.  However,
                                       life will be  very limited when the pH
                                       is below 6 and/or there is high solids

                                       The stainless steels provide greater
                                       corrosion resistance except for liquors
                                       having high chloride and fluoride levels
                                       When the concentrations of the halogen
                                       materials exceeds 500 ppm, pitting of
                                       the stainless is rapid.

     The nickel alloys provide generally excellent corrosion resistance, but
at a substantial cost penalty.  These materials also have moderate to
excellent abrasion resistance.
SLIDE 5-51
                                       This is a summary of the inspection
                                       points for recirculation pumps of wet
             SUMMARY                scrubber systems.
        PUMP EVALUATION           -   ..   .                   ..
                                       The discharge pressure provides a
                                       useful index of the flow rate.  An
                                       increase from the baseline level
                                       generally means a decrease in the
                                       liquor flow rate.

     An increase in the pump motor current is another flow indicator.  As it
increases, the flow increases unless the viscosity has changed dramatically
(which is unlikely in most air pollution control systems).  A major increase
in the solids content can also affect the pump currents.

     An increase in the pump noise and/or vibration is a possible indication
of cavitation.  This is often accompanied by a decrease (possibly slight) in
the discharge pressure and a decrease in the liquor flow.  Whenever cavitation
is suspected, the suction line should be examined carefully for sites of gas
pockets, sites of air infiltration, the elevation of the suction line intake,
and the configuration of the intake.

     For pumps using water seals, there should be a small quantity of seal
water continually draining from the stuffing box.  The lack of visible drain-
age is a sign of inadequate seal water supply and this can lead to premature
failure of bearings and corrosion of the shaft.

     Another factor which should be checked is possible pump misalignment
conditions due to forces imposed on the pump by the discharge piping.  The
provisions for flushing out any pumps handling slurries (total solids contents
greater than 3% by weight) during outages and the provisions to prevent
freezing during system outages should be checked.


SLIDE 5-52
        AND FiriNG SYSTEMS
The objectives of this section include:
(1) the evaluation of liquor flow rates
in systems without flow monitors,  and
(2) the evaluation of operation and
maintenance problems due to piping and
valve related conditions.

The principal problems associated with
the piping included pluggage or erosion
in systems handling slurries.  Improper
piping supports can place undesirable
loads on the pump and the nozzle
headers.  If the piping system is not
designed properly, it is difficult to
flush out settled material, it is
difficult to drain lines during cold
period outages, and it is difficult to
replace worn or corroded segments.
SLIDE 5-53

                                       In order to make a rough estimate of
                                       the flow in a pipe, it is necessary to
                                       know the pipe dimensions.  The pipe
      1 ~ I PS - 40 ~ CS                 sizes are often specified as shown in
                                       the example on the slide.

                                       The first number is the nominal pipe
                                       size.  This may be followed by an
                                       alphabetic code which denotes the type
                                       of pipe, such as IPS for standard pipe.
                                       The next code specifices the schedule
                                       which is an indication of the pipe's
                                       ability to withstand internal pressures
                                       The letter directly following the
                                       schedule codes represents the types of
                                       materials used for the pipe.  Any letters
                                       following the hyphen present information
                                       concerning liners or other special
                                       design requirements.

     If  it is impossible to get the piping data from drawings or other plant
records, the dimensions should be measured.  Either the outside diamter
(termed  the O.D.) or the pipe circumference should be measured.  These values
can then be used with standard pipe dimension tables and flow rate guidelines
to estimate the flow rate.

SLIDE 5-54
              PIPE SIZES
  Nominal Sin







This slide presents the  pipe  inside and
outside diameters for certain common
nominal pipe sizes.  It  should be re-
membered that the nominal  diameters used
in standard piping handbooks  (and est-
ablished in ASTM standards) do not
exactly match the measured diameter.

The table value is actually closer to
the inside pipe diameter (termed the
I.D.) for most of the pipes.   In the
case of very small pipes,  there are
substantial differences  between the
nominal value and both the inside and
outside diameters.
     This data has been  excerpted  from tables applicable to steel pipes.  The
values are different for each  major  class of pipe including polyvinyl chloride
pipe (PVC), iron pipe, fiberglass  reinforced plastic (FRP), and copper pipe.
SLIDE 5-55
     SCH.  No. =  1OOO P/S

        P =  Pressure, Ibf/in2
        S =  Allowable
             Stress, Ibf /in2
                           The next  task  is to estimate the pipe
                           inside area which is related to the
                           pipe  schedule.   The schedule number
                           represents the  ability of the pipe to
                           withstand the  actual internal pressures
                           It is approximated by the equation
                           shown here.

                           As the schedule number goes up, the
                           pipe  can  take  higher pressures.

                           The most  common schedule pipe used in
                           wet scrubber systems is the schedule 40
                           which is  approximately equivalent  to
                           pipe  which was  characterized as "stan-
                           dard  strength"  before the schedule
                           designation was common.  If no other
                           information is  available, it should be
                           assumed that the pipe of interest is a
                           schedule  40.
     Other typical pipes  include schedule 80 and 160.  There are schedule
numbers ranging from 5 to 160.   The wall thickness increases as the schedule
number increases.

SLIDE 5-56                             Once the pipe inside  dimensions are
                                       identified in the  applicable table, it
                                       is necessary only  to  use a  standard
                                       pipe velocity factor  to  calculate the
      TYPICAL LIQUID VELOCITIES        flow rate.  Unfortunately,  there is a
               IN PIPES                 substantial range  in  the design flow
  Type of Liquid            Average Velocities    rates based Partially on. engineering
                       (Feet Per Second)    perogatives and  partially on the
  _.  ...                       f        characteristics  of the materials.
  Clear Water                 8 to 15
  Light Slurries                6 to 12
  Heavy Slurries                5 to  8        A range of typical values for pipes
                                       handling water,  light slurries and
                                       heavy slurries are shown in this
                                       figure.  Note that flow  rates in the
                                       suction lines of pumps are  consid-
                                       erably lower than  those  specified in
                                       the slide.  Also,  lines  with only
                                       gravity flow are much lower.

     For a pipe with a nominal size of 2 inches (circumference  7 and three
quarters inches), the capacity at  an assumed rate of 5  feet  per second would
be 52.25 gallons per minute.   At an assumed rate of 15  feet  per minute, the
capacity would be 156.75 gallons per minute.

     High liquor velocities can be used whenever there  are no abrasive mater-
ials in the stream which would erode the piping and/or  pipe  liners.  Low
liquor velocities are used for slurries.  However, they must not be so low
that settling of the liquor is facilitated.

     Once a pipe is installed, the actual inside dimensions  may vary from
those specified in the table.  Erosion will result in some enlargement of the
pipe while settling can reduce the area open for flow.  Nevertheless, use of
this approach allows calculation of "ballpark" liquor flows  and thereby aids
in the  evaluation of the overall system conditions.

SLIDE 5-57

        REDUCING PIPE EROSION        Possible ways to minimize pipe erosion
    1. REDUCE SUSPENDED SOLIDS LEVELS        are listed on this slide.  By far the
    2. INCREASE TURN RADII                  most effective is  to  reduce the sus-
    3. DECREASE LIQUOR VELOCITIES            pended solids level and  solids particle

    I'. S^SaiSSKooNCEMmATioN     sizes ^rou8h P** S-eatment <* the
    6. INCREASE PIPE WALL THICKNESS          recirculation liquor. This has other
    7. INSTALL WEAR PLATES ON ELBOWS        obvious benefits for  the pump and

     The liquor velocities can be  decreased by use of a slightly larger pipe
size.   Evaluation of the tables presented in the Appendix will  demonstrate
that major reductions in the velocity will occur by increasing  the pipe dia-
meter by 1 inch.

     A  higher schedule pipe can be used to increase the time necessary before
replacement of pipe  segments.  This simply provides more  metal  to  be lost
before  the pipe  is seriously weakened.



SLIDE 5-58
                                       Pluggage is also best reduced by
                                       lowering the suspended solids content
                                       of the liquor.  This is accomplished
                                       by (1) increasing the purge rate,
                                       (2) improving solids settling and/or
                                       filtering, and (3) decreasing the liquor
                                       pK.  The latter would reduce the quan-
                                       tity of calcium and magnesium compounds
                                       which are precipitating from solution.

                                       The pipe sizes should be selected to
                                       provide sufficient velocity to con-
                                       tinually cleanse the pipes.  If this is
                                       not possible due to erosion conditions,
                                       then provisions for routine clean-out
                                       should be included.

     The lines are flushed by connecting a clean water source to Tee fittings
located at every major turn of the piping.  All the piping should be sloped
slightly downward and have drains at low points so that the solids can be
easily removed.  The sloped pipe with drain connections also aids in draining
the system during cold weather periods to avoid freezing.

     Piping systems with chronic problems should have flanged pipe connections
so it is possible to easily remove and clean out a section.   This also helps
when replacing worn or corroded piping.
SLIDE 5-59

                                       The piping system should be rigidly
                                       supported so that loads are not
                                       transmitted to either the pump or the
                                       scrubber.  The vertical pipe run
                                       illustrated in this slide needs a pipe
                                       support either at the base or a hanger
                                       near the top to carry the load.  It
                                       should be remembered that the weight
                                       consists of both the pipe and the
                                       liquor within - and this can be con-
                                       siderable.  For a 50 foot vertical run
                                       of 4 inch Schedule 40 steel pipe, the
                                       contained liquor weighs approximately
                                       275 pounds and the pipe itself weighs
                                       540 pounds.

     The weight of the full pipe combined with normal vibration and shock can
cause misalignment of the pump and/or leakage at pipe fittings and flanges.

SLIDE 5-60
     Sagging Pipe
The weight of the pipe can cause
sagging in long unsupported horizontal
runs.  As shown in this sketch, the
sagging places undesirable loads on the
pipe fitting at each end.  It also
allows a low spot in the line which
complicates draining of the line for
freeze protection and the removal of
solids during flushing.

Pipe supports should be provided at
regular intervals to reduce deflections
and the line should be intentionally
sloped to facilitate drainage.
SLIDE 5-61
                                       Bleed valves should be placed at points
                                       of the line where air is likely to
                                       accumuluate.  This slide shows a pipe
                                       leading to a header around the scrubber
                                       throat.  The high point next to the
                                       shut-off valve is one common point of
                                       air accumulation.

                                       Another common area of accumulation is
                                       the nozzle header itself.  The nozzles
                                       should be oriented at a point which has
                                       a lower elevation than the top portion
                                       of the header.

                                       While the air will often be carried away
                                       harmlessly, it could damage the control
                                       valve and the nozzles.  It should be
                                       bleed off after start-up of the scrubber

SLIDE 5-62

             1. GATE
             2. GLOBE
             3. CHECK
             4. BALL
There are a number of valve designs,
each having different applications and
service limits.  The major categories
are listed on the adjacent slide.

The main considerations are the
usefulness for shut-off service versus
the usefulness for flow control.  Also,
the vulnerability of the materials with
respect to slurry abrasion and pluggage
and with respect to corrosion must be
considered when selecting valves.

The next set of slides presents the
basic design features plus the
advantages and disadvantages of each
type.  The drawings presented will
demonstrate that many of these appear
similar from an external view.
SLIDE 5-63
                                       A globe valve is shown in this slide.
                                       All globe valves have a disc or plug on
                                       the valve stem which rests against a
                                       metallic seat to provide the seal.  The
                                       name for these valves was derived from
                                       an earlier design which used a globe on
                                       the valve stem rather than the disc or
                                       plugs now common.

                                       All of these have high pressure drop due
                                       to contorted path through the valve.
                                       These are used for both throttling and
     Due to the partition in the lower half of the valve body, this type of
valve impedes line drainage.  Also, solids can accumulate on the metallic seat
and prevent an adequate seal.  These valves are rarely used on slurry carrying

Source:  Air Pollution
         Training Institute
The gate valve shown here is intended
for shut-off service rather than flow
control.  While it is theoretically
possible to control flow with this
design, the high liquor velocities at
the bottom of the disc would cause

Since the disc on the valve stem moves
entirely out of the path of the liquid,
there is very low pressure drop through
the valve.

Deposition of solids within the valve
body could prevent closure of the valve
Therefore, this style is not used for
heavy slurries.

Due to the straight through flow
conditions of a gate valve, there is no
restriction to drainage of the line.
This also minimizes the accumulation of
solids within the valve.
     The quick closing action of gate valves can cause water hammer down the
piping system.  This can damage both the pipe connections and the pump.
SLIDE 5-65
                                       A ball valve is shown in this slide.
                                       The control element is a ball having a
                                       large open area.  When closed, the flow
                                       passage is oriented normal to the pipe
                                       direction and the ball is pressed against
                                       plastic xseat rings.  These valves are used
                                       both shut-off and throttling.
Source:  Air Pollution
         Training Institute

SLIDE 5-66
          VALVES '
Source:  Air Pollution
         Training Institute
                                     Swing check valve  are  designed to prevent
                                     flow of liquid  in  a  reverse direction.
                                     These may be used  to prevent the drainage
                                     of liquid down  out of  an  elevated pipe
                                     back through the pump.

                                     Modest liquid pressure in the forward
                                     direction easily opens the valve.  The
                                     pressure drop to flow  in  the forward
                                     direction is very  low  since there is no
                                     flow obstacle.

                                     Under no flow conditions, the force of
                                     gravity causes  the valve  element to drop
                                     into the closed position. The flow of
                                     liquid in a reverse  direction forces the
                                     valve element against  a seal and thereby
                                     prevents leakage.

                                     These valves must  be installed in a
                                     horizontal position  to allow for the
                                     movement of the check  valve element.
 SLIDE 5-67
           EVALUATION OF
           SPRAY NOZZLES
                                      Nozzles disperse a liquor stream into  a
                                      gas stream.  The important factors  to  be
                                      considered when selecting a nozzle  type

                                          1. Droplet Size Distribution

                                          2. Spray Angle

                                          3. Spray Pattern

                                          4. Droplet Initial Velocity

                                      There are a large number of nozzle
                                      designs to provide different spraying

     Improper nozzle  selection can prevent adequate performance of a wet
scrubber system due both  to poor liquor-gas contact and to weak particle
capture conditions.   Nozzles are also subject to operating problems due to
high liquor velocities.   Liquors with high suspended solids levels can  erode
critical nozzle components and can plug the nozzles.  There are substantial
differences with respect  to the abilities to handle erosive and corrosive



              1. PRESSURE
             2. TWO FLUID
             3. ROTARY
SLIDE 5-68
                                       The are three main categories  of  spray
                                       nozzles.   Most nozzles are  the pressure
                                       type in which the energy is supplied  by
                                       the pressure of the liquid  stream.  There
                                       is limited use of the two fluid nozzles.
                                       These are only used when very  small
                                       liquid droplets are necessary. In  two
                                       fluid nozzles, the energy for  atomization
                                       and dispersion is primarily supplied  by
                                       an air or steam line under  high pressure.
                                       The rotary nozzles are not  used for air
                                       pollution control applications.

     The pressure nozzles can be further subdivided into the full  cone,  hollow
cone, fan, and jet type units.  The jet nozzles are used for surfaces cleaning
and other applications where the energy of droplet impact can be used.  The
other three types are all used extensively in particulate and gaseous wet
scrubber systems.
SLIDE 5-69
                                       The spray pattern  for  the full  cone
                                       type of pressure nozzles is  shown in
                                       this slide.

                                       The full cone spray has relatively even
                                       distribution of drops  across the entire
                                       circular cross section of the spray.  In
                                       some nozzles types, there can be a small
                                       center area  which  is dry. Nozzles are
                                       available which develop either  the
                                       circular or  square patterns.

                                       The uniformity of  the  distribution is
                                       affected by  extremes in the  liquid
                                       pressure. Under very  low pressures, the
                                       cone can deteoriate to a weak "jet"
                                       which resembles a  household  kitchen

     The spray angles usually range from 30 to 90.  Typical operating
pressures range from 20 psig to 120 psig in air pollution control systems.

SLIDE 5-70
                                       This is a typical hollow cone spray.
                                       As the name implies,  the droplets are
                                       released in a narrow  band.   On a cross
                                       section, the liquor appears as an outer
                                       ring around a dry circular  area inside.

                                       This type of nozzle operates with design
                                       spray angles from 30 to 90 and these
                                       angles are relatively constant under
                                       differing liquor conditions.

                                       Operating pressures are similar to the
                                       full cone nozzles. However, the flow
                                       rates are often slightly smaller at a
                                       given pressure.
SLIDE 5-71
                                       Nozzles generating a jet type spray
                                       pattern are less common than the other
                                       two types of pressure nozzles.   These
                                       are used primarily to provide a screen
                                       of liquid droplets across an inlet duct
                                       to a control device.

                                       The spray forms a fan-like pattern. The
                                       spray angles range from almost  0(jet
                                       sprays) to up to 100.

                                       Due to this pattern, nozzles of this
                                       type are inappropriate for the  distri-
                                       bution of liquor across circular and
                                       rectangular areas.

SLIDE 5-72                             Several example full cone type pressure
                                       nozzles are shown in this slide.  The
                                       top nozzle includes an internal spinner
                                       vane for distribution of the liquor
                                       leaving the nozzle.  The lower unit is
                                       termed a "helix" nozzle.  The flow of
                                       liquid past the helix results in a
                                       modified full cone spray.  There is
                                       usually a small dry circular area in the
                                       middle of the spray pattern due to the
                                       nozzle tip.

                                       The nozzles with the internal spinner
                                       vanes are very difficult to rod out
                                       after they become plugged.  They must
                                       be removed for cleaning.  Care is
                                       necessary for the helix type nozzles
                                       when rodding out since it is possible
                                       to damage the metal tip.

     The droplet size distribution is normally finer for the spinner type full
cone nozzles.  They operate at higher liquid pressures than the helix nozzles.
These nozzles are usually not directly interchangable.

SLIDE 5-73                             The droplet size distribution is one of
                                       the more important characteristics of
                                       an operating nozzle.  Unfortunately, it
                                       is difficult to measure and difficult
                                       to even define droplet sizes.  The most
                                       common definition is the volume mean
                                       diameter which is simply the diameter
                                       in which 50% of the liquid collected is
                                       less than the specified value as shown
                                       on the following graph.

                                       Another common definition is the Sauter
                                       mean diameter whih is the droplet
                                       diameter having a volume-to-surface
                                       ratio equal to the overall droplet
                                       population.  This definition is used
                                       in most of the theoretical scrubber

     Other water droplet definitions include the surface median diameter and
the number median diameter.  The definition of "droplet size" must be specified
along with the value.

     The measurement of water droplet sizes is more difficult than solid
particulate since cascade impactor and diffusion battery techniques can not be
used.  Most of the data is based on photography and light scattering.  These
tests are expensive and can not be performed well under field conditions.
Therefore, little droplet size data is available.

    SLIDE 5-74




1    50
    10  20  50  100 200 500 1000   5000
             The general relationship between the
             nozzle operating pressure and the mass
             average droplet diameter (another term
             for the volume mean diameter) is shown
             in this figure.  As the pressure rises,
             the droplet size decreases.

             Since the majority of wet scrubber
             systems operate between 20 and 120 psig,
             it is apparent that the droplets are
             relatively large.  This can have some
             effect on the tendency to become
             reentrained and on the efficiency of
             collecting particles.
         The two fluid nozzles have droplet sizes below that shown for typical
    pressure nozzles.  Nevertheless, the spray droplets are usually above  25
    microns and usually in the range of 50 to 100 microns.  Generally, as  the
    capacity of a nozzle increases, the droplet sizes produced increases  (at
    constant pressures).
    SLIDE 5-75
                 DROPLET SIZE


                                           The physical characteristics of  the
                                           liquor have an influence on the  droplet
                                           sizes generated in the nozzle.   As the
                                           surface tension decreases, the droplet
                                           sizes also decrease.  A decrease in  the
                                           liquor viscosity has a similar effect.
                                           A decrease in the liquid density, which
                                           is related to the solids content, has
                                           an opposite effect in that the size
                                           range increases.
         The surface tension of scrubber liquor could be altered by the additon of
    either surfactants (reduction in surface tension) and of flocculants (increase
    in surface tension usually).  The liquid density is a function of the solids
    content of the recirculation liquor.  Changes in the liquor temperature and
    the solids content could influence the viscosity.  Because of these factors,
    it is unlikely that the droplet size distribution is constant in many wet
    scrubber systems.

    GPM2       VPSI2
SLIDE 5-76
                                       This equation shows the relationship
                                       between the nozzle liquor flow rate and
                                       various operating conditions.

                                       For a nozzle in good condition and
                                       handling liquor of consistent  surface
                                       tension and density, the flow  rate is
                                       related to the square root of  the
                                       nozzle manifold pressure.  A decrease
                                       in this pressure since the baseline
                                       period would supposedly provide an
                                       indicator of decreased liquor  flow.

     Unfortunately, the flow rate through the nozzle is also a function of the
liquor density.  Another complicating factor is that nozzle condition can rarely
be verified.  Pluggage of the nozzle will increase manifold pressure  while
decreasing flow.  Erosion of the nozzle orifice will decrease manifold pressure
while increasing flow.  The erosion and pluggage effect factors have  the
opposite effect on manifold pressure than normal changes in flow rate for a
nozzle in good condition.
SLIDE 5-77

          3. ORIFICE EROSION
          5. MISALIGNMENT
                                       This list includes the most common
                                       nozzle problems for wet scrubber systems.

                                       As a consequence of the nozzle problems,
                                       there can be: (1) inadequate gas-liquor
                                       contact, (2) low liquor flow rate, and
                                       (3) poor particle capture.  All of these
                                       can singly or collectively have a severe
                                       impact on the scrubber performance.

                                       The inspection steps outlined in the
                                       next set of slides will be helpful in
                                       identifying any problems that exist.

SLIDE 5-78
                                       Pluggage of nozzles can occur  due to
                                       high suspended solids levels in  the
                                       liquor and due to scale from ductwork
                                       and scrubber walls which is entrained in
                                       the liquor stream.  Nozzles with small
                                       orifices and internal spinner  vanes  are
                                       most susceptible.

                                       The nozzle shown in this slide is a
                                       typical full cone unit.  This  was taken
                                       from a unit in which pluggage  of all
                                       nozzles occurred on almost a daily
SLIDE 5-79
                                       When the nozzle begins to plug,  the
                                       spray angle is distorted.  Less  than
                                       adequate gas-liquor contact results
                                       for those units in which the main
                                       dispersion technique is the nozzle.

                                       After the nozzle is completely blocked,
                                       the liquor flow reaches zero for this

                                       Symptoms of nozzle pluggage include (1)
                                       high suspended solids levels, (2) high
                                       pH liquor, (3) increased nozzle  dis-
                                       charge pressures, and (4) increased
                                       effluent residual opacity.  If a number
                                       of the nozzles are plugged, the  liquor
                                       flow rate monitor may indicate reduced
                                       liquor flow.

SLIDF 5-80
                                       One means of reducing the severity of
                                       pluggage problems is to use a nozzle
                                       with manual or hydraulic rod-out
                                       capaability.  The nozzle shown in this
                                       slide is equipped with a small rod which
                                       can move through the nozzle orifice.
                                       Obviously, only nozzle types in which
                                       there is no spinner vane or distributor
                                       can have this type of rod-out apparatus.
                                       The whirl type hollow cone nozzles (which
                                       are inherently non-plugging) are the most
                                       appropriate nozzle type to be equipped
                                       with the mechanical rod-outs.

     .In order to use the mechanical rod-out, the nozzle must be mounted on the
wall of the scrubber.  This is often possible in the case of venturi scrubbers,
but is impractical for both the packed tower and tray-type scrubbers.

     The hydraulic rod out systems are composed of a clean liquor supply at
moderate to high pressures which is connected to the nozzle manifold through
an isolation valve.  On regular intervals, the high suspended solids liquor
flow is discontinued and the fresh water is briefly supplied to flush out both
the manifold and the nozzles.
SLIDE 5-81
              Y-TYPE STRAINER
Source:  Spraying Systems, Inc.
Another means of reducing pluggage is
to use strainers in the recirculation
line.  They can either be placed before
the recirculation pump or before entry
to the nozzle headers.  The latter is
shown in this figure.  For each header
at different elevations in the spray
tower scrubber, there should be a
strainer outside the scrubber shell.
This will prevent scale and other large
material from jamming in the small
passages of the nozzle.

The strainer is not effective for
solids which are precipitating out of
solution or other relatively small
particle size solids.

 Source: Spraying Systems Inc.
The strainer can itself be a source
of pluggage.  In fact, if it becomes
blinded, the entire nozzle header is
shut down.  For this reason, it is
important that the strainer be cleaned
en a frequent basis.

To prevent scrubber outages during
cleaning of strainers, a double arrange-
ment, as shown in this slide, can be
used.  One line at a time can be isolated
and the strainer cleaned  while flow
continues through the other.  There is
also a "double basket" unit which can be
shifted from one filter to the other
 without interruping flow.
     The strainer can also be placed before the recirculation pump.  In this
location, it also provides some protection against erosion of the pump impeller.
SLIDE 5-83

Erosion of nozzles is caused by the
mechanical action of suspended solids
passing through the nozzle orifice.  As
the nozzle wears, the spray angle
gradually decreases, thereby affecting
the effectiveness of gas-liquid contact.

One symptom of erosion is a decrease in
the nozzle manifold pressure from base-
line values.  This decrease is more
severe than the slight drop in the pump
discharge pressure which occurs at the
same time.

                                        A  sample  of  the  recirculation  liquor
                                        should  be obtained  in  a  transparent
                                        container as shown  in  this  slide.

                                        The  presence of  high suspended solids
                                        in itself can demonstrate the  potential
                                        for  nozzle erosion  (and  pump impeller
                                        erosion).  However, it is the  settling
                                        rate which is most  indicative  of this
                                        problem.   If the materials  settle
                                        rapidly,  the particle  sizes of this
                                        suspended material  are large.   It is
                                        this large material which has  the most
                                        erosive effect.

      The  pH of  the  sample should also be  measured since this  provides one
 indication of the corrosive nature of the liquor.   Obviously, a material which
 is  subject to corrosive attack will be  more vulnerable  to  erosive action as
 the surface layers  of metal become corroded.  If  nozzle wear  is severe and/or
 frequent, the sample of liquor should be  brought  back to the  lab for  both
 chloride  and fluoride analyses.

      Ways to minimize erosion are similar to those  for reducing plugging of
 nozzles.  These include reductions in the suspended  solids levels, the use of
 strainers before the pump or before each  nozzle header, and the use of the
 proper nozzles for  the service intended.
SLIDE 5-85
                                       To check for nozzle erosion and/or plug-
                                       gage in the absence of nozzle header
                                       pressure gauges (and pump discharge
                                       pressure gauges), it may be possible to
                                       observe the nozzle spray patterns.

                                       When the scrubber is OUT-OF-SERVICE AND
                                       HAS BEEN PURGED OUT, the hatch above
                                       the nozzles should be opened.  Once the
                                       main recirculation pump has been turned
                                       on, the conical spray patterns should
                                       be observed.  If there is damage, both
                                       full cone and hollow cone type nozzles
                                       exhibit a severely distorted pattern.
                                       Often a high powered flashlight is
                                       necessary to see the sprays.

     Under no circumstances should the inspector attempt to see the nozzles
from below the spray headers since the liquor pH levels are often below 4 and
above 9.  Under both conditions,  eye damage is possible if some of the liquor
splashes into the eye.  Also, the scrubber vessel should not be entered.
Footing is difficult inside most  scrubbers, the protective liners can be
damaged, and the vessel is poorly ventilated.


SLIDE 5-86

          1. BRASS
          2. STAINLESS STEEL
          3. CERAMIC
          4. TEFLON
          6. POLYPROPYLENE
                                       The proper materials of construction
                                       should be chosen for the nozzles.  Most
                                       suppliers have a very wide selection of
                                       materials for various corrosive and
                                       erosive conditions.

                                       One option which is not available for
                                       nozzles is the use of rubber linings.
                                       While this approach is very useful for
                                       the protection of pump impellers and
                                       casing and for the protection of some
                                       pipes, it is not applicaple to nozzles.
                                       The velocities are too high and the
                                       clearances to small to permit the use
                                       of linings.

     A partial list of nozzle materials is presented in this slide.  Brass is
generally the least expensive material.  However, it is subject to erosion,
corrosion and pluggage.  Teflon is good for corrosive conditions.  Stainless
steels are excellent for corrosive conditions with the exception of chloride
and fluoride containing liquors.  Nickel alloy stainless steels and the silicon
carbide nozzles are excellent for abrasion resistance and corrosion resistance.
The price of the nozzle increases rapidly as the more resistant materials are
SLIDE 5-87

      4. LIQUOR pH
                                       A summary of the inspection points  for
                                       nozzles is provided in this slide.

                                       For operating systems, the inspection is
                                       normally limited to the nozzle manifold
                                       pressures, the pump discharge pressure,
                                       the liquor turbidity, the rate of solids
                                       settling and the pH.

                                       For units out of service, the nozzles
                                       can be visually inspected.  However, it
                                       is often not possible to clearly see
                                       internal deposits and mild erosion

     A more accurate nozzle evaluation can be performed by observing the spray
patterns during the operation of the recirculation pump (when the scrubber is
out-of-service).  With this approach it is possible to see the internal deposits
and to see the effects of slight erosion.  However, a safe vantage point is
rarely available.

     Scrubber performance deteoriation is usually significant with only one
nozzle plugged or eroded.  For this reason, the evaluation of nozzle condition
is important.

SLIDE 5-88
                                      Many existing  scrubber systems do not
                                      have pressure  gauges on the manifolds
                                      leading to the nozzles.  The arrow in
                                      this slide illustrates one possible
                                      location for a gauge.

                                      There should be a separate gauge for
                                      each header so that it is possible to
                                      identify pluggage or erosion of a single
                                      nozzle in the  group served by the header
                                      Also, a separate gauge is needed for
                                      each level of  spray bars since the liquid
                                      pressures will be different by values
                                      equivalent to  the difference in head.
SLIDE 5-89
There is very little known about the
generation of static electricity during
the spraying of liquor  in wet scrubber
systems.  The action of the liquor
passing over the nozzle orifice should
generate considerable static charges on
both the nozzle body and the droplets.

The static charges  on the droplets
could conceivably affect both the drop-
let size distribution and the effect-
iveness of particle capture. The charges
on the nozzles are  probably drained away
continuously down the grounded header
and piping.

SLIDE 5-90
    I I
                   GAS STREAM
The persistence of the spray pattern
when the nozzle is spraying against
the flow of the gas stream is not well
known.  The spray angle will increase
as the gas velocity increases.

Since the gas flow inside scrubber
vessels and inside venturi throats is
not uniform, the effect on the sprays
is not equal throughout.  This could
conceivably lead to areas within the
scrubber with poor gas-liquor contact.

Scrubbers with persistant compliance
problems may benefit from some trial
and error analyses of different nozzle
types and operating pressures.
     Anything which increases the droplet velocity leaving the nozzle should
favor penetration across opposed gas streams.  This includes the use of small
spray angle nozzles, the use of full cone nozzles, and decreased liquor
pressures.  Also, nozzles which generate larger droplets should be considered,
If none of these are successful, then a redesigned nozzle pattern may be
SLIDE 5-91
                                       The fans, ductwork and hoods of air
                                       pollution control systems are checked
                                       on all level 2,  3 and 4 inspections.

       EVALUATION OF FANS         The effectiveness of pollutant capture
    AND VENTILATION SYSTEMS      at the point of  generation is checked
                                       by observing visible emissions from the
                                       process equipment.  The static pressure
                                       at the hood also provides an indirect
                                       indication of the capture velocities.

     Leakage through the ductwork can lead to significant fugitive emissions,
regardless of whether the system is under positive or negative pressure.   There
is no sense in fine tuning a scrubber system while tolerating massive fugitive
emissions from either the ducts or the process equipment.

     The fans on wet scrubber systems are more vulnerable to operating problems
than those on other types of air pollution control systems.  This is due  to
build-up of entrained droplets and solids on the fan blades, the corrosion of
the fan blades, and the high static pressures which must be developed.  During
the inspection, the potential for fan problems which could lead to wet  scrubber
system outages is evaluated.  Also, the fan performance data is used as an
indirect indication of the gas flow rate through the scrubber vessel.

SLIDE 5-92
         TYPES OF FANS
          1. RADIAL BLADE
          2. BACKWARD CURVED
          3. FORWARD CURVED
                                       Due  to  the high positive and negative
                                       pressures which are  required in wet
                                       scrubber systems,  the centrifugal fan
                                       is the  only  type of  fan which is suit-
                                       able.   The three main categories of
                                       centrifugal  fans are listed in the
                                       adjacent slide.  Only the radial blade
                                       and  backward curved  blade types are
                                       generally used on  wet scrubbers.

                                       The  radial blade fan is slightly less
                                       efficient than the backward curved
                                       blade,  but is less susceptible to solids
                                       build-up on  the fan  blades.

SLIDE 5-93
                                       While  approaching  a wet  scrubber
                                       system,  the vibration  of the  fan  should
                                       be noted.   IF THE  FAN  IS VIBRATING
                                       SEVERELY,  THE AREA SHOULD BE  LEFT
                                       IMMEDIATELY.   THE  DISINTEGRATION  OF THE
                                       FAN AND HOUSING CAN SEND METAL PARTS
                                       (LIKE  SHRAPNEL) OVER A WIDE AREA.

                                       This problem, although not common,
                                       happens frequently enough that all
                                       regulatory agency  inspectors  must res-
                                       pect the seriousness of  this  condition.
                                       Responsible plant  personnel should be
                                       notified of the severe vibration, if
                                       they are not aware of  it already.

     To prevent this accident,  it is necessary to shut down the fan  immediately.
This means that the pollutant laden gases must be temporarily vented through the
bypass stack.  Regulatory agency inspectors should not oppose the temporarily
bypassing of the scrubber while the plant personnel conduct an  orderly shut-
down of the process equipment.

SLIDE 5-94

Wet scrubber systems are especially
prone to fan vibration problems due to
the conditions listed in this slide.
Excessive tip speeds result when plant
operators change sheaves of belt driven
fans without consulting the fan manu-
facturers.  They exceed the structural
capability of the fan wheel at the
higher than anticipated rotational

As with most maintenance problems,
severe fan vibration related outages
should not occur frequently at a given
plant.  The fundamental problem should
be identified by plant personnel and
corrected before the unit is restarted.
All similar units at the plant should
also be fixed as soon as possible.
SLIDE 5-95
The main reason for evaluating the fan
performance is to determine if the fan
can deliver the necessary gas flow rate
under the present conditions in the
scrubber vessel and the ductwork.  No
attempt should be made to quantify the
flow rate.  Instead, the objective is to
determine if the flow rate has changed
significantly since the baseline period.
                                       The next set of slides concerns the
                                       operating principles of centrifugal
                                       fans.  The performance curves are very
                                       similar to those discussed earlier with
                                       respect to centrifugal pumps.

SLIDE 5-96

                   FAN CHARACTERISTIC
            GAS FLOW-
This is a typical fan performance
curve.  The unit must operate at some
point along this line.

The "No Flow" point is the intersection
of the curve with the vertical axis.
This is the point at which the maximum
static pressure is provided by the  fan.
The "Free Flow" point is the intersec-
tion of the curve with the horizontal
axis.  The maximum gas flow is delivered
here, but at a negligible static pressure.
The fan normally operates in a middle
position, away from both extremes.
     The position and shape of this curve  depends  on  the type of fan blades,
the fan housing, and the inlet duct configuration.  Each fan has a different
fan performance curve.  The only factor which  can  change this curve for an
existing fan is a change in the rotational speed.
SLIDE 5-97

                  OPERATING POINT

                    FAN CHARACTERISTIC
           GAS FLOW 
The new curve added  in  this  graph is
the system resistance curve.   This is
the static pressure  required  to move
the specified quantity  of  gas against
the resistance of  the ductwork, hoods,
and wet scrubber vessel.   The system
flow resistance is proportional to the
square of the gas  flow  rate.

The point at which the  system resistance
curve intersects the fan performance
curve is the system  operating point.
The fan and system reach this automat-
ically as the unit is started.

SLIDE 5-98
                   BACKWARD CURVED FAN
          GAS FLOW-
The fan motor horsepower curve is shown
in this graph.  It rises as the gas flow
increases in much the same way that the
pump motor horsepower increases with
liquor flow.

Since the fan motor current is propor-
tional to the brake horsepower, the motor
current serves as an indirect indication
of gas flow rate.  Even slight changes
in the currents mean major changes in the
gas flow rates.
      As with pump curves, no attempt is made to quantify the gas flow rate
based on the motor currents.  The relationship between motor currents and brake
horsepower (the form in which characteristic fan curves are presented) involves
the load factor.  This can not be measured easily during an inspection.  There
is also some question concerning the accuracy of fan characteristic curves when
applied to existing systems.  The geometry of the inlet and outlet ducts of the
fans can modify flow characteristics to the extent that the characteristic
curves are no longer strictly applicable.

SLIDE 5-99



             Q  flowrate, ACFM
             d  density factor,
                                       Before making the comparison of the
                                       present motor currents to the baseline
                                   !    data,  it is necessary to correct for the
                                   >    gas density.  The equation shown in this
                                   1    slide  is used to correct the present data,

                                       Obviously,  it is necessary to know the
                                       gas temperature in the fan to perform
                                       this correction.  If on-site tempera-
                                       ture monitors are not available, it is
                                       necessary to measure the temperature
                                       (level 3 and 4 inspections only).  For
                                       fans downstream of the scrubbers the
                                       gas temperature is normally in the range
                                       of 120F to 140 F.

     This correction is necessary since a fan it behaves like a shovel, moving
a certain volume of gas during each rotation.  However, the density of the gas
being moved is a strong function of the temperature and is also influenced by
the local static pressures and humidities.  The work being done by the fan
increases as the density increases (cold gas  temperatures).

     The correction factors which should be used are presented below for common
static pressures and temperatures.  Since most fans are on the downstream side
of wet scrubber vessels, the data here is for saturated conditions.  For fans
ahead of the wet scrubbers, psychrometric charts should be used to determine
the density at the specific gas temperatures and mois-ture level.  This should
then be corrected for the fan inlet static pressure.
                        GAS DENSITY CORRECTION FACTORS
Gas Temperature, F
















                                     Static Pressure, Inches of Water


































 _IDE 5-100
                                       The operating point of  the  system can
                                       change if there has been  a  shift in the
                                       system flow resistance.   An increase in
                                       the resistance lowers the curve  in the
                                       direction shown by arrow  #1.  Decreases
                                       in resistance result in a shift  to the
                                       left as shown by arrow  #2.

                                       Air infiltration lowers flow resistance
                                       since the gas stream travels a shorter
                                       path through the system  A  decrease in
                                       the liquid flow rate or a decrease in
                                       the gas velocities through  the scrub-
                                       ber results in significantly lower gas
                                       flow resistance.

     An increase in the flow resistance is less common in wet  scrubber  systems.
It can occur due to pluggage of packed beds or demisters.  Increased liquor flow-
rates can also have this effect.  However, it is more common to  have decreases
in the liquor flow rate due to nozzle pluggage, line freezing  and  pump  impeller

SLIDE 5-101
                                       There are  three  common fan drive arrange-
                                       ments used on  wet  scrubber systems.   In
                                       direct  drive units,  the fan rotational
                                       speed is fixed by  the motor speed.  On
                                       alternating current  motors this means
                                       that the fan speed can not vary.  The
                                       speed of direct  current motors can be
                                       easily  varied  over a wide range.  However
                                       it  is very rare  to find a direct current
                                       motor on a wet scrubber fan.

                                       The most common  arrangement is the belt
                                       drive fan.  This has small sheaves on
                                       the motor  and  large  sheaves on the fan.
                                       A set of from  two  to six belts is used
                                       to  drive the fan.  Fan rotational speed
                                       can be  changed by  changing the sheaves.

     Some of the large scrubber installations  can use variable speed drives.
These have hydraulic couplings for transfer of the shaft  energy from the motor
and the fan.  The rotational speed of the  fan  can be  easily and rapidly varied
over a wide range in response to process operating conditions.

SLin 5-102
                                       These curves illustrate the  shifts  in
                                       the operating point when the rotational
                                       speed of the fan changes.  Even  a slight
                                       change in the fan speed can  make a
                                       noticeable change in the gas flow rates.

                                       Increased fan speed allows higher gas
                                       flow rates and better pollutant  capture
                                       at the process source.   Fan  speed is
                                       sometimes increased when the capacity of
                                       the process equipment is being increased,
                                       All increases in fan speed are inten-
                                       tional .

     Decreases in fan speed are usually the result of a change in the sheaves
(on belt driven units).  This may be done in an effort to reduce the energy
cost of the fan which is often the single largest operating cost of the wet
scrubber system.  On direct drive (alternating current) fans,  the fan speed
can only be decreased by replacing the motor.

     Belt slippage can result in a 100 to 300 r.p.m. reduction in the fan
speed.  This is usually accompanied by a very annoying and noticeable squeal.
SLIDE 5-103
                                       If there has been a significant change
                                       in the fan motor current (after the gas
        CAM CWAI iiATirtM              density correction), but the fan rota-
        FAN EVALUAHUN              tional speed has not changed, then there
            SUMMARY                 has been a change in the system resistance.
                                       The most common explanations include air
                                       infiltration and reduced liquor flow.

                                       If there has been both a significant
                                       change in the corrected fan current and
                                       the fan speed, then the operators have
                                       been making adjustments to the system.
                                       This may have been done to increase gas
                                       flow rate or to reduce energy consumption.
                                       In the case of reduced gas flow rate, it
                                       is advisable to check for fugitive
                                       emissions from process equipment.

     During  the evaluation of fan operation, the condition of the fan housing
should be noted.  Obvious corrosion here is often accompanied by corrosion of
the fan wheel and the ductwork leading to the fan.


         1. Erosion due to Abrasive

         2. Corrosion to Acidic Gases
           and Moist Duct Surfaces

         3. Severe Thermal Expansion
           and Contraction
SLIDE 5-104
                                       The physical condition  of  the  ductwork
                                       and hoods  (if present)  should  be check-
                                       ed whenever there  are symptoms of gas
                                       flow rate  decreases  or  there are fug-
                                       itive emissions.   There is considerable
                                       potential  for trouble with these non-
                                       moving parts of the  wet scrubber system.
                                       Some of  the contributing factors are
                                       listed on  this slide.

                                       Erosion  is a common  problem on wet scrub-
                                       bers handling high concentrations of
                                       large diameter particulate. Unlike most
                                       air pollution control devices, the gases
                                       accelerate when they enter scrubbers.
                                       This aggravates the  erosion potential.

      Most wet scrubber systems handle gas streams with one or more corrosive
components.  During start-up, absorption of these gases can occur on  downstream
ductwork which has a light coating of moisture  on the surfaces.

     It is common for gases leaving process equipment to  be at temperatures of
500 to 2000 F.  While passing to the scrubber  vessel, these gases are cooled
to temperatures less than 300 F.  During start-up and shut-down of the system,
there can be major differences in the rates of  expansion  and contraction of
the ductwork.  This can lead to air infiltration  points.due to the ductwork
SLIDE 5-105
                                       One of the most common  sites of duct
                                       erosion is at  sharp  turns.   The inertia
                                       of large diameter  particles results in
                                       severe erosion of  a  portion of the duct
                                       as shown in  the top  part  of the slide.

                                       It is common practice to  install wear
                                       plates on the  outer  surfaces of the
                                       elbow to minimize  the frequency of duct

                                       Another approach is  to  reduce the duct
                                       velocity by  reducing the  gas flow rate
                                       or by increasing the radius of the turn.

     Erosion may become a problem on systems in which the fan  speed has been
increased to increase overall production capacity.  The gas velocity will
increase in direct proportion to the increase in the  actual cubic  feet per
minute of gas flow.  The normal gas transport velocities  range from 3000 feet
per minute to 4500 feet per minute.  However, erosion can occur  even in this

                          4OO J-
100 200  300 4OO 9OO  6OO  700
     Equivalent Ltngth, fttl
SLIDE 5-106
                                        Air infiltration sites are often  hard
                                        to find due to the inaccessibility  of
                                        the ductwork and due to the combined
                                        effect of a large number of small
                                        erosion and corrosion holes.   A duct
                                        temperature profile can be prepared to
                                        determine if infiltration does exist
                                        and to determine the most probable
                                        areas for the problem.

                                        The profile is constructed by  measuring
                                        the gas temperature in the duct at  all
                                        points with safe and convenient access.
                                        The data is plotted as shown in this
                                        slide.  The graph starts with  the
                                        location of the process equipment and
                                        proceeds along the ductwork to the
                                        scrubber.  The sudden drop near the
                                        right of the graph shows is the effect
                                        of the scrubber.

     Although this approach  can  not be used on all wet scrubber systems, it  is
convenient in many cases.  It  is necessary to have some baseline data so that
normal temperature decreases due to radiation and convection can be differen-
tiated from the cooling which  results from the infiltration of ambient air.
                            ZOO E
SLIDE 5-107
                                        A similar duct profile can be  prepared
                                        using the oxygen concentrations  in  gas
                                        streams from boilers and similar com-
                                        bustion systems.  The measured oxygen
                                        data is plotted along the ductwork  line
                                        from the combustion chamber to the

                                        The oxygen concentration should  not
                                        change much.  There will usually be some
                                        slight infiltration across the fan  and
                                        the scrubber vessel, but this  is usually

     This type of profile can  only  be  prepared for combustion sources having
oxygen concentrations in the range  of  2 to 12%.  It is not very effective  for
most driers since these often  operate  at 17 to 19% oxygen.  These values are
too close to the ambient level of 20.9% to provide any reasonable sensitivity
in detecting air infiltration.
   IOO 200  SOO 40O  90O COO  TOO

                                       Another means to check the  significance
  	       I                           of air infiltration  is to compare the
  \y S  Y  St.                       hood static pressure with the baseline
              '                       values.

     -rj   ,           \7  I   *t       ^e hd static pressure is proportional
     V "~  /JtwTjg'? VelOCITy     to the velocity pressure in the duct
                                       leading from the hood.  The constant "C"
                                       is primarily determined by  the geometry
      C, L. nod!  Sk'QtlC           ^ t'le hd'  However, with the baseline
        h                              comparison, it is not necessary to know
            rTGSSUre                "C" unless the hood  configuration has
                                       been modified significantly.

     The hood static pressure is normally in the range of -0.5 inches W.C. to
-2.0 inches W.C.  Therefore, it  should be measured by an inclined  manometer or
by a low-range diaphragm gauge.   The measurement port should be in the duct
immediately after the hood.  For maximum accuracy, there should be 4 ports
spaced 90 around circular ducts.  Due to the potential for pollutant exposure
near the hoods,  direct accessibility to the port location is usually not
desirable.   Instead, the port should be connected by means  to tubing to a safe
and convenient measurement location.

Lecturer's Notes
     Some of the attendees may ask why a complete traverse  should  not be done
to get very accurage static pressure data across the entire duct.   It should
be pointed out that  the effort required for this is equivalent to  simply doing
a complete velocity  pressure traverse and calculating flow  rate directly.  The
static pressure measurement is meant to be a convenient short-cut.  Also, it
is often unsafe directly adjacent to a hood and a pitot traverse can not be
SLIDE 5-109
                                       Even if the gas flow rate through the
                                       hood has not changed since the base-
                                       line period, it is possible to have
                                       poor pollutant capture.   This can be
                                       caused by a damaged hood or by cross

                                       The hoods can be damaged by overhead
                                       cranes.  When the hood partially re-
                                       stricts access to the process
                                       equipment, the operators often move the
                                       hood away permanently.  Both of these
                                       mean that the hood is not handling some
                                       plant area and less of the pollutant
                                       laden gases.

Source:  Kational Audiovisuals Center


                                      Two explanations for reduced gas flow
                                      at the hood are the partial closure of
                                      the blast gates in the downstream duct
                                      and the accumulation of solids which
                                      serve as a "damper" on the system.

                                      A photograph of a blast gate is shown
                                      here.  It is simply a guillotine dam-
                                      per which can close off all or part of
                                      the duct when the process is not being
                                      operated.  Some operators can change
                                      the positions of these on several of
                                      the ducts without being aware that the
                                      entire system is adversely affected.

     In systems handling  large  quantities of large diameter particulate or
which have oversized  ducts with low gas velocities, it is possible for solids
to accumulate.   Initially this  simply restricts gas flow.  If the deposits
exceed the load bearing capability of the duct supports, the entire duct will
sag or fall.   Clean-out ports can be used to remove accumulated materials when
the scubber system is out-ot-service.
SLIDE 5-111
                                      The next few slides address the wet
                                      scrubber system materials of construc-
                                      tion.  The proper selection and main-
                                      tenance is largely responsible for the
                                      successful performance of the system.

                                      As an inspector, it is important to
                                      understand what can go wrong.  The goal
                                      is to minimize both the obvious and the
                                      repeat mistakes.

     The selection  of  materials of construction is not a single decision, but
a long series of judgements concerning each individual component of the system.
Rarely are the same materials appropriate in each portion of the unit.  These
judgements must be  based  on reasonable estimates of the chemical and physical
conditions to which the materials will be exposed.  It is important to consider
both the steady-state  conditions and the exposures during process upset and


           1. METALS

           2. ORGANIC COATINGS
             AND LININGS

           3. CERAMIC AND
                                       The three basic categories of materials
                                       are listed in this slide.  The metals
                                       commonly used include, but are not
                                       limited to: carbon steels, austenitic,
                                       ferritic and martensitic stainless
                                       steels, and various types of high nickel
                                       stainless steels.

                                       There are a large variety of organic
                                       liners for metal surfaces.  These in-
                                       clude polyester and epoxy materials.
                                       The polyester materials can be pro-
                                       vided with a flaked glass reinforce-
                                       ment.  Included in this category are
                                       the natural rubber and neoprene sheet

     The ceramic and inorganic materials include, but are not limited to pre-
fired brick, hydraulic bonded concretes and chemically bonded concretes.
These materials provide both corrosion and erosion resistance in especially
vulnerable areas of the wet scrubber system.

Lecturer's Notes
     The selection of the specific materials to be used is a complicated task
and should remain the sole perogative of the plant operator and designers.
The regulatory agency should not encourage the use of certain materials simply
because these were used successfully elsewhere.  There are too many site
specific factors which must be considered in the selection of materials.
SLIDE 5-113

              1.  Liquor pH
              2.  Chloride
                                       The areas subject to corrosion are all
                                       the wetted parts of the scrubber system
                                       These include the scrubber vessel, pumps,
                                       piping, outlet ductwork, fans, and
                                       recirculation tanks.

                                       In these wetted areas, the most important
                                       factors affecting the corrosion rate are
                                       the pH and the chloride concentration.
                                       Neither of these are constant in a
                                       scrubber system.  The pH is generally
                                       lowest in the scrubber outlet.  The
                                       chloride concentration can be higher in
                                       solids deposits than in the recirculating

                                       This graph illustrates  the  general  re-
                                       lationship between  pH and chloride
                                       concentration on the rates  of  pitting
                                       and crevice corrosion (two  common modes
                                       of metal  damage) for AISI 316L stain-
                                       less steel.  At  the pH  levels  of  4  and
                                       above which are  common  in wet  scrubber
                                       systems,  the chloride concentrations
                                       above 1000 ppm result in severe damage.
                                       Even at levels as low as 100 ppm, there
                                       can be damage.  It  is apparent that
                                       higher chloride  concentrations can  be
                                       tolerated at higher pH  levels.
  Source:  Chemical  Engineering
          June  5, 1978,  Page  163
SLIDE 5-115
                                       It is apparent from the slide provided
                                       above that pH levels in the range of 1
                                       to 4 are especially prone to corrosion,
                                       even at very low chloride levels.  It is
                                       important that the unit always be main-
                                       tained above this level.  Problems often
                                       occur when the scrubber system is shut-
                                       down and not purged of acidic gases.
                                       Also, the failure of an alkaline addition
                                       system can lead to sudden drops in the pH.

                                       A short term drop in the pH levels can
                                       initiate corrosion of materials that
                                       would not otherwise be damaged.  Once
                                       the pitting action has started, it can
                                       continue under the conditions which were
                                       previously acceptable.

     Only the nickel alloys are relatively immune to the low pH related types
of corrosion damage.  These are rarely used due to the very high cost of the
I l

SLUT 1-116

         1. CREVICES
         4. LOW pH
                                       Localized  deposits  of  solids  should be
                                       avoided wherever  possible.  They can be
                                       rich in chloride  levels  and create
                                       oxygen depleted areas  near the metal
                                       surface.   This can  result in  accelerated
                                       corrosion  in  localized portions of the

                                       Crevices should also avoided.  These
                                       provide sites for crevice corrosion.
SLIDE 5-117

           1. Blistering
           2. Debonding
           3. Chemical Attack by
             Scrubber Liquor
           4. Nonuniform Coating
           5. Erosion of Liner
                                       Organic linings  are  less costly than
                                       corrosion resistant  metals.   However,
                                       they are susceptible to the  problems
                                       listed here.

                                       Temperature excursions  are a common
                                       factor in liner  failure.  They can lead
                                       to both blistering and  debonding of the
                                       liner from the base  metal it was intended
                                       to protect.  The loss of liquor flow can
                                       lead to short term temperature spikes.

     Proper surface preparation is critical to the success  of  the liner.  The
metal surface must be cleaned and then coated with a primer.  The coating must
be applied uniformly and at the proper thickness.  There should be  no voids or
pinholes in the liner.  Surface preparation is also important  when  repairs are
being made to damaged portions of the liner.

     Organic liners can have a limited life in the high liquid and  gas stream
velocity areas of the scrubber.  It does not take long  to remove portions of a
liner which is typically 40 to 80 mils thick (0.04 to 0.08  inches)  when highly
abrasive particulate is present.


       1. Polyesters          - 250 F
       2. Epoxy            - 250 F
       3. Vinyl Esters          - 360F
       4. Fluoropolymer
                         - 400 F
The temperature limits of common types
of organic liners are presented in this
slide.  Slightly higher short term
transient temperatures can usually be
tolerated, but continuous operating
conditions should be lower.

Th fluoropolymers have the highest
allowable temperature and a relatively
high cost.  These material are used
mainly in areas where high temperatures
during shut-down or system upsets are
     The temperatures listed above are for dry conditions.
wet conditions are lower.
                     The maximums  for
     The temperature limits for all of these materials could easily  be  exceed-
ed if the recirculation pump fails.  Systems in which there is  a  presaturator
or evaporative cooler are obviously less susceptible to  this type of damage
since two separate pumps must fail in order to have a sudden excursion.

     Bypassing is necessary on any system when the gas exceeds  normal tempera-
tures.  On units where the bypass is controlled by manually activated dampers,
the damage to the liners may have already occurred before  the hot gas is
directed up the bypass stack.  In any case, the scrubber system should  be
purged of hot and pollutant laden gas trapped inside.
SLIDE 5-119
           RUBBER LINERS



The rubber liners are applied  as  sheets.
It is important  that they  be layered
properly so  that scrubber  liquor  will
not be forced underneath the layers and
attack the adhesive.

As with the  organic liners,  it is
important to maintain the  temperature
at low levels to prevent damage.   It is
also necessary to prepare  the  surface
to accept the adhesive.

SLIDE 5-120
                                       For existing systems, there is sometimes
                                       a need to evaluate changes in the mat-
                                       erials of construction in order to mini-
           TEST SPOOLS FOR              mize system failures.  One way of per-
 EVALUATING MATERIALS OF CONSTRUCTION    forming these tests is to use a test
          1 WEIGHT LOSS                  spool containing samples of a number of
          2 PITTING                      different metals with or without liners.
          3. CREVICE FORMATION             The spool is placed in the portion of
                                       the scrubber system experiencing fre-
                                       quent materials problems.

                                       The materials are compared based on the
                                       general rate of weight loss, the rate
                                       of pitting and the depth of crevice
                                       formation.  This can be done on several
                                       occasions so that the rates of corrosion
                                       can be compared with present materials.


5-1.  The correct answer is "b".  Pluggage is not a likely explanation for the
      observed rainout.  The gas velocity through the demister is 29.03 feet
      per second, assuming that the entire demister is open.  This velocity is
      above the normally accepted limits for chevron demisters.  The rainout
      is probably due to the reentrainment of droplets from the downstream
      edges of the demister.  The demister is undersized.  Those who answered
      "a" may protest that pluggage is also conceivable.   While this is true,
      it would only aggravate the situation with the obviously inadequate
      demister.  Their answer is wrong since correction of the pluggage con-
      dition would not alleviate the rainout conditions,  only improve it

5-2.  Answer "b" is correct.  It takes much less energy for a fan to move a
      cubic foot of gas at 325 F than at 125 F.  The gas has a much lower
      density at higher temperatures.  As an analogy, relate the effort in-
      volved in shoveling a light fluffy snow to that of shoveling a wet snow
      If anyone is having trouble with this concept, go back and review the
      section of motor current correction factors.  It may also be helpful to
      briefly review the ideal gas laws.

5-3.  Those who have been answering "b" are on a hot streak.  It is correct
      again.  However, answer "c" is equally correct.  The squeal usually
      indicates drive belt slippage.  The reduction in the fan rotational
      speed leads directly to a reduction in the gas flow rate.  It would be
      worthwhile to check the scrubber pressure drop since this is related to
      the square of the gas flow rate.  The presence or absence of fugitive
      emissions should also be checked.

5-4.  The correct answer is "b" again.  Pipe sizes for different materials are
      not identical.  It is necessary to consult standard tabulations of sizes
      to determine the actual inside and outside diameters denoted by the pipe
      nominal size.

5-5.  The correct answer is "d".  The increase in the nozzle header pressure
      and the decrease in the scrubber pressure drop both suggest a reduction
      in the liquor flow rate due to nozzle pluggage.  The high liquor
      turbidity also suggests the potential for nozzle pluggage.  Cavitation,
      answer "a",  would also lead to a reduction in the liquor flow rate and
      a drop in the scrubber pressure drop.  However, it would also decrease
      the nozzle header pressure.


5-1.   The gas flow rate measured downstream from a 3-pass chevron demister is
      67,500 ACFM.  The average gas temperature at the port used to measure
      the gas flow rate is 126 F.  The demister static pressure drop is 1.2
      inches of water and the diameter of the circular demister is 8 feet.  Is
      pluggage a likely explanation for the observed rainout from the stack?

      a.  Yes.
      b.  No.
      c.  Maybe.

5-2.   Does it take more energy for a centrifugal fan to move a cubic foot of
      gas at 325 F than it does to move a cubic foot at 125 F?

      a.  It takes more energy at 325 F than at 125 F.
      b.  It takes less energy, at 325 F than at 125 F.
      c.  There is no difference in the energy requirements.

5-3.   During an inspection of a wet scrubber system, a squeal is heard in the
      vicinity of the fan.  Is this a symptom of an operating problem?

      a. Yes, the gas velocity at the fan inlet is excessive.
      b. Yes, the fan rotational speed has probably decreased.
      c. Yes, the gas flow rate through the scrubber system has
         probably decreased.
      d. No, this is normal around fans.
5-4.  Is a 1 inch PVC pipe the same size as a 1 inch steel pipe?

      a.  Yes.
      b.  No.
      c.  The outside diameters are the same, but the inside diameters differ.
      d.  The inside diameters are the same, but the outide diameters differ.
      e.  The hydraulic diameters are identical.

5-5.  The recirculation liquor has a very high turbidity.  The liquid pressure
      at the nozzle header has increased from a baseline average of 45 psig to
      62 psig.  The scrubber pressure drop has decreased from a baseline
      average of 17 inches W.C. to 14 inches W.C.  The gas temperature of the
      scrubber inlet stream has decreased from 350 F to 334 F.  What
      possible problems should be checked during the remainder of the

      a.  Pump cavitation.
      b.  Erosion of the spray nozzles.
      c.  Process operating conditions.
      d.  Pluggage of the spray nozzles.
      e.  None of the above.



5-6.  Only answers "c" and "e" are correct.   All of the others listed,  with
      the exception of guillotine valves, are for shut-off type service.
      There is no such thing as a guillotine valve for liquids.

5-7.  No.  Pump cavitation does not conclusively demonstrate air infiltration
      into the suction line of the pump.  Cavitation is the localized vapor-
      ization of liquor components near the impeller due to low pressures in
      this part of the pump.  It can be caused by air infiltration or
      anything which reduces the Net Positive Suction Head.

5-8.  The seal water is meant to protect the bearings, therefore answer "a"
      is correct.  Following the bearing damage, excessive vibration and  pump
      failure will occur.  Therefore, answers "c" and "d" are also correct.
      Anyone having answers "b" and "e" needs to review the pump section.

5-9.  The main objective of this question is to illustrate that there is  a
      lot which can be done during a level 2 inspection.  In this case, the
      following answers are correct  - "b",  "d", "f", "h", and "j".  The
      reason for checking the pH is to determine if there is potential for
      scaling due to chemical precipitation on the demister blades.  Answers
      "d", "f", and "h" all help evaluate the effectiveness of the cleaning
      action.  Answer "j" is correct since it is possible that an increase
      in overall gas flow rate due to production increases has resulted in
      more carry-over of liquor from the top stage of the scrubber to the
      demister.  The latter is especially troublesome if the freeboard dis-
      tance is small.


5-6.  What types of valves are normally used for throttling liquid flow rates?

      a.  Check valves
      b.  Foot valves
      c.  Globe valves
      d.  Gate valves
      e.  Ball valves
      f.  Guillotine valves
      g.  All of the above

5-7.  Does cavitation of a pump conclusively demonstrate that air is
      infiltrating the suction line of the pump?

      a.  Yes.
      b.  No.
      c.  Maybe.

5-8.  A recirculation pump is handling a liquor having a suspended solids
      level of 2%.  If the seal water is accidently stopped, what possible
      problems can occur?

      a.  Bearing failure
      b.  Accelerated impeller wear
      c.  Excessive vibration
      d.  Pump failure
      e.  Reduced Net Positive Suction Head
      f.  All of the above

5-9.  A demister is suffering chronic rainout problems and there have been a
      large number of community complaints  During a level 2 inspection, it is
      determined that there is a demister cleaning system which is operated at
      least once per shift.  Is there anything else which should be checked
      during this level 2 inspection?

      a.  No.  A level 3 inspection should be conducted in the near future.
      b.  Yes.  Plant personnel should be asked to measure the pH of the
          demister wash liquor.
      c.  No.  A stack test is obviously necessary.
      d.  Yes.  The duration of the cleaning cycle should be determined.
      e.  No.  Slight rainout is inevitable from demisters.
      f.  Yes.  The pressure of the demister wash water line during cleaning
          should be determined if possible.
      g.  No.  Obviously cleaning should be discontinued to reduce the
          quantity of water on the demister which can be reentrained into
          the gas stream going up the stack.
      h.  Yes.  The turbidity of the demister wash liquor should be
          qualitatively evaluated.
      i.  No.  Small gaps should be opened between demister sections to reduce
          the gas velocity through the demister to more reasonable velocities.
      j.  Yes.  The freeboard distance and production rates should be checked.


5-10.  Answer "d" is correct,  the inlet damper serves all of these functions.
       This is a subject that  was not addressed during the lecture.  It is
       included to illustrate  that some useful information can be obtained
       only by working the problems.

5-11.  The correct answer is "b".  The objective of the demister spray nozzles
       is to clean off the entire demister surface.  The hollow cone nozzles
       would miss large areas  directly below the nozzles.

5-12.  The chloride concentration of 0.2% is equivalent to 2000 ppm which is a
       very high level!  The pH of the liquor should be determined (answer "a"),
       if at all possible since there is a strong relationship between the rate
       of corrosive attack and the pH.  If the pH is less than 7, most metals
       are vulnerable.  The type of metal is important since there is a major
       difference in susceptibilities.  Those with higher molybdenum, chromium
       and nickel are less vulnerable.  The nickel alloys may experience no
       problems under these conditions.  Answer "d" is also correct for obvious

       There can be considerable room for disagreement on answer "e".  The
       plant should have the right to use whatever materials are most econ-
       omical as long as they  do not cause unnecessary excess emission con-
       ditions.  If they can shut down the system before violations occur, it
       may be possible to use  cheap sacrifical materials.  On the other hand,
       they should not claim that corrosion control is a "mysterious art" and
       that frequent bypass conditions are inevitable.

5-13.  The plant data is not reasonable.  Answer "b" is correct.  The pipe
       velocity assuming Schedule 40 pipe is approximately 19 feet per second
       which is about 50% higher than normally used maximum transport

5-14.  Answer "c" is correct.   This is another one of those education questions
       buried in the midst of  the review problems and questions. Those who
       answered "e" should get at least partial credit for recognizing a
       question which is not central to the job of agency inspector.  This is
       just a "nice-to-know" fact.

5-15.  The Austenitic stainless steels are not magnetic while the carbon steels
       obviously are.  A magnet is a convenient and quick way to determine the


5-10.  What is the purpose of the damper on the inlet to the fan?

       a.  To improve gas stream loading into the fan wheel
       b.  To control the gas flow rate through the system
       c.  To protect the fan motor from overloads
       d.  All of the above

5-11.  Would a hollow cone spray nozzle be appropriate for demister cleaning

       a.  Yes.
       b.  No.
       c.  Maybe.

5-12.  The measured chloride concentration in the effluent liquid stream of a
       scrubber is 0.2%.  What should be done to evaluate the potential for
       serious corrosion?

       a.  Determine the pH of the scrubber liquor.
       b.  Nothing.  The chloride concentration is below the threshold levels
           necessary to contribute to corrosion.
       c.  Request information of the type of metals used in the scrubber.
       d.  Check for obvious corrosion.
       e.  Corrosion is strictly a plant economic consideration and not an
           appropriate concern for regulatory agency inspectors.

5-13.  During an inspection an attempt is made to calculate the present
       liquid-to-gas ratio for a scrubber.  However, there is no liquid flow
       monitor.  Plant personnel report that the 3" steel pipe supplying the
       scrubber is handling 435 gallons per minute.  Is this data reasonable?

       a.  Yes.
       b.  No.
       c.  Maybe.

5-14.  Is AISI 316L stainless steel different from AISI 316 stainless steel?

       a.  No.  They are just trying to confuse us.
       b.  Yes.  The AISI 316L has less alloy materials and is cheaper and more
           subject to corrosion.
       c.  Yes.  The AISI 316L has less carbon.  It is both easy to fabricate
           parts and less subject to a certain type of corrosion.
       d.  I really don't think this is one of the better questions.

5-15.  Is it possible to differentiate a carbon steel from a 300 series
       stainless steel during a level 2 inspection?

       a.  Yes.  But only on a good day.
       b.  Yes.  I can also leap over tall scrubbers in a single bound.
       c.  Yes.  With a magnet.


                                    LECTURE 6

                                 LIQUOR ANALYSES
                                        This lecture concerns the analyses of
                                        liquor samples  obtained while inspect-
                                        ing wet scrubber  systems.  These tests
                                        help to identify  the fundamental causes
                                        of corrosion, erosion and pluggage of
                                        the scrubber components.

                                        The surface tension affects the rate of
                                        solids settling,  the spray droplet size,
                                        and the ease of particle capture.

                                        The conductivity  and the oxidation/
                                        reduction potential are of interest when
                                        evaluating odor scrubbers.  The alkalin-
                                        ity and sulfates  levels are important to
                                        sulfur dioxide  removal systems.

     With the exception of the pH measurement, all of  the analyses must be
conducted at the  control agency laboratory.  The type  of instrumentation
required and the  quantity of sample necessary are discussed in this section.
The importance of proper sample acquistion techniques  are emphasized.

1. Suspended Solids
2. Dissolved and Total Solids
3. Turbidity
4. pH
5. Sulfates
6. Alkalinity
7. Surface Tension
8. Conductivity
9. Oxidation-Reduction Potential


       1. Take Representative Samples

       2. Use Proper Sampling

       3. Protect the Samples
                                       There is .very little sense in performing
                                       highly accurate and demanding analyses
                                       on samples that have been taken at the
                                       wrong location or handled improperly.
                                       These three sampling principles must be
                                       satisfied and thisis not as easy as it
                                       may seem.

                                       The logical starting point in acquiring
                                       samples is to review the scrubber flow
                                       chart to determine the locations at
                                       which samples should be taken. Sampling
                                       times should be carefully chosen to pro-
                                       vide the maximum diagnostic information.

     The procedures used to acquire any samples should be briefly but completely
described in the field inspection notes.  The names of plant persbnnel author-
izing sample acquistion should also be recorded in the notebook.

     Obviously, all samples should be labeled with information such as location
of sample collection, date and time of collection, and notation of any informa-
tion that may change before analysis (temperature, pH, appearance).  Also, if a
sample must be stored for any period of time, the general practice is to refrig
-erate it at 4 C.
                                       One of the first questions faced in
                                       sampling is whether to use a grap or a
                                       composite sample.

                                       A grap sample is one taken at one part-
                                       icular time and indicates the condition
                                       of the stream at that one time.  A com-
                                       posite sample is a mixture of smaller
                                       grap samples taken over an extended
                                       period of time and is representative of
                                       the stream over that longer period of

     In the case of a liquor analysis, a number of grap samples taken at half
hour intervals and analyzed separately could be preferred over a composite
sample covering the same time period.  This is because the composite could
average out any irregularities which, as an example, may have occurred because
of an increased gas flow to the scrubber.  Also, these grap samples can be
taken as a set at the scrubber inlet and outlet, so a comparison can be made
and the performance of the scrubber determined.


        1. Open all Sample Valve
         Slowly and Wear Eye
         Protection at All

        2. Avoid Rotating Mixers
         in Tanks and Other
         Moving Equipment.

        3. Avoid Direct Contact
         with Liquor.

        4. Do Not Drop Objects
          Into Tank of Vessel.
Safety procedures deserve special  con-
sideration when discussing sampling.
The potential safety hazards listed  in
this slide should be considered prior to
beginning any sampling work.

The most common problem is splashing
liquor from taps downstream of the
recirculation pump.  With typical  line
pressures in the range of 20 to 100
psig, it is possible to get an eyeful
if the valve is opened rapidly.  Highly
alkaline liquors can cause severe  eye
damage.  This liquor is also almost
always hot.
     Direct skin contact with the liquor  being  sampled is almost never wise.
Some of these may contain pathogenic  bacteria and  viruses and most contain
skin irritants.

     When leaning over mixing and recirculation tanks, it is easy to drop
pens and other materials carried in shirt pockets  into the tank.  It is con-
ceivable that this will be carried into the  pump suction line and damage the
pump impeller.  The dropped material  may  also contribute to pluggage of the
pump suction line strainer.
SLIDE 6-5                              The  turbidity of the liquor is one of
                                       the  most  important operating parameters
                                       when anaylzing systems with chronic
                                       nozzle  plugging problems and/or bed
                                       plugging  problems.

                                       Turbidity is  the measure of the clarity
                                       or cloudiness of the liquor.  It is
                                       caused  by the presence of suspended
                                       matter  in a finely divided state.
                                       Particulate matter,  precipitates, and
                                       organic matter all contribute to the
                                       turbidity.  The terms "suspended mat-
                                       ter" and  "turbidity" should not be con-
                                       fused,  although they are closely relat-
                                       ed.   Suspended matter is the amount of
                                       material  in a sample which can be
                                       trapped by a  filter.  Turbidity is a
                                       measurement of the optical scattering
                                       and  absorption of light through a

     The turbidity should be evaluated qualitatively as soon as the sample is
obtained since it can change rapidly.  If quantitative data is desired, the
analyses should be done the same day.  In most cases,  the sample can be stored
in the dark for up to twenty-four hours if  it  is wrapped in aluminum foil and
not exposed to extreme temperatures.

           JTU  -  NTU
It is important to understand the test
methods for turbidity since some plants
measure this on a regular basis.  In a
few cases, the inspector may also wish
to have the agency lab perform the

The standard method for determining the
turbidity has been based on the use of
the Jackson candle turbidimeter.  How-
ever, the lowest value that can be
measured on the instrument is 25 units.
     With the need to measure samples in the range of zero to five units, an
alternative method is used incorporating nephelometers which measure the inten-
sity of light scattered at right angles to the incident beam.  Since there is
no  direct relationship between the optics of the two methods, turbidities
measured on a nephelometer are expressed in nephelometric turbidity units (NTU)
and those measured on the candle turbidimeter as Jackson turbidity units (JTU).
The nephelometer is preferred because of its greater precision, sensitivity,
and range.

                                       A typical nephelometer is shown here.
                                       This instrument must be calibrated
                                       using standards in each turbidity range

                                       The sample is shaken vigorously and
                                       then poured into the turbidity tube
                                       after air bubbles have been allowed to
                                       escape.   It is important that the tube
                                       be scrupulously clean and have no flaws
                                       or scratches.  Fingerprints on the tube
                                       and air  bubbles clinging to the sides
                                       will also cause erroneously readings.

     For samples above 40 NTU, the sample should be diluted with one or more
volumes of distilled water until the turbidity  falls into a measurable range.
The turbidity of the original sample is simply  the turbidity of the diluted
sample multiplied by the dilution factor.  For  example, if two volumes of
distilled water were added to one volume of sample and a reading of 30 NTU
was obtained, the turbidity of the original sample would be 90 NTU.

     Manufacturers of turbidimeters often use different optical designs in
their units and this can result in different turbidity reading of a particular
sample.   Therefore, analyses performed by the agency lab may differ somewhat
from values routinely recorded by plant tests.   Changes in the sample during
transport to the agency lab can also contribute to observed differences.


                                      The solids which quickly settle out of
                                      solution should be removed before taking
                                      the turbidity measurement.

                                      The more material that settles to the
                                      bottom of the sampling tube in a short
                                      time, the greater the potential for
                                      erosive wear of pump impellers, valves
                                      and nozzles.  This is because rapidly
                                      settling solids have large diameters.
                                      This large material is naturally erosive
                                      in high velocity areas.

                                      When taking the sample, the presence of
                                      rapidly settling solids should be noted
                                      since this is as important as the sample
          TOTAL SOLIDS
                                      The suspended solids are of interest
                                      whenever the system being evaluated has
                                      had erosion or pluggage problems.  The
                                      dissolved solids are important in any
                                      system prone to scaling.  Both the dis-
                                      solved and suspended solids are important
                                      when liquor is being sprayed into an
                                      evaporative cooler or a presaturator for
                                      gas cooling.

                                      This is not an absolute distinction
                                      between suspended and dissolved solids.
                                      The nature of the filter used in sep-
                                      arating the materials influencing the
                                      results.  Some of the important factors
                                      include: (1) the nature of the material
                                      in suspension, (2) the pore size of the
                                      filter, (3) the area and thickness of the
                                      filter, and (4) the amount of material on
                                      the filter mat.

     The temperature used  to  dry  the  sample has an important influence on the
results because weight  losses due to  the volatilization of organic mater,
mechanically occluded water,  water of crystallization, and gases from chemical
decomposition are all dependent on the drying temperature.  Most residuals are
dried at 103 to 105 C  (217 to 221 F).  At this temperature, some mechanically
occluded water and water of crystallization are retained.  Volatilization of
organics will be inconsequential.  The temperature used for drying the sample
should be specified along  with the results.

SLIDE 6-10

              FOR THE
        1. Indicator Paper
        2. pH Meter (Battery Powered)
                                       The pH of both the scrubber inlet and
                                       scrubber outlet liquors should be tested
                                       In the majority of cases, the inlet
                                       liquor has a higher pH than the outlet
                                       liquor due to the absorption of acidic
                                       gases such as sulfur dioxide and carbon

                                       The same sample used for qualitatively
                                       evaluting the turbidities can be used
                                       for the pH tests.

     The two available techniques for pH analysis are listed here.  Indicator
paper should not be used whenever highly accurate data is necessary since it
is good to only plus or minus a full pH unit.  As the paper ages, the accur-
acy decreases.  The battery powered pH meters generally provide data good to
plus or minus 0.1 pH units.                                       '

     Solutions which chemically attack the pH paper dyes include, but are not
limited to hypochorite and permanganate.  These units and those with highly
colored liquors should not be evaluated using pH paper.
SLIDE 6-11
         Use Fresh Buffer Solutions to
         Calibrate Battery Powered pH
         Meter or to Check Indicator
                                       Liquor pH should be measured immediately
                                       after obtaining the sample since it  is
                                       subject to change.  Prior to each
                                       measurement, the pH meter should be
                                       adjusted using buffer solutions of
                                       approximately 4, 7 and  10.  Since these
                                       buffers can age, fresh  solutions should
                                       be obtained on a regular basis.

                                       If indicator paper is being used, it is
                                       a good practice to occassionaly check
                                       the response of this paper against buffer
                                       solutions.  This can be done at the  agency
                                       lab before leaving for  any field work.

      It is important to check all instruments prior to beginning the field
work.  In the case of the battery powered pH meter, the battery should be
checked and the condition of the pH electrode checked.  A spare battery is
usually advisable.  A small quantity of deionized water is necessary for
washing the pH electrode during measurements.

SLIDE 6-12
                                       Tensionmeters  are  used  to  quantify  the
                                       surface  tension  of a  liquor  sample.
                                       After  centrifuging for  removal  of the
                                       suspended solids,  the sample is placed
                                       in a holder having a  large surface  area,
                                       The sample is  raised  into  position  so
                                       that the platinum-iridium  ring  of the
                                       tensiomenter is  submerged  approximately
                                       3 mm.

                                       After  approximately 30  minutes, the
                                       sample holder  is slowly lowered until
                                       the ring breaks  through the  surface.
                                       The force involved in breaking  the
                                       surface  is measured and converted to a
                                       reading  in dynes/cm.  The  evalution is
                                       usually  done several  timesi

     Unfortunately, there are no reliable field checks  for changes  in  the
surface tension.  This can change signficantly  in day-to-day operation due to
the addition of surfactants and flocculants.
SLIDE 6-13
                                       Alkalinity is the capacity of a liquor
                                       to neutralize a strong acid to a
                                       designated pH.  The alkalinity of a
 ALKALINITY = C03~  +  HC03~ + OH~     fmPle is the combined effect of car-
                                       bonate, bicarbonate and hydroxide ion
                                       concentrations in the liquor.  It is
                                       usually expressed as the equivalent
                                       concentration of calcium carbonate.

                                       The analysis procedure involves the
                                       titration of the sample with an acid
                                       endpoint.  First phenophtalein is put
                                       into the liquor and the sample is
                                       titrated until the phenolphtahlein
                                       turns from red to colorless.  This is
                                       approximately a pH of 8.3.  The quan-
                                       tity of acid and its normality can be
                                       used to calculate the "phenolphtahlein"

     Next a small quantity of methyl orange indicator is placed in the solution
and the titration is resumed.  This has an endpoint at approximately 4.5 pH.
The total quantity of acid necessary to reach the methyl orange endpoint can be
used to calculate the "total" alkalinity.

     The alkalinity is of most interest in the evaluation of sulfur dioxide
control systems.  The removal of sulfur dioxide can be a function of the
alkalinity under some operation conditions.

SLIDE 6-14

            1. GRAVIMETRIC
            2. TURBIDIMETRIC
                                       There  are  two  general  methods  of  test-
                                       ing  for  sulfates  in  scrubber liquors:
                                       gravimetric  and turbidimetric.  The
                                       gravimetric  is the most  accurate.  How-
                                       ever there are a  number  of  chemical
                                       interferences  in  the analysis.  The
                                       turbidimetric  procedures are subject
                                       only to  suspended solids and liquor
                                       color  problems.   In  most cases, the
                                       turbidmetric procedure is satisfactory.

                                       In this  technique, the sulfate ion is
                                       precipitated as barium sulfate after
                                       the  addition of barium chloride.  The
                                       resulting  turbidity  is determined by a
                                       nephleometer,  filter photometer or
                                       spectrophotometer and  compared to a
                                       curve  prepared from  standard sulfate
SLIDE 6-15
                                       The chlorides concentration is of
                                       interest whenever corrosion is observed
                                       or anticipated.

                                       Due to the high solubility of chloride
                                       compounds, there is very little which
                                       can happen to a sample during transport
                                       which would affect the chlorides con-
                                       centration.  For this reason, the
                                       sample precautions which are discussed
                                       earlier for other analyses, are not as
                                       important for chlorides.

     The chlorides can be determined using a specific chloride ion electrode
similar to that used for pH determinations.  It can also be measured using a
silver nitrate titration.  Potassium permanganate is used as the endpoint
indicator in this test.  Both analytical approaches are accurate for the
concentrations of concern in wet scrubber systems.

SLIDE 6-16

                                       Fluorides are of concern in  particulate
                                       wet scrubbers only because of  the  cor-
                                       rosive action.  The concentration  of
                                       fluroides in some gaseous scrubbers is
                                       important since this potentially limits
                                       the absorption of fluoride materials  in
                                       the gas stream.

                                       The fluorides can be determined by a
                                       specific fluoride electrode  test.  The
                                       colorimetric test is more accurate. How-
                                       ever, it is much more time consuming.

                                       Due to the interferences caused by
                                       chlorides, sulfates and carbonates, it
                                       is necessary to distill the  sample
                                       before starting a fluoride colorimetric

     The fluoride concentration is determined photometrically at a  specific
wavelength.  The absorbance is compared against known concentrations  of
fluoride prepared for known solutions.
SLIDE 6-17
                        Volume (ml)


The sample volumes necessary to conduct
the analyses discussed in the lecture
are provided in this slide.  In all
cases, 1 liter (1000 ml) is sufficient
to conduct the specific test.  It  should
be noted, however, that more than  this
amount will be needed if multiple  tests
of a single parameter are needed or if
there is interest in several parameters.

Samples should be stored in bottles
which will not affect the material to be
tested.  Polypropylene bottles are the
most common containers since these are
relatively inert and unbreakable.
     The analyses should be performed as  soon as  possible.   The  maximum holding
times are generally considered to be 7 days for all  of  the  tests except the
turbidity test which has a limit of 1 day.  Of course,  exposure  to  significant
temperature changes can result in changes in the  samples.


SLIDE 6-16

          TPQT MPTHnn^               This is a brief summary of the test
          It&l witmuuo               methods used for liquor analyses.
 Parameter       S.M.      EPA    ASTM       These test numbers  should be specified
 Suspended &                               when discussing the test results so
 Dissolved                                  that there is no confusion regarding
 Solids          208      160    D1888       the specific analytical procedures used.
 Alkalinity        403      310    D 1067
                                         The abbreviation S.M.  stands for stand-
 Chlorides        408      325    D 512       ^ methods ag published in Standard
 Fluorides        414      340    D1179       Methods for the Examination of Water and
 Surface                                   Wastewater, 14th Edition.
 Tension         None      None    D 1590
 _ ,.           .OT      ,,c    n _...       The EPA test procedures numbers are from
 Suifates         427      375    D 516       publication EPA-600/4-79-020, dated
                                         March, 1979.

                                         The abbreviation ASTM  stands for the
                                         American Society of Testing Materials,
                                         1984 Standards.


6-1.  The correct answer is "c".  The type of sample which is most represent-
      ative of the conditions being evaluated should be used.  Long term
      averages are usually evaluated using composite samples.  Short term
      extreme conditions are usually evaluated using grap samples.

6-2.  There is no direct relationship between the two different measures of
      turbidity.  The correct answer is "d".

6-3.  The correct answers are "b", "c", and "d".  All of these affect the
      degree of light scattering within the instrument.  The large diameter
      particulate do not cause a "measurement error" since they contribute to
      the sample turbidity.

6-4.  The correct answer is "d".  Higher temperatures can result in the
      volatilization of organic compounds and other problems discussed in
      the lecture.

6-5.  There are no field instruments available for spot checking the liquor
      surface tension.  The tensionmeter is too susceptible to problems to
      permit field use.  The correct answer is "d".


6-1.  Are composite samples more useful than grap samples?

      a. Yes
      b. No
      c. It depends on the purpose of the liquor analyses
      d. None of the above

6-2.  If the measured turbidity is 34 JTUs,  what is the value
      of the turbidity expressed in NTUs?

      a. 68 NTUs
      b. 34 NTUs
      c. 17 NTUs
      d. It can not be determined from the information given.

6-3.  Which of the conditions listed below can cause errors in
      turbidity measurements?

      a. The presence of large diameter suspended particles
      b. Fingerprints on the sample tube
      c. Scratches on the sample tube
      d. Air bubbles
      e. All of the above
6-4.  What temperature is generally used for drying of solids samples?

      a. 50 to 75F
      b. 100 to 105F
      c. 150 to 175F
      d. 215 to 220F
      e. 250 to 265F
      f. 295 to 305F
      g. 345 to 355F

6-5.  What field instruments are useful for spot checking the liquor
      surface tension?

      a. Tensionmeters
      b. Bubbleometers
      c. Nephleometers
      d. None of the Above


                                 LECTURE 7

                          INSPECTION AND EVALUATION

                                       The  single most important  factor which
                                       affects  the  performance of participate
                                       wet  scrubber systems is the particle
  INSPECTION AND EVALUATION      size distribution.  This lecture starts
                OF                    with a discussion of particle  size and
  ^ARTICULATE WET SCRUBBERS     the  changes  in size which  can  occur in
                                       the  scrubber.

                                       Scrubber static pressure drop  has been
                                       used extensively in the past to judge
                                       the  adequacy of scrubber operation.
                                       The  uses and limitations of pressure
                                       drop are briefly examined.

                                       Inspection procedures for  each major
                                       category of  scrubber are addressed. The
                                       purpose  of these sections  is to present
                                       the  data and observations  which are most
                                       useful for identifying commonly reported

The two mechanisms .primarily responsi-
ble for particle capture in scrubbers
are impaction and diffusion.

Impaction occurs when the particle  in-
ertia is so high that the particle  can
not move around an obstacle in the
gas stream.  As shown in the slide,  the
inertia is proportional to the square
of the particle diameter.  Impaction is
much higher for large particles  than
for very small particles.  This  is  one
of the reasons that particle size is
important to scrubber performance.

In addition to the particle size, im-
paction is related to the difference in
particle and obstacle velocites.  This
is important since the relative  veloci-
ties developed in scrubbers differ
Diffusion  is the random movement of
small particles due  to  collisions with
gas molecules.  The  rate of  diffusion
is inversely proportional to the
particle diameter.   It  is significant
only for very small  particles which have
very little total mass.

               IMPORTANCE OF
               PARTICLE SIZE
              ARBITRARY CURVE
          T3  To.o 100.
The combined effect of impaction and
diffusion is a performance curve
similar to the one shown here.  Impac-
tion is very effective for particles
which are larger than 10 microns, but
becomes less effective as the particle
size decreases to the 0.2 to 0.5 micron
range.  Diffusion begins to exert some
influence in the 0.2 to 0.5 range and
becomes more effective as the particle
size decreases.

The peak of the curve represents the
particles in the range where neither
impaction nor diffusion are especially
Lecturer *s Notes
     The left side of the curve is often not important when considering mass
emissions from the scrubber system.  Particle size data for this range is also
more difficult to obtain.

If the performance curve for a given
scrubber were known, and the particles
had a uniform size, it would be a simple
matter to design a wet scrubber.  Unfor-
tunately, there are a number of very
important factors which make this imprac-
tical.  These include: (1) the wide
variation in particle sizes, (2) the
influence of particle surface on impac-
tion, and (3) the influence of liquor
characteristics on impaction.

The most important of these is the
variation in the particle size distribu-
tion in the scrubber inlet gas stream.

                   o .
SLIDE 7-6                              The untreated gas stream never contains
                                       particles with a uniform size.  There
                                       is a distribution of sizes as suggest-
                                       ed in this slide.

                                       The largest of the particles are in the
                                       range of 50 to 100 microns.  As a frame
                                       of reference, this is approximately the
                                       diameter of a human hair!  The smallest
                                       particles (of any significance to air
                                       pollution emissions) are in the range
                                       of 0.1 microns.  A particle of this
                                       size has approximately one millionth
                                       the mass of a 100 micron particle.

      One of the challenges in designing a scrubber system is determining the
type of scrubber vessel that is most appropriate for the size distribution
which exists.  It is obviously easier to collect particles in the'10 to 100
micron range than it is to collect the particles in the 0.1 to 10 micron range.
In fact, all of the scrubber types perform very well on the 10 to 100 micron
particles.  However, there are substantial differences in the capability to
remove the 0.1 to 10 micron material.

Lecturer's Notes
     In addition to differences in physical size, there are also  differences
in particle shape and in particle specific gravity.  All of these have an
impact on the behavior of the particle In the scrubber.

Si.TP^ 7-7                              Condensation of vapors can occur as the
                                       gas stream cools while passing through
                                       the scrubber vessel.  These vapors could
                                       result from a variety of causes including,
                                       but not limited to incomplete combustion,
                                       vaporization of raw material components,
                                       and the generation of high concentration
                                       of acidic compounds in the process

                                       If this material condenses on the surfaces
                                       of existing particles, the overall size
                                       distribution shifts slightly.  If it con-
                                       denses as a homogeneous particle, a large
                                       number of very small particles are created.
                                       These homogeneous particles often grow to
                                       reach final particle sizes in the range
                                       of 0.1 to 1.0 microns.

     It is important to realize that the condensation and particle growth
processes require a finite amount of time.  It starts as the gas  stream enters
the  scrubber and continues until the gas stream is no longer supersaturated
with the vaporous material.  This means that some of the very small  particles
may  not exist as particles until the gas stream is partially through the
scrubber.  Also, the particle size distribution is changing as the gas stream
passes through the scrubber.  Scrubbers differ with respect to their capability
to handle this complicated situation.
                    '.i'/ PARTICLE

                       X. SHATTERED
                      .;/.  DROPLET

                        / PARTICLES
Very small particles can also  be  gen-
erated by the evaporation of droplets
containing solids.  This can occur in
evaporative coolers or presaturators
handling gas-streams of high gas  temp-
eratures.  The total quantity  of  solids
put back into the gas stream can  comprise
a significant fraction of the  total mass
present in the small particle  range.
                        t -*
                          One additional mechanism for the  develop-
                          ment of small particles is the  shattering
                          of agglomerates as illustrated  here.   The
                          high gas velocities necessary to  ensure
                          good impaction can result in the  shatter-
                          ing of the agglomerates as they move  in
                          the gas stream.  The individual particles
                          are more difficult to capture than  the
                          agglomerate since they have much  lower

       Diameter, Microns
Jue to the formation of very small
particulate matter, it is possible to
have a major fraction of the parti-
culate mass in  a  size range which is
beyond the capability of the scrubber.

Unfortunately,  the  fraction efficiency
curve, as shown on  the slide is rarely
known for the specific scrubber being
inspected.  Also, the particle size
data is never known during the period
of the inspection.  There are no in-
struments with  which the inspector can
:ake a quick sample and determine if
vhere has been  a  shift in the particle
size distribution.
     Changes  in  the  particle size distribution can be  inferred from changes in
the process operating conditions and from the visible  emissions levels.  It is
apparant that the  particle size of most concern in scrubber  performance is also
the size range in  which liqht scattering is most effective.  A sudden increase
in the residual  opacity without any. other obvious changes  in scrubber opera-
ting conditions  may  indicate a change in particle size distribution character-
S^TDF. 7-11
There is no question that  the  pressure
drop is a very important operating
parameter for most types of  particulate
wet scrubber systems.  However,  there
are some very important limitations
which must be considered when  using this
data.  The next set of slides  examines
the uses and limitations of  the  static
pressure data.

SLIDE 7-12
 "When compared at the same power con-
  sumotion, all scrubbers give subsiantialiy
  the same degree of collection of a given
  dispersed dust, regardless of the mechanism
  involved and regardless of whether the
  pressure drop is obtained by high gas flow
  rates or high water flow rates."
                          The use of static pressure  drop data
                          has been based primarily  on the Contact
                          Power Theory which is  summarized in the
                          two equations to the left.   The first
                          states that the penetration (which is a
                          way of expressing emissions) is propor-
                          tional to the energy consumed in the gas
                          phase plus the energy  consumed in the
                          liquid phase.

                          The gas stream power input  was always
                          considered to be the dominant factor.
                          In the late 70's EPA funded studies
                          indicated that the liquid stream power
                          input for certain types of  scrubbers was
                          less important than indicated by the
                          equation.  This reduced the Contact
                          Power Theory to a simple  proportionality
                          between the emissions  and the pressure
SLIDE 7-13
                                        The  generally assumed relationship
                                        between  static pressure drop and over-
                                        all  scrubber performance based on the
                                        Contact  Power Theory is shown in this
                                        slide.   In  some cases, curves have  been
                                        compliled for "similar" scrubbers in a
                                        certain  industry category.  These cor-
                                        relations can suffer from large plant-
                                        to-plant particle size variations.

                                        Other variables which contribute to the
                                        scatter  in  the data include variations
                                        in the surface characteristics of the
                                        particles,  variations in the liquor
                                        characteristics, and variations in  the
                                        degree of gas-liquor maldistribution.

     The net  result of the plant-to-plant differences and the variations over
time at any given plant render these correlations  almost meaningless for the
purposes of the inspector.  The scatter in  the  data is too great to draw mean-
ingful conclusions from an industry wide pressure  drop-emissions correlation.

SLIDE 7-14
       20 _     ASPHALT PLANTS J
                   10     20

            PRESSURE DROP, Inches
                      This  is  one  extreme example of the degree
                      of  scatter which is possible when data
                      from  more than one scrubber system is
                      used  in  a correlation.   In this case, the
                      correlation  attempts to relate emissions
                      from  Hot Mix Asphaltic  Concrete Plants
                      using mechanically aided scrubbers.

                      This  degree  of scatter  should not exist
                      if  the relationship between pressure
                      drop  and emissions is strong and if the
                      particle sizes distributions are
Lecturer's Notes
     This is the first of several examples intended to illustrate  that  the
evaluation of particulate wet scrubber performance is more complex than simply
recording the static pressure drop.
SLIDE 7-15

      .05 i-
This is another example of an industry
wide correlation of wet scrubber perfor-
mance.  It is for venturi scrubbers on
coal preparation plant thermal driers.
There is no obvious correlation between
the pressure drop and particulate emis-
sions rate.
    i  I
              20   30  40 SO   70

             PftESSUKf DROP, ln
SLIDE 7-16
               T T
                          Flint A
                         T Plant B
                         A Plant C
                         O punt 0
                          Pilnt Plant
         0.02    5.05   0.10
          EMISSIONS, Gr/ttF
This is published data  for  venturi
scrubbers serving 4 commercial  lime
kilns and one pilot scale lime  kiln.
There appears to be a relationship
between the pressure drop and the
particulate emissions.   However,  it
should be noted that the data is
plotted in log-log coordinates  for
the convenience of the  authors.  The
degree of scatter may be much less
than the previous two slides, but it
is still too high for use by  inspectors,
Lecturer's Notes
     The main point of  this  slide  is that there are a number of published
correlations of the type  shown  in  this graph.  The authors were simply
illustrating the  general  relationship between the pressure drop and  the
emissions.  They  were not advocating that the performance can be evaluated  by
use of the static pressure drop alone.
SLIDE 7-17

< 0.20

I 0.10

 SLIDE  7-18
 .03 -
m -ul
      60    62    64   66    68    70
      PRESSURE DROP, Inch** (Minute* 5 -11)
One way to minimize the scatter  in  the
pressure drop - emissions correlations
is to limit it to a specific  plant.
This slide presents a correlation for
three venturi scrubbers on  three Q-BOP
units at the same plant.  The reduced
variability is probably due to the  fact
that the systems were identical  and  the
liquor quality was very similar.

For single site correlations, the
variability should be reduced to only
those conditions which change with  time
at the site.  This conceivably allows
for the preparation of a meaningful
correlation which could be'used  during
an inspection.
     There are never enough stack tests on a specific site to adequately
 define this correlation.   Furthermore, there is always the possibility that
 there has been a sudden shift in the one or more of the particle generation
 mechanisms.  The pressure drop data must be used carefully.
 SLIDE 7-19
          5    10    It    20     25

           VCNTURI PRESSURE DROP, Incntl notor
The consequences of a shift in  process
operating conditions is illustrated  in
this slide.  The two curves relate the
outlet particulate emissions  to the
pressure drop of a pilot scale  venturi
scrubber serving a coal-fired boiler.

The only major difference is  the coal
characteristics.  The emissions are  10
to 20 % higher with the McKay coal
supply.  In other types of applica-
tions, there can be a much greater
shift in the site specific performance.

SLIDE 7-20

                                       Another potential source of error in the
                                       use of the Contact Power type correlations
                                       is the erroneous application of the
                                       original equation.

                                       The author of the original paper derived
                                       the equation from Bernoulli's Law.  The
                                       0.158 constant which appears in slide
                                       7-17 represents the inverse of the gas
                                       density at 70 F and 14.7 psia.  Although
                                       this was stated in the article, the
                                       importance of gas density was forgotten
                                       by some.

     A rederivation of the Contact Power theory (see Wet Scrubber Performance
Evaluation Manual, EPA 340/1-83-022) indicates that the relationship should be
as shown in the above slide.  The pressure drop divided by the average gas
density should be correlated with the total energy consumed by the scrubber.
The average gas density can vary substantially from scrubber to scrubber.  It
is a function of the gas temperature and the static pressure as indicated in
the equation.

     A check of the change in gas densities before and after some high pres-
sure drop scrubbers also indicates that there can be more than a 10% change.
This means that the incompressible flow assumption on which the Contact Power
Theory was based is also in.error.

Lecturer's Notes
     The point regarding compressible flow is not very important for field
inspectors.  They do need to understand, however, that the gas density is an
important variability.  Gas temperature measurements are made during inspec-
tions to aid in estimating the densities before and after the unit.

              DROPLET SIZE



SLIDE 7-21

                                      Two other  factors of importance to
                                      particulate scrubber performance are
                                      the surface tension of the liquid and
                                      the surface characteristics of the
                                      particle.  As illustrated in this slide
                                      (see middle column), the liquids with
                                      high surface tension often yield large
                                      droplets when sprayed from nozzles.
                                      This decreases the number of impaction
                                      targets for particles passing through
                                      the scrubber.  It is also more diffi-
                                      cult for a particle to penetrate into
                                      the droplet when the liquid surface
                                      tension is high.

      Particles composed primarily of  hydrocarbons or coated with'an organic
material are less wettable.   This  also hinders the coalescence of the parti-
cle into the water drop.  Unfortunately,  the  particles which result from the
condensation of incompletely burned fuels and other hydrocarbon materials can
be difficult to "wet" due to the surface  characteristics and difficult to
impact due to the very small size  range.

     The chemicals added to  the system at the pond, the clarifier, or the
recirculation tank can have  a large influence on  the surface tension of the
liquor going to the scrubber.  This can conceivably have an impact on the
efficiency of the overall scrubber. Unfortunately, both the particle surface
characteristics and the liquor surface tension are difficult to evaluate
during the inspection.

SLIDE 7-22
             The remainder  of  the  lecture will
             concern specific  types  of  scrubbers.
             The focus of this material  is  on the
             relevant operating  parameters  for  each
             type to order  to  identify  common prob-
             lems.  The inspection procedure is
             "tailored" for each group.

             Each of these  categories is actually a
             group of different  designs  which share
             some basic similarities.   The  specific
             inspection procedures must  be  adjusted
             for these minor differences.   It is the
             responsibility of each  field inspector
             to make these  changes in the inspection
             procedure and  to  perform the inspection
             in a safe manner.

SLIDE 7-23
      Source: Air Pollution
              Training  Institute
This is a sketch of a spray  tower
scrubber.  It is the simplest  type  of
wet scrubber and it has  the  lowest
overall particulate removal  capability.
This is partially due to the low rel-
ative velocities between the liquor
droplets formed at the nozzles and  the
particles moving with the gas  stream.
Remember that impaction  is proportional
to the relative velocity of  the particle
to the droplet.

Due to the limited capability  of the
unit, it should not be used  at sources
for which a major fraction of  the  parti-
culate matter is in the  0.1  to 5 micron
     Another common version  of  a  spray  tower scrubber has the spray nozzles
arranged on a vertical header near the  center of the cylindrical shell.  The
gas enters tangentially  so that there is some cyclonic action to aid particle

Lecturer's Notes
     Another particle capture mechanism that could contribute to particle
removal in spray tower scrubbers  is electrostatic attraction.  Static charges
could conceivably occur  on droplets sprayed from high pressure nozzles.
SLIDE 7-24

       1. Average Opacity (Residual)
       2. Minimum and Maximum Opacities
       3. Droplet Reentrainment
       4. Liquor Flow Rate
       5. Nozzle Operating Pressures
       6. Liquor pH
       7. Liquor Turbidity
       8. Nozzle Operating Condition
       9. Shell Condition
This is a list of  the  operating data
and observations which should be made
during routine inspections  of spray
tower scrubbers.

The emphasis is placed on nozzle per-
formance problems  such as pluggage,
erosion, and corrosion.  Since the
nozzles can rarely be  observed,  in-
direct symptoms of these problems must
be used.  These include nozzle pres-
sure, liquor pH, and liquor turbidity.
     One parameter not listed  here is  the static pressure drop.  Performance
is not a strong function  of  the  normally low static pressure drops in this
type of scrubber.  While  the liquor flow rate is listed explicity, it is
rarely measured by on-site instruments.   In these cases, changes in the the
liquor flow must be determined from pump performance conditions and/or changes
in the nozzle operating conditions.

     Evaluation of the ductwork  and shell physical condition is especially
important since many of these  scrubbers  are made with unlined carbon steel.
Low pH excursions can lead to  rapid and  severe damage.

SLIDE 7-25
                                        This is a photograph of a simple spray
                                        tower scrubber serving a Hot Mix
                                        Asphaltic Concrete plant drier.  The
                                        fan  is ahead of the scrubber vessel and
                                        not  shown here.  The stack discharge is
                                        directly above the frame of the

                                        One  of the first steps in any scrubber
                                        system inspection is the evaluation of
                                        the  visible emissions.  The residual
                                        opacity should be observed, using the
                                        established reference methods. Any
                                        variations in the opacity are normally
                                        due .to changes in process conditions.
                                        The  timing of these cycles'or spikes
                                        should be noted so that the process
                                        equipment performance can be checked
                                        later in the inspection.

     The physical condition of  the  shell  and the ductwork should be checked
for signs of erosion and corrosion.   Spray  tower scrubbers are used on sources
of large particulate which can  be very  erosive.  The absorption of carbon dio-
xide and sulfur dioxide can reduce  the  liquor pH to the corrosive range.  Some
smaller systems do not have alkaline  addition systems which add neutralizing
materials on a continuous basis.

SLIDE 7-26
                                        These are potential symptoms of nozzle
                                        pluggage.  The increase in the nozzle
                                        header pressure from baseline levels
                                        occurs only when the flow rate is
                                        increased or the nozzles have plugged.
                                        If  the pump motor currents have not
                                        changed since the baseline period and
                                        the pump discharge pressure is also
                                        similar, it is unlikely that the flow
                                        rate has increased.

                                        The presence of high suspended solids
                                        in  the recirculation liquor is often
                                        associated with nozzle pluggage.  The
                                        turbidity of the recirculation liquor
                                        should be qualitatively evaluated.  If
                                        it  appears to be high, the sample can
                                        be  taken for a suspended solids test.

     For systems that are operating,  the type of nozzle presently being used
should be determined.  This should  be compared with the type used previously
to see if the present nozzles are more susceptible to pluggage.  The type of
spray and the spray angle should also be noted on any data sheets concerning
the nozzles.
1. Increased Quality
2. Increased Nozzle
  Header Pressure
3. Unchanged Pump Motor
4. Unchanged Pump
  Discharge Pressure
5. High Liquor Turbidity
6. Small Ponds
7. Low Pump Intake
8. Corroded Piping and
9. Scaling Conditions in
  Scrubber Vessel

SLIDE 7-27
                                       Several of the items listed on the last
                                       slide concern settling pond related
                                       nozzle pluggage problems.   This area
                                       should be part of the inspection when-
                                       ever nozzle pluggage problems are

                                       This is a photograph of a  pond for a
                                       small spray tower scrubber.  The turbid-
                                       ity of the pond water near the pump
                                       intake should be checked.   The sample
                                       should be taken at a safe  and convenient
                                       location in the last zone  of the pond.
                                       If the turbidity is high,  the settling
                                       characteristics are not satisfactory.

     The position of the pump intake should be carefully checked.  It must be
deep enough to prevent cavitation of the pump, but not so deep that silt from
the bottom of the pond is carried into the suction line.

Lecturer's Notes
     The performance of settling ponds can often be improved by the construc-
tion of several distinct settling zones separated by overflow weirs.  It may
be necessary to occassionally remove the settled material in the  first zone.
SLIDE 7-28
                                       Whenever nozzles are removed for clean-
                                       ing or replacement,  the type of damage
                                       should be briefly described in the
                                       maintenance records.

                                       The objective of the records is to pre-
                                       vent repeat failures.  Either the fund-
                                       amental cause of the nozzle problem
                                       should be rectified  or a nozzle which
                                       is less vulnerable should be used.

                                       The field inspector  should plan to
                                       inspect the scrubber the first time
                                       that it comes out of service and the
                                       aozzles are being checked.  In this
                                       way, a first hand opinion can be formed
                                       concerning the cause of the problem.

SLIDE 7-29
                                        Pluggage of a small number of nozzles
                                        in  the same general location within the
                                        scrubber system can lead to poor gas-
                                        liquor distribution.  This may not have
                                        a major effect on the nozzle header
                                        pressure or the pump operating condi-
                                        tions.  The only way to identify these
                                        problems is to observe nozzle perform-
                                        ance at a time when the scrubber is out
                                        of  service.

                                        From a vantage point above the nozzle
                                        header, the spray angles of the nozzles
                                        are observed when the recirculation
                                        pump is turned on.  Distorted spray
                                        angles and completely plugged nozzles
                                        can be seen with a bright flashlight.

     Under no circumstances  should an inspector enter the scrubber to check
the conditions of  the nozzles  or lean through the hatch to see the spray
angles.  There can be oxygen deficient conditions and high concentrations of
toxic pollutants trapped  in  a  scrubber which is out-of-service.

     This is an especially effective way to find nozzle problems which are
causing excess emission conditions.  However, it is rare to find a spray tower
scrubber with a safe and  convenient access hatch to view the nozzles.  This
should not be attempted unless the inspector can comply with all plant and
agency safety policies.
SLIDE 7-30
          Leakage from Positive
          Pressure Scrubbers
          1. Reduced Gas Flow
          2. Visible Leaks
          3. Audible Leakage Points

          Infiltration Into Negative
          Pressure Scrubbers
          1. Audible Infiltration
          2. Reduced Hood Static
          3. Fugitive Emissions
Gas leakage can occur due  to corrosion
of the ductwork and scrubber shell.
These can be identified as visible
leaks from the scrubber and as  audible
leaks from ductwork.  The  drop  in gas
flow through the scrubber  can be quan-
tified by conducting a pitot traverse
at the stack.

Air infiltration into negative  pressure
spray tower scrubber systems is diffi-
cult to identify.  There is little
decrease in the fan inlet  gas temperature
since the temperature is normally
120 F to 140  F at this point.
      There is also very little change in the scrubber outlet  static  pressure
 since the  resistance to flow through these systems is normally  low.   A pitot
 traverse at the stack outlet is not useful for quantifying  the  leakage since
 gas  flow rate does not change substantially.  The best symptoms of air infil-
 tration are increased fugitive emissions, reduced hood static pressure (see
 Lecture #5),  and audible leakage sites.

                         Mist eliminator
                         Liquid tpriyi
This is a sketch of a packed bed scrub-
ber .  These are used primarily for gas
absorption or for gas cooling, both of
which are facilitated by the large
liquid surface area on the packing.
They have only a very limited cap-
ability for removal of particulate.
However, there are applications where
both gases and particulate must be

Particle removal by impaction is limit-
ed due to the low velocities between
the particles in the gas stream and the
liquid on the packing.  These scrubbers
are rarely effective for particles less
than 3 microns.
  Source: Air Pollution
   Training Institute

     Another style of packed bed has horizontal gas flow through a vertical
packed bed.  The liquor is introduced at the top and from the front of the
packing and flows in a cross current direction relative to the gas stream.
SLIDE 7-32
                                       This photograph shows some of the most
                                       common types of packing material used
                                       in packed bed scrubbers.  The one in
                                       the upper left corner is a cross part-
                                       ition ring,  the ones in the lower left
                                       are Intalox saddles.  Tellerettes are
                                       in the lower center of the slide.  Pall
                                       rings are in the lower right and a Ras-
                                       chig ring in the uppper right.  Gravel
                                       is another material which is commonly

                                       All of the packing materials are avail-
                                       able in various sizes, ranging from
                                       1/2 inch to 3 inches.  The materials of
                                       construction include synthetic plastics,
                                       ceramics,  porcelain, and metal.  The
                                       packing size and configuration affects
                                       the overall pressure drop and liquid
                                       hold-up within the bed.
  Source:  Air Pollution
   Training  Institute

SLIDE 7-33
                                        This is a  list of the inspection data
                                        and observations which should be made
                                        during a routine inspection of a packed
                                        tower scrubber.  The primary emphasis  is
                                        on any conditions which promote bed
                                        pluggage,  bed channeling, and poor
                                        liquor distribution.

                                        On level 3 inspections, it is necessary
                                        to have accessible measurement ports at
                                        the scrubber inlet and outlet.  Ports
                                        between beds in series are also helpful.

                                        As with the spray tower scrubbers,  these
                                        systems are often small and lack any on-
                                        site instrumentation.  In these cases,
                                        the liquor flow rate must be estimated
                                        from the pump operating characteristics.

     Reentrainment  is less common with this type  of scrubber since the gas
velocities  up  through the bed are low.  The only  opportunity for reentrainment
is while the gas  stream passes around the nozzles at the top of the scrubber.
However, these nozzles should not be generating fine droplets which could  be
carried upwards with the gas stream.  The function of the nozzles is simply to
uniformly distribute the liquor on the top surface of the packing.

     1. Average Opacity (Residual)
     2. Minimum and Maximum Opacities
     3. Presence or Absence of Detached Plume
     4. Droplet Reentrainment
     5. Inlet and Outlet Gas Temperatures
     6. Shell Condition
     7. Liquor Flow Rate
     8. Nozzle Operating Pressures
     9. Liquor pH
    10. Liquor Turbidity
    11. Rate of Addition of Alkaline Material
            BED PLUGGAGE IN
           1. High Static Pressure
             Drops Across Beds
           2. High Liquor Turbidity
           3. High Liquor pH
           4. High Solids Content
             in Inlet Gas Stream
SLIDE 7-34
                                        Packed  beds  are prone to pluggage  since
                                        the liquid  stream is not flowing rapidly
                                        enough  to continually remove accumulated
                                        materials.   The sources of the  solids
                                        include: (1) suspended solids in the
                                        recirculation liquor, (2) precipitated
                                        dissolved solids from the recirculation
                                        liquor,  and  (3) impacted solids from the
                                        gas stream  on the first bed.

                                        The symptoms which may indicate the
                                        development  of bed pluggage are listed
                                        on this slide.  An increase in  the
                                        static  pressure drop across the entire
                                        scrubber or  any individual bed  must be
                                        due to  either a gas flow increase  or
                                        pluggage.   The gas flow rate can be
                                        evaluated using the fan motor currents
                                        or a  pitot  traverse.  In the case  of
                                        severe  pluggage, there could be a  drop
                                        in gas  flow rate and increased  fugitive

      The  liquor turbidity should always be  low at  the inlet of a packed  tower
scrubber.   An increase in the pH may suggest that  some precipitated solids are
scaling  the packed bed.

SLIDE 7-35
                                       Channeling can occur whenever  part  of
                                       the packing material is  incompletely
                                       wetted or when the gas stream  flow  up
                                       the bed(s) is very nonuniform.   The
                                       latter can be caused by  solids  deposits
                                       withing the bed.

                                       Channeling is especially difficult  to
                                       avoid when the liquor flow  rate is  low.
                                       For this reason, attempts should be made
                                       to evaluate the liquor flow rate using
                                       either the on-site gauges or the pump
                                       operating conditions.

     On large packed tower scrubbers with multiple beds.it is common  practice
to have liquid redistributors between the beds.  For all packed t6wer
scrubbers, the spray nozzles must have the proper spray angle and  must be
located at the appropriate distance from the top of the bed.
           1. Reduced Liquor
             Flow Rate
           2. High Turbidity Liquor
           3. High Solids Content
             of Inlet Gas Stream
SLIDE 7-36

                                       Channeling can be especially  severe  in
                                       the cross flow type of packed bed
                                       scrubbers.  There is a natural tendency
                                       for the liquor to flow to  the bottom of
                                       the bed.  Under low flow conditions,  a
                                       major fraction of the packing at the top
                                       remains unwetted.  This reduces the
                                       amount of particulate captured and
                                       significantly reduces gas  absorption.

                                       On units which have worked well
                                       previously, the most useful symptoms of
                                       this problem include a decrease in the
                                       total liquor flow rate or  a change in
                                       the nozzle header pressure (indicating a
                                       problem with the front spray  nozzles).

     For units which have suffered a chronic channeling problem,  it  may be
possible to substitute large capacity nozzles for the top header  and reduce
flow to the lower header.  The use of smaller diameter packing in the top
portion of the bed can lead to greater flow resistance, thereby shifting some
of the gas flow rate to the lower portion of the bed.  The latter approach  must
be done carefully so that the gas absorption is not hindered by the  shorter
retention time in the bed.


SLIDE 7-37
                                       Sneakage can occur around the bottoms of
                                       the cross flow packed beds.  This is
                                       normally prevented by internal weir
                                       seals which maintain a head of liquor
                                       greater than the static pressure of the
                                       gas stream.  However, some of the gas
                                       stream will bypass the packed bed if the
                                       weirs are improperly sized or corroded.

                                       This is not a problem with the counter-
                                       current flow (vertical flow) type pack-
                                       ed bed.  The packing extends from one
                                       side of the scrubber vessel to the other
                                       without any open areas which could
                                       permit sneakage.
  Source: Air Pollution
   Training Institute

     Sneakage is identified by measuring the static pressure drop across the
entire scrubber or the individual beds.  A decrease in the pressure drop which
is not accompanied by a gas flow rate decrease is a clear sign of sneakage.
The gas flow rate can be measured using a pitot tube or estimated from the fan
operating conditions.
SLIDE 7-38
                      Mist eliminator

                      Liquid iprayt
This is a sketch of a single stage
moving bed scrubber.  This unit has
hollow spheres as packing material which
are entrained by the gas stream.
Impaction of particulate occurs on the
droplets which are formed within the
turbulent bed.  The liquor is introduced
from the top using a set of nozzles
similar to those used in packed bed
scrubbers.  There can be a number of
beds in series.

These are used for both particulate
control and gas absorption.  They are
especially effective for sources which
have sticky materials which would clog a
conventional packed bed scrubber.
   Source: Air Pollution
   Training Institute

SLIDE 7-39

     1. Average Opacity (Residual)
     2. Minimum and Maximum Opacities
     3. Droplet Reentrainment
     4. Presence or Absence of Detached Plume
     5. Pressure Drop Across Each Stage
     6. Inlet and Outlet Gas Temperature
     7. Condition of Shell
     8. Liquor Flow Rate
     9. Nozzle Operating Pressures
    10. Liquor pH
                                        The routine inspection observations  and
                                        measurements for moving bed scrubbers
                                        are listed in this slide.

                                        Reentrainment is more of a problem with
                                        these units than with the spray  towers
                                        and packed beds discussed previously.
                                        This is due to the higher gas velocities
                                        through the beds and the possible forma-
                                        tion of fine droplets within the turbu-
                                        lent bed.

                                        Both the static pressure drop across the
                                        scrubber and the liquor flow rate are
                                        important operating parameters.  Gas
                                        absorption and particulate'removal are
                                        favored at high liquor-to-gas flow
                                        rates.  Particulate removal is favored
                                        at high static pressure drops.

     The liquor turbidity is not  very important since the moving bed scrubber
is inherently resistant to pluggage.   The movement of the beds prevents the
accumulation of solids and the  spray  nozzles generally have pluggage resistant
large orifices.  The liquor pH  is important primarily when corrosion of the
scrubber vessel or the recirculation  pump is possible.  At very high pH
levels, scale deposits can occur  in the scrubber sump and in portions of the
screens which retain and support  the  packing.

SLIDE 7-40
                                        Poor gas-liquor distribution can  occur
                                        due to improper inlet duct config-
                                        uration, low liquor flow rate,  the
                                        presence of precipitated solids on  the
                                        support screens or nozzle problems.
                                        One symptom of this condition is
                                        a reduction in the pressure drop  across
                                        one of more of the stages.  If  this
                                        occurs without any obvious changes  in
                                        the gas flow rate or the liquor flow
                                        rate,  poor distribution is likely.

                                        On those few units with observation
                                        windows (which remain partially trans-
                                        parent) , it is possible to visually
                                        identify severe maldistribution.  The
                                        hollow spheres will tend to rotate
                                        across the bed away from the area of
                                        highest gas velocity.

     When the distribution  is  poor,  the gas stream will not reach the  adiabatic
saturation temperature.  The temperature probe discussed in Lecture #2 (dev-
eloped by Shifftner) can be used  in  the outlet gas duct to evaluate the  degree
of saturation.

SLIDE 7-41
                                        The performance of the moving bed  scrub-
                                        ber is partially dependent on the  gas
                                        flow rate through the scrubber.  These
                                        units have limited turndown capability
                                        since the area of gas flow can not be
                                        easily reduced.  The droplet size  pop-
                                        ulation and size distribution are  both
                                        dependent on the gas velocity.

                                        Changes in the gas flow rate can occur
                                        due to: (1) gas leakage in positive
                                        pressure units, (2) infiltration in
                                        negative pressure units, and (3) re-
                                        duced process operating rates in all
                                        types of units.

     The preferred method  for  estimating the gas flow rate is to perform  a
pitot traverse at the  outlet of  the scrubber or at the stack.  Alternatively,
changes in the gas flow  can be identified from changes in the corrected fan
motor currents and fan speed (Lecture #5).  Audible sites of gas leakage
and infiltration should  be noted during the inspection.
        1. Reduced Static Pressure
        2. Lower Fan Motor Currents
        3. Decreased Fan Speed
        4. Decreased Production Rate
        5. Audible Gas Leakage or
        6. Reduced Gas Flow Rate
SLIDE 7-42
          1. Gradual Absorption of
          2. Exposure to High Gas
          3. Exposure to Low Gas
                                        Premature failure of the hollow sphere
                                        packing materials can reduce the over-
                                        all performance of the scrubber and
                                        present a threat to the recirculation

                                        The absorption of chemicals into the
                                        packing material leads to gradual  loss
                                        of the'natural elasticity.  Due to the
                                        turbulent motion of the packing, it is
                                        possible to shatter the brittle spheres.
                                        Exposure to moderately high gas temp-
                                        eratures due to temporary loss of  liquor
                                        flow can have the same effect.

     Spheres exposed to low  gas  pressures during shipment can be seriously
weakened due to the difference between the internal pressure (basically sea
level pressure) and the external air  pressure.  After a short period of use,
they can have a high rate of failure.

     The small fragments from the shattered spheres can be retained in the
recirculation system if the  settling  rates in the recirculation tank are  poor.
These fragments can blind a  strainer  on the suction line or can accelerate
abrasion of the pump impeller and lining.

SLIDE 7-43
           1. High Demister Static
            Static Pressure Drop
           2. High Turbidity Demister
            Cleaning Water
           3. Absence of Demister
            Cleaning System
           4. Rainout from Stack
           5. Mud "Lip" at Stack
           6. I.D. Fan Vibration
The demisters can be troublesome  for
moving bed scrubbers when  the  liquor
used for cleaning the demister is the
same as the recirculated liquor.   These
types of scrubbers often use a liquor
with moderate to high suspended solids
levels.  Another cause of  problems is
inadequate freeboard distance  (see
Lecture #5 for definition).  The  liquor
carried from the top stage will drop
back down if the freeboard distance is
great enough.

The symptoms of demister problems are
listed in this slide.  The pressure drop
across the cyclonic demisters  or  chevron
demisters is usually in the range of  0.5
to 2.0 inches.  Higher static  pressures
indicate partial pluggage.
SLIDE 7-44
                          Liquid intei
This is a sketch of a  sieve  plate scrub-
ber.  As with all  tray type  scrubbers,
it consists of one or  more horizontal
stages mounted in  a vertical shell.   The
liquor is introduced at the  top through
a simple delivery  pipe.  The height  of
the liquor on the  stage is controlled by
the overflow weir  on the opposite side
of the tray.  The  liquor passes from
tray to tray by means  of downcomers.

The gas stream passes  upward through the
holes in the tray.  Atomized droplets
formed when the gas passes through the
liquid layer serve as  the impaction
targets for capturing  particles.
   Source: Air Pollution
    Training Institute

     This type of scrubber  is  not  as  common as spray tower or venturi type
scrubbers.  Its efficiency  is  moderate  to good for small particles.  The main
operating variables include the  liquid  flow rate,  the gas flow rate, the height
of liquor on each tray, the number of trays in series and the suspended solids
content of the liquor.  As  with  all scrubbers, the pH is also important.

SLIDE 7-45
                                        The impingement plant scrubber  shown in
                                        the sketch is similar to  the  sieve
                                        plate scrubber shown in the previous
                                        slide.  The holes in the  trays  of
                                        impingement tray units are much smaller
                                        and more numerous.  Due to the  higher
                                        gas velocities through the holes, the
                                        particulate matter collection is more
                                        efficient than the sieve  plate  units.
                                        This advantage is gained  at the expense
                                        of increase sensitivity to pluggage of
                                        the very small holes.

                                        The operating parameters  important to
                                        impingement scrubbers are identical to
                                        those which are important for the sieve
                                        plate scrubbers.  The inspection pro-
                                        cedures are also similar.
Source: Air Pollution
 Training Institute
SLIDE 7-46

     1. Average Opacity (Residual)
     2. Minimum and Maximum Opacities
     3. Droplet Reentrainment
     4. Presence or Absence of Detached Plume
     5. Pressure Drop Across Each Stage
     6. Liquor Flow Rate
     7. Liquor Turbidity
     8. Liquor pH
     9. Condition of Shell
                                        The inspection observations and
                                        mesurements for tray type scrubbers are
                                        summarized on the adjacent slide.

                                        The liquor quality is extremely  impor-
                                        tant due to the susceptibility to  plug-
                                        gage of the trays.  A sample of  the
                                        liquor should appear almost clear  and
                                        have a total suspended solids content of
                                        less than 1% by weight.

                                        The pressure drop across each stage can
                                        be used to evaluate a variety of pro-
                                        blems which affect particulate control.
                                        Low pressure drop can be caused  by low
                                        gas flow rate, low liquor flow rate,  low
                                        liquor levels on the trays, or sneakage
                                        of the gas around the trays.

     The outlet gas temperature  is useful for identifying severe maldistribu-
tion or inadequate liquor  flow rates.   The pH is especially important since
there are a number of wetted  scrubber  components which are vulnerable to
corrosion.  These include  the trays,  impingement targets (if used), inlet weir
box, overflow weirs and  downcomers.

      SLIDE  7-47
                               INLET WEIR SOX
                          END WEIR
                          MAINTAINS LEVEL ON
Reduced gas flow rate can lead to
reduced particulate removal in several
different ways.  The lower velocity
through the holes and the liquor layer
reduces the effectiveness of impaction.
In severe situations, the gas velocity
can be so low that the liquor "weeps"
through the holes.  In this case, the
gas-liquor distribution is very poor and
there are few small droplets to serve as
impaction targets.

Reduced gas velocity can be identified
by using the static pressure drop across
each of the stages.  Decreases from the
baseline values indicate reduced gas
flow rate.  Values less than 1.5 inches
W.C. indicate potential "weeping".
           When low static  pressure  drops are observed, it  is useful to estimate
      changes in the gas  flow rate since the baseline  period.   If  possible, a pitot
      traverse should be  conducted on  the outlet  of  the scrubber or in the  stack.
      The fan motor current and  speed  should also be noted.

           Audible air infiltration  points  in the outlet  duct or fan (negative  pres-
      sure systems) should  be noted.   Gas leakage (positive  pressure systems) ahead
      of the scrubber vessel should  be noted.
      SLIDE 7-48
                            INLET WEIR BOX
Pluggage of trays has the opposite
effect of reduced gas flow rates.  The
observed static pressure drop across the
trays increases.  This increase may be
most severe for the bottom tray since
it handles the liquor with the highest
solids content and since it is the
tray exposed to the inlet gas stream.

Another symptom of pluggage problems is
the liquor turbidity.  A sample of the
recirculation liquor should appear
relatively clean.
           If  there  is  an  opportunity  to  view  the  trays while the  scrubber  is out-of-
      service,  the presence  of  solids  on  the trays can be confirmed.  Under no cir-
      cumstances should the  inspector  enter the  scrubber vessel since there can be
      oxygen deficient  or  toxic gases  contained  inside.  Also, the corrosion resis-
      tant liners can be easily damaged.

SLIDE 7-49
                                       Sneakage around the trays can occur when
                                       the  pressure drop across the trays ex-
                                       ceed expected values.  The downcomer
                                       weir shown  in this sketch must be high
                                       enough  so that the resistance to gas
                                       flow up through the downcomer is too
                                       high.   If the designer did not antici-
                                       pate the present high static pressure
                                       drops across the tray, this weir may be
                                       too  short and gas may be sneaking around
                                       the  tray.   The static pressure drop
                                       across  the  tray will often exhibit rapid
                                       variations  when sneakage up the down-
                                       comer is occurring.
     Sneakage can also occur around the outer  edges  of  each tray.  These must
be secured and sealed completely around the tray.  Even moderately small gaps
between the tray and the scrubber wall will allow  significant  gas sneakage and
a permanently reduced pressure drop across the tray.
SLIDE 7-50

         1. SLOPED TRAY
         2. PLUGGED HOLES
           ON TRAYS
         5. EXCESSIVE GAS
                                      Nonuniform gas-liquor distribution can
                                      occur due to a number of tray related
                                      conditions.  These are indicated on the
                                      adjacent slide.

                                      The tray must be level to ensure a
                                      uniform layer of liquid across the top
                                      of each tray.  The lower resistance in
                                      the areas with low liquid levels have
                                      increased gas flow rates which only
                                      aggravate the distribution problem.
                                      Unfortunately, it is difficult to
                                      identify the presence of non-level trays
                                      since the pressure drop does not de-
                                      crease substantially.

     Non-level trays can occur  due  to  poor installation, failure of tray sup-
ports,  or bowed trays.   The cause of the problem can be determined only by an
internal inspection by  plant personnel.

     Solids can accumulate adjacent to the tray overflow weir.  This closes off
a portion of the tray to gas flow and  increase gas flow elsewhere on the tray.

   SLIDE  7-51
                            INLET WEi," BOX
                                       High gas flow rates can be another
                                       source of gas-liquor maldistribution
                                       problems.  The high velocities can cause
                                       pluggage of the holes in the middle of
                                       the tray as shown in the sketch to the
                                       left.   This forces the gas stream to
                                       pass up through the holes on the outer
                                       edge of the tray.

                                       Pluggage in one portion of the tray due
                                       to either high gas flow rates or the
                                       build-up adjacent to the overflow weir
                                       will cause increased static pressure
                                       drop.   This is due to the higher
                                       velocities necessary for the gas stream
                                       to pass through the few open holes.

     During the inspection,  an attempt  should be made to assess the changes in
the gas flow rate since the  baseline period.   The procedures used are identical
to those discussed in slide  7-52 regarding low gas flow rates (see also
Lecture #5).
    SLIDE 7-52

                                          A mechanically aided  scrubber operates
                                          quite differently  from all other  types
                                          of  particulate scrubbers.  Due to the
                                          shaft energy supplied to  the gas  stream,
                                          there is a static  pressure increase
                                          rather  than a pressure drop. The  only
                                          other type of scrubber which operates in
                                          a similar manner is the ejector scrub-
                                          ber which is rarely used  for removal
                                          of  particulate.

                                          The liquor quality is again critical
                                          with the mechanically aided scrubbers.
                                          High levels of suspended  solids can lead
                                          to  erosion of the  fan blades or solids
                                          accumulation on the fan blades.

      Source: Air  Pollution
       Training  Institute

         This type of  unit is  normally  small,  with gas flow rates in the range of
    1,000 ACFM to  10,000 ACFM.  Like most  small systems, there are rarely measure-
    ment  ports for static pressure and  gas temperature.  Few  systems have liquor
    flow  rate meters.

SLIDE 7-53

        1. Average Opacity (Residual)
        2. Minimum and Maximum Opacities
        3. Droplet Reentrainment
        4. Scrubber Rotational Speed
        5. Scrubber Static Pressure Rise
        6. Liquor Flow Rate
        7. Nozzle Operating Pressure
        8. Liquor Turbidity
        9 Liquor pH
       10. Condition of Shell
                                        This list  summarizes the useful data and
                                        observations  for mechanically aided
                                        scrubbers  of  the type depicted in the
                                        previous slide.   The emphasis is on the
                                        static pressure  increase across the
                                        scrubber,  since  this is related to the
                                        effectiveness of particle capture.

                                        The liquor turbidity of the recircula-
                                        tion liquor should be checked as an
                                        indication of the total suspended solids
                                        content of the liquor.  The nozzle
                                        operating  pressures and the pump
                                        discharge  pressures can be evaluated to
                                        determine  changes in liquor flow rates
                                        and possible  pluggage problems in the

     Decreased  static  pressure rise across the scrubber may indicate a change
in the scrubber rotational speed.  Data concerning the  speed should be request-
ed.  During level  3  inspections, the speed can be measured if there is safe
access to the main shaft.   It is also helpful to  measure the gas flow rate
through the scrubber by means of a pitot  traverse in the stack.  Reduced gas
flow rates are  usually due to decreased scrubber  speeds.

     If there is reduced gas flow, there  is some  potential for fugitive
emissions from  the process equipment.  The hood static  pressure (if measured)
should be checked  and  visible emission observations  should be conducted.
SLIDE  7-54
           1. Fixed Throat Venturis
           2. Variable Throat
           3. Flooded Disc Scrubbers
           4. Rod Decks Scrubbers
           5. Orifice Scrubbers
                                        A number  of different gas-atomized
                                        scrubbers have been introduced  in
                                        Lecture #2.  Each of these has  unique
                                        advantages and is susceptible to
                                        different operating problems.   While the
                                        inspection procedure is basically the
                                        same  for  all types, it is necessary to
                                        "tailor"  the inspection procedure to
                                        each  specific type.  Some ares  of
                                        emphasis are presented in the next  set
                                        of  slides.

SLIDE 7-55

       1. Average Opacity (Residual)
       2. Minimum and Maximum Opacities
       3. Presence or Absence of Detached
       4. Droplet Reentrainment
       5. Inlet and Outlet Static Pressures
       6. Inlet and Outlet Gas Temperatures
       7. Inlet Oxygen and Carbon  Dioxide
       8. Recirculation Liquor Flow Rate
       9. Nozzle Operating Pressures
      10. Pipe Skin Temperature
      11. Recirculation Liquor Turbidity
      12. Recirculation Liquor pH
      13. Evaporative Cooler or Presaturator
        Liquor Turbidity
      14. Condition of Shell and Ductwork
                                         This a fairly complete  list of the
                                         inspection observations and measurements
                                         for  gas-atomized scrubbers.  Not all of
                                         these inspection points have to be per-
                                         formed on each inspection.

                                         The  static pressure drop divided by the
                                         average gas density is  almost always im-
                                         portant since this is related to the over-
                                         all  effectiveness of particulate removal
                                         in most cases (see earlier  portion of
                                         Lecture #7).

                                         The  liquor suspended solids level is
                                         critical when the recirculation liquor
                                         is used for evaporative cooling ahead of
                                         the  scrubber.  It is also important for
                                         any  units in which the  liquor is sprayed
                                         into the gas stream
     The outlet  gas temperature is measured to provide an indication of severe
gas-liquid maldistribution.  These is tan  especially serious  problem with gas-
atomized scrubbers since there is only  one very brief opportunity for particle
capture.  Poor distribution at the location of maximum gas velocity results in
substantially reduced particulate removal.  Most of the scrubbers discussed
previously are less susceptible to this problem since there  are  several
"collection  zones" in series.

     Gas-atomized scrubbers are more prone to erosion problems than other types
of particulate scrubbers.  This is the  result of the high gas velocities in the
restricted area  (the "throat") and due  to the sharp changes  in flow direction
common in most designs.
SLIBE 7-56
                                         This is a sketch of a  simple fixed
                                         throat venturi scrubber.   A decrease in
                                         the corrected pressure drop can be due
                                         to  a drop in the gas flow rate or a drop
                                         in  the liquid-to-gas ratio.  As
                                         indicated below, the pressure drop can
                                         be  adequately represented by these two
                                         terms and a proportionality constant.
                                                             {Q,  /Q
     Source: Air Pollution
                                         Where:   P = Static Pressure Drop
                                                  C = Proportionality Constant
                              . -, '                 V = Throat Velocity
                                             QI  /Qg = Liquid-to-Gas Ratio

     Changes in  the  gas flow rate can  be  evaluated directly  by  means of a pitot
traverse or indirectly based on the  fan operating conditions.   The liquid flow
rate can be evaluated directly using on-site gauges or estimated  based on the
pump operating conditions.

SLIDE 7-57
                                       Maldistribution of the gas and liquid
                                       can result from improper nozzle
                                       placement, improper throat design,  or
                                       partial  pluggage of the nozzles.   The
                                       problem  stems from the difficulty of
                                       spraying liquid from the side wall into
                                       a gas stream moving between 20,000 to
                                       40,000 feet per minute.  This is  equi-
                                       valent to spraying liquid out of  a car
                                       moving between 200 and 400 miles  per
                                       hour! As one may expect, much of the
                                       liquor will be deflected and will not
                                       penetrate far into the throat.  It is
                                       possible to incompletely irrigate the
                                       middle of the throat.

     One symptom of this problem is outlet gas  temperatures which are above the
saturation temperature.   This can be measured using the temperature probe dis-
cussed in Lecture #4.  It is common practice to include manual rod out
capability on all side mounted nozzles so that  plugging is minimized.  The loss
of even one nozzle in some units can significantly reduce performance due to
incomplete liquor distribuition across the gas  stream.

     The reason that distribution is so important in venturi scrubbers is that
the point of maximum impaction is the entry to  the throat.  Here, the gas
velocity is high and the liquor velocity is near zero.
SLIDE 7-58
                                       Erosion is common in the three areas
                                       shaded in the fixed throat venturi
                                       sketch.  The high velocities within the
                                       throat (arrow #1) are responsible for
                                       the erosion in this area.  The 90turn
                                       near the bottom of the diverging section
                                       (arrow #2) are responsible for damage in
                                       this area.  There can also be some
                                       erosion in the tangential entry to the
                                       cyclonic demister (arrow #3).

                                       The damage to the elbow and the demister
                                       tangential entry can be easily seen
                                       during a walk around inspection of the
                                       unit.  On negative pressure units, both
                                       areas are under high negative pressures
                                       and will have severe infiltration if
                                       there is damage.
     The problems can be minimized by maintaining the pH in a noncorrosive
range.  In the case of the elbow, a shallow recession of 6 to 9 inches can be
made directly below the diverging section of the throat.  This "flooded elbow"
blunts the abrasive action of the turning gas stream.

SLIDE 7-59
                                       This is a side view of an adjustable
                                       throat mechanism for a venturi scrubber.
                                       A scrubber with these internal dampers
                                       would look similar to that shown in the
                                       previous slides.  There is another com-
                                       mon version which has a single damper
                                       mounted on one side of the inlet.  In
                                       this case, the "throat" is often on the
                                       tangential inlet duct to a cyclonic

                                       Venturi scrubbers with these dampers can
                                       suffer severe abrasion of the dampers due
                                       to the high gas velocities in the
                                       restricted area.  The symptom of this
                                       problem is reduced static pressure drop
                                       'without any significant changes in the
                                       gas flow rate or the liquor flow rate.
                                       Due to the sensitivity of the pressure
                                       drop to throat velocities, even a little
                                       damper erosion can result in a static
                                       pressure decrease from baseline levels.

    The liquor inlet configuration of this particular design is quite different
from the array of side mounted nozzles depicted in the previous sketches.
While it obviously does not have spray penetration problems, this design is
also not immune to maldistribution problems.  It is possible for the liquor
to incompletely wet the sloped sides of the section which leads to the throat.
This results in incomplete distribution of the liquor across the throat.

SLIDE 7-60

                                       This is a photograph of the liquor inlet
                                       and converging section of a venturi
                                       scrubber.  In this cases, the liquor
                                       swirls down to the throat in a manner
                                       which resembles a dentist bowl.

                                       Maldistribution of the gas and liquor is
                                       possible if one or more of the pipes
                                       leading to the scrubber plugs.  On
                                       systems in which a warm liquor ( 90 to
                                       140 F) is recirculated, it is often
                                       possible to identify these plugged
                                       lines.  There is a difference in- the
                                       pipe skin temperatures with the plugged
                                       line being several degrees colder than
                                       the others.

     The pipe skin temperature can be measured using either a battery powered
thermocouple or a thermister.  The location for the measurement on each inlet
pipe is shown by the arrows in the photograph.  In some cases, it is possible
to identify plugged lines simply by touch.


SLIDE 7-61
                                       This is a cut-away sketch of a flooded
                                       disc gas-atomized scrubber.   In this
                                       type of scrubber, the "throat" is the
                                       concentric area between the  disc and the
                                       outer shell.   The throat area is changed
                                       by moving the disc assembly  up or down
                                       in the tapered section of the inlet
                                       column.  The  liquor comes up the center
                                       support of the disc and flows out over
                                       the top.  The liquor is atomized on the
                                       outer edges by the high velocity gas
     For proper gas-liquor distribution, it is very important to maintain the
disc level.  If it is tipped slightly,  the liquor will flow to one side and
only partially irrigate the annular area.   The maldistribution problem will be
aggravated by the constricted passage on the side with liquor and the enlarged
opening next to the high side of the disc.

     Due to its position facing the inlet gas stream,.the flooded disc must be
very abrasion resistant.  Linings should be checked regularily and replaced

     These scrubbers perform in basically the same manner as the venturi
scrubbers discussed earlier.  .The inspection procedures for evaluating
decreased pressure drop and materials of construction problems are identical.
The flooded disc scrubbers are less susceptible to high suspended solids levels
in the liquor since nozzles are not used.
SLIDE 7-62
  Source: Air Pollution
   Training Institute
 This is a sketch of a variable rod type
 venturi scrubber.   The "throat" of this
 unit is the rectangular area between the
 rods.  This area can be varied by moving
 the rods.  Some versions of this design
 have several rod decks in series.  The
 liquor is introduced through several
 large nozzles above the rod deck.

"This unit is susceptible to erosion due
 to the high velocity particulate laden
 gas stream.  The rods must be checked
 routinely and replaced whenever the
 erosion has progressed significantly.
 Rod erosion can often be identified as
 reduced pressure drop without a change
 in gas or liquor flow rates.
     Gas-liquor maldistribution problems can result from improper nozzle
selection, improper nozzle placement, and nozzle erosion.  This can often be
detected by evaluation of the outlet gas temperature.


7-1.  The best answers are "b" and "e".   It is very possible that  the asphalt
      plant is presently operating at higher mix temperatures and  this is
      causing some additional volatilization of the components from the
      asphalt binder used in the drum mixer.  It is also possible  that the
      binder injection point has been moved forward toward the burner or that
      the binder recently received has a lower smoke point.   Any of these
      process changes would result in large quantities of submicron organic
      particles which condense while passing through the scrubber.   These
      particles would be difficult to capture and difficult to "wet". The
      possibility of these process related problems could be evaluted by
      observing the mix temperature monitored in the control room  and by
      reviewing records on the grade of asphalt binder and its smoke point.

      Answer "b" remains a possible explanation since there are normally only
      a few nozzles above the throat.  Pluggage of one would leave a major
      portion of the throat without any water droplets and zero particle
      collection efficiency for this zone.  The nozzle header pressure should
      have increased slightly if one nozzle plugged.  However, these gauges
      are often not reliable due to solids accumulation in the inlet and
      due to severe vibration.  To check out the gauge, the pump discharge
      pressure and the pump motor currents should be checked.  Unfortunately,
      these are rarely available on small systems such as drum mixers.  The
      point of this part of the question is that it is often wise  to check
      the condition of the spray nozzles.  This can usually be done when
      the asphalt plant is not operating.

      Answer "a" is not correct since the decrease in pressure drop is not
      very large.  It would be unlikely that a drop of this magnitude would
      result in an increase in opacity from 5% to 65%.

7-2.  Only answers "c" and "d" are correct.  The stem of the gauge has probably
      corroded away since the system is not operating at the time.  The latter
      can be easily confirmed.  Concerning answer "a", it is highly unlikely
      that the system would operate this far below normal saturation
      temperatures.  It would require massive quantities of very cold liquor
      to depress the gas temperature to this level.   Answer "b" is totally
      incorrect since liquor is not sprayed into a cyclonic demister.


7-1.  A venturi scrubber with an adjustable throat damper is being used to
      control the particulate emissions from a drum mix type asphaltic concrete
      plant.  The residual opacity has increased from 5% to 70% since the last
      stack test.  The pressure drop is now 17 inches W.C. and the baseline
      values ranged from 18 to 19%.  There is no liquor flow meter.  However,
      the nozzle header pressure has remained constant at 45 psig.  The inlet
      gas temperature now is 283 F compared with baseline values ranging from
      276 to 294 F.  What are some of the possible explanations for the
      present high opacity?

      a.  Serious erosion of the throat damper has decreased the throat
          velocity, thereby reducing impaction.

      b.  One or more of the liquor inlet nozzles is plugged.

      c.  The liquor flow rate has decreased substantially.

      d.  There is some oil scum on the surface of the settling pond.

      e.  The process operating conditions and/or raw materials have

     This is a slide of a dial type thermometer in the upper section of a
     cyclonic demister.  The indicated temperature is approximately 65 F.
     What can be concluded from this data?

     a.  Since the gas stream is below normal saturation temperatures, the
         gas-liquor distribution is probably adequate.

     b.  The liquor sprayed into the cyclonic demister is too cold.

     c.  The gauge is not operating correctly.

     d.  The scrubber system is presently out-of-service

     e.  All of the Above



7-3.  Answer "f" is the best.  The increase in pressure drop across a packed
      bed scrubber is usually due to either an increase in the gas flow rate
      or to the accumulation of solids within the bed.   While the liquor flow
      rate has only a little impact on pressure drop,  the decrease in liquor
      flow rate may indicate other developing problems.  For this reason,  the
      presence of audible pump cavitation should be checked.  The process raw
      materials and operating conditions should also be checked to determine if
      the particulate loading in the inlet gas stream could have increased.
7-4.  Answers "b" and ' c" could be correct.  The depressed temperature of
      line 3 suggests the potential for pluggage.  Answer "c" has been
      included only to caution the attendees that the pipe skin temperature
      evaluation is not absolutely reliable.  There is at least a slim
      possibility that all the lines are open and in good condition.

7-5.  This is a repeat of a question used in Lecture #5.  The only correct
      answers are "c" and "e".  The consequences of fan disintegration should
      not be underestimated.

7-6.  The pressure drop will increase due to the higher gas velocities through
      the throat.  This question was included since venturi scrubbers with
      throat inserts are common.  These were not discussed in the lecture
      portion since the inspection procedures are identical to those for fixed
      throat Venturis.


7-3. The pressure drop across a packed bed scrubber has increased from 6 inches
     of water to 11 inches of water.  The liquor flow rate as indicated by an
     on-site gauge has dropped slightly.  The inlet gas temperature has dropped
     from 164 F to 145 F.  What are the logical follow-up inspection points?

     a.  The gas flow rate through the scrubber should be checked using
         a pitot traverse and using the fan operating conditions.

     b.  The inlet liquor turbidity should be qualitatively evaluated.

     c.  The potential for pump cavitation should be checked.

     d.  Changes in process raw materials and fuels should be checked.

     e.  Answer s a,b,and c
     f.  Answers a,b,c, and d

7-4.  A venturi scrubber being inspected has four tangential liquor inlets and
      one center flush line above the throat.  A check of the pipe skin temp-
      eratures indicates the following: line 1 - 124 F, line 2 - 123 F,
      line 3 - 120 F, line 4 - 124 F, and line 5 - 125 F.  What are the
      possible explanations for these results?

      a.  Line 5 is partially or completely plugged.

      b.  Line 3 is partially or completely plugged.

      c.  All of the lines are open and in good condition.

7-5.  A fan downstream of a cupola venturi scrubber is vibrating severly during
      the inspection.   What should be done next?

      a.  A pitot traverse should be done to determine if this condition
          has adversely affected the gas flow rate,

      b.  The fan motor current and speed should be measured.

      c.  The inspection should be interrupted due to the potentially
          dangerous situation.

      d.  This is strictly a maintenance problem and should be ignored.

      e.  A responsible plant employee should be advised of the situation.

7-6.  An operator of a fixed throat venturi scrubber has proposed adding
      a small plate across the throat to decrease the open throat area.
      If the gas flow rate remains constant, will this increase or decrease
      the static pressure drop?

      a.  Increase

      b.  Decrease


7-7.  Answer "b  is correct.  The hollow cone nozzles do not provide good
      gas-liquor distribution in spray tower scrubbers.  Answer "a" is not
      correct even though hollow cone nozzles are,  in fact, less prone to
      pluggage.  In this case the operator is simply exchanging a maintenance
      problem for a performance problem (which leads to excess emissions).
      Answer "c" is logical.  However, this may be expensive.  In may be
      possible to eliminate the problem simply by finding nozzles which are
      not prone to pluggage at the prevailing solids levels at the plant.

7-8.  Answer "c" is correct.   It is possible it have a major fraction of
      the particulate in the submicron range and still have the quoted
      mass median particle size.  Possible causes include vapor condensation
      and particle regeneration.  The object of this question is to emphasize
      the importance of the size distribution.

7-9.  The efficiency will decrease due to the lower gas velocities.  Answer
      "a" is correct.  The residence time is not important in particulate
      removal systems.

7-10. The only logical follow-up inspection point listed is the check for
      fugitive emissions from the process equipment (Answer "d").  The position
      of the adjustable throat dampers can not be determined externally.  Also,
      it is more likely that the observed decrease in pressure drop is due to
      the downstream air infiltration problem than a change in the damper
      position.  The pitot traverse in the stack will not be very helpful since
      in this position, both the gas and air flows will be measured together.
      To evaluate the quantity of infiltrated air it would be necessary to
      conduct a pitot traverse ahead of the scrubber in addition to the one in
      the stack.


7-7.  An operator of a spray tower scrubber has had chronic problems with
      full cone spray nozzles.  To minimize the problem,  it is proposed that
      all of these be replaced with hollow cone spray nozzles.  Is this a
      logical approach?

      a.  Yes. Hollow cone nozzles are less prone to pluggage.

      b.  No. Hollow cone nozzles have spray patterns which do not
          provide good gas-liquor distribution in spray tower scrubbers.

      c.  No. The liquor suspended solids levels should also be reduced,
          if possible.

7-8.  The mass median particle size in the inlet gas stream to a spray tower
      scrubber is 7.0 microns.   Should it be possible to achieve an outlet
      particulate concentration of 0.10 grains/ACF if the scrubber is in good
      operating condition?

      a.  Yes. This is within the normal capability of spray tower scrubbers.

      b.  No. This is too small for spray tower scrubbers.

      c.  Maybe. It depends on the size distribution of the particulate matter.

7-9.  The gas flow rate to an impingement plate scrubber has decreased 40% due
      to a permanent drop in the production rate.  Will this have a beneficial
      or an adverse effect on the particulate removal efficiency of this unit?

      a.  Efficiency will decrease due to lower gas velocities through the
          holes in the tray.

      b.  Efficiency will increase due to higher gas residence times.

      c.  Efficiency will not be affected by this change.

7-10. The static pressure drop across a venturi scrubber has dropped from a
      baseline level of 28 inches W.C. to 21 inches W.C.   The liquor flow rate
      has not changed. However, the gas temperature to the scrubber has dropped
      from a baseline level of 241 F to 230 F.  Severe air infiltration is
      noted in the cyclonic demister of the scrubber.  What are the logical
      follow-up inspection points?

      a.  The location of adjustable throat dampers should be checked.

      b.  The air infiltration rate should be quantified by means of a-
          pitot traverse in the stack.

      c.  Process operating conditions should be checked to determine
          the reason for the inlet gas temperature drop.

      d.  The hood static pressure should be checked and equipment served by
          the scrubber should be checked for possible fugitive emissions.



7-11.  Answers "b" and "c" are both correct.  Obviously,  it is possible to
       climb the short stack and measure the static pressure (if conditions
       on the platform are safe).  However,  the static pressure here will be
       very close to ambient static pressure which is zero.  Therefore, the
       static pressure can be calculated as the difference between +9.8 inches
       and either -1/2 or  + 1/2 inches.  The result is an estimated static
       pressure of 9.3 inches to 10.3 inches.   This approach saves the effort
       of climbing the stack.

7-12.  Answers "b", "c" and "d" could all be correct.  The anti-fearning
       solution would obviously have some beneficial impact on foaming in
       the scrubber.  It would also have some impact on the liquor surface
       tension which in turn affects the droplet size distribution and the
       effectiveness of impaction.  It is difficult to determine without
       stack tests whether the anti-foaming solution will have a beneficial
       or adverse impact on performance.  However, the inspector should note
       the quantities and types of anti-foaming solutions presently being used,


7-11.  During an inspection of a venturi scrubber, the static pressure ahead of
the scrubber is measured as + 9.8 inches W.C.  The only port downstream of the
scrubber at which the static pressure could supposedly be measured is the stack
sampling port on the platform 75 feet above the ground.  The stack terminates
approximately 4 feet above the sampling elevation.  What should be done to
determine the static pressure drop across the scrubber?

     a.  The pressure drop can not be determined since the fan is between
         the scrubber vessel and the stack.

     b.  Take a guess that the static pressure is between -1/2 inches to
         + 1/2 inches and calculate the pressure drop.

     c.  Go up and measure the static pressure at this port.

7-12.  During an inspection of a scrubber system, the operator is observed
dumping a gallon of anti-foaming solution each hour into the recirculation
tank.  What can happen to the system due to the addition of these chemicals?

     a.  Corrosion is dramatically accelerated.

     b.  There less foam flowing off the top of the recirculation tank and
         within the scrubber. Therefore, scrubber performance is improved.

     c.  Particle i.mpaction effectiveness is probably affected.

     d.  Droplet formation in the scrubber is affected.


                              LECTURE 8
                      INSPECTION  AND EVALUATION
                            GAS ABSORBERS

                                      This lecture  concerns wet  scrubber sys-
                                      tems used for the  control  of gaseous
                                      compounds,  acid  vapors and odor-causing
                                      organic vapors.  It  does not specifi-
                                      cally address sulfur dioxide flue gas
                                      desulfurizations systems since this is
                                      covered in a  separate U.S. EPA workshop
                                      program.  However, the principles for
                                      gaseous scrubbers  also apply to the
                                      S02 control units.

                                      The basic operating  principles of this
                                      category of wet  scrubbers  are intro-
                                      duced. This is necessary to establish
                                      the most important parameters and to
                                      illustrate their differences from the
                                      particulate scrubbers discussed in
                                      Lecture 7.

      The  specific  types of wet scrubber systems used for different applica-
tions are  discussed.  Inspection techniques for evaluating  common modes of
failure are presented.  This incorporates much of the previous material from
Lectures 3, 4,  5  and  6  into a complete inspection procedure.

            ARE CAPTURED
             BY DIFFUSION

             IS CAPTURED
                                      There are numerous differences between
                                      gaseous absorbers and particulate wet
                                      scrubbers.  One of the most important
                                      is listed in this slide.

                                      Since most of the pollutants are cap-
                                      tured by means of diffusion rather than
                                      impaction, certain parameters are impor-
                                      tant for absorbers which were not very
                                      important for particulate scrubbers.
                                      For example, the residence time in the
                                      scrubber becomes important in gaseous
                                      scrubbers since it takes time for the
                                      molecules to diffuse to the surface of
                                      the liquid and to transfer across the
                                      gas and liquid films.

     The gas temperature  becomes  important in gaseous scrubbers since diffu-
sion becomes more rapid as  the  temperature increases, while the solubility of
most gases increases as the liquid  temperature decreases.  The scrubber pres-
sure drop which is central  to the performance of particulate scrubbers is less
inmportant with- the gaseous scrubbers.  The liquor surface tension is also less
             ARE CRITICAL
                                       The characteristics of the liquor
                                       stream are critical to the performance
                                       of a  gaseous scrubber.  In the case of
                                       the particulate scrubber, the liquor
                                       characteristics are important only
                                       with  regard to maintenance problems
                                       such  as erosion, pluggage and corro-

                                       With  gaseous absorbers, the liquor
                                       temperature, pH, and composition
                                       can all influence the performance of
                                       the air pollution control device.

 SLIDE 8-4
             ARE HIGHER
 The quantity of liquor used in gaseous
 scrubbers is much larger than that used
 in particulate scrubbers.   One of the
 reasons is that the maximum possible
 surface area for absorption is neces-
 sary.   More liquor normally favors
 higher collection efficiencies.   In the
 case of the particulate scrubbers,  there
 is a broad range in which  the liquid-to-
 gas ratio is not very  important.   That
 does not apply to the  gaseous scrubbers.
 SLIDE 8-5
     Source:  Air Pollution
             Training Institute
The sketch shown in the circle on the
right of this slide illustrates the
microscopic process of absorption.
Some of the gas molecules are diffusing
across the interface between the gas
and liquid streams.  The overall rate
of pollutant transfer from the gas
stream to the liquid stream is depen-
dent on the liquid surface area
available and on the concentrations of
the pollutant which exist in the liquid
and gas phases.  Turbulent mixing of
both the gas and liquid streams favors
absorption by decreasing the time re-
quired to cross the interface between
the two phases.
     Obviously, increased gas residence times favor the absorption of  pollu-
tants in a scrubber by allowing more time for diffusion to  be  completed   This
is an especially important difference between absorbers~and particulate'wet
scrubbers.   With the latter, the impaction process occurs  almost  instanteously
as a discrete event,  while absorption is the collective process  of mass  trans-
fer from the gas phase to the liquid phase.   Absorption is  time  dependent.  In
Lecture 7 only the effectiveness of  impaction is  discussed,  not  the "rate of
                                                                of diffusional

                                       Mass transfer occurs in  both  directions
                                       until there are equilibrium concentra-
                                       tions of the specific  compound  in  the
                                       liquid and gas streams.  Once this
                                       equilibrium condition  has  been  reached,
                                       there is no net transfer of pollutants
                                       into the liquid stream and the  rate  of
                                       pollutant collection is  zero.

                                       At this point, there are equal  numbers
                                       of the specific molecules  crossing the
                                       interface in each  direction.
 Source: Air Pollution
    Training Institute




 w o.i
           0.002 0.006  0.010  0.014
               MOLE FRACTION S02
               IN WATER	-
The equilibrium concentrations are an
important operating limit for the wet
scrubber systems.  This slide shows one
equilibrium relationship for sulfur
dioxide in water at 50C.

The units used in the graph are  "mole
fraction".  This is simply a ratio of
the number of molecules of the pollu-
tant versus the number of molecules of
the liquid.  A 0.1 mole fraction S02
concentration is equivalent to 100,000
ppm (or .1% by volume).  A useful
source for this data is the vapor pres-
sures of the pollutant over.the
specific liquid of interest.



S 04
     W2 0.3


 This  is a  repeat of the graph shown
 above.   The  equilibrium lines for 30C
 and 70C have been added to illustrate
 the strong temperture dependence of the
 equilibrium  concentrations.  Gases are
 much  more  soluble in cold liquids than
 in hot  liquids.
            0.002 0.006  0.010  0.014
               MOLE FRACTION S02
               IN WATER	
Pollutants, which  release  large quanti-
ties of energy when dissolved,  can have
curved equilibrium lines.   The  graph
shown earlier illustrates  the strong
effect that temperature  has on  the
equilibrium levels.  At  high tempera-
tures, gases are less  soluble.   When
energy is released to  the  solution the
temperature increases  and  the equili-
brium levels decrease.   This result is
the curved line shown  in this graph.

This type of curve can occur whenever
gases such as HF and HCL result in a
temperature gradiant across  the scrub-
ber.  A portion of the unit^ may have
very low rates of  mass transfer under
these conditions.

SLIDE 8-10

                                       In some cases involving air pollution
                                       control systems, the pollutant con-
             5 H-.^!-.               centrations are sufficiently low that
                  Q  Q               the equilibrium data can be adequately
                                       represented by Henry's Law.  This is
                                       shown in the adjacent slide.

                                       It simply states that there is a
                                       straight line relationship between the
                                       gas stream and liquid stream concentra-
                                       tions of the specific compound.  The
                                       slope of the equilibrium relationship
                                       is the Henry's Law Constant.  In these
                                       cases, the equilibrium can be obtained
                                       from standard references.

     Henry's Law is not followed whenever the molecule dissociates upon enter-
ing the liquid solution.  Pollutants which dissociate include hydrochloric
acid and hydrofluoric acid.  For all molecules which do react once dissolved,
the equilibrium relationship is normally curved, and it can only be obtained
SLIDE 8-11

                                       The primary objective of the last
      FACTORS WHICH SHIFT THE       several slides has been to demonstrate
         EQUILIBRIUM CURVE           that the equilibrium relationship  in  a
                                       wet scrubber can change.  Any of the
     1. CHANGE IN GAS TEMPERATURE           factors listed on this slide can cause
     2. HEAT RELEASE DURING ABSORBTION          hf t   th    values
     3. CHEMICAL REACTIONS IN LIQUID          3 Stlirt 1J1 tneS6 values 

                                       The performance of an absorber  is  de-
                                       pendent on the operating temperature
                                       and the chemical reactions in the
                                       liquid stream.  High concentrations of
                                       pollutants with high heats of dissolu-
                                       tion can also cause an adverse  shift  in
                                       the equilibrium line.

      Due to  the number of variables which affect the equilibrium conditions,
there is no  one set of charts which can be universally applied to the  wet
scrubber systems.

SLIDE  8-12
          !b to!* in = lb mole out
       G.(in) T U.(in) G.(out) + L.(out)
                                         The importance of the liquid to  ga<
                                         ratio is illustrated in the next
                                         several set of slides.  This slide
                                         begins with a material balance aroi
                                         the total system.  The equation  be]
                                         the scrubber sketch states that wha
                                         goes in also comes out!

                                         The second equation is a material b
                                         ance for the pollutant material.  S
                                         the concentrations of pollutants ar
                                         small relative to the gas and liqui
                                         streams, this equation reduces to t
                                         third equation shown.
SLIDE 8-13
                                        The  third equation shown in the slid
                                        above  defines a line with the slope
                                        equal  to the liquid-to-gas ratio.

                                        Point  number one is determined by  th(
                                        concentration of the pollutant in  the
                                        inlet  gas stream and the outlet liquc

                                        Point  number two is determined by  the
                                        concentration of the pollutant going
                                        the  stack and by the inlet liquor

                                        The  straight line between these two
                                        points is the operating line.  This
                                        defines  the  liquor and gas stream
                                        concentrations of the pollutant at an;
                                        point  in  the scrubber.

     The difference  between the equilibrium line and the operating line is t\
driving force for diffusion.   The rate of mass transfer is proportional to
this driving force.

 SLIPS 8-14
                OPERATING UNES-
                  As the liquid-to-gas  ratio  is
                  increased, the concentration of the
                  pollutant material in the effluent
                  stream decreases.  Line  number two has
                  a liquid-to-gas ratio which is approx-
                  imately twice that of line  one.   The
                  effluent liquid concentration is much
                  lower with higher liquid-to-gas ratios.
SLIDE 8-15

SLIDE 8-16

    7. pH
                                       Some of  the major  absorber operating
                                       parameters used  during the inspection
                                       are listed in  this slide.

                                       The inlet gas  temperature  and the inlet
                                       liquor temperature are important since
                                       they will largely  determine the opera-
                                       ting temperature of the absorber.  High
                                       temperatures adversely affect the total

                                       The characteristics of the inlet liquor
                                       stream, are -important since they define
                                       the minimum stack  concentration of the
                                       pollutant.  Factors such as the liquor
                                       pH and the hypochlorite concentration
                                       are important.

     The liquid-to-gas ratio is  important since it is a major factor in
determing the rate of absorption.   It also can  affect the degree of liquor-gas
SLIDE 8-17
           HCI SOURCES
          1. High Concentration
           Effluent from
           Chlorination Reactors

          2. Low Concentration
           Effluent from
           Waste Incinerators
                                       The  principal sources of HCI include
                                       organic  chlorination reactors and
                                       chlorinated  waste incinerators.  These
                                       two  sources  differ with respect to the
                                       concentration of the HCI vapor in the
                                       gas  stream and with respect to the ef-
                                       fluent gas stream temperature.  The
                                       control  system designs must be different
                                       to adquately handle these two different

                                       In the high  HCI concentration applica-
                                       tions, recovery of the HCI as a 30 to
                                       38%  weight percent solution is econ-
                                       omically possible.  In the low concen-
                                       tration  applications, there*is too
                                       little acid  to justify recovery.

     The heat of absorption must  be  taken into  account for the high concentra-
tion HCI sources.  It releases approximately 800 BTUs per pound of HCI upon
absorption.  As discussed earlier, this  heat release to the solution has an
adverse impact on the equilibrium concentrations.

SLIDE 8-18



                3o22242628S032S4 36 WT %
          .	,    	J	1	ub
         ooos 0.001  OKS 0130 aiss  ais2 0210 MCX.E
The equilibrium curves for HC1 in water
at several temperatures are shown in
this slide.  The right side of the
graph shows the relationship at high
concentrations of acid in water.  The
left side of the graph is an extra-
polation to the origin.  This was done
to illustrate a Henry's Law type rela-
tionships at low HC1 concentrations.

The strong effect of temperature is
evident in the equilibrium data.
Anything which increases the gas
temperature will lead to reduced HC1
SLIDE 8-19

                                       A typical control system of a high con-
                                       centration HC1 scrubber is shown here.
                                       It consists of three ejector venturi
                                       scrubbers in series with a tail end
                                       packed tower scrubber.

                                       Absorption water is brought to the last
                                       stage and moves forward through the
                                       system to the first stage.  The heat of
                                       absorption is removed in the first two
                                       stages.  The last ejector venturi and
                                       the packed tower operate at cold
                                       temperatures to maximize absorption.
                                       There is also a heat exchanger on the
                                       liquid stream inlet to the first
                                       scrubber to minimize the operating
                                       temperature in the first 'stage.

     Due to the counter-current arrangement of the liquid and gas streams, the
HC1 concentration in the gas stream leaving the last ejector venturi is rela-
tively low.  Nevertheless, this would not satisfy most regulatory limitations.
The packed tower is necessary as a polishing scrubber.  This scrubber has rel-
atively clean liquor at the inlet so that the stack levels of HCL can be min-

SLIDE 8-20
                                       The important inspection points  for  the
                                       system shown in the last slide are
                                       listed here.  The pH of the inlet
                                       liquor to the packed tower scrubber  is
                                       of interest since this determines  the
                                       minimum achievable outlet concentration
                                       of HCI.  The pH should be relatively
                                       high, with normal conditions  being in
                                       the 7 to 10 range. The temperature of
                                       this stream should also be kept  to a
                                       minimum. The outlet gas temperature  is
                                       the best indicator of an increase  in
                                       the operating temperature of  the
                                       scrubber.  Increases from baseline
                                       levels suggest reduced removal

     The liquor recirculation rate to the packed tower scrubber is important
since this partially determines the rate of absorption.  This is rarely mon-
itored directly.  Indirect indications of flow include the pump discharge
pressure and packed tower scrubber inlet line pressure.

     The packed tower scrubber can be overwhelmed by HCI if the ejector scrub-
bers do not perform properly.  The data which should be obtained is  the static
pressure rise across each ejector and the gas stream temperatures after each
ejector scrubber.  Reduced liquor flow rates can be identified by increases in
the gas stream temperatures.
SLIDE 8-21

                                       Reentrainment from the  packed  tower  is
                                       especially objectionable  due to  the
                                       potentially corrosive nature of  the
                                       effluent liquor.  The most  common
                                       types of demisters are  chevrons  and
                                       mesh pads.

                                       Any reentrainment which does occur is
                                       probably due to partial pluggage of
                                       the demister.  Excessive  design  vel-
                                       ocities are rare, due to  the inherently
                                       low gas velocities necessary for the
                                       packed bed.     ~         

SLIDE 8-22
                                       Low gas  velocities  through the scrub-
                                       ber system  can  result  from a number of
                                       quite different problems.   These are
                                       indicated on  the modified  sketch to the

                                       Anything which  reduces the liquid pres-
                                       sure at  the ejector nozzle will reduce
                                       the gas  flow  rate.   The operating con-
                                       dition of the recirculation pumps
                                       should be checked if the discharge
                                       pressures are low or if the static
                                       pressure increase across any of the
                                       ejector  units is lower than the base-
                                       line levels.
     Problems with the ejector scrubber  nozzle  can  also reduce the gas flow
rate.  These high pressure nozzles are especially prone to pluggage and
erosion.  Obviously, the liquor quality  is  important  in preserving these
vulnerable nozzles.
                       GAS OUTLET
                        PACK ED TOWER
                       WEAK AGIO
SLIDE 8-23

                                       This is a  second  type  of  high HC1 con-
                                       centration scrubber  system.   Absorption
                                       of HC1 takes  place on  the inside tube
                                       surfaces of a vertical heat  exchanger
                                       with graphite tubes.   The absorbing
                                       water (with acid) flows downward as a
                                       film along with the  gas.   This is a
                                       co-current flow arrangement.

                                       The heat of absorption is removed as
                                       quickly as it is  released,  thereby
                                       maintaining the equilibrium vapor
                                       pressure of HC1 as low as possible.
                                       This system yields high strength acid
                                       (38% or greater), but  the removal of HCL
                                       is incomplete in  the cooler/absorber.
                                       This is due to the inherent- limitations
                                       of a co-current scrubber.

     To meet emission requirements, a  packed bed  tail gas scrubber is often
used.  The inlet liquor to this scrubber is relatively clean  so  that the stack
concentration can be low.  Automatic control of the  entire  system can be based
on either the packed bed exit liquor temperature  or  the  cooler/absorber exit
liquor acid strength.

SLIDE 8-24

         1. Exit Gas Temperature
         2. Exit Liquor Temperature
         3. Inlet Liquor Temperature
         4. Inlet Liquor pH
         5. Inlet Liquor HC1 Content


         1. Static Pressure Drop
         2. Cooling Water Temperature
         3. Product Acid Rate
         4. Product Acid Strength
The inspection points  for  the  falling
film absorption system are very similar
to those for the ejector-packed bed
scrubber system discussed  earlier.
These are listed on  the adjacent slide.

All of these parameters are related
directly to the equilibrium concen-
tations or to the rate of  absorption in
the scrubber system.

Note that there must be a  fan  with this
system.  Changes in  the gas flow rate
can be identified by the evaluation of
the fan motor currents and the fan
inlet gas temperatures.
     The liquor flow  rate  to  both the packed tower and the cooler/absorber  are
approximately the  same  since  the exit liquor from the packed tower  flows  to
the top of the cooler/absorber.   While there may not be a flow monitor  on this
line, it is possible  to approximate the liquor flow rate from the flow  of the
strong hydrochloric acid.   It is necessary to account for the quantity  of HCL
absorbed and the quantity  of  cooling water added near the bottom of  the

      As with any  scrubber, it  is also necessary to check for apparent  air
infiltration due to problems  with the scrubber shells or the ductwork.  Also,
the presence of reentrainment from the packed tower stack should be  noted.
SLIDE 8-25
This is an example  of  a low HC1 con-
centration wet  scrubber system.  It
is used on sources  such as waste
incinerators where  the concentration of
HC1 is less than  1000  ppm and the gas
stream temperature  is  very high.

The evaporative cooler ahead of the
scrubber is necessary  to drop the gas
temperature down  to a  range in which
absorption is possible.  HCJ. is removed
in a venturi scrubber  which also' serves
as a particulate  removal device.
     The pressure  drop  across the venturi throat is governed more  by  the
particulate removal  requirements than by the HC1 removal requirements.  The
control of HC1  is  primarily dependent on the pH of the liquor.  It  is main-
tained at alkaline levels  by the addition of caustic (normally 5 to 10% by
weight).  It takes 1.1  pounds of caustic for each pound of HC1 absorbed.

SLIDE 8-26
    F  = C x V2 x (L/G)
           P = Static Pressure Drop
           C = Constant
           V m Gas Velocity in Throat
           L " Liquid Flow Rate
           G = Gas Flow Rate
                                       The equation shown  here is the formula
                                       which approximates  the  static pressure
                                       drop in venturi  scrubbers  (presented
                                       earlier in Lecture  #7).  It is possible
                                       to achieve the same pressure drop at
                                       numerous combinations of gas stream
                                       velocities and liquid-to-gas ratios.

                                       With a scrubber  intended for both gas
                                       and particulate  removal, the correct
                                       combination of gas  velocities and
                                       liquid-to-gas ratios are necessary.
                                       The pressure drop is not a reliable
                                       indicator of the performance of the unit
                                       with respect to  HC1 removal.

     For this reason, the liquid flow rate should be obtained  from plant
gauges or estimated from pump performance data.  The temperature of the
recirculation liquor should also be determined.  This can  be measured directly
at the recirculation tank or measured indirectly using  the skin temperatures of
the piping leading to the scrubber inlet.
                       VtMTUHI SOtUME*
                       WITH CYCLONIC
SLIDE 8-27

                                       The  pH  of  the liquor leaving the scrub-
                                       ber  sump should be determined.  In this
                                       co-current type of flow arrangement, it
                                       is this value which determines the mini-
                                       mum  concentration of HCL which can exist
                                       in the  stack (due to equilibrium

                                       This pH also is important with regard
                                       to the  rate of corrosion of the scrub-
                                       ber  vessel.  As discussed in Lecture
                                       #5,  the rate of corrosion is governed
                                       by both the pH and the chloride con-
                                       tent.   At  the high chloride levels
                                       which are  inherently involved in HC1
                                       scrubbers, the pH must be relatively
                                       high at all points in the system.

     The scrubber sample  should  not  be taken at  the pump discharge since at
this point the recirculation  liquor  has  been neutralized by the caustic added
to the recirculation  system.

SLIDE 8-28
         NoOH Solution
 Clz Gas

                          Packed Tower
            Spent Scrubbing
      A chlorine absorption  system appropri-
      ate for control  of  emergency spills and
      appropriate  for  small  continuous sources
      is shown in  this slide.   It consists of
      an initial ejector  venturi followed by
      another ejector  venturi  and a packed
      bed combination  scrubber.   The ejectors
      are-generally used  since they are ideal
      scrubbers for applications requiring
      high liquid-to-gas  conditions and there
      is no need for a separate  fan to move
      the gas stream.

      In the first ejector  venturi, there is
      some liquid  temperature  rise due to the
      heat of absorption  which is over 600
      BTUs per pound of chlorine'.
     The solubility  of  chlorine in water is very small.  Therefore,  it is
necessary to use caustic  to react with any dissolved chlorine  to yield the
hypochlorite ion as  indicated in the reaction shown below:
          Cl   +2  NaOH  	
NaCl  + NaOCl  + H  0
     A once through  liquor flow system is generally used  due  to the small
scale of the equipment.
SLIDE 8-29

      1. Flow Rates of All Inlet
       Liquor Streams
      2. Gas Stream Exit
      3. Gas Flow Rate to
      4. Static Pressure Rise
       Across Ejector
      5. Pump Discharge Pressure
       and Motor Currents
      The inspection  of  these scrubbers is
      similar to  that for  any other gaseous
      absorption  system.   The liquid-to-gas
      ratio is important  since this affects
      the rate of absorption in all three of
      the scrubber  vessels arranged in series.

      The gas flow  rate  and the capture of
      the chlorine  at the  site of release are
      obviously important.  This is evaluated
      by checking the static pressure rise
      across the  ejector  Venturis.  If this
      appears low,  the ejector nozzle pressure
      or the pump discharge pressure should be
     Since these are  once-through flow systems, the quality  of  the liquor
coming into the last  stage  (the packed tower scrubber) is not usually a
problem.  The pH of the  inlet NaOH solution should be sufficiently high to
ensure very high efficiency chlorine removal.  The temperature  of  the exit gas
stream should be measured  to indicate any conditions which have increased
temperature and thereby  reduced chlorine absorption.

SLIDE 8-30
        GAS OUTLET
                                       This  scrubber  system is often used in
                                       water treatment and sewage treatment
                                       plants for  the control of large
                                       releases  of chlorine.

                                       The large NaOH storage and recircula-
                                       tion  tank contains sufficient caustic
                                       (5 to 10  weight percent solution) to
                                       neutralize  one ton of  chlorine.  In the
                                       event of  a  spill,  a chlorine detector
                                       activates a remote alarm system and
                                       starts the  scrubber recirculation pump.
                                       At the same time,  all openings and vents
                                       in the room where  the spill occurred
                                       are closed. The ejector venturi draws
                                       in the gas, neutralizes the chlorine,
                                       and returns the scrubbed gas to the

     A single stage system is adequate because the efficiency per pass is not
an important consideration where  there is no escape of gas to the surroundings.
A typical system will neutralize  the  chlorine to a 1  ppm.level in a matter of

     The wet chlorine environments are highly corrosive.   The common materials
of construction include titanium, PVC and special  FRP fabrications.  The in-
tegrity of the ductwork and scrubber  vessel  should be checked during all

SLIDE 8-31
                                        It is unusual to find these scrubbers
                                        operating during any routinely sched-
                                        uled inspection.  Therefore, the in-
                                        spection must be limited to an eval-
                                        uation of the "capability to comply"
                                        rather than the operating conditions.

                                        The level detector on the caustic
                                        storage and recirculation tank should
                                        indicate a normal level of caustic.
                                        The plant records should be checked to
                                        confirm that there is, in fact, caustic
                                        in the tank.  The recirculation pump
                                        and piping shoul'd appear ~tv be in good
                                        working order.

     The system should  be  checked  on a routine basis to ensure that the
chlorine detector and the  recirculation pump are operational.  The ductwork
should also be in good  condition.


SLIDE  8-32
                                         The principal sources of fluorine emis-
                                         sions are the phosphate fertilizer
                                         industry and the  primary aluminum
                                         industry.  The specific sources in
                                         these industries  emit both gases and
                                         particulate matter which must be remov-
                                         ed by the control system.

                                         To avoid contamination of natural
                                         waters, fluoride  systems usually
                                         involve recycle streams from a pond.
                                         The high flouride levels can present an
                                         equilibrium problem  under extreme con-
                                         ditions and the quality of the recycle
                                         liquor can adversely affect pumps,
                                         nozzles and scrubber vessels.

     The stringent regulatory requirements for fluorides means that it often
necessary  to  have  several scrubber units  is series to achieve the necessary
outlet gas  stream  concentration.  As  the  system grows in complexity, the
static pressure  drop requirements can become large.
1. Gas Streams Often Contain
  Both Gases and Particulate
  Forms of Fluoride
2. Liquor is Often High in
  Fluoride Concentration and
  in Suspended Solids Levels
3. Liquor is Highly Corrosive

4. Control Requirements are
SLIDE 8-33
  g 10
       120  140  ICO  110  200
         M as
                                        The  problem with high fluoride  content
                                        recycle  liquor streams is illustrated
                                        in this  graph.  The lower line  repre-
                                        sents  the conditions during  a baseline
                                        period when the liquor temperature is
                                        low.   An increase in the liquor temp-
                                        erature  alters the equilibrium  concen-
                                        trations as shown in the higher line.
                                        With fluoride scrubbers, it  is  important
                                        to maintain proper operating tempera-
                                        tures  to prevent low efficienty due to
                                        equilibrium conditions.
                  ILIC A

SLIDE 8-34
      1.  Saturated Gas Temperature
      2.  Temperature of Scrubbing
      3.  Fluoride Concentration of
         Recycle Liquor
      4.  Inlet Fluoride Concentration
         and Physical Form
      5.  Allowable Fluoride Emissions
      6.  Scrubber Effectiveness
      7.  Demister Effectiveness
The design parameters for all types of
fluoride scrubbers  are listed in this
slide.  They  become the inspection
points for operating units.

This list starts  with the saturated gas
temperature for the reasons discussed
in the previous slide.  All of the
other parameters  are similar to those
discussed with respect to other types
of gas absorbers.
SLIDE 8-35
                                        One  type  of scrubber used for the
                                        control of  fluorides from wet process
                                        phosphoric  acid plants is shown here.
                                        Due  to the  simultaneous presence of
                                        gases and particulate, there are a
                                        combination of control techniques
                                        within a  single scrubber vessel.
                                        The  initial device is a venturi  throat
                                        which  is  irrigated from a set  of deluge
                                        nozzles above the converging section.
                                        The  venturi is used for particulate
                                        removal.   The next stage is a  large
                                        cross  flow packed bed for gas  absorp-
                                        tion.  This is irrigated by front
                                        sprays, a distributor at the top,  and
                                        the  carry-over spray from the  venturi.
                                        All  of this liquor- drains' -into the pond
                                        water  sump.

      A  mist eliminator is used to prevent the transfer of the high fluorides
liquor  into the fresh water system downstream.   A partition is used to  keep
the  two .liquor supplies separate.  Within the fresh water portion of  the
scrubber,  the absorption is completed  using a liquor with low fluoride  content
and  low liquor temperature.  This fresh  water section of the scrubber vessel,
in a sense, serves as a separate "tail gas" scrubber.

SLIDE 8-36

                                       Inspection points  for  the  fluoride
                                       scrubber shown in  the  previous  slide
                                       are listed here.

                                       The pressure drop  across the  venturi
                                       scrubber is important  since this  in-
                                       dicates the degree of  particulate re-
                                       moval in the venturi.   Carry-over of
                                       particulate into the contact  bed  could
                                       lead to partial pluggage and  channel-
                                       ing.  The total liquid flow in  streams
                                       5 and 8 are related to the absorption
                                       rate in the scrubber.   The fluoride
                                       content of this liquor is  important.
     The temperature and fluoride content of  the  fresh  water  supply  is import-
ant in determining the minimum fluoride concentration that  can  be  present in
the effluent gas stream.  The outlet gas temperature also indicates  the pre-
vailing absorption temperature.  The flow rate of  stream 2  has  a direct impact
on the rate of absorption in the fresh water  section of the scrubber.
SLIDE 8-37


                                       Anything which allows  mixing  of the
                                       pond water sump  liquor and  the  fresh
                                       water sump liquor will reduce the
                                       collection efficiency  of  the  scrubber
                                       system.  The increase  in  the  fluoride
                                       content will reduce  the absorption of
                                       fluoride in the  last stage.

                                       This mixing of the two liquors  can
                                       occur due to failure of the demister
                                       between the two  compartments, due to
                                       failure of the liquid  level control-
                                       lers, or due to  failure of  the  part-
                                       ition between the two  sumps.

     Due to the high fluoride levels often existing in  the  pond  recycle'
liquor, it is necessary to neutralize with lime.  If the pH becomes  too high,
some precipitation of calcium fluoride can occur in the contact  bed  and other
portions of the scrubber system.  This can have a very  adverse effect  on the
contact bed and the first mist eliminator.  For this reason,  the pH  of the
liquor in line 1 (a portion of which becomes streams 5  and  8) should be
checked during the inspection.

SLIDE 8-38
Due to the severely corrosive nature of
wet fluoride environments,  the integrity
of the materials of construction in the
entire scrubber system should be visual-
ly checked.  Areas of possible corrosion
and air infiltration include the hoods,
ductwork, fans, and pumps.   The scrubber
vessel is normally constructed of
fluoride resistant materials.

Air infiltration into the scrubber
system will obviously increase the
quantity of untreated gas released to
the atmosphere.
SLIDE 8-39

                                       In the production of ROP Triple Super-
                                       phosphate,  there are several sources of
                                       silicon tetrafluoride.   High concentra-
                                       tions of SiF4 are evolved from .the
                                       Acid/Rock Mixer, the Curing Den and the
                                       Cutter.  These sources  are often vented
                                       to a scrubber system similar to that
                                       shown in this slide. The principal
                                       purpose of the first two scrubber
                                       vessels is the concentration and
                                       recovery of the SiF4.  The last scrub-
                                       ber stage is necessary  for compliance
                                       with environmental requirements.

                                       The first stage of absorption is done
                                       with 16 to 20% by weight acid while the
                                       second is done with 2 to 5% by weight
                                       acid.  The performance  of both of these
                                       are of interest to the  inspector only
                                       because problems..here could_ overload the
                                       tail gas scrubber.

      Recycled  pond  water  is  used for the final gas stream cleaning, since this
 has minimum fluoride  levels  and minimum temperatures.  The unit illustrated
 here is a cyclonic  spray  tower scrubber.

 SLIDE  8-40
                                        Common inspection points for the tail
                                        gas scrubber shown in the previous
                                        slide include those listed here.  The
                                        quality of the pond water is of central
                                        importance.  The fluoride levels should
                                        be as low as possible and the liquor
                                        should be in the range of 7 to 10 pH.

                                        The recycle liquor flow rate affects
                                        the removal efficiency of the scrubber.
                                        This flow rate should be obtained from
                                        on-site monitors or estimated from
                                        recirculation pump operating
      The operating condition of the fan is important since this governs the
 gas flow rate from the various SiF4 sources.  This fan is vulnerable to
 fluoride attack and carry-over liquor droplets from the second stage scrubber.

      1. LIQUOR pH
        FLOW RATE
 SLIDE 8-41
                                      SiF4 continues  to  evolve  in the curing
                                      pile.  These emissions  are collected in
                                      a building evacuation system and treat-
                                      ed in a simple  tail  gas scrubber.   The
                                      concentration is too low  to economi-
                                      cally recover the  material.  The type
                                      of scrubber illustrated here is a
                                      cyclonic  spray  tower similar to the one
                                      discussed in the previous two slides.

                                      The inspection  of  this  unit again  em-
                                      phasizes  the recycle liquor quality and
                                      flow rate.  Corrosion and reentrain-
                                      ment problems should also be evaluated.

SLIDE 8-42                             These are the primary -problems which
                                       must be addressed in the design and
                                       operation of odor scrubbers.

                                       Like many fluorine scrubbers, the ef-
                                       fluent gas often containds both parti-
                                       culate matter and and vapors.  Systems
                                       must have a combination of scrubbing
                                       techniques to handle both types of

                                       Very high removal efficiencies are
                                       necessary since odors can be detected
                                       by some individuals at very low concen-
                                       trations.  Scrubbers having an inlet
                                       concentration of 100,000 odor units
                                       often must reduce this to less than a
                                       100 odor units in the effluent.

     Unlike the previous scrubber systems, there is more than one compound
which must be removed.  In fact, it is highly probable that sources such as
food product driers and rendering plants have 10 to 25 major components in the
gas stream.  The composition is rarely known.  The various compounds all have
different solubilities and this complicates the use of the equilibrium rela-
tionships discussed earlier.
      1. Both Paritculate and
        Vapors Must be
      2. Very Highly Removal
        Efficiency of Vapors
      3. Numerous Compounds
        of Varying Solubilities
SLIDE 8-43                             These are the most common absorbents
                                       used in odor scrubbers.  The concen-
                                       trations of the solutions generally
                                       vary between 0.5% to 5.0% by weight.
                                       The removal efficiency is not as highly
                                       dependent on the oxidant concentration
                                       as might be expected.  Most field tests
                                       indicate that there is a certain
                                       minimum concentration necessary to
                                       react with the odorous compounds.
                                       Higher concentrations of oxidant yield
                                       only slightly additional odor removal.

                                       The effectiveness of each of the com-
                                       pounds varies for different chemical
                                       species.  However, there is very little
                                       test data to aid in the selection of
                                       the most effective oxidant for the com-
                                       pounds identified in the gas stream.
                                       The oxidant is selected based on vendor
                                       experience in similar sources.

     There are certain odor causing materials which are essentially unreactive
with these common oxidizing agents.  The absorption of these unreactive mat-
erials (often termed "refractory" chemicals) is a function of the equilibrium
concentrations and the effectiveness of the scrubber.  Unfortunately, in some
units the equilibrium concentrations can be quickly reached, thus limiting the
performance of the system.

SLIDE 8-44
         pH SHOULD BE
        HIGHER THAN 10
In the case of hypochlorite scrubbers,
optimum odor reduction occurs when the
pH is above 10.  Under these conditions
the chemical equilibrium shown in this
slide shifts to primarily hypochlorite
ion (OC1 ).  This is the species which
reacts with the absorbed pollutant
compounds.  The hypochlorous acid is
unreactive.  The pH is adjusted using a
caustic solution
SLIDE 8-45

             8 - 10
                     For permanganate scrubbers, the optimum
                     liquor pH is between  8 and 10.  In this
                     range, the hydroxyl ion-(OH ) aids in
                     the chemical attack of some absorbed


SLIDE 8-46
        1, Liquor pH
        2. Liquor Oxidant
        3. Liquor Flow Rate
        4. Liquor Inlet
        5. Gas Exit Temperature
        6. Venturi Pressure Drop
        7. Packed Bed Pressure Drop
        8. Condition of Scrubber
          Shell, Fan and Ducts
        9. Presence of Retrainment
        10. Gas Flow Rate
                                        These are the inspection points  for
                                        odor scrubbers.  The liquor oxidant
                                        concentration and pH are two of  the
                                        most important variables.  The oxidant
                                        concentration can not be measured
                                        during the inspection.  The on-site
                                        conductivity monitor or oxidation-
                                        reduction monitor is used to determine
                                        if there has been a shift in the oxi-
                                        dant concentration.

                                        As with all. absorbers, the operating
                                        temperature and the liquid-to-gas ratio
                                        are important. The gas temperature
                                        leaving the scrubber provides a  good
                                        indication of the operating
                                        temperature.  The flow rate can  be
                                        evaluated based on the recirculation
                                        pump discharge pressure and motor

     The static pressure drop  across  the venturi provides a good indication of
the particulate removal effectiveness.   The static pressure drop across the
packed tower is useful for  identifying  plugging problems within the bed.

     The gas flow rate can  be  measured  at the scrubber outlet using a pitot
tube or estimated from the  fan operating parameters.  The fan rotational
speed, inlet gas temperature and  motor  currents are necessary when evaluating
gas flow rate changes.

     The condition of the scrubber  vessel shell, the ductwork and fans  should
be visually evaluated during the  inspection.  Any air infiltration can  reduce
the quantity of odorous gas pulled  from the process equipment.  The stack area
should be checked for possible reentrainment from the packed tower stack.
This is especially objectionable  in the case of odor scrubbers due 'to the
highly alkaline pH and the  presence of  the oxidant compounds.


8-1.  The correct answer is "c", the mole fraction is 0.097.  The molecular
      weight of HCL is approximately 37.5. Therefore, 18 pounds is equivalent
      to 0.4d pound moles.  The molecular weight of water is 18.  Therefore 80
      pounds of water is equivalent to 4.44 pound moles.  The mole fraction of
      HCL is 0.48 divided by (0.48 + 4.44) or simply, 0.097.

8-2.  Answers "a" and "c" are possible.  At this pH, only a small fraction of
      the hypochlorite ion exists in solution.  Most of it is tied up as
      hypochlorous acid.  Since only a little hypochlorite ion is available to
      react with dissolved pollutants, it is possible that some of these
      pollutants are reaching the saturation concentration.  After this is
      reached, there will be no more net transfer of the pollutant to the
      scrubber liquor.  If the quantity of odorous material in the inlet gas
      stream is small, there may be sufficient reactants to adquately remove
      the odorous material.  In this case, however, much of the hypochlorous
      acid solution will be wasted in the purge stream of the scrubber.

8-3.  Answers "a", "b" and "c" are all possible.  There has probably been a
      drop in the liquid-to-gas ratio of the scrubber.  An increase in the
      inlet fluoride concentration is possible, but less likely.

8-4.  Gases are more soluble at cold temperatures.  Therefore, the observed
      increase in exit gas temperatures will have an adverse effect on the
      fluoride removal efficiency.


8-1.  What is the mole fraction of HC1 if there are 18 pounds of HC1 and 82
      pounds of water? (0.095)

      a.  18
      b.  0.18
      c.  0.097
      d.  0.00457
      e.  It can not be determined from this data

8-2.  An operator of a hypochlorite scrubber for a animal rendering plant is
      not presently adding caustic to the solution.  The pH measured in the
      recirculation tank is 7.6.  What statements could be true about the
      system at the present time?

      a.  The unit is operating satisfactorily, but a large quantity of the
          hypochlorite solution is being wasted.

      b.  Odor removal is not very effective since a pH in the range of 2 to 5
          is necessary to initiate the oxidation reaction in the scrubber.

      c.  Some of the odorous materials are reaching equilibrium
          concentrations in the recirculated liquor and are no longer being
          removed effectively.

      d.  Plugging of the packed tower scrubber is probable under these

      e.  All of the above

8-3.  The effluent liquor concentration of fluoride ion has increased by 46%
      since the baseline period.  What does this possibly indicate?

      a.  The inlet concentration of HF has increased dramatically since
          the baseline period.

      b.  The liquid flow rate to the scrubber has dropped significantly since
          the baseline period.

      c.  The gas flow rate has increased substantially since the baseline

      d.  Severe air infiltration is occurring near the top of the scrubber
          vessel.                                      ._        	

8-4.  The exit gas temperature from a fluoride scrubber has increased 34 F
      since the baseline period.  Will this increase or decrease the
      fluoride removal efficiency?

      a.  Increase fluoride removal efficiency

      b.  Decrease fluoride removal efficiency



8-5.  Answers "a", "c", "d", and "e" are all correct.  In high concentration
      sources of HC1 and HF, it is important to dissipate the heat of absorp-
      tion in the first scrubber stage and then to complete the absorption in a
      tail gas scrubber.  This is also necessary when recovering high con-
      centration HC1.  A-particulate removal section is often used first to
      prevent pluggage of the packed tower absorption sections.  The concept
      of transfer units was not discussed specifically..  This is related to
      the required control efficiency.

8-6.  Answers "b" and "c" are possible.  The ambient air passing through the
      unit will strip out fluoride compounds until the equilibrium concentra-
      tion in the liquor is reached.

8-7.  All of these favor absorption.  Although not listed here, the liquid-to-
      gas ratio is equally important.

8-8.  There is no indication that the gas flow rate has increased.  However,
      the static pressure drop across the packed bed has increased substan-
      tially. Answer "c" is very probable.


8-5.  Why are several scrubbers often used in series on absorber systems?

      a.  To allow removal of the heat of absorption without adversely
          affecting absorption efficiency.

      b.  To allow removal of corrosive gases before the gas stream
          reaches the particulate removal section of the scrubber.

      c.  To allow for the concentration of a recoverable product

      d.  To allow removal of particulate before the gas stream reaches the
          gas removal section of the scrubber.

      e.  To increase the number of Transfer Units of the scrubbing system.

8-6.  What would happen to a fluoride scrubber using recycled pond water of
      3% by weight fluorides, if the inlet duct coming to the scrubber were
      handling only ambient air?

      a.  Absorption of fluorides would be high, due to the low gas

      b.  A small quantity of fluorides would be stripped from solution.

      c.  The stack concentration of fluorides would be higher than the
          inlet stream.

      d.  None of the above.

8-7.  Which of the following conditions favor absorption

      a.  Turbulence

      b.  Time

      c.  Low temperature

      d.  High liquid surface areas

8-8.  During an inspection of a packed tower absorber, it is noticed that the
      pH has dropped from 10.6 to 10.4  The static pressure drop across the
      bed has increased from 4 inches to 7 inches and the exit gas temperature
      has remained relatively constant.  The fan rotational speed is constant,
      but the motor current is down slightly.   What is probably occurring in
      this unit.                                         .      -

      a. The gas flow rate has decreased.

      b. The gas flow rate has increased.

      c. The bed is partially plugged.


                                      LECTURE 9

                                 INSPECTION SAFETY
SLIDE  9-1

     1.  Inhalation of Toxic Gases
     2.  Inhalation of Toxic Particles
     3.  Inhalation of Asphyxiants
     4.  Burns on Hot Surfaces
     5.  Entrapment in Rotating Equipment
     6.  Falls off Ladders
     7.  Falls on Icy Surfaces
     8.  Falls from Weak Roofs and
     9.  Electrical Shock
    10.  Static Electrical Shock
    11.  Eye Injuries
    12.  Noise
    13.  Cold Stress
    14.  Fan Disintegration
    15.  Steam Burns
    16.  Contact with Pathogenic
    17.  Contact with Skin Absorbable
Inspection safety  is the most  important
topic in  this workshop program.   There
are a number of potential health and
safety  hazards regardless of the level
of inspection.  A  partial list of the
types of  hazards are provided  in this
slide.  The inspector must be  constantly
alert so  that these  can be avoided.

The purpose of this  lecture is to make
everyone  involved  in field activities
aware of  the possible hazards  near wet
scrubber  systems.  Most of these are
easily  avoided as  long as^ they are

The information presented here is not
intended  to replace  or supersede any
safety  guidelines  adopted by the agency
of by the plant being inspected.

                                        There are a number of factors which make
       FACTORS rnwTmmiTiMr-           regulatory agency personnel potentially
  TO                   PBLEMS                                       *"*
         1 . Lack of Familiarity with
          Hazards at Specific Plant              One of the most important of these  is
         2. Distractions Due to                  the lack of familiarity with the loc-
          Conversations with Plant              ations of the hazards at the specific
          Personnel                       plant.  It is easy to overlook trip
         3. Attempts by Plant Personnel            hazards such as valve stems and low
          to Hurry Inspector                  support rods. High traffic
                                        areas may be in the same general area  as
                                        the scrubber system.  Also, some plants
                                        have high voltage cables and tracks.
                                        Even though these are marked, it is
                                        possible for the unwary inspector  to
                                        contact the energized lines.

     A contributing factor  to the safety and health risk are the distractions
inherent in conducting  an inspection.  The field inspector spends much of  the
time asking the  plant representative questions about changes since the last
visit.   Also,  it is not uncommon for the inspector to have to patiently listen
to a long list of arguments and complaints from the plant personnel.  Both
the routine questions and the occassional arguments distract the person con-
ducting  the inspection.

     An  additional  complicating factor is the tendency of a few plant repre-
sentatives  to  "hurry" the inspector through the plant.  The combined effect of
a lack of familiarity and fairly rapid movement around the equipment creates
favorable conditions for a  serious accident.

                                        These are several other factors which
        FACTORS CONTRIBUTING          Can make a reulatory agency inspector
   TO INSPECTION SAFETY PROBLEMS      especially at risk.

         1. Hypersensitivity to Specific            Due to the large number of different
           Pollutants                      facilities, it is possible for an
         2. Lack of Acclimatization to             inspector to encounter low levels  of a
           Specific Pollutants                  very iarge number of pollutants.   There
         3. Synergistic Interactions              is a reasonable probability  that an
                                        inspector who is hypersensitive to a
                                        certain chemical will encounter this
                                        material at some time during his or her
                                        career.         ~

     Unlike plant personnel, inspectors can rarely become acclimated to the
materials which  are sometimes encountered when inspecting wet scrubber systems
and the  associated  process  equipment.  There is also the possibility for  some
synergistic interactions between pollutants inhaled in different plants and
those retained in the lung.  On plants with hot processes, it possible to have
very hot and/or  humid conditions around the scrubber.  The inspector rarely
spends  the  several  days necessary to become acclimated to this heat stress.


      1. High Positive and Negative
        Static Pressures
      2. Wet Walking and Climbing
      3. Icy Walking and Climbing
      4. Fan Disintegration Due to
        Solids Carry-over
      5. Explosive Gases and
        Paniculate in Gas Stream
                                       The  intrinsic nature of wet scrubber
                                       systems  makes them especially prone to
                                       safety and health hazards!

                                       They operate at higher pressure
                                       extremes (both positive and negative)
                                       than any other type of air pollution
                                       control  device.  This means that the
                                       potential for gas leakage out into the
                                       breathing zone can be high.

                                       Leaks of water or entrained water from
                                       the  stack can make all walking surfaces
                                       around the equipment hazardous, espec-
                                       ially in cold weather.  There are a
                                       number of sharp obstacles around the
                                       scrubber that would make any fall

     The wet and muddy conditions  can  also  render fixed and portable ladders
dangerous to climb.  The foot  rungs  can  be  either muddy or icy.  It is often
difficult to secure portable ladders on  the wet surfaces.

     Wet scrubbers are often used  on gas streams handling potentially explosive
dusts and gases.  It is the only type  of collector which can not inherently
ignite the mixture.  However,  the  improper  use  of measurement probes and
power tools ahead of the scrubber  systems can create explosive conditions.
Furthermore, there is potential for  fan  disintegration due to solids carry-over
from the scrubber vessel.

SLIDE 9-5                              Due  to the reasons presented in the
                                       previous set of slides, it is important
                                       that each agency have a routine safety
                                       training program for all individuals
                                       involved in wet scrubber system inspect-
                                       ion  (and all other field activities).
                                       This should address recognition of the
                                       problems and the agency policies
                                       regarding proper safety procedures.

                                       There should be a medical monitoring
                                       program  for all field personnel.  This
                                       involves an initial physical to confirm
                                       that the individual is physically able
                                       to conduct the inspection.  This exam
                                       then serves as the "baseline" for
                                       evaluating the health of the inspector
                                       in the future.  This is important since
                                       some problems take time to develop.

     There should be written safety  procedures  which contain all of the agency
safety policies regarding  personnel  protective  equipment and the performance of
inspections.  They should  include  any  specific  safety requirements at the
plants to be inspected.

            1. Hard Hat
            2. Gloves
            3. Respirators
            4. Safety Shoes
            5. Hearing Protection
            6. Eye Protection
                                       The next  set  of  slides presents the
                                       general safety principles which should
                                       be observed during the inspection of
                                       any air pollution control system.

                                       The inspector should bring all the
                                       necessary personal protective equipment
                                       and be throughly trained in the proper
                                       use of the equipment.   Sources have
                                       often distributed respirators and
                                       other protective equipment without
                                       realizing that the individuals did not
                                       know how  to use  them.

                                       Hards hats are necessary primarily for
                                       protection against head blows against
                                       overhead  obstacles.  The safety shoes
                                       provide a slip resistant sole

     Respirators are necessary for the various inhalation hazards potentially
encountered at the specific plant.  It should be remembered that each
respirator is effective only for a small number  of specific pollutants.

     The need for gloves should not be underestimated.   These are necessary for
climbing ladders with rough foot rungs.  Special gloves are also necesary when
handling liquors with skin absorbable components or  with pathogenic organisms.
            OF EXPOSURE
           1. Dizziness
           2. Nausea
           3. Lightheadedness
           4. Drowsiness
           5. Eye or Nose Irritation
           6. Chest Pains
                                       Whenever these non-specific symptoms are
                                       felt,  the inspection should be interrupt-
                                       ed.  The inspector should proceed to an
                                       area with fresh air.  The inspection
                                       should not be resumed until the cause of
                                       the  ill feelings are identified.  These
                                       are  the initial symptoms of exposure to
                                       a large number of pollutants.  Remaining
                                       in the area can quickly lead to serious
                                       health problems.

         Work at Controlled Pace

         Do Not Place Absolute Trust
         in Plant Personnel Regarding
         Inspection Safety
The last two basic safety principles are
listed on this slide.  The importance of
conducting the inspection at a control-
led pace can not be overemphasized.  In
this way, the common walking and climbing
hazards can be avoided.  There is also
less chance or becoming trapped in areas
with high pollutant concentrations.

Most field inspectors visit between 25
and 100 different facilities each year.
While most plant personnel are safety
conscious, it is inevitable that the
inspector will encounter a few plants
each year at which the personnel are
either not concerned or arfe not aware of
the potential problems.  The inspector
must never fall into the bad habit of
abdicating judgment regarding inspection
safety to the plant personnel.  Some-
times they fail to realize that the
inspector is not aware of potential
safety hazards.

                                       The  next  set  of  slides concerns the
                                       numerous  walking and  climbing hazards
                                       which  can exist  in  the vicinity of wet
                                       scrubber  systems.

                                       Slippery  areas are  very common due to
                                       leakage of water from pump seals,
                                       rainout of scrubber liquor from the
                                       stack, and the occassional overflow of
                                       tanks.  During cold weather periods
                                       these  wet areas  freeze.

                                       The  large number of pipes and electrical
                                       conduits  provide a  number of trip
                                       hazards.         _

     Corrosion of the scrubber  vessel  walls and  platform supports can make
elevated platforms dangerous.   The  ladder leading to and from the platform can
also present safety hazards.

 SLIDE  9-10
                                       This photograph shows the area around a
                                       centrifugal pump.  The entire area is
                                       covered with water and wet pulp fibers.
                                       The water is due to the constant slight
                                       leakage of pump seal water.  The wet
                                       pulp is due to an occassinonal overflow
                                       of foam from the recirculation tank.
                                       This makes the area around the pump very
                                       slippery.  A fall here could result in a
                                       head injury on one of the footings shown
                                       in the slide.

                                       During the inspection there is a natural
                                       tendency to look around or up at the
                                       various system components.  Inspectors
                                       must be constantly aware of  slip hazards
                                       around pumps.
SLIDE 9-11
                                       This  slide  is  similar  to  the  one  above.
                                       The only difference  is that the wet  area
                                       has frozen.  Obviously, care  is neces-
                                       sary  when walking on the  ice.

SLIDE 9-12
                                       This is a view of a railroad siding next
                                       to a packed  tower scrubber system.   It
                                       is apparent  that there  is some ice
                                       approximately 15 feet ahead.  What  may
                                       not be apparent is that there is another
                                       patch of ice in the foreground.  While
                                       this area looks like dirt, it is
                                       actually "black ice".  It is simply
                                       frozen water with a high suspended
                                       solids content.  This can form when the
                                       ambient temperature is  very low.
SLIDE 9-13
                                       This is a view of a platform supporting
                                       a small rod deck scrubber.   A small
                                       puddle of water has accumulated in a
                                       depression and frozen.

                                       It would be easy to overlook this patch
                                       of ice since there are  a number of
                                       overhead obstacles (out of  view of the
                                       slide) which must be avoided while
                                       walking around the scrubber.  A fall
                                       could result in a serious injury due to
                                       the sharp objects in the general area.
     During cold weather periods,  it should be assumed t~hat almost"all elevated
platforms will have some frozen puddles or other slipper areas.   Since some of
them do not have hand rails, it is particularly important to avoid these
slippery areas.

                                       This board has been placed  on a snow
                                       covered roof  to improve the walking
                                       surface from  a flooded disc scrubber to
                                       the  access ladder (see in the upper
                                       right hand corner of the photograph).
                                       However,  the  board has become covered
                                       with a thin layer of ice due to water
                                       which has dripped off an adjacent roof
                                       and  refrozen.  A fall on this plank
                                       could result  in a fall of 15 feet off
                                       the  roof.  Note that the roof does not
                                       have any railings to impede a fall.
SLIDE 9-15

                                       This is a temporaty walkway over an
                                       excavated area.  These should be used
                                       only when: (1) the ends are secured, (2)
                                       the wood appears to be in good condi-
                                       tion, and (3) there are hand rails.
                                       Alternative routes are generally pre-
                                       ferable to these temporary walkways.

                                       Under no circumstances should inspectors
                                       use single boards as planks between two
                                       platforms, between two building roofs,
                                       or over open tanks.  The support beams
                                       between two adjacent control systems or
                                       around a single scrubber should never be
                                       used for walking or climbing. Further-
                                       more, ladders should not Tie" used, as

     It is not unusual for the field inspector to be ridiculed by plant
personnel for refusing to walk across support beams or to use weak planks
between high platforms.  Inspectors must develop the self discipline to ignore
this ridicule and to maintain safe inspection procedures at all time.

SLIDE 9-16
                                       This is a view of the settling pond for
                                       a rod deck scrubber.   It has a sloped
                                       ground level entry to permit a front end
                                       loader to occassionaly remove the solids
                                       from the first two zones.  The walking
                                       area near the pond is very slippery.
                                       The unwary inspector  could easy end up
                                       taking a swim in the  pond.  Due to the
                                       heavy winter clothes  and the sloped side
                                       of the pond, this could result in a fatal
                                       accident.  Also, the  liquid temperature
                                       in the first zone can be as high as 140
                                       F and the pond can contain toxic sus-
                                       pended solids.

     While access to activated sludge ponds is usually restricted', these can be
especially dangerous.  The specific gravity of the pond liquor can be so low
that swimming and floating is impossible.

     The areas immediately around basins and ponds should be avoided by the
field inspector.  Samples of the liquor should not be obtained at any location
where it is easy to fall into the pond.
SLIDE 9-17
                                       There are many locations around wet
                                       scrubber systems where steam clouds can
                                       suddenly envelop localized areas.  This
                                       makes walking particularily hazardous.

                                       This is a view of the same area shown in
                                       the previous slide.  It was taken 15
                                       seconds after the previous slide.  The
                                       cloud is due to the contact of a cold
                                       breeze across the warm pond liquor.  The
                                       inspector who fails to slow down as the
                                       cloud passes could easily get too close
                                       to the pond entry.
     The inspector should not proceed until there is adequate visibility.  Some
make the assumption that they are completely familar with the plant.  This can
be a very bad assumption since plant personnel may have forgotten to replace a
grating, or have left some obstacle in the walking path.  Many changes can
occur between inspections.

                                       Several safety chechs should be made
                                       before climbing up to the elevated
                                       platforms around the wet scrubber
                                       vessels or the stack sampling areas.

                                       The supports should be visually inspec-
                                       ted for obvious corrosion.  Also, the
                                       integrity of the ladder supports should
                                       be observed.  Rotted wooden plants or
                                       gaps in the gratings should be checked.

                                       The potential for entrapment in a
                                       rising cloud of high temperature steam
                                       or a toxic cloud of fugitive emissions
                                       should be considered before going to the
                                       platform.  If there are intermittant
                                       process operations which could create
                                       these highly dangerous conditions, the
                                       inspection should only be done when that
                                       portion of the plant is not running.

     Inspectors should never underestimate the potential problems resulting
from rising steam clouds and/or toxic clouds of pollutants.  These can form
suddenly due to process upsets or intermittant process operations.  It is
difficult to get off platforms when both visibility and breathing are impaired.
Respirators should be taken when going to elevated platforms.
SLIDE 9-19
                                       There are some  elevated  surfaces  which
                                       may  not  be able to withstand  any
                                       additional load.   An  inspector  who  walks
                                       across a roof,  as  shown  in  this slide,
                                       may  fall through.   It is important  to
                                       stay within designated walking  areas.
                                       It is also prudent to walk  behind the
                                       plant personnel.

SLIDE 9-20
                                       This is a picture of the floor around a
                                       packed bed wet scrubber.  The entire
                                       system is in a very dimly lit building.
                                       While walking between the stockpiled
                                       materials near the scrubber,  it is easy
                                       to miss the small raised portion of the
                                       floor.  The severity of the accident
                                       depends on what is hit on the way down.

                                       Whenever entering a building from the
                                       outside, it is necessary to wait briefly
                                       for the eyes to adjust to the low light
                                       conditions.  Many scrubbers are placed
                                       in enclosed areas to protect piping from
                                       freezing during winter off-line periods.
SLIDE 9-21
                                       While walking around the scrubber sys-
                                       tem, it is easy to become preoccupied
                                       with inspection details.  The valve stem
                                       shown in this slide sticks out far into
                                       the walkway at about the height of a
                                       knee.  It is very hard to see due to the
                                       lack of light within the building (the
                                       photograph was shot with 1000 speed film
                                       and a 100 watt bulb approximately 2 feet
                                       away).  This is just one example of the
                                       many trip hazards which can exist around
                                       the wet scrubber system.

 SLIDE  9-22
                                       This is a photograph of a small beam at
                                       about head height which is close to an
                                       access ladder.  A painful and serious
                                       injury could occur to those who fail to
                                       wear a hard hat.  It is surprising how
                                       many plants do not require these hats.
                                       It is also surprising how many overhead
                                       beams, conduits, valve stems, pipes, and
                                       other obstacles exist around a wet
                                       scrubber system.
SLIDE 9-23
                                       While walking around a wet scrubber sys-
                                       tem it is easy to forget about rotating
                                       equipment in the general area.  This
                                       slide shows a partially covered fan
                                       sheave and drive belt.  This was along a
                                       very narrow path to a rod deck scrub-
                                       ber.  It is possible for loose clothing
                                       to get caught between the rapidly moving
                                       belt and sheave.

                                       One way to minimize the risk of entrap-
                                       ment in rotating equipment is to avoid
                                       wearing loose clothing.   Ties should not
                                       be worn during inspections.

     The area immediately around the  rotating equipment~should beTavoided to
the extent possible.   If there is only  one path to the control system and
there is a reasonalbe risk of entrapment  even when caution is exercised,  then
the inspection should not be done!

                                       This is a winch beside a narrow path to
                                       the same system discussed in the last
                                       slide.  It is 4 feet above the walking
                                       surface and the cable cuts over the path
                                       that the inspector must take.  The oper-
                                       ation of the winch is controlled by
                                       plant personnel who can not see the
                                       scrubber from their work station.   A
                                       serious injury could occur if an inspec-
                                       tor placed a hand on the winch while
                                       trying to duck under the obstacles.  It
                                       should be assumed that equipment which
                                       is designed to move will start suddenly!
SLIDE 9-25
                                       Climbing  ladders  is  a  common  part  of wet
                                       scrubber  system inspections.   There are
                                       periods when  these ladders  can be  very

                                       This  slide illustrates a common problem
                                       with  ladders  around  wet scrubber sys-
                                       tems.  The first  person up  the ladder
                                       (normally the plant  representative)
                                       deposits  a layer  of  mud or  sludge  on
                                       the foot  rungs.   This  makes the ladder

SLIDE 9-26
This slide illustrates one possible way to
a ladder.  There is a temptation to hold
on to the side rails of the ladder to
avoid the mud or sludge shown on the
previous slide.  However, it is easy for
a foot to slip off the foot rungs under
these conditions.  With the hands on the
side rails,  an inspector may not be able
to maintain a grasp on the ladder when
the foot slips.

The inspector in this slide is making
the mistake of trying to carry portable
instruments while climbing.  These
significantly reduces the grip on the
SLIDE 9-27
                                       This slide  illustrates another  possible
                                       way to  climb a  ladder.  The  hands are
                                       placed  on the foot  rungs and the
                                       inspector is wearing gloves  which
                                       improve his grip  on the ladder.   The
                                       portable instruments are being  carried
                                       on  a side pouch which  does not  impede
                                       the climbing motion.

                                       Any large instruments  should be trans-
                                       ported  to the platform or roof  by means
                                       of  a rope (with a bucket in  some  cases).
                                       Obviously,  it is  important that nothing
                                       falls during lifting and that the rope
                                       is  not  used near  power lines.  The wind
                                       speed should be Tow enough "to prevent
                                       swinging of the rope.

SLIDE 9-28
                                       There should be at least 9 inches of
                                       clearance between the foot rungs and any
                                       obstacle behind l^he ladder.  This is
                                       necessary to ensure that the foot rests
                                       securely and completely on the foot
                                       rung.  The person shown in this slide
                                       should have been climbing by placing the
                                       back of the heel against the foot rung.

                                       While the large majority of ladders on
                                       wet scrubbers have the necessary clear-
                                       ance, occassionally there are pipes,
                                       support beams or electrical conduits
                                       placed too close to the ladder.
SLIDE 9-29
                                       Repaired portable ladders such as shown
                                       in this slide should not be used under
                                       any circumstances.   If  it has been
                                       necessary to fix one of the rungs,  it is
                                       possible that some  of the other rungs
                                       have also weakened.

                                       All of  the foot  rungs should be inspec-
                                       ted prior to use.   The  ladder should not
                                       be used if any of the rungs appear  to be
                                       rotted  or if a rung  has separated from
                                       the side rail.

 SLIDE 9-30
                                        One of  the basic requirements of  a
                                        portable ladder  is  that  it  be secure  at
                                        the bottom.   It  is  often difficult to
                                        find a  location  near  wet scrubber sys-
                                        tems "which is free  of a  coating of
                                        sludge  or mud.

                                        This slide shown a  portable ladder
                                        sitting on a  slippery layer of sludge
                                        next to a rod deck  scrubber.  There is a
                                        possibility that the  ladder will  slip at
                                        the bottom as an inspector  climbs this

      In  addition  to  locating  a  dry  spot for the ladder,  it is necessary  to have
 the  right  type  of  slip  resistant protector on  the bottom of  the ladder.   Two of
 the  most common slip protectors are spurs  and  pads.
SLIDE 9-31
                                       This is the same ladder shown in the
                                       previous slide.  Another common problem
                                       with the portable ladders involves weak
                                       upper supports.  Close examination of
                                       the slide illustrates that the small
                                       angle iron which is supporting this
                                       ladder has be cut approximately 80% of
                                       the way through.  The load created on
                                       this beam as the inspector climbs will
                                       be enough to break the angle iron.

                                       Ladders should not be resting on small
                                       support beams, pipes or electrical con-
                                       duit.   These were not constructed to
                                       withstand the 25 to 100 pounds of lat-
                                       eral force which-can develop.  Also the
                                       ladder should not be placed against a
                                       slippery wall.

     The portable ladders should be inclined  on an angle so that the ladder
will not tip over and so that the base will not slip out.   As a general rule
the triangle defined by a sloped ladder should have a height which is 4 times
the base.   The ladder should never be near high voltage power lines.

SLIDE  9-32
      Thermal Radiation
      Other Radiation
Potential eye injuries which can  occur
while inspecting wet scrubber  systems
are listed on this slide.  The most
common of these is chemical burn  from
fumes or splashes.  It is important  to
wear eye protection while inspecting wet
scrubber systems.
SLIDE 9-33
                                       This is a photograph of a  valve on  the
                                       discharge line of a wet scrubber pump.
                                       The liquor is under approximately 90
                                       psig pressure and the pH is quite high.
                                       If care is not taken in sampling the
                                       liquor, it can splash into the unpro-
                                       tected eye.  This can result in a severe
                                       burn and/or blindness.  The valve must
                                       be opened gradually and the receiving
                                       container must not facilitate splashing.
                                       The inspector should wear splash goggles
                                       while this is being opened.  Plant  per-
                                       sonnel should take a.ll liquor samples.

 SLIDE  9-34
f \ *^^.
                                       This slide  shows  three  types of eye
                                       protection  in  general use for wet
                                       scrubber inspections.   Most plants
                                       require  eye protection  and inspectors
                                       should be sure that theirs satisfies
                                       plant requirements.  It is suggested
                                       that eye protection be  used even if not
                                       specifically required.  At the very
                                       least, it will prevent  the introduction
                                       of  chemicals and  foreign materials into
                                       the eye  by  careless rubbing.
SLIDE 9-35
                            It is recommended that  field  inspectors
                            avoid wearing contact lenses  unless
                            these are specifically  allowed  by  plant
                            and agency safety personnel.  It is
                            conceivable that hard contacts  can
                            increase the damage  done  to the eye by a
                            foreigh body which gets trapped behind
                            the lense.  Soft contact  lenses, parti-
                            cularily the gas permeable ones, may
                            make the eye more susceptible to
                            chemical damage.
Lecturer's Notes
  ,   There are differing  opinions regarding the potential advantages and  dis-
advantages of contact  lenses during work in industrial facilities.   Until this
is settled satisfactorily, it is prudent to avoid the contact lenses.   These
are also not allowed during the use of any full face mask respirator.

SLIDE 9-36

      2 - 3 FEET AWAY.
Noise exposure related hearing loss is
not a common problem in the inspection
of wet scrubbers.  The most probable
sources of noise are the process equip-
ment served by the scrubber system.  The
only significant source of noise on the
scrubber system is the fan.  Units which
are operating a high tip speeds can have
an appreciable noise level.

The best way to minimize noise related
problems is to minimize the amount of
time spent in the proximity to the
noise source.  Hearing protection should
also be used whenever it is difficult to
understand someone talking'in a normal
tone of voice from more than 2 feet
SLIDE 9-37
               AND BURNS
Some of the problems which seem the
least likely on wet scrubber systems are
the ones that can have the most serious
consequences.  These include explosions,
burns, and electrical shock. -The next
set of slides briefly introduces ways to
minimize the risk due to these problems.

SLIDE 9-38
                                       This slide  shows  flames  engulfing  an
                                       access  ladder  to  a  cupola  wet  scrubber
                                       system.   This  occurs  when  the  plant is
                                       "dropping bottom".  The  inspector  should
                                       not go  near the scrubber system  when
                                       this is  about  to  occur.

                                       Plant personnel are usually  quite
                                       careful  about  advising inspectors  about
                                       this operation.   The  problem occurs when
                                       the cupola  operator is unaware of  the
                                       presence of the inspector  on the
                                       platform of the scrubber.  The inspector
                                       must remain aware of  plant operations
                                       and must not assume that the operators
                                       are always  aware  of his  or-her presence.
                                       After all,  inspections occur only  once
                                       or twice a  year and it is  easy for the
                                       operator to forget.

     This is one of the many reasons why it is  always advisable to  perform the
inspection in the company of a plant representative.   This individual will know
which operators must know about the inspector  and  will recognize  when something
is about to occur at the plant which could endanger the  inspector.
SLIDE 9-39
                                       Most  plants  have  areas where  explosions
                                       could be initiated  by smoking.  While
                                       the plant personnel are warned  repeat-
                                       edly  about such areas, the  inspector may
                                       not recognize  the hazard.   DO NOT TAKE
                                       SMOKING  MATERIALS ON INSPECTIONS OF WET
                                       SCRUBBER SYSTEMS.

SLIDE 9-40
                                       This is one type of portable thermo-
                                       couple used for measuring"gas, liquid,
                                       and pipe skin temperatures.  It should
                                       not be taken into potentially explosive
                                       areas since most battery powered inst-
                                       ruments can initiate explosions.  All
                                       flashlights used should be explosion

                                       Potential safety problems with battery
                                       powered thermocouples, pH meters and
                                       flashlights should be discussed with
                                       plant personnel before use in the plant,
SLIDE 9-41

                                       It is sometimes necessary to obtain a
                                       sample of fuel oil or other material
                                       stored in drums.  When transferring the
                                       liquid from a storage drum to a sample
                                       bottle, is is possible to build up a
                                       high static charge on the sample bottle
                                       due to splashing.  An explosion is
                                       possible if the drum and sample bottle
                                       are not properly grounded and bonded.

                                       This slide shows a storage drum and a
                                       small clip which is part of the bonding
                                       line.  This clip has so rusted that it
                                       would not provide a good contact.  Also,
                                       the grounding line to the drum has been

     Samples should not be taken under the circumstances shown in the slide.
A metallic sample bottle should be used and a grounding/bonding cable in good
condition should be connected between the bottle and the drum.  Another cable
in good condition should connect the drum to the grounding rod.  Plastic and
glass bottles should not be used since it is impossible to ground these
properly.  Unfortunately, agency lab quality assurance personnel often are not
aware of the significant explosion hazards and that often request field inspec-
tors use plastic or glass bottles to prevent contamination.

SLIDE 9-42
                                       Several times during the previous
                                       lectures the potential dangers of fan
                                       disintegration have been mentioned.
                                       This can occur on wet scrubber systems
                                       due to the carry-over of liquor and
                                       solids from the demister.  The erosion
                                       or solids accumulation on the fan blades
                                       lead to unbalanced conditions.  Due to
                                       the high rotational speed the lack of
                                       balance can ultimately lead to the
                                       disintegration of the fan wheel and fan

                                       Other causes of fan disintegration
                                       include bearing failure and aerodynamic
                                       forces (fan operating in unstable region
                                       of fan curve).

     The area around the scrubber should be left immediately if the vibration
appears to be excessive.  A responsible plant representative should be notified
about the situation.
SLIDE 9-43
                                       Static grounding/bonding cables should
                                       be used whenever making measurements at
                                       the inlet ducts of evaporative coolers
                                       and scrubber vessels.   Static electrical
                                       charge accumulation can occur whenever
                                       the relative humidity  is low (high gas
                                       temperatures) and the  particulate mass
                                       concentration is high.   It is conceiv-
                                       able that the charge will reach a suf-
                                       ficient voltage to arc within the duct
                                       and cause an explosion.

                                       It should be noted that this problem has
                                       not been reported or discussed in the
                                       literature.   However,  the author has
                                       been able to develop high voltages on a
                                       pitot system which resembles the inlet
                                       to a wet scrubber system.

     The gas streams in the inlet duct usually have more than  enough
particulate to sustain an explosion and many of these have the necessary oxygen
levels.  Scrubbers are often used specifically becuase of the  potentially ex-
plosive nature of the inlet gas stream.  For all of these reason, the .probes
should be bonded to a grounded portion of the plant using the  grounding/bond-
ing cables.

SLIDE 9-44
  Elevated Sampling Platforms
  Areas Adjacent to Process Vents and Discharge Points
  Partially Confined Areas
  Fugitive Process Emissions
  Fugitive Emissions from Solids Discharge Equipment
                                       The  next  set  of  slides concerns the
                                       large number  of  inhalation hazards which
                                       can  be  encountered  during inspection of
                                       wet  scrubber  systems.   One of the fund-
                                       amental principles  of  industrial hygiene
                                       is that inhalation  exposures should be
                                       minimized or  eliminated through the
                                       application of engineering controls.  In
                                       the  case  of the  field  inspector, this is
                                       not  a realistic  possibility.  Most ex-
                                       posures occur because  of fugitive leaks
                                       of the  pollutant-laden gas stream out
                                       into the  area immediately surrounding
                                       the  wet scrubber system.

     These conditions occur by accident and often are not  identified by plant
personnel.  Other sources of exposure are contact with  the downdraft from
nearby stacks or rising clouds of toxic pollutants released from intermittant
process operations.  Both types of exposure can  result  when inspectors are
present on elevated platforms around the scrubber or on stack sampling plat-
forms .

     Since the exposures can not be easily  limited by engineering controls, the
inspector must substitute awareness of the  potential problem  areas and
awareness of the warning properties of all  chemicals present  in the general
area.  The inspector must know when certain areas should be avoided and what
respirators and other protective clothing to use in  the areas which must be
visited.  The choice of respirators is complicated by the  lack of monitoring
data for the types of materials present.  The  conditions are  highly variable
and this makes monitoring data subject to error.  Furthermore, there is rarely
any monitoring data in the specific Ipcations  where  the inspector may
experience the most significant exposures.
SLIDE 9-45

                                       One  common  source of fugitive emissions
                                       are  the  open  4 inch stack sampling ports
                                       sometimes used when measuring scrubber
                                       operating conditions.  This is a photo-
                                       graph  of several inspectors attempting
                                       to use an oxygen analyzer at a 4 inch
                                       port having less than 1 inch W.C. pos-
                                       itive  pressure.   Even at this low
                                       pressure, a substantial quantity of the
                                       gas  can  escape through the port into the
                                       breathing zone of. the inspector.

                                       These  large diameter ports should be
                                       avoided  whenever possible.  The ports
                                       should be between 1/4 inch and 1 inch
                                       diameter.   Only ports in areas with good
                                       natural  ventilation should be used.

SLIDE 9-46
                                       There can be areas around scrubber sys-
                                       tems which have poor ventilation.   Any
                                       fugitive leaks which occur in these area
                                       result in high localized pollutant con-
                                       centrations.  These can exceed the cap-
                                       abilities of some respirators.

                                       This photograph shows a fan serving a
                                       large venturi scrubber.  The fan and
                                       scrubber are enclosed on three sides by
                                       building walls.  A gap in the isolation
                                       sleeve on the fan or corroded ductwork
                                       could lead to very high concentrations
                                       near the fan.  All fan housings or
                                       partially enclosed areas surrounding
                                       fans must be approached carefully.
SLIDE 9-47
                                       This  is  a  close-up  photograph  of  the
                                       isolation  sleeve  on the  discharge side
                                       of  the fan shown  in the  slide  above.
                                       There are  a number  of  gaps which  are
                                       leaking  pollutant laden  gas  into  the
                                       area  around the scrubber.

 SLIDE 9-48
                                       This is the scrubber control cabinet
                                       which is located less than 3 feet from
                                       the cracked isolation sleeve (see last
                                       two photographs).  An inspector trying
                                       to determine the operating conditions of
                                       the scrubber system could be fumigated
                                       with toxic or oxygen deficient gases.
SLIDE 9-49
                                      This  is a view of a pump house.  High
                                      concentrations of vaporous material can
                                      accumulate in this area.  These must be
                                      approached cautiously since ventilation
                                      in pump houses can be limited.

SLIDE 9-50
                                      High concentrations of pollutants can
                                      occur almost anywhere in wet scrubber
                                      systems which operate at positive
                                      pressures (fan ahead of the scrubber
                                      vessel).  This slide illustrates a
                                      scrubber system under positive pres-
                                      sure.  Wet scrubber systems operate at
                                      higher static pressures than all other
                                      types of air pollution control devices.

                                      All partially confined areas around
                                      areas of possible fugitive leaks should
                                      be avoided.  The inspector must remain
                                      constantly alert for symptoms of possi-
                                      ble exposure.
SLIDE 9-51
                                      Avoiding hazards is the best way to
                                      minimize risk.  Many of the materials
                                      inhaled during the inspection have poor
                                      warning properties.  In other words,  the
                                      person may have no physical sensation
                                      that there are high levels of pollutants
                                      in the air.

                                      The inhalation of dust and fume rarely
                                      causes any immediate physical discomfort
                                      or impairment.  For this reason, it is
                                      possible for undesirable quantities of
                                      toxic materials such as lead, arsenic
                                      and asbestos to reach the lungs where
                                      they can be slowly absorbed by the

     The chemical and  physical asphyxiants are another group of chemicals with
very poor warning properties.  Chemical asphyxiants, such as carbon monoxide and
hydrogen sulfide, can  occur  at life threatening levels without any odor or taste
preception.   The most  common physical asphyxiant, carbon dioxide, also does not
have any odor.                                         __        	

     Most organic compounds  and nitrogen dioxide are not very soluble and can
penetrate into  the deep  lung.  The initial symptoms of exposure are non-
specific and may not be  recognized by the inspector who is preoccupied with
conversations with plant personnel.  These symptoms include dizziness,
headache, light-headedness,  and nausea.  Acute exposure can result in pul-
monary edema hours after the exposure.  It should also be remembered that non-
soluble chemicals are  not removed effectively in wet scrubbers.  That means
that high concentrations can exist in both the inlet and outlet gas streams.

SLIDE 9-52
Route of Entry


 Inhalation of Gas

 At High Concentrations There Is No Odor
Consequences   Chemical Pneumonia May Develop Several
             Hours After Exposure
                                        The next three slides  illustrate the
                                        differing characteristics  of  common air
                                        pollutants which can be  encounted while
                                        inspecting wet scrubber  systems.

                                        At low concentrations, hydrogen sulfide
                                        is an eye irritant and it  has a very
                                        disagreeable rotten eggs odor.  If these
                                        symptoms are noted, the  inspector should
                                        leave the area immediately.   Exposure to
                                        higher concentrations  of hydrogen sul-
                                        fide can occur in areas  close to the
                                        point where these symptoms were first
                                        noted.  At moderate to high concentra-
                                        tioi s, hydrogen sulfide  is an very
                                        deadly chemical and there  is  no odor at
                                        all!  High concentrations  of  hydrogen
                                        sulfide immediately overcome  the
                                        olefactory senses.

     It is possible to walk into a confined or partially confined area with
toxic concentrations  of  hydrogen sulfide and not be aware of  its  presence at
all.  Brief exposure  to  such conditions can lead to pulmonary edema  and other
serious respiratory problems in 6 to 12 hours after the exposure.  In other
words there is a delayed response during which the victim feels only slightly
ill.  The exposure can also result in immediate death.

     Due to the almost total lack of warning properties, respirators do not
provide an adequate defense.  There are no commercially available respirators
rated for hydrogen sulfide.
SLIDE 9-53

Route of Entry   Inhalation of Gas

Symptoms      Initial Symptoms Include Cough, Chills,
             Fever, Headache, Nausea
Consequences   Acute Pulmonary Edema May Follow Five
             to Twelve Hours After Exposure
                              During the exposure  to nitrogen oxides
                              only mild bronchial  irritation may be
                              experienced.  Concentrations of 100 to
                              150 ppm are dangerous  for periods of 30
                              to 60 minutes.

                              Nitrogen oxides are  generated in almost
                              all combustion processes.  While they do
                              not have a distinctive odor, it is some-
                              times possible to  see  the orange color
                              of nitrogen oxides.
       These gases  are examples of the non-soluble  chemicals which can be
treated in wet  scrubber systems.'  They are often accompanied by other combus-
tion related pollutants such as sulfur dioxide, ozone,  carbon monoxide and
particulate matter.   Any respirator used in areas of  fugitive gas leakage must
be capable of handling all of these potentially dangerous  gases.

 SLIDE 9-54
Route of Entry



Inhalation of Fibers

Intense Irritation of Eyes, Nose, and Throat

Respiratory Problems
Chlorine is one of a number of  chemicals
which are partially soluble in  mucous
membranes.  The initial  site  of attack
includes the eyes, nose, and  throat.   It
has relatively good warning properties.

Exposure can occur due to an  accidental
release from process equipment.  Inspec-
tors must be aware of plant warning
sirens and know what to  do if a cloud of
chlorine is approaching  their location.
       Chlorine is often stored for use in odor scrubbers.   It  is also a common
 process chemical.  Inspectors in areas vulnerable  to  sudden chlorine releases
 should be equipped with emergency respirators.
 SLlrfE 9-55
                                        The wind  socks  and pennants on high  
                                        places  in the plants provide a good
                                        indication of prevailing wind direction.
                                        These should be observed whenever an
                                        inspection is being performed in a plant
                                        which could conceivably suffer an acci-
                                        dental  spill or process release. As soon
                                        as the  warning  siren sounds or it is
                                        apparent  that a gas cloud is approach-
                                        ing, all  personnel should move to a safe
                                        position.  It is also helpful to call in
                                        to a central location to report that
                                        everyone  has reached a safe location.
                                        This call may prevent others from get-
                                        ting hurt while attempting a "rescue" of
                                        the inspection  group.    ~

SLIDE 9-56

          Concentration of Contaminants
          Forms of Contaminants
          Oxygen Levels
          Size and Shape of Head
                                       The selection of the appropriate res-
                                       pirator for each inspection is a very
                                       important and complicated task.  This
                                       provides a very brief overview of some
                                       important points.  The readers are
                                       strongly advised to get expert assist-
                                       ance in the selection, fitting, main-
                                       tenance and use of respirators.

                                       The respirators must be selected based
                                       on a number of factors, some of which
                                       are listed on this slide.

     One of the most important factors is the concentration of the material.
The respirator must satisfactorily perform at these concentrations.  It is also
important to know if the concentration is in the range that is considered to be
Immediately Dangerous to Life and Health (IDLH) and if the concentration is in
the explosive range.  These areas should not be entered by regulatory agency
field inspectors.

     Unfortunately, the concentrations of the contaminants are rarely known
because the exposures are due to accidential and/or intermittent conditions.
Also, the inspector visits many different localized sites around the control
system and there is rarely any monitoring data available for all of these

     It is very important to know what the oxygen level is at the various areas
to be visited.  Many wet scrubber systems handle gas streams with very low
oxygen levels of 3 to 6%.  Even some small leaks can lead to localized oxygen
concentrations below 19.5%, the point at which oxygen deficiency becomes a

     The warning properties of the materials must be known.  This is best done
by the file review before starting the inspection.  If some of the chemicals
are irritants, a full face piece unit may be required, regardless of the
concentration.  If the chemical(s) can be absorbed through the skin, protec-
tive clothing may be necessary in addition to a respirator.

     The physical form of the material (gas, vapor, fume, dust) must be known
to the extent possible.  This is not as obvious as it would seem since the form
of the contaminant can change in the wet scrubber or after release from the
stack.  There can be condensation of vaporous material to form submicron
particles.  There can also be stripping of dissolved compounds to form gases.
The moist conditions can also promote atmospheric reactions between several
pollutants.                                                  -

     The size and shape of the individual's head should be considered in the
selection of respirators.  There are usually several models of each type
available, and the unit chosen must be comfortable and fit tightly.

SLIDE 9-57
                                       There are a number of requirements con-
                                       cerning the the use of respirators.
                                       The material which follows has been
                                       excerpted from OSHA Standard 1910.13A.
                                       The full text of the OSHA Standard and
                                       other material concerning the safe use
                                       of respirators should be read.

                                       The user should be instructed and train-
                                       ed in the proper use and limitations of
                                       the specific respirators.

                                       Whenever practicable, the respirators
                                       should be assigned to individual work-
                                       ers for their exclusive use.

     Respirators should be regularly cleaned and disinfected.  Those issued for
the exclusinve use of one worker should be cleaned after each day's use, or
more often if necessary.  Those used by more than one worker should be thoroug-
ly cleaned and disinfected after each use.

     Respirators should be stored in a convenient, clean, and sanitary location
between uses.  The trunk of a car is not adequate.

     Respirator should be routinely inspected during cleaning.  Worn or
deteriorated parts should be replaced.  Respirators for emergency use such as
self-contained devices should be thorougly inspected at least once a month and
after each use.

     Appropriate surveillance of work area conditions and the degree of ex-
posure or stress should be maintained.

     Persons should not be assigned to tasks requiring use of respirators
unless it has been determined that they are physically able to perform the work
and to use the equipment.  A local physician should determine what health and
physical conditions are pertinent.  .The respirator user's medical status should
be reviewed periodically.

     Written standard operating procedures governing the selection and use of
respirators should be established.

SLIDE 9-58
    Municipal Incinerators
    Pathological Incinerators
    Foodstuff Processors
    Genetic Engineering Firms
The adjacent slide is a partial  list
of the possible sources of  biological
hazards.  It is obviously important  to
avoid direct contact with contaminated
materials.  The appropriate respirators
should be selected based on agency and
plant industrial hygiene guidelines. Eye
protection should be worn in situations
where splashing or contaminated  water  is
possible.  It is important  to avoid  any
rubbing of the eyes at any  time  since
this is an easy entry route for  patho-
genic organisms.  After the inspection
the work cloths should be washed and the
inspector should shower.
SLIDE 9-59
                                        Here  is one example of a commonly
                                        encountered potential biological hazard.
                                        This  inspector is attempting to obtain a
                                        scrubber liquor sample.  Since it is
                                        possible that the liquor contains
                                        pathogenic organisms, the inspector
                                        should  avoid contamination of his skin
                                        and clothing.  THIS IS THE WRONG WAY TO
                                        TAKE  THE SAMPLE.

                                        It is far better  to sample in a area
                                        where there is no direct contact with
                                        the liquor and no possibility for
                                        splashing of the  liquor.


SLIDE 9-60

                                      This  is  the most important safety
                                      precaution that should be taken during
                                      the inspection of wet scrubber systems.

                                      UNDER NO CIRCUMSTANCES SHOULD AN AGENCY
                                      INSPECTOR ENTER ANY PORTION OF THE WET
                                      SCRUBBER SYSTEM.  Oxygen deficiency
                                      and/or high concentrations of highly
                                      toxic pollutants can be trapped in
                                      scrubber vessels, tanks, ductwork, and
                                      other areas.  The conditions can persist
                                      even  after the system has been off-line
                                      for a period of time.  It is often
                                      difficult to detect the dangerous

     It takes  special training and personal  protective equipment to make safe
internal inspections of air pollution control systems.  Regulatory agency
personnel do not have either this training or equipment.  Furthermore, there
are certain safety procedures that must be observed at each plant.

     Regardless of the possible encouragement by plant personnel or the natural
curiosity of the inspector, entry inside the equipment should not be done.
Everthing thing that must be done by an inspector can be done satisfactorily
and safely  outside the equipment.


9-1.  All of these are potential areas of high pollutant concentrations.   They
      should all be approached very carefully.

9-2.  The correct answer is "d".  It is important to use the  grounding/bonding
      cables whenever there is any possibility for static electricity.  This is
      most likely at the inlets to wet scrubber systems.

9-3.  Answers "b", "c", and "d" are correct.   Often the plant personnel are not
      using hard hats, safety shoes, hearing  protection and respirators.   The
      inspector should not abdicate his or her judgement to plant personnel
      since there are a few who are not safety conscious and  a few who  are
      totally oblivious to health and safety  risks.

9-4.  The correct answer if "e". The inspector should always  be accompanied by
      a plant representative who: (1) knows the warning siren codes and plant
      evacuation procedures, (2) notifies process operators of the inspection
      activities, and (3) knows the safe routes around process and scrubber

9-5.  The correct answer is obviously "b", most pollutants have very poor or
      nonexistent warning properties.

9-6.  The correct answer is "h", all of these are possible symptoms of  ex-
      posure.  The inspector should proceed immediately to a  well ventilated


9-1.  Areas around wet scrubber systems which have often have poor
      ventilation and high pollutant concentrations include the

      a.  Fan houses
      b.  Walkways between adjacent scrubbers
      c.  Walkways adjacent to duct expansion joints
      d.  Pump houses

9-2.  Before inserting a probe into a gas stream it is important to check which
      of the following items:

      a.  The grounding/bonding, cable is in good condition
      b.  The ground clamp does not interfere with the probe
      c.  The clamp has penetrated any paint or corrosion layer
      d.  All of the Above

9-3.  When selecting personal safety equipment necessary for an inspection,
      the inspector should be guided by which of the following:

       a.  What the plant representative and other plant personnel are using
       b.  Plant policies
       c.  Agency policies
       d.  Common sense

9-4.   An inspector should not work alone during an inspection, unless the
       following conditions exist:

       a.  Plant personnel are too busy to accompany the inspector.
       b.  The inspector is very familiar with the plant.
       c.  No entry into pratially confined or confined areas are anticipated.
       d.  The inspector has all of the necessary personal protection
       e.  None of the above

9-5.  Most gaseous contaminants have good "warning properties".  Therefore the
      inspector is usually aware they are present.

      a.  True
      b.  False

9-6.  Which of following symptoms may indicate exposure to air contaminants?

      a.  Headache                                       "        ~~     -
      b.  Drowsiness
      c.  Shortness of breath
      d.  Nausea
      e.  Loss of coordination
      f.  Eye irritation
      g.  Answers a,b,c,d,f
      h.  All of the above



9-7.  Hydrogen sulfide is especially dangerous since it has no odor at high
      concentrations.  Answer "d" is correct.

9-8.  Answer "c" is correct.  The equipment should not be entered even though
      the plant personnel seem to be feeling fine inside the unit.  It is
      always possible that they will develop serious respiratory problems in
      the next several hours due to high concentrations of pollutants having
      no warning properties.  Everything can usually be seen from an access
      hatch.  If it can not be seen just take their word for it.


9-7.  At high concentrations what best describes the odor of hydrogen

      a.  Fragrant
      b.  Sewer
      c.  Rotten Eggs
      d.  No Odor

9-8.  During the inspection of a rod deck scrubber,  the operator states that
      a chronic gas-liquor distribution problem has been solved by movement of
      both the spray headers and the rod deck.    He suggests that you follow
      him into the scrubber to confirm that this has been done properly.  What
      should the inspector do to complete this  inspection?

      a.  Review the drawings and do not waste  time on the equipment
      b.  Make sure the plant personnel enter first, and then follow
          them inside to confirm the modifications have been completed.
      c.  Limit the inspection to what can been seen through an access
          hatch without going inside.




            Bibliography: Scrubber Types and Operating Principles

1-1        Atkinson,  D.  S. F.  and W.  Strauss.  Droplet Size and Surface
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1-2        Boll,  R.  H.  Particle Collection and Pressure Drop in Venturi
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1-3        Buonicore, A.  J.,  and L.  Theodore.  Industrial  Control Equipment
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1-4        Calvert,  S.,  H. Barbarika and G.  Monahan. American  Air Filter
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1-5        Calbert,  S.  Venturi and Other Atomizing  Scrubbers:  Efficiency
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1-6        Calvert,  S.  "Engineering Design of  Fine  Particle Scrubbers."
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1-7        Calvert,  S.,  S. C.  Yung,  H. F. Barbrika, and L. E.  Sparks. Entrain-
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          Symposium. EPA-600/2-77-193, May 2-3,  1977.

1-8        Calvert,  S.,  I. L.  Jashnani, and S. Yung. Entrainment Separators
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1-9        Calvert,  S.,  S. Yung, and J. Yung.  Entrainment Separators for
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1-10      Calvert,  S.;  Barbarika, H.  F.; and  Monahan, G.  M. Evaluation
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1-11      Calvert,  S.,  H. F.  Barbarika, and  G.  M.  Monahan, G. M. Evaluation
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1-12      Calvert,  S.  Scrubber Performance for Particle  Colleciton. Proceed-
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1-13      Calvert,  S.,  and N. C. Jhaveri. Flux Force/Condensation Scrubbing.
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          Number 10: Pages 946-951.  October  1974.


            Bibliography: Scrubber Types and Operating Principles

1-14      Calvert,  S.  J., Goldschmid,  D.  Leith,  and D.  Mehta.  Wet Scrubber
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1-15      Calvert,  S.,  D. Lundgren,  and D.  S.  Mehta. Venturi  Scrubber
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1-17      Cole,  R.  M.,  T. M.  Kelso,  N. D. Moore,  and  R.  F.  Robards. "Evalua-
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1-19      Green, G. P.  Operating Experience with  Particulate Control Devices.
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1-20      Gurney, A.,  R. J. Chironna,  "Condensible Organics Removal with
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1-21      Hesketh,  H.  E. Fine Particle Collection Efficiency Related to
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1-23      Hubbert,  G.  Wet Collector Design, Operation and Maintenance.
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1-24      Javorsky, B.  S. Gas Cleaning with Foam Scrubber. Fi1ibration
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            Bibliography: Scrubber Types and Operating Principles
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1-28      McCain,  J.  D.  "CEA Variable Throat Venturi Scrubber Evaluation",
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          A Single and  Two-Stage Variable-Throat Venturi Scrubber. Atmospheric
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1-30      Muir,  D.  M.,  and Y.  Miheisi. Prediction of Collection Efficiency
          and Pressure  Drop  in Venturi Scrubbers. Paper presented at the
          Symposium on  Dust  Control.  Manchester, England, March 21-22,
          1978,  sponsored by Institute of Chemical  Engineering, London,
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1-31      Nguyen,  X.  T.  On the Efficiency of a Centrifugal Fan Wet Scrubber.
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1-32      Anon,  "Power  Factor and Conservation", Power, May 1973, Pages

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1-34      Richards, J.  R. and R. Segall. Wet Scrubber Performance Eval-
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1-35      Semrau.  K.  T., C.  L.  Witham, and W.  W. Kerlin. Energy Utilization
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            Bibliography: Scrubber Types and Operating Principles

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                             Bibliography: Pumps

2-1       Biheller, J.H., "Check Your New Centrifugals Against This 16
          Point List", Power, January 1974, Pages 60-61.

2-2       Bieheller, J.H., "What You Need To Know About Pump System Head
          Curves", Power, March, 1982. Pages 53-56.

2-3       Birk, J. R., Peacock, J.  H., "Pump Requirements for the Chemical
          Process Industries",  Chemical  Engineering, February 18, 1974,
          Pages 16-124.

2-4       Buse, F., "The Effects of Dimensional Variations on Centrifugal
          Pumps", Chemical Engineering,  September 26, 1977, Pages 93-100.

2-5       Cunningham, E. R., "Pumps Without Seals", Plant Engineering,
          August 4, 1977, Pages 66-75.

2-6       Fraser, W. H., "Working with Centrifugal Pumps", Plant Engineering,
          June 12, 1975, Pages 120-122.

2-7       Fraser, W. H., "Points to Weigh in Applying Centrifugal Pumps",
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2-8       Holmes, E., Et al, "  Handbook  of Industrial Pipework Engineer-
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2-9       Huang, S. Y., "Preventing Cavitation Under Conditions of Partial
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2-10      Karassik, I. J., "Are You Short on NPSH? Nine Ways to Improve
          Unfavorable Suction Conditions", Combustion, July 1980, Pages

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          Inc. 1967.

2-12      Lobanoff, V., "Specific Speed  is a Useful Index for Pump Design
          and Selection", Power, June 1979.

2-13      Luley, R., "Selecting a Centrifugal Pump", Plant Engineering,
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2-14      Neerken, R. F., "Pump Selection for the Chemical Process Indus-
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2-15      Neerken, R. F., "Selecting the Right Pump". Chemical Engineering,
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2-16      O'Keefe, W., "Pumps", Power. June 1972.

                             Bibliography: Pumps

2-17      Reynolds,  J.  A.,  "Pump Installation and Maintenance", Chemical
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2-18      Roche,  R.  H., "Mechanical  Seals in Centrifugal  Pumps", Plant
          Engineering,  February 19,  1981, Pages 100-103.

2-19      Rosenberg, H. S.,  Et al.,  "Construction Materials for Wet Scrub-
          bers",  Volume I,  EPRI Final  Report No. CS-1736, March 1981,
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2-20      Stindt, W. H., "Pump Selection", Chemical  Engineering, October
          11, 1971,  pages 43-49.

2-21      Whitmore,  C.  H.,  H.  Wojda, and W. Marietta, "Reducing the Operating
          Noise of Industrial  Hydraulic Systems", Parker Hannifin Reprint
          PC-1, October 1972.

2-22      Yedidiah,  S., "Analyzing Suction Performance of Centrifugal
          Pumps", Plant Engineering, October 3, 1974, Pages 69-71.

2-23      Yedidiah,  S., "Avoiding Cavitation in Centrifugal Pumps", Machine
          Design, March 6,  1980, Pages 265-269.

2-24      Yedidiah,  S., "Faulty Piping Layout Can Ruin a Centrifugal Pump",
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2-25      Yedidiah,  S., "Diagnosing Troubles of Centrifugal Pumps, Part
          I", Chemical  Engineering,  October 24, 1977, Pages 124-128.

2-26      Yedidiah,  S., "Diagnosing, Part II", Chemical Engineering, November
          21, 1977,  Pages 193-199.

2-27      Yedidiah,  S., "Diagnosing, Part III", Chemcial  Engineering,
          December 5, 1977,  Pages 141-143.

2-28      Yedidiah,  S., "Methods for Preventing Water Hammer Damage to
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2-29      Yedidiah,  S., "Performance Curves: Key to Centrifugal Pump Selec-
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2-31      Yedidiah,  S., "Selection and Application of Nonclog Centrifugal
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2-32      Yedidiah,  S., "Tracking Down Problems in Centrifugal Pumps",
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                           Bibliography: Corrosion

3-1       Adams,  A.  B.,  Jr.  Corrosion Problems with Wet Scrubbing Equipment.
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          Number  4:  Pages 303-397.  April 1976.

3-2       Adams,  A.  B.,  Jr.,  "Corrosion Problems with Wet Scrubbing Equip-
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          Texas,  1976.

3-3       Ashbaugh,  W.  G., "Materials Selection for Chemical  Process Equip-
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3-4       Ashbaugh,  W.  G., "Materials Selection for Chemical  Process Equip-
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3-5       Banks,  J.  H.,  "Corrosion Control  with Fiberglass-Reinforced
          Plastics in the Power Industry",  Presented at the Air Pollution
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          Control Equipment,  Atlanta, Georgia, January 17-19, 1978.

3-6       Baum, B.,  and  C. H.  Parker, "Role of Plastics, Especially PVC,
          in Incinerator Corrosion," Polymer News, Volume 2,  Number 5-6:
          Pages 37-47.  1975.

3-7       Benzer, W. C., "Steels,"  Chemical Engineering. Volume 77, Number
          22:  Pages  101-110,  1970.

3-8       Borenstein, M., "Special  Construction Materials for Scrubbers,"
          Air Pollution  Control and Design Handbook, Chapter 40, Marcel
          Dekker, New York,  1977.

3-9       Boyd, W. K.,  and P.  D.  Miller, "Materials Selection for Design
          of Pollution  Control Equipment,"  Paper 71-DE-12, American Society
          of Mechanical  Engineers,  New York, 1971.

3-10      Burda,  P.  A.,  "Corrosion Protection of Wet Scrubbers," Power
          Engineering,  Volume 79, Number 8: Pages 48-51, 1975.

3-11      Burda,  P.  A.,  "Linear Polarization Method for Corrosion Rate
          Measurements  in Limestone Slurry Scrubber," Materials Performance,
          Volume  14, Number  6: Pages 27-31, 1975.   .  ~I~~~H

3-12      Conybear,  J.  G., "Corrosion Concerns in Waste Incinerators,"
          Resolving  Corrosion Problems in Air Pollution Control  Equipment,
          National Association of Corrosion Engineers, Houston,  Texas,

                           Bibliography: Corrosion

3-13      Crow, G.  L., "Corrosion Tests Conducted in Prototype Scrubber
          Systems," Presented at the Air Pollution Control Association
          Seminar on Corrosion Problems in Air Pollution Control Equipment,
          Atlanta,  Georgia, January 17-19, 1978.

3-14      Engdahl,  R. B.., and D. A. Vaughn, "The Corrosion Research Needs
          for Air Cleaning Equipment," Resolving Problems in Air Pollution
          Control Equipment,  National Association of Corrosion Engineers,
          Houston,  Texas, 1976.

3-15      Ewan, E.  B., "High  Performance Functional  Coatings," Paper No,
          259 presented at the National Association of Corrosion Engineers'
          Corrosion/79, Atlanta, Georgia, March 12-16, 1979.

3-16      Feige, N. D., "Corrosion Service Experience and Economics of
          Titanium's Usage in Gas Scrubbing Equipment for Refuse Incinera-
          tors," Paper No. 138 presented at the National Association of
          Corrosion Engineers International Corrosion Forum, Chicago,
          March 4-8, 1974.

3-17      Gilbert,  W., "Selecting Materials for Wet Scrubbing Systems,"
          Pollution Engineering, Volume 5, Number 8: Pages 28-29, 1973.

3-18      Gleason,  T. G., "How to Avoid Scrubber Corrosion," Air Pollution
          Control and Design Handbook, Chapter" 41, Marcel Dekker, New
          York,  1977.

3-19      Gleason,  T. G., "Halt Corrosion in Particulate Scrubbers," Chemical
          Engineering, Volume 84, Number 23: Pages 145-48, 1977.

3-20      Gleekman, L. W., "Nonferrous Metals," Chemical Engineering,
          Volume 77, Number 22: Pages  111-118, T9~7Tn

3-21      Gleekman, L. W., "Nonferrous Metals," Chemical Engineering,
          Volume 79, Number 27: Pages  47-49, 19771

3-22      Graver, D. L., "Forms of Corrosion," Resolving Corrosion Problems
          in Air Pollution Control Equipment, National Association of
          Corrosion Engineers, Houston, Texas, 1976.

3-23      Haaland,  H. H., and J. L. Ma, "Corrosion Problems in Wet Precipi-
          tator  Design," Resolving Corrosion Problems in Air Pollution
          Control Equipment,  National Association of Corrosion Engineers,
          Houston,  Texas, 1976.                       .._        __

3-24      Hamner, N. E., Corrosion Data Survey - Non Metals, 5th Ed.,
          National  Association of Corrosion Engineers, Houston, Texas,

3-25      Hamner, N. E., Corrosion Data Survey - Metals, 5th Ed., National
          Association of Corrosion Engineers, Houston, Texas, 1975.

                           Bibliography: Corrosion

3-26      Handwerk, R. J., "Recycling Water Effectively," Foundry, Volume
          100, Number 7: Pages 40-43, 1972.

3-27      Harpel,  W. L., D. T. Murray, A. J. Graffeo, and J. C. Steel hammer,
          "The Chemistry of Scrubbers,'" Combustion, Volume 47, Number
          9:  Page  33, 1976.

3-28      Harpel,  W. L., and J. P. Terry, "Water Treatment Technique for
          Preventing Scaling and Fouling in Gas Scrubbing Systems," Plant
          Engineering, Volume 32, Number 2: Pages 155-57, 1978.

3-29      Henthorne, M., "Good Engineering Design Minimizes Corrosion,"
          Chemical Engineering, November 15, 1977, Pages 163-166.

3-30      Holt, W. H., "Fiberglass-Reinforced Plastic Construction in
          Baghouses," Resolving Corrosion Problems in Air Pollution Control
          Equipment, National Association of Corrosion Engineers, Houston,
          Texas,  1976.

3-31      Hoxie,  E. C., "Discussion of Materials of Construction for Wet
          Scrubbers for Incinerator Applications," Resolving Corrosion
          Problems in Air Pollution Control Equipment, National Association
          of Corrosion Engineers, Houston, Texas, 1976.

3-32      Hoxie,  E. C., and G. W. Tuffnel, "A Summary of INCO Corrosion
          Tests in Power Plant Flue Gas Scrubbing Processes," Resolving
          Corrosion Problems in Air Pollution Control Equipment, National
          Association of Corrosion Engineers, Houston, Texas, 1976.

3-33      Hughson, R. V., "High-Nickel Alloys for Corrosion Resistance,"
          Chemical Engineering, Volume 83, Number 24: Pages 125-36, 1976.

3-34      Javetski, J., "Solving Corrosion Problems in Air Pollution Control
          Equipment - Part I," Power, Volume 122, Number 5: Page 72, 1978.

3-35      Javetski, J., "Solving Corrosion Problems in Air Pollution Control
          Equipment - Part II," Power, Volume 122, Number 6: Page 80,

3-36      Kirchner, R. W., "Corrosion of Pollution Control  Equipment,"
          Chemical Engineering Progress. Volume 71, Number 3: Pages 58-63,

3-37      Klodt,  D. T., "Corrosion of Air Pollution Control Equipment
          in the  Mineral Industries," Mineral Industrie's Bu 11 ettn,-Volume
          16, Number 1: Pages 1-14, 1973";

3-38      Lahr, P. T., "Pumping Corrosive Scrubbing Liquids," Resolving
          Corrosion Problems in Air Pollution Control Equipment, National
          Association of Corrosion Engineers, Houston, Texas, 1976.

                           Bibliography: Corrosion

3-39      Landrum,  R.  J.,  "Designing for Corrosion Resistance of Air Pollu-
          tion Control  Equipment," Resolving Corrosion Problems in Air
          Pollution Control  Equipment,  National  Association of Corrosion
          Engineers, Houston,  Texas, 1976.

3-40      Lizlovs,  E.  A.,  "Laboratory Corrosion  Test for Stainless Steels
          for SCL Scrubber Service," Materials Performance, Volume 17,
          Number^: Pages  36-37,  1978":

3-41      Lomasney, H.  L., "Testing Wet Scrubber Lining Materials," Paper
          No. 39 presented at  the National  Association of Corrosion Engi-
          neers' Corrosion/79, Atlanta, Georgia, March 12-16, 1979.

3-42      Maier, J. H., "Analysis of Wet, Dirty  and Corrosive Combustion
          Gases," Proceedings  of the 20th Annual ISA Analysis Instrument
          Symposium, Pittsburgh,  Pennsylvania, May 12-15, 1974.

3-43      Mappes, T. E. and R. D. Terns. An Investigation of Corrosion
          in Particulate Control  Equipment. EPA-340/1-81-002, February

3-44      McDowell, D.  W.  Jr., "Problems in Wet  Gas Scrubbing Systems,"
          Presented at the Air Pollution Control Associatin Seminar on
          Corrosion Problems in Air Pollution Control Equipment, Atlanta,
          Georgia,  January 17-19, 1978.

3-45      Michaels, H.  T., and E. C. Hoxie, "Some Insight into Corrosion
          in SOp Exhaust Gas Scrubbers," Presented at the Air Pollution
          Control Association  Seminar on Corrosion Problems in Air Pollution
          Control Equipment, Atlanta, Georgia, January 17-19, 1978.

3-46      Miller, P. D., "Corrosion Studies in Municipal Incinerators,"
          Battelle Memorial Laboratories, Columbus, Ohio, 1972.

3-47      Mistry, N. T., "Material Selection for Gas Scrubbers," Materials
          Performance.  Volume 15, Number 4: Pages 27-33, 1976.

3-48      Mockbridge,  P. C., and D. W. McDowell, Jr., "Materials and Corro-
          sion Problems in a Fly Ash Scrubbing System," Materials Performance,
          Volume 13, Number 4: Pages 13-17, 1974.

3-49      Moreland, P.  J., and J. G. Mines, "The Concept and Developement
          of Corrosion Monitoring," Materials Performance, Volume 18,
          Number 2: Pages 65-70, 197?:~~,

3-50      Nowak, F., "Corrosion Problems in Incinerators," Combustion,
          Volume 40, Number 5: Pages 32-40, 1968.

3-51      Paul, G., "Dealing with High Chloride Concentrations in Closed-Loop
          Sulfur Dioxide Scrubbers," Industrial  Water Engineering, Volume
          15, Number 1: Pages  24-28, 1978.

                           Bibliography: Corrosion

3-52      Sakol, S. L., and R. A. Schwartz. Construction Materials for
          Wet Scrubbers. Chemical Engineering Progress, Volume 70, Number
          8:  Pages 63-68. August 1974.

3-53      Sheppard, W. L., "Uses of Chemically Resistant Masonry in Air
          Pollution Control," Presented at the Air Pollution Control Associ-
          ation Seminar on Corrosion in Air Pollution Control Equipment,
          Atlanta, Georgia, January 17-19,  1978.

3-54      Shinskey, F. G., "pH Controls for SCL Scrubbers," Air Pollution
          Control and Design Handbook, Chapter 37, Marcel Dekker, New
          York, 1977.

3-55      Steel, C. J., "Corrosion Protection Strategy for Pollution Control
          Equipment," Pollution Engineering, Volume 10, Number 3: Pages
          49-50, March 1978.

3-56      Thaxton, L. A., and A. G. Zourides, "Corrosion Problems in Specific
          Pollution Control Equipment," Paper No. 196, presented at the
          5th International Pollution Engineering Exposition and Congress,
          Anaheim, California, November 9-11, 1976.

3-57      Velzy, C. 0., "Materials of Construction for Wet Scrubbers for
          Incinerator Applications," Resolving Corrosion Problems in Air
          Pollution Control Equipment, National  Association of Corrosion
          Engineers, Houston,-Texas, 1976.

3-58      Zarfoss, J. R., "Clean Air from Paper Mill  Recovery Boilers
          Without Corrosion," Resolving Corrosion Problems in Air Pollution
          Control Equipment,  National  Association of  Corrosion Engineers,
          Houston, Texas, 1976.


                           Bibliography: Demisters

4-1       Calvert,  S.  State-of-Art Survey of Mist Elimination in the U.S.A.
          EPA-600/7-78-037, March 1978. Pages 180-193.

4-2       Conkle,  H.  N.,  H. S. Rosenberg, and S. T.  DiNovo, "Guidelines
          for the Design of Mist Eliminators for Lime/Limestone Scrubbing
          Systems," EPRI  FP-327, December 1976.

4-3       Hanf, E.  B.  Design Considerations for  Venturi  Entrainment Separa-
          tors. Presented at the American Institute of Chemical Engineering
          National  Meeting. Cincinnati, Ohio, May 16-19, 1971.

4-4       Jashnani, I. L. and S. Calvert. Wet Scrubber Entrainment Separa-
          tors. Presented at the Air Pollution Control Association Annual
          Meeting,  Denver,  June 9-13, 1974. Paper 74-230.

4-5       Schifftner,  K.  C. How to Check Scrubber Entrainment. Pollution
          Engineering, July 1982, pages 38-39.


                            Bibliography:   Nozzles

5-1       Bete Fog Nozzle,  Inc. Catalog 81A.  1981.

5-2       Bieber,  D.,  and A.  B. Buhl, "Spray Nozzles in Air Pollution  
          Control", Spraying  Systems Co. Pollution Abatement Manual, December
          27,  1974.

5-3       Cox, R.  K.,  "Spraying Droplets To Order,"Automation, Volume
          21,  August 1974.

5-4       Gleason, T.  G., "Halt Corrosion in Particulate Scrubbers," Chemical
          Engineering, October 24, 1977.

5-5       Rosenberg, H. S.,  Et. All, "Construction Materials For Wet Scrub-
          bers," Volume I,"  EPRI Final  Report No.  CS-1736, March 1981.

5-6       Spraying Systems  Co. Pollution Abatement Manual. No Date.

5-7       Tate, R. W., "Spray Nozzles for Pollution Control," Pollution
          Engineering, April  1973.


                     Bibliography: Monitoring Instruments

6-1        Olszewski, Richard, "Conditioning Air For Pneumatic Systems."
          Instruments Control Systems, Sept., 1976, Volume 49, Number
          9, Pages 119-122.

6-2       Griffin, M. F.  and J.  H. Grzenda, "The Magnetic Flowmeter Operating
          Principles Installation And Use," Advances in Instrumnetation,
          Volume 36, Part 2, Proceedings of the ISA Conference and Exhibit,
          Anaheim, California, October 6-8, 1981.

6-3       Grezenda, J.  H., "Understanding Magnetic Flowmeters," Plant
          Engineering,  April 30, 1981, Volume 35, Number 9, Pages 67-70.

6-4       Hall, John, "Flowmeters-Matching Applications and Devices,"
          Instruments & Control  Systems, February, 1978, Volume 51, Number
          2, Pages I/-22.

6-5       Harrison, Paul, "Flow Measurement-A State of the Art Review,"
          Chemical Engineering,  January 14, 1980, Pages 97-104.

6-6       Liptak,  Bela  G., "Magnetic Flowmeters," Instrument Engineers
          Handbook, Volume I, Process Measurement, Pages 478-487.

6-7       Lomas, D. J., "Selecting the Right Flowmeter-Part I: The Six
          Favorites," Instrumentation Technology, Volume 24, Number 5,
          May, 1977, pages 55-62.

6-8       Lomas, D. J., "Selecting the Right Flowmeter-Part II: Comparing
          Candidates,"  Instrumentation Technology, Volume 24, Number 6,
          June, 1977, pages  71-77.

6-9       Mclntyre, Craig, "Nuclear Weight Scales in Hostile Environments,"
          Advances in Instrumentation, Volume 36, Part 2, Proceedings
          of the ISA Conference and Exhibit, Anaheim, California, October
          6-8, 1981.

6-10      Olszewski, Richard, "Conditioning Air for Pneumatic Systems,"
          Instruments & Control  Systems, Sept., 1976, Volume 49, Number
          9, Pages 119-123.

6-11      Sandford, Jim,  "What You Should Know About Flow Monitoring De-
          vices,"  Instruments Control Systems, Sept., 1976, Volume 49,
          Number 9. Pages 25-32.

6-12      Watson,  Bruce,  "Magnetic Flowmetering: Problems and Solutions,"
          Engineering and Mining Journal. Oct., 1973, Volume 174, Number
          10.  Pages 96-97.~       

6-13      Wallace, Leonard M., "Sighting in on Level Instruments," Chemical
          Engineering,  February 16, 1976, Pages 95-104.

6-14      Webb, A. S.,  "Electromagnetic Flowmetering," Instrumentation
          Technology, Journal of the Instrument Society of America7"Vo"lume
          21,  Number 3, March, 1974, pages 29-36.



7-1       Creason, S.  C., Selection and Care of pH Electrodes. Chemical
          Engineering. Octobe'r 23, 1978. pp. 161-163.

7-2       Cross,  F. L., Jr.  and H. E. Hesketh.  Handbook for the Operation
          and Maintenance of Air Pollution Control Equipment. Technomic
          Publishing Co., 1975.

7-3       Czuchra, P.  A., "Operation and Maintenance of a Particulate
          Scrubber System's  Ancillary Components." Presented at the U.S.
          EPA Environmental  Research Information Center Seminar on Operatin
          and Maintenance of Air Pollution Equipment for Particul ate Control.
          Atlanta, Georgia.  April  1979.

7-4       Gilbert, W., "Troubleshooting Wet Scrubbers." Chemical Engineering,
          October 24,  1977.  pages 140-144.                       ;

7-5       Kelly,  W. J. Maintaining Venturi - Tray Scrubbers. Chemical
          Engineering, December 1978. pp. 133-137.

7-6       Schifftner,  K.  C.  Venturi Scrubber Operation and Maintenance.
          Presented at the U.S. EPA Environmental Research Information
          Center  Seminar  on  Operatin and Maintenance of Air Pollution
          Equipment for Particulate Control. Atlanta, Georgia, April 1979.


                    Bibliography:   Industrial Application

8-1       Carpenter, B. H., D. W. Van Osdell, D. W. Coy; and R. Jablin.
          "Pollution Effects of Abnormal Operations in Iron and Steel
          Making - Volume II. Sintering, Manual  of Practice." U.S. Environ-
          mental Protection Agency. Publication 600/2-78-1186. June  1978.

8-2       Ensor, D. S., B. S. Jackson, S. Calvert, C. Lake, D. V. Wallon,
          R. E. Nilan, K. S. Campbell, T. A. Cahill, and R. G. FLocchini.
          Evaluation of a Particulate Scrubber on a Coal-Fired Utility
          Boiler. EPA Contract No. 68-02-1802, November 1982.

8-3       Ekono, Inc.  Environmental Pollution Control, Pulp and Paper
          Industries,  Part I-Air. U.S. Environmental Protection Agency,
          Research Triangle Park, N.C. Publication 625/7-76-01. October

8-4       Environmental Science and Engineering, Inc. Field Surveillance
          and Enforcement Guide: Wood Pulping Industry. U.S. Environmental
          Protection Agency, Research Triangle Park, N.C. Publication
          450/3-75-027. March 1975.

8-5       JACA Corporation. Model Operation and Maintenance Guidelines
          for Asphalt Concrete Plants. U. S. Environmental Protection
          Agency, Washington, D.C. Final Report. Contract No. 68-01-4135,
          Task 44.

8-6       Kemner, W. F. and R-. W. Mcllvaine. Review of Venturi Scrubber
          Performance on Q-BOP. Vessel C at the Fairfield Work of the
          United States Steel Corporation, Birmingham, Alabama. Final
          Report to U.S. Environmental Protection Agency. Contract 68-01-4147
          Task 03. Feburary 1979.

8-7       LaMantia, C. R., R. R. Lunt, I. L. Jashnani, R. G. Donnelly,
          E. Interess, L. R. Woodland, and M. E. Adams, "Application of
          Scrubbing Systems to Low Sulphur/Alkaline Ash Coals," EPRI FP-595,
          December 1977.

8-8       Lemon, E. D. Wet Scrubbing Experience with Fine Borax Dust.
          Journal of the Air Pollution Control Association, Volume 27,
          Number 11: Pages 1020-1052. November 1977.

8-9       National Asphalt Paving Association. The Maintenance and Operation
          of Exhaust Systems in the Hot Mix Plant. Information Series
          52 (second edition) and 52A (combined volumes). 1975.

8-10      Lemon, E. "Wet Scrubbing Experience with Fine"Borax DiTstr." Second
          EPA Fine Particle Scrubber Symposium.  U.S. Environmental Protection
          Agency, Research Triangle Park, N.C. Publication 600/2-77-193
          pages 25-34. September 1977.

                    Bibliography:  Industrial Applications

8-11      Nixon, D., and C. Johnson. "Particulate Removal and Opacity
          Using a Wet Venturi Scrubber - The Minnesota Power and Light
          Experience." Second Symposium on the Transfer and Utilization
          of Particulate Control Technology. U.S. Environmental Protection
          Agency, Research Triangle Park, N.C.  Publication EPA-600/9-80-
          039a. September 1980.

8-12      Patankar, U., and K. E. Foster. "Evaluation of the Drum-Mix
          Process for Asphalt Concrete Manufacturing." Presented at the
          Seminar on Asphalt Industries Environmental Solutions. January

8-13      PEDCo Environmental, Inc. Operation and Maintenance of Particulate
          Control Devices in Kraft Pulp Mill and Crushed Stone Industries.
          Environmental Protection Agency, Research Trianlge Parkj N.C.
          Publication 600/2-78-210. October 1978.

8-14      Scheroenan, J. A., and L. V. Binz. "Controlling Air Pollution
          While Recycling Asphalt Pavements Through a Drum Mix Plant."
          Presented at the Canadian Technical Asphalt Association Meeting.
          November 1979.

8-15      Steiner, B. A. and Thompson, B. J. Wet Scrubbing Experience
          for Steel Mill Applications. Second EPA Fine Particle Scrubber
          Symposium. U.S. Environmental Protection Agency, Research Triangle
          Park, N.C. Publication EPA 600/2-77-193. pages 5-24. September

8-16      Steiner, B. A., and R. J. Thompson. Wet Scrubbing Experience
          for Steel Mill Applications. Journal  of the Air Pollution Control
          Association, Volume 27, Number 1: Pages 1069-1975. November

8-17      U.S. Environmental Protection Agency. Atmospheric Emission for
          the Pulp and Paper Manufacturing Industry. Publication EPA-450/1-73-
          002. September 1973.

                               Liquor Analysis
9-1       American Society of Testing Methods. Annual Book of ASTM Standards,
          Part 31. Water. "Standard Test Method for Surface Tension of
          Water." 1982.

9-2       Franson, M.  A., "Turbidity," Standard Methods for the Examination
          of Water and Wastewater. Fourteenth Edition, Published by American
          Public Health  Association, 1976.


10-1       Beachler,  D.,  and J.  A.  Jahnke.  APTI Course 413. Control of
          Participate Emissions. Student Manual. EPA 450/2-80-066, October

10-2       Calvert,  S.,  J.  Goldshihd,  D.  Leith, and D. Mehtor. Wet Scrubber
          System Study,  Volume  I,  Scrubber Handbook. EPA-R2-7s-118a (PB-213--
          016),  August  1972.

10-3       Dickerson,  R.  C., and B. N.  Murthy.  Study of Wet Scrubbers for
          Odor Control.  Preprint,  EPA, RTP, N.C., National Environmental
          Research  Center,  1973.

10-4       Drockta,  H.,  and  R.  L. Lucas.  Information Required for the Selec-
          tion and  Performance  Evalution of Wet Scrubbers. Journal of
          the Air Pollution Control  Association, Volume 22, Number 6:
          Pages  459-462. June  1972.

10-5       Eckert, J.  S.  Wet Packed Gas Scrubbers. Australian Chemical
          Process Engineering  (Sydney),  Volume 25, Number 9: Pages 13-18.
          September  1972.

10-6       Ellison,  W.,  and  R. M. Mark. Designing Large Wet Scrubber Systems.
          Power  Volume  116, Number 2:  Pages 67-69. February 1972.

10-7       Gardenier,  H.  E.  A Manufacturer's View of Scrubber Collectors.
          Presented  at  Specialty Conference on Design, Operation, and
          Maintenance of High Efficiency Particulate Control Equipment.
          St. Louis,  March  29-30,  1973.

10-8       Mayinger,  F.,  and M.  Neumann.  Dust Colleciton in Venturi-Scrubbers.
          German Chemical  Engineering, Volume 1, Number 5: Pages 289-293.
          November  1978.


                       Bibliography:  Alkaline Additions

11-1       Elder,  H.  W.  and W.  H.  Thompson,  "Removal  of Sulfur Dioxide
          from Stack Gases:  Recent Developments in Lime-Limestone Wet
          Scrubbing  Technology,"  Transactions of the American Society
          of Mechanical  EngineersT July,1973, Pages 150-154.

11-2       Rosenbert, H.  S.,  Et a!.,  "Construction Materials For Wet Scrub-
          bers,"  Volume I, EPRI Final Report No. CS-1736,  March 1981,
          Pages 3/59 -  3/64.

11-3       Anonymous, "Lime for Water  and  Wastewater  Treatment," BIF Engineer-
          ing Data,  June,  1969.




                             Sample Critique Form
                      Wet Scrubber Inspection Techniques
I. For each statement circle the one response that is the closest to your

   1. Overall, I think this program was:
      a. excellent
      b. good
      c. fair
      d. poor

   2. The program content was geared to a level that was generally:
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      b. too elementary
      c. too difficult
      d. inappropriate for my background

   3. I think the organization of the program material was:
      a. completely clear and useful; excellent
      b. for the most part, clear and useful; good
      c. some topics were organized in a clear and useful manner, while others
         were not; fair
      d. there was little apparent organization in this course; poor

   4. After reading the progarra handouts, I think they are:
      a. well written and useful documents
      b. fairly well written documents, but nevertheless useful
      c. poorly written documents that ai*e of limited utility
      d. neither well written nor useful documents
      e. I have not been able to read the manuals yet

   5. The amount of time allotted for this program was:
      a. sufficient
      b. too long
      c. too short
      d. this program should last 	number of days

   6. For future programs, there should be:          -  ....      ~	.
      a. no substantive changes
      b. more practical application of the program material
      c. more theory presented as a basis for the material taught
      d. more of a "balance" provided between theory and practical application

Sample Critique - Wet Scrubber Inspection Techniques
II. Please check the statement that represents the extent of your agreement
    with each of the following statements. READ EACH ITEM CAREFULLY.
                                   Strongly  Agree  Disagree  Strongly   No
                                   Agree                      Disagree  Opinion
11. The program content was
    useful for my professional
12. The program content was
    what I had expected.
13. The program content was too
14. The program content was too

15. The program content was
    up to date.                     	

16. During the program I felt
    challenged to learn.            	

17. Generally, the program materials
    were presented in an interesting

18. The program content was well
    coordinated among the speakers  	

19. The speakers were well
    prepared for most class sessions._

20. The speakers were quite
    knowledgeable about their subject

Sample Critique - Wet Scrubber Inspection Techniques
                                   Strongly  Agree  Disagree  Strongly   No
                                    Agree                     Disagree  Opinion
21.  The questions raised during the
    lectures were usually answered
    to my satisfaction.

22.  The production quality of the
    audio-visual materials was
    technically adequate.

23.  The audio-visual materials aided
    my understanding of the topics
24. Overall, I was pleased with this

25. I think my technical skills
    and/or knowledge have been
    strengthened was a result of
    this program

26. I think I will be able to use
    what I have learned from this
    program in my current position.
III. Additional comments

27.  The "best" part of this program was:
28.  The "worst" part of this program was:

Sample Critique - Wet Scrubber Inspection Techniques

29. I consider the most needed improvements in this program to be:
30.  Other Comments:
V. General Information:

31.  Years of air pollution experience:
     a. less than 2 years
     b. between 2 and 5 years
     c. between 5 and 10 years
     d. more than 10 years

32.  Present responsibilities .(circle all which apply)
     a. field inspection
     b. permit review
     c. stack sampling
     d. management and supervision
     e. ambient air monitoring
     f. other

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