EPA 340/1-83-025
Coal-Fired Industrial Boiler
        Inspection Guide
                    by
            PEDCo Environmental, Inc.
              11499 Chester Road
            Cincinnati, Ohio 45246-0100
             Contract No. 68-01-6310
             Work Assignment No. 9
           EPA Project Officer: John Busik
         EPA Task Manager: Howard Wright
      U.S. ENVIRONMENTAL PROTECTION AGENCY
        Stationary Source Compliance Division
       Office of Air Quality Planning and Standards
               401 M Street, S.W.
             Washington, DC 20460

               December 1983

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                                  DISCLAIMER


     This report was prepared by PEDCo Environmental, Inc., Cincinnati, Ohio,
under Contract No. 68-01-6310, Work Assignment No. 9.  It has been reviewed by
the Stationary Source Compliance Division of the Office of Air Quality Plan-
ning and Standards, U.S. Environmental Protection Agency, and approved for
publication.  Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency.  Mention
of trade names or commercial products, is not intended to constitute endorse-
ment or recommendation for use.  Copies of this report are available from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia 22161.

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                                    CONTENTS
                                                                          Page

Disclaimer                                                                  -}-,-
Figures                                                                     -jv
Tables                                                                     v1l-

1.   Introduction                                                            i

     1.1  Purpose and Scope                                                  2
     1.2  Compliance Inspections                                             3

2.   Coal-Fired Boiler Processes                                             5

     2.1  Stoker-Fired Boilers                                               8
     2.2  Pulverized Coal Firing                                            27
     2.3  Fans                                                              40
     2.4  Use of the F-Factor                                               46

3.   Pollution Control Equipment                                            50

     3.1  Multicyclones                                                     50
     3.2  Fabric Filters                                                    66
     3.3  Electrostatic Precipitators                                       82
     3.4  Scrubbers                                                        108

4.   General Preparatory and Pre-Inspection Procedure                      122

     4.1  File Review                                                      122
     4.2  Safety Precautions                                               130
     4.3  Safety and Inspection Equipment                                  133
     4.4  Pre-entry Observations                                           134
     4.5  On-Site Inspection Checklists                                    135

5.   Compliance Determination                                              148

References                                                                 153

Appendix A - Pollution Control Device Diagnostic Checklists and Data
             Sheets                                                       /\-l

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                                    FIGURES
Number
                                                                         Page
  1       Basic water-tube boiler arrangement                               7
  2       The effect on uncontrolled particulate loading
           of washing a coal to reduce its ash content                     11
  3       ABMA recommended limits of coal sizing for underfeed stokers     13
  4       ABMA recommended limits of coal sizing for overfeed stokers      14
  5       ABMA recommended limits for coal sizing for spreader stokers     15
  6       Single-retort, horizontal  underfeed stoker                       17
  7       Chain-grate stoker with rear ash discharge                       20
  8       Travel ing-grate spreader stoker with front ash discharge         22
  9       Spreader stoker with gravity-flow fly ash return                 24
 10       Typical stoker boiler flue gas static pressure                   26
 11       Dry-bottom pulverized-coal-fired unit                            29
 12       Intervene burner                                                 33
 13       Dual-register field-test burner                                  34
 14       Components and functions of a controlled-flow/split-flame
           coal  burner                                                     35
 15       Operating characteristics  of radial-blade centrifugal  fan         41
 16       Fan characteristic curves   effect of speed change               43
 17       Fan characteristic curves   effect of system pressure drop
           change                                                          44
 18       Multicyclone collector                                           51
 19       Cross  section of an individual  cast iron  collection tube          52

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Figures (continued)


                                                                         Page

 20       Fractional  efficiency curves for multicyclone                    53

 21       Particulate fallout on dirty gas tube sheet                      55

 22       Inlet turning vane wear because of abrasion                      57

 23       Scale on inside of collection tube                               57

 24       Plugged outlet tube                                              59

 25       Plugged conical section                                          60

 26       Clean side  air leaks                                             62

 27       Example of  leaks in clean gas outlet tubes  and clean
           gas tube sheet                                                  62

 28       Clean side  air leaks                                             63

 29       Poor distribution and cross hopper flow                          64

 30       Typical reverse-pulse baghouse during cleaning                   68

 31       Impaired cleaning in a reverse-air fabric filter                 71

 32       Bridging near baghouse shell caused by  cooling a poorly
           insulated  fabric filter                                         73

 33       Methods of  bag attachment in shaker and reverse-air
           fabric filters                                                  74

 34       Abrasive damage caused by accumulation  of dust on the
           tube sheet                                                      76

 35       Correct and incorrect installation of bags                        78

 36       Proper method of installing bag in tube sheet with
           snap rings                                                      80

 37       Basic processes involved in electrostatic precipitation          84

 38       Typical electrostatic precipitator with top housing              85

 39       Typical temperature-resistivity relationship                     86

 40       ESP instrumentation diagram                                      88

 41       Vibrator and rapper assembly, and precipitator high-
           voltage frame                                                   93
                                       v

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Figures (continued)

                                                                         Page
 42       A sample opacity chart                                          107
 43       Importance of particle size on wet scrubber penetration          109
 44       Tray scrubber                                                   m
 45       Spray tower                                                     HI
 46       Moving bed scrubber                                             112
 47       Cyclonic spray tower                                            113
 48       Bob type venturi  scrubber                                       115
 49       Venturi  scrubber  components                                     116
 50       Mist eliminators                                                 120
 51       Fabric filter inspection  flowsheet                              145
 52       Scrubber inspection flowsheet                                    146
 53       Electrostatic precipitator  inspection flowsheet                  147

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                                    TABLES


Number                                                                   Page

  1       Maximum Allowable Fuel Burning Rates                              9

  2       Interpretation of Fan Operating Conditions                       45

  3       Fan Data, Temperature Correction                                 46

  4       Maintenance Schedule for Electrostatic Precipitators             94

  5       Summary of Problems Associated With ESP's                        96

  6       Recommended Recordkeeping Requirements                          102

  7       Effects of Changes in Normal Operation on ESP Control Set
           Readings                                                       104

  9       Plume Characteristics and Combustion Parameters                 129

 10       Boiler Plant Gas Properties                                     132

 11       Fabric Filters Counterflow Inspection Diagnostic Section        136

 12       Scrubbers Counterflow Inspection Diagnostic Section             138

 13       Electrostatic Precipitators Counterflow Inspection Diagnos-
           tic Section                                                    141

 14       Summary of the Effects of Several Operating Parameters of
           Boilers, ESPs, and Fabric Filters on Particulate Emission
           Rates                                                          150
                                      Vll

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                                   SECTION 1
                                 INTRODUCTION

     Coal-fired boilers are^widely used in industrial plants throughout the
United States to provide process steam, space heat, and electricity in factory
and office buildings.  Nationwide it is estimated that there are approximately
144,000 industrial coal-fired boilers, equivalent to 25,260 watts or 86,200 x
106 Btu/h of capacity.  These boilers are within the size range from 20 to 400
x 106 Btu/h.  At an estimated average capacity factor of 20 percent, these
boilers generate about 2.6 x 106 tons of particulate matter, 1.7 x 106 tons of
sulfur dioxide, and 0.3 x 106 tons of nitrogen oxides per year.  This repre-
sents a contribution of 10 percent of total U.S. particulate emissions from
manmade sources.  The size of this emission category suggests that air pollu-
tion control inspectors should devote considerable effort to the evaluation,
surveillance, and recommendation of remedial procedures for these sources.
Furthermore, if the prices of oil and gas escalate relative to coal in the
future, industry may rely on coal to an even greater extent at existing and
new facilities, which would further increase the significance of these sour-
ces.
     Although individual boilers differ significantly in size and design,
certain general guidelines are appropriate for their inspection and evalua-
tion.  This  inspection guide provides information that will enable an air
pollution control agency inspector to check a boiler operation quickly and
efficiently, and at the same time make a thorough determination of its per-
formance relative to the appropriate agency's particulate air pollution con-
trol rules  and  regulations.
     Although coal-fired industrial boilers emit significant amounts of sulfur
dioxide (S02) and nitrogen oxides (NO ) as well as particulate matter, the
                                     s\
control of  S02  and NO  is beyond the scope of this inspection guide.  Few
                     y\
industrial  boilers are currently subject to S02 and  NO  regulations that
                                                      ys.
require the installation of control systems.  Thus,  this manual is devoted to

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participate control for coal-fired industrial boilers within the size range
from 20 to 400 Btu/h.   Oil-fired and gas-fired boilers are not discussed.
1.1  PURPOSE AND SCOPE
     This inspection guide provides technical information and procedures to
assist state and local inspectors in conducting compliance inspections and
performing evaluations of coal-fired industrial boilers.   It includes brief
descriptions of several relatively common types of boilers and reference
material to assist the inspector in evaluating emission sources.   The guide
also describes several types of control equipment typically used on indus-
trial-sized boilers and provides several checklists to ensure that important
operating factors for this control equipment are not overlooked during the
evaluation.
     The intent of this guide is to provide inspectors with the necessary
information to verify whether sources are meeting their operating permit
requirements.  Certain portions contain information on combustion parameters
that may be used as indicators of source performance between compliance tests.
Documented changes in these parameters may be used to indicate whether a
source needs to adopt more extensive operation and maintenance (O&M) proce-
dures to ensure continued compliance.  When a clearly defined cause-and-effect
relationship cannot be established for a given source, documented changes in
various operating parameters can support the need for a compliance test.
Baseline conditions generally are recorded during a period of known compli-
ance, typically during a compliance stack test; these baseline data include
information on boiler operating conditions and key operating parameters of the
control equipment.
     Each state has adopted a state implementation plan (SIP) describing how
it  intends to attain and maintain the National Ambient Air Quality Standards
(NAAQS).  Individual state regulations vary considerably.  For example, par-
ticulate emission limits for a 10 million Btu/h boiler vary from 0.12 Ib/h in
Massachusetts to 0.8 Ib/h in  Iowa.  The regulation for Nebraska is fairly
typical and is summarized as  follows:

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 A.   Existing Equipment:
      Q S 10  MM Btu/h                          0.60  Ib  TSP/MM  Btu
      10 < Q  < 3800  MM Btu/h                   E  = 1.026Q  '233  Ib  TSP/MM  Btu
      Q  3800 MM Btu/h                       0.15  Ib  TSP/MM  Btu
 B.   New Equipment (constructed after  8-17-71)      0.10 Ib  TSP/MM  Btu
      The purpose of this  industrial boiler  manual  is  to  aid  inspectors in
 obtaining continuing  compliance with  local  regulations.

 1.2   COMPLIANCE INSPECTIONS
      Compliance inspections  can be conducted  at various  levels of detail,
 depending on agency resources  and the agency's  assessment  of the  significance
 of a particular source.   A very simple inspection  might  include only the
 observation  of visible emissions from all of  the boiler  stacks at a plant.  A
 more complete inspection  would include a walk-through of the plant, during
 which visible emissions would  be read and some  information obtained concerning
 the  boiler,  its control equipment, and operating and  maintenance  schedules.
 In a very detailed  inspection,  the inspector would use test  equipment to
 estimate air and exhaust  gas flow rates, oxygen levels,  pressure  drops, etc.
 The  inspector would also  record information on  power  consumption  by control
 equipment and compare plant  records with readings  obtained during previous
 inspections.   Calculations based on the information obtained during the in-
 spection would be used to determine whether a stack test is  warranted.
      A visible evaluation of emissions should be made according to EPA Method
 9 or a corresponding  state procedure.   Thus, an established  change in opacity
 from previously established baseline  conditions could be used to  indicate
.whether some operating parameter or group of parameters  has  changed.  A signi-
 ficant increase in  opacity could also indicate  the need  for  a more detailed
 inspection.
      Worthwhile operating data  on the boiler and its  control equipment include
 fuel  characteristics,  oxygen and carbon monoxide concentrations in the flue
 gas,  flue gas  temperatures, scrubber  inlet and  outlet temperatures, water flow
 rates,  pressure drop  if a scrubber or multicyclone is used,  electrostatic
 precipitator parameters,  etc.   Boiler parameters such as firebox  draft stream
 flow,  fuel rate,  temperatures,  etc.,  should be  recorded  also.  Unfortunately,

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all of these data may not be routinely available.  For example, few installa-
tions are likely to monitor carbon monoxide regularly, even though its mea-
surement is simple and useful for combustion air adjustment.  Where scrubbers
are used, the inspector should be concerned with any significant change in the
scrubber pressure drop or the liquid-to-gas ratio.  The inspector also should
check the scrubber pumps, water pressure indicators, and the water flow into
the settling pond or tank.  The flue gas flow rate is related to the fuel
firing rate and can be estimated from the boiler data.
     This manual does not describe how to perform different levels of inspec-
tions for each control device.   Since the reference documents used in the
preparation of this manual do not describe inspection levels for all  four
types of control equipment, it was beyond the scope of this guide to develop
the level of inspection checklists for each boiler and control device type.
However,  the checklists in the Appendix can be modified by the, inspector for
different levels of inspections.
                                      4

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                                   SECTION 2
                          COAL-FIRED BOILER PROCESSES

     Industrial coal-fired boilers are widely used in many sections of the
country.  Although their popularity tends to fluctuate with fuel supplies,
fuel costs, mining regulations, and environmental policies, these units are
expected to be used for many years to come.  Despite recent trends toward
cleaner fuels such as oil, gas, or electricity, a large amount of coal not
only will continue to be burned for industrial purposes in the foreseeable
future, but the amount of coal used for this purpose is quite likely to in-
crease.  Local agency inspectors will be responsible for ensuring that these
industrial coal-burning units are operated in a manner that minimizes the
emission of air pollutants.
     Combustion in a boiler is the controlled oxidation of the carbon, hydro-
gen, and sulfur contents of coal to release heat, which is extracted as steam
via heat exchangers.  The quantity and quality of the steam produced are a
function of the boiler design, its state of repair, and operating conditions.
Heat exchange  efficiencies and steam quality are regulated by combustion
conditions, which include coal feed, air distribution, water flow distri-
bution, etc.   Although the coal's sulfur content is a relatively minor source
of  heat, it is very significant in terms of corrosion and pollution.  Theore-
tically, the other two chemical elements,  carbon and hydrogen,  combine with
oxygen and burn to completion  according to the following reactions:
                      C + 02 = C02 + 14,100 Btu/lb of C
                    2H2 + 02 = 2H20 +  61,100  Btu/lb of H2
     Air  is the source of oxygen  for coal-fired  boilers.   As shown, the com-
bustion reactions are exothermic, and  they release about 14,100 Btu/lb of
carbon burned  and 61,100  Btu/lb of  hydrogen burned.
     Efficient combustion  releases  as  much of this heat as possible while
minimizing losses from  incomplete combustion  and excess air.   For  complete

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combustion to occur in a minimum of excess air, three requirements must be
satisfied:  the temperature must be high enough to ignite the constituents,
there must be sufficient turbulence for complete mixing, and there must be
sufficient time for the combustion reactions to reach completion.   These fac-
tors are often referred to as the "three T's" of combustion.  An understanding
of combustion and certain empirical and theoretical combustion relationships
allows an inspector to make a proper evaluation of a steam generating plant
and its performance characteristics.  Various combustion concepts  are inte-
grated into the discussions that follow.
     Several factors influence a plant's decision as to whether to fire pul-
verized coal or to use one of several different types of stokers.   The prac-
tical steam-output limit of boilers equipped with mechanical stokers is about
400,000 Ib/h (although many engineers limit the application of stokers to
somewhat lower steam capacities).  Within their capacity range, mechanical
stokers are well suited for the production of steam or hot water.   When appli-
cable, stokers are often preferred over pulverizers because of their greater
operating range, their capability of burning a wide range of solid fuels, and
their lower power requirements.  In addition to almost any coal, many byprod-
ucts and waste fuels (e.g., coke breeze, wood wastes, wood bark, and bagasse)
can be burned successfully in stoker-fired boilers.  However, pulverized
coal-fired boilers can change load more rapidly.
     Figure 1 shows a simplified cross section of a typical industrial, na-
tural-circulation boiler.   As the coal is burned on a grate or in  suspension
above the grate, heat is released and transferred to water-filled  boiler tubes
by radiation and convection.   Combustion air below and above the grate is ad-
justed by the use of dampers to achieve optimum combustion and to  minimize
smoke generation.  The steam-water mixture that forms in the water tubes in
the refractory walls of the boiler (risers) passes into an optional separation
drum at the top of the boiler, as shown in the figure, and then into a final
separation drum (called a steam drum) if there is no intermediate  separation
drum.  Downcomers from the, steam drum recirculate water to the mud drum at the
bottom of the boiler.   Sludge and solids that accumulate in the mud drum are
discharged with dissolved water impurities through a blowdown line at the
bottom of the mud drum.   Feedwater (to replace water and steam losses, blow-
down, etc.) is metered into the steam drum via a level controller.

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             Steam Nozzle
Figure 1.   Basic water-tube  boiler arrangement.

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2.1  STOKER-FIRED BOILERS
     Early in the history of the steam boiler, mechanical stokers were devel-
oped as an improvement over hand-firing.  Most small and medium-size indus-
trial boilers are fired with stokers.  Several types of stokers are available,
but all are designed to feed fuel onto a grate within the furnace and to
remove the ash residue.  Stokers permit higher burning rates than with hand-
firing, and their continuous firing permits improved combustion control and
high efficiency.  The greatest impetus for the development of stokers came
from two sources:  1) objections to smoke emissions resulting from hand-firing
and imperfect combustion, and 2) the inherent limitations on steam output from
manually stoked boilers.
     Over the years a great deal of effort has been made to maximize furnace
efficiency; i.e., to convert into steam as much of the combustion-released
heat as possible.  With regard to furnace design, several factors have been
identified as affecting boiler efficiency:
     1.   Type of fuel and method of firing; i.e., the use of coal, oil,
          or gas, and whether it is burned in suspension or on a grate.
     2.   Energy released per cubic foot of furnace volume (per unit of
          time).
     3.   Cold fraction, the ratio of water-cooled surface to refractory
          surface.
     4.   The size distribution of the coal.
     5.   Air-fuel ratio (A minimum of excess air is generally pre-
          ferred. )
     6.   Temperature of preheated air.
     7.   Heating value of the coal.
     8.   Type of water wal1.
     9.   Geometrical considerations, such as positions of tubes and
          burners.
    10.   Cleanliness of furnace, especially the surfaces of water-
          cooled tubes.
    11.   The ash fusion temperature of the coal; i.e., the temperature
          at which the coal ash melts and forms slag.
                                       8

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     The maximum allowable heat release per unit of grate area for a given
stoker type and capacity has been determined by experience.   Table 1 lists
recommended fuel burning rates (Btu/h per ft2 of grate area) for various types
of stokers, based on the use of coals suited to the stoker type in each case.
Furnace heat-release rates for spreader stokers are limited to 25,000 to
32,000 Btu/h per ft3 of furnace volume; the lower value is the more conser-
vative.  Coals that have lower ash fusion temperatures generally require lower
furnace heat-release rates.

                TABLE 1.  MAXIMUM ALLOWABLE FUEL BURNING RATES.
                       Type of Stoker
          Spreader - stationary and dumping grate
          Spreader - traveling grate
          Spreader - vibrating grate
          Underfeed - single or double retort
          Underfeed - multiple retort
          Chain grate and traveling grate
Btu/h per ft2
   450,000
   750,000
   400,000
   425,000
   600,000
   500,000
     Mechanical stokers generally are classified into three principal groups,
which are based on the method of introducing fuel to the furnace:
     1.   Underfeed stokers
     2.   Chain-grate and traveling-grate stokers
     3.   Spreader stokers
     The spreader stoker is the most frequently used in the capacity range
between 75,000 to 400,000 Ib of steam per hour because it responds rapidly to
load swings and can burn a wide range of fuels.  Underfeed stokers of the
single-retort, ram-feed, side-ash-discharge type are used principally for
heating and for small industrial units with capacities of less than 30,000 Ib
of steam per hour.  Larger underfeed stokers of the multiple-retort, rear-ash-
discharge type have been largely displaced by spreader stokers.  Chain- and
traveling-grate stokers, while still used in some areas, are gradually being
displaced by the spreader and vibrating-grate types'.

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2.1.1  Stoker Coal Properties
     Operators are generally not involved in obtaining coal supply contracts,
so they don't need to be experts on all the coal properties.   However, the
operator is responsible for firing the purchased coal as efficiently and
cleanly as possible, and for informing his supervisors of coal related problem
areas.
     There are several coal properties which have a direct effect on stoker-
boiler emissions and efficiency.  The operator should be aware of these pro-
perties.
Coal Ash-
     Coals which are higher in ash content tend to produce higher particulate
emissions.  This may not always be the case.
     The type of ash makes a difference.  In recent tests1 on a traveling
grate overfeed stoker a washed coal and an unwashed coal from the same mine
were fired in the stoker.  The unwashed coal had 10 percent ash, but when
washed the same coal had only 4 percent ash.  In this case (Figure 2) there
was a tremendous difference in particulate loadings because much of the ash in
the unwashed coal was a clay-like material which was easily carried out of the
furnace by the flue gas.
     In tests2 on other stokers, coals with different ash contents were fired
in the same stoker with very little or no change in particulate loading.
Coal Moisture
     Coal has two forms of moisture.  First, inherent moisture is a part of
the chemical composition of the coal.  Second, surface moisture which is due
to rain or conditions at the mine.  Although the inherent moisture cannot be
changed, the surface moisture can sometimes be avoided.
     Coal moisture causes two problems.  If excessive, it may make the coal
hard to ignite, and it will always reduce the boiler efficiency.
Coal Sul fur-
     About 95 percent of the sulfur in the coal is converted during combustion
to S02 and S03, commonly called SO .  The remaining 5 percent is retained in
                                  ){                           i
the ash.  Therefore, by burning a lower sulfur coal you reduce your sulfur
oxide emissions.  Of course, there is another reason to burn a low sulfur
                                       10

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   3
   CO
     g
     s
   2 
  t- in
   -
  a.
  Sg
                       UNWASHED COAL
                            10Z ASH
                                        HASHED COAL
                                        m ASH
              20.0     40.0     60.0     80.0
                    PERCENT DESIGN CRPflCITY
l	
 100.0
 Figure 2.   The effect on  uncontrolled particulate loading
of washing  a coal to reduce  its ash content  (Reference 1).
                               11

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 coal,  the sulfur emissions  are very corrosive  if they  condense  on  exposed
 metal  parts.   The S03  instantly combines  with  water  vapor  (H20)  to form sul-
 furic  acid (H2S04).
 Coal Fines
     The  common  definition  of  coal  fines  is  the  percentage of coal  which
 passes through a 1/4"  screen.   Too  many coal fines can lead to  high particu-
 late loadings  because  they  are easily  carried  out of the furnace,  and high
 combustible heat losses  because the particulate  matter carries  carbon out of
 the furnace with it.   High  fines may also lead to severe clinkering problems.
     When firing a high  fines  coal,  make  sure  that the fines are evenly dis-
 tributed  on the  grate, and  are not  segregated  in one area  only.  The manner in
 which  the coal is loaded into  the hopper  is  important  because it may lead to
 stratification.
     A coal which was  low in fines  when it left  the  mine may be high in fines
 when it reaches  the furnace because of all the handling it receives.  Coals
 which  break up and produce  fines more  easily than others are called highly
 "friable"  coals.   The  American Boiler  Manufacturers  Association has published
 guidelines  for the recommended size consistency  of coal for firing  in differ-
 ent types  of stokers.  These are presented in  Figures  3, 4, and 5.   Every
 attempt should be made to operate within  these guidelines.
 Ash Fusion  Temperature
     Some  coals  tend to  clinker, slag, and foul  the  boiler more than others.
 This is because  the ash  from these  coals  becomes  sticky and begins to melt at
 lower  temperatures.  These coals have  low ash  fusion temperatures.   Clinker-
 ing, slagging, and fouling will  decrease  boiler  efficiency by reducing the
 amount  of  heat absorbed  by the  boiler  and by increasing the stack gas heat
 loss.    Firing a  coal with a lower ash  fusion temperature than that for which
 the boiler was designed  can also lead  to  reduced  boiler capacity, and it may
 require operation  of the boiler  at  a higher and  less efficient excess air
 level.
 Free Swelling Index (FSI)~
     The free swelling index provides  an  indication of the  caking character-
 istics of coal when burned on  fuel  beds.   The caking characteristic of coal  is
the tendency of coal  to melt together  into a solid mass when rapidly heated.

                                       12

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Fuel to be delivered across sfoker hopper without
                                                    size segregation
95
90
80
70
60
50
40
Q)
$ 30
'" 25
Si 20
I 15
1 10
3 8

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 Size distribution of lower rank coals (Index 28.35) should fall nearer the upper curve, and

 size distribution of higher rank coals (Index 40  50) should' fall nearer the lower  curve.

 Fuel to be delivered across stoker hopper without size segregation.
1
 .
95
90
80
70
60
50
XO
30
25
20
15

10
 8
 6
 4
 3
                 X
/
               8
                      US Sfd sieve designation
                                                *
                                                I   ROUND  HOLE
                                                   screen, inches
Figure 4.  ABMA recommended limits  of coal  sizing for overfeed  stokers.
                                        14

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  FUEL TO BE DELIVERED ACROSS STOKER HOPPER WITHOUT SIZE SEGREGATION
 . ALL COAL TO PASS THROUGH 1% in. MESH SCREEN
05
90
80
70
yj 60
5 50
55 43
 30
0 25
X 20
K
t- 15
u
g '0
tf 8
6
4
3
2
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                     US STO SIEVE DESIGNATION
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I  ROUND M SCREEN. INCHES
Figure  5.  ABMA recommended limits for coal sizing for  spreader stokers.
                                  15

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The free swelling index (FSI) is reported on a scale of 1 to 9 in increments
of 1/2.  Coals having a FSI from 1 to 3 are generally referred to as free
burning, from 3h to 5 as moderately caking, and from 5% to 9 as strongly
caking.  Caking characteristics have little or no effect on the performance of
spreader stokers.  However, free burning and moderately caking coals are
preferred for overfeed stokers and underfeed stokers.
2.1.2  Underfeed Stokers
     Underfeed stokers, either single- or multiple-retort, consist essentially
of a trough or troughs into which coal is pushed by  rams or screws.  Part of
the combustion air is introduced into the fuel bed through tuyeres or grate
bars.  Movement  of the coal discourages its fusion into large masses that
cannot be burned efficiently.  Volatile matter is distilled off the coal in
these  retorts and burns above the incandescent fuel  bed.  The partly coked and
somewhat caked coal then  falls  into the air-admitting  tuyeres or grate bars,
where  the fixed  carbon is burned out.  The  coal  is progressively pushed  side-
wise or forward  until the refuse is discharged to the  ashpit.
     In an  underfeed  stoker  (Figure 6), coal  is  fed  from  the  hopper to a cen-
tral retort by means  of a reciprocating ram.   In very  small heating stokers, a
screw  conveys the coal from  the hopper to  the retort.   A  series  of small
auxiliary pushers in  the  bottom of  the retort assist in moving the coal  rear-
ward,  and as  the retort  is filled,  the coal  is moved upward to spread to each
side over the air-admitting  tuyeres  and  side  grates.
     In a single-retort  underfeed  stoker,  the coal  is  introduced into a  re-
tort;  the  incoming  coal  progressively forces  the other coal out  of the  retort
and onto  the  side grates.  This feeding  action from the retort outward  places
the entire  fuel  bed under compression and automatically closes any holes that
may tend to form in the  bed and thus overcomes a common obstacle to efficient
 firing.
      Ease and simplicity of operation are characteristics of  the single-retort
 stoker.   All  adjustments are made from the stoker front,  and  practically all
 of the fuel bed is visible and accessible through the furnace doors in  the
 stoker front.  Cleanout doors provide access to the air chambers under  the
 stoker, so that accumulated siftings may be cleaned out easily.
                                        16

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          OVERFIRE
               AIR
 COAL
HOPPER
                         PUSHER'BLOCKS

                                  AIR CHAMBER
                         SIDE VIEW
      COMBUSTION  X"
      GRATEv
                           RETORT^
                           PUSHER
                           BLOCK
                        END VIEW

 Figure 6.  Single-retort, horizontal underfeed stoker.
                            17

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     As the coal rises in the retort, it is subjected to heat from the burning
fuel above, which ignites the coal.  Volatile gases that are distilled off mix
with the air supplied through the tuyeres and side grates.   The volatile
mixture burns as it passes upward through the incandescent zone, and overfire
air sustains the ignition of the rising coal and insures complete combustion.
Burning continues as the incoming raw coal continually forces the fuel bed to
each side.  Combustion is completed by the time the bed reaches the side-dump-
ing grates.  The ash is intermittently discharged to shallow pits, where it is
quenched and then removed through doors at the front of the stoker.
     The multiple-retort stoker is an extension of the single-retort stoker.
It is nothing more than a series of single-retort stokers built into the same
unit, with an appropriate mechanism provided to operate the various components
in unison.
     In the underfeed section of a multiple-retort stoker fuel bed, parallel
rows of hills and valleys of coal  extend  from the front wall to the discharge
ends of the retorts.  The hills occur over the relatively inactive retort
areas because no provisions are made for  air admission.  The coal  is supplied
through a  reciprocating feed, which produces a certain amount of  segregation
in  the fuel bed.  The coarse coal  finds  its way to the tuyeres  near the  front;
the fines  travel the  length of the retort.  High  combustion rates in a thin
active fuel bed occur over the tuyeres where air  is  admitted.   The overfeed
section shakes  down and  levels out these  alternately thick  and  thin parallel
ribbons.3
     As this  irregular mass  of burning  fuel  reaches  the  overfeed  section,  it
is  quickly shaken  down to  uniform  thickness  by the  reciprocating  action  of the
grates  in this  area.  The  fuel bed is  now level,  compact, homogeneous,  and
extremely active because  of  the  stroke  control and  correct  air  feed.   As a
result, the fuel  bed  should  be burned  out uniformly across  the  stoker width by
the time  the  fuel  reaches  the  dump grates or ash  discharge  section.
     The  multiple-retort inclined  underfeed stoker is used  in  many plants that
 have relatively constant loads  or  light loads  of  long duration.   This type of
 stoker can handle these  loads  without objectionable smoke more  easily than the
 spreader  stoker can.
      With multiple-retort stokers, overfire-air  systems generally have a
 separate  high-pressure fan that develops a pressure of approximately 16 inches

                                        18

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H20.  This fan is operated intermittently to prevent smoke at low loads or
during sudden firing rate increases, which cause distillation of large quanti-
ties of volatile gases.  Forced draft is supplied to the entire grate area,
which is divided into several pressure zones parallel to the retort, each
under separate damper control.  The air pressure compensates for the thickness
of the fuel bed; the greatest pressure is applied to the thickest portion over
the retort.
     Many small underfeed stokers that handle relatively steady heating loads
operate with start-stop control.  Stokers that are operated to suit a varying
load should be equipped with a modulating combustion control that varies the
coal-feed rate and keeps the air supply in step with steam demand.   The fur-
nace draft should be controlled through operation of the boiler outlet damper.
Primary combustion air is supplied by a forced-draft fan.
2.1.2  Chain-Grate and Traveling-Grate Stokers
     The traveling-grate stoker is very versatile for solid fuel burning, and
nearly every type of mined fuel can be burned successfully in the various
types of stokers.   In addition, waste and byproduct fuels such as coke breeze,
garbage, and municipal refuse can be burned efficiently and effectively.   The
traveling-grate stoker has also been used in chemical processes to produce
coke and carbon dioxide.
     In chain-grate stokers,  assembled links, grates, or keys are joined
together in an endless belt arrangement that passes over sprockets or return
bends at the front and the rear of the furnace.   As shown in Figure 7, coal is
fed from the hopper onto the moving assembly and enters the furnace after it
passes under an adjustable gate that regulates the thickness of the fuel  bed.
Because the coal flow through the furnace is usually at right angles to the
primary air flow,  these furnaces are sometimes referred to as crossfeed
stoker-fired furnaces.  As the layer of coal on the grate enters the furnace,  .
radiation from the furnace gases heats and ignites the coal and the combusti-
ble gases that are driven off by distillation.   As the fuel bed moves along,
it continues to burn and grows progressively thinner.   At the far end of its
travel, the grate  discharges  the ash into the ashpit.   Although they differ
structurally,  the  operation of chain-grate and other traveling-grate stokers
is quite similar.
                                       19

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2.1.3   Spreader  Stokers
     Sometimes called overfeed  stokers,  spreader  stokers  incorporate the
principles of pulverized coal and  stoker firing in that fines are burned  in
suspension and heavier pieces of fuel  are burned  on the grate.  Feeding and
distributing mechanisms continually project coal  into the  furnace above an
ignited fuel bed.  With this method of firing, coal characteristics have  less
effect  on the fuel bed than'",they do in other types of stokers.  However,  fuel
characteristics  may cause the spreader stoker to  smoke if  it is operated
outside acceptable design ranges.  Flash drying of the incoming fuel, rapid
release of volatile matter, and suspension burning of the  fuel make this
method  of firing widely applicable.  Practically  all types of coal have been
successfully burned in spreader stokers, as have  a wide variety of cellulose
fuels,  including bagasse, wood chips,  bark, hogged wood, sawdust, shavings,
coffee  grounds,  and furfural residue.
     Figure 8 shows the principal components of a spreader stoker.  As the
name implies, the spreader stoker projects the fuel with a uniform spreading
action  into the  furnace above the ignited fuel bed, which permits suspension
burning of the fine fuel particles.  The heavier pieces that cannot be sup-
ported  in the gas flow fall to the grate for combustion in a thin fast-burning
bed.  Compared with other types of stokers, firing is highly responsive to
load fluctuations.   The almost instantaneous ignition accommodates any in-
crease  in the firing rate, and the thin  fuel bed can be burned out rapidly if
the load suddenly decreases.
     Although several different means  are available for feeding and distribu-
ting coal, the overthrow rotor design  is used most widely.  Its function is to
provide a well-distributed fuel  supply at varying rates to match instantaneous
increases in loads.   A feed plate moves coal from the supply hopper over an
adjustable spill  plate,  from which it falls onto an overthrow rotor equipped
with curved blades to provide uniform coal distribution over the furnace area.
     The modern spreader stoker installation consists of feeder-distributor
units in the widths and numbers  required to distribute the fuel  uniformly over
                                       21

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                                        22

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 the width of the grate, specifically designed air-metering grates, forced-
 draft fans for both undergrate and overfire .air, dust collecting and reinject-
 ing equipment, and combustion controls to coordinate fuel and air supply with
 load demand.
      The first spreader-stokers, developed in the early 1930's, used station-
 ary high-resistance air-metering grates, from which the ash was removed-man-
 ually.   This  spreader stoker application was limited to boilers with steam
 capacities below 30,000 Ib/h.   These stationary grates were soon followed by
 dumping-grate designs, which provided grate sections for each feeder and
 correspondingly divided undergrate air plenum chambers.   This permitted the
 temporary shutoff of fuel  and air to a grate section for ash removal  without
 affecting other sections of the stoker.
      In the late 1930's the continuous-ash-discharge traveling grate of the
 air-metering  design was introduced which brought the spreader stoker into
 immediate and widespread popularity.   The elimination of interruptions  for ash
 removal  and the thin,  fast-burning fuel  bed enabled average burning  rates to
 be  increased  approximately 70  percent over the  stationary-  and dumping-grate
 types.   This  stoker is generally competitive  in  sizes up to about  525 ft2 of
 grate area, which  corresponds  to a steam capacity somewhat  over 400,000 lb/h.3
 The  furnace width  required for stokers above  this size usually increases
 boiler  costs  over  those required for  pulverized-coal  or  cyclone units with
 narrower and  higher furnaces.
     Although  reciprocating and  vibrating continuous-cleaning  grates  also have
 been developed,  the continuous-ash-discharge  traveling-grate stoker is  pre-
 ferred  for large boilers because  of its  higher burning rates.   For all  contin-
 uous-ash-discharge  spreader stokers,  the  normal practice  is to  remove the
 ashes at  the feed end  (front)  of  the  stoker.  This permits the most satisfac-
 tory fuel distribution  pattern and provides maximum residence time on the
 grates for complete combustion of the fuel.
     The  traveling-grate spreader stoker  (Figure  9) has self-adjusting air
 seals at  both the front and rear of the grate.  These effectively reduce
 leakage and stratification  of air along the front and rear furnace walls,
where it  cannot be utilized efficiently in the combustion process.
     An overfire air system with pressures from 27 to 30 in. H20 is essential
for successful suspension burning.  It is customary to provide at least  two
                                       23

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                                              STEAM OUTLET
     TO STACK
FLY ASH
RETURNX
                                                  COAL FEEDER
        Figure 9.  Spreader stoker with gravity-flow
       fly ash return.  (Courtesy of Babcock & Wilcox)
                              24

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 rows of evenly spaced high-pressure air jets in the rear wall of the furnace
 and one row in the front wall (Figure 9).  This air mixes with the furnace
 gases and creates the turbulence required to burn out all of the residual
 fixed carbon in the fuel and any carbon monoxide that may form.
 Fly-Ash Collection and Reinjection Systems
      Because partial suspension burning results in a greater carryover of
 particulate matter in the f,lue gas than occurs with other types of stokers,
 particulate control equipment is required for spreader stokers.   Multicyclone
 collectors are generally used.   Fines are deposited in a hopper for discharge
 to the ash disposal system, and coarse carbon-bearing particles  may be skimmed
 off and returned to the furnace for further burning.4
      When plant physical  layout permits location of the collecting and set-
 tling hopper outlets at a sufficient height,  the fly ash flows  by gravity to a
 distributing hopper directly behind the rear  wall  of the furnace,  as  shown in
 Figure 9.   Pneumatic systems in which high-pressure air is  the conveying
 medium have been  used extensively  to reinject the  fly ash into the  furnace in
 the high-temperature zone just  above the  fuel  bed.   Reproduction  of the fly
 ash into the furnace can  increase  boiler  efficiency by 2 to  3 percent.4
 Control--
      Although  the  spreader  stoker  can  accommodate  varying loads,  such loads
 require  close  control  of  fuel and  air  supply  to  achieve  best results.  Many
 types  of automatic combustion controls  are available,  from simple positioning
 types  used  on  relatively  small  installations  to  more elaborate air-flow  and
 steam-flow  regulators  in  larger plants.
 2.1.4  Emissions

     Regardless of the type of fuel that is to be burned  in  underfeed, travel-
 ing grate, or spreader stokers, the importance of size segregation cannot be
 overemphasized.  If all the fines are on one side of the stoker and all the
 coarse coal is on  the other, the fines will tend to mat over and the coarse
 coal will burn rather freely.  The resulting maldistribution of air through
the fire can cause overheating of the grate surface and other stoker parts.  A
ragged fire also indicates bad burning characteristics.  Figure  10 shows
typical static pressure readings in a stoker coal-fired boiler.   Thus, the
                                       25

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Feeder
                 Steam Drum
          Baffle
                                Flue
                              Gas Flow
                                                      Flue Gas to
                                                Stack or Common
                                                       Breeching
                                                  Induced
                                                 Draft Fan
                                               Economizer
                                               or Airheater

1 1

\ /
y
/' \
k \
     ^Stoker Grate
                                                                          .Mechanical
                                                                           Dust Collector
                                  Elevation View
 1. Furnace: 0.15 inches of water
 2. Boiler Outlet: 1.20 inches of water
 3. Economizer or Airheater Inlet: 1.25
    inches of water
 4. Economizer or Airheater Outlet: 3.75
    inches of water
 5. Mechanical Dust Collector Inlet: 3.80
    inches of water
6. Mechanical Dust Collector Outlet: 7.30
   inches of water
7. Hopper Area of Mechanical Dust Collector:
   6.95 inches of water
8. Induced Draft Fan Inlet: 7.35 inches
   of water
        Figure  10.  Typical  stoker boiler flue gas  static pressure.
                                          26

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 importance of being  sure that the different coal sizes are thoroughly mixed
 before they are  fed  to a stoker  is apparent.
     Overfire air, sometimes referred to as secondary air, is commonly used in
 furnaces that fire bituminous coal.  The overfire air helps to eliminate
 smoke, and if properly adjusted, improves combustion efficiency.  Because
 turbulent mixing of  air and gas  is necessary, the air pressure and volume must
 be sufficient to create the proper turbulence.
     The overfire air should range between 5 and 15 percent of the total
 combustion air requirement.  The overfire air requirement is a function of the
 coal quality and the amount of excess air in the furnace proper.  Air at pres-
 sures below 6 in. H20 may not be effective in creating turbulence.  At some
 installations, relatively small  quantities of air at pressures up to 25 or 30
 in. H20 are injected to improve  combustion conditions in the furnace and to
 reduce particulate emissions.  Air penetration is a function of the static
 pressure and the volume of air per fuel discharge nozzle, and extreme care
 must be used in  locating and adjusting the overfire air jets.

 2.2  PULVERIZED  COAL FIRING
     Annual consumption of bituminous coal and lignite in the United States is
 about 500 million tons; more than three-fourths of this amount is used to
 generate steam.   A high percentage of the coal burned for steam generation is
 in pulverized form, especially in the electric utility industry; however, many
 large industrial  boilers also fire pulverized coal.   The main advantage of
 pulverized coal   is that almost any quality of coal  can be burned if the boiler
 is designed properly, because the coal  is ground to minus 200 mesh to ensure
 its combustion.
     Experience  shows that stoker firing is more economical  than pulverized
 coal  firing for  units with capacities of less than  100,000 Ib  of steam per
 hour5;  these lower-capacity units can tolerate the  lower efficiency of a
 stoker.   In larger plants,  where fuel cost is a larger fraction  of the oper-
ating cost, pulverized-coal  firing is generally more economical.
Pulverized Coal  Systems--
     In  a pulverized-coal  system, the coal  is first pulverized and then  de-
livered  to the burners  with sufficient  air to promote efficient  combustion.
                                       27

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The coal feed must be varied rapidly (within specified design limitations) to
match load requirements.  About 15 to 20 percent of the air required for
combustion is used to transport the coal to the burner.  This air, known as
primary air, also dries the coal in the pulverizer.  The remaining 80 to 85
percent of the combustion air, known as secondary air, is introduced at the
burner.  Figure 11 shows a typical pulverized-coal-fired boiler.  The two
basic components of a pulverized-coal system are:
     0    The pulverizer (arranged to operate under pressure or suc-
          tion), which  reduces the coal size to the required fineness.
     0    The burner, which mixes the pulverized coal and air in the
          right proportions and delivers the mixture to the furnace for
          combustion.
Other necessary components are:
     0    Fan(s) to supply primary air  to the pulverizer and to deliver
          the coal-air  mixture to the burner(s).
     0    Raw-coal feeder, which controls the rate of coal fed  to each
          pulverizer.
     0    Source (steam or gas air heater)  of hot primary air supply  to
          the pulverizer for drying the coal.
     0    Coal- and air-conveying lines.
     Coal must be pulverized until particles are small enough to  assure proper
combustion,  and the surface moisture must be removed  from the coal.   In the
direct-firing system,  the coal delivered to the  burner is suspended in the
primary air; at the burner, the coal and primary air  must then  be mixed ade-
quately with the secondary air.
     Coal and air feed to the  pulverizer is controlled by one of  two  methods:
1)  proportioning the  coal feed to the  load  demand  and adjusting the primary-
air supply  to the rate of coal  feed, or 2)  proportioning the primary  air
through the pulverizer to the  load  demand and adjusting the  coal  feed to  the
rate of air flow.   In either  case,  a predetermined air-coal  ratio is  main-
tained for  any  given  load.
     The direct-firing system  eliminates the  need  for storage facilities  for
pulverized  coal  and permits the  use  of high-temperature  (~650F)  inlet  air  to
the pulverizer  for  drying  high-moisture coals.   A  minor  disadvantage  of the
                                        28

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TEMPERED AIR FAN -f
                I V
    PULVERIZER/U
   Figure 11.   Dry-bottom pulverized-coal-fired unit.
              (Courtesy of Babcock & Wilcox)
                             29

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direct-firing system is that the pulverizer turndown range is usually limited
to about 3 to 1 because the air velocities in the lines and other parts of the
system must be maintained above the minimum values to keep the coal  in suspen-
sion.  In practice, most boiler units have more than one pulverizer, each of
which feeds multiple burners.  Load variations beyond 3 to 1 are generally
accommodated by shutting down or starting up a pulverizer and the burners that
it supplies.
     Idle burners are subject to considerable radiant heat from the furnace
and can attain temperatures above the coking temperatures of the coals.  The
use of alloy metals provides longer life for burner parts; however, if these
parts are not adequately cooled below the coking temperature before being
placed in service, coke may form and severely damage them.  The easiest way to
cool the fuel discharge nozzles is to run cold primary air through the pulver-
izer and burners for 5 to 10 minutes and then immediately feed the coal before
the  nozzles can reheat.  Because there is no simple way to cool selected
burners on a single pulverizer before bringing them into service, a pulverizer
and  all its burners should be operated at once.
     Large boilers with air  heaters have a sizable heat inertia, and at full
load, it requires  upward of  6 hours for temperatures throughout the unit to
stabilize.  A significant time period is also necessary for  such boilers to
re-equilibrate after a load  change.
     The temperature of the  primary air entering the pulverizer may run 650F
or more, depending on the surface moisture of the coal and the type of pulver-
izer.  Coal grinding to a fineness of 200 mesh (90 percent)  is necessary to
assure maximum efficiency and to minimize the deposit  of  ash  and carbon on the
heat-absorbing surfaces.
Exhausters  and Blowers
     If the pulverizer operates  under pressure,  the primary-air  fan handles
clean air and  is  not abraded by  the pulverized coal.   In  this case, a  high-
efficiency  fan with an efficient rotor  design  and high tip speed can be  used.
If the pulverizer operates  under suction,  however,  the fan must  handle pul-
verized-coal-laden air.  This  requires  that  the  fan  housing  be designed  to
withstand a potential  explosion  pressure  of  200  psi within the fan  to  comply
with National  Fire Protection  Association  requirements.   Furthermore,  because
                                        30

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 the fan  is subject to excessive wear,  its design  is  limited to heavy paddle-

 wheel construction and hard-metal or other protective-surface coatings.  All
 of these construction features are detrimental to the fan's mechanical effi-
 ciency.

 Standards of Burner Performance-

      Operators of pulverized-coal equipment should expect burner performance
 to meet the following conditions:

      1.    The coal feed and air supply should match the load demand over
           a predetermined operating range.   For most applications, igni-
          . tion of the pulverized coal  must be stable without the use of
           support!ng fuel over a load range of approximately 3 to 1.
           Most steam boilers are equipped with several  pulverizers so
           that a wider capacity range can be readily obtained by varying
           the number of burners and pulverizers in use.

      2.    Unburned combustible loss  should be less than  2 percent   With
           most well-designed installations  it is  possible to keep the
           unburned combustible loss  under 1 percent with excess  air in
           the range of 15 to 22 percent,  measured at the furnace  outlet
           I his loss is a  good indication  of burner condition and  pulver-
           izer condition.   Coal  fineness  and  carbon  should be  checked
           daily.

     3.    Adjustments  to  the burner  should  not be  necessary to maintain
           flame  shape.  The design should be  such  that formation  of
           deposits  are avoided that  could interfere  with continued
           efficient and reliable  burner performance  over the operatina
           range.

     4.   Only minor repairs  should be  necessary during  the annual
          overhaul.  Burner parts subject to abrasion may  require more
          frequent  replacement.  Alloy  steel should be used for parts
          that cannot be protected by cooling  or other means to avoid
          damage from  high  temperatures.

     5.   Safety must be paramount under  all operating conditions.

Ignition Stability--

     For ignition stability, the temperatures of the primary air and coal
leaving the pulverizer must be at least 130F for units  burning coal with more
than 30 percent volatile matter; temperatures up to 180F may be required if
the volatile matter of the coal is as low as 22 percent.   For coals with at
least 25 percent volatile  matter,  the maximum temperature of the primary
                                       31

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air-coal mixture leaving the pulverizer is approximately 150F; higher temper-
atures increase the tendency for coking on the burner parts.
Modern Burner Types--
     Intervane burners are the most commonly found burner in industrial coal-
fired boilers.  Circular and cell type burners also are used.  Figures 12, 13,
and 14 show typical burners that fire pulverized coal.  Burners are available
that fire pulverized coal, oil, gas, or any combination of these three fuels;
however, the firing of pulverized-coal combined with oil in the same burner
should be restricted to short emergency periods.,  It is not recommended for
long operating periods because of possible coke formation in the burner.
Usually, the maximum heat  input per burner is about 165 million Btu per hour.
At full boiler load the secondary-air port velocity ranges from 4000 fpm for
small boilers, where unheated secondary air is used, to 6000 fpm for a dry-
ash-removal furnace with 600F air.  Velocities of 7500 fpm are common with
circular burners  in slag-tap furnaces.
Lighters (Igniters) and Pilots
     Although  ignition and control  equipment  for pulverized-coal firing is
similar to  that  for oil and gas,  it is  used differently.  In pulverized-coal
applications,  igniters must be  kept operating for hours, until the  temperature
in the  combustion zone  is  high  enough  to  assure self-sustaining ignition  of
the  main fuel.
     The self-igniting  characteristics  of pulverized  coal vary from one fuel
to another, but  for  most  coals  ignition can be maintained without  auxiliary
fuel  down  to  about one-third  of the burner capacity.   When  the pulverized coal
being  fired has  less  than  25  percent volatile matter,  it may be necessary to
activate the igniters  even at high loads.  This particularly applies  to coal
that is wet or frozen  or  when coal  feed to the pulverizers  is  disrupted.   If
the  ignitor is not activated  when the coal feed to  the pulverizer  is  inter-
 rupted, ignition may be lost  momentarily; when the  coal  flow is  reestablished,
 an adjacent burner may reignite the burner with explosive  force  and damage the
 burner and/or the boiler.
                                        32

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 Oil
 Igniter
Detector*'
                Figure  12.   Intervene  burner.
                              33

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         IGNITOR
  INNER
REGISTER
                                 OUTER
                               REGISTER
  PERFORATED
PLATE AIR HOOD
FLAME SCANNER
    TANGENTIAL
    COAL  INLET
                                                     MOVABLE SLEEVE
            SPLIT FLAME
            COAL NOZZLE
            Figure 14.   Components and functions of a
             controlled-flow/split-flame coal  burner.
                                 35

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Excess Air
     More excess air is required for satisfactory combustion of pulverized
coal than for oil or natural gas.  One reason for this is the inherent maldis-
tribution of coal to individual burner pipes and to the fuel discharge noz-
zles.  At high loads, the minimum acceptable quantity of unburned combustible
matter usually requires about 15 percent excess air at the furnace outlet.
This allows for the normal maldistribution of primary air, secondary air, and
coal.  Higher excess air values may be necessary to avoid slagging or fouling
of the heat absorption equipment.
     The designer of a pulverized-coal-fired unit must consider the burner
arrangment and the furnace configuration to minimize slagging or fouling of
the boiler.  An increase in excess air will permit satisfactory performance
with most designs, but this may be uneconomical as a long-term substitute for
good basic design.
Starting Cold Boilers and Operating at Low Loads
     Because coal is difficult to ignite, any unburned fuel that escapes on
startup is dry dust with a high ignition temperature.  This dust does not
readily cling to surfaces and is carried out of the unit with the products of
combustion.  The only potential problem is that this dust can accumulate in
hoppers or in dust collectors.  These containers should be emptied frequently
so that the unburned material cannot build up to the point that it ignites and
damages equipment.
     During startup, oil burners with mechanical atomizers can be used to
sustain ignition of pulverized coal with little risk of air-heater fires.
Only a small amount of oil is used, and the resulting deposits are generally
inconsequential.
     Coal-fired boilers produce significant quantities of particulate matter,
S02, and NO .  The level of each of these pollutants is related to the firing
           J\
method, the combustion efficiency, the pollution-control equipment, and the
fuel characteristics.
     The quantity of S02 produced is' nearly proportional to the coal sulfur
content, but the pulverizers directly reject some pyritic sulfur (usually not
more than about 5 percent of the total coal sulfur content).  Because sulfur
affects the ash fusion temperature, the coal sulfur content affects boiler
design and operating characteristics.

                                       36

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     The generation of NO  is strongly related to the combustion method and
                         s\
combustion controls.  Free nitrogen in the coal tends to be a significant
contributor to overall NO  emissions.   Most NO  controls deal with the adjust-
                         X.                    s\
ment of combustion air to the burners of pulverized-coal-fired boilers.
Staged combustion or off-stoichiometric firing produces lower peak flame
temperatures by limiting the amount of air available for combustion.   This
generally produces long diffusion-limited flames and thus provides longer
reaction times at lower temperatures for complete combustion.  Excess air,
usually 15 to 30 percent, is gradually introduced to the flame.  The minimum
attainable NO  emissions are generally dictated by the nitrogen content of the
fuel.  Tangential or corner-fired pulverized-coal-fired boilers tend to pro-
duce less NO  than wall-fired units.
            s\
     The particulate emission rate is a function of the coal ash content and
the firing method.  Pulverized-coal-fired boilers emit between 70 and 85
percent of the ash in the coal as fly ash.  In contrast, a stoker-fired boiler
emits only 3.0 to 50 percent of the coal ash with the flue gas.  In addition,
the particulate matter generated by stoker boilers tends to be much coarser
than the ash from pulverized-coal-fired boilers, and it generally contains
considerably more carbon.  These factors affect the selection of control
equipment for specific boilers.
Malfunctions
     Although numerous boiler malfunctions can occur, the two most common
operational problems result from inferior fuel quality and the use of  improper
excess air levels.  The selected excess air levels are often much higher than
necessary for complete combustion, which decreases boiler efficiency and in-
creases the amount of fuel required to develop a given quantity of steam.  Too
much excess air can also increase emissions.
     The nitrogen and oxygen  in the excess air produce a dilution effect.
Although the peak flame temperature may increase with excess air, the  average
flame temperature decreases as a result of the dilution.  This decrease in
average temperature reduces the radiant heat transfer to the furnace walls,
and  in extreme cases, the extra gas volume may carry unburned  fuel out of the
furnace zone.
     The volume of  excess air increases the velocity of the  flue gas through
the  convective tube passes because  the volume  between the tubes is fixed.

                                       37

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This velocity increase improves the heat transfer rate in the convective
section slightly, but the improved heat transfer rate fails to offset the
corresponding decrease in heat transfer in the radiant zone described earlier.
Thus, excess air effects a net heat transfer loss.   The usual indicators are
increases in the temperature and in the oxygen (02) concentration at the
stack.
     Proper excess air levels range from 20 to 30 percent for pulverized-coal-
fired boilers.  The excess air level for best boiler efficiency is generally
one that produces a very low carbon monoxide (CO) concentration.  Boiler
excess air can be monitored via C02 or 02 monitors at the outlet of the radi-
ant heat zone.  Typically, CO levels are maintained at approximately 100 ppm,
and maximum levels of 400 ppm are usually established to preclude explosions
resulting from CO pockets within the boiler.
     The symptoms of sootblower failure are the same as those for high excess
air.  Sootblowers use steam or compressed air to clean deposits from the
boiler tubes.  The ash load and ash properties dictate sootblowing require-
ments.  Continuous sootblowing may be required for some pulverized-coal-fired
boilers.  Failure to blow the soot from the boiler tubes allows deposits to
form, which reduce the heat transfer rate through the tubes.  The resulting
decrease in efficiency is characterized by an increase in stack temperature;
02 and C02 levels are unaffected.
      Coal sizing is not a big problem for pulverizers; the maximum allowable
top size for most pulverizers is about 2 inches.  Very high  quantities of
fines may cause problems in some pulverizers, but most are easily capable of
producing the required fineness (70 to 75 percent through a  200-mesh screen).
      Most pulverized-coal-fired boilers have at least one extra pulverizer to
allow routine maintenance to be performed without reducing the boiler load.
Selection of  the number of pulverizers needed to handle the  desired  load is
based on the  heat content and grindability  of the coal because these charac-
teristics affect pulverizer capacity.  Because pulverizers are expensive,
excess capacity  is held to a minimum.  If the grindability of the coal de-
creases  (making  it more difficult to grind) or if the heat content of the coal
decreases, existing pulverizers may not be  sufficient to maintain the neces-
sary  steam rate.
                                        38

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     Changes  in the  ash  content  and  other  characteristics  of the coal can
significantly affect boiler  operation.  A  high-ash  coal  can increase the
sootblowing requirement  or increase  heat losses  as  a  result of  impaired heat
transfer.  A  more serious problem  is  an increase in the  slagging potential of
the ash.  This can necessitate derating the boiler  to prevent slagging.  A
sticky ash coating that  reduces  heat  transfer efficiency can make boiler oper-
ating conditions difficult to control.  Sticky ashes  can be hard to remove,
and they may  form localized  hot  spots, which damage the  boiler  tubes.  Coal
blending sometimes leads to  similar problems as  a result of the formation of
eutectic ash  from the blended coal.   This  ash has a lower  fusion temperature
than the ash  for either  coal by  itself.
     Improvement in  coal quality can'also  lead to operating problems in a
pulverized-coal-fired boiler.  If  a nonslagging  coal  is  burned  in a boiler
designed for  a slagging  coal, furnace walls may  be  too clean, and too much
radiant heat  may be  absorbed, which makes  it difficult for the superheater to
produce the necessary steam  temperatures.   A reduction in  sootblowing can
alleviate this problem.
     Fineness of the coal from the pulverizers should be checked frequently.
Failure to feed coal of  requisite  fineness to the burners may impair combus-
tion and thereby allow carbon carryover to the control equipment, which causes
inefficient boiler operation.  Excessively fine pulverization wastes energy
and reduces pulverizer capacity.    If Eastern bituminous  coal is burned, 70 to
75 percent of the coal  should pass through a 200-mesh screen.   Somewhat less
fineness (60  to 65 percent)  is necessary with Western subbituminous coal
because of the noncaking properties of this coal.
     A tube leak eventually causes boiler shutdown and also affects control
equipment operation.   Waterwall,  boiler tube,  and economizer tube leaks have
the greatest effects on control  equipment operation.  Significant quantities
of water can escape  into the flue gas, plug multicyclones and fabric filters,
and make ash removal  from electrostatic precipitator (ESP) plates difficult.
     Freezing conditions can affect coal  flow to the boilers.   The coal  can
hang up in chutes,  hoppers, feeders,  or even rail cars.  In stoker boilers,
frozen fuel  can cause underfire  air to channel  to uncovered portions of the
grate,  which reduces the underfire air to  other portions of the grate.   This
can cause distortion of the grates, as both the ash layer and the underfire

                                       39

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air help to protect the grates.  In addition, the channeling of the air
changes local excess air conditions and increases emissions.

2.3  FANS
     The gas flow rate is a key parameter in the evaluation of the performance
of any pollution control system.  The inspector should rely on current pitot
tube measurements to determine the flow rate of the pollution control system.
     In some cases, fan data can be used to estimate the gas flow during the
inspection.  Using a published fan curve, the inspector should correct all
readings to standard conditions and determine the gas flow in standard cubic
feet per minute.  An estimate made in this manner is subject to errors because
of the variability in fan performance, fan modifications that may have been
made, and the mechanical condition of the fan.  If a fan curve is not avail-
able, the inspector can use the F-factor method (discussed in Section 2.4) to
estimate flue gas and fuel rates.
     Fan data can be used to diagnose changes that have occurred since the
last previous inspection.  In many cases, however, baseline data are not
available because fan parameters are not routinely measured during convention-
al inspections.  A radial-blade centrifugal fan is typically used for dirty
gas service.  Operating characteristics are illustrated by the curve in Fig-
ure 15, which applies to a New York Blower Company size 332 general industrial
fan with an LSD wheel operating at 1460 rpm at standard conditions.  Static
pressure losses in the control equipment and ductwork (curve A) are propor-
tional to the square of the flow rate.  The fan develops less static pressure
at higher flow rates, however; thus it has a strong negative slope (curve B).
The intersection of the system line and the fan pressure drop curves defines
the operating point of the system.  At this point, the gas flow rate is 8,400
scfm (approximately 40,000 Ib steam/h boiler), and the brake horsepower (curve
C) is approximately 24.5.
     A major problem with boilers is that as they get older they tend to lose
capacity because the fan cannot accommodate increases in excess air, inleak-
age, and general system deterioration (such as fabric filter blinding, in-
creases in ductwork friction, etc.).  A reduction in boiler load is usually
required to compensate for this, but plants sometimes replace the fan drive
sheaves to speed up the fan.  The latter is not always a feasible remedy.

                                       40

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   12
   11
.5  10
LLJ
a:

CO

-------
     Effects of fan speed on operating characteristics are shown by the curves
in Figure 16.  In Case 1, a speed increase leads to a greater gas flow rate
and higher static pressure.   Increasing the fan speed may be a feasible course
of action at plants where the boiler gas flow is insufficient; however, the
fan must be operated within its acceptable published range of speeds.   In-
creased flows can adversely affect fabric filters or ESP's.   On the other
hand, a decrease in fan speed (perhaps to save energy) decreases the flow sub-
stantially; Case 2 shows such reduced gas flow.  A decrease in fan speed can
reduce the collection efficiency of cyclones and wet scrubbers because these
control devices depend on gas velocity for particle collection.
     Other changes in fan operation may occur without the operator's know-
ledge.  For example, the fan motor current may either increase or decrease
when the system static pressure drop increases; Case 3 in Figure 17 represents
a total system pressure drop increase from the baseline condition.  An in-
crease in the fan motor current would accompany this change, as indicated in
Table 2.  The static pressure increase may be due to a variety of factors.
Static pressure decreases can be caused by the following factors:
     0    A change in the gas flow rate.
     0    Changes in operating conditions such as control device short-
          circuiting (open access doors, gaps in ductwork, open by-pass
          dampers).
     0    Decreased scrubber liquor flow.
The cause of the change can be analyzed further by measuring the gas tempera-
ture at the fan inlet.  A low temperature suggests either an open access hatch
or a serious leak in the ductwork.
     In addition to analyzing the fan operation, the inspector should visually
check the physical condition of the fan and note the following:
     0    Blade abrasion
     0    Deposits
     0    Corrosion of the wheel and fan housing.
                                       42

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   12
   10
LU
CC.
=>
oo
1/1
LU
CC   Q
a.   -*
x-- CASE  1 ,  FAN AP
                          ' ' 7      8        9      10
                         GAS FLOW RATE, SCFM  x  10 3
                                   11
12
     Figure 16.  Fan characteristic curveseffect of speed change.
                                     43

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   12
o 11
 

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             TABLE  2.   INTERPRETATION  OF  FAN  OPERATING  CONDITIONS
             (RADIAL-BLADE  TYPE  ONLY)  SHOWN ON  FIGURES  15  AND  16.
Case
1
2
3
4
Fan parameters
Calculated
APsp at 70F
Decreased
Increased
Increased
Decreased
Calculated
amps at 70F
Decreased
Increased
Decreased
Increased
Fan speed,
rpm
Decreased
Increased
Unchanged
Unchanged
Possible causes
Fan speed increase (sheave
change or belts tightened)
Fan speed decrease (sheave
change or loose belts)
a) Filter blinding
b) Filter cleaning problem
c) Hopper overflow
d) Scrubber bed plugged
e) Decreased gas flow
f) Reset damper
a) Baghouse leaks
b) Shortcircuiting
c) Decrease in liquor flow
d) Increase in gas flow
e) Reset damper
The inspector should be sure to lock the fan out of service before attempting
to conduct a physical inspection.
     Blade abrasion and deposits indicate excess emissions of large particles
(10|jm) and suggest a particulate control device malfunction.   Fan operating
parameters indicate a number of important changes in control  device operating
conditions.  For an estimate of actual flow rates, the certified rating curve
for the fan must be corrected to the gas temperature at the fan inlet by using
the factors in Table 3.
     Generally, if the fan operating parameters (static pressure, motor cur-
rent, fan speed) are within 10 percent of the baseline condition and if the
gas temperature at the fan inlet is within 20F, it is unlikely that gas flow
changes have caused mass emissions to change significantly from baseline
conditions.
                                       45

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                 TABLE 3.   FAN DATA,  TEMPERATURE CORRECTION.'
Temp
20
40
60
80
100
120
140
160
180
200
Factor
0.91
0.94
0.98
1.92
1.06
1.09
1.13
1.17
1.21
1.25
Temp
220
240
260
280
300
320
340
360
380
400
Factor
1.28
1.32
1.36
1.40
1.43
1.47
1.51
1.55
1.59
1.62
Temp
420
440
460
480
500
520
540
560
580
600
Factor
1.66
1.70
1.74
1.77
1.81
1.85
1.89
1.92
1.96
2.00
          aThe published flow rate from the fan curve is multiplied by
           the above factors to estimates actual flow at fan inlet
           temperature.  Adapted from "Basic Energy/Environment Analysis,"
           NAPA Information Series 67, by C. Heath, August 1978.
2.4  USE OF THE F-FACTOR
     Stack sampling teams have used the F-factor as an accepted method of
obtaining heat input of combustion sources through measurement of gas velocity
and gas conditions for the purpose of determining gas volume.   During inspec-
tions of combustion sources, inspectors often find that both the heat input
and gas conditions are determinable but the gas volume is the unknown factor.
The F-factor method is used to ascertain the missing value needed for the
evaluation of control equipment performance.
     Thn simplest case is one in which both wet and dry F-factors (Fw and F^)
are available for a known fuel.  The oxygen content is usually determined on a
dry basis; thus, an equation relating gas volume, temperature, and moisture
may be written:
stack
Q = heat input rate x [(F, x Correction ^ +
                                                          temperature
                  w
     where Q = gas flow rate, acfm;
     Stack oxygen correction factor =
     Temperature correction factor =
            20.9
                    ;  and
                                       46

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 EXAMPLE   Heat input rate = 100 x 106 Btu/h (using bituminous coal) or
                              1.667 x 106  Btu/min
      Fd = 9,820 dscf/106  Btu
      FW = 10,680 wscf/106 Btu
      Temperature = 350F
      Oxygen content =5.0%
      Q  = 1.667  x [9,820 x (20J:95>0) + (10,680  -  9,820)]  x
       =  1.667  (12,908  +  860)  x
                                 810
                                 528

       =  1.667  (13,768)(1.53)
       =  35,210  acfm  at  350F.
     The  term (FW  - Frf)  accounts  for water  produced  during  the  combustion
process and assumes that excess  fuel moisture  does not  significantly  affect
the values for  FW.  For  fuels where moisture content is  significant and may be
variable, however, the above formula is usually not  applicable.  When this is
the case, utilization of a fuel moisture correction  factor  is usually re-
quired.   This is particularly true  in the firing of  wood or bark, in  which the
moisture  content may be  as much as  50 percent  of the fuel weight.  If the
weight percent of  the water in the  fuel is  known the equation would be:
     Q =  heat input rate x [(Fd x stack oxygen correction)

       +     %Hs,0  (in fuel, wt.) x  21.41
          1 - %H20 x 10e  Btu/lb fuel, dry
       +  ^w ~ Fd^ x temPerature correction.                              (2)
This formula accounts for the vaporization  of the moisture  in the fuel as well
as the formation of water due to combustion.  The term
                             %H?0 (in fuel, wt.) x 21.41
                         1 - %H20 x 10 Btu/lb fuel,  dry
converts the weight percent moisture content to a value of  standard cubic feet
per million Btu for the proper units in the equation.  (Note:   For the sake of
simplicity,  not all units are shown in the preceding equation.)  The value of
FW will be known in all  cases where high moisture contents are encountered,
and the term (FW - Fd) is then taken to be zero.

                                       47

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     Another situation frequently encountered is the combination firing of
fuels.   This requires knowledge of the firing rates of each fuel or the per-
centage of total heat input accountable to each fuel.   The total gas volume is
then the sum of each individual F-factor calculation at the same excess air/
temperature conditions.  The following example will utilize both equations
previously shown.

EXAMPLE  Heat input rate = 100 x 106 Btu/h
           50% of heat input attributed to coal
           50% of heat input attributed to wood bark at 50% moisture and
            9,000 Btu/lb (dry basis)
           Stack temperature = 350F
           Stack oxygen content = 10.5 percent
Gas volume due to coal combustion would be calculated as follows:
     Fd = 9,820 dscf/106 Btu
     FW = 10,680 wscf/106 Btu
Q =
     Heat input = 50 x 10s Btu/h = 0.833 x 106 Btu/min
    0.833 [(9820 x 20.92-'i0>5) + (10,680 - 9,820)] x
  = 0.833  (19,734 + 860) x 1.53
  = 26,250 acfm at 350F.
Gas volume due to wood bark combustion would be calculated as follows:

      Fd =  9,640 dscf/106 Btu
      %H20  =  50% or 0.50
      Heat  input = 0.833 x 106  Btu/min
n - 0 RT*  ffqfi40 x     20.9    . +    .5 X  21.41  -.    350 + 460
Q - 0.833  LC9640 X 20.9 - 10.5' +  (1 - .5)(.009)J X    528

  = 0.833  (19,375 + 2,380) x 1.53
  = 0.833  (21,755) 1.53
  = 27,725 acfm at 350F
Total gas  volume = 26,250 + 27,725 = 53,975 acfm at  350 F, 10.5% 02.
                                        48

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     Another related F-factor method utilizing the FW value may be used for
quick calculations of the gas volume.   The equation is
Q = heat input rate x [F-  + stack oxygen correction factor] x cort,ection   (3)
                            ? LrUXIX *JS\J y^-' I  VV I I -\* V I Wl I  I V* vvr i j *x PflY*Y*PPT 1 OH

Although technically less accurate than Equations 1  or 2, it will provide an
estimated gas volume with little error at a moisture content of 10 percent or
less.  This equation will provide a different value  from that derived by Equa-
tion 1 because of the method of measuring stack oxygen.  The methods used in
the field during an inspection (either 02 Fyrite or Orsat) provide their
measurements on a dry gas basis, whereas Equation 3 is intended to be used
with the oxygen measurement on a wet gas basis.  The effect of using the dry
basis measurement is that the equation will produce results that are biased
high.  As the moisture content in the gas stream increases, the error becomes
more significant.
                                        49

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                                   SECTION 3
                          POLLUTION CONTROL EQUIPMENT

     The selection of pollution-control equipment for industrial boilers to
meet particulate emission standards depends on fuel type, method of combus-
tion, fuel and ash characteristics, and the costs of available equipment to
meet prescribed emission requirements.  The available particulate-control
devices include multicyclones, fabric filters, electrostatic precipitators
(ESP's), and scrubbers.  Each of these devices is discussed separately in the
following subsections.

3.1  MULTICYCLONES
3.1.1  Introduction
     The principal mechanical collector used on older industrial boilers is
the multicyclone (Figure 18), which consists of several dozen to several
hundred tubes.  Only a few inches in diameter, each tube is a small cyclone
collector.  As shown in Figure 19, each of these tubes consists of a collec-
tion tube, a gas outlet tube, and a turning vane.  When the unit is operating
properly, gas flows helically down through the annular area between the outer
cylinder and the gas outlet tube, and concentrations of particles move down
the collection tube wall into the hopper.  At the collection tube outlet, the
vertical component of air flow reverses, and the cleaned gas passes upward out
of the tube through the gas outlet tube.
     Because the multicyclone is not very efficient in the collection of
particles smaller than 10 urn in diameter, it cannot be used to control parti-
culate matter from pulverized-coal-fired boilers.  Since stoker-fired boilers
emit larger particles, multicyclones can be used to control particulate emis-
sions if emission regulations are not too restrictive.  Figure 20 presents
typical fractional efficiency curves for a multicyclone collector.   Combustion
problems can produce significant quantities of particulate matter as smoke,
but smoke particles are so small that they will pass through a multicyclone.
                                       50

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b.  Individual tube
from multicyclone
collector.
                                    a.  Typical  multicyclone collector.
                       Figure 18.  Multicyclone collector.
                                       51

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                          CLEAN GAS
   TUBULAR GUARD
                                      OUTLET TUBE OR
                                      CLEAN GAS OUTLET TUBE
                                            DIRTY GAS
                                            TUBESHEET
                           SPIROCONE
                           OR TRICONE
    INLET VANE, RAMP
    OR SPINNER
   ANNULAR AREA
 OUTER CYLINDER
EXTRA THICKNESS
AT WEAR POINTS
                                                    LOCKNUT
CONICAL SECTION
                        FLY ASH PARTICLES

  Figure 19.   Cross section of an individual  cast iron collection tube.
                                52

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                                       AP = 3.0" H20
                                       AP = 2.0" H20
                                       AP = 1.0" H20
                                       MULTICYCLONE COLLECTOR
                                       12" DIAMETER TUBES
                                     I
0
10
20
30       40
PARTICLE SIZE urn
50
60
70
80
     Figure 20.  Fractional efficiency curves for multicyclone.
                                  53

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3.1.2  Operation and Maintenance
     There are several operating conditions and/or malfunctions that can
reduce cyclone performance.  Most of these conditions result in disturbance of
the cyclone vortex, pluggage of gas passages, or interference with the dust
discharge from the cyclone tube.  The following subsections identify the major
failure mechanisms and their effect on collector efficiency.
Gas and Particulate Maldistribution 
     For each cyclone tube to receive the same amount of dust or grain load-
ing, the distribution of gas flow must be uniform both horizontally and verti-
cally across the multicyclone inlet.  Proper duct inlet design requires the
use of turning vanes in many cases.  Sharp duct turns or improperly joined
ducts may result in particle stratification at the outer radius of the turn
which causes increased abrasion and/or dust buildup on the approach to the
collector tube inlet turning vanes.  Figure 21 shows deposits at the entrance
to the inlet of a multicyclone section as a result of particle fallout.
Gas Volume and Pressure Drop
     If the collector is to operate at maximum efficiency, the gas volume and
pressure drop must be at maximum design values.  Operation above design pres-
sure drop may result in increased turbulence and decreased collector efficien-
cy.  Conditions that result in high gas volumes and high pressure drops in-
clude operation at high excess air, ambient air inleakage in the duct prior to
the collector, and boiler  overload.  High excess air and boiler overload are
not generally observed in  utility boiler operations but are common in indus-
trial boiler applications.
     When the boiler is operated at reduced load (firing rate), it generates
less-than-design flue gas  volume and the collection efficiency decreases.  The
reduction in efficiency can be significant when the boiler is operating at 20
to 25 percent below design gas volume.
Inlet Turning Vane Wear
     The inlet turning vane or ramp is designed to impart a tangential motion
to the inlet gas stream of the collector.  This tangential motion is trans-
formed into the vortex in  the collecton tube.  Impaction of particulate on the
turning vane surface results in abrasion and metal wear over the life of the
                                       54

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Figure 21.   Particulate fallout on dirty gas tube sheet.
                            55

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collection tube.  Severe damage results in disturbance of the vortex and in-
creased gas turbulence that limits collection efficiency.   Figure 22 shows
abrasive wear of inlet turning vanes.
Inlet Turning Vane Material Buildup--
     Material buildup on the turning vane or ramp may occur as a result of
particle fallout or it may develop as a scale.   The scale occurs as sulfuric
acid condenses on the cool metal surfaces at low boiler load conditions.  Fly
ash combines with the acid and forms a hard scale when the boiler load and
flue gas temperatures increase.
     The effect of inlet material buildup on collection efficiency is similar
to turning vane wear in that the turning vane vortex is disturbed or it fails
to form.  An improperly developed vortex results in turbulence and short
circuiting of the gas volume to the gas outlet tube without particle separa-
tion.
Collection Tube Weai
     Contact of abrasive particulate with the walls of the collection tube
results in erosion of the tube and eventual failure of the collector tube.
Normal wear occurs at the bottom of the cast iron tube.  As the metal thins,
holes may appear along the bottom of the tube or the dust outlet may become
ellipical or egg shaped.  These conditions result in a poorly formed gas
vortex and an increase in surface roughness and turbulence.  Erosion of the
dust outlet opening increases particle reentrainment and decreases cyclone
collection efficiency.
Collection Tube Scale
     Scaling in the collection tube as a result of acid dew point condensation
results in increased surface roughness and particle reentrainment in the
outlet gas vortex.  Scaling may be periodically scoured by the fly ash  in the
vortex or it may develop  into complete blockage depending on boiler operating
temperatures, load swing, and concentration of S03 in the flue gas stream.
Figure 23 shows scale development on the inside of a collection tube.
Gas Outlet Tube Blockage
     Scaling of the collector may also occur in the gas outlet tube.  Because
the cross sectional area  of the outlet tube is less than the collection tube,
                                        56

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Figure 22.   Inlet turning vane wear because of abrasion.
    Figure 23.   Scale on inside of collection tube.
                           57

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a thick scale may close the tube completely.   The removal  of larger abrasive
particles in the collection tube limits the self-cleaning scouring effect in
the outlet gas stream.
     Partial blockage of the outlet gas tube and increased static pressure
drop reduce the gas volume passing through the tube and the separation effi-
ciency.  Complete blockage of the gas outlet removes the tube from service in
a similar manner to blockage of the inlet turning vane.  Figure 24 illustrates
a plugged outlet tube.
Dust Outlet Tube Blockage
     Severe scaling of the cyclone collection tube may result in complete
closure of the dust outlet opening at the bottom of the tube.  Once plugged
particulate begins to build up in the tubes, the turning vanes are restricted
and there is no flow through the tube because of increased pressure drop.  As
with inlet turning vane blockage, the loss of the collection tube reduces the
effective size of the collector and increases the gas volume through the
remaining tubes.  Figure 25 shows a plugged dust outlet tube.
Air Inleakage Into Ash Hopper--
     In most industrial boiler applications, the flue gas handling fan is
located down stream of the multicyclone (ID fan).  This location places the
collector and duct work under negative atmospheric pressure.  Any opening in
the flue gas stream results in significant air inleakage into the system.
     Inleakage into the hopper area creates a gas flow from  the hopper through
the dust outlet of the collector tubes and into the gas outlet tubes.  This
flow,  depending on the condition of the hopper seals, may account for 10 to 20
percent of the collector gas volume.  The upward flow of gas through the
narrow dust discharge opening at the bottom of the'collection tube increases
reentrainment of fine particulate at the dust outlet and reduces collector
efficiency.  Major points  of hopper inleakage are:  gaskets  between shell
flanges, poor welds,  gasket between ash hopper and ash valve, ash valve,
manhole door gaskets, door frame gasket, and inspection port.
Collection  Bypass
     Bypass of small  volumes of flue gas through the dirty  gas and clean gas
tube sheet  allows a significant weight of particulate  to be  emitted.  Major
areas  of bypass are the gasket seal between the collection  tube and the  dirty
                                        58

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Figure 24.   Plugged outlet tube.
                59

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Figure 25.   Plugged conical section.
                  60

-------
gas tube sheet (Figure 26); welded or pressed joints between clean gas outlet
tubes and the clean gas tube sheet (Figure 27); welded or bolted joints be-
tween tube sheets and collector shell (Figure 28); and welded or bolted joints
between tube sheet sections (Figure 28).
     Penetration may also occur through holes on the leading edge of the gas
outlet tube in the dirty gas plenum.   The tubes are exposed to the dirty gas
and abrasive damage occurs as the gas is directed to the collection tube
turning vanes.  In most cases the pressure drop across the penetration point
is equivalent to the collector pressure drop (3 to 4 inches H20) and allows
substantial gas bypass through the orifice.
     Because most bypass occurs internally to the collector, it is difficult
to determine the points of inleakage while the collector is on-line.  A visual
inspection of the tube sheet, outlet tubes, gaskets, and welds can identify
major penetration points and allow for correction.  Many penetration points,
however, are hidden and will be observed only under a static pressure differ-
ential.  To find these leaks the collector must be sealed, pressurized and
penetration observed visually with a white aerosol smoke.
Hopper Cross Flow                  *.
     Because of space limitations, multicyclone collectors are designed with
multiple rows of collection tubes in the direction of gas flow.  To achieve
maximum efficiency the design must ensure that all collection tubes receive an
equal volume of flue gas.  As gas passes through the initial leading row of
tubes, the total gas volume is reduced and the gas velocity in the plenum is
reduced.  To maintain uniform velocity in many designs, the clean gas tube
sheet is inclined.  In theory, this should maintain uniform flow to each row
of tubes, but in practice the pressure drop across each row of tubes is not
uniform and more gas is directed to the first tube rows.  Systems having
several tube rows and large nonsegmented hoppers experience cross hopper
ventilation.  Flue gas flows out of the dust discharge opening of the inlet
tube.  It flows across the hopper and up through the dust discharge of the
back collection tubes (Figure 29).  Flow across the hopper interferes with
dust discharge and causes fine particulate to be reentrained.  Flow into the
dust outlet also disturbs the gas vortex which also prevents collection tube
dust discharge.
                                       61

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WASHER
        DIRTY GAS AREA
                             CLEAN GAS AREA
                                  -71 CLEAN GAS TUBE
                                                 HOLD DOWN CLAMP
                                     CROSS SECTION OF TUBE MOUNTING
                  Figure 26.  Clean side air leaks.
J
                 LEAK
         DIRTY GAS AREA
                                                 CLEAN GAS TUBE
                                              ROLLED INTO TUBE SHEET
                                               X
                                              CLEAN GAS
                                              TUBE SHEET
                                       CLEAN GAS TUBE
                                                         T
                                  CROSS SECTION OF TUBE MOUNTING
              Figure 27.  Example  of  leaks in clean gas
              outlet tubes and clean gas tube sheet.
                                62

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COLLECTOR
   WALL
                          CLEAN GAS TUBE
                   LEAK

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NORMALL
BETWEEN CL
            NORMALLY SEALED WELDED
          BETWEEN CLEAN GAS TUBE SHEET
              AND SIDE WALL CASING
                                                                   LEAK
                                                         'CLEAN GAS TUBE SHEET
                                                           XL
CROSS SECTION OF TUBE MOUNTING
                       Figure 28.   Clean side air leaks.
                                      63

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     Cross hopper ventilation can be prevented by using a welded baffle at the
hopper valley.   Segmenting the hopper provides a more uniform pressure drop
distribution across the tube sheet.   Cross flow is aggravated when the tubes
are plugged, when scale has formed on outlet tubes, or when there is hopper
infiltration.
3.1.3  Inspection Procedures
     The inspector should perform the following at the start of the boiler
multicyclone inspection:
     1.   Determine opacity.
     2.   Measure system pressure drop.
     3.   Measure air volume.
     4.   Measure system temperature.
     5.   Measure fan speed.
     6.   Measure fan static pressure.
     7.   Measure inlet particle size distribution (if possible).
     8.   Measure hopper discharge weight (if possible).
     9.   Measure wet bulb and dry bulb temperatures.

     After these external inspections are completed, the following internal
inspections should be performed at a future time when the unit can be taken
off line and cooled sufficiently.  Note:  Be sure and follow proper safety
procedures described on Pages 130 to 133 for confined entry.
     1.   Check for inlet distribution buildup.
     2.   Check for inlet vane plugging.
     3.   Check for outlet tube plugging.
     4.   Check for hopper bridging.
     5.   Check for inleakage (corrosion, moisture, or scale).
     6.   Check for leakage between clean and dirty air sides.
                                       65

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      Using the manufacturers'  design parameter specifications  (tube diameter,
 number of tubes,  etc.) the inspector should calculate the inlet velocity at
 maximum and minimum process flow conditions.   These calculated values  indicate
 the multicyclone  efficiencies  at maximum and minimum boiler  conditions.   The
 inspector may find that recirculation or flow control  is  required  at low
 boiler loads for  compliance with emission standards.
      During system field evaluations, the inspector should note observations
 at both low and high boiler loads.   The  external  inspection  allows  the  in-
 spector to obtain sufficient data to estimate air volume  (using fan speeds,
 static pressure,  and temperature) and to determine whether a potential  oper-
 ating problem exists (e.g.,  moisture content or weight discharge from hopper).
 These data,  when  used with stack test data,  allow future  comparisons of system
 operating conditions and performance.  The  internal  inspection reveals  oper-
 ating design problems that may not be determined  by external inspections.
 Such  problems (e.g.,  uneven  distribution,  inlet plugging,  inleakage, and
 leakage from the  clean-to-dirty side) are  not always  indicated by changes in
 system static pressure but can significantly  reduce overall  efficiency.   From
 the external  and  internal  inspection data  and from efficiency  data  supplied by
 the manufacturer,  the inspector can determine the multicyclone mass  emission
 rate  and can anticipate  long-term maintenance and operational  problems.

 3.2  FABRIC  FILTERS
 3.2.1  Introduction
      Fabric  filters  are  becoming increasingly popular  for  the  control of
 particulate  matter from  pulverized-coal-fired boilers, and they  are  used occa-
 sionally on  stoker-fired boilers.   The particulate 'collection  efficiency of
 fabric  filters  is  higher than  for  any other device.  Other principal advan-
 tages are  that  they minimize emissions and circumvent  the  resistivity problems
 associated with some  coals.  The capital costs  of fabric filters generally are
 less than  those of ESP's,  but  they  are more than  those of  mechanical collec-
 tors or  scrubbers.  The  operating costs  for fabric  filters are usually some-
what higher  than those for ESP's and  mechanical collectors, but  lower than
 those for  scrubbers.
                                       66

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     A problem in the application of fabric filters to stoker-fired boilers is
control of coal properties and the combustion process.  A spreader-stoker
operation is sensitive to the size of the coal, particularly the quantity of
fines in the coal.  Excessive fines cause carbon carryover that sometimes
blinds the fabric with sticky particulate matter.  Blinding results in exces-
sively high pressure drops, a reduction in the air flow through the boiler,
and a reduction in boiler capacity.
     The fabric filter is usually designed for high-temperature operation, and
either fiberglass or polytetrafluoroethylene bags are used.  Reverse-air and
pulse-jet bag cleaning mechanisms may be used.  Reverse air units (on indus-
trial plants) are generally limited to an air-to-cloth ratio (A/C) of 2.5
acfm/ft2 of cloth area.  Pulse-jet units can operate at an A/C of 4.0 to 4.5
acfm/ft2.  A precleaner such as a multicyclone or a simple impaction baffle
plate is usually employed to remove the larger, more-abrasive particles before
they enter the fabric filter.  The normal operating pressure drop across a
fabric filter is between 3 and 6 inches H20.  Higher pressure drops have been
experienced on industrial systems.  A typical fabric filter is shown in Fig-
ure 30.
3.2.2  Operation and Maintenance
     Theoretically, fabric filters can achieve mass collection effiencies  in
excess of 99.5 percent when particles are as small as 0.1 urn.  In practice,
many process conditions and installation problems can reduce both the collec-
tion efficiency and the time available for service.  Fabric filters require
extensive preventive maintenance and  inspection to reduce periods of excess
emissions.  The subsequent subsections discuss operation and maintenance of
.fabric filters.   Because reverse air  units are more commonly used, the empha-
sis  is on this type.
Factors  Affecting Bag  Life--
     Dust is removed from the gas  stream by passing the gas through a porous
fabric upon which the  dust deposits and builds a dust cake layer.  The effi-
ciency of dust collection depends  on  the integrity of the  fabric  structure
supporting the dust cake.  Any deterioration of  the fabric structure that
allows localized  failure increases the penetration of dust through the system.
                                        67

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Temperature Excursion
     The most common cause of bag failure from polymer chain breakage is
exposure to high temperatures.  Exposure to temperatures at or near the recom-
mended continuous operating temperatgre level results in random chain breakage
with reduced tensile strength over the life of the fabric.  Typical life of
fiberglass bags at 325F is between 12 and 24 months in service on a indus-
trial boiler.  The life may be greatly reduced if the fabric filter is simul-
taneously exposed to acids and moisture.
     Exposure to temperatures above the recommended continuous operating
temperatures for a few minutes may not result in immediate failure, but will
reduce the overall life of the fabric.  The effects of repeated temperature
excursions on tensile strength are cumulative.  A high-temperature alarm with
an automatic method for bag protection (e.g., quenching, dilution, or bypass)
should be provided.
Pressure Drop
     In normal operation, the system  pressure drop remains between the upper
limit set for cleaning (time  duration between cleaning periods or pressure)
and  the lower level after cleaning.   An  increase in static pressure drop
between cleaning  (upper limit) indicates  a change in fabric/cake resistance
(permeability).   This  change  can  result  from  changes in amount of cake buildup
retained, oil deposits from the compressed air system, or moisture from in-
leakage.  The increased pressure  drop may be  tolerated if it  is not severe  or
if it does  not decrease ventilation performance because of decreased  volume of
gas  exhausted.
      If an  increase  in pressure drop  occurs,  attempts  should  be made  to diag-
nose the  cause  (oil,  moisture), and corrective action  should  be taken.  An
increase  in cleaning  energy beyond manufacturers' recommendations  should  not
be made,  because  it  shortens  bag  life.
Cake Release
      The  ability  to  remove  collected  particulates  (cake)  from the  fabric
 surface determines the cleaning  frequency required  for the  filter  system.
 Factors that affect the  energy necessary to  remove  the cake  include  cake
 composition, porosity, and the effectiveness of  the energy  transfer  to the
 cake/filter interface.

                                        69

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      The  presence  of moisture  either  from  operation  below the dewpoint or from
 inleakage through  the shell  presents  a  similar  problem.  The cake release is
 impaired,  and  increased  energy is  required to remove the cake.  When the
 boiler  is  shut down,  it  is advisable  to continue to  operate the baghouse for
 one  complete cycle (including  cleaning).   This  operation purges it with clean
 air  to  avoid condensation and  ensure  that  bag contaminants are removed.
 Cleaning  Intensity
      The  removal of the  dust cake  requires  the  breaking of the cake structure.
 Too  little energy  does not break the  cake,  and  too much energy increases bag
 failure because of fiber abrasion.  The proper  intensity is defined as the
 minimum amount necessary to  remove the  proper amount of cake.  Each boiler is
 unique, and identical boilers  at a site may not have the same cake release
 properties because of source variability and/or gas  stream characteristics.
 Therefore, the required  cleaning intensity  must be matched to the system.
      The proper cleaning of  the bag requires the flexing of the surface to
 dislodge the cake.   If bag tension is low,  the  bag may be flexed adequately at
 the  top, but the standing wave dampens  as  it is transmitted downward.   The
 installation of each  bag must  be checked to ensure proper tension.  Manufac-
 turers' literature  should be consulted  to determine  the correct tension
 method.  The fabric may  elongate because of the weight of dust collected
 between cleaning cycles  or bag tongues  may  slip in hangers.   Thus, tension may
 change with time of service.
      In reverse-air collectors, the cake is released by collapsing the bag
with  reversal  of gas  flow.    The bag is  flexed,  and the cake removed from the
 surface by the cleaning  gas.    In systems with short  bags [i.e.,  bags less than
 2.5 m (8 ft) long], bags may be allowed  to  collapse,  almost completely.   The
bag must be reinflated in a  snap action, and a  dwell  time must be allowed for
the dislodged  cake to flow from the bag  before  gas filtration commences.   In
this case low  bag tension results in complete closure of the bag near the
thimble, reduction of reverse gas flow through the bag, and consequently
reduction of cleaning efficiency (Figure 31).
Tube Sheet Bridging
     In shaker or reverse-air fabric filters,  dust cake is collected on the
interior surface of the bags.  The removal  of the collected dust cake  requires
                                       70

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                          TOP VIEW
                                            AREAS WHERE
                                             CLEANING
                                            IS PREVENTED
                                            BECAUSE OF
                                            BAG CLOSING
                          SIDE VIEW
                                    FLOW OF REVERSE  AIR
Figure  31.  Impaired cleaning  in a reverse-air  fabric filter.
                                  71

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 the free fall of the dust through the thimble and into the dust hopper.   When
 systems are uninsulated or when the gas temperature is near the dewpoint, cake
 accumulates on the underside of the tube sheet and on the inside of the thim-
 bles.   Heat is transferred from the tube sheet to the uninsulated baghouse
 shell.   The colder metal reduces dust temperatures and causes agglomeration
 and deposition on the surface.
      As caking increases,  the ability of the dust to discharge through the
 thimble is reduced.   Eventually, complete bridging of the bag results.   In
 severe  cases, the accumulation  may extend several feet into the bag.   The
 bridging occurs most commonly near the baghouse shell  (outside rows)  or  near
 doors where air inleakage  from  deteriorated gaskets  occurs (Figure 32).   The
 bridge  may normally'be dislodged by flexing the bag  with the hand near the top
 of the  thimble.   The dust  above the bridge, because  it is exposed to  the gas
 stream,  is free flowing and discharges after the cooler cake is broken near
 the tube sheet.
     The breaking of the cake only returns  the bag to  service for a short
 period;  bridging soon recurs.   Continued operation in  this condition  decreases
 net cloth area and increases  pressure  drop.   The higher A/C ratio increases
 bag abrasion  and decreases  bag  life.   The solution to  the problem is  to  reduce
 heat loss through the tube  sheet/shell  by installing insulation or increasing
 the system temperature.
 Abrasion
     The failure of  the  fabric  may occur over a  long period of  time because of
 the abrasive  action  of dust particles  on individual  fibers  in the  structure.
 The failure may  result from general abrasion  over a  large  area  or  specific
 attacks  in concentrated  areas.
     Local intensive  abrasion,  which results  in  premature  bag failure, is
 undesirable and  can be prevented.   High  abrasion  rates  are  commonly associated
with improper bag  installation  or  design  flaws in  the collector.   Some common
causes of failures are described below.   Each case of abrasion  failure must be
addressed separately  to  determine  if corrective  action may be taken to reduce
the frequency of failures.
     In shaker and reverse-air  fabric filters, the bag can be attached to the
tube sheet by a thimble  and clamp  ring design or by a snap ring design.
Figure 33 shows the two methods of attachment.  Dust enters the baghouse

                                       72

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Figure 32.   Bridging near baghouse shell caused by
     cooling a poorly insulated fabric filter.
                         73

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                         THIMBLE AND CLAMP  RING  DESIGN
                POOR
                                BETTER
CLAMP
                             INCREASED
                             ABRASION
1



J 	 <\
BAG


1
w^w^
LONG
t THIMBLE

1


.x- LONG CUFF AND
* REDUCED ABRASION
,L 	
w///m,
/ >
GAS flOV y TUBE SHEET '
               POOR
              BAG
         CUFF
         WITH
         SNAP
         RINS
      POOR
                                SNAP RING DESIGN
                        SHORT  CUFF
                        NO THIM8LE
   INCREASED
^ABRASION
                             BETTER
                                                       BAG
                                                   CUFF WITH
                                                   SNAP RING
                                                                     LONG CUFF AND
                                                                   ,REDUCED ABRASION
                                                          6AS FLOW
                  Figure 33.   Methods  of bag attachment in
                   shaker and reverse-air fabric  filters.
                                               TUBE SHEET
                                                   AND
                                                 THIMBLE
                                        74

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filter at the hopper in a horizontal direction and must turn vertically to
enter the tube sheet thimbles.  Heavy particles with higher inertia do not
follow the flow and therefore do not enter the opening parallel to the thimble
walls.  The particles impact on the walls of the thimble and, if the thimble
is short, on the fabric above the thimble.  The action of the particles strik-
ing at an angle to the fiber surface increases abrasion.  Roughly 90 percent
of bag failures occur near the thimble.  The use of double-layered fabric
(cuffs) or longer thimbles reduces the failure rate.
     In the snap ring system no thimble is used, and in some cases a cuff is
not used.  This exposes the bag to rapid abrasion a few inches above the snap
ring.   Add-on tube sheet thimbles may be used to reduce the effect.
     Baffle plates or diffusers may be used to deposit large particles in the
hopper before they contact the bags.  The orientation of the plates is criti-
cal, however, because deflection of incoming gas into the hopper can resuspend
collected dust and increase effective dust loading through the tube sheet.
The resuspension is reduced if the hoppers are operated with continuous dust
removal; thus, dust remains below the gas inlet.  A cyclone also may be in-
stalled as a precleaner to remove larger particles and reduce inlet loading.
     It is common practice not to remove dust that accumulates on the clean
side of the tube sheet.  The presence of dust is not a significant problem as
long as penetration is not occurring.  Heavy dust accumulation, however,
results in rapid abrasive failure; of serviceable bags.   When the dust that has
been emitted from previous bag failures settles on the tube sheet and collects
around a bag, the weight collapses the bag and forms an orifice (Figure 34).
The reduction in area increases gas velocity and therefore abrasive damage to
the bag in the area of the restriction.  The increased tension of the bag also
results in abrasion of the bag where it contacts the top edge of the thimble.
Prompt removal of accumulated dust from the tube sheet after a bag failure can
reduce damage to other bags.
Chemical Attack
     The fabric types used in fabric filters in industrial boilers are Nomex
      
Teflon , and coated fiberglass.  Nomex is particularly susceptible to sulfuric
acid attack below the acid dewpoint.  Fiberglass is susceptible to attack by
hydrogen fluoride (HF) although this normally is not a problem in industrial
                                       75

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                                                                               BAG
                                                                               DAMAGE
                                                                             OCCURS HERE
                                                                       '.1 j'l i 'icS ^CJ'.;--
Figure  34.  Abrasive damage caused by accumulation  of dust  on the tube  sheet.
                                          76

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boilers.   The fabric filter should be operated at the lowest temperature con-
sistent with avoiding moisture or acid condensation.
     When boilers frequently shut down, bags can quickly be destroyed because
of temperature excursions through the acid and moisture dewpoints.   Shutdown
should be accomplished by exhausting flue gases from the filter with dilution
air (ambient) before cooling gases below the dewpoint.  The purging removes
the S02 and water vapor before condensation can occur on bag surfaces.
Installation of Bags
     The improper installation of bags can result in premature failure of the
bags and increased emissions.  The capital cost due to these failures can
become significant and reduce production if downtime is required to change
bags.  This subsection is included to supplement manufacturers' instructions
for installation of bags.  The items covered are those that have been demon-
strated by field experience to result in high bag failure rates.
     Bags in shaker and reverse-air systems should be installed from the outer
walls toward the center of the compartment.  Bags should be hung according to
manufacturers' recommendations by loop/hanger, eye-bolt/J-hook, or tongue/
hanger assemblies.  Each bag should also be inspected before hanging to ensure
that it has no holes, is the proper size, and has a proper seam.  Normally,
the bags should be hung by row, the cuffs should be placed over thimbles, and
the ring clamps should be attached.  The fit of the bag over the thimble
should be checked, and loose fitting bags should be discarded.  Small bags
that fail to meet specifications should not be forced over the thimbles.
     After a bag is clamped, the tension should be adjusted to the manufac-
turer's specifications by using a spring tensioning device or tightening the
bag to a known length.   In no case should the bag be  allowed to hang  freely
and  fold over the thimble.   Also, tension must be uniform  in all bags to
provide uniform cleaning efficiency.
     When a bag farther  than the second row from the  walkway must be  replaced,
the  intervening bags  should  be temporarily removed to allow safe installation
of the replacement bag.  Otherwise,  the intervening bags can be stretched and
damaged, the proper  installation and tensioning of the  replacement bag  can  be
difficult.  Figure 35 illustrates correct and  incorrect installation  of bags.
To avoid snagging and puncturing bags, maintenance personnel should not carry
tools while  in the compartment.

                                       77

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       oo
DAMAGE
                     oo
        CORRECT
       INCORRECT
Figure 35.  Correct and incorrect installation of bags.
               78

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     The proper installation of a snap-ring-type bag requires collapse of the
ring inward with the fingers and insertion of the cuff into the tube sheet
opening.  The circular portion of the ring should be placed in the seat, and
the ring should be released.  Fingers should be placed inside the ring allow-
ing the bag to collapse into the tube sheet opening, and the ring should be
pressed into place.  The bag should be tensioned as necessary (Figure 36).
Hopper Bridging
     Bridging is a term applied to the blocking of dust discharge through an
opening by the agglomeration of the dust.  Bridging commonly occurs a short
distance above the apex of the fabric filter hoppers and results in partial or
complete closure of the discharge.
     Common causes of the agglomeration are moisture, oils, and temperature
drop.   In fabric filters that operate below or near the dewpoint, the added
drop in temperature in the hopper as a result of radiative cooling initiates
agglomeration of the dust.  Moisture enhances agglomeration of the dust, and
cake gradually builds up.   The area available for dust discharge is reduced
and complete bridging eventually occurs.   Agglomeration can be initiated by a
drop in dust temperature resulting from air inleakage through flanges, gas-
kets,  doors, or weld failures in the hopper.
     Continuous or repeated occurrences of hopper bridging indicate a chronic
temperature or moisture control problem in the ventilation and control equip-
ment system.  Careful inspection of hoppers should be made to determine gas
inleakage points, and repairs should be made.   Bridging is not a common prob-
lem in tight systems that are insulated and that operate at proper tempera-
tures.
Dampers
     Dampers are used to direct gas flows ov isolate compartments for cleaning
or repair.   If these dampers do not function to seal the compartment in shaker
fabric filters or to change the direction of gas flow in reverse-air fabric
filters, proper cleaning of the bags cannot be accomplished.   Malfunction
increases pressure drop, but in multiple-compartment systems does not neces-
sarily shut the system down.  Because all dampers leak under adverse condi-
tions,  dampers and seats should be inspected to minimize leakage.
                                       79

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               SNAP RING
               WOUND WITH
                  FIBER
                        TUBE SHEET
Figure 36.   Proper method  of  installing bag in tube sheet with snap rings.
                                    80

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 Compressed  Gas  System--
      The  air  used  to  activate  the  dampers  and  pulse-clean  bags must  be  clean
 and  dry.  An  in-line  gas  dryer (such  as  a  dessicant,  refrigerant,  or filter)
 should  be used  to  remove  oil and water from  the  gas  stream prior to  introduc-
 tion to the filter.   As a safety precaution, a reserve  tank with blowdown
 should  be used  at  the filter to collect  oil  and  water.   If not collected, oil
 and  water blind bags  and  can freeze in diaphragms during cold weather.  The
 dryer should  be serviced  according to the  manufacturer's recommendations.  An
 internal  inspection of the filter  bags should  be conducted periodically to
 check for oil and  water.
 Pulse Diaphragms--
      Pulse  diaphragms are used to  open the valve seat in pulse-jet cleaning
 systems and provide a sharp finite surge of  compressed  gas  through the blow
 tube to the venturi.   The diaphragm in the closed position  is held against the
 seat by compressed air and a spring.  The  compressed air is discharged through
 a solenoid  valve and  creates a pressure differential, which pulls the dia-
 phragm  from the  seat.  This momentarily allows passage  of  gas under  the seat.
 Closure of  the  solenoid valve  reestablishes the  seal.
      The  solenoid commonly fails because of water freezing  in the gas stream
 or because  of electrical  failure.   In either case, the  cleaning pulse cannot
 be initiated.    If the  solenoid does not seat, a  constant release of  compressed
 gas  is heard.
      The  cleaning system  can also fail because of diaphragm rupture  or impro-
 per  diaphragm seating.  Constant bleeding  of compressed gas into the blow tube
 is then heard.
      A reduction in cleaning efficiency can occur if the diaphragm returns to
 the  seat  sluggishly.   This can be caused by water, oil,  or grit fouling the
 return spring, and can be  detected audibly as a sharp pulse that trails off.
      In evaluating the pulse cleaning system, the -inspector should inspect the
 reserve air tank for water and listen for malfunctions of each pulse system
through one cleaning cycle.
3.2.3  Inspection Procedures
      Internal  inspections of fabric filters are the only truly reliable means
for  identifying fabric filter problems.   An external  check only determines

                                       81

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gross emissions (high opacities) caused by missing or torn bags.   Items  that
should be checked in an external inspection include:
     0    Pulse jet system pressure
     0    Solenoids
     0    Reverse air blowers
     0    Shakers
     0    The solids removal system, including the screw conveyor, the
          pneumatic conveying system, heaters, and vibrators.
Pressure drop across each compartment and the total fabric system should be
measured.  However, pressure drop measurements are only effective for indicat-
ing  if a compartment is out of  service since pressure drop tends to equalize
over the compartments, even those with missing or plugged bags.  Comparison of
the  overall pressure drop with  previous inspection measurements can indicate
trends in overall fabric filter condition.
     Internal inspections can indicate many of the problems and malfunctions
discussed earlier.  However, internal inspections must be made with the unit
off-line; adequate  safety precautions should be taken to insure that safety is
not  compromised.  Safety precautions are  outlined in Section 4.
     The internal inspection checks the condition of the fabric bags.  The  in-
spector  should  look for bag tears,  bag deterioration either  by erosion or cor-
rosion,  missing bags,  bags with oil from  a compressed-air  system, wet bags
from acid dewpoint  problems or  inleakage,  improper bag tension, and deposits
on the clean  air side  of the fabric filter.   Hoppers can be  checked for incom-
plete solids  removal and corrosion.  Appendix A contains a detailed checklist
for  performing  a fabric filter  inspection.

3.3   ELECTROSTATIC  PRECIPITATORS
3.3.1   Introduction
      Electrostatic  precipitators  incorporate  three basic  processes:   1) trans-
fer  of  electric charge to  suspended particles in  the gas  stream,  2)  estab-
lishment of an electric field  to  remove  the  particles  to  suitable collecting
electrodes, and 3)  removal  of  particles  from the  electrodes  and particle
                                        82

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 collection with  as  little  Toss  to  the  atmosphere  as  possible.   Figure  37
 illustrates  these basic  processes.
     An  ESP  consists  of  a  thermally  insulated  steel  housing,  its  internal  com-
 ponents,  and its power supply equipment.   The  internal  components  include
 grounded steel plates (collecting  electrodes)  and metal  rods  or wires  (dis-
 charge electrodes)  that  are  suspended  between  the plates.   The  discharge elec-
 trodes are insulated  from  ground and are  negatively  charged at  15,000  to
 80,000 volts d.c.6  The  electrical field  between  the wires  and  plates  ionizes
 electronegative  gas molecules (e.g., 02,  S02)  that charge the suspended parti-
 cles.  The electrical charge creates a force on the  particles (about 3000
 times the force  of  gravity)  that pulls them toward the  collection  plates.  The
 collected dust particles are removed by periodical rapping  of the  collection
 plates,  which causes  the dust to fall  in  sheets into a  receiving hopper.
     Most precipitators  use  plate-type collection electrodes and pyramidal
 hoppers.  Figure 38 presents an example of this type of  precipitator.  Gas
 flow through the ESP  is  normally horizontal.
 3.3.2  Resistivity  Effects
     Dust resistivity outside the  range of 108 to 1010 ohm-cm can  greatly
 limit precipitator performance.   Fly ash  resistivity depends primarily on the
 chemical composition  of the  ash, the ambient flue gas temperature, and the
 amounts of water vapor and sulfur  trioxide (S03)  in  the  flue gas.   At tempera-
 tures below  80C (175F), current  conduction occurs  principally along the
 surface  layer of the dust and is related  to the absorption of water vapor and
 other conditioning agents in the flue  gas.  Resistivity  of fly ash is inverse-
 ly related to the amount of  S03 and moisture in the  flue gas.   Because low-
 sulfur coal   releases very little S03,  high-resistivity fly ash results.  At
 elevated temperatures up to  200C  (400F), conduction takes place primarily
 through the bulk of the material, and  resistivity depends on the chemical
composition of the material.   Carbon carry-over has  very low resistivity and
 is hard to hold on the collecting plates.   Above  200C (400F),  resistivity is
generally below the critical  value of 1010 ohm-cm.   Figure 39 shows a typical
relationship  between resistivity and temperature.
                                       83

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                                                                        Transformer-Rectifier
                                                                                           Ground Switch Box
                                                                                           on Transformer
         Top End
          Frames
     High Voltage
       Conductor
         High Tension
     Support Insulators
       Perforated
     Distribution
          Plates
    Bottom End
        Frames
Upper H.T. Hanger Assembly
 (Hanger and Hanger Frame)
          Upper H.T. Wire
           Support Frame
                                                                                                   Discharge Electrode
                                                                                                   Vibrator
                                                                                                        Collecting Electrode
                                                                                                        M.I.G.I. Rappers
           Top Housing
           Hot Roof
           Access Door

           Hot R6of
                                                                                                         Side
                                                                                                         Frames
           Discharge
           Electrode

           Access Door
           Between
           Collecting Plate
           Sections

            Precipitator
            Base Plate

            Slide Plate
            Package

            Support Structure
            Cap Plate
                                                         Steadying Bars
                                                                                              Lower H.T.
                                                                                              Steadying Frame
Collecting
Electrodes
                 Figure  38.    Typical electrostatic  precipitator with top  housing.
     Courtesy of Research  Cottrell.
                                                          85

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(RESISTIVITY]
                                         1111111
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                         TEMP., C
Figure 39.   Typical temperature-resistivity relationship.
                             86

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3.3.3  Instrumental on
     Reliable ESP performance depends on the effective control of operating
parameters.  An ESP should be equipped with instrumentation to monitor and
record the major operating parameters that indicate ESP performance, and the
inspector should be able to understand these basic ESP data.
     Electrostatic precipitator instrumentation includes monitors for power
input, rapper intensity, and hopper dust levels.  The power input parameters
include precipitator current, voltage, and spark rate.  The instrumentation is
generally located close to the ESP unit.  When a plant has more than one ESP,
a centrally located control room may contain the instrumentation for all of
the ESP units.
     An ESP power supply usually includes several transformer-rectifier (T-R)
sets, each having one or more' bus sections.   Primary voltage and current are
measured for each T-R set; spark rate, secondary voltage, and current are
measured for each bus section.   Sometimes oxygen and temperature are measured
at the ESP inlet.   An opacity sensor is frequently located at the ESP outlet
to indicate emission levels.   The ESP shown in Figure 40 has four primary
voltmeters and four primary ammeters.  Instrumentation on the secondary side
consists of eight voltmeters, eight ammeters, and eight spark rate meters.
Primary Instrumentation
     Most ESP's are equipped with a primary voltmeter, and normal operating
voltage is 250 to 460 volts.   An indication of zero voltage on the primary
side may be due to an open primary circuit.   An indication of high voltage on
the primary is unlikely, but it could be due to an open transformer primary
circuit or an improper connection.   A faulty, open, or disconnected precipita-
tor; an open.bus;  or a faulty rectifier will  also cause the primary voltage to
be high.   An indication of low voltage on the primary side could result from
several conditions such as a leak in the high-voltage insulation, a high dust
level in the hoppers, excessive dust on the electrodes, or swinging elec-
trodes.
     The ammeter on the primary side of the ESP indicates that the current is
being drawn by the ESP.   Together,  the current and voltage readings on the
primary side indicate the power input to a particular section of an ESP.
Sometimes an ammeter is labeled to indicate the normal range of primary
                                       87

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88

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current, but the range is different for each unit, depending on design, size,
and operating conditions.  Baseline conditions established during a compliance
test are a more reliable indication of proper operation.  Any deviation from
this range indicates abnormal operation.  If the primary current and voltage
are both zero, this indicates an open primary circuit.  Low primary current
combined with high primary voltage suggests an open transformer primary or
secondary circuit.  Low primary current and voltage indicate an open d.c.  rec-
tifier.
     Irregular primary current coupled with low primary voltage indicates a
high-resistance short in the circuit.  Possible causes are an electrode short
with dust in the hopper, excessive dust on collecting surfaces, excessive dust
on electrodes, support insulator arcing, or the presence of foreign materials.
A broken swinging electrode will cause an intermittent short, which is indi-
cated by low primary voltage and cycling primary current.
Secondary Instrumentation
     Because primary instrumentation can be very misleading, the use of
secondary meters is often more useful.  Secondary instrumentation indicates
the electrical parameters for individual bus sections.  The instrumentation
generally includes a kilovoltmeter, a mi Hiammeter, and a spark rate meter for
each bus section.   The secondary voltmeter, which shows the voltage at the
discharge electrodes, is sometimes labeled to indicate the normal operating
voltage range.  The indicated range may not be very reliable, however, and
baseline conditions from a compliance test are probably a better indicator of
proper operation.   Zero voltage on the secondary may be due to an open primary
circuit.  High voltage on the primary side and no voltage on the secondary
side indicate a faulty, open, or disconnected precipitator; an open bus; or a
faulty rectifier.
     Low voltage on the secondary side coupled with the low voltage on the
primary side could result from several operating problems such as a leak in
the high-voltage insulation, excessive dust in the hoppers or on the elec-
trodes, or swinging electrodes.   Correction may require shutdown.
     The secondary ammeter indicates the discharge electrode current.   The
current and voltage readings on the secondary side indicate the power input to
the discharge electrodes.
                                       89

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     The secondary current is measured in mi Hi amperes.   The secondary ammeter
is usually labeled to indicate the normal secondary current range.   Deviation
from that range indicates improper operating conditions  in the precipitator.
The absence of secondary current and voltage indicates an open primary cir-
cuit.  Minimal secondary current in association with high voltage is generally
due to an open transformer primary or secondary circuit.  An open d.c. recti-
fier will cause a low current flow and low voltage in the circuit.   As with
primary circuitry, irregular secondary current coupled with low secondary
voltage indicates a high-resistance short in the circuit.  The short is usual-
ly caused by excessive dust, foreign materials, or arcing.  Again,  a broken
swinging electrode causes an intermittent short, which  is indicated by low
voltage and cycling current.  On coal-fired industrial  boilers, the optimum
spark rate is around 100 sparks per minute.  Excessive  sparking reduces avail-
able power for particle charging; a low  spark  rate indicates a reduction in
power supply.
External Instrumentation--
     Certain  instruments external to the ESP that are useful for diagnosis of
ESP  operation include instruments that measure inlet gas  flow, inlet  gas
temperature,  and  flue gas opacity at the ESP outlet.  Instruments also monitor
the  condition of  the hopper  ash discharge system and the  rapping system.
Because  federal and state regulations generally limit the opacity of  the flue
gases as well as  particulate emissions,  many ESP installations are  equipped
with continuous opacity  recorders.
     The gas  flow rate and  temperature are  indicators of ESP  loading.  Varia-
tions from  the  normal design ranges will affect ESP  performance  and should be
investigated.
     Efficient  removal of ash from  the hoppers is  important for  proper ESP
performance.  Ash removal systems at  ESP installations  are  generally  equipped
with instrumentation  for monitoring hopper  emptying  cycles.   Hopper level
alarms  are  also common  and  useful.   Control  panel  lights are  used  to  indicate
the operation of  hopper  heaters  and vibrators. Zero motion switches  may be
 used on rotary  air-lock valves and  on screw conveyors to detect  malfunctions.
 Pressure switches and alarms may be used on pneumatic dust handling systems  to
 detect operating problems.
                                        90

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3.3.4  Operation and Maintenance
     The following subsections present ESP operating procedures and mainten-
ance requirements and describe common ESP malfunctions.  This  information will
help .the inspector determine whether or  not the company has an adequate main-
tenance program.
Power Supply
     During normal operation, the power  to the ESP  is optimized by automatic
controls that vary the power in response to the spark rate.
Rappers and Vibrators
     The rapper system mechanically removes dust from the collecting plates.
The most common system consists of magnetic-impulse, gravity-impact rappers
that periodically impact the collecting  plates to remove dust deposits.  The
main components of the system are the rappers and the electrical controls.
The electrical controls provide separate adjustments for various groups of
rappers; these can be independently adjusted from zero to maximum rapping
intensity.   The control cycles are adjusted to regulate the release of dust
from the collecting plates and to prevent undesirable puffing from the stack.
     During normal operation, a short-duration d.c.  pulse through the coil of
the rapper supplies the energy to elevate the steel  slug.   The slug is raised
by the magnetic field of the coil and then allowed to fall back and strike an
anvil bar connected to a bank of collecting electrodes within the precipita-
tor.  The shock transmitted to the collecting electrodes dislodges the accumu-
lated dust.  In some applications, the magnetic-impulse, gravity-impact rapper
is used to clean the ESP discharge wires.  For this  purpose, the rapper
strikes the electrode supporting frame in the same manner, except that an
insulator isolates it from the high voltage of the frame.   Some installations
have mechanical  rappers consisting of a  single hammer assembly mounted on a
shaft which raps each frame.   A low-speed gear motor is linked to the hammer
shaft by a drive insulator, fork, and linkage assembly.   Rapping intensity is
governed by the hammer weight,  and frequency is governed by the shaft rotation
speed.
     A vibrating system can be used on either the collecting plates or the
discharge wires to dislodge accumulations of particles.   The vibrator is an
electromagnetic device whose coil  is energized by alternating current.   Each

                                       91

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time the coil is energized, the resulting vibration is transmitted through a
rod to the high-tension-wire supporting frame or collecting plates (Figure
41).  The number of vibrators depends on the number of high-tension frames or
collecting plates in the system.
     For each installation, a certain intensity and period of vibration will
produce the best collecting efficiency.  Low intensity will result in heavy
buildup of dust on the discharge wires which reduces the sparkover distance
between the electrodes.  This limits the power input to the ESP and tends to
suppress formation of the ions required for precipitation.  Dust buildup also
alters the normal distribution of electrostatic forces in the treatment zone
and can lead to oscillation of the discharge wires and the high-tension frame.
Because reentrainmeht from rapping can be a significant portion of the total
emissions, it is important that the rapping system be adjusted to minimize
reentrainment.
Maintenance Requirements
     At each ESP installation, the inspector should encourage the facility
operator to follow a preventive maintenance schedule that lists the ESP parts
to be checked and maintained daily, weekly, monthly, quarterly, and in speci-
fied situations.  Such a schedule will help to ensure that the unit functions
properly on a daily basis and that emission violations and opacity problems
are minimized. Table 4 summarizes the maintenance procedures that the inspec-
tor can use to aid the source in setting up an effective preventive mainten-
ance program.
3.3.5  Malfunctions
     ESP equipment components are subject to failure or malfunction that can
cause an increase in emissions.  Malfunctions may be caused by faulty design,
installation, or operation of the ESP, or they may involve electrical, gas
flow, rapping, or mechanical problems.  The inspector should be aware of the
common ESP malfunctions, their  effects on emissions, corrective actions, and
preventive measures.  Generally stat,e  and local control agencies require plant
officials to report excess emissions that are caused by ESP malfunctions.
Table 5 lists common ESP problems.
     Monthly records of all malfunctions should be kept by plant and unit,
along with total hours that T-R sets are operated, number of hours T-R sets
                                        92

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DISCHARGE
ELECTRODE
VIBRATOR
DISCHARGE
ELECTRODE
VIBRATOR
                                                        DISCHARGE  ELECTRODE VIBRATOR
                                                          AND INSULATOR ASSEMBLY
   COLLECTING
   ELECTRODE
   RAPPER
                           RAPPER
                          COUPLING
  COLLECTING ELECTRODE RAPPER
   AND INSULATOR ASSEMBLY
                   Figure 41.  Vibrator and rapper assembly,
                     and precipitator high-voltage frame.
                                       93

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   TABLE 4.   MAINTENANCE SCHEDULE FOR ELECTROSTATIC PRECIPITATORS.
Enter on daily log

1.   Boiler operating parameters
2.   Flue gas analysis
3.   Coal characteristics
4.   T-R control set readings
5.   Transmissometer calibration

Check daily

1.   T-R control set readings
2.   Rapper and vibrator control settings
3.   Ash removal system
4.   T-R control room ventilation system

Check Weekly

1.   Operation of rappers and vibrators
2.   Control sets (for internal dirt)
3.   Air filters for control sets and ESP penthouse

Enter on weekly log

1.   ESP voltage-current data
2.   Graph ESP voltage-current  data

Check monthly

1.   Pressurization of ESP penthouse
2.   Standby fan operation (manually)

Perform quarterly

1.   Clean and  dress contact surfaces of  HW-FW electrical  distribution.
2.   Lubricate  pivots.

Perform semiannually

1.   Clean and  lubricate access door  hinges  and test connections.
2.   Inspect exterior  for  loose insulation,  corrosion,  loose  joints,  and
      other defects.
3.   Check for  points  of gas leakage  (in  or  out).
                                   94

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TABLE 4.  (continued)

     Perform annually

     1.    Thorough internal inspection:

          Check for possible leaks of oil,  gas,  or air at gasketed
           connections.
          Check for corrosion of any component.
          Check for broken or misaligned wires,  plates,  insulators,
           rappers, etc.
          Check high-voltage switchgear and interlocks
          Check all insulators and check for hairline cracks  or tracking.
          Check expansion joints on hot ESP's.

     2.    Check for signs of hopper leakage, reentrainment of particulate,
           distribution  plate blockage,  and poor gas  distribution.

     3.    Check for dust buildup in inlet and outlet  flues.

     4.    Check for dust buildup in hoppers.
                                      95

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                                                 100

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are not operating, maximum number of sets out at one time, and monthly/yearly
availability of the ESP unit.  Daily logs should be kept for each ESP, with
remarks on outages in each section of the ESP.
3.3.6  Inspection Procedures
Data Collection and Review of Operating Records--
     The inspector should review both process and ESP operating records for
completeness and for changes in operation that may have affected ESP perform-
ance.   Table 6 lists a number of items for which records should be kept.
Malfunctions of both the process and the ESP should be discussed with plant
officials, and the inspector should determine what is being done to remedy any
recurrent problems.
     The first item that the inspector should check is the control sets for
the ESP, which are usually located in a room near the ESP.  Plant personnel
should provide a diagram showing which fields are served by which T-R sets, as
a guide for determining out-of-service fields when reading the T-R sets.
Control panels can include primary and secondary current and voltage meters,
and a spark rate meter.  If the ESP has several sections, the voltage, cur-
rent,  and spark rate should be recorded for each section.  The control set
readings should be compared with calibrated or design values for each section.
The inspector should check the daily log of control readings to determine
whether the readings have been drifting from normal.   Drift may indicate such
problems as air leakage into air heaters or into ducts leading to the ESP,
dust buildup on ESP internals, and/or deterioration of electronic control
components.  The inspector should also note inoperative meters, the number of
power supplies on manual control, and T-R sets on automatic control that may
be operating below design specifications to reduce wire breakage.
     The inspector can utilize the meters to aid in diagnosing other ESP prob-
lems.   The effects of fluctuating gas conditions on control readings are
presented below:
     1.   The voltage increases and the current decreases when the gas
          temperature increases.   Arcing can also develop.  The voltage
          decreases and the current increases when the gas temperature
          decreases.
                                       101

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-------
     2.    The  current  and  voltage  increase when  the  moisture  content  of
          the  gas  increases  for  any  given condition.

     3.    The  voltage  increases  and  the  current  decreases  when  there  is
          an  increase  in the concentration of the  particulate matter.

     4.    The  voltage  increases  and  suppresses current when there  is  a
          decrease in  the  particle size.

     5.    The  voltage  increases  and  depresses current when there  is a
          higher gas velocity through the ESP.

     6.    Reduced voltage  may be caused  by air inleakage that causes
          sparkover in localized areas.

     7.    A number of  ESP  fields in  series will  show voltage-current
          ratios decreasing  in the direction of  gas  flow.

     8.    The  voltage  is drastically reduced and the current  increases
          when a hopper fills with dust  and  causes a short.

     9.    Violent arcing,  indicated  by the meters  swinging between zero
          and normal,  occurs if a discharge  electrode breaks.

    10.    The voltage  drops  to zero  at a high current reading if  a T-R
          unit shorts.

    11.    A voltage increase with normal current levels occurs  if a
          discharge rapper fails and the discharge wires build  up with
          dust.

    12.    A voltage decrease with normal current levels under sparking
          conditions occurs  if a plate rapper fails.

     Table 7 presents  specific examples  of  the effect of changing conditions
on ESP control set readings.  These  examples are typical of  what  the  inspector
may find.  The inspector should become familiar  with these meter  reading
techniques so as to detect problems  during  an inspection.

Electrical Equipment--
     The T-R sets., rappers,  and/or vibrators are often located on top of the
ESP in the penthouse.   The control sets  are  most commonly found in the boiler
control  room.   The T-R sets, insulators, and rapper/vibrators should be in-

spected.
     The inspector should examine insulators for moisture and cracking from

arc-over.  Cracks can be spotted with a bright light during   inspection.   Cor-
rosion of the insulator compartment is another indication of moisture buildup.
                                       103

-------
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-------
The inspector should check to see that the pressurization fan for the top
housing or insulator compartment is operating properly,  and that air filters
for control sets and the top housing are not plugged.   The condition of access
hatch covers should also be noted.
     The inspector should check rapper and vibrator action visually and/or by
feel.  A uniform rhythmic tapping of metal to metal characterizes rappers;
vibrators emit a loud buzzing sound.   Any irregular sounds may indicate impro-
per rapper or vibrator operation.  The plant should provide a diagram of the
rapping system sequence so that the inspector can verify that all of the
rappers or vibrators are operating properly.  Rapping intensity should be
checked against design, and any indication of reduced rapping intensity should
be questioned.
ESP Housing
     The inspector should examine the exterior of the ESP housing for corro-
sion, loose insulation, exterior damage, and loose joints.  The ducts entering
the ESP should be checked; if they show corrosion, the interior of the ESP
also may be corroded.  The inspector should check for fugitive emissions (with
positive pressure systems) or air inleakage (with negative pressure systems)
at loose joints and as a result of other exterior damage.
Ash Handling System
     The inspector should check to see that the evacuation rate for the ash
hoppers prevents ash accumulation.   Inlet field hoppers, for example, normally
collect 60 to 80 percent of the total catch and must be emptied much more
often than the downfield hoppers.  If level alarms are used, the inspector
should ensure that they are operating properly.
     The inspector should look for problems in the ash evacuation and removal
system, including water pump failure (a water pump may be used to create the
vacuum), vacuum line disconnections, rotary air lock malfunctions, and se-
quencing control failures.
     If ash is removed from a collection silo by truck,  the inspector should
ensure that the truck fill pipe extends far enough into the truck to minimize
fugitive emissions.
                                       105

-------
Process  Instrumentation
     After finishing with the ash handling system, the inspector should check
a number of process parameters that can affect ESP performance.  For example,
readings of gas flow, gas velocity, excess air, gas temperature, pressure
drop, moisture, flue gas analysis, soot blowing intervals, and opacity should
be taken if possible.  Many instruments in the boiler control room have con-
tinuous  readouts.  Figure 42 shows an example trace from a continuous opacity
monitor.  Variations in process readings from the normal design ranges should
be investigated in conjunction with ESP control set readings and visual obser-
vations  made during the inspection for possible effects on ESP performance.
Internal Inspection
     If  an ESP is down for scheduled maintenance or because of a malfunction
during an inspection, the inspector should take time to check inside the unit
and observe the dust accumulation on plates and wires.  (Note:   Be sure and
follow proper safety procedures described on Pages 129 or 132.)  The discharge
wires should only have a slight coating of dust, with no corona tufts (dough-
nut-shaped ash accumulations).  Thickness of dust buildup on plates is normal-
ly between 0.3 and 0.6 cm (1/8 to 1/4 in.).  If the plates have more than 0.6
cm (1/4  in.) of dust, the rappers are not cleaning properly.   If the collect-
ing plates are almost metal clean, this may be an indication of high gas
velocity, extremely coarse fly ash, too high a rapping intensity, or too low
an operating voltage for good precipitation.   The inspector may notice this if
a section has been shorted out prior to the inspection.
     The inspector should note whether or not the discharge electrodes are
centered between the collecting plates from top to bottom to ensure optimum
performance.   Also'any broken or missing discharge'electrodes should be noted.
The company should keep records of wire breakage to help determine if multiple
wire breaks in the same area may be due to alignment problems.   Random wire
breakage is probably caused by dust buildup on wires or plates.
     The inspector can check for air inleakage from door openings by noting
the amount of corrosion on collecting plates adjacent to inspection hatches,
and from the hoppers by checking on the lower portion of the collecting
plates.   Air inleakage also causes nonuniform gas flow which can reduce ESP
efficiency.
                                       106

-------
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107

-------
     The inspector should have plant personnel open the hopper access door and
then check for corrosion, which indicates air inleakage as mentioned previous-
ly.  He/she should check for dust buildup in the upper corners of the hopper
and for debris, such as fallen wires and weights, within the hoppers.  If
discharge electrode weights have dropped 3 inches or more, this indicates a
broken wire.  Chronic ash buildup is an indication of low operating tempera-
tures, insufficient heat insulation, or inadequate hopper emptying.

3.4  SCRUBBERS
3.4.1  Introduction
     Wet scrubbers capture particulates into either liquid droplets, sheets,
or jets.  The principal physical mechanism used in commercially available
systems is inertia! impaction.  Other physical phenomena aiding capture in-
clude Brownian diffusion (random movement.that leads to particulate capture),
diffusiophoresis (particle migration toward site of condensation due to dif-
ferences in mass concentration), and thermophoresis (particle movement toward
colder temperature due to differences in momentum transferred in molecular
collisions).  Diffusion only applies to small particles of about 0.05 urn.
Unfortunately, neither impaction nor diffusion is very effective for 0.1- to
l-|jm diameter particles that are small enough to follow gas streamlines around
the droplets but too large for effective collection by diffusion.  Figure 43
illustrates the effect of particle size on impaction and diffusion.
     Some boilers use scrubbers for particulate emission control, but scrub-
bers are not generally used because of high operating costs.  A scrubber is
more practical for controlling particulate matter from a spreader-stoker
boiler than from a pulverized-coal-fired boiler because the stoker boiler
produces larger particles and relatively low mass loadings.  Pressure drop,
water flow rate, suspended and dissolved solids, plugged and eroded pipes and
nozzles, pump wear, and particle size all affect scrubber particulate removal
efficiency.
     Particulate scrubbers types include:  impingement plate, centrifugal
spray, self-induced spray, disintegrator, moving bed, ejector, foam, and
venturi.  Centrifugal scrubbers are frequently found on stoker boilers; ven-
turi scrubbers are more commonly used on pulverized-coal-fired boilers.
                                       108

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      DIFFUSION
      IS DOMINANT i
      MECHANISM
IMPACTION
IS DOMINANT
MECHANISM
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       EDITJO     100     100.

            PARTICLE DIAMETER, micrometers
          Figure 43.   Importance of particle size
                on wet scrubber penetration.
                              109

-------
     Impingement scrubbers use perforated or slotted plates containing target
plates opposite all openings to cause an cbrupt change in direction (and
acceleration) of contaminant laden air (see Figure 44).   When flooded with
scrubbing liquid, these designs produce a high surface area froth of scrubbing
liquid on its top surface and turbulence, both of which contribute to particu-
late removal and gas absorption.
     A spray tower is a gas absorption device developing high liquid surface
areas through the use of a spray nozzle(s), hydraulically or pneumatically
atomized.  It is not very effective at removing particulates and rarely used
on industrial boilers (see Figure 45).
     Dynamic scrubbers utilize a fan, impeller or other motive device to
mechanically produce small droplets which enhance gas absorption and particu-
late removal.  These are typically sprayed fans, coupled with droplet removal
devices.
     Moving bed scrubbers were developed primarily as an alternative to packed
bed scrubbers in applications with both particulate and gaseous contaminants.
As shown in Figure 46, the gas enters at the lower side of the unit and passes
upward through a series of beds each of which is 10% to 25% full of light-
weight packing.  The liquor is introduced at the top through a set of nozzles
and passes through the beds countercurrent to the gas flow.  The bed is fluid-
ized by the moving gas stream; this results in the formation of liquid drop-
lets and sheets in the turbulent zone of the bed.  A chevron demister or
equivalent serves as the main entrainment separator.
     A cyclonic scrubber is a spray tower variation in which gas is spun
cyclonically in a vessel with scrubbing liquid sprayed concurrently into the
stream (see Figure 47).
     In the venturi scrubber the boiler exhaust gas and entrained particulate
matter are accelerated to a high velocity in the venturi throat.  The high gas
velocity shatters the water in the scrubber and forms small water droplets
that provide impact targets for the particles.  The particles collide with the
water droplets and stick to them, agglomerating into larger droplets that are
then fairly easy to remove from the gas stream.   High throat velocities, high
liquid-to-gas ratios, and resulting high pressure drops through a scrubber
enhance efficiency.
                                       110

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                           Clean gas
          Plates
Dirty gas-
          Figure 44.   Tray scrubber.
 Clean gas
 outlet
Entraintnent
separator
                           Liquor inlets
                             Dirty gas
                             inlet
                Liquor outlet

          Figure 45.   Spray tower.
                       Ill

-------
      Clean gas
                    Mist eliminator

                    Spray nozzles
                     Mobile  packing
                         Dirty gas
Figure 46.   Moving Bed Scrubber.
                112

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         Clean gas
         outlet
                     Entrainment
                     separator
                     Central
                     spray tree
                      Liquor
                      inlet
                     Dirty gas inlet
                     (tangential)
        Liquor outlet
Figure 47.   Cyclonic spray tower.
                113

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     Typical venturi scrubbers (see Figures 48 and 49) are made of 316 stain-
less steel.  Most designs use a flooded elbow and a variable throat to control
pressure drop.  The flooded elbow provides a trough of water to capture the
larger water droplets and particulate matter that exit the scrubber and to
prevent abrasion of the elbow at the turn.  The venturi throat may be circu-
lar, rectangular, or oval; the throat area is changed by moving hinged plates,
a bob, or some other surface inside the venturi to control the pressure drop.
Water is introduced into the scrubber immediately ahead of the venturi throat.
Venturi scrubbers are more compact and versatile than the other types, and
they cost less than other scrubbers of comparable efficiency.
3.4.2  Operation and Maintenance
     Most scrubber problems involve liquid flow, corrosion and erosion, scal-
ing and plugging, entrainment, and/or gas flow.  These problems are described
in the paragraphs which follow.
Liquid Flow
     Common problems with liquid flow include build-up at the wet-dry inter-
face, poor liquid distribution, loss of seal, and malfunctioning pumps.
     If the scrubber design improperly allows dry dust laden gas to contact
the juncture of the scrubbing liquid and the vessel, dust build-up will occur.
Good designs prevent this contact by extending ductwork sections sufficiently
into the scrubber and by thoroughly wetting all scrubber surfaces through a
reliable method such as gravity flush or sprays.
     The gas and liquid must be properly distributed for the given applica-
tion.  Improperly distributed flows can be aggravated by the influence of
baffles (needed or accidental), mechanical failure, wear, scaling in headers,
or improper design.  Flow distribution problems are most common in packed and
spray towers.  The swirling of scrubbing liquid, especially on cyclonic de-
vices, can cause severe wear and draining problems unless arrested by anti-
swirl plates in the scrubber or rapid continuous draining.
     Most scrubbers operate near atmospheric or ambient conditions.   A pump
recirculates the scrubbing medium, and a liquid seal prevents pump cavitation.
This seal may be at the top of a quencher or from an overflow connection.
Loss of seal can cause entrainment or plugging and instrumentation malfunc-
tion.
                                       114

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                        clean  gas out
      dirty
  water in
                               slurry out
Figure  48.   Bob  type venturi  scrubber.
                     115

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                                            GAS OUTLET
              GAS INLET
    CW>
PRESATURATOR
                                                       WATER
                                                       TREATMENT
                                                   *-PURGE
                  Figure 49.  Venturi scrubber components.
                                  116

-------
     Accelerated wear of the centrifugal pump impeller occurs at high sus-
pended solids (flyash) levels.   The best way to minimize scrubber downtime due
to pump malfunctions is to minimize the total quantity of suspended solids,
especially the larger suspended particles (greater than 25 micrometers).   A
clarifier or centrifugal separator can improve the quality of liquor passing
through the pump by reducing suspended particle loadings.
Corrosion and Erosion
     Corrosion is a major factor in shortening the operation life of a scrub-
ber whether properly designed or not.   Wells or pockets of liquid should be
avoided and points of stress should be adequately flushed.  Relatively small
levels of chlorides and fluorides can attack many types of materials, espe-
cially the 300 series stainless steels.  Internal members usually should be
thicker than the shell.
     It is important to maintain the pH of the scrubbing liquid well above the
levels at which carbon steel (the most common material used in scrubber con-
struction) is attacked.  A pH of 6 or greater is usually satisfactory.   Other-
wise, FPP or expensive nickel/chrominum alloys such as Haste!loy must be used.
Maintenance of an appropriate pH is usually accomplished through the use of
alkaline additives such as soda ash, lime, or limestone.  If a pH of 6 or
greater is maintained, significant sulfur dioxide removal  (greater than 75%)
will occur.  The operation of the pH monitor used to control the rate of
additive injection should be checked at least on a daily basis unless long
term operating experience justifies a less frequent inspection.   A portable pH
meter or pH paper can be used for this check.  It is preferable to obtain a
sample from the sump of the scrubber since this is often the point of minimum
pH.
     The recirculation rate is an important factor in determining the extent
to which halogenated compounds are building-up in the scrubbing liquid.
     One convenient means to monitor potential corrosion problems is to pre-
pare small coupons (small circular samples) of the various materials used
throughout the scrubber system.  These are placed in racks which can be mount-
ed at various locations in the scrubber.  During every outage these are vis-
ually inspected for pitting and cracking and are weighed for material loss.
This information provides an early indication of developing corrosion prob-
lems.

                                       117

-------
     The scrubber is susceptible to erosion due to high velocities of the
liquid stream and suspended solids within the stream.  High gas stream velo-
cities can also lead to erosion.  Venturi throats on venturi scrubbers are
subject to velocities as high as 20,000 to 40,000 feet per minute.  Other high
wear areas are those which inhibit gas flow such as elbows and gas distribu-
tion structures.
     Nozzles are also susceptible to erosion.  Using special ceramics and
reducing the scrubbing liquid solids content can minimize problems.   Some
nozzle designs, such as those that include an internal spinner vane, can lead
to accelerated erosion.  Deluge-type nozzles or nozzles without internal
structures are least susceptible to erosion.
Scaling and Plugging
     Scaling is the plating out of deposits on a scrubber surface.  Usually it
is harmless unless the scrubber part cannot function because of the deposit.
Scaling is caused by interactions of the chemical composition, solubility,
temperature, and pH of the scrubbing liquid.  It is a difficult problem to
diagnose; a good deal of research has been done on calcium-based S02 scrubber
scaling problems.7  Proper control starts with the scrubber design and process
control.
     Spray nozzles are extremely susceptible to plugging problems due to the
high liquid stream velocities and suspended solids content.  The most common
types of nozzles in use include the hollow cone and the full cone.  The latter
is particularly prone to pluggage due to the presence of an internal spinner
vane.  The vane is installed to achieve the full cone spray pattern which is
necessary for distribution of liquor on a moving bed scrubber.  Improper
header design allows particles to settle which may .plug nozzles.  Centrifugal
separators can be used to remove particles before they reach the nozzles.
Scale problems can also be solved by separators, but proper control  of scrub-
ber chemistry is a better approach.
     Instrument lines can become blocked from particle settling or scale
deposits.  Specially designed instrument fittings and connections may be
required for use with scrubbers.  Instrument probes in continuously circula-
ting loops have less blockage problems than probes in dead-ended lines.
                                       118

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Mist Entrainment
     Entrainment occurs when the droplet separator is not functioning proper-
ly.  Nearly all scrubbers have some entrainment losses.   A properly designed
system can eliminate entrainment carryover.  Droplets impinge on eliminator
surfaces and return to the scrubber.  Figure 50 shows two types of mist elimi-
nators.
Gas Flow--
     Vibration is most common in wet dynamic scrubbers and in the fans on wet
fan venturi or cyclonic systems.   It is best controlled by monitoring and
scheduled preventive maintenance to remove scale deposits and to lubricate and
balance equipment.  Fan vibration can sometimes be caused by air flow factors
and, in these cases, can be eliminated by adjusting or modifying the inlet or
outlet dampers or modifying the inlet or outlet ductwork.  Even gas distribu-
tion through the scrubber is important to obtain maximum particle wetting and
collection.  Gas maldistribution can be checked with pressure gauges and can
be eliminated by using inlet baffles or gas distribution plates, by adjusting
inlet dampers, and by proper scrubber design that eliminates gas bypasses.
     If the gas stream entering the scrubber is very hot (greater than 300F),
it is often desirable to cool the gas stream.   This protects the scrubber
materials of construction, especially corrosion and abrasion resistant lin-
ings, from thermal shock and degradation.   Gas stream cooling can be accom-
plished in evaporative coolers or presaturators.   Multiple cooling zones may
be necessary for large temperature differences.
3.4.3  Inspection Procedures
     To evaluate the performance of a wet scrubber, the  inspector should check
the following areas:
     0    Liquid circulation,
     0    Gas flow,
     0    Gas pressure drop,
     0    Liquid pH,
     0    Scrubber corrosion, and
     0    Nozzle and shell erosion.

                                       119

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               WIR6-MESH MIST ELJMINATOR
                          TDBZ-EANK MIST EL1KCIATOR
Figure  50.   Mist eliminators.





                   120

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The recirculation pump and fan should be operating.  If there is no scrubber
liquid circulating through the system or the flue gas is being bypassed, the
inspector should recommend a follow-up inspection when the scrubber will be
operational.  If there is circulation, the inspector should follow the liquid
flow through the system (liquid flow is generally counter to gas flow).
     Next, the inspector should confirm that the pumps are on, and if so, the
inspector should read the flow meter (if any).   In the line going to the spray
nozzles, low pressure indicates erosion of the nozzles and likely increases in
the water spray droplet size.  If the line pressure does not change when the
flow is temporarily shut off (the inspector must not adjust valves), the noz-
zles are plugged.  Localized higher shell temperatures (5 to 10F above nor-
mal) also indicate an area with plugged nozzles.   If possible, static pressure
drop across each stage should be recorded to help in problem diagnosis.
     To complete the check of the liquid system,  the inspector should measure
the temperature and the pH of the sump liquor.   It is advisable to take a
liquor sample; however, the expense should not be incurred unless there are
reasons to suspect operational and/or corrosion problems (chain-of-custody
procedures must be followed).  During the inspection, the corrosion and ero-
sion of the scrubber shell (look for holes) and component parts should be
routinely checked.
                                       121

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                                   SECTION 4
               GENERAL PREPARATORY AND PRE-INSPECTION PROCEDURE

     To conduct a successful inspection of an industrial  power plant requires
careful preparation.   Such preparation includes:
     0    Becoming familiar with the boiler and its control  equipment,
     0    Reviewing past operating practices,
     0    Procuring and testing the necessary inspection equipment to be
          sure it is working properly,
     0    Inspecting the plant's exterior to obtain information  about
          operating practices, and
     0    Advising key plant personnel well in advance so that they are
          available to answer questions and take part in the inspection.
          (The cooperation of key plant personnel is critical to the
          success of the inspection.)
Advanced preparation on the part of the inspector can save valuable time, both
for the inspector and for plant personnel.  A well-informed and prepared
inspector generates a degree of confidence that makes plant personnel more
inclined to provide information critical to completing a comprehensive compli-
ance assessment.

4.1  FILE REVIEW
     A logical starting point for Agency  inspectors  is a review of the plant's
file.  The following items  should be  checked, and copies of the first two
items  in the  following list should be obtained from  the inspection files.
     0   Pending compliance  schedules;
     0   Construction and/or operating permits pertaining to source pro-
          cesses;
     0   Past conditions  of  noncompliance;
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     0    Malfunction frequency and causes; and
     0    History of abnormal operations.
The inspector should also obtain a copy of the overall plant layout drawings,
and these should be reviewed before plant entry.
     The inspector should prepare a concise file containing basic plant infor-
mation, process descriptions, flowsheets, and acceptable operating conditions.
This file should also contain the following to facilitate the inspection:
     0    A chronology of control actions, inspections, and complaints
          concerning each major source in the plant,
     0    A flowsheet identifying sources, control devices, monitors,
          and other information of interest,
     0    All permits for each major source, and
     0    Previous inspection checklists.
     Based on available information, the inspector should select a time for
the inspection when processes are likely to be operating at representative
conditions.   This is especially important for plants with batch operations or
other irregular operating schedules (e.g., seasonal).
     The inspector should carry the following tools and safety gear for all
inspections:
     0    Hard hat,
     0    Safety glasses or goggles,
     0    Gloves,
     0    Coveralls,
     0    Safety shoes (steel-toed),
     0    Ear protectors,
     0    Tape measure,
     0    Flashlight,
     0    Manometer or differential  pressure gauges,
     0    Stopwatch,
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     0    pH paper,
     0    Duct tape, and
     0    Pocket guide of industrial hazards.
Safety equipment is particularly important.   It is the inspector's responsi-
bility to have safety equipment before entering the plant.   Access to certain
industrial facilities may be legally restricted or refused by plant represen-
tatives if the inspector is not wearing the designated equipment.
     The following equipment can be left in a central location and only car-
ried to the source when needed:
     0    Pipe wrench,
     0    Respirator with appropriate cartridge(s),
     0    Velocimeter,
     0    Pump and filter system,
     0    Bucket,
     0    Combustion gas analyzer,
     0    Thermometers or thermocouples,
     0    Multimeter,
     0    Sample bottles,
     0    Strobe,
     0    Inductance ammeter,
     0    Tachometer,
     0    Oxygen and combustibles meter,
     0    Self-contained breathing equipment, and
     0    Rope.
     A uniform inspection procedure^helps both the source operators and regu-
latory agency inspectors in the routine evaluation of the performance of air
pollution control equipment.  The fundamental principle of the procedure is
that performance is diagnosed by comparing observed operating conditions at
                                       124

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 the  site  with  baseline  operating conditions.   It is  recognized that field
 measurements are  sometimes  subject  to  error or impossible  to  make;  therefore,
 diagnosis is based  on trends  rather than  individual  parameter readings.  Even
 if some basic  data  are  missing,  reasonable  conclusions  may still  be drawn.
     The  techniques described in this  report allow the  inspector  to rapidly
 identify  any significant changes in performance  and  the possible  reasons for
 the  changes.   Although  these  techniques provide  a method of assessing compli-
 ance, they do  not necessarily provide  definite evidence of noncompliance, nor
 do they necessarily recommend specific remedies  for  problems  that are encoun-
 tered.
     Inspectors should  have a technical background and  some field experience.
 As with any work involving equipment, care  must  be exercised  and formal safety
 training  is highly  recommended for  this activity and for any  field  work in-
 volving air pollution control  equipment.
     No single technique can  satisfy all  source  characteristics and  inspection
 circumstances.   Inspectors and source operators  may have to modify  standard
 procedures for specific circumstances.
     A key inspection step is to determine  baseline operating parameters soon
 after a boiler is installed and  the shakedown period has been successfully
 completed.  These baseline parameters,  which can be developed during a stack
 test, will provide a site-specific reference point for assessing future boiler
performance.   The parameters  include:
          Steam production data such as temperature,  pressure, and
          pounds per hour;
     0    Fuel  use - pounds or tons  of  coal  per hour;
     0    Fuel  quality - Btu/lb,  ash, sulfur, and moisture;
          Combustion air temperature and  ambient humidity;
     0    Firebox draft;
     0    Flue  gas temperature and flow rate;
     0    Flue  gas 02, CO,  and C02.
                                  5
          Firebox,  superheater, and  air preheater temperatures;
          Induced-draft  fan  speed, pressure  drop, and air flow;
                                       125

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     0    Overfire air damper settings;  and

     0    Pollution control  system parameters.

     The same inspection procedures and forms should be used for both the

baseline assessment and the routine evaluation.   To round out a reference

file, the inspector should:

     0    Obtain a set of general arrangement drawings of the control
          equipment and dust or sludge handling system;

     0    Evaluate the stack test location and procedures to ensure that
          the emissions data will be accurate and representative; and

     0    Carefully inspect and describe all internal conditions if such
          inspections can be conducted safely.   Photographs are extreme-
          ly valuable and should be taken (with permission from the
          source) if it is safe to do so;

     0    Note the sounds of operating components such as rappers and
          solenoids;

     0    Obtain a complete set of boiler operating conditions, fan
          characteristics, and raw fuel characteristics; and

     0    Obtain opacity readings.

     Because the inspector is most concerned with emissions, it is generally

advisable to begin the inspection by looking at the stack.  Then, the inspec-

tor should check the control equipment and finish with an inspection of the

boiler and the control room.  This minimizes inspection time and reporting re-

quirements and maximizes the amount of useful information obtained.  Specific-
ally, the information on emissions and control equipment, which is the most

relevant to the inspection is obtained early in the inspection and can then be

used later either to narrow the scope of the inspection or to terminate the

inspection without evaluating the boiler equipment.

     0    Pre-Inspection Steps

               Review the source files.
               Schedule the inspection.
               Check the inspection equipment.
               Observe the plant surroundings.
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     0    Inspection Procedures
               Request entry to the plant.
               Interview plant official(s).
               Observe the stack effluent.
               Check the continuous monitor(s).
               Measure or record the fan parameters and evaluate the
                physical condition.
               Analyze the control equipment performance and condition.
               Check the flue gas system (ductwork).
               Evaluate process operating conditions.
               Check raw materials and/or fuels.
     0    Post-Inspection Steps
               Conduct exit interview with plant official(s).
               Update source files..
               Prepare report.
     Prior to entering a plant, the inspector should observe the surrounding
areas.   Various signs of operating practices and plant emissions that can aid
in the source evaluation include:
     0    Deposits on cars parked near the plant,
     0    Other signs of dust and fly ash fallout downwind of the plant,
     0    Fugitive emissions near plant boundaries,
     0    Conditions around the product and/or waste storage piles, and
     0    Conditions near lagoons and sludge ponds.
Some of the inspector's observations may suggest that fugitive emission
sources should be added to the inspection agenda.  A summary of weather condi-
tions also should be included in the inspection report.
     Upon arrival at the plant offices, the inspector should notify appropri-
ate plant personnel and show his/her credentials to the plant representative.
Generally, the inspector should not sign a visitor release form.
     If entry is refused for part or all of a facility within the scope of the
inspection,  the inspector should carefully note 1) the alleged reason(s) for
the refusal  of entry,  2) the name and title of the plant official who refused
entry,  and 3) the time and date that entry was requested.   Immediately after
such refusal, the inspector should notify his/her supervisor by telephone and
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provide the above information.  Under no circumstances should the field in-
spector attempt to inform plant personnel of the potential legal consequences
of refusal of entry.
     Once entry is granted, the inspector should conduct an initial interview
with appropriate plant personnel.  Some of the points for discussion are:
     0    The purpose of the inspection,
     0    The type of measurements to be made,
     0    The samples (if any) to be acquired,
     0    The systems to be inspected,
     0    Changes in plant management that need to be noted in the
          agency file,
     6.   Process flowsheets necessary to confirm that reported plant
          operating conditions are still pertinent, and
     7.   Operating records required by New Source Performance Standards
          (NSPS) and/or for determinations of operating conditions speci-
          fied in permits.
Appropriate regulatory requirements should be reviewed carefully, and their
specific applications to the source in question should be discussed with
appropriate staff members.
     Other issues the inspector should be prepared to discuss include:
     0    Authority for the inspection;
     0    Agency organization;
     0    Scope, timing, and organization of the inspection (preferred
          inspection agenda); and
     0    Treatment of confidential data.
     The inspector should ask plant officials about the operational status and
types and frequencies of malfunctions for all processes and pollution control
equipment being inspected.   If equipment is not at or near normal conditions,
the reasons for deviation should be 'noted, and the times when units can- be
expected to be operating at normal conditions should be recorded for use in
scheduling followup inspections.
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     Emission opacities should be observed and recorded according to Method 9
procedures.  In many cases, an agency can initiate an enforcement action
solely on the basis of visible emission observations.  In some cases, however,
opacity information can be used to diagnose changes in system performance.
     The color of the effluent is another plume characteristic that should be
observed.  For boilers, the color is an indirect indication of operating
conditions.  The list in Table 9 was compiled by EPA's Control Programs Devel-
                           \
opment Division.

          TABLE 9.  PLUME CHARACTERISTICS AND COMBUSTION PARAMETERS.
     Plume color
Possible operating parameters to investigate
     White

     Gray
     Black


     Reddish brown

     Bluish white
Excess combustion air; loss of burner flame in
 oil-fired furnace
Inadequate air supply or distribution
Lack of air; clogged or dirty burners or insufficient
 atomizing pressure, improper oil preheat;  improper
 coal size
Excess furnace temperatures or excess air;  burner
 configuration
High sulfur content in fuel
     Baseline operating parameters for the boiler and its control equipment
may be available from Agency files prior to the inspection.   A typical source
file contains information on permit activity, previous inspections, and emis-
sion tests.  The files generally describe the boiler and provide additional
data on its capacity and control equipment; this information gives the inspec-
tor a perspective on the overall operation of the facility.   The source files
also may contain information on citizen complaints; equipment malfunctions,
opacity levels, and the overall compliance status of the boiler or boilers at
the plant.  This information helps the inspector to focus attention on those
boilers that seem to have problems.
     File data on previous emission tests and other inspections should be used
to establish a baseline for comparison with information obtained during future
                                       129

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 inspections or tests.   Such information also helps to establish a normal
 operating range for the boiler and its control  equipment and permits  the
 inspector to readily note any deviations.

 4.2  SAFETY PRECAUTIONS
      Safety precautions must be taken  during plant inspections  because  heavy
 equipment movement,  high-temperature process equipment,  high-pressure steam,
 toxic gases,  and noise  are common.  Extreme  caution  should  be taken to  avoid
 burns and the possibility of slipping  and  falling.   Several  specific situa-
 tions are of concern in terms  of the inspector's overall  safety.
      One  special  concern is  the potential  for a boiler explosion.  Although an
 explosion is  unlikely,  the possibility does  exist, especially during nonstand-
 ard operating conditions that  might be encountered during special tests.  The
 inspector should  be  familiar with  specified  evacuation routes and procedures
 before entering the  boiler area.
      Because  a mixure of pulverized coal and  air burns rather freely, suspend-
 ed  coal dust  in air  can  be quite explosive.   Hence, pulverized coal or coal
 dust  must not be  dispersed in  air except within equipment where conditions are
 controlled at all times.   Fine  dust can be dispersed into the air by means
 that  are  not  always  expected or predictable;  thus, it is important to avoid
 accumulation  of coal dust  anywhere in  the plant except in coal storage spaces.
 Even  there the suspension  of dust in the air must be avoided.  In general, it
 is hazardous  to blow dust  off surfaces with air lances.   Vacuum cleaners
designed  for  this purpose  are preferred.  Fundamental safety precautions and
burner lighting and operating sequences for coal are summarized in the follow-
ing rules:

     1.   Never allow coal dust to accumulate except in specified stor-
          age facilities.
     2.   Never allow the suspension of coal  or dust in the  air  except
          in drying,  pulverizing, or burner equipment or in  interconnec-
          ting ductwork.
     3.    Purge the furnace and its setting before  introducing any liqht
          or spark.
     4.    Have a lighted torch or spark-producing  device  in  operation
          before introducing fuel  into  a furnace.

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      5.    Maintain a lighted torch or spark-producing device in opera-
           tion while introducing fuel  into a furnace.
      6.    Maintain sufficient primary air and coal  flows  to the burners.
 Compliance with these rules  requires  a conscientious  operating staff and  good
 housekeeping throughout the  plant.
      Another major safety concern at  any plant is  entry into a confined area.
 The cardinal  rule  for entering a confined area is  "never  trust your senses."
 What may appear to be a harmless sitation may well  be a potential  threat.   The
 three most common  conditions constituting a threat are:
      0    Oxygen deficiency,
      0    Combustible gases  and vapors,  and
      0    Toxic gases and vapors.
      An  inspector  should always anticipate that any one or a combination  of
 the above conditions might exist in a confined area such  as ductwork, stack,
 open tanks,  penthouse,  or the internal  portion of  a wet scrubber or ESP.
 Tests for flammability,  oxygen deficiency,  and toxicity must be made before an
 inspector enters any confined area.   No  one factor will provide more safety
 than the knowledge of the potential threats that may  exist within  the area  to
 be  inspected.   Armed with this knowledge,  the inspector can take appropriate
 precautions  and use the proper equipment to minimize  any  potential  dangers.
      Many treatment chemicals used and handled in  the  boiler area  are corro-
 sive or  skin  irritants.   Care must be  taken to avoid  contact with  these chemi-
 cal  reagents,  which may include sodium hydroxide (NaOH),  sulfuric  acid
 (H2S04),  and  chlorine.   Table 10 shows  the  physical,  flammable,  and toxic
.properties oficommon gases that may be encountered  in  a boiler plant.   Many
 solids may also be hazardous to the skin and eyes;  contact should  be avoided.
 The inspector should wear appropriate  eye  protection  (glasses  with  side
 shields)  at  all  times within the plant.
      Many surfaces in the boiler plant are  extremely  hot.   The inspector
 should constantly  be on  the  alert for  piping,  ductwork, or equipment that may
 present  a potential  hazard.   Protective  clothing (long-sleeved shirts,  gloves,
 etc.)  should  be worn to  avoid burns as a result of  accidental  contact with  hot
 surfaces.
                                       131

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                    TABLE 10.  BOILER PLANT GAS PROPERTIES.
Gas
Carbon monoxide
(CO)
Carbon dioxide
(C02)
Methane (CH4)
Sulfur dioxide
(S02)
Nitrogen dioxide
(N02)
Physical
characteristics
Colorless
Odorless
Colorless
Odorless
Colorless
Odorless
Colorless
Suffocating odor
Brown
Pungent odor
Flammability lower
explosive limit
(LEL), % volume
12.5
Nonflammable
5
Nonflammable
Nonflammable
Toxicity threshold
limit valves
(TLV's), % volume
0.005
0.5
Nontoxic
0.0005
0.0005
     The inspector should remove loose objects such as jewelry, ties, and hair
ribbons before entering the work area.  Because of the close quarters in many
boiler rooms and the possible contact with moving equipment while taking
measurements, any object that might become entangled must be removed.
     In addition to the general concerns noted above, an inspector that con-
ducts an internal inspection of any control equipment must:
     0    Observe interlock and electrical lockout procedures,
     0    Observe confined entry procedures,
     0    Watch footing,
     0    Never work alone,
     0    Wear protective equipment,
     0    Purge unit before entry,
     0    Use grounding straps particularly around ESPs, and
     0    Never enter full or partially full hoppers (wet- or dry-
          bottom).   Empty hoppers may have ash lodged overhead which
          also presents a danger if accidently dislodged.
                                       132

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     Finally, the inspector needs to be aware of and obey all safety require-
ments set forth by plant personnel.  Many plants have specific safety proce-
dures that must be obeyed; therefore, the inspector must meet with plant
personnel prior to the inspection to discuss special safety requirements
pertinent to the plant.
4.3  SAFETY AND INSPECTION EQUIPMENT
     During an inspection, the inspector should use appropriate protective
clothing and safety equipment and follow all company rules and recommenda-
tions.  The inspector should wear safety glasses with sideshields for protec-
tion.  Hearing protection, such as ear plugs, should also be used in high-
noise-level areas.  Steel-toed shoes and a hard hat are required for protec-
tion against overhead hazards and heavy objects.  A long-sleeved shirt,
gloves, and trousers should also be worn for protection.   Dust and mist re-
spirators should be used around potentially dusty operations.   In some cases a
gas mask may be required.  When the inspector is required to enter a confined
area, he/she may need to use self-contained breathing apparatus.
     The equipment used during an inspection varies according to the time
allotted and the level of the inspection.  For example, a detailed inspection
requires a pi tot tube and manometer for measuring the pressure drop across the
appropriate control equipment, a thermometer or thermocouple for measuring
stack gas temperatures, a wet bulb/dry bulb thermometer and psychrometric
chart for determining moisture, a tachometer for measuring fan speed, an
ammeter for measuring fan motor current (on large fans, current usage may
exceed the measurement range of hand-held ammeters), and an oxygen meter
and/or Fyrite or Orsat for determining 02 concentration and gas composition.
A flashlight, tape measure, and pressure gauge device may also be necessary.
     A camera can be useful to provide a graphical description of problems
arising from poor maintenance and housekeeping.   Control  equipment problems
can also be so documented.  Immediately after taking a photograph, the in-
spector should note the situation represented in the picture and the time,
date, weather conditions, and pertinent directional information.   Unfortunate-
ly, the plant owner or operator may be reluctant to allow photographs to be
taken within a facility.  Therefore, permission must be obtained prior to
taking such photographs.

                                       133

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     A compass is useful for determining source locations relative to each
other, to the sun, and to the inspector.  A stopwatch for timing visible
emissions observations is also useful.

4.4  PRE-ENTRY OBSERVATIONS
     Before entering the facility, the inspector should record pertinent pre-
entry observations such as sources of fugitive dust.   The inspector should
also note the weather conditions (especially precipitation and windspeed)
during and prior to the inspection.
     Pre-entry observations also afford an opportunity to document the facil-
ity's general housekeeping practices and give the inspector an overall picture
of the plant layout for comparison with file information.
     While outside company property, the inspector is generally free to use a
camera to photograph any visible problems, including excessive visible emis-
sions.  Data regarding any photographs that may be taken (e.g., date, time of
day, weather conditions, position relative to the source) must be recorded
immediately.  As mentioned in Section 4.3, the inspector must obtain permis-
sion from plant personnel to take any photographs while on plant property.
     Visible emission observations are important in determining the operating
conditions of some processes and their associated control equipment.  When
recording visual opacity readings, the inspector should follow EPA Method 9
procedures or appropriate State procedures.  Windspeed, sky condition, and
other weather data should be recorded for future use, as the reading may be
challenged in court.  A diagram is also important in identifying the parti-
cular source being observed (e.g., the No. 3 coal-fired power boiler) and the
observer's orientation relative to the sun and theisource.  The inspector
should record opacity readings on the observation form for a specified dura-
tion, depending on the local requirements.  Any periodicity of smoke emis-
sions, such as intermittent puffs, should be noted.  In some cases, it may be
possible to correlate variations in opacity with corresponding fluctuations in
boiler load or other boiler operating parameters.
     Sometimes opacity readings are best obtained before the inspector enters
the plant or after he/she leaves the plant property.   The inspector should
compare the visual measurements with available readings from the plant's
                                       134

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continuous emission monitoring equipment for the same time period.   The fre-
quency of calibration of these continuous emission monitors should be noted.
     If the Agency's policy is to provide the plant with a copy of the opacity
readings taken during the inspection, the plant official receiving the copy
should sign and date the original record of the opacity readings.

4.5  ONSITE INSPECTION CHECKLISTS
     During the onsite inspection, the inspector may find it useful to have a
series of checklists on which to record the information obtained.   Tables 11
through 13 are checklists for fabric filters, scrubbers, and ESP's respective-
ly.  Figures 51, 52, and 53 are flowsheets that can be used in conjunction
with the inspection of those control devices.
     Appendix A contains additional checklists that may be useful.   These
checklists include a cover page (Table A-l) that may be used with the check-
lists for fabric filters (Table A-2), scrubbers (Table A-3), electrostatic
precipitators (Table A-4),_and mechanical collectors (Table A-5).
                                        135

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V
B
H


B
O
XJ
s
3
144

-------
               NO
 Check pressure drop across
 each compartment;  also,
 check1 condition of lines
 and pressure gauges.

 ENTER RESULTS  ON LINES Al,
 Bl,  Cl, Dl,  and  El, OF
 CHECKLIST.
            I
Check cleaning system:
     -Pulse jet pressu're
    ,-Solenoids
     -Reverse air blowers
     -Shakers

ENTER RESULTS IN SECTIONS
B, C, and D OF CHECKLIST.
            1
Check solids removal equip-
ment:
     -Screw conveyor
     -Pneuo-stic system
     -Heaters
     -Vibrators
ENTER RESULTS. IN SECTION E
 OF CHECKLIST.
                                                        YES - ENTER UNIT
        Can
      Internal
    Inspection  be
      Performed?
                         Check condition of bags:
                             ^Bag tears
                             Bag deterioration
                             -Dropped  bags
                             -Oily bags
                             -Wet bags
                             -Improper bag tension
                             -Deposits on floor

                       ENTER RESULTS IN REPORT.
           Are
        there  any
     indications of
     nonoptimal per-
       formance?
                      Check clean' air chamber for
                      possible leakage.

                      Check hoppers
                         Incomplete solids  removal
                         Corrosion
ENTER UNIT TO CONFIRM
EVALUATIONS.   MAY NEED
TO RESCHEDULE INSPECTION.
                                                      END INTERNAL  FABRIC FILTER
                                                               INSPECTION.
                       NO - END  FABRIC FILTER INSPECTION
          Figure 51.    Fabric  filter inspection flowsheet.
                                      145

-------
1
^ 	
r
Reschedule inspection
for a tine when unit is
operational
i
T
Inspect internal parts:
Nozzle condition
Presensp. of corrosion
Presense of erosion
Presence of scaling
1

Check integrity of shell
retention grids, and othe
parts.
         I
Check slurry handling
system.
                                                            Check pumps on purge,
                                                            make-up, and recircula-
                                                            tion lines.

                                                            Read flow meters if aval]
                                                            able. Check liquor temp
                                                            on  inlets and outlets.

                                                           ENTER RESULTS  IN  SECTIONS
                                                           A AND B.	j
                                                            Check pressure gauges am
                                                            differential pressure
                                                            monitors across the fol-
                                                            lowing:
                                                              Spray nozzles
                                                              Scrubber beds
                                                              Venturi throat
                                                              Deminters
                                                           ENTER RESULTS ON CHECK-?
                                                           LTST.	
                                                            Check sump and recircu-
                                                            lation tanks:
                                                              -Liquor temperature
                                                              -Liquor pH
                                                          ENTER RESULTS
                                                           1ST.	
                                                                         ON  CHECK-
            1
 Check inlet conditions:
   -Gas temperature
   -Presaturator water
    flow rate


ENTER RESULTS ON  CHECKLIST
                               END SCRUBBER INSPECTION
                Figure  52.   Scrubber  inspection flowsheet.
                                          146

-------
   Perform Internal
   Inspection.
                                      NO
Top section,  check:
     -Rappers
     -Drives
    .-Insulators
     -Heaters
     -Blowers
 Electrical Field section,
 checV:
     -Alignment
     -Build-up
     -Rappers
     -Drives
     -Insulators
     -Erosion
     -Corrosion
Check:
     -Hopper section
     -Build-up
     -Corrosion
     -Hopper baf lies
Check:
     Gas distribution devices
ESP  -Inlet
     -Outlet
     -Ductwork
     -Corrosion
     -Erosion
     -Plugging
     -Rapping  systems
End ESP  inspection,  return
for operational  inspection.
                                                            Is
                                                        Precipitator
                                                         Operating?
                                                                  YES
                                               Identify  bus section numbering
                                                 system.
                                               Check for bus sections which
                                                 are not operating.
                                              Check electrical characteris-
                                                tics of each bus section
                                                that is operating.
                                                Primary voltage
                                                -Primary current
                                                -Secondary current
                                                -Secondary voltage (if
                                                measured)
                                                -Spark rate
                                              Check rapper sequence and
                                                timing.
                                              Check insulators purge and
                                                heating system.

                                              ENTER RESULTS IN APPROPRIATE
                                              PLACES ON CHECKLIST.
                                             Check operational status
                                               Hopper heaters & vibrators
                                               Solids removal system

                                             ENTER RESULTS  ON CHECKLIST.
                                                                       NO >>  END
                                                                          ESP IN-
                                                                          SPECTION.
                                             Reschedule  operational  In-
                                             spection.   Recomnend mainte-
                                             nance vork.
                                                   END ESP INSPECTION.
 Figure  53.   Electrostatic  precipitator inspection  flowsheet.
                                       147

-------
                                   SECTION 5
                           COMPLIANCE DETERMINATION

     When the inspection has been completed, the inspector should conduct an
exit interview with the source.   During that meeting he/she should:
     0    Ask clarifying questions as necessary,
     0    Review inspection notes so that there is general agreement on
          the technical facts, and
     0    Discuss the need for a followup inspection or additional
          records.
     After returning to the office, the inspector should prepare an inspection
report.  All conclusions based on observations and calculations should be
clearly stated, and a diagnostic checklist for each control device in the
plant should be included.  The report should also document:
     0    Any change in responsible plant personnel,
     0    Requested permit changes or reported process modifications,
     0    Results of evaluation,
     0    Action requested,
     0    Inspector's signature, and
     0    Date of inspection.
A copy of the report should be kept in the inspector's source file and in the
Agency's central file.
     Comprehensive inspections require that the inspector have an established
baseline for each parameter during a period of known compliance.  The baseline
should document all pertinent operating parameters as they relate to the
emission characteristics of the source, including all process and control
equipment parameters.  In collecting pertinent data, the Agency should be
certain (1) the data are needed, (2) that a change in the value of a parameter
                                       148

-------
has an effect on the operation of the source, and (3) that the data are accur-
ate.  Checklists (as presented in Section 4) are especially useful.  The
baseline establishes a fixed point of operation and the appropriate values of
operating parameters against which other determinations can be made.   The
emission test at that point of operation documents the emissions that may be
correlated with process and control equipment operating characteristics de-
rived during the test.  The baseline test results are useful in subsequent
routine inspections.  When an operation and maintenance program or permit to
operate is issued based on a range of process and control equipment para-
meters, the Agency must be able to measure these parameters.  For this reason,
maintenance and calibration of the key parameter instrumentation are required
prior to the performance test.  Additional instrumentation also may be needed
in some cases.
     The baseline must be used for documenting deviations from normal condi-
tions for each process or control device operating parameter.   A substantial
change in the parameter is evaluated based on its impact on overall emission
levels.  For example, an increase in boiler firing rate would be evaluated
because of its impact on the uncontrolled emission rate from the boiler.
     The efficiency of the ESP serving a coal-fired boiler can be estimated by
using variables that define the power input to the system and the gas flow
being treated.  The equation that is generally applied is a modified version
of the Deutsch-Anderson equation.  This equation contains a parameter that
must be estimated or calculated from a previous baseline performance test.  To
apply this method, the inspector must be able to determine the flue gas flow
rate through the ESP and the power input to the ESP.   He/she must also be able
to determine that the unit is in reasonably good operating condition (no gross
gas maldistribution, power distribution imbalances, high resuspension rates,
or high rapper reentrainment) because poor conditions can severely impair the
performance of the ESP.
     The performance of an ESP should be evaluated in relation to previous
baseline tests and observations.   In rare cases, it is possible that stack
tests have been conducted over a range of boiler loads and at several ESP
power input levels.   In such cases, an inspector may be able to estimate
emissions if operating parameters are within the range of operating conditions
                                       149

-------
that have been tested.   Table 14 lists the effects of several  operating para-
meters of boilers, ESPs, and fabric filters on particulate emissions.

     TABLE 14.  SUMMARY OF THE EFFECTS OF SEVERAL OPERATING PARAMETERS OF
       BOILERS, ESPS, AND FABRIC FILTERS ON PARTICULATE EMISSION RATES.
Parameter
Firing rate
Primary air
Excess air
ESP power input
ESP superficial velocity
Fabric filter
air-to-cloth ratio
Fabric filter
pressure drop
Flue gas oxygena
Primary air temperature
Visible emissions
Change
Increase
Increase
Increase
Decrease
Decrease
Increase
Increase
Increase
Decrease
Increase
Effect on parti cul ate
emission rate
Increase
Increase
Increase
Increase
Decrease
Increase
Increase
Increase
Decrease
Increase
           If  increase  in oxygen is a result of an increase in
           primary air  volume.

     The inspection provides information on the key operating parameters of
the boiler and pollution control equipment.  Based on increases or decreases
in specific parameters, the inspector can determine whether emissions have
increased or  decreased.  Without a stack test, the inspector cannot determine
compliance with the standards.  Similarly, without visible emissions measure-
ments, he/she cannot determine compliance with the visible emissions standard.
Based on the  data collected during an inspection, however, the inspector can
subjectively  determine compliance.
     The data should be arranged in an orderly fashion (as shown in the check-
list order),  and for each recorded parameter the baseline data and the latest
inspection data should be tabulated for comparison.   Beside each tabulated
value the  inspector should note the impact of the parameter on the source
                                       150

-------
emissions (i.e., no change, an increase, or a decrease).   This process pro-
vides a useful table of increases and decreases in emissions for the inspec-
tor's subjective evaluation.
     A few specific equations can be applied to the data to provide additional
information on emissions.   The inspector should be familiar with the Deutsch-
Anderson equation for electrostatic precipators for use in estimating ESP
emissions.8  Plots of ESP voltage-current data can be effective for diagnosing
malfunctions that can cause an increase in emissions.9  Several manufacturers
of particulate scrubbers also use empirical equations to calculate emissions,
and the inspector should be familiar with these equations as well.  Sources
equipped with fabric filters must be evaluated subjectively because no suit-
able equations are available for estimating emissions from fabric filters
based on data that would be collected- during an inspection.
     During an inspection the following differences in operation from the
baseline conditions were noted:
                                                         Effect
          Fuel consumption
          Air flow
          Steam production
          Fan motor current
          Fabric filter3
           pressure drop
          Opacity
Baseline
250 Ib/h
63,000 acfm
2050 Ib/h
30 amps
3 in. H20
5%
! 9 in. H20
Inspection
210 Ib/h
53,000 acfm
1700 Ib/h
26 amps
2 in. H20
10%
6 in. H20
on emissioi
Decrease
Decrease
Decrease
Decrease
Decrease
Increase
Increase
 Overal1
     Based on the information in Table 14, it is possible that the unit would
not be in compliance with the particulate emission standard if the boiler were
operating at baseline conditions.  The increase in opacity of emissions from
the fabric filter indicates that the filter has missing bags, torn bags, or
other bag problems.
                                       151

-------
     The relationship between pressure drop and the air flow through a fabric
filter is nearly linear.  Based on the fuel consumption, heat content, stack
oxygen, and F factor, the air volume changed from 63,000 acfm to 53,000 acfm.
With a 3 in. H20 pressure at baseline conditions the pressure drop at the time
of the inspection should be 2.5 in. H20 or slightly higher than the observed
value.
     The fan data indicate a drop  in current usage due to the decreased air
flow and the drop in static pressure.  Since the pressure drop across the fan
is only 2 in. H20 instead of the 2.5 in. H20 expected using the F-factor, it
can be assumed that a bag is torn  or missing.  This confirms the higher opa-
city exhibited by the fabric filter.
                                        152

-------
                                   REFERENCES


  1.   Langsjoen,  P.  L.,  J.  0.  Burlingame, and J.  E.  Gabrielson.  Field Tests of
      Industrial  Stoker  Coal-Fired Boilers for Emissions Control and Efficiency
      Improvement -  Site K.   EPA-600/7-80-138a, U.S.  Environmental Protection
      Agency,  Research Triangle,  Park,  N.C.   May 1980.

  2.   American Boiler Manufacturers Association.   A Guide to Clean and Effi-
      cient Operation of Coal  Stoker Fired Boiler.   Prepared for the Department
      of Energy under Contract No.  EF-77-C-01-2609 and for the U.S.  Environmen-
      tal  Protection Agency under Contract No.  IAG-D7-E681 by KVB, Inc.  and the
      ABMA, Arlington, VA.   April  1981.

  3.   The  Babcock &  Wilson  Company.   Steam/Its  Generation and Use.   38th ed.
      The  Babcock &  Wilson,  Company,  New York,  New York.   1975.  p.  11-2.

  4.   Reference 3.   p. 11-3.

  5.   Reference 3.   p. 9-1.

  6.   Szabo, M. F.,  Y. M. Shah, and S.  P.  Schliesser.   Inspection Manual  for
      Evaluation  of  Electrostatic  Precipitator  Performance.   EPA-340/1-79-007,
      U.S.  Environmental  Protection Agency,  Washington,  D.C.   March  1981.
      p. 4-5.

  7.   PEDCo Environmental,  Inc.  Summary Report on  S02  Control  Systems  for
      Industrial  Combustion  and Process  Source, December  1977,  Volume  I  Indus-
      trial  Boilers  (Power and Steam).   Prepared  for  the  U.S.  Environmental
      Protection  Agency,  Industrial  Environmental  Research  Laboratory,  Research
      Triangle  Park,  N.C., under Contract No. 68-02-3173.   Cincinnati,  Ohio
      December  1977.

  8.   John  A. Danielson,  ed.  Air Pollution  Engineering Manual.   2nd ed.
      AP-40, U.S.  Environmental Protection Agency, Research Triangle Park, NC.
      May 1973.   pp.  153-155.

  9.   Reference 6.  pp.  4-13 and 4-19 to  4-22.

10.   Fryling, G.   R., ed.  Combustion Engineering.  Combustion  Engineering,
      Inc., New York, New York.  1966.

11.  Zerban, A.  H.,  and E.  P. Nye.   Power  Plants, 2nd ed.  International
     Textbook Company,  Scranton,  Pennsylvania.  1960.
                                       153

-------
12.  Richards, J. R.   Plant Inspection Manual - Techniques for Evaluating
     Performance of Air Pollution Control Equipment - Inspection Procedures
     and Performance Evaluation.  Prepared for U.S. Environmental Protection
     Agency Air Enforcement Branch, Region IV, by PEDCo Environmental, Inc.,
     under Contract No. 68-02-3512 (PN 3525-9), Durham, NC.  1981.

13.  PEDCo Environmental, Inc.   Simplified Operation and Maintenance Manual
     for Operators of Oil- and Gas-Fired Boilers.   Draft manual prepared for
     U.S. Environmental Protection Agency, Stationary Source Compliance Divi-
     sion, under contract No. 68-01-6310, Task 54.  Cincinnati, Ohio.  1983.
14.  Devitt, T., et al
15.



16.


17.



18.
                     The Population and Characteristics of Industrial/
Commercial Boilers.   Prepared for U.S. Environmental Protection Agency
Industrial Environmental Research Laboratory - Research Triangle Park by
PEDCo Environmental, Inc., under Contract No. 68-02-263, Task 19 (PN
3310S).  Cincinnati, Ohio.  1979.
Hudson, J. A.
Steam Plant.
Knoxville.
et al.   Design and Construction of Baghouses for Shawnee
Tennessee Valley Authority Division of Engineering Design,
 19.


 20.



 21.


 22.



 23.

 24.
Reigel, S. A.   Fabric Filtration Systems Design, Operation and Mainten-
ance.   Overland Park, Kansas.  1981.

Billings, C. E., and J. E. Wilder.   Major Applications of Fabric  Filters
and Associated  Problems.  Environmental  Engineering  Science,  Chestnut
Hill, Massachusetts.  1981.

PEDCo Environmental, Inc.  Plant  Inspection  Workshop - Techniques  for
Evaluating Performance of Air Pollution  Control  Equipment.  Volume III.
Process and  Control Equipment Flowcharting Techniques.  Prepared for U.S.
Environmental Protection Agency Air Enforcement  Branch, Region  IV.
Durham, North Carolina.  1981.

Schmidt,  C.  M.   Good Operating Practices for Industrial  Boilers.   Cleve-
land, Ohio.  1979.

PEDCo Environmental,  Inc.    Kraft Pulp Mill  Inspection Guide.  EPA-340/
1-83-017, U.S.  Environmental  Protection Agency,  Division  of  Stationary
Source  Enforcement, Washington, DC.  1983.

National  Coal  Association.    Layout and Application of Overfire Jets for
Smoke Control.   Washington,  D.C.   1962.

National  Research  Agency of the Bituminous  Coal  Industry.   How to Reduce
Stack  Dust from Small  Stationary  Plants.  Pittsburgh, Pennsylvania.
1952.

Smith,  E. H.  Underfeed Stokers.   Worcester, Massachusetts.

 Reed,  L.  E., and L.  J.  Flaws.   The Reduction of Smoke Emission from
 Coal-burning Ships with Forced-draught Boilers.   R.S.H.2.  1960.
                                        154

-------
25.
Boubel, W. et al.   General Inspection Procedures and Design Methodology
for Evaluating the Performance of Cyclone Separators.  Draft report
prepared for U.S. Environmental Protection Agency, Division of Stationary
Source Enforcement, Washington, D.C., by PEDCo Environmental, Inc. under
Contract No.  68-01-4147.  Cincinnati, Ohio.  1980.
26.
Engineering-Science.  Wet Scrubber Performance Manual.
U.S. Environmental Protection Agency, Washington, D.C.
                                                             EPA-340/1-83-022,
                                                             September 1983.
                                       155

-------

-------
            APPENDIX A

POLLUTION CONTROL DEVICE DIAGNOSTIC
    CHECKLISTS AND DATA SHEETS
                A-l

-------
  TABLE A-l.   CONTROL DEVICE  DIAGNOSTIC CHECKLIST AND  COVER PAGE
    INSPECTION
         REPORT-
                                        REPORT NUMBER
      PLANT NAME
      PLANT I.D.
                                        SPECIAL ACTION RECOMMENDED (Yes)   (Ho)
     I.  GENERAL INFORMATION

    A. Sources Inspected 	
      Production Status
    B.  Reasons for Inspection (Check Appropriate Items)
       Routine Inspection 	,_
       Complaint Investigation
       Stack Testing Observed _
       Special Studies 	
       Other           	
            Compliance Progress 	
            Permit Review/Renewal
            Tax Certification 	
            Emergency Episode 	
            Equipment Malfunction
    C.  Plant Representative Contacted (Name and Title)
    D.  Inspection Procedures and Conditions

       Prior Notice  (Check One) Yes 	 No

       Time/Date 	
Duration On-Site
       Type Inspection  (Check One)  Counterflow

                                 Other 	

       Weather 	-	
                     Follow-Up
                  Wind Direction
    II.   PRE-INSPECTION INTERVIEW

    A. Production Status:  Normal 	
    B. Control Equipment:  Normal 	
    C. Permit/Compliance Schedule Changes Needed:  Yes
    D. Comments
                Abnormal
                Abnormal
                             No
(continued)
                                        A-2

-------
TABLE  A-l (continued)
                                                   Report Number
            III.  INSPECTION RESULTS

            A.  General Conclusions

               All Sources in Compliance with:

                 Mass Emission Regulations:
                 Visible Emission Regulations:
                 Fuel Quality Regulations:
                 Continuous Monitoring Regulations: .Yes
                 Sampling/Testing Requirements:
                 Recordkeeping Requirements:
                 Permit Stipulations:
                 Special Orders:
                 O&M Practices:
                 Housekeeping:
Good
Good
Yes
,Yes
Yes
.Yes
Yes
Yes
Yes
Yes
Average
Average
No
No
No
No
No
No
No
No


N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Poor
Poor
            B.  Specific Conclusions

               Compliance Questionable Due To:

                 Changes in Raw Materials and/or Fuels
                 Production Rates Increases
                 Operational  Changes  in Process 	
                 Deterioration  of Process Equipment
                 Operational Problems in Control Equipment (Check Appropriate Items  Below)
Electrostatic^
Precipitators
Resistivity
TR Sets
Insulators
Discharge Wires
High Velocity
Gas Distribution
Rappers
Solids Handling
Plate Warpage
Mass Overload
Other
Fabric
Filters .
Tears/Pinholes
Blinding
Bleeding
Cleaning System
Hopper Overflow
Corrosion





Wet
Scrubbers
Low Liquor Flow
Gas Flow Rate Low
Bed Plugging
Nozzle Erosion
Demisters
Throat Adjustment
 Tray Collapse
Corrosion

            C.  Samples Taken  (Describe)
            D.  Comments/Recommended Action
                                              Inspector

                                              Reviewer
                                           Date

                                           Date
                                                 A-3

-------
               TABLE A-2.  FABRIC FILTER INSPECTION DATA SHEET
A. INSPECTION INFORMATION
   1.   IDENTIFICATION
        Company_
        Plant Name
        Plant  I.D. Number_
        Address
        Control Device/System Number_
        Process Served
    2.    PROCEDURES  AND  CONDITIONS
         Prior  Notice:   Yes	No_
         Time(s)  On-Site	
         Type  Inspect!on_

         Inspectors	
         Plant Representatives_
         Information Claimed Confidential:   Yes       No
                                      A-4

-------
TABLE A-2 (continued)
B. Visible  Emissions
   Observations
                  Inspection  No.
                  Equipment No.	
                  Confidential:   Yes
                  Page No.	of
                                                                  No
   1.    STACK CHARACTERISTICS
        Location	
        Hei ght	
        Temperature	
        Exi t Dimensions
        Orientation
        Other Information
   2.    STACK EFFLUENT
        Detached Plume:
        Color
No
Yes
Distance
        Puffing:   Yes	.	  No	
        Opacity
    Time       Average Opacity        Observation Point
                                       Sheet No.
   3.   FUGITIVE EMISSIONS
        Control Device:  Yes
          No
        Solids Removal System:  Yes	No	
        Process:  Yes	No	^
        Continuous__	 Intermittent
        Adjacent Deposits:  Yes	 No	
                                       A-5

-------
 TABLE A-2 (continued)
C. Fan Data
          Inspection  No.	
          Equipment No.	
          Confidential:   Yes
          Page  No.	of
        FAN MOTOR
        Manufacturer
        Model No.
        Rated Horsepower _
        Volts
        Maximum R.P.M.
        Operating Current:  Panel
         Type_
         Maximum Amps	
         Service factor
              Other
        DRIVE
        Direct
Belt
  Other
        Sheath Reduction	_	
        Audible Belt Slippage:  Yes	
                   No
        FAN
        Manufacturer
        Model No.
        Fan Vibration_	
        Gas Temperature at inlet,
        Fan R.P.M.
        Fan Static Pressures:  Inlet
         Type_
        Differential Static Pressures:
        Fan Housing Condition	
        Dampers	
        Fan Exit
       Measured
Outlet	
     Panel
                                       A-6

-------
TABLE A-2 (continued)
D. Fabric Filter Data
  1.   DESCRIPTIVE INFORMATION
       Fabric Filter Type
       Manufacturer 	
       Model No.
       Plant Inventory No.
       Date Installed
  2.   LOCATION
       Building/Area
       Inside
 Inspection No. 	
 Equipment No.	
. Confidential:  Yes	 No
 Page No.	of  	
 Outside
  3.   LAYOUT (SKETCH FABRIC FILTER, FAN, INLET, SOLIDS REMOVAL, ETC.)







-
-














-

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- -









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....
















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---





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                                      A-7

-------
TABLE A-2 (continued)

E.Fabric Filter External
  Inspection
    Inspection No.  	
    Equipment No. 	
    Confidential:   Yes
    Page No.  	of
                                                                  No
  1.   SOLIDS REMOVAL
       Valve Type:  Rotary
Flapper
Other
       Valve Speed/Frequency _     	
       Transport Equipment:  Screws	
       Transport Equipment Operating:  Yes	
       Transport Equipment Discharging Solids:   Yes
       Characterize Discharge _^____
           Other
                No
                       No
       Hopper Vibrators:  "Yes
       Hopper Insulation:  Yes
       Hopper Level Indicators
          No  _
           No
       Hopper Condition
       Disposal Method
  2.   SHELL CONDITIONS
       Insulated:  Yes
             No
       Possible Weld/Seam Gaps, Characterize
                                      A-8

-------
TABLE A-2 (continued)
E. Fabric Filter External
  Inspection
Inspection No.
Equipment No.
Confidential:
Page No.	
                                                         Yes
No
                                                           of
  3.   OPERATING CONDITIONS
       Static Pressure on Clean Side,
       Static Pressure on Dirty Side,
       On-site Monitor, Differential Static Pressure
       Tap Conditions	
       Gas Inlet Temperature
                              _ in.  H?.0
                              _ in.  H20
                                    H?.0
        in.
  4.   CLEANING SYSTEMS
       Type 	
       Frequency
       Air Pressure,
       Drier:  Yes
                               PSIG
      No
       Evidence of Water and/or Oil Problems
       Solenoids  Inoperative
  5.
PRECLEANERS
Type
Static Pressures: Inlet
Gas Inlet Temperature
Outlet in
F
                                      A-9

-------
TABLE A-2 (continued)
I- Fabric Filter  Internal
  Inspection
Inspection No.
Equipment No.
Confidential:
Page No. 	
                                                         Yes _
                                                           of
No
       PURPOSE
       Reason(s) Necessary
             Inventory Check
            Comprehensive  Inspection
            Other
       Safety Evaluation  (Describe if applicable)
            Respirator Necessary _^	
            Temperature 	
            02 	;	__
            Combustibles 	
            Electrical Grounding
            Mechanical Hazards _
            Noise 	
            Other
       Inspection Conducted:  Yes 	
       Inspection Not Performed Due to Safety

  2.   BAG LAYOUT (ATTACH DRAWING)
       No. of bags 	
       Length 	
         No
       Diameter
       Material  (Characterize)
                               ft
                                                                         in.
       Attachment(s)
                                      A-10

-------
TABLE A-2 (continued)

R Fabric Filter Internal
  Inspection
  3.   HATCH CONDITIONS
       Gaskets
       Corrosion
       Bolts/Ears
       Ease of Access
  4.   LEAK JETS
       Location
       Number
  5.    BAG CONDITIONS
Inspection No. 	
Equipment No. 	
Confidential:  Yes	No
P.age No. 	of	
                                     A-11

-------
Table A-2 (continued)
F.  Fabric  Filter Internal
   Inspection
Inspection No. 	
Equipment No. 	
Confidential:  Yes
Page No. 	of
                                                                   No
   6.    HOPPERS  AND BLAST PLATES
   7.    CLEANING  APPARATUS
                                      A-12

-------
TABLE A-2 (continued)
G  Samples
   1.    SOLIDS DEPOSITS
        Sample No.
        Location Obtained
        Date/Time Obtained
        Results
Inspection No. 	
Equipment No. 	
Confidential:  Yes
Page No. 	  of
                                                                   No
        FABRIC  SAMPLES
        Sample  No. 	
        Location Obtained _
        Date/Time Obtained
             Permeability
            Tensile Strength
            Count
            Weight/Yard5
       OTHER
                                      A-

-------
TABLE A-2 (continued)
H  Ventilation System
Inspection No.  	
Equipment No. 	
Confidential:  Yes __	No
Page No. 	of	__
   1.    DUCTS (SHOW STATIC PRESSURES ON LAYOUT.)
" i
 i

->
L -J
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....





































































































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i
































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_._


	
_.






....


.









   2.    HOOD
        Configuration
        Average Capture Velocity 	
        Thermal Drafts (Characterize)
                               ft/mi n
        Cross Currents (Characterize)
        Estimated Effectiveness
                                      A-14

-------
TABLE A-2 (continued)
I Process
  1.   PROCESS TYPE
       Characterize Source
       Operating Schedule
Inspection No.	
Equipment No. 	
Confidential:  Yes
Page No.    	  of
                                                                  No
  2.    OPERATION
       Product Type During Inspection
       Production Rate During Inspection
       Raw Materials During Inspection
       Fuels During Inspection
                                     A-15

-------
TABLE A-2 (continued)
J  Fabric Filter  Evaluation
Inspection No.  	
Equipment No.  _____
Confidential:   Yes
                 of
                                                                No










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-------
TABLE A-2 (continued)
J Fabric Filter Evaluation
Inspection No.
Equipment No.
Confidential:
                                                          Yes
No




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-------
TABLE A-2 (continued)
K  Summary
               Inspection No.
               Equipment No. 	
               Confidential:
               Page No. 	
                                                          Yes _
                                                            of
                      No
   1.   CONTROL SYSTEM PERFORMANCE
        System Air Flow Based on Fan Data.
        System Air Flow Based on Pi tot Traverse
        System Air Flow Based on Process   	
        Actual Air to Cloth Ratio
        Design Air to Cloth Ratio
        Fabric Compatibility with Environment
   2.   ADDITIONAL COMMENTS
                                             ACFM
   3.   SHEETS  INCLUDED
A.
G.
Preparer:
Reviewer:
B.
H.
Name
Date
Name
Date
C. D. E. F.
I. J. K.
Signature

Signature

   Copies Received
Initials
Date
                                     A-18

-------
TABLE A-2 (continued)
   Fabric  Filter  Supplemental
   Information
Inspection No. _____
Equipment No.	
Confidential:  Yes _
Page No.	   of
                                                                   No
                                     A-19

-------
LOCATION
DESIGNATION
 TABLE A-3.  WET SCRUBBER INSPECTION DATA SHEET.

	'    	   DATA SHEET NO.	
	              DATE
CLAIMED
CONFIDENTIAL  Yes
           NO
                                  INSPECTOR(S)
                                  INSPECTION NO.
    DESCRIPTIVE INFORMATION
     Wet Scrubber Type
     Manufacturer 	
     Model Number
     Date Installed
     Process/Source Controlled 	
     Particulate Characteristics
B.  COMPONENT INFORMATION  (Describe if  applicable)
     1.  Gas Pretreatment:
         Presaturator	
         Cyclones	'
         Settling Chamber	
         Other
         Demister:
         Cyclone _
         Chevron
         Fiberous Mat
         Other
         Pumps:
         Number
         Recirculation 	
          Pump Manufacturer
         Recirculation
          Pump Rated Horsepower
         Recirculation Pump Type
                                A-20

-------
TABLE A-3 (continued)
          Inspection No.
          Data Sheet No.
          Preparer 	
                                   Confidential:  Yes
                               No
B.  COMPONENT INFORMATION (continued)
     4.  Fan/Motor (Specify)
         Fan Manufacturer	
         Blade Type:   Radial.	
         Drive:  Direct
         Damper Position  .
          Backward
               Belt
Forward
         Motor Manufacturer
         Model No.
         Rated Horsepower 	
         Location:  Forced Draft
                Induced Draft
     5.  Instrumentation  (Check if Applicable)
         Differential
         Pressures:
         Temperatures
Throat
                         Separator
                         Demister
         pH:
Gas Outlet 	
Gas Inlet 	
Liquor Inlet
Liquor Outlet
Recirculation
Exit Liquor
                         Fan Motor Current
                         Other
         Flow Rates:
         Motor Current:
Nozzle Pressure
Recirculation 	
Makeup 	
Purge 	
Fan 	
Pump 	
                                A-21

-------
TABLE A-3 (continued)
                               Inspection No.
                               Data Sheet No.
                               Preparer   .
B.
                               Confidential:   Yes	 No	

COMPONENT INFORMATION  (continued)
 6.  Materials of Construction  (Specify type  and gauge)
         Presaturator
         ..Throat    	
         Scrubber  Shell  	
         Trays/Bed Supports
         Demister	
         Fan Housing  	
                                 A-22

-------
TABLE A-3 (continued)
Inspection No.

Data Sheet No.

Preparer    '
                                    Confidential:  Yes   No
C.  DIAGRAM
     1.  Sketch wet scrubber  system.   (Show all major compon-
         ents and processes controlled.)
     2.   Sketch wet scrubber layout  (each  square  I1  x .1')
                                A-23

-------
TABLE A-3  (continued)
Inspection No.
Data Sheet No.
Preparer 	
                                   Confidential:  Yes
                     No
F.  SAMPLE ANALYSIS
     Scrubber Liquor Effluent
          Sample No. 	
          Location Obtained 	
          Date/Time Obtained
          Results:
          Suspended Solids ^	
          Dissolved Solids 	
          PH 	;	
          Chloride
     Scrubber Recirculation
          Sample No. 	
          Location Obtained
          Date/Time Obtained
          Results:
          Suspended Solids 	
          Dissolved Solids 	
          PH 	
          Chloride
               ppm
               ppm

               ppm
               ppm
               ppm

               ppm
     Other
                                 A-24

-------
TABLE A-3 (continued)                 Inspection No.
                                   Data Sheet No.
                                   Preparer 	
                                   Confidential:   Yes	 No

G.  CONTROL SYSTEM PERFORMANCE
     Gaseous Flow 	;	 ACFM
      (implied from fan operation)"
     Gaseous Flow	    	 ACFM
      (calculated from pitot traverse):
     Gaseous Flow	 ACFM
      (implied from process operation)
     Liquor Flow 	  	 gpm
     L/G Ratio ,	
     Bypass (% of total gas flow)	%
     Throat Velocity	 FPS
     Superficial Velocity  (design) 	'    FPM
                           (effective) 	 FPM
     Visible Emissions  (residual) 	 %
H.  ADDITIONAL COMMENTS
                    Sheets Included:  A 	 B 	 C
                                      D 	 E 	 F
                                      G     H
                    Inspector's Signature
                    Date Prepared 	
                    Reviewer's Signature
                    Date Reviewed 	
                    Date Filed 	

                               A-25

-------
         TABLE A-4.   ELECTROSTATIC PRECIPITATOR INSPECTION DATA SHEET.
A. INSPECTION  INFORMATION
1.    IDENTIFICATION
     Company_
     Plant Name
     Plant I.D. Number_
     Address   	
     Control Device/System Number_
     Process Served	
2.   PROCEDURES AMD CONDITIONS
     Prior Notice:  Yes	No_
     Time(s) On-Site	'
     Type  Inspection_

     Inspectors
      Plant  Representatives_
      Information Claimed Confidential:   Yes_
No
                                      A-26

-------
TABLE A-4 (continued)
B. Visible Emissions
   Observations
                                   Inspection No.
                                   Equipment No._
                                   Confidential:
                                   Page No.	
                                                       Yes_
                                                       of
                                No
1.
STACK CHARACTERISTICS
Location	
Hei ght	
     Temper a ture_	
     Exit Dimensions_
     Orientation
     Other Information^

2.   STACK EFFLUENT
     Detached Plume:
     Color
                 No
Yes
Distance
     Puffing:   Yes
     Opacity
 Time       Average Opacity
                                  No
                              Observation Point
                              Sheet No.
3.    FUGITIVE EMISSIONS
     Control  Device:   Yes	
     Solids  Removal  System:   Yes
     Process:   Yes	No	
     Continuous
                           No
                                  No
     Adjacent Deposits:   Yes
                                 Intermittent
                              No
                                     A-27

-------
TABLE A-4  (continued)
C. Fan Data
1.
3.
FAN MOTOR
Manufacturer
     Model No.
     Rated Horsepower_
     Volts
     Maximum R.P.M.
     Operating Current:  Panel	

     DRIVE
     Direct          ,         Belt
     Sheath Reduction
     Audible Belt Slippage:  Yes
FAN
Manufacturer_
Model No.
                                   Inspection No.
                                   Equipment No._
                                   Confidential:
                                   Page No. 	
                                                       Yes_
                                                        of
                                  Type_
                                _. Maximum Amps	
                                _ Service factor_
                                       Other
                                             Other
                                            No
               No
                                       Type.
     Fan Vibration	
     Gas Temperature at inlet,
     Fan R.P.M.
     Fan Static Pressures:  Inlet
     Differential Static Pressures:
     Fan Housing Condition	
     Dampers	
     Fan Exit
                                Measured
Outlet	
     Panel
                                     A-23

-------
TABLE A-4 (continued)
D. Electrostatic Precipitator
   Data
1.    DESCRIPTIVE INFORMATION
     Type	
     Manufacturer
     Model  Number
     Plant Inventory Number_
     Date Installed'
     Number of Chambers
Inspection No.
Equipment No._
Confidential:
Page No. 	
                                                       Yes_
                                                        of
No
     Number of Fields in Series	
     Specific Collection Area (Ft2'/1000 Ft3)_
     Design Superficial  Viscosity (Ft/Sec)	
     Pulse Energization  (Yes/No)	
     LOCATION
     Building/Area_
     Elevation
     LAYOUT (SKETCH FIELD LAYOUT AND NUMBER FIELDS,  SHOW FANS)
                                     A-29

-------
TABLE A-4 (continued)
E. Electrostatic  Precipitator
   External  Inspection
Inspection No.
Equipment No._
                                        Confidential:   Yes	No_
                                        Page No.       of	
x.   HOPPER LAYOUT (SKETCH TOP VIEW AND NUMBER; SHOW SOLIDS HANDLING
     SYSTEM)
c..
HOPPER DESCRIPTION
Vibrators:  Yes	
Heaters:  Yes	
Insulatipn:  Yes_	
Level Indicators:  Yes
                                       No_
                                       No
                                       No
                                       No
           Type_
     Physical Condition (Characterize)^
     Transport Equipment:  Screws	Pneumatic_
     Transport Equipment Operating:  Yes	
     Characterize Discharge	
                 Other
           No
                                      A-30

-------
 TABLE A-4  (continued)
 E.Electrostatic  Precipitator
   External  Inspection
                                    Inspection No.
                                    Equipment No._
                                    Confidential:
                                    Page No-.
                                                       Yes
                                                       of
No
3.   HOPPER VALVES
     Type:  Screw
     Speed/Cycle Times
     Blade Type_
                                   Other
4.
.RAPPER  LAYOUT (SKETCH TOP VIEW,  SHOW DISCHARGE WIRE UNITS AS D,
 COLLECTION  PLATE UNITS AS C AND  DISTRIBUTION  PLATE UNITS AS X).
                                    A-31

-------
TABLE A-4 (continued)
E. Electrostatic  Precipitator
   External  Inspection
Inspection No.
Equipment No._
Confidential:
Page No.	
                                                       Yes_
                                                       of
No
5.   RAPPER PERFORMANCE (Continued)
     COLLECTION PLATE RAPPERS
No.
Ci
C2
C3
C*
C5
C6
C7
C8
C9
Cio
Cn
Ci2
Cl3
Cm
Cis
Cl6
Cl7
Cl8
Cig
C20
Time Interval
(Minutes)




















Duration
(Seconds)



-
















Comments




















                                       A-32

-------
TABLE A-4 (continued)
E. Electrostatic Precipitator
   External Inspection
5.   RAPPER PERFORMANCE
     DISCHARGE WIRE RAPPERS
Inspection No.
Equipment No._
Confidential:
Page No.    	
                                                       Yes
                                                       of
No
No.
Di
D2
D3
D.,
Ds
D6
D7
De
D9
Dio
DM
Dj2
Dis
DII
Dl5
Die
Dl'7
Die
Dig
D20
Time Interval
(Minutes)




















Duration
(Seconds)














.?*





Comments













-.






                                    A-33

-------
 TABLE A-4  (continued)
E.Electrostatic PrecipUator
  External Inspection
                                  Inspection No.
                                  Equipment No._
                                  Confidential:
                                  Page No.	
                                                      Yes_
                                                      of
No
5.
 6.
RAPPER PERFORMANCE (Continued)
DISTRIBUTION PLATE RAPPERS
No.
Xi
X2
X3
Xi,
X5
Xfi
Time Interval
(Minutes)






Duration
(Seconds)






Comments






RAPPER DESCRIPTION
DISCHARGE WIRES
     Type	
           Number
          Manufacturer
          Air Pressure
      COLLECTION  PLATES
          Type	
           Number
           Manufacturer _
           Air Pressure __
      DISTRIBUTION PLATES
           Type	
           Number 	
           Manufacturer
           Air Pressure
                                     A-34

-------
 TABLE A-4 (continued)
E. Electrostatic Precipitator
   External  Inspection
Inspection No._

Equipment No.
                                        Confidential:  Yes     No
                                        Page No.	of
7.   TRANSFORMER - RECTIFIER SET LAYOUT (SKETCH TOP VIEW SHOWING T-R
     SETS ON CHAMBERS AND FIELDS)
8.   TRANSFORMER - RECTIFIER SET DESCRIPTION

     Power Control:   Yes       No
Mode Voltage Current Spark Rate
No.
T-R!
T-R2
T-R3
T-R,,
T-R5
T-R6
T-R7
T-R8
T-R9
T-Rio
Plant
No.










Manufacturer










Model
No.










Milliamp
Rating



i






Type










                                     A-35

-------
TABLE A-4 (continued)
E.Electrostatic Precipitator
  External Inspection
Inspection No.
Equipment No._
Confidential:
Page No. 	
                                                       Yes_
                                                        of
No
9. TRANSFORMER - RECTIFIER SET CONDITIONS
No.
T-R-la
T-R-lb
T-R-2a
T-R-2b
T-R-3a
T-R-3b
T-R-4a
T-R-45
T-R-5a
T-R-5b
T-R-6a '
T-R-6b
T-R-7a
T-R-7b
T-R-8a
T-R-8b
T-R-9a
T-R-9b
T-R-lOa
T-R-lOb
Primary
current
amperes)




















Primary
voltage
(volts)




















Secondary
current
(mi 11 iamps)




















Secondary
voltage
(kilovolts)




















Spark
rate
7^/mi n




















Control
mode
M-manual
A-automatic



*
















                                       A-36

-------
 TABLE A-4  (continued)
E. Electrostatic Precipitator
   External Inspection
Inspection No.
Equipment No.
                                        Confidential:  Yes	No_
                                        Page No.       of  	
 10.  OPERATING INFORMATION
     Gas Inlet Temperature, F
     Hopper Heater Operational Indicator Lights (Identify units not on)

     Penthouse Heater/Blower Operational Indicator Lights (Identify units
     not on)	;	

     Comments
 11.  OPACITY MONITORS
     Opacity - Minimum, %	
               Average, % 	,
               Maximum, %	
     Spikes (Characterize Frequency, Duration, Intensity)
     Calibration Spikes (Characterize Levels, Frequency)_
     Comments
                                     A-37

-------
TABLE A-4 (continued)
F. Electrostatic Precipitator
  Interal  Inspection
Inspection No.	
Equipment No.	
Confidential:  Yes	No_
Page No.	of	
1.   PURPOSE
     Reason(s) Necessary_
     SAFETY EVALUATION
     Lockout Procedure Followed
     Plant Employee Performing Lockout_
     Grounding Straps Available:  Yes_
     Time Period De-energized (Hours)_
     Purge Completed:  Yes:	
     02, %          	;
     Combustibles, %_
     Noise
     Other
           No
     No
     Inspection Not Conducted''Due to Potential Hazards ( Characterize)
2.   AREAS INSPECTED (SKETCH TOP VIEW AND INDICATE ENTRY POINTS)


                                     A-38

-------
 TABLE A-4 (continued)                   Inspection No..

F. Electrostatic Precipitator           Equipment No._
   Internal  Inspection
                                        Confidential:   Yes	No_

                                        Page	of	'
3.   HATCH CONDITIONS

     Gaskets
     Corrosion
4.   PENTHOUSE CONDITIONS

     Purge Air	
     Heater(s)
     Insulators
     Alignment of Collection Plates_
     Comments
                                     A-39

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 TABLE A-4 (continued)
   Electrostatic Precipitator
   Internal  Inspection
Inspection No.
Equipment No:_
Confidential:
Page No.
                                                       Yes_
                                                       of
No
5.   ELECTRODE CONDITIONS
     DISCHARGE WIRES
          T.VPe
          Di ameter_
          Material
          Spacing and Length_
          Conditions    	
     COLLECTION PLATES
          Type	
          Ma ten' al	.
          Spacing and Length_
          Conditions	
          Alignment,
                                    A-40

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TABLE A-4 (continued)

F.  Electrostatic Precipitator
   Internal  Inspection
6.   INTERNAL SUPPORTS

     Describe
8,
     Conditions
7.   GAS DISTRIBUTION EQUIPMENT

     Type	
     Condition
HOPPERS

Baffle Condition
     Hopper Condition_
                                   Inspection No.

                                   Equipment No.
                                        Confidential:  Yes	No_

                                        Page No.	of	
                                      A-41

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TABLE A-4 (continued)
Q.   Continuous Monitor Evaluation
Inspection No._
Equipment No.
                                         Confidential:   Yes	No_
                                         Page No.	of	
 1.    DESCRIPTIVE DATA
      Manufacturer	
      Model
      Type.
      Date Installed
      Single or Multiple Breeching (Describe Sources)
      NSPS Applicable:   Yes_
         No
 2.    TRANSMISSOMETER
      LAYOUT (SHOW LOCATION RELATIVE TO FLOW RESTRICTIONS)
                                       A-42

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TABLE A-4 (continued)                   Inspection No.
G. Continuous Monitor Evaluation        Equipment No.
                                        Confidential:  Yes	No_
                                        Page No.	of
2.   TRANSMISSOMETER (Continued)
     Approximate Path Length, (Feet)_
     Mounting (Characterize)
     Vibration (Characterize)
     Housing (Characterize)
     Purge Air (Condition of Blowers and Hoses)
     Filters (Characterize Type and Describe Condition)
     Alignment (Window Check)
3.   CONSOLES
     Breeching/Stack Correlation
     Zero/Span_
     Comments
                                     A-43

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TABLE A-4 (continued)
H, Electrostatic Precipitator
   Evaluation
Inspection No.
Equipment No._
                                        Confidential:  Yes	No_
                                        Page No.	of	
1.   FILES/ADMINISTRATIVE
     Specification Sheets Available:  Yes_
     Prints Available (Characterize)	
              No
     Supervisor of Unit_
     0 and M Personnel (Describe Staff and Organization^
2.   RECORDKEEPING
             
     Type Records__
     Operating Records  (List Parameters)_
     Diagnostic Records  (Characterize)__
3.   PROCEDURES
     Spare Parts Inventory (Characterize^
     O&M Plan (Characterize)
     Troubleshooting  (Character!ze)
                                     A-44

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TABLE A-4 (continued)
I. Samples
Inspection No..
Equipment No._
Confidential:
Page No.	
                                                       Yes_
                                                       of
No
1.    Solids
     Sample No.	
     Location Obtained__
     Date/Time Obtained_
     Results
2.   Other Samples
     Sample No.	
     Location Obtained
     Date/Time Obtained_
          Permeability
          Tensile Strength_
          Count
          Weight/Yard2
3.   Other
                                     A-45

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TABLE A-4 (continued)
J. Electrostatic Preclpltator
   Evaluation
                            Inspection No.
                            Equipment No._
                            Confidential:
                            Page No.	
                                                       Yes_
                                                       of
                                  No
1.   POWER INPUT
     Collection Plate Area/field
          Inlet
          Other
     Discharge Wire Length/Field
          Inlet
          Other
Field
 1.
 2.
 3.
 4.
 5.
 6.
 7.
 8.
 9.
10.
11.
12.
13.
14.
15.
 Secondary
 Currents
(Milllamps)
 Power
 Input
(Watts)
    Current Densities
(Mi 11lamps/Ft)    Watts/Ft2
                                     A-46

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TABLE A-4 (continued)                   Inspection No..
K. Process                              Equipment No.
                                        Confidential:  Yes	No_
                                        Page No._	of	
1.   PROCESS TYPE
     Characterize Source
     Operating Schedule
2.   OPERATION
     Product Type During Inspection^
     Production Data During Inspection_
     Raw Materials During Inspection_
     Fuels During Inspection^
                                     A-47

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TABLE A-4 (continued)
L.Summary
 1.   POWER  INPUT
 2.   MECHANICAL
 3.   SOLIDS REMOVAL
Inspection No.
Equipment No._
                                         Confidential:   Yes	No_
                                         Page	of	
 4.   EFFLUENT QUANTITY/CHARACTERISTICS
 5.   OTHER


6. SHEETS .
A. B.
D. E.
G. H.
C.
F.
I.
J. K.
Preparer: Name
Signature
Date
Reviewer: Name
Signature
Date
 Copy Received:   Initials_
Date
                                      A-48

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          TABLE A-5.  MECHANICAL COLLECTOR INSPECTION DATA SHEET.

LOCATION 	  DATA SHEET NO. 	__.
DESIGNATION	  INSPECTION NO.     . .
CLIENT	;	  INSPECTOR(S) 	
PN	                 DATE
CLAIMED
CONFIDENTIAL Yes        No
A.  DESCRIPTIVE INFORMATION
     Mechanical Collector  Type
          Cyclone 	 Settling Chamber
          Cyclone Bank 	 Double Vortex Cyclone
          Multiclone	 Other (describe)
     Manufacturer
     Model Number
     Date Installed
     Process/Source Controlled
     Particulate Characteristics
B.  COMPONENT INFORMATION
     1.  Cyclone
          Diameter of Body	^^ ft>
          Cone Angle	 degrees
          Material of Construction	
          Gauge of Metal 	
          Number of Cyclones
         Hoppers
          Number 	
          Slope 	
          Insulation:  Yes 	 No
          Heating:  Yes	 No
          Vibrators:   Yes 	  No

                               A-49

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TABLE A-5  (continued)
Inspection No.
Data Sheet No.
Preparer 	
                                   Confidential:  Yes
                     No
B.  COMPONENT INFORMATION  (continued)
     3.  Solids Removal,  (Check applicable items and provide
         dimensions)   \       .    >
          Rotary Valves     '	
          Flapper Valves	'
          Screw Conveyors 	
          Pneumatic Conveyors
          Free Fall
         Fan/Motor
          Fan Manufacturer 	
          Model Number 	_
          Blade Type:  Radial
          Drive:  Direct
Backward
Forward
        Belt
          Motor Manufacturer
          Model Number
          Rated Horsepower
          RPM
          Location:  Forced Draft
      Induced Draft
C.  SYSTEM LAYOUT
                                A-50

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TABLE A-5 (continued)                  Inspection No.
                                   Data Sheet No.
                                   Preparer 	
                                   Confidential:  Yes	 No	

D.  EXTERNAL INSPECTION
     Fan Inlet Static Pressure .	-	 in. of
     Fan Outlet Static Pressure	 in. of
     Fan Motor Current	 amperes
     Fan Rotational Speed	 rpm
     Fan Damper Position	
     Gas Temperature at Fan Inlet 	 F
     Fan Vibration  (low, moderate, severe)
                    Corroded
                                                                2
Static Pressure at Collector Outlet	       in. of H~0
Static Pressure at Collector Inlet 	 in. of H_0
On-site Differential Pressure Gauge Reading 	 in. of H.,0
Gas Temperature at Collector Inlet 	 F
Rotary Valve Rotational Speed 	 rpm
Flapper Gate Frequency	 (#/hr) '
Hopper Conditions (Check if applicable)
               Cold 	
               Dented	
               Warped 	
                                A-51

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 TABLE A-5 (continued)
Inspection No.
Data Sheet No.
Preparer 	
                                   Confidential:   Yes    No
E.  INTERNAL INSPECTION
     Hoppers (plugged or corroded)
     Hopper Baffles Nonexistent  (Characterize  potential abra-
     sion)	:
     Inlet Vanes Plugged/Eroded  (Characterize severity)
     Cones Plugged  (location,  number)
     Flow Disturbances  (Characterize  severity)
     Outlet Tube Erosion  (Characterize  potential bypassing)
     Corrosion  (Characterize)
      Scaling  (Characterize)
                                A-52

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TABLE A-5 (continued)                 Inspection  No.
                                   Data  Sheet  No.
                                   Preparer  	
                                   Confidential:   Yes   No
F.  CONTROL SYSTEM PERFORMANCE.
     Air Flow Rate  (implied from  fan  operation)  	 ACFM
     Air Flow Rate  (calculated from pitot tube)  	'     ACFM
     Air Flow Rate  (implied from  process  operation)  	 ACFM
     Inlet Velocity 	 FPS
     Opacity 	_...  '	 %
G.  ADDITIONAL COMMENTS
                         Sheets  Included:   A	 B	 C
                                            E    F   G
                          Inspector's  Signature
                          Date  Prepared  	
                         Reviewer's  Signature
                         Date  Reviewed  	
                         Date  Filed
                                A-53

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                                   TECHNICAL REPORT DATA
                            (Please read JaUmctions CM the reverse before completing)
 1. REPORT NO.
  EPA-450/1-84-025
                              2.
                                                           3. RECIPI-ENT'S ACCESSION NO.
 4 TITLE AND SUBTITLE
  Coal-Fired Industrial" Boiler  Inspection Guide
             5. REPORT DATE
                Issued January 1984
                                                           6. PERFORMING ORGANIZATION CODE
7, AUTHOR(S)
  William- E. Gallagher, Gerald  A.  Isaacs, Thomas C.
  Ponder, Jr., and Robert A.  Ressl
             8. PERFORMING ORGAN.IZATI'ON REPORT NO.

               '3560-3-9
9 PERFORMING ORGANIZATION NAME AND ADDRESS
  PEDCo Environmental,  Inc.
  11499 Chester Road
  Cincinnati, Ohio  45246-0100
                                                           10. PRC'GBAM ELEMENT NO.
             11. CONTRACT/GRANT NO.
                                                              68-01-6310
 12. SPONSORING AGENCY NAME AND ADDRESS
                                                           13. TYPE OF REPORT AND PERIOD COVERED
                                                              Final.
                                                           14. SPONSORING AGENCY CODE
 15. SUPPLEMENTARY NOTES
  U.S. EPA Project  Officer  - John R. Busik, Stationary  Source Compliance Division
 16. ABSTRACT                                \       '        '                        ~~~
       This document provides guidance for evaluating;the performance of coal-
  fired industrial  boilers relative to a. pollution  control  agency's particulate'
  air pollution  control  rules and regulations.  The guidance and checklists' in
  this document  enable an air pollution control agency inspector to check a
  boiler operation  quickly and efficiently.  A  thorough description, of stoker-
  fired and pulverized coal-fired industrial boilers helps  prepare the inspector
  for the field  inspection.   Pollution control  equipment typically used on
  industrial boilers (multicyclones, fabric filters,  electrostatic -precipita-   .
  tors, and scrubbers) is described as well as  common problems and possible
  solutions that influence the operation and maintenance of these devices.

       Baseline  data for a boiler and its pollution control  equipment normally   .
  are established during a compliance stack test.   Information contained in  this
  report shows the  agency inspector how to compare  current  boiler-operations to
  the baseline data for a compliance determination.   This is particularly useful
  when a clearly defined cause-and-effect relationship cannot be established for
  a given source.
17.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
  BOIlers
  Pollution
  Particles
  Control Equipment
                                              b.IDENTIFIERS/OPEN ENDED TERMS
"Industrial,  Stoker-fired,
  Pulverized  Coal-fired
Air  Pollution Control
Particulate  Emissions
Multicyclones, Fabric
  Filters,  ESPs, Scrubbers
                                                                         c. COSATI Field/Croup
ISA

13B
14G
13B
13..plS.T.RIBUTigN STATEMENT ,        ....   -, -r   i
  unlimited.   Available from'National Tech-
  nical  Information Service, 5085 Port Royal
  Road,  Springfield,  Virginia 22161
         .
      assi
                           21. NO.
                                    GES
20. SECURITY CL.ASS (This pant)
  Unclassified
                           72. PRICE
EPA Form 2JZO-1 (9-73)

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