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Air
APTI
Course Sl:445
Introduction to Baseline
Source Inspection Techniques
REFERENCE
FIELD INSPECTION
NOTEBOOK
-------
REVISED
OCTOBER 1983
FIELD INSPECTION
NOTEBOOK
SOURCE
DATES
Prepared by
Engineering-Science
Durham, North Carolina
919-682-9611
form*
U.S. Environmental Protection Agency
Stationary Source Compliance Division
Contract 68-01-6312
Work Assignments 62 and 99
-------
TABLE OF CONTENTS
Section Page
Safety Guidelines Front & Back Covers
Inspection of Air Pollution Control Systems 1
Inspection of Pulse Jet Fabric Filters 2
Inspection of Reverse Air and Shaker Fabric Filters 12
Inspection of Electrostatic Precipitators 21
Inspection of Cyclone and Multi-Cyclone Collectors 32
Inspection of Venturi Scrubbers 40
Inspection of Spray Tower Scrubbers 50
Inspection of Tray-type, Moving Bed, and Packed Bed Scrubbers 56
Selection of Measurement Ports and Use of Portable Instruments....65
Velocity Traverses 69
Measurement of Oxygen and Carbon Dioxide in Combustion Gas
Streams 74
Checking the C02 and 0? Measurements 75
Using the C02 and 02 Measurements 75
Nomograph for Estimating Flue Gas Composition, Excess Air or
Type of Fuel 76
Opacity Measurements - Slant Angle 77
High Temperature Psychrometric Chart 78
Fans 79
Fan Performance 80
Relative Air Density Factor 81
Density of Solids 82
Density of Liquids 83
Sieve Number vs. Particle Size 83
Selected Geometric Relationships 84
Conversion Factors 35
-------
SAFETY GUIDELINES Front
Cover
1. The work should be interrupted IMMEDIATELY whenever the inspector
experiences the nonspecific symptoms of exposure, including but not
limited to. the following: headache, eye or nose irritation, nausea,
dizziness, drowsiness, vomiting, loss of coordination, chest pains, or
shortness of breath. The inspector should proceed to a well ventilated
area and reevaluate the potential inhalation hazards.
2. The inspection should be conducted at a controlled pace in order to
avoid careless accidents. NEVER HURRY.
3. Hardhats and safety shoes should be worn during all inspections, even
when not required by plant safety policies.
4. If necessary personal protective equipment such as a respirator is not
available, areas of potential exposure should be avoided.
5. Hearing protection should be used whenever it is difficult to hear
another person speaking in a normal tone of voice at a distance of 3 feet.
6. Contact lenses should NOT be worn during inspections. Eye protection
must conform with plant requirements.
7. Internal inspections of air pollution control equipment should NOT be
conducted unless the inspector has the proper training and equipment
for confined space entry.
8. Areas of potentially high pollutant concentrations should be entered
only if the proper personal protection equipment is available. A par-
tial list of such areas includes weather enclosures above precipita-
tors, walkways between control systems operating at positive pressure,
pump houses, fan houses, and measurement ports on positive pressure
ducts.
9. When climbing ladders, the horizontal rungs should be grasped. Both
hands must be free for climbing - equipment should not be carried in
either hand.
10. All portable sampling equipment should be properly grounded whenever
there is possibility of static shock or explosion. A partial list of
areas with high static electrical charge include solvent storage vessels,
fuel storage facilities, and downstream of electrostatic precipitators.
-------
SAFETY GUIDELINES (Continued) Back
Cover
11. Prior to walking across elevated horizontal walkways such as roofs and
catwalks, the Inspector should evaluate the potential exposure to steam
and pollutant releases from the process below and the potential for
falls due to structural problems with the walkway. The latter can be
due to corrosion of the supports or excessive accumulation of solids on
the roof.
12. Work clothes contaminated with materials such as Inorganic lead or mer-
cury should be washed separately from street clothes. Disposable shoe
covers should be used when Inspecting such facilities.
13. Insulated gloves should be used whenever handling sampling probes and
equipment withdrawn from hot gas streams.
14. Inspectors should NOT smoke while conducting field work. Smoking should
be done only 1n sucTTareas designated as safe by plant policies.
15. The Inspection should be Interrupted Immediately whenever a severely
vibrating fan 1s found In the vicinity of the equipment being evaluated.
Disintegration of fans can send shrapnel over a large area and even
through walls 1n extreme cases.
16. The Inspection should be terminated whenever the wind chill factor Is
below -20°F- Extreme caution 1s warranted whenever there 1s freezing
rain or sleet.
17. Areas adjacent to damaged nuclear-type hopper level detectors and nuclear
continuous weighing systems should be avoided.
18. Emergency phone numbers should be recorded 1n the front of the field
notebook for each plant. Inspectors should be familiar with the plant
emergency system including warning siren codes.
19. Inspectors should never be unaccompanied while 1n the vicinity of the
process or air pollution control equipment.
20. All plant safety requirements and all agency safety procedures must be
satisfied at all times.
NOTE: It should not be assumed that all acceptable safety measures are con-
tained in this and other publications; other or additional measures
may be required under particular or exceptional circumstances.
-------
INSPECTION OF AIR POLLUTION CONTROL SYSTEMS
Early diagnosis of emerging operating problems or air pollution control
equipment is essential in order to minimize emissions and to minimize
repair costs due to subsequent component damage. The inspection proce-
dure is designed to identify ABNORMAL operating conditions which M_AY_ be
indicative of common system malfunctions.
The data and information compiled during an inspection does not provide
a definite measure of the pollutant emission rate. This can only be
provided by the applicable Reference Test Methods.
The performance of air pollution control systems is dependent on numer-
ous complex and interrelated variables. Accordingly it is necessary to
evaluate performance on a _U N IT -_S PEC_I_R C basis. The procedure utilizes
comparisons of present o pe r atTng" "YondTt ions against previous _B_AJSEL_I_NE
levels of each variable.
To maximize the accuracy of the inspection data, the inspector may
occasionally need to use a number of portable instruments. These are
used in lieu of permanently mounted instruments on control systems to
the extent necessary. The measurements may be made by the agency in-
spector or by plant personnel in the presence of the inspector.
The inspection should be terminated whenever it is apparent that emis-
sions have not increased significantly since the baseline period. If
problems probably exist, the focus of the inspection should be narrowed
to the GENERAL ^FACTORS which conceivably contribute to the increased
emissioliTI The "inspector must confirm that plant personnel recognize
that a problem exists and that the proposed corrective actions have a
reasonable chance for successful and timely repair. Due to the com-
plexity of the interrelated performance variables and the lack of time,
it is generally impractical for the inspector to positively identify
the SPECIFIC operating problem.
Limits
The inspection procedures presented in the following sections are use-
ful for a large number of common air pollution control systems. There
are, however, a number of somewhat unique control systems which demand
revised inspection techniques. The inspector should modify the inspect-
ion procedures to the extent necessary for such sources.
Nothing should be- done which jeopardizes the health and safety of the
inspector and/or the plant personnel. Furthermore, the inspector should
attempt to minimize any inconvenience to plant personnel while accomplish-
ing the assigned task in a timely manner.
-------
INSPECTION OF PULSE JET FABRIC FILTERS
DIAPHRAGM VALVES.
TOP ACCESS HATCHES
PILOT VALVE
ENCLOSURE
COMPRESSED AIR
RESERVIOR
BLOW TUBES AND
VENTURIS
TUBE SHEET
DIRTY" SIDE
HATCH
BAGS SUPPORTED
ON CAGES
SOURCE: Air Pollution Training Institute
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INSPECTION OF PULSE JET FABRIC FILTERS
Components and Operating Principles
Most pulse jet units have a felted fabric bag supported by an
internal cage. The dust cake builds up on the outside of each
bag. Clean gas passes up through the bags to a clean air plenum
at the top of the baghouse. The bags are cleaned row-by-row using
compressed air normally at pressures of 60 to 120 psig. Compressed
air in the reservior is momentarily released through a diaphragm
valve to the blow tube above each row of bags. Holes or nozzles
above each bag allow a "pulse" to travel down the bag. The flex-
ing of the fabric plus a modest reverse air action cause a portion
of the dust cake on the outside of the bag to be dislodged and
fall to the hopper.
i "'''
INTERNAL CAGE SUPPORT
SOURCE: Air Pollution Training Institute
A top access unit is shown in the figure above. A number of
hatches on the top of this type of filter allow access to the
clean side of the collector for checking and replacement of bags.
Another common design supports the bag and cage assemblies below
the tube sheet. The main access hatch is usually on the side of
the collector or in the hopper area.
When abrasive particulate matter is present, many pulse jet col-
lectors utilize a "blast" plate or deflection plate so that much
of this material is directed into the hopper and not against the
fabric surface.
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INSPECTION OF PULSE JET FABRIC FILTERS
1. Components and Operating Principles (Continued)
One of the basic design parameters of a pulse Jet filter 1s the
"Gas-to-Cloth" ratio which Is simply the number of cubic feet of
gas (at actual conditions) passing through the average square foot
of cloth per unit time. The normal units are (FtJ/M1n)/Ft' or
simply Ft/Mln. Most commercial units are 1n the range of 4 to 10
Ft/m1n. Remember that this 1s an average number and that the
actual "velocities' through the cloth will vary throughout a
baghouse even under normal conditions. If part of the bags are
Inadequately cleaned or 1f sticky/wet material blocks part of the
fabric surface, then the local "velocities" through the remainder
of the fabric may be much higher than desirable.
The pressure drop across the fabric filter Is Influenced by numer-
ous factors 1nclud1ng,but not limited to, the gas flow rate, the
condition of the fabric, the presence of holes and tears, and the
permeability of the dust cake. It 1s often difficult to evaluate
the significance of changes from baseline pressure drops without
taking Into account other Information.
Increased Pressure Drop - This 1s most often due to Inadequate
cleaning of the bags or to blinding of the fabric. The presence
of water and oil 1n the compressed air supply can contribute to
the blinding of the material. Improper start-up procedures and
condensed aerosols can also blind the fabric.
When the pressure drop has Increased from baseline levels, the
process equipment and hoods should be checked to confirm that
there 1s still adequate particulate matter capture.
Decreased Pressure Drop - This 1s often due to a decrease In the
overall gas flow rate through the collector (check fan damper
position, fan speed, or blockage of Inlet duct to filter). Bag
holes and tears can reduce pressure drop, however, the change Is
normally slight since the gas flow through the hole will simply
Increase until the pressure drop through the hole 1s equivalent
to that across the rest of the fabric. Emissions often reach un-
desirable levels well before the overall pressure drop decreases
substantially.
Other factors which can lead to a reduced pressure drop relative
to baseline levels Include an Increase In the cleaning Intensity
(check the compressed air pressure) and an Increase In the clean-
Ing frequency. A change which Increases the particle size distri-
bution at the Inlet to the pulse jet collector may also cause a
decrease 1n the pressure drop.
Severe air Infiltration across the top hatches of a pulse jet
filter can significantly reduce the quantity of gas pulled from
the process equipment through the baghouse. This results In a
decreased pressure drop and Increased fugitive emissions from the
process.
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INSPECTION OF PULSE JET FABRIC FILTERS
5
Baseline and Diagnostic Inspection Data
Stack
Fan
Fabric Filter
Average Opacity
Peak Opacity During Puffs
Duration and Timing of Puffs
Inlet Gas Temperature
Speed
Damper Position
Motor Current
Inlet Gas Temperature
Outlet Gas Temperature
Inlet Static Pressure
Outlet Static Pressure
Inlet Og and C02 Content (Combustion Sources)
Outlet 02 and C02 Content (Combustion Sources)
Qualitative Solids Discharge Rate
Air Reservior Pressure
Frequency of Cleaning
Presence or Absence of Clean Side Deposits
Audible Air Infiltration
3. Routine Inspection Data
Average Opacity
Duration and Timing of Puffs
None
Inlet and Outlet Gas Temperatures
Inlet and Outlet Static Pressures
Presence or Absence of Clean Side Deposits
Air Reservior Pressure
Audible Checks for Air Inleakage
Qualitative Solids Discharge Rate
Inspection Methodology: The following sequence of inspection steps is often
the most expeditious and effective means to identify abnormal operating
conditions of typical pulse Jet fabric filters. As with other types of
air pollution control devices the inspector should respect the complexity
of the interrelated operating variables.
Fabric Filter
A. Routine Inspections
Confirm Process Operation -
Evaluate Plume Characteristics -
The sources controlled by the fabric
filter should be very briefly
checked to confirm that operation
is representative.
Determine average opacity. Most
pulse jet collectors operate
with less than 5% opacity, so
values approaching 5% may sug-
gest operating problems'!" If
puffs are observed, the timing
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INSPECTION OF PULSE JET FABRIC FILTERS
6
4. Inspection Methodology (Continued)
Fabric Filter -
should be noted so that It Is
possible to Identify the row
being cleaned just before the puff.
The pressure drop across the
collector should be noted. If
there Is an on-slte gauge, proper
operation of the gauge should be
confirmed by observing meter re-
sponse during the pulsing cycle.
If there Is some question about
the condition of the gauge or
Its connecting lines, the Inspec-
tor should request plant person-
nel to disconnect one line at a
time to Identify any plugged or
crimped lines (disconnecting
lines may not be possible 1f
there Is a differential pressure
transducer connected to the
gauge lines).
If the on-slte gauge Is not
operational or not available,
the static pressure drop should be
measured using portable Instrumen-
tation. Preferably these measure-
ments should be made at Isolated
ports Installed specifically for
the portable Instrumentation.
It Is Important to make the
measurements on the Inlet and
the outlet one at a time so that
plugged tap holes and lines can
be Identified.
Check operation of the cleaning
system by noting the air reservoir
pressure (DO NOT REMOVE THIS
GAUGE). Check for air leakage
around the ends of the reservoir,
and the connections to each of
the diaphragm valves. These
valves are normally activated on
a frequent basis, therefore, It
Is usually possible -to observe a
complete cleaning cycle. Each
valve should have a crisp thud
when activated. Valves which
fall to activate or which produce
a weak, wet newspaper splat are
usually not working properly.
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INSPECTION OF PULSE JET FABRIC FILTERS 7
4. Inspection Methodology (Continued)
If too many of these are out-of-
servlce 1t 1s probable that the
local a1r-to-cloth ratios are
high, causing excessive emissions
through the baghouse and/or
Inadequate pollutant capture at
the source. Even if all diaphragm
valves are working properly,
reduced cleaning effectiveness
can result due to low compressed
air pressures.
If the compressed air pressures
are too high, especially for
units with a high design air-to-
cloth ratio, it is possible that
the intense cleaning action will
result 1n some seepage of dust
through the fabric immediately
after cleaning when the fabric
crashes back into the support
cage. This will cause a momentary
puff of 5-10% opacity.
Holes and tears can lead to
puffs of 5-30$ during the cleaning
cycle. During the pulse the
material bridged over these
areas 1s removed, thereby allowing
particulate to leak through. As
soon as the pulse dissipates,
material tends to bridge over
the holes again, eventually
healing the area. As the size
of the holes and tears grows, the
duration of the puff increases.
Continuous emissions results
when the holes and tears become
too large to bridge over.
The discharge of solids from the
filter hopper should be observed
j_f there is a safe and convenient
means to do so. Solids are
usually discharged ,on a fairly
continuous basis (following each
pulsing of a row).
-------
INSPECTION OF PULSE JET FABRIC FILTERS
8
4. Inspection Methodology (Continued)
B. Diagnostic Evaluation
If the opacity 1s high (con-
tinuous or puffs).
For top load type designs check the
clean side of several compartments -
IF THESE CAN SAFELY BE. ISOLATED
BY THE OPERATOR AND IF NO
POLLUTANT CAPTURE PROBLEMS WILL
RESULT AT THE SOURCE ORIGIN.
Even slight dust deposits can be
a sign of major problems (most
of the dust In the clean side
plenum Is carried out due to the
relatively high gas velocities).
Dust near one or more bag outlets
may suggest Inadequate sealing
on the tube sheet. Holes and
tears may disperse dust throughout
the top side of the tube sheet
thereby making 1t difficult to
Identify the bag with the hole.
The operator may wish to use
fluorescent dye at a later date
to Identify the problem.
If the pressure drop 1s high,
opacity Is high, and/or process
fugitive emissions are noted.
Opacity Is continuously high,
frequent bag failures are
reported, failures are pri-
marily at the bottom.
For a top access type design, the
possibility of blinding of the fabric
can be checked from the top access
hatch. 011 and water 1n the
compressed air line 1s sometimes
partially responsible for the
blinding which takes part of the
fabric area out of service.
For conventional pulse jet
collectors the possibility for
blinding can only be checked at
the dirty side access hatch.
Safety requirements apply as above.
A crusty cake Is sometimes
evidence of excessive moisture
and/or sticky deposits on the bags.
For both types of pulse jet col-
lectors, 1t Is possible to suffer
premature bag failure at the bottom
1f the support cages are slightly
warped and the bags rub at the
bottom. This can be checked
from a dirty side access hatch.
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INSPECTION OF PULSE JET FABRIC FILTERS 9
Inspection Methodology (Continued)
Note: The hatches at the tops
of hopper areas should only be
opened by the operator and then
with extreme caution. Hot solids
can flow rapidly out of these
hatches.
If available, the bag failure
charts for the baghouse should
be examined. A sample chart is
shown 1n the adjacent figure.
The plan view sketch shows the
pattern of bag failures since the
last rebagging. If there is a
distinct spatial pattern, it is
quite possible that the damage
1s due to abrasion (inlet gas
blasting, Inlet swirling, and/or
rubbing against internal supports).
By including the date of the bag
removal, and the elevation of
the apparent damage (T-top, M-
middle, B-bottom) it is possible
to identify many common modes of
failure. Operators using such
charts have been able to minimize
both excess emission incidents
and bag replacement cost. A
rapid increase in the rate of
failure often suggests that there
has been significant deterioration
of fabric strength due to chemical
attack, high temperature excursions,
or simply normal exhaustion of the
material (see lower figure).
If there are any bags which have
been removed from service recently
and will be discarded, a simple
rip test should be performed. If
1t 1s possible to rip the cloth
by inserting a screw driver and
pulling, it is probable that the
bag damage was the result of
chemical attack, high temperature
excursions, moisture attack, or
routine fabric exhaustion. Most
fabrics damaged by abrasion re-
lated problems can not be ripped,
even near the site of the damage.
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INSPECTION OF PULSE JET FABRIC FILTERS
10
INLET PLENUM
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oogoo©
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ooo
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OOQOQD
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15
14
13
12
11
10
8
WALKWAY
ACCESS HATCH
COMPARTMENT
YEAR
BAG FAILURE CHART
o
10
a
IA
1
TIME, Y«ars
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INSPECTION OF PULSE JET FABRIC FILTERS JJ
4. Inspection Methodology (Continued)
Opacity 1s high and there Is Bag and cage assemblies which have
a distinct pattern to the been removed previously should be
types of holes and tears. carefully Inspected. Often the
point of bag failure is next to
a sharp point on the support
cage. Premature failure may
also be caused by cages which do
not provide enough support for
the fabric.
If all the bags have failed at
the top, there 1s a possibility
that the compressed air nozzles
are misaligned and therefore,
the pulse is directed at a narrow
area at the top of the bag.
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INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS
12
SHAKER MOTOR
DIRTY GAS - C-
&"-&
HANGER ASSEMBLY
•HOPPER
ANTI-COLLAPSE
RINGS
BAGS
CLAMP
TUBE SHEET
SOURCE: Air Pollution Training Institute
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INSPECTION OF REVERSE AIR AND SHAXER FABRIC FILTERS
13
i. Components and Operating Principles
Most commercial units use a woven fabric bag which is suspended
from the top of the compartment and clamped to the tube sheet below.
The bags do not usually have interior cages, however, most have sev-
eral sewn anti-collapse rings to facilitate discharge of collected
dust. The partlculate laden gas stream enters the baghouse below
the tubesheet and passes up through the inside of each bag. The
dust cake, which is responsible for most of the filtering, builds up
on the Inside surface. On a regular schedule, each of the compart-
ments are isolated from the main gas stream and the bags are cleaned.
In shaker units, the bags are gently shaken for 5 seconds to 2 min-
utes using a mechanical assembly with oscillations of approximately
4 cycles per second. For a reverse air collector, a fan is used to
direct some filtered or ambient air through the bags from the outside
to the Inside thereby dislodging the dust cake. After each shake
or reverse air cleaning period it is usually desirable to have a
brief null period before restoring the effluent gas flow through
the bags.
'Thimble'
Stainless
Steel
Clamp
Cell Plate
Thimble Connection
Cuff with
Spring
*—Steel--<
Band Cell
Snap Band Connection
Bags may be clamped to the bottom tube sheet either by clamping to
a raised thimble or by expansion of the bag shape ring into a recess
below the tube sheet. The thimble should be high enough to absorb
some of the abrasive action of the entering gas stream. It also
must have rounded edges to reduce the cutting of the bags during the
cleaning cycle. The snap ring assemblies must be snug to reduce the
chance of leakage. The tube recesses for the snap rings must be
well cleaned before Installing new bags and the bag snap rings must
not be permanently disformed.
Tens1on1ng of a bag is very important. For shaker units it is pos-
sible to check bag tension by grasping the bag between two fingers
and twisting. If it is possible to rotate it more than 45 degrees,
then the tension is probably too low. If the shaker bag is complete-
ly taut, then there is a risk that it will be pulled loose from the
tube sheet during cleaning. The reverse air bag, on the other hand,
should be completely taut in appearance.
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INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS
1. Components and Operating Principles (Continued)
The useful Hfe of bags 1s primarily dependent on the following:
(1) proper fabric selection and baghouse design to minimize chemi-
cal attack and abrasive failure, (2) proper cleaning Intensity and
frequency, (3) proper start-up procedures to minimize add dewpolnt
problems, and (4) operation below the maximum rated temperature of
the fabric. Operation on a continuous basis should usually be
approximately 50*F below the maximum rated temperature stated In the
adjacent table. Short term temperature excursions more than 50°F
above the maximum rated temperatures can lead to bag loss even when
the duration of the Incident 1s only 5 to 10 minutes.
The maximum rated temperatures and general performance characteris-
tics of common commercial fabrics Is listed In the following table.
The comments concerning the variability of pressure drop 1n pulse
jet collectors are also applicable to reverse air and shaker col-
lectors. The A1r-to-Cloth ratios are usually between 1 and 3 ft/m1n.
As with pulse jet collectors, the local "velocities" through a
given compartment and between compartments may differ significantly.
-------
PROPERTIES OF COMMON C(
CIAL FABRICS
Fabric
Cotton
Wool
Nylon
Polypro-
pylene
Polyethylene
Orion*
Dynel®
Dacron*
Ryton*
Nomex*
Teflon*
Fiberglass
Maximum
Rated
Generic name Temperature,
Natural fiber
eel lulose
Natural fiber
protein
Nylon poly amide
Polyolefin
Polyolefin
Acrylic
copolymer
Modacrylic
Polyester
Polyphenylene
sulfide
Nylon
arimid
Fluorocarbon
Glass
170
170
200
200
200
225
275
275
375
400
500
500
Acid
°F resistance
Poor
Very good
Fair
Excellent
Very good-
excel lent
Good-
excellent
Good -very
good
Good
Good-
excellent
Fair
Excellent
Fair-good
Fluoride
resistance
Poor
Poor-fair
Poor
Poor
Poor-fair
Poor-fair
Poor
Poor-fair
Good
Good
Poor-fair
Poor
Alkali
resistance
Fair-good
Poor-fair
Very good-
Excellent
Very good-
excellent
Fair
Good-very
good
Fair-good
Good-
excellent
Excellent
Excellent
Fair
Flex and
abrasion
resistance
Fair-good
Fair
Very good-
Very good-
excel lent
Good
Fair
Fair-good
Very good
i— •
o
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— i.
3
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—i.
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— i.
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Q-
Excellent
Very good-
excel lent
Fair
Poor
i — i
CO
-o
m
n
-H
( — 1
0
0
70
rn
m
70
1/1
m
70
o
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^x^
m
70
2
DO
TO
» — *
T-|
1 — 1
| —
— 1
m
LT>
Stainless steel
(type 304)
1500
Excellent Excellent Excellent Good
-------
INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS
2. Baseline and Diagnostic Inspection Data
15
Stack
Average Opacity
Opacity During the Cleaning Cycles (for each compartment)
Fabric Filter Date of Compartment Rebagging
Inlet Static Pressure (Average)
Outlet Static Pressure (Average)
Minimum, Average, and Maximum Gas Inlet Temperatures
Average Og and COg Concentrations (Combustion Sources Only)
Average 03 and C02 Concentrations (Combustion Sources Only)
Time to Complete a Cleaning Cycle of All Compartments
Length of Shake Period
Length of Null Period
Bag Tension (Qualitative Evaluation)
Rate of Dust Discharge (Qualitative Evaluation)
Presence or Absence of Audible Air Infiltration
Presence or Absence of Clean Side Deposits
Stack Test
Fan
Emission Rate
Gas Flow Rate
Stack Temperature
03 and COj Content
Moisture Content
Fan Speed
Fan Motor Current
Gas Inlet and Outlet Temperatures
Damper Position
3. Routine Inspection Data
Stack
Average Opacity
Opacity During the Cleaning Cycles (for each compartment)
Fabric Filter Inlet and Outlet Static Pressures
Inlet Gas Temperature
Rate of Dust Discharge (Qualitative Evaluation)
Presence or Absence of Audible Air Infiltration
Presence or Absence of Clean Side Deposits
Ripping Strength of Discarded Bags
Inspection Methodology: The following sequence of inspection steps is often
the most expeditious and effective means to identify abnormal operating condi-
tions of typical pulse jet fabric filters. As with other types of air pollu-
tion control devices the inspector should respect the complexity of the inter-
related operating variables.
A. Routine Evaluation
Confirm Process Operation -
The sources controlled by the
fabric filter should be very
briefly checked to confirm that
operation is representative.
-------
INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS
17
4. Inspection Methodology (Continued)
Evaluate Plume Characteristics -
Fabric Filter -
Determine the average opacity.
Most reverse air and shaker col-
lectors operate with less than 5%
opacity. • Values approaching this
may suggest operating problems. If
the opacity drops when a specific
compartment has been isolated for
cleaning it is a probable sign of
holes or tears of bags in that com-
partment. Often shaker collectors
have opacity spikes immediately fol-
lowing the cleaning cycle. Both con-
ditions warrant further evaluation.
The pressure drop across the col-
lector should be noted. If there
is an on-site gauge, proper opera-
tion of the gauge should be confirm-
ed. If there is some question about
the condition of the gauge or its
connecting lines, the inspector
should request plant personnel to
disconnect one line at a time to
identify any plugged or crimped
lines (disconnecting lines may not
be possible if there is a differen-
tial pressure transducer connected
to the gauge lines).
If the on-site gauge is not opera-
tional or not available, the static
pressure drop should be measured using
portable instrumentation. Preferably
these meaurements should be made at
isolated ports installed specifically
for the portable instrumentation. It
is important to make the measurements
on the inlet and the outlet one at
a time so that plugged tap holes and
lines can be identified. Care must
be exercised while nodding out tap
holes since on some designs it is
possible to poke a hole in the bag
adjacent to the tap hole.
The pressure drop across each com-
partment should be determined during
the cleaning cycle. In shaker col-
lectors, the pressure drop during the
cleaning of a compartment should be
zero. Nonzero values indicate damper
leakage problems. In reverse air col-
lectors, back flow will cause a measur-
able pressure drop with a polarity
opposite that of the filtering cycle.
-------
4.
INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS
Inspection Methodology (Continued)
18
B. Diagnostic Evaluation
If air leakage 1s suspected,
or gas outlet temperature 1s
Tow, or pressure drop 1s low.
If the opacity Is high con-
tinuously or during most of
the operating period, or
the pressure drop 1s much
greater than'the baseline,
or the pressure drop 1s much
Tower than the baseline.
If there Is no on-s1te gauge and
the unit operates at an elevated
gas temperature, then the gas
temperature should be measured.
This can be done at a point on
the Inlet duct to the collector
or at one of the tap holes (If
direct access to the Interior of
the collector Is possible).
The rate of solIds discharge
should be checked if this can be
done safely and conveniently.
Solids are usually discharged
only during the beginning of the
cleaning 1n each compartment.
A1r Inleakage through access
hatches, solids discharge valves,
hopper flanges, and fan Isolation
sleeves should be quickly checked
by listening for the sound of
Inrushlng air-
Check 02 and C02 levels at the
Inlet and outlet of combustion
source fabric filters. The
measurement point on the Inlet
must be between the solIds
discharge valve and the tube
sheet, so that the potential
Inleakage at this point 1s also
taken Into account. There should
not be more than a 1% rise (e.g.
1n at 61 02, out at 7% 02) 1n
the 02 levels going from the
Inlet to the outlet.
The presence and nature of the clean
side deposits should be checked by
viewing conditions from the hatch.
Note: The compartment must be
Isolated by the operator before
attempting to do the Internal
Inspection. All safety procedures
must be carefuTTy followed. The
Inspector should not, under any
circumstances, enter the compart-
ment.
-------
INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS
Inspection Methodology (Continued)
19
The presence of snap ring leakage
is often indicated by enlarged
craters in the clean side deposits
around the poorly sealed bags.
Holes and tears can sometimes be
located by the shape of dust
deposits next to the holes.
Poor bag tension is readily
apparent from the access hatch.
Improper discharge of material
from the bags can often be
confirmed by noting that the bags
close to the hatch are full of
material one or more diameters up
from the bottom. Deposits on the
bags should also be noted.
If there is more than a trace of
material on the clean side tube
sheet, it is probable that emis-
sions from this compartment have
been and may still be substan-
tially above the baseline levels.
If available, the bag failure
charts for the baghouse should be
examined. A sample chart is shown
in the section on pulse jet collec-
tors. The plan view sketch shows
the pattern of bag failures since
the last rebagging. If there is a
distinct spatial pattern, it is
quite possible that the damage is
due to abrasion (inlet gas blast-
ing, inlet swirling, and/or rub-
bing against internal supports).
By including the date of the bag
removal, and the elevation of the
apparent damage (T-top, M-middle,
B-bottom) it is possible to iden-
tify many common modes of failure.
Operators using such charts have
been able to minimize both excess
emission incidents and bag replace-
ment cost. A rapid, increase in
the rate of failure often suggests
that there has been significant
deterioration of fabric strength
due to chemical attack, high
temperature excursions, or simply
normal exhaustion of the material.
-------
INSPECTION OF REVERSE AIR AND SHAKER FABRIC FILTERS 20
4. Inspection Methodology (Continued)
If there are any bags which have
been removed from service recently
and will be discarded, a simple
rip test should be performed.
If 1t Is possible to rip the
cloth by Inserting a screw
driver and pulling, 1t 1s
probable that the bag damage
was the result of chemical
attack, high temperature
excursions, moisture attack,
or routine fabric exhaustion.
Most fabrics damaged by abrasion
related problems cannot be
ripped, even near the site of
the damage.
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS
21
Components and Operating Principles
Gas entering the electrostatic precipitator. is decelerated to an
average velocity ranging from 2 to 8 feet per second. Gas distri-
bution screens minimize the variability of local velocities at
the precipitator inlet (see top figure on next page). There are
a number of power supplies, termed transformer-rectifier sets, on
the top of the precipitator to energize the various fields. Each
transformer-rectifier (T-R) set converts alternating current at 400
- 480 volts A.C. to a pulsed direct current at 15,000 to 60,000
volts. Each T-R set is connected to a set of the discharge wires
or electrodes (see lower figure). The large collection plates and
the precipitator shell are grounded.
Ions formed near the discharge wires impart an electrical charge
on the particles causing the particles to migrate toward the
collection plates at a rate dependent on the size of the particles
and the strength of the electrical field.
The rappers are used to routinely remove solids from the collection
plates, discharge wires, and gas distribution screens.
OUTLET
CHAMBER A
FIELD 3
FIELD 4
FIELD 2
CHAMBER B
SOURCE: Air Pollution Training Institute
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS
22
RAPPERS
DISCHARGE
ELECTRODES
HOPPERS
TRANSFORMER-RECTIFIER
SET (One of Four Shown)
GAS DISTRIBUTION
SCREFNS
COLLECTION PLATES
SOURCE: Air Pollution Training Institute
It.
TRANSFORMER-RECTIFIER
SETS
SOURCE: Air Pollution
Training Institute
ELECTRODE SHROUD
DISCHARGE ELECTRODE
ELECTRODE SHROUD
BOTTLE WEIGHT
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS 23
1. Components and Operating Principles (Continued)
The T-R sets are arranged in series and operate independently.
Each fi-eld removes 701-85% of the participate that enters, there-
fore most of the material is removed in the initial fields.
Many precipitators have parallel sets of fields termed chambers.
Solid partitions prevent gas flow between chambers.
Once the particulate accumulates on the collection plates, the
static electrical charge must be dissipated to the ground (see
top figure). When the resistivity of the material is high, the
dissipation of the charge is difficult. This charge on the par-
ticles tends to hold the dust layer on the plates thereby reduc-
ing the power input and increasing the necessary rapping intensity.
Units with high resistivity rarely suffer rapping reentrainment,
however the reduced power consumption can significantly reduce
particle collection.
When the resistivity of the material is low, the dissipation of
the charge is very rapid. The dust layer is only weakly held to
the plates, thereby favoring reentrainment if rapping is too
intense, if the gas distribution is poor, if the gas velocities
are high in certain areas, and if the aspect ratio is high. Power
inputs significantly above baseline levels may indicate increased
emissions due to low dust resistivity.
The electrical charge can be conducted along the outer surface of
the particles in the dust layer if the gas temperature is low
enough to allow adhesion of water molecules, sulfur trioxide mole-
cules, or similar charge carrying species. The effectiveness of
this charge dissipation path is very sensitive to temperature
(below 350°F) with shifts of only 10° to 20°F sufficient to cause
major resistivity shifts.
If the temperature is high, the charge can be dissipated along a
path through the bulk of the particle. The resulting resistivity-
temperature curve is shown by the dark line. Between the zone of
surface conductivity and the zone of bulk conductivity there is a
peak resistivity value. The peak resistivity and the position of
the peak relative to gas temperature may shift due to a variety of
factors.
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS
Single Particle
Bulk
Conductivity—
Surface
Conductivity
Participate
Layer
Collection
Plate
10
12
I
= 10
t/1
10
URVE Due TO
.SURFACE CONDUCTIVITY
RESISTIVITY CURVE DUE TO
BULK AW XRFACE
CONOUCTIVITY
0.-KE DUE TO
auu COWUCTIVITT
I
200 300 400 500
GAS TEMPERATURE
600
-------
INSPECTION OF.ELECTROSTATIC PRECIPITATORS
Baseline and Diagnostic Inspection Data
25
Stack
Precipitator
Stack Test
Process
Average Opacity
Peak Opacity during Puffs
Duration and Timing of Puffs
Presence of Detached or Secondary Plumes
Primary Voltages (Volts, A.C., in all fields)
Secondary Voltages (Kilovolts, D.C., in all fields)
(Note: This is often not available)
Primary Currents (Amps, A.C., in all fields)
Secondary Currents (Milliamps, D.C., in all fields)
Spark Rate (in all fields estimated by counting
the fluctuations of the primary voltage meter)
Air Inleakage through Hoppers and Hatches (Qualitative
Evaluation)
Rapper Frequencies and Intensities
Gas Inlet Temperatures
Gas Outlet Temperatures
Particulate Emission Rate
Gas Flow Rate
Gas Oxygen, Carbon Dioxide, and Moisture Concentrations
Production Rate
Raw Material Composition
Precipitator
Routine Inspection Data
Stack Average Opacity
Peak Opacity during Puffs
Duration and Timing of Puffs
Presence of Detached or Secondary Plumes
Primary Voltages (Volts, A.C., in all fields)
Secondary Voltages (Kilovolts, D.C., in all fields)
(Note: This is often not available)
Primary Currents (Amps, A.C., in all fields)
Secondary Currents (Milliamps, D.C., in all fields)
Spark Rate (in all fields estimated by counting
the fluctuations of the primary voltage meter)
Air Inleakage through Hoppers and Hatches (Qualitative
Evaluation)
Gas Inlet Temperatures
Inspection Methodology: The following sequences of inspection steps
are often the most expeditious and effective means to identify abnormal
operating conditions of electrostatic precipitators. While the con-
clusions which may be reached regarding the general types of operating
problems are often valid, the inspector should always respect the com-
plexity of the numerous interrelated operating variables that affect
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS
26
Evaluate Plume Characteristics -
Transmissometer -
4. Inspection Methodology (Continuedl
A. Routine Inspection
Confirm Process Operation - The source controlled by the
electrostatic precipitator
should be very briefly checked
to confirm that operation is
representative.
Determine average opacity and
presence or absence of unusual
plume characteristics such as
detached zones or secondary for-
mation. If puffing is observed,
the timing and intensity of the
puffing should be recorded.
Determine shifts in average opac-
ity during the previous 4 to 8
hours. The intensities and fre-
quency of emission spikes should
be carefully evaluated. If the
instruments are accessible, the
adequacy of the purge air blowers,
optical alignment, and mounting
should be confirmed.
Precipitator Electrical Cabinets - Record power data for each cham-
ber, starting with the inlet
field and proceeding in order to
the outlet fields. The primary
voltages and secondary currents
should be plotted. If the
resistivities are in the moder-
ate range, the secondary currents
will increase from inlet to
outlet while the voltages will
drop slightly. The spark rate
(estimated by counting the fluc-
tuations of the primary voltage
meter) will usually decrease
from inlet to outlet.
When the above trends are not
apparent and/or all of the
fields have shifted signifi-
cantly from baseline levels,
the most probable cause is a
change in particle resistivity.
This could be due to a change
in gas temperatures, raw
material/fuel composition, or
process operation changes.
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS 27
Inspection Methodology (Continued'
A typical -set of curves for a
unit (one chamber, four fields
in series) having moderate
resistivity is shown on the
following page. If there is an
increase in the resistivity the
secondary currents in all fields
will drop substantially, while the
spark rate will increase even in
the outlet field (field 4). Under
low resistivity conditions, the
secondary currents will increase
substantially, limited only by
the current limit of the T-R set.
Sparking during low resistivity
conditions will be very low even
in the inlet field. While these
curves are generally applicable,
it should be noted that a number
of practical opperational factors
can alter the trends on a given
unit. This can occur due to
operation under manual control
or due to undersized T-R sets.
By plotting the voltage, current,
and spark rate curves in the
vertical arrangement (see oppo-
site figure), it is possible
to quickly scan the data for
shifts in the voltage/current
ratio for a given power supply.
This is a good indication of
internal component problems and
shifts in resistivity.
If only a small section of the
precipitator exhibits unusual
electrical readings, the most
probable cause is one or more
mechanical problems. This
includes, but is not limited
to, rapper failure, insulator
failure, discharge wire move-
ment and malalignment, hopper
overflow, and air inleakage.
If the average opacity is close
to baseline levels and the field-
by field trends are typical of
moderate resistivity, and there
are no observed puffs, then the
-------
INSPECTION OF 'ELECTROSTATIC PRECIPITATORS
28
£ 40
30
20
10
PRESENT DATA
BASELINE
1500
500
CJ
uu
CO
Current limit
PRESENT DAT
BASELINE
-240
09
30
u 20
10
BASEllNE
PRESENT
DATA
FIELDS
-------
INSPECTION OF-ELECTROSTATIC PRECIPITATORS
29
Inspection Methodology (Continued]
B. Diagnostic Evaluation
If the power input to a large
part of the precipitator has
dropped, and the secondary
currents TmTlliamps, D.C.)
have dropped significantly,
and the sparking rate has
Increased even in the outlet
fields, then it is possible
that the dust resistivity has
increased since the baseline
period.
If puffing is observed at the
stack or on the transmisso-
meter strip chart, and the
secondary currents on most
fields including the inlets
have increased to values close
to the T-R set ratings, and
the sparking rate has de-
creased, then it is possible
that the dust resistivity has
decreased significantly since
the base-line period.
inspection should be terminated
since the precipitator is prob-
ably performing close to baseline
levels. If abnormal operating
variables are noted then the
inspection should proceed with
the Diagnostic Inspection.
Check for changes in the inlet gas
temperature. For cold-side utility
boiler units a shift upward may be
significant. Also check fuel sulfur
content of fuel. Any conditions
which favor $03 formation should
also be evaluated (such as excess
air rates). For certain sources,
the moisture content is important.
The degree to which the emissions
have increased due to the increase
in resistivity can be roughly
estimated using the power input-
mass emission correlation (See
equations at end of the Section).
It is important to evaluate power
Input on a chamber by chamber
basis. In some units there is a
significant difference in the
dust resistivities in the various
chambers and this can have a
large impact on emissions while the
overall power input for the total
system remains relatively unchanged.
If possible check for changes in
the inlet gas temperatures (using
plant instruments). For coldside
utility boilers, a downward
shift of only 10°-20°F may be
significant. Also check fuel
sulfur content, and the composition
of collected material (carbonaceous
material often reduces resistivity).
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS
30
4. Inspection Methodology (Continued)
If the "normal" secondary
current trends, primary
voltage trends, and spark
rate trends are observed,
1t 1s probable that the.
dust has a moderate resisti-
vity.
If there are apparently low
secondary currents In a small
segment of the preclpltator
and the resistivity 1s In the
moderate to high range, then
1t 1s possible that some of
the collection plate rappers
are not working.
If voltages are low In one or
more fields and the currents
have Increased the problem may
be due to a high resistance
short or to "tracking" on the
high voltage Insulator(s). This
may result In Insulator failure
and T-R set trip out.
Units with excessive rapping
Intensities, low aspect ratios,
and/or high gas velocities (such
as greater than 5-6 fps) may be
prone to reentralnment. The
rappers should be checked for
frequency and intensity-
Emissions generally Increase as
the power Input Is Increased when
the resistivity Is low. The degree
of problem can not be estimated
using available correlations. The
Increase In opacity (averaging 1n
the puffs) provides a more reliable
rough estimate.
If several fields are out of service
on a unit with moderate resistivity,
the Increase In emissions from base-
line levels can be roughly estimated
using a power Input-mass emissions
correlation. If this 1s not
available assume each field removes
751 of the partlculate matter
entering the field. Therefore, a
single chamber unit with 3 fields
would have a fractional penetration
equivalent to 0.25 x 0.25 x 0.25
which Is approximately 0.02. The
same unit with one field out of
service would have emissions of
0.25 x 0.25 or approximately 0.06.
Check rapper operation on the roof
of the preclpltator. Proper opera-
tion should be determined by listen-
Ing to each rapper as It 1s acti-
vated. Do not touch the rappers
since In some very unusual cases,
the D.C. power may be on outer case
of the rappers.
Check operation of insulator heat-
ers (1f present) by checking In-
dicator light usually In precip-
Itator substation. If penthouse
purge air blowers are present,
these should be checked. The
blowers are usually on the pre-
clpltator roof.
-------
INSPECTION OF ELECTROSTATIC PRECIPITATORS
31
Inspection Methodology (Continued)
If a number of fields are out of
service due to wire failure, it
is possible that the fundamental
causes include: electrical ero-
sion at "end-of-fields", electri-
cal erosion at points of close
clearance, corrosion and/or metal
fatigue at crimps.
Often it is possible to examine
a number of the wires which have
already been removed. These are
usually left on the precipitator
roof and/or next to access hatches.
To the extent possible, the mode
of failure should be determined
by checking the type and location
of the failure. The operator's
proposed corrective action to
minimize future wire breakage
should be discussed in some
detail.
ESP APPROXIMATE ESTIMATE OF POWER INPUT
Using Secondary Voltages
n Secondary Secondary
ZVoltge x Current
(kv) / ma
Vd.c.,
1 « 1
where: n * no. of fields in the chamber
Power Input
Using Primary Voltages
Watts
ACFM x 103
Watts -
z
1 - 1
Primary
Yoltge
volts
a.c.
Primary
Current
amps
a.c.
x 0.75
Corona Input * Watts
ACFM x 11H
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
32
INDIVIDUAL TUBE
TYPICAL MULTI-CYCLONE COLLECTOR
SOURCES: Howden, James & Co. Ltd. and Joy Manufacturing Co.
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS 33
!• Components and Operating Principles
In a cyclone or a cyclone tube, a vortex is created within the
cylindrical section by either injecting the gas stream tangen-
tial ly or by passing the gas stream through a set of spinner
vanes. Due to particle inertia, the particles migrate across the
vortex gas streamlines and concentrate near the cyclone wall.
Near the bottom of the cyclone cylinder the gas stream makes a
180 degree turn and the particulate matter is discharged either
downward or tangentially into hoppers below. The treated gas
passes upward and out of the cyclone.
1.1 Simple Cyclones
The simple cyclone consists of an inlet, cylindrical section,
conical section, gas outlet tube, and the dust outlet tube. On
some units there is a solids discharge valve such as a rotary
valve or a flapper gate. A typical tangential inlet, axial outlet
cyclone is shown in the adjoining figure.
Particle separation is a function of the gas flow throughout the
cyclone cylindrical diameter. At higher gas flow rates and smal-
ler cylinder diameters the particle inertia is greater thereby
resulting in higher collection efficiency. There is an upper
limit, however, where the increased turbulence caused by higher
gas velocities can disrupt the particle collection.
Medium efficiency single cyclones are usually less than 6 feet in
diameter and opperate at static pressure drops of 1 to 4 inches
of water. Overall collection efficiency is a function of the
inlet particle size distribution.
1.2 Multiple Cyclones
A multiple cyclone consists of numerous small-diameter cyclones
operating in a parallel fashion. The high efficiency advantage
of small-diameter tubes is obtained without sacrificing the
ability to treat large effluent volumes.
The individual cyclones, with diameters ranging from 3 to 12
inches, operate at pressure drops from 2 to 6 inches of water.
The inlet to the collection tubes is axial, and a common inlet
and outlet manifold is used to direct the gas flow to a number of
parallel tubes. The number of tubes per collector may range from
9 to 200 and is limited only by the space available and the ability
to provide equal distribution of the gas stream to each tube. Prop-
erly designed units can be constructed and operated with a collec-
tion efficiency of 90 percent for particles in the 5 to 10 ymA
range. The importance of particle size is illustrated in the
collection efficiency curves shown in the figure. For any
given particle size, the collection efficiency is a strong
function of the gas flow rate. Multiple cyclones are less
efficient at low flow rates than at the design flow rates.
It is important that the Inlet duct to the multiple collector be
properly oriented so there is no induced gas maldistribution
among the cyclone tubes. There must also be allowances for the
expansion of the ductwork and collector as the equipment heats
up to normal operating temperatures.
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
PLAN VIEW
GAS
IN"
GAS
INLET
c
en
S
i
i
__•
^^M
-^
.IHORICAL
£CTIQN
SECTIONAL VIEW
OUTLET TUBE
DUST DISCHARGE
TUBE
LARGE DIAMETER TUBES
— MEDIUM DIAMETER TUBES
SMALL DIAMETER TUBES
20 30 40 50 60
AERODYNAMIC PARTICLE DIAMETER, umA
70 80 90
TOO
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
35
Baseline and Diagnostic Inspection Data
Stack/ Average Opacity
Discharge Minimum and Maximum Opacities
Duration and Timing of Puffs
Fan Presence or Absence of Vibration
Fan Speed
Motor Current
Inlet Gas Temperature
Inlet Static Pressure
Outlet Static Pressure
Inlet Gas Temperature
Outlet Gas Temperature
Inlet 0? 4 CO? Concentrations (Combustion System)
Outlet 02 4 CO? Concentrations (Combustion System)
Gas Flow Rate (Pitot Tube or Process Estimate)
Solids Discharge Rate (Qualitative Estimate)
Stack Test Particulate Emission Rate
Average Opacity
Minimum and Maximum Opacities
Stack Temperatures
Stack 02 4 C02 Concentrations
Cyclone/Mul-
tiple Cyclone
Routine Inspection Data
Stack/
Discharge
Fan
Cyclone/Mul-
tiple Cyclone
Average Opacity
Minimum and Maximum
Duration and Timing
Opacities
of Puffs
Presence or Absence of Vibration
Inlet Static Pressure
Outlet Static Pressure
Inlet Gas Temperature (High Temperature Units)
Outlet Gas Temperature (High Temperature Units)
Inlet 02 4 C02 (Combustion Sources Only)
Outlet 02 4 CO? (Combustion Sources Only)
Gas Flow Rate (Pitot Tube or Process Estimate)
Solids Discharge Rate (Qualitative Estimate)
Integrity of Ducts and Collector
Operation of Solids Discharge Valve (If Any)
Audible Air Infiltration
Apparent Deformation of Cyclone Shell
Apparant Corrosion of Cyclone Shell
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
36
4. Inspection Methodology
A. Routine Inspection
Confirm Process Operation -
Evaluate Plume Characteristics •
Cyclones -
The sources controlled by the cy-
clone/multiple cyclone should
be briefly checked to confirm that
process operation is representative.
Opacity spikes on an intermittant
basis may be indicative of process
releases of small particles which
are beyond the capability of the
collector. The duration and timing
of the spikes should be recorded so
that the process equipment can be
inspected later.
On some units the average opacity
is not very indicative of operating
conditions since the particle size
of the material being handled is
too large to scatter light effec-
tive effectively. Therefore, the
opacity can be low while the mass
emissions are high. Oust deposits
in the immediate vicinity of the
discharge point often provide a
useful indication of this condition.
Check the pressure drop across the
cyclone using the onsite gauge. If
this is not available or not operat-
ing, use a portable gauge. Lower
than normal pressure drops are usual-
ly the result of a decrease in the
gas flow rate. Erosion of the out-
let tubes may cause a similar
condition.
Evaluate the integrity of the cylin-
drical section and the conical sec-
tion. Deformation of the conical
section by a sledge hammer can cause
a permanent reduction in the effi-
ciency. Holes due to erosion and
corrosion can allow air infiltra-
tion with resulting loss in effi-
ciency and a reduction in the gas
flow from the process hood.
Evaluate the rate of solids dis-
charged from the conical section
(if safe).
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
Inspection Methodology (continued)
57
Multiple Cyclones -
The check for air infiltration
should be'made first. If the col-
lector serves a combustion source,
air infiltration can be estimated
by measuring the §2 concentration
before and after the collector
(00-2 measurements would also be
made 1n order to confirm the 02
tests). An increase of more than
1% 02 indicates an undesirable
level of infiltration.
If the unit is not on a combustion
source, a general check for infil-
tration should be made. Audible
leaks near the discharge valve,
welds, ducts, and access hatches
should be noted.
The stactic pressure drop should
be measured using the on-site
gauge or using portable gauges.
At the same locations that the
static pressures are measured, the
gas temperature should be measured.
The gas flow rate should either
be measured with a pitot tube or
estimated from a process parameter
(such as the steam rate at a
boiler). Using the equation
below, the expected pressure
drop should be calculated.
where:
Q » flowrate, ACFM
d « density factor,
dimensionless
The density factor can be obtained
from the psychrometric chart in
this notebook.
-------
4.
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
Inspection Methodology (continuedl
38
B. Diagnostic Evaluation
Audible air infiltration
or a measured 03 increase
of more than 1%.
If the measured pressure
drop is less than 75% of
the estimated "pressure
drop and the opacity has
incresed slightly.
If the calculated value is not with-
in ^25J of the measured pressure
drop, there has probably been a
significant change 1n the resistance
to gas flow. Internal problems
which may cause this Include pluggage
of spinner vanes, pluggage of outlet
tubes, erosion of outlet tube exten-
sions, weld failures, and gasket
failures.
If the oxygen concentration at
the Inlet to the collector has
Increased substantially (combus-
tion units), then any observed
Increase in opacity may be due
to combustion related problems.
Check the hopper area for any
conditions which would inhibit
proper solids discharge. This
could include deformations due
to sledge hammers, fires, or
air infiltration.
To the extent possible, a check
should be made to determine the
source(s) of the infiltration.
Some common areas include the
solids discharge valve, hopper
welds, shell welds, and access
hatches.
If the problem areas cannot be
easily identified and corrected,
plant personnel should perform
smoke tests.
At the earliest opportunity,
plant personnel should make an
internal inspection to determine
if the outlet tube extensions
have suffered erosion damage
or 1f any gaskets or tube sheet
welds have failed.
-------
INSPECTION OF CYCLONE AND MULTI-CYCLONE COLLECTORS
39
Inspection Methodology (continuedl
If the measured pressure
drop is more than 125%
of the estimated pressure
drop and the opacity has
increased slightly.
If the opacity has increased
slightly but there is no
significant air infiltration
and the calculated and mea-
sured pressure drops are
almost equal.
At the earliest opportunity,
plant personnel should make an
internal inspection to determine
if there is partial or complete
pluggage of the inlet vanes or
outlet tubes.
At the earliest opportunity,
plant personnel should make an
internal inspection to determine
if any of the following conditions
exist: (1) pluggage of some of
the dust outlet tubes, (2) erosion
of the hopper baffle plate which
inhibits hopper recirculation, or
(3) build-up of deposits on the
insides of the tubes which results
in particle bounce back into the
exit gas stream.
-------
INSPECTION OF VENTURI SCRUBBERS
INLET
CONVERGING
SECTION
THROAT
DIVERGING
SECTION
OUTLET
CYCLONIC SEPARATOR
SOURCE: Air Pollution Training Institute
z
o
.6
.4
.2
DIFFUSION _
IS DOMINANT
MECHANISM I
. IMF-ACTION
IS DOMINANT
MECHANISM
IMPORTANCE OF
PARTICLE SIZE
ARBITRARY CURVE
0.01 0.05 1.0 10.0 100.
PARTICLE DIAMETER, MICRONS^.
-------
INSPECTION OF VENTURI SCRUBBERS
Components and Operating Principles
Particulate laden gas from the process source is often treated in
a presaturator in order to reduce the inlet gas temperature to the
scrubber. As the cooled gas enters the converging section of the
venturi it is accelerated. Water injected at this point is atomized
to a large number of fine droplets which then serve as targets for
the particulate. The large difference between the gas stream and
the water droplets1 velocities results in impaction of the particles.
The effectiveness of the particulate impaction is proportional to
the gas velocity in the throat, the effectiveness of the liquor
distribution across the throat, and the particle size distribution.
The pressure drop across the throat is directly related to the
energy utilized to atomize the liquor and to impact the particles
into the droplets. Since the pressure drop is very difficult to
measure at this point this value is usually approximated by taking
the pressure drop across the scrubber as a unit.
VENTURI THROAT
SOURCE: Air Pollution Training Institute
The importance of particle size is emphasized in the adjacent
figure. For particles greater than 1 to 2 microns, impaction is
so effective that the penetration (emissions) are quite low. Very
fine particles in the less than 0.1 micron range are also collected
efficiently due to the rapid diffusion of these particles. (Note:
Diffusion collection is related to the surface area of droplets
and the time available for collection, it is not a strong function
of pressure drop). There is a particle range between 0.2 to 1.0
microns where neither impaction nor diffusion is highly effective.
Particles in this size range are especially difficult to collect.
-------
INSPECTION OF VENTURI SCRUBBERS
2. Baseline and Diagnostic Inspection Data
Stack
Scrubber
Stack Test
Fan
Duct Work
Average Opacity
Minimum and Maximum Opacities During Process Cycles
Mist Reentral nment
Inlet Gas Temperature
Outlet Gas Temperature
Inlet Static Pressure
Inlet 02/C02 Content
Outlet Static Pressure
Rec1rculat1on Liquor pH
Rec1rculat1on Liquor Suspended Sol Ids
Rec1rculat1on Rate
Rec1rculat1oan Liquor Temperatures
Adjustable Throat Mechanism Position
Quantity of Surfactant, Flocculant, and/or Ant1-
f earning Agent Added Per Day
Presaturator Total Sol Ids
Emission Rate
Gas Velocity and Flow Rates
Stack Temperatures
Stack O/CO Content
Fan Speed
Motor Current
Gas Temperature
Vibration (Minimal, Moderate, Severe)
Presence or Absence of Holes
Hood Static Pressure
3. Routine Inspection Data
Stack Average Opacity
Minimum and Maxzlmum Opacity During Process Cycles
Presence or Absence of Fallout
Scrubber Inlet and Outlet Static Pressures
Inlet Gas Temperature
Liquor Line Skin Temperatures
Redrculatlon Liquor pH
Rec1rculat1on Liquor Turbidity (Qualitative Evaluation)
General Condition of Shell
Presaturator Turbidity (Light, Moderate, Severe)
Fan Vibration (Minimal, Moderate, Severe)
Duct Hork Presence or Absence of Holes
Hood Static Pressure
-------
INSPECTION OF YENTURI SCRUBBERS
4. Inspection Methodology
A. Routine Inspection
Stack -
Fan and General System Condition -
Scrubber Inlet Measurement Port -
The opacity of the emissions from
the scrubber is usually a good
Indicator of performance. Un-
fortunately, the opacity is often
difficult to evaluate since the
condensed water droplets from
the scrubber obscure the light
scattering particles. If the
plume can be read at the point
of discharge, the opacity can
have diagnostic meaning.
The average opacity and cycles
1n the opacity should be
determined to the extent possible
(see above). The magnitude and
timing of the opacity cycles
can be of use in determining
process operational factors
which affect the particle size
and quantity of particulate in
the gas to the scrubber-
The presence of material fallout
near the stack or the presence
of a lip of crusted material at
the stack mouth both may indicate
carryover of material from the
demister.
Excessive fan vibration due either
to build-up of material on the
blades or erosion of the blades
can be a serious safety problem.
When excessive vibration is
present, the inspection should
not be continued since there is
a possibility of fan disintegration.
The port should be upstream
from the point of liquor
Injection and at a position as
free of immediate flow disturbances
as possible. The static pressure
should be measured using the
portable static pressure gauge
after ensuring that the port is
clear. The gas temperature
-------
INSPECTION OF VENTURI SCRUBBERS
4. Inspection Methodology (Continued)
Scrubber Throat -
Outlet Measurement Port -
Reclrculation System -
should be measured at the same
point with care to minimize air
Infiltration with cooling of
the thermocouple probe.
The skin temperatures of all liquor
lines to the venturf throat should
be checked. Low temperature
of one line relative to the
other lines may Indicate pluggage
of that HneTrhis can severely
affect emissions since the
liquor to gas distribution 1s
usually Improper 1n such cases.
The position of the adjustable
throat mechanism should be
noted (manual systems only).
The static pressure downstream
of the throat should be measured.
The port should be located
after the diverging section of
the venturl and preferably
before any mesh pads or chevron
denrfsters. These devices add
several Inches of pressure drop
without appreciably affecting
particulate efficiency.
Due to the high negative static
pressures In this part of the
scrubber (sometimes greater than
-15 Inches), care must be taken
to prevent the problems related
to air leakage during measurements,
such as the aspiration effect.
The pH for all scrubbers should
be measured in a fresh sample
of the reclrculation liquor
which should be requested from
the plant representative. If
the solution 1s highly colored
or would chemically attack pH
paper, a portable pH meter must
be used.
-------
INSPECTION OF YENTURI SCRUBBERS
4- Inspection Methodology (Continued)
Presaturator-
Ducts and Hoods -
B. Diagnostic Evaluation
If the opacity is high or the
static pressure drop is low.
The turbidity of the liquor
should be qualitatively evaluated.
High levels of suspended solids
may result from a reduction of
the purge and make-up flows or
from higher levels of particulate
coming into the system.
Operation at very high pH levels
(greater than 10) may cause
precipitation of materials out
of solutions thus causing the
same condition. At high levels
of suspended solids, nozzles
are vulnerable to pluggage and
or erosion.
The presaturator liquor turbidity
should be checked. The liquor
used here should appear very
clear- If not, it is possible
to reintroduce substantial
quantities of material back
into the gas stream as the spray
droplets evaporate. This can
have an adverse impact on the
particulate removal efficiency
since the particle size of the
regenerated material is quite
small.
The ducts leading to and from
the scrubber should be checked
for holes. Common problems
Include erosion at elbows,
open cleanout ports, and weld
failure. The hood static pres-
sure should be recorded since
this is related to the total
gas flow up through the hood.
Check the liquor flow rate at
the sump drain, check the pump
discharge pressures, and re-
check the skin temperatures
of the liquor lines to the
venturi throat. If possible.
request that the operator
isolate and rod out nozzles.
-------
INSPECTION OF YENTURI SCRUBBERS
4. Inspection Methodology (Continued)
Opacity Is high, but static
pressure drop 1s close to
baseline levels.
Corrosion damage apparent.
M1st reentralnment.
Check the position of the
adjustable throat mechanism.
This affects the throat velocity
which Is a major factor In
determining the pressure drop
and collection efficiency.
If liquor flow 1s close to
baseline levels and the throat
mechanism Is unchanged ( or Is
fixed by design), then reduced
gas flow rate 1s the probable
explanation. Check gas flow
rate using a pitot tube.
Check for possible condensation
of submlcron aerosols from
organic and/or metallic vapors
evolving from the process
equipment.
Check for evaporation regeneration
of particulate due to the use
of high solIds content liquor
1n quench chambers, presaturators,
or atomizing venturf nozzles.
Review properties of materials
used In the wet scrubber (see
attached table). Depending on
type of material, evaluate the
specific chemical problems
which most likely could occur.
This evaluation normally Involves
liquor analyses for things
such as chlorides. A cursory
design review can be made to
confirm the presence or absence
of galvanic cells due to Improper
contact of dissimilar metals.
Check the pressure drop across the
demister, If possible. An Increase
1n the pressure drop suggests some
pluggage of the demister which can
lead to localized high velocities.
The operation of the demister clean-
Ing sprays should be checked by
plant personnel.
-------
INSPECTION OF YENTURI SCRUBBERS
4. Inspection Methodology (Continued)
pH less than 6.
Fugitive emissions
at the process hood.
A detailed check for corrosion
should be made. If there is an
alkaline additive system, this
should be checked to determine
why there is an inadequate add-
ition rate.
Air Infiltration points in the
scrubber, the fan (especially the
Isolation sleeves), and the ducts
should be checked. On combustion
sources, the extent of infiltration
should be evaluated using 02 and
measurements before and after the
scrubber and at various locations
along the ducts (if safely accessi-
ble). The total gas flow rate
through the scrubber can be de-
termined using the pi tot tube.
-------
PROPERTIES OF MATERIALS USED IN THE CONSTRUCTION OF WET SCRUBBERS AND AUXILIARY COMPONENTS
Material
Properties
Corrosion resistance
Uses
Cast Iron
Carbon steel
Austenltlc
stainless
steels
(201. 202.
301. 302.
304. 310.
316. 317)
High strength; low
ductility; brittle;
hard; low cost
Good strength, duct-
ility, and work-
ability; low cost
Iron-chromlum-nleke1
alloy; not hardenable
by heat; hardenable by
cold working; nonmag-
netic; cost 3 to 10
times more than carbon
steel; alloys with ML"
designation (e.g., 316L)
have lower carbon con-
tent for Improved weld-
ability
Gray or white case Irons exhibit
fair resistance to mildly corro-
sive environments; high-silicon
case Irons exhibit excellent re-
sistance In a variety of environ-
ments (hydroflourlc acid Is an
Important exception); case Irons
are susceptible to galvanic cor-
rosion when coupled to copper al-
loys, stainless steels
Fair to poor In many environments;
low pH and/or high dissolved
solids In moist or Immersion
service leads to corrosion;
properly applied protective
coatings give appropriate pro-
tection In many applications;
susceptible to galvanic corro-
sion when coupled to copper
alloys, stainless steels
Good In oxidizing environments; fair
In non-oxidizing environments;
susceptible to pitting and stress
corrosion cracking In chloride
solutions. Type 310 resists high
temperature corrosion; types 316
and 317 contain molybdenum for
better chloride and pitting
resistance.
Pump casings, valve cas-
ings, piping; often
used with linings In
corrosive service
General purpose In non-
corrosive environ-
ments
Scrubber vessels; fans;
stacks and ductwork;
Mist eliminators;
quench chambers
•a
m
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CD
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50
(Continued)
-------
PROPERTIES OF MATERIALS USED IN THE CONST
ION OF WET SCRUBBERS AND AUXILIARY COMPONENTS
Material
Properties
Corrosion resistance
Uses
Nickel alloys
(Inconela,
lncoloya,
Monela,
Hastalloysb-
Chlor1metc.
and others)
Fiberglass-
reinforced
plastics
(FRP)
Wood
Good strength, costs more
than 10 times as much
as carbon steel; also
expensive to fabricate;
commonly alloyed with
chromium, Iron or
copper
Good chemical resistance;
poor abrasion resis-
tance; cannot be used
In high-temperature
service; low hardness
High tensile and shear
strength perpendicular
to grain; low tensile
and shear strength par-
allel to grain; low
hardness; poor abrasion
resistance; cannot be
used for high-temper-
ature service
Excellent resistance In most en-
vironments; not resistant 1n
strong oxidizing solutions such
as ammonium and HNO^; most have
good resistance to stress corro-
sion; some nickel-copper alloys
have good resistance to hydro-
fluoric acid
Excellent In many corrlslve en-
vironments; actual results de-
pend on type of plastic resin
used
Good resistance In dilute acids
(Including hydroflourlc acid);
susceptible to biological at-
tack under certain conditions;
deteriorates In alkaline
solutions
Scrubber vessels, fans;
stacks and ductwork;
mist eliminators
Scrubber vessels, piping,
mist eliminators, duct-
work and stacks
Scrubber vessels, tanks,
especially In fluoride
exposure; fir and cy-
press are popular
species
CO
-o
m
o
o
o
LSI
O
73
cz
03
DO
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73
CO
a Registered trademark of Huntlngton Alloys, Inc.
b Registered trademark of the Stelllte Division of the Cabot Corporation
c Registered trademark of the Durlron Company, Inc.
-
U3
-------
INSPECTION OF SPRAY TOWER SCRUBBERS
50
SPRAY HEADERS
SPRAY NOZZLES
SUMP
OUTLET
INLET
SIMPLE SPRAY TOWER SCRUBBER
SOURCE: Air Pollution Training Institute
-------
INSPECTION OF SPRAY TOWER SCRUBBERS
51
Components and Operating Principles
Spray tower scrubbers are the simplest type of wet scrubber and
generally have the lowest overall particulate collection efficien-
cy. They are not usually effective for particles below 5 ymA.
This type of scrubber normally consists of a vertical contact cham-
ber with an array of spray nozzles as shown in the figure above.
The particle laden gas stream enters near the bottom of the scrub-
ber and passes upward at a velocity of 2 to 4 feet per second. The
spray nozzles may consist of sophisticated liquid atomizing nozzles
or may simply be small holes drilled into the spray header. The
spray droplet size can vary from 200 microns to 1000 microns de-
pending on the type of nozzle and the operating pressure. Particu-
late collection efficiency is a function of a number of variables
including the gas velocity, the spray droplet velocity, the spray
droplet size, the nozzle spray angle, the height of the scrubber,
and the liquid-to-gas ratio.
Spray tower scrubbers are sometimes used for gaseous absorption
and for odor control. In this case, important operating parameters
include the liquid-to-gas ratio, the liquor pH (for some applica-
tions), and the residence time in the scrubber.
The major components which comprise this type of scrubber system
include a demister, a recirculation pump, and a liquor recircula-
tion and treatment circuit. The latter can include clarifiers
and alkaline addition systems. In some cases there are no moni-
toring instruments for liquor pH, liquor flow rate, or gas stream
temperature. The most common performance problems include pluggage
of the liquor spray nozzles, erosion of the spray nozzles, corro-
sion of the shell, and mist reentrainment.
a. Impin^emrnt spray
nozzle
b. Solid cone spray nozzle
c. Helical cone ipray nozzle
Common Types of Commercial Spray Nozzles
SOURCE: Air Pollution Training Institute
-------
INSPECTION OF SPRAY TOWER SCRUBBERS
Baseline and Diagnostic Inspection Data
52
Stack Average Opacity
Minimum and Maximum Opacities During Process Cycles
Apparent M1st Reentralnment
Fan Fan Vibration (Minimal, Moderate, Severe)
Fan Speed
Fan Motor Current
Gas Inlet Temperature
Scrubber Rec1rculat1on Liquor pH
Rec1rculat1on Liquor Suspended Solids
Redrculatlon Liquor Turbidity (Light, Moderate, Heavy)
Rec1rculat1on Liquor Flow Rate
Nozzle Operating Pressure
Apparent Shell Erosion or Corrosion
Inlet 02 and C02 (Combustion Sources Only)
Duct Work Presence or Absence of Obvious Holes
Hood Static Pressure
Hood Capture Effectiveness (Good, Moderate, Poor)
Stack Test Emission Rate
Gas Flow Rate
Stack Temperature
Stack 02 and C02
Internal View Nozzle Condition
from AccessPresence or Absence of Deposits on Demlsters
Hatch (if safe)
3. Routine Inspection Data
Stack Average Opacity
Minimum and Maximum Opacities During Process Cycles
M1st Reentralnment
Fan Vibration (Minimal, Moderate, Severe)
Scrubber Redrculatlon Liquor pH
Rec1rculat1on Liquor Turbidity (Light, Moderate, Heavy)
Redrculatlon Liquor Flow Rate
Nozzle Operating Pressure
Apparent Shell Erosion or Corrosion
Duct Work Presence or Absence of Obvious Holes
Hood Static Pressure
-------
INSPECTION OF SPRAY TOWER SCRUBBERS
Inspection Methodology
A. Routine Inspection
53
Stack -
Fan -
Scrubber -
Spray tower scrubbers are usually
used only on sources generating
large size particulate matter. Due
to the low light scattering charac-
teristics of large particulate,
a low opacity does not always mean
low mass emissions.
The presence or absence of mist
fallout in the vicinity of the
scrubber discharge should be
noted. This is usually a symptom
of demister failure. In some
cases, this is accompanied by a
small deposit of material at
the stack discharge.
Opacity spikes on an intermittant
basis may be indicative of process
releases or small particle size
material which is beyond the capa-
bility of the collector. The
duration and timing of the spikes
should be recorded so that the
process equipment can be inspected
later.
Excessive fan vibration either due
to build-up of material on the blades
of the fan or erosion of the blades
can be a serious safety problem. If
excessive vibration is present, the
inspection should be discontinued
immediately because of the possibility
of fan disintegration.
The operation of the recirculation
pump and the condition of the liquor
piping and nozzles should be checked.
An increase in the nozzle operating
pressure often indicates partial
or complete pluggage of the spray
nozzles or spray header. If the
nozzle pressure gauge is not oper-
ating (or available), the pump dis-
charge pressure should be noted.
The liquor flow rate should be
checked using the on-site gauge
(if available). If there is no
gauge it is sometimes possible to
estimate the flow rate by observing
the discharge from the scrubber to
the pond or the recirculation tank.
-------
INSPECTION OF SPRAY TOWER SCRUBBERS
4. Inspection Methodology (continued)
Ducts and Hoods -
B. Diagnostic Evaluation
Apparent mist reentrainment.
The integrity of the scrubber shell
should be evaluated. If there is
apparent-erosion or corrosion damage,
it is likely that substantial air
infiltration is occurring (negative
pressure systems). This can reduce
source capture effectiveness.
The pH of the recirculation liquor
should be measured using a sample
from the scrubber sump, the point
of minimum pH. Rapid corrosion can
occur if the pH in a carbon steel
system drops below 6 (a magnet will
stick to carbon steel).
The ducts leading to and from the
scrubber should be checked for holes.
elbows, open cleanout traps, and
weld failure. The hood static
pressure should be recorded since
it is related to the total gas
flow up through the hood.
The liquor turbidity should be
checked by drawing a sample from
the sump discharge or the pump
discharge. A high turbidity liquor
can cause erosion or pluggage of
the nozzles and headers.
This can be caused by excessive
velocities through the scrubber
itself or by partial pluggage of
the demister. The demister can be
checked for pluggage when the
scrubber is down and purged. The
gas velocities can be checked by
dividing the total actual cubic
feet per minute (determined by
a pitot traverse) by the cross
sectional area of the scrubber
(in square feet). An increase in
the fan R.P.M. or an increase in
the fan motor current (corrected
to ambient conditions) also
indicates an increase in gas flow
rates relative to the baseline
period.
-------
INSPECTION OF SPRAY TOWER SCRUBBERS
Inspection Methodology
55
High opacity with an increase
in the nozzle operating
pressure.
Opacity high with a decrease
in the nozzle operating
pressure.
pH below 6.
Fugitive emissions at the
process hood.
The most probable cause of this per-
formance problem is the partial or
complete pluggage of spray nozzles
or possibly the main supply header.
At the earliest opportunity, plant
personnel should shut down the unit,
purge it, and observe the operation
of the nozzles. A distorted spray
angle indicates a partial pluggage.
A drastically narrowed spray angle
indicates almost complete pluggage.
Plugged nozzles should be cleaned
out or replaced.
If there is evidence of frequent
nozzle pluggage, the total and
suspended solids content of the
recirculation liquor should be
determined. In the case of a
high solids content the liquor
treatment system may have to be
modified.
Nozzle erosion due to high suspended
solids can cause these symptoms.
The erosion of the nozzle orifice
leads to a decrease in the spray
angle with a resultingly poor spray
distribution across the gas stream.
The same symptoms may be caused by
a reduction in the liquor flow rate
which could occur with pump impeller
wear.
A detailed check for corrosion
should be made. If there is an
alkaline additive system, it should
be checked to determine the cause
of the inadequate addition rate.
Check for air infiltration points
in the scrubber, the fan (especially
the isolation sleeves), and the ducts.
On combustion sources, the extent
of infiltration should be evaluated
using 03 and C02 measurements at
various locations along the ducts
(if there is safe accessibility) and
before and after the scrubber. The
total gas flow rate through the
scrubber can be determined using
the pi tot tube.
-------
INSPECTION Of TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS
dean gi*
56
PUto
Dim gas-
SOURCE:
TRAY-TYPE SCRUBBER
Air Pollution Training Institute
dean gas
Mitt eliminator
\=^
MOVING BED SCRUBBER
SOURCE: Air Pollution Training Institute
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS 57
1- Components and Operating Principles
Tray-type, moving bed, and packed bed scrubbers are used primarily
for particulate control, however the moving bed and packed bed scrub-
bers are also frequently used for control of mists and gaseous pol-
lutants. For all three categories of scrubbers, the gas stream is
usually introduced into the scrubber near the bottom and passes up
through the scrubber in a counterflow manner with respect to the
liquor (there is one common packed towever scrubber which is ori-
ented horizontally with the liquor flowing down the packing by
gravity). Particulate removal is due primarily to impaction on
liquor droplets and liquor sheets. The effectiveness of impaction
is proportional (1) to the relative velocity between the particle and
the target (droplet or sheet), (2) to the particle density, and (3) to
the square of the particle diameter. In some cases, the liquor
surface tension and the particle surface characteristics can modify
the effectiveness of the impaction capture mechanism. Important
parameters with relation to gas absorption include liquor surface
area, residence time, and liquor chemical characteristics such as
the pH.
1.1 Tray-Type Scrubbers
Tray-type scrubbers consist of a vertical shell with one or
more plates mounted horizontally. The liquor is introduced near
the top of the scrubber, below the demister. It flows across the
top tray and then down to the lower tray(s) by means of downcomers.
(In some units the liquor drains down directly through the tray
orifices). As the liquor passes across each stage, it is exposed
to the high velocity gas streams passing up through the orifices in
the trays. Impaction of the gas entrained particulate occurs on
the sheets of liquor and on the droplets which are atomized by
the gas stream as it passes up through the tray. The most common
types of tray-type scrubbers are the sieve plate and impingement
plate scrubbers. The differences in the tray design for these
scrubbers is illustrated in the figure below:
The sieve plate scrubber has moderately large orifices and in
some cases the liquor drains down directly through these holes
without the need for downcomers. The impingement plate has
numerous very small holes and impingement targets above each.
The impingement plate scrubber is prone to pluggage problems due
to these very small holes.
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS
58
dean gu
Dirty gat
COUNTERCURRENT PACKED TOWER
SOURCE: Air Pollution Training Institute
Water sprays
CROSSFLOW PACKED TOWER
SOUREC: Air Pollution Training Institute
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS 59
1.2 Moving Bed Scrubbers
This type of scrubber includes one or more trays of light weight
packing usually consisting of polypropyle/ie or fluorocarbon spheres.
This packing is free to move within the bed which is only 20% to
40% full. The packing is restrained by screens above and below
the bed. The pollutant laden gas stream passes up through the
beds, thereby fluidizing the packing. Particulate and gaseous
absorption occurs on the droplets and liquor sheets formed in the
turbulent bed. The liquor is introduced near the top (below the
deroister) using a set of spray nozzles. The demister can be mesh
pads, chevrons or an unirrigated bed of packing. The removal effi-
ciencies for particulate matter are very high, even in the 1 to 2
micron size range.
1.3 Packed Tower Scrubbers
A packed tower scrubber is similar to the moving bed scrubber
with the exception that the packing is firmly restrained. The
liquor is introduced immediately below the demister and passes
down through the bed as sheets. The primary purpose of the
packing is to maximize the surface area available for absorption
of gaseous material. Nozzle pluggage, nozzle erosion, and scaling
can all lead to channeling of the liquor (poor liquid-gas distri-
bution). These units are not intended for high efficiency collec-
tion of particulate matter in the less than 3 micron range or
for sources with high inlet mass loadings; they are better suited
for gaseous absorption. Some common types of packings are illus-
trated below. In some units, gravel has also been successfully
used.
Berl saddle
Inolox taddle
Common types of Packing Material
SOURCE: Air Pollution Training Institute
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS
2. Baseline and Diagnostic Inspection Data
Stack Average Opacity
Minimum and Maximum Opacities During Process Cycles
Apparent M1st Reentral ranent
Fan Fan Vibration (Minimal, Moderate, Severe)
Fan Speed
Fan Motor Current
Gas Inlet Temperature
Scrubber Static Pressure Drops Across Each Tray or Bed
Presaturator Liquor Total Sol Ids
Presaturator Liquor Turbidity (Light, Moderate, Heavy)
• Redrculatlon Liquor pH
Rec1rculat1on Line Pressure at Nozzles (If Any)
Inlet and Outlet Gas Temperatures
Inlet 03 and C0£ (Combustion Sources Only)
Apparent Shell Erosion or Corrosion
Duct Work Presence or Absence of Obvious Holes
Hood Static Pressure
Hood Capture Effectiveness (Good, Moderate, Poor)
Stack Test Emission Rate
Gas Flow Rate
Stack Temperature
Stack 02 and C0£
3. Routine Inspection Data
Stack Average Opacity
Minimum and Maximum Opacities During Process Cycles
M1st Reentral nment
Fan Vibration (Minimal, Moderate, Severe)
Scrubber Static Pressure Drops Across Each Tray or Bed
Presaturator Liquor Turbidity (Light, Moderate, Heavy)
Rec1rculat1on Liquor Turbidity (Light, Moderate, Heavy)
Recirculation Liquor pH
Recirculatfon Line Pressures at Nozzles (If Any)
Apparent Shell Erosion and Corrosion
60
Duct Work Presence or Absence of Obvious Holes
Hood Static Pressure
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS
Inspection Methodology
A. Routine Inspection
61
Stack -
Fan -
Scrubber -
The opacity is usually a good
indicator of scrubber perform-
ance. Unfortunately, the
opacity is often difficult
to evaluate since condensed
water droplets obscure light
scattering particulate. If
the plume can be observed
at a point before the conden-
sation of water droplets
(preferably at the stack
discharge point), the opac-
ity can have diagnostic
meaning.
The presence or absence of
mist fallout in the vicin-
ity of the scrubber discharge
should be noted. This is
usually a symptom of demister
failure. In some cases, this
is accompanied by a small de-
posit of material in the area
of the stack discharge.
Excessive fan vibration, due
either to build-up of material
on the fan blades or erosion
of the blades, can be a serious
safety problem. If excessive
vibration is present, the
inspection should be discon-
tinued immediately because of
the possibility of fan dis-
integration.
The static pressure drops across
each tray or bed should be evalu-
ated using operational on-site
gauges or portable instruments.
It is important to confirm that
the measurement ports are not
plugged regardless of which in-
strumentation is used. The sta-
tic pressure drops should be
be compared with baseline values.
A reduction in the static pres-
sure over time is usually due
to a decrease in the gas flow
rate. An increase could be due
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS 62
4. Inspection Methodology (continued)
to Increased gas flow rate or
partial pluggage of the trays
or beds.
On combustion sources, the In-
let oxygen concentration
should be measured and compared
with the baseline values. An
Increase In the Og concentra-
tion can signal a deteriora-
tion In the combustion process
and the consequent generation
of more partlculate than can
be adequately controlled In
the scrubber.
The reclrculatlon liquor tur-
bidity should be checked. If
the turbidity appears high
there Is the potential for
pluggage of the tray orifices
(Impingement plate scrubber)
or build-up within the pack-
Ing (packed bed scrubber).
The presaturator (1f present)
liquor turbidity should be
checked. The liquor used here
should appear very clear. If
not, It 1s possible to relntro-
duce substantial quantities
of material back Into the
gas stream as the spray
droplets evaporate. This
can have an adverse Impact
on the partlculate removal
efficiency since the particle
size of the regenerated
material 1s quite small.
The pH of the Hquor leaving
the scrubber should be de-
termined by using either
the on-s1te meter of a por-
table pH meter (or Indicator
paper). Low pH can have an
adverse effect on'the ability
of the system to absorb gases
like HF and SO? and may also
result 1n accelerated corro-
sion of the scrubber shell.
A high pH (above 10) Indicates
-------
INSPECTION OF TRAY-TYPE,, MOVING BED, AND PACKED BED SCRUBBERS 63
inspection Methodology (continued)
the possibility of precipi-
tation of calcium and
magnesium compounds,
with a resulting build-up
on the packing materials or
the walls of the scrubber
vessel which ultimately can
lead to the gas-liquor mal-
distribution.
The line pressure at the
nozzles should be checked.
This is to confirm that
there has not been any
pluggage or erosion of
nozzles themselves which
could result in maldistri-
bution of the gas and
liquor streams. An in-
crease in the nozzle oper-
ating pressure suggests
pluggage. A decrease in
the pressure relative to
the baseline values sug-
gests either a reduction
in the liquor flow rate
or erosion of the nozzles.
Ducts and Hoods -
B. Diagnostic Evaluation
Opacity is high and
static pressure drops
across trays or beds
are lower than base-
line values.
The ducts leading to and
from the scrubber should
be checked for holes.
Common problems include
erosion at elbows, open
cleanout ports, and weld
failure. The hood static
pressure should be record-
ed since this is related
to the total gas flow
up through the hood.
Check the gas flow rate
through the scrubber.
Confirming symptoms of
low gas flow rate include
a reduction in the fan motor
current (corrected to stand-
ard conditions) and a re-
duction in the scrubber inlet
static pressure. The flow
rate can be measured using
a pi tot tube.
-------
INSPECTION OF TRAY-TYPE, MOVING BED, AND PACKED BED SCRUBBERS 54
4. Inspection Methodology (continued)
Opacity 1s high, but
static pressure drops
are close to baseline
values.
Opacity 1s high, but
static pressure doprss
are greater than baseline
values or gas flow rates
appear to be less than
baseline values.
M1st reentralnment.
In the moving bed and tray-
type scrubbers, the low
pressure drops can also be
due to a reduced liquor flow
rate. This can be confirmed
by rechecklng the on-slte
meter, by visually checking
flow out of the scrubber sump,
or by checking the reclrcu-
latfng liquor nozzle operat-
ing pressure.
Check for possible condensa-
tion of subnrfcron aerosols
from organic and/or metallic
vapors evolving from the
process equipment.
Check for evaporation regen-
eration of parti oil ate due
to the use of high solids
content liquor 1n presatu-
rators, or quench chambers.
To confirm sol Ids levels,
analyze liquor samples.
In Impingement plate scrub-
bers, an Internal check
should be made by plant
personnel at the earliest
opportunity to determine
1f there 1s some pluggage
of the tray orifices.
Check the pressure drop
across the demlster 1f
possible. An Increase 1n
the pressure drop may sug-
gest some pluggage of the
demlster which can lead
to localized high veloci-
ties. The operation of
the demlster cleaning sprays
should be checked by
plant personnel.
Apparent corrosion
damage.
Recheck the liquor pH
measured and Inquire
about start-up and
shut-down procedures.
-------
SELECTION OF MEASUREMENT PORTS AND USE OF PORTABLE INSTRUMENTS
65
i. General Guidelines
(a) Make measurements only when necessary and with the full knowledge
and consent of the operator.
(b) Conform to all union-company policies regarding measurements.
(c) Do not disconnect static pressure lines which lead to a differential
pressure (D/P) transducer.
(d) Only measurement ports which are safe and convenient to reach
should be used. If appropriate ports are not presently available,
modifications can be requested for future inspections. New ports
can usually be easily Installed at the next major outage. Heroic
efforts should not be made to reach improperly located existing
ports.
2. Specific Guidelines
(a) The static pressure ports for venturi scrubbers should usually be
1n the locations shown in the figure below. The inlet port can be
anywhere along the inlet duct to the scrubber but it should not be
in the immediate area of the liquor injection point since it will be
very difficult to keep clear- The outlet port can be anywhere except
in the diverging section of the venturi since in some cases it 1s
conceivable that boundary layer separation may occur. If the outlet
port is after the demister, the pressure drop for the overall unit
will be several inches of water higher than measured just before
the demister.
GAS INLET
LIQUOR
INLET
DIVERGING
SECTION
GAS OUTLET
DEMISTER
LIQUOR OUTLET
-------
SELECTION OF MEASUREMENT PORTS AND USE OF PORTABLE INSTRUMENTS
66
2. Specific Guidelines (Continued)
(b) Almost all electrostatic preclpltators have measurement ports for
stack sampling. Due to the size of the ducts, however, single point
temperature and 02/C02 measurements may not be representative of the
bulk gas stream. With such ducts, It Is necessary to traverse the
duct to measure conditions at as many points as necessary and then
average the results. This Is not very time consuming for temperature
(1f a sufficient thermocouple 1s available) however, It Is difficult
for the 02/C02 readings. For this reason, such measurements are
rarely made.
The large duct problems associated with electrostatic preclpltators
are also common to large fabric filter systems.
(c) The clean side static pressure port for fabric filters should not be
Immediately above the tube sheet since the build-up of solids can
make 1t very difficult to keep the port clean during the measurements.
(d) The ports for most fabric filters and mechanical collectors can be
anywhere 1n the ductwork leading to and from the units. The ports
should be 1n areas as far away as possible from flow disturbances
and should be approximately 3/4" to 1" In diameter so that a
pi tot tube can be used.
3. Avoiding the Problems of A1r Inleakage through Ports under Negative
Pressure
Air Inleakage causes the following measurement problems:
Lower than actual Gas Temperatures.
Higher than actual 02 Levels.
Higher gr Lower Static Pressures.
When the static pressure 1s greater than -10" W.6. the Inleakage
around the probe can cause an aspiration effect which results in
readings significantly more negative than actual conditions. This
is illustrated in the figure below.
AIR INFILTRATION
NeCATIVI
PRESSURE
DUCT
COPPER PROBE
RUBBER STOPPER
Note: Aspiration induces additional
suction at probe.
-------
SELECTION OF MEASUREMENT PORTS AND USE OF PORTABLE INSTRUMENTS 67
Avoiding the Problems of Air Inleakage through Ports under Negative
•'fPC c i ir*O ( r r\n + * **t.~ J \ •' • T .•!« r . • r
ressure (Continued"
The severity of this problem increases as the static pressure
decreases from -10 inches to -120 inches. The condition is often
indicated by an audible sound of Inleakage (assuming plant noise
levels are sufficiently low).
The aspiration effect may be avoided by using the S-type pi tot
tube for static pressure measurements (disconnect the impact side
of the tube) or by using a copper tube (1/2 or 1/4" 0.0.) as shown
1n the figure below. Even 1f leakage 1s occurring the tip of the
probe 1s not significantly affected using either approach. (It is
often necessary to electrically ground the copper probe or pitot
tube.)
NEGATIVE
PRESSURE
DUCT
COPPER PROBE
RUBBER STOPPER
Use of the extended copper tube can also be useful for the Fyrite
and temperature measurements. In both cases, it is important to
bend the tube upstream of the port, so that the effect of air
leakage 1s minimized. The thermocouple wire may be threaded
through the copper tube to ensure that the probe stays in the
Intended location.
If the rigid dial-type thermometers are being used it is important
to seal the port very well in order to avoid lower than actual
results. This can be done with rubber stoppers or similar materials,
Since there are no stoppers large enough for large 4" ports often
encountered at stack sampling locations, it 1s convenient to use a
round sanding disk (sold for small drills) in place of the stopper.
Gloves and other fabric materials can also be used, however, it is
much more difficult to ensure that the seal is maintained.
-------
SELECTION OF MEASUREMENT PORTS AND USE OF PORTABLE INSTRUMENTS 58
3. Avoiding the Problems of Air Inleakage through Ports under Negative
Pressure (Continued)
Extreme care must be taken to ensure that the probe and/or the
port seal (eg. glove, rubber stopper) is not sucked Into a nega-
tive pressure duct. This 1s particular-fly a problem when the
port 1s fairly large and the duct Is at a large negative static
pressure. For such ports, the sampling probe should be secured
by a disk and a. rubber stopper 1n series as shown In the figure
below.
4. Avoiding Problems with Positive Pressure Ports
Positive pressure ports larger than 1" diameter should not be
used under any circumstances. While opening such a port It is
possible to unintentionally fumigate all personnel 1n the general
vicinity. Even with small positive pressure ports, the port must
be opened carefully and sealed quickly.
5. Grounding and Bonding
In some gas streams It 1s conceivable that a high static electri-
cal charge will build up on the metal probe during the measurement
work. A spark to the gounded duct wall could initiate an explosion
1f the dust concentration and the oxygen concentration were suffi-
cient. Build-up of static can be avoided by attaching an electrical
bonding wire from the probe to the duct wall- This should be con-
nected prior to inserting the probe into the duct. The duct itself
should be grounded. If there 1s any question concerning the ade-
quacy of the grounding and bonding apparatus or concerning the ex-
plosive potential of the gas stream, the measurement should not be
made. Use of a bonding wire is illustrated in the figure below.
DUCT WALL
COPPER TUBE
, /-RUBBER STOPPER
/ TUBING
ELECTRICAL
BONDING WIRE
GROUNDING CLAMP
GROUNDING TAB
-------
VELOCITY TRAVERSES
69
Selection of Measurement Site
A. Preferred Measurement Site Location
(1) At least 8 diameters downstream, and
(2) At least 2 diameters upstream
B. Minimum Measurement Site Location
(1) At least 2 diameters downstream, and
(2) At least 1/2 diameters upstream
C. Rectangular Cross Sections - Equivalent Diameter
2 L W
L + W
2. Traverse Points
A. Minimum Number of Traverse Points - Use Figure 1
0.5
OUCT OIAMCTEM UPSTREAM FROM 'LOW DISTURBANCE (OISTAMCI Al
1.0 l.i 2.1
M
MWIMUU NUMIf I OF TKAVf ME POINTI
• * * « ft t
1 1 1 1 1
• HIGHER NUMBER IS FOR
RECT ANGULAR STACKS OR OUCTS
1 1
T
T
A
1
^H
i
i
7
DISTUWANCE
HtASURtMIMT
:- «TE
DOTUIVANCt
16 STACK DIAMETER > a*i • 124 «j
1
12
| SOU!* -
HACK DIAMETER • 0.30 TO O.C1 • (12-24 i«J
1 1 ! 1 I I I
J 4 » »
OUCT OIAMCTEMS OOWNSTMIAM FROM FLOW OltTUKBANCS (DISTANCE •>
Figure 1. Minimum Number of Traverse Points For Velocity Traverses
(From 48 FR_ 45035, September 30, 1983)
-------
VELOCITY TRAVERSES
70
2. Traverse Points (Continued)
B. Location of Traverse Points
(1)
Circular Stacks - Traverse points located on two perpendicular
diameters of the stack at locations such as shown 1n Figure 2
and at distances determined from Table 1. For stacks with
diameters less than 24 inches, do not locate a traverse point
within 0.5 inches of the stack wall.
TIAVCMSC
POINT
Figure 2. An Example of the Locations of Traverse Points in a Circular
Stack. (FromfR, Vol. 42, No. 160, Pg. 41758, Aug. 18, 1977)
TABLE 1. PERCENT OF STACK DIAMETER FROM INSIDE WALL TO TRAVERSE
POINT FOR CIRCULAR STACKS
Tr»v«rjt
point
nunber
on t .
dlaatttr
1
2
3
4
5
6
7
8
9
10
11
12!
13'
14
15
16
17
18
19
20:
21
22
23
24
Number of traverse points on a diameter
2
14.6
as. 4
•
4.
6.7
25.0
75.0
93.3
6
4.4
14.6
29.6
70.4
85.4
95.6
8
3.2
10.5
19.4
32.3
67.7
80.6
89.5
96.8
10
2.6
8.2
'l4.6
22.6
34.2
65.8
77.4
85.4
91.8
97.4
•
12
2.1
6.7
11.8
17.7
25.0
35. 6
64.4
75.0
82.3
88.2
93.3
97.9
14
1.8
5.7
9.9
14.6
20.1
26.9
36.6
63.4
73.1
79.9
85.4
90.1
94.3
98.2
16
1.6
4.9
8.5
12.5
16.9
22.0
28.3
37.5
62.5
71.7
78.0
83.1
87.5
91.5
95". 1
98.4
18
1.4
4.4
7.5
1C. 9
14.6
18.8
23.6
29.6
38.2
61.8
70.4
76.4
81.2
85.4
89.1
92.5
95.6
98.6
20
1.3
3.9
6.7
. 9.7
12.9
16.5
20.4
25.0
30.6
38.8
61.2
69.4
75.0
79.6
83.5
87.1
90.3
93.3
96.1
98.7
22
1.1
3.5
6.0
8.7
11.6
14.6
18.0
21.8
26*.2
31.5
39.3
60.7
68.5
73.8
78.2
82.0
85.4.
88.4
91.3
94.0
96.5
98.9
24
1.1
3.2
5.5
7.9
10.5
13.2
16.1
19.4
23.0
27.2
32.3
39.8
60.2
67.7
72.8
77.0
80.6
83.9
86.8
89.5
92.1
94.5
96.8
98.9
-------
VELOCITY TRAVERSES
71
Traverse Points (Continued)
(2) Circular Stacks With Diameters Greater than 24 Inches
Do not locate a traverse point within 1.0 inch at the stack
*al1. Adjust to the larger of at least 1.0 inch or a distance
equal to the nozzle inside diameter. If the adjusted points
overlap with the next traverse point, treat as two points in
the velocity traverse and in the recording of the data.
(3) Rectangular Stacks
(a) Determine the grid configuration from Table 2. Notice
that the minimum number of traverse points for rectangular
stacks is 9.
TABLE 2. DETERMINATION OF GRID CONFIGURATION
No. of Traverse
Points
9
12
16
20
25
30
36
42
49
Grid
Configuration
3 x
4 x
4x4
5x4
5x5
6 x 5
6x6
7x6
7 x 7
3
3
(b) Divide the stack into the grid configuration as determined
from Table 2. Locate a traverse point at the centroid of
each grid. An example is shown in Figure 3.
o I
I
o e
Figure 3. An Example of a Rectangular Stack Divided into a 4 x 3 Grid
Configuration for Twelve Traverse Points.
-------
VELOCITY TRAVERSES 72
3. Verification of Absence of Cyclonic Flow
The presence or absence of cyclonic flow at the traverse location must
be verified if any of the following conditions exist:
o such devices as cyclones and inertlal demisters following
venturi scrubbers are present, or
o tangential inlets OP other duct configurations which tend to
Induce swirling are present.
Procedure
(1) Level and zero the manometer.
(2) Connect a Type S pitot tube to the manometer.
(3) Place the pitot tube at each traverse point so that the face
openings of the pi tot tube are perpendicular to the stack
cross-sectional plane. At this position, the pitot tube is
at 0° reference.
(4) If the differential pressure (An) 1s null (zero) at each
point, an acceptable flow condition exists.
(5) If the n is not zero at 0° reference, rotate the pitot
tube (_+ 90°) until a zero reading is obtained.
(6) Note the angle of the null reading.
(7) Calculate the average of the absolute values of the angles.
Include those angles of 0°
(8) If the average is greater than 10°, the flow conditions of
the stack are unacceptable.
4. Measurement of Stack Gas Velocity and Volumetric Flow Rate
A. Conduct a pretest leak-check on the apparatus.
B. Level and zero the manometer.
C. Measure the velocity head Up) at each of the traverse points and
record these measuremennts on the form presented in Figure 4.
D. Measure the stack gas temperature.
E. Conduct a post-test leak check.
F. Calculate the average stack gas velocity and volumetric flow rate
using the simplified equation (assuming air at standard pressure):
vs * 2.9 Cp ^vay ) avg "Y^'s' avg
where: vs » average stack gas velocity (ft/sec),
Cp = pitot tube coefficient (dimensionless, usually
varies between 0.83 and 0.87),
AP * velocity head (manometer reading) of stack
gas (in. H^), and
Ts » absolute stack temperature (460° + stack gas
temp, in °F).
-------
VELOCITY TRAVERSES
73
4' Measurement of Stack Gas Velocity and Volumetric Flow Rate (Continued!
Qs = 3600 vsA
where: Qs = fiow rate (scf/hr).
A = cross-sectional area of stack (ft2), and
Tstd * standard absolute temperature (528°R).
Traverse
PX.NO.
Vel. Hd..^»
mm (inj H£0
Stack Ttmpcratura
lj.0C(8F)
Avtrajt
Tfc»K(OR)
mm Kg (iajig}
SIT
Figure 4. Velocity Traverse Data (From FR, Vol
Aug. 18, 1977). ~
42, No. 160, Pg. 41763,
-------
MEASUREMENT OF OXYGEN AND CARBON DIOXIDE 74
IN COMBUSTION GAS STREAMS
FYRITE* ANALYZER METHOD
Instrument "Checks (Dally Before Use)
1. Check fluid level In center tube — 1t should be between 1/8 and 5/8
of an Inch after zeroing.
2. Sampling assembly — leak check.
3. Filter packing — visually check to assure that the packing Is
clean and not clogged.
4. Check fluid absorbing power —
Oxygen - Measure Oj 1n ambient air (concentration of
20.9%). Several successive readings should
be within 1/2% of each other, at approximately
20.9%.
Carbon Dioxide - Blow a deep breath at a steady rate for 3 or 4
seconds Into the sampling hose with the filter
saturator tube removed. Several successive
readings should be within 1/2S of each other,
at approximately 4% to 5%.
2. Operation
1. If the flue gases are not saturated with moisture, the filter pack-
Ing must be moistened.
2. Place the metal sampling tube at least 2 1/2 Inches Into the flue
gas.
3. Feed the gas sample Into the Fyrfte« by squeezing the aspirator
bulb IS times.
4. Invert the Fyrfte* several times to allow contact of the gas and
the fluid.
5. Read the concentration (1n percent) directly from the scale located
on the center bore.
-------
CHECKING THE C02 AND 02 MEASUREMENTS 75
Combustion systems operate with a definite relationship between the
carbon dioxide and oxygen concentrations in-the flue gas. The measure-
ments made using the Fyrite* analyzers (or equivalent devices) may be
checked using the following table. If the sum of the 02 and C02
measurements are not within the general ranges specified in the table,
it is probable that there were some measurement errors.
Sum of the 02 and C02
Fuel Concentrations
Natural Gas 13% - 19%
#2 Oil 15% - 20%
#6 Oil 17% - 20%
Bituminous Coal, Lignite, and
Sub-bituminous Coal
Anthracite Coal
Coke
Refuse and Wood
18% -
19% -
19% -
18% -
21%
21%
21%
22%
The measurements should be repeated if the sum of the 02 and C02
concentrations do not fall within this range. The presence of high
CO concentrations could invalidate the ranges shown above.
USING THE 02 AND C02 MEASUREMENTS
The 02 and C02 data can be used to determine the excess air rate of the
combustion system using the nomograph on page 76. A straight line drawn
between the 02 and C02 points should be extended to the left axis to
read off the the excess air rate. The proper fuel type being burned
should be indicated by extending the line to the right axis.
-------
NOMOGRAPH FOR ESTIMATING FLUE GAS COMPOSITION,
EXCESS AIR OR TYPE OF FUEL
76
1500-1
CO
en
8
X
w
400-
300-
200-
100-
50-
19
'18
— 1
— 2
— 3
•10
A •
4 — _
at
a
6 (N
8
8 *
10
15
20
Refuse, Baric
and Wood
r— Methane
_ Average Natural Gas
— Ethane
— Propane
— Pentane
— Gasoline
- #2 Fuel Oil
Bunker "C" Oil
(ft6 Fuel Oil)
• Bituminous Coal
" T-Sub-bituminous & Lignite
r Anthracite
Coke
SOURCE: Entropy Environmentalists, Inc.
Research Triangle Park
North Carolina
-------
OPACITY MEASUREMENTS
SLANT ANGLEt
77
The purpose of measuring the slant angle of the observer in relation to the
stack is to correct the observed opacity. Observed opacity can be higher
than actual opacity because as the angle of observation increases, the
pathlength of light through the plume increases and more light is scattered
by the particles in the plume. Thus, the observed opacity increases.
To correct the observed opacity, the following formula is used in which the
observed opacity is converted to a decimal format (eg. 60? opacity is 0.60) and
then subtracted from 1. This difference is then raised to the cosine phi
power. The resulting value is then subtracted from 1 to get the corrected
opacity.
1
-[u-
'obs
cos
where: Oc
Oobs
corrected opacity (decimal)
observed opacity (decimal)
cos <*> * cosine of the observation angle (dimensionless)
measured by abney level, clinemeter, trigonometric
relationships (i.e., distance to stack and stack
height relative to the observer as sides of a right
triangle) or other surveying device
cos 4>
t Use of the slant angle correction is a matter of agency policy. Inclusion of
this section is only to facilitate use of opacity as a diagnostic tool, not
necessarily for use in enforcement proceedings.
-------
HIGH TEMPERATURE PSYCHROMETRIC CHART
(ENGLISH UNITS)
DRY BULB TEMPERATURE { °F )
-------
FANS 79
.nges in Fan Speed
For a given fan and exhaust system, a change in the fan speed
will result in the following changes:
Gas flow rate will vary directly proportional to the speed.
Fan static pressure will vary as the square of the speed.
Fan horsepower will vary as the cube of the speed.
Fan speed may increase because of:
1. A change in the fan and motor sheaves.
2. A change in the fan motor.
Fan speed may decrease due to:
1. Slippage of belts (usually 100-200 rpm and
accompanied by a distinctive squeal).
2. A change in the fan and motor sheaves.
3. A change in the fan motor.
Changes in System Resistance
For a given fan operating at a constant speed a change in
the system characteristic curve due to resistance changes
in the ductwork or control device will result in the
following changes:
If the resistance increases:
1. The gas flow rate will decrease.
2. The static pressure will increase.
3. The horsepower will decrease (accordingly
the fan motor current will decrease).
If the resistance decreases:
1. The gas flow rate will increase.
2. The static pressure will decrease.
3. The horsepower will increase.
Changes in Gas Temperature
For a given fan and exhaust system and a constant fan speed,
a change in the gas temperature will result in the following:
1. The. fan speed will remain unchanged.
2. The fan horsepower (and motor current) will vary
inversely with temperature and proportional to
gas density (see figure in text).
3. Fan static pressure will vary inversely with gas
temperature.
-------
FAN PERFORMANCE
0)
3
t/1
I/I
4)
1/1
S.
4)
01
I
0)
.X
3
0)
2
CO
Typical Performance Curve
The actual operating point of
a fan on a given system is
determined as the intersection
of the system characteristic
curve and the fan static pressure
curve. The system characteristic
curve 1s usually proportional to
the square of the gas flow rate.
Gas Volume, CFM
-------
RELATIVE AIR DENSITY FACTOR
Gas density at 60°F Is 0.0765 lbs/Ft.3
This graph provides a rough estimate of gas density at elevated
gas temperatures. Actual gas densities are a function of gas
composition (1^0 and C02 content), and gas pressure.
0.2 0.3 0.4 0.5 0.6 0.7 0.8
Relative Air Density Factor, d I at 60°F and 14.7 psia |
-------
DENSITY OF SOLIDSt
82
Component
Asphalt
Barley, bulk
Bauxite
Cement,
Portland, loose
Portland, clinker
Clay
Coal,
anthracite
bituminous
charcoal
lignite
Coke, breeze
Lump petroleum
Corn, Rye, bulk
Dolomite
Earth
dry, loose loam
packed
moist, loose loam
packed
Feldspar, broken
Granite, crushed
Gravel
dry, loose
packed
wet
Gypsum, broken
crushed
ground
Iron
Lead
Density
(Ib/ft3)
69-94
39
159
94*
95*
63*
55-60*
43-54*
17-36
69-87
30-34*
40-50*
45
181
76*
94
73*
100
90-100*
98*
96-110*
100-119
119
90-94*
90*
50-56*
120-155*
707
Component
L1me, mortar
quick (In bulk)
slaked
Limestone,
broken
sized 2x1/2"
ground-200 mesh
M1ca
muscovlte
blotlte
Oats, bulk
Phosphate rock,
broken
pebble
Pitch
Riprap
limestone
sandstone
shale
Rock salt
Sand,dry
wet
Slag,
bank, crushed
furnace, granu-
lated
Stone, various
crushed
Sulfur,
ground-100 mesh
ground-200 mesh
Tar, bituminous
Wheat, bulk
Density
(Ib/ft3)
103-111
50-60
81-87
95*
92*
65*
162-200
172-187
168-193
26
75-85*
90-100*
67-69
81-87
87
106
50*
90-105*
105-125*
80*
60*
135-212
85-105*
75-85*
50-55*
75
48
t Bulk materials only.
* As they occur 1n material handling and processing operations.
-------
DENSITY OF LIQUIDS
Component
Benzene
Gasoline
Nitric Add (100%)
Petroleum
SuIfuric Acid (100%)
Water
Density
(Ib/ft3)
55
41-43
94
55
114
62
83
SIEVE NUMBER vs. PARTICLE SIZE
Sieve Number
80
100
120
140
170
Particle Size
(Mm diameter)
177
149
125
105
88
Sieve Number
200
230
270
325
400
Particle Size
(Mm diameter)
74
62
53
44
37
-------
SELECTED GEOMETRIC RELATIONSHIPS
Areas
Square A »
Rectangle A » L x U
Triangle A « b x h
W
Circle
b
«>
Vs
e
Cylinder A =
Volumes
Rectangular Container V » L x W x h
WJ
Pyramid Hopper
V » L x W x Ir
3 "*'
h
y
Trough Hopper
V » b x h x L
2
Velocity
Velocity = Gas Flow Rate/Area « ACFM/Ft
-------
CONVERSION FACTORS 85
^mperature
C - (5/9) (F-32)
C - K-273
F = (9/5) C + 32
F = (9/5) (K - 273) + 32
K - C + 273
K = (5/9)(F - 32) + 273
R « F + 460
Length
1 Inch = 2.54 cm
1 foot * 0.3048 m
1 m » 39.37 Inches
Area
1 ft2 = 929.03 cm2
1 1n.2 » 6.452 cm2
1 km2 * 0.386 mi2
1 m2 » 10.764 ft2
1 yd2 - 0.836 m2
Velocity
1 m/sec = 3.28 ft/sec
1 ft/sec = 0.3048 m/sec
Capacities & Volume
1 barrel (oil) » 42 gallons (oil)
1 cm3 = 0.061 in.3
1 in.3 = 16.387 cm3 * 16.387 ml
1 m3 » 1.308 yd3
1 yd3 - 0.765 m3
1 gallon (U.S.) = 231 in.3 « 3.785 liters
1 liter = 61.0255 in.3 * 0.264179 U.S. gallons
Weights or Masses
1 gram » 15.432 grains = 2.205 x 10~3 pounds
1 grain « 6.4799 x 1CT2 grams = 2.286 x 10~3 oz
1 kg » 2.205 pounds » 35.274 oz
1 oz * 437.5 grains 3 28.35 grams
1 Ib « 7000 grains = 453.592 grams
1 ton (short) = 2000 IDS » 0.907 metric ton
1 ton (metric) « 2204.62 Ibs » 1000 kg » 1.1023 short tons
-------
CONVERSION FACTORS (Continued)
Flow
m3/sec - 35.31 ft3/sec
1 fWsec » 28.32xlO-3 m-Vsec » 28.32 Hters/sec -
1 Hter/sec - 1.000 x 10~3 nH/sec « 35.32 x 103 ft3/sec
Pressure
1 dyne/cm2 « 10~6 bar
1 mm Hg(std.) « 1.934 x 10'2 lb/1n2
1 Ib/ln2 « 51.715 nm Hg
1 atmosphere (std.) « 760 mm Hg (std.) - 14.696 lb/1n2
Energy & Work
1 calorie * 4.186 abs. joules
1 abs. kw-hr * 3.6 x 10° abs. joules
1 ft-lb « 1.356 abs. joules
1 abs. joule * 0.239 calorie
Power
1 abs. watt « 1 abs. joule/sec » 0.239 cal/sec » 0.057 Btu/m1n
1 cal/sec « 4.186 abs. watts
1 h.p. (electrical) » 746 abs. watts
1 h.p. (mechanical) = 550 ft-lb/sec » 745.7 abs. watts
1 Btu/m1n » 17.584 abs. watts * 252 cal/m1n
Emission Rates
1 gm/sec
1 kg/hr =
1 Ib/hr >
Prefixes
• 0.1323 Ibs/m1n
2.205 Ibs/hr
0.454 kg/hr
Multiples
103
102
10
10-1
io-2
ID'3
10-6
10-9
10-12
Prefixes
tera
glga
mega
kilo
hecto
deka
ded
centl
micro
nano
p1co
Unit
trillion
billion
million
thousand
hundred
ten
tenth
hundredth
thousandth
millionth
billionth
trill1onth
Occasionally MM 1s used for million and M for thousand.
1s not recommended.
Symbols
T
G
M*
k
h
da
d
c
m
v
n
P
However, this
-------
FIELD BOOK NO. Confidential Data
Yes No
Plant Data
Name:
Address:
Phone:
Representative(s):
Plant CDS or Other Identifying Number:
Type of Plant and Process Description:
EMERGENCY NUMBERS:
Agency Data
Name:
Inspector Name(s)_
Phone:
------- |