EPA 340/1-83-025
Coal-Fired Industrial Boiler
Inspection Guide
by
PEDCo Environmental, Inc.
11499 Chester Road
Cincinnati, Ohio 45246-0100
Contract No. 68-01-6310
Work Assignment No. 9
EPA Project Officer: John Busik
EPA Task Manager: Howard Wright
U.S. ENVIRONMENTAL PROTECTION AGENCY
Stationary Source Compliance Division
Office of Air Quality Planning and Standards
401 M Street, S.W.
Washington, DC 20460
December 1983
-------
DISCLAIMER
This report was prepared by PEDCo Environmental, Inc., Cincinnati, Ohio,
under Contract No. 68-01-6310, Work Assignment No. 9. It has been reviewed by
the Stationary Source Compliance Division of the Office of Air Quality Plan-
ning and Standards, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency. Mention
of trade names or commercial products, is not intended to constitute endorse-
ment or recommendation for use. Copies of this report are available from the
National Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia 22161.
-------
CONTENTS
Page
Disclaimer -}-,-
Figures -jv
Tables v1l-
1. Introduction i
1.1 Purpose and Scope 2
1.2 Compliance Inspections 3
2. Coal-Fired Boiler Processes 5
2.1 Stoker-Fired Boilers 8
2.2 Pulverized Coal Firing 27
2.3 Fans 40
2.4 Use of the F-Factor 46
3. Pollution Control Equipment 50
3.1 Multicyclones 50
3.2 Fabric Filters 66
3.3 Electrostatic Precipitators 82
3.4 Scrubbers 108
4. General Preparatory and Pre-Inspection Procedure 122
4.1 File Review 122
4.2 Safety Precautions 130
4.3 Safety and Inspection Equipment 133
4.4 Pre-entry Observations 134
4.5 On-Site Inspection Checklists 135
5. Compliance Determination 148
References 153
Appendix A - Pollution Control Device Diagnostic Checklists and Data
Sheets /\-l
-------
FIGURES
Number
Page
1 Basic water-tube boiler arrangement 7
2 The effect on uncontrolled particulate loading
of washing a coal to reduce its ash content 11
3 ABMA recommended limits of coal sizing for underfeed stokers 13
4 ABMA recommended limits of coal sizing for overfeed stokers 14
5 ABMA recommended limits for coal sizing for spreader stokers 15
6 Single-retort, horizontal underfeed stoker 17
7 Chain-grate stoker with rear ash discharge 20
8 Travel ing-grate spreader stoker with front ash discharge 22
9 Spreader stoker with gravity-flow fly ash return 24
10 Typical stoker boiler flue gas static pressure 26
11 Dry-bottom pulverized-coal-fired unit 29
12 Intervene burner 33
13 Dual-register field-test burner 34
14 Components and functions of a controlled-flow/split-flame
coal burner 35
15 Operating characteristics of radial-blade centrifugal fan 41
16 Fan characteristic curves — effect of speed change 43
17 Fan characteristic curves — effect of system pressure drop
change 44
18 Multicyclone collector 51
19 Cross section of an individual cast iron collection tube 52
-------
Figures (continued)
Page
20 Fractional efficiency curves for multicyclone 53
21 Particulate fallout on dirty gas tube sheet 55
22 Inlet turning vane wear because of abrasion 57
23 Scale on inside of collection tube 57
24 Plugged outlet tube 59
25 Plugged conical section 60
26 Clean side air leaks 62
27 Example of leaks in clean gas outlet tubes and clean
gas tube sheet 62
28 Clean side air leaks 63
29 Poor distribution and cross hopper flow 64
30 Typical reverse-pulse baghouse during cleaning 68
31 Impaired cleaning in a reverse-air fabric filter 71
32 Bridging near baghouse shell caused by cooling a poorly
insulated fabric filter 73
33 Methods of bag attachment in shaker and reverse-air
fabric filters 74
34 Abrasive damage caused by accumulation of dust on the
tube sheet 76
35 Correct and incorrect installation of bags 78
36 Proper method of installing bag in tube sheet with
snap rings 80
37 Basic processes involved in electrostatic precipitation 84
38 Typical electrostatic precipitator with top housing 85
39 Typical temperature-resistivity relationship 86
40 ESP instrumentation diagram 88
41 Vibrator and rapper assembly, and precipitator high-
voltage frame 93
v
-------
Figures (continued)
Page
42 A sample opacity chart 107
43 Importance of particle size on wet scrubber penetration 109
44 Tray scrubber m
45 Spray tower HI
46 Moving bed scrubber 112
47 Cyclonic spray tower 113
48 Bob type venturi scrubber 115
49 Venturi scrubber components 116
50 Mist eliminators 120
51 Fabric filter inspection flowsheet 145
52 Scrubber inspection flowsheet 146
53 Electrostatic precipitator inspection flowsheet 147
-------
TABLES
Number Page
1 Maximum Allowable Fuel Burning Rates 9
2 Interpretation of Fan Operating Conditions 45
3 Fan Data, Temperature Correction 46
4 Maintenance Schedule for Electrostatic Precipitators 94
5 Summary of Problems Associated With ESP's 96
6 Recommended Recordkeeping Requirements 102
7 Effects of Changes in Normal Operation on ESP Control Set
Readings 104
9 Plume Characteristics and Combustion Parameters 129
10 Boiler Plant Gas Properties 132
11 Fabric Filters Counterflow Inspection Diagnostic Section 136
12 Scrubbers Counterflow Inspection Diagnostic Section 138
13 Electrostatic Precipitators Counterflow Inspection Diagnos-
tic Section 141
14 Summary of the Effects of Several Operating Parameters of
Boilers, ESPs, and Fabric Filters on Particulate Emission
Rates 150
Vll
-------
-------
SECTION 1
INTRODUCTION
Coal-fired boilers are^widely used in industrial plants throughout the
United States to provide process steam, space heat, and electricity in factory
and office buildings. Nationwide it is estimated that there are approximately
144,000 industrial coal-fired boilers, equivalent to 25,260 watts or 86,200 x
106 Btu/h of capacity. These boilers are within the size range from 20 to 400
x 106 Btu/h. At an estimated average capacity factor of 20 percent, these
boilers generate about 2.6 x 106 tons of particulate matter, 1.7 x 106 tons of
sulfur dioxide, and 0.3 x 106 tons of nitrogen oxides per year. This repre-
sents a contribution of 10 percent of total U.S. particulate emissions from
manmade sources. The size of this emission category suggests that air pollu-
tion control inspectors should devote considerable effort to the evaluation,
surveillance, and recommendation of remedial procedures for these sources.
Furthermore, if the prices of oil and gas escalate relative to coal in the
future, industry may rely on coal to an even greater extent at existing and
new facilities, which would further increase the significance of these sour-
ces.
Although individual boilers differ significantly in size and design,
certain general guidelines are appropriate for their inspection and evalua-
tion. This inspection guide provides information that will enable an air
pollution control agency inspector to check a boiler operation quickly and
efficiently, and at the same time make a thorough determination of its per-
formance relative to the appropriate agency's particulate air pollution con-
trol rules and regulations.
Although coal-fired industrial boilers emit significant amounts of sulfur
dioxide (S02) and nitrogen oxides (NO ) as well as particulate matter, the
s\
control of S02 and NO is beyond the scope of this inspection guide. Few
y\
industrial boilers are currently subject to S02 and NO regulations that
ys.
require the installation of control systems. Thus, this manual is devoted to
-------
participate control for coal-fired industrial boilers within the size range
from 20 to 400 Btu/h. Oil-fired and gas-fired boilers are not discussed.
1.1 PURPOSE AND SCOPE
This inspection guide provides technical information and procedures to
assist state and local inspectors in conducting compliance inspections and
performing evaluations of coal-fired industrial boilers. It includes brief
descriptions of several relatively common types of boilers and reference
material to assist the inspector in evaluating emission sources. The guide
also describes several types of control equipment typically used on indus-
trial-sized boilers and provides several checklists to ensure that important
operating factors for this control equipment are not overlooked during the
evaluation.
The intent of this guide is to provide inspectors with the necessary
information to verify whether sources are meeting their operating permit
requirements. Certain portions contain information on combustion parameters
that may be used as indicators of source performance between compliance tests.
Documented changes in these parameters may be used to indicate whether a
source needs to adopt more extensive operation and maintenance (O&M) proce-
dures to ensure continued compliance. When a clearly defined cause-and-effect
relationship cannot be established for a given source, documented changes in
various operating parameters can support the need for a compliance test.
Baseline conditions generally are recorded during a period of known compli-
ance, typically during a compliance stack test; these baseline data include
information on boiler operating conditions and key operating parameters of the
control equipment.
Each state has adopted a state implementation plan (SIP) describing how
it intends to attain and maintain the National Ambient Air Quality Standards
(NAAQS). Individual state regulations vary considerably. For example, par-
ticulate emission limits for a 10 million Btu/h boiler vary from 0.12 Ib/h in
Massachusetts to 0.8 Ib/h in Iowa. The regulation for Nebraska is fairly
typical and is summarized as follows:
-------
A. Existing Equipment:
Q S 10 MM Btu/h 0.60 Ib TSP/MM Btu
10 < Q < 3800 MM Btu/h E = 1.026Q °'233 Ib TSP/MM Btu
Q £ 3800 MM Btu/h 0.15 Ib TSP/MM Btu
B. New Equipment (constructed after 8-17-71) 0.10 Ib TSP/MM Btu
The purpose of this industrial boiler manual is to aid inspectors in
obtaining continuing compliance with local regulations.
1.2 COMPLIANCE INSPECTIONS
Compliance inspections can be conducted at various levels of detail,
depending on agency resources and the agency's assessment of the significance
of a particular source. A very simple inspection might include only the
observation of visible emissions from all of the boiler stacks at a plant. A
more complete inspection would include a walk-through of the plant, during
which visible emissions would be read and some information obtained concerning
the boiler, its control equipment, and operating and maintenance schedules.
In a very detailed inspection, the inspector would use test equipment to
estimate air and exhaust gas flow rates, oxygen levels, pressure drops, etc.
The inspector would also record information on power consumption by control
equipment and compare plant records with readings obtained during previous
inspections. Calculations based on the information obtained during the in-
spection would be used to determine whether a stack test is warranted.
A visible evaluation of emissions should be made according to EPA Method
9 or a corresponding state procedure. Thus, an established change in opacity
from previously established baseline conditions could be used to indicate
.whether some operating parameter or group of parameters has changed. A signi-
ficant increase in opacity could also indicate the need for a more detailed
inspection.
Worthwhile operating data on the boiler and its control equipment include
fuel characteristics, oxygen and carbon monoxide concentrations in the flue
gas, flue gas temperatures, scrubber inlet and outlet temperatures, water flow
rates, pressure drop if a scrubber or multicyclone is used, electrostatic
precipitator parameters, etc. Boiler parameters such as firebox draft stream
flow, fuel rate, temperatures, etc., should be recorded also. Unfortunately,
-------
all of these data may not be routinely available. For example, few installa-
tions are likely to monitor carbon monoxide regularly, even though its mea-
surement is simple and useful for combustion air adjustment. Where scrubbers
are used, the inspector should be concerned with any significant change in the
scrubber pressure drop or the liquid-to-gas ratio. The inspector also should
check the scrubber pumps, water pressure indicators, and the water flow into
the settling pond or tank. The flue gas flow rate is related to the fuel
firing rate and can be estimated from the boiler data.
This manual does not describe how to perform different levels of inspec-
tions for each control device. Since the reference documents used in the
preparation of this manual do not describe inspection levels for all four
types of control equipment, it was beyond the scope of this guide to develop
the level of inspection checklists for each boiler and control device type.
However, the checklists in the Appendix can be modified by the, inspector for
different levels of inspections.
4
-------
SECTION 2
COAL-FIRED BOILER PROCESSES
Industrial coal-fired boilers are widely used in many sections of the
country. Although their popularity tends to fluctuate with fuel supplies,
fuel costs, mining regulations, and environmental policies, these units are
expected to be used for many years to come. Despite recent trends toward
cleaner fuels such as oil, gas, or electricity, a large amount of coal not
only will continue to be burned for industrial purposes in the foreseeable
future, but the amount of coal used for this purpose is quite likely to in-
crease. Local agency inspectors will be responsible for ensuring that these
industrial coal-burning units are operated in a manner that minimizes the
emission of air pollutants.
Combustion in a boiler is the controlled oxidation of the carbon, hydro-
gen, and sulfur contents of coal to release heat, which is extracted as steam
via heat exchangers. The quantity and quality of the steam produced are a
function of the boiler design, its state of repair, and operating conditions.
Heat exchange efficiencies and steam quality are regulated by combustion
conditions, which include coal feed, air distribution, water flow distri-
bution, etc. Although the coal's sulfur content is a relatively minor source
of heat, it is very significant in terms of corrosion and pollution. Theore-
tically, the other two chemical elements, carbon and hydrogen, combine with
oxygen and burn to completion according to the following reactions:
C + 02 = C02 + 14,100 Btu/lb of C
2H2 + 02 = 2H20 + 61,100 Btu/lb of H2
Air is the source of oxygen for coal-fired boilers. As shown, the com-
bustion reactions are exothermic, and they release about 14,100 Btu/lb of
carbon burned and 61,100 Btu/lb of hydrogen burned.
Efficient combustion releases as much of this heat as possible while
minimizing losses from incomplete combustion and excess air. For complete
-------
combustion to occur in a minimum of excess air, three requirements must be
satisfied: the temperature must be high enough to ignite the constituents,
there must be sufficient turbulence for complete mixing, and there must be
sufficient time for the combustion reactions to reach completion. These fac-
tors are often referred to as the "three T's" of combustion. An understanding
of combustion and certain empirical and theoretical combustion relationships
allows an inspector to make a proper evaluation of a steam generating plant
and its performance characteristics. Various combustion concepts are inte-
grated into the discussions that follow.
Several factors influence a plant's decision as to whether to fire pul-
verized coal or to use one of several different types of stokers. The prac-
tical steam-output limit of boilers equipped with mechanical stokers is about
400,000 Ib/h (although many engineers limit the application of stokers to
somewhat lower steam capacities). Within their capacity range, mechanical
stokers are well suited for the production of steam or hot water. When appli-
cable, stokers are often preferred over pulverizers because of their greater
operating range, their capability of burning a wide range of solid fuels, and
their lower power requirements. In addition to almost any coal, many byprod-
ucts and waste fuels (e.g., coke breeze, wood wastes, wood bark, and bagasse)
can be burned successfully in stoker-fired boilers. However, pulverized
coal-fired boilers can change load more rapidly.
Figure 1 shows a simplified cross section of a typical industrial, na-
tural-circulation boiler. As the coal is burned on a grate or in suspension
above the grate, heat is released and transferred to water-filled boiler tubes
by radiation and convection. Combustion air below and above the grate is ad-
justed by the use of dampers to achieve optimum combustion and to minimize
smoke generation. The steam-water mixture that forms in the water tubes in
the refractory walls of the boiler (risers) passes into an optional separation
drum at the top of the boiler, as shown in the figure, and then into a final
separation drum (called a steam drum) if there is no intermediate separation
drum. Downcomers from the, steam drum recirculate water to the mud drum at the
bottom of the boiler. Sludge and solids that accumulate in the mud drum are
discharged with dissolved water impurities through a blowdown line at the
bottom of the mud drum. Feedwater (to replace water and steam losses, blow-
down, etc.) is metered into the steam drum via a level controller.
-------
Steam Nozzle
Figure 1. Basic water-tube boiler arrangement.
-------
2.1 STOKER-FIRED BOILERS
Early in the history of the steam boiler, mechanical stokers were devel-
oped as an improvement over hand-firing. Most small and medium-size indus-
trial boilers are fired with stokers. Several types of stokers are available,
but all are designed to feed fuel onto a grate within the furnace and to
remove the ash residue. Stokers permit higher burning rates than with hand-
firing, and their continuous firing permits improved combustion control and
high efficiency. The greatest impetus for the development of stokers came
from two sources: 1) objections to smoke emissions resulting from hand-firing
and imperfect combustion, and 2) the inherent limitations on steam output from
manually stoked boilers.
Over the years a great deal of effort has been made to maximize furnace
efficiency; i.e., to convert into steam as much of the combustion-released
heat as possible. With regard to furnace design, several factors have been
identified as affecting boiler efficiency:
1. Type of fuel and method of firing; i.e., the use of coal, oil,
or gas, and whether it is burned in suspension or on a grate.
2. Energy released per cubic foot of furnace volume (per unit of
time).
3. Cold fraction, the ratio of water-cooled surface to refractory
surface.
4. The size distribution of the coal.
5. Air-fuel ratio (A minimum of excess air is generally pre-
ferred. )
6. Temperature of preheated air.
7. Heating value of the coal.
8. Type of water wal1.
9. Geometrical considerations, such as positions of tubes and
burners.
10. Cleanliness of furnace, especially the surfaces of water-
cooled tubes.
11. The ash fusion temperature of the coal; i.e., the temperature
at which the coal ash melts and forms slag.
8
-------
The maximum allowable heat release per unit of grate area for a given
stoker type and capacity has been determined by experience. Table 1 lists
recommended fuel burning rates (Btu/h per ft2 of grate area) for various types
of stokers, based on the use of coals suited to the stoker type in each case.
Furnace heat-release rates for spreader stokers are limited to 25,000 to
32,000 Btu/h per ft3 of furnace volume; the lower value is the more conser-
vative. Coals that have lower ash fusion temperatures generally require lower
furnace heat-release rates.
TABLE 1. MAXIMUM ALLOWABLE FUEL BURNING RATES.
Type of Stoker
Spreader - stationary and dumping grate
Spreader - traveling grate
Spreader - vibrating grate
Underfeed - single or double retort
Underfeed - multiple retort
Chain grate and traveling grate
Btu/h per ft2
450,000
750,000
400,000
425,000
600,000
500,000
Mechanical stokers generally are classified into three principal groups,
which are based on the method of introducing fuel to the furnace:
1. Underfeed stokers
2. Chain-grate and traveling-grate stokers
3. Spreader stokers
The spreader stoker is the most frequently used in the capacity range
between 75,000 to 400,000 Ib of steam per hour because it responds rapidly to
load swings and can burn a wide range of fuels. Underfeed stokers of the
single-retort, ram-feed, side-ash-discharge type are used principally for
heating and for small industrial units with capacities of less than 30,000 Ib
of steam per hour. Larger underfeed stokers of the multiple-retort, rear-ash-
discharge type have been largely displaced by spreader stokers. Chain- and
traveling-grate stokers, while still used in some areas, are gradually being
displaced by the spreader and vibrating-grate types'.
-------
2.1.1 Stoker Coal Properties
Operators are generally not involved in obtaining coal supply contracts,
so they don't need to be experts on all the coal properties. However, the
operator is responsible for firing the purchased coal as efficiently and
cleanly as possible, and for informing his supervisors of coal related problem
areas.
There are several coal properties which have a direct effect on stoker-
boiler emissions and efficiency. The operator should be aware of these pro-
perties.
Coal Ash-
Coals which are higher in ash content tend to produce higher particulate
emissions. This may not always be the case.
The type of ash makes a difference. In recent tests1 on a traveling
grate overfeed stoker a washed coal and an unwashed coal from the same mine
were fired in the stoker. The unwashed coal had 10 percent ash, but when
washed the same coal had only 4 percent ash. In this case (Figure 2) there
was a tremendous difference in particulate loadings because much of the ash in
the unwashed coal was a clay-like material which was easily carried out of the
furnace by the flue gas.
In tests2 on other stokers, coals with different ash contents were fired
in the same stoker with very little or no change in particulate loading.
Coal Moisture—
Coal has two forms of moisture. First, inherent moisture is a part of
the chemical composition of the coal. Second, surface moisture which is due
to rain or conditions at the mine. Although the inherent moisture cannot be
changed, the surface moisture can sometimes be avoided.
Coal moisture causes two problems. If excessive, it may make the coal
hard to ignite, and it will always reduce the boiler efficiency.
Coal Sul fur-
About 95 percent of the sulfur in the coal is converted during combustion
to S02 and S03, commonly called SO . The remaining 5 percent is retained in
){ i
the ash. Therefore, by burning a lower sulfur coal you reduce your sulfur
oxide emissions. Of course, there is another reason to burn a low sulfur
10
-------
3
CO
g
s
2 §
t- in
£ -
a.
Sg
UNWASHED COAL
10Z ASH
HASHED COAL
m ASH
20.0 40.0 60.0 80.0
PERCENT DESIGN CRPflCITY
—l
100.0
Figure 2. The effect on uncontrolled particulate loading
of washing a coal to reduce its ash content (Reference 1).
11
-------
coal, the sulfur emissions are very corrosive if they condense on exposed
metal parts. The S03 instantly combines with water vapor (H20) to form sul-
furic acid (H2S04).
Coal Fines—
The common definition of coal fines is the percentage of coal which
passes through a 1/4" screen. Too many coal fines can lead to high particu-
late loadings because they are easily carried out of the furnace, and high
combustible heat losses because the particulate matter carries carbon out of
the furnace with it. High fines may also lead to severe clinkering problems.
When firing a high fines coal, make sure that the fines are evenly dis-
tributed on the grate, and are not segregated in one area only. The manner in
which the coal is loaded into the hopper is important because it may lead to
stratification.
A coal which was low in fines when it left the mine may be high in fines
when it reaches the furnace because of all the handling it receives. Coals
which break up and produce fines more easily than others are called highly
"friable" coals. The American Boiler Manufacturers Association has published
guidelines for the recommended size consistency of coal for firing in differ-
ent types of stokers. These are presented in Figures 3, 4, and 5. Every
attempt should be made to operate within these guidelines.
Ash Fusion Temperature—
Some coals tend to clinker, slag, and foul the boiler more than others.
This is because the ash from these coals becomes sticky and begins to melt at
lower temperatures. These coals have low ash fusion temperatures. Clinker-
ing, slagging, and fouling will decrease boiler efficiency by reducing the
amount of heat absorbed by the boiler and by increasing the stack gas heat
loss. Firing a coal with a lower ash fusion temperature than that for which
the boiler was designed can also lead to reduced boiler capacity, and it may
require operation of the boiler at a higher and less efficient excess air
level.
Free Swelling Index (FSI)~
The free swelling index provides an indication of the caking character-
istics of coal when burned on fuel beds. The caking characteristic of coal is
the tendency of coal to melt together into a solid mass when rapidly heated.
12
-------
Fuel to be delivered across sfoker hopper without
size segregation
95
90
80
70
60
50
40
Q)
$ 30
'"» 25
•Si 20
I 15
1 10
3 8
-------
Size distribution of lower rank coals (Index 28—.35) should fall nearer the upper curve, and
size distribution of higher rank coals (Index 40 — 50) should' fall nearer the lower curve.
Fuel to be delivered across stoker hopper without size segregation.
1
£.
95
90
80
70
60
50
XO
30
25
20
15
10
8
6
4
3
X
/
8
US Sfd sieve designation
*
I ROUND HOLE
screen, inches
Figure 4. ABMA recommended limits of coal sizing for overfeed stokers.
14
-------
FUEL TO BE DELIVERED ACROSS STOKER HOPPER WITHOUT SIZE SEGREGATION
. ALL COAL TO PASS THROUGH 1% in. MESH SCREEN
05
90
80
70
yj 60
5 50
55 43
§ 30
0 25
X 20
K
t- 15
u
g '0
tf 8
6
4
3
2
I
x
X
/
X
X
J,
/
s
/
/
/
V
/
X
/
/
/
/
x
X
X
/
/
• jf
/
/
/
t
/
/
/
/
I
p
$ 8 £ ™ ®
US STO SIEVE DESIGNATION
i
I ROUND M£»« SCREEN. INCHES
Figure 5. ABMA recommended limits for coal sizing for spreader stokers.
15
-------
The free swelling index (FSI) is reported on a scale of 1 to 9 in increments
of 1/2. Coals having a FSI from 1 to 3 are generally referred to as free
burning, from 3h to 5 as moderately caking, and from 5% to 9 as strongly
caking. Caking characteristics have little or no effect on the performance of
spreader stokers. However, free burning and moderately caking coals are
preferred for overfeed stokers and underfeed stokers.
2.1.2 Underfeed Stokers
Underfeed stokers, either single- or multiple-retort, consist essentially
of a trough or troughs into which coal is pushed by rams or screws. Part of
the combustion air is introduced into the fuel bed through tuyeres or grate
bars. Movement of the coal discourages its fusion into large masses that
cannot be burned efficiently. Volatile matter is distilled off the coal in
these retorts and burns above the incandescent fuel bed. The partly coked and
somewhat caked coal then falls into the air-admitting tuyeres or grate bars,
where the fixed carbon is burned out. The coal is progressively pushed side-
wise or forward until the refuse is discharged to the ashpit.
In an underfeed stoker (Figure 6), coal is fed from the hopper to a cen-
tral retort by means of a reciprocating ram. In very small heating stokers, a
screw conveys the coal from the hopper to the retort. A series of small
auxiliary pushers in the bottom of the retort assist in moving the coal rear-
ward, and as the retort is filled, the coal is moved upward to spread to each
side over the air-admitting tuyeres and side grates.
In a single-retort underfeed stoker, the coal is introduced into a re-
tort; the incoming coal progressively forces the other coal out of the retort
and onto the side grates. This feeding action from the retort outward places
the entire fuel bed under compression and automatically closes any holes that
may tend to form in the bed and thus overcomes a common obstacle to efficient
firing.
Ease and simplicity of operation are characteristics of the single-retort
stoker. All adjustments are made from the stoker front, and practically all
of the fuel bed is visible and accessible through the furnace doors in the
stoker front. Cleanout doors provide access to the air chambers under the
stoker, so that accumulated siftings may be cleaned out easily.
16
-------
OVERFIRE
AIR
COAL
HOPPER
PUSHER'BLOCKS
AIR CHAMBER
SIDE VIEW
COMBUSTION X"
GRATEv
RETORT^
PUSHER
BLOCK
END VIEW
Figure 6. Single-retort, horizontal underfeed stoker.
17
-------
As the coal rises in the retort, it is subjected to heat from the burning
fuel above, which ignites the coal. Volatile gases that are distilled off mix
with the air supplied through the tuyeres and side grates. The volatile
mixture burns as it passes upward through the incandescent zone, and overfire
air sustains the ignition of the rising coal and insures complete combustion.
Burning continues as the incoming raw coal continually forces the fuel bed to
each side. Combustion is completed by the time the bed reaches the side-dump-
ing grates. The ash is intermittently discharged to shallow pits, where it is
quenched and then removed through doors at the front of the stoker.
The multiple-retort stoker is an extension of the single-retort stoker.
It is nothing more than a series of single-retort stokers built into the same
unit, with an appropriate mechanism provided to operate the various components
in unison.
In the underfeed section of a multiple-retort stoker fuel bed, parallel
rows of hills and valleys of coal extend from the front wall to the discharge
ends of the retorts. The hills occur over the relatively inactive retort
areas because no provisions are made for air admission. The coal is supplied
through a reciprocating feed, which produces a certain amount of segregation
in the fuel bed. The coarse coal finds its way to the tuyeres near the front;
the fines travel the length of the retort. High combustion rates in a thin
active fuel bed occur over the tuyeres where air is admitted. The overfeed
section shakes down and levels out these alternately thick and thin parallel
ribbons.3
As this irregular mass of burning fuel reaches the overfeed section, it
is quickly shaken down to uniform thickness by the reciprocating action of the
grates in this area. The fuel bed is now level, compact, homogeneous, and
extremely active because of the stroke control and correct air feed. As a
result, the fuel bed should be burned out uniformly across the stoker width by
the time the fuel reaches the dump grates or ash discharge section.
The multiple-retort inclined underfeed stoker is used in many plants that
have relatively constant loads or light loads of long duration. This type of
stoker can handle these loads without objectionable smoke more easily than the
spreader stoker can.
With multiple-retort stokers, overfire-air systems generally have a
separate high-pressure fan that develops a pressure of approximately 16 inches
18
-------
H20. This fan is operated intermittently to prevent smoke at low loads or
during sudden firing rate increases, which cause distillation of large quanti-
ties of volatile gases. Forced draft is supplied to the entire grate area,
which is divided into several pressure zones parallel to the retort, each
under separate damper control. The air pressure compensates for the thickness
of the fuel bed; the greatest pressure is applied to the thickest portion over
the retort.
Many small underfeed stokers that handle relatively steady heating loads
operate with start-stop control. Stokers that are operated to suit a varying
load should be equipped with a modulating combustion control that varies the
coal-feed rate and keeps the air supply in step with steam demand. The fur-
nace draft should be controlled through operation of the boiler outlet damper.
Primary combustion air is supplied by a forced-draft fan.
2.1.2 Chain-Grate and Traveling-Grate Stokers
The traveling-grate stoker is very versatile for solid fuel burning, and
nearly every type of mined fuel can be burned successfully in the various
types of stokers. In addition, waste and byproduct fuels such as coke breeze,
garbage, and municipal refuse can be burned efficiently and effectively. The
traveling-grate stoker has also been used in chemical processes to produce
coke and carbon dioxide.
In chain-grate stokers, assembled links, grates, or keys are joined
together in an endless belt arrangement that passes over sprockets or return
bends at the front and the rear of the furnace. As shown in Figure 7, coal is
fed from the hopper onto the moving assembly and enters the furnace after it
passes under an adjustable gate that regulates the thickness of the fuel bed.
Because the coal flow through the furnace is usually at right angles to the
primary air flow, these furnaces are sometimes referred to as crossfeed
stoker-fired furnaces. As the layer of coal on the grate enters the furnace, .
radiation from the furnace gases heats and ignites the coal and the combusti-
ble gases that are driven off by distillation. As the fuel bed moves along,
it continues to burn and grows progressively thinner. At the far end of its
travel, the grate discharges the ash into the ashpit. Although they differ
structurally, the operation of chain-grate and other traveling-grate stokers
is quite similar.
19
-------
O)
0)
03
-C
u
in
10
IB
J_
03
0)
s-
•p
«f—
3=
s-
Ol
o
10
O)
+J
m
O5
c
5
a)
D)
20
-------
2.1.3 Spreader Stokers
Sometimes called overfeed stokers, spreader stokers incorporate the
principles of pulverized coal and stoker firing in that fines are burned in
suspension and heavier pieces of fuel are burned on the grate. Feeding and
distributing mechanisms continually project coal into the furnace above an
ignited fuel bed. With this method of firing, coal characteristics have less
effect on the fuel bed than'",they do in other types of stokers. However, fuel
characteristics may cause the spreader stoker to smoke if it is operated
outside acceptable design ranges. Flash drying of the incoming fuel, rapid
release of volatile matter, and suspension burning of the fuel make this
method of firing widely applicable. Practically all types of coal have been
successfully burned in spreader stokers, as have a wide variety of cellulose
fuels, including bagasse, wood chips, bark, hogged wood, sawdust, shavings,
coffee grounds, and furfural residue.
Figure 8 shows the principal components of a spreader stoker. As the
name implies, the spreader stoker projects the fuel with a uniform spreading
action into the furnace above the ignited fuel bed, which permits suspension
burning of the fine fuel particles. The heavier pieces that cannot be sup-
ported in the gas flow fall to the grate for combustion in a thin fast-burning
bed. Compared with other types of stokers, firing is highly responsive to
load fluctuations. The almost instantaneous ignition accommodates any in-
crease in the firing rate, and the thin fuel bed can be burned out rapidly if
the load suddenly decreases.
Although several different means are available for feeding and distribu-
ting coal, the overthrow rotor design is used most widely. Its function is to
provide a well-distributed fuel supply at varying rates to match instantaneous
increases in loads. A feed plate moves coal from the supply hopper over an
adjustable spill plate, from which it falls onto an overthrow rotor equipped
with curved blades to provide uniform coal distribution over the furnace area.
The modern spreader stoker installation consists of feeder-distributor
units in the widths and numbers required to distribute the fuel uniformly over
21
-------
«-5
(U
O)
(0
-C
O)
(0
c
o
1
o
S-
0)
•o
(0
2
Q.
Ol
+J
(T3
O)
O)
c
Ol
00
Q)
D)
22
-------
the width of the grate, specifically designed air-metering grates, forced-
draft fans for both undergrate and overfire .air, dust collecting and reinject-
ing equipment, and combustion controls to coordinate fuel and air supply with
load demand.
The first spreader-stokers, developed in the early 1930's, used station-
ary high-resistance air-metering grates, from which the ash was removed-man-
ually. This spreader stoker application was limited to boilers with steam
capacities below 30,000 Ib/h. These stationary grates were soon followed by
dumping-grate designs, which provided grate sections for each feeder and
correspondingly divided undergrate air plenum chambers. This permitted the
temporary shutoff of fuel and air to a grate section for ash removal without
affecting other sections of the stoker.
In the late 1930's the continuous-ash-discharge traveling grate of the
air-metering design was introduced which brought the spreader stoker into
immediate and widespread popularity. The elimination of interruptions for ash
removal and the thin, fast-burning fuel bed enabled average burning rates to
be increased approximately 70 percent over the stationary- and dumping-grate
types. This stoker is generally competitive in sizes up to about 525 ft2 of
grate area, which corresponds to a steam capacity somewhat over 400,000 lb/h.3
The furnace width required for stokers above this size usually increases
boiler costs over those required for pulverized-coal or cyclone units with
narrower and higher furnaces.
Although reciprocating and vibrating continuous-cleaning grates also have
been developed, the continuous-ash-discharge traveling-grate stoker is pre-
ferred for large boilers because of its higher burning rates. For all contin-
uous-ash-discharge spreader stokers, the normal practice is to remove the
ashes at the feed end (front) of the stoker. This permits the most satisfac-
tory fuel distribution pattern and provides maximum residence time on the
grates for complete combustion of the fuel.
The traveling-grate spreader stoker (Figure 9) has self-adjusting air
seals at both the front and rear of the grate. These effectively reduce
leakage and stratification of air along the front and rear furnace walls,
where it cannot be utilized efficiently in the combustion process.
An overfire air system with pressures from 27 to 30 in. H20 is essential
for successful suspension burning. It is customary to provide at least two
23
-------
STEAM OUTLET
TO STACK
FLY ASH
RETURNX
COAL FEEDER
Figure 9. Spreader stoker with gravity-flow
fly ash return. (Courtesy of Babcock & Wilcox)
24
-------
rows of evenly spaced high-pressure air jets in the rear wall of the furnace
and one row in the front wall (Figure 9). This air mixes with the furnace
gases and creates the turbulence required to burn out all of the residual
fixed carbon in the fuel and any carbon monoxide that may form.
Fly-Ash Collection and Reinjection Systems—
Because partial suspension burning results in a greater carryover of
particulate matter in the f,lue gas than occurs with other types of stokers,
particulate control equipment is required for spreader stokers. Multicyclone
collectors are generally used. Fines are deposited in a hopper for discharge
to the ash disposal system, and coarse carbon-bearing particles may be skimmed
off and returned to the furnace for further burning.4
When plant physical layout permits location of the collecting and set-
tling hopper outlets at a sufficient height, the fly ash flows by gravity to a
distributing hopper directly behind the rear wall of the furnace, as shown in
Figure 9. Pneumatic systems in which high-pressure air is the conveying
medium have been used extensively to reinject the fly ash into the furnace in
the high-temperature zone just above the fuel bed. Reproduction of the fly
ash into the furnace can increase boiler efficiency by 2 to 3 percent.4
Control--
Although the spreader stoker can accommodate varying loads, such loads
require close control of fuel and air supply to achieve best results. Many
types of automatic combustion controls are available, from simple positioning
types used on relatively small installations to more elaborate air-flow and
steam-flow regulators in larger plants.
2.1.4 Emissions
Regardless of the type of fuel that is to be burned in underfeed, travel-
ing grate, or spreader stokers, the importance of size segregation cannot be
overemphasized. If all the fines are on one side of the stoker and all the
coarse coal is on the other, the fines will tend to mat over and the coarse
coal will burn rather freely. The resulting maldistribution of air through
the fire can cause overheating of the grate surface and other stoker parts. A
ragged fire also indicates bad burning characteristics. Figure 10 shows
typical static pressure readings in a stoker coal-fired boiler. Thus, the
25
-------
Feeder
Steam Drum
Baffle
Flue
Gas Flow
Flue Gas to
Stack or Common
Breeching
Induced
Draft Fan
Economizer
or Airheater
©
1 1
©
\ /
y
/' \
k \©
^Stoker Grate
.Mechanical
Dust Collector
Elevation View
1. Furnace: —0.15 inches of water
2. Boiler Outlet: —1.20 inches of water
3. Economizer or Airheater Inlet: —1.25
inches of water
4. Economizer or Airheater Outlet: —3.75
inches of water
5. Mechanical Dust Collector Inlet: —3.80
inches of water
6. Mechanical Dust Collector Outlet: —7.30
inches of water
7. Hopper Area of Mechanical Dust Collector:
—6.95 inches of water
8. Induced Draft Fan Inlet: —7.35 inches
of water
Figure 10. Typical stoker boiler flue gas static pressure.
26
-------
importance of being sure that the different coal sizes are thoroughly mixed
before they are fed to a stoker is apparent.
Overfire air, sometimes referred to as secondary air, is commonly used in
furnaces that fire bituminous coal. The overfire air helps to eliminate
smoke, and if properly adjusted, improves combustion efficiency. Because
turbulent mixing of air and gas is necessary, the air pressure and volume must
be sufficient to create the proper turbulence.
The overfire air should range between 5 and 15 percent of the total
combustion air requirement. The overfire air requirement is a function of the
coal quality and the amount of excess air in the furnace proper. Air at pres-
sures below 6 in. H20 may not be effective in creating turbulence. At some
installations, relatively small quantities of air at pressures up to 25 or 30
in. H20 are injected to improve combustion conditions in the furnace and to
reduce particulate emissions. Air penetration is a function of the static
pressure and the volume of air per fuel discharge nozzle, and extreme care
must be used in locating and adjusting the overfire air jets.
2.2 PULVERIZED COAL FIRING
Annual consumption of bituminous coal and lignite in the United States is
about 500 million tons; more than three-fourths of this amount is used to
generate steam. A high percentage of the coal burned for steam generation is
in pulverized form, especially in the electric utility industry; however, many
large industrial boilers also fire pulverized coal. The main advantage of
pulverized coal is that almost any quality of coal can be burned if the boiler
is designed properly, because the coal is ground to minus 200 mesh to ensure
its combustion.
Experience shows that stoker firing is more economical than pulverized
coal firing for units with capacities of less than 100,000 Ib of steam per
hour5; these lower-capacity units can tolerate the lower efficiency of a
stoker. In larger plants, where fuel cost is a larger fraction of the oper-
ating cost, pulverized-coal firing is generally more economical.
Pulverized Coal Systems--
In a pulverized-coal system, the coal is first pulverized and then de-
livered to the burners with sufficient air to promote efficient combustion.
27
-------
The coal feed must be varied rapidly (within specified design limitations) to
match load requirements. About 15 to 20 percent of the air required for
combustion is used to transport the coal to the burner. This air, known as
primary air, also dries the coal in the pulverizer. The remaining 80 to 85
percent of the combustion air, known as secondary air, is introduced at the
burner. Figure 11 shows a typical pulverized-coal-fired boiler. The two
basic components of a pulverized-coal system are:
0 The pulverizer (arranged to operate under pressure or suc-
tion), which reduces the coal size to the required fineness.
0 The burner, which mixes the pulverized coal and air in the
right proportions and delivers the mixture to the furnace for
combustion.
Other necessary components are:
0 Fan(s) to supply primary air to the pulverizer and to deliver
the coal-air mixture to the burner(s).
0 Raw-coal feeder, which controls the rate of coal fed to each
pulverizer.
0 Source (steam or gas air heater) of hot primary air supply to
the pulverizer for drying the coal.
0 Coal- and air-conveying lines.
Coal must be pulverized until particles are small enough to assure proper
combustion, and the surface moisture must be removed from the coal. In the
direct-firing system, the coal delivered to the burner is suspended in the
primary air; at the burner, the coal and primary air must then be mixed ade-
quately with the secondary air.
Coal and air feed to the pulverizer is controlled by one of two methods:
1) proportioning the coal feed to the load demand and adjusting the primary-
air supply to the rate of coal feed, or 2) proportioning the primary air
through the pulverizer to the load demand and adjusting the coal feed to the
rate of air flow. In either case, a predetermined air-coal ratio is main-
tained for any given load.
The direct-firing system eliminates the need for storage facilities for
pulverized coal and permits the use of high-temperature (~650°F) inlet air to
the pulverizer for drying high-moisture coals. A minor disadvantage of the
28
-------
TEMPERED AIR FAN -f
I V
PULVERIZER/U
Figure 11. Dry-bottom pulverized-coal-fired unit.
(Courtesy of Babcock & Wilcox)
29
-------
direct-firing system is that the pulverizer turndown range is usually limited
to about 3 to 1 because the air velocities in the lines and other parts of the
system must be maintained above the minimum values to keep the coal in suspen-
sion. In practice, most boiler units have more than one pulverizer, each of
which feeds multiple burners. Load variations beyond 3 to 1 are generally
accommodated by shutting down or starting up a pulverizer and the burners that
it supplies.
Idle burners are subject to considerable radiant heat from the furnace
and can attain temperatures above the coking temperatures of the coals. The
use of alloy metals provides longer life for burner parts; however, if these
parts are not adequately cooled below the coking temperature before being
placed in service, coke may form and severely damage them. The easiest way to
cool the fuel discharge nozzles is to run cold primary air through the pulver-
izer and burners for 5 to 10 minutes and then immediately feed the coal before
the nozzles can reheat. Because there is no simple way to cool selected
burners on a single pulverizer before bringing them into service, a pulverizer
and all its burners should be operated at once.
Large boilers with air heaters have a sizable heat inertia, and at full
load, it requires upward of 6 hours for temperatures throughout the unit to
stabilize. A significant time period is also necessary for such boilers to
re-equilibrate after a load change.
The temperature of the primary air entering the pulverizer may run 650°F
or more, depending on the surface moisture of the coal and the type of pulver-
izer. Coal grinding to a fineness of 200 mesh (90 percent) is necessary to
assure maximum efficiency and to minimize the deposit of ash and carbon on the
heat-absorbing surfaces.
Exhausters and Blowers—
If the pulverizer operates under pressure, the primary-air fan handles
clean air and is not abraded by the pulverized coal. In this case, a high-
efficiency fan with an efficient rotor design and high tip speed can be used.
If the pulverizer operates under suction, however, the fan must handle pul-
verized-coal-laden air. This requires that the fan housing be designed to
withstand a potential explosion pressure of 200 psi within the fan to comply
with National Fire Protection Association requirements. Furthermore, because
30
-------
the fan is subject to excessive wear, its design is limited to heavy paddle-
wheel construction and hard-metal or other protective-surface coatings. All
of these construction features are detrimental to the fan's mechanical effi-
ciency.
Standards of Burner Performance-
Operators of pulverized-coal equipment should expect burner performance
to meet the following conditions:
1. The coal feed and air supply should match the load demand over
a predetermined operating range. For most applications, igni-
. tion of the pulverized coal must be stable without the use of
support!ng fuel over a load range of approximately 3 to 1.
Most steam boilers are equipped with several pulverizers so
that a wider capacity range can be readily obtained by varying
the number of burners and pulverizers in use.
2. Unburned combustible loss should be less than 2 percent With
most well-designed installations it is possible to keep the
unburned combustible loss under 1 percent with excess air in
the range of 15 to 22 percent, measured at the furnace outlet
I his loss is a good indication of burner condition and pulver-
izer condition. Coal fineness and carbon should be checked
daily.
3. Adjustments to the burner should not be necessary to maintain
flame shape. The design should be such that formation of
deposits are avoided that could interfere with continued
efficient and reliable burner performance over the operatina
range.
4. Only minor repairs should be necessary during the annual
overhaul. Burner parts subject to abrasion may require more
frequent replacement. Alloy steel should be used for parts
that cannot be protected by cooling or other means to avoid
damage from high temperatures.
5. Safety must be paramount under all operating conditions.
Ignition Stability--
For ignition stability, the temperatures of the primary air and coal
leaving the pulverizer must be at least 130°F for units burning coal with more
than 30 percent volatile matter; temperatures up to 180°F may be required if
the volatile matter of the coal is as low as 22 percent. For coals with at
least 25 percent volatile matter, the maximum temperature of the primary
31
-------
air-coal mixture leaving the pulverizer is approximately 150°F; higher temper-
atures increase the tendency for coking on the burner parts.
Modern Burner Types--
Intervane burners are the most commonly found burner in industrial coal-
fired boilers. Circular and cell type burners also are used. Figures 12, 13,
and 14 show typical burners that fire pulverized coal. Burners are available
that fire pulverized coal, oil, gas, or any combination of these three fuels;
however, the firing of pulverized-coal combined with oil in the same burner
should be restricted to short emergency periods., It is not recommended for
long operating periods because of possible coke formation in the burner.
Usually, the maximum heat input per burner is about 165 million Btu per hour.
At full boiler load the secondary-air port velocity ranges from 4000 fpm for
small boilers, where unheated secondary air is used, to 6000 fpm for a dry-
ash-removal furnace with 600°F air. Velocities of 7500 fpm are common with
circular burners in slag-tap furnaces.
Lighters (Igniters) and Pilots—
Although ignition and control equipment for pulverized-coal firing is
similar to that for oil and gas, it is used differently. In pulverized-coal
applications, igniters must be kept operating for hours, until the temperature
in the combustion zone is high enough to assure self-sustaining ignition of
the main fuel.
The self-igniting characteristics of pulverized coal vary from one fuel
to another, but for most coals ignition can be maintained without auxiliary
fuel down to about one-third of the burner capacity. When the pulverized coal
being fired has less than 25 percent volatile matter, it may be necessary to
activate the igniters even at high loads. This particularly applies to coal
that is wet or frozen or when coal feed to the pulverizers is disrupted. If
the ignitor is not activated when the coal feed to the pulverizer is inter-
rupted, ignition may be lost momentarily; when the coal flow is reestablished,
an adjacent burner may reignite the burner with explosive force and damage the
burner and/or the boiler.
32
-------
Oil
Igniter
Detector*'
Figure 12. Intervene burner.
33
-------
Of
oc
\
U9q.eme.Lp i)out 29
s_
0)
c
3
-P
i/>
0)
I
TJ
0)
5-
QJ
•P
D)
0)
3
Q
CO
CL>
D)
34
-------
IGNITOR
INNER
REGISTER
OUTER
REGISTER
PERFORATED
PLATE AIR HOOD
FLAME SCANNER
TANGENTIAL
COAL INLET
MOVABLE SLEEVE
SPLIT FLAME
COAL NOZZLE
Figure 14. Components and functions of a
controlled-flow/split-flame coal burner.
35
-------
Excess Air—
More excess air is required for satisfactory combustion of pulverized
coal than for oil or natural gas. One reason for this is the inherent maldis-
tribution of coal to individual burner pipes and to the fuel discharge noz-
zles. At high loads, the minimum acceptable quantity of unburned combustible
matter usually requires about 15 percent excess air at the furnace outlet.
This allows for the normal maldistribution of primary air, secondary air, and
coal. Higher excess air values may be necessary to avoid slagging or fouling
of the heat absorption equipment.
The designer of a pulverized-coal-fired unit must consider the burner
arrangment and the furnace configuration to minimize slagging or fouling of
the boiler. An increase in excess air will permit satisfactory performance
with most designs, but this may be uneconomical as a long-term substitute for
good basic design.
Starting Cold Boilers and Operating at Low Loads—
Because coal is difficult to ignite, any unburned fuel that escapes on
startup is dry dust with a high ignition temperature. This dust does not
readily cling to surfaces and is carried out of the unit with the products of
combustion. The only potential problem is that this dust can accumulate in
hoppers or in dust collectors. These containers should be emptied frequently
so that the unburned material cannot build up to the point that it ignites and
damages equipment.
During startup, oil burners with mechanical atomizers can be used to
sustain ignition of pulverized coal with little risk of air-heater fires.
Only a small amount of oil is used, and the resulting deposits are generally
inconsequential.
Coal-fired boilers produce significant quantities of particulate matter,
S02, and NO . The level of each of these pollutants is related to the firing
J\
method, the combustion efficiency, the pollution-control equipment, and the
fuel characteristics.
The quantity of S02 produced is' nearly proportional to the coal sulfur
content, but the pulverizers directly reject some pyritic sulfur (usually not
more than about 5 percent of the total coal sulfur content). Because sulfur
affects the ash fusion temperature, the coal sulfur content affects boiler
design and operating characteristics.
36
-------
The generation of NO is strongly related to the combustion method and
s\
combustion controls. Free nitrogen in the coal tends to be a significant
contributor to overall NO emissions. Most NO controls deal with the adjust-
X. s\
ment of combustion air to the burners of pulverized-coal-fired boilers.
Staged combustion or off-stoichiometric firing produces lower peak flame
temperatures by limiting the amount of air available for combustion. This
generally produces long diffusion-limited flames and thus provides longer
reaction times at lower temperatures for complete combustion. Excess air,
usually 15 to 30 percent, is gradually introduced to the flame. The minimum
attainable NO emissions are generally dictated by the nitrogen content of the
fuel. Tangential or corner-fired pulverized-coal-fired boilers tend to pro-
duce less NO than wall-fired units.
s\
The particulate emission rate is a function of the coal ash content and
the firing method. Pulverized-coal-fired boilers emit between 70 and 85
percent of the ash in the coal as fly ash. In contrast, a stoker-fired boiler
emits only 3.0 to 50 percent of the coal ash with the flue gas. In addition,
the particulate matter generated by stoker boilers tends to be much coarser
than the ash from pulverized-coal-fired boilers, and it generally contains
considerably more carbon. These factors affect the selection of control
equipment for specific boilers.
Malfunctions—
Although numerous boiler malfunctions can occur, the two most common
operational problems result from inferior fuel quality and the use of improper
excess air levels. The selected excess air levels are often much higher than
necessary for complete combustion, which decreases boiler efficiency and in-
creases the amount of fuel required to develop a given quantity of steam. Too
much excess air can also increase emissions.
The nitrogen and oxygen in the excess air produce a dilution effect.
Although the peak flame temperature may increase with excess air, the average
flame temperature decreases as a result of the dilution. This decrease in
average temperature reduces the radiant heat transfer to the furnace walls,
and in extreme cases, the extra gas volume may carry unburned fuel out of the
furnace zone.
The volume of excess air increases the velocity of the flue gas through
the convective tube passes because the volume between the tubes is fixed.
37
-------
This velocity increase improves the heat transfer rate in the convective
section slightly, but the improved heat transfer rate fails to offset the
corresponding decrease in heat transfer in the radiant zone described earlier.
Thus, excess air effects a net heat transfer loss. The usual indicators are
increases in the temperature and in the oxygen (02) concentration at the
stack.
Proper excess air levels range from 20 to 30 percent for pulverized-coal-
fired boilers. The excess air level for best boiler efficiency is generally
one that produces a very low carbon monoxide (CO) concentration. Boiler
excess air can be monitored via C02 or 02 monitors at the outlet of the radi-
ant heat zone. Typically, CO levels are maintained at approximately 100 ppm,
and maximum levels of 400 ppm are usually established to preclude explosions
resulting from CO pockets within the boiler.
The symptoms of sootblower failure are the same as those for high excess
air. Sootblowers use steam or compressed air to clean deposits from the
boiler tubes. The ash load and ash properties dictate sootblowing require-
ments. Continuous sootblowing may be required for some pulverized-coal-fired
boilers. Failure to blow the soot from the boiler tubes allows deposits to
form, which reduce the heat transfer rate through the tubes. The resulting
decrease in efficiency is characterized by an increase in stack temperature;
02 and C02 levels are unaffected.
Coal sizing is not a big problem for pulverizers; the maximum allowable
top size for most pulverizers is about 2 inches. Very high quantities of
fines may cause problems in some pulverizers, but most are easily capable of
producing the required fineness (70 to 75 percent through a 200-mesh screen).
Most pulverized-coal-fired boilers have at least one extra pulverizer to
allow routine maintenance to be performed without reducing the boiler load.
Selection of the number of pulverizers needed to handle the desired load is
based on the heat content and grindability of the coal because these charac-
teristics affect pulverizer capacity. Because pulverizers are expensive,
excess capacity is held to a minimum. If the grindability of the coal de-
creases (making it more difficult to grind) or if the heat content of the coal
decreases, existing pulverizers may not be sufficient to maintain the neces-
sary steam rate.
38
-------
Changes in the ash content and other characteristics of the coal can
significantly affect boiler operation. A high-ash coal can increase the
sootblowing requirement or increase heat losses as a result of impaired heat
transfer. A more serious problem is an increase in the slagging potential of
the ash. This can necessitate derating the boiler to prevent slagging. A
sticky ash coating that reduces heat transfer efficiency can make boiler oper-
ating conditions difficult to control. Sticky ashes can be hard to remove,
and they may form localized hot spots, which damage the boiler tubes. Coal
blending sometimes leads to similar problems as a result of the formation of
eutectic ash from the blended coal. This ash has a lower fusion temperature
than the ash for either coal by itself.
Improvement in coal quality can'also lead to operating problems in a
pulverized-coal-fired boiler. If a nonslagging coal is burned in a boiler
designed for a slagging coal, furnace walls may be too clean, and too much
radiant heat may be absorbed, which makes it difficult for the superheater to
produce the necessary steam temperatures. A reduction in sootblowing can
alleviate this problem.
Fineness of the coal from the pulverizers should be checked frequently.
Failure to feed coal of requisite fineness to the burners may impair combus-
tion and thereby allow carbon carryover to the control equipment, which causes
inefficient boiler operation. Excessively fine pulverization wastes energy
and reduces pulverizer capacity. If Eastern bituminous coal is burned, 70 to
75 percent of the coal should pass through a 200-mesh screen. Somewhat less
fineness (60 to 65 percent) is necessary with Western subbituminous coal
because of the noncaking properties of this coal.
A tube leak eventually causes boiler shutdown and also affects control
equipment operation. Waterwall, boiler tube, and economizer tube leaks have
the greatest effects on control equipment operation. Significant quantities
of water can escape into the flue gas, plug multicyclones and fabric filters,
and make ash removal from electrostatic precipitator (ESP) plates difficult.
Freezing conditions can affect coal flow to the boilers. The coal can
hang up in chutes, hoppers, feeders, or even rail cars. In stoker boilers,
frozen fuel can cause underfire air to channel to uncovered portions of the
grate, which reduces the underfire air to other portions of the grate. This
can cause distortion of the grates, as both the ash layer and the underfire
39
-------
air help to protect the grates. In addition, the channeling of the air
changes local excess air conditions and increases emissions.
2.3 FANS
The gas flow rate is a key parameter in the evaluation of the performance
of any pollution control system. The inspector should rely on current pitot
tube measurements to determine the flow rate of the pollution control system.
In some cases, fan data can be used to estimate the gas flow during the
inspection. Using a published fan curve, the inspector should correct all
readings to standard conditions and determine the gas flow in standard cubic
feet per minute. An estimate made in this manner is subject to errors because
of the variability in fan performance, fan modifications that may have been
made, and the mechanical condition of the fan. If a fan curve is not avail-
able, the inspector can use the F-factor method (discussed in Section 2.4) to
estimate flue gas and fuel rates.
Fan data can be used to diagnose changes that have occurred since the
last previous inspection. In many cases, however, baseline data are not
available because fan parameters are not routinely measured during convention-
al inspections. A radial-blade centrifugal fan is typically used for dirty
gas service. Operating characteristics are illustrated by the curve in Fig-
ure 15, which applies to a New York Blower Company size 332 general industrial
fan with an LSD wheel operating at 1460 rpm at standard conditions. Static
pressure losses in the control equipment and ductwork (curve A) are propor-
tional to the square of the flow rate. The fan develops less static pressure
at higher flow rates, however; thus it has a strong negative slope (curve B).
The intersection of the system line and the fan pressure drop curves defines
the operating point of the system. At this point, the gas flow rate is 8,400
scfm (approximately 40,000 Ib steam/h boiler), and the brake horsepower (curve
C) is approximately 24.5.
A major problem with boilers is that as they get older they tend to lose
capacity because the fan cannot accommodate increases in excess air, inleak-
age, and general system deterioration (such as fabric filter blinding, in-
creases in ductwork friction, etc.). A reduction in boiler load is usually
required to compensate for this, but plants sometimes replace the fan drive
sheaves to speed up the fan. The latter is not always a feasible remedy.
40
-------
12
11
.5 10
LLJ
•a:
CO
-------
Effects of fan speed on operating characteristics are shown by the curves
in Figure 16. In Case 1, a speed increase leads to a greater gas flow rate
and higher static pressure. Increasing the fan speed may be a feasible course
of action at plants where the boiler gas flow is insufficient; however, the
fan must be operated within its acceptable published range of speeds. In-
creased flows can adversely affect fabric filters or ESP's. On the other
hand, a decrease in fan speed (perhaps to save energy) decreases the flow sub-
stantially; Case 2 shows such reduced gas flow. A decrease in fan speed can
reduce the collection efficiency of cyclones and wet scrubbers because these
control devices depend on gas velocity for particle collection.
Other changes in fan operation may occur without the operator's know-
ledge. For example, the fan motor current may either increase or decrease
when the system static pressure drop increases; Case 3 in Figure 17 represents
a total system pressure drop increase from the baseline condition. An in-
crease in the fan motor current would accompany this change, as indicated in
Table 2. The static pressure increase may be due to a variety of factors.
Static pressure decreases can be caused by the following factors:
0 A change in the gas flow rate.
0 Changes in operating conditions such as control device short-
circuiting (open access doors, gaps in ductwork, open by-pass
dampers).
0 Decreased scrubber liquor flow.
The cause of the change can be analyzed further by measuring the gas tempera-
ture at the fan inlet. A low temperature suggests either an open access hatch
or a serious leak in the ductwork.
In addition to analyzing the fan operation, the inspector should visually
check the physical condition of the fan and note the following:
0 Blade abrasion
0 Deposits
0 Corrosion of the wheel and fan housing.
42
-------
12
10
LU
CC.
•=>
oo
1/1
LU
CC Q
a. -*
x-- CASE 1 , FAN AP
' ' 7 8 9 10
GAS FLOW RATE, SCFM x 10 3
11
12
Figure 16. Fan characteristic curves—effect of speed change.
43
-------
12
o 11
-------
TABLE 2. INTERPRETATION OF FAN OPERATING CONDITIONS
(RADIAL-BLADE TYPE ONLY) SHOWN ON FIGURES 15 AND 16.
Case
1
2
3
4
Fan parameters
Calculated
APsp at 70°F
Decreased
Increased
Increased
Decreased
Calculated
amps at 70°F
Decreased
Increased
Decreased
Increased
Fan speed,
rpm
Decreased
Increased
Unchanged
Unchanged
Possible causes
Fan speed increase (sheave
change or belts tightened)
Fan speed decrease (sheave
change or loose belts)
a) Filter blinding
b) Filter cleaning problem
c) Hopper overflow
d) Scrubber bed plugged
e) Decreased gas flow
f) Reset damper
a) Baghouse leaks
b) Shortcircuiting
c) Decrease in liquor flow
d) Increase in gas flow
e) Reset damper
The inspector should be sure to lock the fan out of service before attempting
to conduct a physical inspection.
Blade abrasion and deposits indicate excess emissions of large particles
(10|jm) and suggest a particulate control device malfunction. Fan operating
parameters indicate a number of important changes in control device operating
conditions. For an estimate of actual flow rates, the certified rating curve
for the fan must be corrected to the gas temperature at the fan inlet by using
the factors in Table 3.
Generally, if the fan operating parameters (static pressure, motor cur-
rent, fan speed) are within 10 percent of the baseline condition and if the
gas temperature at the fan inlet is within 20°F, it is unlikely that gas flow
changes have caused mass emissions to change significantly from baseline
conditions.
45
-------
TABLE 3. FAN DATA, TEMPERATURE CORRECTION.'
Temp
20
40
60
80
100
120
140
160
180
200
Factor
0.91
0.94
0.98
1.92
1.06
1.09
1.13
1.17
1.21
1.25
Temp
220
240
260
280
300
320
340
360
380
400
Factor
1.28
1.32
1.36
1.40
1.43
1.47
1.51
1.55
1.59
1.62
Temp
420
440
460
480
500
520
540
560
580
600
Factor
1.66
1.70
1.74
1.77
1.81
1.85
1.89
1.92
1.96
2.00
aThe published flow rate from the fan curve is multiplied by
the above factors to estimates actual flow at fan inlet
temperature. Adapted from "Basic Energy/Environment Analysis,"
NAPA Information Series 67, by C. Heath, August 1978.
2.4 USE OF THE F-FACTOR
Stack sampling teams have used the F-factor as an accepted method of
obtaining heat input of combustion sources through measurement of gas velocity
and gas conditions for the purpose of determining gas volume. During inspec-
tions of combustion sources, inspectors often find that both the heat input
and gas conditions are determinable but the gas volume is the unknown factor.
The F-factor method is used to ascertain the missing value needed for the
evaluation of control equipment performance.
Thn simplest case is one in which both wet and dry F-factors (Fw and F^)
are available for a known fuel. The oxygen content is usually determined on a
dry basis; thus, an equation relating gas volume, temperature, and moisture
may be written:
stack
Q = heat input rate x [(F, x Correction ^ +
temperature
w
where Q = gas flow rate, acfm;
Stack oxygen correction factor =
Temperature correction factor =
20.9
; and
46
-------
EXAMPLE — Heat input rate = 100 x 106 Btu/h (using bituminous coal) or
1.667 x 106 Btu/min
Fd = 9,820 dscf/106 Btu
FW = 10,680 wscf/106 Btu
Temperature = 350°F
Oxygen content =5.0%
Q = 1.667 x [9,820 x (20J°:95>0) + (10,680 - 9,820)] x
= 1.667 (12,908 + 860) x
810
528
= 1.667 (13,768)(1.53)
= 35,210 acfm at 350°F.
The term (FW - Frf) accounts for water produced during the combustion
process and assumes that excess fuel moisture does not significantly affect
the values for FW. For fuels where moisture content is significant and may be
variable, however, the above formula is usually not applicable. When this is
the case, utilization of a fuel moisture correction factor is usually re-
quired. This is particularly true in the firing of wood or bark, in which the
moisture content may be as much as 50 percent of the fuel weight. If the
weight percent of the water in the fuel is known the equation would be:
Q = heat input rate x [(Fd x stack oxygen correction)
+ %Hs,0 (in fuel, wt.) x 21.41
1 - %H20 x 10e Btu/lb fuel, dry
+ ^w ~ Fd^ x temPerature correction. (2)
This formula accounts for the vaporization of the moisture in the fuel as well
as the formation of water due to combustion. The term
%H?0 (in fuel, wt.) x 21.41
1 - %H20 x 10« Btu/lb fuel, dry
converts the weight percent moisture content to a value of standard cubic feet
per million Btu for the proper units in the equation. (Note: For the sake of
simplicity, not all units are shown in the preceding equation.) The value of
FW will be known in all cases where high moisture contents are encountered,
and the term (FW - Fd) is then taken to be zero.
47
-------
Another situation frequently encountered is the combination firing of
fuels. This requires knowledge of the firing rates of each fuel or the per-
centage of total heat input accountable to each fuel. The total gas volume is
then the sum of each individual F-factor calculation at the same excess air/
temperature conditions. The following example will utilize both equations
previously shown.
EXAMPLE — Heat input rate = 100 x 106 Btu/h
50% of heat input attributed to coal
50% of heat input attributed to wood bark at 50% moisture and
9,000 Btu/lb (dry basis)
Stack temperature = 350°F
Stack oxygen content = 10.5 percent
Gas volume due to coal combustion would be calculated as follows:
Fd = 9,820 dscf/106 Btu
FW = 10,680 wscf/106 Btu
Q =
Heat input = 50 x 10s Btu/h = 0.833 x 106 Btu/min
0.833 [(9820 x 20.92-'i0>5) + (10,680 - 9,820)] x
= 0.833 (19,734 + 860) x 1.53
= 26,250 acfm at 350°F.
Gas volume due to wood bark combustion would be calculated as follows:
Fd = 9,640 dscf/106 Btu
%H20 = 50% or 0.50
Heat input = 0.833 x 106 Btu/min
n - 0 RT* ffqfi40 x 20.9 . + .5 X 21.41 -. 350 + 460
Q - 0.833 LC9640 X 20.9 - 10.5' + (1 - .5)(.009)J X 528
= 0.833 (19,375 + 2,380) x 1.53
= 0.833 (21,755) 1.53
= 27,725 acfm at 350°F
Total gas volume = 26,250 + 27,725 = 53,975 acfm at 350° F, 10.5% 02.
48
-------
Another related F-factor method utilizing the FW value may be used for
quick calculations of the gas volume. The equation is
Q = heat input rate x [F- + stack oxygen correction factor] x cort,ection (3)
«? LrUX«IX *JS\J y^-' I V»V I I »-\* V I Wl I I «V* vvr i j *x PflY*Y*PPT 1 OH
Although technically less accurate than Equations 1 or 2, it will provide an
estimated gas volume with little error at a moisture content of 10 percent or
less. This equation will provide a different value from that derived by Equa-
tion 1 because of the method of measuring stack oxygen. The methods used in
the field during an inspection (either 02 Fyrite or Orsat) provide their
measurements on a dry gas basis, whereas Equation 3 is intended to be used
with the oxygen measurement on a wet gas basis. The effect of using the dry
basis measurement is that the equation will produce results that are biased
high. As the moisture content in the gas stream increases, the error becomes
more significant.
49
-------
SECTION 3
POLLUTION CONTROL EQUIPMENT
The selection of pollution-control equipment for industrial boilers to
meet particulate emission standards depends on fuel type, method of combus-
tion, fuel and ash characteristics, and the costs of available equipment to
meet prescribed emission requirements. The available particulate-control
devices include multicyclones, fabric filters, electrostatic precipitators
(ESP's), and scrubbers. Each of these devices is discussed separately in the
following subsections.
3.1 MULTICYCLONES
3.1.1 Introduction
The principal mechanical collector used on older industrial boilers is
the multicyclone (Figure 18), which consists of several dozen to several
hundred tubes. Only a few inches in diameter, each tube is a small cyclone
collector. As shown in Figure 19, each of these tubes consists of a collec-
tion tube, a gas outlet tube, and a turning vane. When the unit is operating
properly, gas flows helically down through the annular area between the outer
cylinder and the gas outlet tube, and concentrations of particles move down
the collection tube wall into the hopper. At the collection tube outlet, the
vertical component of air flow reverses, and the cleaned gas passes upward out
of the tube through the gas outlet tube.
Because the multicyclone is not very efficient in the collection of
particles smaller than 10 urn in diameter, it cannot be used to control parti-
culate matter from pulverized-coal-fired boilers. Since stoker-fired boilers
emit larger particles, multicyclones can be used to control particulate emis-
sions if emission regulations are not too restrictive. Figure 20 presents
typical fractional efficiency curves for a multicyclone collector. Combustion
problems can produce significant quantities of particulate matter as smoke,
but smoke particles are so small that they will pass through a multicyclone.
50
-------
b. Individual tube
from multicyclone
collector.
a. Typical multicyclone collector.
Figure 18. Multicyclone collector.
51
-------
CLEAN GAS
TUBULAR GUARD
OUTLET TUBE OR
CLEAN GAS OUTLET TUBE
DIRTY GAS
TUBESHEET
SPIROCONE
OR TRICONE
INLET VANE, RAMP
OR SPINNER
ANNULAR AREA
OUTER CYLINDER
EXTRA THICKNESS
AT WEAR POINTS
LOCKNUT
CONICAL SECTION
FLY ASH PARTICLES
Figure 19. Cross section of an individual cast iron collection tube.
52
-------
AP = 3.0" H20
AP = 2.0" H20
AP = 1.0" H20
MULTICYCLONE COLLECTOR
12" DIAMETER TUBES
I
0
10
20
30 40
PARTICLE SIZE urn
50
60
70
80
Figure 20. Fractional efficiency curves for multicyclone.
53
-------
3.1.2 Operation and Maintenance
There are several operating conditions and/or malfunctions that can
reduce cyclone performance. Most of these conditions result in disturbance of
the cyclone vortex, pluggage of gas passages, or interference with the dust
discharge from the cyclone tube. The following subsections identify the major
failure mechanisms and their effect on collector efficiency.
Gas and Particulate Maldistribution —
For each cyclone tube to receive the same amount of dust or grain load-
ing, the distribution of gas flow must be uniform both horizontally and verti-
cally across the multicyclone inlet. Proper duct inlet design requires the
use of turning vanes in many cases. Sharp duct turns or improperly joined
ducts may result in particle stratification at the outer radius of the turn
which causes increased abrasion and/or dust buildup on the approach to the
collector tube inlet turning vanes. Figure 21 shows deposits at the entrance
to the inlet of a multicyclone section as a result of particle fallout.
Gas Volume and Pressure Drop—
If the collector is to operate at maximum efficiency, the gas volume and
pressure drop must be at maximum design values. Operation above design pres-
sure drop may result in increased turbulence and decreased collector efficien-
cy. Conditions that result in high gas volumes and high pressure drops in-
clude operation at high excess air, ambient air inleakage in the duct prior to
the collector, and boiler overload. High excess air and boiler overload are
not generally observed in utility boiler operations but are common in indus-
trial boiler applications.
When the boiler is operated at reduced load (firing rate), it generates
less-than-design flue gas volume and the collection efficiency decreases. The
reduction in efficiency can be significant when the boiler is operating at 20
to 25 percent below design gas volume.
Inlet Turning Vane Wear—
The inlet turning vane or ramp is designed to impart a tangential motion
to the inlet gas stream of the collector. This tangential motion is trans-
formed into the vortex in the collecton tube. Impaction of particulate on the
turning vane surface results in abrasion and metal wear over the life of the
54
-------
Figure 21. Particulate fallout on dirty gas tube sheet.
55
-------
collection tube. Severe damage results in disturbance of the vortex and in-
creased gas turbulence that limits collection efficiency. Figure 22 shows
abrasive wear of inlet turning vanes.
Inlet Turning Vane Material Buildup--
Material buildup on the turning vane or ramp may occur as a result of
particle fallout or it may develop as a scale. The scale occurs as sulfuric
acid condenses on the cool metal surfaces at low boiler load conditions. Fly
ash combines with the acid and forms a hard scale when the boiler load and
flue gas temperatures increase.
The effect of inlet material buildup on collection efficiency is similar
to turning vane wear in that the turning vane vortex is disturbed or it fails
to form. An improperly developed vortex results in turbulence and short
circuiting of the gas volume to the gas outlet tube without particle separa-
tion.
Collection Tube Weai—
Contact of abrasive particulate with the walls of the collection tube
results in erosion of the tube and eventual failure of the collector tube.
Normal wear occurs at the bottom of the cast iron tube. As the metal thins,
holes may appear along the bottom of the tube or the dust outlet may become
ellipical or egg shaped. These conditions result in a poorly formed gas
vortex and an increase in surface roughness and turbulence. Erosion of the
dust outlet opening increases particle reentrainment and decreases cyclone
collection efficiency.
Collection Tube Scale—
Scaling in the collection tube as a result of acid dew point condensation
results in increased surface roughness and particle reentrainment in the
outlet gas vortex. Scaling may be periodically scoured by the fly ash in the
vortex or it may develop into complete blockage depending on boiler operating
temperatures, load swing, and concentration of S03 in the flue gas stream.
Figure 23 shows scale development on the inside of a collection tube.
Gas Outlet Tube Blockage—
Scaling of the collector may also occur in the gas outlet tube. Because
the cross sectional area of the outlet tube is less than the collection tube,
56
-------
Figure 22. Inlet turning vane wear because of abrasion.
Figure 23. Scale on inside of collection tube.
57
-------
a thick scale may close the tube completely. The removal of larger abrasive
particles in the collection tube limits the self-cleaning scouring effect in
the outlet gas stream.
Partial blockage of the outlet gas tube and increased static pressure
drop reduce the gas volume passing through the tube and the separation effi-
ciency. Complete blockage of the gas outlet removes the tube from service in
a similar manner to blockage of the inlet turning vane. Figure 24 illustrates
a plugged outlet tube.
Dust Outlet Tube Blockage—
Severe scaling of the cyclone collection tube may result in complete
closure of the dust outlet opening at the bottom of the tube. Once plugged
particulate begins to build up in the tubes, the turning vanes are restricted
and there is no flow through the tube because of increased pressure drop. As
with inlet turning vane blockage, the loss of the collection tube reduces the
effective size of the collector and increases the gas volume through the
remaining tubes. Figure 25 shows a plugged dust outlet tube.
Air Inleakage Into Ash Hopper--
In most industrial boiler applications, the flue gas handling fan is
located down stream of the multicyclone (ID fan). This location places the
collector and duct work under negative atmospheric pressure. Any opening in
the flue gas stream results in significant air inleakage into the system.
Inleakage into the hopper area creates a gas flow from the hopper through
the dust outlet of the collector tubes and into the gas outlet tubes. This
flow, depending on the condition of the hopper seals, may account for 10 to 20
percent of the collector gas volume. The upward flow of gas through the
narrow dust discharge opening at the bottom of the'collection tube increases
reentrainment of fine particulate at the dust outlet and reduces collector
efficiency. Major points of hopper inleakage are: gaskets between shell
flanges, poor welds, gasket between ash hopper and ash valve, ash valve,
manhole door gaskets, door frame gasket, and inspection port.
Collection Bypass—
Bypass of small volumes of flue gas through the dirty gas and clean gas
tube sheet allows a significant weight of particulate to be emitted. Major
areas of bypass are the gasket seal between the collection tube and the dirty
58
-------
Figure 24. Plugged outlet tube.
59
-------
Figure 25. Plugged conical section.
60
-------
gas tube sheet (Figure 26); welded or pressed joints between clean gas outlet
tubes and the clean gas tube sheet (Figure 27); welded or bolted joints be-
tween tube sheets and collector shell (Figure 28); and welded or bolted joints
between tube sheet sections (Figure 28).
Penetration may also occur through holes on the leading edge of the gas
outlet tube in the dirty gas plenum. The tubes are exposed to the dirty gas
and abrasive damage occurs as the gas is directed to the collection tube
turning vanes. In most cases the pressure drop across the penetration point
is equivalent to the collector pressure drop (3 to 4 inches H20) and allows
substantial gas bypass through the orifice.
Because most bypass occurs internally to the collector, it is difficult
to determine the points of inleakage while the collector is on-line. A visual
inspection of the tube sheet, outlet tubes, gaskets, and welds can identify
major penetration points and allow for correction. Many penetration points,
however, are hidden and will be observed only under a static pressure differ-
ential. To find these leaks the collector must be sealed, pressurized and
penetration observed visually with a white aerosol smoke.
Hopper Cross Flow— *.
Because of space limitations, multicyclone collectors are designed with
multiple rows of collection tubes in the direction of gas flow. To achieve
maximum efficiency the design must ensure that all collection tubes receive an
equal volume of flue gas. As gas passes through the initial leading row of
tubes, the total gas volume is reduced and the gas velocity in the plenum is
reduced. To maintain uniform velocity in many designs, the clean gas tube
sheet is inclined. In theory, this should maintain uniform flow to each row
of tubes, but in practice the pressure drop across each row of tubes is not
uniform and more gas is directed to the first tube rows. Systems having
several tube rows and large nonsegmented hoppers experience cross hopper
ventilation. Flue gas flows out of the dust discharge opening of the inlet
tube. It flows across the hopper and up through the dust discharge of the
back collection tubes (Figure 29). Flow across the hopper interferes with
dust discharge and causes fine particulate to be reentrained. Flow into the
dust outlet also disturbs the gas vortex which also prevents collection tube
dust discharge.
61
-------
WASHER
DIRTY GAS AREA
CLEAN GAS AREA
-71 CLEAN GAS TUBE
HOLD DOWN CLAMP
CROSS SECTION OF TUBE MOUNTING
Figure 26. Clean side air leaks.
J
LEAK
DIRTY GAS AREA
CLEAN GAS TUBE
ROLLED INTO TUBE SHEET
X
CLEAN GAS
TUBE SHEET
CLEAN GAS TUBE
T
CROSS SECTION OF TUBE MOUNTING
Figure 27. Example of leaks in clean gas
outlet tubes and clean gas tube sheet.
62
-------
COLLECTOR
WALL
CLEAN GAS TUBE
LEAK
"
1
c
<
C
t
>
3
2
01
o
"•v -
^\ \
t
c
<
C
L
3
J
2
HI
o
lr\ .
CLEAN GAS AREA
^\v\\\\\"\:
I
DIRTY GAS AREA
NORMALL
BETWEEN CL
NORMALLY SEALED WELDED
BETWEEN CLEAN GAS TUBE SHEET
AND SIDE WALL CASING
LEAK
'CLEAN GAS TUBE SHEET
XL
CROSS SECTION OF TUBE MOUNTING
Figure 28. Clean side air leaks.
63
-------
5-
O>
Q.
Q.
O
JC
to
t/>
o
u
TJ
C
(0
C
o
•r~
•P
$-
•P
j.
o
o
D-
CM
-------
Cross hopper ventilation can be prevented by using a welded baffle at the
hopper valley. Segmenting the hopper provides a more uniform pressure drop
distribution across the tube sheet. Cross flow is aggravated when the tubes
are plugged, when scale has formed on outlet tubes, or when there is hopper
infiltration.
3.1.3 Inspection Procedures
The inspector should perform the following at the start of the boiler
multicyclone inspection:
1. Determine opacity.
2. Measure system pressure drop.
3. Measure air volume.
4. Measure system temperature.
5. Measure fan speed.
6. Measure fan static pressure.
7. Measure inlet particle size distribution (if possible).
8. Measure hopper discharge weight (if possible).
9. Measure wet bulb and dry bulb temperatures.
After these external inspections are completed, the following internal
inspections should be performed at a future time when the unit can be taken
off line and cooled sufficiently. Note: Be sure and follow proper safety
procedures described on Pages 130 to 133 for confined entry.
1. Check for inlet distribution buildup.
2. Check for inlet vane plugging.
3. Check for outlet tube plugging.
4. Check for hopper bridging.
5. Check for inleakage (corrosion, moisture, or scale).
6. Check for leakage between clean and dirty air sides.
65
-------
Using the manufacturers' design parameter specifications (tube diameter,
number of tubes, etc.) the inspector should calculate the inlet velocity at
maximum and minimum process flow conditions. These calculated values indicate
the multicyclone efficiencies at maximum and minimum boiler conditions. The
inspector may find that recirculation or flow control is required at low
boiler loads for compliance with emission standards.
During system field evaluations, the inspector should note observations
at both low and high boiler loads. The external inspection allows the in-
spector to obtain sufficient data to estimate air volume (using fan speeds,
static pressure, and temperature) and to determine whether a potential oper-
ating problem exists (e.g., moisture content or weight discharge from hopper).
These data, when used with stack test data, allow future comparisons of system
operating conditions and performance. The internal inspection reveals oper-
ating design problems that may not be determined by external inspections.
Such problems (e.g., uneven distribution, inlet plugging, inleakage, and
leakage from the clean-to-dirty side) are not always indicated by changes in
system static pressure but can significantly reduce overall efficiency. From
the external and internal inspection data and from efficiency data supplied by
the manufacturer, the inspector can determine the multicyclone mass emission
rate and can anticipate long-term maintenance and operational problems.
3.2 FABRIC FILTERS
3.2.1 Introduction
Fabric filters are becoming increasingly popular for the control of
particulate matter from pulverized-coal-fired boilers, and they are used occa-
sionally on stoker-fired boilers. The particulate 'collection efficiency of
fabric filters is higher than for any other device. Other principal advan-
tages are that they minimize emissions and circumvent the resistivity problems
associated with some coals. The capital costs of fabric filters generally are
less than those of ESP's, but they are more than those of mechanical collec-
tors or scrubbers. The operating costs for fabric filters are usually some-
what higher than those for ESP's and mechanical collectors, but lower than
those for scrubbers.
66
-------
A problem in the application of fabric filters to stoker-fired boilers is
control of coal properties and the combustion process. A spreader-stoker
operation is sensitive to the size of the coal, particularly the quantity of
fines in the coal. Excessive fines cause carbon carryover that sometimes
blinds the fabric with sticky particulate matter. Blinding results in exces-
sively high pressure drops, a reduction in the air flow through the boiler,
and a reduction in boiler capacity.
The fabric filter is usually designed for high-temperature operation, and
either fiberglass or polytetrafluoroethylene bags are used. Reverse-air and
pulse-jet bag cleaning mechanisms may be used. Reverse air units (on indus-
trial plants) are generally limited to an air-to-cloth ratio (A/C) of 2.5
acfm/ft2 of cloth area. Pulse-jet units can operate at an A/C of 4.0 to 4.5
acfm/ft2. A precleaner such as a multicyclone or a simple impaction baffle
plate is usually employed to remove the larger, more-abrasive particles before
they enter the fabric filter. The normal operating pressure drop across a
fabric filter is between 3 and 6 inches H20. Higher pressure drops have been
experienced on industrial systems. A typical fabric filter is shown in Fig-
ure 30.
3.2.2 Operation and Maintenance
Theoretically, fabric filters can achieve mass collection effiencies in
excess of 99.5 percent when particles are as small as 0.1 urn. In practice,
many process conditions and installation problems can reduce both the collec-
tion efficiency and the time available for service. Fabric filters require
extensive preventive maintenance and inspection to reduce periods of excess
emissions. The subsequent subsections discuss operation and maintenance of
.fabric filters. Because reverse air units are more commonly used, the empha-
sis is on this type.
Factors Affecting Bag Life--
Dust is removed from the gas stream by passing the gas through a porous
fabric upon which the dust deposits and builds a dust cake layer. The effi-
ciency of dust collection depends on the integrity of the fabric structure
supporting the dust cake. Any deterioration of the fabric structure that
allows localized failure increases the penetration of dust through the system.
67
-------
D)
•p-
C
(0
0)
u
O)
c
•r~
S-
2
TJ
CU
10
3
O
x:
cn
03
0)
ui
o.
O)
0)
0)
(0
(J
O
co
S-
3
D)
68
-------
Temperature Excursion—
The most common cause of bag failure from polymer chain breakage is
exposure to high temperatures. Exposure to temperatures at or near the recom-
mended continuous operating temperatgre level results in random chain breakage
with reduced tensile strength over the life of the fabric. Typical life of
fiberglass bags at 325°F is between 12 and 24 months in service on a indus-
trial boiler. The life may be greatly reduced if the fabric filter is simul-
taneously exposed to acids and moisture.
Exposure to temperatures above the recommended continuous operating
temperatures for a few minutes may not result in immediate failure, but will
reduce the overall life of the fabric. The effects of repeated temperature
excursions on tensile strength are cumulative. A high-temperature alarm with
an automatic method for bag protection (e.g., quenching, dilution, or bypass)
should be provided.
Pressure Drop—
In normal operation, the system pressure drop remains between the upper
limit set for cleaning (time duration between cleaning periods or pressure)
and the lower level after cleaning. An increase in static pressure drop
between cleaning (upper limit) indicates a change in fabric/cake resistance
(permeability). This change can result from changes in amount of cake buildup
retained, oil deposits from the compressed air system, or moisture from in-
leakage. The increased pressure drop may be tolerated if it is not severe or
if it does not decrease ventilation performance because of decreased volume of
gas exhausted.
If an increase in pressure drop occurs, attempts should be made to diag-
nose the cause (oil, moisture), and corrective action should be taken. An
increase in cleaning energy beyond manufacturers' recommendations should not
be made, because it shortens bag life.
Cake Release—
The ability to remove collected particulates (cake) from the fabric
surface determines the cleaning frequency required for the filter system.
Factors that affect the energy necessary to remove the cake include cake
composition, porosity, and the effectiveness of the energy transfer to the
cake/filter interface.
69
-------
The presence of moisture either from operation below the dewpoint or from
inleakage through the shell presents a similar problem. The cake release is
impaired, and increased energy is required to remove the cake. When the
boiler is shut down, it is advisable to continue to operate the baghouse for
one complete cycle (including cleaning). This operation purges it with clean
air to avoid condensation and ensure that bag contaminants are removed.
Cleaning Intensity—
The removal of the dust cake requires the breaking of the cake structure.
Too little energy does not break the cake, and too much energy increases bag
failure because of fiber abrasion. The proper intensity is defined as the
minimum amount necessary to remove the proper amount of cake. Each boiler is
unique, and identical boilers at a site may not have the same cake release
properties because of source variability and/or gas stream characteristics.
Therefore, the required cleaning intensity must be matched to the system.
The proper cleaning of the bag requires the flexing of the surface to
dislodge the cake. If bag tension is low, the bag may be flexed adequately at
the top, but the standing wave dampens as it is transmitted downward. The
installation of each bag must be checked to ensure proper tension. Manufac-
turers' literature should be consulted to determine the correct tension
method. The fabric may elongate because of the weight of dust collected
between cleaning cycles or bag tongues may slip in hangers. Thus, tension may
change with time of service.
In reverse-air collectors, the cake is released by collapsing the bag
with reversal of gas flow. The bag is flexed, and the cake removed from the
surface by the cleaning gas. In systems with short bags [i.e., bags less than
2.5 m (8 ft) long], bags may be allowed to collapse, almost completely. The
bag must be reinflated in a snap action, and a dwell time must be allowed for
the dislodged cake to flow from the bag before gas filtration commences. In
this case low bag tension results in complete closure of the bag near the
thimble, reduction of reverse gas flow through the bag, and consequently
reduction of cleaning efficiency (Figure 31).
Tube Sheet Bridging—
In shaker or reverse-air fabric filters, dust cake is collected on the
interior surface of the bags. The removal of the collected dust cake requires
70
-------
TOP VIEW
AREAS WHERE
CLEANING
IS PREVENTED
BECAUSE OF
BAG CLOSING
SIDE VIEW
FLOW OF REVERSE AIR
Figure 31. Impaired cleaning in a reverse-air fabric filter.
71
-------
the free fall of the dust through the thimble and into the dust hopper. When
systems are uninsulated or when the gas temperature is near the dewpoint, cake
accumulates on the underside of the tube sheet and on the inside of the thim-
bles. Heat is transferred from the tube sheet to the uninsulated baghouse
shell. The colder metal reduces dust temperatures and causes agglomeration
and deposition on the surface.
As caking increases, the ability of the dust to discharge through the
thimble is reduced. Eventually, complete bridging of the bag results. In
severe cases, the accumulation may extend several feet into the bag. The
bridging occurs most commonly near the baghouse shell (outside rows) or near
doors where air inleakage from deteriorated gaskets occurs (Figure 32). The
bridge may normally'be dislodged by flexing the bag with the hand near the top
of the thimble. The dust above the bridge, because it is exposed to the gas
stream, is free flowing and discharges after the cooler cake is broken near
the tube sheet.
The breaking of the cake only returns the bag to service for a short
period; bridging soon recurs. Continued operation in this condition decreases
net cloth area and increases pressure drop. The higher A/C ratio increases
bag abrasion and decreases bag life. The solution to the problem is to reduce
heat loss through the tube sheet/shell by installing insulation or increasing
the system temperature.
Abrasion—
The failure of the fabric may occur over a long period of time because of
the abrasive action of dust particles on individual fibers in the structure.
The failure may result from general abrasion over a large area or specific
attacks in concentrated areas.
Local intensive abrasion, which results in premature bag failure, is
undesirable and can be prevented. High abrasion rates are commonly associated
with improper bag installation or design flaws in the collector. Some common
causes of failures are described below. Each case of abrasion failure must be
addressed separately to determine if corrective action may be taken to reduce
the frequency of failures.
In shaker and reverse-air fabric filters, the bag can be attached to the
tube sheet by a thimble and clamp ring design or by a snap ring design.
Figure 33 shows the two methods of attachment. Dust enters the baghouse
72
-------
Figure 32. Bridging near baghouse shell caused by
cooling a poorly insulated fabric filter.
73
-------
THIMBLE AND CLAMP RING DESIGN
POOR
BETTER
CLAMP
INCREASED
ABRASION
1
J <—\
BAG
1
w^w^
LONG
t THIMBLE
1
•
.x- LONG CUFF AND
* REDUCED ABRASION
,L
w///m,
/ >
GAS flOV y TUBE SHEET '
POOR
BAG
CUFF
WITH
SNAP
RINS
POOR
SNAP RING DESIGN
SHORT CUFF
NO THIM8LE
INCREASED
^ABRASION
•BETTER
BAG
CUFF WITH
SNAP RING
LONG CUFF AND
,REDUCED ABRASION
6AS FLOW
Figure 33. Methods of bag attachment in
shaker and reverse-air fabric filters.
TUBE SHEET
AND
THIMBLE
74
-------
filter at the hopper in a horizontal direction and must turn vertically to
enter the tube sheet thimbles. Heavy particles with higher inertia do not
follow the flow and therefore do not enter the opening parallel to the thimble
walls. The particles impact on the walls of the thimble and, if the thimble
is short, on the fabric above the thimble. The action of the particles strik-
ing at an angle to the fiber surface increases abrasion. Roughly 90 percent
of bag failures occur near the thimble. The use of double-layered fabric
(cuffs) or longer thimbles reduces the failure rate.
In the snap ring system no thimble is used, and in some cases a cuff is
not used. This exposes the bag to rapid abrasion a few inches above the snap
ring. Add-on tube sheet thimbles may be used to reduce the effect.
Baffle plates or diffusers may be used to deposit large particles in the
hopper before they contact the bags. The orientation of the plates is criti-
cal, however, because deflection of incoming gas into the hopper can resuspend
collected dust and increase effective dust loading through the tube sheet.
The resuspension is reduced if the hoppers are operated with continuous dust
removal; thus, dust remains below the gas inlet. A cyclone also may be in-
stalled as a precleaner to remove larger particles and reduce inlet loading.
It is common practice not to remove dust that accumulates on the clean
side of the tube sheet. The presence of dust is not a significant problem as
long as penetration is not occurring. Heavy dust accumulation, however,
results in rapid abrasive failure; of serviceable bags. When the dust that has
been emitted from previous bag failures settles on the tube sheet and collects
around a bag, the weight collapses the bag and forms an orifice (Figure 34).
The reduction in area increases gas velocity and therefore abrasive damage to
the bag in the area of the restriction. The increased tension of the bag also
results in abrasion of the bag where it contacts the top edge of the thimble.
Prompt removal of accumulated dust from the tube sheet after a bag failure can
reduce damage to other bags.
Chemical Attack—
The fabric types used in fabric filters in industrial boilers are Nomex
®
Teflon , and coated fiberglass. Nomex is particularly susceptible to sulfuric
acid attack below the acid dewpoint. Fiberglass is susceptible to attack by
hydrogen fluoride (HF) although this normally is not a problem in industrial
75
-------
BAG
DAMAGE
OCCURS HERE
'.1 j'l i 'icS ^CJ'£.;--«
Figure 34. Abrasive damage caused by accumulation of dust on the tube sheet.
76
-------
boilers. The fabric filter should be operated at the lowest temperature con-
sistent with avoiding moisture or acid condensation.
When boilers frequently shut down, bags can quickly be destroyed because
of temperature excursions through the acid and moisture dewpoints. Shutdown
should be accomplished by exhausting flue gases from the filter with dilution
air (ambient) before cooling gases below the dewpoint. The purging removes
the S02 and water vapor before condensation can occur on bag surfaces.
Installation of Bags—
The improper installation of bags can result in premature failure of the
bags and increased emissions. The capital cost due to these failures can
become significant and reduce production if downtime is required to change
bags. This subsection is included to supplement manufacturers' instructions
for installation of bags. The items covered are those that have been demon-
strated by field experience to result in high bag failure rates.
Bags in shaker and reverse-air systems should be installed from the outer
walls toward the center of the compartment. Bags should be hung according to
manufacturers' recommendations by loop/hanger, eye-bolt/J-hook, or tongue/
hanger assemblies. Each bag should also be inspected before hanging to ensure
that it has no holes, is the proper size, and has a proper seam. Normally,
the bags should be hung by row, the cuffs should be placed over thimbles, and
the ring clamps should be attached. The fit of the bag over the thimble
should be checked, and loose fitting bags should be discarded. Small bags
that fail to meet specifications should not be forced over the thimbles.
After a bag is clamped, the tension should be adjusted to the manufac-
turer's specifications by using a spring tensioning device or tightening the
bag to a known length. In no case should the bag be allowed to hang freely
and fold over the thimble. Also, tension must be uniform in all bags to
provide uniform cleaning efficiency.
When a bag farther than the second row from the walkway must be replaced,
the intervening bags should be temporarily removed to allow safe installation
of the replacement bag. Otherwise, the intervening bags can be stretched and
damaged, the proper installation and tensioning of the replacement bag can be
difficult. Figure 35 illustrates correct and incorrect installation of bags.
To avoid snagging and puncturing bags, maintenance personnel should not carry
tools while in the compartment.
77
-------
oo
DAMAGE
oo
CORRECT
INCORRECT
Figure 35. Correct and incorrect installation of bags.
78
-------
The proper installation of a snap-ring-type bag requires collapse of the
ring inward with the fingers and insertion of the cuff into the tube sheet
opening. The circular portion of the ring should be placed in the seat, and
the ring should be released. Fingers should be placed inside the ring allow-
ing the bag to collapse into the tube sheet opening, and the ring should be
pressed into place. The bag should be tensioned as necessary (Figure 36).
Hopper Bridging—
Bridging is a term applied to the blocking of dust discharge through an
opening by the agglomeration of the dust. Bridging commonly occurs a short
distance above the apex of the fabric filter hoppers and results in partial or
complete closure of the discharge.
Common causes of the agglomeration are moisture, oils, and temperature
drop. In fabric filters that operate below or near the dewpoint, the added
drop in temperature in the hopper as a result of radiative cooling initiates
agglomeration of the dust. Moisture enhances agglomeration of the dust, and
cake gradually builds up. The area available for dust discharge is reduced
and complete bridging eventually occurs. Agglomeration can be initiated by a
drop in dust temperature resulting from air inleakage through flanges, gas-
kets, doors, or weld failures in the hopper.
Continuous or repeated occurrences of hopper bridging indicate a chronic
temperature or moisture control problem in the ventilation and control equip-
ment system. Careful inspection of hoppers should be made to determine gas
inleakage points, and repairs should be made. Bridging is not a common prob-
lem in tight systems that are insulated and that operate at proper tempera-
tures.
Dampers—
Dampers are used to direct gas flows ov isolate compartments for cleaning
or repair. If these dampers do not function to seal the compartment in shaker
fabric filters or to change the direction of gas flow in reverse-air fabric
filters, proper cleaning of the bags cannot be accomplished. Malfunction
increases pressure drop, but in multiple-compartment systems does not neces-
sarily shut the system down. Because all dampers leak under adverse condi-
tions, dampers and seats should be inspected to minimize leakage.
79
-------
SNAP RING
WOUND WITH
FIBER
TUBE SHEET
Figure 36. Proper method of installing bag in tube sheet with snap rings.
80
-------
Compressed Gas System--
The air used to activate the dampers and pulse-clean bags must be clean
and dry. An in-line gas dryer (such as a dessicant, refrigerant, or filter)
should be used to remove oil and water from the gas stream prior to introduc-
tion to the filter. As a safety precaution, a reserve tank with blowdown
should be used at the filter to collect oil and water. If not collected, oil
and water blind bags and can freeze in diaphragms during cold weather. The
dryer should be serviced according to the manufacturer's recommendations. An
internal inspection of the filter bags should be conducted periodically to
check for oil and water.
Pulse Diaphragms--
Pulse diaphragms are used to open the valve seat in pulse-jet cleaning
systems and provide a sharp finite surge of compressed gas through the blow
tube to the venturi. The diaphragm in the closed position is held against the
seat by compressed air and a spring. The compressed air is discharged through
a solenoid valve and creates a pressure differential, which pulls the dia-
phragm from the seat. This momentarily allows passage of gas under the seat.
Closure of the solenoid valve reestablishes the seal.
The solenoid commonly fails because of water freezing in the gas stream
or because of electrical failure. In either case, the cleaning pulse cannot
be initiated. If the solenoid does not seat, a constant release of compressed
gas is heard.
The cleaning system can also fail because of diaphragm rupture or impro-
per diaphragm seating. Constant bleeding of compressed gas into the blow tube
is then heard.
A reduction in cleaning efficiency can occur if the diaphragm returns to
the seat sluggishly. This can be caused by water, oil, or grit fouling the
return spring, and can be detected audibly as a sharp pulse that trails off.
In evaluating the pulse cleaning system, the -inspector should inspect the
reserve air tank for water and listen for malfunctions of each pulse system
through one cleaning cycle.
3.2.3 Inspection Procedures
Internal inspections of fabric filters are the only truly reliable means
for identifying fabric filter problems. An external check only determines
81
-------
gross emissions (high opacities) caused by missing or torn bags. Items that
should be checked in an external inspection include:
0 Pulse jet system pressure
0 Solenoids
0 Reverse air blowers
0 Shakers
0 The solids removal system, including the screw conveyor, the
pneumatic conveying system, heaters, and vibrators.
Pressure drop across each compartment and the total fabric system should be
measured. However, pressure drop measurements are only effective for indicat-
ing if a compartment is out of service since pressure drop tends to equalize
over the compartments, even those with missing or plugged bags. Comparison of
the overall pressure drop with previous inspection measurements can indicate
trends in overall fabric filter condition.
Internal inspections can indicate many of the problems and malfunctions
discussed earlier. However, internal inspections must be made with the unit
off-line; adequate safety precautions should be taken to insure that safety is
not compromised. Safety precautions are outlined in Section 4.
The internal inspection checks the condition of the fabric bags. The in-
spector should look for bag tears, bag deterioration either by erosion or cor-
rosion, missing bags, bags with oil from a compressed-air system, wet bags
from acid dewpoint problems or inleakage, improper bag tension, and deposits
on the clean air side of the fabric filter. Hoppers can be checked for incom-
plete solids removal and corrosion. Appendix A contains a detailed checklist
for performing a fabric filter inspection.
3.3 ELECTROSTATIC PRECIPITATORS
3.3.1 Introduction
Electrostatic precipitators incorporate three basic processes: 1) trans-
fer of electric charge to suspended particles in the gas stream, 2) estab-
lishment of an electric field to remove the particles to suitable collecting
electrodes, and 3) removal of particles from the electrodes and particle
82
-------
collection with as little Toss to the atmosphere as possible. Figure 37
illustrates these basic processes.
An ESP consists of a thermally insulated steel housing, its internal com-
ponents, and its power supply equipment. The internal components include
grounded steel plates (collecting electrodes) and metal rods or wires (dis-
charge electrodes) that are suspended between the plates. The discharge elec-
trodes are insulated from ground and are negatively charged at 15,000 to
80,000 volts d.c.6 The electrical field between the wires and plates ionizes
electronegative gas molecules (e.g., 02, S02) that charge the suspended parti-
cles. The electrical charge creates a force on the particles (about 3000
times the force of gravity) that pulls them toward the collection plates. The
collected dust particles are removed by periodical rapping of the collection
plates, which causes the dust to fall in sheets into a receiving hopper.
Most precipitators use plate-type collection electrodes and pyramidal
hoppers. Figure 38 presents an example of this type of precipitator. Gas
flow through the ESP is normally horizontal.
3.3.2 Resistivity Effects
Dust resistivity outside the range of 108 to 1010 ohm-cm can greatly
limit precipitator performance. Fly ash resistivity depends primarily on the
chemical composition of the ash, the ambient flue gas temperature, and the
amounts of water vapor and sulfur trioxide (S03) in the flue gas. At tempera-
tures below 80°C (175°F), current conduction occurs principally along the
surface layer of the dust and is related to the absorption of water vapor and
other conditioning agents in the flue gas. Resistivity of fly ash is inverse-
ly related to the amount of S03 and moisture in the flue gas. Because low-
sulfur coal releases very little S03, high-resistivity fly ash results. At
elevated temperatures up to 200°C (400°F), conduction takes place primarily
through the bulk of the material, and resistivity depends on the chemical
composition of the material. Carbon carry-over has very low resistivity and
is hard to hold on the collecting plates. Above 200°C (400°F), resistivity is
generally below the critical value of 1010 ohm-cm. Figure 39 shows a typical
relationship between resistivity and temperature.
83
-------
CD
•£.
O
IS)
LlJ
UJ
O
Di
O
c
O
-p
ra
-P
U
CU
Q.
U
•P
ro
•P
o
o
cu
r—
CU
c:
0)
>
'o
>
QJ
10
I/)
CU
U
O
a.
u
ca
CO
cu
O)
84
-------
Transformer-Rectifier
Ground Switch Box
on Transformer
Top End
Frames
High Voltage
Conductor
High Tension
Support Insulators
Perforated
Distribution
Plates
Bottom End
Frames
Upper H.T. Hanger Assembly
(Hanger and Hanger Frame)
Upper H.T. Wire
Support Frame
Discharge Electrode
Vibrator
Collecting Electrode
M.I.G.I. Rappers
Top Housing
Hot Roof
Access Door
Hot R6of
Side
Frames
Discharge
Electrode
Access Door
Between
Collecting Plate
Sections
Precipitator
Base Plate
Slide Plate
Package
Support Structure
Cap Plate
Steadying Bars
Lower H.T.
Steadying Frame
Collecting
Electrodes
Figure 38. Typical electrostatic precipitator with top housing.
Courtesy of Research Cottrell.
85
-------
o
i/o
t-H
to
1000/TEMP., °K
3.2 2.8 2.4 2.0 1.6 1.2
10
14
10
13
10
12
00 in
t—i IU
11
10
10
10=
SURFACE
RESISTIVITY__ \ | VOLUME
M RESISTIVITY
I COMPOSITE
•OF SURFACE!
AND VOLUME,
(RESISTIVITY]
1111111
70 150 250 400 600 800 1000
100 200 300
TEMP., °C
Figure 39. Typical temperature-resistivity relationship.
86
-------
3.3.3 Instrumental on
Reliable ESP performance depends on the effective control of operating
parameters. An ESP should be equipped with instrumentation to monitor and
record the major operating parameters that indicate ESP performance, and the
inspector should be able to understand these basic ESP data.
Electrostatic precipitator instrumentation includes monitors for power
input, rapper intensity, and hopper dust levels. The power input parameters
include precipitator current, voltage, and spark rate. The instrumentation is
generally located close to the ESP unit. When a plant has more than one ESP,
a centrally located control room may contain the instrumentation for all of
the ESP units.
An ESP power supply usually includes several transformer-rectifier (T-R)
sets, each having one or more' bus sections. Primary voltage and current are
measured for each T-R set; spark rate, secondary voltage, and current are
measured for each bus section. Sometimes oxygen and temperature are measured
at the ESP inlet. An opacity sensor is frequently located at the ESP outlet
to indicate emission levels. The ESP shown in Figure 40 has four primary
voltmeters and four primary ammeters. Instrumentation on the secondary side
consists of eight voltmeters, eight ammeters, and eight spark rate meters.
Primary Instrumentation—
Most ESP's are equipped with a primary voltmeter, and normal operating
voltage is 250 to 460 volts. An indication of zero voltage on the primary
side may be due to an open primary circuit. An indication of high voltage on
the primary is unlikely, but it could be due to an open transformer primary
circuit or an improper connection. A faulty, open, or disconnected precipita-
tor; an open.bus; or a faulty rectifier will also cause the primary voltage to
be high. An indication of low voltage on the primary side could result from
several conditions such as a leak in the high-voltage insulation, a high dust
level in the hoppers, excessive dust on the electrodes, or swinging elec-
trodes.
The ammeter on the primary side of the ESP indicates that the current is
being drawn by the ESP. Together, the current and voltage readings on the
primary side indicate the power input to a particular section of an ESP.
Sometimes an ammeter is labeled to indicate the normal range of primary
87
-------
88
-------
current, but the range is different for each unit, depending on design, size,
and operating conditions. Baseline conditions established during a compliance
test are a more reliable indication of proper operation. Any deviation from
this range indicates abnormal operation. If the primary current and voltage
are both zero, this indicates an open primary circuit. Low primary current
combined with high primary voltage suggests an open transformer primary or
secondary circuit. Low primary current and voltage indicate an open d.c. rec-
tifier.
Irregular primary current coupled with low primary voltage indicates a
high-resistance short in the circuit. Possible causes are an electrode short
with dust in the hopper, excessive dust on collecting surfaces, excessive dust
on electrodes, support insulator arcing, or the presence of foreign materials.
A broken swinging electrode will cause an intermittent short, which is indi-
cated by low primary voltage and cycling primary current.
Secondary Instrumentation—
Because primary instrumentation can be very misleading, the use of
secondary meters is often more useful. Secondary instrumentation indicates
the electrical parameters for individual bus sections. The instrumentation
generally includes a kilovoltmeter, a mi Hiammeter, and a spark rate meter for
each bus section. The secondary voltmeter, which shows the voltage at the
discharge electrodes, is sometimes labeled to indicate the normal operating
voltage range. The indicated range may not be very reliable, however, and
baseline conditions from a compliance test are probably a better indicator of
proper operation. Zero voltage on the secondary may be due to an open primary
circuit. High voltage on the primary side and no voltage on the secondary
side indicate a faulty, open, or disconnected precipitator; an open bus; or a
faulty rectifier.
Low voltage on the secondary side coupled with the low voltage on the
primary side could result from several operating problems such as a leak in
the high-voltage insulation, excessive dust in the hoppers or on the elec-
trodes, or swinging electrodes. Correction may require shutdown.
The secondary ammeter indicates the discharge electrode current. The
current and voltage readings on the secondary side indicate the power input to
the discharge electrodes.
89
-------
The secondary current is measured in mi Hi amperes. The secondary ammeter
is usually labeled to indicate the normal secondary current range. Deviation
from that range indicates improper operating conditions in the precipitator.
The absence of secondary current and voltage indicates an open primary cir-
cuit. Minimal secondary current in association with high voltage is generally
due to an open transformer primary or secondary circuit. An open d.c. recti-
fier will cause a low current flow and low voltage in the circuit. As with
primary circuitry, irregular secondary current coupled with low secondary
voltage indicates a high-resistance short in the circuit. The short is usual-
ly caused by excessive dust, foreign materials, or arcing. Again, a broken
swinging electrode causes an intermittent short, which is indicated by low
voltage and cycling current. On coal-fired industrial boilers, the optimum
spark rate is around 100 sparks per minute. Excessive sparking reduces avail-
able power for particle charging; a low spark rate indicates a reduction in
power supply.
External Instrumentation--
Certain instruments external to the ESP that are useful for diagnosis of
ESP operation include instruments that measure inlet gas flow, inlet gas
temperature, and flue gas opacity at the ESP outlet. Instruments also monitor
the condition of the hopper ash discharge system and the rapping system.
Because federal and state regulations generally limit the opacity of the flue
gases as well as particulate emissions, many ESP installations are equipped
with continuous opacity recorders.
The gas flow rate and temperature are indicators of ESP loading. Varia-
tions from the normal design ranges will affect ESP performance and should be
investigated.
Efficient removal of ash from the hoppers is important for proper ESP
performance. Ash removal systems at ESP installations are generally equipped
with instrumentation for monitoring hopper emptying cycles. Hopper level
alarms are also common and useful. Control panel lights are used to indicate
the operation of hopper heaters and vibrators. Zero motion switches may be
used on rotary air-lock valves and on screw conveyors to detect malfunctions.
Pressure switches and alarms may be used on pneumatic dust handling systems to
detect operating problems.
90
-------
3.3.4 Operation and Maintenance
The following subsections present ESP operating procedures and mainten-
ance requirements and describe common ESP malfunctions. This information will
help .the inspector determine whether or not the company has an adequate main-
tenance program.
Power Supply—
During normal operation, the power to the ESP is optimized by automatic
controls that vary the power in response to the spark rate.
Rappers and Vibrators—
The rapper system mechanically removes dust from the collecting plates.
The most common system consists of magnetic-impulse, gravity-impact rappers
that periodically impact the collecting plates to remove dust deposits. The
main components of the system are the rappers and the electrical controls.
The electrical controls provide separate adjustments for various groups of
rappers; these can be independently adjusted from zero to maximum rapping
intensity. The control cycles are adjusted to regulate the release of dust
from the collecting plates and to prevent undesirable puffing from the stack.
During normal operation, a short-duration d.c. pulse through the coil of
the rapper supplies the energy to elevate the steel slug. The slug is raised
by the magnetic field of the coil and then allowed to fall back and strike an
anvil bar connected to a bank of collecting electrodes within the precipita-
tor. The shock transmitted to the collecting electrodes dislodges the accumu-
lated dust. In some applications, the magnetic-impulse, gravity-impact rapper
is used to clean the ESP discharge wires. For this purpose, the rapper
strikes the electrode supporting frame in the same manner, except that an
insulator isolates it from the high voltage of the frame. Some installations
have mechanical rappers consisting of a single hammer assembly mounted on a
shaft which raps each frame. A low-speed gear motor is linked to the hammer
shaft by a drive insulator, fork, and linkage assembly. Rapping intensity is
governed by the hammer weight, and frequency is governed by the shaft rotation
speed.
A vibrating system can be used on either the collecting plates or the
discharge wires to dislodge accumulations of particles. The vibrator is an
electromagnetic device whose coil is energized by alternating current. Each
91
-------
time the coil is energized, the resulting vibration is transmitted through a
rod to the high-tension-wire supporting frame or collecting plates (Figure
41). The number of vibrators depends on the number of high-tension frames or
collecting plates in the system.
For each installation, a certain intensity and period of vibration will
produce the best collecting efficiency. Low intensity will result in heavy
buildup of dust on the discharge wires which reduces the sparkover distance
between the electrodes. This limits the power input to the ESP and tends to
suppress formation of the ions required for precipitation. Dust buildup also
alters the normal distribution of electrostatic forces in the treatment zone
and can lead to oscillation of the discharge wires and the high-tension frame.
Because reentrainmeht from rapping can be a significant portion of the total
emissions, it is important that the rapping system be adjusted to minimize
reentrainment.
Maintenance Requirements—
At each ESP installation, the inspector should encourage the facility
operator to follow a preventive maintenance schedule that lists the ESP parts
to be checked and maintained daily, weekly, monthly, quarterly, and in speci-
fied situations. Such a schedule will help to ensure that the unit functions
properly on a daily basis and that emission violations and opacity problems
are minimized. Table 4 summarizes the maintenance procedures that the inspec-
tor can use to aid the source in setting up an effective preventive mainten-
ance program.
3.3.5 Malfunctions
ESP equipment components are subject to failure or malfunction that can
cause an increase in emissions. Malfunctions may be caused by faulty design,
installation, or operation of the ESP, or they may involve electrical, gas
flow, rapping, or mechanical problems. The inspector should be aware of the
common ESP malfunctions, their effects on emissions, corrective actions, and
preventive measures. Generally stat,e and local control agencies require plant
officials to report excess emissions that are caused by ESP malfunctions.
Table 5 lists common ESP problems.
Monthly records of all malfunctions should be kept by plant and unit,
along with total hours that T-R sets are operated, number of hours T-R sets
92
-------
DISCHARGE
ELECTRODE
VIBRATOR
DISCHARGE
ELECTRODE
VIBRATOR
DISCHARGE ELECTRODE VIBRATOR
AND INSULATOR ASSEMBLY
COLLECTING
ELECTRODE
RAPPER
RAPPER
COUPLING
COLLECTING ELECTRODE RAPPER
AND INSULATOR ASSEMBLY
Figure 41. Vibrator and rapper assembly,
and precipitator high-voltage frame.
93
-------
TABLE 4. MAINTENANCE SCHEDULE FOR ELECTROSTATIC PRECIPITATORS.
Enter on daily log
1. Boiler operating parameters
2. Flue gas analysis
3. Coal characteristics
4. T-R control set readings
5. Transmissometer calibration
Check daily
1. T-R control set readings
2. Rapper and vibrator control settings
3. Ash removal system
4. T-R control room ventilation system
Check Weekly
1. Operation of rappers and vibrators
2. Control sets (for internal dirt)
3. Air filters for control sets and ESP penthouse
Enter on weekly log
1. ESP voltage-current data
2. Graph ESP voltage-current data
Check monthly
1. Pressurization of ESP penthouse
2. Standby fan operation (manually)
Perform quarterly
1. Clean and dress contact surfaces of HW-FW electrical distribution.
2. Lubricate pivots.
Perform semiannually
1. Clean and lubricate access door hinges and test connections.
2. Inspect exterior for loose insulation, corrosion, loose joints, and
other defects.
3. Check for points of gas leakage (in or out).
94
-------
TABLE 4. (continued)
Perform annually
1. Thorough internal inspection:
Check for possible leaks of oil, gas, or air at gasketed
connections.
Check for corrosion of any component.
Check for broken or misaligned wires, plates, insulators,
rappers, etc.
Check high-voltage switchgear and interlocks
Check all insulators and check for hairline cracks or tracking.
Check expansion joints on hot ESP's.
2. Check for signs of hopper leakage, reentrainment of particulate,
distribution plate blockage, and poor gas distribution.
3. Check for dust buildup in inlet and outlet flues.
4. Check for dust buildup in hoppers.
95
-------
CO
a.
co
LU
o
LU
o
o
co
co
CO
LU
CO
o
U_
o
co
in
LU
CO
a
91
b
3
I
91
iH
U
g
9)
b
DM
g
•H
U
U
91
U
U
V
b
o
U
%,
B
B 91
O i-l
U
u *4
ft IM
O UH
<*• 91
U O*
V)
[U
to
3
n
°
§
*H
u
E
3
U-I
I-l
£
91 91
b a.
14-1 O
b
8*
9) b •
a. o •
CLUH B
o o
r-l U
U B b
91 91 91
-C 3 O.
o tr o
^
91 •
o 6
b r-4
4J UH
U
at a
— i a
91 00
C u
00 U
•H U
1-4 b
e b
91 O
as u
u
U b
91 91
UJ 3
UH 0
to t-H
X "O
r-l B
rH S)
q
U 91
•H O X
u B U
to g E
0 I 01
b b -H
•o o o
B b UH
U O» 9t
a
b
&
a.
0
I
a
91
B
to
b
o a
O 7
O
B O.r-1
00 3 Uj
T4 -O
M -4 U
at —4 fa
•a 3 oo
.0
b b
O .C O
o n o
a. < a.
9t
O
b
rj «J
91 E
rH 9>
91 B
E
b oo
S, ~a
w
u
91 1
J= K
U 91
•• 4J
§c
91
91 -H
•H O
.0 -H
O UH
O. 3
to
b B
•H b
O O
P3 'I I
f
91
•O
• 0
b
4J
U
9)
91
91
CJ
a
a
91
OS
•s
U
1 3
iH -0
u-i at
iu b
u
o
at
E 3
0 -O
u u
3 E
•a 91
3
B
0
•H
JJ
4<
O
91
X
u
a
b
91
a.
o
j:
u
2.
01
B
M
10
91
3
3
t
91
•J
•8
b
91
E
IH
rH
U
X
rH
B
91
3
er
2
a
9)
b
u
O
91
rH
91
B
O
u
3
iH
b
4J
to
•H
^
n
b
«
g
ul
b
o
o
B.
4J
U
91
O.
a
B
•H
• «
b
b
O
U-I
01
to
91
U
X
91
B"
tu
>
91
E
3
to
•H
•H
E
3
3
O
b
Si
r4
U
B
91
3
rr
91
b
U-I
a
b
91
O.
o.
n
b
b
a
to
to
91
U
91
0
91
3
T3
B
O
J=
b
(0
91
91
b
b
O
CO
B
91
B
91
b
>r4
tr
91
b
§
•H
to
3
§
O
(U
1
n
o
o. u a.
J= 3 u 00 3
a a m .e B -a
b 3 0) 01 10 U 9IOOiHrH9l m bbeo j: u
iH9l9IJ3Bb9IE O>H *a9)u*
(ObXE9ia* to oo a. 01 -H 91
tOT3bUO«3B 10 ^U b9l
o
a
4J
a
0)
E
O
•H
a
a
1
S
o
B
O
B
91
b
a
91
b •
91 a)
£ B
E-< 91
rH
• O
a b
•H O.
to
15 rH
91 O
> -H
u a
q b
JJ 01
•H a.
rH O
Q
3 UH
cr o
n B
o
B iH
0 W
U
•a E
91 3
01
-------
TJ
0)
3
C
•r~
-P
C
O
o
LO
c
o
4J
tj
U-i
tw
CO
0)
u
g
to
1
4J
B
01
5,
b
c-
B
O
U
ffl
OJ
^
4J
U
01
kl
kl
o
ffl
u
E
Ol
i-l
U
tM
14-1
01
a.
CO
u
OJ
tn
1
01
B
0
•H
U
Malfun
1 kl
01 01
ki a jf co
u-i o u 01 •
kl Ol 4J 01
o ax: ffl oi
b o -< oo
01 ki Q- ffl
a o — u
a.u-1 E ai 3
o o TJ o
x; >> -H o
•H U kl 00
.* U ffl 4J E
CJ C U O H
0) 0) 01 01 ki
JS 3 0.-H 3
u cr o oi -a
S 3
n o
f-H i-(
O* U-l
OJ
ki 01
kl 00
0
ki tn u
•H 01 OJ
ffl 4J kl
O> ffl kl
OJ rH O
a: a. u
o
E
•H
U
•H
144
01
•O
01
U
3
•a
0)
02
tn
tn 0)
ki iH
01 4J
O- IH
a. b
o a tn
x: •-< oi
3 ki
E 00 3
— 1 4) 4-1
ki a
a. ki ki
3 i-t 01
•o a.
•H 3 B
•H O 01
3 >-l 4J
XI UJ
x: tn 'Si
tn ffl .H
•.
.* u
u a
01 01
6 §•
•o
0
kl
u
01
01
kl
v4
n
a.
OJ
1 1 4J
•H 01 3
u-i E
oj o 1-1
4J
«-* Q) Q)
3 3
ffl >>
01 0 T3
ki E 01
O 01 CJ
01 i-l 3
O O T3
flow
ctrodes
n oi
ffl *-(
00 OJ
B B
OJ 01
> M
a o
E ki
=3 a
i
o
U OJ
0 -1
01
00
E 00
-1 E
4J -r4 CO
ffl 00 01
kl E T3
XI -H O
1"< 3 kl
> S 4J
1 O
—1 <-> 4)
0 S
O E 01
01 -C
01 3 u
oo cr
B Ol 01
a ki ki •
CO C,
^ CO 01
O 01 01 ki
01 00 Ji kl
X Q Q O
CJ 4J B CJ
n
a I i
oo an
1 h f<
-H OJ M
• *> ffl a. oi
tn e L.
01 kt OJ
Tl O 4J 01
0 C
kl 00 B 3
«J E -H T3
O i-l OJ
OJ E 1/1 k,
*H O B
Ol -H O O
4J -H 4J
ffl "O ffl 01
01 B ki ki
"H O 01 3
CJ CJ 4J 4J
CJ
c
a>
1-1
u
•H
-
4J r~ 1 «-4
U 0) — 1 C.
•H ^ U 3
> oi ki in
IH n
4J E a. ki
01 O OJ
•rf OJ 3
co x: B o
01 « -H Q.
kl ffl U-l
01
4J 01 X 4J
M > rt ffl
3 -H -1 3
"13 tn ffl cr
tn 3 01
x; oi tn TS
00 0 3 ffl
M X B E
a: M 3 M
rH
OJ
> 4J
01 3
— 1 O- O
E O
01 iH 4J
4J
ffl ki 01
3 0) OO
cr 3 ffl
OJ O 4J ,~.
T3 O..H 3
ffl O O
B u-i > _i
i-i O —
^
JJ
•H
•H
U
u reels
ements
In-sit
measur
i
u
01
n
01
in
n •
Ol E
kl O
O -H
E 4J
•H ffl
N
4J a
•H B
> 0
•H TH
^
0
kl
B 4J
0 B
•H 0
4-1 CJ
n
N "U
-H ffl
sectJona
ectif ier
01 ki
4-1 E
re u o
3 01 -H
or a. 4J
01 0 Q
•a b b
ffl Q. OJ
E e a
I-l VH O
tn
01
•§
u
u
01
01
14-1
o
B
i
00
•H
f-l
Q
CO
01
XI
a
tn
ffl
01
CO
01
>
0
XI
re
CO
a
0)
i
re
CO
u
E
•—I
U
•H
U-l
U-l
01
E
iH
6
o
•H
4J
u
3
•a
01
a:
m
V
O "
kl 00
4J E
CJ -H
QJ ^
o> a
a.
B tn
0
Ol
4J tn
re n
— i a)
B x
3 OJ
CJ
cj tn
n oi
tn
x: 3
CO ffl
•< CJ
ffl
E
o
kl
o
CJ
u
4J
F-H
O
E
reduction
00
E
ki
3
cr
01
ai
Ol
00
kl
ra
0
01
00
«
i
•- kl -H
>, tn o k,
«-H ffl uj 3
G >, Jt m
01 ki 0 01
3 TJ OJ kl
cr x; a
OJ TJ CJ
b B 01
•5 sil
CJ -H
•vH 4J
U ffl
ffl kl
4J OJ
»H a
•-I O
a
3 "4-1
cr o
a B
o
E •<
o u
u
•O E
0) 3
CO U-l
01
3 a
CJ
tn u
1-1 «
•a
E
OJ O
XI i-l
u
>> n
-j -a
B ffl
o h
oo
E OJ
ffl T3
u
OJ
09 U
e E
OJ a
o o
kl U^
a b
oi
B a
o
•H 01
u B
ffl •*
a oj
•H 4J
CJ 01
OJ 01
x: u
H a
(U
3
•H
4-)
C
O
U
ca
-------
T3
0}
04
c
o
u
M
01
•r*
U
V
b
5
Q
O
E g
O "H
U
U M
U U-t
V U-i
U4 QJ
w a.
e/J
U
0)
n
t3
m
c
o
•H
U
CJ
1
i
S§
O u
X 0 u
.0 O
.e .0 •
X 69 di
•H |rj U CO
01 .H E O
O U
X Ot •**
UJ 03 U U
•rl tO tO iJ.
•U 01 b X
B b u oi
OI U B
•0 E 01 UJ
>-j -r< o o
,
03
a
01
»-i
CO
1
y 01
B B
01 -H
i-l to
O b O,
•rt U CO
uj B Id
01 01 .6
b 00
b 3
01 U O
3 co b
0 3 J=
_] "0 u
b
X
01
'E
o
u
u
09
3
•a
I
Eh
09
b
Ol OI
oo a.
09 a.
Jt 0
a j=
01
B 00
•n 3
o
b b
b 1
0 B
"H B 1
X t) 18 E
—1C 10
4J 3 03 0.
B O b X
01 b o oi
3 tO O
cr -a oi
01 E 00
b 0 B E
UJ in O 10
vj Q 4J m «
U b CJ B
01 b Ol b O
50 a o -H
U 09 Uj 09
,
09
10
01
to
01
CO
I
O b
03 Q
•H a.
ta 03
- 01
01 03
> B
o 01
CO B
•O i-l
IJ
0 U
u to
oo o
BUB
•H E O
.H ^1 -rt
vu n a
to to oi
eo oo 03
u
E
01 X
cj o
b E
01 01
D.U
rj 01
i-J UJ 01
5 oi oi
03 03
B
tO iJ 03
03
X a. 01
-< 0 -<
E b B
O TJ 3
E
o
iJ
4J
a
I-J.
•H a.
CO
b f*1
01
D.UJ
2 °
8-g
iJ -H
4J
1 b
00
•rt 01
03 >
01 *«H
•a «->
u
j:
g
to
01 03 B
•• 00 01 to
09 O. 10 4J b
W CO 03 tO uj
tO U 09 i-J
Q. 10 O. E
x-a a. o
JO E 01 -J
3 •a > n
§O to O B
b Ol £ Ol
o a -o • u
b oi •
O b 03 01 u
u B O ->4 b E
(0 01 UJ tO 3 -H
u u b 4J O
•H 03 01 Q a
a. x B o b
iH 09 -H U 01 3
o —i a. oi
oi b -a B TJ
b 01 E O 8
D-i-f O i-l u T>
•H b iJ.
OJ o B 01 CO O
N a 01 a. a to
60 iJ JD 01 01
b 01 pH 01 >
oi u 09 a. 3 o
E uj a B -i a
u to .B eo uj to
09 01
oo o
01 10
3
A oi
3 u
SUE
•rl 0) i-l
Sb O
oi a
B a.
iJ B 3
JO 0) 01
•CUT)
1 03
01 .*
b b ot to oo
a o b oi B
•H O) i-J iJ 0)
i-l u n a
•H 01 03 b 3 O •
U U 01 iH 10 b 01
B B u (8 o TJ O
3 i-l tO B
*j •• a u a
« g a x o E g
i-l O Q i-l 63 b
.a -H b 3 oi o o
i-l -U O fO > -H UJ
00 to 01 uj b
•H U 03 6 T) •* Ol
•H -H 00 Ol BO.
00 0. 3 u X 00
oi -H i-j to a IH B
2 0 a oi B 03
^
o
I-l
Jl
09
01
01
b
3
4J
2 .
01 w
8-5
oi o
H a
B
o
03
o
b
b
8
UJ
o
n
u
03
01
u
E
o
1-1
09
•H.
1
§
01
b
to
01
b •
01 09
iSg
J3
' O
09 b
09
s «
E
01 O
> 1-1
iJ U
u a
n b
U 01
s §•
10
ir'o
„ g
E -H
O u
u
•O E
OJ 3
03 UJ
03
3 o)
CJ
03 00
•H 10
T)
B
01 O
u
x to
*-H t)
E 10
0 b
oo
B 01
a -o
u
01
a u
"o o
a. b
01
§ °-
u S
10 -H
u B
IJ b
Q. Ol
3
B
•H
-p
C
O
O
98
-------
o
u
LT>
ca
eo
O
ft, O
O
C
01
•H
CJ
i-l
VM
VM
01
C
c
o
•H
4J
CJ
3
eu
3
u
tn eo
kl kl
o cu
4J O.
CO S
3 4-1
to
C 3
•H O
t-4
C '• i
to O
«' CU
tn eo
01 D
4-1 CO
CO U
»— i eu
a. ja
• -a
01 01
01 — 1
ki 3
•H O
00
to
00
00
3
r-4
a.
01
a.
o
X
0)
1^4
>
e
CL, 0
•• t!
co c
H ea
a. tn
a M
o oi
JS U
to
VM 01
o j:
e
o
(0
3
00
B 01
•H U
C
kl 10
01 C
a. oi
P. 4j
o c
J= 1-1
0) E
4J
CO ki
3 CD
v a.
oi o
•a ki
c s"
c
o
•H
U
rH
3
CO
c
r- 1
2
£^
j:
en
o
X
00
c
01
3
to
to
.*
CO
01
M
cu
o
CO
Ol
3
4J
n
•a
•H
o
to
o
eu
w
3
01
i-l
•
C
0
•H
4-t
to
en
e
01
•a
c
o
o
1 C
1 to O
U kt kl 1-4
C .0 0) 4J
3 01 1-4 O. CJ
VM c > a. c u
-40 03.0
§1-4 M £ VM C
4J. 01 0) r-4
cj o) tx o eg ki
B c > a 4J B oi
oi 3 -H o c tn u
4JeUVM<0.n 1-1 4-1 kl >— 4
eo oo "H > jr cu 1-1
xeora VM *aoo@VM
cnj^STJO OI-H.H
CO • -H CX Ol 4J kl
oocukiO4^ 0.3 cu
Choice o -a 3
•H 3OIO) ^t t» C O
^stnO-HE T3-HfC!rH
Ol eo -H O 4-» 4J JS
>00^010J fH4JT3
C 3 CO O -4 C tj
0 1 1 1 "-> -4 J3 0 0 01
cj -a ki c - 1 oo
1C eocneuSeuuc
-do cnkiuo— icjeo
co-H -HoeOkiO3J"
<4J i;4Js:vMcnwo
ki
o
'VM
CO
J
u a.
3 a
to
cr ki
01
•a vu
CO' O
i
0)
M
3
to e
tfl 1-1
9)
B 4-1
c
" §
3 3
•0 ki
u
-H CO
CO C
CJ -H
•H
U 00
ex c
O -H
01
u
3
•a
01
kl
^
9
B
eo >,
Ol CJ
O eu
kl 1H
4J CJ
CJ i-l
Ol !M
rH VM
01 01
•a
4J
01
3
•TJ
CO
C eo
M i-4
•H S
CO
eu u
•0 ki
01
kl CX
o a
o cq
CU K
1 —4
•H 1-4
> CO
»
cc a
C kl
•H 0
ex u
a. eo
a ki
kl JO
•
S
to
01
to
4J
•H
X
eu
Cu
S
3
T3
01
>fc
Ol
O
J3
eo
m
eo
01
B
CO
. 01
o
J3
CO
CO
CO
CU
a
CO
tn
•o
c
CO
J=
to
to
en
c
•H
to
kl
U
C
eu
01
c
00
•H
0)
01
•o
kl
§
cu
01
tn
§
c
1-1
o
&
u
u
CO
ex
S
1-4
kl
O
oo
c
1-4
4J *
co eu
U CJ
.0 kl
•H O
U
c
01
•H
u
i-4
VM
VM
01
CO
01
CJ
3
•o
01
kl
Ol
0
kl
-0 0
CU VM
4J
to oo
3 C
^ a
eo a
CO CO
•H kl
B
ki
CO CU
ki ex
Oi O
ex M
ex ex
00
c
•H
a.
a
a
ki
(U C/)
-I
.0
• o
01 ki
1-1 a
n
CO -H
.e co
c
01 O
> —I
•H 4J
U CO
CO kl
U 01
-4 Cv,
^ O
n
3 VM
cr o
to c
o
C i-l
O iJ
o
TJ e
01 3
to VM
W
3 10
U
to to
C CO
O M
00
C 01
to -a
ej
cu
tn u
e c
01 co
o o
kl VM
O. kl
01
§ a
CO -H
U S
CJ 0)
tu tj
o en
ki
en o
01 4J
VM >H
VM ex
01 -H
u
Ol 01
iC kl
H CX
CO
0)
3
C
•H
4->
C
O
U
99
-------
•o
(U
•r-
-P
o
u
in
UJ
CO
E
O
u
U
UH
u
a
01
§
a
B 4J
01 'J
01 10
3 <-•
01 O 1
.O O JC
oo
b j: -ri
01 o j:
b " E
0 * -rt
a a
E Ol 4J
b co o
4J 4-1 JS
—1 a
B o
•rf > b
1 O
E _a a
o .c co
b ol
CO r-l
E
O
•H
CO
E
•rl
8
co
u
B
Ol O
b U
3
VI T3
CJ rH
3 01
4J U4
60
01 E
00 iH
n u
4J CO
r^ r-l
0 3
>
E 01
•H rH
q iH
i to
a
»/
n 60
01 3
)H rH
D.
b E
•n 3
to
a. ..
u b
b QJ
•« -H
a o
b ja
o
O B
TJ -rl
a
b
01
- CL
5
a
^ U-l
10 O
01
r-l 60
B
b i-l
01 60
rH 00
•rl 3
O rH
CO O.
(
0}
rH
J3
O
o.
1
3
a
s
•H
S
CO
01
rH
U
a
b
01
a.
a
o
•e
u
o
u
CO
rH
3
a
E
X
4-1
b
a
b
O
4J
to
rH
100
-------
are not operating, maximum number of sets out at one time, and monthly/yearly
availability of the ESP unit. Daily logs should be kept for each ESP, with
remarks on outages in each section of the ESP.
3.3.6 Inspection Procedures
Data Collection and Review of Operating Records--
The inspector should review both process and ESP operating records for
completeness and for changes in operation that may have affected ESP perform-
ance. Table 6 lists a number of items for which records should be kept.
Malfunctions of both the process and the ESP should be discussed with plant
officials, and the inspector should determine what is being done to remedy any
recurrent problems.
The first item that the inspector should check is the control sets for
the ESP, which are usually located in a room near the ESP. Plant personnel
should provide a diagram showing which fields are served by which T-R sets, as
a guide for determining out-of-service fields when reading the T-R sets.
Control panels can include primary and secondary current and voltage meters,
and a spark rate meter. If the ESP has several sections, the voltage, cur-
rent, and spark rate should be recorded for each section. The control set
readings should be compared with calibrated or design values for each section.
The inspector should check the daily log of control readings to determine
whether the readings have been drifting from normal. Drift may indicate such
problems as air leakage into air heaters or into ducts leading to the ESP,
dust buildup on ESP internals, and/or deterioration of electronic control
components. The inspector should also note inoperative meters, the number of
power supplies on manual control, and T-R sets on automatic control that may
be operating below design specifications to reduce wire breakage.
The inspector can utilize the meters to aid in diagnosing other ESP prob-
lems. The effects of fluctuating gas conditions on control readings are
presented below:
1. The voltage increases and the current decreases when the gas
temperature increases. Arcing can also develop. The voltage
decreases and the current increases when the gas temperature
decreases.
101
-------
n
4J
B
0)
g
i s
UJ
UJ
oz
i— i
tJ
t— i
Q.
UJ
UJ
O
O
O
UJ •_
01 1
O 01
UJ 3
f^ o*
•p" QJ
in M
S &*
£ 1
•
IO
111
1
CO
s
1—
n •
n en 4)
4J BE
B fl fl
01 • TJ •-!
E w IB -a
01 Cn 0) 01
U E U U
3 -H tn
tn TJ -H E
18 10 E O
0) 01 U
E *-i in «-i
0)
>iT3 O 4J
rH 01 -1 U-l
•rH E tJl-H
10 -H M
•a o
•01 01 « - 01
M 4J 4> .*
J3 - » E Cf> -i
•H 4J 01 01 10 10
rH E t7* Ul JJ CL
18 0) 18 14 rH 01
U IJ 4J 3 O
VH rH O > -
JJ 3 O 01
E O > en Cn4J
0) E E 18
W rH rH 18 (0 <8 10 ~^
H O 4J E E M !-i !-i
u tn fi fi o> oi i8
4J E it U O. a Q.
B H Hi O. O O 05
O
o
0)
1-1
3
to
n
01
u
a
1-1
ia
•H
4J
•i-l
B
JJ
•H
01
10
a
E
0
u
S
Ifl
a
E
0)
4J
V)
V)
X
3
O
r;
4J
a
0
1-1
•a
0)
-i
3
ress
0.
4J
•H
n
E
01
4J E
E 0
•H -rH
4J
-O 10
B H
10 O
•H
>1 14
O 0)
E 4J
S «
tr
01 U
M O
M-l VM
y y
O U
01 0)
£ £
u u
rH1 JH
ifl 10
Q Q
C
o
•H
B 4J
O -H
•H -a
4J E
10 o
U 0
a
o o
4J
M fl
01 rH
& 3
a n
(0 E
K H
4J
n
^
in
B
O
•rH
4-1
(0
O
ifl
01
»
01
(0
rH
10
,_4
0)
S
>•
fl
a
in
M
g.
a
o
•a
B
10
m
0)
3
rH
5
U-J
O
01
g1
10
M 01
0) 10
4J -1
<0 0)
en m
rH
4J
B
o
e]
^1 rH
05 4J 00 \
U --H 3
1-3 rH 4J
M 18 M SB CQ
O 3 3
co tr 1-1 • •
H £ >
rH 3 01 K
01 W rf X
3
fo
B
O
•rH
4J
10
E
0)
^|
4->
tn
B
•H
e«
E
•rH
•a
o
o
0)
M 1-1
0 O
a n
4J 4J
u u
ifl ifl
0 0
—1 1^
10 10
H rH
3 3
O O
•rH fl
0 0
E tn E n
10 4J 18 4J
4J B 4J B
B O B O
10 10
S m S m
rH rH
•H -rH
ifl (0
Q C
rH
rH O
0 U
1-1 JJ
JJ B
B O
O O
° S
S 0
0 rH
rH IH
UJ
M
M fl.
•rH Ifl
10 1
1 £
* O
O rH
rH <4-l
. O
rH
IS CM
10 U
m w
10 rH
Cn U
rH
01 -H
3 U
•-I ~~
fa
^,
Ifl
•o
^1
0)
a
n
!fc
Q
rH
£%
J^
o
Ul
M
0
01
ifl
4J
in
rH
•H
Ifl
Q
U)
rH
10
^
14
01
JJ
B
•H
rt>
owin
rH
J%
JJ
i
41
JQ
•rH
VH
u
0)
0)
TJ
q
4J
£
c
o
'
^ 0
c
" §
w <2
0) ^
0) 1
tn
B
•rH
•M
3
O
O
O
in
&
tn
W
M
O
(4
0)
i-H
•rH
O
•—•
0)
o
•1-1
JJ
O
E
3
rH
10
X
102
-------
2. The current and voltage increase when the moisture content of
the gas increases for any given condition.
3. The voltage increases and the current decreases when there is
an increase in the concentration of the particulate matter.
4. The voltage increases and suppresses current when there is a
decrease in the particle size.
5. The voltage increases and depresses current when there is a
higher gas velocity through the ESP.
6. Reduced voltage may be caused by air inleakage that causes
sparkover in localized areas.
7. A number of ESP fields in series will show voltage-current
ratios decreasing in the direction of gas flow.
8. The voltage is drastically reduced and the current increases
when a hopper fills with dust and causes a short.
9. Violent arcing, indicated by the meters swinging between zero
and normal, occurs if a discharge electrode breaks.
10. The voltage drops to zero at a high current reading if a T-R
unit shorts.
11. A voltage increase with normal current levels occurs if a
discharge rapper fails and the discharge wires build up with
dust.
12. A voltage decrease with normal current levels under sparking
conditions occurs if a plate rapper fails.
Table 7 presents specific examples of the effect of changing conditions
on ESP control set readings. These examples are typical of what the inspector
may find. The inspector should become familiar with these meter reading
techniques so as to detect problems during an inspection.
Electrical Equipment--
The T-R sets., rappers, and/or vibrators are often located on top of the
ESP in the penthouse. The control sets are most commonly found in the boiler
control room. The T-R sets, insulators, and rapper/vibrators should be in-
spected.
The inspector should examine insulators for moisture and cracking from
arc-over. Cracks can be spotted with a bright light during inspection. Cor-
rosion of the insulator compartment is another indication of moisture buildup.
103
-------
2
D£.
§
o
o
a.
V5
UJ
O
r-l
I-
LU
Ou
O
DC
i
to
U-l
CD
1
CJ
u_
o
to
o
UJ
UJ
U JJ I
18 B >
•O 4) -O
B t4
O -< -
O 3 <
4) 0 E
(0
>iJJ •
M C 0
<0 41 •
E H 18
O. O <
>. 4) •
M O* U
B iO .
E JJ fl
•H rH
U O «
a »
Effect
B
O
•H
JJ
•H
•o
O
u
o
o
(N
O
in
o
o
m
•a
10
o
rH
i-H
rH
3
rH
5
"J
*
rH
O
m
CM
in
in
o
vo
•(N
4)
1 U
B B
01 10
O JJ
B in
O '"H
u in
0)
jj ti
in
volume and du
lion decrease,
•eases
J-J W
in to u
18 tl 0)
U JJ -O
r*J
X,
rH
^*
S)
rH
rH
10
U-4
T)
10
O
rH
£
01
jJ
in
>t
to
N
in
rH
O
0
in
n
in
01
in
.stance increa
•H
01
01
•a
m
0
rH
JJ JJ
B in
18 3
JJ T3
Ul
B B
O-H
O
01
T3 Ul
18 18
O 01
u
E B
01 -.H
JJ
tn jj
>i 3
"
o
in
OI
I
o
CM
O
1
o
in
o
in
m
1
0
o
01
B
•H
J^
tl
10 >.
Ul O -H
£>
stance rises,
eases because
eased resisti
•rl t4 tl
in o o
0) E B
&. -H -H
4)
tl
3
JJ
10
IH
01 01
a oi
E ui
01 10
JJ 0)
ti
tn u
<0 B
O -H
*
O
rH
f\J
in
0
CO
fS
01
0)
01
stance decrea
Ul
tn
Ul
18
0)
O
01
•a
0)
3
JJ
18
01
a
E
01
JJ
01
as
in
o
o
n
in
CO
o
00
i-H
Ul
01
tn
stance decrea
•H
Ul
JJ
Ul
3
•o
J3
JJ
•H
3
n
rH
rH
•H
U-l
tl
OI
a
a
o
Oi
w
W
VD
o
O
1
o
o
in
i
o
o
o
(*».
1
muni
E 'H 01 'O
•^ rH 1 tl
rH • 3 18
O 18 Ul -^ JJ 01
E -iH O. o &
0 ^ to 3
JJ O 0) U rH 0)
B T3 U-i J3
rH . O 0)
rH tl r< JS JJ B
18 B JJ JJ B 18
U-i (8 O DO
01 01 E CU
18 01 -iH tl B W
E B 01 JJ -iH
01 U-l fi 01 O 01
0) 0) O -H E W Si
U 3 -H •< JJ
E JJ JJ BI
18 01 tl B JJ • 01
JJ J3 Ifl -H C in T3
U) O, ff< 0) B -H
•H >, 6 rH O Ul
01 tl £ViH O -H JJ
0) 10 O 3 -H JJ 3
os > jj 01 > 10 o
01
•a
o
M
JJ
o
01
1— 1
01
41
0!
IH
10 U)
O ifl
n a>
•H M
r-
o
+
0
0
o
K
1
o
M
U-l
urrent passes
to the ESP
u
0 0)
Z 01
IH
0)
•rH
•.H
JJ
O
01
1
IH
g
o
UH 0)
01 JJ
B ti
ifl 0
S JS
E-i 01
CO
o
o
o
in
o
n
ro
01
cr> I
18 -H
O 01
ui O
•rl B
•O 18
JJ
builds up on
trodes. Resis
JJ O
Ul 01
Q 01
Jj
2,
a
nj
g
01
JJ
01
01
01
tr>
ti
10
Si 0]
O rH
0) -H
•H <0
Q *w
«
i ra
Ul B
•iH O
t3 'rl Pi
JJ 0>
(8 -H 0)
B -a .*
O T3
tl < O
0 JJ
ses because o
ge decreases.
age required
ent constant
18 IH JJ ti
01 18 rH tl
ti J3 O 3
O U > O
O
*~
o
in
in
vo
cs
4)
^
18
JJ
rH Qj
0 01
> 01
,
01 O
king increase
be reduced ti
ent constant
ti jJ IH
18 Ul IJ
a 3 3
to E o
t.
8,
Ou
nj
J^
Q)
4J
rJ
r-4
Cu
_,
0
•H
JJ
oi in
rH 1-4
i-H -H
8m
U-l
o
rH
104
-------
The inspector should check to see that the pressurization fan for the top
housing or insulator compartment is operating properly, and that air filters
for control sets and the top housing are not plugged. The condition of access
hatch covers should also be noted.
The inspector should check rapper and vibrator action visually and/or by
feel. A uniform rhythmic tapping of metal to metal characterizes rappers;
vibrators emit a loud buzzing sound. Any irregular sounds may indicate impro-
per rapper or vibrator operation. The plant should provide a diagram of the
rapping system sequence so that the inspector can verify that all of the
rappers or vibrators are operating properly. Rapping intensity should be
checked against design, and any indication of reduced rapping intensity should
be questioned.
ESP Housing—
The inspector should examine the exterior of the ESP housing for corro-
sion, loose insulation, exterior damage, and loose joints. The ducts entering
the ESP should be checked; if they show corrosion, the interior of the ESP
also may be corroded. The inspector should check for fugitive emissions (with
positive pressure systems) or air inleakage (with negative pressure systems)
at loose joints and as a result of other exterior damage.
Ash Handling System—
The inspector should check to see that the evacuation rate for the ash
hoppers prevents ash accumulation. Inlet field hoppers, for example, normally
collect 60 to 80 percent of the total catch and must be emptied much more
often than the downfield hoppers. If level alarms are used, the inspector
should ensure that they are operating properly.
The inspector should look for problems in the ash evacuation and removal
system, including water pump failure (a water pump may be used to create the
vacuum), vacuum line disconnections, rotary air lock malfunctions, and se-
quencing control failures.
If ash is removed from a collection silo by truck, the inspector should
ensure that the truck fill pipe extends far enough into the truck to minimize
fugitive emissions.
105
-------
Process Instrumentation—
After finishing with the ash handling system, the inspector should check
a number of process parameters that can affect ESP performance. For example,
readings of gas flow, gas velocity, excess air, gas temperature, pressure
drop, moisture, flue gas analysis, soot blowing intervals, and opacity should
be taken if possible. Many instruments in the boiler control room have con-
tinuous readouts. Figure 42 shows an example trace from a continuous opacity
monitor. Variations in process readings from the normal design ranges should
be investigated in conjunction with ESP control set readings and visual obser-
vations made during the inspection for possible effects on ESP performance.
Internal Inspection—
If an ESP is down for scheduled maintenance or because of a malfunction
during an inspection, the inspector should take time to check inside the unit
and observe the dust accumulation on plates and wires. (Note: Be sure and
follow proper safety procedures described on Pages 129 or 132.) The discharge
wires should only have a slight coating of dust, with no corona tufts (dough-
nut-shaped ash accumulations). Thickness of dust buildup on plates is normal-
ly between 0.3 and 0.6 cm (1/8 to 1/4 in.). If the plates have more than 0.6
cm (1/4 in.) of dust, the rappers are not cleaning properly. If the collect-
ing plates are almost metal clean, this may be an indication of high gas
velocity, extremely coarse fly ash, too high a rapping intensity, or too low
an operating voltage for good precipitation. The inspector may notice this if
a section has been shorted out prior to the inspection.
The inspector should note whether or not the discharge electrodes are
centered between the collecting plates from top to bottom to ensure optimum
performance. Also'any broken or missing discharge'electrodes should be noted.
The company should keep records of wire breakage to help determine if multiple
wire breaks in the same area may be due to alignment problems. Random wire
breakage is probably caused by dust buildup on wires or plates.
The inspector can check for air inleakage from door openings by noting
the amount of corrosion on collecting plates adjacent to inspection hatches,
and from the hoppers by checking on the lower portion of the collecting
plates. Air inleakage also causes nonuniform gas flow which can reduce ESP
efficiency.
106
-------
o o
O
C/5
LU QQ
> O
Ul i
1-
.c
u
u
(0
Q.
O
O)
'a.
fO
in
CM
0)
O)
107
-------
The inspector should have plant personnel open the hopper access door and
then check for corrosion, which indicates air inleakage as mentioned previous-
ly. He/she should check for dust buildup in the upper corners of the hopper
and for debris, such as fallen wires and weights, within the hoppers. If
discharge electrode weights have dropped 3 inches or more, this indicates a
broken wire. Chronic ash buildup is an indication of low operating tempera-
tures, insufficient heat insulation, or inadequate hopper emptying.
3.4 SCRUBBERS
3.4.1 Introduction
Wet scrubbers capture particulates into either liquid droplets, sheets,
or jets. The principal physical mechanism used in commercially available
systems is inertia! impaction. Other physical phenomena aiding capture in-
clude Brownian diffusion (random movement.that leads to particulate capture),
diffusiophoresis (particle migration toward site of condensation due to dif-
ferences in mass concentration), and thermophoresis (particle movement toward
colder temperature due to differences in momentum transferred in molecular
collisions). Diffusion only applies to small particles of about 0.05 urn.
Unfortunately, neither impaction nor diffusion is very effective for 0.1- to
l-|jm diameter particles that are small enough to follow gas streamlines around
the droplets but too large for effective collection by diffusion. Figure 43
illustrates the effect of particle size on impaction and diffusion.
Some boilers use scrubbers for particulate emission control, but scrub-
bers are not generally used because of high operating costs. A scrubber is
more practical for controlling particulate matter from a spreader-stoker
boiler than from a pulverized-coal-fired boiler because the stoker boiler
produces larger particles and relatively low mass loadings. Pressure drop,
water flow rate, suspended and dissolved solids, plugged and eroded pipes and
nozzles, pump wear, and particle size all affect scrubber particulate removal
efficiency.
Particulate scrubbers types include: impingement plate, centrifugal
spray, self-induced spray, disintegrator, moving bed, ejector, foam, and
venturi. Centrifugal scrubbers are frequently found on stoker boilers; ven-
turi scrubbers are more commonly used on pulverized-coal-fired boilers.
108
-------
DIFFUSION
IS DOMINANT i
MECHANISM
IMPACTION
IS DOMINANT
MECHANISM
LU
LU
Q-
.4
ARBITRARY CURVE
EDITJO 100 100.
PARTICLE DIAMETER, micrometers
Figure 43. Importance of particle size
on wet scrubber penetration.
109
-------
Impingement scrubbers use perforated or slotted plates containing target
plates opposite all openings to cause an cbrupt change in direction (and
acceleration) of contaminant laden air (see Figure 44). When flooded with
scrubbing liquid, these designs produce a high surface area froth of scrubbing
liquid on its top surface and turbulence, both of which contribute to particu-
late removal and gas absorption.
A spray tower is a gas absorption device developing high liquid surface
areas through the use of a spray nozzle(s), hydraulically or pneumatically
atomized. It is not very effective at removing particulates and rarely used
on industrial boilers (see Figure 45).
Dynamic scrubbers utilize a fan, impeller or other motive device to
mechanically produce small droplets which enhance gas absorption and particu-
late removal. These are typically sprayed fans, coupled with droplet removal
devices.
Moving bed scrubbers were developed primarily as an alternative to packed
bed scrubbers in applications with both particulate and gaseous contaminants.
As shown in Figure 46, the gas enters at the lower side of the unit and passes
upward through a series of beds each of which is 10% to 25% full of light-
weight packing. The liquor is introduced at the top through a set of nozzles
and passes through the beds countercurrent to the gas flow. The bed is fluid-
ized by the moving gas stream; this results in the formation of liquid drop-
lets and sheets in the turbulent zone of the bed. A chevron demister or
equivalent serves as the main entrainment separator.
A cyclonic scrubber is a spray tower variation in which gas is spun
cyclonically in a vessel with scrubbing liquid sprayed concurrently into the
stream (see Figure 47).
In the venturi scrubber the boiler exhaust gas and entrained particulate
matter are accelerated to a high velocity in the venturi throat. The high gas
velocity shatters the water in the scrubber and forms small water droplets
that provide impact targets for the particles. The particles collide with the
water droplets and stick to them, agglomerating into larger droplets that are
then fairly easy to remove from the gas stream. High throat velocities, high
liquid-to-gas ratios, and resulting high pressure drops through a scrubber
enhance efficiency.
110
-------
Clean gas
Plates
Dirty gas-
Figure 44. Tray scrubber.
Clean gas
outlet
Entraintnent
separator
Liquor inlets
Dirty gas
inlet
Liquor outlet
Figure 45. Spray tower.
Ill
-------
Clean gas
Mist eliminator
Spray nozzles
Mobile packing
Dirty gas
Figure 46. Moving Bed Scrubber.
112
-------
Clean gas
outlet
Entrainment
separator
Central
spray tree
Liquor
inlet
Dirty gas inlet
(tangential)
Liquor outlet
Figure 47. Cyclonic spray tower.
113
-------
Typical venturi scrubbers (see Figures 48 and 49) are made of 316 stain-
less steel. Most designs use a flooded elbow and a variable throat to control
pressure drop. The flooded elbow provides a trough of water to capture the
larger water droplets and particulate matter that exit the scrubber and to
prevent abrasion of the elbow at the turn. The venturi throat may be circu-
lar, rectangular, or oval; the throat area is changed by moving hinged plates,
a bob, or some other surface inside the venturi to control the pressure drop.
Water is introduced into the scrubber immediately ahead of the venturi throat.
Venturi scrubbers are more compact and versatile than the other types, and
they cost less than other scrubbers of comparable efficiency.
3.4.2 Operation and Maintenance
Most scrubber problems involve liquid flow, corrosion and erosion, scal-
ing and plugging, entrainment, and/or gas flow. These problems are described
in the paragraphs which follow.
Liquid Flow—
Common problems with liquid flow include build-up at the wet-dry inter-
face, poor liquid distribution, loss of seal, and malfunctioning pumps.
If the scrubber design improperly allows dry dust laden gas to contact
the juncture of the scrubbing liquid and the vessel, dust build-up will occur.
Good designs prevent this contact by extending ductwork sections sufficiently
into the scrubber and by thoroughly wetting all scrubber surfaces through a
reliable method such as gravity flush or sprays.
The gas and liquid must be properly distributed for the given applica-
tion. Improperly distributed flows can be aggravated by the influence of
baffles (needed or accidental), mechanical failure, wear, scaling in headers,
or improper design. Flow distribution problems are most common in packed and
spray towers. The swirling of scrubbing liquid, especially on cyclonic de-
vices, can cause severe wear and draining problems unless arrested by anti-
swirl plates in the scrubber or rapid continuous draining.
Most scrubbers operate near atmospheric or ambient conditions. A pump
recirculates the scrubbing medium, and a liquid seal prevents pump cavitation.
This seal may be at the top of a quencher or from an overflow connection.
Loss of seal can cause entrainment or plugging and instrumentation malfunc-
tion.
114
-------
clean gas out
dirty
water in
slurry out
Figure 48. Bob type venturi scrubber.
115
-------
GAS OUTLET
GAS INLET
CW>
PRESATURATOR
WATER
TREATMENT
*-PURGE
Figure 49. Venturi scrubber components.
116
-------
Accelerated wear of the centrifugal pump impeller occurs at high sus-
pended solids (flyash) levels. The best way to minimize scrubber downtime due
to pump malfunctions is to minimize the total quantity of suspended solids,
especially the larger suspended particles (greater than 25 micrometers). A
clarifier or centrifugal separator can improve the quality of liquor passing
through the pump by reducing suspended particle loadings.
Corrosion and Erosion—
Corrosion is a major factor in shortening the operation life of a scrub-
ber whether properly designed or not. Wells or pockets of liquid should be
avoided and points of stress should be adequately flushed. Relatively small
levels of chlorides and fluorides can attack many types of materials, espe-
cially the 300 series stainless steels. Internal members usually should be
thicker than the shell.
It is important to maintain the pH of the scrubbing liquid well above the
levels at which carbon steel (the most common material used in scrubber con-
struction) is attacked. A pH of 6 or greater is usually satisfactory. Other-
wise, FPP or expensive nickel/chrominum alloys such as Haste!loy must be used.
Maintenance of an appropriate pH is usually accomplished through the use of
alkaline additives such as soda ash, lime, or limestone. If a pH of 6 or
greater is maintained, significant sulfur dioxide removal (greater than 75%)
will occur. The operation of the pH monitor used to control the rate of
additive injection should be checked at least on a daily basis unless long
term operating experience justifies a less frequent inspection. A portable pH
meter or pH paper can be used for this check. It is preferable to obtain a
sample from the sump of the scrubber since this is often the point of minimum
pH.
The recirculation rate is an important factor in determining the extent
to which halogenated compounds are building-up in the scrubbing liquid.
One convenient means to monitor potential corrosion problems is to pre-
pare small coupons (small circular samples) of the various materials used
throughout the scrubber system. These are placed in racks which can be mount-
ed at various locations in the scrubber. During every outage these are vis-
ually inspected for pitting and cracking and are weighed for material loss.
This information provides an early indication of developing corrosion prob-
lems.
117
-------
The scrubber is susceptible to erosion due to high velocities of the
liquid stream and suspended solids within the stream. High gas stream velo-
cities can also lead to erosion. Venturi throats on venturi scrubbers are
subject to velocities as high as 20,000 to 40,000 feet per minute. Other high
wear areas are those which inhibit gas flow such as elbows and gas distribu-
tion structures.
Nozzles are also susceptible to erosion. Using special ceramics and
reducing the scrubbing liquid solids content can minimize problems. Some
nozzle designs, such as those that include an internal spinner vane, can lead
to accelerated erosion. Deluge-type nozzles or nozzles without internal
structures are least susceptible to erosion.
Scaling and Plugging—
Scaling is the plating out of deposits on a scrubber surface. Usually it
is harmless unless the scrubber part cannot function because of the deposit.
Scaling is caused by interactions of the chemical composition, solubility,
temperature, and pH of the scrubbing liquid. It is a difficult problem to
diagnose; a good deal of research has been done on calcium-based S02 scrubber
scaling problems.7 Proper control starts with the scrubber design and process
control.
Spray nozzles are extremely susceptible to plugging problems due to the
high liquid stream velocities and suspended solids content. The most common
types of nozzles in use include the hollow cone and the full cone. The latter
is particularly prone to pluggage due to the presence of an internal spinner
vane. The vane is installed to achieve the full cone spray pattern which is
necessary for distribution of liquor on a moving bed scrubber. Improper
header design allows particles to settle which may .plug nozzles. Centrifugal
separators can be used to remove particles before they reach the nozzles.
Scale problems can also be solved by separators, but proper control of scrub-
ber chemistry is a better approach.
Instrument lines can become blocked from particle settling or scale
deposits. Specially designed instrument fittings and connections may be
required for use with scrubbers. Instrument probes in continuously circula-
ting loops have less blockage problems than probes in dead-ended lines.
118
-------
Mist Entrainment—
Entrainment occurs when the droplet separator is not functioning proper-
ly. Nearly all scrubbers have some entrainment losses. A properly designed
system can eliminate entrainment carryover. Droplets impinge on eliminator
surfaces and return to the scrubber. Figure 50 shows two types of mist elimi-
nators.
Gas Flow--
Vibration is most common in wet dynamic scrubbers and in the fans on wet
fan venturi or cyclonic systems. It is best controlled by monitoring and
scheduled preventive maintenance to remove scale deposits and to lubricate and
balance equipment. Fan vibration can sometimes be caused by air flow factors
and, in these cases, can be eliminated by adjusting or modifying the inlet or
outlet dampers or modifying the inlet or outlet ductwork. Even gas distribu-
tion through the scrubber is important to obtain maximum particle wetting and
collection. Gas maldistribution can be checked with pressure gauges and can
be eliminated by using inlet baffles or gas distribution plates, by adjusting
inlet dampers, and by proper scrubber design that eliminates gas bypasses.
If the gas stream entering the scrubber is very hot (greater than 300°F),
it is often desirable to cool the gas stream. This protects the scrubber
materials of construction, especially corrosion and abrasion resistant lin-
ings, from thermal shock and degradation. Gas stream cooling can be accom-
plished in evaporative coolers or presaturators. Multiple cooling zones may
be necessary for large temperature differences.
3.4.3 Inspection Procedures
To evaluate the performance of a wet scrubber, the inspector should check
the following areas:
0 Liquid circulation,
0 Gas flow,
0 Gas pressure drop,
0 Liquid pH,
0 Scrubber corrosion, and
0 Nozzle and shell erosion.
119
-------
1 t 4J J~\\\m\ ~T'T "II 11
^l,j . ^™*ii*» —— • _*-Sn* *; ^S? »'^
WIR6-MESH MIST ELJMINATOR
TDBZ-EANK MIST EL1KCIATOR
Figure 50. Mist eliminators.
120
-------
The recirculation pump and fan should be operating. If there is no scrubber
liquid circulating through the system or the flue gas is being bypassed, the
inspector should recommend a follow-up inspection when the scrubber will be
operational. If there is circulation, the inspector should follow the liquid
flow through the system (liquid flow is generally counter to gas flow).
Next, the inspector should confirm that the pumps are on, and if so, the
inspector should read the flow meter (if any). In the line going to the spray
nozzles, low pressure indicates erosion of the nozzles and likely increases in
the water spray droplet size. If the line pressure does not change when the
flow is temporarily shut off (the inspector must not adjust valves), the noz-
zles are plugged. Localized higher shell temperatures (5 to 10°F above nor-
mal) also indicate an area with plugged nozzles. If possible, static pressure
drop across each stage should be recorded to help in problem diagnosis.
To complete the check of the liquid system, the inspector should measure
the temperature and the pH of the sump liquor. It is advisable to take a
liquor sample; however, the expense should not be incurred unless there are
reasons to suspect operational and/or corrosion problems (chain-of-custody
procedures must be followed). During the inspection, the corrosion and ero-
sion of the scrubber shell (look for holes) and component parts should be
routinely checked.
121
-------
SECTION 4
GENERAL PREPARATORY AND PRE-INSPECTION PROCEDURE
To conduct a successful inspection of an industrial power plant requires
careful preparation. Such preparation includes:
0 Becoming familiar with the boiler and its control equipment,
0 Reviewing past operating practices,
0 Procuring and testing the necessary inspection equipment to be
sure it is working properly,
0 Inspecting the plant's exterior to obtain information about
operating practices, and
0 Advising key plant personnel well in advance so that they are
available to answer questions and take part in the inspection.
(The cooperation of key plant personnel is critical to the
success of the inspection.)
Advanced preparation on the part of the inspector can save valuable time, both
for the inspector and for plant personnel. A well-informed and prepared
inspector generates a degree of confidence that makes plant personnel more
inclined to provide information critical to completing a comprehensive compli-
ance assessment.
4.1 FILE REVIEW
A logical starting point for Agency inspectors is a review of the plant's
file. The following items should be checked, and copies of the first two
items in the following list should be obtained from the inspection files.
0 Pending compliance schedules;
0 Construction and/or operating permits pertaining to source pro-
cesses;
0 Past conditions of noncompliance;
122
-------
0 Malfunction frequency and causes; and
0 History of abnormal operations.
The inspector should also obtain a copy of the overall plant layout drawings,
and these should be reviewed before plant entry.
The inspector should prepare a concise file containing basic plant infor-
mation, process descriptions, flowsheets, and acceptable operating conditions.
This file should also contain the following to facilitate the inspection:
0 A chronology of control actions, inspections, and complaints
concerning each major source in the plant,
0 A flowsheet identifying sources, control devices, monitors,
and other information of interest,
0 All permits for each major source, and
0 Previous inspection checklists.
Based on available information, the inspector should select a time for
the inspection when processes are likely to be operating at representative
conditions. This is especially important for plants with batch operations or
other irregular operating schedules (e.g., seasonal).
The inspector should carry the following tools and safety gear for all
inspections:
0 Hard hat,
0 Safety glasses or goggles,
0 Gloves,
0 Coveralls,
0 Safety shoes (steel-toed),
0 Ear protectors,
0 Tape measure,
0 Flashlight,
0 Manometer or differential pressure gauges,
0 Stopwatch,
123
-------
0 pH paper,
0 Duct tape, and
0 Pocket guide of industrial hazards.
Safety equipment is particularly important. It is the inspector's responsi-
bility to have safety equipment before entering the plant. Access to certain
industrial facilities may be legally restricted or refused by plant represen-
tatives if the inspector is not wearing the designated equipment.
The following equipment can be left in a central location and only car-
ried to the source when needed:
0 Pipe wrench,
0 Respirator with appropriate cartridge(s),
0 Velocimeter,
0 Pump and filter system,
0 Bucket,
0 Combustion gas analyzer,
0 Thermometers or thermocouples,
0 Multimeter,
0 Sample bottles,
0 Strobe,
0 Inductance ammeter,
0 Tachometer,
0 Oxygen and combustibles meter,
0 Self-contained breathing equipment, and
0 Rope.
A uniform inspection procedure^helps both the source operators and regu-
latory agency inspectors in the routine evaluation of the performance of air
pollution control equipment. The fundamental principle of the procedure is
that performance is diagnosed by comparing observed operating conditions at
124
-------
the site with baseline operating conditions. It is recognized that field
measurements are sometimes subject to error or impossible to make; therefore,
diagnosis is based on trends rather than individual parameter readings. Even
if some basic data are missing, reasonable conclusions may still be drawn.
The techniques described in this report allow the inspector to rapidly
identify any significant changes in performance and the possible reasons for
the changes. Although these techniques provide a method of assessing compli-
ance, they do not necessarily provide definite evidence of noncompliance, nor
do they necessarily recommend specific remedies for problems that are encoun-
tered.
Inspectors should have a technical background and some field experience.
As with any work involving equipment, care must be exercised and formal safety
training is highly recommended for this activity and for any field work in-
volving air pollution control equipment.
No single technique can satisfy all source characteristics and inspection
circumstances. Inspectors and source operators may have to modify standard
procedures for specific circumstances.
A key inspection step is to determine baseline operating parameters soon
after a boiler is installed and the shakedown period has been successfully
completed. These baseline parameters, which can be developed during a stack
test, will provide a site-specific reference point for assessing future boiler
performance. The parameters include:
Steam production data such as temperature, pressure, and
pounds per hour;
0 Fuel use - pounds or tons of coal per hour;
0 Fuel quality - Btu/lb, ash, sulfur, and moisture;
Combustion air temperature and ambient humidity;
0 Firebox draft;
0 Flue gas temperature and flow rate;
0 Flue gas 02, CO, and C02.
5
Firebox, superheater, and air preheater temperatures;
Induced-draft fan speed, pressure drop, and air flow;
125
-------
0 Overfire air damper settings; and
0 Pollution control system parameters.
The same inspection procedures and forms should be used for both the
baseline assessment and the routine evaluation. To round out a reference
file, the inspector should:
0 Obtain a set of general arrangement drawings of the control
equipment and dust or sludge handling system;
0 Evaluate the stack test location and procedures to ensure that
the emissions data will be accurate and representative; and
0 Carefully inspect and describe all internal conditions if such
inspections can be conducted safely. Photographs are extreme-
ly valuable and should be taken (with permission from the
source) if it is safe to do so;
0 Note the sounds of operating components such as rappers and
solenoids;
0 Obtain a complete set of boiler operating conditions, fan
characteristics, and raw fuel characteristics; and
0 Obtain opacity readings.
Because the inspector is most concerned with emissions, it is generally
advisable to begin the inspection by looking at the stack. Then, the inspec-
tor should check the control equipment and finish with an inspection of the
boiler and the control room. This minimizes inspection time and reporting re-
quirements and maximizes the amount of useful information obtained. Specific-
ally, the information on emissions and control equipment, which is the most
relevant to the inspection is obtained early in the inspection and can then be
used later either to narrow the scope of the inspection or to terminate the
inspection without evaluating the boiler equipment.
0 Pre-Inspection Steps
Review the source files.
Schedule the inspection.
Check the inspection equipment.
Observe the plant surroundings.
126
-------
0 Inspection Procedures
Request entry to the plant.
Interview plant official(s).
Observe the stack effluent.
Check the continuous monitor(s).
Measure or record the fan parameters and evaluate the
physical condition.
Analyze the control equipment performance and condition.
Check the flue gas system (ductwork).
Evaluate process operating conditions.
Check raw materials and/or fuels.
0 Post-Inspection Steps
Conduct exit interview with plant official(s).
Update source files..
Prepare report.
Prior to entering a plant, the inspector should observe the surrounding
areas. Various signs of operating practices and plant emissions that can aid
in the source evaluation include:
0 Deposits on cars parked near the plant,
0 Other signs of dust and fly ash fallout downwind of the plant,
0 Fugitive emissions near plant boundaries,
0 Conditions around the product and/or waste storage piles, and
0 Conditions near lagoons and sludge ponds.
Some of the inspector's observations may suggest that fugitive emission
sources should be added to the inspection agenda. A summary of weather condi-
tions also should be included in the inspection report.
Upon arrival at the plant offices, the inspector should notify appropri-
ate plant personnel and show his/her credentials to the plant representative.
Generally, the inspector should not sign a visitor release form.
If entry is refused for part or all of a facility within the scope of the
inspection, the inspector should carefully note 1) the alleged reason(s) for
the refusal of entry, 2) the name and title of the plant official who refused
entry, and 3) the time and date that entry was requested. Immediately after
such refusal, the inspector should notify his/her supervisor by telephone and
127
-------
provide the above information. Under no circumstances should the field in-
spector attempt to inform plant personnel of the potential legal consequences
of refusal of entry.
Once entry is granted, the inspector should conduct an initial interview
with appropriate plant personnel. Some of the points for discussion are:
0 The purpose of the inspection,
0 The type of measurements to be made,
0 The samples (if any) to be acquired,
0 The systems to be inspected,
0 Changes in plant management that need to be noted in the
agency file,
6. Process flowsheets necessary to confirm that reported plant
operating conditions are still pertinent, and
7. Operating records required by New Source Performance Standards
(NSPS) and/or for determinations of operating conditions speci-
fied in permits.
Appropriate regulatory requirements should be reviewed carefully, and their
specific applications to the source in question should be discussed with
appropriate staff members.
Other issues the inspector should be prepared to discuss include:
0 Authority for the inspection;
0 Agency organization;
0 Scope, timing, and organization of the inspection (preferred
inspection agenda); and
0 Treatment of confidential data.
The inspector should ask plant officials about the operational status and
types and frequencies of malfunctions for all processes and pollution control
equipment being inspected. If equipment is not at or near normal conditions,
the reasons for deviation should be 'noted, and the times when units can- be
expected to be operating at normal conditions should be recorded for use in
scheduling followup inspections.
128
-------
Emission opacities should be observed and recorded according to Method 9
procedures. In many cases, an agency can initiate an enforcement action
solely on the basis of visible emission observations. In some cases, however,
opacity information can be used to diagnose changes in system performance.
The color of the effluent is another plume characteristic that should be
observed. For boilers, the color is an indirect indication of operating
conditions. The list in Table 9 was compiled by EPA's Control Programs Devel-
\
opment Division.
TABLE 9. PLUME CHARACTERISTICS AND COMBUSTION PARAMETERS.
Plume color
Possible operating parameters to investigate
White
Gray
Black
Reddish brown
Bluish white
Excess combustion air; loss of burner flame in
oil-fired furnace
Inadequate air supply or distribution
Lack of air; clogged or dirty burners or insufficient
atomizing pressure, improper oil preheat; improper
coal size
Excess furnace temperatures or excess air; burner
configuration
High sulfur content in fuel
Baseline operating parameters for the boiler and its control equipment
may be available from Agency files prior to the inspection. A typical source
file contains information on permit activity, previous inspections, and emis-
sion tests. The files generally describe the boiler and provide additional
data on its capacity and control equipment; this information gives the inspec-
tor a perspective on the overall operation of the facility. The source files
also may contain information on citizen complaints; equipment malfunctions,
opacity levels, and the overall compliance status of the boiler or boilers at
the plant. This information helps the inspector to focus attention on those
boilers that seem to have problems.
File data on previous emission tests and other inspections should be used
to establish a baseline for comparison with information obtained during future
129
-------
inspections or tests. Such information also helps to establish a normal
operating range for the boiler and its control equipment and permits the
inspector to readily note any deviations.
4.2 SAFETY PRECAUTIONS
Safety precautions must be taken during plant inspections because heavy
equipment movement, high-temperature process equipment, high-pressure steam,
toxic gases, and noise are common. Extreme caution should be taken to avoid
burns and the possibility of slipping and falling. Several specific situa-
tions are of concern in terms of the inspector's overall safety.
One special concern is the potential for a boiler explosion. Although an
explosion is unlikely, the possibility does exist, especially during nonstand-
ard operating conditions that might be encountered during special tests. The
inspector should be familiar with specified evacuation routes and procedures
before entering the boiler area.
Because a mixure of pulverized coal and air burns rather freely, suspend-
ed coal dust in air can be quite explosive. Hence, pulverized coal or coal
dust must not be dispersed in air except within equipment where conditions are
controlled at all times. Fine dust can be dispersed into the air by means
that are not always expected or predictable; thus, it is important to avoid
accumulation of coal dust anywhere in the plant except in coal storage spaces.
Even there the suspension of dust in the air must be avoided. In general, it
is hazardous to blow dust off surfaces with air lances. Vacuum cleaners
designed for this purpose are preferred. Fundamental safety precautions and
burner lighting and operating sequences for coal are summarized in the follow-
ing rules:
1. Never allow coal dust to accumulate except in specified stor-
age facilities.
2. Never allow the suspension of coal or dust in the air except
in drying, pulverizing, or burner equipment or in interconnec-
ting ductwork.
3. Purge the furnace and its setting before introducing any liqht
or spark.
4. Have a lighted torch or spark-producing device in operation
before introducing fuel into a furnace.
130
-------
5. Maintain a lighted torch or spark-producing device in opera-
tion while introducing fuel into a furnace.
6. Maintain sufficient primary air and coal flows to the burners.
Compliance with these rules requires a conscientious operating staff and good
housekeeping throughout the plant.
Another major safety concern at any plant is entry into a confined area.
The cardinal rule for entering a confined area is "never trust your senses."
What may appear to be a harmless sitation may well be a potential threat. The
three most common conditions constituting a threat are:
0 Oxygen deficiency,
0 Combustible gases and vapors, and
0 Toxic gases and vapors.
An inspector should always anticipate that any one or a combination of
the above conditions might exist in a confined area such as ductwork, stack,
open tanks, penthouse, or the internal portion of a wet scrubber or ESP.
Tests for flammability, oxygen deficiency, and toxicity must be made before an
inspector enters any confined area. No one factor will provide more safety
than the knowledge of the potential threats that may exist within the area to
be inspected. Armed with this knowledge, the inspector can take appropriate
precautions and use the proper equipment to minimize any potential dangers.
Many treatment chemicals used and handled in the boiler area are corro-
sive or skin irritants. Care must be taken to avoid contact with these chemi-
cal reagents, which may include sodium hydroxide (NaOH), sulfuric acid
(H2S04), and chlorine. Table 10 shows the physical, flammable, and toxic
.properties oficommon gases that may be encountered in a boiler plant. Many
solids may also be hazardous to the skin and eyes; contact should be avoided.
The inspector should wear appropriate eye protection (glasses with side
shields) at all times within the plant.
Many surfaces in the boiler plant are extremely hot. The inspector
should constantly be on the alert for piping, ductwork, or equipment that may
present a potential hazard. Protective clothing (long-sleeved shirts, gloves,
etc.) should be worn to avoid burns as a result of accidental contact with hot
surfaces.
131
-------
TABLE 10. BOILER PLANT GAS PROPERTIES.
Gas
Carbon monoxide
(CO)
Carbon dioxide
(C02)
Methane (CH4)
Sulfur dioxide
(S02)
Nitrogen dioxide
(N02)
Physical
characteristics
Colorless
Odorless
Colorless
Odorless
Colorless
Odorless
Colorless
Suffocating odor
Brown
Pungent odor
Flammability lower
explosive limit
(LEL), % volume
12.5
Nonflammable
5
Nonflammable
Nonflammable
Toxicity threshold
limit valves
(TLV's), % volume
0.005
0.5
Nontoxic
0.0005
0.0005
The inspector should remove loose objects such as jewelry, ties, and hair
ribbons before entering the work area. Because of the close quarters in many
boiler rooms and the possible contact with moving equipment while taking
measurements, any object that might become entangled must be removed.
In addition to the general concerns noted above, an inspector that con-
ducts an internal inspection of any control equipment must:
0 Observe interlock and electrical lockout procedures,
0 Observe confined entry procedures,
0 Watch footing,
0 Never work alone,
0 Wear protective equipment,
0 Purge unit before entry,
0 Use grounding straps particularly around ESPs, and
0 Never enter full or partially full hoppers (wet- or dry-
bottom). Empty hoppers may have ash lodged overhead which
also presents a danger if accidently dislodged.
132
-------
Finally, the inspector needs to be aware of and obey all safety require-
ments set forth by plant personnel. Many plants have specific safety proce-
dures that must be obeyed; therefore, the inspector must meet with plant
personnel prior to the inspection to discuss special safety requirements
pertinent to the plant.
4.3 SAFETY AND INSPECTION EQUIPMENT
During an inspection, the inspector should use appropriate protective
clothing and safety equipment and follow all company rules and recommenda-
tions. The inspector should wear safety glasses with sideshields for protec-
tion. Hearing protection, such as ear plugs, should also be used in high-
noise-level areas. Steel-toed shoes and a hard hat are required for protec-
tion against overhead hazards and heavy objects. A long-sleeved shirt,
gloves, and trousers should also be worn for protection. Dust and mist re-
spirators should be used around potentially dusty operations. In some cases a
gas mask may be required. When the inspector is required to enter a confined
area, he/she may need to use self-contained breathing apparatus.
The equipment used during an inspection varies according to the time
allotted and the level of the inspection. For example, a detailed inspection
requires a pi tot tube and manometer for measuring the pressure drop across the
appropriate control equipment, a thermometer or thermocouple for measuring
stack gas temperatures, a wet bulb/dry bulb thermometer and psychrometric
chart for determining moisture, a tachometer for measuring fan speed, an
ammeter for measuring fan motor current (on large fans, current usage may
exceed the measurement range of hand-held ammeters), and an oxygen meter
and/or Fyrite or Orsat for determining 02 concentration and gas composition.
A flashlight, tape measure, and pressure gauge device may also be necessary.
A camera can be useful to provide a graphical description of problems
arising from poor maintenance and housekeeping. Control equipment problems
can also be so documented. Immediately after taking a photograph, the in-
spector should note the situation represented in the picture and the time,
date, weather conditions, and pertinent directional information. Unfortunate-
ly, the plant owner or operator may be reluctant to allow photographs to be
taken within a facility. Therefore, permission must be obtained prior to
taking such photographs.
133
-------
A compass is useful for determining source locations relative to each
other, to the sun, and to the inspector. A stopwatch for timing visible
emissions observations is also useful.
4.4 PRE-ENTRY OBSERVATIONS
Before entering the facility, the inspector should record pertinent pre-
entry observations such as sources of fugitive dust. The inspector should
also note the weather conditions (especially precipitation and windspeed)
during and prior to the inspection.
Pre-entry observations also afford an opportunity to document the facil-
ity's general housekeeping practices and give the inspector an overall picture
of the plant layout for comparison with file information.
While outside company property, the inspector is generally free to use a
camera to photograph any visible problems, including excessive visible emis-
sions. Data regarding any photographs that may be taken (e.g., date, time of
day, weather conditions, position relative to the source) must be recorded
immediately. As mentioned in Section 4.3, the inspector must obtain permis-
sion from plant personnel to take any photographs while on plant property.
Visible emission observations are important in determining the operating
conditions of some processes and their associated control equipment. When
recording visual opacity readings, the inspector should follow EPA Method 9
procedures or appropriate State procedures. Windspeed, sky condition, and
other weather data should be recorded for future use, as the reading may be
challenged in court. A diagram is also important in identifying the parti-
cular source being observed (e.g., the No. 3 coal-fired power boiler) and the
observer's orientation relative to the sun and theisource. The inspector
should record opacity readings on the observation form for a specified dura-
tion, depending on the local requirements. Any periodicity of smoke emis-
sions, such as intermittent puffs, should be noted. In some cases, it may be
possible to correlate variations in opacity with corresponding fluctuations in
boiler load or other boiler operating parameters.
Sometimes opacity readings are best obtained before the inspector enters
the plant or after he/she leaves the plant property. The inspector should
compare the visual measurements with available readings from the plant's
134
-------
continuous emission monitoring equipment for the same time period. The fre-
quency of calibration of these continuous emission monitors should be noted.
If the Agency's policy is to provide the plant with a copy of the opacity
readings taken during the inspection, the plant official receiving the copy
should sign and date the original record of the opacity readings.
4.5 ONSITE INSPECTION CHECKLISTS
During the onsite inspection, the inspector may find it useful to have a
series of checklists on which to record the information obtained. Tables 11
through 13 are checklists for fabric filters, scrubbers, and ESP's respective-
ly. Figures 51, 52, and 53 are flowsheets that can be used in conjunction
with the inspection of those control devices.
Appendix A contains additional checklists that may be useful. These
checklists include a cover page (Table A-l) that may be used with the check-
lists for fabric filters (Table A-2), scrubbers (Table A-3), electrostatic
precipitators (Table A-4),_and mechanical collectors (Table A-5).
135
-------
^y
o
1— I
o
LU
O
I-H
J—
CO
o
*ZI
§
1— I
O
o
t— t
r—
O
LU
0.
to
2:
n
3:
0
«_J
u.
ct:
LU
i —
z:
=>
o
o
CO
LU
— 1
1—1
u_
o
t— 1
CO
11
. — |
rH
in
•
^_j
CO
j«
r^
B
O
JJ
Rfecoraraendei
60 .-x
B 0
it •
JS ^^
|?
B .B
-^ N_/
rtc
B
O
TJ
U
•3
IT
3
•c tit
0 >
I if
a -ri
.0 O
0 01
a.
co
, u
t*J 1J CX OI T3 -H o
O CJ CJ rH 01 14 U
JJ -O U rH AJ CO
^ G JO B tl to
•WTlVjOJ-rlOIAJB
N^ O CO CO U B Tl
EU4 3 CO B T| AJ
§O 01 01 Q.
O J! J= O W Ji B
to «*J O U O CJ 01
b 01 Vi eg 3 tl AJ
*M OIX tl Br-tJSAJ
K-I cxUJJTiti-io eg
c-> in ^ .» ^, n^
1
^
1 1
1 1
r-(
Id UUMtdMMU,
o
1
1
1 fe
1
z" z
• CO CO
CO > >
> efl Q] ca
cd B
0) M M O
0) r-l r-l O O Tl
M ^-. rt J3 CM CM CO
3 > U T-I — t — 1 H
CO COCO TlCOAA 3
CJ C0> tXCOv-'v^T3O
rH 01 « >, 01 CJ K
O b JJ O .C .C -o «)
.B CXI^ v^ CJ CO CO O
B O rt T| T| Ij X
-r-l OICOXXBJSJCOICO
CM CO V CO CO T| T(
S^^TITI oooij;
O -C5 co^^edAJ
O r-> 01 19 rH B
CO VrrHJJCOJ3B*-fCXai
H 01 -H « CO M 3 .
to j-iixo tiTi3rJcr
01 «-4OC3CO£c3JJcOOJ
H Tibcxcaooiuoirj
be
X
J
O > VJ 1
-•.B 0 -H «
AIO*M«M 14VV •
Tl VM O 3 rH •
roAJcOTltltMO3rJ
01 S>'° O • 01 AJ
COeX«OtlIO'CjrJjB3
co a ja M oi u »4
BB«W BOAJCO
AJ « oi TI a? «
a«HOie>-.r<>M 01
n a -a «w B
6 Tl 0 Tl J4 B *
^MrJCOTlAJUTlCXB
O 01 J3 B tl O Tl
AJ X AJ 01 J= 01 U
^-.CAJV-'-OCJ co-a a
t-J Tl b Tl Tl 0
•-^ Tl B U 01 T|
B E"° IfS^N-JtJ
3OJ4-H CO -O to tl
cou^OJ-iAJOJcgcocx
IJtlCSrHUOIOlO
U-IOIJ303COAJUB
M exo u u 'i eo ex>ri
1
H
il
tO W W HUMM M
1
z z[z z
z z z z
^vt
js to o
^ M > | 5<
01 • T! w eo 01
ij to rC oi ex
3 > tu K p.
torn >> o JJ >. o T)
CO O O CO Ji J3 01
01 M B • CM. O •** AJ
»-" o oi v |s> TI ca
cxin 3 v^1 c« u CB rH
^» Jr co co to,-. 3
t) A ois~..« a to a
eavr->M>-,OC tl O JS
AJ 3 CO
U-l AJ rH *rl
M « U-l rH
1
MM M
J
P
01
eo
M
C9
XX
r-J M rH
rH Tl eg
3 £
13 X at
at) u
KB £
CO 01 t>
3
a tr a
X o oi ^
CO rJ M
T| -O COU4 M
&l jz a
B o) TI CO
iH >> u co B ••
T3 JJ 3 CO Tl c
CJ Tl 01 01 B ' ' 0
oi o to u id "O T|
rH efl OJ O 01 CD AJ
« cx H o rH :: «
o tx TI cj -J o
tc CX
aj • • « jj «:
o
cJ cj
136
-------
-a
0)
3
O
U
QQ
•
01 »W
D T-l
J3 U
O 01
CX
in
01 x-.
E 01
•rt a
01 a
a i>
S£
01 -^
60 U
a o
^ a.
01 en
•< *~"
03
_-J
le Operating Prob:
5
CO
o
• 1
o o a
— ,E K « 0
sv | o u •".•*«
' f< 14 4J
a u -^ ta U
1-1 O T3 0 «l
o ,*** g^
e cx e «
bo 10 o >x fl
B C U -H
•*H *r4 CO «l
U u J3 I)
W r-( -H «w Li
0 E j= o a
3 0 U • «
«> u-l 0) c C
vi -a -o o
•w Cl B -rt -H f3
M o. a r co -R
10 tri ooooaeMfM
(-9
•-< f-t M
W U U H )j W w N
O O O
to t-^ u
HI 1
ha!
1 1
1 1
•< < < <
Z Z Z 5=
eg
cx i >
O CO ft
VI Ol XJ Ol
t3 VI OJ > . M
CX U -H 01 B
ai ci oi u r-t -H
vi vi > o. rt ja n
3 01 -r-l O Vl -rt a
CO 13 *-» B O CO Ol
CO CO (0 **H CX CO r-l
Ol 01 Vl O O O
vi jc ci e E to o
cx ex a -rt c o >s
Vl O u-i o bl 4J
B 01 ^ B Vlr-4Bl-l
3 co si -H Vi o T UZ O)>*O Be>OEAj to to 3 to eT
B •*-*<*H33OcljC^cT'T«cl
eg Cxijcr^comixcorQeoxvi
O —• tM c->-3•u^^Dr^cO
a
__
~^ 0
A|J
CO AJ
4)
co a
B O
jj
3 *-<
M 0
c
O t) •
AJ
^^ C B
t-3 -r* 1.
x^/ C
f9 W C
§ o e
co pper
i Filter house prs
drop high
• Solids-removal i
J ~« CM
.
"
es
H
^
•<
^
g
Q
X
01
termittent
. Indicator level
n
CN
w
^
z
•<
^
Vi
o
•g
a
Ol C
> 01
and/or inoperatj
. Heaters nonexist
•*
CM
K
•^
•<
z"
B
01
o
inoperative
, Vibrators nonexJ
•o
1-1
•^
<
E
•o
c
13
o
OJ Vl
> V.
nnd/or inoperatj
i Hopper valves cc
VO
CM
td
1
<
Z
D
^}
V
01
ex
o
-H
CD
Vl
01
cx
cx
o
r-^
CM CM CM O
1
to
U EO P7 ei9
-------
o
uu
CO
o
to
o
1
o
CL
CO
S
u_
UJ
O
CJ
CO
QC
UJ
03
CO
an
o
CO
CM
CO
^J
1 «1
<
«]
•a
c
4f
O
O)
US
C 0
«§£i
•3^
O 0
C JC
J3 U
<*"'
I
AJ
U
tj
3
•o a
CJ >•
Ol
CS
« >»
o *<
M U
a u
VC (X
cj n
^
CO
B
•-I
J3
0
VI
a,
w
c
•«-<
AJ
«
VI
Ol
<§•
u
•H
5
IX
13
- °
O AJ AJ
— «. o ca
A lol 01
. B"
t& o _^
c u u
•H «
AJ CU AJ
eel AJ CO
VI 0
•H VI
IM -O O
O 01 ^.
§18
o
c-J-rt 0
B co a
3 01 0
CO 3 -rl
er AJ
•M 01 O
W W «S
o o u~) vi r«*
1
M
1
(d M W W M
0 0
o" 35 m
0) O)
:= z a
ca S
ex o
a <-<
3
a o
> eo vi
T< en 13
AJ C£
CO 01
U AJ VI
o> cu 3 -a
ex r-i a co
O AJ CO M
B 3 JS 0) to
» -HO to H 3
o v4 ex r-i
rH o -a j= ex
t«. M a vi
« «j >> u a
IT AJ jo o)
O 0) AJ -r4 JO r-l
3 0. 01 01 0 3 N
0 E r-l e M VI. H
•r4 3 c eg ex o o
>J &• n en o v> X
is -c «M n ^ in
•
—
A
•r-
CQ
t>
e
o a>
t: e>
•jj «J
> 01 B a
AJ
s e
CO O AJ
co o m
ft) Q)
603
AJ O*
O 0)
AJ 01 (Si
u
ex vi •
B a
S » o
AJ O O
ctf CM a
m 10 en • f*- c*> n
1
w
[TJ U W W W W
^K
r-l 0
0) r-l
> 3! 01
o ex 3 ex
.a r-i o
eg Vi d u js.
o > -o co
M 3 ' T<
o o- u 01 j= r^
— < -r4 O U •
^^ r-l AJ 3 eX bO
•H en B >
^r? (J (J CJJ 0) 4
»0 JC O 0 Ol AJ
^^ -r4 tO-H B •-> U ^-> 01
- j: -HAJ . ex • Vi >
te j= «j tuco woo
> ex r-i^^Aj>vi>4jja
« g '>,3mcgao>c9acg
01 AJ u V Vi JQ >
O '^O'l-l SO3OUO
CO « M rt CJ ft OCOVicOi-ICM
VO>eXOOrHVOVXA
*-^O ecjOeaSrHUa^^c/J^-'W*^
r>l r> •» to »o r-
o
r^
A|-g
4
CO S
5°
•rt ^4
co er .
n en o)
AJ
-C OJ
jj r) do
B « J= . r-l
C3 f oo Q
jC ai o ex > p
M u -a B co C
•H u a u u
S JC CO AJ U U
to ta. > X
Ol -r* CO O. Vl O 01
u j= a o , A co -H
li -n 01 o W .
O O r-l X " O ---,
rH C U efi -rl Ol . *-*
t» CX3^IXA ..
-------
T5
3
C
C
O
u
***/
c\i
,— i
LU
l
£3
o
*r-(
-1
•o
OJ
•o
e
«j
|
s
&
c o
*a — *
U 1
<§ «2
|j?
C 0
0 0
c J3
-°s
'c
o
AJ
e
u
'o
,-)
TJ a
s- •
V U-l
CO T<
-0 O
O OJ
o.
to
c QJ
•H 3
•J 01
B >
« ^
U -H
bo U
O OJ
W Om
V CO
Q
§
r-l
J3
O
PH
CO
a
1
e
J3
a
a
o
CL,
j^
- U
o B «
~« ,-o u so
A |c B> 3
a o
C3 6) O
CO OJ 3 19
eo B er
C O. QJ W
"3
(4 V A} V
U •-)
0 CO li O
31 M
>-^ O B Q.
1-3 O O
^^s51'
3J^9
TO O T3 4J
V O B
M U CX.JLJ
\o "^ *o in
I
'•-1
W M W &3
g
s ^
S o o.
o •-< o
•r< W
01 ^^ O <^
n) . 3 • «l
bO to cr to M
J=J > -H > 3
et u o) <-< a co
-^ oj m
x j= •-« > " s> «
M *J O T-* O *J -—*
OJ -H 3 T-t « ^1 O, •
u jc o «J aJ QJ bo
a JD j3 M >
(X ^t *M *M QJ ti
aJ o(*^ O &M JO
S -n o o jo «
O OQ.OQ.O3O
r-< .caec^E^^'co
fxi O.OJAOJAOV
0 H ^ I- "3
CO
o — M «n •»
Q
e
• S)
03
•-• t-J a
A PM o
- U4 -rf
© 9J *-> £J
U4 AJ e)
•£ c OS -H
a) a • o
l^ CO U 01
OJ «J U
«-» o. ja u
O >->J5 O
JO 3 0
v^ o •> U
B *" -o -S
3 M C -O
CO 0 3 SI
(log
H* cl 03 -3
»n »n m
I
w
M .'J M
-£
52;
,,.
•^
J=
to
•H
O.
0 J3
M fcO
0) x^ A
S >*4i jc
CO «0 *O W)
Q> T-: -H
(-» ej ^3 js
cu > fra
C VJJ J3 *J P.
tH ft! td
tf. J3 ,*-» *^
cc & *~^ o o
3 3 O P 3
r-i u ^ u OJ OJ tn •> *- — ^
W >~i -^*OOMC«H PdCL)
NCUOP^KON C3
r-l O^O.-1-IOO O tl ..—
N fc *O ^3 ^J CJ Z vO *2« O '^
N 0 4->
O .».*. • *]jj C
« o
g tJ
« »~3 "^^^
CO
-------
<*«\
•o
Ol
3
C
•f*
•*->
O
u
v-/
•
CsJ
t-H
LU
f
E
5
U
•O
Cl
•o
B
u
§
o
u
"*
E C?
1-1 -^
AJ 1
69 *-4
rH
rt ^-i
B -^
LI o
O U
E JC
•° ii
B
O
•rl
U
S^
3
"S "
> *"
Ll >%
0 U-l
•3 iH
J3 O
0 Cl
0.
en
U rl
B 41
•rl 3
rH -H
u a
o
*i i
O -rl
CO U
B tl
Ll CX
u to
Jg
03
.0
O
Li
CO
B
•rl
AJ
B
U
t)
5-
r-l
5
•0
o
A-
• C
O U
A||
CO C
i-i 14
a
o
B T-l
O U
•rl 0)
AJ eu •
O -f4 B
01 U 3
ex cu-H i-i
B 01 JJ _O
M C
a -H
•rl
-H S S
D.
AJ 0) Cl B
a U r-l -rl O
I-l CO 3 U
c -a 01 C
u-« a a LI a
O JZ J2 3 r-l
u
t-3 LI
v^ o
I*
Q U
«M JC
t~t u
i/l O
H M
1U U
6) M-1
*J
CO O
•H ^H
B A
o to
4J •*-!
gt
f-i AJ
U^ -rl
a
I-l O
«J r-l
H CO "
fi) >
AJ 0
. e> o a
E
0) • .
a — • CM
tJ
~^
CO
a AJ a
m 3 JD
01 UH B
BJ ^ 3
B a
I) B "2
a c u-i
Ll -rl O
m
I
M
CO
O rl
U J3
to >
Li B
C3-rV
.
fl .
•
O
A
•rl
09
U
B
-H
AJ
a
•M
U-l
O
tJ
1
0
UJ
'*"'
•JT
w
o
r-l
« i f\T
C 0
0) U
e -o
AJ
tQ QJ
5 3
•a D
-< 03
u
AJ rl
a a.
o
fi 1
Jtf
'd 3
O 0
•rl
AJ AJ
U B
«; ej
3
•rl rl
AJ
0 Vl
L| ^
U O
0 -rl
tl TJ •
3 II AJ
tr B B
i> e u
Li -H AJ
•* •*
i
1-9
W M
1
<:|
*l
<
52
B
01
CO
B
r;
U
O
' o
S
•a j=
x-»-rl 00
- > -rl
M OJ JS
« €) SX
^ -?g5-rf
Li U CO 03 03
3 O V -rl 0.
AJ CO --' > O
E
0) •
M
. .
CM CO
0 •
^'3
•H O
0
B O.
C£ 03
•rl -rl
AJ
« rS
rl 0)
U4 Ll
0 1)
AJ
" •
e o.
3 B
0 U
O.
o a S
0 3
•X IO
>- 0
a co B
Ll V -rl
f , .^^
Vi
Li > O
003
r-( O"
Cl -rl
AJ O. r-l
c] O JC
r-l Ll t>0 U-l
P- t) -H O
AJ
OJ O JQ
r-l HO
1
e > •
M — « CM
rj
•H
o)
p
M
a
w
C
•^
to
M
-o
-------
•
•z.
O
HH
i —
LU
to.
O
1—
to
o
C3
«J "M*
B 1-1
C U
O 4>
O.
iH
S "•>
•H 3
t^ *— 1
4) d
a >
« >>
B ^4
to o
« 41
VI O.
W U}
•5 "^
rating Problems
4)
e
A
^
O
a>
0
t^
A u o
B ^ 4J
-H 1-1 e
U 0)
CB CO *J
60 -H C
a B o
i-l 01 O
U 1J
Q VI
Vi 3 3
U «M
Uj i-l r-t
O CO 3
W -H .*
s^ , o
e B *
3 41 O
a 3
cr-o
u a
f. , QJ £J C 41
OB (3 V< 01 4) VI
O eg 41 41 H M> VI
IO4)^^ -U -H Vi VI 3
+ | M C C >u 330
•i-'u-So i-l 0 O. 4)
C B O 4J - VI
•a-S^^j: o >, VIX"
W JT VI O. >% 3 — < 4) O"41 >.
tao B-UBV e otJeow Vi
— t
.
^-i
-< •< g
» Z «
a
•H
u
o j; M
C £10
> ^ ic e
O ttJ •}
^ vf f -5
4) 3 u J= .a -1
bO p. AJ bo i-l ca
B i-l CO C
u 01 41 X -H C
r-4 CO B > 41
g g g Erfr* S
X '-sJZ O -rl Jt 41
«J01t»o)-fO.Vl "O"'1
•-* t*4 to -* m ^
-M j>
O "
0 0
' "* j
*
141
-------
(continued)
*
CO
tH
UJ
B
O
^ .
0
^
•o
"O
a
g
u
S.
C 0
U I
iS +2>
«-4
' §2
t. 0
o u
B j:
•° ii
a
o
XJ
ti
U
3
*O ti
I.X
ft) U-t
CO -H
JD a
O V
ex.
u ^-%
31
0) s)
C6
0 -rl
to o
el U
VI CL
a tn
Operating Problems Av
(
u
5
B
B
O
cu
^
0
A|
B
""
B
I
1»
1-1 -rl
o a
ex
*-N O
w .u
JJ
B o
3 U
§.
M V"
in O es in en o
•-4 -+
.1
w
J
MM M U MM
HI
< l<
1
^ *< ^ **«
z z a z
Vi n
o ti
JJ O Vi
e 1 «j in. -rl
a o u • -H S
M o S -H •i1
•H 0 r-J. TJ 0
S M «M B X to
1-1 -rl • tO VI
C) 9 H -H 01
C£. 01 r-l J= J= J=
vi • a u u , <-x to u
(3 O •) > ftlB*«-*B
J B S JJ-HJS-H
u e t-i -o o B -a
o JJ JJ to (JVi-^K
-H i-< C C U B BUB
o f-< JJ a. vviOA!
U tl-H3OOO.OiO.VI
^ o>"WC«oe3«
pa •< CM r> -
no n *•
•rl -rl
U-l 4J «M O
00 00
3 r-l
C? O • - W >
"^ O.U U
B ^ ? S S
g J4 H 3 0
ffi O w 3
« u o-
lu r; o <4-l fl)
M O 4J M VI
m m m CM m m
1
M
M M M M M M
^
55
1 O TJ •>
VI -rl t) 0 J JD 0) QJ t3 r-
JJ JC • -rl P VI rH
-rl tOJT P O U 0 0)
o ,rH «)
> JJ 0) O JJ VI r-( rH C
0 U rH X E « B « 0
•J VICOJ.J M Vl*tiVlVi
> B B -rl 0 B«U°>
i ^ JJ JJ U U-l 3 O O. O- W
a OfHea -H ouco.u
ffl rH 0 «J Q. B r-l l> 0 0 C
01 (x>ViO 3 (i, « C K IU
» U B
OK •• • O •• •
±3 ta —itM.m 2 r-i CM o
" .
S •< A
w
00
m
I
(-3
VI
o
w
i?
cS
**«. •*
98 S
o
«J
branches
4. Rappers on distribu-
tion plates not: used
n: E is external, and I :
iued)
•3 -r-
31
142
-------
^•^
•o
3
+J
C
O
u
VH-'
.
on
rH
LU
_J
CO
e ^
H >>
JO U
0 OJ
o.
01
a *-.
C "o?
0) 03
0 >
•9
UJ
0 i-l
00 O
a ci
u ex
OJ CO
B
g
r-l
JO
O
U
a.
00
B
•rl
XI
•9
rl
J.
|
JO
•rl
a
09
o
P*
- JC
o
—>. e
A|_e
09 X
C
09 C
oo a
B c
•H -n
XI
2 "e
I
O I
XI
«••> c
U] -H
XI
e a
3 V
to 3
o
*w 6
M ILi
in wi
pj U
_
-
^
'fcj
1
^s
z
Cl
00
B
a
u
0)
« rH Cl
B JS ta
5 22
JD -H r-t
2 > S
tv, 09
H4 J<
n ex,
u a
§*"* c3 .4.4
2 ^
•
M
r-l
O xi
1 OJ «8
B Li
•n ex
1 O
XI Ll
e> ix
u ex
3 1
>. cr
Cl
1
WWW
1
l^*
te
1
•<;
^
•o
a
•O BO
xi «J 3
B to
0) B r-l
SU 09 CO
h JS o
3 u u
rS XI 3 U
M xi o] «M i-l
•o «3 3 BO
O «9 U XI
«J 6 CO S 09
oj o ex o 3
co o co ,-5 CJ
C^-^ lX
o
-i.B
A^C
09 X
•rl U
Cl
B O
oe «
B C
•rl iH
XI
s *«
u-i E
. 0 OJ
XI
^-, c
u
e «
3 C)
«Q 3
C7
*• | cJ
n k
'
m m
.
1
M
r-l M
1
1
^|<
^fe
1
^ « W
4 JD
r* OJ O
O 00 kl
8 MO.
«l HI
erf r. to
U B
CO 00 f4
•a -H -a
i-l -a o
•3 Br^
CO A «*1 rg rsj CN| O
i
P4 • M P4 W W M HI
!l I 1
1 1 1
s= s: z zfelz z
1 1 1
^ ^ *£ •*£ •< •<; • O O U
XI r-l Cl XI B XI flj
EO OS i-l o O 0
C 3 TJ B m B B 0
sj o OB LI o ;
QOJs:cjr-
M -» « M> r-. 03 0*
**! ^3
—<
1
(-1
W M
1 1
- 09 O
4 09 -d XI
9 Ll Ll 0) X
• OJ OJ OC CJ
ex cx-o
j D- a. -H •« , — s
iS5£ '•' -^
H dl
0-J _ g
B 'i-
•H "*""
XI ^
•e O
o 0
q * ,
143
-------
<—N
•o
0)
c
c
o
o
^_/
__1
m
UJ
__l
CQ
Q
0
XJ
U
•<
5
*0
C
U
1
5
cj
t!
C O
1-1 -*
xj' 1
09 — •
•—I
i?
o u
B
O
XJ
<9
U
3
•o "a
A) ^
e >,
CJ UJ
El -r4
-0 O
O SJ
(O
B "i?
-r< ^3
£ >
03 >*
« -t-4
So
** s.
41 ua
B
g
0
A.
CO
5
XJ
O
M
•i
£•
C
1 5
o
•
o
•H
A
w
•H
u
g
^H
4J
id
0
^.^
- t-3
§
B
a. M
CX e] XJ
o .3 B
jz a a
^ ^J 1
V 1 CO
« -S S
Q) » 0
0.0 M ^
OJr-l -^ n)
««•' -< »
• • *
CM n -^
-g
o *
— • ti
A|S
eo
e
o
B *^.
eo-o
E B
•H CO
XJ
•J d
u o
• -rl
O U
9
*-*-a
t-> o
*
a
P. XI
g^S
*> a
t)
v-l JB
M O
M •-;
B
o> o
u u
a qj
UJ 01 D
HO B
CO B -CO
M i-i eo-rt
OS i-l xl
W et .e o
H B •>
O iH ^* CO
5 ca 1-1 xi
O a. c
m on
H a
Z c) • -
W X -1 CM
£ .
"*
>
0
• •
t-i
pa
i
Vi
3
o eo ca
>-i B ai
•H 0
CO T3 01
*-» ej a)
BOM
\
«I 0
>> CX B
M a. cu
e) O 3
•0 W cr
•
CO
*
.'i
p
Q)
'J
a
M
•O
B
al
xternal,
V
B
H
„
B
O
XJ
s
3
144
-------
NO
Check pressure drop across
each compartment; also,
check1 condition of lines
and pressure gauges.
ENTER RESULTS ON LINES Al,
Bl, Cl, Dl, and El, OF
CHECKLIST.
I
Check cleaning system:
-Pulse jet pressu're
,-Solenoids
-Reverse air blowers
-Shakers
ENTER RESULTS IN SECTIONS
B, C, and D OF CHECKLIST.
1
Check solids removal equip-
ment:
-Screw conveyor
-Pneuo-stic system
-Heaters
-Vibrators
ENTER RESULTS. IN SECTION E
OF CHECKLIST.
YES - ENTER UNIT
Can
Internal
Inspection be
Performed?
Check condition of bags:
^Bag tears
—Bag deterioration
-Dropped bags
-Oily bags
-Wet bags
-Improper bag tension
-Deposits on floor
ENTER RESULTS IN REPORT.
Are
there any
indications of
nonoptimal per-
formance?
Check clean' air chamber for
possible leakage.
Check hoppers
Incomplete solids removal
Corrosion
ENTER UNIT TO CONFIRM
EVALUATIONS. MAY NEED
TO RESCHEDULE INSPECTION.
END INTERNAL FABRIC FILTER
INSPECTION.
NO - END FABRIC FILTER INSPECTION
Figure 51. Fabric filter inspection flowsheet.
145
-------
1
^
r
Reschedule inspection
for a tine when unit is
operational
i
T
Inspect internal parts:
Nozzle condition
Presensp. of corrosion
Presense of erosion
Presence of scaling
1
Check integrity of shell
retention grids, and othe
parts.
I
Check slurry handling
system.
Check pumps on purge,
make-up, and recircula-
tion lines.
Read flow meters if aval]
able. Check liquor temp
on inlets and outlets.
ENTER RESULTS IN SECTIONS
A AND B. j
Check pressure gauges am
differential pressure
monitors across the fol-
lowing:
Spray nozzles
Scrubber beds
Venturi throat
Deminters
ENTER RESULTS ON CHECK-?
LTST.
Check sump and recircu-
lation tanks:
-Liquor temperature
-Liquor pH
ENTER RESULTS
1ST.
ON CHECK-
1
Check inlet conditions:
-Gas temperature
-Presaturator water
flow rate
ENTER RESULTS ON CHECKLIST
END SCRUBBER INSPECTION
Figure 52. Scrubber inspection flowsheet.
146
-------
Perform Internal
Inspection.
NO
Top section, check:
-Rappers
-Drives
.-Insulators
-Heaters
-Blowers
Electrical Field section,
checV:
-Alignment
-Build-up
-Rappers
-Drives
-Insulators
-Erosion
-Corrosion
Check:
-Hopper section
-Build-up
-Corrosion
-Hopper baf £lies
Check:
Gas distribution devices
ESP -Inlet
-Outlet
-Ductwork
• -Corrosion
-Erosion
-Plugging
-Rapping systems
End ESP inspection, return
for operational inspection.
Is
Precipitator
Operating?
YES
Identify bus section numbering
system.
Check for bus sections which
are not operating.
Check electrical characteris-
tics of each bus section
that is operating.
—Primary voltage
-Primary current
-Secondary current
-Secondary voltage (if
measured)
-Spark rate
Check rapper sequence and
timing.
Check insulators purge and
heating system.
ENTER RESULTS IN APPROPRIATE
PLACES ON CHECKLIST.
Check operational status
Hopper heaters & vibrators
Solids removal system
ENTER RESULTS ON CHECKLIST.
NO •>>• END
ESP IN-
SPECTION.
Reschedule operational In-
spection. Recomnend mainte-
nance vork.
END ESP INSPECTION.
Figure 53. Electrostatic precipitator inspection flowsheet.
147
-------
SECTION 5
COMPLIANCE DETERMINATION
When the inspection has been completed, the inspector should conduct an
exit interview with the source. During that meeting he/she should:
0 Ask clarifying questions as necessary,
0 Review inspection notes so that there is general agreement on
the technical facts, and
0 Discuss the need for a followup inspection or additional
records.
After returning to the office, the inspector should prepare an inspection
report. All conclusions based on observations and calculations should be
clearly stated, and a diagnostic checklist for each control device in the
plant should be included. The report should also document:
0 Any change in responsible plant personnel,
0 Requested permit changes or reported process modifications,
0 Results of evaluation,
0 Action requested,
0 Inspector's signature, and
0 Date of inspection.
A copy of the report should be kept in the inspector's source file and in the
Agency's central file.
Comprehensive inspections require that the inspector have an established
baseline for each parameter during a period of known compliance. The baseline
should document all pertinent operating parameters as they relate to the
emission characteristics of the source, including all process and control
equipment parameters. In collecting pertinent data, the Agency should be
certain (1) the data are needed, (2) that a change in the value of a parameter
148
-------
has an effect on the operation of the source, and (3) that the data are accur-
ate. Checklists (as presented in Section 4) are especially useful. The
baseline establishes a fixed point of operation and the appropriate values of
operating parameters against which other determinations can be made. The
emission test at that point of operation documents the emissions that may be
correlated with process and control equipment operating characteristics de-
rived during the test. The baseline test results are useful in subsequent
routine inspections. When an operation and maintenance program or permit to
operate is issued based on a range of process and control equipment para-
meters, the Agency must be able to measure these parameters. For this reason,
maintenance and calibration of the key parameter instrumentation are required
prior to the performance test. Additional instrumentation also may be needed
in some cases.
The baseline must be used for documenting deviations from normal condi-
tions for each process or control device operating parameter. A substantial
change in the parameter is evaluated based on its impact on overall emission
levels. For example, an increase in boiler firing rate would be evaluated
because of its impact on the uncontrolled emission rate from the boiler.
The efficiency of the ESP serving a coal-fired boiler can be estimated by
using variables that define the power input to the system and the gas flow
being treated. The equation that is generally applied is a modified version
of the Deutsch-Anderson equation. This equation contains a parameter that
must be estimated or calculated from a previous baseline performance test. To
apply this method, the inspector must be able to determine the flue gas flow
rate through the ESP and the power input to the ESP. He/she must also be able
to determine that the unit is in reasonably good operating condition (no gross
gas maldistribution, power distribution imbalances, high resuspension rates,
or high rapper reentrainment) because poor conditions can severely impair the
performance of the ESP.
The performance of an ESP should be evaluated in relation to previous
baseline tests and observations. In rare cases, it is possible that stack
tests have been conducted over a range of boiler loads and at several ESP
power input levels. In such cases, an inspector may be able to estimate
emissions if operating parameters are within the range of operating conditions
149
-------
that have been tested. Table 14 lists the effects of several operating para-
meters of boilers, ESPs, and fabric filters on particulate emissions.
TABLE 14. SUMMARY OF THE EFFECTS OF SEVERAL OPERATING PARAMETERS OF
BOILERS, ESPS, AND FABRIC FILTERS ON PARTICULATE EMISSION RATES.
Parameter
Firing rate
Primary air
Excess air
ESP power input
ESP superficial velocity
Fabric filter
air-to-cloth ratio
Fabric filter
pressure drop
Flue gas oxygena
Primary air temperature
Visible emissions
Change
Increase
Increase
Increase
Decrease
Decrease
Increase
Increase
Increase
Decrease
Increase
Effect on parti cul ate
emission rate
Increase
Increase
Increase
Increase
Decrease
Increase
Increase
Increase
Decrease
Increase
If increase in oxygen is a result of an increase in
primary air volume.
The inspection provides information on the key operating parameters of
the boiler and pollution control equipment. Based on increases or decreases
in specific parameters, the inspector can determine whether emissions have
increased or decreased. Without a stack test, the inspector cannot determine
compliance with the standards. Similarly, without visible emissions measure-
ments, he/she cannot determine compliance with the visible emissions standard.
Based on the data collected during an inspection, however, the inspector can
subjectively determine compliance.
The data should be arranged in an orderly fashion (as shown in the check-
list order), and for each recorded parameter the baseline data and the latest
inspection data should be tabulated for comparison. Beside each tabulated
value the inspector should note the impact of the parameter on the source
150
-------
emissions (i.e., no change, an increase, or a decrease). This process pro-
vides a useful table of increases and decreases in emissions for the inspec-
tor's subjective evaluation.
A few specific equations can be applied to the data to provide additional
information on emissions. The inspector should be familiar with the Deutsch-
Anderson equation for electrostatic precipators for use in estimating ESP
emissions.8 Plots of ESP voltage-current data can be effective for diagnosing
malfunctions that can cause an increase in emissions.9 Several manufacturers
of particulate scrubbers also use empirical equations to calculate emissions,
and the inspector should be familiar with these equations as well. Sources
equipped with fabric filters must be evaluated subjectively because no suit-
able equations are available for estimating emissions from fabric filters
based on data that would be collected- during an inspection.
During an inspection the following differences in operation from the
baseline conditions were noted:
Effect
Fuel consumption
Air flow
Steam production
Fan motor current
Fabric filter3
pressure drop
Opacity
Baseline
250 Ib/h
63,000 acfm
2050 Ib/h
30 amps
3 in. H20
5%
! 9 in. H20
Inspection
210 Ib/h
53,000 acfm
1700 Ib/h
26 amps
2 in. H20
10%
6 in. H20
on emissioi
Decrease
Decrease
Decrease
Decrease
Decrease
Increase
Increase
Overal1
Based on the information in Table 14, it is possible that the unit would
not be in compliance with the particulate emission standard if the boiler were
operating at baseline conditions. The increase in opacity of emissions from
the fabric filter indicates that the filter has missing bags, torn bags, or
other bag problems.
151
-------
The relationship between pressure drop and the air flow through a fabric
filter is nearly linear. Based on the fuel consumption, heat content, stack
oxygen, and F factor, the air volume changed from 63,000 acfm to 53,000 acfm.
With a 3 in. H20 pressure at baseline conditions the pressure drop at the time
of the inspection should be 2.5 in. H20 or slightly higher than the observed
value.
The fan data indicate a drop in current usage due to the decreased air
flow and the drop in static pressure. Since the pressure drop across the fan
is only 2 in. H20 instead of the 2.5 in. H20 expected using the F-factor, it
can be assumed that a bag is torn or missing. This confirms the higher opa-
city exhibited by the fabric filter.
152
-------
REFERENCES
1. Langsjoen, P. L., J. 0. Burlingame, and J. E. Gabrielson. Field Tests of
Industrial Stoker Coal-Fired Boilers for Emissions Control and Efficiency
Improvement - Site K. EPA-600/7-80-138a, U.S. Environmental Protection
Agency, Research Triangle, Park, N.C. May 1980.
2. American Boiler Manufacturers Association. A Guide to Clean and Effi-
cient Operation of Coal Stoker Fired Boiler. Prepared for the Department
of Energy under Contract No. EF-77-C-01-2609 and for the U.S. Environmen-
tal Protection Agency under Contract No. IAG-D7-E681 by KVB, Inc. and the
ABMA, Arlington, VA. April 1981.
3. The Babcock & Wilson Company. Steam/Its Generation and Use. 38th ed.
The Babcock & Wilson, Company, New York, New York. 1975. p. 11-2.
4. Reference 3. p. 11-3.
5. Reference 3. p. 9-1.
6. Szabo, M. F., Y. M. Shah, and S. P. Schliesser. Inspection Manual for
Evaluation of Electrostatic Precipitator Performance. EPA-340/1-79-007,
U.S. Environmental Protection Agency, Washington, D.C. March 1981.
p. 4-5.
7. PEDCo Environmental, Inc. Summary Report on S02 Control Systems for
Industrial Combustion and Process Source, December 1977, Volume I Indus-
trial Boilers (Power and Steam). Prepared for the U.S. Environmental
Protection Agency, Industrial Environmental Research Laboratory, Research
Triangle Park, N.C., under Contract No. 68-02-3173. Cincinnati, Ohio
December 1977.
8. John A. Danielson, ed. Air Pollution Engineering Manual. 2nd ed.
AP-40, U.S. Environmental Protection Agency, Research Triangle Park, NC.
May 1973. pp. 153-155.
9. Reference 6. pp. 4-13 and 4-19 to 4-22.
10. Fryling, G. R., ed. Combustion Engineering. Combustion Engineering,
Inc., New York, New York. 1966.
11. Zerban, A. H., and E. P. Nye. Power Plants, 2nd ed. International
Textbook Company, Scranton, Pennsylvania. 1960.
153
-------
12. Richards, J. R. Plant Inspection Manual - Techniques for Evaluating
Performance of Air Pollution Control Equipment - Inspection Procedures
and Performance Evaluation. Prepared for U.S. Environmental Protection
Agency Air Enforcement Branch, Region IV, by PEDCo Environmental, Inc.,
under Contract No. 68-02-3512 (PN 3525-9), Durham, NC. 1981.
13. PEDCo Environmental, Inc. Simplified Operation and Maintenance Manual
for Operators of Oil- and Gas-Fired Boilers. Draft manual prepared for
U.S. Environmental Protection Agency, Stationary Source Compliance Divi-
sion, under contract No. 68-01-6310, Task 54. Cincinnati, Ohio. 1983.
14. Devitt, T., et al
15.
16.
17.
18.
The Population and Characteristics of Industrial/
Commercial Boilers. Prepared for U.S. Environmental Protection Agency
Industrial Environmental Research Laboratory - Research Triangle Park by
PEDCo Environmental, Inc., under Contract No. 68-02-263, Task 19 (PN
3310S). Cincinnati, Ohio. 1979.
Hudson, J. A.
Steam Plant.
Knoxville.
et al. Design and Construction of Baghouses for Shawnee
Tennessee Valley Authority Division of Engineering Design,
19.
20.
21.
22.
23.
24.
Reigel, S. A. Fabric Filtration Systems Design, Operation and Mainten-
ance. Overland Park, Kansas. 1981.
Billings, C. E., and J. E. Wilder. Major Applications of Fabric Filters
and Associated Problems. Environmental Engineering Science, Chestnut
Hill, Massachusetts. 1981.
PEDCo Environmental, Inc. Plant Inspection Workshop - Techniques for
Evaluating Performance of Air Pollution Control Equipment. Volume III.
Process and Control Equipment Flowcharting Techniques. Prepared for U.S.
Environmental Protection Agency Air Enforcement Branch, Region IV.
Durham, North Carolina. 1981.
Schmidt, C. M. Good Operating Practices for Industrial Boilers. Cleve-
land, Ohio. 1979.
PEDCo Environmental, Inc. Kraft Pulp Mill Inspection Guide. EPA-340/
1-83-017, U.S. Environmental Protection Agency, Division of Stationary
Source Enforcement, Washington, DC. 1983.
National Coal Association. Layout and Application of Overfire Jets for
Smoke Control. Washington, D.C. 1962.
National Research Agency of the Bituminous Coal Industry. How to Reduce
Stack Dust from Small Stationary Plants. Pittsburgh, Pennsylvania.
1952.
Smith, E. H. Underfeed Stokers. Worcester, Massachusetts.
Reed, L. E., and L. J. Flaws. The Reduction of Smoke Emission from
Coal-burning Ships with Forced-draught Boilers. R.S.H.2. 1960.
154
-------
25.
Boubel, W. et al. General Inspection Procedures and Design Methodology
for Evaluating the Performance of Cyclone Separators. Draft report
prepared for U.S. Environmental Protection Agency, Division of Stationary
Source Enforcement, Washington, D.C., by PEDCo Environmental, Inc. under
Contract No. 68-01-4147. Cincinnati, Ohio. 1980.
26.
Engineering-Science. Wet Scrubber Performance Manual.
U.S. Environmental Protection Agency, Washington, D.C.
EPA-340/1-83-022,
September 1983.
155
-------
-------
APPENDIX A
POLLUTION CONTROL DEVICE DIAGNOSTIC
CHECKLISTS AND DATA SHEETS
A-l
-------
TABLE A-l. CONTROL DEVICE DIAGNOSTIC CHECKLIST AND COVER PAGE
INSPECTION
REPORT-
REPORT NUMBER
PLANT NAME
PLANT I.D.
SPECIAL ACTION RECOMMENDED (Yes) (Ho)
I. GENERAL INFORMATION
A. Sources Inspected
Production Status
B. Reasons for Inspection (Check Appropriate Items)
Routine Inspection ,_
Complaint Investigation
Stack Testing Observed _
Special Studies
Other
Compliance Progress
Permit Review/Renewal
Tax Certification
Emergency Episode
Equipment Malfunction
C. Plant Representative Contacted (Name and Title)
D. Inspection Procedures and Conditions
Prior Notice (Check One) Yes No
Time/Date
Duration On-Site
Type Inspection (Check One) Counterflow
Other
Weather -
Follow-Up
Wind Direction
II. PRE-INSPECTION INTERVIEW
A. Production Status: Normal
B. Control Equipment: Normal
C. Permit/Compliance Schedule Changes Needed: Yes
D. Comments
Abnormal
Abnormal
No
(continued)
A-2
-------
TABLE A-l (continued)
Report Number
III. INSPECTION RESULTS
A. General Conclusions
All Sources in Compliance with:
Mass Emission Regulations:
Visible Emission Regulations:
Fuel Quality Regulations:
Continuous Monitoring Regulations: .Yes
Sampling/Testing Requirements:
Recordkeeping Requirements:
Permit Stipulations:
Special Orders:
O&M Practices:
Housekeeping:
Good
Good
Yes
,Yes
Yes
.Yes
Yes
Yes
Yes
Yes
Average
Average
No
No
No
No
No
No
No
No
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Poor
Poor
B. Specific Conclusions
Compliance Questionable Due To:
Changes in Raw Materials and/or Fuels
Production Rates Increases
Operational Changes in Process
Deterioration of Process Equipment
Operational Problems in Control Equipment (Check Appropriate Items Below)
Electrostatic^
Precipitators
Resistivity
TR Sets
Insulators
Discharge Wires
High Velocity
Gas Distribution
Rappers
Solids Handling
Plate Warpage
Mass Overload
Other
Fabric
Filters .
Tears/Pinholes
Blinding
Bleeding
Cleaning System
Hopper Overflow
Corrosion
Wet
Scrubbers
Low Liquor Flow
Gas Flow Rate Low
Bed Plugging
Nozzle Erosion
Demisters
Throat Adjustment
• Tray Collapse
Corrosion
C. Samples Taken (Describe)
D. Comments/Recommended Action
Inspector
Reviewer
Date
Date
A-3
-------
TABLE A-2. FABRIC FILTER INSPECTION DATA SHEET
A. INSPECTION INFORMATION
1. IDENTIFICATION
Company_
Plant Name
Plant I.D. Number_
Address
Control Device/System Number_
Process Served
2. PROCEDURES AND CONDITIONS
Prior Notice: Yes No_
Time(s) On-Site
Type Inspect!on_
Inspectors
Plant Representatives_
Information Claimed Confidential: Yes No
A-4
-------
TABLE A-2 (continued)
B. Visible Emissions
Observations
Inspection No.
Equipment No.
Confidential: Yes
Page No. of
No
1. STACK CHARACTERISTICS
Location
Hei ght
Temperature
Exi t Dimensions
Orientation
Other Information
2. STACK EFFLUENT
Detached Plume:
Color
No
Yes
Distance
Puffing: Yes . No
Opacity
Time Average Opacity Observation Point
Sheet No.
3. FUGITIVE EMISSIONS
Control Device: Yes
No
Solids Removal System: Yes No
Process: Yes No ^
Continuous__ Intermittent
Adjacent Deposits: Yes No
A-5
-------
TABLE A-2 (continued)
C. Fan Data
Inspection No.
Equipment No.
Confidential: Yes
Page No. of
FAN MOTOR
Manufacturer
Model No.
Rated Horsepower _
Volts
Maximum R.P.M.
Operating Current: Panel
Type_
Maximum Amps
Service factor
Other
DRIVE
Direct
Belt
Other
Sheath Reduction _•
Audible Belt Slippage: Yes
No
FAN
Manufacturer
Model No.
Fan Vibration_
Gas Temperature at inlet,
Fan R.P.M.
Fan Static Pressures: Inlet
Type_
Differential Static Pressures:
Fan Housing Condition
Dampers
Fan Exit
Measured
Outlet
Panel
A-6
-------
TABLE A-2 (continued)
D. Fabric Filter Data
1. DESCRIPTIVE INFORMATION
Fabric Filter Type
Manufacturer
Model No.
Plant Inventory No.
Date Installed
2. LOCATION
Building/Area
Inside
Inspection No.
Equipment No.
. Confidential: Yes No
Page No. of
Outside
3. LAYOUT (SKETCH FABRIC FILTER, FAN, INLET, SOLIDS REMOVAL, ETC.)
-
-
•
-
1
....
- -
.
....
—
-
—
—
—
---
.-.._
- —
—
--
•---
--•-
•
"•'•'
-
-
...
--
-•-
— -
—
.....
__.
...
__.
--
—
. _.
- -
__
—
1
i
1
i
i
i
{
i
.. i .
i
i
i
i
I
1
"V
" r
i
••-I
i
__..._
i
i _
i ,
• i
i 1
!._
i
I
+1
-
_
_
i
n
.:!
. ..
A-7
-------
TABLE A-2 (continued)
E.Fabric Filter External
Inspection
Inspection No.
Equipment No.
Confidential: Yes
Page No. of
No
1. SOLIDS REMOVAL
Valve Type: Rotary
Flapper
Other
Valve Speed/Frequency _ • •
Transport Equipment: Screws
Transport Equipment Operating: Yes
Transport Equipment Discharging Solids: Yes
Characterize Discharge _^____
Other
No
No
Hopper Vibrators: "Yes
Hopper Insulation: Yes
Hopper Level Indicators
No _
No
Hopper Condition
Disposal Method
2. SHELL CONDITIONS
Insulated: Yes
No
Possible Weld/Seam Gaps, Characterize
A-8
-------
TABLE A-2 (continued)
E. Fabric Filter External
Inspection
Inspection No.
Equipment No.
Confidential:
Page No.
Yes
No
of
3. OPERATING CONDITIONS
Static Pressure on Clean Side,
Static Pressure on Dirty Side,
On-site Monitor, Differential Static Pressure
Tap Conditions
Gas Inlet Temperature
_ in. H?.0
_ in. H20
H?.0
in.
4. CLEANING SYSTEMS
Type
Frequency
Air Pressure,
Drier: Yes
PSIG
No
Evidence of Water and/or Oil Problems
Solenoids Inoperative
5.
PRECLEANERS
Type
Static Pressures: Inlet
Gas Inlet Temperature
Outlet in
°F
A-9
-------
TABLE A-2 (continued)
I- Fabric Filter Internal
Inspection
Inspection No.
Equipment No.
Confidential:
Page No.
Yes _
of
No
PURPOSE
Reason(s) Necessary
Inventory Check
Comprehensive Inspection
Other
Safety Evaluation (Describe if applicable)
Respirator Necessary _^
Temperature
02 ; __
Combustibles
Electrical Grounding
Mechanical Hazards _
Noise
Other
Inspection Conducted: Yes
Inspection Not Performed Due to Safety
2. BAG LAYOUT (ATTACH DRAWING)
No. of bags
Length
No
Diameter
Material (Characterize)
ft
in.
Attachment(s)
A-10
-------
TABLE A-2 (continued)
R Fabric Filter Internal
Inspection
3. HATCH CONDITIONS
Gaskets
Corrosion
Bolts/Ears
Ease of Access
4. LEAK JETS
Location
Number
5. BAG CONDITIONS
Inspection No.
Equipment No.
Confidential: Yes No
P.age No. of
A-11
-------
Table A-2 (continued)
F. Fabric Filter Internal
Inspection
Inspection No.
Equipment No.
Confidential: Yes
Page No. of
No
6. HOPPERS AND BLAST PLATES
7. CLEANING APPARATUS
A-12
-------
TABLE A-2 (continued)
G Samples
1. SOLIDS DEPOSITS
Sample No.
Location Obtained
Date/Time Obtained
Results
Inspection No.
Equipment No.
Confidential: Yes
Page No. of
No
FABRIC SAMPLES
Sample No.
Location Obtained _
Date/Time Obtained
Permeability
Tensile Strength
Count
Weight/Yard5
OTHER
A-
-------
TABLE A-2 (continued)
H Ventilation System
Inspection No.
Equipment No.
Confidential: Yes __ No
Page No. of __
1. DUCTS (SHOW STATIC PRESSURES ON LAYOUT.)
" i
• i
«->
L -J
1
—
r
__
i
....
.
i
i
...
..
_...
...
_._
_.
....
.
2. HOOD
Configuration
Average Capture Velocity
Thermal Drafts (Characterize)
ft/mi n
Cross Currents (Characterize)
Estimated Effectiveness
A-14
-------
TABLE A-2 (continued)
I Process
1. PROCESS TYPE
Characterize Source
Operating Schedule
Inspection No.
Equipment No.
Confidential: Yes
Page No. of
No
2. OPERATION
Product Type During Inspection
Production Rate During Inspection
Raw Materials During Inspection
Fuels During Inspection
A-15
-------
TABLE A-2 (continued)
J Fabric Filter Evaluation
Inspection No.
Equipment No. _____
Confidential: Yes
of
No
O
.0
u
TS
*O
0
o
o
o
en.
CP—N
= c
*J I
tl —
DC ^
E JC
U U
O (U
Jifi
-e ^*
*
c
o
^
19
J
t> 2>
U) •-
.0 O
O 01
o.
tn
c a
U 19
« >
n
m >»
01 —
00 U
O
U
a.
00
c
V
jj
Of
.0
tn
o
a.
^
o
- *'It
tn w — •
— O TJ
V
u» O. C
CO W O
— — w
(S — —
u - w
u-i £
0 V U
Ul — j£
»-* U
E V
E I- J=
SOU
w fe-
i- -c
u. or C
— a. n,
If* If
t£ u;
a. i
0 "1
u 01
Tj u
a
u u
3 0
trt -o
ui a>
V 0)
u JC
a.
u
^' IT IO
y:1 c AJ
V3| ~»
cd o> ti
cj *J — tn
c -^ — < a
tti cu. j= a.
o
t-t
U — ' r-J
o
1
e s o
tl 0 — ,0
" — A 10
09 O Ui u
« 61 — t {j
.& a. *oi
v» « (X
.* C CO V,
o — • c c
ti — --3
.C W i-r
9 • LJ rt
-o ti c
• ai V- u- u
V» ^ 3 O (J
U O *-» t-i .
re w 3 *-* e to
Of ^ -0 ft)
v. s- , e a
on e i- c.
. — 1
u w !-•' u ^-< ui u: txj uj tc to ^-.uju:icajii.;
coo
Ul to3 ta
to c -o c.
W ** « C IOJC TJ C-
>c-c-Qd u -H to e -u ai .r. o
— Ol-'HRj 3 -rWUOJOl-l >
4>EO; W(U 71 C X4*C j-i(UM 13 C w
w — a. uj^i tr, 3 d>>a in > 1-1 c •-' o *->
i-CQJO 0>U -HiJfV-^OO3 C
9>cct>ct; u. — « w i-
tt. rt — c o >i o.-^ unj-r-t ain) vc oo a;
OM- CfTU K >UX C^W— C C.
C V* ^^ C"^ OCJCi O QJ CJ 11 •*•* C
•- * 1- G ^ —* « OJ O ^-4D.C4JCD.>D.4J .^ C
tfl *I O i- AJ QJ O-^OCJ-iCCi-^'t/;Crt«--4C &
3"O EOC"U*O JItlCl-i tfJ E t-
O — O CCJCQt -HI4J4J WCCO « C
C t- O ^^ CL *H Cf "O *^JOO(U(UR9OOQ/CJ
4/0.0*.* -i je 3 . .JC.-HE— *^-*Jcxu.-^.aa.c.*JE'^>
^-•-'>C-tlC3BOO* Uil — (O—(J-'-t3"^(5O^3-OQ.O,(XCe'HC
3Oaj_cn)or^-«a; o -^'-ion)xn:rc:s— SO
ol • - • •
*** «•* • *^ •£ rv«- oo rs ( *~^ rN) n >j 1^1 vo f** co cr* o »~*
UJ
A-if;
j;
z
V
«"^
M
1
01
•
C
Lj
«
K
(U
Ul
•—
ut
1
u
o
•fc
-------
TABLE A-2 (continued)
J Fabric Filter Evaluation
Inspection No.
Equipment No.
Confidential:
Yes
No
~
•Z
u
_
Recommmuk'
00 ^
c o
2 i
E .*
U .j
O 01
C JZ
-0 U
*
c
5 |
u
ca
0 1
- j
3
a >
u x
01 --1
J= O
O Ol
c.
W
OP .-^
C 01
—1 3
01 Id
U) £»
s2 x
•4-1
01 1-1
00 O
TO 41
U D-
O> CO
> •**
in
e
ot
r-l
.e
o
u
d.
00
c
T4
IJ
in
u
01
S
Ol
^
01
U9
O
0.
Page No
— • >. o" . v, i
„ i S . •?. -0 -• e o -H «
• • I - 1 'J • • " Q U^ tu kl 9) 41
— 4 — » -j c;otn *-i tw o 3 *-<
'.2 5 Cg „ =r .5- .2S3i^ I1" 5^
v: 2 e .2 = « u „ &;• » g « w^ '
scv. oo ^:w*-3 oow ^i uiuuu
*•— j o c ' c c y-1 co^-ito
Ij'~'S';nyi»-HO^«
f!*^'r;-oc X >M<*-i
^cSfJ^zr" ' " g 3 „ s .* B .
o s s-J s, - 1: s o s ."s s g** g-^
4-1 -3 o »-* xj tc -uxuajjiajw
^ c ^ C QJ HO /-\ c *-J *~* T3 SJ (0 *t3 (
•^"oalnSc-S ti^^Jyi^ wm^
eE'-g SB"* Bg'|s^^lt
.?=•?• J= o 14 j4 B 30J<:5 ^-o3
j-. ui u u o u u f. tuouuuiu'ji:
-^L*r33cyu ucirt— »«(y4-i— w-Ucs *-4O.OOOOV)D.^
n m ir CM » » M
1
i i
1
1
-
t3 UJU:^-.U:UI-HU' u sju; wuuJi-j
»
1
'• ~i •-$ < < <
2 z Z Z Z
•^ -^ < < •<
2 2 .., 5^5
f~* *~t
. OO 00
oo > >
> a M m ^ .^
"" 1) Nf .v- g _ -g. » _ »
2-«2SS^ 2«^ " « § «
01 5«^4«7A ^ S^t^Sxl
I S^ Bsirig £g g S^|£
o o ""S-.S'S.c °"" " ^'S2«
•H Qt CO JC JC C .C ~* QJ 60 rti *A* Si •> ^ " ^
a. MVOOM-H ^H ^w^jlu'^ocftiS
I fls-sl??^ fl •^'I'xffl&sl-r
S 'Ho'aui^iuqS' ^ ^o'ScS'Em-H"'^
fl3 • • . 4 W
0 - CM r-1 ^» ^' vo" r^ co" S -.' CM' c^ ^ ,X vo" r^
^ * •
A _ -1 -J
Of
o
" A («*j
' tn o
3 -^ 01 rs
"• 00 3 . .
4 *H @ e
J tQ -^4
3 U 1*4 41
3 14-4 O T3
-1 .00
S ^ 0 -
3 to u 3
•j N-' 0
\ 4J W .
1 1 &S J
J- M 01 0 .C
2 4J 3 00
5 ^ a d ^
« n
* r t
x w t-j
w a ti) w
i
<
z"
«<
^
x .c
•H 00
i-l •*
3 *
•o -ax
ai no
« 1-1 e
•a no ID
^3 fi cr
to » £ o 01
U C oo u p
O -H ^| ^3 ujuj
O bd .c C
•0 IJ c 01 ^4 00
O T-I X U Ul C
OT C -O 4J 3 fO «) o cn u n
o *H ,-< aj ai o 41
o c « o. u c —i
-------
TABLE A-2 (continued)
K Summary
Inspection No.
Equipment No.
Confidential:
Page No.
Yes _
of
No
1. CONTROL SYSTEM PERFORMANCE
System Air Flow Based on Fan Data.
System Air Flow Based on Pi tot Traverse
System Air Flow Based on Process
Actual Air to Cloth Ratio
Design Air to Cloth Ratio
Fabric Compatibility with Environment
2. ADDITIONAL COMMENTS
ACFM
3. SHEETS INCLUDED
A.
G.
Preparer:
Reviewer:
B.
H.
Name
Date
Name
Date
C. D. E. F.
I. J. K.
Signature
Signature
Copies Received
Initials
Date
A-18
-------
TABLE A-2 (continued)
Fabric Filter Supplemental
Information
Inspection No. _____
Equipment No.
Confidential: Yes _
Page No. of
No
A-19
-------
LOCATION
DESIGNATION
TABLE A-3. WET SCRUBBER INSPECTION DATA SHEET.
' DATA SHEET NO.
DATE
CLAIMED
CONFIDENTIAL Yes
NO
INSPECTOR(S)
INSPECTION NO.
DESCRIPTIVE INFORMATION
Wet Scrubber Type
Manufacturer
Model Number
Date Installed
Process/Source Controlled
Particulate Characteristics
B. COMPONENT INFORMATION (Describe if applicable)
1. Gas Pretreatment:
Presaturator
Cyclones '
Settling Chamber
Other
Demister:
Cyclone _
Chevron
Fiberous Mat
Other
Pumps:
Number
Recirculation
Pump Manufacturer
Recirculation
Pump Rated Horsepower
Recirculation Pump Type
A-20
-------
TABLE A-3 (continued)
Inspection No.
Data Sheet No.
Preparer
Confidential: Yes
No
B. COMPONENT INFORMATION (continued)
4. Fan/Motor (Specify)
Fan Manufacturer
•Blade Type: Radial.
Drive: Direct
Damper Position .
Backward
Belt
Forward
Motor Manufacturer
Model No.
Rated Horsepower
Location: Forced Draft
Induced Draft
5. Instrumentation (Check if Applicable)
Differential
Pressures:
Temperatures
Throat
Separator
Demister
pH:
Gas Outlet
Gas Inlet
Liquor Inlet
Liquor Outlet
Recirculation
Exit Liquor
Fan Motor Current
Other
Flow Rates:
Motor Current:
Nozzle Pressure
Recirculation
Makeup
Purge
Fan
Pump
A-21
-------
TABLE A-3 (continued)
Inspection No.
Data Sheet No.
Preparer .
B.
Confidential: Yes No
COMPONENT INFORMATION (continued)
6. Materials of Construction (Specify type and gauge)
Presaturator
..Throat
Scrubber Shell
Trays/Bed Supports
Demister
Fan Housing
A-22
-------
TABLE A-3 (continued)
Inspection No.
Data Sheet No.
Preparer '
Confidential: Yes No
C. DIAGRAM
1. Sketch wet scrubber system. (Show all major compon-
ents and processes controlled.)
2. Sketch wet scrubber layout (each square I1 x .1')
A-23
-------
TABLE A-3 (continued)
Inspection No.
Data Sheet No.
Preparer
Confidential: Yes
No
F. SAMPLE ANALYSIS
Scrubber Liquor Effluent
Sample No.
Location Obtained
Date/Time Obtained
Results:
Suspended Solids ^
Dissolved Solids
PH ;
Chloride
Scrubber Recirculation
Sample No.
Location Obtained
Date/Time Obtained
Results:
Suspended Solids
Dissolved Solids
PH
Chloride
ppm
ppm
ppm
ppm
ppm
ppm
Other
A-24
-------
TABLE A-3 (continued) Inspection No.
Data Sheet No.
Preparer
Confidential: Yes No
G. CONTROL SYSTEM PERFORMANCE
Gaseous Flow ; ACFM
(implied from fan operation)"
Gaseous Flow ACFM
(calculated from pitot traverse):
Gaseous Flow ACFM
(implied from process operation)
Liquor Flow • gpm
L/G Ratio ,
Bypass (% of total gas flow) %
Throat Velocity FPS
Superficial Velocity (design) ' FPM
(effective) FPM
Visible Emissions (residual) %
H. ADDITIONAL COMMENTS
Sheets Included: A B C
D E F
G H
Inspector's Signature
Date Prepared
Reviewer's Signature
Date Reviewed
Date Filed
A-25
-------
TABLE A-4. ELECTROSTATIC PRECIPITATOR INSPECTION DATA SHEET.
A. INSPECTION INFORMATION
1. IDENTIFICATION
Company_
Plant Name
Plant I.D. Number_
Address
Control Device/System Number_
Process Served
2. PROCEDURES AMD CONDITIONS
Prior Notice: Yes No_
Time(s) On-Site '
Type Inspection_
Inspectors
Plant Representatives_
Information Claimed Confidential: Yes_
No
A-26
-------
TABLE A-4 (continued)
B. Visible Emissions
Observations
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
No
1.
STACK CHARACTERISTICS
Location
Hei ght
Temper a ture_
Exit Dimensions_
Orientation
Other Information^
2. STACK EFFLUENT
Detached Plume:
Color
No
Yes
Distance
Puffing: Yes
Opacity
Time Average Opacity
No
Observation Point
Sheet No.
3. FUGITIVE EMISSIONS
Control Device: Yes
Solids Removal System: Yes
Process: Yes No
Continuous
No
No
Adjacent Deposits: Yes
Intermittent
No
A-27
-------
TABLE A-4 (continued)
C. Fan Data
1.
3.
FAN MOTOR
Manufacturer
Model No.
Rated Horsepower_
Volts
Maximum R.P.M.
Operating Current: Panel
DRIVE
Direct , Belt
Sheath Reduction
Audible Belt Slippage: Yes
FAN
Manufacturer_
Model No.
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
Type_
_. Maximum Amps
_ Service factor_
Other
Other
No
No
Type.
Fan Vibration
Gas Temperature at inlet,
Fan R.P.M.
Fan Static Pressures: Inlet
Differential Static Pressures:
Fan Housing Condition
Dampers
Fan Exit
Measured
Outlet
Panel
A-23
-------
TABLE A-4 (continued)
D. Electrostatic Precipitator
Data
1. DESCRIPTIVE INFORMATION
Type
Manufacturer
Model Number
Plant Inventory Number_
Date Installed'
Number of Chambers
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
No
Number of Fields in Series
Specific Collection Area (Ft2'/1000 Ft3)_
Design Superficial Viscosity (Ft/Sec)
Pulse Energization (Yes/No)
LOCATION
Building/Area_
Elevation
LAYOUT (SKETCH FIELD LAYOUT AND NUMBER FIELDS, SHOW FANS)
A-29
-------
TABLE A-4 (continued)
E. Electrostatic Precipitator
External Inspection
Inspection No.
Equipment No._
Confidential: Yes No_
Page No. of
x. HOPPER LAYOUT (SKETCH TOP VIEW AND NUMBER; SHOW SOLIDS HANDLING
SYSTEM)
c..
HOPPER DESCRIPTION
Vibrators: Yes
Heaters: Yes
Insulatipn: Yes_
Level Indicators: Yes
No_
No
No
No
Type_
Physical Condition (Characterize)^
Transport Equipment: Screws Pneumatic_
Transport Equipment Operating: Yes
Characterize Discharge
Other
No
A-30
-------
TABLE A-4 (continued)
E.Electrostatic Precipitator
External Inspection
Inspection No.
Equipment No._
Confidential:
Page No-.
Yes
of
No
3. HOPPER VALVES
Type: Screw
Speed/Cycle Times
Blade Type_
Other
4.
.RAPPER LAYOUT (SKETCH TOP VIEW, SHOW DISCHARGE WIRE UNITS AS D,
COLLECTION PLATE UNITS AS C AND DISTRIBUTION PLATE UNITS AS X).
A-31
-------
TABLE A-4 (continued)
E. Electrostatic Precipitator
External Inspection
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
No
5. RAPPER PERFORMANCE (Continued)
COLLECTION PLATE RAPPERS
No.
Ci
C2
C3
C*
C5
C6
C7
C8
C9
Cio
Cn
Ci2
Cl3
Cm
Cis
Cl6
Cl7
Cl8
Cig
C20
Time Interval
(Minutes)
»
Duration
(Seconds)
-
Comments
A-32
-------
TABLE A-4 (continued)
E. Electrostatic Precipitator
External Inspection
5. RAPPER PERFORMANCE
DISCHARGE WIRE RAPPERS
Inspection No.
Equipment No._
Confidential:
Page No.
Yes
of
No
No.
Di
D2
D3
D.,
Ds
D6
D7
De
D9
Dio
DM
Dj2
Dis
DII»
Dl5
Die
Dl'7
Die
Dig
D20
Time Interval
(Minutes)
Duration
(Seconds)
.?*»
Comments
-.•
A-33
-------
TABLE A-4 (continued)
E.Electrostatic PrecipUator
External Inspection
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
No
5.
6.
RAPPER PERFORMANCE (Continued)
DISTRIBUTION PLATE RAPPERS
No.
Xi
X2
X3
Xi,
X5
Xfi
Time Interval
(Minutes)
Duration
(Seconds)
Comments
RAPPER DESCRIPTION
DISCHARGE WIRES
Type
Number
Manufacturer
Air Pressure
COLLECTION PLATES
Type
Number
Manufacturer _
Air Pressure __
DISTRIBUTION PLATES
Type
Number
Manufacturer
Air Pressure
A-34
-------
TABLE A-4 (continued)
E. Electrostatic Precipitator
External Inspection
Inspection No._
Equipment No.
Confidential: Yes No
Page No. of
7. TRANSFORMER - RECTIFIER SET LAYOUT (SKETCH TOP VIEW SHOWING T-R
SETS ON CHAMBERS AND FIELDS)
8. TRANSFORMER - RECTIFIER SET DESCRIPTION
Power Control: Yes No
Mode Voltage Current Spark Rate
•No.
T-R!
T-R2
T-R3
T-R,,
T-R5
T-R6
T-R7
T-R8
T-R9
T-Rio
Plant
No.
Manufacturer
Model
No.
Milliamp
Rating
i
Type
A-35
-------
TABLE A-4 (continued)
E.Electrostatic Precipitator
External Inspection
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
No
9. TRANSFORMER - RECTIFIER SET CONDITIONS
No.
T-R-la
T-R-lb
T-R-2a
T-R-2b
T-R-3a
T-R-3b
T-R-4a
T-R-45
T-R-5a
T-R-5b
T-R-6a '
T-R-6b
T-R-7a
T-R-7b
T-R-8a
T-R-8b
T-R-9a
T-R-9b
T-R-lOa
T-R-lOb
Primary
current
amperes)
Primary
voltage
(volts)
Secondary
current
(mi 11 iamps)
•
Secondary
voltage
(kilovolts)
Spark
rate
7^/mi n
Control
mode
M-manual
A-automatic
*
A-36
-------
TABLE A-4 (continued)
E. Electrostatic Precipitator
External Inspection
Inspection No.
Equipment No.
Confidential: Yes No_
Page No. of
10. OPERATING INFORMATION
Gas Inlet Temperature, °F
Hopper Heater Operational Indicator Lights (Identify units not on)
Penthouse Heater/Blower Operational Indicator Lights (Identify units
not on) ;
Comments
11. OPACITY MONITORS
Opacity - Minimum, %
Average, % ,
Maximum, %
Spikes (Characterize Frequency, Duration, Intensity)
Calibration Spikes (Characterize Levels, Frequency)_
Comments
A-37
-------
TABLE A-4 (continued)
F. Electrostatic Precipitator
Interal Inspection
Inspection No.
Equipment No.
Confidential: Yes No_
Page No. of
1. PURPOSE
Reason(s) Necessary_
SAFETY EVALUATION
Lockout Procedure Followed
Plant Employee Performing Lockout_
Grounding Straps Available: Yes_
Time Period De-energized (Hours)_
Purge Completed: Yes:
02, % ;
Combustibles, %_
Noise
Other
No
No
Inspection Not Conducted''Due to Potential Hazards ( Characterize)
2. AREAS INSPECTED (SKETCH TOP VIEW AND INDICATE ENTRY POINTS)
A-38
-------
TABLE A-4 (continued) Inspection No..
F. Electrostatic Precipitator Equipment No._
Internal Inspection
Confidential: Yes No_
Page of '
3. HATCH CONDITIONS
Gaskets
Corrosion
4. PENTHOUSE CONDITIONS
Purge Air
Heater(s)
Insulators
Alignment of Collection Plates_
Comments
A-39
-------
TABLE A-4 (continued)
Electrostatic Precipitator
Internal Inspection
Inspection No.
Equipment No:_
Confidential:
Page No.
Yes_
of
No
5. ELECTRODE CONDITIONS
DISCHARGE WIRES
T.VPe
Di ameter_
Material
Spacing and Length_
Conditions
COLLECTION PLATES
Type
Ma ten' al .
Spacing and Length_
Conditions
Alignment,
A-40
-------
TABLE A-4 (continued)
F. Electrostatic Precipitator
Internal Inspection
6. INTERNAL SUPPORTS
Describe
8,
Conditions
7. GAS DISTRIBUTION EQUIPMENT
Type
Condition
HOPPERS
Baffle Condition
Hopper Condition_
Inspection No.
Equipment No.
Confidential: Yes No_
Page No. of
A-41
-------
TABLE A-4 (continued)
Q. Continuous Monitor Evaluation
Inspection No._
Equipment No.
Confidential: Yes No_
Page No. of
1. DESCRIPTIVE DATA
Manufacturer
Model
Type.
Date Installed
Single or Multiple Breeching (Describe Sources)
NSPS Applicable: Yes_
No
2. TRANSMISSOMETER
LAYOUT (SHOW LOCATION RELATIVE TO FLOW RESTRICTIONS)
A-42
-------
TABLE A-4 (continued) Inspection No.
G. Continuous Monitor Evaluation Equipment No.
Confidential: Yes No_
Page No. of
2. TRANSMISSOMETER (Continued)
Approximate Path Length, (Feet)_
Mounting (Characterize)
Vibration (Characterize)
Housing (Characterize)
Purge Air (Condition of Blowers and Hoses)
Filters (Characterize Type and Describe Condition)
Alignment (Window Check)
3. CONSOLES
Breeching/Stack Correlation
Zero/Span_
Comments
A-43
-------
TABLE A-4 (continued)
H, Electrostatic Precipitator
Evaluation
Inspection No.
Equipment No._
Confidential: Yes No_
Page No. of
1. FILES/ADMINISTRATIVE
Specification Sheets Available: Yes_
Prints Available (Characterize)
No
Supervisor of Unit_
0 and M Personnel (Describe Staff and Organization^
2. RECORDKEEPING
»
Type Records__
Operating Records (List Parameters)_
Diagnostic Records (Characterize)__
3. PROCEDURES
Spare Parts Inventory (Characterize^
O&M Plan (Characterize)
Troubleshooting (Character!ze)
A-44
-------
TABLE A-4 (continued)
I. Samples
Inspection No..
Equipment No._
Confidential:
Page No.
Yes_
of
No
1. Solids
Sample No.
Location Obtained__
Date/Time Obtained_
Results
2. Other Samples
Sample No.
Location Obtained
Date/Time Obtained_
Permeability
Tensile Strength_
Count
Weight/Yard2
3. Other
A-45
-------
TABLE A-4 (continued)
J. Electrostatic Preclpltator
Evaluation
Inspection No.
Equipment No._
Confidential:
Page No.
Yes_
of
No
1. POWER INPUT
Collection Plate Area/field
Inlet
Other
Discharge Wire Length/Field
Inlet
Other
Field
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Secondary
Currents
(Milllamps)
Power
Input
(Watts)
Current Densities
(Mi 11lamps/Ft) Watts/Ft2
A-46
-------
TABLE A-4 (continued) Inspection No..
K. Process Equipment No.
Confidential: Yes No_
Page No._ of
1. PROCESS TYPE
Characterize Source
Operating Schedule
2. OPERATION
Product Type During Inspection^
Production Data During Inspection_
Raw Materials During Inspection_
Fuels During Inspection^
A-47
-------
TABLE A-4 (continued)
L.Summary
1. POWER INPUT
2. MECHANICAL
3. SOLIDS REMOVAL
Inspection No.
Equipment No._
Confidential: Yes No_
Page of •
4. EFFLUENT QUANTITY/CHARACTERISTICS
5. OTHER
6. SHEETS .
A. B.
D. E.
G. H.
C.
F.
I.
J. K.
Preparer: Name
Signature
Date
Reviewer: Name
Signature
Date
Copy Received: Initials_
Date
A-48
-------
TABLE A-5. MECHANICAL COLLECTOR INSPECTION DATA SHEET.
LOCATION DATA SHEET NO. __.
DESIGNATION INSPECTION NO. . .
CLIENT ; INSPECTOR(S)
PN DATE
CLAIMED
CONFIDENTIAL Yes No
A. DESCRIPTIVE INFORMATION
Mechanical Collector Type
Cyclone Settling Chamber
Cyclone Bank Double Vortex Cyclone
Multiclone Other (describe)
Manufacturer
Model Number
Date Installed
Process/Source Controlled
Particulate Characteristics
B. COMPONENT INFORMATION
1. Cyclone
Diameter of Body ^^ ft>
Cone Angle degrees
Material of Construction
Gauge of Metal
Number of Cyclones
Hoppers
Number
Slope
Insulation: Yes No
Heating: Yes No
Vibrators: Yes No
A-49
-------
TABLE A-5 (continued)
Inspection No.
Data Sheet No.
Preparer
Confidential: Yes
No
B. COMPONENT INFORMATION (continued)
3. Solids Removal, (Check applicable items and provide
dimensions) \ . >
Rotary Valves '
Flapper Valves '
Screw Conveyors
Pneumatic Conveyors
Free Fall
Fan/Motor
Fan Manufacturer
Model Number _
Blade Type: Radial
Drive: Direct
Backward
Forward
Belt
Motor Manufacturer
Model Number
Rated Horsepower
RPM
Location: Forced Draft
Induced Draft
C. SYSTEM LAYOUT
A-50
-------
TABLE A-5 (continued) Inspection No.
Data Sheet No.
Preparer
Confidential: Yes No
D. EXTERNAL INSPECTION
Fan Inlet Static Pressure . - in. of
Fan Outlet Static Pressure in. of
Fan Motor Current amperes
Fan Rotational Speed rpm
Fan Damper Position
Gas Temperature at Fan Inlet °F
Fan Vibration (low, moderate, severe)
Corroded
2
Static Pressure at Collector Outlet • in. of H~0
Static Pressure at Collector Inlet in. of H_0
On-site Differential Pressure Gauge Reading in. of H.,0
Gas Temperature at Collector Inlet °F
Rotary Valve Rotational Speed rpm
Flapper Gate Frequency (#/hr) '
Hopper Conditions (Check if applicable)
Cold
Dented
Warped
A-51
-------
TABLE A-5 (continued)
Inspection No.
Data Sheet No.
Preparer
Confidential: Yes No
E. INTERNAL INSPECTION
Hoppers (plugged or corroded)
Hopper Baffles Nonexistent (Characterize potential abra-
sion) :
Inlet Vanes Plugged/Eroded (Characterize severity)
Cones Plugged (location, number)
Flow Disturbances (Characterize severity)
Outlet Tube Erosion (Characterize potential bypassing)
Corrosion (Characterize)
Scaling (Characterize)
A-52
-------
TABLE A-5 (continued) Inspection No.
Data Sheet No.
Preparer
Confidential: Yes No
F. CONTROL SYSTEM PERFORMANCE.
Air Flow Rate (implied from fan operation) ACFM
Air Flow Rate (calculated from pitot tube) ' ACFM
Air Flow Rate (implied from process operation) ACFM
Inlet Velocity FPS
Opacity •_...• ' %
G. ADDITIONAL COMMENTS
Sheets Included: A B C
E F G
Inspector's Signature
Date Prepared
Reviewer's Signature
Date Reviewed
Date Filed
A-53
-------
-------
TECHNICAL REPORT DATA
(Please read JaUmctions CM the reverse before completing)
1. REPORT NO.
EPA-450/1-84-025
2.
3. RECIPI-ENT'S ACCESSION NO.
4 TITLE AND SUBTITLE
Coal-Fired Industrial" Boiler Inspection Guide
5. REPORT DATE
Issued January 1984
6. PERFORMING ORGANIZATION CODE
7, AUTHOR(S)
William- E. Gallagher, Gerald A. Isaacs, Thomas C.
Ponder, Jr., and Robert A. Ressl
8. PERFORMING ORGAN.IZATI'ON REPORT NO.
'3560-3-9
9 PERFORMING ORGANIZATION NAME AND ADDRESS
PEDCo Environmental, Inc.
11499 Chester Road
Cincinnati, Ohio 45246-0100
10. PRC'GBAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-01-6310
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Final.
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
U.S. EPA Project Officer - John R. Busik, Stationary Source Compliance Division
16. ABSTRACT \ '• ' ~~~
This document provides guidance for evaluating;the performance of coal-
fired industrial boilers relative to a. pollution control agency's particulate'
air pollution control rules and regulations. The guidance and checklists' in
this document enable an air pollution control agency inspector to check a
boiler operation quickly and efficiently. A thorough description, of stoker-
fired and pulverized coal-fired industrial boilers helps prepare the inspector
for the field inspection. Pollution control equipment typically used on
industrial boilers (multicyclones, fabric filters, electrostatic -precipita- .
tors, and scrubbers) is described as well as common problems and possible
solutions that influence the operation and maintenance of these devices.
Baseline data for a boiler and its pollution control equipment normally .
are established during a compliance stack test. Information contained in this
report shows the agency inspector how to compare current boiler-operations to
the baseline data for a compliance determination. This is particularly useful
when a clearly defined cause-and-effect relationship cannot be established for
a given source.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
BOIlers
Pollution
Particles
Control Equipment
b.IDENTIFIERS/OPEN ENDED TERMS
"Industrial, Stoker-fired,
Pulverized Coal-fired
Air Pollution Control
Particulate Emissions
Multicyclones, Fabric
Filters, ESPs, Scrubbers
c. COSATI Field/Croup
ISA
13B
14G
13B
13..plS.T.RIBUTigN STATEMENT , .... -, -r i
unlimited. Available from'National Tech-
nical Information Service, 5085 Port Royal
Road, Springfield, Virginia 22161
.
assi
21. NO.
GES
20. SECURITY CL.ASS (This pant)
Unclassified
72. PRICE
EPA Form 2JZO-1 (9-73)
-------
------- |