United States
Environmental Protection
Agency
Industrial Environmental Researc
Laboratory
Research Triangle Park NC 277
Research and Development
EPA-600/S7-81-143  Dec. 1981
Project  Summary
Performance  Evaluation  of  an
Industrial  Spray  Dryer  for
SO2  Control

James A. Kezerle, Steve W. Mulligan, Dave-Paul Dayton, and Patricia J. Perry
  TRW conducted a continuous moni-
toring test program  at the Amcelle
Plant of the Celanese Fibers Company
in Cumberland,  MD,  to evaluate the
performance of a dry process flue gas
desulfurization system. This system
treated flue gas from a coal-fired
stoker boiler. Tests involved methods
specified by EPA for 30-day compli-
ance testing, which requires a mini-
mum of 22 days of data containing at
least 18 hours of data per day and two
data points per hour.
  Hourly and daily averages of results
are  presented as well as averages for
the entire test period. Operating
experience with the spray-dryer/ bag-
house system is summarized for a 5-
month period ending with the comple-
tion of testing on September  3O,
1980. Brief descriptions of the test
site, the flue gas cleaning system, and
the continuous monitoring system are
included. Manual sampling techniques
for data verification are described and
the  systems for data acquisition, data
analysis, and quality  assurance, pre-
pared specifically for this program, are
presented. Raw process and emissions
data are included in the appendices.
  Results  based on 23 days of data
showed the mean SO2 removal effi-
ciency to be 70  percent over the
compliance test  when the sulfur
content of the coal averaged 2 percent.
In general, efficiency was 60-80
percent, except for periods of system
upset. Particle removal efficiency was
99.7 percent. Participate emissions
averaged 0.030 g/m3 (0.013gr/dscf)
during the 2 days these data were
taken.
  This Project Summary  was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).

Introduction
  TRW Inc., under contract to the U.S.
EPA, tested the dry S02 control system
serving the coal-fired (No.  5) boiler at
the  Amcelle  Plant of the Celanese
Fibers Company in  Cumberland, MD.
Celanese ordered the flue gas cleaning
system in January 1979. Construction
of the system by Rockwell International
and Wheelabrator-Frye was completed
in October 1979. Boiler installation was
not  completed, however, until  mid-
December 1979. Acceptance testing of
the  FGC system was completed on
February 21, 1980.
  TRW began collecting data for the
demonstration test phase in May 1980.
Installation and certification of instru-
mentation at the site for the performance
testing were  performed according to
provisions for  S02 compliance testing
and began in late April  1980. The
objective of the program was to collect
30 days of continuous monitoring data,
representing  proper operation of the
flue gas cleaning system, using compli-
ance test methods. Problems with the

-------
 boiler, the FGC system, and the con-
 tinuous monitoring system delayed
 completion of  this test phase  until
 September 30, 1980.

 System Description
   Celanese Fibers Company installed
 the coal-fired boiler in 1979 to supple-
 ment the  existing  oil-  and gas-fired
 boilers at their Amcelle  Plant. This
 installation was undertaken to improve
 the  economics of supplying process
 steam for the production  of synthetic
 fiber. A spray  dryer and  fabric filter
 combination was chosen to provide flue
 gas desulfurization (FGD) on the bases
 of cost, the lack of available space for
 ponding wastes from a wet FGD
 scrubber, and the need to provide good
 control  of particulate emissions.
   The flue gas treatment system was
 purchased as a turnkey installation from
 Rockwell International and Wheelabrator-
 Frye, Inc. A flow diagram of the system
 is presented in Figure 1.
                          Coal-Fired Boiler

                            The coal-fired water-tube boiler at the
                          Amcelle Plant is identified as the plant's
                          No. 5 boiler. The boiler is an Erie City
                          spreader-stoker with a traveling grate
                          for continuous  ash discharge. This
                          boiler had previously been retired from
                          service at a Celanese plant in Rome, GA.
                          The boiler was  retubed when  it was
                          reconstructed at the Cumberland, MD,
                          plant. Table 1 specifies design data for
                          this boiler.
  The coal-fired boiler is rated at 156
million kJ/hr (148 million Btu/hr) with
secondary boiler fuels of gas or No. 6
fuel oil. At the boiler's maximum rating
of 68,000 kg steam/hr (150,000 Ib/hr)
when fired by a combination of coal and
oil or gas, the flue gas to be treated by
the  dry  FGD  system  is  41.4 mVs
(87,000 acfm) at 216°C (420°F). At the
boiler's nominal coal-fired rating of
49,900 kg steam/hr (110,000 Ib/hr),
the flue gas to be treated is 30.7 mVs
(65,000 acfm) at 193°C (380°F).
                           Table 1.    Boiler Data - Amcelle Plant Boiler No. 5

                                                         Erie City Spreader-Stoker Coal and Natural Gas
Boiler Type Fuel
Type
Fuel Heating Value
Sulfur Content
Ash Content
Coal
Bituminous
29,056 kJ/kg
(12,500 Btu/lb)
1.0 to 2.0 percent
8.0 to 20.0 percent
Gas
Natural Gas
37.2 MJ/m3
(1,000 Btu/ft3)
0.0 percent
0.0 percent
                                             Lime Fill
                                             (From Trucks)'
                                                         Lime\
                                                         Storage
                                                         Silo
                                                                     Be/t Feeder
                                                                     I    \Slaker
                                                              Lime   '—|-1J
                                                              SystemaaVatGi'it Screen
                                                                          Lime Slurry
                                                                                  Opacity
                                                                                  &S02
                                                                                  lnstruments\
Coal
Hopper &
Storage
t!Z7

AAJ
 Coal
 Unloading
 Conveyor
                    Silo
                    Feedbucket
                    Conveyor
          Silo Reclaim
          Conve yor/Ele vat or
                                                                            Ash Unloading
                                                                            (To Trucks')
 Figure 1.
Celanese boiler and flue gas cleaning system.

                     2

-------
   Analyses of randomly selected coal
 samples are presented in Table 2. The
 sulfur content of the coals received
 during the test period was  1.25-2.76
 percent, with a mean of 2.02 percent
 (dry basis).
   Table  3 illustrates  flue gas  design
 conditions for various coal firings.

 Spray Dryer
   The gas cleaning system is designed
 to provide FGD removals of from 70
 percent (for 1 percent sulfur coals) to 87
 percent (for 2 percent sulfur coals) from
 half to full boiler load. Most of this SO2
 removal  takes place in the spray dryer
 where the S02-laden flue gas is passed
 through  a finely dispersed fog of lime
 slurry and water.
   The spray dryer consists of a single,
 6.1 -m (20-ft) diameter vessel containing
 a rotary atomizer (Figure 2). This rotary
 atomizer  (Bowen wheel) is  driven  at
 approximately 16,000 rpm.  The  lime
 slurry is  fed to the wheel at a liquid-to-
 gas ratio of 0.04 l/m3 (0.3  gal./1000
 acf), where it is centrifugally dispersed
 into the gas stream. A swirling motion is
 imparted to the flue gas as it  enters the
 top of the spray dryer through a fixed-
 vane rotary ring to increase turbulent
 mixing of the flue gas and the  lime
\ slurry.
   Approximately 20 percent of the flue
 gas bypasses the spray dryer, thus
 providing reheat to  raise  the gas
 temperature  prior to its entry into the
 fabric filter. This  is necessary for dry
 operation and compensates for the
 temperature drop in the fabric filter. The
 amount of water fed to the spray dryer is
 automatically adjusted to hold the gas
temperature from the spray dryer at a
set value.

Lime System
  The lime system is depicted in Figure
3. The dry storage silo stores about a 10-
day lime supply. High-calcium pebble
quicklime  is gravity fed into the lime
slaker where it is mixed with water to
provide a 20 to 30 percent (by weight)
slurry. The lime system can provide 125
percent of required capacity when the
boiler is fired at its maximum rate with 2
percent sulfur coal and overtired gas or
oil. The lime system pumps and piping
can be automatically flushed with water
to prevent deposits.
              I  I  Spray   }
              X Atomizer•£*'
Figure 2.    Spray dryer.
Table 2. Selected Coal Analyses
Vol* Ash
Sample No. % %
1 (8-22-80)
2(8-29-80)
3(9-12-80)
4 (9-23-80)
19.9
31.6
17.2
33.14
14.95
18.96
13.97
16.81
Sulfur
1.58
1.92
1.36
2.24
HHV
kJ/kg Btu/lb
29.860
27,998
30,153
29,411
12.846
12.045
12.972
12,653
 * Volatile matter.

 Table 3.    Flue Gas Characteristics - Amcelle Plant Boiler No. 5
 Fuel
 Steam Production
 Flue Gas Temperature
 Flue Gas Flow Rate
 S02 Concentration
 SO2 Exhaust Rate
 Paniculate Loading
 Coal
 49.900 kg/hr (110.000 Ib/hr)
 193°C (380°F)
 30.7 m3/s (65,000 acfm)
 800 to 2,500 ppm
 113 to 363 kg/hr (250 to 800 Ib/hr)
 8.5 to 11.9 g/m3 (3.7 to 5.2 gr/dscf)
 Lime
Slaker
                             Water
                                                                    Slurry
                                                                     Tank
Figure 3.    Lime system.


Fabric Filter
  The fabric filter, a four-compartment
pulse-jet baghouse manufactured by
Wheelabrator-Frye,  Inc.,  is shown in
Figure 4. Each compartment contains
225 bags. The baghouse can operate
with three compartments on-line when
the boiler is operating at its  nominal
coal-firing rate to produce 49,896 kg/hr
(110,000 Ib/hr) of steam.
  The air-to-cloth ratio is 2.2 - 6.8 with a
design pressure drop of 500 Pa (2.0 in.
H20). The filter medium is a fiberglass-
reinforced felt manufactured by Huyck.

Description of Continuous
Monitoring System

Instrumentation
  The  continuous  monitoring  system
used  in  the  performance evaluation
consisted of four major groups: the filter
probes and process sample lines, the
gaseous analyzers, the data acquisition
and recording system, and the remote
temperature sensing system. Upon
arrival at the  test  site,  these  four
separate  systems were assembled  and
aligned into one comprehensive system.

Sampling System
  Sampling  locations are shown in
Figure 5.  The inlet sample point was in
the rectangular duct between the boiler
and the spray dryer. The outlet sample
point was in the circular cross-section
of the stack. The intermediate sample
point was not monitored.

-------
To Stack
                                                                From Spray
                                                                   Dryer
                                                Spent Sorbent
                                                  and Fly Ash
Figure 4.    Fabric filter.
                                        The  filter probe assemblies utilized
                                      stainless steel filters (20-/um mesh)
                                      attached to 76-cm (30-in.) long stainless
                                      steel tubes with an o.d. of 1.3 cm (0.5
                                      in.) and an  i.d.  of  0.6  cm  (0.2 in.).
                                      Connected to this tubing was  about 30
                                      m (100  ft) of electrically heat-traced
                                      sample line, constructed of 0.6-cm (0.2-
                                      in.) Teflon tubing. The sample lines were
                                      kept at 121°C (250°F) to prevent con-
                                      densation from the gas sample.
                                        The gas samples collected at the inlet
                                      to the spray dryer and at the outlet of the
                                      baghouse were dried with a gas condi-
                                      tioner. This gas conditioner contained
                                      two dual stainless steel condenser traps
                                      suspended in a  medium of  ethylene
                                      glycol  cooled by a Hanke refrigeration
                                      unit with copper cooling coils to approx-
                                      imately 3°C  (37°F).  The sample was
                                      pulled  through the condenser traps by
                                      two Teflon and stainless steel pumps
                                      and then delivered to the analyzers. The
                                      gas conditioner system was connected
                                      to a  timer  that allowed the condenser
                                      traps and heat-traced sample lines to go
                                      into  the 700  kPa (100 psi) blowback
                                                                     Legend
                                                               W  v  Contaminanted Air Flow
                                                                     Flue Gas - SOz and Fly Ash
                                                                     Scrubbing Solution
                                                                     Clean Air Flow
                                                                                     Outlet
                                                                                  Sample Point
                                                 Inlet
                                              Sample Point
                                  Combustion
                                      Air
                                                                          '{Spent Dry Salts?
                              Outside Air from
                              Forced Draft Fan
                Air Preheater
 Absorbent A/kali
Solution Scrubbing
       Tank
Intermediate
Sample Point
Dry Product
 Disposal
 Induced
Draft Fan
 Figure 5.    Two-stage dry FGD system with TRW sampling positions indicated.

                                  4

-------
 mode for 3 minutes of every hour. A
 schematic of this sampling system
 (Figure 6) shows the path of sample gas
 from the probe to the analyzers and the
 path of output data from the analyzers to
 the data logger.


 Flue Gas Analyzers
   Flue  gas  was  analysed  using a
 Thermo-Electron Pulsed Fluorescent
 S02 Analyzer, Model 40, andaBeckman
 Paramagnetic 02 Analyzer, Model 755.
 These analyses  were conducted con-
 tinuously for both the inlet of the spray
 dryer and the outlet of the baghouse.
 The inlet S02 analyzer operated on a 0-
 5000 ppm full-scale range with a 1-V
 full-scale output, while the  inlet O2
 analyzer operated on a 0-25 percent of
 total gas volume full-scale range with a
 10-mV full-scale output. The outlet S02
 analyzer operated on a 0-500 or 0-1000
 ppm full-scale range, depending  on the
 concentration of S02 in the flue gas at
the location of the outlet sample probe.
The outlet Oz analyzer operated on the
same range as the inlet O2 analyzer, but
with a 1-V full-scale output.
  The SO2  and  O2  analyzers were
certified according to  procedures out-
lined in "Performance Specifications 2
and 3  for Continuous Monitors in
Stationary Sources" as specified by EPA
(44 Federal Register 58602, 1979).
  Relative accuracy was determined for
the S02 analyzers using the  average
response times for the analyzers ob-
tained  during  response time tests.
These determinations ensured close
agreement between the  results  from
the S02 analyzers and EPA reference
methods (specifically. Reference Method
6 for S02).
  Calibration  errors were also deter-
mined for each of the four analyzers.
Directly after the daily calibration of the
instruments, zero, mid-level, and high-
level calibration gases were randomly
introduced into the respective  analyzer
until  a set of five  points  for  each
concentration (zero, mid-level, and
high-level) was obtained.
  Both of the S02 analyzers and both of
the O2 analyzers  passed all  of the
certification  requirements. In addition,
all calibration gases used for instrument
certification  or  instrument calibration
were either traceable  to  National
Bureau of Standards reference gases or
underwent the calibration gas certifica-
tion. The latter gases  were obtained
from  the  EPA  repository and were
certified by EPA personnel prior to use in
the tests at Celanese. The S02 and 02
analyzers were calibrated daily between
the hours of 0800 and 1200.
Data Acquisition System
  The  Data  Acquisition System  con-
sisted  of a Fluke  Data Acquisition
system, a dual-pen Fisher 5000 Record-
all recorder, and a Leeds and Northrop
six-channel multipoint recorder.
                                                                                                          Hi-Range
                                                                                                        Mid-Range
                                                                                                           Exhaust
*Data Acquisition System.


Figure 6.    Flue gas sampling and analysis system.

-------
Temperature Sensors
  Two 60-cm (24-in.) long chromel-
alumel thermocouples were  mounted
parallel to the filter probes.  These
thermocouples measured flue gas
temperatures at the inlet and outlet of
the FGD system. They were hard wired
into the Fluke Data Acquisition system,
using about 30 m  (100 ft) of  chromel-
alumel thermocouple wire.

Results
  Data on S02 removal that were typical
of the fully operating dry FGD system
performance and whose relative accu-
racy was fully  documented were col-
lected only during the final month of the
tests. This period of "good" data collec-
tion ran from  August  28  through
September 30, 1980. The boiler gen-
erally ran at a steady load (about half of
the rated value because  of  seasonal
reduction in steam  requirements)
throughout most of this period, and the
FGD system operated almost contin-
uously.
  Hourly averages of S02 emissions in
parts per million were calculated from a
minimum of two data points per hour.
These hourly  averages  were then
corrected to zero  percent oxygen
dilution and  converted to pounds per
million Btu. Calculations of S02 removal
efficiency were then based on these
average hourly S02 emission values.
  S02 emissions in pounds per million
Btu were determined using the F-factor
technique. An F-factor for dry flue gas
from coal of 9820 dscf/106 Btu (263.9
mVGJ) was used. Heat input to the
boiler  was calculated from  available
data.  Hourly averages of steam  flow
were used  to derive hourly values of
coal feed rate from values of total daily
coal consumption.
  Typical data for  inlet and outlet S02
concentrations are shown in Figures 7
and 8. These data are representative of
the 23 days when continuous monitoring
methods met EPA's compliance criteria,
including collection of data for over 18
hours  per day with  the FGD  system
treating boiler flue gas. Figure 7 shows
that outlet S02 concentration, mea-
sured in the stack, closely follows the
SO2 concentration at the inlet to the
spray  dryer. This curve indicates no
corrective action being taken to adjust
slurry  flow rate for varying  inlet S02
concentration. With the FGD system in
automatic control,  the outlet  SOa
concentration (see Figure 8) was rela-
tively constant, indicating that the slurry
flow  was adjusted to accommodate
|2000-|
s
c
| /eooH


I 7200H
O
O
oo
   800-
a  4oo-|
                   Inlet*
                                       Inlet
Figure 7.
 S'
 o
 -7600H
 i.
 c
 1/200-
 o
 O 800-
 oo
 •O
 ~ 400-
          0200 0400 0600 0800 1000  1200 1400  1600 1800. 2000 22002400

                                   Time of Day
            Average hourly SO2 concentrations for September 3, 1980, with FGD
            system controlled manually.
 o
 u
 5
                 Inlet
Figure 8.
           0200 0400 0600 0800 WOO 1200 1400 1600  1800 2000 2200 2400

                                    Time of Day
              Average hourly SO2 concentrations for September 8,  1980, with dry
              FGD system controlled automatically.
even rapid changes in inlet SO2concen-
tration.
  Although the FGD system was de-
signed to operate automatically, this
was not always possible because  of
malfunctions in the stack S02 monitor
which provided feedback to the spray
dryer control system. Problems with this
monitor necessitated extended periods
of manual  operation. Under manual
operation, the slurry flow  sometimes
became so high that the outlet concen-
trations were 50 ppm or less. On these
occasions,  SO? removal efficiencies
exceeded 90 percent.
                                         The average daily  S02 removal
                                       efficiencies for the  continuous moni-
                                       toring period cited earlier are given in
                                       Figure 9. Except for periods of system
                                       upset, removal efficiency was 60-80
                                       percent. The only prolonged period of
                                       low  S02 removal occurred between
                                       September 3 and 6 and stemmed from
                                       inability to maintain steady boiler load
                                       and  slurry pumping problems. The
                                       mean S02 removal efficiency for the 23
                                       days of performance data was 70 per-
                                       cent,  and the standard  deviation from
                                       this  mean was ±9  percent. However,
                                       over the last  week of  the  tests,  the

-------
  u
 .OJ
  S
  o

  0)
 et
  M
 O
 oo
                                    Large Load
                                   Fluctuations
                       Slurry
                      Pumps
                     Inoperable
         8/28
                                                    Plugged
                                                  Spray Dryer
                                                    Repaired
                             Baghouse
                               Bags
                              Changed
I    I   I    I    I   I   I    I    I   I   I    I    I   I    I    I   I   I   I      rl   I    I   I    I    I   I
     8/31               9/5                9/10              9/15   9/17   9/24              9/30
                                                           Date
                      5/77   9/24
                          9/25
 Figure 9.    Average daily SO2 removal efficiency for dry FGD system.
 average daily SOa  removal  efficiency
 was 78.5 percent, based on 23 hours of
 hourly averaged data for each day.
   The  emission rate  and removal
 efficiency of particulate matter for this
 FGD system were determined by three
 isokinetic sampling runs on June 2 and
13, 1980. Testing for particulate matter
 was conducted according to EPA Method
 5 using a RAC  Stacksampler sampling
 train. Results of these tests are sum-
 marized in Table 4.


 System Availability and
 Operating  Experience
   Table 5 summarizes the availability of
 the  boiler and  FGD system during the
 tests. The boiler went down for refractory
 repairs on April 20.  From then through
 the  end of the  program on September
 30,  the boiler  was off-line approxi-
 mately  12 percent of the time. It was on-
 line but running abnormally an addi-
 tional 5 percent. Thus, boiler problems
 prevented representative characteriza-
 tion of the FGD system  for about 17
 percent of the  time TRW was  on site.
 This amounted to 672 of 3.912 hours in
 the period.
   The  FGD system was off-line  (not
 operating at all) about 23 percent of the
 time. The  FGD system  operated ab-
 normally an additional 12 percent of the
 time. During  this time the slurry feed
 rates were so  low or unsteady that
 monitoring of any significant S02
 scrubbing  was prevented. Thus, the
                         Table 4.    Particulate Emissions Results
Date
Run No.
6-2-80
BI5-1
6-2-80
BI5-2
6-3-80
BI5-3
Average
                         Inlet Concentration
                          g/m3 (gr/dscf)


                         Run No.
                         Outlet Concentration
                          g/m3 (gr/dscf)


                         Particle Removal
                          Efficiency. %
 9.43
 (4.12)

 B05-1

 0.0334
 (0.0146)
99.65
 8.44
 (3.69)

  B05-2

 0.0159
 (0.00697)
99.81
11.78
(5.15)

 B05-3

 0.0400
(0.0175)
99.66
                         Table 5.    System Availability
 9.88
 (4.32)
 0.0298
 (0.0130)


99.70
Availability*, %
Component
Boiler
FGD System
Spray Dryer
Lime Feed System
Fabric Filter
Apr-Sep
82.2
62.4
81.8
83.2
99.8
Aug-Sep
(720 hr)
93.3
73.2
97.8
76.5
98.9
Sep 25-30
(144 hr)
100.0
96.2
100.0
96.2
100.0
                         *The percentage of time in the period that the component operated normally.
                         FGD system was unavailable 35 percent
                         of the time, or a total of 1,354 hours.
                          Availability of the system was signifi-
                         cantly improved  in September when
                         most of the continuous monitoring data
                         were collected. During this period the
                         FGD  system was off-line less than 19
                         percent of the  time and  operated
                  abnormally an additional 8 percent of
                  the time, giving an  availability of 73
                  percent.
                    Operating problems and their effects
                  on the program were broken down into
                  four system components: the boiler, the
                  lime feed system, the spray dryer, and
                  the fabric filter. Problems  with  each

-------
component impact the  entire FGD
system.

Steam Boiler
  A problem which affected the per-
formance of the FGD system was the
variability of coal  quality. Coal sulfur
content varied widely throughout the
early part of the program. The quality
became less variable near the end of the
program, but  proximate  analyses  of
daily coal  deliveries  showed sulfur
contents of 1.25 -  2.76 percent. When
operating in automatic control to keep
the outlet S02 concentration at a set
value,  the  FGD system responded  to
rapid changes  in inlet SC>2 concentra-
tion so that hourly averages of emissions
remained constant. In manual control,
the outlet S02 concentration followed
the inlet concentration in the absence of
operator adjustment. With uniform coal
quality  and automatic control of  slurry
flow, large fluctuations  in  inlet S02
concentrations were absent and a
steady  outlet S02  concentration was
maintained.
  Another  problem which  relates  to
coal supply involves the amount of fines
in the coal. Coal fines, when suddenly
dumped into the furnace, cause rapid
changes in boiler load and flue gas flow,
changes in SC>2 emissions, and increased
particulate  matter and opacity levels in
the stack. Fast changes in  flue gas flow
and SOz concentration made it difficult
for the spray dryer to keep SOa emissions
at a desired level. Such large and rapid
load fluctuations occurred on September
5, 6, and 7.  Data collected on these days
were not included in overall averages.

Lime  Feed System
  The slurry is fed to the atomizer  by
progressing cavity pumps;  under design
conditions, one pump is in use and one
is a spare.  However,  to cope with the
higher  sulfur  coals encountered, the
single pump had to be operated at high
speeds and this led to rapid pump wear.
To alleviate this, the  system was
modified to use both pumps in parallel.
This was the normal mode of operation
throughout the latter  part of  the test
period.
  Most other problems with the lime
feed system related to plugging some-
where  in the system because of  grit in
the lime. Although grit was supposed to
have been  removed by screens  inside
the slaker, damaging quantities of it
passed through or bypassed the screens
into the rest of the system. Failure to
remove grit caused excessive wear in
the pumps and plugging in the slaker, in
the flow lines, in the slurry pump, and in
valves.  Dual-element screen filters
were  eventually installed in the  feed
system, but  not enough  time elapsed
before the end of the program to assess
whether they solved the problem.

Spray Dryer
  Maldistribution of lime slurry in the
atomizer resulted in the wetting of the
dryer wall  and discharge of damp
material from the dryer. It was corrected
by redesign.
  Other problems encountered with the
spray dryer also related to the atomizer.
The  rotary atomizer was subject to
clogging with grit particles if they were
not screened sufficiently from the
slurry. The spray dryer was shut down
for cleaning when this clogging occurred.
Another problem was failure of the
bearings supporting the  shaft of the
atomizer wheel caused by an imbalance
due to grit  plugging the atomizer wheel.

Fabric  Filter
  The most  serious problem with the
baghouse  was the unexpectedly  high
pressure drop through the fabric filter.
This was apparently caused by moisture
on the bags  which occurred during an
upset and  combined with ash and lime
to form a  coating  that increased the
resistance to flow. To lower the pressure
drop through the baghouse, design and
process changes were made, including
increasing the pulse-jet air volume by
approximately 15 percent. Tests since
this modification indicate that  this has
solved the problem.

Conclusions and
Recommendations
  The two-stage dry FGD system in-
stalled at the Celanese Fibers Company's
Amcelle Plant required 28 - 46 hours of
maintenance each week and close
operating  supervision for continuous
operation.  Some of this  maintenance
was performed  while the system  was
operating so there was no interruption
in SOa removal. The average  S02
removal efficiency demonstrated over a
30-day  period,  based on 23  days of
acceptable data, was 70 percent.  This
level  of performance was achieved
while burning coal with an  average
sulfur content of about 2.0 percent on a
dry basis. System guarantees called for
70 percent SOa removal  for 1 percent
sulfur coal and 87 percent SO2 removal
for 2 percent sulfur coal. Compared with
these goals, the demonstrated  S02
removal was low. Over the last 6 days of A
the tests,  after several operational \
difficulties had  been  resolved, SO2
removal efficiency averaged 78.5 per-
cent,  a marked improvement  over
earlier results but still below the stated
goal with 2 percent sulfur coal.
  Boiler operators operate  the  FGD
system along with their other duties.
Modifications made to the system after
operating experience  had been gained
have the potential to  make this a more
reliable  system.  As  described above,
most of the'operating problems relate to
plugging caused by grit in the slurry and
water vapor condensing in the flue gas
due to low operating  temperatures.
Both of these problems can be solved by
changes in operation and design. Main-
tenance needs will also be reduced by
these modifications.
  Because of problems  experienced
thus far, redundancy  of critical compo-
nents is recommended.  Specifically,
three slurry pumps are needed with two
on-line at all times and one as a spare. A
spare atomizer will  limit spray dryer
shutdowns due to atomizer failure.
Filters should be  set  up to provide
uninterrupted slurry flow to the spray
dryer while one filter element is being
replaced or cleaned. A means of keeping
the outlet SOa monitor operating con-
tinuously  is needed. Since  feedbac
from the outlet S02 monitor is used i
controlling lime slurry flow to the spray
dryer, this will permit a steadier outlet
SOa level and more consistent  FGD
system performance  via  operation  in
automatic control.
                                  8

-------
J Kezerle. S. Mulligan, D. Dayton, and P. Perry are with TRW, Inc., P.O. Box
  13000, Research  Triangle Park, NC 27709.
Theodore G. Brna is the EPA Project Officer (see below).
The complete report, entitled "Performance Evaluation of an Industrial Spray
  Dryer for SCb Control," (Order No. PB 82-110 701; Cost: $21.00, subject to
  change) will be available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
        Telephone:  703-487-4650
The EPA Project Officer can be contacted at:
        Industrial Environmental Research Laboratory
        U.S.  Environmental Protection Agency
        Research Triangle Park,  NC 27711
                                                                        •ft U.S. GOVERNMENT  PRINTING OFFI CE :1 981 --559-092/3356

-------
                                                    (D



                                                    f
                                                                 q =

                                                                 Is
                                                                 D :
                                                                 3 fi
                                                                 0) -
                                                                 -'«
                                                                 O:
                                                                 X
                                                                 O>
                                                                 00
C!
                                                          m

-------