United States
                    Environmental Protection
                    Agency
 Hazardous Waste Engineering
 Research Laboratory
 Cincinnati OH 45268
                    Research and Development
EPA/600/S2-85/121 July 1986
f/EPA         Project  Summary
                    Evaluation  of  Pilot-Scale  Air
                    Pollution  Control  Devices  on  a
                    Refuse  and  Coal-Fired  Boiler

                    Fred D. Hall, John M. Bruck, and Diane N. Albrinck
                      This study, funded by the U.S. Envi-
                    ronmental Protection  Agency (EPA),
                    Hazardous  Waste  Engineering  Re-
                    search Laboratory (HWERL) was con-
                    ducted to evaluate prototype air pollu-
                    tion control devices on "waste-as-fuel"
                    processes. The site, Ames, Iowa, cofires
                    pulverized coal and refuse-derived fuel
                    (RDF) in a tangential-fired, suspension
                    boiler.  A test  program  was  imple-
                    mented to evaluate a pilot electrostatic
                    precipitator (ESP), pilot venturi scrub-
                    ber, and pilot fabric filter in controlling
                    particulate and gaseous air pollutants.
                    Each device was slipstreamed ahead of
                    the plant's full-scale ESP, and operated
                    as a primary control device. The pilot
                    scrubber was also tested downstream
                    of the full-scale ESP, and was evaluated
                    as a secondary control device.
                      This Project Summary was devel-
                    oped by EPA's Hazardous Waste Engi-
                    neering  Research Laboratory, Cincin-
                    nati, OH, to announce key findings of
                    the research project that is fully docu-
                    mented in a separate report of the same
                    title (see Project Report ordering infor-
                    mation at back).

                    Introduction
                      The nature and magnitude of atmo-
                    spheric pollutant  emissions caused by
                    the thermal conversion of waste to en-
                    ergy are not yet well defined. Thus far,
                    pollutants identified  in air emissions
                    from various resource recovery opera-
                    tions include particulates, metals, chlo-
                    rides, sulfur oxides (SOX), nitrogen ox-
                    ides (NOX),  and  polycyclic  organic
                    materials (ROMs).
                      Fabric filters have been  successfully
                    applied  to preprocessing operations,
 and ESPs are the most common air pol-
 lution  control  equipment  used  on
 cofired boilers and mass-burn incinera-
 tors. Full-scale  fabric filters have not
 been applied to waste-as-fuel combus-
 tion processes, and wet scrubbers have
 been used on incinerators with less suc-
 cess than ESPs. Since available infor-
 mation  indicated that state-of-the-art
 devices proved effective in controlling
 pollutants of concern from waste-as-
 fuel processes, alternative devices such
 as wet ESPs, and jet ejector scrubbers
 were not considered for this study.

 Test Plans and Results
  Four   different  pollution   control
 devices were tested. The fabric filter in-
 stalled at the Ames solid waste recovery
 plant was sampled to evaluate particu-
 late removal efficiency. The fabric filter
 treats particulate-laden gas, at in-plant
 temperature, from seven sources in the
 plant—the air density separator/RDF cy-
 clone exhaust, primary shredder, sec-
 ondary disc screen, and a number of
 conveyor transfer points. Results indi-
 cate that the fabric filter effectively con-
 trols particulates generated by various
 sources in the plant. While no attempts
 were made to  optimize operation or
collection efficiency of the unit, it re-
moved an average of 97.8 percent of the
particulates.
  A pilot ESP, pilot scrubber, and pilot
fabric  filter  were also tested. All the
devices  were controlling  combustion
gases from the cofired Boiler 7 at the
Ames Power Plant. The boiler burns pul-
verized  coal and RDF in a tangential fir-
ing mechanism  at different fuel ratios
ranging from 0 to 25 percent RDF on a

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Btu basis. Emissions are currently con-
trolled with an ESP.
  Emissions  were  characterized  by
simultaneously measuring selected pol-
lutants at the inlet and outlet of each
control device. The full range of boiler
fuel ratios was studied for each device.
Operating parameters that varied dur-
ing mobile venturi scrubber testing in-
cluded pressure drop across the venturi
throat, gas  flow rate,  and scrubbing
liquor flow rate. The  gas flow rate in-
creased with the scrubber liquor flow
rate in such a manner that the liquid-to-
gas ratio remained constant. Testing
was performed at pressure drops of 2.5,
5.0, and 7.5 kPa (10, 20, and 30 in. H2O).
  The operating parameters that were
varied during pilot ESP testing included
the number of energized fields, specific
collection area (SCA), and gas flow rate.
Tests were performed at 3, 4, and 5 en-
ergized fields and at SCAs of 16.4, 21.9,
and 27.3 m2 per m3/h (300, 400, and 500
ft2/acfm).
  The pilot fabric filter was operated at
an air-to-cloth range of 0.46  to 0.91 m3/
min per m2 (1.5 to 3.0 acfm per ft2). The
unit was equipped with reverse air, me-
chanical shake, or a combination of the
two for cleaning the fabric.
  Figure 1 shows the  slipstream and
sampling  locations.  All the  control
devices were slipstreamed into the sys-
tem upstream of the existing ESP. Addi-
tional  scrubber tests were  performed
while  slipstreaming  flue  gas  down-
stream of the full-scale ESP, thus repre-
senting  a  secondary control  device.
Samples were taken at the inlet and out-
let  of  each pilot control device  while
boiler conditions, fuel composition, and
control  device  operating  conditions
were  monitored. A  Method 5 source
sampling train was used to sample each
 Colorado
  Coal
          RDF
                            Boiler
                            Firing
                           RDF and
                           Pulverized
                             Coal
         Sampling Locations:

         ASH - ESP ASH Co/lection Hopper
           C - Coal Mixture (Unpulverized)
           El - ESP Inlet
          EO - ESP Outlet
           SI - Scrubber Inlet
          SL - Unfiltered Scrubber Liquor
          SO - Scrubber Outlet
           Ft - Preprocessed RDF
          FFI - Fabric Filter Inlet
         FFO - Fabric Filter Outlet
                                                                                                       Stack
Figure 1.    Schematic of pilot control devices at Ames, Iowa.

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control device at the  inlet and outlet.
These samples were analyzed for total
participate, halides, elemental analysis
(by spark  source mass  spectrometry),
and selected metals (by atomic absorp-
tion analysis).
  Discrete grab samples of coal, RDF,
ESP ash, fabric filter ash, and scrubber
liquor were collected  at  the time of
emission testing. Coal  samples  were
taken  before the pulverizer, and  pro-
cessed refuse samples were collected at
the atlas storage bin before the fuel en-
tered the pneumatic feed to the boiler.
Tables 1 and 2  show  the  ultimate and
proximate  analyses of  coal and  RDF
grab samples. Table 1 shows the results
of samples taken during ESP and scrub-
ber tests and Table 2  shows results of
fabric filter tests.
  During all primary  device tests, the
particulate removal efficiency was 99
percent.  The  efficiency  remained
roughly the same for coal plus RDF tests
at all  pressure drops, and efficiency de-
creased  with increasing pressure drop
for the tests with coal  only. This obser-
vation led to the conclusion that an op-
erating parameter other than pressure
drop  affected removal efficiency to a
greater degree. Midwest Research Insti-
tute investigated this theory and  re-
ported that the  observed contradiction
in the data ".. .was due to  the longer
residence time created by a lower pres-
sure drop and partly due to the fluctua-
tion of  particle size  distribution..."
Pressure drop in the scrubber was
maintained by adjusting gas and liquor
flow rates,  not throat  size. The results
also suggest that RDF input to the boiler
may enhance particulate collection in a
venturi scrubber. This observation is
somewhat  misleading, however, be-
cause  inlet particulate  loading also ap-
pears to  increase with  RDF input. Chlo-
rides were also  sampled and analyzed,
and the results are as follows:
  Chloride emissions increase when fir-
  ing  RDF, when compared with coal
  only tests.
  A water/lime solution in a venturi
  scrubber is highly effective in con-
  trolling chloride emissions.
The secondary scrubber tests resulted
in particulate removal efficiencies rang-
ing from 75 to 95 percent.
  The  results of particulate testing on
the pilot  ESP, specifically the effects of
SCA and fuel type on  removal  effi-
ciency, indicate the following:
  The  number of energized  fields and
  SCA, when increased  within design
  limits,  tend to enhance  particulate
Table 1.    Average Fuel Analyses-Pilot Scrubber and ESP Test Runs Only (Values in Weight
          Percent Except as Shown)
	Coal3	RDF"

Fuel as received
  Proximate analysis

    Water
    Ash
    Volatile matter
    Fixed carbon

  Heating value, MJ/kg
              (Btu/lb)

Dry fuel

  Ultimate analysis
 16.13
  9.27
 36.54
 38.06

 23.68
(10,180)
 13.25
 12.78
 61.36
 12.61

 15.45
(6,644)
Ash
Carbon
Hydrogen
Oxygen b
Sulfur
Nitrogen
Heating value, MJ/kg
(Btu/lb)
11.06
73.53
1.38
9.73
3.13
1.17
28.21
(12,130)
14.83
50.31
3.97
30.37
.38
.14
17.80
(7,654)
aAverage of selected grab samples.
bCalculated by difference.
Table 2.    Average Fuel Analyses-Pilot Fabric Filter Test Runs Only (Values in Weight Percent
          Except as Shown)
                                            Coal"                         RDF"

Fuel as received

  Proximate analysis
    Water
    Ash
    Volatile matter
    Fixed carbon

  Heating value, MJ/kg
              (Btu/lb)

Dry fuel

  Ultimate analysis

    Ash
    Carbon
    Hydrogen
    Oxygenb
    Sulfur
    Nitrogen

  Heating value, MJ/kg
              (Btu/lb)
 16.06
 15.96
 31.53
 36.50

 21.25
 (9,122)
 18.92
 61.81
  4.13
  9.60
  4.38
  1.16

 25.32
(10,869)
  5.74
  9.64
 70.57
 14.05

 17.38
(7,460)
 10.23
 46.83
  6.16
 36.17
  .27
  .34

 18.44
(7,913)
aAverage of selected grab samples.
bCalculated by difference.

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  collection efficiency regardless of the
  coal and RDF mixture.
  At a specific SCA, RDF input to the
  boiler tends to decrease ESP collec-
  tion efficiency; however, a further in-
  crease in RDF input does not neces-
  sarily continue  to decrease ESP
  performance.
  The lead concentrations measured at
the ESP inlet and outlet show a definite
increase in lead emissions with in-
creased RDF; however, the highest lead
emission measured was less than 5 mg/
dry std. m3, and the overall average was
0.71 mg/dry std. m3.
  For fabric filter tests, Figure 2 shows
the effects of pressure drop and type of
fuel on paniculate collection efficiency.
Significant trends cannot be recognized
within the  collection efficiency  range
shown.  Regardless of pressure drop or
fuel type, paniculate collection effi-
ciency was 99 percent or  greater.
  The control of lead emissions was
shown to be very effective. Only one of
five outlet samples  was above the de-
tectable limit of 0.007 mg/dry  std. m3,
with a concentration of 0.03 mg/dry std.
m3. Lead emissions did, however,  in-
crease  with  increasing RDF input.
Chloride emissions, again, increased as
RDF increased, with very little control
exhibited by  the fabric filter (20 to  30
percent removal). Fluoride emissions
did not change significantly throughout
the range of operating conditions.

Conclusions
  Total  uncontrolled paniculate  emis-
sions at the Ames test site were not sig-
nificantly different in tests of coal only
        and of coal plus RDF. Some trace ele-
        ments and gaseous chlorides increased
        significantly when  burning RDF. Lead
        and zinc emission concentrations were
        about three times higher and gaseous
        chlorides about 10 times higher when
        burning 25 percent RDF (Btu basis). Nei-
        ther the  scrubber, ESP, nor fabric filter
        paniculate  removal  efficiencies
        changed as the portion  of heat  input
        supplied by RDF increased.
         Conventional  state-of-the-art air pol-
        lution control devices were found to be
        effective in controlling the pollutants in-
        vestigated: paniculate,  trace  metals,
        SOX, and halides. The fabric filter and
        ESP were more efficient in controlling
        paniculate emissions than gaseous pol-
        lutants. A venturi scrubber was very ef-
        fective in removing the gaseous pollu-
        tants. Specific operating parameters,
        which were varied  on the respective
        control devices, can optimize pollutant
        removal  efficiencies.
01 o
<=c u
« c
11
is
I
       700
Co
to
       98.5
             Numbers Indicate Fabric
                Fitter Run Number
               38,39.40,
               41,43,47
                             42,45,46,
                             48,51
                     Coal Only
                     Coa, & RDF
            33.34,35.
            37'44
                                                            • 25,26,27.28.
                                                             29,30,31,32,36
                     .5
1.0         1.5        2.0

    Pressure Drop, kPa
                                                                2.5
Figure 2.    Paniculate removal efficiency as a function of fabric filter pressure drop

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