EPA
TECHNOLOGY
TRANSFER
                                   62362-77
                          FABRIC FILTER
                          PARTICULAR CONTROL
                          ON COAL-FIRED
                          UTILITY BOILERS:
                          NUCLA CO.
                          AND SUNBURY PA.
U.S. ENVIRONMENTAL
PROTECTION AGENCY
'. ENVIRONMENTAL
. RESEARCH
  INFORMATION
  CENTER

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                 EPA
                 TECHNOLOGY
                 TRANSFER
                                            FABRIC FILTER
                                            PARTICUATE CONTROL
                                            ON COAL-FIRED
                                            UTILITY BOILERS:
                                            NUOLA, CO.
                                            AND SUNBURY, PA.
U.S. ENVIRONMENTAL
PROTECTION AGENCY
  ENVIRONMENTAL
. RESEARCH
  INFORMATION
  CENTER
EPA-625/2-77-013

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Sunbury plant profile
                                                   .:-,:               ;,,7:_      _
                                             -S  :=-n:-!kLi;::'r!!?j«?~-r,E.T--ss«-r;;».j


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    Fabric filters are one of the oldest means of
controlling aerosol particles. Since the 1950's, they
have been used widely as air cleaning devices in
asphalt plants, cement manufacturing, carbon black
plants, glass furnaces, and a variety of ferrous and
nonferrous foundry operations. To date their use in
the electric utility industry has  been limited, primarily
because of reservations about the durability of the
                            filter bags under harsh stack gas conditions. The use
                            of new glass fabrics and the development of high-
                            temperature lubricants to enhance bag life, however,
                            has rekindled electric utility interest in fabric filters
                            as a means of controlling particulate emissions. As
                            shown in Table 1, four utilities currently use fabric
                            filters, and eleven more are under construction.
Table 1.  Status of Fabric Filter Installations in the Electric Utility Industry
            Unit
 ^Pennsylvania
  Power and Light Co.

=r~ Pennsylvania
"Power and Light Co.

5- Colorado Ute
- Electric Association
^Public Service Co.
 _of Colorado
  Southwestern Public
^ Service Co.
g.r ,  "  -      '          ..
~-- Texas Utilities
- Service Inc.
I^Board of Public Utilities
   "      Location
. * fc_    -  •
   PP--
    Sunbury, Pa.
                                               s Mr
                           rHoItwood, Pa.


                          . „ Nucla, Colo.
                             Cameo, Colo.
  I?***'
  plAmarillo, Texas

    Mount Pleasant,
    jexas

      nsas City,
    Kansas
      of Colorado Springs  f Colorado Springs,
r'        ••"•  "   '    jpcoio.
i,	     .:  .: :   • •  -.  ".. .- I m •-
'- Colorado Ute          , |^Meatrose, Colo.
£ Electric Assn.

i^Crisp  County Power  Co.
                                 _
                                 bituminous coal
                                   estern coal
                                                           ybbituminous

                                                           .ignite
 }1 Minnesota Power
 f^& Light Co.
   Nebraska Public Power
 — Public Service of
 :  Colorado

 ^ Texas Utilities
    Tbrdele, Ga.
   "tohasset, Minn.
    Jellevue, Nebr.
   palisade, Colo.
                             Bpbertson City,
                               xas
Note:   N/A = Information not available.
                                                            Combination of
                                                            etroleum coke
                                                            hd anthracite

                                                            Combination of
                                                            etroleum coke
                                                               anthracite,  ,
                                                                           . ,p^ Operational
                                                                           J FT since 1973
                                                  1
                                                                                                    -,_;J
                                                                                                      1
                                                    ^Operational
                                                    if* <;inrf> Innp  '
                                                    te—
                                                      ;since June, 1975

                                                                                Operational
                                                                                '      1974
                                     N/A
                                                                               ^Startup: Mid-1977
                                                                                Startup:
                                                                                jjune 1978

                                                                              " Startup:
                                                                                March 1978

                                                                                Startup: 1979

                                                                              ^Startup: 1980
                                                                                -j—-
                                                                                Startup: 1977
                                                                                Startup: 1975
                                                                                Startup: 1978

                                                                                Startup: 1977
                                                                                -i.^
                                                                                Startup: 1977
                                                                              / Startup: 1980

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     Electrostatic precipitators are by far the pre-
ferred control devices for participates in the electric
power industry. Their low maintenance requirements
and high control efficiencies have resulted in their
widespread acceptance. Recently, however, a num-
ber of circumstances have enabled fabric filters to
compete with electrostatic precipitators. The increase
in demand for solid fuels has caused  many utilities
to depend upon variable coal supplies, which in turn
results in a varying chemical composition of the
fuels. The abundant low-sulfur fuel in the Western
states may soon replace some dwindling supplies in
the Eastern  coal fields. With dwindling fuel supplies,
increased attention is being paid to the use of mixed
fuels; Pennsylvania Power  and Light Company, for
example, uses anthracite waste and petroleum coke
at its Sunbury Station. Each of these circumstances
can affect the performance of electrostatic precipi-
tators. Variations in fuel composition, for instance,
                        alter the ash surface chemistry which affects the
                        electrical resistivity of the particulates. Electrostatic
                        precipitator efficiency is a direct function of particle
                        resistivity.  Fabric filter efficiencies, on the other
                        hand, are  much less dependent upon ash surface
                        chemistry. For high sulfur fuels, the condensation
                        and oxidation of sulfur oxides on paniculate surfaces
                        decreases  particle resistivity and  hence enhances
                        precipitator efficiency. Thus, the trend toward lower
                        sulfur fuels could adversely affect electrostatic pre-
                        cipitator performance. Fabric filters, on the other
                        hand, are  well suited for low-sulfur fuels. In fact,
                        lower sulfur  content aids bag filter operation, since
                        high concentrations of sulfur trioxide can accelerate
                        fabric deterioration. Table 2 summarizes the per-
                        formance  characteristics of fabric filters and electro-
                        static precipitators with respect to selected  power
                        plant operating conditions and fuel  properties.
Table 2.  Performance Characteristics of Fabric Filters and Electrostatic Precipitators
c	
1     Power Plant Variable
:  Maximum Collection
;	Efficiency	

i, Fuel S Concentrations

,  Ash Metallic Qxi.de
;  Concentration
  Paniculate Loading
  Flow Rate
  Temperature
      Hot Side
                  ESP
                 "It
                                                                                Fabric Filter
                      Cold Side
•   99.0 to 99.8    * F ' 99.0 to>99.T*W
I                 I P-    "   -- "• ~
s                 -S
f-
       Minor
 ^Dependence
                  r Very Important
 i                •- I. .        r
 '- No Dependence   ' Very Important
  o Dependence3
  «.    '        ^
  %^  v f,   ,  l  «i*
3^1ov Dependence
 " Loading Swings Decrease Collec-   _ . Ip'et Loading Does Not Signifi-
 f tion Efficiency Significantly          L cantly Affect Efficiency. All
 i- •                  i '       "  • i ^1 |2?riatioris fn Outfet tConcentra-  ^ ^
• In.   -       .       ,.,-,,",  ,.,.T™ ™,|       are^ampened Considerably
J t-    •         >  .'  i,r      »•->  •   ™J ^S**"1   -«r»»iiic^ ass (,*"jf.'vj -  ^    r^s, Mt
 t Nonuniform Velocity Distribution  _ ^Wide Velocity Range Does Not
 i Causes Decreased Collection      , SiSn'^'cant'y Affect Performance
                 '                                     '
  ffiq
1 ..... UN   '
I Non
                         .     ^  »..             ..    „       »        .
    onuniform Flue Gas Temperature   ^.No Temperature Dependence for
                              , f. Causes Decreased Collection       m Collection Efficiencyb
                                ^.Efficiency
                                                                        -s
                                                                      _J
aHigh SOX concentration in gas streams causes high deterioration rates in many fabrics.

 Multiple temperature excursions through the acid dew point will increase fabric deterioration rates.

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    As previously mentioned, two coal-fired stations
have been using fabric filters since 1973 — the Nucla
Plant of the Colorado Ute Electric Station and the
Sunbury Station of the Pennsylvania Power and Light
Company. Each of these operations  is described in
Table 3.

    The Nucla fabric filtration facility was designed
to control the entire particulate load from the three j
stoker-fired boilers of the 39 MW facility. This instal-'
lation, shown on the cover,  has been able to meet  !
the Colorado air pollution regulations with ease.    j
Every boiler has its own baghouse which consists of
six independent compartments, each containing 112
bags for a total of 672 bags per baghouse. The
design gas flow through each baghouse is 86,240
acfm at 360°F. Bag cleaning  is accomplished by a
combination of reverse air and gentle shaking. The

Table 3. Description of the Nucla and Sunbury Fabr
   air used to clean the bags is cleaned flue gas recycled
   from the baghouse discharge. Cleaning all six com-
   partments requires about 30 minutes, with the
   cleaning cycles initiated automatically by preset
   limits for baghouse pressure drop.
       The Sunbury powerplant operated for 2 years
   using the original bags with only slight problems
   and without appreciable bag failures. Tests per-
   formed on samples of the two year old fabric and
   new fabric indicated the used fabric to be nearly as
   strong as the new  material. At  Nucla, changes in the
   baghouse thimble plate improved bag wear. One
   baghouse containing over 600 fiberglass bags, oper-
   ated 6 months without a bag failure.
c Filtration Facilities
SiLocation

^Total MW Capacity

fiCombustion Units

=rInstallation  Date

jiCoal Type
_....    , _......  ........    ,

^Manufacturer
H .           ,   , --

tCJeaning Technique


  Fabric Type

 :Number of  Baghouses

ENumber of  Bags Per
^Baghouse

HBag Size

LAir/cloth ratio (net)

  Pressure Drop at Full Load
                               ucla, Colorado

                                MW
                            15^ ^  mj    „     ^ u ^ ^* ~ 1
                            r Three Spreader Stokers
                                 '-":-      ••-   -"1
                              )ecember 1973

                             Bituminous,
                             f(0.6 to 1.8%  S)
^A/heelabrator-Frye (Baghouse)
|W,W. Crisweil Co. (Bags)

 Combination of shaking and
'"'everse air flow
                            |,Graphite/silicone coated fiberglass

                            r3
                              ;2 ft. long x 8 in. diameter

                              K,  ,;     •.
                             +* ^             * 4
                             5 in. of water
                                                                              Sunbury
                                                              1
               -SJOsimokin Dam, Pennsylvania
               S^ „ ^™v,   _     T" j- „      *   *, H^ „  *
                ;>s MW     "   J*

               iFpur pulverized fuel boilers

               Sfebruary 1973

               ^Anthracite and Petroleum  Coke
                (1.2 to 3.2% S)

              , Western Precipitation  (Baghouse)
              f^Menardi-Southern Co. (Bags)

                Reverse air flow
              1  Teflon coated fiberglass
I
j
                30 ft. long x 12 in. diameter
               ^3 in. of water on 2 year old bags

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    The pressure drop across the Sunbury baghouse
at full load was a nearly constant 2.5 in.h^O. During
the two years of operation, baghouse increase in
pressure drop was less than 1.0 in.H2O. The average
pressure drop across the Nucla bags was approxi-
mately 4.5 in. H2O.

    The Sunbury steam electric station, shown on the
inside cover, replaced an electrosatic precipitator
collection system which was unable to meet the
particle control efficiency required by state regula-
tions. The fuel, a combination of low sulfur anthracite
and high sulfur petroleum coke in proportions of
15 to  35 percent coke by weight, produced a high
resistivity in the ash  which led to decreased precipi-
tator efficiency. The replacement bag filter system
has met the Pennsylvania regulations since its initial
operation in 1973. Each Sunbury baghouse handles
222,000 acfm at temperatures on the order of 325°F.
Individual baghouses contain 1260 bags which are
divided equally among 14 compartments. Every 30
minutes, the entire system is cleaned by a sequential
cleansing of each individual compartment.

    The bag filtration system installed at these
utilities is depicted schematically in Figure 1. The
only major differences in the designs of these instal-
lations is the variation in the fabric cleaning method
employed by these facilities and the coarse particle
removal system installed upstream from the fabric
filter. The Nucla facility employs a combination of
gentle shaking and reverse air flow for cleaning,
while the Sunbury system  uses only reverse air flow
as depicted  in Figure 2. The Sunbury facility also
differs in the application of a mechanical collector
which removes the larger  particulate matter in the
flue gas (about 70 percent) prior to bag filtration. At
Nucla, a single deflection  baffle is  used to remove
the coarser particles from  the filter influent
Figure 1.  Schematic Diagram of a Flue Gas Cleaning
System Incorporating a Fabric Filter Baghouse
Figure 2.  Gas Flow Through Baghouse Compart-
ments During Normal Operation and Cleaning
                                    MECHANICAL
                                    COLLECTOR
                                                                                1-GAS INLET DAMPER-OPEN
                                                                                2-CAS INLET DAMPER-CLOSED
                                                                                3-BAC COLLAPSING DAMPER-OPEN
                                                                                4-BAC COLLAPSING DAMPER-CLOSED
                                                                                5-OUTLET DAMPER-OPEN

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Nucla plant profile


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Sunbuiy - view of upper walkway, bag tension springs and bag caps

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    The U.S. EPA Industrial Environmental Research
Laboratory in Research Triangle Park, North Carolina
sponsored field sampling programs at both the Nucla
and Sunbury facilities. Emission testing  and analysis
was performed by CCA/Technology Division,
Bedford, Massachusetts. A major objective of the
project was to characterize the performance of fab-
ric filter systems used to remove particulates from
boiler flue gases.* Total mass emission  rates were
measured using the standard EPA Method 5 techni-
ques. Isokinetic sampling of both the inlet and outlet
ducts, which provided accurate determination of
particulate mass concentrations, allowed for precise
measurement of bag filter efficiencies.  Thirty-one
tests were run at the Sunbury facility. The average
mass  emission rate of 0.0&46 pounds of particulates
per 106 Btu of coal fired Corresponded to an average
weight collection efficiency of 99.91 percent. Twenty-
two runs at the Nucla Plant indicated an average
mass  emission rate of 0.01 pounds per  106 Btu input
to the boiler and a collection efficiency of 99.84
percent.

    Both  facilities easily satisfied the local particulate
emission regulations that the previously installed   I
Sunbury electrostatic precipitators and the Nucla
mechanical collectors had been unable to meet.
Note that the emissions form both facilities  are also
considerably less than the New Source Performance
Standards of 0.1 pounds per 106 Btu input for fossil
fuel-fired steam generators. Filter efficiency as a
function of particle diameter was also determined
using inertial impactors. Daily isokinetic impactor
sampling combined with condensation nuclei
counter and diffusion denuder data on submicron
particle concentrations  provided accurate determi-
nation of the mass mean diameter, defined to be the
diameter at which 50 percent of  the mass emitted is
composed of particles with larger diameters. The
mass median diameters at the outlets of the bag-
houses from Sunbury and Nucla  were 3.9 and  8.3
microns, respectively.

    The test programs measured emission rates for a
variety of fuel compositions and  boiler and bag filter
operating conditions. No significant deviations from
the average emission rates were  noted for variations
in firing rate, fuel sulfur content, or ash content of
the coal-coke mixture.

    Only the condition of the filter bags was found
to affect the mass mean diameter measurements.
Measurements when new bags were in use indicated
a slightly lower (about 10 percent) mass median
diameter for the effluent particulate matter than did
the results of tests on used bags. No other test
caused any significant degradation of the fabric
filter performance.
 The Industrial Environmental Research Laboratory's Utilities and jndustrial Power Division has issued reports on the Nucla and
 Sunbury Plants. More detailed information is available in the follbwing reports:

 EPA 600/2-76-077a:  Fractional Efficiency of a Utility Boiler Baghpuse
                  — Sunbury Steam-Electric Station. March 1976.
 EPA 600/2-75-013a:  Fractional Efficiency of a Utility Boiler Baghjause
                  — Nucla Generating Plant. August 1975.

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Sunbury - view of exterior walkways to baghouse and exhaust ducts

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    Available information on the capital investments
required for the fabric filter installations at Nucla    j
and Sunbury are summarized in Tables 4 and 5.
Because both Nucla and Sunbury were retrofit con-
structions replacing original mechanical and electro-
static precipitator equipment, a direct cost comparison
between the two facilities is difficult. The Sunbury
construction costs, for example, include the installa-
tion of an ash slurry pumping and piping facility for
a settling pond  more than two miles away from the
plant. The data  in Tables 4 and 5, however, do
provide a useful frame of reference for judging
some of the costs encountered in fabric filter
installation.
Table 4.  Sunbury Steam Electric Station Bag Filter In
                        Item
                                                 "I
                                                         Capital investments for ESP are comparable to
                                                     baghouse costs. Figure 3 presents the estimated
                                                     range of fly ash precipitator costs for both hot and
                                                     cold side ESPs designed to remove high resistivity
                                                     particulates. Cost data for a typical ESP installation at
                                                     the TVA Gallatin Steam  Plant is presented in Table 6.
                                                     This ESP controls the particulate emissions from one
                                                     300 MW unit at a design efficiency of 95 percent.

                                                         Annual operating costs of the Nucla and
                                                     Sunbury baghouses are  summarized in Tables 7
                                                     and 8. For 1977, the Nucla and Sunbury facilities had
                                                     estimated annual operating costs of $1.15 per acfm
                                                     and $0.82 per acfm, respectively. Using an electro-
                                                     static precipitator operating at 92 to 95 percent, the
                                                     TVA Gallatin  Steam Plant operating costs were
                                                     estimated to  be $0.61  acfm.
                                                  stallation Cost Breakdown (1972 $)
                                                        aterial Cost
PFour baghouses
sJQesJgn and Engineering
£ Vacuum cleaning system
 % Platforms and ladders
 : Supplements and contingencies
Upland.and land rights
-. Foundation and site preparation
  Ash slurry pump house
 KAsh removal  system-baghouse
   sh slurry system
 ^Additions and improvements
  Electrical equipment
^Overhead

  ~ Total capital expenditure
 ST.: Total capital expenditure
 fe (1977 estimate)3
aSca!e factor from Chemical Engineering M & S equipment cost index 1972 - 4th quarter
                                                       1,266,985

                                                          30,415
                                                          95,105
                                                          39,800
                                                          90,800
                                                         241,500
                                                         343,000
                                                            v3"5a
                                                          55,400
                                                          35,600
Total Cost

2,286,985" "
  563,140
   74T22.5
  116,310
  161,030
  " 1,500
  192,500

  179'60°
  414,700
  221,100
 '       r
   72,000
  662,800'

 ,500,100'
                                                                                                     \
                                                                                   1976.

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Table 5.   Nucla Steam Electric Station Bag
Filter Installation Cost Breakdown (1974 $)
h I Item :

I Three baghouses
; Ash conveyor system
aiiiRetrpfit 	 items 	 	 	 	 	 	 	 	 	
k Overhead
tT Engineering and fee
,.. P P 3
i Total capital expenditure
F Total capital expenditure
j: (1977 estimate)3
*Tptal 	 Cost

B 1,740,000
250,000
210,000
, 120,000
300,000
Sz
2,620,000
3,188,000

• t
-, 	 f

1

I

1
i
i
i
i
aScale factor from Chemical Engineering, M & S
 equipment cost index 1972 - 4th quarter 1976.
Figure 3.  Estimated range of fly,ash precipitator
costs —hot and "enlarged" (cold).  (From JAPCA
September 1974 article by N. W. Frisch and
D. W. Coy of Research-Cottrell, Inc.)
                                                                 20
                                                               o  15. •
                                                                     1000 MW plant
                                                                     subbituminous coal
                                                                     99.5% efficiency
                                                                                               10'
                                                                Cold precipitator operating resistivity, ohm-cm
Table 6.   Average Costs of ESP Operation at the Gallatin Steam Plant
j: Capital Cost ~
* • i '*
i , i i
t ESP
& 	 ! , •' t
* ' i f
s Direct Operating Costs
1 	 !, :.. , 	 , !
I;; ; 	 	 : 	 	 I
| Utilities

1 ESP maintenance
*' Ash handling fuel consumption
2 Ash handling maintenance labor
1 and material

j Indirect Operating Costs
! Total Annual Operating Cost
7 Total Annual Operating Cost (1977 Estimate)3
-
IT-

HI

IS
1-

P"


r

L



".fi~
" 1" ' " "^ "1,324,000
~* f. ^ I^R tf3^ a, ai^, p
(Annual average 1969-1971
"" »IS-St"lSSEttll^--fW1P 1?
"* 7,835

"* " ' - ; ' "%5iD8( ""
2,200
58,980

r . i "2 a'j
	 164,100
235,215
343,470

, J

f- s| r»« "f
figures)
rfSMSftS s*






1
t
f
_,
1
: 1

""-> I

sfTtST hi






i i
I
i
i
s
aSca!e factor from Chemical Engineering, M & S equipment cost index 1972 - 4th quarter 1976.

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                                                                                                                                      1
Nucla - view of rappers located on top of baghouse

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Sunbury - view of hoppers capturing flyash

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                                                    Table 7.  1976 Nucla Bag Filter Installation
                                                    Operating Cost Estimate
                                                      K      &                   ——iSi-^.---*     ... .  _
                                                                                      /year    ^Percent j
                                                                                      ia£^....r^.:^ Sft^'n', w>*w^T-i
                                                     aScale factor from Chemical Engineering, M & S
                                                      equipment cost index 1972 - 4th quarter 1976.
Table 8.  Average Annual Operating Costs at Sunbur^ S.E.S. Bag Filter Installation (1973, 1974, 1975)
  Direct Costs
    Operation and maintenance labor
    Maintenance material
  ^Utilities
  |. Ash handling

  Tndirect Costs
  l^pepreciation — 4.9%
          t — 3.4%
  ^Insurance — 0.1 %
  s,TTaxes

  tjotal Annual Operating Cost

        , 1977 estimate3
aScale factor from Chemical Engineering, M & S equi
                                                                                    Percent
             ^'"^"1
             ^?,337
             JASPS.
                                                                               complete baghouse
                                                                             Placement each year)
jment cost index 1972 - 4th quarter 1976.

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     The successful application of fabric filtration to
the coal-fired utility boilers at Nucla and Sunbury
Indicate their potential for further electric utility
installation. Bag filters should be considered for all
new and retrofit particulate control systems when
the following conditions are present:
  •  control efficiencies exceeding 95 percent
      are required
  •  effluent gas flow rate varies widely due to
      frequent load changes or regular cycling
  •  fuel composition is variable resulting in
      changing chemical concentration on the fly
      ash surfaces
  •  high ash resistivity causing inefficient particle
      collection by electrostatic precipitators.
    In some cases, high-volume systems using ESPs
could benefit from the installation of a baghouse in
parallel to the ESP to reduce the volume flow and
increase its efficiency.

    New fabric materials have eliminated the excess
maintenance requirements of the original baghouse
designs, resulting in operating costs comparable to
electrostatic precipitators. Initial capital investments
are also similar and lower in situations where collec-
tion efficiency requirements are greater than 99
percent. Therefore, as new, more restrictive regula-
tions are promulgated and the use of low-sulfur,
Western coals increases, the fabric filter will become
the first choice for many utility boiler operations
firing solid fuels.
Sunbury - filter bag support frames and tension adjusting device

       This capsule report has  been prepared jointly by Technology Transfer and the Utilities and Industrial
  Power Division, Industrial Environmental Reasearch Laboratory. For further information write  to:

                                      Particulate Technology Branch
                                Utilities and Industrial Power Division, IERL
                                    Research Triangle Park, N.C. 27711

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