Characterization And Control Of Radionuclide Emissions From Elemental Phosphorus Production


 vvEPA
U.S
RTF, *. C, 27711
United States
Environmental Protection
Agency
                     Office of Air Quality
                     Planning and Standards
                     Research Triangle Park NC 27711
EPA-460/0 00-frT»
February 1989
            Air
Characterization and
Control of Radionuciide
Emissions From
Elemental Phosphorus
Production
EPA/450/3-89/020

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                           EPA=t50/3-88-Ot5
Characterization and Control
  of Radionuclide Emissions
       From Elemental
   Phosphorus Production
          Emissions Standards Division
      U.S. ENVIRONMENTAL PROTECTION AGENCY
          Office of Air and Radiation
       Office of Air Quality Planning and Standards
       Research Triangle Park, North Carolina 27711
            February 1989

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This report has been reviewed by the  Enission  Standards Division of the Office of Air Quality  Planning and
Standards, EPA, and approved for publication.   Mention of trade names  or comercial products is  not intended
to constitute endorsenent or recoraendation for use.  Copies of this report are available  through the Library
Services Office (MD-35),  O.s. Environaental Protection Agency,  Research Triangle  Park, North Carolina 27711,
or fron National Technical Infornation Services, 5285  Port Royal Road,  Springfield, Virginia 22161.

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                                            PREFACE

               Midwest Research Institute (MRI) prepared this report for the U. S.
          Environmental Protection Agency, Office of Air Quality Planning and
          Standards on Contract No. 68-02-4379, Work Assignment 12, Ms. Elizabeth
          Grainger and Mr. Lee Beck served as technical project monitors.
               The report was prepared by Mr. Dennis Wallace, Ms. Katy Allen, and
          Mr. Jim Obremski in MRI's Environmental Engineering Department.  Mr. Mark
'          Turner, Mr. Butch Smith, and Ms. Carol Athey provided valuable comments
<          and other members of the Environmental Engineering Department contributed
          to specific portions of the report.
          Approved for:
          MIDWEST RESEARCH INSTITUTE
                                   ,1
          Roy Neulicht, Program Manager
          Environmental Engineering Department
          December 12, 1988

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                             TABLE OF CONTENTS
 LIST OF FIGURES	   iv

 LIST OF TABLES	   v



 SECTION 1.0   INTRODUCTION	   1-1

 SECTION 2.0   ELEMENTAL PHOSPHORUS INDUSTRY DESCRIPTION	   2-1
              2.1  INDUSTRY CHARACTERIZATION	   2-1
              2.2  ELEMENTAL PHOSPHORUS PRODUCTION PROCESSES	   2-5
                  2.2.1  Process Description	   2-5
                  2.2.2  Radionuclide Distributions	   2-10
              2.3  REFERENCES FOR SECTION 2	   2-14

 SECTION 3.0   EMISSIONS FROM ELEMENTAL PHOSPHORUS PLANTS	   3-1
              3.1  SOURCES OF RADIONUCLIDE EMISSIONS	   3-1
              3.2  KILN EMISSION CHARACTERIZATION	   3-9
                  3.2.1  Mass Emission Rates of Po-210, Pb-210
                           and PM	   3-9
                  3.2.2  Acid Gas Emissions	   3-17
                  3.2.3  Po-210 and Pb-210 Particle Size
                           Di stri buti ons	   3-17
              3.3  KILN BASELINE EMISSIONS	   3-21
              3.4  REFERENCES FOR SECTION 3	   3-23

 SECTION 4.0   EMISSION CONTROLS	   4-1
              4.1  DESCRIPTION OF APPLICABLE CONTROL SYSTEMS	   4-2
                  4.1.1  Spray Towers	   4-2
                  4.1.2  Venturi Scrubbers	   4-6
                  4.1.3  Wet ESP's	   4-10
                  4.1.4  SD/FF Systems	   4-17
                  4.1.5  HEPA Filters	   4-23
              4.2  PERFORMANCE OF ALTERNATIVE CONTROL TECHNOLOGIES...   4-29
                  4.2.1  Venturi Scrubbers	   4-30
                  4.2.2  Wet ESP's	   4-35
                  4.2.3  SD/FF Systems	   4-38
                  4.2.4  HEPA Filters	   4-41
              4.3  COST OF CONTROL TECHNOLOGIES	   4-41
                  4.3.1  Venturi Scrubber Cost Assumptions	   4-44
                  4.3.2  Wet ESP Cost Assumptions	   4-44
                  4.3.3  SD/FF Cost Assumptions	   4-44
                  4.3.4  HEPA Filter Cost Assumptions	   4-45
              4.4  REFERENCES FOR SECTION 4	   4-47

SECTION 5.0   CONTROL ALTERNATIVE PERFORMANCE AND COST	   5-1
              5.1  DEFINITION OF CONTROL ALTERNATIVES	   5-1
              5.2  PERFORMANCE OF CONTROL ALTERNATIVES	   5-3
              5.3  COSTS OF CONTROL ALTERNATIVES	   5-12
              5.4  REFERENCES FOR SECTION 5	   5-29

APPENDICES A-E:   SEPARATE CBI VOLUME
                                    111

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Figure 2-1.
Figure 3-1.
Figure 3-2.
Figure 3-3.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 4-5.
Figure 4-6.
Figure 4-7.
Figure 4-8.
Figure 4-9.
Figure 4-10.
Figure 4-11.
Figure 5-1.
Figure 5-2.
                              LIST OF  FIGURES
General elemental phosphorous plant process  flow	   2-7
Vapor pressure curves for Po and Pb	   3-4
Summary of Po-210 emission data	   3-13
Summary of Pb-210 emission data	   3-14
Countercurrent flow spray tower	   4-3
Venturi scrubber	   4-7
Wetted-throat venturi scrubber	   4-8
Adjustable-throat venturi scrubber	   4-9
Illustration of ESP operating principles	   4-12
Circular-plate type wet ESP	   4-14
Flat-plate type wet ESP	   4-15
Spray dryer/fabric filter system	   4-18
Pulse-jet fabric filter	   4-21
The HEPA filter performance curve	   4-25
Examples of HEPA filter systems	   4-27
Capital costs of control alternatives	   5-17
Annualized costs of control alternatives	   5-18
                                    iv

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                               LIST  OF  TABLES
                                                                       Page

TABLE 2-1.  PRODUCTION OF ELEMENTAL PHOSHPORUS  1967-1987	   2-3

TABLE 2-2.  USERS OF ELEMENTAL PHOSPHORUS BY-PRODUCT SLAG	   2-4

TABLE 2-3.  OPERATING ELEMENTAL PHOSPHORUS PLANTS,  1988	   2-6

TABLE 2-4.  Po-210 CONCENTRATIONS IN ELEMENTAL  PHOSPHORUS PROCESS
              STREAMS	   2-12

TABLE 2-5.  Pb-210 CONCENTRATIONS IN ELEMENTAL  PHOSPHORUS PROCESS
              STREAMS	   2-13

TABLE 3-1.  RADIONUCLIDE EMISSIONS FROM ELEMENTAL PHOSPHORUS
              OPERATIONS	   3-2

TABLE 3-2.  NODULE COOLER EMISSION ESTIMATES	   3-6

TABLE 3-3.  SUMMARY OF TEST CONDITIONS	   3-10

TABLE 3-4.  CALCINER PM EMISSION DATA	   3-11

TABLE 3-5.  CALCINER RADIONUCLIDE EMISSION DATA	   3-12

TABLE 3-6.  ACID GAS EMISSION LEVELS	   3-18

TABLE 3-7.  PARTICLE SIZE DISTRIBUTION BASED ON IMPACTOR SAMPLES	   3-19

TABLE 3-8   PARTICLE SIZE DISTRIBUTION BASED ON SASS CYCLONE
              SAMPLES	   3-20

TABLE 3-9.  BASELINE Po-210 AND Pb-210 EMISSIONS	   3-22

TABLE 4-1.  ESTIMATED EFFICIENCY OF MONSANTO SCRUBBER	   4-34

TABLE 4-2.  ESTIMATES OF VENTURI SCRUBBER PERFORMANCE	   4-36

TABLE 4-3.  SUMMARY OF ESP EFFICIENCY CALCULATIONS	   4-39

TABLE 4-4.  ASSUMPTIONS USED IN ESTIMATING DIRECT AND INDIRECT
              COSTS	   4-43

TABLE 5-1.  PARTICLE SIZE DISTRIBUTIONS FOR Po-210 and Pb-210	   5-5

TABLE 5-2.  ESTIMATED FRACTIONAL EFFICIENCIES FOR VENTURI  SCRUBBER
              CONTROL ALTERNATIVES	   5-6

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                        LIST OF TABLES (continued)
                                                                      Page

TABLE 5-3.   ESTIMATED FRACTIONAL EFFICIENCIES FOR WET ESP CONTROL
               ALTERNATIVES	  5-7

TABLE 5-4.   ESTIMATED PERFORMANCE FOR VENTURI SCRUBBER OPTIONS	  5-9

TABLE 5-5.   ESTIMATED Po-210 EMISSION LEVELS ACHIEVED BY CONTROL
               ALTERNATIVES	  5-10

TABLE 5-6.   ESTIMATED Pb-210 EMISSION LEVELS ACHIEVED BY CONTROL
               ALTERNATIVES	  5-11

TABLE 5-7.   REDUCTION OF Po-210 EMISSIONS FROM BASELINE	  5-12

TABLE 5-8.   REDUCTION OF Pb-210 EMISSIONS FROM BASELINE	  5-13

TABLE 5-9.   CAPITAL COST OF CONTROL ALTERNATIVES	  5-15


TABLE 5-10.  ANNUALIZED COST OF CONTROL ALTERNATIVES	  5-16

TABLE 5-11.  SUMMARY OF COSTS FOR VENTURI SCRUBBER—10 INCH
               PRESSURE DROP	  5-19

TABLE 5-12.  SUMMARY OF COSTS FOR VENTURI SCRUBBER—25 INCH
               PRESSURE DROP	  5-20

TABLE 5-13.  SUMMARY OF COSTS FOR VENTURI SCRUBBER—40 INCH
               PRESSURE DROP	  5-21

TABLE 5-14.  SUMMARY OF COSTS FOR VENTURI SCRUBBER—80 INCH
               PRESSURE DROP	  5-22

TABLE 5-15.  SUMMARY OF COSTS FOR WET WALLS ELECTROSTATIC/
               PRECIPITATOR—200 SCA	  5-23

TABLE 5-16.  SUMMARY OF COSTS FOR WET WALLS ELECTROSTATIC/
               PRECIPITATOR—400 SCA	  5-24

TABLE 5-17.  SUMMARY OF COSTS FOR WET WALLS ELECTROSTATIC/
               PRECIPITATOR—600 SCA	  5-25

TABLE 5-18.  SUMMARY OF COSTS FOR WET WALLS ELECTROSTATIC/
               PRECIPITATOR—800 SCA	  5-26

TABLE 5-19.  SUMMARY OF COSTS FOR SPRAY DRYER/FABRIC FILTER	  5-27

TABLE 5-20.  SUMMARY OF COSTS FOR HEPA FILTRATION SYSTEM	  5-28
                                    VI

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                             1.0  INTRODUCTION

     The U. S. Environmental Protection Agency's (EPA's)  Office of
Radiation Programs  (ORP)  is developing a  National  Emission Standard  for
Hazardous Air Pollutants  (NESHAP) under the  authority of  Section 112 of
the Clean Air Act for radionuclide emissions from  elemental  phosphorus
production facilities.  Background information  on  the elemental  phosphorus
production processes, radionuclide emissions from  these processes,
availability of control techniques that could reduce these emissions, and
the performance and costs of alternative  control techniques  is  needed to
support that regulatory development effort.   The ORP will  use that
background information to define regulatory  alternatives  and to  evaluate
the emission reductions, risk levels, and costs  associated with  each of
the regulatory alternatives.
     This report presents the results of  a study conducted by the
Industrial Studies Branch (ISB) in EPA's Office  of Air Quality Planning
and Standards (OAQPS) that was designed to collect the background
information.  The specific objectives of the  study were to identify  the
sources of radionuclide emissions, particularly polonium-210 (Po-210) and
lead-210 (Pb-210), from elemental phosphorus  production; to determine
baseline emissions levels of Po-210 and Pb-210 for the  key emission
sources at each operating elemental  phosphorus plant;  to identify feasible
control alternatives; and to estimate the performance  and cost of those
control alternatives.  Although all  potential sources of Po-210 and Pb-210
from elemental phosphorus production were considered, this study focused
on Po-210 and Pb-210 emissions from the calcining (or nodulizing
operations)  because previous studies indicated that those operations are
the primary sources of radionuclide  emissions from the process.
Consequently, this report deals primarily with the characterization and
control of Po-210 and Pb-210 emissions from nodulizing calciners or kilns,
but other sources of emissions are addressed briefly.
     The objectives identified above were addressed through three primary
data gathering and analysis tasks.   First, all emission data generated by
EPA and elemental  phosphorus facilities  over the past 10 years were
compiled and analyzed.   As a consequence  of these analyses, data gaps were
                                    1-1

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identified, and an emission test program that addressed those gaps was
conducted concurrently with this study.  The results of that test program
are included in this report.  Second, plant visits were conducted at each
of the five operating facilities to collect data on process and control
system operations, process residuals and emissions, and control system
performance and cost.  Finally, additional information on control system
performance and costs was obtained through a literature review, contact
with knowledgeable EPA personnel, and telephone contacts with control
equipment vendors.
     The results of this study are presented in the four sections which
follow.  Section 2 contains a description of the elemental phosphorus
industry.  It describes the elemental phosphorus production process and
presents data on the distribution of radlonuclides in process streams and
residues.  Section 3 discusses emissions from the elemental phosphorus
production process.  Sources of radlonuclide emissions are identified, and
estimates of Po-210 and Pb-210 emissions from the different sources are
presented.  Detailed information on Po-210, Pb-210, particulate matter
(PM), and add gas emissions from the calcining/nodulizing operation is
presented, and baseline estimates of PM and radionuclide emissions from
those operations are developed for each operating facility.  Section 4
addresses control of calciner/nodulizing kiln radionuclide emissions.
Potential control techniques are described, and procedures for estimating
the performance and cost of these techniques are presented.  Specific
control alternatives for calciner operations are defined in Section 5, and
estimates of the performance and costs of these alternatives are
developed.
                                    1-2

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               2.0  ELEMENTAL  PHOSPHORUS  INDUSTRY  DESCRIPTION

     Phosphate rock is the basic raw material used in the production  of
phosphorus and phosphorus products.  About 10 percent of the phosphate
rock mined in the U.S. is used in the production of elemental phosphorus,
which is produced by a high-temperature reduction process.   Environmental
releases associated with the elemental phosphorus process include air
emissions of criteria pollutants such as particulate matter  (PM) and
sulfur dioxide (S02)  as well as the acid gas hydrogen fluoride (HF),
liquid effluent streams that have low pH and contain radionuclide
materials, and large quantities of slag materials that must be stored or
disposed as solid waste.  The primary concern of this study is the
potential for emission of two radionuclide daughters of uranium-238
(U-238)~polonium-210 (Po-210) and lead-210 (Pb-210)~during the high-
temperature operations.
     This section briefly describes the elemental  phosphorus industry and
the elemental phosphorus production processes as a background for under-
standing radionuclide emission problems and control  alternatives.  The
discussion is divided into two subsections.  The first provides  an overall
description of the industry and identifies operating plants  and  their
capacities.  The second describes the elemental  phosphorus  production
process, identifies production and waste streams,  and presents  the distri-
bution of Po-210 and  Pb-210 among those streams.
2.1  INDUSTRY CHARACTERIZATION
     Elemental  phosphorus is produced from the reaction  of phosphate ore
with silica and carbon (coke)  in  a high-temperature  electric furnace.   The
key raw material  with  respect  to  both the product  and  radionuclide
emissions is the phosphate ore.   Phosphate ore deposits  are  located
principally in  three  regions of the United States:
     1.   Southeastern  region (mainly Florida, but  also South  Carolina,
North Carolina, and Georgia);
     2.   Northern Rocky Mountain  region  (eastern Idaho,  western Wyoming,
northern Utah,  and  southwestern Montana);  and
     3.   Middle Tennessee.
                                   2-1

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     Most of the phosphate rock used in this country's phosphate rock  and
phosphate fertilizer industries is taken from Florida reserves, but most
of the ore used in elemental phosphorus production is obtained from the
Tennessee and Rocky Mountain regions.  The phosphate ores from the three
principal regions are distinct in their radiological characteristics.
Generally, ores from the southeastern region have the highest radionuclide
concentrations, followed respectively by those from the northern Rocky
Mountain region and those from middle Tennessee.  The radioactivity
content of phosphate rocks from different deposits within the same general
region, however, may vary widely.  Details on the radioactivity levels of
the ores used at operating elemental phosphorus plants are presented in
Section 2.2.
     The principal products of the elemental phosphorus industry are
elemental phosphorus and two by-products associated with its production—
calcium silicate slag and ferrophosphorus (FeP).  The production rates of
elemental phosphorus for the years 1967 through 1987 are shown in
Table 2-1.l  Typically, calcium silicate slag is produced at a rate of 8
to 9 Mg per Mg of elemental phosphorus produced, and ferrophosphorus is
produced at a rate of 0.1 to 0.3 Mg per Mg of elemental  phosphorus
produced.
     Elemental phosphorus is used primarily in the manufacture of high-
grade phosphoric acid,  which serves as a feedstock in the production of
chemicals and food products.  In 1986, 50 percent of the supply was used
to produce sodium tripolyphosphate, and small quantities (about 20,000 Mg)
were exported.3  End uses include detergents, metal  treatment, foods and
beverages, and chemicals.3
     Historically, the  calcium silicate slag produced in this  process  has
been used as an aggregate material.   Some of the uses of this  material  are
given in Table 2-2.2  However, as outlined in Section 2.2.2.,  this  slag
may contain Po-210 and  Pb-210, and it has been demonstrated  to contain
U-238.  Consequently,  concerns have been raised  about use  of the
material.  Information  collected  from plant  visits during  this study
indicates that most  slag currently is being  stockpiled at  plant sites.
     The other major by-product is ferrophosphorus.   Plant contacts
indicated that the market for this product is limited, but some is sold in
                                   2-2

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  TABLE 2-1.  PRODUCTION OF ELEMENTAL PHOSPHORUS  1967-1987'

               Production,                       Production,
Year            Mg  (tons)         Year            Mg  (tons)


1987        312,117 (343,329)      1975       408,642 (449,506)

1986        330,652 (363,717)      1974       476,523 (524,175)

1985        326,582 (359,196)      1973       477,748 (525,523)

1984        350,966 (386,063)      1972       490,990 (540,089)

1983        332,772 (366,050)      1971       495,535 (545,089)

1982        328,354 (361,189)      1970       542,323 (596,555)

1981        387,334 (426,067)      1969       566,347 (622,982)

1980        392,482 (431,730)      1968       557,585 (613,343)

1979        417,765 (459,541)      1967       533,642 (587,006)

1978        401,158 (441,274)

1977        391,174 (430,291)

1976        396,959 (436,655)
                             2-3

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  TABLE 2-2.  USES OF ELEMENTAL PHOSPHORUS  BY-PRODUCT SLAG2
Neutralizer for acidic soils
Road ballast
Manufacture of Portland cement
Manufacture of slag concrete blocks
Slag wool as thermal insulation
Ceramic bodies and glazes
Railroad ballast and roadbeds
Fill for septic tank drainage fields
Roadway, substation, and soil stabilization at commercial
  facilities and utility installations
Municipal sewage plant filter beds
Aggregate for parking lot and driveway paving
Built-up roofing aggregate
                              2-4

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specialty markets such as specialty steels, cast alloys, and  paint
pigments.  One plant sells the ferrophosphorus to a plant that  processes
it to recover vanadium.
     In 1980, eight elemental phosphorus plants were operating  in the
U.S.  However, since that time, the two Florida plants, Mobil in Pierce
and Stauffer in Tarpon Springs, have shut down as a result of high
electrical costs in that State.  Recently, Monsanto dismantled  its
facility in Columbia, Tennessee.  Consequently, only five plants currently
are operating, and this number is not expected to increase in the
foreseeable future.  Table 2-3 identifies the five operating plants and
presents estimates of their operating capacities for phosphorus production
and of the quantity of phosphate ore that would be required to produce
this capacity.  The estimates are based on quantities published by EPA in
1983.   During plant visits performed during July and August 1988,
industry personnel indicated that capacities had not changed since 1983.
They also indicated that production rates vary from 50 to 100 percent of
capacity depending upon market demand.
2.2  ELEMENTAL PHOSPHORUS PRODUCTION PROCESSES
2.2.1  Process Description
     Elemental phosphorus is produced by a thermal  process  that uses
silica as a fluxing agent for the calcium present in phosphate feed ore.
Phosphate is reacted with silica and coke in a reducing atmosphere to form
elemental phosphorus (PH), CO, and calcium silicate slag.   In addition,
by-product FeP is formed from the reaction of elemental phosphorus with
coke and iron oxide.  Simplified equations for the  process  are:
      4 CasF(POJ3+18 Si02+30 C * 18  CaO-Si02-l/9  CaF2+30 CO*+3P^t     (1)
           (ore)                        (slag)
              2 P205+10 C * 10 COt+P^t  (intermediate  reaction)          (2)

                       2 Fe203+6C+Pu * 4 FeP+6 CO+                     (3)

     Figure 2-1 presents  a simplified process  flow diagram  that  generally
represents the process  used at the  five operating plants.   The paragraphs
                                   2-5

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         TABLE 2-3.  OPERATING ELEMENTAL PHOSPHORUS PLANTS, 1988
Plant
FMC Corporation, Pocatello, Idaho
Monsanto Co., Soda Springs, , Idaho
Stauffer Chemical Co., Silver Bow,
Phosphorus
capacity,
I? Mg/yr
(10 tons/yr)
123 (135)
95 (105)
38 (42)
Ore
requirements,
1§3 Mg/yr
(10 tons/yr)
1,470 (1,620)
1,000 (1,100)
380 (420)
  Mont.

Stauffer Chemical Co., Mt.  Pleasant,
  Tenn.

Occidental Chemical Co., Columbia,
  Tenn.
41 (45)


45 (50)
440 (480)


490 (540)
                                   2-6

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below describe the major components of this process and identify points  in
the process where operations differ significantly among the plants.
     Phosphate ore is mined offsite and is shipped by rail or truck to
each of the five plants for processing.  The three western plants receive
their ore from Idaho mines that operate about 7 months per year.  These
plants stockpile large amounts of ore during the summer months to continue
process operations during the winter months.  The two Tennessee plants
receive ore from Tennessee mines 12 months per year.  At each of the
plants, the ore is stockpiled and then processed before it is fed to the
calciner.  The specific processing steps vary depending upon the ore
characteristics and calciner operations as described below.
     At FMC, the ore is screened to remove oversized material, which is
sent to an ore crusher for processing.  The screened material and fines
generated by the process are formed into briquettes by briquette
presses.  The briquettes are screened, and the fines are recycled to the
briquetting process.  The briquettes are then used as feed to the
calciner.
     At the other four plants, as-received ore is blended with recycled
fines to form the feed to the calciner.  The principal difference in the
facilities is that the Tennessee plants use an ore that has been washed.
Consequently, the moisture content of the calciner feed is higher at these
plants than at the western plants.
     The prepared phosphate ore blend is fed to one of two types of
"calciners"—a traveling-grate calciner (FMC only)  or a rotary kiln.  The
objective of the calcining process is to remove moisture from the ore,
combust any volatile constituents in the ore,  and produce a feedstock for
the electric furnace that is physically stable and  appropriately sized.
In the traveling-grate calciner,  the preformed briquettes  are placed in
pallets to a fixed depth.  The pallets move through the calciner,  and the
briquettes are heated to a temperature of about 1300°C (2400°F)  by
overfire burners that are fueled  by CO or natural gas.   An induced draft
fan pulls the combustion gases downward through the bed.   In  the rotary
kiln, the phosphate ore blend is  fed continuously to the upper end  of the
kiln.  As the ore moves through the kiln,  moisture  and  volatiles  are
driven off, and the remaining material  is heated to a  temperature  of about
                                   2-8
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1300°C (2400°F) by combustion gases that flow through the  kiln counter-
current to the ore.  At those temperatures, the ore  is  heated  to its
incipient melting point, and the tumbling action of  the kiln agglomerates
the material into larger nodules.  Typically, the kilns have a solids
residence time of about 4 h.  The kilns are fueled by a combination of  CO,
coal, and natural gas.
     Both types of calciners generate large quantities of  high-temperature
combustion gases.  Volumetric flows for the calciners currently operating
range from about 3,700 to 11,000 m3/nrin (130,000 to  400,000 acfm)  at
temperatures in the range of 320° to 430°C (600° to  800°F).  Two of the
five plants use a waste heat boiler for energy recovery.   The  gases from
the kiln or boiler are treated in an air pollution control system  before
they are discharged to the atmosphere.  The air pollution  control  systems
for the five plants are described in Section 4.  Details on the combustion
gas characteristics and kiln operating rates are presented in  Appendices A
through E.
     The nodules or briquettes that leave the calciner are air cooled and
subjected to crushing and sizing operations.   Materials that are
approximately 1.5 to 2.5 cm (0.6 to 1.0 in.)  in diameter are sent to the
feed proportioning area for the electric furnace.   Undersized material  is
recycled to the ore blending area and subsequently through the calciner.
     The nodulized or briquetted phosphate feed material is sent to a
proportioning area where it is mixed with sized coke and silica to obtain
the required weight proportion of furnace feed (burden).  A proper ratio
of Si02 to CaO is required to form slag with  the necessary flow properties
to facilitate removal  from the furnace.   Coke is added as  a carbon source
to reduce the intermediate reaction product P205 to  elemental
phosphorus.   This proportioned furnace feed burden  is conveyed  to the
furnace burden bins.
     The electric furnace is a large chamber  lined with  carbon  blocks  in
the lower section.   Three consumable carbon electrodes  extend  through  the
roof to conduct the electric current.   An  electric arc  is  formed between
the electrodes and  the furnace lining.   The burden material is  gravity  fed
continuously to the top of the furnace from where  it  progresses downward
until  it is  heated  and eventually melts  in  the  intense  heat of  the
                                   2-9
-------
electric arc.  At the heat source, the maximum temperature can reach
4400°C (7950°F).  At 1400° to 1800°C (2550° to 3270°F), silica becomes a
strong add that reacts with the calcium phosphate to yield a calcium
silicate slag and P205.  The P205 in turn reacts with the carbon in the
coke and is reduced to CO and P^.
     The elemental phosphorus is driven off as a vapor in the CO off-gas
stream.  The slag and ferrophosphorus continually collect in the bottom of
the furnace in molten layers with the denser ferrophosphorus layer below
the slag layer.  Periodically, these molten by-products are tapped
separately.  Slag is tapped approximately once each hour and
ferrophosphorus up to several times each day.  The slag and
ferrophosphorus are air cooled in a pit and stockpiled for later use.
     At three of the five facilities, the furnace product gases are
treated for dust removal in an electrostatic precipitator (ESP).  At the
other two facilities, the gas stream is routed directly to the phosphorus
recovery processes.  The gas stream from the ESP, or from the furnace at
those plants that do not have an ESP, are sent to water spray condensers
where the gases are cooled and the phosphorus is condensed to a liquid.
The condensed phosphorus is collected under water, purified by filtering,
and then pumped to underwater storage.  The gas stream from the condenser
is primarily CO.  Essentially all of the phosphorus-free CO is recycled to
fuel the nodulization process.  The remaining CO is recycled to other
plant operations or exhausted through flare stacks.  Plant personnel
indicated that CO is flared only on days when the kiln is not operating.
2.2.2  Radionuclide Distributions
     The primary objective of this study is to evaluate Po-210 and  Pb-210
emissions from elemental phosphorus plants (particularly from the
nodulizing kiln or calciner) and to develop alternatives for the control
of these emissions.  Consequently, the  distribution of Po-210 and Pb-210
among the different process streams is  of interest.  The paragraphs below
summarize the information that has been collected on these distribu-
tions.  This information is based on comprehensive studies of elemental
phosphorus production conducted for EPA prior to  1983,  test  data developed
by EPA in 1983 and 1984, and data supplied by the plants  during  earlier
EPA studies and during site visits conducted for  this  study.
                                   2-10
-------
     Both Po-210 and Pb-210 are volatile metals.  As such, It is quite
likely that they will be volatilized in the calciner and leave the
calciner with the combustion gas stream.  However, data from the five
operating facilities indicate that at least some of the Po-210 and Pb-210
remains in the nodules that are fed to the electric furnace.  Plant
environmental personnel and industry research personnel contacted during
this study all agreed that any Po-210 and Pb-210 that does reach the
electric furnace would be volatilized and returned to the kiln with the
CO.  Available data generally support this conclusion, but limited data
from the EPA facility studies indicate that some Po-210 and Pb-210 is
deposited in the slag.   However, these data should be viewed with caution
because slag streams are difficult to sample and analyze and because
Po-210 and Pb-210 concentrations in the slag depend on the age of the
slag.  This age dependence results from decay of other radiouclides that
are known to be present in the slag.
     Tables 2-4 and 2-5 summarize available data on Po-210 and Pb-210 in
elemental phosphorus streams.   These  data generally suggest that most
Po-210 and Pb-210 concentrates in the kiln exhaust stream,  but they do not
demonstrate conclusively that  this stream is the only pathway for these
constituents.  In particular,  they indicate that significant  quantities of
Po-210 and Pb-210 remain in the slag  in some cases.   During plant visits,
plant personnel  indicated that these  levels appear to overestimate  the
quantities of radionuclides in the slag.   Monsanto research personnel
indicated that slag sampling was difficult, and  accurate values  could  not
be obtained.16  However, they  estimate  that Po-210 concentrations in  the
slag are about 5 to 10 pCi/g.
                                   2-11
-------
TABLE  2-4.   Po-210  CONCENTRATIONS IN  ELEMENTAL PHOSPHORUS  PROCESS  STREAMS
Process stream
Ore



Nodu 1 es


Slag

Ferrophosphorus
Inlet PM


FMC, Monsanto,
1 daho 1 daho
22a 91 b
21? 126"
23J
23*
<2.6a 1.9b
8?
9.8J
<16a

<0.6a
2,5(X>9 1 ,920"
2,600!"
4,400*
Po-210 concentrations, pCi/g
Stauffer Occidental, Monsanto,
Mont. Tenn. Tenn. Tenn.
36? 3.5d 4.1e 4.1f
40'


41' 0.091 3.3f


<2C (fresh) 0.4d <0.8f
2.7C (piled)
<1.9C 0.05d 1.0f
3,400'

Stack PM
                   19,0009   37,000b      37,000'
                   25,000!"    5,000"
                   53,000K   35,000"
1,200°
^Based on EPA  test  data  collected
DBased on EPA  test  data  collected
 and recycle feed.
"•Based on EPA  test  data  collected
                                  in
                                     1977 as presented in Reference 4.
                                     1984 as presented in Reference 5;
    includes combined ore
 ____ ___ _. ..  ----  ____  — ------  ...  1982 as presented in Reference 6. •
 Based on data supplied  to EPA by  facility as presented in Reference 2.
eOata presented in  Reference 2.  Concentrations assumed to be equal to those measured at the
 Monsanto, Tennessee,  facility  in  1982  as presented in Reference 7.
 Based on EPA  test  data  collected  in  1982 as presented in Reference 7.
DBased on test data collected by EPA  in 1984 as presented in Reference 8.
.Based on EPA  test  data  collected  in  1988 as presented in Reference 9.
'.Based on test data collected by EPA  in 1984 as presented in Reference 10.
J Based on data supplied  to MRI by  facility during 1988 site visit and reported in
 Reference 11.  Nodule estimates based  on average of three measurements made through bed;
.values ranged from 5.8  to 14.9.
 Based on EPA  test  data  collected  in  1988 as presented in Reference 12.
                                                                              in
 Based on data  supplied  to MRI by  facility during 1988 plant visit as reported
 Reference 13.
mBased on emission  test  data collected by the facility in 1985 through 1987 as reported in
 Reference 11.
"Based on emission  test  data collected by the facility in 1988 as reported in Reference 14.
°Based on data  supplied  to MRI by  the facility during 1988 plant visit as reported in
 Reference 15.
                                           2-12
-------














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2.3  REFERENCES FOR SECTION 2

 1.  Bureau of Census, U. S. Department of Commerce.  Current  Industrial
     Reports:  Inorganic Chemicals.  Washington, D.C.  1968-1987.

 2.  Stula, R. T., R. E. Balanger, C. L. Clary, R. F. May, M.  E. Spaeth,
     and J. P. Swenson.  Airborne Emission Control Technology  for the
     Elemental Phosphorus Industry, Final Report for EPA Contract
     No. 68-01-6429.  Science Applications, Inc.  La Jolla, California.
     January 1984.

 3.  U. S. Department of the Interior, Preprint from the 1985  Minerals
     Yearbook:  Phosphate Rock.  Pittsburgh, Pennsylvania.  1986.

 4.  Eadie, G. and D. Bernhardt.  Radiological Surveys of Idaho Phosphate
     Ore Processing—The Thermal Process Plant.  Prepared for  U. S.
     Environmental Protection Agency.  Las Vegas, Nevada.  Technical Note
     ORP/LV-77-3.  November 1977.

 5.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
     Poloniun-210 from Calciners at Elemental  Phosphorus Plants:  Monsanto
     Plant, Soda Springs, Idaho.  Washington,  O.C.  September  1984.

 6.  Andrews, V.  Emissions of Naturally Occurring Radioactivity:
     Stauffer Elemental Phosphorus Plant.  Prepared for U. S.
     Environmental Protection Agency.  Las Vegas, Nevada.  Publication
     No. EPA-520/6-82-019.  November 1982.

 7.  Andrews, V.  Emissions of Naturally Occurring Radioactivity:
     Monsanto Elemental Phosphorus Plant.  Prepared for U. S.
     Envirorwental Protection Agency.  Las Vegas, Nevada, Publication
     No. EPA-520/6-82-021.  November 1982.

 8.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
     Polonium-210 from Calciners at Elemental  Phosphorus Plants:  FMC
     Plant, Pocatello, Idaho.  Washington, D.C.  June 1984.

 9.  Radian Corporation.  Draft Final Emission Test Report,  Monsanto
     Elemental Phosphorus Plant, Soda Springs, Idaho.  Prepared for U.  S.
     Environmental Protection Agency under Contract No.  68-02-4338.
     Research Triangle Park, North Carolina.  October 1988.

10.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
     Poloniun-210 from Calciners at Elemental  Phosphorus  Plants:  Stauffer
     Plant, Silver Bow, Montana.  Washington,  D.C.   August 1984.

11.  Memo and attachments from Wallace.,  D., and K.  Leeds, Midwest
     Research Institute, to Beck, L., EPA/ISB.  August 9, 1988.  Site
     Visit~FMC Corporation, Pocatello,  Idaho.
                                   2-14
-------
12.   Radian Corporation.  Draft Final  Emission Test Report,  FMC Elemental
     Phosphorus Plant, Pocatello,  Idaho.   Prepared for U.  S.  Environmental
     Protection Agency under Contract  No.  68-02-4338.   Research Triangle
     Park, North Carolina.  October 1988.

13.   Memo and attachments from Wallace,  D.,  and J. Obremski,  Midwest
     Research Institute, to Beck,  L.,  EPA/ISB.   August 23, 1988.   Site
     V1sit~Stauffer Elemental  Phosphorus  Plant, Mount Pleasant,
     Tennessee.

14.   Memo and attachments from Wallace D.,  and K. Leeds, Midwest  Research
     Institute, to Beck, L., EPA/ISB.  August  9, 1988. Site  Visit—
     Monsanto Elemental Phosphorus Plant,  Soda Springs, Idaho.

15.   Memo and attachments from Wallace,  0.,  and J. Obremski,  Midwest
     Research Institute, to Beck,  L.,  EPA/ISB.   August 23, 1988.   Site
     Visit—Occidental Elemental Phosphorus  Plant, Columbia,  Tennessee.

16.   Telecon.  Wallace, D., Midwest Research Institute, with  Abbot,  D.,
     Monsanto Chemical Company.  July  12,  1988.   Radionuclides  in
     Phosphorus Process Streams.
                                  2-15
-------
-------
              3.0  EMISSIONS FROM ELEMENTAL PHOSPHORUS PLANTS

     The primary objectives of  this  study  are  to  estimate current emission
 rates of the radionucTides Po-210 and  Pb-210 from elemental  phosphorus
 plants and to evaluate control  measures for those emissions.   This section
 identifies potential sources of Po-210 and Pb-210 emissions,  presents
 estimates of emission levels, and provides information on the  character-
 istics of the emissions as a basis for the control technology  assessments
 that are presented in Sections  4 and 5.  The discussion  addresses the
 different sources of radionuclide emissions within the elemental
 phosphorus process, but it focuses on  emissions from the calcining (or
 nodulizing) operation because emissions from the  calciner are  much greater
 than those from all other plant  operations combined.  The three sections
 below provide a brief discussion of the different  emission sources and the
 estimated levels of emissions from these sources,  discuss  calciner
 emissions in detail, and present estimates of baseline emissions  for
 calcining operations at the five operating facilities.
 3.1  SOURCES OF RADIONUCLIDE EMISSIONS
     The Po-210 and Pb-210 concentration data presented  in Section  2.2.2
 indicated that these radionuclides are present at  significant  levels  in
 three elemental phosphorus production streams—the ore feed, calcined
 nodules, and slag from the electric furnaces.   If the processing,
 handling, or storage of these process streams  generates particulate matter
 (PM) emissions, then Po-210 and  Pb-210 are emitted to the atmosphere.  The
 operations that result in emissions include high-temperature furnaces
 (specifically the calciner and the electric furnaces);  nodule cooling,
 crushing, and screening;  and  transfer and  storage of  ore, nodules, slag,
 electric furnace ESP catch,  and calciner  air pollution  control  device
 (APCD)  catch.   The paragraphs  below briefly describe  each of these sources
 and present preliminary estimates of  the  levels of Po-210 and Pb-210
 emissions from these sources.   Table  3-1 provides  a summary of these
 preliminary estimates  for  the  different sources as a  means of comparing
 the relative levels  of  emissions from those sources.  These estimates are
 based on information collected  by EPA surveys and  sampling programs that
were conducted  in support  of the 1983 NESHAP proposal.1'3   More detailed
                                   3-1
-------





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 information  on  calciner  emission rates  is  presented in Section 3.2.  No
 additional data on  emissions from sources  other than the calciner were
 identified during this study.
     The  principal  source of Po-210 and  Pb-210  emissions from elemental
 phosphorus production is the nodulizing  kiln or calciner.   Emissions from
 the calciner are generated via three mechanisms.   First, both Po-210 and
 Pb-210 are relatively volatile metals as evidenced by the vapor pressure
 curves shown in Figure 3-1."*'S  The horizontal  axis of the  curve indicates
 temperature  and the vertical axis indicates the partial  pressure of the
 Pb-210 and Po-210 at temperature.  The maximum  concentration  that the
 metal can achieve in vapor phase is the ratio of the partial  pressure to
 760 mmHg.  At the temperatures reached in  the calciner/kiln ore bed
 (-1300°C), significant quantities of Po-210 and  Pb-210 are  volatilized and
 exit the  kiln as vapor in the combustion gas stream.   These vapor-phase
 metals generally condense on surfaces of PM that is  entrained  in the
 combustion gas  before they penetrate the air pollution control  system.
 Second, as the  combustion gases are drawn  through  the  ore bed of the
 moving grate-calciner or the tumbling ore  in a kiln, relatively  large
 quantities of PM are entrained in the combustion gas stream.  These
 entrained particles, which contain Po-210  and Pb-210,  also are exhausted
 from the  calciner with the combustion gases.  Third, Po-210 and  Pb-210  can
 be volatilized  in the electric furnace and returned to the kiln  in the  CO
 fuel stream.  The Po-210 and Pb-210 again will  leave the kiln as vapor  and
 condense  on  PM  surfaces downstream from the kiln.
     Data on the relative concentrations of Po-210 and Pb-210 in the ore
 feed and  nodule product were collected by EPA at three facilities.
 These data indicate that on a mass basis assuming the nodule mass flux  is
 about 80 percent of the ore mass -flux,  less than 10 percent  of the Po-210
 and 20 to 60 percent of the Pb-210 are retained  in the nodules for rotary
 kiln operations.  For the moving  grate calciner, about 30 percent of the
 Po-210 and almost all  of the  Pb-210  remain  in  the nodules.   These losses
represent the quantity of material  lost  to  the calciner/kiln combustion
gases via the first two  mechanisms.   Mo  data on  the quantity of Po-210 and
Pb-210 that return  to  the calciner/kiln  with the CO were identified during
this study.   However,  the quantities  are  expected to be relatively small
                                   3-3
-------

2 ..
                                                 E3:

l  L
 »00
aoo        3oo       looo      120.0
                  Temperature (*C)
                                                                    1800
       Figure 3-1.   Vapor  pressure curves for  Po and Pb.
                                  3-4
-------
because of the cleaning/condensation process used  to  remove dust and
phosphorus from this stream.  Table 3-1 presents preliminary estimates of
the total quantities of Po-210 and Pb-210 that are emitted from the
nodulizing kiln or calciner.1" '9  These estimates are  based on limited
test data and on control levels in place before 1983  and  will  be updated
in Section 3.2.  However, they do serve to compare the  relative magnitude
of calciner emissions to emissions from other processes.
     Nodules are discharged from the calciner/kiln to the nodule cooler
where they are air cooled.  The high-velocity airflow in  the coolers
results 1n entrainment of PM, which contains Po-210 and Pb-210.   However,
data generated by EPA, which are presented in Table 3-1,  indicate that
with the exception of emissions generated at FMC, these emissions are
negligible in comparison to calciner emissions.  These  data are  supported
by the emission estimates shown in Table 3-2, which are based  on the PM
emission limits that States have established for nodule cooling  emissions
and the concentrations of Po-210 and Pb-210 that have been  measured  in
nodules.$~3»10  These estimates are based on the assumption that Po-210
and Pb-210 are uniformly distributed throughout the calcined nodules.
This assumption is likely to produce conservatively high  estimates because
volatilization in the calciner or kiln will  deplete Po-210  and Pb-210  near
nodule surfaces.  These surface materials are more likely to be  eroded  and
entrained during cooling.   The differences at FMC may result from the  high
temperature of the cooler exhaust which is estimated to be  in the 200°  to
300°C (400° to 600°F) range.  It is possible that Po-210 could be
volatilized from the nodule bed in the cooler and that a portion of the
volatilized material  could be emitted  as a vapor at the exhaust gas
temperatures.
     The nodules are removed from the  cooler and subjected to crushing and
screening operations to generate  a feed that is  sized  appropriately for
the electric furnace.  Again,  fugitive PM emissions from these operations
can contain Po-210 and  Pb-210.   However,  the data  in  Table 3-1 indicate
that emissions of Po-210 and Pb-210  from crushing  and  screening operations
are estimated  to be less than  0.001  Ci/yr  at each  of  the three plants
tested by EPA.
                                   3-5
-------
               TABLE 3-2.   NODULE COOLER EMISSION ESTIMATES
Facility
FMC
Monsanto
Stauffer
Allowable
PM, lb/hl°
S3
31
12
Nodule activity
level, Ci/q6'8
Po-210
8
1.9
4
Pb-210
27
5.6
7
Estimated
emissions, Ci/yr
Po-210
0.003a
O.001
<0.001a
Pb-210
0.009a
0.001
<0.001
aNote that these emission levels are lower than those measured by EPA in
 earlier studies as reported in References 1 and 3.
                                   3-6
-------
      The  final  processing  step  that  is  a potential  source of Po-210 and
 Pb-210  emissions  is  the  electric  furnace.   The Po-210  and Pb-210 that
 enter the furnace with the nodules are  partitioned  among  four discharge
 streams—slag,  ferrophosphorus, primary phosphorus/CO  gas stream, and
 fugitive  emissions from  furnace tapholes.   The data presented in
 Section 2.2.2  indicate that of the total  Po-210 that enters  the plant with
 the ore,  5 to  60  percent is contained in the  slag and  less than
 0.1 percent  is  contained in the ferrophosphorus.  For  Pb-210, the
 percentages  range from 20  to 60 percent and less than  0.1 percent for slag
 and ferrophosphorus,  respectively.   Plant personnel  contacted during  site
 visits  indicated  that these estimated Po-210  concentrations  are higher
 than  the  concentrations  that they would expect to remain  in  the slag  given
 the high  temperatures reached in the furnace.   Also, as described in
 Section 2, radionuclides in the slag are difficult  to  sample  and analyze,
 and the concentrations that were reported have large uncertainties.
 Consequently, the information on distribution  of Po-210 and  Pb-210  is  not
 considered to be  reliable.
      The  Po-210 and Pb-210  that are emitted from the tapholes may be
 captured  by  localized hoods and collected by the emission  control system,
 or they may  be emitted to the atmosphere through furnace  shop windows,
 doors,  and roof monitors.   No data are  available on the quantities that
 are collected by  the  emission control system.   However, the data  in
 Table 3-1  indicate that  as much as 0.31 Ci/yr  of Po-210 and 0.005 Ci/yr of
 Pb-210  are emitted from  the furnaces.  Note that these levels are quite
 small in comparison to kiln emissions.  The Po-210 and Pb-210 that are
 entrained in the  phosphorus/CO stream can be collected in the ESP (if one
 is used), condensed with the phosphorus, or returned to the kiln with the
 CO.  Plant personnel   had no data on the radionuclide content of the ESP
 dust but did indicate that virtually no radionuclides were collected with
 the phosphorus.  The  kiln emission rates account for any Po-210 or Pb-210
 that returns to the kiln with  the CO.
     Fugitive PM emissions  from transfer and storage of ore,  nodules,  and
waste streams also can be a source of Po-210 and Pb-210.   The only storage
 and transfer operations for which  emission data are  available are those
 related  to nodule handling. Generally,  these  operations  are  enclosed, and
                                   3-7
-------
emissions are controlled by hooding systems with collection in scrubbers
or baghouses.  Measurements conducted by EPA prior to 1983 indicate that
emissions from these operations are less than 0.001 Ci/yr for each of the
five plants.  Generally, emissions from ore handling and kiln air pollu-
tion control device catch handling also can be assumed to be negligible
because alKplants currently use some type of wet collection, and the
moisture in these streams will  limit fugitive emissions.  No data were
identified on the level of emissions from the handling of slag or ESP
catch.  However, the data on plant production rates, slag generation
rates, and radionuclide concentrations in the slag presented in
Section 2.0 were used to generate "worst-case" estimates of Po-210 and
Pb-210 emission rates from slag handling.  These emission estimates were
obtained by multiplying the activity levels in the slag (see Tables 2-4
and 2-5) by the annual PM emission rates determined from the following
equations for material handling (Eq. 3-1) and wind erosion from active
storage areas (Eq. 3-2): u

                      E. - l.lSxlO"3 (U/2'2j '  • 9W                 (3-1)
                                      (M/2) '
where
     E! = materials handling PM emissions, kg/yr
      U = mean wind speed, m/s
      M = material moisture content, percent
      W = plant P4 production capacity,  Mg/yr
and
                       E, • Z.ffixlofrjj.H                           (3-2)

where
     E2 = emissions from wind  erosion,  kg/yr/acre
      S = silt content of slag,  percent
      P = percentage of days with  >0.25 mm precipitation  per year
      f = percentage of time wind  exceeds  5.4  m/s
As a worst case the mean wind  speed was assumed  to  be  15  m/s,  the  material
moisture content 0.25 percent, the silt content  10  percent, the  percentage
                                   3-8
-------
of time the wind exceeds 5.4 m/s 100 percent, and the  percentage of days
with precipitation 0 percent.  Under these worst-case  scenarios, all
plants are estimated to have Po-210 and Pb-210 emissions  of  less than
0.003 C1/yr for materials handling and less than 0.0003 Ci/acre/yr for
wind erosion.
3.2  KILN EMISSION CHARACTERIZATION
     As indicated by the information presented in Section 3.1,  the
nodulizing kiln (or calciner) is by far the greatest source  of  Po-210 and
Pb-210 emissions from elemental phosphorus production.  Consequently,
control technology analyses presented in Section 4.0 focus on this
emission source.  This section provides a comprehensive review  of
available calciner emission data.  It is divided into three  subsections.
The first presents information on Po-210, Pb-210, and PM  emission  rates.
The second discusses acid gas emissions from the calcining operation,  and
the third presents data on Po-210 and Pb-210 particle size distributions.
3.2.1  Mass Emission Rates of Po-210, Pb-210 and PM
     The emissions of PM and radionuclides from elemental phosphorus  plant
calcining operations have been tested extensively by both EPA and  the
facilities since 1977.  Data are available for four of the five  operating
facilities.  Although these tests provide a firm basis for regulating
radionuclide emissions, evaluation of the data to identify general emis-
sion trends is complicated by the plant-to-plant variations in processes
and air pollution control  systems and by the inherent uncertainties that
result from complex sampling situations (high moisture, high temperature,
and cyclonic flows) and radionuclide analytical  techniques.   The available
test data are summarized in Tables  3-3 through 3-5.   Table 3-3 identifies
test locations and presents information on stack gas conditions.
Table 3-4 presents PM emission rates and  concentrations,  and Table 3-5
presents Po-210 and Pb-210 emission concentrations  and  annual emission
rates.
     Figures 3-2 and 3-3 present  a  more detailed  summary  of  the  emission
concentration data for Po-210 and Pb-210,  respectively.   In  each figure,
run-specific emission concentrations  are  presented for  the test  series
that are summarized in Table 3-5.   The data  are  grouped into  one of four
levels  of control—no control,  low-energy  scrubber,  venturi  scrubber, and
                                   3-9
-------An error occurred while trying to OCR this image.
-------
                   TABLE 3-4.  CALCINER PM EMISSION  DATA
Test
IDa
A
B
C
0
E
F
G
H
I
J
K
L
M
0
P
Q
R
S
T
U
V
w
Control measure13
None
None
SS/Cyc
SS/Cyc
SS/Cyc
SS/Cyc
SS/Cyc
SS/Cyc
SS/Cyc
LEV/Ch
LEV/Ch
ST
ST/HEV/Cyc
None
ST
ST/WESP
LES
None
LEV/Ch
LEV/Ch
ST
ST/HEV/Cyc
Concentration
g/dson
1.0
6.9
0.089
0.32
0.14
NA
NA
0.046
0.062
0.032
0.018
0.34
0.023
4.4
0.14
0.060
0.27
1.09
0.082
0.095
0.59
0.027
gr/dscf
0.45
3.0
0.039
0.14
0.063
NA
NA
0.020
0.027
0.014
0.008
0.15
0.010
1.9
0.060
0.026
0.12
0.48
0.036
0.041
0.26
0.012
Emission rate
kg/h
98.4
835
12.0
35.9
13.7
8.44
8.84
5.31
9.44
4.72
2.77
77.6
4.72
184
4.54
1.81
49.0
246
21.9
20.8
104
4.90
Ib/h
217
1,840
26.4
79.1
30.3
18.6
19.5
11.7
20.8
10.4
6.1
171
10.4
406
10.0
4.0
108
541
48.3
45.8
230
10.8
*See references on Table 3-3.
 SS/Cyc = slinger scrubber with cyclone mist eliminator.
    LEV » low-energy venturi.
    HEV = high-energy venturi.
     ST = spray tower
     Ch = Chevron-blade mist eliminator.
    LES = low-energy scrubber.
   WESP = wet electrostatic precipitator.
                                   3-11
-------
TABLE 3-5.  CALCINER RADIONUCLIDE EMISSION DATA
Test . Po-210 emissions
IDa Control measure" pCi/g PM nCi/dscm
A None 4,100 4.6
B None 1,050 6.2
C SS/Cyc 17,000 1.44
D SS/Cyc 12,000 3.04
E SS/Cyc 27,000 3.80
F SS/Cyc 25,000 1.47
G SS/Cyc 29,000 1.43
H SS/Cyc 21,000 0.961
1 SS/Cyc 18,000 1.10
J LEV/Ch 37,000 1.18
K LEV/Ch 38,000 1.96
L ST 37,000 12.5
M ST/HEV/Cyc 10,000 0.23
N ST/WESP 0.23
0 None
P ST 37,000 4.88
Q ST/WESP 31,000 1.61
R LES 850 0.23
S None 4,400 4.8
T LEV/Ch 55*000 4.5
U LEV/Ch 51,000 4.9
V ST 39,000 23
H ST/HEV/Cyc 35,000 0.95
?See references on Table 3-3.
Ci/yr
3.3C
6.1C
1.4C
2.6C
2.7C
1.2d
1.7d
0.72d
1.36d
1.24d
2.04d
21C
0.35d


1.2C
0.37C
0.36d
8.0C
9.0C
7.9C
30C
1.4e

Pb-210
pCi/g PM
39
28
330
74
330






9,700


2,900
4,800
4,600
180
180
200
1,300
2,200
8,200

emissions
nCi/dscm
0.04
0.19
0.03
0.02
0.05






3.3

0.34
12.5
0.65
0.25
0.049
0.20
0.015
0.12
7.3
0.23


Ci/yr
0.029*
0.18C
0.026C
0.016C
0.039C






5.6C


4.0C
0.1 6C
0.056C
0.075d
0.32C
0.030C
0.19C
9.5C
0.34e

SS/Cyc = stinger scrubber with cyclone mist eliminator.
LEV =• 1 ow-energy ventur i .
HEV a high-energy ventur i .
ST = spray tower
Ch » Chevron-blade mist eliminator.
LES = low-energy scrubber.
WESP = wet electrostatic precipitator.
"•Assumes plant operates 85 percent of time.
''Based on facility assumptions on operating rates.
eAssumes plant operates 95 percent of time.




































                     3-12
-------An error occurred while trying to OCR this image.
-------An error occurred while trying to OCR this image.
-------
wet ESP.  The emission data presented  in Table  3-5 and Figures 3-2 and 3-3
were not subjected to rigorous  statistical  analyses,  but the graphical
displays in Figures 3-2 and 3-3 provide substantive information on the
Po-210 and Pb-210 emissions from different  facilities with different
control systems.  The paragraphs below discuss  the overall variability of
the Po-210 and Pb-210 concentrations, with  particular emphasis on  the
variability of emissions over time, and identify  data that can be  used to
assess control device performance and the effects of  new control systems
on Po-210 and Pb-210 emissions.
     The data presented in Figures 3-2 and  3-3  indicate  that measured
emissions for individual test runs range over almost  3 orders of magnitude
for both Po-210 (approximately 0.1 to 30 nCi/dscm)  and Pb-210 (less  than
0.01 to 9 nCi/dscm).  Contributors to this  variability include the
inherent imprecision in the sampling and analysis  method,  changes  in
operating conditions at a plant over time,  plant  to plant  differences  in
ore feed characteristics and calciner operating conditions,  and different
levels of add-on air pollution control.  The data  collected  to date are
not sufficient to quantify the contributions of these  different mechanisms
to the overall variability in emissions.  However, careful examination of
the data in Figures 3-2 and 3-3 leads to the following qualitative
observations.
     1.  The run-to-run variation within a given test  sequence is
relatively small.   Generally the largest measured concentration for a
given test is less than two to three times the smallest measured
concentration.  For Po-210, the two exceptions are Test A which ranges
from about 2 nCi/dscm to 9 nCi/dscm (a factor of 4.5) and Test B which
ranges from 0.4 to 16 nCi/dscm (a factor of 40).  For Pb-210, primary
exceptions are Test B which ranges from 0.04 to 0.3 nCi/dscm (a factor of
7.5), Test E which ranges  from 0.02 to 0.12 nCi/dscm (a factor of 6), and
Test U which ranges from 0.04  to 0.3 nCi/dscm (a factor of 7.5).  Each of
these tests was conducted  on one of the two moving grate  calciners.  On
balance,  these data suggest that variation  associated with sampling and
analysis  imprecision  is  reasonable,  i.e.,  the variability in a 3-run test
that is attributable  to  sampling and analysis imprecision is likely to  be
a factor of 3 or less.   The data also  suggest that emissions from moving
grate calciners are more  variable  than those from  kilns.

                                   3-15
-------
     2.  The test-to-test variability at the same plants at different
times generally is greater than the within test run-to-run variability at
those same facilities.  Four sets of Po-210 test data  illustrate this
observation.  Tests L and V were conducted at the outlet of the Monsanto
spray tower in 1983 and 1988, respectively.  The within test range was
spanned by a factor of less than 1.5 for both tests while average
emissions for the two tests were 12.5 nCi/dscm and 23  nCi/dscm, a factor
of about 2.  Tests at the outlet of the low-energy venturi scrubber at FMC
were conducted in 1987 (Tests J and K) and 1988 (Test  T).  The within test
run-to-run range spanned a factor of 2 or less for all three tests.
However, average the emission concentration in 1987 was about 1.6 nCi/dscm
and the average in 1988 was about 4.5 nCi/dscm, a factor of about 3.
Tests were conducted at the outlet of the high energy  venturi scrubber in
1987 (Test M) and 1988 (Test W).  The 12 measurements  in 1987 ranged over
a factor of about 4 while the 3 measurements in 1988 ranged over a factor
of about 1.5.  In contrast, the average emissions in 1987 were
0.23 nCi/dson while those in 1985 were 0.95 nCi/dscm,  a factor of over
4.  Because the individual test runs in 1985 represent different
scrubbers, the range is larger than would be found for test runs on a
single scrubber.  Hence, the between test range is slightly larger than
the within test range.  Finally, tests were conducted at the outlet of the
ESP at Stauffer in 1979 (Test N) and 1983 (Test Q).  Within test run-to-
run variability range over a factor of less than 2 for each test while
average concentrations for the two tests were 0.23 nCi/dscm (1979) and
1.61 nCi/dscm (1983), a factor of between 7 and 8.  These data, in
combination with those presented in (1)  above,  suggest that the
contribution of operating variability to overall variability in emission
measurements is somewhat greater than the contribution of sampling and
analysis imprecision.
     3.  Control systems comprising a spray tower and high  energy venturi
or a spray tower and wet ESP can achieve significant reductions (greater
than 90 percent) in Po-210 and Pb-210 emissions.  This observation is
based on comparison of the tests at the  outlet  to the Monsanto spray tower
(Tests L and V) to the emissions at the  venturi  outlet (Tests  M and  W)  and
the tests at the spray tower inlet (Test 0),  spray tower outlet (Test  P)
                                   3-16
-------
and ESP outlet (Tests Q and N) at Stauffer.  The performance of these
control systems is analyzed 1n more detail in Section  4.
3.2.2  Acid Gas Emissions
     Elemental phosphorus calcining operations are sources  of acid  gas
emissions that can include S02, HF, HC1, and P205.  However,  the primary
constituents are S02 and HF.  These acids are generated by  fluorides and
sulfides that are contained in the phosphate ores and  in coal  that  is used
to supplement the CO as fuel in the calciner.  This study is  not concerned
directly with acid gas emissions, but they do play an  important role in
evaluating emission control alternatives.  Consequently, available  data
were collected from emission test reports, and information  on  acid  gas
levels was requested from plant personnel during plant visits.   The
limited data that were obtained are presented in Table 3-6.
3.2.3  Po-210 and Pb-210 Particle Size Distributions
     The control  technology assessments in Chapter 4 require an estimate
of the particle size distributions of Po-210 and Pb-210 emissions.  The
only radionuclide-specific particle size data that were identified  during
this study were those generated by EPA in support of NESHAP development.
During that comprehensive test program, particle size data were collected
at the inlets and outlets of control systems at the three Western plants
using one of two  methods—a cascade impactor or the SASS cyclones.  The
data generated from that program are tabulated in Tables 3-7 and 3-8 for
the impactor samples and SASS samples, respectively.
     The data in  Table 3-7 indicate the distributions at the scrubber
inlet are distinctly different from those at the outlet at FMC.  In
general, the inlet data are bimodal  with significant  fractions of the
emissions less than 1.0 urn and greater than  10 ym in  diameter.  At the
outlet, over 70 percent of the Po-210 and Pb-210 were in the two fractions
that were less than 0.9 urn in diameter except for the Pb-210 on Calciner
No. 1 at FMC.   Consequently,  additional  controls must focus  on submicron
PM.
     The data in  Table 3-7 also indicate that the distributions of both
Po-210 and Pb-210 at Stauffer and  Monsanto are  different from those  at
FMC.   However, the SASS results in Table 3-8  and the  cascade impactor
tests in Table 3-7 indicate that the distributions  at  Monsanto are
                                   3-17
-------
TABLE 3-6.  ACID GAS EMISSION LEVELS
Facility
FMC, Idaho
Monsanto, Idaho
Stauffer, Mont.
Stauffer, Tenn.

Occidental, Tenn.
Location
Stack
Stack
Kiln
exhaust
Kiln
exhaust
Stack
Stack
HF levels
ppmv kg/h
18-40 6-8
1.5
45
180
0.7
66
S02 levels
ppmv kg/h
200

68
250
64
774
Ref.
14,15
17
3
21
21
20
                3-18
-------
TABLE 3-7.  PARTICLE SIZE DISTRIBUTION BASED ON IMPACTOR  SAMPLES
Pollutant
Po-210










Pb-210










Control
level
None


Low-energy
scrubber



ESP
Venturi

None


Low-energy
scrubber



ESP
Venturi

Facility/
location
FMC/2-1
FMC/2-2
FMC/1
FMC/2-2
FMC/1 -1
FMC/1 -2
Stauffer
Monsanto
Stauffer
Monsanto
FMC/1
FMC/2-1
FMC/2-2
FMC/1
FMC/2-2
FMC/1 -1
FMC/1 -2
Stauffer
Monsanto
Stauffer
Monsanto
FMC/1
Percentage of pollutant in size ranqe
Approximate particle size 0-50, urn
<0.5
33.5
23.8
65.0
70.7
71.6
85.8
52.2
60.0
50.1
70.0
72.5
41.5
12.4
30.0
61.2
26.9
21.3
60.0
60.0
54.1
60.0
53.5
0.3-O.9
3.9
2.6
7.5
6.1
3.1
2.9
21.6
26.5
23.5
18.0
7.8
6.2
2.4
12.5
11.8
17.9
23.4
18.1
26.5
22.4
26.5
14.5
0.9-1 .5
4.9
3.8
6.0
7.5
1.6
2.3
12.9
6.8
16.5
5.3
5.7
9.5
1.8
13.3
4.6
21.4
8.5
14.3
7-5.
14.1
8.5
11.0
1 .5-3
5.8
5.2
6.9
5.6
1.3
1.4
8.9
4.7
4.4
4.7
5.5
11.8
1.3
12.2
8.8
4.8
12.8
5.2
4.0
4.9
3.5
10.5
J-IO
18.0
15.6
7.6
6.8
1.9
2.5
3.4
1.4
3.5
1.4
5.8
13.0
32.3
19.0
9.5
13.1
17.0
2.0
1.8
3.3
1.2
8.2
>10
33.9
49.0
7.0
3.3
20.4
5.1
1.0
0.6
2.0
0.6
2.7
18.0
49.7
13.0
4.0
15.8
17.0
0.4
0.2
1.2
0.3
2.3
                             3-19
-------
TABLE 3-8.  PARTICLE SIZE DATA BASED ON SASS CYCLONE SAMPLES

                                        Percentage  of pollutant
                                     	in  size range
                                         Approximate particle
                                             size D-50,
Pollutant
Po-210

Pb-210

Facility
Stauffer
Monsanto
Stauffer
Monsanto
Location
Spray tower
outlet
ESP outlet
Stack
Spray tower
outlet
ESP outlet
Stack
<1
72.2
91.2
94.6
92.4
96.9
93.7
1-3
9.6
0.3
.3.7
4.0
1.1
4.3
3-10
0.4
0.1
0.5
0.2
0.1
0.6
>10
17.8
8.4
1.2
3.4
1.9
1.4
                           3-20
-------
comparable to those at Stauffer.  In the absence of other  information,
these data suggest that distinct particle size distributions should be
used for moving grate calciners (FMC) and nodulizing kilns  (all other
plants) in the control technology assessments.  The data from the earlier
tests indicate that the cascade impactor data from Stauffer and the
Monsanto values from 1988 are the most reliable data for kiln particle
size estimates.  The cascade impactor data from FMC are the only data
available for the moving grate calciner.
3.3  KILN BASELINE EMISSIONS
     Baseline estimates of the annual emissions of Po-210 and Pb-210 from
each of the five operating facilities were developed on the basis of
actual  emissions at the control device outlet and regulatory emission
levels.  Actual baseline emission estimates are based on the most recent
emission tests conducted by either the facility or EPA.  Regulatory
baseline emission estimates were based on the PM emission limits imposed
by the  States and best estimates of radionuclide activity levels in PM
emissions.  The results of these analyses are presented in Table 3-9.
                                   3-21
-------
             TABLE 3-9.  BASELINE Po-210 AND Pb-210 EMISSIONS
Actual
emissions, Ci/yr
Facility
FMC-Idahoa
Monsanto- Idaho0
Stauffer-Monte
Stauffer-Tenn.h .
Occi dental -Tenn.
Po-210
10.0b
1.4d
0.74f
0.281.
0.31J
Pb-210
0.14C
0.34d
O.llf
0.0581.
0.064J
PM
emission
limit, Ib/h
304
33
589
78.4
437
Regulatory
baseline, Ci/yr
Po-210
57
4.9
6.0
0.26
1.5
Pb-210
0.29
1.3
0.89
0.0056
0.31
?Based on facility production data.
DBased on EPA tests of 1983 and 1988.
^Assumes 90 percent operation.
°Based on EPA 1988 tests.
^Assumes kiln operates 85 percent of time.
rBased on EPA 1983 tests.
'Based on twice Montana limit for No. 2 kiln.
 Estimated based on data supplied by facilities.  Operating rate estimated
.to be in the range of 85 to 100 percent of capacity.
.Estimated based on Occidental emissions and relative plant capacities.
JBased on plant tests conducted in 1985.
                                   3-22
-------
3.4  REFERENCES FOR SECTION 3

 1.  Eadle, G. and Bernhardt, D.  Radiological  Survey of  Idaho Ore
     Processing—The Thermal Process Plant.   Prepared for U. S.
     Environmental Protection Agency.  Las Vegas,  Nevada.  Technical  Note,
     ORP/lV-77-3.  November 1977.

 2.  Andrews, V.  Emissions of Naturally Occurring Radioactivity from
     Monsanto Elemental Phosphorus Plant.  Prepared for U. S. Environ-
     mental Protection Agency.  Las Vegas, Nevada.  Publication
     No. EPA-520/6-82-021.  November 1982.

 3.  Andrews, V.  Emissions of Naturally Occurring Radioactivity from
     Stauffer Elemental Phosphorus Plant.  Prepared for U. S. Environ-
     mental Protection Agency.  Las Vegas, Nevada.  Publication
     No. EPA-520/6-82-019.  November 1982.

 4.  Weast, R. C., ed.  CRC Handbook of Chemistry  and Physics, 64th
     Edition.  Cleveland.  The Chemical Rubber  Company.  1984.
     p. D-196.

 5.  Brooks, L. S.  The Vapor Pressure of Polonium.  Journal  of the
     American Chemical Society.   77:3211.  1955.

 6.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
     Polonium-210 from Calciners at Elemental Phosphorus Plants:   FMC
     Plant, Pocatello, Idaho.   Washington, D.C.  June 1984.

 7.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
     Polonium-210 from Calciners at Elemental Phosphorus Plants:   Monsanto
     Plant, Soda Springs, Idaho.  Washington, D.C.  September 1984.

 8.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
     Polonium-210 from Calciners at Elemental Phosphorus Plants:   Stauffer
     Plant, Silver Bow, Montana.  Washington, D.C.  U.  S.  EPA.
     August 1984.

 9.  Stula, R. T., R.  E. Balanger, C.  L.  Clary, R. F.  May, M.  E.  Spaeth,
     and J. P. Swenson.  Airborne Emission Control Technology for the
     Elemental Phosphorus Industry,  Final  Report for  EPA Contract
     No. 68-01-6429.   Science  Applications, Inc.  La  Jolla, California.
     January 1984.

10.  Memo and attachments from Leeds,  K.,  Midwest Research Institute,  to
     Beck, L., EPA/ISB.  October 14,  1988.  State Emissions Standards  for
     Elemental Phosphorus Plants.

11.  Cowherd,  C.,  G. Muleski,  and  J. Kinsey.   Control of Open Fugitive Dust
     Sources.   Prepared for  U. S.  Environmental  Protection Agency.   Research
     Triangle Park,  North Carolina.  Publication No.  EPA-450/3-88-008.
     September 1988.
                                   3-23
-------
12.  Radian Corporation.  Emission Testing of Calciner Off-Gases At FMC
     Elemental Phosphorus Plant, Pocatello, Idaho.  Emission Test Final
     Report, Volume I.  Prepared for U. S. Environmental Protection Agency
     under Contract No. 68-07-3174.  Research Triangle Park, North
     Carolina.  August 1984.

13.  Letter from Hebert, F., FMC, to O'Neal, G., EPA.  September 6,
     1985.  Summary of 1985 emission test results.

14.  Letter from Bowman, M., FMC Corporation, to Magno, P., EPA/ORP.
     February 26, 1988.  Summary of FMC emission data.

15.  Memo and attachments from Wallace 0., and K. Leeds, Midwest Research
     Institute, to Beck, L., EPA/ISB.  August 9, 1988.  Site Visit—FMC
     Corporation, Pocatello, Idaho.

16.  Radian Corporation.  Emission Testing of Calciner Off-gases at
     Monsanto Elemental Phosphorus Plant, Soda Springs, Idaho.  Emission
     Test Final Report, Vol. I.  Prepared for U. S. Environmental
     Protection Agency under Contract No. 68-02-3174.  Research Triangle
     Park, North Carolina.  August 1984.

17.  Memo and attachments from Wallace, D., and K. Leeds, Midwest Research
     Institute to Beck, L., EPA/ISB.  August 9, 1988.  Site Visit--
     Monsanto Elemental Phosphorus Plant, Soda Springs, Idaho.

18.  Letter from Wind, 0., Monsanto Chemical Company, to McLaughlin, T.,
     EPA/ORP.  May 10, 1988.  Emission data from Monsanto, Soda Springs,
     facility.

19.  Radian Corporation.  Emission Testing of Calciner Off-Gases At
     Stauffer Chemical Elemental Phosphorus Plant, Silver Bow, Montana.
     Emission Test Final Report, Volume I.  Prepared for U. S.
     Environmental Protection Agency under Contract No. 68-07-3174.
     Research Triangle Park, North Carolina.  August 1984.

20.  Memo and attachments from Wallace, 0., and J. Obremski, Midwest
     Research Institute, to Beck, L., EPA/ISB.  August 23, 1988.  Site
     Visit—Occidental Elemental Phosphorus Plant, Columbia, Tennessee.

21.  Radian Corporation.  Draft Final Emission Test Report, FMC Elemental
     Phosphorus Plant, Pocatello, Idaho.  Prepared for U.  S. Environmental
     Protection Agency under Contract No. 68-02-4338.   Research Triangle
     Park, North Carolina.  October 1988.

22.  Radian Corporation.  Draft Final Emission Test Report, Monsanto
     Elemental Phosphorus Plant, Soda Springs, Idaho.   Prepared for U. S.
     Environmental Protection Agency under Contract No.  68-02-4338.
     Research Triangle Park, North Carolina.  October 1988.
                                   3-24
-------
23.   Memo and attachments from Wallace,  D.,  and J.  Obremski,  Midwest
     Research Institute,  to Beck,  L.,  EPA/ISB.  August  23,  1988.   Site
     Visit—Stauffer Elemental Phosphorus  Plant, Mount  Pleasant,
     Tennessee.
                                  3-25
-------
-------
                           4.  EMISSION CONTROLS

     The  nodulizing kiln or calciner  is by far the most  significant source
of Po-210 and Pb-210 emissions from elemental phosphorus production.  This
section describes and assesses control technologies that can  be  used to
reduce those emissions.  Generally Po-210 and Pb-210 are volatilized in
the kiln  or calciner and preferentially condense on the  fine  particles in
the calciner PM emission stream.  The control systems that are installed
in the industry effectively collect large particles, but they are  not
effective controlling fine particle emissions.  Consequently, the  technol-
ogies examined in this section are those that have been  demonstrated to
achieve high control efficiencies on fine particles.  However, control  of
Po-210 and Pb-210 emissions is complicated by two factors.  First,  because
the temperature of the flue gas leaving the kiln may be  400°C (750°F)  or
higher, significant concentrations of Po-210 can remain  in the vapor phase
(see Figure 3-1).  Second, the exhaust contains relatively high  concentra-
tions of  S02 and HF; these acid gases can condense in the control  system
leading to subsequent corrosion and deterioration of performance.
Mechanisms for cooling the exhaust gases and reducing the acid gas  concen-
tration in the gases are discussed later in this section.
     Applicable control  systems for the kiln or calciner emissions  are
examined  in the three subsections below.   The first describes the control
systems;  discusses the operating principles of each system;  and  identifies
key design and operating parameters which  affect  performance, as measured
by Po-210 and Pb-210 reduction, and costs.   The  second  describes proce-
dures for estimating the performance of each  type of  control  system and
discusses the emission data that are available on system performance.  The
third describes the general procedures for  estimating the costs for each
control  system and presents assumptions used  to develop  estimates for
major cost elements for  each of the control  systems.  Details of specific
control  alternatives and the performance and  cost of  those alternatives
are contained in  Section 5.
                                   4-1
-------
4.1   DESCRIPTION OF APPLICABLE CONTROL SYSTEMS
     The four fine PM control techniques examined during this study are
wet electrostatic precipitators (wet ESP's), venturi scrubbers, spray
dryers with pulse jet fabric filters (SD/FF's), and high-efficiency
particulate air (HEPA) filters.  The wet ESP and venturi scrubber were
selected because they are the control systems that are used at operating
elemental phosphorus plants.  The SD/FF and HEPA were selected as high-
efficiency PM control devices that have excellent potential for
controlling Po-210 and Pb-210 emissions but that have not been applied to
elemental phosphorus plants.  The SD/FF systems have been applied
successfully to combustion sources and mineral and metallurgical furnaces
and have demonstrated high control efficiencies for condensible metals and
acid gases.  The HEPA filter has been demonstrated to achieve high control
efficiencies on radionuclide emissions from uranium industry processes.
     Four of the five operating elemental  phosphorus facilities currently
operate spray towers as either the primary control system or as a gas
conditioning technique.  These spray towers will remove coarse PM as well
as acid gases from the gas stream.  All of the control techniques, except
the SD/FF, can benefit from inclusion of a spray tower upstream of the
primary fine PM control device to reduce temperature, gas volume, and acid
gas concentration.
     The five subsections below address spray towers and the four fine PM
control techniques individually.  Each section includes a description of
the control technique, a discussion of the operating principles for the
technique, and identification of the key design and operating parameters.
4.1.1  Spray Towers
     A spray tower is one of the most simply constructed wet scrubbers,
comprising a cylindrical vessel  constructed of steel, plastic, or wood and
one or more sets of nozzles that are used  to spray liquid into" the gas
stream.  The exhaust gas generally enters  the bottom of the tower and
nnves upward as shown in Figure 4-1.L  Liquid, generally water or a slurry
of water and lime, is sprayed downward from one or more levels to provide
a countercurrent flow of liquid  and gas in the tower.   This countercurrent
flow exposes the exhaust gas with  lowest pollutant concentration  to the
freshest scrubbing liquor.
                                   4-2
-------
Liquid
sprays
     Figure 4-1.  Countercurrent flow spray tower.1
                            4-3
-------
     As a preconditioner upstream from a fine PM control device, a spray
tower serves three functions.  First, it reduces the temperature of the
gas stream by evaporative cooling.  This temperature reduction enhances
Po-210 and Pb-210 control by increasing condensation, and it reduces the
gas volume that must be treated by the fine PM control system.  Second,
the spray tower reduces the concentration of S02 and HF in the control
stream by absorption.  The HF is a highly soluble gas and is absorbed
readily in water.  However, because S02 is less soluble than HF, a lime
slurry typically is used to enhance S02 removal.  Plant personnel
contacted during this study indicate that operating spray towers generally
achieve S02 reductions of 75 percent and HF reductions of 99 percent or
more.2*3  Third, the spray tower removes coarse PM from the gas stream.
Typical efficiencies for spray towers are reported to be 90 percent on
particles 5 urn in diameter or greater and 60 to 80 percent on particles in
the 3 to 5 urn size range."*  The test data presented in Table 3-4 indicate
that a PM control efficiency of about 97 percent was achieved by the spray
tower at Stauffer.
     The primary PM collection mechanism for spray towers is inertial
impaction of particles to liquid droplets.  Key parameters that affect
particle collection by impaction for particles of a given size are
scrubbing zone height, gas velocity in the spray tower (generally pressure
drop (AP) across the tower is used as a surrogate),  liquid-to-gas (L/6)
ratio, and spray droplet size.  The pressure drop across the tower and the
L/6 ratios affect operating cost as well  as  performance.  Typical values
of operating characteristics for spray towers are:
     AP5                     0.25-0.5 kPa (1 to 4 in.  w.c.)
     L/6 ratio5              1.3 to 2.7 a/m3 (10 to  20 gal/kacfm)
     Droplet size1           500 to 1,000 urn
     The primary acid gas collection mechanism in spray towers is
absorption.   Removal  of a gaseous pollutant  by absorption requires
intimate contact between the exhaust stream  and the  sorbent  liquid.   Three
steps are involved in absorption.  In the first step,  the gaseous
pollutant diffuses from the bulk area of  the gas phase to the gas-liquid
interface.  In the second step,  the gas moves (transfers)  across  the
interface to the liquid phase.  This step is extremely rapid  once the  gas
                                   4-4
-------
molecules (pollutant) arrive at the interface area.   In the third  step,
the gas diffuses into the bulk area of the liquid, thus making  room  for
additional gas molecules to be absorbed.  The rate of absorption (mass
transfer of the pollutant from the gas phase to the liquid phase)  depends
on the diffusion rates of the pollutant in the gas phase  (first step) and
in the liquid phase (third step).  For HF, which is highly soluble,  the
rate is gas-phase controlled.  For the less soluble S02,  the rate  is
liquid-phase controlled and depends on the reaction rate  of S02 with  lime
to form calcium sulfate.
     The following design factors enhance gas diffusion,  and, therefore,
absorption:
     1.  Large interfacial contact area between the gas and liquid phases;
     2.  Good mixing of the gas and liquid phases (turbulence); and
     3.  Sufficient residence or contact time between the phases for
absorption to occur.
     An important factor affecting the amount of a pollutant that can be
absorbed is its solubility.  Solubility governs the amount of liquid  (L/G
ratio) required and the necessary contact time.  More soluble gases  (such
as HF) require less liquid.  Also, more soluble gases will be absorbed
faster.  Solubility is a function of temperature.  As temperature
increases, the amount of gas that can be absorbed by a liquid decreases.
The solubility and gas scrubbing efficiency also are affected by the pH of
the scrubbing liquor.   Plant personnel indicate that for S02, efficiency
increases monotonically with the pH of the scrubbing liquor (i.e.,  an
increase of pH will increase scrubber efficiency).   However,  for HF, the
optimal scrubbing efficiency is achieved at a pH of about 7.5 to 8.0, and
higher pH levels result in significant decreases in efficiency.   The pH in
the spray towers at the elemental  phosphorus  plants in Tennessee generally
is maintained in the range of 7.5 to 8.O.3  Personnel  at the  western
elemental  phosphorus plants indicated  that the characteristics  of  their PM
and water necessitate  maintenance of pH in the range of 4.5 to  5.0  to
inhibit precipitation  and  scaling in the scrubbing  system.
                                   4-5
-------
4.1.2  Venturl Scrubbers
     A venturi scrubber is a high-efficiency PM control device that
enhances particle collection by generating high-velocity, turbulent flow
conditions in the gas stream.  A venturi scrubber consists of three
sections—a converging section, a throat section, and a diverging section
as shown in Figure 4-2.   The exhaust stream enters the converging
section, and gas velocity and turbulence increase.  Liquid is introduced
either at the throat or at the entrance to the converging section.  In the
throat, the gas stream is mixed with the droplets that are sheared from
the walls, and gaseous and particulate pollutants are transferred from the
gas stream to these droplets.  The exhaust stream then exits through the
diverging section.  Venturis can be used to collect both particulate and
gaseous pollutants, but they are more effective in removing particles than
in removing gaseous pollutants.
     Liquid can be injected at the converging section or at the throat.
Figure 4-3 shows liquid injected at the converging section.  Because this
type of venturi provides a liquid coat on the throat surface, it is very
effective for handling hot, dry exhaust gases that contain dusts that tend
to cake on or abrade a dry throat.  Generally, this wet throat approach is
more appropriate for application to elemental phosphorus kiln or calciner
operations for two reasons.  First, because the gas stream contains high
concentrations of HF and S02, the wetting/drying phenomena that occurs at
the throat in dry throat applications can result in increased corrosion.
Second, the PM in these exhaust streams has a tendency to scale,  and this
scaling is enhanced in a dry throat.  Consequently, the wetted throat has
fewer operation and maintenance problems and achieves better long-term
performance than the dry throat.
     Manufacturers have developed modifications to the basic venturi
design to maintain scrubber efficiency by changing the pressure drop for
varying exhaust gas rates.   One particular development is the annular-
orifice, or adjustable-throat,  venturi  scrubber (Figure 4-4).   The throat
area is varied by moving a plunger, or adjustable disk,  up or down in  the
throat, decreasing or increasing the annular opening.   Gas flows  through
the annular opening and atomizes liquid that is sprayed  onto the  plunger
or swirled in from the top.  One of the two venturi  scrubbers  installed  at
                                   4-6
-------
                                 Converging
                                   section
                              - Throat
                              _ Diverging
                                  section
Figure 4-2.  Venturi scrubber.1
                4-7
-------
Liquid
 inlet
Liquid
 inlet
       Figure 4-3.  Wetted-throat venturi  scrubber.1
                             4-8
-------
 Liquid inlet
Figure 4-4.  Adjustable-throat venturi scrubber.1
                        4-9
-------
elemental phosphorus plants is a movable throat venturi.  The other is a
fixed-throat, tandem-nozzle unit.
     Venturis are the scrubbers used most commonly at elemental phosphorous
plants and are capable of achieving the high particle collection effi-
ciency.  As the exhaust stream enters the throat, its velocity increases
greatly, resulting in droplet atomization and turbulent mixing of the gas
with any liquid present.  Particulate matter in the gas is collected in
these droplets, primarily by impaction.  These liquid droplets then are
removed from the scrubber exhaust stream by cyclonic separators or chevron-
blade mist eliminators.
     Particle removal efficiency increases with increasing pressure drop
(resulting in high gas velocity and turbulence.)  Venturis can be operated
with pressure drops ranging from 1 to 25 kPa (5 to 100 in. w.c.).  Venturi
scrubbers that operate with pressure drops of less than 12.5 kPa (50 in.
w.c.) have been installed on nodulizing kilns.  At these pressure drops,
the gas velocity in the throat section is usually between 30 and 120 m/s
(100 and 400 ft/s).  An increase in pressure drop increases operating
costs because of the energy required by the fan to remove the large air
volumes from the kilns at higher static pressures.  It also increases
capital cost because thicker construction materials are required to handle
the lower static pressures in the ductwork.
     The liquid injection rate, or L/G ratio, also affects particle
collection.  The L/G ratio depends on the temperature (evaporation losses)
of the incoming exhaust stream and the particle concentration.   Most
venturi systems operate with an L/G ratio of 0.4 to 1.3 z/m3 (3 to
10 gal/1,000 ft ).  Liquid-to-gas ratios less than 0.4 z/m3
(3 gal/1,000 ft3) are usually not sufficient to cover the throat,  and add-
ing more than 1.3 z/m  (10 gal/1,000 ft3) does not usually significantly
improve particle collection efficiency.1  The two operating venturi
scrubbers in the elemental phosphorus industry have L/G ratios  of  about
0.8 z/m3 (6 gal/1,000 ft3) and 2.4 z/m3 (18 gal/1,000 ft3).
4.1.3  wet ESP's
     Electrostatic precipitators are high-efficiency  PM collection devices
that have been applied widely to a variety of combustion sources  and
metallurgical furnaces that have a wide range of combustion  gas
                                   4-10
-------
characteristics.  Particle collection  is  accomplished  by exposing the gas
stream to a high-energy electrical  field  which  charges particles and moves
them to an oppositely charged surface  (the collection  electrode) where
they are collected.  The primary characteristic that distinguishes wet
ESP's from dry ESP's is the use of  liquid flow  rather  than rapping to
remove the collected PM from the collection electrode.   The discussion
below addresses only wet ESP's.
     The basic principles of the electrostatic  precipitation process are
(1) development of a high-voltage direct  current that  is used to charge  .
particles in the gas stream, (2) development of an electric field in the
space between the discharge electrode  and the positively charged collec-
tion electrode that propels the negatively charged ions  and particulate
matter toward the collection electrode, and (3) removal  of  the  collected
particulate by use of water flushing.  These basic principles of the
electrostatic precipitation process are illustrated in Figure 4-5.
     The electrostatic precipitation process occurs within  an enclosed
chamber; a high-voltage transformer (to step up the line voltage)  and a
rectifier (to convert AC voltage to DC) provide the power input.   The
precipitation chamber has a shell made of metal, tile, or fiberglass-
reinforced plastic (FRP).  Suspended within this shell are  the  grounded
collecting electrodes (usually plates), which are connected  to  the
grounded steel framework of the supporting structure and  to  an  earth-
driven ground.  Suspended between the collection plates  are  the discharge
electrodes, also known as corona electrodes, which are insulated from the
ground and negatively charged with voltages ranging from  20  kV  to
100 kV.  The large difference in voltage between the negatively charged
discharge electrode and positively charged collection electrode creates
the electric field that drives the negatively charged ions and particles
toward the collection electrode.
     The last segment of the process covers  the  removal of the dust from
the collection electrodes.   In wet ESP's,  the collected particulate matter
is removed by an intermittent or continuous  stream of water that flows
down over the collection electrodes and into a receiving sump.  The liquid
from the sump is circulated through a treatment  system  to remove suspended
particles and adjust  pH.
                                   4-11
-------
EARTHED COLLECTOR
ELECTRODE AT
POSITIVE POLARITY
ELECTRICAL   CHARGED
FIELD        PARTICLE
                                            DISCHARGE ELECTRODE
                                            AT NEGATIVE POLARITY
UNCHARGED     _L J_
PARTICLES    (-J-) =
                                   PARTICLES ATTRACTED
                                   TO COLLECTOR ELECTRODE
                                   AND FORMING DUST LAYER
                                                                   HIGH VOLTAGE
                                                                   CURRENT SUPPLY
      Figure  4-5.   Illustration  of ESP  operating  principles.1
                                      4-12
-------
     The major differences In the types  of  wet  ESP's  are the  shape  of the
collector, whether treatment of the gas  stream  is  vertical or horizontal,
whether incoming gas is preconditioned with water  sprays, and whether the
entire ESP is operated wet.  Figures 4-6 and 4-7 show two types  of  wet
ESP's, the circular-plate variety and the square or rectangular  flat-plate
type.  One wet ESP currently is installed on one nodulizing kiln.   The ESP
is a circular-plate type with a spray tower upstream  of the ESP  to
condition the gas stream.  Plant personnel  indicated  that when the  ESP
reaches the end of its useful life, they probably  will install a flat-
plate system because it is easier to maintain than the circular-plate
unit.
     The casing can be constructed of steel  or  FRP, and discharge
electrodes can be carbon steel, special  alloys, or FRP, depending on the
corrosiveness of the gas stream.  The system that  presently is in use  has
FRP plates, but plant personnel indicated that  these  plates have not
lasted well in the cold winter environment  in Montana.  However, because
the kiln exhaust is corrosive and liquid  pH  must be maintained at 5 or
less, the plates must be constructed of  FRP  or  corrosion-resistant alloys.
     In circular-plate wet ESP's, the circular  plates are irrigated
continuously; this continuous flow provides  the electrical  ground for
attracting the particles and also removes them  from the plate.  These
systems can generally handle flow rates of 850  to 2,800 m3/nrin (30,000 to
100,000 ft /min).  Preconditioning sprays remove a significant amount of
particulate by impaction.   Pressure drop through these units  usually
ranges from 0.25 to 0.75 kPa (1 to 3 in. w.c.).8
     Rectangular flat-plate units operate in basically the  same manner as
the circular-plate wet ESP's.   Water sprays   in an inlet  plenum or in an
upstream spray tower precondition the incoming gas  and provide some
initial  particulate removal.   The water sprays are  located  over the  top of
the electrostatic fields,  and  collection plates  are irrigated  continu-
ously.   The collected particulate flows downward into  a  trough that  is
sloped to a drain.   Typically  the water is treated  onsite to remove  the
suspended solids, and treated  water is  recycled  to  the system.  Plant
personnel  indicated that the water for  the ESP currently operating at  an
elemental  phosphorous facility  is  treated to a pH of about 5 to prevent
scaling  on the plates.

                                   4-13
-------
CLEAN GAS
                                          DISCHARGE
HOOD
     ACCESS
     MANWAY
PRECIPITATOR
     HIGH VOLTAGE
     INSULATOR
      PRECIPITATOR
      BASE
      PRECONDITIONEH
      SPRAYS
PRECONOITIONER
     GAS INLET

      PAECONOITIONER
      DRAIN
                               WATER
                               DISTRIBUTOR
                                                          COLLECTION
                                                          CYLINDER
                                                          EMITTING
                                                          ELECTRODE
                               VENTURI/DRAIN
                               GUTTER
                                                          STRAIGHTENING
                                                          VANES
                                                          ACCESS MANWAY
                                PRECIPITATOR
                                DRAIN
               Figure 4-6.   Circular-plate type wet ESP.
                                        4-14
-------
                                          GAS
                                          OUTLET
  HOOD
         PURGE AIR
         MANIFOLD
    ACCESS
    MANWAV
PRECIPITATOH
 WATER
 DISTRIBUTOR
  ACCESS
  DOOR
  COLLECTING
  PLATE
  EMITTING
  ELECTRODE
 VENTURI/ORAIN
 CUTTER

PRECONDITIONER
ENTRY INLET
         PRECONOITIONER
         DRAIN
                       ACCESS
                       MANWAV
                                                                    HIGH VOLTAGE
                                                                    INSULATOR
               GAS DISTRIBUTION
               BAFFLES
                                                                 PRECIPITATOR
                                                                 DRAIN
QUENCH/SCRUBBING
SPRAY
                                                         GAS
                                                         INLET
               Figure 4-7.   Flat-plate  type wet  ESP.
                                    4-15
-------
     The performance of a wet ESP is affected by design and operating
properties of the system as well as flue gas conditions.  Key design
characteristics include the specific collection area (SCA), the aspect
ratio, and gas flow distribution.  Key operating characteristics  include
particle size resistivity, temperature, and H20 content of the gas stream.
     The SCA is defined as the ratio of collection surface area to the gas
flow rate into the collector.  Expressed in metric units,
                                                     2
                    SPA - total collection surface, m             /c   , ,•*
                                  1,000 m3/h
     Increases in the SCA of a precipitator design will, in most  cases,
increase the collection efficiency of the precipitator.  Most conservative
designs call for an SCA of 20 to 25 m2 per 1,000 m3/h (km3/h) (350 to
400 ft  per 1,000 acfm [kacfm]) to achieve a collection efficiency of more
than 99.5 percent.  The general range of SCA is between 11 and 45 m2 per
km /h (200 and 800 ft  per kacfm), depending on precipitator design
conditions and desired collection efficiency.8'9  The wet ESP currently
                                                        2   3
operating on a nodulizing kiln has an SCA of about 9.3 m /km /h
(170 ftVkacfm).
     The aspect ratio (AR) is the ratio of the effective length to the
effective height of the collector surface.  The AR can be calculated using
Equation 4-2.
AP - effective length, m (
MK " effective height, m (
                                                ft)
                                                ft)
Typical AR's for ESP's range from 0.5 to 2.0.   However,  for high-
efficiency ESP's (those having collection efficiencies of >99 percent),  -
the AR used in precipitator design should be greater than 1.0, usually 1.0
to 1.5.
     Gas flow through the ESP chamber should be slow and evenly
distributed through  the unit.  The gas velocities  in the duct leading into
the ESP are generally between 6 to 24 m/s (20  and  80 ft/s).   The gas
velocity into the ESP must be reduced for adequate particle  collection.
This velocity reduction is achieved by using an expansion inlet plenum.
The inlet plenum contains perforated diffuser  plate openings to distribute
                                   4-16
-------
the gas flow evenly through the precipitator.  Typical  gas  velocities  in
the ESP chamber range from 0.6 to 2.4 m/s  (2 to 8 ft/s).  With  an  aspect
ratio of 1.5, the optimum gas velocity is  generally between 1.5 to 1.8 m/s
(5 to 6 ft/s).
     Resistivity is a measure of how difficult it is for a  given particle
to conduct electricity.  The higher the measured resistivity (the  value
being expressed in ohm-cm), the harder it  is for the particle to transfer
the charge.  Resistivity is influenced by  the chemical  composition of  the
gas stream and PM, the moisture content of the gas stream,  and  the
temperature.  Resistivity must be kept within reasonable limits  for the
ESP to perform as designed.  The preferred range is 108 to  1010  ohm-cm.
     Temperature is important because it affects resistivity and because
it affects the condensation of Po-210.  The use of a spray  tower upstream
from the scrubber will reduce the temperatures of the gas stream to about
70°C (150°F) and condense virtually all of the Po-210 in the gas stream.
4.1.4  SD/FF Systems
     The SD/FF system is a multipollutant control  system that is used to
control PM emissions as well as to reduce the concentrations of acid gases
in the stream.  The SD/FF comprises two primary components—a spray dryer
or absorber and a pulse jet fabric filter.  In the spray dryer, the gas
stream is cooled, vapor-phase Po-210 and Pb-210 condense on the surfaces
of the PM in the gas stream and the lime that is  injected into the spray
dryer, and HF and S02 are absorbed in the lime slurry.   The evaporative
cooling in the spray dryer results in a dry,  particulate-laden gas
stream.  The PM is removed from the gas stream in  a pulse jet fabric
filter.  The paragraphs below describe the spray dryer  system and the
fabric filter separately.
     In the spray drying process,  sorbent is  injected  into  the gas  stream
as a liquid or liquid slurry spray with sufficient  moisture  to promote
rapid adsorption of the acid gases.   However,  the  evaporative cooling of
the acid gases vaporizes the moisture from the  sorbent  and produces a dry
PM which must be collected.   Systems that have  been  installed on
combustors and furnaces have used  varied  mechanisms  to  introduce sorbent
to the gas stream.   Sorbent  may be  injected through  liquid nozzles  or
rotary atomizers.   It may be screw-fed  or pneumatically  blown in dry and
                                   4-17
-------
rewetted by water-only nozzles, or it may be injected wet or dry into a
fluidlzed bed with overhead water sprays.  The ensuing discussion focuses
upon one of these systems—the atomizing spray dryer absorber—because it
is the most likely to be applied to metallurgical furnaces such as those
in elemental phosphorus plants.
     Figure 4-8 illustrates a typical spray drying process.    Lime is
slaked, mixed with water, and then pumped as a slurry to a feed tank.
Depending on the inlet concentration of pollutants, slurry is metered into
the spray absorber (shown with a rotary atomizer in Figure 4-8).  Flue gas
heat is sufficient to dry the slurry into a solid powder within the
reactor vessel, and some of the solids are collected in the bottom of the
absorber vessel while the remainder are collected in the particle
collector.  Recycle of solids back to the feed tank may be selected as an
option if sorbent utilization is very low or higher removals of gaseous
pollutants are desired.
     The lime feed rate to the spray dryer affects acid gas removal
efficiencies; it also has a significant impact on cost.  The control of HF
and S02 are governed by the following chemical reactions.

                   Ca(OH)2+S02 * CaS03  •  1/2 H20+l/2 H20          (Eq. 4-3)

              CaS03 • 1/2 H20+l/2 02+3/2 H20 * CaSO\ • 2 H20     (Eq. 4-4)

                        Ca(OH)2+2HF - CaF2 • 2 H20        %       (Eq. 4-5)

Data collected from combustion processes indicate that acceptable levels
of acid gas control can be achieved at a 1.5:1 stoichiometric ratio of
lime to HF and S02 combined.  At that stoichiometric ratio,  the
requirements for lime addition are 1.7 kg lime per kg  of S02  and 2.8 kg of
lime per kg of HF emitted from the kiln.
     Temperatures should be maintained at levels that  promote condensation
of volatile metals such as Po-210 and Pb-210 and, at the same time,
prevent liquid condensation.  The control of this process to  achieve
optimal temperatures is relatively simple.   The spray  dryer outlet  flue
gas temperature and moisture are controlled to a narrow range.   Sorbent is
                                   4-18
-------
                            1. LIME FEEDER
                            2. UMESLAKER
                            3. FEEDTANK
                            4. HEAD TANK
                            5. SPRAY ABSORBER
                            6. DUST COLLECTOR
                            7. STACK
                                       DRY WASTE
Figure 4-8.   Spray dryer/fabric filter system
                                             10
                      4-19
-------
thereby precluded from contacting downstream surfaces as a wet powder
leading to solids buildup.  The system also is operated well above the
dewpoints of any acid gases.  Temperatures are typically controlled at
110" to 160°C (230° to 320°F) by limiting the amount of water injected.10
     The particulate matter that leaves the spray dryer must be controlled
by a high-efficiency PM collector.  The control device typically employed
on metallurgical furnaces is a fabric filter.  Generally, fabric filters
are classified by the type of cleaning mechanism that is used to remove
the dust from the bags.  The three types of units are mechanical shakers,
reverse air, and pulse jet.  Essentially all fabric filters that are
employed with spray dryers are pulse jet units.  The paragraphs below
briefly describe the design and operating characteristics of pulse jet
filters and identify key design parameters for SD/FF systems.
     A schematic of a pulse jet filter is shown in Figure 4-9.  Bags in
the baghouse compartment are supported internally by rings or cages.  Bags
are held firmly in place at the top by clasps and have an enclosed bottom
(usually a metal cap).  Dust-laden gas is filtered through the bag,
depositing dust on the outside surface of the bag.  Pulse jet cleaning is
used for cleaning bags in an exterior filtration system.
     The dust cake is removed from the bag by a blast of compressed air
injected into the top of the bag tube.  The blast of high pressure air
stops the normal flow of air through the filter.  The air blast develops
into a standing or shock wave that causes the bag to flex or expand as the
shock wave travels down the bag tube.  As the bag flexes, the cake
fractures and deposited particles are discharged from the bag.   The shock
wave travels down and back up the tube in approximately 0.5 seconds.
     The blast of compressed air must be strong enough for the shock  wave
to travel the length of the bag and shatter or crack the dust cake.  Pulse
jet units use air supplied from a common header which feeds into a nozzle
located above each bag.  In most baghouse designs, a venturi  sealed at the
top of each bag is used to create a large enough pulse to travel  down and
up the bag.  The pressures involved are commonly between 414  kPa and
689 kPa (60 and 100 psig).  The importance of the venturi  is  being
questioned by some pulse jet baghouse vendors.   Some baghouses  operate
with only the compressed air manifold above each bag.11
                                   4-20
-------
                         ruse SHEET
 CLEAN AIR PLENUM

 PLENUM ACCESS—H


 BLOW PIPE


 INDUCED FLOW
TO CLEAN AIR OUTLET
  AND EXHAUSTER
DIRTY AIR INLET & OIFFUSER
       Figure 4-9.   Pulse-jet fabric filter.
                           4-21
-------
     Most pulse jet filters use bag tubes that are 10 to 15 cm (4 to
6 in.) in diameter.  Typically, the bags are 3.0 to 3.7 m (10 to 12 ft)
long, but they can be as long as 7.6 m (25 ft). x  Generally, these bags
are arranged in rows, and the bags are cleaned one row at a time in
sequence.  Cleaning can be initiated by a pressure drop switch, or it may
occur on a timed sequence.
     The key design and operating parameters for a SD/FF are the air-to-
cloth ratio (or the filtration velocity), the bag material, operating
temperature in the filter, operating pressure drop across the filter, and
the lime usage rate in the spray dryer.
     The air-to-cloth ratio is actually a measure of the superficial gas
velocity through the filter medium.  It is a ratio of the flow rate of gas
through the fabric filter (at actual conditions) to the area of the bags
and is usually measured in units of m /min  of cloth area (acfm/ft ).  No
operating data are available for elemental phosphorus systems, but
generally, the air-to-cloth ratio on SD/FF systems is in the range of 1.5
to 3 m3/min/m2 (5 to 10 acfm/ft2) of bag area.10
     Bag material selection generally is based on prior experience of the
vendor.  Key factors that generally are considered are:  cleaning method,
abrasiveness of the particulate matter and abrasion resistance of the
material, expected operating temperature, potential chemical degradation
problems, and cost.  No information was obtained on types of material
typically used for metallurgical applications.   However,  given the
temperature and acid gas concentrations in the nodulizing kiln exhaust
gases, some type of teflon-coated synthetic material  is likely to be the
material of choice.
     The operating temperature of the fabric filter is of critical
importance.  Since the exhaust gas from nodulizing kilns  or  calciners can
contain HF and S02, the unit should be operated at sufficiently high
temperatures to ensure that no surface temperatures drop  below the acid
dewpoint.  Otherwise, condensation of acid gases  will  result in corrosion
of the housing or bags.  Gas temperatures maintained  at about  150°C
(300°F) ensure that no surfaces are cooled below  the  dewpoint.  At the
same time, temperatures should be as low as possible  to ensure  complete
condensation of Po-210.  Above a maximum temperature  that  is dependent on
                                   4-22
-------
filter type, bags will degrade or  in  some  cases  fail completely.   Gas
temperatures should be kept safely below the  allowed maximum.   Temperature
of the inlet gas to the fabric filter is maintained at appropriate levels
by adjusting the liquid flow rate to  the spray dryer.
     Pressure drop in fabric filters  generally is maintained within a
narrow range.  For pulse jet filters,  the  upper  end of the range typically
is 2.5 to 3.7 kPa (10 to 15 in. w.c.).  Pressure drops below the minimum
indicate that either (1) leaks have developed, or (2) excessive cleaning
is removing the base cake from the bags.   Either phenomenon results  in
reduced performance.  Pressure drops  greater  than the maximum indicate
that either (1) bags are "blinding,"  or (2) excessive cake is building on
the bags because of insufficient cleaning.  The  primary problem that
results from excess pressure drop is  reduced  flow through the system  and
positive pressure in the kiln.  Over  time, high  pressure drops also  lead
to bag erosion and degradation.
4.1.5  HEPA Filters
     High-efficiency particulate air filters  are commonly used in
industries that require high-efficiency removal of particulate matter in
the submicron range.  These stringent  levels  of air cleaning may be .
necessary either to protect human health or to produce a particulate-free
work environment.  The HEPA technology is used extensively in nuclear,
military, pharmaceutical, aerospace,  microelectronics,  research, and
health care applications.
     By definition,  a HEPA filter is  a throwaway, extended-pleated-medium,
dry filter with (1)  a rigid casing enclosing the  full  depth of the pleats,
(2) a minimum particle removal  efficiency of 99.97  percent for 0.3-um
thermally generated,  monodisperse dioctylphthalate  (OOP)  particles, and
(3) a maximum pressure drop of 0.25 kPa (1.0 in.  w.c.) when clean  and
operated at rated airflow capacity.12
     Diffusion and  inertial  impaction  are the primary mechanisms for
particle collection  by HEPA filtration.  The effectiveness of  these
mechanisms varies with particle size,  airflow velocity through  the  medium,
and,  to some extent,  particle  density.  At  a constant air  velocity, the
diffusion mechanism  predominates  as particle size decreases;  inertia!
impaction accounts for collection  of  larger sized particles.   For a given
                                   4-23
-------
particle size, the effectiveness of diffusion decreases and  inertial
collection increases as flow velocity increases.  For a given particle
size and velocity, an increase in particle density decreases the
effectiveness of diffusion and increases the effectiveness of the inertial
effect.
     The HEPA filter efficiencies are based on numbers of particles
removed, not on mass removed as is common with air pollution control
devices.  Parameters that are commonly used to describe HEPA filtration
performance are the efficiency, penetration, and decontamination factor
(DF).  Each of these terms is defined below.

                    Efficiency, percent =  (U-0)/U  *  100           (Eq. 4-6)
                    Penetration, percent = (D/U) * 100           (Eq. 4-7)
                       Decontamination factor = U/D              (Eq. 4-8)

where:
     U » upstream particle count
     D » downstream particle count

The DF is commonly used to compare filter performance because it
demonstrates differences between filter performances more distinctly than
either efficiency or penetration.   For example,  a 99.995 percent efficient
filter (DF=20,000) is twice as effective as a 99.99 percent efficient
filter (DF=10,000), and six times  as effective as a 99.97 percent
efficient filter (DF=3,333).
     Within a single filter,  performance varies  depending on particle
size.  Lowest removal efficiencies (highest penetration)  occur for
particles in the 0.07- to 0.12-um  range (Figure  4-10).   Design
efficiencies are determined by challenging the filter with 0.3 um
mondispersed OOP particles.  Filters are  designed  to achieve efficiencies
ranging from 99.97 percent to 99.999 percent for this particle size.
     The properties of a HEPA filter that  are of primary  concern when
designing a system are its particle collection efficiency, airflow
capacity, and pressure drop.   The  HEPA filters are available in  a range  of
sizes and capacities.  The largest capacity filter available is
                                   4-24
-------
p
E
N
E
T
R
A
T
I
0
N
      10'
10'
                           % PENETRATION VS. PARTICLE SIZE
      10

                   .07
                         .1                      .2

                           PARTICLE SIZE (MICRON)
.3    .4
                 Figure 4-10.   The HEPA filter performance  curve.
                                        4-25
-------
(0.6 m)x(0.6 m)x(0.3 m) ([24 in.]x[24 in.]x[11.5 in.]) and  is  rated  at
57 ra3/min (2,000 ft3/nrin) airflow.  To accommodate large airflows,
multiple filters are arranged in banks.  Filters usually are removed  and
replaced when the pressure drop across the filter reaches twice  the  clean
filter pressure drop, i.e., 0.5 kPa (2.0 in. w.c.).
     The environmental conditions to which the filter system will be
exposed must be considered when designing a HEPA filter system.  Key
environmental parameters requiring consideration are temperature,
moisture, corrosion potential, and vibration potential.  The combined
influence of these parameters will affect the selection of a filter for a
particular application.  Unfortunately, the application of HEPA  filters to
severe environmental conditions often requires a compromise in filter
properties.  Manufacturers frequently have information on the ability of
components used in the construction of filters to resist chemical or
environmental factors, but the combined effects of humidity, chemical
agents, and heated air upon filters and the interrelationship with the
construction materials are typically unknown.  Destructive environmental
testing is recommended when the suitability of a filter for a specific
environment is in doubt.
     A HEPA filter consists of five components:  the filter medium, the
medium separators (optional), the media-to-frame sealant,  the filter
frame, and the filter housing.  Figure 4-11 is a schematic of a typical
filter and arrangement of multiple filters in a filter bank.
     The filter medium may be folded and supported  by corroguated metal
separators, typically aluminum,  or be preformed and self-supporting.   It
may be composed of asbestos,  cellulose,  microglass  fibers,  plastics,  or
ceramic materials, or blends  thereof.   Fire-resistant filter media are
usually composed of fiberglass,  sometimes  with a small  percentage of
asbestos added to improve resistance to  HF,  or ceramic  material.
Proprietary media designed for enhanced  HF resistance are  available.   The
HEPA filter media are rated at 100 percent relative humidity conditions
and will tolerate both high humidity and direct wetting.   However,  exces-
sive amounts of moisture,  either from airborne droplets or  condensation  on
the element can completely plug  the filter and result in failure  by over-
pressure.  The important factors in moisture  resistance are  the wet
                                   4-26
-------
Figure 4-11.  Examples of HEPA filter systems.1
                                              12
                      4-27
-------
tensile strength of the media, which is related to media rupture under
high overpressure, and its water repellency, which is related to the
plugging that produces the high overpressure.
     The sealant is the most sensitive component of the filter apparatus
with respect to environmental conditions.  The sealant traditionally used
to seal the fiber core into the frame is a heat- and moisture-resistant
elastomeric adhesive.  Commonly used sealants are chemically expanded
self-extinguishing urethane foam; solid urethane; neoprene; or silicone.
Filters that will be operated continuously at high temperatures of about
200°C  (400°F) may be sealed with compressed glass-fiber matting,
refractory adhesives, or silicone.  The qualities desirable in a sealant
are (1) moisture and corrosion resistance, (2) ability to withstand
radiation exposure and alternating exposure to heat and cold or dry to
humid  air, and (3) maintenance of seal integrity at design operating
conditions and potential transient conditions.
     Filter frames are available in a variety of fire-retardant materials
including rigid urethane, 1.9-cm (0.75 in.) exterior grade particle board,
1.9-cm (0.75-in.) plywood, 14 gauge Type 409 or 304 stainless steel, or
zinc or aluminum coated steel.  Metal frames are selected when a high
degree of corrosion resistance is required, or when continuous wetting or
high humidity at high temperatures is expected.  Under these conditions,
wood frames have been found to absorb moisture and swell, rupturing the
filter-to-frame seal and permitting filter by-pass to occur.  The sides of
the filter are sealed to the frame with an appropriate sealant.   When high
sound or vibration levels are expected, wood frames are preferred over
metal ones (other factors being equal)  because of their superior vibration
damping characteristics.
     Prior to operation, one or more HEPA filters are mounted into  a
filter housing that consists of the requisite number  of holding  frames  to
accommodate the number of filters to be installed.  The housing  typically
is zinc- or aluminum-coated corrosion-resistant steel,  or stainless
steel.  Critical  aspects of the mounting fixture  are  (1)  the structural
integrity; (2) tolerances on dimensions,  flatness,  alignment,  and the
finish of the filter seating surface;  (3)  the method  of  sealing  the
mounting fixture into the filter housing;  (4)  rigidity  of filter  clamping
devices; and (5)  the degree and uniformity of filter  gasket  compression.

                                   4-28
-------
     When a corrosive environment  such as that  found  in the nodulizing
 kiln exhaust exists, stainless  steel  is recommended for ductwork  and
 filter housings.  Even  this material  may be  insufficient in highly
 corrosive atmospheres,  and epoxy-  or  vinyl-coated  stainless steel or
 fiber-reinforced plastics may be necessary.
     In severe applications like those in elemental phosphorus  plants,  it
 may be necessary to modify and  improve the environment  to which the system
 will be exposed by pretreating  the air prior to entry into  the  HEPA
 system.  Scrubbers may  be employed upstream to remove corrosive
 constituents such as inorganic  acids.  Consideration  must be given to
 moisture carryover if wet scrubbers are used.  Demisting devices  should  be
 added downstream of wet scrubbers  to  reduce the moisture content  of the
 gas stream, and the gas stream  should be reheated  to  prevent condensation
 from occurring on the filter element.  A prefilter system may be  added
 upstream of the HEPA system to  reduce particulate  loading and increase
 HEPA filter life.  Prefilters should  be provided if the particulate
 loading exceeds 2.3 mg/m3 (0.001 gr/acf).  The decision to  install
 prefilters should be based on providing the best operational balance
 between HEPA filter life and capital and maintenance  costs  for  the
 prefilters.  Generally, the use of a prefiltration system will  extend HEPA
 life by a factor of 2.  Estimates of filter life for  HEPA filters are
 presented as a part of  the cost analyses in Section 4.3.
     The principal costs in operating a HEPA filtration system  are energy
 costs (i.e., fan power), replacement filters, and  labor.  The frequency of
 changing the filters is the primary factor affecting  these  costs.   For
 elemental phosphorus applications,  replacement filters  and  labor may
 constitute over 90 percent of the total  cost of owning  a  system (including
 capital  costs)  over a 20-year period.
 4.2" PERFORMANCE OF ALTERNATIVE CONTROL TECHNOLOGIES
     One of the primary objectives  of this study is to  assess the ability
of the alternative control  technologies  to reduce  Po-210  and Pb-210 emis-
 sions from nodulizing kiln or calciner operations.   This  subsection pre-
sents available information on the  performance of each of the four primary
control  techniques and establishes  procedures for estimating Po-210 and
Pb-210 control  efficiencies for the specific control  alternatives  that are
                                   4-29
-------
evaluated on a pi ant-by-plant basis in Section 5.0.   In general,  these
procedures are based on estimates of overall PM control efficiencies  or
particle-size-specific control efficiencies.  The Po-210  and  Pb-210
efficiencies then can be estimated on the basis of the Po-210 or  Pb-210
concentrations in the PM or in specific size fractions.   To the degree
that emission data are available, the validity of the estimating
procedures was evaluated by comparing estimated efficiencies  to measured
control efficiencies.  Each of the four control techniques is  addressed in
individual subsections below.
4.2.1  Venturi Scrubbers
     The control efficiency of venturi scrubbers is highly dependent  on
particle size distribution and on the L/G ratio and pressure  drop across
the scrubber.  The penetration across a venturi scrubber  (where penetra-
tion is 1 minus control efficiency) for a particle of specific diameter
can be estimated by the following equations which was developed by Yung
and Calvert.   The equations presented below are used to develop
performance estimates for venturi scrubber control options in Section 5.
                     4 K  +4.2-5.02 K
where:
     Pt(d_) = penetration for one particle size
          B = parameter characterizing the liquid-to-gas ratio,
              dimensionless
        Kp0 = inertia! parameter at throat entrance,  dimensionless

Note:  Equation 4-9 was developed assuming that the venturi has an
Infinite-sized throat length.  This is valid only when a, 'as defined
below, is greater than 2.0.
                                   3*
where:
      i = throat length parameter,  dimensionless


                                   4-30
-------
      ir =  venturi throat  length, can
      CQ =  drag coefficient for the liquid  at  the throat  entrance,
           dimension! ess
      PS =  gas density, g/on
      D^ =  droplet diameter, cm
      PI =  liquid density, g/cm
                         °d - b
                          d     gt
where:
      Dj = droplet diameter, cm
     v_t = gas velocity in the throat, cm/s
     L/G = liquid-to gas ratio, dimensionless

                              B = (L/G) X-                     (Eq. 4-12)
                                        VD
where:
       B « parameter characterizing liquid-to-gas ratio, dimensionless
     L/G = liquid-to-gas ratio, dimensionless
      P! = liquid density, g/cm3
      Pg = gas density, g/cm
      C0 = drag coefficient for the liquid at the throat entrance,
           dimensionless
where:
     K_0 = inertia!  parameter at the throat entrance,  dimensionless
      d- = particle  aerodynamic resistance diameter,  cmA
     v_t = gas velocity in the throat,  cm/s
      ug = gas viscosity,  g/cm • s
      dd = droplet diameter,  cm
                                    d  V
                              K
                               po


                                   4-31
-------
where:
     Kp0 = inertial parameter at the throat entrance, dlmensionless
      dpg = particle aerodynamic geometric mean diameter, cmA
     v-£ = gas velocity in the throat, cm/s
      Ug = gas viscosity, g/cm • s
      dd = droplet diameter, cm
                       Cn = 0.22 + N-U+O.IS                  (Eq. 4-15)
                                    Reo
where:
       Cg = drag coefficient for the liquid at the throat entrance,
            dimensionless
     NReo * Reynolds number for the liquid droplet at the throat inlet,
            dimensionless

                               KRM * *-S&                     (Eq. 4-16)

where:
     NReo = Reynolds Number for the liquid at the throat entrance,
            dimensionless
      vqt = 9as velocity in the throat, cm/s
       •*                               2
       \>g = gas kinematic viscosity, cm /s
       Od = droplet diameter, cm

                           dpg = dpg(Cfxap)°'5                  (Eq. 4-17)
where:
     dpg = particle aerodynamic geometric mean diameter,
     dps = particle physical, or Stokes, diameter, wm
      C^: = Cunningham slip correction factor, dimensionless
      pp = particle density, g/cm
                          C  . ! +    .                          (Eq. 4.18)
                                        PS
                                   4-32
-------
where:
      Of = Cunningham  slip correction  factor,  dimensionless
       T = absolute temperature,  K
     dps = particle physical, or  Stokes,  diameter,  urn

                              m rl.21xlQ3  AP.1/2
                          vgt   I    (175}]

where:
     v_^ = gas velocity in throat, cm/s
      AP » pressure drop, cm H20
     L/G = volumetric  liquid-to-gas  ratio, dimensionless

In general, only the pressure drop and L/G ratio were allowed  to  vary  in
the analyses conducted during this study.  All other values were  held
constant at the following levels:
     pl = 1,000 kg/m
     Pg = 1.0 kg/m3
     wg = 2.0x10"  g/cm-s
     Vq - 0-2 cm2/s
     Emission testing was conducted recently at the inlet and  outlet of  a
high-energy venturi scrubber at the Monsanto facility in Soda  Springs,
Idaho.  The data in Section 3.0 indicate that the Po-210 emissions were
measured at 23 nCi/dscm at the inlet and 0.95 nCi/dscm at the  outlet, a
reduction of about 96 percent.   The particle size distribution estimates
from the 1988 EPA tests at the Monsanto spray tower outlet was used to
estimate the Po-210 control  efficiency using the above equations.  The
results, which are tabulated in Table 4-1, estimate that the overall
efficiency of the venturi  scrubber in controlling Po-210 would be about
75 percent,  a level that is  significantly less than the measured value
obtained by  Monsanto.   Two factors may have contributed to this large
difference as described below.
     First,  the data in Table  4-1  illustrate the sensitivity of these
calculations  to the particle  size  distribution, particularly the
distribution  in the submicron  fraction.  The particle  size distribution
that  was used for these calculations  introduces uncertainty to the
                                   4-33
-------
          TABLE 4-1.  ESTIMATED EFFICIENCY OF MONSANTO SCRUBBER

  Particle diameter
Range
TOTAL
Assumed
  mean
Po-210
fraction
Fractional
penetration
   Total
penetration

<0.5
0.5-0.9
0.9-1.5
1.5-3
3-10
>10
A
0.35
0.67
1.26
2.12
5.48
10
B
0.600
0.265
0.075
0.040
0.018
0.012
C
0.397
0.034
0.0011
0.000097
—
—
BxC
0.238
0.0090
0.00008
0.000004
—
—
                                                  0.25
                                   4-34
-------
 analyses  because the  particle  size was measured  in  the ductwork  between
 the  spray tower and the  venturi.  This high moisture  stream  from the spray
 tower  is  difficult to sample,  and the inherent difficulties  associated
 with particle size sampling in the high moisture exhaust stream  can result
 in significant measurement errors.   If the actual particle size  at the
 venturi inlet is different than that assumed for the  calculation,  the
 model  will produce biased results.
     Second, the measurements  of PM particle size at  the venturi  inlet and
 outlet indicate that  the efficiency of the venturi  is uniform overall
 particle  size ranges.  In light of the strong dependency of  venturi
 scrubber  performance  on  particle size suggested  by  the performance model
 and  generally supported  by other venturi scrubber test data, this  finding
 is quite  surprising.  The estimated efficiency of 95 percent or greater  in
 particles  less than 0.5  ym in  size is particularly  surprising.  Conse-
 quently,  the measured efficiency may be biased high and should be  used
 with caution.
     In light the differences  in the predicted and measured results  at
 Monsanto, analyses based on a combination of measured performance  at
 Monsanto  and FMC and estimated performance based on the Yung/Calvert model
 were selected for estimating venturi  scrubber performance.   The estimated
 performance of the Monsanto and FMC is scrubbers presented  in Table 4-2.
 The model is well  established in the  technical  literature and generally is
 used by vendors for scrubber design.   Because the analysis  are somewhat
 uncertain the results presented in Section 5 should  be interpreted with
 caution because they are highly sensitive  to particle  size  distribution
 and measurement limitations.
 4.2.2  Wet ESP's
     For applications of ESP's  to  a specific type of industrial  process
 such as elemental  phosphorus  nodulizing  kilns or  calciners,  the  primary
design factor that  affects  ESP  performance  is the SCA, which  is  a ratio of
the collection plate area to  the volumetric  flow  through the  ESP.   This
relationship is  incorporated  in the Deutsch-Anderson equation for estimat-
 ing ESP efficiency:

                           n = 1-exp  (-w(A/Q)]                   (Eq.  4-20)
                                   4-35
-------
          TABLE 4-2.  ESTIMATES OF VENTURI SCRUBBER PERFORMANCE
Facility
Monsanto4
FMCb

Pressure
drop
High
Maximum0
Typical d
Po-210
Inlet
4,052
1,075
1,075
Outlet
172
1,065
1,208
Pb-210
Inlet
1,280
43.6
43.6
Outlet
40.58
26.1
4.1
Efficiency
Po-210
96
Neg. .
Neg.
Pb-210
97
40
91
^Reference 13.
Reference 14.
 Adjustable low-energy throat  venturi  scrubber operated  at  system maximum
 AP.
 Adjustable throat low-energy  venturi  scrubber operated  at  typical
 operating AP.
                                  4-36
-------
 where:
      n = collection efficiency  of  the ESP
      A = collecting plate  area,  m2
      Q = volumetric gas  flow  rate, m  /s
      w = migration  velocity,  m/s

 The equation  indicates that ESP  collection  efficiency increases with
 increasing values of the SCA  and the  migration  velocity.   The  migration
 velocity is a function of  the characteristics of  the emission  stream
 (particularly resistivity  and particle size distribution)  and  wet  ESP
 design parameters such as  electrode arrangement and  field  strengths.
 Mathematically, the migration velocity can  be estimated as:

                        w = S  dp kc (for  dp  < 5  um)              (Eq. 4-21)
                                    or
                           w = Sdp  (for dp 5 um)                 (Eq. 4-22)
 with                               pE E
                                    and   y
                              kc  =  1+0.172/dp                    (Eq. 4-23)

where:
     kc = Cunninham correction factor, dimensionless
     dp = particle diameter, um
      p = 3D/D+2 where D is the dilectric constant (generally about 1 for
          air)
     EC = charging field strength,  V/m
     Ep = collecting field strength, V/M
     u- = dynamic viscosity, g/cm»s
      S = constant of proportionality

In practice, w is determined empirically based on test data from similar
operations.   For this study, the  data from the 1983 EPA PM tests at
Stauffer were used to develop estimates for  w.  The procedure is described
below.
                                   4-37
-------
     The first step in developing size-specific values for w was  to
estimate S, as a constant, based on the measured removal efficiency  for
the smallest fraction of PM at Stauffer.  This constant value for S  was
then used to estimate size-specific migration velocities using
Equations 4-21, 4-22, and 4-23.  Table 4-3 summarizes the calculations
used to determine S and presents estimates of w for the different size
ranges of Po-210 emissions that were measured by EPA during the 1983 test
program.  These values of w are used to estimate control efficiencies for
the different wet ESP control alternatives presented in Section 5.
     Data from sites other than Stauffer are not available to assess the
validity of the ESP model.  However, the overall efficiency for Po-210 as
measured by the EPA Method 5 tests at Stauffer was compared to the
predicted efficiency based on the migration velocities reported in
Table 3-2.  The Method 5 tests measured an inlet concentration of Po-210
of 4.88 nCi/dscm and an outlet concentration of 1.61 nCi/dscm, a  reduction
of 67 percent.  The model based on the impactor inlet data also estimated
a 67 percent efficiency.  Consequently, the model  appears to yield
consistent results for Stauffer.  However, data are not available to
determine how well the model  can be generalized to other facilities  and to
control systems with different design parameters.
4.2.3  SD/FF Systems
     Estimation of the efficiency of SD/FF systems in removing Po-210 and
Pb-210 from the nodulizing kiln/calciner exhaust is much more complicated
than was the case for venturi scrubbers or wet ESP's because information
on the performance of these systems is quite scarce.  Mo specific informa-
tion was found on the removal of Po or Pb emissions from metallurgical
furnace exhaust streams, and  only limited information was obtained for  Pb
removal from combustion gas streams.   Further, no  general  models are
available on the performance  of fabric filters,  and data are not adequate
to establish the effect of spray dryers on fabric  filter performance.
Hesketh notes that pulse jet  PM emissions are  unusual  in  that  large
particles may be released because of  the agglomeration  and  the  high
cleaning energy.15  Fractional  particle size collection has  little
practical significance because  size and number concentrations change
radically over the filtration/cleaning cycle.   For  any  specific
                                   4-38
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            TABLE 4-3.  SUMMARY OF ESP EFFICIENCY CALCULATIONS
1.




Key input parameters
n = 0.558 ,
Q = 11.35,m3/s
A = 364 m
d_ = 0.35 um
(from test)




2.  Calculate w for d » 0.35 ym

     w = l-ln(l-n)] Q/A
       * 0.0255 m/s

3.  Calculate kc for dp = 0.35 ym

    kr = 1+0.172/0.35
       = 1.491

4.  Calculate S

    S = w/dpkc = 0.489 m/s»vin

5.  Estimated values of w for different particle size ranges
  range, uro        average,  um

       <0.5           0.35              0.0255
    0.5-0.9           0.67              0.0411
    0.9-1.5           1.16              0.0651
      1.5-3           2.12              0.112
       3-10           5.48              0.268
        >10          14                 0.643
                                   4-39
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application, pulse jet collection efficiency is reported to be a function
of inlet concentration, filtration velocity, pulse intensity, pulse
duration, and pulse form.15  Test data generally show that for a specific
process with fabric filter operating parameters held at steady conditions,
the outlet concentration of a pulse jet filter remains relatively
constant.  Under such conditions, the efficiency of the fabric filter  is
primarily a function of the total inlet concentration.
     The findings described above suggest a procedure for estimating
Po-210 and Pb-210 removal efficiencies for OS/FF systems based on the
following assumptions:
     1.  The PM removal efficiency of a pulse jet fabric filter is not
particle-size dependent;
     2.  At the temperatures achieved in a SD/FF system, essentially all
Pb-210 and Po-210 is in particle form.  Consequently, Po-210 and Pb-210
are removed by the fabric filter at the same efficiency as total PM;
     3.  Pulse jet fabric filters associated with SD/FF systems have been
shown to achieve outlet PM concentrations in the range of 22 mg/dscm
(0.01 gr/dscf) to below 2.2 mg/dscm (0.001 gr/dscf).l0'16  An outlet
concentration of 22 mg/dscm (0.01 gr/dscf) will  provide a conservative
estimate of achievable PM control efficiency; and
     4.  The PM concentration at the inlet to the fabric filter is a
combination of the solvent/acid gas reaction products and the PM emitted
from the kiln.
     Under the assumptions described above,  the  Po-210 and  Pb-210 control
efficiencies can be estimated as follows:

        Fff-i  .        Inlet  PM concentration-Outlet PM concentration
        trnciency  =               Inlet PM concentration

Obviously, no data are available to validate this  procedure  for  nodulizing
kilns or calciners.  However,  estimates  of the efficiency were developed
for a "model  facility"  under the following set of  assumptions which  are
based on "typical"  levels reported by  elemental  phosphorus facilities.
     SO2 concentration       1,200 ppmv
     HF concentration        600 ppmv
     PM concentration        4,000 mg/dscm
                                   4-40
-------
 Under these  assumptions,  the  estimated PM efficiency of the fabric filter
 is 99.87 percent.  Although specific data are  not  available for metal-
 lurgical furnaces, data from  SD/FF  systems on  municipal combustors
 indicate that efficiencies of about 99.9 percent can be achieved for
 volatile metals  such as lead, arsenic, and cadmium.1
 4.2.4  HEPA  Filters
     No data were located on  the performance of HEPA filters on combustion
 systems or high-temperature furnaces.  However, the  fractional  efficiency
 curve in Figure  4-10 Indicates that a minimum  efficiency of greater than
 99.998 percent is achieved on particles in the 0.1 to 0.2 ym size range
 and that efficiencies generally are greater than 99.999 percent.   For  this
 study, the overall efficiency conservatively was assumed to be
 99.998 percent.
 4.3  COST OF CONTROL TECHNOLOGIES
     The capital and annualized costs for each of the applicable  control
 devices were determined following the guidelines established in Capital
 and Operating Costs of Selected Air Pollution  Control  Systems (GARD
 Manual) and  in the EAB Cost Control Manual,  Third Edition.17'18   These
 manuals were prepared for the U. S. EPA to provide technical assistance  to
 regulatory agencies in estimating the cost of air pollution'control
 systems.  The costs in the GARD Manual  are based on  December 1977 dollars
 and those in the EAB Cost Control Manual  generally are  based on 1986
 dollars.  The costs were adjusted to mid-1988 dollars using  indices
 provided in  Chemical Engineering and by the  Bureau of Labor  Statistics.
 Since the same basic procedure was used to cost each of  the  control
 techniques, a cost program was developed  for use on a microcomputer.  The
 paragraphs below describe the general  cost methodology and key assumptions
 that were used to cost control options.   Detailed assumptions for each
 operating facility are presented in Appendices A through E.
     The costs were  calculated assuming that each of the fine PM control
measures,  with the exception of the SD/FF, were added to control the
exhaust  from an existing spray tower.  The existing system removes most of
the large particles,  quenches  and cools the  exhaust gas stream (thus,
reducing gas volume  and  ensuring condensation  of gaseous radionuclide
                                   4-41
-------
emissions), and properly conditions the stream for treatment by the other
options.
     Capital costs include the direct and indirect costs to purchase  and
install the necessary ductwork, control device, fan systems, and stack.
Direct capital costs include instruments, controls, taxes, freight,
foundations, supports, erection and handling, electrical work, piping,
insulation, painting, and site preparation.  Indirect capital costs
include engineering and supervision, construction and field expenses,
construction fee, startup performance test, and contingencies.  Table 4-4
presents the assumptions used for direct and indirect cost estimates based
on information given in the GARD manual.  All ductwork was sized based on
a gas velocity of 20 meters per second (m/s) (4,000 ft/min).  Site-
specific estimates of the length of additional ductwork to connect the
existing control system with the add-on control device were developed for
the analyses in Section 5.  Stack diameters were calculated to provide a
stack gas velocity of 18 m/s (3,600 ft/min).  All stack heights are
assumed to be 15 m (50 ft) for the add-on equipment.   With the exception
of connecting ductwork, no special retrofit costs were included in the
cost analyses.  Based on information collected during plant visits, no
retrofit problems are expected at these facilities.
     Annualized costs include the total  utility costs, the total  operating
labor costs, the total  maintenance costs,  the total overhead costs, the
capital charges, and the total  waste disposal costs.   The annualized costs
were based on 8,640 hours per year of operation (360  days).  The  utility
costs reflect actual utility costs in the  area of each facility as
presented in Appendices A through E.  The  operating and maintenance labor
costs were determined using an  average hourly wage of $12/hour  (h).  The
operating labor hours per shift for each control  device were 4  h/shift for
SD/FF's, 2 h/shift for scrubbers, and 1  h/shift for ESP's.   The main-
tenance labor was assumed to be 1 h/shift  for ESP's and scrubbers  and
2 h/shift for SD/FF's.
     The quantity of sludge or  dry waste collected by the add-on  control
devices was determined  based on the efficiency  of  particulate removal.   In
the case of the SD/FF,  the quantity of lime  added  to  the  system also  is
considered.  The cost to dispose of the  waste in  a secured  landfill was
                                   4-42
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  TABLE  4-4.  ASSUMPTIONS  USED  IN  ESTIMATING  DIRECT AND INDIRECT COSTS3

                                                     ESP      VS       FF


Direct costs

  Purchased equipment costs                           .
    1.  Control device                               ARD     AR        AR
    2.  Auxiliary equipment                          AR       AR        AR
    3.   Instruments and controls                     0.10     0.10      0.10
    4.  Taxes                                        0.03     0.03      0.03
    5.  Freight                                      0.05     0.05      0.05

  Total                                              1.00     1.00      1.00
                                                          i
  Installation direct costs
    HFoundations and supports                     0.04     0.06      0.04
    2.  Erection and handling                        0.50     0.40      0.50
    3.  Electrical                                   0.08     0.01      0.08
    4.  Piping                                       0.01     0.05      0.01
    5.  Insulation                                   0.02     0.03      0.07
    6.  Painting                                    0.02     0.01      0.02
    7.  Site preparation                            AR       AR        AR
    8.  Facilities and buildings                    AR       AR       AR

  Total                                              1.67     1.56      1.72

Indirect costs

  Installation indirect costs
    1.  Engineering and supervision                 0.20     0.10     0.10
    2.  Construction and field expenses             0.20     0.10     0.20
    3.  Construction fee                            0.10     0.10     0.10
    4.  Startup                                     0.01     0.01     0.01
    5.  Performance test                            0.01     0.01     0.01
    6.  Model  study                                 0.02     0.02     0.02
    7.  Contingencies                               0.03     0.03     0.03

  Total        -                                     2.24     1.91     2.17

aThe numerical  factors -are  multiplied  by  the purchased equipment  costs to
.obtain total  costs.
 AR  = as required.
                                   4-43
-------
assumed to be $20/ton.  The waste is considered to be hazardous for  these
calculations because of the concentration of radioactive material.   (For
comparison, it should be noted that the cost of disposing of nonhazardous
wastes is approximately $5/ton.)
4.3.1  Venturi Scrubber Cost Assumptions
     The capital and annualized costs for venturi scrubbers were based on
procedures established in the GARD manual and on equipment costs
established therein.  Because of the large airflow encountered at most
kilns, two identical scrubber systems in parallel were costed on one-half
of the total exhaust stream.  Radial fans were costed because of their
ability to operate at high pressures and temperatures in an abrasive gas
stream.  The costs of the starter motor, direct and V-belt drives, and'
dampers are included in the fan costs.  The corrosiveness (fluorides) of
the gas stream entering a scrubber from the rotary kiln calciner requires
that fabricated equipment cost estimates be based on the use of a
combination of Hastelloy and Type 316 stainless steel.  Plate thickness of
the fan housing and ductwork was determined based on system static
pressure.  Details on the cost inputs for venturi scrubber control options
for each facility are presented in Appendices A through E for the
individual facilities.
4.3.2  Wet ESP Cost Assumptions
     Capital and annual ized costs for the ESP were based on an EPA cost
update.19'20  The primary factor, other than SCA, that affects ESP costs
is material of construction.  The corrosiveness (fluorides)  of the gas
stream entering an ESP from the rotary kiln calciner requires that
fabricated equipment the ductwork and ESP housing be constructed  of a
corrosion resistant material.   Costs for these components were based  on
the use of Type 316 stainless  steel.  Collecting electrodes  also  were
assumed to be constructed from Type  316 stainless steel.
4.3.3  SD/FF Cost Assumptions
     Spray dryer/fabric filter systems  provide efficient  collection of
both condensible PM and acid gases.   Key design parameters  that affect
system performance and costs are lime addition,  gas  temperature entering
the FF, FF air-to-cloth ratio,  and pressure drop through  the  system.   Lime
addition rates were calculated  under the assumption  of a  1.5:1
                                   4-44
-------
stoichlometric ratio of lime to HF and S02 combined.  The gas temperature
at the FF inlet was assumed to be 150°C (300°F).  An air-to-cloth ratio  of
1:1.2 mVmVniln (4:1 ft2/ft3/min) and a system pressure drop of 3.1  kPa
(12.5 in. w.c.) were used.
     Total direct costs for the SD/FF unit were estimated on the basis of
the cost equation:

                             C= 7.115 Q°'517

where:
     C
     Q = volumetric flow, acfm
     C = total direct cost, $x!03 in December 1987
This cost equation is based on comprehensive information collected by EPA
as a part of the municipal waste combustion study.  Vendors contacted
during this study indicated that these costs would provide reasonable
±30 percent estimates.
4.3.4  HEPA Filter Cost Assumptions
     Calciner gas stream characteristics that affect HEPA filter design
and costs are moisture content, inorganic acid content, and loading in the
gas stream to be treated.  A spray tower is assumed to exist upstream of
the HEPA filtration system; the high moisture content of the spray tower
exit gases requires treatment of the gases by a demister and reheater
upstream of the HEPA filter.  These components were included in the cost
of the HEPA system.  Because the exhaust gases are corrosive,  Type 304
stainless steel housings and filter frames, acid-corrosion resistant
filter media, and vinyl-clad aluminum separators are included  in the cost
of the system and replacement filters to provide the best available
corrosion resistance.   Because the PM loading in the gas stream exceeds
the recommended maximum of 2.3 mg/m3 (0.001 gr/acf),  the cost  of a
prefiltration system is included in the total  system cost.   Estimated
costs of the HEPA system, consisting of the prefilters,  HEPA filters,
prefilter/HEPA filter  bank housing, demister,  reheater,  and  demister/
reheater housing were  obtained from equipment  vendors.
                                   4-45
-------
     A major operating cost for HEPA filters is filter replacement.  The
operating life of a HEPA depends on the increase in pressure drop
resulting from particle collection within the filter media.  A general
guideline used to design filter systems is 4 lb/1,000 ft3/nrin rated
capacity (1.82 kg/1,000 ft3/nrin).12  Filter life was estimated by assuming
a HEPA capacity of 7.9 lb/1,000 ft3/m1n (3.6 kg/1,000 ft3/min) per filter
based on vendor information. *   The methodology used to estimate filter
life consisted of the following steps:
     1.  Obtain particle size distribution in spray tower exit gas stream
from test data (where available);
     2.  Predict the mass of particles removed by prefiltration using
design prefilter removal efficiencies for a given particle size;
     3.  Predict mass of particles removed by HEPA filter using filter
design HEPA removal efficiencies;
     4.  Assume a filter capacity for HEPA filter and calculate HEPA
filter operating life with and  without use of a prefilter;
     5.  Calculate prefilter life as two times the HEPA filter life
without the use of a prefilter; and
     6.  Calculate HEPA filter  life as the HEPA capacity divided by the
particulate loading rate into the HEPA filter.
     Estimation of the labor cost to replace prefilters and HEPA filters
as they are exhausted is based  on 0.25 hours of labor per filter per
replacement cycle.  For example,  filter replacement for a 36 filter bank
requires 9 hours.
     Exhausted filters are expected to exhibit increased concentrations of
particulate matter containing Po-210 and Pb-210.   To reduce the risk of
inhalation of particles that may  become airborne  as a result of filter
handling during the replacement process, an automatic bagout containment
system is included in the system  cost.   Automatic bagout facilitates
removal of exhausted filters without direct operator contact.   Heavy duty
PVC bags are installed inside the filter housing  between the filters and
the housing access door.  When  the door is  opened,  the bags  form  a  barrier
between the operator and the contaminated  filter.   By working  through the
bag, the operator can remove the  filter and draw  it into the bag  without
direct contact.  The cost of replacement bags was  included  in  the estimate
of replacement material  cost.

                                   4-46
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4.4  REFERENCES FOR SECTION 4

 1.  Joseph, G., and D. Beachler, APTI Course SI:412C Wet Scrubber Plan
     Review.  U. S. Environmental Protection Agency.  Research Triangle
     Park, N.C.  Publication No. EPA 450/2-82-020.  March 1984.

 2.  Memo and attachments from Wallace, D. and K. Leeds, Midwest Research
     Institute, to Beck, L., EPA/ISB.  August 9, 1988.  Site Visit--
     Monsanto Elemental Phosphorus Plant, Soda Springs, Idaho.

 3.  Memo and attachments from Wallace, D. and J. Obremski, Midwest
     Research Institute, to Beck, L.t EPA/ISB.  August 23, 1988.  Site
     Visit—Stauffer Elemental Phosphorus Plant, Mount Pleasant,
     Tennessee.

 4.  Schifftner, K. and H. Hesketh.  Wet Scrubbers, A Practical
     Handbook.  Chelsea, Lewis Publishers, Inc.  1986.

 5.  U. S. Environmental Protection Agency.  Control Techniques for
     Particulate Emissions from Stationary Sources—Volume I.  Publication
     No. EPA-450/3-81-005a.  Research Triangle Park, N.C.  September 1982.

 6.  Reference was eliminated to prevent disclosure of CBI data.

 7.  Memo and attachments from Wallace, D. and J. Obremski, Midwest
     Research Institute, to Beck, L., EPA/ISB.  August 9, 1988.  Site
     Visit—Stauffer Elemental Phosphorus Plant, Silver Bow, Montana.

 8.  U. S. Environmental Protection Agency.  Operation and Maintenance
     Manual  for Electrostatic Precipitators.   Publication
     No. EPA/625-1-85/017.  Research Triangle Park, N.C.  September 1985.

 9.  Beachler, D., APTI Course SI:412B, Electrostatic Precipitator Plan
     Review.  Prepared for U. S. Environmental Protection Agency.
     Research Triangle Park, N.C. •  Publication No. EPA 450/2-82-019.
     July 1983.

10.  Sedman, C.  and T. Brna.  Municipal Waste Combustion Study:  Flue Gas
     Cleaning Technology.   Prepared for U. S. Environmental  Protection
     Agency.  Research Triangle Park, N.C.  Publication
     No. EPA 530-SW-87-021d.  June  1987.

11.  Beachler, 0., APTI Course SI:412A, Baghouse Plan Review.   Prepared
     for U.  S. Environmental Protection Agency.   Research Triangle Park,
     N.C.  Publication No. EPA 450/2-82-005.   April  1982.

12.  Burchsted,  C. A., Fuller, A. B., and Kahn,  J.  E.   Nuclear Air
     Cleaning Handbook.  Oak Ridge  National  Laboratory,  Oak  Ridge,
     Tennessee.   ERDA  Publication No. 76-21.   1976.
                                   4-47
-------
13.  Radian Corporation.  Draft Final Emission Test Report.  Monsanto
     Elemental Phosphorus Plant, Soda Springs, Idaho.  Prepared for U. S.
     Environmental Protection Agency under Contract No. 68-02-4338.
     Research Triangle Park, North Carolina.  October 1988.

14.  Radian Corporation.  Draft Final Emission Test Report.  FMC Elemental
     Phosphorus Plant, Pocatello, Idaho.  Prepared for U. S. Environmental
     Protection Agency under Contract No. 68-02-4338. Research Triangle
     Park, North Carolina.  October 1988.

15.  Hesketh, H.  Air Pollution Control.  Ann Arbor, Ann Arbor Science.
     1981.

16.  Environment Canada.  The National Incinerator Testing and Education
     Program:  Air Pollution Control Technology,  Report EPS 3/UP/2.
     Ottawa, Ontario.  September 1986.

17.  GARD, Inc.  Capital and Operating Costs of Selected Air Pollution
     Control Systems.  Prepared for U. S. Environmental Protection
     Agency.  Research Triangle Park, N.C.  Publication
     No. EPA 450/5-80-002.  December 1978.

18.  U. S. Environmental Protection Agency.   EAB  Control Cost Manual,
     Third Edition.  Publication No. EPA 450/5-87-001A.  Research Triangle
     Park, N.C.  February 1987.

19.  Turner, J. H. et al.  Sizing and Costing of  Electrostatic
     Precipitators.  Part I.  Sizing Considerations.  Journal of the Air
     Pollution Control Association.   38(4):458-421.

20.  Turner, J. H. et al.  Sizing and Costing of  Electrostatic
     Precipitators.  Part II.   Costing Considerations.   Journal  of the Air
     Pollution Control Association.   38(5):715-726.

21.  Telecon.  Allen, K.,. Midwest Research Institute,  with Clark,  R.,
     Environmental Product Sales, Inc.,  Raleigh,  N.C.   August 12,  1988.
                                   4-48
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               5.0  CONTROL ALTERNATIVE PERFORMANCE AND  COST

     Information on the feasibility, performance,  and costs of alternative
emission control techniques for elemental phosphorus  process  calciners and
nodulizing kilns is needed to assess potential regulatory limits  for
Po-210 and Pb-210 emissions.  This section defines  viable control
alternatives and presents information on the performance and  capital  and
annualized costs of those alternatives for each of  the five operating
facilities.  Nationwide reductions in Po-210 and Pb-210  emissions  also are
estimated, and total nationwide capital and annualized cost estimates are
presented.  The results presented in this section are based on the
emission data presented in Section 3.0 and the performance  and cost
estimation procedures presented in Section 4.0 for  different  control
technologies.
5.1  DEFINITION OF CONTROL ALTERNATIVES
     As outlined in Section 4, four fine PM control techniques  were
identified as having potential for control of Po-210  and  Pb-210 emissions
from calciners—venturi scrubbers, wet electrostatic  precipitators
(ESP's), spray dryers with pulse jet fabric filters (SD/FF's)  and  high
energy particulate air (HEPA)  filters.  Ten different  control  alternatives
based on these four technologies were examined.  Four  of  the  alternatives
are based on venturi scrubbers at different pressure drops  (AP's), four
are based on wet ESP's with different specific collecting areas (SCA's),
and one each is based on a SD/FF system and a HEPA filter system.   The
paragraphs below describe the  control alternatives and the assumptions
that were used to assess performance and cost of  these systems.
     Four of the control alternatives comprise venturi scrubbers operated
downstream from a spray tower.  Four different pressure drops were
examined~2.5 kPa (10 in.  w.c.),  6.2 kPa (25  in.  w.c.), 10 kPa  (40 in.
w.c.),  and 20 kPa (80 in.  w.c.).   The values  from 2.5 kPa to 10 kPa
represent the range of AP's  for  venturi  scrubbers  at recently  installed
control  systems on  elemental phosphorus  plant  calcining operations.  The
20 kPa  level  was selected  as a control alternative  that is more stringent
than the controls typically  used  in  the  industry,  but  that has been
applied  to other metallurgical processing  facilities.   Two other
                                   5-1
-------
assumptions were made in evaluating the performance and costs of the
venturi scrubber control alternatives.  First, a spray tower was assumed
to be used upstream from the venturi to control acid gases and condition
the gas stream for the venturi.  All of the operating facilities except
FMC currently have a spray tower as a part of their control system that is
assumed to be useable as the conditioning system for the venturi.  Second,
for all the venturi scrubber control alternatives, the L/G ratio was
assumed to be 1.3 a/m3 (10 gal/1,000 ft3).  This value was selected
because it represents the upper end of the range typically found in
venturi scrubber applications.  A cyclonic mist eliminator also was
assumed for all venturi scrubber alternatives.  Note that although FMC
does not have a spray tower in their systems, no tower was costed for this
study.  The low energy scrubber that FMC has in place as assumed to
provide coarse PM control and gas conditioning.
     The four ESP control alternatives that were considered comprised
spray towers for acid gas control and gas stream conditioning followed by
flat-plate wet ESP's.  The four SCA levels that were considered were
39.4 (m/s)"1 (200 ftVkacfm), 78.8 (m/s)"1 (400 ftVkacfm), 118 (m/s)"1
(600 ftVkacfm), and 158 (m/s)'1 (800 ftVkacfm).   These four SCA levels
are higher than the SCA at the one wet ESP that is applied to a nodulizing
kiln.  However, that unit is an older unit with relatively low PM removal
efficiency.  The range of 39.4 to 158 (m/s)"1 (220 to 800 ftVkacfm)  is
representative of the SCA levels typically found on metallurgical  and
mineral processing facilities.  The spray tower upstream from the ESP will
remove acid gases from the gas stream and reduce the temperature to 65° to
70°C (150° to 160°F) to assure that the Po-210 and Pb-210 are condensed
before they enter the ESP.
     The ninth control alternative is the SD/FF control  system described
in Section 4.1.4.  For this alternative,  the exhaust stream is vented
directly to the spray dryer without pretreatment.   No SD/FF systems have
been applied to elemental phosphorus facilities.   However,  they were
selected as a stringent control  technique because  they have been
demonstrated to control acid gases and condensation PM in other
metallurgical  and mineral processing operations such as  aluminum reduction
and glass manufacturing.  Key assumptions that were made to estimate
                                   5-2
-------
performance and cost are that  sufficient moisture will  be added to reduce
gas temperature to 120°C (250°F) at the inlet to the  FF,  that lime will  be
added at a 1.5 stoichiometric  ratio for HF and S02  combined,  and that a
pulse jet fabric filter capable of maintaining an outlet  grain loading of
0.023 g/dscm (0.01 gr/dscf) will be installed.
     The final control alternative comprises a spray  tower scrubber,  a
reheat system, a prefilter, and a HEPA filter in sequence.  The spray
tower is used to reduce the acid content of the gas stream and to remove
larger sized PM.  The reheat system is needed to raise  the gas stream
temperature sufficiently to prevent condensation of moisture  and inorganic
acids in the HEPA filter.  The prefilter is used to reduce  the PM loading
to the HEPA filter and thereby extend its life.  The  HEPA filter system
has not been applied to elemental phosphorus facilities and generally is
not applied to furnaces that generate gas volumes as  large  as  those
generated by elemental phosphorus process calciners or nodulizing kilns.
However, the system was selected for consideration because  HEPA filters
have been used successfully to control radionuclide emissions  from uranium
processing facilities and they do provide a much greater  level  of control
than is provided by the other control  alternatives.
5.2  PERFORMANCE OF CONTROL ALTERNATIVES
     The performance of each of the 10 control  alternatives was  calculated
based on the reduction from baseline emissions  that could be achieved  by
application of the control  alternative.   For each control alternative  and
each operating facility,  annual emissions  of Po-210 and Pb-210 were
estimated using the procedures described in Section 4.  These estimated
emission levels were compared to the baseline emission estimates  that  are
presented in Table 3-9 to determine achievable  emission reductions.
     Performance models for venturi  scrubbers and wet  ESP's are presented
in Sections 4.2.1 and 4.2.2,  respectively.   Application of these models
requires information on the emission rate  of  Po-210  and Pb-210 at the
venturi  and ESP inlet and on  the particle  size  distribution of these
emissions.   The estimates of  Po-210  and  Pb-210  emission rates  at the
                                   5-3
-------
scrubber/ESP inlet, based on the assumptions that a spray tower is located
upstream from primary control device are:
                               Emissions, Ci/yr
     Faci1i ty                Po-210         Pb-210
     FMC                      10             0.14
     Monsanto                 30             9.5
     Stauffer, Montana        2.4            0.32
     Stauffer, Tennessee      0.28           0.058
     Occidental               0.31           0.064
The estimates for FMC, Monsanto, and Stauffer, Montana, are based on tests
conducted by EPA in 1983 and 1988 that measured emissions at the outlet of
low-energy scrubbers at those facilities.1"3  Because the control systems
at the two Tennessee plants consist of spray tower scrubbers, the emission
estimates for those two facilities are based on the baseline emissions
from those facilities that were presented in Table 3-9.  Estimates of the
particle size distribution for these emissions are presented in Table 5-1.
Separate estimates were developed for moving grate calciners (FMC) and
rotary kilns (all other facilities).
     The performance models presented in Chapter 4 and available test data
were used to develop estimates of the fractional efficiencies that could
be achieved by the venturi scrubber and wet ESP control alternatives for
the six particle size fractions identified in Table 5-1.  The results of
the model calculations are presented in Table 5-2 for the four venturi
scrubber alternatives and in Table 5-3 for wet ESP's.  Generally, the
models indicated that all of the control measures are relatively effective
in removing particles greater than 1 urn in diameter.   However, only the
high efficiency systems (venturi scrubbers with AP's  of 10 kPa or greater
and wet ESP's with an SCA of 78.8 (m/s)"1) are effective in controlling
particles less than 1 ym in diameter, which is the size fraction in which
the Po-210 and Pb-210 are concentrated.
     Because the model results and test results agreed well for wet ESP's,
the fractional efficiencies presented in Table 5-3, the particle size
distributions presented in Table 5-1, and the estimated annual inlet
emission rates presented above were used directly to  estimate annual
Po-210 and Pb-210 emission rates.
                                    5-4
-------
      TABLE 5-1.  PARTICLE SIZE DISTRIBUTIONS FOR Po-210 AND Pb-210a
Po-210
Particle
Range
<0.5
0.5-0.9
0.9-1.5
1.5-3
3-10
>10
size, um
Median
3.5
0.67
1.16
2.12
5.48
14
Moving
grate6
76.0
4.0
3.8
2.8
3.7
9.6
Rotary
kilnc
52.2
21.6
12.9
8.9
3.4
1.0
Pb-210
Moving
grate5
36.5
17.7
11.5
8.8
13.2
12.3
Rotary
kilnc
60.0
18.1
14.3
5.2
2.0
0.4
aAssumed to be at the outlet to a spray tower upstream from the high-
 efficiency PM collector.
"Based on size distribution at the FMC slinger scrubber outlet.
cBased on size distribution at outlet from spray tower at Stauffer.
                                   5-5
-------
TABLE 5-2.   ESTIMATED FRACTIONAL EFFICIENCIES FOR VENTURI SCRUBBER
                      CONTROL ALTERNATIVES
Fractional efficiencies
Particle size, urn
Range
<0.5
0.5-0.9
0.9-1.5
1.5-3
3-10
>10
Median
3.5
0.67
1.16
2.12
5.48
14
AP (kPa)
= 2.5
10.0
49.9
86.5
98.1
99.8
>99.9
6.2
31.2
80.6
96.8
99.5
99.9
>99.9
10
46.9
89.7
98.5
99.8
>99.9
>99.9
20
69.9
96.5
99.5
99.9
>99.9
>99.9
                               5-6
-------
TABLE 5-3.  ESTIMATED FRACTIONAL EFFICIENCIES FOR WET ESP
                  CONTROL ALTERNATIVES
Particle
Range
<0.5
0.5-0.9
0.9-1.5
1.5-3
3-10
>10
size, urn
Median
3.5
0.67
1.16
2.12
5.48
14

SCA (m/s )
= 39.4
63.4
80.2
92.3
98.8
>99.9
>99.9
Fractional efficiencies
78.8
86.6
96.1
99.4
>99.9 -
>99.9
>99.9
118
95.1
99.2
99.9
>99.9
>99.9
>99.9
158
98.2
99.8
>99.9
>99.9
>99.9
>99.9
                          5-7
-------
     As discussed in Section 4.3, the measured efficiencies for Po-210 and
Pb-210 at Monsanto were significantly higher than the efficiencies
estimated by the scrubber model.  Consequently, the estimated scrubber
efficiencies estimated by the model were adjusted to compensate for the
apparent low bias of the model.  Table 5-4 presents the estimates of
scrubber performance for the four control alternatives for Po-210 and
Pb-210 for rotary kiln and moving grate calciners.  The left half of this
table presents the modeled results based on the data presented in
Tables 5-1 and 5-2.  The right half of the table presents the adjusted
results.  The basis for these adjusted results and the calculation
procedures are documented in Reference 4.
     The adjusted efficiencies presented in Table 5-4 were applied to the
emission rates presented above to estimate controlled emissions under each
of the four venturi scrubber options.  The results are presented in
Tables 5-5 and 5-6.  These emission rates presented in Tables 5-5 and 5-6
were compared to the baseline emission rates presented in Table 3-7, and
emission reductions were calculated.  These results are presented in
Table 5-7 for Po-210 and 5-8 for Pb-210.
     Control efficiencies also were developed for the SO/FF and the HEPA
using the procedures described in Section 4.2.  Efficiencies for the SD/FF
system were calculated based on an assumed outlet loading of 0.023 g/dscm
(0.01 gr/dscf) and estimated inlet loadings of 13 g/dscm (5.7 gr/dscf) for
rotary kilns and 15 g/dscm (6.7 gr/dscf) for moving grate calciners.
These inlet loading estimates are based on the uncontrolled PM emission
rates measured at FMC and Stauffer in 1984 and the quantity of lime added
to the system to control S02 at concentrations of 500 ppmv and HF at
1,500 ppmv.1*3  The resultant efficiencies are 99.82 percent for rotary
kilns and 99.85 percent for moving grates.  For the HEPA filter,  the
efficiency was assumed to be 99.998 percent as described in Section 4.2.4.
     The estimated efficiencies defined above then were used to estimate
Po-210 and Pb-210 emissions for each of the five operating facilities.
Since the HEPA filter is installed downstream from a spray tower,  the
emission rates presented above were used as "uncontrolled" emission
rates.  The SD/FF system does not include a spray tower.   Consequently,
"uncontrolled" emissions were estimated using the spray tower outlet rates
defined above and the assumption that the spray tower is  almost 65 percent

                                    5-8
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efficient in removing Po-210 and Pb-210 from the exhaust  stream.   This
65 percent efficiency estimate is based on the performance measured  by  EPA
at Stauffer.3  The resulting emission estimates are presented  in
Tables 5-5 and 5-6 for Po-210 and Pb-210, respectively.   The reductions
from baseline are presented in Tables 5-7 and 5-8.  Both  of these  control
alternatives achieve a significant reduction in emissions beyond those
that are estimated for venturi scrubbers and wet ESP's.
5.3  COSTS OF CONTROL ALTERNATIVES
     Capital and annualized costs for each of the 10 control alternatives
evaluated were developed using the procedures described in Section 4.3.
Nationwide and plant specific capital and annualized cost summaries for
each control alternative are presented in Tables 5-9 and  5-10, respec-
tively.  Nationwide capital and annualized costs for the  10 control
alternatives are compared graphically in Figures 5-1 and 5-2.  A more
detailed breakdown of costs for each alternative is presented in
Tables 5-11 through 5-20.  Details on the cost inputs for the venturi
scrubber, wet wall ESP, SD/FF, and HEPA filter system for each facility
are presented in Appendices A through E.
                                   5-14
-------
















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     Control  Alternative
            Capital  Costs
Control
    VS/10
    VS/25
    VS/40
    VS/80
WESP/200
WESP/400
WESP/600
WESP/800
    SD/FF
    HEPA
         0   10   20   30   40   50   60   70
                   Cost-$ Millions
         •I FMC    ISSS3 Monsanto CD Occidental
         ^^ Stauf, MT i^ Stauf, TN

       Figure 5-10 Capital costs of control alternatives.
                     5-17
-------
     Control  Alternative
         Annualized Costs
Control
    VS/10
    VS/25
    VS/40
    vs/ao
WESP/200
WESP/400
WESP/600
WESP/800
    SD/FF
    HEPA
               10
40
               20    30
              Cost-$ Millions
   •I FMC     ISS3 Monsanto CH Occidental
   WZ& Stauff.MT lOini Stauff.TN
Figure 5-2. Annualized costs of control alternatives.
50
                    5-18
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5.4  REFERENCES FOR SECTION 5

1.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
    Polonium-210 from Calciners at Elemental Phosphorus Plants:  FMC
    Plant, Pocatello, Idaho.  Washington, D.C.  June 1984.

2.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
    Polonium-210 from Calciners at Elemental Phosphorus Plants:  Monsanto
    Plant, Soda Springs, Idaho.  Washington, D.C.  September 1984.

3.  U. S. Environmental Protection Agency.  Emissions of Lead-210 and
    Polonium-210 from Calciners at Elemental Phosphorus Plnats:  Stauffer
    Plant, Silver Bow, Montana.  Washington, D.C.  August 1984.
                                   5-29
-------
                                   TECHNICAL REPORT DATA
                            /Please react Insmtcnons on [He reverse before completing/
1. REPORT MO^y
 EPA-45Q/>00 £15
                              2.
                                                           3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
 Characterization and Control of Radionuclide
 Emissions  From Elemental Phosphorus Production
              5. REPORT DATE
               February 1989
              6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
                                                           8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND AOORESS
 Midwest Research Institute
 Suite 350
 401 Harrison  Oak Blvd
 Gary. NC  27513
              10. PROGRAM ELEMENT NO.
              Work Assignment 12
              11. CONTRACT/GRANT NO.
              EPA Contract No. 68-02-4379
12. SPONSORING AGENCY NAME AND AOORESS
 Elizabeth A.  Grainger, Project Officer
 Industrial  Studies Branch, Emissions Standards  Division
 OAQPS
 U.S. Environmental Protection Agency, RTP. NC   27711
              13. TYPE OF REPORT AND PERIOD COVERED
              May 1988  to February 1989
              14. SPONSORING AGENCY CODE
15. SUPfM-EMENTARY NOTES
is. ABSTRACT  xhis  report presents the.results of  a study conducted by  the  Industrial
Studies Branch in EPA's Office of Air Quality Planning and Standards  that  was  designed
to collect  background information on radionuclide emissions from elemental phosphorus
production  processes.  The Office of Radiation  Programs will use this  information to
evaluate  the National Emission Standard for Hazardous Air Pollutants  for radionuclide
emissions from elemental phosphorus production  in response to litigation by the  Sierra
Club.

     Information gathered included all emission data generated over  the past  10  years
by EPA and  elemental phosphorus facilities, test  results  of the test program conducted
concurrently with  this  study (two scrubbers), data compiled from plant visits  to  each
of the five operating facilities, and data acquired  through review of published
literature, contact  with knowledgeable EPA personnel,  and telephone contacts with
control equipment  vendors.

     This report provides descriptions of the elemental phosphorus production  processes,
radionuclide emissions  from those processes, availability of control techniques  that
could reduce those emissions,  and the performance and  costs of alternative  control
techniques.
                               KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                                             b.lDENTIFIERS/OPEN ENDED TERMS
                           c. COSATI Held/Group
 Elemental Phosphorus  production, air
 emissions, radionuclide emissions, acid
 gas emissions, particulate matter emissions
 spray towers, scrubber, ESP, fabric filter,
 high efficiency particulate air filter
 Elemental phosphorus
 production, air  pollutior
 air emission,  air
'pollution control  equip-
 ment, air emission
 standards
3. DISTRIBUTION STATEMENT
EPA Form 2220-1 (Re». 4-77)   = = evious EDITION .5 OBSOLETE
                                              19. SECURITY CLASS (This Report/
                                                                         21. NO. OF PAGES
                                             20. SECURITY CLASS
                                                                        •22. PRICE
-------