United States Office of EPA 130/6-81-003
Environmental Protection Federal Activities October 1981
Agency Washington, DC 20460
&EPA Environmental
Impact Guidelines
For New Source
Phosphate Fertilizer
Manufacturing Facilities
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This document is available to the public through the National Technical
Information Service, Springfield, Virginia 22161.
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EPA-130/6-81-003
October 1981
ENVIRONMENTAL IMPACT GUIDELINES
FOR NEW SOURCE
PHOSPHATE FERTILIZER
MANUFACTURING FACILCTIKS
EPA Task Officer:
Frank Rusincovitch
US Environmental Protection Agency
Office of Federal Activities
Washington, D.C. 20460
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Preface
This document is one of a series of industry-specific Environmental Impact
Guidelines being developed by the Office of Federal Activities (OFA) for
use in EPA's Environmental Impact Statement preparation program for new
source NPDES permits. It is to be used in conjunction with Environmental
Impact Assessment Guidelines for Selected New Source Industries, an OFA
publication that includes a description of impacts common to most industrial
sources.
The requirement for Federal agencies to assess the environmental impacts
of their proposed actions is included in Section 102 of the National
Environmental Policy Act of 1969 (NEPA), as amended. The stipulation that
EPA's issuance of a new source NPDES permit as an action subject to NEPA
is in Section 511(c)(l) of the Clean Water Act of 1977. EPA's regulations
for preparation of Environmental Impact Statements are in Part 6 of Title
40 of the Code of Federal Regulations; new source requirements are in
Subpart F of that Part.
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TABLE OF CONTENTS Page
List of Figures iv
List of Tables .- vii
INTRODUCTION 1
1.0 OVERVIEW OF THE INDUSTRY 3
1.1 SUBCATEGORIZATION 7
1. 2 MARKETS AND DEMANDS 10
1.3 PROCESSES 16
1.3.1 Background Information 16
1.3.2 Major Processes of Phosphate Fertilizer
Manufacture 21
1.3.3 Auxiliary Support Systems.,.,,.,.,,,,.,,,,,,,,,,,... 84
1.4 SIGNIFICANT ENVIRONMENTAL PROBLEMS 88
1.4.1 Raw Materials 88
1.4.2 Process-Related Problems 89
1.4.3 Pollution Control 92
1.4.4 Location 92
1.5 TRENDS 93
1.5.1 Locational Trends 93
1.5.2 Trends in Raw Materials 96
1.5.3 Process Trends 98
1.5.4 Trends in Pollution Control 100
1.5.5 Environmental Impact Trends 102
1. 6 POLLUTION CONTROL REGULATIONS 105
1.6.1 Water Pollution 105
1.6.2 Air Pollution 109
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Page
1.6.3 Land Disposal of Wastes 116
1.6.4 Monitoring Requirements 117
2.0 IMPACT IDENTIFICATION 118
2.1 PROCESS WASTES 118
2.1.1 Materials Balance and Typical Waste
Characteristics 118
2.1.2 Environmental Impact of Industry Wastes 139
2.1.3 Other Impacts 148
2.1.4 Modeling of Impacts 151
3.0 POLLUTION CONTROL 153
3.1 STANDARDS OF PERFORMANCE TECHNOLOGY: END-OF-PROCESS
CONTROLS AND EFFECTS ON WASTE STREAMS (AIR EMISSIONS) 153
3.1.1 Dust Control in Raw Materials Handling
Handling Operations 153
3.1.2 Control of S02 from Contact Process Sulfuric
Acid Plants 154
3.1.3 Control of Acid Mist Emissions from Contact
Process Sulfuric Acid Plants 157
3.1.4 Control of Fluoride Emissions 160
3.2 STANDARDS OF PERFORMANCE TECHNOLOGY: IN-PROCESS
CONTROLS AND EFFECTS ON WASTE STREAMS AND EMISSIONS 167
3.2.1 Sulfuric Acid Plant Effluent Control 167
3.2.2 Wet Process Phosphoric Acid - Pond Water Dilution
of Sulfuric Acid 168
3.2.3 Ammonium Phosphate Self-Contained Process 169
3.3 STANDARDS OF PERFORMANCE TECHNOLOGY: END-OF-PROCESS
CONTROLS AND EFFECTS ON WASTE STREAMS (WASTEWATER
EFFLUENTS) 170
3.3.1 Gypsum Pond Water Treatment 170
3.3.2 Gypsum Pond Water Seepage Control 174
3.3.3 Other End-of-Process Controls 174
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3.4 STATE OF THE ART TECHNOLOGY: END-OF-PROCESS CONTROLS AND
EFFECTS ON WASTE STREAMS (SOLID WASTE) 176
3.4.1 Disposal in Gypsum Ponds and Piles 177
3.4.2 Disposal in Abandoned Mine Pits 177
3.4.3 Disposal in Sea Outfalls 177
3.4.4 Resource Recovery 178
3.5 POLLUTION CONTROL RECOMMENDATIONS EXCERPTED FROM THE
CENTRAL FLORIDA PHOSPHATE INDUSTRY FINAL AREAWIDE
ENVIRONMENTAL IMPACT STATEMENT 179
4 .0 OTHER CONTROLLABLE IMPACTS 181
4.1 AESTHETICS 181
4.2 NOISE 181
4.3 ENERGY SUPPLY 183
4.3.1 Cogeneration 184
4.3.2 Energy Consumption and Conservation 184
4.4 SOCIOECONOMICS 186
5.0 EVALUATION OF AVAILABLE ALTERNATIVES 190
5.1 SITE ALTERNATIVES 190
5.2 ALTERNATIVE PROCESSES , DESIGNS , AND OPERATIONS 192
5.3 NO-BUILD ALTERNATIVE 192
6.0 REGULATIONS OTHER THAN POLLUTION CONTROL 193
7.0 REFERENCES 195
iii
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LIST OF FIGURES
Figure Page
1. U. S. phosphate fertilizer exports 14
2. Phosphate rock supply-demand projections 14
3. Location of major phosphate rock deposits in the
United States 18
4. Schematic diagram of phosphate fertilizer industry 22
5. Contact-process sulfuric acid plant burning elemental
sulfur - single absorption 27
6. Dual absorption sulfuric acid plant flow diagram 31
7. Rock grinding (flow rate per ton rock) 35
8. Normal superphosphate flowsheet 37
9. Precipitation and stability of calcium sulfates in
phosphoric acid 42
10. Wet process phosphoric acid flowsheet 43
11. Flow diagram for Prayon phosphoric acid plant 45
12. Dorr-Oliver reaction system (vacuum-cooled) 45
13. Flow diagram for Singmaster and Breyer dihydrate
phosphoric acid process 47
14. Flow diagram of Singmaster and Breyer hemihydrate-dihydrate
process , . . . . 47
15. Tilting pan filtration system 48
16. Operating cycle of rotary horizontal tilting pan
filter 48
17. Concentration and clarification of phosphoric acid 51
18. Stauffer process for wet process superphosphoric
acid 55
19. Vacuum evaporation SPA concentration processes 55
iv
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LIST OF FIGURES (Cont . )
20. Triple superphosphate (run of pile) (flow rate per
ton ROP) ...
Page
21. Granulated triple superphosphate (flow rate per
ton GTSP) ..... .................... 61
22. Monoammonium phosphate plant (flow rate per ton MAP). ... 54
23. Flowsheet for production of diammonium phosphate
(DAP) ...... ..................... 65
24. Details of pipe reactor in drum granulator ......... 69
25. Flow diagram of granulation pilot plant using pipe
reactor process for NPK fertilizers ............ 70
26. Pipe-reactor/pugmill process. .... ........... 73
27. Pipe reactor and vapor disengager ............. 74
28. Pipe-reactor/drum-granulator process without a
preneutralizer ....... . ............... 76
29. Pipe-cross reactor/drum-granulator process ......... 78
30. Typical ammoniation-granulation plant using the
pipe-cross reactor. ........ ............ 79
31. Plant pipe reactor system for production of high-
polyphosphate liquid fertilizer .............. 83
32. Locations of phosphate fertilizers and ammonia
production. ... ..... . ............... 94
33. Sulfuric acid plant - double catalysis (flow rates
per ton 100% I^SO^) .................... 119
34. Contact process sulfuric acid plants,
SO emissions ....................... 124
35. Contact process sulfuric acid plants,
acid mist emissions .................... 125
36. Wet process for production of phosphoric acid ....... 127
37. Production of superphosphoric acid ............. 127
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LIST OF FIGURES (Cont.)
Figure Page
38. Major gypsum pond equilibrium -j^g
39. Pond water treatment system 173
40. Recommended minimum cross section of dam 176
41. Gypsum pond water seepage control 176
vi
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LIST OF TABLES
Table £S8£
1. Phosphate rock sold or used by producers in the United States
for all uses 12
2. Phosphate trade - U.S. and world 13
3. Marketable production of phosphate rock in the United States,
by region 15
4. Description of phosphate fertilizer complexes in the United
States by unit operations 24
5. Sulfuric acid manufacture from elemental sulfur 29
6. Phosphate rock crushing, grinding, and screening 34
7. Normal superphosphate production 39
8. Wet process phosphoric acid production 49
9. Concentration and clarification of wet process
phosphoric acid 53
10. Superphosphoric acid production 57
11. Granular triple superphosphate production 52
12. Ammonium phosphate production 67
13. Supply pattern for sulfur in the United States 97
14. Water effluent disposal and containment practices for
the phosphate fertilizer industry 103
15. Standards of performance for new sources for wastewater
effluents 107
16. New source performance standards for emissions of air
pollutants from sulfuric acid plants and phosphate
fertilizer manufacturing facilities HO
17. Federal ambient air quality standards HI
18. Nondeterioration increments for S02 and particulate
matter in areas with different air quality
classifications 113
19. Sulfuric acid production materials balance 120
20. New source performance standards compliance test
results for sulfuric acid plants 122
21. Phosphate rock processing materials balance 123
vii
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LIST OF TABLES (Cont.)
Table Page
22. Phosphoric acid materials balance 128
23. Normal superphosphate materials balance .... ^3^
24. Granular triple superphosphate materials balance. ...... 132
25. Ammonium phosphate materials balance 133
26. Typical equilibrium composition of gypsum pond water 135
27. Analysis of solids from wet process phosphoric acid 137
28. Scrubber performance in wet process phosphoric
acid plants 161
29. Spray-crossflow packed bed scrubber performance in
diammonium phosphate and granular triple superphosphate
plants 163
30. Venturi scrubber performance in superphosphoric acid
and diammonium phosphate plants 165
31. Cyclonic spray tower performance in wet process
phosphoric acid, diammonium phosphate, and run of
pile triple superphosphate plants ..... 166
32. Energy for fertilizer nutrient production 186
viii
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INTRODUCTION
The Clean Water Act requires that the United States Environmental Pro-
tection Agency (USEPA) establish standards of performance for categories of
new source industrial wastewater dischargers. Before the discharge of any
pollutant to the navigable waters of the United States from a new source in
an industrial category for which performance standards have been proposed,
a new source National Pollutaiit Discharge Elimination System (NPDES) permit
must be obtained from either USEPA or the State (whichever is the adminis-
tering authority for the State in which the discharge is proposed). The
Clean Water Act also requires that the issuance of a permit by USEPA for a
new source discharge be subject to the National Environmental Policy Act
(NEPA), which may require preparation of an Environmental Impact Statement
(EIS) on the new source. The procedure established by USEPA regulations
(40 CFR 6 Subpart F) for applying NEPA to the issuance of new source NPDES
permits may first require preparation of an Environmental Information
Document (EID) by the permit applicant. Each EID is submitted to USEPA and
reviewed to determine whether there are potentially significant effects on
the quality of the human environment resulting from construction and opera-
tion of the new source. If there are, USEPA publishes an EIS on the action
of issuing the permit.
The purpose of these Guidelines is to provide industry-specific guid-
ance to USEPA personnel responsible for determining the scope and content
of EID's and for reviewing them after submission to USEPA. It is to serve
as supplementary information to the previously published Environmental
Impact Assessment Guidelines for Selected New Source Industries (USEPA
1975), which includes the general format for an EIA and those impact assess-
ment considerations common to all or most industries. Both that document
and these Guidelines should be used in the development of an EID for a new
source phosphate fertilizer manufacturing facility.
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These Guidelines provide the reader with an indication of the nature
of the potential impacts on the environment and the surrounding region from
construction and operation of phosphate fertilizer plants. In this capacity,
the volume is intended to assist USEPA personnel in the identification of
those impact areas that should be addressed in an EID. In addition, these
Guidelines present (in Section 1.0) a description of the industry; demand
for industry output, its principal processes and environmental problems;
and recent trends in location, raw materials, processes, pollution control,
and environmental impacts. This "Overview of the Industry" is included to
familiarize USEPA staff with existing conditions in the industry.
Although this document may be transmitted to an applicant for inform-
ational purposes, it should not be construed as representing the procedural
requirements for obtaining an NPDES permit or as representing the applicant's
total responsibilities relating to the new source EIS program. In addition,
the content of an EID for a specific new source application is determined
by USEPA in accordance with Section 6.604(b) Title 40 of the Code of Federal
Regulations and this document does not supersede any directive received by
the applicant from USEPA's official responsible for implementing that
regulation.
These Guidelines are divided into six sections. Section 1.0 is the
"Overview of the Industry," described above. Section 2.0, "Impact Identi-
fication," discusses process-related wastes and the impacts that may occur
during construction and operation of the facility. Section 3.0, "Pollution
Control," summarizes the technology for controlling environmental impacts.
Section 4.0 discusses other impacts that can be mitigated through design
considerations and proper site and facility planning. Section 5.0, "Evalua-
tion of Alternatives," summarizes possible alternatives to the proposed
action and discusses evaluation of their consideration and impact assessment.
Section 6.0 describes regulations other than pollution control that apply
to the industry. Section 7.0 is a list of references, arranged by topic,
which are useful for additional or more detailed information.
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1.0 OVERVIEW OF THE INDUSTRY
These Guidelines deal with phosphate fertilizer manufacturing in the
United States as it is today and as it is presently evolving. "Phosphate
Fertilizer Manufacturing" refers to that industry which takes phosphate
rock, a relatively insoluble raw material, and processes it to produce a
number of water-soluble phosphorus-containing chemicals which are further
utilized in the manufacture of fertilizers. The products of these pro-
cesses are fertilizer materials, some of which could be applied directly.
In practice this is rarely done because most areas which can benefit from
fertilizers suffer from soil deficiencies besides that of available phosphorus.
For most purposes, then, the phosphate fertilizer industry produces inter-
mediate products which are used in other segments of the fertilizer or
inorganic chemical industries.
Some phosphate fertilizer plants produce a single product primarily,
while others are integrated complexes which produce a full range of phos-
phate fertilizer products, and may produce a number of other chemical
products at the same facility. It is common for one company to be involved
in industry segments ancillary to phosphate fertilizer manufacture. For
example, many companies are located at or near the mine site for phosphate
rock and may be involved both in the ore extraction and processing as well
as in the manufacturing processes to produce phosphate fertilizers or other
phosphate chemicals.
The inter-relationships and distinctions among industry segments can
be summarized as follows:
1) Phosphate mining industry - this is a segment of the mining
industry which extracts phosphate ores and processes them to
produce marketable quality "phosphate rock". Most ores are
sedimentary deposits of the mineral fluorapatite and associated
impurities, along with clays, sands, or other rock matrix. These
constituents usually must be separated to concentrate the phos-
phate bearing deposits which are referred to as "phosphate rock,"
"phosrock", "phosphate rock concentrate", and "beneficiated phosphate
rock." The phosphate mining industry is described more fully in
Section 1.3.1.
3
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2) Phosphate fertilizer industry - as described before, this industry
uses phosphate rock from the phosphate mining processes and manu-
factures phosphate fertilizer chemicals.
3) Non-phosphate fertilizer industries - in reference to the
phosphate fertilizer industry, these industries include the
"nitrogen" or "nitrogenous" fertilizer industry and the "potas-
sium" or "potash" fertilizer industry. A minor, often overlooked,
industry engaged in fertilizer production, is the "natural" or
"organic" fertilizer industry. The products of the nitrogen and
potash fertilizer industries are also usually considered inter-
mediate products, which are combined with other materials or
processed further for specific applications.
4) Mixed (and blended) fertilizer industry - this is the industry
which actually produces most of the fertilizer materials com-
mercially marketed. Phosphate, nitrogen, and potassium fertilizer
chemicals, along with various fillers, coating agents, insecti-
cides, and other useful additives are combined by this industry
to produce popular blends or formulations tailored to the needs of
certain geographic areas. In the parlance of the industry, "mixed
fertilizer" refers to a fertilizer containing more than one of the
primary plant nutrients (phosphorus, nitrogen, potash). There are
three types of mixing plants:
• Bulk blending plants physically mix dry fertilizer materials,
without chemical reaction, to produce a dry, granular mixed
fertilizer.
• Ammoniation-granulation plants chemically react liquid and/or dry
raw materials in a granulator to produce a dry fertilizer with
the constituent nutrients blended in each granule.
• Liquid mixing plants are either "hot" or "cold". Hot mix plants
are termed "hot" because of the exothermic reaction between phos-
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phoric acid and ammonia; they produce a liquid mixed fertil-
izer. Cold mix plants physically mix liquid materials to de-
rive a liquid mixed fertilizer without a chemical reaction
(USEPA 1976f).
Rapid developments are underway in the mixed fertilizer industry.
New liquid fertilizers are being developed and promoted with con-
current development of improved spreading equipment. Slurry-type
mixtures are being marketed as fluid fertilizers, to be applied us-
ing conventional liquid spreading machinery.
5) Phosphorus and non-fertilizer phosphate industries - USEPA effluent
guidelines and standards have established the "non-fertilizer"
terminology to encompass the manufacture of certain phosphorus-
derived chemicals that are widely used for purposes other than
soil fertilization. This broad industry category includes the pro-
duction of phosphorus and ferrophosphorus by smelting phosphate
ore; production of phosphoric acid, phosphorus pentoxide, phos-
phorus trichloride, and phosphorus oxychloride directly from ele-
mental phosphorus; production of sodium tripolyphosphate and
animal feed grade and human food grade calcium phosphate from
phosphoric acid; defluorination of phosphate rock by high tem-
perature and other treatments; defluorination of phosphoric
acid; and purification of sodium phosphates from wet process
phosphoric acid (the "wet process" is described in detail in
Section 1.3.2.4). The above processes produce products used
in such applications as human food additives and animal feed
supplements, plastics manufacture, metal treating, detergent
builders, and incendiary chemicals.
For the most part, the industry segments other than the phosphate
fertilizer industry will not be discussed further in these Guidelines. They
will, however, be referred to, due to the interrelationships of industry
segments.
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Mixed fertilizers are usually described based on their NPK formulation -
that is, on the ratio by weight of the percentage of nitrogen, phosphorous,
and potassium contained in the formulation. For example, the formulation
for a typical mixed liquid fertilizer (ammonium polyphosphate) is 11-37-0,
meaning that 11% of the weight is nitrogen, 37% is phosphorus (expressed as
P»0 equivalent), and none is potassium. These ratios are also referred to
as "nominal grades" based on their identification of the percentages of
each primary nutrient irrespective of the type of chemical compound in
which each may occur.
The NPK formulation is not a descriptor normally used for the basic
phosphate fertilizer chemicals with the exception of ammonium phosphates.
Because of their economic importance as an intermediate to numerous bulk
blended and liquid fertilizers and because the production processes for
ammonium phosphates are commonly performed in phosphate fertilizer complexes,
effluents from these processes are frequently combined with the waste
streams from other phosphate fertilizer processes and treated together.
For these reasons, ammonium phosphates are covered under phosphate fertilizer
industry effluent and emissions guidelines rather than those for mixed
fertilizer industries, and are included in this Guidelines document.
For phosphate rock and its products the phosphorus content is commonly
expressed in one of four ways:
• BPL (bone phosphate of lime or tricalcium phosphate - Ca~(PO,)9)
• Phosphorus pentoxide (Vj0^
• Elemental phosphorus (P.)
• Phosphoric acid (H-PO,)
The common industry practice is to report all phosphorus-containing
materials in terms of the equivalent content of phosphorus pentoxide (P-0,.).
That practice is used throughout this document, unless otherwise stated.
The table below illustrates the relationships among the four sets of
units:
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Conversion factors for phosphorus content units.
To convert from To Multiply by
H3P04 % P 0.316
H3P04 % P205 0.724
BPL % P 0.1997
BPL % P205 0.4576
P20_ % H3P04 1.381
P205 % BPL 2.1853
Source: U.S. Environmental Protection Agency. 1979a. Source assessment:
Phosphate fertilizer industry. Office of Research and Development, Washing-
ton, B.C. Prepared by Nyers, J.M., G.D. Rawlings, E.A. Mullen, C.M. Mos-
cowitz, and R.B. Reznik, Monsanto Corp., Dayton OH, 201 p.
For example, orthophosphoric acid (phosphoric acid concentrated to its
highest common H»PO, content) would be expressed as 75% H_PO,, 54% P^O,.,
and 24% P.
1.1 SUBCATEGORIZATION
Effluent Guidelines and Standards (commonly called "effluent guide-
lines") are established by USEPA for specified pollutants which are regulated
at specified allowable levels for various industry segments (Point Source
Categories). In the Code of Federal Regulations USEPA sets forth effluent
guidelines under Part 418 for the Fertilizer Manufacturing Point Source
Category (40 CFR 418). This Guidelines document applies only to Subpart A,
Phosphate Subcategory, of 40 CFR 418.
The provisions of the Phosphate Subcategory apply to discharges resulting
from the manufacture of :
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sulfuric acid by sulfur burning;
wet process phosphoric acid;
normal superphosphate;
triple superphosphate; and
ammonium phosphates.
The five regulated processes represent those processes which, due to
either the character or the quantity of their wastes, produce effluent
streams capable of significant environmental degradation, as identified in
the Development Document for the Fertilizer Manufacturing Point Source
Category (USEPA 1974a). There are four additional processes (described in
Section 1.3) for which either no waste stream is normally produced or the
waste stream is regulated under one of the other processes with which it is
closely associated. The nine basic processes can be described as follows:
• Sulfuric Acid by Sulfur Burning is the dominant process in the
United States. Virtually all plants use sulfuric acid to treat the
raw phosphate rock (acidulation) and produce phosphoric acid.
Sulfuric acid is usually produced on the premises by burning molten
sulfur in the presence of air to produce SO. gas. In the usual
process, known as the "contact process," the SO2 is further oxidized
to form SCL using a catalyst contact surface. The sulfur trioxide
(S0») gas is then hydrolized in a number of steps by the addition
of water to form sulfuric acid (H_SO,) of the required concentrations,
• Phosphate Rock Processing - Crushing, Grinding, and Screening
reduces the phosphate rock feedstocks to sizes optimal for reaction
in further processes. This operation may be performed at a pro-
cessing plant associated with the mine, at a central point in a
fertilizer plant, or as a beginning operation feeding into another
process.
« Normal Superphosphate Production is a process which was initially
developed more than a century ago. Ground phosphate rock is reacted
with sulfuric acid to produce a water-soluble but, by today's
standards, low analysis phosphate.
» Wet Process Phosphoric Acid Production is the foundation of the
phosphate fertilizer industry. Ground phosphate rock and sulfuric
acid are reacted to form phosphoric acid and to precipitate calcium,
sulfur, and other unwanted materials in insoluble forms that can be
separated from the acid. The product, when completely processed,
is an intermediate used to produce high analysis fertilizers.
• Phosphoric Acid Concentration is a continuation of the processing
of wet process phosphoric acid whereby water is removed to improve
concentration and reactability of the. acid and also to improve
shipping and storing efficiencies when sold as a product.
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• Phosphoric Acid Clarification completes the processing of wet
process phosphoric acid. Solids are caused to floculate or precipi-
tate and are separated to avoid later problems in storage and
handling. If not removed early in the production of the acid,
solids will precipitate out as the acid ages in forms and locations
that can incapacitate handling and process equipment.
• Superphosphoric Acid Production is a process to remove additional
water and further concentrate the P?0, equivalent content of phos-
phoric acid. The product is used in production of certain high
analysis fertilizers.
• Triple Superphosphate Production reacts phosphoric acid with
phosphate rock to produce a high analysis -solid fertilizer which
can be applied directly or can be used as a feedstock in the pre-
paration of high analysis mixed fertilizers.
• Ammonium Phosphate Production yields highly concentrated sources
of water soluble plant food which combine nitrogen and phosphorus
in a single granule. The product is less bulky than dry mixes of N
and P straight fertilizers, and easy to apply and handle due to the
granular form in which it is usually produced. The granular form
mitigates caking and dust problems. In addition, ammonium phosphates
are more profitable to produce than some other products such as
triple superphosphates.
As a chemical category, ammonium phosphates include monoammonium phosphate
(MAP), diammonium phosphate (DAP), and a vast range of other ammoniated
phosphates containing different ratios of ortho- and polyphosphate molecular
components called collectively ammonium polyphosphates (APP). MAP and DAP
are the "ammonium phosphates" included in the regulated processes of the
Phosphate Subcategory (40 CFR 418). APP's are regulated under Subpart G,
Mixed and Blend Fertilizer Production Subcategory. The essential distinction
is that MAP and DAP are included in the Basic Fertilizers Phosphate Subcategory
because they are produced at the same plants as the other basic phosphate
fertilizer materials, even though they are technically mixed, containing
both N and P nutrients. APP's on the other hand are produced in the numerous
mixing plants in areas of application throughout the country. APP's are
produced by reacting superphosphoric acid and ammonia or, in recent process
improvements, phosphoric acid and ammonia, which are basic or straight
fertilizer materials shipped into the mixing plants from basic fertilizer
manufacturers.
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1.2 MARKETS AND DEMANDS
The markets and economics of fertilizer use indicate a worldwide trend
toward increasing overall demand on which are superimposed sometimes widely
fluctuating market conditions from year to year. Demand is expected to
continue increasing, but a host of variables confound the best efforts of
industry experts accurately to predict short-term specific product demands.
Despite these uncertainties, and allowing for reluctance by industry spokes-
men to announce expansion plans before commitments are firm and site proper-
ties secured, the phosphate fertilizer industry appears to be increasing
long-range production capacities.
United States demand for phosphates has grown steadily since World War
II with rapid growth since 1965. Growth has been based on the farmer's
need to maximize yield, but the market has been stimulated by the development
of new fertilizer products which make application easier and less costly.
Mixed fertilizers account for 85.18% of current phosphate fertilizer consumption
(TVA 1979). These products incorporate a balance of NPK nutrients in a dry
blend or liquid mix, and also can include sulfate, micronutrients, lime,
soil conditioners, and pesticides. Thus, with timed release coatings,
fertilization and pest control that used to require several operations, can
be done at one time. In addition, local plants market soil analysis services
as part of their product. Fertilizers are blended in these plants to
supply the needs of the particular soil, and the company delivers and may
even apply the fertilizer mix.
Production and consumption patterns of phosphate rock products are
decidely toward a continuing concentration in wet process phosphoric acid
production, which reflects the market for concentrated P~0 content and
mixed and blend final fertilizer products. Rock consumption in normal
superphosphate (NSP) declined sharply in 1978. NSP is a product of low
H?2®5 content and diminishing importance, which is now manufactured primarily
in small, low technology plants in close proximity to the sales area. NSP
is used primarily as a direct application fertilizer or as a constituent in
some dry blended fertilizers. Production of triple superphosphate has
remained at a level of 5% to 6% of total phosphate fertilizer production,
10
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for use in dry blended fertilizers primarily. The most recent production
figures for phosphate rock and P^O- content are broken down by product use
in Table 1.
Largely through the efforts of the United Nations Food and Agriculture
Organization (FAO), the United States Agency for International Development
(AID), the Tennessee Valley Authority (TVA), and other United States institu-
tions and businesses, overseas interest in fertilizer use has grown into a
substantial market. The effectiveness of fertilizers has been a foundation
for many achievements of the "green revolution" in agriculture. That plus
the huge United States market and limited long-term United States supplies,
have brought new foreign competitors into the phosphate fertilizer field.
Among them, Morocco stands alone as the potential "Saudi Arabia" of phosphate
rock. With proven reserves of at least 10 billion tons of phosphate rock,
Morocco holds 62.2% of the 16.065 billion-ton world reserve, which is based
on economically recoverable rock at 1974 prices. The United States holds a
reserve of roughly 2.5 billion tons. Furthermore, the Moroccan reserve may
be as large as 40 billion tons (Stowasser 1975). From 1964 to 1973, the
United States exported approximately 23% of domestic production (Stowasser
1977) and accounted for roughly 38% of world production (USEPA 1978b).
The USSR and Morocco accounted for approximately 20% and 17%, respectively,
of world production, and both countries are currently increasing production
capacity. More recently, figures for United States phosphate exports,
excluding phosphate rock, show increases in United States exports (Harre in
TVA 1978a) (Table 2 and Figure 1).
Despite recent improvements in the United States export market, pro-
ducers are accustomed to unprofitable periods of one or more years as large
fluctuations have traditionally occurred in both exports and domestic
consumption. The markets are extremely sensitive to price, as was indicated
in 1975 when inventory buildup of phosphate rock abruptly exceeded demand
after five years of short supply (TVA 1977a). This sudden lack of sales
was due to higher prices set by the industry to offset costs of recent
capital expansion. In that instance, Morocco cut prices drastically to
stimulate sales, and United States suppliers were forced to follow suit.
The most recent summary of production and dollar values of U.S. phosphate
rock is given in Table 3.
11
-------
Table 1. Phosphate rock sold or used by producers
in the United States for all uses (1000 metric tons).
1977
1978
Use
Domestic:
Wet process phosphoric acid
Normal superphosphate
Triple superphosphate
Def luorinated rock
Direct applications
Elemental phosphorus
Ferrophosphorus
Total (1)
Exports
Grand Total (1)
Rock
27,024
913
1,852
298
36
3,904
180
34,207
13,230
47,437
P2°5
Content
8,377
283
587
99
7
1,011
46
10,410
4,251
14,660
Rock
29,322
- 298
1,781
193
39
4,371
200
36,204
12,570
48,774
P2°5
Content
9,000
93
571
65
7
1,135
52
10,923
4,025
14,948
(1) Data may not add to totals shown because of independent rounding.
Source: U.S. Department of the Interior, Bureau of Mines. 1979. Mineral
industry surveys, phosphate rock - 1978. Washington, D.C. 6 p.
12
-------
Table 2. Phosphate trade - U.S. and world.
World
U.S.
Year
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
Total
consump-
tion
10,578
11,311
12,675
13,955
14,949
16,111
16,957
18,175
18,818
19,844
21,096
22,440
24,114
22,653
24,129
26,479
Total.
trade
1,275
1,328
1,560
1,683
1,802
2,049
2,650
2,554
2,634
2,630
3,343
3,891
4,117
4,151
3,799
4,337
Trade as
% of
consumption
12
12
12
12
12
13
16
14
14
13
16
17
17
18
16
16
Total.
trade
257
248
363
392
400
713
1,039
902
767
815
999
1,264
1,347
1,498
1,974
2,268
Trade as
% of
world trade
20
19
23
23
22
35
39
35
29
31
30
32
33
36
52
52
1. 1,000 metric tons of P^
Source: Harre, E.A. and H.A. Handley. 1978. World fertilizer trade and
the U.S. market outlook. _In_ Situation 78, TVA Fertilizer Con-
ference. National Fertilizer Development Center, Bulletin Y-131,
Muscle Shoals, Alabama, p. 17-24.
13
-------
MILLION SHORT TONS OF P,0, •
/
/
Figure 1. U.S. phosphate fertilizer exports.
Source: Harre, E.A. and Hazel A. Handley. 1978. World fertilizer trade and
the U.S. market outlook, Situation 78, TVA Fertilizer Conference, August 15-
16, 1978, St. Louis, Missouri. Bulletin Y-131. National Fertilizer Develop-
ment Center, Muscle Shoals AL, 83 p.
80
i 60
£
I
20
10
1930
1985
1990
1995 2000
YEAR
2005
2010
2015
2020
Figure 2. Phosphate rock supply - demand projections.
Source: Adapted from Stowasser, W.F. 1977a. Phosphate rock, the present and
future supply and demand. Letter from U.S. Bureau of Mines to R.E. McNeill,
USEPA, Region IV, February 18 in USEPA 1978b.
14
-------
Table 3. Marketable production of phosphate
rock in the United States, by region.
(1000 metric tons and 1000 dollars)
1977:
Fla. & N. Carolina
Tennessee
Western States
(1)
Rock
40,575
1,747
4,934
P2°5
Content
12,679
442
1,440
$Value
718,393
14,253
89,011
Total 47,256 14,561 821,657
1978:
Fla. & N.
Tennessee
Carolina
Western States (1)
43,258
1,709
5,070
13,421
442
1,469
817,165
14,047
97,608
Total 50,037 15,332 928,820
(1) Includes Alabama, California, Missouri, Montana, Utah,
and Wyoming.
Source: U.S. Department of the Interior, Bureau of Mines.
1979. Mineral industry surveys, phosphate rock -
1978. Washington, D.C. 6 p.
15
-------
Projections of United States production and consumption (Figure 2) of
phosphate rock indicate that Tennessee production* will terminate around
1990. North Carolina production is expected to grow slowly through 1985 and
then increase rapidly to a maximum mining rate of 20 million tons by 2000.
This will occur as the Florida production rate is expected to reach a
plateau of 48 million tons between 1985 and 1990 and then to decline as
higher grade ores play out and production turns to lower grades. The
western states' production is expected to increase slowly and continue
steadily at approximately 8 million tons per year (USDI 1977). It seems
likely that the United States will become a net importer of phosphate rock
early in the 21st century.
1.3 PROCESSES
1.3.1 Background Information
1.3.1.1 The Development of Modern Fertilizers - Historical Perspective
The use of fertilizers has from early on been closely interrelated for
the three primary plant nutrients - nitrogen, phosphorus, and potash. In
1840, Justus Liebig published results of his investigations into the elements
plants need as nutrients, and laid the foundations of fertilizer science.
Liebig identified ammonia (as ammonical liquor from coal gas, treated with
gypsum), potash (from wood ash), and phosphorus and lime (from the treatment
of ground bones with sulfuric acid), as well as other elements beneficial
to plants. Liebig also described the ability of superphosphate to fix
ammonia (superphosphate is the product of treating phosphate rock with
sulfuric acid). By 1853, 14 firms in England, one in Austria, and three in
the United States were producing "superphosphate of lime" by acidulation of
bone meal (Russel et al. 1977). The search for other sources of phosphorus,
as bones became an undependable supplier, led eventually to phosphate rock
deposits, but superphosphate remained the dominant P fertilizer for more
than 100 years.
*
Tennessee production is used for "furnace grade" phosphoric acid and
elemental phosphorus and does not figure in as fertilizer production.
16
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The United States Government established ammonia plant facilities and
laboratories at Muscle Shoals, Alabama, in 1918 to produce synthetic ammonia
needed in the World War. In 1933, the TVA was established as a regional
resource development agency. TVA's mandate included the national responsi-
bility for improving fertilizer manufacture and use through research,
development, and education programs. During World War II, the ammonium
nitrate was made available for fertilizer use, and TVA intensified develop-
ment of other fertilizer materials, including improved phosphate fertilizers.
Because of its role in education, through its National Fertilizer Development
Center, TVA has been a catalyst in developing both new fertilizer materials
and processes, and the markets and demands to utlize them. The Fertilizer
Institute (TFI), based in Washington, D.C. has been active as a forum for
discussion and dissemination of industry views and technical developments,
and has recently become involved in symposia on environmental regulations
and pollution control technology.
1.3.1.2 Phosphate Rock Mining and Processing
The phosphate mining industry is not included in the subject matter of
this document. Since most phosphate rock mined, however, is used for
production of fertilizer materials, most mining operations include phosphate
fertilizer processing in their corporate activities. For example, of 34
major phosphate industry operations in the large Central Florida District,
18 perform processing of phosphate fertilizer or animal feed grade products
(USEPA 1978b). Examined by company organization, the vertical integration
is even more apparent. Many of the mining/beneficiation operations are
owned by one parent company which may hold as many as three mining operations
dedicated largely to supplying feedstocks for one or more processing plants
of the same parent company. Mining and processing are briefly described
below to assist the reader in distinguishing between the mining and manufac-
turing functions in an integrated facility-
After any prospecting and mining claims are complete, the mining
operation concentrates on matrix or ore extraction and beneficiation of the
ore. Figure 3 is a map showing the locations of the major phosphate deposits
in the United States. Ore is actually mined in only four areas - Florida,
North Carolina, Tennessee, and several western contiguous states.
17
-------
NUMEROUS SCATTERED FIELDS
OF PHOSPHATE ORES
Figure 3. Location of major phosphate rock deposits
in the United States.
Source: Stowasser, W.F. 1977. Phosphate - 1977. Publication No. MCP-2,
U.S. Department of Interior, Bureau of Mines, Washington, B.C., 18 p. in
USEPA 1979a.
18
-------
Extraction of the matrix or ore is done by different processes depend-
ing on the location and characteristics of the deposits. In Florida, which
accounts for roughly 78% of the United States production of phosphate rock,
deposits are alluvial. The phosphate-rich beds are a loosely consolidated
conglomerate of phosphate pebbles and clays, known as matrix. The thin
overburden deposits are unconsolidated sediments. Mining is conducted by
stripping overburden from the matrix desposits by use of electrically
driven "walking draglines" equipped with buckets of 20 to 65 cubic yard
capacities and booms of 165 to 275 feet (USEPA 1978b). In successive moves
of the draglines, matrix is removed and spoil from succeeding cuts is
sidecast. As the ore is removed it is stacked in a sluice pit where hydraulic
monitors (high-pressure water guns) slurry the ore into pumps for transport
by pipeline to the washing plant (USEPA 1978b). One recent alternative is
to remove oversize material near the mine pit and move dewatered and deslimed
(clay removed) matrix by overland conveyors to the washing plant (Timberlake
1978).
In North Carolina the process is basically the same. The North Caro-
lina deposits occur in interbedded phosphatic clays, limestones, and sands
(USEPA 1971) Hydraulic sluicing and transport are also used in North
Carolina where, as in Florida, level terrain and excellent pumping character-
istics make these methods feasible.
In Tennessee, the high grade brown rock deposits are a weathered
phosphatic limestone that occurs in a north-south belt across the state
(Figure 3). Deposits are concentrated in small pockets of phosphate sands
surrounded by silica sands. Mining is done by open pit methods. In Tennessee
and also the western states, however, overburden is removed well in advance
of actual mining operations (USEPA 1974a). Draglines and small power
shovels are used to mine the phosphate sand, which is hauled by truck or
rail to the processing plant.
In the western United States, phosphate deposits are mined in Idaho,
Montana, Wyoming, and Utah, and account for 14% of United States production
(Harre 1976). Western deposits are "hard rock" (consolidated) layers,
with degree of hardness generally decreasing the farther north is the
location. Conventional earth moving equipment is used to remove 5 to 50
19
-------
feet of overburden. In Utah, the hard rock must be blasted with dynamite.
In softer rock areas, "rippers" are used, which are toothed machines that
gouge and break the rock from the surface. In Montana, two small underground
mines are operated, using the room-and-pillar method, which is a kind of
underground quarrying. Western rock is usually transported by rail to
processing plants.
Benef iciation is the upgrading of the ore by application of processes
to the mined matrix or ore to remove inert materials (such as silica sand)
or extremely fine materials that cannot be economically separted. Florida
and North Carolina beneficiation processes vary from plant to plant, depending
on grade, size, and ratio of pebbles to fines. A generalized procedure
starts with washing. The matrix slurry (20 to 50% solids) is passed through
a series of screens, mills, and washers which break down the matrix to
separate phosphate-bearing pebbles from sand and clays. Coarse screening
obtains a first fraction of oversize phosphate ore. Further processing of
the remaining matrix is done by cyclones to remove very fine sands and
colloidal size materials. These are pumped to settling ponds and the re-
maining fraction undergoes a series of flotations (with tailings going to
settling ponds) and finally the ore is dried. Some ore is ground and
stored in silos, from which it is transferred to railroad hopper cars for
transport (USEPA 1978e).
Tennessee ores are beneficiated by a similar process, except that all
water is added at the beneficiation plant since matrix is received dry, and
cyclones are operated in a water medium rather than air. A further step
for most Tennessee ore is nodulizing in kilns, which prepares the ore for
use in electric arc furnaces for production of elemental phosphorus (USEPA
1978d).
Western ore beneficiation starts with crushing and/or scrubbing.
Subsequent sizing is done by further crushing, grinding, and size classi-
fication. Very fine and colloidal size materials are discharged to a slime
pond or thickened for storage as a solid waste. The product is dried or
may be calcined before shipment as a product.
20
-------
Calcining is an operation done on some phosphate rock which is high in
organic content or which will be used in processes requiring higher phos-
phate content. The rock is subjected to temperatures of 650-975 C
(1200-1800 F) in rotary drum calcining units (USEPA 1978b). Organics are
destroyed and tramp iron materials are removed magnetically. Because of
the high energy demands of calcining, it is not done as routinely as it was
in the past. Alternate methods can be used in some cases to remove impuri-
ties in later processes.
The product of the above processes, ground beneficiated phosphate rock
or concentrate, is the raw material for a number of basic fertilizer and
phosphorus chemical processes. Additional grinding may be performed after
transport, or farther along in the plant complex. The beneficiation pro-
cess produces slurry effluents that have caused notorious pollution problems
in the past in the form of phosphatic clay slurries, or slime ponds. The
magnitude of the disposal problem is indicated by the fact that approximately
one ton of slimes (dry weight) is produced per ton of beneficated phosphate
rock (USEPA 1977b). Just one of the larger mining operations in Florida
produces 111.4 billion gallons per year of slimes, with up to 45% by weight
-0.5 microns in size. These slimes are typically only 5% solids by weight
(Hocking 1978). Florida slimes are usually about 70% water after 15 or
more years' dewatering and occupy, therefore, more volume than the original
matrix from which they were derived (White et al. 1978).
1.3.2 Major Processes of Phosphate Fertilizer Manufacture
The phosphate fertilizer industry utilizes nine separate processes, as
discussed in Section 1.1. Figure 4 shows the relationships of basic,
intermediate, and final product materials involved in phosphate-containing
fertilizers. The two important basic processes are sulfuric acid (H SO,)
production and wet process phosphoric acid production. Sulfuric acid is
produced and reacted with prepared phosphate rock to form either NSP or wet
process phosphoric acid. NSP is used primarily as a direct application
material or as a constituent in dry blended fertilizers.
21
-------
PHOSPHATE ROCK
V°4
NORMAL
SUPERPHOSPHATE
TRIPLE
SUPERPHOSPHATE
¥°4
PHOSPHORIC
ACID
PHOSPHATE FERTILIZER PRODUCTS
AMMONIUM
PHOSPHATES
Products not included in the
phosphate fertilizer subcategory
Figure 4. Schematic diagram of phosphate fertilizer industry.
Source: Adapted from U.S. Environmental Protection Agency. 1971. Inorganic
fertilizer and phosphate mining industries, Water pollution and control.
Prepared by Battelle Memorial Institute, Richland WA, 226 p. ^.n USEPA 1979a,
22
-------
Wet process phosphoric acid is concentrated and clarified to product
strength and is used to produce triple superphosphate or mono- or diamraoniura
phosphate. Alternately, wet process phosphoric acid can be further concentrated
and impurities removed to form superphosphoric acid (SPA). Wet process
phosphoric acid is also used in production of blend fertilizer products or
sold to other industrial users. The concentration of wet process phosphoric
acid to form SPA is a process not specifically included in the phosphate
fertilizer effluent guidelines Development Document (USEPA 1974a). Because
of specialized operations and problems, however, and because the process is
done only at plants also producing phosphoric acid (utilizing common waste
streams, utilities, and pollution controls), a description of the superphos-
phoric acid manufacturing process is included.
In Figure 4, the product blocks with hatching represent mixed or blend
fertilizers which are not covered in these Guidelines. The ammonium phos-
phates are technically mixed fertilizers because they contain more than one
of the basic plant nutrients, but they were included in the subcategori-
zation for phosphate fertilizer manufacture (and in this document) because
~-\
they are normally produced in the same facilities as basic fertilizer
materials and contribute to the same waste streams (By telephone, Dr.
Elwood Martin, USEPA, January 26, 1979).
The phosphate fertilizer industry is remarkable for the degree of
integration maintained among the processes at a typical installation. Con-
sequently, the majority of the United States production is carried on at
plant complexes, and the wastewater and gaseous effluents have largely been
channeled into combined streams with common treatment systems to the extent
this is feasible, or unless contaminants from certain processes may produce
conditions more costly to treat at a later point.
The integrated character of the industry can be appreciated with
reference to Table 4. The table shows that of the 114 plants in operation
(in 1976) over 70% produce one type of phosphate fertilizer material only,
and less than 30% of the plants consist of multiunit operations. Those
relatively few multiunit plants, however, account for more than 80% of the
total volume of phosphate fertilizers (USEPA 1979a).
23
-------
Table 4. Description of phosphate fertilizer complexes in the
United States by unit operations.
Unit operations
at plant site
WPPA only
NSP only
DAP only
WPPA, SPA
WPPA, NSP
WPPA, TSP
WPPA, DAP
NSP, TSP
WPPA, TSP, DAP
WPPA, SPA, DAP
WPPA, NSP, TSP
NSP, TSP, DAP
WPPA, SPA, TSP, DAP
WPPA, NSP, TSP, DAP
SPA, NSP, TSP, DAP
TOTAL
Number of plants
with this combination
7
54
20
3
1
2
10
1
6
2
1
1
4
1
1
114
Percent
of total
6.1
47.3
17.4
2.6
0.9
1.8
8.8
0.9
5.3
1.8
0.9
0.9
3.5
0.9
0.9
100
WPPA - Wet process phosphoric acid.
DAP - Diammonium phosphate.
NSP - Normal superphosphate.
SPA - Superphosphoric acid.
TSP - Triple superphosphate.
Source: US Environmental Protection Agency. 1979a. Source assessment:
Phosphate fertilizer industry. Office of Research and Develop-
ment, Washington, DC. Prepared by Nyers, J.M., G.D. Rawlings,
E.A. Mullen, C.M. Moscowitz, and R.B. Reznik, Monsanto Corp.,
Dayton OH, 201 p.
24
-------
In addition, although effluent guidelines apply to both single unit
and multi-unit operations, those standards were promulgated cognizant of
the operating procedures of the integrated complexes, in which contaminated
water is typically used for all processes where presence of contaminants is
not critical. For example, contaminated water is recycled for use in wet
scrubbers, to rinse precipitates from filters, and to supply barometric
condensers and heat exchangers (USEPA 1979a, USEPA 1974a). Each time the
water is recycled, the levels of contaminants are increased, but a key
point applicable to the process descriptions in the sections which follow
is that typically this contaminated wastewater is aot discharged from the
complex. It is a process effluent or wastestreara, but it is not a regularly
discharged effluent. The Source Assessment conducted by Monsanto researchers
during 1976 and 1977 (USEPA 1979a) revealed that only approximately 8% of
all phosphate fertilizer plants still routinely discharge wastewater.
These figures do not reflect, however, that most existing plants still
have the need to discharge water for certain periods of time during most
years. Because the recycled water systems are usually a series of large
outdoor ponds, extended heavy rains necessitate discharge of excess accu-
mulated water. Excess water can also develop due to occasional miscalcula-
tions or misadjustments- of chemical reaction processes, resulting in errors
in water management plans. In general, plant operators attempt to avoid
such discharge events due to USEPA and state requirements for pretreatment
of discharged wastewaters, at additional cost to the operators. Further
wastewaters from uses which are not involved in production processes (non-
process wastewaters) can be discharged continuously and in many cases are
kept separate from process wastewaters to effect economies in treatment
costs.
25
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1.3.2.1 Sulfuric Acid Production
Production of phosphoric acid by the wet process requires almost one ton
of sulfur (as sulfuric acid) for each ton of P205 produced. In the United
States virtually all sulfuric acid is produced by the contact process, which
represented 99.3% of total production in 1971 and had increased to 99.8% in
1976 (USEPA 1978a). Since New Source Performance Standards (NSPS) for S02
were promulgated in 1971, the "double" or "dual" absorption process has become
the system of choice because of its efficacy as a combined process option/emis-
sions control system that meets the NSPS for SO-.
All contact sulfuric acid manufacturing processes incorporate three basic
operations:
(1) burning of sulfur or sulfur-bearing feedstocks to form SCL;
(2) catalytic oxidation of S02 to SO ; and
(3) absorption of SO in a strong acid stream.
The least complicated systems burn elemental sulfur. Additional operations
are required to remove moisture, organics, and particulates prior to catalysis
and absorption when feedstocks such as spent acid and acid sludge are used
(USEPA 1978a).
Elemental Sulfur Burning Sulfuric Acid Production - Single Absorption
Elemental sulfur is the feedstock for sulfur burning contact process acid
for about 68% of total U.S. production (USEPA 1978a) and for sulfuric acid
produced at fertilizer plants for captive use it is the only feedstock in use
(USEPA 1977b, USEPA 1978b). The process is represented by the schematic flow
diagram, Figure 5.
In this process molten elemental sulfur is filtered and sprayed into a
dry air stream inside a furnace. Combustion air has been predried by passing
it through a drying tower containing 93.2-99% sulfuric acid. The high furnace
temperature auto-ignites the sulfur and oxidizes it to form SO^. This exothermic
26
-------
BLOWER
STEAM DRUM
SLOWDOWN •*-
STEAM JO
^ATMOSPHERE
BOILER CONVERTER
STORAGE
ACID PUMP
TANK
PRODUCT
Figure 5. Contact-process sulfuric acid plant burning
elemental sulfur - single absorption.
Source: U.S. Environmental Protection Agency. 1971a. Background information
for proposed new source performance standards. Office of Air Programs,
Research Triangle Park NC in USEPA 1978a.
27
-------
reaction releases large amounts of heat. The mixture of SCL and excess com-
bustion air (8-11% SO by volume) reaches temperatures of 980-1140 C (1800-
2000 F) as it leaves the furnace. It is cooled by being routed through a
boiler, where steam is generated and the temperature of the SO -air mixture is
reduced to an optimum temperature for chemical conversion of the SO^ to S0_.
The cooled S0? gas, together with predried air, then enters the solid
catalyst converter where it is converted to SO in a series of three or four
steps. Several different catalysts are available, but vanadium pentoxide is
the most commonly used. Each of the conversion steps takes place under a
different reaction condition to achieve optimum conversion of S02 to S0_. The
gas temperatures in each conversion stage rise until equilibrium is approached;
the gases are cooled after each intermediate stage as well as after the final
stage. The gas exiting the converter is cooled in an economizer (heat exchanger)
to temperatures between 230 and 260 C (450-500 F). At this stage S02-S0
conversion efficiency is about 98%.
Following conversion the SO gas is circulated upward through a packed
absorption tower. The tower contains ceramic packing with 98-99% sulfuric
acid (H SO,) circulating downward, counter to the gas current. The SO,, is
readily hydrolized to H-SO, by the water in the acid. Since the hydrolysis
reaction is also exothermic, the acid circulating from the tower flows through
cooling coils and then to the pump tank whence it is recirculated. The acid
strength and temperature are carefully regulated to prevent excessive SO,, re-
lease. Normally, absorption efficiency is essentially 100%.
The pump tank acts as a reservoir for process sulfuric acid. The en-
riched 98-99% acid enters the pump tank, and a portion is recycled through the
absorption tower. Also a portion of the acid is cycled to the air drying
tower. In this operation the 98-99% acid is first diluted to approximately
93% and circulated through the drying tower, counter-current to the upward
circulating air. Moisture in the air is absorbed by the acid (slightly diluting
it further) and the dry air enters the furnace. The 93% diluted acid returns
to the pump tank for mixing with the 98-99% acid flowing in from the absorp-
tion tower. Product acid is the excess over drying tower and absorption tower
recycle requirements. It is diluted with water to the desired concentration
28
-------
(normally 93%) and is pumped to storage as the pump tank is monitored and
maintained at a constant level.
The basic requirements and functions of suIfuric acid production are
summarized in the following table:
Table 5. Sulfuric acid manufacture from elemental sulfur.
Input Materials
• Sulfur
• Air
• Water (make-up water)
Utilities
• Cooling water (process water)
• Electrical energy
• Filter acid
• Steam (production)
Waste Streams
• Tail gas (containing SO and acid mist)
• Cooling water blowdown
• Boiler blowdown
Product
e Sulfuric acid, which may be used for
—normal superphosphate processing
—wet process phosphoric acid production
—ammonium phosphate processing
—ammoniation/granulation/drying
—out of plant sales
Several terms introduced above are used repeatedly in industrial process
descriptions:
Make-up water is feed water that is of acceptable quality for utili-
zation within a process, including use as a raw material.
Process water is any water which, during the manufacturing process, comes
into contact with any raw material, intermediate, product, or by-product,
or with gas or liquid that has accumulated such constituents.
29
-------
Slowdown is the purge from the system of a small portion of the con-
centrated water (from a boiler or recirculating process stream) in order
to maintain the maximum level of dissolved and suspended solids in the
system.
Tail gas is the accumulated captive gaseous waste stream at the end of a
process.
Elemental Sulfur Burning Sulfuric Acid Production - Double ^sorption
The double absorption process, which was used partially as the rationale
for the SCL NSPS has become the control system of choice by sulfuric acid
manufacturers since the NSPS were promulgated in 1971. Because it is a very
widely utilized process option, rather than an add-on emission control system
such as an ammonia scrubber, it is described at this point and is referenced
in the Section 3.2 discussion of pollution control technology.
Figure 6 is a process flow diagram which incorporates the double absorp-
tion system. The essential feature that differentiates it from the single
absorption process is the addition of the second absorption tower. The second
tower is installed at a point intermediate between the first and final SCL-to-SCL
catalytic conversion steps. This second absorption process permits the achieve-
ment of a greater conversion of SO, to SO- and significantly reduces the
quantity of SO, in the effluent gas stream. Double absorption plants achieve
SO- conversion efficiencies of 99.5+% as compared with approximately 98%
efficiencies for single absorption plants. Wastewater effluents are the same
for either process in regard to quantities and contaminant levels.
In either process option, single or double absorption, the cooling tower
closed loop and the boiler for waste heat removal are standard systems.
Closed loop cooling systems function with forced air and water circulation to
effect water cooling by evaporation. Evaporation acts to concentrate the
natural water impurities as well as the treatment chemicals required to inhibit
scale growth, corrosion, and bacteria growth. Such cooling systems require
routine blowdown to maintain impurities at an acceptable operating level. The
blowdown quantity will vary from plant to plant and is dependent upon the
cooling water circulation system.
30
-------
98% ACID PRIMARY HEAT CONVERTER ECONOMIZER SECONDARY 98% ACID
ABSORBER EXCHANGER ABSORBER
Figure 6. Dual absorption sulfuric acid
plant flow diagram.
Source: U.S. Environmental Protection Agency. 1971a. Background information
for proposed new source performance standards. Office of Air Programs,
Research Triange Park NC in USEPA 1978a.
31
-------
"The type of process equipment being cooled normally has no bearing on
the effluent quality. Cooling is by an indirect (no process liquid contact)
means. The only cooling water contamination from process liquids is through
mechanical leaks in heat exchanger equipment. Such contamination does period-
ically occur and continuous monitoring equipment is used to detect such equip-
ment failures" (USEPA 1974a).
The boiler in the sulfuric acid process is the only steam generation
equipment operated in a phosphate fertilizer plant. Medium pressure (9.5-52
atm) steam systems are the most generally used (USEPA 1974a). No contamina-
tion of boiler water is caused by process gases, except minor amounts through
leakage.
Sulfuric Acid Production by Burning of Spent Acid and Other By-Products
Where spent acid, sludge, and similar feedstocks are employed, the pro-
cesses are more elaborate and expensive than sulfur-burning plants due to the
fact that the S0_ gas stream is contaminated. Sulfur from the Frasch process
(Sec. 1.3.3.1) is the usual raw material for sulfuric acid production for
phosphate fertilizer manufacture. By-product acid is not produced and seldom
used because of possible adverse effects of the impurities on the phosphoric
acid process (USEPA 1977b).
There have been instances of short supply of Frasch sulfur caused by
sudden increases in phosphate fertilizer capacity around the world (Slack
1968) but U.S. producers generally purchase sulfuric acid when necessary to
supplement in-plant production. Normally, other types of sulfur feedstock are
not utilized by the phosphate fertilizer industry.
1.3.2.2. Phosphate Rock Processing - Crushing, Grinding, and Screening
Beneficiated phosphate rock usually requires additional processing to
reduce the ore to the particle size range for optimal phosphoric acid pro-
duction. Crushing and grinding are done with ball, ring-roller, or bowl
mills, and with hammer mills. The first three are rotational mills where the
feed material is crushed and ground (respectively) by:
32
-------
(1) crushing among steel balls in a rotating compartment (a type of
"tumbling mill");
(2) crushing between a grinding ring and two or more rollers which
rotate orbitally around the outer surface of the ring;
(3) crushing between rotating rollers and the inner surface of a
grinding ring within a bowl shaped chamber.
Hammer mills operate by crushing material by impact and grinding. The hammers
(massive protrusions in a variety of shapes) project from a rotating shaft
which rotates in a housing containing grinding plates or liners (Perry 1969).
After the rock enters the mill system, flow through sizing and reclam-
ation circuits is by pneumatic means when dry grinding is performed. Air is
constantly exhausted from the mill system to prevent precipitation of moisture
released from the fractured rock and entrained rock particles are removed
usually by bag type filters before the air is vented to the atmosphere.
Figure 7 illustrates the process flow for rock grinding.
An alternative to this process is wet grinding of phosphate rock. It was
in the period of 1973-1975 that the first commercial installations were developed
for use in conjunction with wet process phosphoric acid production. The major
objective was to reduce energy requirements by eliminiating drying of the
rock. Wet grinding also eliminates the need for dry storage of incoming rock
and greatly reduces problems in collection and handling of dust. Wet grinding
is accomplished with the addition of small amounts of water to the feed, and
flow of ground rock to the phosphoric acid process is in the form of a slurry.
The wet grinding process is operating well in several installations and is
considered a promising recent technological advance. At one new source plant
the operator is planning to utilize wet phosphate rock without any grinding
(USEPA 1978p). In that instance at the proposed Swift Creek Chemical Complex
in Hamilton County, Florida, the operator will utilize phosphate ore from the
Hawthorn geologic formation, which occurs in sand-size particles unlike the
pebble-size ore in the central Florida Bone Valley formation and the massive
hard rock ores of western states.
33
-------
No wastewater effluents are produced by either dry or wet grinding. Only
small amounts of water (Figure 7) are utilized for indirect cooling of lubri-
cating oil and mechanical equipment. Exact amounts utilized for cooling in
wet grinding were not determined, but would also be very minor. The water
added to phosphate rock for wet grinding is incorporated into the process
reactants. The required basic materials for the phosphate rock grinding,
crushing, and screening process are listed in the following summary:
Table 6. Phosphate rock crushing, grinding, and screening.
Input Materials
• Phosphate rock, as mined for certain high grade ores, or beneficiated
• Air (not consumed; dry grinding only)
• Water (make-up water; wet grinding only)
Utilities
• Cooling water (process water)
• Electrical energy
Waste Streams
• Air (containing particulate phosphate rock)
• Cooling water (non-contaminated discharge; water has increased
temperature only)
Product
Ground phosphate rock (dry grinding)
Ground phosphate rock slurry (wet grinding)
Since phosphate rock being ground is for reaction in a particular down-
stream process or, in the case of some high grade ores, for sale to other
industries, the desired particle size varies according to ultimate use. For
example, most wet-process phosphoric acid in the United States is produced
from 35-mesh to 150-mesh particulate (0.4mm-0.09mm), the size of medium to
very fine sand. Standard practice has been to grind to the very fine sand
sizes to optimize chemical reaction of the phosphate rock. Energy is required
whenever size reduction is used to achieve these sizes (some sizing is first
accomplished by screening in the beneficiation process). Less energy is
34
-------
LEGEND
MAIN ROCK
MINOR ROCK
•MINOR AIR
EXHAUST AIR
PHOS. ROCK
COOLING WATER
(8~ 150 GAL/TON)
33 ~ 625 l/kkg
COOLING WATER
(8~ 150 GAL/TON)
33 ~ 625 l/kkg
TON = SHORT TON
kkg = METRIC TON
DUST
COLLECTOR
PRODUCT
Figure 7. Rock grinding (flow rate per ton rock)-
Source: Adapted from U.S. Environmental Protection Agency. 1974a. Develop-
ment document for effluent limitations guidelines and new source performance
standards for the basic fertilizer chemicals segment of the fertilizer
manufacturing point source category. Office of Air and Water Programs,
Washington DC, 168 p.
35
-------
required when less grinding is required, and at least one process, the Kellogg
Lopker process (Anonymous 1972a), is in use in England which requires less
grinding (90-95% -40 mesh). Depending on the phosphate rock source, some
portion of this sizing is accomplished by screening alone. No United States
plants are utilizing the Kellogg-Lopker process at this time.
1.3.2.3 Normal Superphosphate Production
Because of its low investment costs and ease of preparation, NSP is still
produced in small plants throughout the United States. The process involves
reacting phosphate rock with sulfuric acid to form monocalcium phosphate:
The monocalcium phosphate produced is water-soluble and the phosphate is
available to plant uptake in soil solutions. The calcium sulfate (gypsum) is
not separated from the monocalcium phosphate, which makes use of this ferti-
lizer more popular in areas of sulfur deficient soils.
Processes may utilize batch or continuous process modes with various
modifications, but the basic process operations do not vary. Figure 8 re-
presents a normal continuous process operation. Phosphate rock which has been
ground to 90% -100 mesh (0.15 mm.) is fed at a controlled rate to a mixer
where it is thoroughly mixed with 65-75% sulfuric acid. The acid-rock mixture
is a slurry which is discharged to a pug mill where additional mixing and
reaction takes place. The reaction is very rapid and exothermic.
A pug mill consists of a horizontal cylindical or trough shaped chamber
containing one or two rotating shafts fitted with short heavy paddles. The
slurry is fed into one end of the mill and is both cut through and forced
forward by the paddles until the slurry is discharged through an opening at
the other end of the mill. Residence time in the pug mill for NSP production
is two minutes or less.
From the mill the slurry discharges to a slow moving conveyor (continuous
den) where the reaction continues and the slurry stiffens to a plastic mass.
36
-------
SULFURIC ACID
WATER
U)
-J
PONF /"T.""3 ~
i D»\ /
PUG MI
! c
1
S r
CAL
\ 1
Z*t-f MIXER
LL
ONTINUOUS DE
CUTTERO^
'~O CONVEYOR ()
1
i
ES •*•
— -GROUND PHOSPHATE ROCK
i
EXHAUST GAS
Nj
11
() CONVEYOR
i
i
"N
^>l
1
metric ton P205
WATER
*• GAS DISCHARGED
f
i
1 » WASTEWATER
0.9 to .0 m3
EXHAUST GAS metric ton P205
BUILDING * PULVERIZER » PROD
Figure 8. Normal superphosphate flowsheet.
Source: Adapted from U.S. Environmental Protection Agency. 1971. Inorganic fertilizer and phosphate mining
industries, Water pollution and control. Prepared by Battelle Memorial Institute, Richland WA, 226 p.
-------
(In batch processes the den is internally stationary, with no conveyor). Den
residence time varies from one to four hours. As the plastic mass leaves the
conveyor it is cut into chunks. At this stage evolving gases have given it a
honeycomb appearance.
The cut up product is transferred to a storage area, where it "cures" for
two to six weeks, depending on process conditions, as the slowing reaction
between rock and acid continues. If granulated final product is being produced
granulation is usually done before curing. Otherwise, when curing is complete
the solidified NSP is fed through a pulverizer (hammermill usually) where it
is crushed and screened.
Returning to the mixer and pug mill reaction, calcium fluoride contained
in the phosphate rock is also attacked by the sulfuric acid. This reaction
forms hydrofluoric acid (HF), which reacts with silica in the rock to form
SiF, plus water. This in turn reacts with some of the water to form fluo-
silicic acid (H SiF,) , but some of the SiF, is volatilized before reaction
with water can take place. The proportion of SiF, volatilized depends on
concentration of H SO, used. The higher the acid concentration the more SiF,
is evolved. SiF, is also evolved through the denning operation, with a small
amount forming during the curing step. In actual operations the mixer and den
are enclosed and emissions are scrubbed with water to remove fluorides and any
acid mist and dust particles. Air from the curing building is also circulated
through the wet scrubber to remove the smaller amounts of fluorides evolved in
that stage.
In integrated phosphate fertilizer complexes (producing phosphoric acid
and/or triple superphosphate and/or ammonium phosphates) the scrubber uses the
common contaminated water (or pond water) stream; that is, in most instances,
a closed loop wastewater circulation that does not usually require discharge
from the plant system. Solids removed or precipitated in this solution are
contained in the gypsum pond, or filtered out and stacked on the premises. In
smaller plants producing NSP only or primarily, the scrubber liquor is usually
run into beds of limestone to precipitate CaF_, which is considered to be a
solid waste (USEPA 1979a).
38
-------
The basic process constituents for NSP production are summarized below:
Table 7. Normal superphosphate production.
Input Materials
• Pulverized phosphate rock
• Sulfuric acid
• Water (make-up water to dilute sulfuric acid)
Utilities
• Electrical energy
• Scrubber water
Waste Streams
• Air (particulate phosphate rock, acid mist, fluorides)
• Water (process water) - the only process water involved is scrubber
effluent
• Solids - CaF and dust absorbed in scrubber effluent are precipitated
or allowed to settle out in gypsum ponds
Product
Normal superphosphate - generally sold as fertilizer or dry mixed
with other fertilizer materials and sold as solid mixed fertilizer
1.3.2.4 Wet Process Phosphoric Acid Production
Phosphoric acid is the most important intermediate manufactured by the
phosphate fertilizer industry because it is a basic ingredient to every pho-
sphate fertilizer product which the industry produces other than normal super-
phosphate and salable phosphate rock. Phosphoric acid can be produced by
either the digestion of phosphate rock with a mineral acid (wet process) or by
hydration of phosphorus with air in an electric furnace (thermal process). The
acid produced by the thermal process, which requires considerable energy con-
sumption, is known as furnace grade acid and is of higher purity than wet
process acid. Furnace grade acid is used for animal feeds, detergents, fire
retardant chemicals, and other industrial phosphorus products, but is no
longer used to produce phosphate fertilizers (USEPA 1979a).
39
-------
Wet process acid contains more impurities than does furnace grade acid,
and is known as merchant grade phosphoric acid. All phosphate fertilizer
production from phosphoric acid in the United States uses wet process acid.
The wet process is based on reaction of phosphate rock with a suitable strong
acid to produce phosphoric acid and an acid salt. The choice of strong acid
depends on such factors as cost and availability, simplicity of operation,
materials of construction and type of equipment required, and the waste streams
and end products generated. In the United States, sulfuric acid is far and
away the most widely used, but nitric and hydrochloric acid can also be used.
In 1973 98.77% of all wet process phophoric acid utilized sulfuric acid acidula-
tion, with 1.23% utilizing nitric acid and no plants using hydrochloric acid
(USEPA 1974a). Current data on type of acid used for acidulating phosphate
rock is not readily available, but no mention of commercial use of acids other
than sulfuric has been noted in references since the surveys done for the
USEPA Development Document (USEPA 1974a).
In general, nitric acid acidulation has been characterized by complex
multi-stage processes, requiring use of additional mineral acids and organic
solvents, with serious consequent corrosion problems. Furthermore, several
additional stages involving costly cooling, crystallizing of dissolved calcium
nitrate, and addition of additional reagents to precipitate calcium, results
in typically viscous phosphoric acid of 27 to 35% P-,0,.. Alternatives to
remove calcium cleanly require use of ammonia, which is itself an energy-
consuming somewhat costly product to manufacture. The simplest of nitric acid
acidulation processes utilizes ammoniation of the acidulated acid-rock solution
to produce nitric phosphate, a fertilizer material, but the phosphoric acid is
not obtained, having been present only in the solution, and some of the phosphate
becomes tied up in calcium phosphate, which is not water soluble and therefore
not useful as a fertilizer (Slack 1968). For such reasons, nitric acid acidula-
tion is not widely used and has normally been employed only when nitric acid
is a cheap or readily available coproduct in an industry. No further discussion
of nitric acid acidulation is warranted in this Guidelines document.
40
-------
Sulfuric Acid Acidulation of Phosphate Rock
The popular process of acidulation of phosphate rock with sulfuric acid
has the advantage of quick formation of calcium sulfate dihydrate, or gypsum
(CaSO,'2H20) . All acidulation processes produce gaseous and liquid effluents
which must be controlled, but disposal of the solid by-products formed poses
the most cumbersome potential problem. 1.76 metric tons of phosphate rock
concentrate (average 32% P2°5^ and lt53 metric tons of sulfuric acid (average
93% H2SO,) are reacted per metric ton of phosphoric acid produced (USEPA
1977b). Typically. 4.6 to 5.2 metric tons of gypsum by-product are formed per
metric ton of phosphoric acid (USEPA 1979a). Nonetheless, as described in the
discussion of nitric acid acidulation, the formation of a stable, filterable
by-product which does not take significant amounts of phosphate ion out of the
system is a distinct advantage.
Besides the dihydrate form, it is also possible with sulfuric acid diges-
tion processes to precipitate calcium sulfate as the hemihydrate (CaSO, '^H-O)
or the anhydrite (CaSO.) form. The dihydrate process has offered basic advan-
tages over the other two processes, such as less severe operating conditions,
lower rates of corrosion, better f ilterability , and lower capital cost.
Figure 9 shows the precipitation conditions for calcium sulfates in phosphoric
acid .
A flowsheet typical of the dihydrate process is shown in Figure 10.
Ground beneficiated or concentrated phosphate rock is fed continuously to a
reaction system where it is mixed with sulfuric acid. The sulfuric acid is
diluted, sometimes with contaminated process water, to a proper strength
depending on the process design and on phosphate rock composition to ensure
optimal dihydrate crystallization. Some commercial processes also recycle
some dilute phosphoric acid into the reaction system. Older plants may have
one or more digestion or attack tanks, but in more recent installations the
the reaction system is a single large compartmented tank. In this attack
vessel, the rock and acid react to form dihydrate (gypsum) and phosphoric acid
according to the following reaction:
41
-------
120
100
o
o
a:
on
LU
O-
60
40
20
HEMIHYDRATE
PRECIPITATED; ANHYDRITE
(CaS04) STABLE
DIHYDRATE(CaS04-2H20)
PRECIPITATED; ANHYDRITE
STABLE
DIHYDRATE PRECIPITATED
AND STABLE
10
20
_L
_L
30
40 50
ACID CONCENTRATION, PERCENT P205
60
Figure 9. Precipitation and stability of calcium
sulfates in phosphoric acid.
Source: Slack, A V. 1967. Chemistry and technology of fertilizers.
Wiley & Sons, Inc., New York NY, p. 69-97 in USE?! 1979a
John
42
-------
Vu4
PHOSPHATE 1
ROCK *1
D
HH 1 LK ~
RECYCLE fpLUOF
ACID J FUM!
4 1 '
iii
~p_
UDE '
IS
> VENT TO ATMOSPHERE
FLUORINE
Sf.RllRRFR
r WATER
i ! J
R
r— — WATER
: : 1 g
y
. 1 ,-
r
L
ACID
* UONCLNIkAlUK
GYPSUM SLURRY
TO GYPSUM POND
~ — WATER
-*• VENT TO ATMOSPHERE
FLUORINE
SCRUBBER
PHOSPHORIC
STORAGE
Figure 10. Wet process phosphoric acid flowsheet.
Source; Adapted from U.S. Environmental Protection Agency. 1971. Inorganic
fertilizer and phosphate mining industries, Water pollution and control.
Prepared by Battelle Memorial Institute, Richland WA, 226 p.
43
-------
To obtain complete reaction commercial processes mix or recirculate the
rock-gypsum-acid slurry through the tank compartments. The temperature in the
attack vessels is also controlled (usually at about 75 C) to ensure formation
of dihydrate. The reaction is exothermic, with higher heats produced when
more concentrated acids are used. Cooling water, vacuum coolers, air sparging
(flowing air through a liquid) and dilution and cooling of the acid are tech-
niques used to control process temperatures.
Retention time in the attack vessel varies with different process designs
from 3 to 8 hours. Efficiencies of commercial systems are usually in excess
of 96% extraction of VyO? from the rock. The recirculation of the slurry
controls the supersaturation necessary to attain good growth of gypsum crystals.
Th« gypsum crystals must be easily filtered and retain a minimum of P?0 •
Regardless of process design, the calcium fluoride constituent of the
phosphate rock ore will also react during acidulation to produce hydrogen
fluoride according to the following reaction:
CaF9 + H SO. +• 2HF + CaSO,
f- / H 4
In addition, calcium fluoride reacts with phosphoric acid according to the
reaction:
04)2 + 2HF
The hydrogen fluoride evolved may leave the slurry as a gas or it can react
with silica present in the phosphate rock:
SiO + 6HF * H9SiF, + 2H00
*• *• o 2
During the later acid concentration steps, fluosilicic acid (H2SiF6) in the
phosphoric acid solution can dissociate by the following reaction:
H2SiF6 -*-SiF4 + 2HF
The fluoride products formed can all volatilize and are major emission species
44
-------
in the contaminated emission stream. All reaction systems include a system to
pass evolved gases through wet scrubbers to remove fluorides, along with acid
mists and particulates.
Each system design varies as to the number and location of sgitaior.- or
recirculation mechanisms and in the locations and methods of phosphate rock
and sulfuric acid points. In the United States, approximately 75% of all wet
process reaction systems or "trains" use the Prayon or the Prayon/Dorr-Oliver
systems. Figures 11 through 14 illustrate schematically four systems using
different equipment, but the basic process and the resulting product and
by-products are essentially the same.
The acid slurry in all systems flows from the digester to a filter system
where the gypsum solids are removed. A typical filter system yields two
phosphoric acid streams:
a 30-32% P20 product stream;
an approximately 20% P90,- content acid stream which recycles to the
digestor.
Figures 15 and 16 illustrate the widely used tilting pan filtration system,
Slurry is discharged onto the filter and the undiluted mother liquor (product)
is collected and pumped to a surge tank, from which it is fed into the next
process (concentration).
The residual slurry on the filter pans is washed in three stages by a
continuous countercurrent stream to remove additional phosphoric acid. These
streams ultimately recycle into the digestor system and the filter cake is
washed from the filter by recycled contaminated water (gypsum pond water) and
pumped to the gypsum pond for cooling and solids settling.
Wet process phosphoric acid production conditions are shown in Table 3n
45
-------
WATER
93% H2S04
TO SEWER
WATER
STEAM
cJo cJo do cJo
-------
COOLING WATER
H2S04 ACID
WATER
DILUTER COOLER
' (OPTIONAL)
VAPOR TO -— c-s
FLUORINE RECOVERY I
CONDENSER AND VACUUM JJ- -
RECYCLE ACID
FROM FILTER
,-3 —. VAPOR TO
|[ FLUORINE RECOVERY
- II CONDENSER AND VACUUM
PRIMARY DIGESTER
SECONDARY DIGESTER
Figure 13.
Flow diagram for Singmaster and -Breyer
dihydrate phosphoric acid process.
WATER-
H2SO«
ROCK
HEMIHYDRATE
VACUUM
COOLER
PHOSPHATE Q
eivv —i V
NO. I REACTOR
HEMIHYDRATE
NO. I DIGESTER
GYPSUM
NO. 2 DIGESTER
GYPSUM
Figure 14.
Flow diagram of Singmaster and Breyer
hemihydrate-dihydrate process.
Figures 13 and 14 reprinted from Phosphoric Acid, Volume I, A.V. Slack, Editor,
by permission of Marcel Dekker, Inc., Year of first publication 1968.
47
-------
SLURRY
FROM -
REACTOR
Jt
WASH WATER
LIQUOR
TO MAIN
VACUUM PUMP AND
FUMES TO
WET SCRUBBER
1ST WASH
Y
2ND WASH
3RD WASH
FILTRATE
RECEIVERS
J L
Y Y
DISCHARGE CAKE
I I I
MULTI - COMPARTMENT FILTRATE SEAL TANK
I I
WEAK ACID
TO ATTACK TANK'
RECYCLE
WATER
- PROCESS
EFFLUENT
WATER
RECYCLE
• TO EVAPORATOR
TO GYPSUM POND
Figure 15. Tilting pan filtration system.
Source: U.S. Department of Health, Education, and Welfare. 1970. Atmospheric
emissions from wet process phosphoric acid manufacture. Raleigh NC, 86 p.
in USEPA 1979a.
CAKE WASHING
CAKE DEWATERtNG
FEED SLURRY
CAKE DISLODGING
AND DISCHARGING
Figure 16.
Operating cycle of rotary horizontal
tilting pan filter.
Reprinted from Phosphoric Acid, Volume I, A.V. Slack, Editor, by permission of
Marcel Dekker, Inc., Year of first publication 1968.
48
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Table 8. Wet process phosphoric acid production.
Input Materials
• Phosphate rock (ground)
• Sulfuric acid
Utilities
• Steam (from sulfuric acid process)
— for vacuum induction when vacuum flash coolers are used
- in stream ejectors to clean noncondesibles in systems using flash
coolers
• Cooling water
• Process water
• Electrical energy
Waste Streams
• Tail gas
- particulates of phosphate rock
- sulfur oxides and acid mists
fluorides
• Gypsum solids
• Contaminated water (from cooling and scrubbers)
Product
• Phosphoric acid (26-32% P^)
- this is an intermediate product
- product is too weak for either sale or for econimic use in
other phosphate fertilizer products
- product is passed to next process for concentration
Note: Fluorides and, to a minor extent, gypsum can also be treated as
recoverable coproducts. These products of pollution control systems
are discussed in Section 3.0.
1.3.2.5 Phosphoric Acid Concentration
The phosphoric acid produced in the sulfuric acid digestion process is
too low in concentration for sale or for processing of dry phosphate fertili-
zers. Concentration of the 26-32% P~0 phosphoric acid is accomplished by
49
-------
vacuum evaporation of water from the acid solution. The acid is circulated
through a shell-and-tube heat exchanger and then through a series of three
flash chambers under vacuum pressure conditions, each separated by a shell-and-
tube heat exchanger, as shown in Figure 17. The flash chambers or evaporators
provide comparatively large liquid surface areas where water vapor can be
released with minimum phosphoric acid entrainment.
Some of the phosphoric acid along with minor acid impurities, including
fluorides, volatilize with the water vapor. The evolved vapors pass to a
barometric condenser, where they are condensed and, arlong with condensed steam
and process cooling water, flow to a hot well. From the hot well the contami-
nated water is recycled back to the phosphoric acid reaction process, where it
is fed into the barometric condenser used with the acid flash cooler. Vapors
from the hot well are vented to the wet scrubber system.
The above process describes a tube-type forced-circulation evaporator. It
is the prevailing method currently in use, largely because it tends to generate
fewer air emissions than other methods. This is so because practically all
the vapors are condensed (Slack 1968). Operating conditions, however, are
harsh. The acid stream is very corrosive and special non metallic materials
must be used for construction. Precipitation of solids within the system is
also a chronic problem that has been partically solved but still prompts
continuous research and development of equipment and process modifications.
Efficiency of the process depends on composition of the feed and its level of
impurities, and on available utilities, such as cooling water and steam sources;
but a properly designed forced-circulation evaporator can recover over 99.5%
of the ?205 during concentration of acid from 30 to 54%.
Industry and process design engineers (Slack 1968) have noted that phos-
phoric acid concentration and clarification in most operations are now con-
sidered part of the phosphoric acid process. The utility streams are integrated
between and among the process units in most installations. Waste streams are
generally treated by the same equipment. Common scrubbers are used for the
emissions, and wastewater contaminants are incorporated into the common contami-
nated water system.
50
-------
PROCESS WATER
HEAT
EXCHANGER
STEAM
TO TO FILTER
GYPSUM CAKE WASH
POND
RECYCLED TO EVAPORATOR
FEED TANK OR
TO GYPSUM POND
STEAM
EVAPORATORS ( THREE IN SERIES )
VENT TO SCRUBBER
TO BAROMETRIC
CONDENSER IN
REACTION SECTION
VENT TO SCRUBBER
STORAGE
Figure 17. Concentration and clarification of phosphoric acid.
Source: U.S. Department of Health, Education and Welfare. 1970, Atmospheric emissions from wet-process
phosphoric acid manufacture. Raleigh NC, 86 p. in USEPA 1979a.
-------
The requirements for phosphoric acid concentration and clarification are
tabulated together in Section 1.3.2.6.
1.3.2.6 Phosphoric Acid Clarification
This process as currently practiced in the United States is often con-
sidered as a final stage to the concentration process rather than full scale
process. Physical treatment of the acid is used, rather than more expensive
solvent extraction methods as used in Europe and Mexico.
Impurities in wet process acid, such as iron and aluminum phosphates,
soluble gypsum, and fluosilicates form supersaturated solutions in 54% P^O
phosphoric acid, and will precipitate during storage. These precipitates
cause problems in unloading tank cars and further processing using the acid.
Recycled contaminated water is used to cool the acid to optimum temperatures
and the acid is stored in a detention chamber to promote precipitation of
solids. The precipitated impurities are then separated from the acid by
settling and/or centrifuging (see Figure 17). The resulting sludge is either
sent to the gypsum pond, processed into a low quality fertilizer, or recycled
to the evaporator feed tank. Recirculation of the sludge adds precipitated
solids to the evaporator feed, providing crystal surfaces in the acid. Since
salts coming out of solution during the evaporation process will tend to
deposit on these crystals rather than on evaporator surfaces, scaling is
reduced. The clarified acid is then stored at ambient temperatures (USEPA
1979a).
The basic requirements for the integrated concentration and clarification
processes of phosphoric acid are summarized in Table 9:
1.3.2.7 Superphosphoric Acid Production
Superphosphoric acid is produced by further concentration of the 54% P-O.
phosphoric acid to 66% or greater P^O^ equivalent. Concentration is either by
submerged combustion or by vacuum evaporation. The 54% P^Cv phosphoric acid
feed, from the wet process, is in the ortho form; that is, molecular composi-
tion is H.PO,. In the concentration process, elevated temperatures cause
molecular dehydration and molecules combine into polyphosphoric acid chains
52
-------
Table 9. Concentration and clarification of wet process phosphoric acid,
Input Materials
• Phosphoric acid (26-32% P^O^)
Utilities
• Steam (for vacuum condensers, heat exchangers, and flushing
barometric condensers)
• Process water (for barometric condensers and acid cooling)
• Electrical energy (blowers, pumps, and scrubbers)
Waste Streams
• Contaminated water (from cooling and condensers)
• Emissions (fluorides and acid mist from hot well)
• Acid sludge
Product
• Concentrated phosphoric acid (54% P2^5^' use<^ f°r
- salable product
- production of triple superphosphate
- production of ammonia phosphates
- further concentration to superphosphoric acid
- production of dry mixed and liquid blend fertilizers
• Acid sludge (potential coproduct for sale as low analysis fertilizer
if not handled as a solid waste)
53
-------
(USEPA 1979a). For example, tripolyphosphoric acid is formed by the following
reaction:
3H3P04 - H5P301Q + 2H20
Superphosphoric acid (SPA) is a mixture of orthophosphoric acid and poly-
phosphoric acid molecules of differing chain lengths. Wet process acid is
normally concentrated to 68.5 to 72% P^ by conventional processes.
Major impurities in wet process phosphoric acid'are calcium, iron, alumi-
num, magnesium, potassium, sodium, fluorine (HF, H2SiF6, SiF^), and sulfate.
These materials precipitate at different temperatures and acid concentrations,
but one overall effect is great potential for scaling and high viscosity. The
concentration processes used commercially are designed to restrict scaling and
clogging problems.
Submerged Combustion
This process takes advantage of an old maxim that "no scale can grow on a
bubble" and effects heat transfer primarily by bubbling a stream of hot com-
bustion gas through the phosphoric acid solution (Slack 1968). A study by
USEPA (USEPA 1974b) noted that this process is considered outmoded and unlikely
to be used in the future. In addition, gaseous emissions are highly polluting
and difficult to control. Currently, only two United States plants (accounting
for approximately 26% of SPA production) use submerged combustion (USEPA
1979a). The fact that submerged combustion also entails high energy consump-
tion in the form of natural gas, make it an unlikely option for new source
facilties.
Vacuum Evaporation
Seven plants in the United States (Section 1.5.1) produce SPA by vacuum
evaporation; four use the Stauffer falling film evaporator and three use the
Swenson forced circulation evaporator. The Stauffer process and the Swenson
process are shown in Figures 18 and 19. The basic processes have been described
by Rawlings, et al. (USEPA 1979a):
-------
WATER
HICH
PRESSURE
STEAM
FALLING FILM
EVAPORATOR
EVAPORATOR RECIRCULATION
RECYCLE PUMP
TANK
TO
SEWER
Figure 18. Stauffer process for wet process superphosphoric acid.
Source: Barber, J.C. 1979. Falling film evaporator process. Adapted from
TVA file drawings. Florence AL.
TO AIR EJECTOR
COOLIN9 WATER
HOT WELL
/
»v
WATER OUT
UJ
'
~l
DOWTHERM
HEATER
SURGE
TANK
F.C. EVAPORATOR
COOLINO
TANK
72%P205
ACIO STORAGE
Figure 19. Vacuum evaporation SPA concentration processes.
Source: Adapted from Rushton, W.E. 1966. Swenson superphosphoric acid
process. Phosphorus and Potassium No. 23, June/July, p. 13-16, 19.
55
-------
In the Stauffer process, clarified 54% P^O,. orthophosphoric acid is con-
tinously fed to the evaporator recycle tank where it mixes with superphosphoric
acid from the evaporator. Some of the mixture (approximately 1.2%) is drawn
off as product acid, but most (approximately 98.8%) is pumped to the top of
the evaporator and is distributed across the heat exchanger tube bundle. The
falling acid, heated by high-pressure steam condensing on the outside of the
tubes, evaporates. The vapors and dehydrated acid then enter the separator
section where entrained acid mist is removed. Product acid flows to the
recycle tank, and the vapor is drawn off, condensed in a barometric condenser,
and delivered to a hot well. Noncondensables are removed by a two-stage steam
ejector and are vented to the hot well. Superphosphoric acid flows to the
recycle tank where it is mixed with more 54% P?0c orthophosphoric acid, and
recycled or removed as product. The approximate recycle to feed acid ratio is
80:1. The product stream is cooled and stored before shipping. Both the hot
well and cooling tank are vented to wet scrubbing systems.
The Swenson process utilizes closed heat exchanger tubes filled with heat
exchanger fluid to provide the heat of reaction. Feed acid (54% P2°s) pumped
into the evaporating system mixes with recycled superphosphoric acid. As the
acid leaves the exchanger tube bundle and enters the flash chamber, evaporation
begins. Vapors are removed by a barometric condenser. Condensed materials
and noncondensed vapors are delivered to a hot well. Product acid flows
toward the bottom of the flash chamber where part (approximately 0.6%) is
removed to a cooling tank and the rest (99.4%) is recycled. An approximate
recycle to feed ratio is 150:1 (compared with 80:1 for the Stauffer process).
Cooling in both systems is accomplished by circulating water through
stainless steel tubes in the holding tank.
72% PoO, is the maximum concentration practical for commercial production
(Dinauer 1971). Any higher concentrations of wet process acid cause handling
problems including pump failure, valve and tubing breakdowns, and overheating
of motors, due to the viscosity of the fluid. The viscosity problems are
largely due to the impurities in wet process acid. Higher concentrations and
many non fertlizer uses of SPA therefore require either furnace acid deriva-
tion or costly extraction of wet process impurities before concentration.
SPA is used primarily in mixed liquid fertilizers, where it makes possible
higher analysis products. The polyphosphate molecules also sequester some of
the iron and magnesium impurities which attain their lowest solubility around
the 54% ?2®5 concentration level for wet process acid, and would cause handling
problems if in liquid fertilizers. Early anticipated marketing advantages of
SPA in reducing shipping costs as compared with less concentrated phosphoric
acid have not been realized due to its handling problems.
A summary inventory of the process requirements follows:
56
-------
Table 10. Superphosphoric acid production.
Input Materials
• 54% P~Cv phosphoric acid
Utilities
• Steam (from sulfuric acid process or auxiliary steam boiler)
• Electrical energy (pumps, circulators, blowers)
• Cooling water
• Natural gas (submerged combustion process)
Waste Streams
• Fluoride emissions
• Sulfur oxides
• Acid mist
• Combustion products (submerged combustion process)
Products
• Superphosphoric acid (68.5 to 72% P^O,.) , used primarily for production
of liquid mixed fertilizers
• Fluorine in the form of CaF or fluosilicic acid are recovered as
coproducts at some installations
Note: SPA production is normally included under existing effluent guidelines
for the phosphate fertilizer manufacturing subcategory. Since SPA is produced
at such facilities and since it can utilize the common contaminated wastewater
system, there is no contradiction implied in the fact that the process is not
specifically identified in effluent guidelines. It was not intended that the
process be excluded; it simply was not chosen to be addressed in the Develop-
ment Document for basic fertilizer chemicals (USEPA 1974a); By telephone. Dr.
Elwood Martin, USEPA, Effluent Guidelines Division, March 27, 1979).
57
-------
1.3.2.8 Triple Superphosphate Production
Triple superphosphate (TSP) is a high analysis phosphate fertilizer (46
to 48.5% P?0 content). TSP can be produced either as run of pile (ROP) or as
granular triple superphosphate (GTSP) . ROP and GTSP can be manufactured in
batch or continuous process modes. ROP triple superphosphate can be used in
hot-mixed fertilizers whereas GTSP is preferable for use in dry bulk blends or
for direct application. ROP, however, involves difficult air pollution prob-
lems due to dust and can cause materials handling problems if shipment is
involved. Most new plants are expected to produce the granular type TSP.
Both processes utilize the same raw materials, ground phosphate rock and
approximately 54% P^O,. phosphoric acid. The basic chemical reaction takes
place by the following reaction (USEPA 1974a):
3H20 — * 3Ca(H2P04)2 » H20
The overall reaction, taking into account the fate of fluorine in the fluora-
patite ore is as follows (USEPA 1971):
^)-»- lOCaH, (P04)2»H20 + 2HF
As is the case in normal superphosphate, the HF reacts with silica to form
SiF , which partially hydrolyzes to form fluosilicic acid (H SiF,) and is
partially evolved as gas. As with NSP, SiF, and H0SiF, are also evolved
*f 2. b
during denning, curing, and storage operations. The similarity between the
ROP and GTSP processes, however, does not go beyond the initial acidulation
operation.
Run of Pile TSP Production
The ROP process is virtually identical to the NSP process except that
phosphoric acid is used instead of sulfuric acid. Figure 20 shows a flow
diagram of the process. Batch mode is carried out in older plants, but con-
tinuous process mode is assumed for process discussion.
58
-------
CLARIFIED OR CONTAMINATED WATER
940 ~ 1040 l/kkg
(225 ~ 250 GAL/TON)
STREAM LEGEND
—— MAIN PROCESS
GAS
MINOR PROCESS
PHOSPHORIC ACID
PHOSPHATE ROCK
I
c
TON = SHORT TON
kkg = METRIC TON
TO ATMOS.
t
I
I
CONTAMINATED WATER
ROP ~ TSP TO CURING
(225 ~ 250 GAL/TON)
940- 1050 l/kkg
Figure 20. Triple superphosphate (run of pile) (flow rate per ton ROP).
Source: Adapted from U.S. Environmental Protection Agency. 1974a. Development document for effluent
limitations guidelines and new source performance standards for the basic fertilizer chemicals segment
of the fertilizer manufacturing point source category. Office of Air and Water Programs, Washington DC.
-------
Most facilities use the continuous cone mixer process developed by TVA in
the 1930's. Finely ground phosphate rock and 54% I^s phosphoric acid are
metered into the cone mixer. The acid enters the cone tangentially at high
velocity, setting up a swirling action that mixes the materials within seconds
(Dinauer 1971). The acidulate is discharged quickly onto a long rubber con-
veyor belt. On discharge, the slurry becomes plastic within 15 to 30 seconds.
The material is conveyed to a den (or, in many cases, the conveyor moves
through a continuous den) where large amounts of noxious gas are evolved and
vented to scrubbers. The mass hardens during this stage and takes on the
vesicular honeycomb appearance as described in NSP production. At the end of
the conveyor, the product is broken up in a rotary mechanical cutter before
being discharged to the storage area for an additional 2 to 4 weeks curing.
Product is crushed and sized after the curing period and processed for ship-
ping or for on-site use in mix fertilizers (USEPA 1974a).
Granular TSP Production
A number of plants produce GTSP by utilization of crushed or ground ROP
material and treatment with water and steam or with 38 to 40% P2°s Phosphoric
acid in rotating or agitating chambers (Dinauer 1971, USEPA 1971). Those pro-
cesses do not produce significant emissions because the major portion of the
fluorides were evolved in the original ROP manufacture (USEPA 1974b), but the
product quality is not as good as with one-step granulation process (USEPA
1977c), described below.
In the direct-slurry process (see Figure 21), the product is a hard,
uniform, pellitized granule produced in enclosed continuous process equipment
which facilitates collection and treatment of dust and fumes. The phosphoric
acid used is 40% p2(-)s' ratner than the 54% used in ROP manufacture. The acid
and ground phosphate rock are mixed together in an agitating tank. The lower
strength acid maintains the resultant slurry as a fluid and allows the chemical
reaction to proceed appreciably toward completion before solidification starts.
After 1-2 hours mixing the slurry is discharged onto recycled undersize dry
GTSP. This takes place in a granulator chamber - either a pug mill or a
rotating drum. Slurry-wetted GTSP granules then discharge into a rotary dryer
where the chemical reaction is accelerated and excess water removed by the
dryer heat. Dried granules are next sized on vibrating screens. Over- and
60
-------
STREAM LEGEND
i MAIN PROCESS
GAS
MINOR PROCESS
CLARIFIED OR CONTAMINATED WATER
660 ~ 750 l/kkg
(158 ~ 180 GAL/TON)
PHOSPHATE ROCK
f~
I
TON = SHORT TON
kkg = METRIC TON
r
3RANULATOR 1
I M
^
1
1
1
1
1
1
DRYER
-*>
DUST
RECOVERY
r
SIZING
CONTAMINATED
WATER
(5 ~ 10 GAL/TON)
21 ~ 40 l/kkg
GTSP OUT
Figure 21. Granulated triple superphosphate (flow rate per ton GTSP).
Source: Adapted from U.S. Environmental Protection Agency. 1974a. Development document for effluent
limitations guidelines and new source performance standards for the basic fertilizer chemicals segment
of the fertilizer manufacturing point source category. Office of Air and Water Programs, Washington DC.
-------
undersized granules are separated and used as recycle material. Product size
granules are cooled and conveyed to storage or shipped directly (USEPA 1974a).
Most plants allow curing for one to five days in a sheltered storage building,
during which some fluorides evolve, before shipping (USEPA 1977c).
In another popular one-step process developed by TVA, finely ground
phosphate rock and recycled fines are reacted with 54% phosphoric acid, but
steam is also introduced to accelerate the reaction and ensure an even mois-
ture distribution in the mix (USEPA 1977c).
A summary of the operating requirements for the direct-slurry GTSP pro-
cess is given below:
Table 11. Granular triple superphosphate production.
Input Materials
• Pulverized phosphate rock
• Phosphoric acid (40% P20 equivalent)
Utilities
Contaminated water (for scrubber)
Steam for reactor or rotary drier (some processes use reaction
heat for drying)
Electrical energy
Waste Streams
Emissions, off-gas from reaction and curing, containing fluorides
and acid mist; particulates of phosphate rock
Contaminated scrubber water
Products
• Triple superphosphate, granular or run of pile
- used in production of dry blended fertilizers
- used in production of fluid fertilizers
• Fluorine, in the form of CaF? or fluosilicic acid, are recovered
as coproducts by some manufacturers
62
-------
1.3.2.9 Ammonium Phosphate Production
Monoammonium phosphate (MAP) and diammonium phosphate (DAP) are basic
concentrated fertilizer materials containing N and P, used in bulk blend
fertilizers and to some extent for direct application. Ammonium polyphos-
phates, conventionally produced by reacting SPA with ammonia, are considered
to be mixed fertilizers and currently are used primarily in fluid fertilizers.
Although not included in the phosphate subcategory, APP processes and products
commonly include MAP and DAP production. For this reason a discussion of
APP's is included in this section.
Monoammonium Phosphate and Diammonium Phosphate Production
Ammonium phosphate fertilizers include a variety of formulations which
differ in the amounts of nitrogen and phosphorus present. In the United
States the most important grades are:
MAP: 11-48-0
13-52-0
11-55-0*
16-20-0
DAP: 16-48-0**
18-46-0
*15 to 25% P205 equivalent is APP (L.B. Nelson 1978 in TVA 1978a)
**approximately 1/3 MAP and 2/3 DAP (Dinauer 1971)
In a typical ammonium phosphate process 40% P-jOr phosphoric acid is
partially reacted wtih ammonia in a preneutralizer or reactor (see Figures 22
and 23). The resultant slurry is sprayed or dripped onto a bed of fine re-
cycled solids in an ammoniator-granulator. Additional ammonia is injected
under the bed to complete reaction and resulting granules are dried and screened,
with undersize material recycled to the ammoniator (Slack 1968a).
63
-------
CLARIFIED OR CONTAMINATED WATER
5000 ~ 6500 l/kkg
(1200 ~ 1500 GAL/TON)
PHOSPHORIC ACID
|
4r
£ — 1
1
1
_*J
i
f
. —
V V
SCRUB
NH,
NH3
VAPORIZER
GRANULATOR
TON = SHORT TON
kkg = METRIC TON
DUST
RECOVERY
T r
DRYER
STREAM LEGEND
MAIN PROCESS
GAS
MINOR PROCESS
TO ATMOS
. I
CONTAMINATED
WATER
(0~ 72 GAL/TON)
0 ~ 300 l/kkg
MAP TO STORAGE
Figure 22. Monoammonium phosphate plant (flow rate per ton MAP),
Source: Adapted from U.S. Environmental Protection Agency. 1974a. Development document for effluent limi-
tations guidelines and new source performance standards for the basic fertilizer chemicals segment of the
fertilizer manufacturing point source category. Office of Air and Water Programs, Washington DC.
-------
PHOSPHORIC ACID
*• GAS DISCHARGED
AMMONIA
OTHER MAT'LS
(OPTIONAL)
AMMONIATOR
GRANULATOR
Figure 23. Flowsheet for production of diammonium phosphate (DAP).
Source: U.S Environmental Protection Agency. 1971. Inorganic fertilizer
and phosphate mining industries, Water pollution and control. Prepared
by Battelle Memorial Institute. Richland WA, 226 p.
65
-------
Basic reactions are as follows:
H PO, + NH3 -»- NH4H2P04 (USEPA 197Aa) or,
(Phosphoric (Ammonia) (Monoammonium
acid) Phosphate)
HPO, + 2NH, -+• (NH.KHPO, (USEPA 197 7c)
34 J 4 z 4
(Diammonium
Phosphate)
A variation, to produce 16-20-0 MAP, utilizes sulfuric acid with the following
reaction, which occurs concurrently with the MAP reaction:
(sulfuric (Ammonium
acid) Sulfate)
The resulting MAP-ammonium sulfate combination usually also contains DAP.
Obviously, these reactions cross idealized product boundaries between straight
and mixed fertilizers, but traditional plant organizations include various
combinations of these processes in phosphate fertilizer complexes. Chemistry
and accurate analyses of some ammonium phosphates have been studied only in
recent years. Also, not all MAP produced is granular; MAP crystal is also
produced and crushed for use in granulation processes for mixed fertilizers.
In MAP production only one preneutralizer tank is used, as opposed to two
tanks which are used for DAP production.
Variations in ammonium phosphate production include use of nitric instead
of sulfuric acid, which in combination with phosphoric acid produces nitric
phosphate or ammonium phosphate nitrate. Another process arrangement allows
the neutralization reaction to go to completion in a series of tanks before
the product slurry is fed to a "blunger," which is a paddle mixer where granu-
lation is completed with the addition of dried recycled fines, (Dinauer 1971),
(USEPA 197 7b). Another variation injects phosphoric acid directly onto a bed
of recycled product fines in a rotary drum granulator and injects ammonia
under the bed of fines. In this arrangement, neutralization and granulation
66
-------
occur in the same piece of equipment. Heat of ammoniation evaporates water in
all these arrangements. (USEPA 1977b). In general, the end products are
varied by the acids used and the N content is varied by the degree of ammonia-
tion (Dinauer 1971).
Cyclone collectors and/or venturi scrubbers are used for dust and off-gas
recovery and recycle in most systems. Wet scrubbers are used for end-of-process
emissions control, using contaminated water. A summary of process requirements
is presented below for ammonium phosphates production including MAP, DAP, and
ammonium sulfates and nitrates:
Table 12. Ammonium phosphate production.
Input Materials
• Anhydrous ammonia
0 Phosphoric acid (30-52% P-O,., depending on product)
• Sulfuric acid
• Nitric acid
Utilities
• Electrical energy for pumps, mills, fans, and blowers
• Fuel for drying - older processes (most recent processes use
heat of ammoniation for drying)
Waste Streams
• Contaminated wastewater for scrubbers (or incoming phosphoric acid
can be used)
• Air emissions - off-gases
- ammonia
fluorides
- phosphate rock particulates
- acid-ammonia mists
Products
Monoammonium phosphate
Diammonium phosphate
Ammonium phosphate nitrate and ammonium nitrate
Ammonium sulfate
Fluorides as CaF^ or fluosilicic acid are potential coproducts
67
-------
Process Variations
The basic MAP and DAP processes described above are in use in plants in
the United States, but recent innovations in technology are being implemented
at numerous locations, sometimes alongside an existing conventional process
train, sometimes in new installations. In other cases, adaptations are made
to existing conventional equipment to incorporate recent technology.
A wide range of process variations are in use. Many of these are propri-
etary, patented, or protected by company secrecy classification. Consequently,
details are not readily available. Furthermore, manufacturers routinely in-
novate and operate using temporary process modifications for trial periods of
several days to several months. If successful these modifications may be
permanently ins tallied. For these reasons, several basic process modifi-
cations are discussed below which are indicative of processes in use, although
operational details vary from plant to plant. Reference is made to TVA pro-
cesses described in pilot plant operations. Due to the cooperative relation-
ship, however, between manufacturers and TVA, these processes are considered
indicative of commercial operations.
Pipe Reactor
One of the most significant process developments for ammoniated granular
fertilizers is the TVA pipe reactor, developed in 1971 (Nelson in TVA 1978a).
The pipe reactor is a process modification in which the acid and ammonia are
reacted in the delivery system and introduced under pressure into the granu-
lation chamber (a pug mill or a drum type granulator) as an atomized melt.
Figure 24 is a detail of a standard pipe reactor arrangement.
Figure 25 shows a pipe reactor system set up for a number of NPK formula-
tions. NP products are produced by excluding the potassium chloride and urea
feeds. A preneutralizer is used to blend part of the ammonia with the acid
(NH«:H,PO, mole ratio of 0.4). This is done to prevent rapid scale formation
downstream in the pipe reactor. In TVA demonstrations, and in some industry
applications, the phosphoric acid feed to the preneutralizer is introduced at
a metered rate to the scrubber handling the ammoniator-granulator exhaust
68
-------
PARTIALLY\
NEUTRALIZED
ACID
DRUM
GRANULATOR
' 6'
ENLARGEMENT
STEAM
FOR
PRESS CLEANOUT
GAGE
PARTIALLY
NEUTRALIZED -CX}-»
ACID
DRAIN
TO LIQUID
FERTILIZER
AMMONIA —OO
STEAM
FOR
CLEANOUT
Figure 24. Details of pipe reactor in drum granulator.
Source: Tennessee Valley Authority. 1974. New developments in fertilizer
technology, 10th demonstration, October 1-2, 1974. National Fertilizer
Development Center. Muscle Shoals AL, 72 p.
69
-------
STEAM
PHOSPHORIC
ACID
PARTIALLY
NEUTRALIZED
ACID
OZZ)
RECYCLE
FEEDER
DRUM
GRANULATOR
31 j-. i
x 6
ONSIZE
PRODUCT
19-19-19
12-24-24
15-30-15
\
Figure 25. Flow diagram of granulation pilot plant using pipe
reactor process for NPK fertilizers.
Source: Tennessee Valley Authority. 1974. New developments in fertilizer technology, 10th demonstration,
October 1-2, 1974. National Fertilizer Development Center. Muscle Shoals AL, 72 p.
-------
gases. Phosphoric acid is more effective than water for ammonia scrubbing and
this arrangement also precludes introducing unwanted water into the process
while recycling costly ammonia. The partially neutralized acid is blended
with additional ammonia to achieve an NH0:H^PO. mole ratio of about 1,05
334
(Hicks 1977). This produces a melt (instead of the slurry in conventional
processes) which is nearly anhydrous. Melt temperature is usually about 430
to 440 F (206-212 C) (TVA 1974). The melt is sprayed from the pipe reactor
onto recycled fines, which they readily agglomerate. The drying takes place
in a cooling chamber utilizing the heat of the melt to complete drying and
solidification (conventional processes require natural gas heaters).
The TVA pipe reactor has largely replaced the tank reactor process
(Nelson in TVA 1978a) and is currently among the more attractive systems
available because emission problems are largely eliminated at the source. The
method of mixing and reaction retards evolution of particulates and produce
strong granules which.generate fewer immediate dust problems and retard dust
emissions in later handling also. The potential energy savings due to elimi-
nation of the need for a fuel-fired dryer has been a major factor in the
interest in pipe reactor systems.
The pipe reactor process is undergoing continuous development by TVA and
improvements have been made both by TVA and by the industry. A discussion of
these modifications and their advantages follows. The first major improvement
had to do with the preneutralizer tanks.
Conventional processes generally all use preneutralizer tanks, as does
the original TVA pipe cross reactor process. For more than 17 years MAP and
DAP processes have employed them. These tanks are usually constructed of
stainless steel or of mild steel with a lining of acid brick. A plant may
have either a single preneutralizer tank or several tanks in series, but in
either case, the moisture content of the slurry can be pumped with a conven-
tional centrifugal pump and uniformly distributed in a granulator. Because of
this high moisture content, the granulator product must be dried. The following
operating problems have been reported by companies that produce MAP and DAP in
processes using preneutralizer tanks:
71
-------
1. Difficulty in pumping and metering the hot slurry from the pre-
neutralizer.
2. Foaming and boiling over of the slurry in the preneutralizer.
3. Difficulty in controlling the slurry level in the preneutralizer.
4. Plugging of the ammonia sparger and poor ammonia distribution in
the preneutralizer.
5. Scarcity and high price of fuel needed for drying the product.
(Parker et al. 1977).
The original pipe reactor put into operation by TVA in December 1973 did
use the preneutralizer but the heat generated in the reaction tube was effec-
tive in evaporating much of the water and produced a slurry or melt much lower
in moisture than those in conventional preneutralizer processes. This process,
which also employed a pugmill, is shown in Figure 26. The nearly anhydrous
melt produced contains 15 to 30% polyphosphate. Also, in this process the
pipe-reactor melt enters a vapor disengager (see Figure 27) where helical
rotary blades spread the melt to facilitate removal of water vapor (steam) and
free ammonia and thus compact and defoam the melt. The melt flows by gravity
down a short heated chute from the disengager to a double-shaft pugmill.
Recycle is fed to the pugmill, and composite scrubbing liquor from the
dust-recovery system (about 40-50% concentration) is added after being heated
in a steam-jacketed vessel containing internal steam coils. Fertilizer mixing
plants have adopted this process for use in mixed formulations. An 11-55-0
grade APP can be produced using this process and the addition of highly concen-
trated (98.5% or greater) urea solution in essentially equal proportions to
the APP melt permits production of 28-28-0 grade, generally considered a mix
fertilizer. Increasing the proportion of urea permits production of a 35-17-0
grade. Although moisture content of material in the pugmill is increased by
the return of scrubbing liquor, only cooling is required to produce granules
of good quality. The polyphosphate content of these products ranges from 15
to 35%, and the moisture content is usually 1% or less. A diatomaceous earth
72
-------
STEAM AND
NONCONDENSABLES
34% WP.
HiPO*
PREEVAPORATOR
75% UREA
SOLUTION
37% HCHO
SOLUTION
TO
•* SCRUBBER
CONDENSER
97-99% UREA
SOLUTION
PUG MILL
6RANULATOR
PRODUCT TO
STORAGE
28-E8-0
35- 17-0
II -56-0
RUSHER
Figure 26. Pipe-reactor/pugmill process.
Source: Parker, B.C., M.M. Norton, and D.G. Salladay. 1977. Developments
in production of granular NP and NPK fertilizers using the pipe and pipe-
cross reactor. Paper presented at FAI-IFDC Seminar. New Delhi, India, 48 p
73
-------
GAS
TO SPRAY
REACTOR
TANGENTIAL
ENTRY
ACID INLET ,
2-INCH PIPE
MELT TO
.GRANULATOR
PIPE
REACTOR
6-INCH PIPE
APPROX.IOFT. LONG
AMMONIA INLET
3-INCH PIPE
WELDED THRU FLANGE
Figure 27. Pipe reactor and vapor disengager.
Source: Parker, B.C., M.M. Norton, and D.G. Salladay. 1977- Developments
in production of granular NP and NPK fertilizers using the pipe and pipe-
cross reactor. Paper presented at FAI-IFDC Seminar. New Delhi, India, 48 p,
74
-------
or kaolin clay conditioner is needed for the 35-17-0 grade product (Parker et
al 1977). Use of this system, which does not require a rotary dryer and
related equipment has substantially reduced both capital and operating cost,
thus accelerating its acceptance in both straight and mixed manufacturing
facilities.
In 1974 TVA demonstrated the use of a drum granulator in a melt-type pipe
reactor process (TVA 1974). This process has been widely accepted, especially
since it eliminates the need for dryers in plants already equipped with conven-
tional TVA ammoniator-granulators. Good granulation can be obtained without
the mixing action of a pugmill by discharging the melt directly into a drum
granulator through a perforated pipe (see Figure 25) rather than a single
orifice. The melt is atomized by the steam that expands through the holes in
the pipe. In this process the size and number of holes are adjusted so that a
pressure of 10 to 15 psig is maintained. Obviously, the presence of a small
amount of water in the melt is now turned to beneficial use, atomizing the
melt. In addition, the rotary vapor disengager is eliminated. Several NP and
NPK formulations and MAP have been produced with this process, which is less
expensive to operate and somewhat more energy efficient than the pugmill pipe
reactor process because the rotary drum requires less horsepower to drive.
Figure 28 is a flowsheet of a modified version of the pipe-reactor/
drum-granulator process in which a preneutralizer is not used. This simpli-
fies the process considerably because a major piece of equipment and its
related piping, transfer and metering equipment, and scrubbing system are not
needed. 11-55-0 MAP (5% polyphosphate) produced using this process compares
favorably with that of the process using a preneutralizer. With this process,
both investment and operating cost are significantly lower because of the
equipment eliminated.
Pipe-Cross Reactor
In 1974, TVA in cooperation with the Missouri Farmers Association developed
a modification of the pipe reactor in which a pipe cross instead of a pipe tee
is used to allow for the introduction of a second acid (sulfuric acid usually)
in addition to phosphoric acid and ammonia. This reactor, called a pipe-cross
75
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ATMOSPHERE
RECIRCULATED
ACID
|i I SCRUBBER
J" 2'xlO1
PHOSPHORC
ACID
ACID
PREHEATER
(OPTIONAL)
DRUM
GRANULATDR
3' x6'
DRYER
3'x24'
(USED AS COOLER)
ONSIZE
PRODUCT
Figure 28. Pipe-reactor/drum-granulator process without a preneutralizer.
Source: Parker, B.C..-M.M. Norton, and D.G. Salladay. 1977. Developments in production of granular NP
and NPK fertilizers using the pipe and pipecross reactor. Paper presented at FAI-IFDC Seminar. New
Delhi, India, 48 p.
-------
reactor (Figure 29) has proved very successful in the production of NP and NPK
grades of granular fertilizers that require little or no drying. Although NPK
formulations have been predominant, MAP has also been produced commercially.
The preneutralizer is also eliminated when the pipe cross reactor is used
(Achorn and Kimbrough in TVA 1978a). Grades such as 12-48-0, 12-12-12, 6-24-24,
8-22-11, 10-40-10, 20-10-10, 17-17-17, 33-11-0, and 18-46-0 have been produced
either in commercial plants or in TVA's pilot plant. Several pipe-cross
reactors are in commercial operation, and others are planned. TVA is con-
tinuing pilot-plant studies of the process to further refine variables and
operating conditions for various grades (L. B. Nelson in TVA I978a). Figure
30 shows a typical ammoniation-granulation plant in which MAP, NP, and NPK
formulations can all be produced.
In addition to the advantages already described for a pipe reactor with-
out preneutralizer the pipe cross reactor offers additional benefits (Parker
et al. 1977):
1. Larger amounts of acid, both phosphoric and sulfuric, can be used
in formulations.
2. There is less formation of troublesome ammonium chloride fume
which is difficult to scrub from exhaust gases.
3. Moisture content of the slurry or melt produced is lower and there
is a more favorable moisture balance in the process.
4. Granular MAP, which is an excellent product for blending, can be
produced more conveniently; a wider range of grades can be
blended with MAP (12-48-0 or 11-55-0) than with DAP (18-46-0).
Non-TVA Commercial Processes
A number of other processes for production of ammonium phosphate are in
use in the United States. The Fisons process and the Swift process utilize
mixing nozzles and the Gardinier process utilizes an all-in-one reactor-tnixer-
spray nozzle. These processes spray the resulting melt or slurry into the top
77
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ATMOSPHERE
RECIRCULATED
AGIO
SCRUBBER
2'xlO"
EXHAUST
iS
GA?
PHOSPHORIC
ACID
ACID
PREHEATER
(OPTIONAL)
STEAM UREA
MELT
PE-
CROSS
REACTOR
PHOSPHORIC ACID!
"-AMMONIA
DRUM
GRANULATOR
3'x6'
PHOSPHORIC
ACID
AMMONIA
- AND
WATER
SULFURIC
ACID
DRYER
3' > 24'
(USED AS COOLER)
RECYCLE FINES
%
L-*-ONSIZE
PRODUCT
Figure 29. Pipe-cross reactor/drum-granulator process.
Source: Parker, B.C., M.M. Norton, and D.G. Salladay. 1977. Developments in production of granular NP
and NPK fertilizers using the pipe and pipecross reactor. Paper presented at FAI-IFDC Seminar. New
Delhi, India, 48 p.
-------
mcmeuumm
SCREENS
*
3»
1
• —
v/
3U»r
•"— 1
1-
r
•4
j
Figure 30. Typical anunoniation-granulation plant using
the pipe-cross reactor.
J30DUCT
L-» PRODUCT
TYPICAL GRftOES
10-20-20
6-24-24
8- 16- 16
12- 12- 12
8- 24-24
16-8-8
12-48-0
8-22-11
10-40-10
tO* 10- 10
17-17- 17
1J- II - 0
18-48- 0
Source: Parker, B.C., M.M. Norton, and D.G. Salladay. 1977.
and NPK fertilizers using the pipe and pipe-cross reactor.
Delhi, India, 48 p.
Developments in production of granular NP
Paper presented at FAI-IFDC Seminar, New
-------
of a reaction tower where the droplets solidfy before reaching the bottom,
with moisture contents of 2 to 6%. The ammonium phosphate produced is generally
in a powdered or nonuniform semigranular form. In 1973 there were 15 Fison
plants in operation or under construction. The Swift process was put into
operation in at least one plant in about 1975. Three Gardinier process plants
were in operation or being developed between 1972 and 1974 (Hicks 1977).
Although processes that produce granular product are advantageous and
expected in new installations, the above three processes are included in this
discussion because it is not uncommon for manufacturers to modify or add on to
existing hardware to improve existing capital equipment or expand production.
In such cases NSPS may have to be met.
Discussion—Ammonium Polyphosphate Production
Production of high polyphosphate fertilizers such as APP is usually done
at mixing plants because it is more economical to ship and more practical to
store the SPA and ammonia feedstocks than the APP and because formulations can
be varied using the feedstocks directly. Some phosphate fertilizer complexes,
however, also produce APP's in order to sequester magnesium and iron impurities
in their wet process acid and thus avoid sludge problems. In addition, MAP
and DAP processes discussed above produce ammonium phosphate products in which
the molecular structure may also contain APP's as polyphosphate chains, depending
on conditions of reaction.
Conventional methods for production of APP's are also in use, especially
in older mixing plants. In a typical process for solid APP, thermal SPA is
ammoniated in a water-cooled reactor at elevated pressure and temperature.
This produces an anhydrous melt that is granulated by mixing with recycled
fines in a pugmill to produce 27-34-0. The product contains nearly equal
amounts of ortho- and polyphosphate (Dinauer 1971). An alternative process
uses orthophosphoric acid directly. The acid is preheated and ammoniated in
two stages. Conditions are controlled so that heat of reaction is used to
cause the molecular dehydration required to form polyphosphate molecules. The
resulting melt is then granulated by mixing it with cooled recycled material
in a pugmill (Dinauer 1971).
80
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A TVA process produces 15-62-0 grade APP from thermal SPA. The acid is
neutralized in a cooled, pressurized reactor with anhydrous gaseous ammonia,,
The melt is granulated in a pugmill, cooled, and screened. Dust is collected
by wet scrubbers and scrubber liquor is recycled into the acid feed. The
product contains 75-80% of the P content as polyphosphate (Lee and Waggoner
1975). Such high concentrations are needed in some liquid fertilizers produced
from the material in order to prevent precipitation of magnesium compounds
(TVA 1974). This process produces granular product, but adding water in a
final step produces a liquid for use as a base for liquid blend fertilizers.
Liquid APP is being produced in a large number of United States commercial
plants by use of a TVA-developed pipe reactor which utilizes wet process super-
phosphoric acid (TVA 1974). In the past it has been difficult to produce
satisfactory 10-34-0 and 11-37-0 liquid fertilizers from wet process SPA in a
conventional tank reactor because the polyphosphate contents of the acid and
products were less than desired. Because of impurities, wet process super-
phosphoric acid normally is too viscous to handle satisfactorily when it is
concentrated to a range that provides much more than 50% of the P2°5 as P°ly~
phosphate. Liquids such as 11-37-0 require at least 65%, and 10-34-0 at least
50%, of their P90r as polyphosphates to prevent precipitation of ammonium
phosphate for extended periods of storage at standard 80 F (27 C) or 32 F (0
C) temperatures. Still higher polyphosphate content of 75% to 80% is required
to avoid precipitation of magnesium compounds. The pipe reactor process
permits production of liquids containing much more polyphosphate than had been
possible previously by conventional methods using wet process acid. An addi-
tional advantage of this process is that feed acid containing only 15% to 30%
of the P^O,. as polyphosphate can be used. This acid is cheaper to produce and
can be stored and handled more easily than acid containing about 50% polyphos-
phate, which was needed with prior technology,.
In the TVA process, liquids containing from 70% to 80% of the P20<. in
polyphosphate form are produced from low-polyphosphate (15% to 30%) wet process
superphosphoric feed acid. Also, either furnace or mixed superphosphoric acid
(a mixture of electric-furnace superphosphoric acid and wet process orthophos-
phoric acid) can be successfully ammoniated simultaneously with wet process
orthophosphoric acid to produce 11-37-0 of high-polyphosphate content. The
81
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high-polyphosphate process consists of reacting the acid with anhydrous gaseous
ammonia in a simple pipe reactor. The heat of reaction results in temperatures
of about 600° to 750° F and converts a large part of the orthophosphate con-
tained in the feed acid to polyphosphates. The reaction product made at the
high temperature is an anhydrous melt of about 10-62-0 grade with 70% to 80%
of the P70r as polyphosphates. As shown in Figure 31, this melt is discharged
continuously into the liquid fertilizer vessel where water and supplemental
ammonia are added. The pH of the fluid is maintained at about 6 as the melt
is dissolved. The fluid in the reaction vessel is maintained at about 150 F
(66 C) by recirculation through a water-cooled heat exchanger (TVA 1974).
Ammonium phosphates have been the leading phosphate fertilizers produced
in the United States since 1968. The process equipment for ammoniation-
granulation usually has the capacity, or is easily modified, to include pro-
duction of numerous NPK formulations. These process modifications are readily
effected by adding in feed systems for granular or fine particulate potassium
solid fertilizers or for nitrogen solids, such as granular urea. Sulfates are
produced by adding in a sulfuric acid feedstream in the reaction system, often
to take advantage of operating improvements it offers, such as reduction in
scaling which occurs with phosphoric acid alone, or to increase polyphosphates
content. APP's can be produced in the same process trains and most NPK products
contain phosphorus in both orthophosphate and polyphosphate forms. Manufacturers
appreciate the flexibility in NPK processes because they can change the product
they are manufacturing in response to market demands, feedstock availability
and profitibility, and to solve operational problems such as scaling or trouble-
some emissions. As discussed in Section 1.1, operations performed at such
plants place them concurrently or at different periods in both phosphate
fertilizer and mixed fertilizer subcateogries. For the most part APP's are
produced at mixing plants, but the similarity in process equipment and formula-
tions, and the inclusion of some APP-rich formulations in MAP production
categories have tended to invalidate conventional categories.
82
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WATER -
GASEOUS
AMMONIA'
r r i'
GASEOUS
' AMMONIA
FEED ACID (10-35 %)
" POLYPHOSPHATE
COOLER
COOLING
WATER
IN
COOLING
• WATER
OUT
COOLING
WATER
IN
COOLING
WATER
OUT
PRODUCT (11-37-0)
TO STORAGE
Figure 31. Plant pipe reactor system for production of
high-polyphosphate liquid fertilizer.
Source: Tennessee Valley Authority. 1974. New developments in fertilizer
technology, 10th demonstration, October 1-2, 1974. National Fertilizer
Development Center. Muscle Shoals AL, 72 p.
83
-------
1.3.3 Auxiliary Support Systems
1.3.3.1 Raw Materials Transportation
Phosphate Rock
Phosphate fertilizer facilities generally receive ground phosphate rock
concentrate by enclosed systems. Pneumatic systems are used for dry material
(USEPA 1978d) and pipelines for slurries. Outdoor storage piles are built
over systems of vertical feed pipes and horizontal conduits enclosing conveyors,
so that feeding into the plant is done by gravity from within the storage pile
and then moved in enclosed conduits. Other plants are delivered phosphate
rock by railroad hopper car. If ground rock is delivered, covered hopper cars
are used. Unloading is done in enclosed transfer areas, and enclosed eleva-
tors move the rock to storage silos. Exhaust systems in the transfer areas and
storage silos are passed through baghouses to recover particulates. When wet
grinding is to be employed at the fertilizer facility, rock can be shipped
unground and stored uncovered.
Sulfur
The prevailing U.S. pattern is to mine, ship, and store sulfur in "all
liquid" systems. This approach makes sense because of the volume of sulfur
used in the United States (world's largest consumer) and is made feasible
because the Frasch process is used to mine the sulfur. The Frasch process
takes advantage of very pure massive deposits of sulfur in salt dome structures
and in other structures along the Gulf Coast in Louisiana, Texas, and Mexico.
In the Frasch process heated water and steam are injected into sulfur beds
through jacketed concentric pipe casings, and sulfur melted by the process is
withdrawn through an annular space in the casing. The Frasch process is
energy intensive but viable, largely because of the advantages of transporting
and handling sulfur in molten form in controlling air pollution and lessening
equipment corrosion. Most uses require that sulfur feedstocks be melted for
processing, so there is a partial payback of energy consumption at that stage.
84
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The conversion to liquid handling systems in the United States began in
the early 1960's (Carrington 1962). Consequently, multi-million dollar liquid
sulfur transportation and handling networks are now well established. Phos-
phate fertilizer facilities receive Frasch sulfur by road and rail tankers,
pipelines, bargelines, and ocean-going tankers. Transportation facilities and
all pumps and tank terminals are equipped with insultation and heating equip-
ment to maintain the sulfur at temperatures between 240 and 320 F (116-160 C)
(Anonymous 1970).
Ammonia
Phosphate manufacturing utilizes ammonia for production of ammonium phos-
phates. Plants that do not produce ammonium phosphates would not use ammonia
in significant quantities (58.45% of the phosphate straight fertilizers pro-
duced from wet process phosphoric acid are ammonium phosphates (USEPA 1974d)).
Ammonium phosphates are produced either at facilities near sources of
phosphate rock or at facilities that produce ammonia or are nearby ammonia
sources. Those facilities that produce ammonia require good sources of natural
gas, and ammonia product is transported by in-plant pipelines and inventories
stored at low temperatures (as low as -50 F or -46 C) in cryogenic tanks.
Facilities which purchase ammonia receive shipments of compressed liquid
anhydrous ammonia or aqua ammonia by barge or road or rail tanker (USEPA
1976b). Throughout the Midwest anhydrous ammonia is available (primarily to
mixing plants) by pipeline networks. Ammonia storage tanks may be cryogenic.
Modern ammonia terminal systems are also designed to deliver ammonia to pressure
tanks at ambient temperatures.
1.3.3.2 Product Handling, Storage, and Transportation
Granular and ground solid products are handled, stored, and loaded for
shipment using some of the same systems or similar systems used for phosphate
rock (1.3.3.1). Loading is done by covered conveyors or from hoppers to
barges, rail hopper cars, or trucks for shipment. Loading areas are usually
enclosed or equipment and receiving vehicles are hooded during transfer.
Materials that are handled using dry transfer facilities are product phosphate
85
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rock, NSP, TSP, and ammonium phosphates. Hopper cars are open, however, and
can lose some dry products as particulates to the air or by spillover from
overloaded hoppers.
Phosphoric acid and SPA require special materials for construction of
storage tanks, pumps, and pipe-work that are strong, flexible, resistant to
strong acids, and able to withstand temperature extremes. Details of selec-
tion of proper materials for process equipment or handling, storage, and
transportation equipment is not a subject of this document. Spill and leakage
prevention can be enhanced, however, by use of suitable materials such as
certain stainless steel alloys, plastics, rubber, and fiberglass.
Phosphoric acid is delivered to tanks and transport vehicles through
pipes and hoses made of the above materials. Phosphoric acid storage tanks
may be flat-bottom or cone-bottom, and are usually constructed of a mild steel
shell with rubber lining. When flat-bottom tanks are used, good design for
leakage control includes construction of tanks on a concrete foundation elevated
to keep the shell from coming in contact with any spilled acid. The foundation
should have grooves (drain spokes) in its upper surface radiating toward the
edges; this transmits any leaking acid from the tank base out from under the
tank to minimize corrosion and allow easier detection (Barber 1975a). Cone-
bottom tanks are used to facilitate removal of settled solids. Since removal
pipes are at the bottom of cone-bottom tanks, the tanks are usually elevated
on a supporting frame (Balay and Kimbrough 1978). Smaller tanks, for inter-
mediate storage, are frequently of the horizontal cylindrical type; these are
supported on concrete buttresses. All storage tanks are ideally surrounded by
a diked-in area large enough to contain the contents of the largest tank
(Barber 1975a).
Phosphoric acid is transported by rail or road tankers (USEPA 1978b).
Superphosphoric acid from wet process acid presents special handling problems
due to its high viscosity. This characteristic can be largely overcome by
loading the acid at elevated temperatures in especially designed insulated
tank, cars known as "hot dog" cars. A stainless steel shell is surrounded by
six inches of polyurethane foam and an outer carbon steel shell. Internal
pipe coils are located around the bottom of the inner shell so that steam and
86
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hot water can be piped in to keep the SPA between 150 and 200 F (52-75 C). The
storage tank and lines to the transfer area are also insulated (Balay and
Achorn 1971).
1.3.3.3 Intake Water Treatment
The only process which requires water treatment is the boiler make-up
water for the sulfuric acid process. Impurities which would scale and foul
boilers are removed by hot lime-zeolite treatment. Raw water is heated by
steam in this lime softening process and filtration is through zeolite filters
and a final anthracite (coal) filter. Impurities are collected in the softener
tank and released by sludge blowoff (USEPA 1974a, Drew Chemical Corp. 1977).
1.3.3.4 Uranium Recovery
There is a small amount of uranium in phosphate rock, and it is dissolved
as part of the 32% acid in the wet-process system. In the 1950's there were
three plants where solvent extraction units were operated commercially. All
were plagued with operating difficulties, both in the uranium plant and in its
effect on the phosphoric acid plant. None was economically successful and all
were shut down in favor of more conventional methods of uranium processing
(USEPA 1976b).
Currently there is a revival of interest in extraction of uranium as
uranium oxide (yellow cake) because improvements have been made in extraction
techniques and because the price of yellow cake has increased from $8 to $43
per pound since the early 1970's. Several plants in central Florida have
experimentally recovered uranium from phosphoric acid, and commercial recovery
is nearing reality. The most likely processes to be used involve liquid-liquid
solvent extraction processes. Uranium Recovery Corporation (URC) in 1974-1975
installed a uranium recovery module consisting of two units, one at the phos-
phoric acid plant of W. R. Grace & Company near Bartow and the other at URC's
central processing plant near Mulberry. The acid-plant unit has been involved
in initial extraction and stripping, while the central-plant unit has been
involved in final production of yellow cake (Engineering and Mining Journal
1975). International Minerals and Chemical Corporation (IMC) is developing a
87
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uranium recovery facility at its New Wales plant. The operation will utilize
a two-cycle solvent extraction process using di(2-ethylhexyl) phosphoric acid
plus trioctylphosphine oxide in kerosene (Interview, J. Allen, IMC, 16 August
1979).
The U.S. Energy Research and Development Administration (ERDA) estimated
that more than 900 metric (1,000 short) tons of uranium oxide would be ex-
tracted in the study area by 1978; this would represent approximately 8 % of
the total U. S. production for 1975 (USERDA 1976). Recent estimates from
central Florida place uranium production at nearly 1500 short tons, about 10%
of U. S. demand. Four chemical companies are currently involved in or setting
up facilities for uranium extraction in Florida. This spin-off industry from
the phosphate industry has been operated quasi-independently in several cases,
as cooperative ventures between the phosphate company and the extracting
company. At least one phosphate processing company has now begun operation of
uranium extraction in their own facilities, and other phosphate complexes are
expected to follow.
1.4 SIGNIFICANT ENVIRONMENTAL PROBLEMS
The discussion in this section is a brief summary of the major environ-
mental considerations associated with phosphate fertilizer manufacturing
facilities. More comprehensive treatment of industry impacts is developed in
Chapters 2.0 through 6.0. Problems inherent with specified factors and materials
are discussed even though environmental effects may normally be mitigated
through process and control techniques. The intent is to identify potential
significant problems which, as a minimum, new source EID's would be expected
to address.
1.4.1 Raw Materials
Phosphate rock. Beneficiated rock has generated serious environmental
problems in poorly controlled facilities. Dust can be a significant air con-
tamination problem at each point of transfer of the materials and in the
grinding process when dry grinding is used. A typical milling operation for
rock grinding associated with a mining operation has the potential to con-
88
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tribute 7 grams of particulate per dry standard cubic meter of exhaust before
emission control (USEPA 1978d). Mass emission rates for rock transfer systems
were not sampled in the 1978 USEPA study, but visible emission measurements
have shown that these systems can be operated with no visible exhaust.
Sulfur and Ammonia. These raw materials and their reaction products
in the environment, have significant potential to contribute to pollution.
Neither sulfur nor ammonia, however, as raw materials present significant
problems to the environment. This is due largely to the efficient handling
and transportation systems in use (1.3.3.1) and due to the expense of the
materials and their obnoxiousness if spilled. Spills are rare and with the
adequate recovery systems in use losses are held to a minimum.
1.4.2 Process-Related Problems
S0n/S0, and Acid Mists. Gaseous oxides of sulfur are used in pro-
duction of sulfuric acid from elemental sulfur. Uncontrolled, these emissions
can exceed 46 kg/metric ton (103 Ib/ton) of sulfuric acid produced (USEPA
1978b). Prior to the promulgation of NSPS in 1971 USEPA measured SO emis-
sions as high as 42.5 kg/metric ton (94 Ib/ton) of 100% sulfuric acid. In
addition, acid mist emissions uncontrolled can be as high as 3.7 kg/metric ton
(9 Ib/ton) of 100% acid. Oxides of sulfur and acid mists are also evolved in
wet process phosphoric acid production, NSP, and TSP production. Acid mists
in these processes include phosphoric acid, nitric acid, and fluosilicic acid.
Fluorine. Significant gaseous emissions of fluorine, including mists,
are evolved in the processes for wet process phosphoric acid, SPA concentra-
tion, TSP, and ammonium phosphates. They are also evolved in NSP processes
but have received less attention (no NSPS have been promulgated) because
production of NSP is small relative to other phosphate fertilizer products.
A major source of fluorine pollution is the gypsum pond which most facili-
ties use to contain solid wastes and act as a reservoir and settling pond for
contaminated process water. Fluorides may be evolved from the gypsum ponds as
volatile fluorine, hydrogen fluoride, and silicon tetrafluoride.
89
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Particulate Air Emissions. Particulates can be generated in all
processes in which phosphate rock is acidulated and in all processes in which
a solid product is manufactured. Those processes with significant potential
for particulate emissions are:
• wet process phosphoric acid production
• NSP production
• TSP production (especially nongranular)
• ammonium phosphates (nongranular)
Solid wastes from gypsum ponds and gypsum stacks have not proven to be a
source of significant particulates.
Process Wastewater. If they were discharged regularly and untreated,
process wastewaters would cause severe and long-lasting or permanent environ-
mental damage to surface water ecosystems. New source facilities will be per-
mitted to discharge only treated process wastewaters. Due to the costs of
pretreatment and the requirements of NSPS, they will discharge only during wet
weather or periods of water balance misadjustments, when the capacity of
storage ponds might otherwise be exceeded. But the possibility of accidential
or uncontrolled discharge cannot be ignored. The gypsum pond (from which any
discharge would emanate) contains harmful pollutants including the following:
• phosphorus
• fluorides
• ammonia
• cadmium
• chromium
• zinc
• vanadium
• arsenic
• uranium
• radium-226
• sulfate
90
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and significant levels of the following parameters:
• pH (extreme acidity, pH 1-2)
• suspended solids
• dissolved solids
• temperature
There is the possibility of environmental problems associated with contami-
nated wastewaters, even with no discharge, if seepage occurs through dikes and
pond bottoms, thereby polluting surface- or groundwaters.
Solid Wastes. The major solid waste is gypsum, which is a by-product
of wet process phosphoric acid production. The quantity of gypsum produced in
a wet process plant ranges from 4.6 to 5.2 metric tons per ton of P2°s Pr°duced.
In volume, this translates to 1,360 cubic meters (1,779 cubic yards) yearly
per metric ton of P2°5 Pr°duced Per day. This is enough material to cover one
acre 1.1 feet deep each year per each metric ton of P^O,. produced on a daily
basis. A representative plant with only one process train produces 630 metric
tons of P2°5*
Disposal is a major materials problem which can become a major pollution
problem if improperly handled. Plants near the mine can dispose of some of
the solid residue in mine pits; most others use gypsum ponds and piles.
Rainfall runoff can cause serious ecological problems if suspended solids and
phosphate and sulfate compounds are washed into surface streams and lakes.
When rainfall drainage is controlled properly, the major concern remaining is
for land use effects, due to the large amount of land used and its unsightli-
ness.
In practice the disposition of waste gypsum rarely qualifies truly as
disposal. Operators often refer to gypsum piles as "storage," and some con-
sider the gypsum to be stockpiled for the future, when it might have an eco-
nomic value. Some waste gypsum has been disposed of in mine pits very near
plants, but this is a very minor portion of the total. Gypsum piles eventu-
ally fill available pits and are graded over original surface levels, to
heights of 50-100 feet or more. No gypsum piles are known to have ever been
91
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retired because plant sites have been expanding or adding on throughout the
history of phosphate fertilizer production rather than shutting down.
1.4.3 Pollution Control
There are no direct environmental problems brought about by pollution con-
trol methods. Air emissions technology removes fluorides and particulates
from gaseous wastestreams and adds them to wastewater effluents. These incre-
ments are not considered a problem because wastewaters are not discharged.
Ultimately, the additional fluorides and particulates (phosphate) and acids
and other minor impurities collected in scrubber liquor become part of the
solid waste disposal problem, but the quantities amount to insignificant
increases.
An indirect environmental impact is a possible slight increase in fluor-
ide emissions from gypsum ponds due to increased levels of fluorides from wet
scrubbers. This is a minor increase which is outweighed by the beneficial
effects of the original fluoride scrubbing.
The only aspect of pollution control which adversely affects the environ-
ment is the cumulative effects of improper maintenance of the equipment.
Catalytic converters in sulfuric acid production are sometimes used when the
catalytic beds should be replaced. In general, emissions control equipment
capable of bettering standards of performance is usually serviced when the
standards are being approached or exceeded. Scrubbers and precipitators
sometimes break down or malfunction. The actual impact of these factors is
not known.
1.4.4 Location
Ambient Air Quality. Ambient air quality is not generally a limiting
factor. Phosphate fertilizer facilities are typically in areas of low popu-
lation density and little other industrial development. Facilities in certain
areas where natural gas and ammonia are produced are often in more indus-
trially developed areas.
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Hydrologic Regime. The ratio of rainfall to evaporation can be a major
concern in maintenance of the plant water balance to meet requirements for no
effluent discharge. Amount of rainfall, drainage properties, and depth to
water table are of importance through their effects on efforts to control
contamination of surface and groundwaters from gypsum disposal areas.
Soils and Geology. Plants which do not have suitable land to lay out or
add on wastewater and solid waste disposal facilities have problems elimi-
nating wastewater discharges and properly storing solid wastes. Unstable or
weak soils and steep topography are elements of plant location that may limit
the capacity to properly handle liquid and solid wastes.
1.5 TRENDS
1.5.1 Locational Trends
1.5.1.1 Geographic Trends
A distinction should be made between trends in phosphate fertilizers
and trends in phosphate rock production. The phosphate fertilizers capacity
in the United States is located about 30% on the Gulf Coast (Texas, Louisiana,
Mississippi), about 50% in Florida, about 10% in the western states, and 10%
scattered throughout the United States including North Carolina (Blouin and
Davis 1975), with more than 80% of domestic production of phosphate rock being
produced by Florida and North Carolina. The reason that the phosphate fertilizer
production figure is significantly lower than proportionate rock production
for Florida and North Carolina is that phosphate rock from those two states is
exported to Gulf Coast states (while sulfur from the Gulf states is returned
to Florida and North Carolina).
These geographic trends are expected to continue with substantial varia-
tions by individual products. For example, Figure 32 shows locations of
phosphoric acid, TSP, ammonium phosphates, and anhydrous ammonia production
facilities projected for 1980. Phosphoric acid plants are usually located at
the phosphate rock source. In some cases they are located near sulfur when
N-P grades are produced. Very few of the acid plants are market located.
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U.S. AND CANADIAN
PHOSPHORIC ACID PLANTS
1980 - •
U.S. AND CANADIAN ANHYDROUS
AMMONIA PLANTS
1980
U.S. AND CANADIAN TRIPLE SUPERPHOSPHATE PLANTS
1980
LEGEND
.1171 CONSTRUCTION < J60.000 T(V
1B6 CONSTRUCTION > 360,000 TAT
Ifff-ON CONSTRUCTION < 3GOJOO T/Y
A ttT&ON CONSTRUCTION > XOJJOO T/Y
U.S. AND CANADIAN AMMONIUM
PHOSPHATE PLANTS
1980
LEGEND
• PRE-1975 CONSTRUCTION
» 1976-ON CONSTRUCTION
Figure 32. Locations of phosphate fertilizers and ammonia production.
Source: Adapted from Lyon, Fred D. 1976. Trends in storage, handling, and
transport. Proceeding of TVA Fertilizer Conference, July 1976. Cincinnati
OH, p. 37-42.
94
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Triple superphosphate plants are located near phosphate rock deposits.
These plants are also located next to phosphoric acid production so as to
utilize sludge from acid operations. All but three are located close to
navigable channels which provide a choice in mode of transportation.
Ammonium phosphates require phosphoric acid and ammonia. Most of the
plants are located either at the phosphoric acid plant or at an ammonia faci-
lity. Only a few small plants are market located. Locations of anhydrous
ammonia facilities illustrate the degree to which ammonium phosphates are
being produced at these facilities (Lyon 1976).
After 1980, the production of mine-oriented materials should continue to
follow the same pattern, with some production continuing in the Gulf Coast
states, increased production in Florida through 1990, and substantially in-
creasing production in North Carolina through the year 2000. The production
in the western states will hold steady or increase slowly through the year
2000. The shipping advantages of concentrated materials such as SPA over
phosphate rock should enforce the trend toward liquid fertilizers and result
in a continuing increase in ammonium phosphate plants located near ammonia
facilities and inexpensive transportation such as pipelines and bargelines.
In Florida the majority of the mining is done in the Central Florida
District east of Tampa Bay. Polk County is the site of most of the current
mining and fertilizer production, with several phosphate chemical plants in
operation in Hillsborough and Manatee Counties. Planned mining and phosphate
production facilities will be built in Hillsborough, Manatee, Hardee, and
DeSoto Counties as the richer Polk County deposits are depleted (USEPA 1978i).
In addition, less extensive deposits are being rained in North Florida.
1.5.1.2 Siting Trends
In Florida, where the majority of phosphate production will take place
over the next 20 years, facilities will be close to mines. Many of the older
facilities will be continued, but new facilities will be located in new mining
areas in Hillsborough, Manatee, Hardee, and DeSoto Counties, and in North
Florida.
9-5
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In North Carolina, increasing production will entail new plant capacity
in the Beaufort County mining area. Phosphate fertilizer plants will continue
to be close to mines to take advantage of slurry transport systems. (Note:
some operators have determined that dry transportation of rock by conveyors to
beneficiation and processing plants may be economically competitive or advan-
tageous for their locations, and these will be used by some plants.)
In general, siting of phosphoric acid production at sulfur and nitrogen
producing facilities will continue. With United States demand for sulfur
growing, it is likely that some new sulfur production capacity will incor-
porate phosphoric acid processes into the facilities. Siting of ammonium
phosphate production will be concentrated in Florida complexes but with a
greater percentage at ammonia producing plants on the Gulf Coast and in the
midwest, and at blending plants along ammonia pipelines and barge systems.
The majority of production of phosphate products will be done at sites
which are complexes for production of more than one product. 84.7% of basic
fertilizers are produced in such complexes. Very few manufacturers are
totally dependent on fertilizer production. Many are subsidiaries of chemical
or petrochemical manufacturers, pipeline companies, steel manufacturers, or
are run by a farm cooperative or a sulfur producing company. Siting may be at
a complex where other materials are produced in completely separate or inte-
grated process trains. The overriding trend in siting is toward large com-
plexes. Economically, it is more profitable to operate a larger complex per
ton of product. Capital investment per ton decreases in larger complexes, and
pollution control costs per ton of PO^S are ^ower *n a 1»500 ton per day
phosphoric acid plant than in one producing 500 tons per day.
1.5.2 Trends In Raw Materials
1.5.2.1 Sulfur
In 1975 consumption of sulfur in fertilizer production was 6.6 million
long tons. Of that, 6.1 million (92%) was used in phosphate fertilizers. By
1985, the projected consumption of sulfur in the United States is 15.1 million
long tons, with 9.3 million projected for fertilizer use. The trend is for
more use of recovered and by-product sulfur. Data projecting sulfur-supply
96
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patterns are summarized in Table 13 (Douglas and Davis 1977).
These changes are not expected to have significant effects on fertilizer
production technology. If economically feasible technology is developed to
recover sulfur from high and medium-sulfur coals burnt in electrical power
plants, this source is expected to become a significant factor by the late
1980's (Douglas and Davis 1977).
Table 13. Supply pattern for sulfur in the United States
Source
Estimated Production
(long tons sulfur equivalent)
1975 1985
Frasch 7.8
Recovered
Ref inery 1.7
Sour gas 1.2
By-product sulfuric acid
Nonferrous smelters 1.0
Stack-gas cleanup -
Pyrites-based sulfur acid 0.4
Other 0.1
Total 12.1
8.2
4.0
3.6
2.0
0.6
0.5
0.2
19.0
Source: Douglas, John R. and Charles H. Davis. 1977. Fertilizer supply and
demand. Chemical Engineering 84(15):88-94.
1.5.2,2 Phosphate Rock
Research is ongoing to develop technology to allow use of lower grades of
rock (TVA 1978b). Use of somewhat lower grades in Florida has already begun,
97
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with the consequence that MAP has become more popular with basic producers of
ammonium phosphates because rock with lower ^2°5 content can be used w^0" are
difficult to use for production of 18-46-0 DAP (Nelson 1978). Expansion of the
Central Florida Phosphate District is expected during the 1980's into counties
surrounding Polk County, which will be using lower grades of phosphate rock
(USEPA 1978b). Techniques under development to extract calcite and dolomite
from phosphate rock, along with the current production of high polyphosphate
liquid base solutions from high iron and magnesium North Carolina ores, point
to a continuing trend to utilize phosphate rock sources previously considered
too low in purity or P20 analysis.
1.5.2.3 Ammonia
Ammonia production currently uses natural gas as a feedstock, of which
the United States has only a 10-year proven reserve. Natural gas is expected
to remain important over the next decade, but developing efficient United
States technology to make ammonia from coal has been widely identified as the
number one national research priority for food production.
1.5.3 Process Trends
Processes are described in detail in Section 1.3. This discussion is a
summary of the important process trends that are expected to be used in new
source facilities and in upgraded existing facilities where they can be adopted.
Sulfuric Acid Production. The double absorption process has gained wide
acceptance and is expected to become the standard because it allows achieve-
ment of NSPS for sulfur oxides. Of 32 new units completed since issuance of
the NSPS only three have not adopted double absorption.
Phosphate Rock Processing. A trend is anticipated to wet grinding of
phosphate rock. Wet grinding reduces particulate emissions and eliminates the
energy-consuming step of drying the beneficiated rock. It is not known whether
facilities that purchase (dried) rock plan to utilize wet grinding. Although
not yet in commercial operation, small pilot projects to produce phosphoric
acid directly from ground unbeneficiated rock have proven relatively encour-
98
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aging; this procedure offers the potential to recover some of the phosphate
content now lost in clay slimes and to reduce the production of slime ponds,
currently a major land use problem at mining facilities (White et al. 1978).
Normal Superphosphate Production. Due to its low analysis, competition
from other fertilizer products, and transportation costs of the phosphate rock
feedstock, production is expected to decline slowly and reach a maintainable
level of about 5% of total processed straight phosphate direct application
materials. This production will be done primarily in small plants in the
market areas.
Wet Process Phosphoric Acid. There are no new trends - sulfuric acid
acidulation is the standard. Auxiliary processes for recovery of uranium
oxide are expected as add-on process loops during acid production and purifi-
cation steps. These involve solvent extraction instead of or in addition to
clarification by settling.
Clarification of Phosphoric Acid. The use of settling and gravity pre-
cipitation techniques should continue. Use of solvent extraction techniques
is not popular in the United States except in connection with uranium recovery,
once the phosphoric acid has been produced. Use of lower grade ores with
higher impurities may result in greater interest in solvent extraction in the
raid-to late 1980's.
Superphosphoric Acid Production. Industry units are divided between
submerged combustion and vacuum evaporation processes. The trend is to vacuum
evaporation to avoid the drawbacks of submerged combustion, which require
extensive scrubbing facilities due to the large volume of effluent gases.
Triple Superphosphate Production. The use of granulator proce. ses is
currently more popular and should continue. Nongranular forms are still
produced largely for use as seed material in granulation-ammoniation pro-
cesses. This practice may continue but is expected to decline further due to
process modifications in ammoniation-granulation plants which use recycled
fines and can use other fertilizer materials in granulation. Nongranular TSP
is troublesome because of potential dust emissions at each handling stage; it
is not wellsuited for dry blended fertilizers.
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Ammonium Phosphate Production. DAP is popular and well-established. Its
production levels are expected to trend downward, however, due to the diffi-
culties in maintaining DAP formulations when lower analysis rock is used in
production. MAP production is expected to regain marketing and production
acceptance due to a number of reasons (Achorn & Kimbrough 1978):
1. Conventional DAP plants can produce MAP with exising equipment
and at the same time eliminate one preneutralizer, reduce am-
monia losses, and produce a lower moisture slurry that requires
no drying.
2. MAP can be produced in a pipe-cross reactor with no preneutralizer.
3. MAP has more versatility for use by the bulk blender since a larger
number of grades can be produced from MAP as compared to using DAP.
4. MAP is compatible with TSP whereas DAP reacts and causes caking when
mixed with most commercially available TSP.
5. MAP can be used to produce suspension fertilizers by the addition
of only ammonia whereas when DAP is used to produce these suspen-
sions, phosphoric acid must be mixed with it and acid storage must be
available at the dealer level.
6. The dual marketing of anhydrous ammonia and MAP is probably more
economically attractive than ammonia and DAP.
7. Most phosphate producers desire to ship mostly P?0 and add ammonia
to the product only to convert the P?0,. to a suitable form for
shipping.
1.5.4 Trends in Pollution Control
Pollution control systems and process designs are described in detail in
Section 3.0. This discussion is a summary of the more widely adopted pollution
control methods being integrated into new source facilities including upgraded
existing facilities.
Wastewater treatment comprises a small segment of effluent control.
Housekeeping, operational, and design controls are the foundations of waste-
water effluent management. Control techniques which are expected include:
• Spill control and monitoring systems in sulfuric acid plants to
contain, treat, and recycle spills and leaks.
100
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• Elimination of discharge during normal operations by achieving
water balance within or among the process trains. Techniques to
meet this criterion include:
1. Use of contaminated water for dilution of sulfuric and phosphoric
acid.
2. Use of recycled contaminated water in wet scrubbers.
3. Routing of condensed contaminated water from steam ejectors
and barometric condensers to the gypsum pond.
4. Sale of scrubber liquor for fertilizer or fluorine recovery.
• Use of surface drainage systems to pass washdown and runoff waters
to the contaminated gypsum pond.
• Design of gypsum ponds to contain specified rainfall events.
• Double-lime treatment of controlled discharge from gypsum ponds
during rainfall events that exceed design capacities.
• Design and siting of gypsum ponds to control seepage and recycle
collected seepage back to the pond.
• Control of NH»-N loading to the gypsum pond by use of self-con-
tained systems in the ammonium phosphate process to recycle or treat
separately secondary wet scrubber liquor.
Control systems expected for gaseous emissions include pollutant control
technologies and design modifications:
• Double absorption process modifications are usually chosen in sul-
furic acid plants. Less popular techniques for new source facilities
such as ammonia scrubbing, sodium sulfite-bisulfite scrubbing, and
molecular sieves have experienced some operational or cost-related
drawbacks.
• Use of acid mist eliminators; a number of systems are acceptable
(Section 3.1).
• Use of baghouse filters and efficiently designed vent and cir-
culation systems for capture and recycling of captured emissions.
• Use of enclosed dry material transfer and handling systems.
• Use of continuous process mills in NSP and TSP production with
scrubbing and recycling of emissions.
• Use of pipe reactors and pipe-cross reactors in granulated fertilizer
production, with the evolution of less ammonia (eliminating pre-
neutralizers) and of lower particulate emissions.
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Trends which attenuate the production of solid wastes include:
• Recycling of acid sludge to the phosphoric acid evaporator feed
tank (USEPA 1979a).
• Production of SPA from high iron and magnesium phosphoric acid
to sequester impurities in solution. This product can be used most
readily in liquid fertilizers.
1.5.5 Environmental Impact Trends
1.5.5.1 Water Quality
Surface water contamination in phosphate processing drainage areas has
been significant in the past. Untreated discharges from gypsum ponds are
characterized by heavy loadings of sediment (suspended filterable solids),
inorganic phosphorus, and fluorides.
Since promulgation of effluent guidelines for the phosphate fertilizer
industry in 1974 regular discharge of gypsum pond effluents have been largely
eliminated. Seepages and accidental discharges still occur and some existing
sources have not completely discontinued regular discharges that will be
prohibited in 1984. New sources constructed since 1974 and most phosphate
fertilizer plants in operation have eliminated regular discharges. Table 14
is a summary of the results of a survey completed by Monsanto Research Cor-
poration in 1976 and 1977 for the USEPA Industrial Environmental Research
Laboratory (USEPA 1979a).
Definitive time series data are not available to compare baseline (pre-
effluent guidelines) and present water quality. It is presumed that the trend
to fewer discharges with specified limits on contaminant concentrations is a
basis for a trend to less serious water pollution problems currently, and in
the future.
The potential for groundwater contamination is based on an assemblage of
variables including permeability of soils underlying gypsum ponds, effective
gypsum pond bottom sealing and seepage control, and depth to water table. A
study by the USEPA Office of Radiation Programs completed in October 1977
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Table 14. Water effluent disposal and containment
practices for the phosphate fertilizer industry,
Wet process
• phosphoric
acid plants
Process water discharged continuously:
Treated
Untreated
Discharge of treated process water only j
No discharge of process water reported
Insufficient information
Total
Fond system onsite for water containment
and reuse:
Continuous discharge from pond system
Discharge only when necessitated by
periods of excessive rainfall
No discharge from pond system reported
Treat pond system with lima to precipitate
fluorides and other contaminants
Uncertain
No pond systea onsite
Information regarding wastewater
handling system incomplete
Recover fluosilicic acid
Number of plants contacted
Number of plants in industry
Percent of industry surveyed
7
3
IP
JO
52
0_
100
90
7
38
45
3
0
0
10
28
29
36
81
(2)8
(1)C
(ll)f
(15)
(0)
(29)
(26)
(2)8
(11)
(13)
(1)
(0)
(0)
(3)
(8)
Superphosphor ic
acid plants
0
0
AA
44
56
0
100
89
0
44
44
11
0
0
11
0
9
9
100
(0)
(0)
(4)f
(4)
(5)
(0)
(9)
(8)
(0)
(4)
(4)
(1)
(0)
(0)
(1)
(0)
Industry
Normal
superphosphate
plants
0
0
6
88
6_
100
36
0
6
23
13
6
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indicates, with a number of qualifications regarding the variability of con-
ditions and performance of individual plants, that there may be no major
wide-spread groundwater contamination by radium-226 levels in gypsum ponds and
effluents (USEPA 1977d). Studies of Florida groundwater, however, are compli-
cated by some high natural background levels of radionuclides and by anoraolous
and incomplete data. Although exceedingly low percolation rates through com-
pacted aged gypsum cake and the underlying clay-permeated sediments have been
reported (Wissa 1977), some local contamination of the water table aquifer is
occurring at some sites, near gypsum stacks and ponds (TRC 1979). It has not
been demonstrated definitively whether migrations of radionuclides take place
through gypsum pond bottoms nor what degree of sealing is effective.
1.5.5.2 Air Quality
Since sulfuric acid and phosphate fertilizer NSPS have been promulgated,
emission levels for particulates, sulfur oxides, acid mists, and fluorides
have mandated performance levels which can be attained using available tech-
nology to control plant process emissions. The phosphate rock segment of the
chemical and fertilizer mineral industry was estimated to have contributed
44,276,000 metric tons of particulate emissions in 1975, or 39% of the total
for all chemical and fertilizer production (USEPA 1978e). The above figures
include the mining and beneficiation processes, but it is evident that par-
ticulates are a major potential emission source for fertilizer handling and
processes. Fluorides are contributed to emission streams in volatile forms
and as constituents of particulate emissions. The overall environmental trend
is for lowered emissions of particulates, sulfur oxides, acid mists, and
fluorides using control technologies. Gypsum ponds have long been posited as
a major virtually uncontrolled source of fluoride emissions. Recent modeling
by Environmental Science and Engineering for the USEPA Industrial Environ-
mental Research Laboratory dispute the significance of volatile emissions and
suggests that fugitive dust from gypsum piles and deposits have been inadver-
tently included in measurements of gypsum pond emissions (USEPA 1978c).
It is clear that the lowering of emissions of fluorides will not be
effective until sources are defined and agreed on. Meanwhile, a general trend
that can be agreed on is that fluoride emissions could ultimately be lowered
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effectively by removing them completely from the waste system as a salable
product, fluosilicic acid (USEPA 1978c). There is a trend toward the recovery
and sales option, but it is not overwhelming due to unfavorable economics in
some areas and for some removal processes.
1.5.5.3 Physiographic Impacts
The major environmental effect of the industry on the quality of the land
resources is the disruption of the topography caused by the accumulation of
gypsum deposits and long term dedication of land areas to gypsum ponds.
Unlike the case of phosphate mines, however, where vast areas have been mined
and/or tied up in slime ponds, fertilizer plants themselves involve relatively
smaller land areas. Past experience has been that these impacts are, however,
equally long term in that no major plants, gypsum piles, or ponds have been
totally retired or reclaimed.
1.6 POLLUTION CONTROL REGULATIONS
1.6.1 Water Pollution
The Federal Water Pollution Control Act (FWPCA) Amendments of 1972
(P.L. 92-500) established two major interrelated procedures for controlling
industrial effluents from new sources, and specifically included phosphate
manufacturing in the list of affected categories of sources. The principal
mechanism for discharge regulation is the NPDES permit. The other provision
is the new source performance standard. The Clean Water Act of 1977
(P.L. 95-217), which amends P.L. 92-500, made no change in these basic pro-
cedures.
The NPDES permit, authorized by Section 402 of FWPCA, prescribes the
conditions under which effluents may be discharged to surface waters. The
conditions applicable to new or expanded phosphate fertilizer manufacturing
facilities will be in accordance with NSPS, adopted by USEPA pursuant to
Section 306, and pretreatment standards promulgated to implement Section
307 (b). Stricter effluent limitations may be applied on a site specific basis
if required to achieve water quality standards.
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The effluent NSPS promulgated for new sources in the Fertilizer Manu-
facturing Point Source, Phosphate Subcategory under 40 CFR 418 are shown in
Table 15. "Calcium sulfate" in Table 15 refers to gypsum or other calcium
sulfate solid materials, which normally include dihydrate, anhydrite, or hemi-
hydrite.
In principle, phosphate fertilizer manufacturing facilities can discharge con-
taminated nonprocess wastewater, with pretreatment, to publicly owned treat-
ment works (POTW). In practice, however, nonprocess wastewater is often
either combined with process wastewater or treated separately and either
discharged or, once treated to remove such constituents as cooling water
treatment chemicals (zinc or chromium compounds, for example), may be combined
with process wastewater.
The USEPA pretreatment regulations stipulate that certain POTW's cate-
gorized by size and influent characteristics develop POTW Pretreatment Pro-
grams. These programs are intended to prevent the introduction of pollutants
by industrial users that would interfere with the operations of treatment
works, would pass through treatment works, or would adversely affect oppor-
tunities to recycle and reclaim wastewaters and sludges.
Regardless of specific limitations required by the Pretreatment Programs,
the regulations (40 CFR 403.5) state the following may not be introduced into
a POTW:
• Pollutants which create a fire or explosion hazard in the POTW.
• Pollutants which will cause corrosive structural damage to the
POTW, but in no case discharges with pH lower than 5.0, unless the
works is specifically designed to accomodate such discharges.
• Solid or viscous pollutants in amounts which cause obstruction to
the flow in sewers, or other interference with the operation of the
POTW.
• Any pollutant, including oxygen demanding pollutants, released in a
discharge or such volume or strength as to cause interference in the
POTW.
« Heat tn amounts which will inhibit biological activity in the
POTW resulting in interference but in no case heat in such quantities
that the temperature at the treatment works influent exceeds 40 C
(104 F) unless the works is designed to accommodate such heat.
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Table 15. Standards of performance for new sources
for wastewater effluents.
The following standards of performance establish the quantity or quality
of pollutants or pollutant properties which may be discharged by a new source
subject to the provisions of this subpart:
(a) Subject to the provision of paragraphs (b) and (c) of this section, the
following limitations establish the quantity or quality of pollutants or
pollutant properties, controlled by this section, which may be discharged by a
point source subject to the provisions of this subpart after application of
the best available demonstrated control technology: there shall be no dis-
charge of process wastewater pollutants to navigable waters (41 FR 20582,
May 19, 1976).
(b) Process wastewater pollutants from a calcium sulfate storage pile runoff
facility operated separately or in combination with a water recirculation
system designed, constructed, and operated to maintain a surge capacity equal
to the runoff from the 25-year, 24-hour rainfall event may be discharged,
after treatment to the standards set forth in paragraph (c) below, whenever
chronic or catastrophic precipitation events cause the water level to rise
into the surge capacity. Process wastewater must be treated and discharged
whenever the water level equals or exceeds the midpoint of the surge capacity
(41 FR 20582, May 19, 1976).
(c) The concentration of pollutants discharged in process wastewater pursuant
to the limitations of paragraph (b) shall not exceed the values listed in the
following table:
Effluent Limitations (mg/1)
Average of daily
Effluent Maximum for values for 30 con-
Characteristic any one day secutive days shall
not exceed
Total Phosphorus (as P) 105 35
Fluoride 75 25
TSS 150 50
(42 FR 16140, March 25, 1977)
The total suspended solids limitation set forth in this paragraph shall be
waived for process wastewater from a calcium sulfate storage pile runoff
facility operated separately or in combination with a water recirculation
system, which is chemically treated and then clarified or settled to meet the
other pollutant limitations set forth in this paragraph (41 FR 20582, May 19,
1976).
107
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Table 15 concluded.
(d) The concentration of pollutants discharged in contaminated nonprocess
wastewater shall not exceed the values listed in the following table:
Effluent Limitations (mg/1)
Average of daily
Effluent Maximum for values for 30 con-
Characteristic any one day secutive days shall
not exceed
Total Phosphorus (as P)
Fluoride
105
75
35
25
(41 FR 20582, May 19, 1976; 42 FR 16140, March 25, 1977)
The effluent guidelines listed above do not presently include standards
for pH. Standards of 8.0 to 9.5 which were previously promulgated were re-
manded in 1976, but limitations on pH of 6-9 are generally set at the State
level or as a condition of the NPDES permit.
The pretreatment standards promulgated for new sources in the phosphate
subcategory are quoted below:
The pretreatment standards under Section 307(c) of the Act for a
source within the phosphate subcategory, which is a user of a
publicly owned treatment works (and which would be a new source
subject to Section 306 of the Act, if it were to discharge pol-
lutants to the navigable waters), shall be the standard set forth
in 40 CFR part 128, except that for the purpose of this section,
40 CFR 128, 133 shall be amended to read as follows:
In addition to the prohibitions set forth in 40 CFR 128, 131, the
pretreatment standard for incompatible pollutants introduced into
a publicly owned treatment works shall be as follows: There shall
be no discharge of process waste water pollutants (40 CFR 418.16).
Note: 40 CFR 128, Environmental Protection Agency Pretreatment Standards,
were issued in the June 26, 1978 Federal Register as 40 CFR 403.
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In addition, there is a restriction on thermal discharges that becomes
effective in June 1981.
Since new sources discharging to PO'TW's do not require NPDES permits,
they are not subject to NEPA under Section 511 (c) of the Federal Water Pol-
lution Control Act, as amended by the Clean Water Act of 1977.
NPDES permits also impose special conditions beyond the effluent limita-
tions stipulated, such as schedules of compliance and treatment standards.
Once facilities are constructed in conformance with all applicable standards
of performance, however, they are relieved by Section 306(d) from meeting any
more stringent standards of performance for 10 years or during the period of
depreciation or amortization, whichever ends first. This guarantee does not
extend, however, to toxic effluent standards adopted under Section 307(a),
which can be added to the facility's NPDES permit when they are promulgated.
Toxic pollutants thus far identified do not include phosphate-fertilizer-related
substances. The process which would be most likely to be considered in future
toxic standards are solvent extraction processes for uranium oxide.
Many states have qualified, as permitted by Public Law 92-500, to ad-
minister their own NPDES permit programs. The major difference in obtaining
an NPDES permit through approved State programs vis-a-vis the Federal NPDES
permit program is that the Act does not extend the NEPA environmental impact
assessment requirements to State programs. It is likely that new facilities
or major expansions of existing facilities will come under increased environ-
mental review in the future. Because the scope of the implementing regula-
tions varies considerably, current information on prevailing requirements
should be obtained early in the planning process from permitting authorities
in the appropriate jurisdiction.
1.6.2 Air Pollution
The Federal regulations applicable to the air emissions from phosphate
fertilizer manufacturing facilities are promulgated under six industry sub-
categories. The NSPS for the Sulfuric Acid Subcategory apply to sulfur di-
109
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oxide and acid mist. The NSPS for the other five subcategories - Wet Process
Phosphoric Acid Plants, Superphosphoric Acid Plants, Triple Superphosphate
Plants, Granular Triple Superphosphate Storage Facilities, and Diammonium
Phosphate Plants - apply to emissions of fluorine and all fluoride compounds
(total fluorides).
The NSPS for the applicable subcategories are shown in Table 16. The
standards for sulfuric acid plants, although promulgated, have been involved
in lengthy litigations and have been virtually non-effective. A review of the
standards was completed in August 1978 (USEPA 1978a) which has recommended
that no revisions be made to the NSPS for sulfur dioxide or acid mists. Some
states have, however, adopted stricter standards, although some of them apply
Table 16. New source performance standards for emissions
of air pollutants from sulfuric acid plants and phosphate
fertilizer manufacturing facilities.
Process
Sulfuric Acid Plants
Wet Process Phosphoric
Acid Plants
Superphosphoric Acid
Plants
Diammonium Phosphate
Plants
Triple Superphosphate
Plants
Granular Triple Super-
phosphate Storage
Facilities
Standard
Sulfur dioxide: 2kg/metric ton (4 Ib/ton) of
100% H2SO, produced.
Acid Mist: (1) No more than 0.075 kg/metric
ton (1.15 Ib/ton) of 100% ^SO, produced.
(2) Not to equal or exceed 10% opacity.
Total fluorides:
ton of
Not to exceed 10.0 g/metric
equivalent ?20 feed (0.020 Ib/ton)
Total fluorides: Not to exceed 5.0 g/metric
ton of equivalent P 0_ feed (0.010 Ib/ton)
Total fluorides: Not to exceed 30 g/metric
ton or equivalent P 0 feed (0.060 Ib/ton)
Total fluorides: Not
ton of equivalent I
to exceed 100 g/metric
205 feed (0.20 Ib/ton)
Total fluorides: Not to exceed 0.25 g/hr/metric
ton of equivalent P-O stored (5.0 x 10 lb/
hr/ton)
Sources: 40 CFR Part 60, 40 CFR Part 422.
110
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only to specific industries or only to combustion sources. The applicability
of these standards should be clarified when considering the impact of any new
source.
It is possible that the Federal sulfur dioxide ambient air quality stan-
dards (40 CFR Part 50), which are nonenforceable goals for acceptable levels
of this pollutant, may be exceeded in the vicinity of phosphate fertilizer
facilities. Depending on site-specific operations, ambient air standards for
particulates could be violated by many types of operations in this industry,
especially in processing and handling phosphate rock and dry phosphate ferti-
lizer products. Standards for sulfur dioxide and particulates are shown in
Table 17.
Table 17. Federal ambient air quality standards.
Sulfur Dioxide
(Ug/m3)
Primary standard:
Annual arithmetic mean 80
Maximum 24-hour concentration not to
be exceeded more than once a year 365
Secondary standard:
Maximum 3-hour concentration not to
be exceeded more than once a year 1,300
Particulates
Primary standard:
Annual geometric mean 75
Maximum 24-hour concentration not to
be exceeded more than once a year 260
Secondary standard:
Annual geometric mean 60
SOURCE: 40 CFR Part 50.
Ill
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Sulfuric acid plants or phosphate rock processing facilities with the
capacity to emit 100 tons (91 kkg, or metric tons) or more per year of any air
pollutant may be prohibited from constructing new facilities in certain areas
under the Clean Air Act (P.L. 95-95) Prevention of Significant Deterioration
(PSD) regulations. Also, any facility (which would include plants which react
phosphoric acid but do not actually process phosphate rock) with the potential
to emit 250 tons (227 kkg) or more per year of any pollutant may be prohibited
from constructing new facilities in certain areas. Alternately, facilities in
either of these two categories could be required to meet stricter air quality
goals than the ambient air standards in other areas. The Clean Air Act Amend-
ments of 1977 (P.L. 95-95) establish three types of areas to which PSD regula-
tions may apply:
• Class I areas, in which almost any deterioration of air quality
is deemed significant.
• Class II areas, in which*a moderate increase in pollution concen-
tration is acceptable, to allow for moderate growth.
« Class III areas, in which a greater pollutant increase is acceptable.
Increases in pollutant concentrations over baseline values are limited in
these areas to those shown in Table 18. The allowable increments are limited
to those which will not cause violations of the ambient air quality standards.
The PSD program requires preconstruction approval of all new sources with
significant potential emissions of SO. or particulate matter. Applicants for
construction permits must demonstrate by monitoring and submission of air
quality data that the new facility will not violate an applicable NSPS or
increment or any air quality standard.
All international parks, national wilderness areas, and national memorial
parks that exceed 5,000 acres, and all national parks that exceed 6,000 acres
are classified as Class I areas. However, an exception may be granted to a
source exceeding the Class I allowable increase on these mandatory Class I
areas if a Federal land manager certifies that the facility will have no
adverse impact on the air quality-related values, including visibility. In
such cases, the allowable increases listed in the last column of Table 18
apply.
112
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Table 18. Nondeterioration increments for 502 and
particulate matter in areas with different air
quality classifications.
Pollutant Class^I Class II Class III Class I exception
(yg/m ) (yg/m ) (yg/m ) (yg/m )
Particulate matter:
Annual geometric mean 5 19 37 19
24-hour maximum 10 37 75 37
Sulfur dioxide:
Annual arithmetic mean 2 20 40 20
24-hour maximum 5* 91 182 91
3-hour maximum 25* 512 700 325
*A variance may be allowed to exceed each of these increments on 18 days
per year, subject to limiting 24-hour increments of 36 yg/m^ for low
terrain and .62 yg/m^ for high terrain and 3-hour increments of 130 yg/m^
for low terrain and 221 yg/m^ for high terrain. To obtain such a variance
requires both State and Federal approval.
SOURCE: Clean Air Act Amendments of 1977.
113
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All other areas are designated as Class II, but states may redesignate
these areas as Class I or III, provided certain requirements of Public Law
95-95 are fulfilled.
Similar air quality regulations may be applied to new facilities or
significantly modified existing facilities in industrial areas where ambient
air standards are being exceeded (nonattainment areas). Permits will be
required for construction and operation of major new or modified sources and
applicants will be required to achieve the "lowest achievable emission rate"
(LAER) of any pollutant which exceeds the standards. This rate is defined as
a rate of emissions which reflects:
e the most stringent emission limitation in the applicable state
implementation plan unless the applicant can demonstrate that such
limitations are not achievable; or
e the most stringent limitation which is actually achieved in prac-
tice by similar facilities.
Public Law 95-95 further requires that the permit to construct and operate
may be issued only if:
• by the time the facility is to commence operation, total allowable
emissions from all existing and new sources in the Air Quality Control
Region, including the new or modified facility, will permit reasonable
further progress toward attainment of the applicable national ambient
air standard for the identified pollutant; or
• the emissions of such pollutant from the new or modified facility
will not cause the total emissions of the pollutant to exceed the
allowance permitted by the implementation plan for the pollutant from
all new or modified sources in the area.
The purpose of these requirements is to allow, under strict stipulations,
that the economic benefits to a region from introduction of new industry or
new expansion of existing industry (new sources) may be obtained. The quali-
fying condition is that the new action must be accomplished in a way to assure
progress toward compliance in the nonattainment area. Thus, permits issued by
USEPA or the approved State agency must require "offsets" in the existing
levels for pollutants which exceed Federal ambient air quality standards.
114
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Offsets are enforceable reductions from the existing sources of air
pollutants which will be greater than the emissions of those pollutants antici-
pated from the new source. A "new air quality benefit" must result from the
combined new project plus the offsets attained (44 FR 3284, Part IV.A.4 and 44
FR 3275). The quantity of offsets must match the new source emissions on a
"more than one-for-one" basis. The manner in which offsets may be attained is
not specified. Several possible approaches have been used:
• when the new source is an expansion of an existing facility, the
owner may install tighter controls on existing operations to achieve
emissions which may be lower than those otherwise required for the
existing sources;
• when the new source is an entirely new plant under a new owner in
the nonattainment area, the applicant may reach an agreement with one
or more existing sources whereby they agree to apply stricter pollu-
tion control measures, presumably in exchange for compensation by the
new source applicant;
• .in some instances, the applicant may purchase outright an existing
facility, especially an obsolete facility with high pollutant emis-
sions, and either clean it up or simply close it down;
• in cases where the state and/or local government are extremely
interested in locating the new source industry in the area, say, due
to the benefits to the local economy, they may assist the applicant
either by putting pressure on the existing sources to achieve stricter
pollution control standards or by public works actions such as paving
of roads in the area to help reduce background particulate emissions.
The amount of time required to process PSD applications could run to
several years in some controversial cases and adequate lead time for design,
for modeling of air quality effects, and for required monitoring (one year)
should be anticipated. The USEPA is committed to a policy of expediting
permit application processing, public participation activities, and internal
reviews so that the entire PSD review process could theoretically be carried
out within 90 days after receipt of a complete and technically substantiated
application. This time, however, could be extended by state review procedures,
litigation, or offset arrangements in a highly industrialized nonattainment
area. Hoffnagle and Dunlap (1978) emphasize that an industry should allow
adequate time for the one-year baseline monitoring. Review and approval by
regulatory agencies of the design of the monitoring plan at the earliest
possible time can be a time saver. Total time involved in the PSD process for
115
-------
the permit applicant may realistically range from 18-43 months, as illustrated
below (Hoffnagle and Dunlap 1978):
Activity
Specify monitoring required
Select vendors and contractors
Procure and install equipment
Conduct 1-yr baseline monitoring
Complete data analysis, modeling
and permit application
Request special model (if
necessary) with agency hearing
and review
Hearings on application and
agency review
Time for
Activity
(Months)
1-2
0-3
1-4
12
1-4
0-6
3-12
Cumulative
Time
(Months)
1-2
1-5
2-9
14-21
15-25
15-31
18-43
1.6.3 Solid Waste Regulations
The Resource Conservation and Recovery Act (RCRA), P.L. 94-580, defines
"solid waste" as including solid, liquid, semisolid, or contained gaseous
materials. Regulations implementing Subtitle C of the Act (40 CFR Part 261)
provide that a solid waste is a hazardous waste if it is, or contains, a
hazardous waste listed in Subpart D of Part 261 or the waste exhibits any of
the characteristics defined in Subpart C. These charcateristics include:
o Ignitability (flash point below 60° C (140° F)
o Corrosivity
o Reactivity
o Toxicity
Hazardous wastes are identified in 40 CFR 261 Subpart D. The hazardous
substances identified at this time in Subpart D do not include the major
solid wastes of the phosphate fertilizer industry. However, this does not
116
-------
eliminate the possibility of industry wastes having "hazardous" designations
in the future. Wastes containing arsenic or cadmium, for example, may be
considered hazardous if the toxic materials can be leached out at concentrations
of 5 mg/1 and 1 tng/1, respectively, using the EP (Extraction Procedure) toxicity
test. The natur of the wastes to be generated by a particular new source
phosphate fertilizer plant will have to be carefully examined to determine the
applicability of the hazardous waste designation.
All new facilities that will generate, transport, treat, store, or dis-
pose of hazardous wastes must notify US EPA of this occurrence and obtain a
USEPA identification number. Storage, treating, and disposal also require a
pe rmi t.
The determination of whether wastes generated or handled are hazardous is
the responsibility of the owner or operator of the generating or handling
facility. The first step is to consult the promulgated list (CFR 261 Subpart
D). If the waste is not listed, the second step is to determine whether the
waste exhibits any of the hazardous characteristics of listed through analytical
tests using procedures promulgated in the regulations of by applying known
information about characteristics of the waste based on process or materials
used.
If it is determined that a hazardous waste is generated, it should be
quantified to determine applicability of the small generator exemption. This
cutoff point is 2,200 pounds per month, but it drops to 2.2 pounds for any
commercial product or manufacturing chemical intermediate having a generic
name listed in Section 261.33. Containers that have been used to contain less
than 21 quarts of Section 261.33 materials and less than 22 pounds of liners
from such containers are also exempt. It is anticipated that this exemption
may be available to many very small plants with, for example, only one machine
tool and one small painting operation. However, as more information is ob-
tained on the behavior of substances in a disposal environment, the terms of
th:'.s exemption may be altered from time to time.
116a
-------
The hazardous waste management system is based on the use of a manifest
prepared by the generator describing and quantifying the waste and designating
a disposal, treatment, or storage facility permitted to receive the type waste
described to which the waste is to be delivered. One alternate site may be
designated. Copies of the manifest are turned over to the transporter and a
copy must be signed and returned to the generator each time the waste changes
hands. If the generator does not receive a copy from the designate' receiving
facility or alternate within 35 days, he must track the fate of the waste
'.'•.rough the transporter and designated facility or facilities. If the mani-
fest copy is not received in 45 days, the generator must file an Exception
Report with US EPA or the cognizant state agency.
A copy of each manifest must be kept for three years or until a signed
copy is received from the designated receiving facility. In turn, the si.aed
copy must be kept for three years. The same retention period applies to each
Annual Report required whether disposal, storage, or treatment occurs on-site
or off-site.
The generator must also:
e package the waste in accordance with the applicable DOT regulations
under 49 CFR Parts 173, 178, and 179;
# label each package in accordance with DOT regulations under 49 CFR 172;
r imrk each package in accordance with the applicable DOT regulations
under 49 CFR 172;
9 nark each container of 110 gallons or less with the following DOT
(49 CFR 172) notice:
"Hazardous Waste - Federal Law Prohibits Improper Disposal.
If found, contact the nearest police or public safety authority
or the U.S. Environmental Protection Agency."
« supply appropriate placards for the transporting vehicle in accordance
with DOT regulations under 49 CFR Part 172, Sub part F.
H6b
-------
Waste in properly labelled and dated containers in compliance with the
regulations may be stored on the generator's premises for up to 90 days with-
out a storage permit. This is to permit time for accumulation for more economic
pickup or to find an available permitted disposal facility.
Due to the cost and stringent design and operating requirements for
permitted landfills, it is anticipated that most new generator plants will
utilize off-site disposal facilities. However, any companies desiring to
construct their own will be subject to 40 CFR Part 264.
Incineration is considered to be "treatment," and, as such, is also
subject to Part 264 as are chemical, physical, and biological treatment of
hazardous wastes, and a permit will be required. Totally enclosed treatment
systems--such as in-pipe treatment of acid and alkaline solutions—are i ot
subject to this part.
Although underground injection of wastes constitutes "disposal" as de-
fined by RCRA, this activity will be regulated by "he underground injection
control (UIC) program adopted pursuant to the Safe Drinking Water Act (P.L.
93-523). The consolidated permit regulations (40 CFR Parts 122, 123, 124)
govern the procedural aspects of this program; the technical considerations
are contained in 40 CFR Part 146.
The disposal of innocuous solid wastes is subject to Subtitle D of RCRA
and the implementing regulations (40 CFR Part 256). Recovery or disposal in
an approved sanitary landfill will be required under a state program. Disposal
in open dumps is prohibited. All existing state regulations which do not meet
the requirements of Subtitle D are superseded.
116c
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1.6.4 Monitoring Requirements
In addition to applying the best available technology to abate and con-
trol adverse environmental impacts from air emissions, wastewater streams, and
land disposal of wastes, an NPDES permit applicant will be required to demon-
strate compliance with applicable pollution control regulations. The NPDES
permit itself may require monitoring, recording, and recordkeeping on flow of
all pollutants that are subject to reduction or elimination under the terms
and conditions of the permit, as well as any other pollutant as required by
the State or USEPA. Monitoring intervals must be sufficiently frequent to
yield data that reasonably characterize the nature of the discharge.
Similarly, monitoring of leachate, runoff, and air emissions will be
required under the Federal RCRA on sites where wastes determined to be hazar-
dous are landfilled. In addition, it is not inconceivable that some type of
monitoring may be required for some, if not all, disposal sites for non-hazar-
dous wastes to ensure that "there is no reasonable probability of adverse
effects on health of the environment" (Section 4004(a), RCRA).
117
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2.0 IMPACT IDENTIFICATION
2.1 PROCESS WASTES
2.1.1 Materials Balance and Typical Waste Characteristics
2.1.1.1 Sulfuric Acid Production
The only wastewater streams produced in the sulfuric acid production
process are blowdown from boilers and cooling towers. Figure 33 illustrates
the blowdown sources and quantities for a typical installation using double
absorption; older units using single absorption produce the same wastewater
quantities. A materials balance for sulfuric acid production is given in
Table 19.
A plant producing phosphoric acid will usually include sulfuric acid
production. The EID should include the operating data categories listed
above. Several plants built since 1971 have installed single absorption
process designs, usually with an ammonia scrubbing type of emission control
system for SO- removal, but double absorption is preferred by most operators,
depending on economic variables (Section 3.2.1).
Cooling Water Contaminants
The EID should include computations of planned quantities of cooling
water blowdown and list the probable range of contaminants, based on operating
parameters and make-up water quality. The quality of cooling system blowdown
varies both with the level of impurities in the make-up water and the amount
and types of inhibitor chemicals used. Data collected for the effluent guide-
lines study (USEPA 1974a) indicated the following normal range of contaminants
in cooling water blowdown:
Contaminant Concentration (mg/1)
Chromate 0-250
Sulfate 500-3000
Chloride 35-160
Phosphate 10-50
Zinc 0-30
TDS 500-10,000
SS 0-50
Biocides 0-100
118
-------
STREAM LEGEND
MAIN LIQUID
(2.2 TON/TON)
OFF GAS
— — MAIN GAS
\ MINOR
FEED STREAM L_
1300— 1670 l/kkg
(310 ~ 400 GAL/TON;
1875 ~ 2080 l/kkg
(450 ~ 500 GAL/TON)
BLOW DOWN
1
[ COOLING H20[4
r
SULFUR
FURNACE
«^,000 ~ 83.500 l/kkg
(3.COO ~ 20.000 GAL/TON)
ED
Ft
:E
w n L
H20 |_
BOILER
r
STEAM
WASTE
HEAT
BOILER
BLOWDOWNl .
5 ~ 10 GAL/TON) 21-
f
1
1
y+
i
CONVERSION
1-»
*"T"
- 40 l/kkg ~~{ !
ACID
1 I
HEAT
EXCH.
COOLING &
PUMPING
ABSORPTION
INTERSTAGE
ABSORPTION
PRODUCT
PROCESS WATER
(15 - 20 GAL/TON)
03 ~ 83 l/kkg
*GN = SHORT TON
kkg = METRIC TON
Figure 33. Sulfuric acid plant - double catalysis
(flow rates per ton 100% H SO ).
Source: Adapted from U.S. Environmental Protection Agency. 1974a. Development document for effluent
limitations guidelines and new source performance standards for the basic fertilizer chemicals segment
of the fertilizer manufacturing point source category. Office of Air and Water Programs, Washington DC,
168 p.
-------
Table 19. Sulfuric acid production materials balance.
Input Materials
(per unit weight of 100% H
Waste Streams
(per unit weight of 100%
Air
Sulfur -
Water
10.6 ton/ton
(10.6 Mg/Mg)
0.33 ton/ton
(0.33 Mg/Mg)
15-20 gal/ton
(3.6-4.8 1/Mg)
• Tail gas
2.2 ton/ton
(2.2 Mg/Mg)
- S0? (single absorption with
no emission controls)
21.5 - 85 Ib/ton
(10.8 - 42.5 kg/Mg)
- SO- (double absorption)
(1.8 Ib/ton)
(0.9 kg/Mg)
- Acid mist (no emission controls)
0.4a> - 9 Ib/ton
(2-50 mg/scf)b>
Discharge water - 710-1000 gal/ton
(170-240 1/Mg)
- Cooling blowdown - 400-600 gal/
ton (96-144 1/Mg)
- Boiler blowdown - 310-400 gal/
ton (74-96 1/Mg)
Notes: a. Lower value from a plant burning high purity sulfur.
b. scf = standard cubic foot.
SOURCE: Adapted from U.S. Environmental Protection Agency. 1978a. A review
of standards of performance for new stationary sources - sulfuric
acid plants; U.S. Environmental Protection Agency. 1974a. Develop-
ment document for effluent limitations guidelines and new source per-
formance standards for the basic fertilizer chemicals segment of
the fertilizer manufacturing point source category; and U.S. Environ-
mental Protection Agency. 1977b. Industrial process profiles for
environmental use, Chapter 22: The phosphate rock and basic ferti-
lizers industry.
120
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The EID should describe the proposed method of treating cooling tower
blowdown. It can be treated separately or combined with other plant effluents
for treatment. The method to be employed depends on the chemical treatment
method used and other cost factors. Those plants which utilize chromate or
zinc treatment compounds generally treat the blowdown stream separately to
minimize effluent treatment costs (USEPA 1974a).
Boiler Blowdown Contaminants
The EID should report anticipated quantities and contaminant levels for
boiler blowdown. The typical range of contaminant concentrations reported in
the effluent guidelines study (USEPA 1974a) for 310-400 gal/ton of boiler
blowdown are listed below:
Contaminant Concentration (mg/1)
Phosphate 5-50
Sulfite 0-100
TDS 500-3,500
Zinc 0-10
Alkalinity 50-700
Hardness 50-500
Silica (Si02) 25-80
To date, no effluent guidelines for either thermal discharge or con-
taminants associated with boiler blowdown have been proposed or promulgated,
but contaminants are monitored and State and/or USEPA regional offices involved
in new source permitting set up contaminant criteria. The EID should demon-
strate that boiler blowdown contaminants levels will conform to the locally
applicable criteria.
Air Emissions
Recent test data are available illustrating compliance with SO^ and acid
mist emissions. The study done by the MITRE Corporation for USEPA to evlaute
sulfuric acid plant NSPS (USEPA 1978a) obtained 29 sets of data representing
all 32 new sulfuric acid units built since the NSPS were issued. The results
indicate tested emission levels which can be compared with EID projections for
S09 and acid mist emissions (Table 20). Figures 34 and 35 display the data
121
-------
Table 20. New source performance standards compliance test
results for sulfuric acid plants
Nominal
UnlL Size
(1001 H2S04)
ML Industries, Inc. Sayreville, N.J. 910
910
IV Agrico Chemical, Inc. So. Pierce, Fla. 1640
CF Chemicals, Inc. Bartou, Fla. 1800
CF Chemicals, Inc. plant City, Fla. 1460
1460
GardLnier, Inc. Tampa, Fla. 2370
1460
W.R. Grace Co. Bartow, Fla. 1460
1460
1460
IMC Chemical Corp. Mulberry, Fla. 1800
1800
1800
Occidental Petroleum Corp. Uhlte Springs, 1640
Fl*' 1640
Am. Cyanamld Co. Savannah, Ga. 730
Miasissippl Chemical Corp. Pascagoula, Miaa. 1370
Texasgulf, Inc. Lee Creek, N.C. 1370
1370
(1000)
(1000)
(1800)
(2000)
(1600)
(1600)
(2600)
(1600)
(1600)
(1600)
(1600)
(2000)
(2000)
(2000)
(1800)
(1800)
(800)
(1500)
(1500)
(1500)
Average S02
Emissions
ItftAg of 1002
0.71
1.9
1.11
0.56
0.76
1.26
0.97
0.87
0.16
1.03
1.2
0.73
0.79
0.65
1.62
0.47
1.17
0.48
0.85
0.91
(1.
42)
(3.7)
(2.
(1.
(1.
(2.
(1.
22)
.12)
.52)
52)
.94)
(1.73)
(0.
(2.
(2.
(1.
(1.
(1.
(3.
(0.
.32)
16)
.3)
.45)
.58)
.30)
.23)
.93)
(2.33)
(0.95)
(1.
(1
.70)
.82)
Emission
of 1001
(lb/ton)
0.018
0.062
0.055
0.010
0.058
0.026
0.036
0.030
0.03
0.02
0.07
0.008
0.008
0-.011
0.071
0.064
0.030
0.064
0.023
0.037
Actual Plant Hcasured
B IlK/Hg
H2S04
(.035)
(.123)
(0.
(0.
(0.
(0.
(0.
109)
.021)
.116)
.052)
.071)
(0.061)
(0.
.06)
(.04)
(0.13)
(0,
.016)
(0.016)
(0
.022)
(0.142)
(0.
(0
(0
(0
(0
.127)
.059)
.128)
.046)
.073)
During NSPS During
Test Mg/day Test
IOOZ H2SO4 (TPD) (Percent)
845
808
1629
1781
1562
1277
2424
1616
1547
1535
1643
2457
2366
2503
1756
1641
779
1387
1474
1313
(929) 0
(888) 0
(1790)
(1957)
(1717)
(1403)
(2664) 015
(177O 0<5
(1700)
(1687)
(1805)
(2700)
(2600)
(2750)
(1930)
(1803)
(856)
(1524)
(1620)
(1443)
Reference
19f5ry et
Mlatry et
1975
CDS, 1978
CDS, 1978
CDS, 1978
CDS, 1978
Garrett ,
Garret t ,
CDS, 1978
Uu. 1978
Wu, 1978
CDS. 1978
CDS , 1978
CDS, 1978
CDS, 1978
CDS. 1978
Gardner,
CDS, 1978
CDS, 1978
CDS, 1978
.1..
al. .
1978
1978
;
1
1
1978
Anlln Corp."
Wood River, 111.
0.072 (0.144)
Agrico Chemical. Inc.
Agrico Chemical, Inc.
Freeport Chemical Co.
Rohn i Baas, Inc.
Donaldeonvllle,
La.
Convent, La.
Deer Park, Tx.
1640 (1800)
1640 (1800)
1460 (1600)
640 (700)
0.55 (1.10)
0.55 (1.11)
1.0 (1.99)
1.16 (2.32)
0.037 (.073)
0.042 (0.085)
0.08 (0.15)
0.041 (0.082)
1830 (2011)
1677 (1843)
1694 (1862)
716 (787)
Shonk, 1978
Shonk. 1978
Spruiell, 1978
Sprulell, 1978
Helms, Calif.
1640 (1800)
0.04 (.07)
Reynolds, 1978
Beker Industries, Inc.
J.R. Slmplot Co.
Allied Chemical Corp.
Conda, Idaho 770 (850) 1.56 (3.02) 0.053 (0.105) 1001 (1100)
Pocatello, Idaho 810 (900)b 0.53 (1.05)b 0.046 (0.092)b 853 (938)b
Anacortes, Wash. 300 (330) 1.70 (3.41)c 0.04 (0.07)c 222 (244)
'This facility was purchased by shell Oil Co. in 1976; the plant is being modified to incorporate . double absorption process for S02 control.
Total output of two units.
cAverage of three units.
Pfaider, 1978
Pfander, 1978
Snowden & Alguard,
1976
Source: U.S. Environmental Protection Agency. 1978a. A review of standards of
performance for new stationary sources - sulfuric acid plants. Prepared by
Marvin Drabkin and Kathryn J. Brooks, MITRE Corp., McLean VA. Variously paged,
80 p.
-------
graphically and indicate a high degree of scatter. This scatter has been
interpreted to indicate problems in the USEPA Method 8 used since 1971 to
monitor compliance. If so, the probable effect has been that some SO- results
are low and some acid mist results are high. Method 8 was revised effective
August 18, 1977 (USEPA 1978a).
2.1.1.2 Phosphate Rock Processing
The EID should include operating data for rock processing, which includes
handling, grinding, and storage of the beneficiated phosphate rock. Table 21
indicates the materials balance for phosphate rock processing.
Table 21. Phosphate rock processing materials balance.
Input Materials Waste Streams
(per unit weight of marketable rock) (per unit weight of marketable rock)
• Phosphate rock - 1 ton/ton • Particulates - less than 20 lb/
(1 Mg/Mg) ton (10 kg/Mg)
• Cooling water - 8-150 gal/ton • Cooling water - 8-150 gal/ton
(33-625 1/Mg) (33-625 1/Mg)
non-contaminated - temperature increase only in discharge.
SOURCE: U.S. Environmental Protection Agency. 1974a. Development document
limitations guidelines and new source performance standards for the
basic fertilizer chemicals segment of the fertilizer manufacturing
point source category; and U.S. Environmental Protection Agency.
1977b. Industrial process profiles for environmental use, Chapter 22:
The phosphate rock and basic fertilizers industry.
The option to utilize wet grinding does not substantially alter the
information in Table 21. The small amount of make-up water introduced in the
grinding operation is transferred to the next process and is equivalent to a
slight lowering of the sulfuric acid concentration in the acidualtion operation.
Definitive data on quantities of particulate air emissions generated are not
available.
123
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-H4 Current EPA NSPS - Sulfuric Acid Plants
500 1000 1500 2000
Plant Production Rate, TPD
2500
3000
Figure 34. Contact process sulfuric acid plants,
SC>2 emissions.
Source: U.S. Environmental Protection Agency. 1978a. A review of standards
of performance for new stationary sources - sulfuric acid plants. Prepared
by Marvin Drabkin and Kathryn J. Brooks, MITRE Corporation, McLean VA.
Variously paged.
124
-------
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-4^--(—I- —(—
ttt~f
-r i +
•+-H
-d^t.
mr
t++4
^^
i±±
:tir
^t
hT-
--H-+
--t-T-i-
3S
i_.
-4-
•-U-
il-
Current EPA NSPS Sulfuric Acid Plants"
"T
Ttdrt+ti
t_a:
rh-^i-
rOi±
in
-n-f
hff-
444
t-t-t-
T
m
^trq
til
rcn
-=rTH
mtg:
Legend:
O - Region 2
O - Region 4
B Region 5
Q - Region 6
^ - Region 9
0 - Region 10
4-1-
•-*-)•-
t
Tttl
+XX£l!HT
tttx
:±:
500
1000 1500 2000
Plant Production Rate, TPD
2500
3000
Figure 35. Contact process sulfuric acid plants,
acid mist emissions.
Source: U.S. Environmental Protection Agency. 1978a. A review of standards
of performance for new stationary sources - sulfuric acid plants. Prepared
by Marvin Drabkin and Kathryn J. Brooks. MITRE Corporation, McLean VA.
Variously paged, 80 p.
-------
2.1.1.3 Wet Process Phosphoric Acid Production, Concentration, and
Clarification
Because of the integrated nature of the phosphate fertilizer processes
downstream of sulfuric acid production, waste streams arising from different
operations are combined for treatment at as few locations as feasible. Infor-
mation compiled in the Source Assessment: Phosphate Fertilizer Industry
(USEPA 1979a) is available to characterize combined and component waste streams
for the more than 80% of the industry which operate multi-unit plants. To
utilize the Source Assessment information, waste stream characteristics are
discussed in reference to integrated processes and treatment.
Wastewater Characteristics
Three types of wastewater streams are generated at phosphate fertilizer
plants:
• contact process water;
• noncontact cooling water;
• steam condensate.
Wastewater sources from the integrated wet process phosphoric acid production
including concentration and clarification are:
(1) For contact process water -
• wet scrubber liquor;
• gypsum slurry;
• barometric condensers;
• acid sludge.
(2) For non-contact cooling water -
• control of exothermic reaction in dilution of sulfuric acid
and acidulation of phosphate rock.
(3) For steam condensate -
• steam jet ejector, vapor condensate from barometric condenser.
Wet Process Phosphoric Acid Processes
The EID should include operating data to support projected waste stream
rates. Table 22 is a materials balance including typical values from the
USEPA Development Document (USEPA 1974a). Figures 36 and 37 illustrate input
and outflow quantities of materials in the production of wet process phosphoric
acid and superphosphoric acid.
126
-------
t I
IN OUT
COOIINO WATER
0 TO 20 m / metric ton P
—5 TO 6 m / metric ton P,0,
5 TO 6 m3/ metric ton PO
— AIR STREAM
— AQUEOUS STREAM
Figure 36. Wet process for production of phosphoric acid.
STEAM _
CONTAMINATED WATER FROM GYPSUM POND
r —
i
PHOSPHORIC ACID <
_L r S
STEAM Pi 3
CONDENSATE
PUMP SEAL WATER
BAROMETRIC
CONDENSER
-On
i
LI STEAM JET
J EJECTOR
CONCENTRATED
PHOSPHORIC ACID
wtu
CONTAMINATED WATER
8 TO 16x10 m/ metric ton P205
2.2 TO 2.4 m3
25
Figure 37. Production of superphosphoric acid.
Source (Figures 36 and 37): U.S. Environmental Protection Agency. 1977a.
(Preliminary) Source assessment: Phosphate fertilizer industry, phosphoric
acid and superphosphoric acid. Office of Research and Development. Washing-
ton DC. Prepared by G.D. Rawlings, E.A. Mullen, and J.M. Nyers, Monsanto
Corporation, Dayton OH, 93 p.
127
-------
Table 22. Phosphoric acid material balance.
Input Materials
(per ton PO^)
Acidulation Phase
• Phosphate rock (32% avg.
- 0.96 ton
^,-
Waste Streams
(per ton P0OJ
• Sulfuric acid (93% avg. H_SO,)
- 1.11 ton
• Non-contact cooling water
- 0 to 4,500 gal
(0 to 19,000 1/Mg)
• Contaminated process water
- 3,800 to 5,000 gal
(16,400 to 20,800 1/Mg)
Concentration Phase
• Contaminated process water
- 550-570 gal
(2500-2600 1/Mg)
0 to 4,500 gal
(0 to 19,000 1/Mg)
3,800 to 5,000 gal
(16,400 to 20,800 1/Mg)
- 550-570 gal (+0.2-0.4 gal)
condensate) (2500-2600 1/Mg)
• Fluorides emissions
- 0.02-0.07 Ib
- 0.60 Ib in poorly controlled
plants
• Combined gypsum wastes from
first two phases
- 1.36 tons (contains 0.5%
fluorine)
Clarification Phase
• Contaminated cooling and wash
water
- 165-770 gal
(690-3200 1/Mg)
- 165-770 gal
(690-3200 1/Mg)
128
-------
Table 22. Phosphoric acid (concluded).
Input Materials
(per ton PO^)
Superphosphoric Acid Phase
• Input quantities not available
Waste Streams
(per ton PnOr)
Fluorides
- less than 0.01 Ib. for
vacuum evaporation process
- 0.12 Ib for submerged com-
bustion process
SOURCES: U.S. Environmental Protection Agency. 1974a. Development document
for effluent limitations guidelines and new source performance
standards for the basic fertilizer chemicals segment of the fer-
tilizer manufacturing point source category; U.S. Environmental
Protection Agency. 1977a. (Preliminary) Source assessment: Phos-
phate fertilizer industry, phosphoric acid and superphosphoric acid,
Office of Research and Development, Washington DC, U.S. Environ-
mental Protection Agency. 1974b. Background information for standards
of performance: Phosphate fertilizer industry, Volume 1, Proposed
standards; U.S. Environmental Protection Agency. 1977c. Final
guideline document: Control of fluoride emissions from existing
phosphate fertilizer plants.
129
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2.1.1.4 Dry Phosphate Fertilizer Production
Plants which produce NSP, TSP, and ammonium phosphates have similar waste
stream characteristics. The wet scrubber liquor is the only process wastewater
stream generated. Recycled gypsum pond water is used in the scrubber system
to reduce the level of fluoride gases and particulate matter evolved from the
mixer, den, and conveyors at NSP and run of pile TSP plants. At granular TSP
plants, offgases from the reactor, mixer, dryer, granulator, cooler, and
screens are absorbed in the scrubbing water. At ammonium phosphate plauts,
wet scrubbers are used primarily for ammonia recovery from the acid neutralizer
and ammoniator-granulator. Weak (28% PO*^) phosphoric acid is used as the
scrubbing liquor and is recycled back to the ammoniator-granulator. Secondary
wet scrubber systems are occasionally used to further remove fluorides, particu-
lates, ammonia, and combustion products issuing from the dryer, cooler, and
product screening operations. This secondary system uses contaminated water
as a scrubber liquor and is therefore a wastewater source (USEPA 1979a).
The wastewater and air emissions produced in the three solid product
processes are similar, with the addition of ammonia to wastewaters in ammonium
phosphates production. Since the processes all yield a salable end product
and do not feed into one another, three separate materials balances are given
in Tables 23, 24,, and 25.
Quantifying data for MAP and DAP ammonium phosphate processes are not
available for feedstocks. Wastewater streams associated with these conven-
tional processes, estimated in the USEPA Development Document, are given
below:
Contaminated Water -
input Waste Stream
MAP - 1200-1500 gal/ton - 0-72 gal/ton*
(5000-6500 1/Mg) (0-300 1/Mg)
DAP - 1200-1500 gal/ton - 1200-1500 gal/ton
(5000-6500 1/Mg) (5000-6500 1/Mg)
*
The fate of the difference in input and waste stream water is not accounted
for.
130
-------
Table 23. Normal superphosphate materials balance.
Input Materials Waste Streams
(per ton of NSP) (per ton of NSP)
Phosphate rock (34% avg. P2°5^
- 1200 to 1220 Ib
(600 to 610 kg/Mg)
Sulfuric acid (100% H2SO, basis) • Fluorine (solid waste or byproduct)
- 700 to 720 Ib - 16 to 20 Ib (as CaF, from removal
(350 to 360 kg/Mg) in limestone beds)
(8 to 10 kg/Mg)
Contaminated water (scrubbers)
- 225 to 250 gal - 225 to 250 gal
(940 to 1040 1/Mg) (940 to 1040 1/Mg)
SOURCES: U.S. Environmental Protection Agency. 1974a. Development document
for effluent limitations guidelines and new source performance
standards for the basic fertilizer chemicals segment of the ferti-
lizer manufacturing point source category; U.S. Environmental Pro-
tection Agency. 1977b. Industrial process profiles for environ-
mental use, Chapter 22: The phosphate rock and basic fertilizers
industry. Office of Research and Development, Cincinnati OH.
131
-------
Table 24. Granular triple superphosphate materials balance,
Input Materials Waste streams
(per ton of GTSP) (per ton of GTSP)
Phosphate rock (34% avg. P^O,-)
- 840 to 880 Ib
(420 to 440 kg/Mg)
Phosphoric acid (53% avg. P^O,.) • Fluorine (solid waste or byproduct)
- 980 to 1020 Ib - 20 to 24 Ib (as CaF, from removal
(490 to 510 kg/Mg) in limestone beds)
(10 to 12 kg/Mg)
- emissions of 0.20 to 0.60 Ib are
reported (0.10 to 0.30 kg/Mg)
• Contaminated water (scrubbers)
- 158-180 gal - 5-10 gal
(660-750 1/Mg) (21-40 1/Mg)
SOURCES: U.S. Environmental Protection Agency. 1974a. Development document
for effluent limitations guidelines and new source performance stan-
dards for the basic fertilizer chemicals segment of the fertilizer
manufacturing point source category; U.S. Environmental Protection
Agency. 1977b. Industrial process profiles for environmental use,
Chapter 22: The phosphate rock and basic fertilizers industry.
Office of Research and Development, Cincinnati OH.
132
-------
Table 25. Ammonium phosphate materials balance
(12-48-0-3.6S, MAP sulfate, 3-inch pipe-cross
reactor with ammoniator-granulator.
Input Materials Waste Streams
(per ton of product) (per ton of product)
• Ammonia
- 293 Ib - 2-3 Ib (recoverable in scrubbers)
(147 kg/Mg) (1.0-1.5 kg/Mg)
• Sulfuric acid (93% H2S04)
- 228 Ib
(144 kg/Mg)
• Phosphoric acid (54% P2°5^
- 1865 Ib
(932 kg/Mg)
• Make-up water
- 59 Ib
(30 kg/Mg)
• Contaminated water (scrubbers)
- 1200-1430 gal* - 1200-1430 gal*
(5000 - 6000 1/Mg) (5000 - 6000 1/Mg)
Surmised, based on DAP scrubber requirements (USEPA 1979a); quantities may
be less with pipe-cross reactor.
SOURCES: Compiled from Parker, B.R., M.M. Norton, and D.G. Salladay. 1977.
Developments in production of granular NP and NPK fertilizers using
the pipe and pipe-cross reactor; U.S. Environmental Protection
Agency. 1979a. Source assessment: Phosphate fertilizer industry.
Office of Research and Development, Washington DC.
133
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2.1.1.5 Gypsum Pond Characteristics
The BID should detail the design and capacity of wastewater storage
arrangements. All contaminated wastewater in new source phosphate fertilizer
facilities will be retained in gypsum ponds or recirculated using cooling
towers. Use of cooling towers is possible but usually economically imprac-
tical. Furthermore, meeting the no-discharge requirement becomes extremely
difficult without the freeboard buffer of the gypsum pond and precise water
balance among processes. More than 90% of the wet process phosphoric acid
plants in the United States use gypsum ponds (TRC 1979).
Besides being a reservoir and cooling pond, the gypsum pond plays an
integral part in the wastewater treatment scheme. The pond serves as a set-
tling basin for gypsum and other waste solids. To function properly and avoid
effluent discharge to surface waters, the size of the gypsum pond at a wet
process phosphoric acid plant is approximately 2.23 x 10 3 km2/metric ton
P«0j./day. Gypsum ponds are located adjacent to the plant complex; they are,
in many cases, abandoned phosphate rock mine pits (USEPA 1979a).
In most plants, more than one wastewater containment area is available.
As one gypsum pond becomes filled, the gypsum slurry is diverted to another
area and the original pond is dried and excavated into piles (TRC 1979). In
large ponds used for both cooling and gypsum settling, the area where gypsum
slurry enters the pond, where most of the gypsum settles, is known as the
gypsum flats. Wet gypsum from this area of the pond is removed by draglines
and transferred to an active gypsum pile while clarified gypsum pond water
farther downstream continues to be recycled to the plant (USEPA 1978c). With
each recycle, the level of dissolved contaminants in the water increases.
After 3 to 5 years of recycle, impurities in the pond waters approach equi-
librium concentrations (USEPA 1978c), a function of pH and temperature, which
is maintained by volatilization and precipitation of impurities (USEPA 1979a).
The typical ranges of equilibrium concentrations are shown in Table 26 (USEPA
1978c).
134
-------
Table 26. Typical equilibrium composition of gypsum pond water.
Contaminant
Phosphorus pentoxide,
equivalent
Fluoride
Sulfate
Calcium
Ammonia
Nitrate
Silica
Aluminum
Iron
PH
Concentration, g/nr
6,000 to 12,000
3,000 to 5,000
2,000 to 4,000
350 to 1,200
0 to 100
0 to 100
1,600
100 to 500
70 to 300
1.0 to 1.8
SOURCES: U.S. Environmental Protection Agency. 1978c. Evaluation of emissions
and control techniques for reducing fluoride emissions from gypsum
ponds in the phosphoric acid industry in U.S. Environmental Protection
Agency. 1979a. Source assessment: Phosphate fertilizer industry.
Office of Research and Development, Washington DC.
At pH less than 2, it is estimated that 80% of the phosphate present
exists as H-jPO,, the remaining 20% being the anion H2?04 (USEPA 1978c). The
major equilibrium of fluoride compounds as depicted in a model developed by
Environmental Science and Engineering, Inc., is shown in Figure 38 (USEPA 1978c).
In addition to the predominant compounds fluosilicic acid (H SiF,) and hydrogen
fluoride (HF), small amounts of fluoride will be present in the water as
soluble and insoluble aluminum and iron complexes. In addition, concentrations
of radium-226 in gypsum pond water reach 60-100 picocuries/liter (USEPA 1974a).
135
-------
ATMOSPHERE
SOLUBLE
Fe AND Al
COMPLEXES
H2SiF6>
SiO,
. :(AI,Fe) F, :':;•-•;•/ CaF? •'•;:;>:'v: (Na,K), SiF, :;.".
: / J ;,'.--.:..••' .•"..'••'.••' ^ 0
Figure 38. Major gypsum pond equilibrium.
Source: U.S. Environmental Protection Agency. 1978c. Evaluation of emissions
and control techniques for reducing fluoride emissions from gypsum ponds in
the phosphoric acid industry. Research Triangle Park NC, 218 p. in USEPA
1979a.
136
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2.1.1.6 Solid Waste Characteristics
There are three sources of solid residue in the phosphate fertilizer
industry (USEPA 1979a):
• gypsum from the filtration of wet process phosphoric acid
• wet process phosphoric acid sludge
• wet scrubber liquor
The quantity of gypsum produced in a wet process phosphoric acid plant
ranges from 4.6 to 5.2 metric tons of gypsum/metric ton P90,- produced. As
3
a rule of thumb, approximately 1,360 m of gypsum will be accumulated yearly
per metric ton of P2°5 Pr°duced per day (Slack 1968).
A second source of solid residue is the phosphate rock from which
impurity-bearing minerals settle out of the clarifier to form acid sludges.
Phosphate rock salts which contribute to the formation of acid sludges in-
clude: fluorine, iron, aluminum, silicon, sodium, and potassium salts.
Table 27 shows an analysis of solids collected at various stages of wet pro-
cess phosphoric acid production.
Table 27. Analysis of solids from wet process
phosphoric acid.
Analysis
Solids from
32% P205 acid (feed
to evaporators)
54% P205 acid from
evaporators
54% P20s acid after
storage
Phosphorus
pentoxide
1.9
6.8
38.9
Calcium
14.8
12.9
3.3
Sulfate
38.9
29.0
4.7
Alu-
minum
0.3
5.1
1.5
Iron
0.2
0.3
9.6
Fluo-
rine
19.9
22.0
12.9
Silica
10.3
5.3
6.1
Reprinted from Phosphoric Acid, Volume I, A.V. Slack, Editor, by permission of
Marcel Dekker, Inc. Year of first publication 1968.
Fluosilicates, fluorides, silica, cryolite (Na or K)3A1F6), sulfates,
unreacted phosphate rock, and various other combinations of the impurities as
complex salts have been identified in the acid sludge. The separated solids
137
-------
can either be dried and sold as fertilizer or sent to the gypsum pond.
Effluent from the clari
ton P0 (USEPA 1974a).
3 3
Effluent from the clarification process ranges from 0.7 m to 3.2 m /metric
The third source of solid residue wastes is the wet scrubber liquor.
At ammonium phosphate plants, for example, the scrubber liquor going to the
gypsum pond contains about 10 g of solid residue/kg P2°5° This solid residue
is primarily hydrated silicon oxides (SiO-'xH-O). Solid residue values for
wet scrubber systems at the other phosphate fertilizer operations are not
available, but they should be/similar to those for ammonium phosphate plants
(USEPA 1979a).
Approximately 99% of the solid residue wastes are stored at
phosphate fertilizer plants. The remaining 1% is sold as a raw
material for various products. Radioactivity of solid wastes varies depend-
ing on process and type of waste. For example, phosphate rock product
contains about 42 picocuries per gram (pCi/g) radium-226, whereas by-product
gypsum from acid plants contains 21-33 pCi/g. Due to the relative solubility
of gypsum, however, seepage water from gypsum piles can be as high as
90-100 pCi/1. An Office of Radiation Programs study has recommended that
moisture control techniques be considered in land disposal of gypsum pile
wastes (USEPA 1977d), but this is not current practice.
Rainfall drainage from the gypsum piles is collected in a ditch and
recycled to the gypsum pond. A major concern regarding these wastes is the
large amount of land area required to store the gypsum and the unsightly
appearance of the piles of gypsum.
To date, there are no data specifically to evaluate the potential
effect on groundwater due to leaching from gypsum piles (USEPA 1979a) . Since
gypsum wastes contain mainly calcium sulfate and lesser quantities of phos-
phates and fluorides, potential adverse effects may be regionally minimal
(USEPA 1979a), but local contamination can be high.
138
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2.1.2 Environmental Impact of Industry Wastes
Effluent guidelines were established for four primary factors and
contaminants:
• phosphorus
• fluorides
• suspended solids
• pH
Air emission-NSPS were established for:
• fluorides
• sulfur dioxide
• acid mist
These pollutants have been selected for direct control and monitoring because
their harmful environmental effects have been well documented. The EID
applicant should address the expected environmental impacts of these pollutants
based on their magnitude and rates of discharge, and their effects interacting
in the particular environmental setting.
Other pollutants in wastewater effluents have been identified as
secondary parameters (USEPA 1974a):
• ammonia
• total dissolved solids
• temperature
• cadmium
• total chromium
• zinc
• vanadium
• arsenic
• uranium
• radium-226
These pollutants require monitoring, but specific effluent guidelines were not
established because treatment of the primary factors and contaminants will
also effect removal of the secondary, and because data sufficient to establish
effluent limitations were lacking (USEPA 1974a). The applicant's EID should
identify sources of the above and any other pollutants, expected discharges,
and effectiveness of treatment techniques.
139
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2.1.2.1 Human Health Impacts
The following listings summarize documented effects of primary and
secondary pollutants on human health (USEPA 1974a).
Fluorides. Fluorides are rare in natural surface waters, but may occur
in detrimental concentrations in groundwaters. Ingestion of fluoride com-
pounds can result in:
• lowering of tooth decay in children - 0.8 to 1.5 mg/1 fluoride ion
in drinking water; but,
• mottling of tooth enamel in children, in quantities (varying with
individuals) above 0.9 - 1.0 mg/1;
• endemic cumulative fluorosis and skeletal effects in adults, in
(varying) quantities above 3 or 4 mg/1;
• death, or severe symptoms, in doses of 250-450 mg; severe symptoms
are "diffuse abdominal pain; diarrhea and vomiting; excessive
salivation, thirst, and perspiration; and painful spasms of the
limbs" (National Academy of Sciences 1971).
Experts disagree on how much airborne fluoride is dangerous, but believe
that levels equivalent to workplace heavy exposure would be required.
Apparently airborne fluorides are largely retained when ingested, but the
dangers of airborne fluorides include resettling and transport into drinking
water or vegetable food supplies (National Academy of Sciences 1971).
Total Suspended Solids. Suspended solids include both organic and
inorganic materials. The inorganic components include sand, silt, and clay.
The organic fraction includes such materials as grease, oil, tar, animal
and vegetable fats, various fibers, sawdust, hair, and various materials
from sewers. These solids may settle out rapidly and bottom deposits are
often a mixture of both organic and inorganic solids. Besides the aesthetic
displeasure associated with turbid waters or with bottom sludges when the
suspended solids settle out, they can cause untreated water to be unpala-
table and:
• suspended particles can absorb pesticide and other chemical
impurities that might not be transported otherwise in the water.
140
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pH (Acidity/Alkalinity). pH is a logarithnic expression of the concen-
tration of hydrogen ions. At pH 7, hydrogen and hydroxyl (OH ) ion con-
centrations in solution are essentially equal and the water is neutral. Lower
pH values indicate acidity and higher values indicate alkalinity, in a
nonlinear relationship. Extremes of pH are harmful or fatal to aquatic life,
but human contact with pH in water is usually avoidable:
• a deviation of 0.1 pH unit from 7.0 may result in eye irritation to
swimmers; appreciable irritation causes severe pain;
• by effects on plumbing fixtures, water lines, and water works struc-
tures, pH below 6.0 can cause high levels of iron, zinc, copper,
cadmium and lead in drinking water.
Ammonia and Nitrate Nitrogen. Ammonia is a common product of the de-
composition of organic matter. Dead and decaying animals and plants along
with human and animal body wastes account for much of the ammonia entering
the aquatic ecosystem. Ammonia exists in its non-ionized form only at
higher pH levels and is the most toxic in this state. The lower the pH, the
more ionized ammonia is formed and its toxicity decreases. Ammonia, in the
presence of dissolved oxygen, is converted to nitrate (NO^) by nitrifying
bacteria. Nitrite (NO ) , which is an intermediate product between ammonia
2 ]
and nitrate, sometimes occurs in quantity when depressed oxygen conditions
permit. Ammonia can exist in several other chemical combinations including
ammonium chloride and other salts. The following direct and indirect stresses
can accrue, to human health:
• Sodium nitrate is a poisonous constituent of mineralized waters;
potassium nitrate is more poisonous. Excess nitrates (500 mg
consumed in one liter of water) cause irritation:
- to mucous linings
- to the gastrointestinal tract (symptom - diarrhea)
- to the bladder ( sympton - diuresis),
• Infant methemoglobinemia, can be caused by more than 10 mg/1 (guide-
line) of nitrate nitrogen (N03-N) in water consumed; symptoms are:
- blood disorders
- cyanosis, a bluish discoloration of the skin, from inadequate
blood oxygenation.
141
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Total Dissolved Solids (IDS). In natural waters the dissolved solids
consist mainly of carbonates, chlorides, sulfates, phosphates, and possibly
nitrates of calcium, magnesium, sodium, and potassium, with traces of iron,
manganese and other substances. Although IDS levels above 500 mg/1 in
drinking water are progressively unpalatable, levels of:
• 4,000 mg/1 are unfit for human use, except in hot climates where
the salt content may be tolerable;
• 5,000 mg/1 in drinking water causes bladder and intestinal irritation.
Cadmium. Cadmium in drinking water supplies is extremely hazardous to
humans, and conventional treatment, as practiced in the United States, does
not remove it. Cadmium is cumulative in the liver, kidney, pancreas, and
thyroid of humans and other animals. Human health effects include:
0 a severe bone and kidney syndrome reported in Japan, from ingestion
of as little as 600 mg/day;
• as a cumulative toxicant, cadmium causes insidious chronic poisoning
in mammals and also fish and probably other animals;
• organic compounds of cadmium may cause mutagenic or teratogenic
(monstrous deformities) effects.
Chromium. In its various valence states chromium is hazardous to humans.
The levels of chromate that are completely safe are so low as to prohibit
determination. Effects of chromium include:
» lung tumors, from inhalation;
• skin sensitizations;
9 in large doses,
- corrosive effects on intestinal tract
- inflamation of the kidneys.
Zinc. Zinc used in industry enters waste streams as both soluble and
and insoluble salts. The soluble salts in drinking water at levels of 5 mg/1
cause an undesirable taste that persists through conventional treatment. Zinc
can have an adverse effect on man and animals at high concentrations.
142
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Arsenic. Arsenic is found to a small extent in nature in the elemental
form. It occurs mostly as arsenites of metals or as mineral pyrites. If
ingested, arsenic compounds can be a sudden or a cumulative poison:
• 100 mg - severe poisoning
• 130 mg - possibly fatal poisoning
• Smaller doses can accumulate and be fatal - arsenic accumulates in
the body faster than it is excreted.
Uranium and Radium-226. Radioactive materials present a host of
hazards through direct exposure or by accumulation in the biological
ecosystem. "Ionizing radiation, when absorbed in living tissue in quantities
substantially above that of natural background levels, is recognized as in-
jurious. It is necessary, therefore, to prevent excessive levels of
radiation from reaching any living organism humans, fishes, and invertebrates.
Beyond the obvious fact that radioactive wastes emit ionizing radiation, they
are also similar in many respects to other chemical wastes. Man's senses
cannot detect radiation unless it is present in massive amounts.
"Radium-226 is one of the most hazardous radioisotopes of the uranium
decay scheme, when present in water. The human body preferentially utilizes
radium in lieu of calcium when present in food or drink. Plants and animals
concentrate radium, leading to a multiplier effect up the food web.
"Radium-226 decays by alpha emission into radon-222, a radioactive
gas with a half life of 3.8 days. The decay products of radon-222, in turn,
are particulates which can be absorbed onto respirable particles of dust.
Radon and its decay products has been implicated in an increased incidence
of lung cancer in those workers exposed to high levels (Bureau of Mines, 1971).
Heating or grinding of phosphate rock would liberate radon and its decay
products to the surrounding atmosphere." (USEPA 1974a).
Guidelines for radiation exposure cannot be defined in terms of threshold
values but it is agreed that exposure to radiation should be held to a minimun
and should be encountered at all only when the necessity is justified.
143
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2.1.2.2 Ecological and Environmental Impacts
Phosphorus. Increases of phosphorus in surface waters have been linked
to a wide range of direct and indirect ecological disruptions. These include:
• proliferation of nuisance water plants;
• accelerated eutrophication of water bodies; and
• bioaccumulation and toxicity (of elemental P) for marine fish.
The plant overgrowth and eutrophication aspect of the effects of increased
phosphorus availability have specific negative effects:
dangerous to swimming, boating, and water skiing;
interferes physically with sport fishing;
interferes with development of fish populations;
vile stenches and tastes associated with water;
ineffectuates standard water treatment processes;
aesthetic effects
- reduced resort trade
- lowered property values;
• contact rashes to human skin; and
• improved breeding environment for flies.
Fluorides. The effects of fluorides on the animal environment are related
to vegetative accumulations and surface water contamination. Effects include:
• chronic fluoride poisoning of livestock when water contains 10-15 mg/1;
• shorter term fluoride poisoning of livestock when water ration contains
30-50 mg/1;
• toxicity to fish in concentrations above 1.5 mg/1.
The effects of acute poisoning in livestock include (National Academy of Sciences
1974):
restlessness
stiffness
anorexia
reduced milk production
nausea and vomiting
incontinence of urine and feces
necrosis of mucosa of digestive tract
weakness and severe depression
cardiac failure
144
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Chronic toxicosis is not always distinguishable from acute symptoms, but
also results in (National Academy of Sciences 1974):
• debilitating osteoarthritis and lameness
• dental enamel lesions
Although milk production in livestock is affected, fluoride transfer to the
milk is very slight. With poultry, however, a greater concentration of
fluoride does show up in the eggs.
Suspended Solids. In the aquatic environment suspended solids cause a
number of problems:
• turbid waters decrease photosynthetic activity of aquatic plants;
• settled solids on stream or lake beds
- eliminate normal benthic species
- reduce dissolved oxygen available in the area
- stimulate populations of benthic sludgeworms and associated
organisms.
pH Effects. Extremes or rapid fluctuations in pH level can create
problems to aquatic organisms including:
• rapid death, and associated rotting of fishkills and generation
of algal blooms;
• increased toxicity of other dissolved substances in the water,
such as
- matalocyanide
- ammonia.
Ammonia and Nitrate Nitrogen. In the aquatic ecosystem, ammonia can
lead to severe impacts:
• fish oxygen uptake is impaired and fish suffocate at 1.0 mg/1
un-ionized ammonia;
• direct toxicity on all aquatic life in levels less than 1.0 mg/1
to 25 mg/1, depending on pH and DO level;
• acceleration of eutrophication by supplying nitrogen through
breakdown of ammonia.
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Dissolved Solids. Dissolved solids levels in water affect aquatic
organisms and in general make water troublesome to industrial uses and for
irrigation. Effects on the ecosystem include:
• loss of habitat at 5,000-10,000 mg/1 for species of freshwater fish;
• death to freshwater fish when salinity is changed rapidly;
• increased toxicity of heavy metals and organic compounds to fish
and other aquatic life.
Temperature. Temperature is one of the most important and influential
ecological water quality characteristics. Temperature determines those
species that may be present; it activates the hatching of young, regulates
their activity, and stimulates or suppresses their growth and development;
it attracts, and may kill when the water becomes too hot or becomes chilled
too suddenly. Colder water generally suppresses development. Warmer water
generally accelerates activity and may be a primary cause of aquatic plant
nuisances when other environmental factors are suitable.
Temperature is a prime regulator of natural processes within the water
environment. It governs physiological functions in organisms and, acting
directly or indirectly in combination with other water quality constituents,
it affects aquatic life with each change. These effects include chemical
reaction rates, enzymatic functions, molecular movements, and molecular ex-
changes between membranes within and between the physiological systems and
the organs of an animal.
The specific mechanisms and results of elevated temperature extremes
include:
• higher chemical reaction rates;
« decreased DO;
& increased bacteria production;
• spawning perturbations;
• increases in predator, parasite, and competing species populations;
• fish food alterations;
• increased synergistic reactivity of pollutants;
• increase in green and blue-green algae and decrease in number and
distribution of benthic organisms (food chain disruptions) ;
• in the presence of sludge, increased gas formation and multiplication
of saprophytes and fungi.
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Cadmium. Cadmium pollution problems are derived from direct toxicity
and synergistic actions with other metals. These include:
• acute and chronic poisoning of aquatic and terrestrial species;
• Increase synergLstlc toxicity of copper ami zinc;
• concentration of cadmium in marine organisms, particularly molluscs.
Chromium. The toxicity of chromium salts toward aquatic life varies
widely with the species, temperature, pH, valence of the chromium, and
synergistic or antagonistic effects, especially that of hardness. Fish
are relatively tolerant of chromium salts, but fish food organisms and other
lower forms of aquatic life are extremely sensitive. Chromium also inhibits
the growth of algae.
In some agricultural crops, chromium can cause reduced growth or death
of the crop. Adverse effects of low concentrations of chromium on corn,
tobacco, and sugar beets have been documented.
Zinc. Zinc is most toxic to aquatic organisms in soft water- Growth
and survival of fresh- and saltwater species have been severely affected:
• 0.1 to 1.0 mg/1 in soft water is lethal to fish;
• presence of copper in the water increases toxicity;
• but presence of calcium or hardness decreases the relative toxicity;
• invertebrate marine organisms are very sensitive - 30 pg/1 retards
growth of the sea urchin;
• marine environment problems include long-term sub-lethal effects of
metallic compounds;
0 zinc sulfate is lethal to many plants.
Vanadium. Vanadium and its compounds cause physiological disorders in
mammals. The major concern is for effects in the aquatic ecosystem:
• the common bluegill fish can be killed by 6 ppm in soft water and by
55 ppm in hard water;
• other fish are similarly affected.
Arsenic. Arsenic ions and compounds can be lethal and harmful in both
water and soil environments. Typical effects are:
• an accumulative poison in oysters and shellfish;
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• arsenic trioxide is extremely harmful to some fish species
(5.3 mg/1 for 8 days);
• arsenic trioxide is lethal to mussels at 16 mg/1 in 3 to 16 days;
• certain food crops are made unmarketable grown in water of 1 mg/1;
• soils containing 4-12 mg/kg are unproductive.
Uranium and Radium-226. The life spans of many animal species are not
long enough to show adverse effects of low level radiation, but radionuclides
tend to be accumulated in the food chain so that the greatest danger from
radionuclides is to species high on the food chain. The potential effects
for human health, or for economic disaster, are severe when food species
accumulate potentially dangerous levels of radionuclides (resulting in a
ban on production if controls are enforced). The most significant pathway
to humans is through the accumulative effects on fish and shellfish, or
through drinking water.
2.1.3 Other Impacts
2.1.3.1 Special Problems in Obtaining, Shipping, Storing, and Handling
of Raw Materials and Products
In most instances potential major problems related to shipping, storing,
and handling are well identified and systems are in place or methods available
to keep these problems in check (1.5.2).
Continuing use of phosphate rock is assured and any special problems
should be discussed that cause impacts related to the mining area, where
the majority of the phosphate processing will be conducted. Phosphate mining
in North Carolina is carried on adjacent to the Pamlico Estuary, below the
water table. Cofferdams and pumps are used to expose phosphate deposits
100 feet deep. Even though the facility is well managed, eutrophication in
the estuary occurs as the result of phosphate laden pumping waters being
discharged to waters with significant nitrogen levels. The wastes of phosphoric
acid production also are disposed in this high-water-level environment.
Potential for leaching and for sedimentation and contamination of surface
waters is high, especially in hurricane conditions.
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In Florida, the significant special problems are related to new mining
areas. The richer deposits still unmined lie below deeper overburdens and
some deposits are in several layers. Higher volumes of overburdens must be
moved and replaced. The effects of this problem on phosphate processing
are less limiting, and the materials can be useful as supplies of sands and
tailings for slime pond dewatering.
Effects of phosphate production on transportation facilities in new
source industries should be assessed. Florida, North Carolina, and Gulf
Coast facilities have good access to ocean, barge (river and intracoastal),
pipeline, rail, and truck transportation. The EID should identify advantages
of alternate transportation modes. When properly controlled, pipeline and
barge transportation offer both environmental and economic advantages.
Since most facilities are near mines, stockpiles of phosphate rock are
not necessary. Facilities that purchase phosphate rock should specify
storage arrangements to prevent particulate air emissions and rainfall
runoff of waters contaminated with phsophorus and TSP. When wet grinding
is to be used the EID should detail whether storage will be exposed to the
weather and what impacts of fugitive particulate emissions and runoff
waters would be.
Ammonia and sulfur are normally stored in sealed tanks. The permit
applicant's EID should address:
• administrative measures to deal with a catastrophic release;
• clean up and isolation techniques;
• collection and treatment systems;
• short-term and long-term effects of a spill on the soil and water
ecosystems;
• human health impacts.
2.1.3.2 Special Problems in Site Preparation and Facility Construction
The environmental effects of site preparation and construction of new
phosphate fertilizer manufacturing facilities are common to land disturbing
activities on construction sites in general. Erosion, dust, noise, vehicular
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traffic and emissions, and some loss of wildlife habitats are to be expected
and minimized through good construction practices wherever possible. At
present, however, neither the quantities of the various pollutants resulting
from site preparation and construction nor their effects on the integrity
of aquatic and terrestrial ecosystems have been studied sufficiently to
permit broad generalizations.
Therefore, in addition to the impact assessment framework provided in
the USEPA document, Environmental Impact Assessment Guidelines for Selected
New Sources Industries, the permit applicant should tailor the conservation
practices to the site under consideration in order to account for and to
protect certain site specific features that warrant special consideration
(e.g., critical habitats, archaeological/historical sites, high quality
streams, or other sensitive areas on the site). All mitigation/conservation
measures that are proposed should be discussed in the EID.
Erosion Control During Construction. The major pollutant at a con-
struction site is loosened soil that finds its way into the adjacent water
bodies as sediment. Common remedial measures include, but are not
limited to, proper planning at all stages of development and application of
modern control technology to minimize the production of huge loads of sedi-
ment. Specific control measures include:
• the use of paved channels or pipelines to prevent surface erosion;
• staging or phasing of clearing, grubbing, and excavation activities
to avoid high rainfall periods;
• the use of storage ponds to serve as sediment traps, where the
overflow may be carefully controlled;
• the use of mulch or seeding immediately following disturbance.
If the applicant chooses to establish temporary or permanent ground
cover, grasses normally are more valuable than shrubs or trees because of
their extensive root systems that entrap soil. Grasses may be seeded by
sodding, plugging, or sprigging. During early growth, grasses should be
supplemented with mulches of wood chips, straw, and jute mats. Wood fiber
mulch has also been used as an antierosion technique. The mulch, prepared
commercially from waste wood products, is applied with water in a hydroseeder.
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Site Selection Factors. The EID should include information to indicate
the capacity of the soils and geology to accommodate production and waste
storage. Problems which would require special consideration include:
• unstable soils;
• steep topography;
• presence of wetlands;
• location relative to floodplains;
• permeability of soils;
• erosion problems during construction and operation.
The applicant is responsible for assessing the effects of the proposed
facility on groundwater quality and quantities. The areas of particular
relevance to the phosphate manufacturing industry are:
• potential and effects of seepage of gypsum pond wastewaters into
aquifers;
• potential for groundwater contamination from storage piles of raw
materials and waste gypsum;
• use of groundwater for process and make-up water.
In western states water supply can be a limiting factor. The EID should
evaluate effects of water consumption in terms of both groundwater and sur-
face water supplies in the region.
2.1.4 Modeling of Impacts
The ability to forecast environmental impacts accurately often is
improved by the use of mathematical modeling of the dispersion and dissipa-
tion of air and water pollutants as well as the effects of storm runoff.
Two of the most widely used and accepted models are:
• DOSAG (and its modifications);
• the QUAL series of models developed by the Texas Water Development
Board and modified by Water Resources Engineers, Inc.
Some of the parameters that these models simulate are:
• dissolved oxygen
• BOD
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• temperature
• pH
• solids
• phosphorus
• NH3
• radioactive materials
Another model, extensively used in modeling estuaries is:
• RECEIV or RECEIV II, developed by Raytheon for the USEPA Water
Planning Division.
The RECEIV models incorporate the salinity parameter.
In addition, there are many available water quality models that were
developed in association with NPDES activity and the need for optimization
of waste load schemes for an entire river basin.
There are also available mathematical models that have been used for air
pollution studies and solid waste management optimization:
• for short-term dispersion modeling of point sources, EPA's PTMAX,
PTDIS, and PTMTP models may be employed;
• for modeling of long-term concentrations over larger areas, the
EPA Climatological Dispersion Model may be used for point and area
sources.
The types of models to be used, their design, and the parameters to be
modeled (or monitored for modeling) will vary in different USEPA regions, State
jurisdictions, and air quality attainment areas. These details should be agreed
upon between the regulating authority and the applicant early in the permitting
stage. Even in instances when USEPA issues a "finding of no significant impact,'
and no EID is required, the processing of a PSD construction permit may still re-
quire air quality modeling and preconstruction monitoring.
In general, the use of mathematical models is indicated when arithmetic
calculations are too repetitious or too complex. Their use also simplifies
analysis of systems with intricate interaction of variables. Models thus
offer a convenient way of describing the behavior of environmental systems.
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3.0 POLLUTION CONTROL
NSPS have been established for air and water discharges based on USEPA
surveys and tests (USEPA 1974a) of facilities in the phosphate subcategory,
40 CFR 418. These investigations include analyses of plant operating data
and sampling of pollutant loadings in wastestreams. Standards of Performance
are based on determinations of efficiency and attainability of pollution
control technology and process options for existing and new facilities. New
sources must attain discharge levels which are indicated as achievable using
the "best practicable control technology currently available" (BPT). BPT is
largely based on technology that was observed in facilities identified as
"exemplary plants" in the USEPA study. "Standards of Performance Technology"
refers to technological options which meet the NSPS. They may be the BPT's
identified by USEPA in the development of the NSPS or they may be
alternatives which meet the NSPS by other techniques. For wastestreams for
which NSPS do not exist, technological control applications which represent
the state of the art are of interest in the EID. The permit applicant must
demonstrate that NSPS will be met. The sections which follow identify and
describe typical Standards of Performance and state of the art technologies
with which NSPS can be met.
3.1 STANDARDS OF PERFORMANCE TECHNOLOGY; END-OF-PROCESS CONTROLS AND EFFECTS
ON WASTE STREAMS (AIR EMISSIONS)
3.1.1 Dust Control in Raw Materials Handling Operations
Enclosed operation and baghouses are typical methods of control at
ground phosphate rock unloading stations. Satisfactory control of dust
emissions from unloading hopper-bottom railroad cars or trucks is achieved by
the use of flexible skirts around bases of the vehicles to contain dust and
flexible-contact hoods to channel emissions to baghouses, which realize high
efficiency in collection of this size particle (60% to 80% of the rock is
less than 74 ym) (Slack 1968). Efficiencies are reported to be greater than
99% (USEPA 1979a).
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Feed hoppers, storage bins, and conveyors are usually enclosed to reduce
particulate emissions and moisture contamination of the rock. When transport
of ground rock from storage bin to feed hopper is accomplished by pneumatic
conveyors, a cyclone separator and baghouse are located at the destination
for control of the bulk material and discharged dust (USEPA 1979a).
3.1.2 Control of S00 Emissions from Contact Process Sulfuric Acid
Plants
There are a few physical mechanisms and many chemical means of removing
SO- from gas streams. Almost any soluble alkaline material will absorb a
significant fraction of S0« even in a crude scrubber. For years, sulfur
dioxide has been removed from many process gases where the S0» adversely
affected the product. The problems of removing SO- from acid plant gases are
principally that of finding the least expensive mechanism consistent with
minimal formation of undesirable by-products. The control processes in use
by the sulfuric acid industry in those units installed since the promulgation
of the NSPS (see Table 20) are reviewed below (USEPA 1978a).
3.1.2.1 Double Absorption Process
The double absorption process (used partially as the basis of the
rationale for the S02 NSPS) has become the SO control system of choice by
the sulfuric acid industry since the promulgation of the NSPS. This process
offers the following advantages over other SO- control process:
• As opposed to single absorption with scrubbing, a greater fraction
of the sulfur in the feed is converted to sulfuric acid.
• There are no by-products.
• Contact acid plant operators are familiar with the operations
involved.
The process, described in Section 1.3.2.1, builds in a second absorption
tower to absorb S03 in the process gas and achieves at least 99.7% overall
conversion of feed sulfur to sulfuric acid (USEPA 1978a). Double absorption
offers the following operational advantages:
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» permits higher inlet S02 concentrations than single absorption
(second absorber handles residual SO from first conversion step);
• higher inlet SO concentrations allow reduced equipment size
(partially offsetting cost of additional absorption equipment);
• spent acid or H2S may be used as feedstock, with appropriate
convential pretreatment;
• no reduction in on-stream production;
• needs no additional manpower.
3.1.2.2 Sodium Sulfite-Bisulfite Scrubbing
Tail gas scrubbing systems are generally applicable to all classes of
contact acid plants. They can provide simultaneous control of SO- and to
some extent SO., and acid mist. To date only the sodium sulfite-bisulfite
scrubbing process has been demonstrated to be capable of meeting the SO-
limit in the most cost effective manner. Other control processes such as
ammonia scrubbing can meet the standard, but costs are relatively highly
dependent on the marketability of by-products, i.e. , ammonium sulfate, for
which there may be little demand (USEPA 1978a).
In the Wellman-Power Gas process, the tail gases are first passed
through a mist eliminator to reduce acid mist. Following mist removal, the
SO., is absorbed in a three-stage absorber with a sodium sulfite solution. A
sodium bisulfite solution results and is fed to a heated crystallizer where
sodium sulfite crystals are formed and S02 gas and water vapor are released.
The crystals are separated from the mother liquor and dissolved in the
recovered condensate for recycle to the absorber. The recovered wet SO™ is
sent back to the acid plant (USEPA 1978a).
In all processes employing sulfite-bisulfite absorption even without
regeneration, some portion of the sulfite is oxidized to sulfate, from which
the sulfur dioxide cannot be regenerated in the heating sequence. This
sulfate must be purged from the system. In the Wellman-Power Gas process,
some thiosulfate is also formed. Apparently the extent of oxidation is
dependent on several factors:
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• oxygen content of the gas stream;
• the temperature and residence time of the liquor in the recovery
sections;
• the presence of contaminants that may act as oxidation catalysts.
Despite the effectiveness of the sodium sulfite-bisulfite scrubbing
process, none of the sulfuric acid plants installed since the promulgation of
the NSPS have employed this process for tail gas SC>2 control (USEPA 1978a).
3.1.2.3 Ammonia Scrubbing
The ammonia scrubbing process uses anhydrous ammonia (NH») and water
make-up in a two-stage scrubbing system to remove SCL from acid plant tail
gas. Excess ammonium sulfite-bisulfite solution is reacted with sulfuric
acid in a stripper to evolve SO- gas and produce an ammonium sulfate
byproduct solution. The SO is returned to the acid plant while the solution
is treated for the production of fertilizer grade ammonium sulfate. The
process is dependent on a suitable market for ammonium sulfate. Since the
promulgation of the NSPS for sulfuric acid plants, one new plant (two units)
and a new unit added to an existing plant, are employing an ammonia scrubbing
system for tail gas S0» emmissions control (USEPA 1978a).
3.1.2.4 Molecular Sieve
This process utilizes a proprietary molecular sieve system in which SCL
is absorbed on synthetic zeolites. The absorbed material is desorbed by
purified hot tail gas from the operating system and sent back to the acid
plant.
Since the promulgation of the sulfuric acid plant NSPS, one new unit has
incorporated a molecular sieve system for S0? control in the original design.
However, extensive operational difficulties with this system have caused this
plant to be retrofitted with a dual absorption system for S09 control
(USEPA 1978a).
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3-1-3 Control of Acid Mist Emissions from Contact Process Sulfuric Acid
Plants
Effective control of stack gas acid mist emissions can be achieved by
fiber mist eliminators and electrostatic precipitators (ESP's). Although
ESP's are frequently used in the purification section of spent acid plants,
none are known to be in use in any new sulfuric acid plants. Even though
ESP's have the advantage of operating with a lower pressure drop than fiber
mist eliminators (normally less than 1 inch of HO), lack of application of
this equipment to new sulfuric acid units is probably due primarily to its
relatively large size and resultant high installation cost compared to fiber
mist eliminators, and to the high maintenance cost required to keep the ESP's
operating within proper tolerances in the acid environment, which is
corrosive to the mild steel equipment.
Fiber mist eliminators utilize the mechanisms of impact ion and
interception to capture large to intermediate size acid mist particles and of
Brownian movement to effectively collect micron to submicron size particles.
Fibers used may be chemically resistant glass or fluorocarbon. Fiber mist
eliminators are available in three different configurations (described below)
covering a range of efficiencies required for various plants.
3.1.3.1 Vertical Tube Mist Eliminators
Tubular mist eliminators consist of a number of vertically oriented
tubular fiber elements installed in parallel in the top of the absorber on
new acid plants and usually installed in a separate tank above or beside the
absorber on existing plants. Each element consists of glass fibers packed
between two concentric 316 stainless steel screens. In an absorber
installation the bottom end cover of the element is equipped with a liquid
seal pot to prevent gas bypassing. A pool of acid provides the seal in the
separate tank design. Mist particles collected on the surface of the fibers
become a part of the liquid film which wets the fibers. The liquid film is
moved horizontally through the fiber beds by the gas drag and is moved
downward by gravity. The liquid overflows the seal pot continuously,
returning to the process (USEPA 1978a).
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Tubular mist eliminators offer a number of advantages and operate
through a range of operating conditions:
* collection method
- inertial impact ion (particles greater than 3y)
- direct interception and Brownian movement (smaller particles:)
• gas velocity is low (6-12 m/min);
3
• volumetric flow is 28.3 standard cubic meters/minute (sin /min);
10-100 elements may be used depending on plant size;
• pressure drop - 13-38 cm (5-15 in) of water, higher drop for higher
efficiency removing particles less than 3^;
• usual efficiency
- 100%, particles larger than 3y
- 99.3%, particles smaller than 3y
Because the vertical tube mist eliminator does not depend only upon impaction
for mist removal, it can be turned down (operated at a volumetric flow rate
considerably below design) with no loss in efficiency. Available information
indicates that the vertical tube mist eliminator is used in the great
majority of new sulfuric acid units for acid mist control (USEPA 1978a).
3.1.3.2 Vertical Panel Mist Eliminators
Panel mist eliminators use fiber panel elements mounted in a polygon
framework closed at the bottom by a slightly conical drain pan equipped with
an acid seal pot to prevent gas bypassing. The polygon top is surmounted by
a circular ring which is usually installed in the absorption tower and welded
to the inside of the absorption tower head. Each panel element consists of
glass fibers packed between two flat parallel 316 stainless steel screens.
In large high velocity towers, recent designs have incorporated double
polygons, one inside the other, to obtain more bed area in a given tower
cross section (USEPA 1978a).
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Operating and efficiency information for vertical panel mist eliminators
follows:
• collection method - inertial impaction;
• gas velocity is somewhat high (120-150 m/min);
• pressure drop - 8 in of water;
• efficiency - 70 mg/m , equivalent to 0-375 Ib/ton of 100% H SO,.
These units are unsatisfactory for spent acid plants but usually find
application in new dual absorption plants for acid mist removal from the
intermediate absorber in order to afford corrosion protection for downstream
equipment.
3.1.3.3 Horizontal Dual Pad Mist Eliminators
Two circular fluorocarbon fiber beds held by stainless steel screens are
oriented horizontally in a vertical cylindrical vessel one above the other,
so that the coarse fraction of the acid mist is removed by the first pad
(bottom contactor) and the fine fraction by the other (top contactor). The
bottom contactor consists of two plane segmented sections installed at an
angle to the horizontal to facilitate drainage and give additional area for
gas contact. The assembly may be located adjacent to or positioned on an
absorption tower.
This unit uses the high velocity impaction mist collection mechanism, as
does the panel mist eliminator; however, the collected acid drains downward
through the pads countercurrent to the gas flow, producing a scrubbing action
as well. Collected acid may be drained from external connections or returned
directly to the absorber through liquid seal traps (USEPA 1978a).
Operating data for the horizontal dual pad mist eliminators are:
• collection method - high velocity impaction;
• superficial velocity - 2.7-3.0 m/s;
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• pressure drop - 23 cm of water (9 in);
• efficiency - 70 mg/m3 (0.375 Ib/ton of 100% I^SOJ provided that a
particle size distribution shows that this level can be met.
3.1.4 Control of Fluoride Emissions
3.1.4.1 Spray-Crossflow Packed Bed Scrubber
The spray-crossflow packed bed scrubber has been accepted for several
years as the most satisfactory fluoride control device available for
wet-process phosphoric acid plants. Most wet-process acid plants built since
1967 probably have installed this scrubber as part of the original design.
During this same time, however, the spray-crossf low packed bed design has
seen less general use in processes other than wet acid manufacture. The
reluctance of the fertilizer industry fully to adopt the spray-crossf low
packed bed scrubber can be traced primarily to concern about its operational
dependability when treating effluent streams with a high solids loading.
Such effluent streams can be handled by placing a venturi scrubber in series
with and before a spray-crossflow packed bed scrubber. Also, improvements in
spray-crossflow packed scrubber design have alleviated the initial problem of
plugging and allow a greater solids handling capacity (USEPA 1977c).
The spray-crossflow packed bed scrubber consists of two sections - a
spray chamber and a packed bed - separated by a series of irrigated baffles.
Scrubber size will depend primarily upon the volume of gas treated. All
internal parts of the scrubber are constructed of corrosion resistant
plastics or rubber-lined steel. Teflon can be used for high temperature
service. General maintenance consists of replacement of the packing once or
twice a year. Both the spray and the packed section is equipped with a gas
inlet. Effluent streams with relatively high fluoride concentrations -
particularly those rich in silicon tetrafluoride - are treated in the spray
chamber before entering the packing. This preliminary scrubbing removes
silicon tetrafluoride thereby reducing the danger of plugging the bed. At
the same time, it reduces the loading on the packed stage and provides some
H
solids handling capacity. Gases low in silicon tetrafluoride can be
introduced directly to the packed section (USEPA 1977c).
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The spray section accounts for approximately 40 to 50% of the total
length of the scrubber. It consists of a series of countercurrent spray
manifolds with each pair of spray manifolds followed by a system of irrigated
baffles. The irrigated baffles remove precipitated silica and prevent the
formation of scale in the spray chamber.
Packed beds of both cocurrent and crossflow design have been tried with
the crossflow design proving to be the more dependable. The crossflow design
operates with the gas stream moving horizontally through the bed while the
scrubbing liquid flows vertically through the packing. Recycled pond water
is normally used as the scrubbing liquor.
Typical operating data for spray-crossflow packed bed scrubbers include:
pressure losses - 1-8 in of water, 4-6 in average;
efficiency - 98.5 - 99.9% are attainable.
Table 28 lists the levels of fluoride control reached by several wet
acid plants tested by the USEPA during the development of standards of
performance. All plants used a spray-packed bed type scrubber to control the
combined emissions from the reactor, the filter, and several miscellaneous
sources and were felt to represent the best controlled segment of the
industry. Gypsum pond water was used as the scrubbing liquid. Emission
rates ranged from 0.002 to 0.015 pounds flouride (as F) per ton P«0,_ input to
the process.
Table 28
. Scrubber performance in wet process phosphoric acid plants.
Plant
A
B
C
D
Scrubber design
spray-cocurrent packed bed
spray-crossf low packed bed
spray-crossf low packed bed
spray-crossf low packed bed
.Average of testing results
Second series of tests
Fluoride emmissions
(Ib F/ton
0.015
0.006
0.002, 0.012
0.011
Source: U.S. Environmental Protection Agency. 1977c. Final guidelines
document: Control of fluoride emissions from existing phosphate
fertilizer plants. Office of Air and Waste Management; Office of
Air Quality Planning and Standards. Research Triangle Park NC, 274 p
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Spray-packed bed type scrubbers have seen only limited service in DAP
and GTSP plants and none at all in run of pile TSP plants. Table 29 presents
performance data, collected during the development of performance standards,
for spray-crossflow packed bed scrubbers treating effluent streams from DAP
and GTSP production, and GTSP storage facilities. In most cases, a
preliminary scrubber (venturi or cyclonic) was used to reduce the loading of
other pollutants (ammonia or solids) prior to treatment in the
spray-crossflow packed bed scrubber. Gypsum pond water was used as the
scrubbing solution except where indicated (USEPA 1977c).
3.1.4.2 Venturi Scrubbers
Venturi scrubbers are primarily particulate collection devices, however,
they are also applicable to gas absorption work and are in widespread use
throughout the phosphate fertilizer industry. They are particularly well
suited for treating effluent streams containing large amounts of solids or
silicon tetrafluoride because of their high solids handling capacity and
self-cleaning characteristics. Operational reliability and low maintenance
requirements are major reasons for the popularity of this scrubber design
(USEPA 1977c).
A venturi provides a high degree of gas-liquid mixing, but the
relatively short contact time and the concurrent flow of the scrubbing liquid
tend to limit its absorption capabilities. When treating effluent streams
requiring a high degree of fluoride removal, Venturis are often used as the
initial component in a multiple-scrubber system.
Two types of venturi scrubbers, gas actuated and water actuated, are in
general use. In both cases, the necessary gas-liquid contacting is obtained
from velocity differences between the two phases and turbulence in the
venturi throat. Both types also require the use of a mist elimination
section for removal of entrained scrubbing liquid. The major difference
between the designs is the source of motive power for operating the scrubber.
In the case of the gas actuated venturi, the velocity of the gas stream
provides the energy required for gas-liquid contacting. The scrubbing liquid
is introduced into the gas stream at the throat of the venturi and is broken
162
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Table 29. Spray-crossflow packed bed scrubber performance
in diammonium phosphate and granular triple
superphosphate plants.
Type of
facility
Sources controlled
Primary controls
Secondary controls
Fluoride emissions'
(lb F/ton P2f>5)
DAP
DAP
TSP
GTSP
• G7SP
Istorane
reactor, granulator,
drier, and cooler
reactor, granulator,
drier, and cooler
reactor, qranulator,
drier, and cooler
reactor, granulator,
drier, and cooler
storage buildina
3 venturi scrubbers
in parallel0
3 venturi scrubbers
in par-all elb
3 venturi scrubbers
in parallel
process qases com-
bined and sent to 2
venturi scrubbers in
parallel followed by
a cyclonic scrubber
3 spray-crossflow
packed bed scrubbers
in parallel
3 spray-crossflow
packed bed scrubbers
in parallel
I
I 3 spray-crossflow
packed bed scrubbers
in parallel
spray-crossflow
! oacked bed scrubber
spray-crossflow
packed bed scrubber
0.034, 0.029C
0.039
0.18, 0.06C
0.21
0.00036C
A/\veraqe of testing results.
^Weak phosphoric acid scrubbing solution.
GSccond series of tests.
rate is in tenns of pounds F per hour per ton of
in storage.
Source- U S Environmental Protection Agency. 1977c. Final guidelines document: Control of fluoride
emissions from existing phosphate fertilizer plants. Office of Air and Waste Management; Office of Air
Quality Planning and Standards. Research Triangle Park NC, 274 p.
-------
into fine droplets by the accelerating gas stream. Pressure drop across the
scrubber is generally high - from 8 to 20 inches of water. A fan is required
to compensate for this loss in gas stream pressure (USEPA 1977c).
In a water actuated venturi, the scrubbing liquid is introduced at a
high velocity through a nozzle located upstream of the venturi throat. The
velocity of the water streams is used to pump the effluent gases through the
venturi. Drafts of up to 8 inches of water can be developed at high liquid
flow rates (USEPA 1977c).
The removal of the fan from the system makes the water acutated ventui
mechanically simpler, more reliable, and less costly than the gas actuated
type. An additional advantage is its relative insensitivity to variations in
the gas stream flow rate. Gas actuated Venturis rely upon the gas stream
velocity for the energy for gas-liquid contacting, therefore, variations in
the gas flow can greatly affect scrubber efficiency. The performance of the
water-actuated venturi depends mainly on the liquid stream velocity.
Water actuated Venturis find application principally as gas absorption
units. Their use is usually limited, however, to small gas streams with
moderate scrubbing requirements. The water-actuated venturi is seldom used
for gas flows greater than 5,000 acfm because of the large water requirements
(USEPA 1977c).
Performance data are available for venturi scrubbers installed in SPA
and DAP plants. This information is presented in Table 30.
3.1.4.3 Spray Tower Scrubber >
Spray towers provide the interphase contacting necessary for gas
absorption by dispersing the scrubbing liquid in the gas phase in the form of
a fine spray. Several types of spray towers are in general use. The
simplest consits of any empty tower equipped with liquid sprays at the top
and a gas inlet at the bottom. Scrubbing liquid is sprayed into the gas
stream and droplets fall by gravity through an upward flow of gas. This
design has the advantages of a very low pressure drop and an inexpensive
construction cost but it can provide only about one transfer unit for
absorption. Entrainment of scrubbing liquid is also a problem (USEPA 1977c).
164
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Table 30. Venturi scrubber performance in superphosphoric acid
and diammonium phosphate plants.
Type of Plant Sources Controlled
Vacuum evap- Barometric conden-
tion SPA
DAP
ser, hotwell, and
product cooling
tank
Reactor, granula-
tor, drier, and
cooler
1. Average of testing results
Control Scrubbing
System Liquid
Water Pond
actuated water
venturi
3 gas Weak acid
actuated (20-22% ^
Venturis
in parallel
Fluoride Emissions
(Ib F/ton P205)
0.0009
1.
0.129
Source: U.S. Environmental Protection Agency. 1977c. Final guidelines
document: Control of fluoride emissions from existing phosphate
fertilizer plants. Office of Air and Waste Management; Office of
Air Quality Planning and Standards. Research Triangle Park NC,
274 p.
Cyclonic spray towers eliminate the excessive entrainment of scrubbing
liquid by utilizing centrifugal force to remove entrained droplets. A
tangential inlet is used to impart a spinning motion to the gas stream.
Water sprays are directed parallel to the gas flow providing crossflow
contacting of the gas and liquid streams. Pressure drops across the scrubber
ranges from 2 to 8 inches of water. Solids handling capacity is high,
however, absorption capacity is limited to about two transfer units (USEPA
1977c).
Fluoride removal efficiencies ranging from 84 to 95% have been reported
for cyclonic spray towers treating wet acid plant effluent gases. Table 31
presents performance data obtained by USEPA for cyclonic spray towers
installed in wet-process phosphoric acid, diammonium phosphate, and run of
pile triple superphosphate plants. In most cases, the control system
consisted of a primary venturi scrubber or cyclonic spray tower followed by a
.secondary cyclonic spray tower. Gypsum pond water was used as the scrubbing
solution except where indicated.
165
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Table 31. Cyclonic spray tower performance in wet process phosphoric acid,
diammonium phosphate, and run of pile triple superphosphate plants.
Type of plant
Sources controlled
Primary controls
Secondary controls
:luoride emissions3
Ib F/ton P90r)
WPPA
DAP
ROP-TSP
ROP-TSP
reactor, filter, and
miscellaneous sources
reactor, granulator,
drier, and cooler
two-stage cyclonic
spray tower
3 cyclonic spray
tower scrubbers in
parallel. Scrub-
bers treating re-
actor-granular
and drier gases
use weak (28-30%
acid
mixing cone, den,
transfer conveyor,
and storage pile
mixing cone, den,
and storage pile
venturi scrubber
2 cyclonic spray
tower scrubbers
in parallel
2 cyclonic spray
tower scrubbers in
parallel treating
reactor-granulatbr
and drier gases
cyclonic spray tower
scrubber with packed
bed section
2 cyclonic spray tower
scrubbers in parallel
0.056
0.380
0.194, 0.2111
0.125
^Average of testing results
^Second series of tests
Source: U.S. Environmental Protection Agency. 1977c. Final guidelines document: Control of fluoride
emissions'from existing phosphate fertilizer plants. Office of Air and Waste Management; Office of
Air Quality Planning and Standards. Research Triangle Park NC, 274 p.
-------
3.2 STANDARDS OF PERFORMANCE TECHNOLOGY; IN-PROCESS CONTROLS AND EFFECTS ON
WASTE STREAMS AND EMMISSIGNS
3.2.1 Sulfuric Acid Plant Effluent Control
This technology is a process design modification which is installed to
prevent accidental entry of contaminated water into surface drainage or
sewage systems. The sulfuric acid plant has no process water effluent, and
boiler blowdown is treated before discharge to the gypsum pond or to surface
waters. Cooling coils in the cooling tower, are vulnerable to accidental
break, causing rapid contamination of cooling water.
Process Description
The process involves installation and operation of the following
facilities:
• a reliable pH or conductivity continuous monitor on either
- combined non-contaminated plant effluent stream (preferred), or
- cooling tower blowdown stream;
• a retaining area along the (usually) non-contaminated effluent
stream capable of holding a 24 hour normal flow;
• a positive cutoff on the retaining area discharge point, such as a
concrete abuttment fitted with a valve.
Optional features which could be built in are:
• lime treatment facilities at the retaining area;
• equipment for transferring the acid water from the retaining area
to
- a contaminated holding area, or
- a recirculation system into an acid-consuming process.
When an acid break occurs an alarm sounds and the retaining area valve
is shut (automatically is preferable). The plant necessarily will be shut
down to locate and repair the leak. The contaminated water in the retaining
167
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area can be treated and neutralized, or be transferred to storage where it
can be treated through central treating facilities, or be recirculated. If
treatment is performed, the standard of performance is lime treatment, which
can raise pH and also remove sulfate by precipitation of gypsum. The
required pH standard is at least 6.
3.2.2 Wet Process Phosphoric Acid - Pond Water Dilution of Sulfurlc Acid
The need to treat phosphate fertilizer process contaminated water is
almost entirely dependent upon the local rainfall/evaporation ratio. Barring
poor water management and concentrated periods of heavy rainfall, fresh water
use and pond water evaporation should be essentially in balance. Any means
of making an in-process change to reduce significantly fresh water use will
create a negative water balance. In turn, this will eliminate the need for
treatment of contaminated water and effect a no discharge condition.
The most effective way of attaining a negative water balance is to
utilize contaminated water for dilution of sulfuric acid. The use of fresh
water for this dilution step represents approximately 50% of the total fresh
water intake to a phosphoric acid plant. Use of contaminated water for
gulfuric acid dilution can:
• eliminate water effluent from the complex (except during extreme
weather conditions);
« increase overall P 0 recovery by the amount of ?„(),. in the
contaminated water.
Two methods for successfully using contaminated water exist. Both are
proprietary. One is a trade secret; the other is protected by patent.
The trade secret procedure involves two key points:
1. a mechanical means to effect dilution without pluggage of
process equipment;
2. redesign of the phosphoric acid reactor cooling system to
remove the heat load formerly removed by the sulfuric acid.
dilution cooler.
168
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The patented process involves sulfuric acid dilution by a two-step
procedure in a manner radically different from current practice. The details
of procesi control, vessel design, and materials are all proprietary
information.
3.2.3 Ammonium Phosphate Self-Contained Process
The best means of reducing NH -N in the contaminated water system is to
prevent its entry into the water. NH -N enters the contaminated water
principally through the ammonium phosphate plant gas scrubber system. A
secondary entry point is washdown or water spillage into a surface drainage
system. These sources can be segregated from the gypsum pond water system
and can be either introduced back into the process or treated for ammonia
removal prior to discharge into the gypsum pond.
One means of doing this is to adjust the in-process water balance to
permit the absorption of the collected water containing NH_-N. The degree of
water balance adjustment is dependent upon the quantity of water in the two
identified streams. Reduction of these water streams to a minimum may
require design changes to maximize scrubber water recirculation.
The principal means of adjusting the ammonium phosphate process water
balance is to increase the concentration of the phosphoric acid feed used in
the plant. In conventional processes 30-40% P20,- phosphoric acid is required
to produce ammonium phosphates. It may be necessary to increase this
concentration to as high as 54% P2°5' This is dePendent uPon the water
quantity to be absorbed and the acid concentration required to produce the
specific ammonium phosphate product.
The TVA pipe reactor and pipe-cross reactor have been demonstrated
effective in meeting these criteria. 54% P^ acid is used and dust-laden
(and fluorine-laden) contaminated water is returned to the product and leaves
the plant as product (Lee and Waggoner 1975). The remaining water in
scrubber liquor is flashed off in the granulator or stripped out by airflow
through the cooler.
169
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3.3 STANDARDS OF PERFORMANCE TECHNOLOGY; END-OF-PROCESS CONTROLS AND EFFECTS
ON WASTE STREAMS (WASTEWATER EFFLUENTS)
3.3.1 Gypsum Pond Water Treatment
The closed-loop contaminated water stored in the gypsum pond must be
treated prior to any discharge necessitated by unusually high rainfall (which
should be in excess of the local 24-hour 25-year frequency event). Once the
storage area approaches capacity it is necessary to begin treating the
contaminated water for subsequent discharge to natural drainage bodies.
Treatment must accomplish NSPS levels for phosphorus, fluorides, and
total suspended solids (TSS) . In most cases pH is also regulated through the
NPDES permit. "Double liming," or a two stage lime neutralization is the
standard of performance procedure.
The first treatment stage provides sufficient neutralization to raise
the contaminated water (containing up to 9000 mg/1 F and up to 6500 mg/1 P)
from pH 1-2 to pH 3.5-4.0. The resultant treatment effectiveness is largely
dependent on constancy of the pH control. At a pH level of 3.5 to 4.0, the
fluorides will precipitate principally as calcium fluoride (CaF ) by the
following reaction:
H2SiF6 -I- 3CaO -I- H20 — > 3CaF2 + 2H20 + Si02
This mixture is held in a quiescent area to allow the particulate CaF? to
settle.
Equipment used for neutralization ranges from crude manual distribution
of lime with localized agitation to a well engineered lime control system
with a compartment ed mixer. The quiescent areas range from a pond to a
controlled settling rate thickener or settler. The partially neutralized
water following separation from the CaF2 (pH 3.5-4.0) now contains 30-60 mg/1
F and up to 5500 mg/1 P. This water is again treated with lime sufficient to
increase the pH level to 6.0 or above. At this pH level calcium compounds,
170
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of CaF2, precipitate from solution. The primary reactions are shown by the
following chemical equation:
CaO
Ca° + H2°
As before, this mixture is retained in a quiescent area to allow the CaHPO
and minor amounts of CaF« to settle.
The reduction of the P value is strongly dependent upon the final pH
level, holding time, and quality of the neutralization facilities,
particularly mixing efficiency. Figure 39 shows a sketch of a well designed
"double lime" treatment facility.
Laboratory and plant data for response of phosphorus and fluoride con-
centrations to pH levels are presented below:
pH Phosphorus (mg/1) Fluoride (mg/1)
laboratory plant laboratory plant
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0 1.2 1.2 4.6 12.5
Source: U.S. Environmental Protection Agency. 1974a. Development document
for effluent limitations guidelines and new source performance stan-
dards for the basic fertilizer chemicals segment of the fertilizer
manufacturing point source category. Office of Air and Water Programs.
Washington DC, 168 p.
Although the starting concentrations are either arbitrary or specific to
certain plants tested by USEPA, the data show that P and F are removed in
significant amounts at higher pH.
-
—
—
500
330
200
120
20
3
-
42
24
18
14
12
8
6
3
-
—
—
13
8.5
6.8
5.8
5.2
4.8
17
14
12.5
12.5
12.5
12.5
12.5
12.5
12.5
171
-------
~* — *^
^ L.
P. STEAM
HOT WATER
TANK
* i r>
SUMP I—(-
» 1 2^L
n
MILK OF
LIME
STORAGE"—*
i i
AE^q
CALCIUM PHOSPHATE
TO GYPSUM POND
POND
TO RIVER OR
PROCESS UNITS
Figure 39. Pond water treatment system.
Source: U.S. Environmental Protection Agency. 1974a. Development document for effluent limitations guide-
lines and new source performance standards for the basic fertilizer chemicals segment of the fertilizer
manufacturing point source category. Office of Air and Water Programs. Washington DC, 168 p.
-------
Data from one plant tested (USEPA 1974a) show that phosphorus
concentrations also decrease with time once pH ranges above 5 are met. When
a 46-hour holding period was employed, the following values were derived:
pH Phosphorus (mg/1)
5.8 20
6.5 9.1
8.3 3.6
The time effect on phosphorus concentration is:
Time-hours ^ Phosphorus (mg/1)
0 7.85 60
5 7.6 29
22 6.7 19
46 6.4 9
Data from three years of double lime treatment of gypsum pond effluent
from one plant at a pH of 5 to 7 show a phosphorus concentration (as P) of 10
to 40 mg/1.
Radium-226 is also precipitated by lime treatment incrementally with
increasing pH as presented below (USEPA 1974a):
Radium-226
pH (picocuries/1)
2.0 (sic) 91
1.5 (sic) 65
4.0 7.6
8.0-8.5 0.04
Double liming is not effective in controlling NH»-N in contaminated
water. This is why the self-contained ammonium phosphate NSPS has been
established. There is no acceptable method of economically removing NH^-N
from aqueous solutions as weak as 20-60 mg/1. It is instead most important
to keep NH^-N from entering the contaminated water system.
173
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3.3.2 Gypsum Pond Water Seepage Control
The contaminated (gypsum pond) water storage areas are surrounded by
dikes except when mining pits are used. The base of these dikes are normally
natural soil from the immediate surroundings. When height of the retaining
dikes must be increased, gypsum from inside the diked area is added to the
top of the earthen base. Dikes in Florida now extend 100-120 ft in vertical
height and tend to have continual seepage of contaminated water through them.
To prevent this seepage from reaching natural drainage streams, it should be
collected and returned to the pond.
Figures 40 and 41 illustrate the design and use of a seepage collection
ditch around the perimeter of the diked area. The ditch should be of
sufficient depth and size to collect contaminated water seepage and to permit
collection of seepage surface water from the immediate outer perimeter. This
is accomplished by erection of a small secondary dike. The secondary dike
also serves as a back-up or reserve dike in the event of a failure of the
major dike.
The design of the seepage ditch in respect to distance from the main
impounding dike and depth is a function of the geology of the area and the
type material used for the dike. Some data suggest that the gypsum pond
bottoms tend to be self-sealing (Wissa 1977). That is, compacted gypsum plus
clay fines and aluminum and iron silicates forced into the interstices may
form an artificial "cement" like layer on the bottom of old gypsum ponds
which is both acid resistant and of very low permeability. In the design of
gypsum ponds and. ditches the applicant must consider the area geology and the
phreatic water level of the impounding dike material to achieve an effective
seepage control system. Water table aquifers, and conceivably deeper
aquifers, have been contaminated in the vicinity of ponds (TRC 1979). An
installation of a pump station at the low or collection point of the seepage
ditch is an essential part of the seepage control system. (USEPA 1974a).
3.3.3 Other End-of-Process Controls
It is reportedly possible for a fertilizer plant to meet the
no-discharge criterion without the use of gypsum ponds for storage. One
174
-------
SLOPE NO GREATER
THAN 2:1
MINIMUM 6 m
_ FREEBOARD,
MINIMUM 1.5m
I
DRAINAGE
DITCH
OUTSIDE TOE
BERM\
WATER LEVEL SLOPE N0 GREATER THAN 2:1
,-INSIDE TOE
JBERM 8 m MINIMUM
\ BORROW PIT
MINIMUM DEPTH 1 m
Figure 40. Recommended minimum cross section of dam.
Reprinted from Phosphoric Acid, Volume I, A.V. Slack, Editor, by permission of
Marcel Dekker, Inc., Year of first publication 1968.
GYPSUM POND
GYPSUM POND ' ^ x-'X'"'^Sv;
BED ^ \ $'j
SEEPAGE DITCH
RETURN TO GYPSUM /-
POND BY PUMP
OUTSIDE OF PLANT
A
SECONDARY ;.
DIKE
SEEPAGE ^ \* s^
-APPROXIMATELY
3m WIDE BY
ABOUT 1 m DEEP
Ji;
*?^\
^.^.'YS^^ff'f^' ^
XX!^2^ SEEPAGE
SEEPAGE
DITCH
SURFACE DRAINAGE
DITCH EXTERNAL TO
THE PLANT
Figure 41. Gypsum pond water seepage control.
Source: Environmental Protection Agency. 1974a. Development document for efflu-
ent limitations guidelines and new source performance standards for the basic
fertilizer chemicals segment of the fertilizer manufacturing point source
category. Office of Air and Water Programs, Washington DC, 168 p. in USEPA
1979a.
175
-------
plant along the Houston Ship Channel in Texas has claimed success by use of
process modifications tailored to its operation (Mabrey 1978). This plant
operates on a relatively small sight and previously took advantage of
once-through channel water (10,000-12,000 gpm) to cool the evaporator and
barometric condenser, and to supply scrubber water for the phosphoric acid
and fertilizer product reactors and for the dryer gas. The water was
neutralized with lime, clarified, and discharged.
To meet Texas Water Quality Board and NPDES permit requirements, zero
discharge (as of March 1978) had been maintained. The plant continues to use
cooling towers to cool and recirculate contaminated water. The key to using
the towers successfully has been to control fluoride emissions from the
phosphate fertilizer processes contaminated wastwater, with pH of 1-3 and
fluoride concentrations of 4000-5000 ppm at equilibrium (Mabrey 1978). NSPS
fluoride emission levels reportedly have been achieved by adjusting the ratio
of fluoride to silica in a company classified procedure. Meanwhile, to
prevent discharge of contaminated runoff water from the piles due to
rainfall, the plant has constructed retaining ponds on top of stabilized
gypsum piles. The retaining procedure has not been thoroughly proven and is
not a typical requirement. It was required due to run off containing NH~-N
contamination from existing gypsum piles caused by wastes from non-phosphate
fertilizer processes also performed at the plant described (Mabrey 1978).
3.4 STATE OF THE ART TECHNOLOGY; END-OF-PROCESS CONTROLS AND EFFECTS ON
WASTE STREAMS (SOLID WASTE)
The quantity of waste gypsum produced in a wet process phosphoric acid
plant ranges from 4.6 to 5.2 metric tons gypsum/metric ton P00 produced
0 / J
(Slack 1968). Approximately 1,360 m of gypsum will be accumulated yearly
2
per metric ton of P20 produced per day; at least 2,230 m of land area per
daily metric ton P^ should be reserved for gypsum disposal (USEPA 1979a).
In the United States and other locations three disposal practices are
currently used: gypsum ponds and piles, abandoned mine pits, and sea
disposal (USEPA 1979a).
176
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3.4.1 Disposal in Gypsum Ponds and Piles
In the United States more than 90% of the phosphate fertilizer plants
use gypsum ponds to collect the slurry. Initially, two or more areas are
converted to lagoons by means of low dikes provided with proper outfalls for
potential effluent discharge. As one area becomes filled, the gypsum stream
is diverted to the second area, and the first section is allowed to dry out
sufficiently to support mechanical equipment. The dike is then increased in
height, using deposited gypsum as the source of material, and the procedure
is repeated. An alternative is the use of draglines to stack wet gypsum from
the gypsum flats area of the pond onto an active gypsum pile to dry
(USEPA 1978c). Existing gypsum piles range in height from 30 m to 36 m
(100-120 ft) (USEPA 1979a).
In the western states where poor land stability or availability prevents
the use of gypsum ponds, gypsum cake from the vacuum filters is transported
by conveyor to gypsum stacks (USEPA 1979a).
3.4.2 Disposal in Abandoned Mine Pits
This disposal technique is practiced primarily in Florida. Instead of
constructing gypsum ponds, abandoned phosphate rock surface mines are used as
gypsum ponds and for other solid residue disposal. A potential environmental
hazard from this disposal technique is the possible leaching of fluorides and
phosphates into the groundwater system. Because the mined-out pits are
closer to subsurface aquifers, their potential for adverse environmental
effects is greater than that of the surface gypsum ponds (USEPA 1979a).
3.4.3 Disposal in Sea Outfalls
This disposal technique, used by less than 2% of the phosphate
fertilizer plants in the United States, but more widely used throughout
Europe, is practiced at plants located in coastal areas. Gypsum is pumped
into the ocean or, in a few cases, discharged into major rivers. After
removal from the vacuum filter, the gypsum is slurried with about a tenfold
quantity of seawater or cooling water (Slack 1968, USEPA 1979a).
177
-------
Seawater is a better solvent for gypsum than fresh water. The
solubility of gypsum in seawater is about 3.5 g/1 as compared to about 2.3
g/1 in fresh water. The solids content of the gypsum slurry is below 5%, low
enough for quick dispersion and dissolution in ocean water (Slack 1968, USEPA
1979a).
3.4.4 Resource Recovery
Soil Treatment
In 1975, approximately 30 x 10 metric tons of gypsum waste were
generated by the phosphate fertilizer industry. Of this total, about 90 x
10 metric tons were applied to calcium-deficient soil in the southern states
for peanut growing. Gypsum was also used for improvement of alkali soils in
California and for land reclamation in coastal areas. It conditions the soil
and causes sodium chloride to leach out faster (USEPA 1979a). Since gypsum
waste contains varying quantities of phosphoric acid, it also serves as a
light fertilizer.
Wallboard Problems
Waste gypsum has been used for wallboard. In the United States, the
dihydrate process for phosphoric acid production produces a gypsum waste high
in phosphoric acid, which results in poor quality wallboard. Also, there is
some concern about the possible low-level radiation effects from wallboard
made of uranium- and radon-containing gypsum wastes.
In Europe .id Japan, where the hemihydrate process is more commonly
used, the resulting gypsum waste is purer, containing less phosphoric acid
and uranium. More of this gypsum waste is used for wallboard. In England,
where only the standard dihydrate process is used, special purification
methods make the by-product suitable for wallboard. This purification step
is more economically feasible in England than in the United States, because
aatural (and purer) gypsum is not as abundant in England as it is in the
United States (USEPA 1979a).
178
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Cement Supplement Problems
Another possible use for gypsum is in cement and other road toppings.
However, the phosphoric acid and other phosphates retard setting and lower
the strength of the hardened body. Fluorine compounds reduce setting time
and lower the concrete strength, but these effects are small compared to the
effects of phosphate contamination. In Florida, there are further concerns
over public exposure to low level radiation from road surfaces containing
gypsum wastes or from road base material containing phosphate rock mining
overburden (USEPA 1979a).
Ammonia and C02 Treatment
Gypsum can be reacted with ammonia and carbon dioxide to form ammonium
sulfate and calcium carbonate. This is an old and well-known practice
applied to natural gypsum, but there has been relatively little application
to by-product gypsum. Only a few plants in India, Japan, and Europe use this
technology (USEPA 1979a).
Silica Thermal Treatment
Another potential resource recovery method is treating by-product gypsum
with silica at high temperatures to produce sulfuric acid. The additional
product of calcium silicate could be used for cement. Although the method is
technically feasible, the high water content of gypsum, the corrosive effect
of fluorides, and the adverse effect of P?°c content on cement quality are
all major drawbacks. Also, due to the price and availability of sulfur in
the United States, this technology is not yet economically feasible (USEPA
1979a).
3.5 POLLUTION CONTROL RECOMMENDATIONS EXCERPTED FROM THE CENTRAL FLORIDA
PHOSPHATE INDUSTRY FINAL AREAWIDE ENVIRONMENTAL IMPACT STATEMENT
The recently published Areawide EIS for the central Florida phosphate
industry lists several recommended practices which are anticipated to be
required for new source phosphate fertilizer facilities in central Florida.
179
-------
Because of the concentration of the industry in that area, and because of
their potential relevance to future policy determinations, the
recommendations are included below. These recommendations are included for
information only, and are not to be taken as final policy. The applicant is
advised to coordinate the scope of the EID with the regional USEPA officials
in all cases, prior to starting work.
USEPA Region IV Phosphate Fertilizer Facility Recommendations
• Meet Federal air quality new source performance standards and design
surge capacity in the USEPA Standards of Performance for New Sources
for process water systems.
• Line gyp ponds with an impervious material unless it can be demon-
strated in the site-specific EIS that such lining is unnecessary in
protecting ground water from chemical and radiological contamination.
• Recirculate process and non-process water. The non-process system
should have the same design surge capacity as required in the
Standards of Performance for New Sources for process water systems.
• Provide for recovery of fluorine compounds from phosphoric-acid
evaporators unless it is determined at the time of permit application
that market conditions are such that the cost of operation (not
including amortization of initial capital cost) of the recovery
process exceeds the market value of the product. If there is an
exception, the site-specific EIS is to contain an estimate of
pond-water fluoride concentrations to be attained and levels of
fluorine emission. Estimated fluorine emissions from new source gyp
ponds should not cause the plant complex to exceed the total
allowable point source fluorine emissions within the plant complex if
a permit is to be issued.
• Encourage recovery of uranium based on economic feasibility data
to be included in the site-specific EIS.
Shortened term: gypsum ponds.
Source: U.S. Environmental Protection Agency. 1978q. Final areawide
environmental impact statement, Central Florida phosphate industry,
Volume 1. EPA 904/9-78-26a. Atlanta GA, 80 p.
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4.0 OTHER CONTROLLABLE IMPACTS
4.1 AESTHETICS
New source phosphate facilities may involve large and complex operations
occupying hundreds of acres. Rock storage and handling areas, haul roads,
rock conveyors, and slurry pipelines, gypsum ponds and piles, dust, erosion,
and sediment-laden streams are aesthetically displeasing to many. Particularly
in rural and suburban areas, phosphate fertilizer manufacturing (and possible
associated mining activity) can represent a noticeable intrusion on the land-
scape. Measures to minimize the impact on the enviornment must be developed
during site selection, plant planning design, and reclamation. The applicant
should consider the following factors where feasible to reduce potential
aesthetic impacts:
• Existing Nature of the Area. The topography and major land uses in
the area of the candidate sites are important. Topographic conditions,
and existing trees and vegetation visual barriers can be used to screen
the operation from view. A lack of topographic relief and vegetation
would require other means of minimizing impact, such as regrading or
planting of vegetation buffers;
• Proximity of Parks and Other Areas Where People Congregate for
Recreation and Other Activities. The location of public use areas
should be mapped and presented in the EID. Representative views
of the plant site from observation points should be described. The
visual effects on these recreational areas should be described in
the EID in order to develop the appropriate mitigation measures;
• Transportation System. The visual impact of new access roads, rail
lines, haul roads, barge docking, pipelines, and storage facilities,
the landscape or waterfront should be considered. Locations, construc-
tion methods and materials, and maintenance should be specified.
4.2 NOISE
The major sources of noise associated with phosphate fertilizer manu-
facturing include:
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• Plant construction equipment (bulldozers, graders).
• Rock transport systems (haul roads, conveyors, pipelines, loading
dozers).
• Rock grinding and handling.
• Boilers and steam venting.
• Product transport systems (truck, railroad and barge loading).
• Land reclamation/grading equipment.
These activities can create significant ambient noise levels that may
decrease with increasing distance from the site. Noise can be attenuated
effectively with thick stands of vegetation or other barriers. Even at dis-
tances of 1,500 to 2,000 feet the increases in noise levels due to manufac-
turing activities still may be noticeable. Noise receptors within a half mile
of the source are the most pertinent for most facilities and should be documented
in the EID.
Noise also can create serious health hazards for exposed workers;
therefore, the necessary source and operational control methods should be
employed. Such measures include:
• Enclosed process machinery.
• Mufflers on engines.
• Lined ducts.
• Partial barriers.
• Vibration insulation.
• Imposed speed limits on vehicles.
• Scheduled equipment operations and maintenance.
A suitable methodology to evaluate noise generated from a proposed new
source facility would require the applicant to:
USEPA has recommended a 75-dBA, 8-hour exposure level to protect from loss
of hearing, and a 55-dBA background exposure level to protect from
annoyance of outdoor activity.
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• Identify all noise-sensitive land uses and activities adjoining
the proposed plant site.
• Measure the existing ambient noise levels of the areas adjoining
the site.
• Identify existing noise sources, such as traffic, aircraft fly-
over, existing mining and other industry, in the general area.
• Determine whether there are any State of local noise regulations
that apply to the site.
• Calculate the noise level of the manufacturing processes, compare
that value with the existing area noise levels and the applicable
noise regulations.
» Assess the impact of the operation's noise and, if required, determine
noise abatement measures to minimize the impact (quieter equipment,
noise barriers, improved maintenance schedules, etc.)
4.3 ENERGY SUPPLY
Cogeneration in industrial processes denotes any form of the simultaneous
production of electrical or mechanical energy and useful thermal energy (usually
in the form of hot liquids or gases) (USDOE 1978).
The permit applicant should evaluate the energy efficiencies and demands
of all methods considered during project planning in the context of an alter-
native analysis. Also, feasible design modifications should be considered in
order to reduce energy needs.
At a minimum, the applicant should provide the following information in
the BID:
• Total external energy demand for operation of the mine.
• Total energy generated on site.
« Energy requirements by type.
• Source of energy off-site.
® Proposed measures to conserve or reduce energy demand
and to increase efficiency of mine operation.
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4.3.1 Cogeneration
Phosphate complexes which produce sulfuric acid on site obtain, due to
the exothermic combustion and absorption reactions, a net yield of energy in
the form of moderate pressure steam. This steam is usually used to generate
the major on-site electrical energy requirements. After generation of elec-
tricity, process steam amounts to about 1,900,000 Btu per ton of 100% sulfuric
acid (Blouin 1975). Highly integrated complexes which produce wet process
phosphoric acid, SPA, and/or conventional process granulated fertilizer products
may consume this energy for steam ejectors, vacuum evaporators, dryers, or
steam powered machinery. The EID should indicate the power demands of pro-
cesses to be used and assess potential for excess steam capacity for cogenera-
tion of marketable electric power. Process options, such as melt-type ammoniator-
granulators should be considered in view of the potential for converting
energy savings from unneeded dryers into power generation. The Public Utility
Regulatory Policies Act of 1979 provides for Federal Energy Regulatory Commission
rules favoring cogeneration facilities, and requiring utilities to buy or sell
power from qualified cogenerators at just and reasonable rates.
4.3.2 Energy Consumption and Conservation
In 1976 the energy consumption in the U. S. was about 74 x 10 Btu
(quads) per year. The U. S. Federal Energy Administration and U. S. Department
of Agriculture estimated the energy consumption in fertilizer production to be
0.621 quad per year. Blouin and Davis' estimate for the chemical fertilizer
industry energy consumption was 0.522 quad per year. Thus 0.7 - 0.8% of the
nation's energy goes for fertilizer production. Table 32 indicates that
roughly 68% of that energy consumption is to for ammonia production, and about
12% for phosphate fertilizer.
Although the phosphate fertilizer industry accounts for a small portion
of total energy consumption, energy conservation practices are of benefit to
the producer, the regional energy supply, and the U.S. economy.
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Table 32. Energy for fertilizer nutrient production.3
Nutrient Energy requirement,
Btu's per pound
N 28,000
P2°5 5,000
K20 4,000
S 4,OOOb'C
a. Source: White, Bill. 1977. Fertilizer cost trends - energy, environment,
transportation. Fertilizer Progress, Volume 8. January-February
1977 in Barber 1978a.
b. Energy for Frasch mined sulfur
c. Source: Blouin, Glenn M. and Charles H. Davis. 1975. Energy require-
ments for the production and distribution of chemical fertilizers
in the U.S. Energy and Agriculture, Proceedings of a workshop.
Southern Regional Educational Board. Atlanta GA, p. 51-67 in
Barber 1978a.
Conservation practices applicable to the phosphate fertilizer industry
are described below (Barber 1978a):
• Wet grinding of phosphate rock instead of dry grinding conserves
energy. Phosphate drying consumes energy and results in the dis-
charge of particulates and operation of abatement equipment.
• Melt-type granulation processes eliminate drying of granulated
fertilizer. Energy is conserved by eliminating the drying step
and by decreasing the volume of air to be treated for air
pollution control.
• Emission of dust from granulation processes is reduced by making
strong granules. Formation of particulates from handling is held
to a minimum and dust control simplified.
• The pipe reactor installed in ammoniator-granulators eliminates
formation of small particulates and reduces the volume of gas to
be treated. Otherwise, high pressure drop scrubbers (about 50
inches of water) are necessary to meet air emission standards.
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• Particulate collecting systems are designed to provide optimum
dust pickup and transport velocities. Long and complicated ducts
give rise to duct stoppages or expenditure of excessive energy
to transport dust at high enough velocity to prevent stoppages.
• Baghouse collectors are used instead of scrubbers for particulate
collection when the particulates have low hygroscopicity and the
gas temperature does not exceed the limit for fabric filters. Bag-
house collectors consume less energy than scrubbers unless gases
have to be heated to overcome the hygroscopicity problem. When
the gases have to be heated, energy for baghouses and scrubbers
is about the same.
• Effluent from granulation processes may be reused in the process or
the effluent may be sold as a fluid fertilizer. This saves energy
for nutrient production and eliminates a waste treatment facility.
In addition, well planned siting of the fertilizer plant can greatly affect
net energy consumption of the operations. The amount of energy consumed in
transportation by the four major transportation modes is shown below in Btu's/
ton-mile (Achorn & Kimbrough 1978) :
Pipeline 450
Barge 500
Rail 700
Truck 2,500-2800
These data indicate that to conserve energy, the applicant should use pipe-
line, barge, and perhaps rail as much as possible, and avoid truck trans-
portation.
Finally, uranium production, which can have significant effects on energy
supply, should be considered. This practice can help toward making phosphate
fertilizer manufacturing a net producer rather than consumer of energy.
4.4 SOCIOECONOMICS
The introduction of a large new phosphate fertilizer facility into a
community may cause land use, economic, and social changes. Therefore, it is
necessary for an applicant to understand the types of impacts or changes that
may occur so that they can be evaluated adequately. The importance of these
changes usually depends on the size of the existing community where the facility
is located. The significance of the changes caused by a facility of a given
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size normally will be greater near a small rural community than near a large
urban area. This generally is due to the fact that a small rural community is
likely to have a nonmanufacturing economic base and a lower per capita income,
fewer social groups, a more limited socioeconomic infrastructure, and fewer
leisure pursuits than a large urban area. There are situations, however, in
which the changes in a small community may not be significant, and conversely,
in which they may be considerable in an urban area. For example, a small
community may have had a manufacturing (or natural resource) economic base
that has declined. As a result, such a community may have a high incidence of
unemployment in a skilled labor force and a surplus of housing. Conversely, a
rapidly growing urban area may be severely strained to provide the labor force
and services required for a new phosphate facility.
The rate at which changes occur (regardless of the circumstances) also is
often an important determinant of the significance of the changes. The appli-
cant should distinguish clearly between those changes occasioned by the construc-
tion of the facility, and those resulting from its operation. The former
changes could be substantial but usually are temporary; the latter may or may
not be substantial, but normally are more permanent in nature. The potential
impacts which should be evaluated include:
Increased consumption and rate of land development.
Land use pattern and compatibility changes.
Economic base multiplier effects.
Population size and composition changes.
Increased labor force participation and lower unemployment rates.
Increased vehicular traffic and congestion.
Loss of prime agricultural land and environmentally sensitive areas.
Increased demand for community facilities and services.
Increased demand for water supply, sewage treatment and solid
waste disposal facilities.
During the construction phase, the impact will be greater if the project
requires large numbers of construction workers to be brought in from outside
the community than if local unemployed workers are available. The potential
impacts include:
• Creation of social tension.
• Short-term expansion of the local economy.
• Demand for increased police and fire protection, public utilities,
medical facilities, recreation facilities, and other public services.
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• Increased demand for housing on a short-term basis.
• Strained economic budget in the community where existing infra-
structure becomes inadequate.
• Increased congestion from construction traffic.
Various methods of reducing the strain on the budget of the local community
during the construction phase should be explored. For example, the company
itself may build the housing and recreation facilities and provide the utility
services and medical facilities for its imported construction force. Or the
company may prepay taxes, and the community may agree to a corresponding
reduction in the property taxes paid later. Alternatively, the community may
float a bond issue, taking advantage of its tax-exempt status, and the company
may agree to reimburse the community as payments of principal and interest
become due.
During operation, the more extreme adverse changes of the construction
phase are likely to disappear. Longer run changes may be profound, but less
extreme, because they evolve over a longer period of time and may be both
beneficial and adverse.
The permit applicant should document fully in the EID the range of poten-
tial impacts that are expected and demonstrate how possible adverse changes
will be handled. For example, an increased tax base generally is regarded as
a positive impact. The revenue from it usually is adequate to support the
additional infrastructure required as the operating employees and their families
move into the community. The spending and respending of the earnings of these
employees has a multiplier effect on the local economy, as do the interindustry
linkages created by the phosphate facilities. The linkages may be backward and
forward. Backward linkages are those of the facility's suppliers. Forward
linkages are those of the facility's markets.
Socially, the community may benefit as the increased tax base permits the
provision of more diverse and higher quality services, and the variety of its
interests increases with growth in population. Contrastingly, the transfor-
mation of a small community into a larger community may be regarded as an
adverse change by some of the residents who chose to live in the community, as
well as by those who grew up there and stayed because of its small town amenities.
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The applicant also should consider the economic repercussions if, for
example, the quality of the air and water declines as a result of various
emissions from the phosphate facility. In some cases, other more traditional
sectors of economic activity may decline because labor is drawn away from them
into higher paying phosphate related or tertiary sector activities. As an
illustration, the fishing sector may decline if water pollution increases, or
if fishermen abandon the occupation in favor of employemnt at the phosphate
facility. Again, the tourist sector may decline if air and water pollution is
noticeable or if the landscape is degraded.
Thus, the applicant's framework for analyzing the socioeconomic impacts
of the location of a phosphate facility must be comprehensive. Most of the
changes described can and should be measured to assess fully the potential
costs and benefits. The applicant should distinguish clearly between the
short-term (construction) and long-term (operation) changes, although some
changes may be common to both (e.g., the provision of infrastructure). The
significance of the changes depends not only on their absolute magnitude, but
on the rate at which they occur. The applicant should also develop and main-
tain close coordination with State, regional, and local planning and zoning
authorities to ensure full understanding of all existing and/or proposed land
use plans and other related regulations.
US EPA's Office of Federal Activities ts developing a methodology to be
used to forecast the socioeconomic impacts of new source industries and the
environmental residuals associated with those impacts.
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5.0 EVALUATION OF AVAILABLE ALTERNATIVES
The alternatives section of the EID should address each reasonable alter-
native equitably. The purpose of this analysis is to identify and evaluate
alternate plans and actions that may accomplish the desired goals of the
project. These alternatives can include process modifications, site reloca-
tions, project phasing, or project cancellation.
For the alternatives to a proposed project to be identified and evaluated
properly, the impact assessment process should commence early in the planning
phase. In this manner, social, economic, and environmental factors against
which each alternatiave is to be judged can be established. Cost/ benefit
analysis should not be the only means whereby alternatives are compared. The
environmental and social benefits of each alternative also must be considered.
In general, the complexity of the alternative analyses should be a function of
the magnitude and significance of the expected impacts of the proposed pro-
cessing operations. A small operation that uses purchased raw materials or
existing by-products may have a relatively minimal impact on a region and
generally would require fewer alternatives presented in the EID.
The public's attitude toward the proposed operation and its alternatives
also should be evaluated carefully. In this way key factors such as aesthetics,
community values, and land use can be assessed properly.
5.1 SITE ALTERNATIVES
The phosphate fertilizer industry locates facilities on the basis of
convenience to raw materials, an adequate labor force and water supply, prox-
imity to energy supplies and transportation, minimization of environmental
problems, and only to a limited extent on the basis of market demand and other
factors. A variety of sites initially should be considered and, following a
detailed analysis of each one, a preferred alternative should be selected that
appears to satisfy the objectives and that is expected to result in the least
adverse environmental impact. When the site is planned in the mining area,
the selection factors will also be related to mining impacts and any integra-
tion possible for processes, handling systems, and common waste disposal sites
and treatment techniques.
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The factors considered in selecting each site, and especially those that
influenced a positive or negative decision on its suitability, should be
carefully documented in the permit applicant's EID. Adequate information on
the feasible alternatives to the proposed site is a necessary consideration in
issuing, conditioning, or denial of an NPDES permit (40 CFR 6, Subpart F).
Proposals to build in areas of steep terrain, unstable soils, wetlands or high
water tables, and urbanized areas should devote comprehensive analysis to
siting alternatives.
Specifically, the advantages and disadvantages of each alternative site
must be catalogued with due regard to preserving natural features such as
wetlands, coastal zones, and other sensitive ecosystems and to minimizing use
of flood plains or other areas of significant adverse environmental impacts.
The applicant should ascertain that all impacts are evaluated as to their
significance, magnitude, frequency of occurrence, cumulative effects, reversi-
bility, secondary or induced effects, and duration. Accidents or spills of
hazardous or toxic substances vis-a-vis site location should be addressed.
When a proposed site is controversial, it may have to be abandoned for a
number of reasons. Such opposition may derive from the fact that the proposed
facility would significantly impact a unique, recreational, archaeological, or
other important natural or man-made resource area. It may destroy the rural
or pristine character of an area. It may conflict with the planned develop-
ment for the area. The site may be opposed by citizen groups. It may have to
be discarded for meteorological and climatological reasons. It may be subject
to periodic flooding, hurricanes, earthquake, or other natural disasters.
If the proposed site location proves undesirable, then alternative sites
from among those originally considered should be reevaluated, or new sites
should be identified and evaluated. Expansion or continued use of an existing
facilities site also could be a possible alternative solution. It is critical
that a permit applicant systematically identify and assess all feasible alter-
native site locations as early in the planning process as possible.
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5.2 ALTERNATIVE PROCESSES DESIGNS, AND OPERATIONS
Typically, when the decision is made to expand manufacturing capacity—
either through a new plant or an addition to an existing one—the type of
facility to be constructed is already fixed; that is, the demand for phos-
phoric acid and/or other end products would have dictated the general types of
processes to be used. The limitation on process alternatives is not as severe
as it once was in dry products because of improved versatility of granulation
processes.
In addition to demand, the process alternatives should be selected on the
basis of availability and quality of required raw materials as well as environ-
mental considerations. The applicant should present clearly and systemati-
cally in the EID the methodology used to identify, evaluate, and select the
preferred process alternatives. In unusual cases where water supplies or raw
materials quality is a constraint or land availability of concern, process
alternatives now only in research or pilot plant stages may be considered by
the applicant. For example, the thermal process for phosphoric acid would
eliminate gypsum-pond-related waste problems, but it has other solids disposal
problems. Other alternatives continuously being investigated include solvent
extraction of wet process acid impurities and use of alternate acids to produce
alternate fertilizer products directly from phosphate rock and eliminate
gypsum wastes (although other wastes may pose other serious difficulties).
5.3 NO-BUILD ALTERNATIVE
In all proposals for facilities developed, the applicant must consider
and evaluate the alternative of not constructing the proposed new source
facility. Because this analysis is not unique to the development of phosphate
fertilizer manufacturing facilities, no detailed guidance is provided as part
of this Guidelines document. The permit applicant is referred to Chapter IV
(Alternatives to the Proposed New Source) in the document, Environmental Impact
Assessment Guidelines for Selected New Sources Industries (USEPA 1975). The
no-build alternative in the present context can include sale of raw materials
to existing facilities in instances where an applicant produces one or more of
the raw materials for phosphate fertilizers and where transportation impacts
may be less severe than impacts of siting a new source phosphate manufacturing
plant in the proposed area.
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6.0 REGULATIONS OTHER THAN POLLUTION CONTROL
The applicant should be aware that there may be a number of regulations other
than pollution control regulations that have some application to the siting
and operation of new phosphate fertilizer manufacturing facilities. The
applicant should coordinate with the appropriate USEPA Regional Administrator
regarding applicability of such regulations to the proposed new source.
Federal statutes which generated regulations that may be pertinent to a pro-
posed facility iaelude:
Council of Environmental Quality, Rules and Regulations for NEPA, Imple-
mentation of Procedural Provisions (40 CFR 1500, rev. Nov. 29, 1978)
Environmental Protection Agency, Implementation of Procedures on the
National Environmental Policy Act (40 CFR 6, November 6, 1979)
Coastal Zone Management Act of 1972
The Fish and Wildlife Coordination Act
The National Environmental Policy Act of 1969
USDA Agriculture Conservation Service Watershed Memorandum 198 (1971)
Wild and Scenic Rivers Act of 1969
The Flood Control Act of 1944
The National Flood Insurance Act of 1968
The National Flood Disaster Protection Act of 1973
Federal-Aid Highway Act, as amended (1970)
The Wilderness Act (1964)
Endangered Species Preservation Act, as amended (1978)
The National Historical Preservation Act of 1974
Executive Orders 11593, 11938, and 11990
Archaeological and Historic Preservation Act of 1974
Procedures of the Council on Historic Preservation (1973)
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Occupational Safety and Health Act of 1979
Safe Drinking Water Act, as amended (1977)
Atomic Energy Act
In connection with these regulations, the applicant should place particular
emphasis on obtaining the services of a recognized archaeologist to determine
the possibilities of disturbing an archaeological site, such as an early
Indian settlement or a prehistoric site. The National Register of Historic
Places also should be consulted for historic sites such as battlefields. The
applicant should consult the appropriate wildlife agency (State and Federal)
to ascertain that the natural habitat of a threatened or endangered species
will not be adversely affected.
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7.0 REFERENCES
The literature references listed in this section include cited references
and additional selected bibliographic references. The listings immediately
below are short form citations arranged according to topics. A complete
listing of full references, arranged alphabetically, follows the short form
citations. These citations are useful for further information in specific
topic areas.
General
Alsager 1978
Anonymous 1978a
Dinauer 1971
Drew Chemical
Corporation 1977
Hooks 1978
Kirk-Othmer 1969
Perry 1969
Russel 1977
Schneider 1976
Slack 1968a
Slack 1968b
USEPA 1975
USEPA 1978b
USEPA 1978e
USEPA 1978h
USEPA 1978i
USEPA 1978g
Subcategorization
USEPA 1974a
USEPA 1974b
USEPA 1974C
USEPA 1976c
Processes (including
trends in processes)
Achorn and
Kimbrough 1974
Achorn et al 1976
Anonymous 1972a
Anonymous 1972b
Anonymous 1972c
Anonymous 1976a
Anonymous 1976d
Balay and Achorn 1971
Balay and Kimbrough
1978
Barber 1976
Barber 1978b
Bostwick 1970
Brown 1976
Market and Demands
Anonymous 1970
Anonymous 1974a
Anonymous 1974b
Anonymous 197 6b
Anonymous 1976c
Anonymous 1976d
Carrington 1962
Douglas and Parker 1977
Douglas and Davis 1977
Harre 1975
Harre 1976
Stowasser 1975
Stowasser 1977
TVA 1977a
TVA 1977b
TVA 1978a
TVA 1979
USDOI 1977
USDOI 1979
U.S. Department of
Commerce 1979
USEPA 1974d
USEPA 1974e
USEPA 1977a
USEPA 1978a
USEPA 1978p
USEPA 1979a
Pollution Control
Technology
Achorn and Barger 1972
Anonymous 1972a
Bakke 1976
Barber 1975a
Barber 1975b
Barber 1978a
Cheremisinoff
et al 1979
Cochrane 1976
Cochrane 1978
Drew Chemical Corp.
Flagg 1978
Industry Trends
(location, raw materials ,
products) _
Anonymous 1975
Barber 1975c
Barber 1978a
Douglas 1978
Hicks 1977
Hignett 1972
Lyon 1976
Parker et al 1977
Russel 1977
Stowasser 1975
Stowasser 1977
TVA 1977a
TVA 1978a
U.S. Department of
Commerce 1979
USEPA 1974d
USEPA 1974e
USEPA 1976d
USEPA 1977a
USEPA 1978a
USEPA 1979a
Human Health
Hodge and Smith 1979
National Academy of
Sciences 1971
Prister 1971
Schiager 1978
TRC 1979
USEPA 1974a
USEPA 1974f
Anonymous 1976e
Aoyama and Inoue 1973
Maslov 1973
Prister 1971
Schiager 1978
USEPA I977d
USEPA 1978p
195
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(Processes Cont.)
Davis 1975
Dell 1967
Dinauer 1971
Donovan 1976
Engineering and
Mining Journal
Hicks 1977
Hignett 1972
Hurst 1976
Hurst and Grouse 1974
Johnson 1967
Lee and Waggoner 1975
Lombardi and
Teller 1976
McCollough 1976
Miyamoto 1975
Orekhov et al 1976
Parker et al 1977
Rushton and Smith 1964
Rushton and Williams
1977
Scott et al 1974
Slack 1968a
Slack 1968b
Stern and Ellis 1970
Striplin and
Achorn 1970
TRC 1979
TVA 1974
U.S. Atomic Energy
Commission
U.S. Energy Research
& Development Admin-
istration 1976
USEPA 1971
USEPA 1974a
USEPA 1974b
USEPA 1974c
USEPA 1976a
USEPA 1976b
USEPA 1976c
USEPA 1976d
USEPA 1977a
USEPA 1977b
USEPA 1978a
USEPA 1978c
USEPA 1979d
USEPA 1979a
White et al 1978
(Pollution Control Cont.) Air quality
Friedman 1976
Gartrell and Barber 1979
Harman and Ramsey 1978
Hill 1976
Mabrey 1978
Malone 1978
Palm 1976
Pflaum 1978
Pound 1976
Powers 1976
Rodgers 1976
TRC 1979
USEPA 1971
USEPA 1974a
USEPA 1974b
USEPA 1974c
USEPA 1976d
USEPA 1977c
USEPA 1978a
USEPA 1978c
USEPA 1978d
USEPA 1978e
USEPA 1978m
USEPA 1978n
USEPA 1978o
USEPA 1979a
Wilson 1978
Wissa 1977
Water Quality
Bouldin et al 1975
DuPuis 1978
Frazier et al 1977
Lehr 1978
USEPA 1974a
USEPA 1976a
USEPA 1976b
USEPA 1976e
USEPA 1977a
USEPA 1978e
USEPA 1978g
USEPA 1978h
USEPA 1978i
USEPA 1979a
Energy
Blouin and Davis 1975
Achorn and Barber 1972
Frazier et al 1977
Hentrickson 1961
McCune et al 1964
Suttie 1969
TRC 1979
USEPA 1974b
USEPA 1976a
USEPA 1976b
USEPA 1976e
USEPA 1977a
USEPA 1977c
USEPA 1978a
USEPA 1978c
USEPA 1978d
USEPA 1978e
USEPA 1978f
USEPA 1978h
USEPA 1978i
USEPA 1978p
USEPA 1978q
USEPA 1979a
Solid Waste
Barber 1975b
Barber 1976
Hocking 1978
Lehr 1978
Palm 1976
Palm and Wissa 1978
USEPA 1974a
USEPA 1976e
USEPA 1977a
USEPA 1978j
USEPA 1979a
White et al 1978
Williams 1975
Wissa 1977
Geology and Geography
Cheremisinoff et al 1979
Pound 1976
Stowasser 1975
U.S. Bureau of
Mines 1977
U.S. Energy Research & Develop-
ment Admistration 1976
196
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Ecology Impacts
(Energy Cont.)
(Geology and Geography Cont.)
Alsager 1978
Aoyama and Inoue 1973
Bouldin et al 1975
Maslov 1976
McCune and Weinstein
1971
National Academy of
Sciences 1971
National Academy of
Sciences 1974
Prister 1971
Suttie 1969
USEPA 1974a
Modeling of Impacts
Engineering and Mining
Journal 1975
USEPA 1978
USEPA 1976a
USEPA 1976b
White 1978
Noise and Vibration
USEPA 1974f
USEPA 1974g
Socioeconomics/Land Use
USEPA 1976e
USEPA 1977d
USEPA 1978J
USEPA 1978p
Williams 1975
Regulations
Beck 1976
Berry 1978
Hoffnagle and Dunlap 1978
Ritch 1978
Sanjour 1978
USEPA 1978k
Alford et al 1976
Alsager 1978
Cheremisinoff et al 1979 Cheremisinoff et al 1979
USEPA 1976e
USEPA 1978b
USEPA 1978h
USEPA 1978j
USEPA 19781
USEPA 1978p
USEPA 1977a
USEPA 1978c
USEPA 1978d
USEPA 1978f
USEPA 1978g
USEPA 1979a
Aesthetics and Cultural
Bouldin et al 1975
USEPA 1978b
USEPA 1978i
197
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Achorn, Frank and J. C. Barber. 1972. Bulk blenders - Environmental control
and OSHA. Fertilizer Progress, Volume 3, p. 24-27, 42, 47-49 (September-
October) and p. 10-13 (November-December).
Achorn, Frank P. and H. L. Kimbrough. 1974. Latest developments in commer-
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D.C. Prepared by Nyers, J.M., G.D. Rawlings, E.A. Mullen, C.M. Moscowitz,
and R.B. Reznik, Monsanto Corp., Dayton, OH, 201 p.
White, Bill. 1977- Fertilizer cost trends - energy, environmental, trans-
portation. Fertilizer Progress. Volume 8, January-February.
White, Bill. 1978. Energy, food, and fertilizers. Fertilizer Progress.
July-August, 5 p.
White, J.C., T.N. Goff, and P.C. Good. 1978. Continuous-circuit preparation
of phosphoric acid from Florida phosphate matrix. U.S. Department of the
Interior, Bureau of Mines, Report of Investigations 8326, Washington,
D.C., 22 p.
Wilson, Miles M. 1978= Fertilizer granulation plant dust collection systems.
In Proceedings of Environmental Symposium, The Fertilizer Institute, New
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209
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Wissa, A.E.Z. 1977- Gypsum stacking technology. Presented at the Annual
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210
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1. REPORT No;
EPA-130/6-81-005
TECHNICAL REPORT DATA
(1 lease read Instructions on the reverse before completing)
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Environmental Impact Guidelines for New Source
Phosphate Fertilizer Manufacturing Facilities
5. REPORT DATE
____ _ ___________________
6. PERFORMING ORGANIZATION CODE
7. AUTHOFKS)
Don R. McCombs, James C. Barber, and Richard Bonskowski
8. PERFORMING ORGANIZATION HLI'ORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Wapora, Inc.
6900 Wisconsin Ave., N.W.
Washington, D.C. 20015
613/A
10. PROGRAM ELEMENT N"6T
11. CONTRACT/GRANT NO.
68-01-4957
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Federal Activities
401 M Street, S.W.
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/100/102
15. SUPPLEMENTARY NOTES
EPA Task Officer is Frank Rusincovitch, (202)755-9368
16. ABSTRACT
This guideline document has been prepared to augment the information previously
released by the Office of Federal Activities entitled Environmental Impact
Assessment Guidelines for Selected New Source Industries. Its purpose is to
provide guidance for the preparation and/or review of environmental documents
(Environmental Information Document or Environmental Impact Statement) which
EPA may require under the authority of the National Environmental Policy Act
(NEPA) as part of the new source (NPDES) permit application review process.
This document has been prepared in seven sections, organized in a manner to
facilitate analysis of the various facets of the environmental review process.
The initial section includes a broad overview of the industry intended to
familiarize the audience with the processes, trends, impacts and applicable
pollution regulations commonly encountered in the phosphate fertilizer industry.
Succeeding sections provide a comprehensive identification and analysis of
potential environmental impacts, pollution control technologies available to
meet Federal standards, and other controlable impacts. The document concludes
with three sections: available alternatives, a listing of Federal regulations
(other than pollution control) which may apply to the new source applicant,
and a comprehensive listing of references for further reading.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Phosphate fertilizer plants
Watet Pollution
Air Pollution
Environmental Impact
Assessment
10A
13B
8. DISTRIBUTION STATEMENT
Release Unlimited
19 SECURITY CLASS fTllis Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
OU.S. GOVERNMENT PRINTING OFFICE: 1981 341-082/262 10
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United States Official Business
Environmental Protection Penalty for Private Use
Agency $300
Washington DC 20460
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