EPA 440/1-73/011
Development Document for
Proposed Effluent Limitations Guidelines
and New Source Performance Standards
for the
BASIC FERTILIZER
CHEMICALS
Segment of the
Fertilizer Manufacturing
Point Source Category
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
NOVEMBER 1973
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publication Notice
This is a development document for proposed effluent limitations
guidelines and new source performance standards. As such/ this report
is subject to changes resulting from comments received during the period
of public comments of the proposed regulations. This document in its
final form will be published at the time the regulations for this
industry are promulgated.
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DEVELOPMENT DOCUMENT
for
PROPOSED EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
BASIC FERTILIZER CHEMICALS SEGMENT OF THE
FERTILIZER MANUFACTURING
POINT SOURCE CATEGORY
Russell E. Train
Administrator
Robert L. Sansom
Assistant Administrator for Air 6 Water Proarams
Allen Cywin
Director, Effluent Guidelines Division
El wood E. Martin
Project Officer
November, 1973
Effluent Guidelines Division
Office of Air and Water Programs
U.S. Environmental Protection Agency
Washington, D. C. 20460
Environmental Protection Agency
RoPUon V, Library
£,;;; ^outti Dearborn Street
Chicago, DM03B 60604
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ABSTRACT
This document presents the findings of an extensive technical study
conducted by Davy Powergas Inc. on the fertilizer industry (contract
number 68-01-1508, Mod. #1).
The study included a detailed and extensive exemplary plant survey,
contacts with consultants and government officials, and literature
search.
The industry survey involved data gathering, sample collection and
analysis, and personal visitation with responsible plant operating
personnel to obtain first-hand information on treatment technology in
commercial use and technology in development and pilot plant stages.
The three main outputs from the study were: industry categorization,
recommendations on effluent guidelines, and definition of treatment
technology. The fertilizer industry was divided into five categories
for more meaningful separation and division of waste water treatment and
development of effluent guidelines. These subcategories are phosphate,
ammonia, urea, ammonium nitrate and nitric acid products. The phosphate
subcategory includes all ancillary operations necessary for phosphate
production (e.g. sulfuric acid and phosphoric acid) . Effluent
guidelines for best practicable control technology currently available,
best available technology economically achievable, and new source
performance standards are recommended for each category.
Treatment technologies such as either in-process or end-of-process add
on units are available or are in advanced development stages to enable
existent and future fertilizer plants to meet the recommended effluent
guidelines.
iii
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CONTENTS
Section
I Conclusions 1
II Recommendations 3
III Introduction 7
IV Industry Categorization 61
V Waste Characterization 65
VI Selection of Pollutant Parameters 77
VII Control and Treatment Technology 81
VIII Cost, Energy and Nonwater Quality Aspect 113
IX Effluent Reduction Attainable Through the
Application of the Best Practicable Control 123
Technology Currently Available — Effluent
Limitations Guidelines
X Effluent Reduction Attainable Through the
Application of the Best Available Technology 131
Economically Achievable -- Effluent Limitations
Guidelines
XI New Source Performance Standards 135
XII Acknowledgments 139
XIII Bibliography 141
XIV Glossary 145
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FIGURES
1. Nitrogen Fertilizers Plant Locations 17
2. Phosphate Fertilizers Plant Locations 21
3. Sulfuric Acid Plant Single Catalysis 25
4. Sulfuric Acid Plant Double Catalysis 26
5. Rock Grinding 30
6. Wet Process Phosphoric Acid H2SOU Acidulation 33
7. NPK Process Nitric Acid Acidulation 35
8. Wet Phosphoric Acid Concentration 37
9. Merchant Grade Phosphoric Acid Clarification 39
10. Normal Superphosphate 41
11. Triple superphosphate (Run-of-Pile R.O.P.) 43
12 Granulated Triple Superphosphate 45
13. Monoammonium Phosphate Plant 48
1U. Diammonium Phosphate Plant 49
15. Ammonia Plant 51
16. Urea Plant 55
17. Ammonium Nitrate Plant 58
18. Nitric Acid Plant 60
19. Sulfuric Acid Effluent Control 83
20. Pond Water Treatment 87
21. Gypsum Pond Water Seepage control 90
22. DAP Self Contained Process 92
23. Wet Process Phosphoric Acid System 94
24. Sulfuric Acid Dilution with Pond Water 95
25. Ammonia/Condensate Stripping 98
26. Integrated Ammonia/Condensate Stripper Unit 99
vi
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V
I
27. Ammonia/Condensate Air Stripping 101
28. Urea Hydrolysis 104
29. Urea Hydrolysis 105
30. Biological Treatment 107
31. Ion Exchange 109
32. Oil/Grease Removal System 111
33. Ammonium Nitrate Effluent Utilization 112
VI1
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TABLES
1. Integration of Production in the Fertilizer Industry 15
2. Water Effluent Treatment Costs Phosphate Subcategory 116
3. Water Effluent Treatment Costs 119
Nitrogen Fertilizer Subcategories
4. Metric Units Conversion Table 148
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SECTION I
CONCLUSIONS
The basic fertilizer chemicals segment of the fertilizer manufacturing
category can be grouped into five subcategories for treatment and
identification of plant effluent waste water: phosphate, ammonia, urea,
ammonium nitrate and nitric acid. The phosphate subcategory includes
sulfuric acid (sulfur burning), phosphoric acid (wet process),
phosphoric acid concentration, phosphoric acid clarification, normal
superphosphate, triple superphosphate, and ammonium phosphates. in
these subcategories the treatment technology does exist, and in some
cases is being used, that would permit each and every existing
fertilizer plant to meet the proposed best practicable control
technology currently available.
Additional treatment methods, in the form of development projects, pilot
plant studies and plant prototype units, along with technology from
other industries are being refined, updated and adapted so that their
use will enable fertilizer plant effluent to conform with the proposed
best available technology economically achievable.
Process modifications and plant waste water separation/collection
systems along with existing treatment methods will provide the necessary
technology to enable new fertilizer manufacturing plants to meet the
proposed new source standards.
The remainder of the fertilizer industry not covered in this study will
be included in a later study.
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SECTION II
RECOMMENDATIONS
Phosj)hate_Subcategory
1. The proposed effluent limitation representing the degree of effluent
reduction attainable through the application of the best practicable
control technology currently available to the phosphate subcategory
is no discharge of process waste water pollutants to navigable
waters. A discharge is allowed under the following conditions.
a. A process waste water impoundment, which is designed,
constructed and operated so as to contain the precipitation
from the 10 year, 24 hour rainfall event as established by the
U.S. National Weather Service for the area in which such
impoundment is located may discharge that volume of
precipitation that falls within the impoundment in excess of
that attributable to the 10 year, 24 hour rainfall event, when
such event occurs.
b. During any calendar month in which the precipitation exceeds
the evaporation for the area in which a process waste water
impoundment is located, as established by the U.S. National
weather Service (or as otherwise determined if no monthly
evaporation data have been established by the National Weather
Service) in the area in which a process waste water impoundment
is located there may be discharged from such impoundment either
a volume of process waste water equal to the difference between
the precipitation and the evaporation for that month or a
volume of process waste water equal to the difference between
the mean precipitation and the mean evaporation for that month
as established by the U. S. National weather Service for the
preceeding 10 year period, whichever is greater.
c. Any process waste water discharged pursuant to subparagraph(b)
above shall not exceed each of the following requirements:
Parameter Maximum daily Maximum average of daily values
concentration for periods of discharge covering
10 or more consecutive days
mg/1 mg/1
phosphorus (P) 20 10
fluoride as (F) 30 15
nitrogen as (N) 10 5
total suspended
nonfilterable
solids 30 15
The pH of the water discharged shall be within the range of 6.0
to 9.0 at all times.
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2. The proposed effluent limitation representing the degree of effluent
reduction attainable by the application of the best available
technology economically achievable is no discharge of process waste
water pollutants to navigable waters. A discharge is only allowed
under the following condition. A process waste water impoundment
which is designed, constructed and operated so as to contain the
precipitation from the 25 year, 24 hour rainfall event as
established by the U.S. National Weather Service for the area in
which such impoundment is located, may discharge that volume of
precipitation that falls within the impoundment in excess of that-.
attributable to the 25 year, 24 hour rainfall event, when such even4:
occurs.
3. The standard of performance representing the degree of effluent
reduction obtainable by the application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives is no discharge of process waste water pollutants
to navigable waters. The same conditions listed for best available
technology economically achievable apply.
Ammonia Subcategory
The proposed effluent limitations for the ammonia subcategory are listed
in the table below. The following abbreviations apply:
BPCTCA - best practicable control technology currently available
BATEA - best available technology economically achievable
BADCT - best available demonstrated control technology
BPCTCA BATEA BADCT
nJSQthly. daily monthly daily fflSBthly daily
Ammonia (NH.3) Nitrogen
kg/kkg (lb/1000)
of product 0.0625 0.125 0.025 0.05 0.055 0.11
Oil and Grease
kg/kkg (lb/1000 Ib)
of product 0.0125 0.025 0.0125 0.025 0.0125 0.025
The above monthly limitations represent the maximum average of daily
values for any period of 30 consecutive days. The daily maximum average
is twice the 30 day maximum average. pH shall be within the range of
6.0 to 9.0 at all times.
Urea_Subcategory
The proposed effluent limitations for the urea subcategory are listed in
the following table:
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BPCTCA BATEA BADCT
SPHthly. d§ii¥ SJPJSthiY. daily 212Dthly daily
Ammonia (NH3) Nitrogen
kg/kkg (lb/1000 Ib)
of product
nonprilled urea 0.0375 0.075 0.015 0.03 0.0325 0.065
prilled urea 0.05 0.1 0.015 0.03 0.0325 0.065
Organic Nitrogen
kg/kkg (lb/1000 Ib)
of product
nonprilled urea 0.0625 0.125 0.025 0.05 0.0375 0.075
prilled urea 0.125 0.25 0.0375 0.075 0.0625 0.125
The above monthly limitations represent the maximum average of daily
values for any period of 30 consecutive days. The daily maximum average
is twice the 30 day maximum average. pH shall be within the range of
6.0 to 9.0 at all times.
Ammoniurn_Nitrate Subcategory
The proposed effluent limitations for the ammonium nitrate subcategory
are listed in the following table.
BPCTCA BATEA BADCT
monthly daily monthly daily 2}22£l}iY dai.ly
Ammonia (NH3) Nitrogen
kg/kkg (lb/"?000 Ib)
of product 0.05 0.1 0.0075 0.015 0.05 0.1
Nitrate (NO3) Nitrogen
kg/kkg (Ib/ToOO Ib)
of product 0.0625 0.125 0.0125 0.025 0.025 0.05
The above monthly limitations represent the maximum average of daily
values for any period of 30 consecutive days. The daily maximum average
average is twice the 30 day maximum average. pH shall be within the
range of 6.0 to 9.0 at all times.
Nitric_Acid_ Subcategory
The proposed effluent limitation representing the degree of effluent
reduction attainable by the application of the best practicable control
technology currently available, best available technology economically
achievable, and best available demonstrated control technology,
processes, operating methods, or other alternatives is no discharge of
process waste water pollutants to navigable waters.
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SECTION III
INTRODUCTION
Section 301(b) of the Act requires the achievement by not later than
July 1, 1977, of effluent limitations for point sources, other than
publicly owned treatment works, which are based on the application of
the best practicable control technology currently available as defined
by the Administrator pursuant to Section 304 (b) of the Act. Section 301
(b) also requires the achievement by not later than July 1, 1983, of
effluent limitations for point sources, other than publicly owned
treatment works. These are to be based on the application of the best
available technology economically achievable which will result in
reasonable further progress toward the national goal of eliminating the
discharge of all pollutants, as determined in accordance with
regulations issued by the Administrator pursuant to Section 304(b) of
the Act. Section 306 of the Act requires the achievement by new sources
of a Federal standard of performance providing for the control of the
discharge of pollutants which reflects the greatest degree of effluent
reduction which the Administrator determines to be achievable through
the application of the best available demonstrated control technology,
processes, operating methods, or other alternatives, including, where
practicable, a standard permitting no discharge of pollutants.
Section 304(b) of the Act requires the Administrator to publish within
one year of enactment of the Act, regulations providing guidelines for
effluent limitations setting forth the degree of effluent reduction
attainable through the application of the best practicable control
technology currently available and the degree of effluent reduction
attainable through the application of the best control measures and
practices achievable including treatment techniques, processes and
procedure innovations, operation methods and other alternatives. The
regulations proposed herein set forth effluent limitations guidelines
pursuant to Section 304 (b) of the Act for the fertilizer manufacturing
category of point sources.
Section 306 of the Act requires the Administrator, within one year after
a category of sources is included in a list published pursuant to
Section 306 (b) (1) (A) of the Act, to propose regulations establishing
Federal standards of performances for new sources within such
categories. The Administrator published in the Federal Register of
January 16, 1973 (38 F.R. 1624), a list of 27 source categories.
Publication of the list constituted announcement of the Administrator's
intention of establishing, under Section 306, standards of performance
applicable to new sources within the fertilizer manufacturing category
of point sources, which included within the list published January 16,
1973.
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Summary, of Methods Used for Development of the Effluent Limitations
Guidelines and Standards of Performance
The effluent limitations guidelines and standards of performance
proposed herein were developed in the following manner. The point
source category was first studied for the purpose of determining whether
separate limitations and standards are appropriate for different
segments within the category. This analysis included a determination of
whether differences in raw material used, product produced,
manufacturing process employed, age, size, waste water constituents and
other factors require development of separate limitations and standards
for different segments of the point source category.
The raw waste characteristics for each such segment were then
identified. This included an analysis of (1) the source flow and volume
of water used in the process employed and the sources of waste and waste
waters in the the plant; and (2) the constituents (including thermal) of
all waste waters, including toxic constituents and other constituents
which result in taste, odor, and color in the water or aquatic
organisms. The constitutents of the waste waters which should be
subject to effluent limitations guidelines and standards of performance-
were identified.
The range of control and treatment technologies existing within each
segment was identified. This included an identification of each
distinct control and treatment technology, including both in-plar.t an>l.
end-of-process technologies, whicn are existent or oapabl- of he:r.•*
designed for each segment. It also included an identification of, in
terms of the amount of constituents (iricludino thermal) and the effluent
level resulting from the application of each of the treatment -.nd
control technologies. The problems, limitations and reliability of each
was also identified. In addition, the nonwater impact of these
technologies upon other pollution problems, including air, solid waste,
noise and radiation were also identified. The eneray requirements of
each control and treatment technology was identified as well as th^- cost
of the application of such technologies.
The information, as outlined above, was then evaluated in order to
determine what levels of technology constituted the "best practicable
control technology currently available," the "best available technology
economically achievable," and the "best available demonstrated control
technology, processes, operating methods, cr other alternatives." In
identifying such technologies, various factors were considered. These
included the total cost of application of technology in relation to the
effluent reduction benefits to be achieved from such application, the
age of equipment and facilities involved, the process employed, the
engineering aspects of the application of various types of control
techniques, process changes, nonwater quality environmental impact
(including energy requirements), and other factors.
Delineat ion ^ of^Study
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The effluent limitations guidelines and standards of performance
proposed in this report were developed from operating data, sampling and
information gathered from some twenty-five (25) plants. The methods and
procedures used in the accumulation of that overall information is
described in the following paragraphs.
Initial consideration was directed to identification and categorization
of the various processes defined as comprising the fertilizer industry.
These processes and the corresponding Standard Industrial Classification
codes are defined as:
Chemical
Sulfuric Acid
Sulfur burning only.
Phosphoric Acid
Including phosphate rock grinding when it is performed
on the immediate vicinity of the acid production unit.
Phosphoric Acid concentration
Phosphoric Acid Clarification
Normal Superphosphate
Triple Superphosphate
Both run-of-pile and granulated processes
Ammonium Phosphates
Ammonia
Urea
Ammonium Nitrate
SIC
2819, 2871
2819, 2817
2819, 2817
2819, 2871
2871
2871
2871
2819
2818
2819
The objective was to categorize the many processes into the least number
of units that are practical for the end purpose of water effluent
monitoring and structuring of specific fertilizer complexes for EPA and
State enforcement officials. Categorization inherently included
determination of those point sources which required separate limitations
and standards. The overall concept was to provide sufficient definition
and information on an unitized basis to allow application of a building
block principle. Such classification of data readily permits the
structuring of total water effluent information for any specific
fertilizer complex regardless of the multiplicity of processes
comprising its make-up.
§§§s_for_Definiti Qn_cf-Technology^Levels_
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The validated data and samples described in the foregoing pages were the
primary basis for choosing the levels of technology which were
considered to be the "best practicable control technology currently
available", the "best available technology economically achievable," and
the "best available demonstrated control technology, process operating
methods, or other alternatives". This selection of the separate
technologies, of necessity, required consideration of such additional
factors as evaluation of the engineering and operational problems
associated with the technology, effect on existing processes, total cost
of the technology in relation to the effluent reduction that would be
realized, energy requirements and cost, the range of control variations
on contaminant concentration and/or quantity, and non-water quality
environmental impact. Information regarding the influence of these
diverse factors was obtained from a number of sources. These sources
include government research information, published literature, trade
organization publications, information from qualified consultants, and
cross reference with related but more commonly non-fertilizer
technologies utilized in other industries.
Implementation
The value of a study such as this is entirely dependent upon the quality
of the data from which it is made. Particular attention was, therefore,
directed to selecting criteria for determining the commercial
installations to be visited and from which to collect information.
Criteria developed for this purpose of plant evaluation and subsequent
sampling consideration are listed below.
1) Discharge Effluent Quantities
Installations with low effluent quantities and/or the ultimate of
"no discharge".
2) Effluent_Contaminant Level
Installations with low effluent contaminant concentrations and
quantities.
3) Effluent_Treatment_MethgdandT Effectiveness
Use of best currently available treatment methods, operating
control, and operational reliability.
1) Water Managernent^Practice
Utilization of good management practices such as main water re-use,
planning for seasonal rainfall variations, in-plant water
segregation and proximity of cooling towers to operating units where
airborne contamination can occur.
5 Land Utilization
10
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Consideration of land area involved in water effluent control system
with the most acceptable being those with the least area.
6) Air_Polluticn_Control
Those plants with the most comprehensive and effective air pollution
control. In turn liquid effluent from such plants may represent the
most serious water effluent condition.
7) Geograghi c Location
Those facilities in close proximity to sensitive vegetation, high
population density, land availability, and areas where local or
state standards are mcst restrictive.
8) Management Operating Philosophy
Plants whose management insists upon effective equipment maintenance
and housekeeping practices.
9) Raw Materia1s
Installations utilizing different raw materials where effluent
contaminants differ in impurity type or concentration.
TO) Diversity of Processes
On the basis that other criteria are met, then consideration was
given to installations having a multiplicity of fertilizer
processes.
11) Production
On the basis that other criteria are equal, then consideration was
given to the degree of above design production rate realized from
equipment that is water pollution sensitive.
Each of the above criteria were, in turn, assigned a range of numerical
grade values to allow an overall numerical evaluation of each plant and
the selection of exemplary plants in each category.
A tentative exemplary plant list was compiled. The initial list was
composed chiefly from the input of three organizations (Section XII -
ref. 30, 38, 39) . These organizations had data and plant information
obtained from permit application, in-hcuse knowledge of the nitrogen and
phosphate fertilizer industries which together with information obtained
through private conversations with knowledgeable industry personnel
completed the list. This list was then presented to the trade
organization for comments and suggestions.
Contact was then made with the plants on the list. Initial contact was
made by the EPA Project Officer to the corporate official suggested by
the trade organization. This was followed with a second contact by the
11
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contractor to the specified plant manager with the objective of
scheduling a plant screening visit. The screening visit served to
acquaint the plant manager with the purpose and intent of the study as
well as the opportunity to consider whether or not there should be
participation. Participation in the study was kept on a strictly
voluntary basis. It is well to clarify that every plant contacted,
willingly cooperated and that industry cooperation was outstanding.
The screening visit also served as either a confirmation of the initial
tentative listing of a plant in an exemplary category or a
reconsideration of that rating. Such an evaluation was made after a
discussion on data availability, review of the facilities for
segregation and flow ironitoring of individual processes, and a plant
inspection trip. A variety of situations were encountered. These
ranged from decisions not to include a specific plant, althouah
exemplary, to learning of another facility which more completely
fulfilled the study objectives. Some plants had complete individual
process effluent records together with sample validation from other
private or state agencies. It was found that the majority of the plants
monitor only the main complex effluent streams and have little or no
knowledge of individual process effluents. Consequently, the screening
visits prompted decisions to both delete and add to the list of plants
exhibiting exemplary water effluent conditions.
Sample_CQllection and Validation_of Data
The most important item in a study of this nature is to obtain data
representative of a given process under all conditions of operation and
range of production rates. Steps and procedures used in selecting data,
stream sampling, and sample analysis were all designed to accomplish
this goal to the best possible degree.
An important step toward this objective was the assignment of only
highly experienced operating personnel to the field work. Six persons
were used. The fertilizer plant operating experience of these six
people ranged from a minimum of 14 years to 24 years with the average
being 20 plus years. With such operational knowledge it was possible to
expeditiously select data, identify specific process streams for
sampling, and conduct sampling under readily discernible plant operating
conditions. The points considered and identified in all data
collection, sampling, and validation were:
1) segregation of process effluent streams so that only an
identifiable single process and/or piece of equipment was
represented.
2) Collection of data and samples at different states of process
conditions such as normal steady state, plant washout when such a
procedure is followed on a routine basis, upset process condition,
operation at above/below plant design rate, and during shutdown
conditions if effluent flow occurs.
12
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3) Evaluation of the effect if any of seasonal rainfall,
particularly on ncn-point effluent and ponds.
U) Establishment of the existence of flow measurement devices
and/or other means of quantitatively measuring effluent flows.
5) Making positive identity of the type, frequency, and handling
of the samples represented by collected data - i.e., such items as
grab, composite, cr continuous types; shift, daily or weekly
frequency, etc. All samples collected by the contractor were
composite samples composed of a minimum of four with the vast
majority containing eight or more grab samples all caught at regular
time intervals throughout the sample period. Sample periods except
'for special conditions were a minimum of four (4) hours.
6) Validation of data via intimate knowledge of plant laboratory
analytical procedures used for sample analysis, check samples
analyzed by independent laboratories, and/or DPG sampling under
known and defined process conditions with sample analysis by an
accredited commerical laboratory, was conducted on each plant
visited. A total of 25 plants were inspected. Of these 10 plants
were selected, based upon the 6 criteria for verification of
effluent limits data.
13
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GENERAL_DESCRIPTIQEL QF THE INDUSTRY
The U.S. fertilizer industry has undergone such significant changes in
the past thirty years that it has lost its old stigma of "mud
chemistry". The sledge hammer and shovel days have been replaced by
large, modern, fume free, plants operated from an air conditioned
control room.
Eighty percent of the volume of agricultural chemicals used today are
materials that were not available in their present form at the time of
World War II. Fertilizer use today, in terms of plant nutrients, is
four and one quarter times as great as it was in 1940. On the
assumption that this fertilizer is properly used, it represents one of
the major reasons why farm yields are up and unit costs are lower. It
has been estimated that the use of commercial fertilizer saves the U.S.
public $13 billion a year on food bills or about $70 a year per person.
Large scale centrifugal compressor ammonia plants, increasing single
train plant capacities from 90-180 to 1400-1800 kkg/day (100-200 to
1500-2000 tons/day); sulfuric acid plant capacity increased from 270-450
to 1800 kkg/day (300-500 to 2000 tons/ day); and development of ammonium
phosphate granule fertilizers: illustrate the dramatic technology
change.
This study considers the production of two of the three basic fertilizer
ingredients - nitrogen (N) and phosphate (P2O5) , the third being
potassium oxide (K20) . The following tabulation indicates the past and
predicted North American consumption growth of the former two
ingredients.
Year '65-70 '70-80
Growth Growth '65-80
170 195 1980 Rate_ _Rate Increase
N 4.5 7.2 11.6 16.9 1056 9* 275X
P205 3.6 5.0 6.3 8.0 7% 5% 122%
Figures Represent Millions Of Metric Tons
It can be noted that N consumption is expected to show the greatest
future growth rates as well as the largest increase in absolute tonnage.
Somewhat coincidentally the N and P.2O5 type of ingredient separation
also applies to production facilities. That is, various N type
fertilizer materials are usually produced in a plant complex which has
only N type process units. Similarly, various phosphate fertilizer
materials are usually produced in a plant complex which has only P1O5
type process units. This is demonstrated by Table 1. As a result of
this natural separation, each of the two types will be discussed
separately throughout this report.
Fertilizer industry jargon identifies two types of product - nonmixed
and mixed. straight fertilizers are defined as those which contain only
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Table 1
No. of
Companies
22
2
2
3
3
1
3
6
1
7
3
1
1
3
1
2
13
5
3
1
16
1
2
1
4
1
1
1
2
1
2
2
1
1
1
3
7
1
1
1
1
;
160
Intergration of Production in the Fertilizer Industry
No. of
NH3 U N.A. A.N. S.A. Wet A. P. TSP SPA Plants
X 22
X 2
X 2
XX 12
XXX 9
I/ X 3
X 1
I/ X X 6
X 6
XX X j
I/ X X 14
I/ X X X 9
X I/ X X X 4
I/ X X X X 4
X 6
XX 3
XX 4
XX 26
XXX 15
XXX 9
XXX 3
X X X X 64
XX X 3
XXX X 8
XXX X 4
X X X X X >()
x x x x i/ xx x "7
XXX 4
X X X X 3
x x /,
X
XXX 6
X XXX 8
XX XXX ',
X X X X 4
x X X X X 5
X X XXX J 5
X 14
XXX 4
X X X X X 6
X X X X A
X X X X X 5
XXXXXXX 7
390
_!/ Not identified individually in data used to develop this list, but must assume existence
of sulphuric acid facility as intermediate to wet acid production.
2l Only 109 firms—includes more than one location of plant operations for some firms.
U Urea
N.A. Nitric acid
A.N. Ammonium nitrate
S.A. Sulfuric acid
Wet Wet phosphoric acid
A.P. Ammonium phosphate
TSP Triple Superphosphate
SPA Superphosphate acid
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a single major plant nutrient. Mixed fertilizers are defined as those
which contain two cr more primary plant nutrients. Mixed fertilizers
can be produced by chemically reacting different ingredients and
utilizing the chemical reaction as the binding force; or simply by
mechanically blending together straight fertilizers. The following
tabulation lists the principal straight and mixed fertilizers produced
in the U.S.
Straight_Fertilizers __ Mixed_Fertilizers
Nitrogen Fertilizers
Ammonia
Urea
Ammonium Nitrate
Phosphate _Ferti lizers
Phosphoric Acid Ammonium Phosphates
Normal Superphosphate
Triple Superphosphate
Nitrogen based fertilizers have in the past realized both the greatest
consumption and industry growth rates of the three basic fertilizer
nutrients (N, P2O5 and K2O) and are predicted to continue to do so for
the near future. A possible reason for this may be due to the fact that
application of N-based fertilizers can create spectacular crop
responses. Such response however is comparatively short lived and can
result in disastrous crop failures unless the N fertilization is
followed with V2O5 and K.2O fertilization within one or two years. This
lead time and/or the realization of the need for F2o5_ and K2_O addition
is certainly contributary to the lag time between N and P2O5_ - K2_O usage
and production.
The compounds used and means of applying nitrogen to the soil have
undergone radical changes since the early nineteen hundreds. Prior to
this time practically all fertilizer nitrogen came from natural organic
materials. Then between 1900 and 1920 the combination of natural
nitrates and by-product ammonia from ccke oven gas, supplied th»
majority of the nitrogen used by the fertilizer industry. This period
concluded with the development of the Haber-Bosch process which made
possible the conversion of atmospheric nitrogen into ammonia.
Refinement of this process and development of single pieces of reliable,
large scale mechanical equipment has been responsible for ammonia
becoming the principal fertilizer material.
Today in the U.S., there are 171 ammonia plants located in 25 different
states producing in excess of 17,000,000 kkg/year (18,700,000
tons/year) . These plants have annual capacities ranging from 10,000 to
435,000 kkg/year (11,000 to 480,000 tons/year). Locations of nitrogen
fertilizer plants are indicated on Figure 1. Ammonia plant locations
16
-------
- ^.,, ,.. ,
r / . ---—'- '5^'\'i '"
17
-------
are selected on the basis of raw material supply and proximity to
market area with the former being the dominating consideration.
Since atmospheric nitrogen can be obtained at any location, the raw
material of importance is hydrogen. Hydrogen feedstock sources for
modern ammonia plants are natural gas and petroleum fractions. In turn
this has selectively placed the highest industrial concentrations of
ammonia plants near sources of these two raw materials, namely
Louisiana, Texas, California, Iowa, Mississippi and Arkansas. The
midwest agricultural section is the major sales market area with Iowa
being the largest consumer state.
Ammonia plants are classified into two categories - those operating with
reciprocating gas compressors and those operating with centrifugal gas
compressors. Generally speaking, those single train plants with annual
capacities of less than 150,000 kkg/year (165,000 tons/year) are
operated with reciprocating compressors while all larger plants, re-
presenting the more mcdern type, operate with centrifugal compressors.
The breakpoint between the two is strictly economic. That is, in order
to realize low per ton production costs industry has been building ever
larger single train plant capacities. Introduction of the centrifugal
unit in this process permitted dramatically increased single unit
compressor capacity which is directly reflected in lower capital costs.
To appreciate the effect of the centrifugal compressors on ammonia
processing requires only a review of what has occurred since 1955. In
1955 single train capacities of 270 kkg/day (300 tons/day) were
considered large plants. Today, 900 kkg/day (1000 tons/day) plants are
commcr., several 1360 kkg/day (1500 tons/day) units are in operation and
plans are being made to build 2300 kkg/day (2500 tons/day) plants.
These larger units have not been without problems in regard to on-stream
time but it is unlikely that future U.S. plants will be less than 900
kkg/day (1000 tons/day) capacity.
As previously mentioned, it is modern practice to use an ammonia plant
as a basic unit and then integrate it with other process units to
manufacture a range cf different products. An important process unit
usually associated with an ammonia plant in a nitrogen fertilizer
complex is nitric acid. There are approximately 124 operating nitric
acid plants in the U.S. with capacities ranging from 7,000 to 240,000
kkg/year (8,000 to 265,000 tons/year). Output from these plants is used
as an intermediate feed stock for the production of ammonium nitrate.
Ammonium nitrate ranks second only to ammonia as a source of fertilizer
nitrogen. Production of this material for fertilizer purposes increased
very rapidly in the period 1950-1965 to the point that it provided 32%
of the total fertilizer N market. Since 1965, use of this fertilizer in
terms of market percentage has been decreasing. This decrease is
expected to continue at a slow rate for the foreseeable future. The
reason for this decline is the increased usage of higher N analysis
materials such as ammonia and urea, 82% and 46% N respectively, as
compared to the 34% N in ammonium nitrate.
Ib
-------
Currently there are 83 plants
in capacity from 9,000
tons/year). Approximately 50
used as fertilizer and the
use. The majority are small ,
Use of urea (46%N) as a source'
development which was prcmpte
2% of the U.S. fertilizer
has increased at an annual 1
total in 1971, a four fo
expected that this growth rate;
located (see Figure 1) in the U.S. ranging
to 295,000 kkg/year (10,000 to 325,000
of the production from these plants is
balance as explosives and other industrial
nd have been in service for many years.
of fertilizer N has been a fairly recent
by shipping costs. In 1957 approximately
r^itrogen was supplied by urea. Consumption
a year rate to approximately 12% of the
d increase in the past 10 years. It is
will continue.
plant, s
There are 59 operational
capacity from 7,000 to 350,
Approximately 75% of the tota
the balance used fcr catt
contains the highest percent l
fact that there are nc stor
that urea will continue to be
Phosphate_Fertilizer Industry
The phosphate fertilizer indu
developments that the nitrogen
years there have been dramati
and industry image.
1955 phosphate was
The majority of phc
production costs and simplicil
being produced in a myriad of
steadily decreased and has
phosphate materials necessitai
efficiencies. In short, art
control methods. In crder t<
acid, triple superphosphate
first necessary to modernize
(see Figure 1) in the U.S. ranging in
000 kkg/year (8,000 to 385,000 tons/year).
production is used as fertilizer N with
e feed and urea-formaldehyde resins. Urea
! of any solid fertilizer. This, plus the
ge and handling explosion hazards, ensures
a popular fertilizer material.
try has not had the spectacular technical
en industry has shown, but in the past 20
changes in production facilities, costs
considered to be the major U.S. fertilizer
sphate nutrient was in the form of normal
Prior to
nutrient.
superphosphate which has a nominal P2O5 percentage of 19- 20%. The low
y of this process resulted in the material
small plants throughout the market area.
Since 1955 normal superphosphate1s share of the phosphate market has
been replaced with more concentrated
ing utilization of special unit operations
equipment and instrumentation designed to optimize system control and
and mud chemistry was displaced with
scientific methods, definition of process variables, and development of
manufacture merchant grade phosphoric
and ammonium phosphate in quantity, it was
nd increase capacity of the essential
intermediate - phosphoric acid. Phosphoric acid manufacture in turn
required larger quantities of sulfuric acid (approx. 2.8 kkg 100%
sulfuric acid for each kkg of P2O5 as phosphoric acid). In the early
1960's, 550 kkg/day (600 tons/day) sulfuric acid plants were considered
large. By 1965, single train sulfuric acid plants of 900-1100 kkg/day
(1000-1200 tons/day) capacity became common with additional capacity
increases to 1400 - 1800 kkg/day (1600-2000 tons/day) by 1967.
Similarly, large wet process phosphoric acid plants in the early 1960's
were 180-270 kkg/day (200-300 tons/day) P2O5 units with multiple pieces
of equipment required to perform single unit operations such as
acidulation and filtration. By 1965, single train phosphoric acid units
19
-------
and single unit operations equipment with capacities of 450 kkg/day (500
tons/day) P2O5 became commonplace followed with an 800 kkg/day (900
tons/day) unit by 1967. several plants in the design stages will have
capacities of 900-1100 kkg/day (1000-1200 tons/day).
As a result normal superphosphate's share of the fertilizer market has
been steadily decreasing. It is expected that normal superphosphates
share of the phosphate market will finally stabilize at approximately
18%. This steady market loss caused several of the smaller plants to
shut down. Today there are approximately 214 plants with capacities
ranging from (15,000 to 300,000 tons/year) still in operation. These
plants are located over a wide cross-section of the market area (See
Figure 2). In contrast to the ether phosphate processes, normal
superphosphate plants are usually not integrated with phosphoric acid
complexes but are most generally connected with fertilizer mix plants.
Essentially all the ether phosphatic fertilizer process units are like
the nitrogen fertilizer industry and are integrated into phosphate
complexes. The majority of these large complexes are located near the
phosphate rock source in Florida. There are a few fairly isolated
complexes located along the Mississippi Piver, North Carolina, Idaho,
Utah and California. The North Carolina and Western units (except
California) utilize locally mined rather than Florida mined phosphate
rock.
Generally wet process phosphoric acid is used as an intermediate.
Steadily increasing quantities of merchant grade acid are annually being
sold but such acid is in turn used either in fertilizer mixing plants or
ir. preparing liquid fertilizer solutions. Merchant grade acid is low
strength (30% P2O_5) acid which has been concentrated to 52-54* P2_O5 and
then processed to remcve a sufficient quantity of solid impurities to
enable it to be shipped and distributed without difficulty. An
additional near future market for merchant grade acid is in th<=
production of high quality technical grade acid. This is presently
dominated by phosphoric acid produced via the electric furnace process
(see the phosphate manufacturing, development document). To date, there
are no facilities producing technical grade acid from merchant grade
acid in the U.S., but serious consideration is being given to such
projects. One procedure for producing such a quality acid is to treat
merchant grade, wet process phosphoric acid via solvent extraction to
remove impurities.
A limited number of phosphoric acid plants also produce fluosilicic acid
(15-25% H2_SiF6) as a by-product of the phosphoric acid concentration or
sulfuric acid digestion steps. The equipment required for this product
is essentially "add on" equipment which does not affect the overall
process. Such production significantly reduces the total amount of
fluorine in the raw waste load.
Currently there are 39 wet process phosphoric acid plants operating in
15 states with capacities ranging from 41,000 to 360,000 kkg/year
(45,000 to 400,000 tons/year) F2O5 (See Figure 2). Five sizeable, new
plants are currently in design and construction stages and will be
20
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FIGURE 2
MAP/DAP
AMMONIUM PHOSPHATE
PLANT LOCATIONS
21
-------
brought on stream in 1974 and 1975. These new units will primarily add
to existing plant capacities and will include only one new manufacturer.
Triple superphosphate (46-48% P2O5), a concentrated fertilizer, has
partially displaced normal superphosphate. This material has enjoyed a
very rapid market growth since 1950 to the point where it is the second
largest quantity of fertilizer phosphate produced. There are two types
of triple superphosphate (TSP) produced. One is a non-uniform
pulverized material designated as run- of-pile (ROP) TSP. The other is
a hard, uniform pelletized material designated as granular TSP or GTSP.
ROP is the older process and from an overall standpoint is a difficult
process to environmentally control. In addition, the product is a
troublesome material to store, handle, and ship. Consequently within
the TSP family, ROP production is at best remaining constant and GTSP
production is constantly increasing. There are several plants which
process ROP into a granular material but this imposes an additional
process step and cost. Practically all new future facilities will
utilize the GTSP process.
TSP production units are always located within a phosphate complex due
to their dependency on phosphoric acid supply. There are approximately
20 ROP production units ranging in capacity from 32,000 to 440,000
kkg/year (35,000 to 600,000 tons/year). Currently, there are 5 GTSP
plants in operation and 3 new plants in design and construction stages.
The majority of the GTSP process units are located within the same
complexes as the ROP units.
Ammonium phosphates are the concentrated, mixed fertilizer products
which in the past 20 years have been the growth phenomena of the
phosphate industry. This category includes both monoammonium (MAP) and
diammcnium (DAP) phosphate grades. The only difference between grades
is the degree of ammoniation. Annual compound rate of growth over the
past ten years has been 19.8%. Such popularity is due to a number of
factors which are are so prominent that ammonium phosphates are certain
to continue as a most important mixed fertilizer material. DAP has
emerged and will continue to be the dominant grade. Both products are
made by neutralizing 30-40% P2.°5 phosphoric acid with the proper
quantity of ammonia.
As with most production processes, plant capacities are constantly being
increased to effect capital cost and production economies. Commonplace
capacities prior to 1973 have been 32-45 kkg/hr (35-50 tons/hour), but
new plants scheduled for completion in 1974 will have instantaneous
single train capacities of up to 90 kkg/hr (100 tons/hour). Currently
there are 53 operating ammonium phosphate plants located in the U.S.
ranging in capacity between 9,000 and 550,000 kkg/year (10,000 and
600,000 tons/year) (See Figure 2).
22
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SPECIFIC PROCESS DESCRIPTIONS
Phosghate Pertilizer_Industry
The phosphate fertilizer industry is defined as eight separate
processes: sulfuric acid, phosphate rock grinding, wet process
phosphoric acid, phosphoric acid concentration, phosphoric acid
clarification, normal superphosphate, triple superphosphate, and
ammonium phosphates.
The two important basic units are sulfuric and wet process phosphoric
acid. The sulfuric acid unit is essential to the phosphoric acid plant
not only for the basic sulfuric acid raw material but also to produce
steam for operation of vacuum and evaporation equipment. Sulfuric acid
is also a basic raw material for normal superphosphate production.
Phosphoric acid is the fcasic raw material for all the other processes.
Essentially all existing phosphate fertilizer complexes are separated
either by geographic location or by area within a general fertilizer
plant from the nitrogen fertilizer operations. Such separation was a
significant factor in establishing the separate fertilizer categories.
Since phosphate fertilizer processes have either sulfuric acid,
phosphate rock, or phosphoric acid in common, the effluents from the
separate processes also have common contaminants which vary only in
concentration. Primary contaminants in the effluents from these units
are fluorine (F) and phosphorus (P). The only contaminant not common to
all units is nitrogen (N). Ammonia is a basic raw material to the
ammonium phosphate process and is the only source of N injection to a
phosphate process effluent. Therefore, with the exception of N, a common
effluent treatment system can be established to treat the F and P
contaminants from all phosphate fertilizer processes. In actual
practice, practically all complexes combine the various unit effluents
into a large recycle water system. This large contaminated recycle
water system is self contained for a large portion of the year. It is
only when the quantity of recycle water increases beyond capacity to
contain it, that effluent treatment is necessary. Increases in recycle
water inventory is usually due to an imbalance between rainfall and
evaporation. In Florida this means that some plants discharge treated
effluent up to four mcnths per year.
23
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gulfuric Acid_- Process Description
General
In the United States, essentially all sulfuric acid utilized in the
manufacture of fertilizer products and intermediates is produced by the
contact process. The process is so named due to the use of a catalyst
surface to speed the oxidation reaction between sulfur dioxide (SO2) and
oxygen (O2) . This reaction occurs when the two gaseous components
"contact" each other on the surface of pelletized vanadium pentoxide
catalyst to form resultant sulfur tricxide (SO3) gas. In turn, the
sulfur trioxide (SO3) gas is hydrolyzed by the addition of water to form
sulfuric acid (H2S04).
Prior to 1930 the contact process was used primarily in Europe for the
manufacture of high strength sulfuric acid (98 + %) and oleums. From
this date forward, American process innovations improved materials of
construction and operating costs to the point that the process became
the most economical method of producing sulfuric acid from elemental
sulfur. In addition to these factors, the process is designed to
capture a high percentage of the energy released by the exothermic
chemical reactions occurring in the oxidation of sulfur (S) to sulfur
trioxide (SO3J . This energy is used to produce steam which is then
utilized for other plant unit operations or converted to electrical
energy. It is the raw water treatment necessary to condition water for
this steam production that generates essentially all the water effluent
from this process.
In the period between 1930 and 1971, practically all contact sulfuric
acid plants built in the U.S. were designed with a "single absorption"
step (see Figure 3). The term "single absorption" refers to the process
point when sulfur trioxide (SO3J gas is hydrolyzed with water to form
product sulfuric acid (H2S04J . This process step is performed after the
gas has passed through all the catalysis stages. Exit gas from a
"single absorption" stage generally contains sulfur dioxide (SO2) at a
concentration level appreciably in excess of the standard established by
EPA of 1.81 kg/kkg (4.0 lb/ ton) 100% acid produced. Since 1971,
however, a process modification is being offered which will allow
compliance to the EPA standard. The modification is the addition of a
second absorption step and is known as the "double absorption" process
(Figure 4). It is most likely that all future plants will utilize the
double absorption technique. Such a process modification will not
affect the characteristics or quantity of sulfuric acid plant water
effluent in any manner.
Process - Single Absorption
The raw materials used to produce sulfuric acid by the contact method
are elemental sulfur, air and water. Molten elemental sulfur is sprayed
into a dry air stream inside a furnace. The elevated furnace
temperature auto-ignites the atomized liquid sulfur to oxidize it to
sulfur dioxide (S02) . This reaction releases a large quantity of heat
24
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which causes the temperature of the resultant S02 - excess air mixture
to rise to 980 - 11UO°C (1800-2000°F) as it exits from the furnace. The
heated gas mixture flews to a boiler for heat removal. Sufficient heat
is removed to reduce the gas mixture temperature to the initial reaction
condition for optimum chemical conversion of S02 to S03.
SO2 conversion to SO3 takes place in a series of three or four steps.
Each conversion step takes place under a a different reaction condition
to achieve the most complete conversion of SO2 to SO3_ possible. This
conversion efficiency in a single absorption process is approximately
98%.
Following the conversion stages, the SO3 gas flows to the bottom of an
absorption tower. In the tower the SO3 gas flows upward through ceramic
packing and counter-cur rent to downward flowing 98-99% H2SO*t. The SO3_
is readily hydrolyzed to H2SO4 by the water in the acid. Hydrolysis of
the SO3_ to H2SOJ4 also releases heat which increases the temperature of
the enriched 98-99% H2SCJ4 acid. After the acid exits the tower it flows
through cooling coils tc offset the temperature increase and then to the
pump tank. From this tank it is again recycled through the absorption
tower.
At the start of the process discussion, it was mentioned that the molten
sulfur is burned in a dry air stream. The drying of the atmospheric air
used in the process is accomplished in the drying tower. Here moist
atmospheric air enters the base of the tower and flows upward counter-*-
currently to concentrated sulfuric acid pumped from the pump tank. This
acid has, however, been diluted from the normal 98-99% H2SOU acid in the
pump tank to approximately 93%. The resultant moist air, 93% acid
contact, removes moisture from the air stream yielding dry air and a
slightly further diluted acid. In turn the dry air flows to the furnace
and the diluted acid flews back to the pump tank for mixing with the
stronger 98-99% acid flowing back from the SO3 absorption tower.
The product is that acid flowing intc the pump tank which is in excess
of drying and absorbing tower recycle requirements. Adjustments to the
rate of product acid removal from the pump tank are determined by
monitoring the pump tank level and maintaining it at a constant level.
The excess (product) acid is diluted with water to the desired product
acid concentration (normally 93% H2SO4) before it is pumped to storage.
Process - Double Absorption
As previously mentioned it is most likely that all new plants built in
the United States in the future will be double absorption process units.
The feature which makes this process different from the single
absorption process described above is the addition of a second
absorption tower. This second tower is installed at a point
intermediate between the first and final SO2 to SO3 catalytic conversion
steps. Utilization of this second absorption tower permits the
achievement of a greater SO2 conversion to SO_3 and thus a significantly
reduced quantity of S02 in the plant effluent gas stream. Double
absorption plants realize SO2 conversion efficiencies of 99.5+ % as
27
-------
compared to single absorption plant efficiencies of approximately 98%.
Both processes have the same water effluent in respect to both quantity
and contaminant levels.
28
-------
Phosphate_Pock Grinding - Process Descrip-tion
General
Phosphate rock that has been mined and beneficiated is generally too
coarse to be vised directly in acidulation to phosphoric acid. The rock
is, therefore, processed through equipment to mechanically reduce it to
the particle size required for optimum phosphoric acid plant process
efficiency.
Process
Size reduction is accomplished with ball, roll or bowl mills. Phosphate
rock is fed into the irills and mechanically ground (Figure 5) . After
the rock enters the mill system, all flow through the sizing and
reclamation circuits is by pneumatic means. Air is constantly exhausted
from the mill system to prevent precipitation of moisture generated from
the rock as a result of grinding. Normally, the exhaust air passes
through a bag type air cleaner to remove entrained rock particulates
before discharge to the atmosphere.
Phosphate rock size reduction in all existing fertilizer plants is an
entirely dry processing circuit and does not directly involve liquid
streams. Minor quantities of water are used for indirect cooling of
lubricating oil and mechanical equipment such as bearings.
Some future rock grinding operations will utilize a wet grinding circuit
rather than the current dry grinding practice. This change is prompted
by a combination of Icwer capital costs and the elimination of the gas
effluent streams associated with both the rock drying and grinding
operations. Use of this new technique will not change the self-
contained nature of the rock grinding circuit. There will be no liquid
effluents other than those mentioned in the dry grinding process.
29
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Phosphate Rock_Digestj8pn 6 Filtration
Process Description
General
Phosphoric acid is the basic building block from which essentially all
mixed fertilizer used in the U.S. is made. The overwhelming majority of
this acid is manufactured by the wet process method. The process
involves changing the state of the phosphate content in phosphate rock
from a practically water insoluble tc a water soluble compound. This is
accomplished by solubilizing the phosphate rock with a highly ionized
acid. Acid type is selected through a combination of factors including
cost, simplicity of process, materials of construction, and the desired
end products. In the U.S., sulfuric acid is by far the most commonly
used acid, but other acids, such as nitric and hydrochloric, can be
utilized.
A statistical compilation of U.S. phosphoric acid producers is shown
below. The figures shew the relative importance of the three mentioned
acid treatment processes and indicates the most prominent process.
Annual
Type of Acidulation Number of Operat- P2O5 % of Total
Process;;
Sulfuric Acid 35* 4,879,000 98.77
Nitric Acid 4 61,000 1.23
Hydrochloric Acid 0 00
39 4,940,000 100.00%
""Including three plants restarted in 1973.
All the acidulation processes have inherent problems with process
effluents, both gaseous and water, as well as by-product disposal.
Successful and acceptable by-product storage and processing of plant
effluents is to a large degree dependent upon the considerations made
for such items during the original plant layout stages. It is much more
difficult and possibly economically impractical in some cases to add
such facilities to an existing plant. Sizable acreage and reasonably
good soil compaction characteristics are required to handle the effluent
and by-product processing arrangements. Those plants located in areas
where land is not available and/or soil stability is poor are at a great
disadvantage. Particular reference is to those installations in Texas
and Louisiana.
31
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Phosphoric Acid
Process Description
Sulfuric Acid Acidulaticn
The raw materials used in this process are ground phosphate rock, 93%
sulfuric acid, and water. Phosphate rock is mixed with the sulfuric
acid after the acid has first been diluted with water to a 55-70% H2_so^
concentration. This mixing takes place in an attack vessel of
sufficient size to retain the raw material mixture for several hours
(Figure 6). The simplified overall chemical reaction is represented by
the following equation:
3 Ca3 (POM) 2 (solid) + 9 H2SOU (liq) + 18 H2O (liq) ^
Phos. Rock Sulf. Acid Water
6 H3POU (liq) + 9 CaSO4 . 2H20 (solid)
Phos. Acid gypsum
In reality phosphate rock is not the pure compound indicated above, but
a fluorapitite material containing minor quantities of fluorine, iron,
aluminum, silica and uranium. Of these the one presenting the most
serious overall process problem is fluorine. Fluorine is evolved from
the attack vessel and ether plant equipment as either the gaseous
compound silicon tetrafluoride (SiF4) or hydrofluoric acid (HF). SiF4
hydrolyzes very quickly in moist air to fluosilicic acid (H^SiF6) and
silica (SiO2). Both SiF4 and HF can be collected in a wet scrubber unit.
Additional fluorine remains in the by-product gypsum in a variety of
fluorine compounds. The combination, therefore, of absorbed gaseous
fluorine effluent and the soluble fluorine compounds in the gypsum are a
major contaminant in the phosphoric acid plant effluent streams.
Following the reaction in the digestor, the mixture of phosphoric acid
and gypsum is pumped to a filter which mechanically separates the
particulate gypsum from the phosphoric acid (approx. 30% P2O5
concentration). The magnitude of the by-product gypsum is best appreci-
ated by the fact that the production of each kkg of P2O5 as phosphoric
acid creates approximately five (5) kkg of gypsum. Normally the gypsum
is sluiced with contaminated water from the plant to a disposal area.
The phosphoric acid separated from the gypsum is collected for further
processing.
32
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Phos]ghoric_Acid
Process_Descri2tion
Nitric Acid Acidulaticn
There are two different nitric acid acidulation processes which have
been used commercially in the United States. One of these has been
discontinued within the past year and currently only one is being used
for fertilizer production.
Nitric acid acidulaticn differs frcm the sulfuric acid acidulation
process in that phosphoric acid is not separated as a product from the
acidulation reaction mixture. Consequently, the division of process
steps between acidulaticn and the final fertilizer product is not
possible.
The raw materials used are generally unground phosphate rock and 57%
nitric acid. Nitric acid and the rock are mixed together in a series
(12-15) of violently agitated small reactor vessels (Figure 7). The
first few vessels serve primarily to dissolve the rock according to the
following chemical reaction.
Ca3(P04)2 + 6HN03 » 3Ca (NO3) 2 + 2H3PO4
Phos. Rock Nitric Acid Calcium Phos. Acid
Nitrate
This reaction essentially places both the reaction products, calcium
nitrate and phosphoric acid, in a mixed liquid form. At this point
either purchased phosphoric or sulfuric acid is added to the process
together with ammonia to produce a specific mix of calcium compounds,
ammonium nitrate, and phosphoric acid. This mixture is then converted
to a dry product. The fertilizer grades produced from this mixture are
limited both as to number and water soluble phosphate content.
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Fhcsphoric_Acid^Concentratign
Process Description
General
Phosphoric acid as produced in the sulfuric acid acidulation process is
generally of too low a concentration (26-30* P2O5) to qualify as either
a salable product cr to be used for processing a final dry fertilizer
product. This P2O5 level can be increased in the 40-54% P2O^ range by
processing the acid through water evaporator units.
Process
Phosphoric acid concentration to 5451 2205 is performed with low pressure
steam as the heat energy source for the evaporation of water from the
acid. Evaporation is accomplished by circulating acid at a high volume
rate consecutively through a shell and tube heat exchanger and a flash
chamber under vacuum pressure conditions. The flash chamber serves to
provide a comparatively large liquid surface area where water vapor can
be easily released without incurring significant phosphoric acid en-
trainment losses. Inherent with the water evaporation is also volati-
lization of minor acid impurities, the principal one being fluorine.
The evolved fluorine together with very minor quantities of phosphoric
acid pass to a barometric condenser and contaminate the condenser water.
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Phosphoric Acid Clarification
Process Description
General
Phosphoric acid after concentration to a 52-5456 ^2OS level becomes a
supersaturated solution to a variety of minor acid impurities, namely
iron and aluminum phosphates, soluble gypsum, and fluosilicates. These
impurities are present in quantities sufficient to create an appreciable
solids accumulation during acid storage. In turn this causes tank car
unloading and customer processing problems. It is, therefore, necessary
to remove these precipitated impurities before the acid can be
considered a salable product.
Process
The process used in the U.S. for removal of precipitated solids from 54%
P2O5 phosphoric acid involves only physical treatment of the acid rather
than the more complicated and expensive solvent extraction processes
utilized in Europe and Mexico (Figure 9). The acid is conditioned at
the proper temperature and time necessary to realize the degree of
solids precipitation required to meet the clarified acid product
specifications. The precipitated impurities are then physically
separated from the acid by settling and/or centrifugation.
Water usage in this process is limited to indirect cooling of the acid
and minor quantities for equipment washing.
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Normal^Superphosphate
Process Description
General
Normal superphosphate was, for many years, by far the most popular
phosphate fertilizer. Since the mid-fifties, however, this popularity
has been in a sharp decline and only in the past few years has the rate
of decline started to moderate. The market share of this fertilizer has
fallen from 68* in 1957 to 42% in 1965 and now appears leveling off at
approximately 18%. The major reasons for this decline include such
items as low P2O5 content (20%) with the associated increased cost of
transportation per ton of nutrient and the trend to larger size plants.
Normal superphosphate can be manufactured in small inexpensive plants
with low production costs per ton of P2O5_. The process is simple and
easy to operate requiring less sulfur per ton of P2O5 than the
production of phosphoric acid. The coirbination of low investment and
simplicity together with recognition of the adverse fertilization effect
of sulfur deficiency in the soil assures that normal superphosphate
production will not die out but sales will be limited to an area in
close proximity to the plant site.
Proces_s
The two raw materials used in the production of normal superphosphate
are 65-75% sulfuric acid and ground phosphate rock. Reaction between
these two materials is both highly exothermic and rapid (Figure 10).
The basic chemical reaction is shown by the following equation:
Ca3(P04)2 + 2H2SOU + H2O >2CaSO4.2H20 + Ca (H2PO4).H2O
Phosphate Sulfuric Water Gypsum Normal Superphos-
Rock Acid phate
The interval of fluidity before the two reactants solidify is very brief
and the mixture is quickly transferred to an enclosed space referred to
as a den. This den may be either an essentially stationary structure or
a continuous slow moving conveyor. In the den the material becomes
plastic relatively quickly. During this phase there is a copious
evolution of obnoxious gas as the crystallization process progresses.
Retention time in the den can range from 1 to 4 hours dependent on the
overall process conditions. At the end of this time the material
becomes a porous mass resembling a honeycomb and is removed from the den
to storage. A storage period of 3 to 8 weeks is required for "curing"
before the normal superphosphate is an acceptable product for shipment.
The "curing" time serves to allow completion of the chemical reaction
between the rock and acid with the subsequent decrease in free acid and
citrate insoluble P2O5 content.
40
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Triple^Superghosphate
Process Description
General
Triple superphosphate (ISP), with its 46.0% - 48.5% P2O5 content, is a
high analysis phosphate fertilizer. As such, it provides transportation
economy which has been instrumental in enlarging its share of the
phosphatic fertilizer market.
This product has in the 1950-1965 period taken over much of the market
lost by normal superphosphate and currently accounts for approximately
24% of the total phosphatic fertilizer market. TSP's share of the
market for the near future is expected to remain relatively constant
primarily because of the tremendous growth of the ammonium phosphates.
TSP production, unlike normal superphosphate, can be most economically
produced close to the phosphate rock source. In the U.S. this means
that approximately 83% of the total production is manufactured in
Florida.
Process
There are two principal types of TSP, Run-of-Pile (ROP) and Granular
Triple Superphosphate (GTSP). Physical characteristics and processing
conditions of the two materials are radically different. ROP material
is essentially a non-uniform pulverized material which creates difficult
air pollution problems in manufacture as well as difficult materials
handling problems in shipment. GTSP is a hard, uniform, pelletized
granule produced in process equipment which permits ready collection and
treatment of dust and obnoxious fumes. Most new plants will be of the
GTSP type.
Both processes utilize the same raw materials, ground phosphate rock and
phosphoric acid. The basic chemical reaction is shown by the following
equation:
Ca3 (PO4) 2 + 4H3_PC4 + 3H2O >3Ca (H2PO4.) 2 . H2O
Phosphate Phosphoric Water Triple Superphosphate
Reck Acid (Monocalcium phosphate)
At this point the similarity between the two processes ends.
The ROP process is essentially identical to the normal superphosphate
process with the exception that phosphoric rather than sulfuric acid is
used as the acidulating acid (Figure 11). Mixing of the 46-54% P2O5
phosphoric acid and phosphate rock normally is done in a cone mixer.
The cone depends solely on the inertial energy of the acid for mixing
power. On discharge from the mixer the slurry quickly (15-30 sec)
becomes plastic and begins to solidify. Solidification together with
the evoluation of much obnoxious gas takes place on a slow moving
conveyor (den) enroute to the curing area. The solidified material
because of the gas evolution throughout the mass takes on a honeycomb
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appearance. At. the point of discharge from the den the material passes
through a rotary mechanical cutter which breaks up the honeycombed ROP
before it discharges onto the storage (curing) pile. Curing occurs in
the storage pile and takes 2-4 weeks before the ROP is ready to be
reclaimed from storage, sized and shipped.
GTSP is produced quite differently (Figure 12). The phosphoric acid in
this process is appreciably lower in concentration (40% P2O5) than the
46-54% Pj2°.5 acid used in ROP manufacture. Forty percent P2O5 acid and
ground phosphate rock are mixed together in an agitated tank. The lower
strength acid maintains the resultant slurry in a fluid state and allows
the chemical reaction tc proceed appreciably further toward completion
before it solidifies. After a mixing period of 1-2 hours the slurry is
distributed onto recycled dry GTSP material. This distribution and
mixing with the dry GTSP takes place in either a pug mill or rotating
drum. Slurry wetted GTSP granules then discharge into a rotary drier
where the chemical reaction is accelerated and essentially completed by
the drier heat while excess water is being evaporated. Dried granules
from the drier are sized on vibrating screens. Over and under-size
granules are separated for use as recycle material. Product size
granules are cooled and conveyed to storage or shipped directly.
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Ajmmo^ium Phosphates
Process Description
General
The ammonium phosphate fertilizers are highly concentrated sources of
water soluble plant food which have had a spectacular agricultural
acceptance in the past twenty years. Production capacity of diammonium
phosphate (DAP) has increased at a compounded rate of 19.8% annually
over the last ten years. The popularity of the ammonium phosphates
results from a combination of factors. These include the ready
adaptability of the production processes to ever increasing single plant
capacities with their associated lower production costs; favorable
physical characteristics which facilitate storage, handling, shipping
and soil application; compatibility with all common fertilizer
materials; transportation economies effected by the shipment of high
nitrogen (18%N) and phosphate (46% P2O5) nutrient content at a single
product cost; and the ability of an N-P-K fertilizer producer to realize
up to twice the profit margin per kkg of P205 from DAP than from
concentrated superphosphate. Such an impressive number of plus factors
insure that ammoniurn phosphate processing (particularly DAP) will
continue to be an important segment of the fertilizer industry.
Ammonium phosphate fertilizers include a variety of different
formulations which vary only in the amounts of nitrogen and phosphate
present. The most important ammonium phosphate fertilizers in use in
the U.S. are:
Monoammonium (MAP] Phosphates
11~- 48-0
13-52-0
11-55-0
16-20-0
Diammonium Phosphates (DAP]_
16-48-0
18-46-0
Diammonium phosphate formulations are produced in the largest tonnages
with DAP (18-46-0) being the most dominant.
Process
The two primary raw materials used to produce ammonium phosphates are
ammonia and wet process phosphoric acid. Sulfuric acid is of secondary
importance but is used in the production of the monoammonium phosphate
grade 16-20-0. As mentioned above, the various grades vary only in the
amounts of nitrogen and phosphate present. It is primarily the nitrogen
that varies and this is accomplished by controlling the degree of
ammoniation during neutralization of the phosphoric acid. The chemical
reactions involved are indicated by the following equations:
46
-------
H3P04 + NH 3 _ ^ NH4H2P04
Phosphoric Ammonia ^ Monoammonium
Acid Phosphate
* H2S04 * 2NH3 _ ^ (NH4) 2SO4
Sulfuric Ammonia Ammonium
Acid Sulfate
* This reaction occurs only in the production of 16-20-0 and
occurs concurrently with the monoammonium phosphate reaction.
The processing steps (Figures 13 and 14) are essentially identical to
those described in the triple superphosphate GTSP process. Ammonia,
either gaseous or liquid, is reacted with 30-40% P2O5 phosphoric acid in
a vertical cylindrical vessel which may or may not have mechanical
agitation. The resultant slurry is then pumped to a mixer where it is
distributed onto dry recycled material. Distribution and mixing takes
place in either a pug mill or rotating drum. Wetted granules then
discharge into a rotary drier where the excess water is evaporated.
Dried granules are separated for use as recycle material. Product size
granules are cooled and conveyed to storage or shipped directly.
47
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Ni;trogen_Fertilizer Industry
The nitrogen fertilizer industry is composed of four basic process
plants: ammonia, urea, ammonium nitrate and nitric acid. Ammonia is
the basic nitrogen fertilizer constituent. It can either be used as the
raw material feed stock for urea ammonium nitrate and nitric acid or it
can be used directly as a fertilizer providing the highest amoun-t- of
available nitrogen per kkg of any of the nitrogen fertilizers.
For the most part, nitrogen fertilizer plants exist, or will be built,
without the interference of a phosphate fertilizer plant. That is, if
there happens to be phosphate fertilizer units at the same plant site as
nitrogen fertilizer units, they are or would be sufficiently separated
so that their waste water effluent streams can be treated individually.
However, the nitrogen fertilizer plants, in many cases, are very closely
integrated and their waste water effluent streams intermixed.
The dependency of the three other plants on an ammonia plant can be seer.
from the process descriptions. Although there are isolated ammonia
plants there are few cases where any of the other process plants, whose
production goes for nitrogen fertilizers, exist by themselves. A nitric
acid plant will be at the same site as an ammonium nitrate plant and an
urea plant will be located next to an ammonia plant. In many cases all
four of these plants will be at the same plant site. (See Table 1).
Ammonia
Process Description
Ammonia, being the base component for the nitrogen fertilizer industry,
is produced in larger quantities than any other inorganic chemical
except sulfuric acid. The total U.S. production in 1971 was 16,000,000
kkg (17,650,000 short tons) with an expected 1972 total close to
16,500,000 kkg (18,200,000 short tons). The size of an ammonia plant
will range from less than 90 kkg/day (100 tons/day) to larger than 1,360
kkg/day (1,500 tons/day) with the newer plants being the laraer sizes.
Ammonia is produced by the reaction of hydrogen with nitrogen in a three
to one (3:1) volume (irole) ratio.
N2 + 3H2 >2NH3
This reaction is carried out in the presence of an iron promoted metal
oxide catalyst at elevated pressure, which favors the ammonia formation,
in a special reaction vessel (converter) (Figure 15). Pressure in the
converter will range from 130 atm (1930 psig) to 680 atm (10,100 psia)
for the smaller plants, less than 550 kkg/day (600 tons/day), using
reciprocating compresscrs to operate at higher pressures and for larger
plants, greater than 550 kkg/day (600 tons/day), operating at lower
pressures using centrifugal machines for gas (syn gas) compression.
This reaction is exothermic and care must be taken to obtain the optimum
temperature which favors both the ammonia equilibrium and rate of
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reaction. Most of the ammonia converters will operate at temperature
from 338°C (550°F) to 421°C (700°F) .
Since at these operating conditions, the conversion of hydrogen and
nitrogen to ammonia is on the order of 10% to 20%, a considerable
quantity of reaction gas (hydrogen, nitrogen, methane, argon, other
inerts, and ammonia) must be cooled to condense ammonia, recompressed,
mixed with fresh make-up gas (syn gas) and reheated for recycle to the
ammonia converter.
The ammonia product, after pressure reduction, is stored in either large
atmospheric tanks at a temperature of -33°C (-28°F) or in large spheres
or bullets at pressures up to 20 atm (300 psig) at ambient temperatures.
The above process description normally describes the "back end" of an
ammonia plant, the airrronia synthesis section, with the "front end" being
designed for the production of the syn gas (make-up feed to ammonia
synthesis section) . The "front end" of an ammonia plant may range from
a very simple gas mixing operation to a very complex gas preparation
operation depending on the raw materials used. The raw material source
of nitrogen is atmospheric air and it may be used in its natural state
as compressed air to a gas preparation unit or as pure nitrogen from an
air plant to a gas mixing unit. Hydrogen, on the other hand, is
available from a variety of sources such as: refinery off-gas, coke
oven off-gas, natural gas, naphtha, fuel oil, crude oil and electrolytic
hydrogen off -gas. At the present time, more than 92% of the total
ammonia produced in the United States uses natural gas as its hydrogen
source and feed to a gas preparation unit, better known as a steam-
methane reforming unit.
Since the steam-methane reforming unit is the most widely used for syn
gas preparation, its process description will be used for describing the
"front end". The steam-methane reforming "front end" can be divided
into the following:
a. Sulfur Removal 5 Gas Reforming
b. Shift Conversion
c. CO2 Removal
d. Methanation
In the sulfur removal and gas reforming section, natural gas at medium
pressures 14 atm (200 psig to 600 psig) is treated for the removal of
sulfur and other high molecular weight hydrocarbons by passing the gas
through a bed of activated carbon. The natural gas is then mixed with
steam and heated before being passed through a bed of nickel catalyst in
the primary reformer. In the primary reformer the natural gas is
reacted at temperatures around 790°C (1,U50°F) with the steam according
to the following reactions:
CxHy. + H2O - >xCO + (y + y/2) H2 (Reform)
52
-------
CO + H2O ^ CO2 + H2 (Shift Conversion)
The reforming reacticr is only partially complete and the shift con-
version reaction proceeds only as far as the operating temperature and
pressure will permit.
The next piece of process equipment, the secondary reformer, is the
location for the introduction of nitrogen as compressed air at a
quantity that will result in a 3:1 volume ratio (hydrogen to nitrogen)
in the final syn gas. The reactions which occur are the completion of
the reforming reaction above and the oxidation of hydrogen to consum^
the oxygen in the compressed air feed. One result of these reactions is
an exit temperature in excess of 930°C (1,700°F). These hot gases then
enter a high pressure steam boiler, 41 atm to 102 atm (600 psig to 1,500
psig), and then into the shift conversion section. The shift reaction
(see above) is favored by low temperatures and is carried out in two
steps with heat recovery between each step. The first step, hiah
temperature shift conversion, is carried out by passing the gas through
a bed of iron oxide catalyst while the second step, low temperature
shift conversion, takes place in conjunction with a copper, zinc,
chromium oxide catalyst at temperatures around 220°C (425°F). Following
additional heat recovery and cooling, where necessary, the gas passes to
the CO2 recovery section.
The CO2 recovery system is not complicated, but there are a number of
types of systems available and each one has its advantages and
disadvantages. The two systems most used in the U.S. are one based on
monoethanolamine (MEA) and a second one based on hot potassium carbonate
and its variations. In each of these cases a circulating solution
either absorbs or reacts with the CO2 in the gas stream reducing its
concentration below 0.1%. The CO2 rich solution is then regenerated in
a stripper using previously recovered heat with the CO2 and some water
vapor being exhausted to the atmosphere.
The final stage in syn gas preparation is to remove any traces of CO and
C02 remaining. This is accomplished in a methanation unit where the gas
is passed through a bed of nickel catalyst resulting in the following
reactions:
+ H20
+ H20
After heat recovery and any necessary cooling the syn gas is ready for
compression and feeding to the ammonia synthesis section.
53
-------
Urea
Process_pescrigtion
Urea is another major source of nitrogen fertilizer produced in the
United States. Some 4,900,000 kkg (5,400,000 short tons) of urea were
produced in the U.S. in 1971.
Basically, there are three urea production processes which differ
primarily in the way the unreacted ammonia and carbon dioxide are
handled.
A. Once-through Process - In this process, no attempt
is made to recycle these gases to the urea process.
The off-gases containing ammonia and carbon dioxide are
used in the production of fertilizer products.
B. Partial Recycle Process - Excess ammonia is recycled
back to the process while any excess carbon dioxide is
vented to the atmosphere or used in another process.
C. Total Recycle Process - Both the ammonia and carbon dioxide
in the off-gas are recycled back to the urea process.
Currently, the total urea production is divided as follows: once
through, 18%; partial recycle, 12%; and total recycle, 70%.
All of the urea production in the United States is produced by the
reaction of ammonia with carbon dioxide which forms ammonium carbamate
(Figure 16). The ammonium carbamate is then dehydrated to form urea.
2NH3 + CO2 >NH4CC2NH2
NH4C02NH2 >NH2CONH2 + H2O
Most urea plants are located at the same plant site as a correspondingly
sized ammonia plant. The ammonia plant not only supplies the needed
ammonia, but also the high purity carbon dioxide.
The carbon dioxide-ammonia reaction to form urea, ammonium carbamate and
water takes place in a reactor vessel at pressures ranging from 137 atm
(2,000 psig) to 341 atm (5,000 psig) and at temperatures from 121°C
(250°F) to 182°C (360°F). Unreacted ammonia and carbon dioxide are also
present in the reactor exit stream. The carbamate forming reaction is
highly exothermic while the carbamate dehydration reaction is slightly
endothermic. Under reactor operating conditions, the dehydration
reaction proceeds to 40% to 60% completion resulting in an overall net
exothermic heat effect. After separation of the ammonia, carbon dioxide
and ammonium carbamate, the resulting solution will be about 70% to 80%
urea. Depending upon product specification this 70-80% solution can be
used as is or it can te further concentrated to a solid product. This
solid product can be formed by prilling, crystallation or a combination
of both. The concentration step takes place in flash evaporators
designed with minimum residence time to prevent the formation of biuret.
54
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(NH2CCNHCONH2 • H20) This biuret has a deleterous effect on crops. The
basic disadvantage in selecting prilling versus crystallization or a
combination is the degree of biuret formation. Prilling gives a product
with about 1% biuret while crystallization only has .1*. A combination
of the two processes results in a biuret content of about .5%.
56
-------
Ammonium Nitrate
Process Description
Ammonium nitrate is a major source of nitrogen fertilizer in the United
States. The total production in the U.S. in 1971 was 7,800,000 kkg
(8,600,000 short tons). It is an excellent fertilizer being high in
nitrogen (35%) and relatively low in cost.
Ammonium nitrate is made by reacting ammonia with nitric acid:
NH3 + HNO3 >NH4NO3
This reaction is carried out in a low pressure vessel called the
neutralizer (Figure 17). The high heat of reaction causes flash
vaporization of water with some ammonia and nitrate going overhead
leaving behind a liquid product which is 8356 by weight ammonium nitrate.
This product known as AN solution can be sold or it can be further
processed into a dry product. The overhead vapors from the neutralizer
may lead to an air pollution problem or if condensed, will have to be
treated before being discharged.
If a dried product is desired, then the 83% AN solution is first
concentrated up to 95% AN and then either prilled or crystallized. If
prills are to be the final form of the ammonium nitrate, the con-
centrated solution is pumped to the top of a 45 meter (150 ft.) to 61
meter (200 ft.) tower where it is sprayed downward into a rising flow of
air. As the ammonium nitrate droplet forms it is solidified before it
hits the bottom of the tower. These prills are then further dried to
reduce the moisture to less than 0.5%. Following cooling, the prills
are then coated with an anti-caking agent such as clay. Concentrator
and prill tower air exhausts can contain significant amounts of fine
particulate ammonium nitrate which represents both a significant air
pollution problem and an indirect water pollution source via runoff and
washoff.
A final dry crystalline ammonium nitrate product requires that the
solution from the concentrator (95% AN) be fed to a continuous vacuum
evaporation crystallizer. The cooling of the solution in the
crystallizer causes crystals to form. A side stream of crystal solution
is taken from the crystallizer and fed to a centrifuge for crystal
separation. The centrifuge supernate is recycled back to the
crystallizer. The crystals are removed from the centrifuge, dried to
less than 0.1% water, cooled and coated with an anti-caking agent.
57
-------
t
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-------
Nitric_Acid
Process Description
Nitric acid is produced by a number of processes in strengths from 55%
to 100% acid. In 1971 there were some 8,450,000 kkg (9,300,000 short
tons) of acid produced of which better than 80% was used for and/or
produced at nitrogen fertilizer complexes. While varying strengths of
acid are produced, the fertilizer industry uses a dilute acid (55% to
65%) .
Nitric acid is produced in the United States by the ammonia oxidation
process (Figure 18). In this process, ammonia is reacted with air to
produce oxides of nitrcgen which are then further oxidized and absorbed
in water producing a 55 to 65% nitric acid. The following reactions
occur in the process:
2NO + 02 >2N02
3NO2 + H2O ^2HNC3 + NO
The initial ammonia oxidation reaction takes place in the converter in
the presence of a platinum-rhodium gauze catalyst at pressures from
atmospheric up to 82 atm (120 psig). The exit gases from the converter
may be in the temperature range of 705°C (1,300°F) to 980°C (1,800°F)
and are used to superheat steam and preheat process air. The gases then
pass through a waste heat boiler to generate steam for the air
compressor drive turbine and for export. The quantity of steam
generated by the process will range from 500 to 1,000 kg/kkg (1,000 to
2,000 Ib/ton) of nitric acid. By this time, due to the lower
temperature, the second reaction involving the oxidation of nitric oxide
to nitrogen dioxide has begun to occur. Following some additional
cooling to 38-49°C (100-120°F), where seme of the water is condensed and
forms nitric acid, the gases are passed up through an absorption column.
Some additional air is also passed up through the column to oxidize the
nitric oxide formed during the absorption step to nitrogen dioxide.
Water (fed to the top of the absorber) acts as the absorbant giving
product nitric acid cut the bottom of the column. The absorber
temperature is held constant by cooling water to improve the absorption
efficiency. Cooling water requirements will range from 104,000 to
146,000 1/kkg (25,000 to 35,000 gal/ten) of product.
The gases leaving the top of the absorber are fairly low in nitrogen
oxides but may be catalytically reacted to further reduce these levels
and, then depending on the process pressure, passed through a hot gas
expander to recover some of the energy needed to drive the process air
compressor. The differential energy required for the air compressor can
be supplied by a helper turbine driven by the steam generated by the
process.
59
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SECTION IV
INDUSTRY_CATEGORIZATigN
The task of dividing the many fertilizer processes into specific
categories was considered one of the most important aspects of the
study. A particular objective was to have the least possible number of
categories in order to simplify the work of both enforcement officials
and industry in the monitoring of effluent streams.
The factors considered in the overall categorization process included
the following:
1. Industry division
2. Problems with separation of individual process effluents within
a plant complex
3. Plant size
U. Plant age
5. Effect of raw material variations
6. Existence, "type and efficiency of air pollution control
equipment
7. Land area available for waste water containment utilization of
wastes
8. Waste load characteristics
9. Treatability of wastes
10. Effect of rainfall - evaporation discrepancies
After completing the majority of the twenty-five (25) separate plant
visits it became clear that only a small number of the above listed
items had real overall meaning for categorization. All items effect
plant effluent conditions and quantities. However, they do not all
necessarily contribute to the categorization of processes. The final
factors used to establish the categorization were:
1. Natural industry division
2. Waste load characteristics
3. Treatability of waste streams either by inter
process reuse cr treatment technology
The application of these listed criteria resulted in the establishment
of 5 subcategories for the industry. These together with their
component processes are listed below:
A. PHOSPHATE SUECATEGORY
1. PHOSPHATE ROCK GRINDING
2. WET PROCESS PHOSPHORIC ACID
3. PHOSPHORIC ACIC CONCENTRATION
4. PHOSPHORIC ACIE CLARIFICATION
5. NORMAL SUPERFHCSPHATE
6. TRIPLE SUPERIHCSPHATE
7. AMMONIUM PHOSPHATES
SULFURIC ACID
61
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B. AMMONIA SUECATEGORY
C. UREA SUBCATEGORY
D. AMMONIUM NITRATE SUECATEGORY
E. NITRIC ACID SUECATEGCRY
IndustrY_Division
The fertilizer industry is composed of multi-product plants. with few
exceptions a phosphate complex does not include nitrogen type processes
(ammonia, urea, ammonium nitrate and nitric acid) . This natural
separation of the industry by the industry coupled with the ether
following factors indicates that phosphate fertilizer chemicals should
constitute a separate category from nitrogen fertilizer chemicals.
2f Individual Process Effluent Within a Plant
Complex
A somewhat surprising fact brought to light in the study was the lack of
information available on specific process effluents within a complex.
Fertilizer complexes are generally not physically designed to keep
individual process streams separate. The reasons for this include:
there previously was no reason to do so; simplification of underground
sewer systems meant joint sewers and the practice of using effluent from
one process as a liquid in another process.
This rationale is appropriate for phosphate fertilizer complexes, mainly
because of the similar treatment technologies involved. However, at
nitrogen fertilizer complexes inadequate treatment of pollutants will
frequently result if the process waste waters from each component
chemical are not dealt with separately.
Plant Size
There is a wide range of plant sizes for most chemicals in the
fertilizer industry. However, plant size will not affect waste water
characteristics or treatability.
Pi an t_ Age
There is also a wide range of plant ages in the fertilizer industry.
This should not affect waste water characteristics or treatability to
the degree where any additional subcategcrization is required.
Ef f ect, of Raw Material Variations
Variations in the raw material will affect waste water characteristics
in operations involving phosphate rock and the resultant phosphoric acid
or phosphate. However, the effluent limitations in such cases take
these variations into account. Another problem is that these variations
are unpredictable and difficult to monitor, making subcategorization
based upon this topic impracticable.
_.of Air Pcllutioni-rCgntrol_E^uipjnent
-------
A major source of process waste water is from air scrubbers employed at
all plants. The treatment technologies proposed are practicable
regardless of the type cr efficiency of air pollution control devices,
and subcategorization is not warranted.
Land Area Ayailable_fcr Waste Water Containment
Confinement of process waste water in large ponds is universally
practiced at phosphate fertilizer plants. These ponds range in size
from 65 to 570 hectares (160 to 1400 acres). However, extremely large
ponds are not necessary to achieve the degree of treatment necessary to
recycle the process waste water. The principal point is that the ponds
now exist and need not be expanded. Use of biological treatment of
ammonia and nitrates in nitrogen fertilizer plants would require space
for treatment ponds. If land availability is a problem, alternate
methods of ammonia and nitrate removal are available.
Waste Load_characteristics
The phosphate and nitrogen segments of the fertilizer industry have
different waste water characterics. For instance a phosphate complex
effleunt would be acidic due to phosphoric, sulfuric, or nitric acids
used in the process. A nitrogen fertilizer complex would generally be
alkaline due to amnronia. Phosphates and fluorides will be present in
the waste waters from a phosphate complex, nitrogen compounds from a
nitrogen fertilizer complex. Within a nitrogen fertilizer complex the
different chemicals will involve different forms of nitrogen. For
instance, ammonia will naturally result from ammonia synthesis. Ammonia
and nitrates will result from ammonium nitrate production. Ammonia and
organic nitrogen will result from urea synthesis. Such differences
warrant subcategorizaticn of these latter chemicals.
Treatability of Wastes
This is the principal factor used in determining subcategorization.
Production of all phosphate fertilizer chemicals requires similar
treatment methods (i.e. neutralization, lime precipitation, and
settling). The only need for a discharge is during periods of excessive
rainfall. No process waste water is even generated in manufacturing
nitric acid. On the ether hand urea, ammonium nitrate and ammonia can
each require a different treatment technique to achieve best practicable
and best available technologies.
Ejffe.ct_of Rainfall^r Evaporation^ Discrepancies
Because of the almost universal use of ponds in the phosphate fertilizer
subcategory lengthy periods where rainfall exceeds evaporation and/or
periods of rainfall of abnormally high-intensity necessitate a
discharge. Rather than create a separate subcategory, this problem is
better handled as a factor by which the standards can be varied, since
for any given month rainfall could exceed evaporation at any location.
63
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SECTION V
WASTE_CHARACTEFIZATION
General
The intent of this section is to describe and identify the water usage
and waste water flews in each individual process. Each type water usage
and effluent is discussed separately and includes a tabulation
indicating ranges of flow and contaminant concentrations for each
process. Flow figures are presented en a per kkg of product basis to
permit ready calculation of flow for any specific production rate.
Water flow information is also presented on individual process water
usage flowsheets tc pictorially indicate the various water flows
relative to the process equipment.
PhQSphate_Fertilizer_Industry
The eight process operations - sulfuric acid, phosphate rock grinding,
wet process phosphoric acid, phosphoric acid concentration, phosphoric
acid clarification, normal superphosphate, triple superphosphate,
ammonium phosphates - in the phosphate fertilizer subcategory have the
following types of water usage and wastes.
A. Water Treatment Plant Effluent
Includes raw water filtration and clarification,
water softening, and water deionization. All these
operations serve only to condition the plant raw water
to the degree necessary to allow its use for process
water and stearr generation.
E. Closed Loop Coding Tower Slowdown
C. Boiler Blowdcwn
D. Contaminated Water
E. Process Water
F. Spills and Leaks
G. Non-Point Source Discharges
These include surface waters from rain or snow that
become contaminated.
H. Contaminated Water (Gypsum Pond Water) Treatment
Each of the above listed types of water usage and wastes are identified
as to flow and contaminant content under separate headings. Detailed
flow daigrams were previously presented in Figures 3 through 14.
65
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A. Water^Treatment Pi ant _Ef fluent.
Basically only the sulfuric acid process has a water treatment effluent:.
This 1300-1670 1/kkg (310-UOO gal/ton) effluent stream consist
principal i.y of only the impurities removed from the raw water (:;u^v ; -
carbonate , bicarbonates, hydroxides, silica, etc.) plus miiio-
quantitie . of treatment chemicals.
Th- d<=qr ;e of water treatment of raw water required is depen lent or :•
steam pressure generated. Generally medium-pressure 9.5-52 atm f1, Jr- 1c ~
csiq) sys :ems are used and do require rather extensive make-up w t --•-r
'.reatment. Hot lime-zeolite water treatment is the most commonly ut-- \,
There are phosphate complexes particularly alonq the Mississippi Fiv r
which use river water both for boiler make-up and process water. Ir
th<=s = plants it is necessary to treat the river water through a set.-l-r
or clarification system to remove the suspended solids present in the
river water before conventional water treatment, is undertaken. Effluent
limitations for water treatment plant effluent components are not
covered in this report. They will be established at a later date.
B. close_dT_Loop Cgoling^Tcwer^Blgwdgwn
The cooling water requirements and normal blowdown quantities are listed
in the followinq table. Effluent limits with respect to thermal
components and rust and bacteria inhibiting chemicals is coolina -^ower
blcwdown or for once through cooling water are not covered in this
report, but will be established at a later date.
66
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Q22iing Water
Process
Circulation Requirement
1/kkg
Discharge Requirement
l/kkg gal/ton
Sulfuric Acid 75000-83000
(per ton 100%)
H2S04
Rock Grinding 33-625
(per ton rock)
Phosphoric Acid 0-19000
(per ton P2O5)
18000-20000 1670-2500
Phcs. A. Cone
(per ton P2O5)
None
Phos. A. Clarifi- 690-3200
cation
(per ton P.2O5)
Normal Super None
(per ton product)
Triple Super None
(per ton product)
Ammon Phos.
(per ton product)
None
8-150
0-4500
None
165-770
None
None
None
33-625*
0-19000*
None
690-3200*
None
None
None
UOO-600
8-150*
0-U500*
None
165-770*
None
None
None
* Non-contaminated only temperature increase in
discharge water.
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 form plant to plant and is dependent upon overall cooling water
circulation system.
The quality of the cooling system blowdown will vary with the make-up
water impurities and inhibitor chemicals used. 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 periodically
occur and continuous monitoring equipment is used to detect such
equipment failures.
67
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The table below lists the normal range cf contaminants that may be found
in cooling water blowdcwn systems.
Contaminant Concentration
mg/1
Chrornate 0-250
Sulfate 500-3000
Chloride 35-160
Phosphate 10-50
Zinc 0-30
TDS 500-10,000
SS 0-50
Biocides 0-100
Cooling tower blowdown can be treated separately or combined with other
plant effluents for treatment. The method to be employed is dependent
upon the chemical treatment method used and cost. Those plants which
utilize chromate or zinc treatment compounds generally treat the
blowdown stream separately to minimize effluent treatment costs.
C.Boiler Blowdown
The only steam generation equipment in a phosphate complex other than
possibly auxiliary package boilers is in the sulfuric acid plant.
Medium pressure, 9.5-52 atm (125-750 psig) , steam systems are the most
generally used.
Boiler blowdown quantities are normally 1300-1670 1/kkg (310-400
gal/ton). Typical contaminate concentration ranges are listed below.
Separate effluent limitations for boiler blowdown with respect to both
thermal discharge and specific contaminants are not covered in this
report. They will be established at a later date.
Contaminate Concentration
mg/1
Phosphate 5-50
Sulfite 0-100
TDS 500-3500
Zinc 0-10
Alkanlinity 50-700
Hardness 50-500
Silica (Si02) 25-80
D•Contaminated_Water JGypsumJPpnd Water)
Contaminated water is used to supply essentially all the water needs of
a phosphate fertilizer complex. The majority of U.S. phosphate
fertilizer installations impound and recirculate all water which has
direct contact with any of the process gas or liquid streams. This im-
6b
-------
pounded and reused water accumulates sizeable concentrations of many
cations and anions, but particularly F and P. Concentrations of 8500
mg/1 F and in excess cf 5000 mg/1 P are not unusual. Acidity of the
water also reaches extremely high levels (pH 1-2). use of such poor
quality water necessitates that the process equipment materials of
construction be compatible with the corrosive nature of the water.
Contaminated water is used in practically all process equipment in the
phosphate subcategory except sulfuric acid manufacturing and rock
grinding. The water requirements of such major water using equipment as
barometric condensers, gypsum sluicing, gas scrubbing equipment, and
heat exchangers are all supplied by contaminated water. Each time the
water is reused, the contaminate level is increased. while this
contaminated water is a major process effluent, it is not discharged
from the complex. The following table lists ranges of contaminated
water usage for each process.
Process
Sulfuric Acid
"Rock Grinding
Wet Process Phosphoric Acid
NPK Process-Nitric Acid
Acidulation
Phosphoric Acid concentra-
tion
Phosphoric Acid Clarifica-
tion
Normal Superphosphate
Triple Superphosphate
Ammonium Phosphate
E.Make-u£_Water
None
None
16400-20800
1000-2300
2500-2600
690-1040
940-1040
660-1040
5000-6500
gal/ton
None
None
3800-5000
240-540
550-570
225-250
225-250
158-250
1200-1500
Make-up water in a phosphate complex is defined as fresh water untreated
except for suspended solids removal. Normally fresh water use to all
process units is held to an absolute minimum. Such restraint is
necessary because all make-up water used finds its way into the
contaminated water system. Excessive fresh water use will therefore
needlessly increase the contaminated water inventory beyond the
containment capacity. This in turn means contaminated water must
undergo costly treatment before discharge to natural drainage whenever
such discharge is permitted.
Normal ranges of make-up water use are listed below for each of the
process units. There is no discharge except into a process stream cr to
the contaminated water system.
69
-------
Make;up_Wat.er_Usage
1/kkg
Sulfuric Acid 63-83 15-20
Rock Grinding None None
Wet Process Phosphoric Acid None None
Phosphoric Acid Concentration 0.8-1.6 0.2-O.U
Phos Acid Clarification None None
Normal Superphosphate None None
Triple Superphosphate None None
Ammonium Phosphates None None
F . Spills and Lgaks
Spills and leaks in most phosphate fertilizer process units are
collected as part of the housekeeping procedure. The collected material
is, where possible, re- introduced directly to the process or into the
contaminated water system. Spillage and leaks therefore do not normally
represent a direct contamination of plant effluent streams that flow
directly to natural drainage.
The primary origin of such discharges is dry fertilizer material which
dusts over the general plant area and then dissolves in rain or meltinq
snow. The magnitude cf this contaminant source is a function of dust
containment, housekeeping, snow/rainfall quantities, and the design of
the general plant drainage facilities. No meaningful data was obtained
on this intermittant discharge stream.
H • Contaminated Water __ (G Y£§um_Pond_ Water] __ Treatment System
The contaminated water treatment system discharge effluent is the only
major discharge stream from a phosphoric acid complex ether than the
water treatment and blcwdown streams associated with the sulfuric acid
process. Discharge from this system is kept to an absolute minimum due
to the treatment cost involved. In fact, several complexes report that
they have not treated and discharged water for several years. The need
to treat and discharge water has been previously mentioned to be
dependent upon the contaminated water inventory. As a result, water
discharged from the treatment system is not done continuously throughout
the year. Once the necessity for treatment occurs, however, the flow is
continuous for that period of time required to adjust the contaminated
water inventory. Norirally, this period is 2-4 months per year, but is
primarily dependent upon the rainfall/evaporation ratio and occurence of
concentrated rainfall such as an abnormal rainy season or a hurricane.
Some phosphate fertilizer installations in the Western U.S. perennially
have favorable rainfall/evaporation ratios and never have need to treat
or discharge water. The quantity of water discharged from the
contaminated water treatment system is strictly dependent upon the
design of the treatment system and has no direct connection to
70
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production tonnage. Contaminated water treatment systems generally have
capacities of 2085-UnO 1/min (500-1000 gpm) .
The common treatment system is a two-stage liming process. Three main
contaminated water parameters, namely pH, F, and P are addressed.
Reported ranges for these parameters after treatment are:
pH 6-9
F 15-40 mg/1
P 30-60 mg/1
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Nitrogen_Ferti1izer_Industry
The four process operations - ammonia, urea, ammonium nitrate, nitric
acid - in the nitrogen fertilizer category, discharge the following
types of waste water.
A.Water treatment plant effluent (includes raw water filtration and
clarification, water softening, and water deionization)
B.Closed loop cooling tcwer blowdown
C.Boiler blowdown
D.Compressor blowdown
E.Process condensate
F.Spills and leaks that are collected in pits or trenches
G.Non-point source discharges that are "collected" due to rain or snow.
Detailed process flow diagrams have previously been presented in Fiaures
15 through 18.
A.Water Treatment Plant Effluent
The total effluent stream from a combined water treatment system will
range from 8 to 20 1/kkg (2 to 5 gal/ton) of product with an ammonia
plant having the larger amount due tc the large amounts of raw water
used. The contaminants in this effluent are mainly due to the initial
contaminants in the raw water and therefore would be specific to the
area and geographic conditions rather than the process plants involved.
If the water treatment plant effluent contains ammonia due to the use of
stripped, process condensate as process or boiler water makeup
(replacing raw water makeup), then the ammonia - N discharge allowance
is applicable. Effluent limitations for specific components (other than
ammonia - N) for treatment plant effluent are not covered in this
report. They will be studied at a later time.
B.Cooling^TQwer Slowdown
The cooling water requirements and expected blowdown requirements for
the four process plants in the nitrogen fertilizer industry are listed
in the table below.
72
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Ammonia
Cooling Water
Circulation Circulation Slowdown Slowdown
Requirement Requirement Requirement Requirement
liter/1/kkg gal/ton liter/1/kkg gal/ton
104,000 tc 25,000 to 1,670 to 400 to 700
417,000 100,000 2,920
Urea 41,700 tc 10,000 to 375 to 90 to 350
167,000 40,000 1,470
Ammonia Nitrate 8,350 to 2,000 to 84 to 20 to 60
29,200 7,000 250
Nitric Acid 104,000 tc 25,000 to 1,250 to 300 to 600
146,000 35,000 2,500
In this closed loop cooling tower system, chemicals are added to inhibit
scale formation, corrosion and the growth of bacteria. Due to the
nature of the make-up water, the inhibitor chemicals and the evaporation
water loss from the tcwer, a quantity of blowdown is required to prevent
excessive build up of chemicals and solids in the circualtion system.
This quantity will vary, as shown in the above table, from plant to
plant depending on the total circulation system.
The quality of this ccoling system blowdcwn will vary mostly with make-
up water condition and inhibitor chemicals and will not be greatly
affected by the process plant associated with it. Any leaks that might
develop in process or machinery exchangers should not significantly
affect the contaminant concentration of the cooling water. The largest
contaminant in the cooling water, that is neither intentionally added as
an inhibitor nor ccmes in with make-up, is ammonia. Due to the
proximity of the cooling tower in relation to any of the four nitrogen
fertilizer operations, atmospheric ammonia is readily absorbed in the
cooling water.
The table below represents some possible range of concentration for some
of the contaminants that might be contained in the cooling water
blowdown.
mg/1 mg/1
Chromate 0-250 Zinc 0-30
Ammonia 5-100 Oil 10-1,000
Sulfate 500-3,000 TDS 500-10,000
Chloride 0-40 MEA 0-10
Phosphate 10-50
This blowdown can be either treated by itself if necessary or combined
with other effluents for total treatment. However, it is recommended
that this stream be treated separately for chromate-zinc reduction since
this is main source of these contaminants (Cr and Zn) to the total plant
73
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effluent. Effluent limitations for noncontact cooling water are not
covered in this report. They will be established at a later date.
C.Boiler Slowdown
The four nitrogen fertilizer processes will generate up to 6,000 kg of
steam/kkg (12,000 It of steam/ton) of product depending on what
processes are at the plant site. Ammonia will have the highest steam
load followed by nitric acid, urea and ammonium nitrate. The pressure
of the steam generated by and/or used in these plants will range from
atmospheric up to 103 atm (1,500 psig).
Depending on the operating pressure of the steam system, the treatment
of the boiler feed water will vary from extensive, including
deionization, at 103 atm (1,500 psig) down to not much more than
filtration at atmospheric pressure. Inhibitor chemicals are also added
tc boilers to prevent corrosion and scale formation throughout the
system.
The combination of make-up water quality and the addition of inhibitor
chemicals necessitates blowdcwn periodically to remove contaminants from
the boiler. Based on the actual steam generated in a nitrogen
fertilizer complex, this blowdown quantity will range from 42 to 145
1/kkg (10 to 35 gal/ten) of product.
Typical compositions cf contaminants in boiler blowdown from nitrogen
complex boilers are as fellows:
Phosphate
Sulfite
TDS
Zinc
mg/1
5-50
0-100
500-3500
0-10
Suspended Solids
Alkalinity
Hardness
Si02
mg/1
50-300
50-700
50-500
10-50
This effluent stream may be treated separately if necessary or combined
with the total effluent for treatment. Effluent limitations for boiler
blowdown will be established at a later date.
D.compressor,Blowdown
This waste water effluent stream has been separated out because it
should contain the largest proportional amount of oil and grease.
Primarily, the blowdcwn containing oil will come from interstage
cooling-separation in the reciprocating compressors operating on ammonia
synthesis gas, on ammonia process air and on urea carbon dioxide. If
these streams can be contained then oil separation equipment can be kept
to a minimum.
Due to the nature and expense of reciprocating compressors they are
usually replaced by centrifugal compressors, when the ammonia plant
74
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capacity reaches 550 kkg/day (600 ton/day). The use of centrifugal
compressors results in much less oil and grease in the blowdown
effluent. The quantity of this blowdown will vary and can run up to 208
1/kkg (50 gal/ton) of product.
E.Process Condensate
Process condensate, although it may have many of the similar
contaminants, will be handled separately for each of the four process
plants.
Ammonia Process Condensate
Process steam supplied tc the primary reformer is in excess of the
stoichiometric amount required for the process reactions and, therefore,
when the synthesis gas is cooled either by heat recovery or cooling
water, a considerable amount of process condensate is generated. The
quantity of this ccndensate will range from 1,500 to 2,500 kg/kkg (3,000
to 5,000 Ib/ton) of product. The contaminants in this condensate may be
ammonia, methanol, some organics from the CO2 recovery system and
possibly some trace metals. The ammonia discharged in this waste stream
can range from 1,200 - 1750 kg/1000 kkg (2400 - 3500 lb/1000 ton).
Urea_Process Condensate^
Following the urea forming reactions the pressure is reduced to allow
ammonia, carbon dioxide and ammonium carbamate to escape from urea
product. Partial condensation of these flashed gases along with the
condensation of water vapor from the urea concentration step results in
a condensate containing urea, ammonium carbamate, ammonia and carbon
dioxide. The quantity of this stream will range from 417 to 935 1/kkg
(100 to 225 gal/ton) cf product. Ammonia discharge in this stream has
been observed at the level of 9,000 kg/1000 kkg (18,000 lb/1000 ton) of
urea product. Urea discharge at the rate of 33,500 kg/1000 kkg (67,000
lb/1000 ton) of urea product has also been cited.
Ammonium Nitrate Process^Cgndensate
The nitric acid-ammonia reaction being highly exothermic causes a large
amount of water to be flashed off taking with it ammonia, nitric acid,
nitrates and some nitrogen dioxide. If climatic conditions or air
pollution regulations require that this stream be condensed then this
contaminated condensate will range between 208 and 458 1/kkg (50 and 110
gal/ton) of product. Ammonia discharges in the stream could be at the
levels of 150 kg/1000 kkg (300 lb/1000 ton) and ammonium nitrate at 7000
kg/1000 kkg (14,000 lb/1000 ton) of ammonium nitrate product.
NitricmAcid^Process^Cgndensate
Using the ammonia oxidation process for production of 55X to 65%
strength acid there are no process condensate effluent streams.
F.Collected Spills and_Leaks
-------
In all process plants there will be a small quantity of material either
spilled, during loading or transferring, or leaking from some pump seal
or bad valve. When this material, whether it be cooling water, process
condensate, carbon dioxide scrubbing solution, boiler feed water or
anything else, gets en a hard surface where it can be collected in a
trench, then it will probably have to be treated before being
discharged. The quantity of this material is not dependent on plant
size, but more on the operating philosophy and housekeeping procedures.
G.Non^Point^pischarges
Rain or snow can be a collection medium for a sizable quantity of
contaminants. These contaminants may be air borne ammonia that is
absorbed as the precipitation falls, or it may be urea or ammonium
nitrate prill dust that is lying on the ground around prill towers. Dry
fertilizer shipping areas may also have urea and/or ammonium nitrate
that can be washed down by rain or snow. Pipe sweat and drip pots are
another potential source of contaminants.
76
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SECTION VI
SELECTION OF POLLUTANT PARAMETERS
General
The selection of pollutant parameters was a necessary early step of the
study. Collection of meaningful data and sampling was dependent on
knowing what fertilizer process contaminants are important so far as
degradation of natural water resources are concerned.
The general criteria considered and reviewed in the selection of
pollutant parameters included:
quality of the plant intake water
products manufactured
raw materials used
environmental harmfulness of the compounds or elements included
in process effluent streams
FHCSPHATE FERTILIZER INDUSTRY
Effluent waste water from the phosphate fertilizer processes must be
treated to reduce the following primary factors and contaminants to
achievable levels: pH, phosphorus, fluorides, ammonia and suspended
solids.
Secondary parameters which should be monitored but do not warrant
establishment of guidelines are: total dissolved solids, temperature,
chemical oxygen demand (COD), cadmium, total chromium, zinc, vanadium,
arsenic, and uranium. The chief reason for not establishing standards
for the secondary parameters is that treatment of the primary parameters
will effect removal of these secondary parameters. Another reason is
that insufficient data exists to establish effluent limitations.
RATIO^ALE^OR_^LECTING_IDENTIFIED_PARAMETERS
2H_-_Alkalinity__I_ Acidity
The pH of an aqueous solution is defined as the negative logarithm of
the hydrogen ion concentration. The pH scale ranges from 0 to 14 and a
pH of 7 represents a neutral solution. A pH of less than 7 indicates an
acidic solution. A pH of greater than 7 indicates an alkaline solution.
The presence of large amounts of ammonia or acids in the waste streams
from this industry will affect the pH of the waste stream.
77
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Phosphorus
Phosphorus is a plant nutrient, and essential for all forms of plant
growth. With favorable conditions, low phosphorus concentrations may
contribute to accelerated algae and vegetation growth which, in turn,
reduces the dissolved oxygen content of the water. This parameter may
appear in any process using either phosphoric acid or phosphate ore.
Fluorides
Soluble fluorides in discharged effluent waters are considered harmful
to animal and plant life. This constituent is present in the waste
streams of this industry because of the fluoride content of phosphate
ores.
Ammonia Nitrogen
Ammonia nitrogen is a contaminant of concern because of its varied
effects on plant life and humans. The majority of this N is oxidized to
nitrites and nitrates.
Total_Chrgmium and Zinc
Cooling tower and boiler blowdowns are the sole source of these metals.
Effluent standards for constituents in noncontact cooling water and
boiler blowdown will be established at a later date.
Cadmium. Arsenic. Vanadium and Uranium
The amounts of cadmium, arsenic, vanadium and uranium present in Florida
and Western phosphate rocks were reviewed. These elements are present
in small concentrations in the rocks as shown by the following table.
In general, these elements are solubilized by the phosphate rock
acidulation process and tend to be retained in the acid rather than
discarded with the gypsum waste. Only cadmium will be found in
measureable quantities in the gypsum pond, although small. A toxic
limitation for -this pollutant will be established which will cover any
discharge of cadmium from the fertilizer categories.
Phosphate Rock
(mg/kg)
Element Flo£id§ Western
Arsenic as AS03 5-30 6-140
Cadmium as CdO 10 150
Uranium as U308 100-200 50-100
Vanadium as V203 10-200 400-4000
78
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NITROGEN FERTILIZER INDUSTRY
SIGNIFICANT WASTE_VjATIB^PARAMETEgS
Effluent waste waters frcm a nitrogen fertilizer complex must be treated
to maintain the following primary parameters within the recommended
guidelines: ammonia nitrogen, organic nitrogen, nitrate nitrogen, pH,
and oil and grease.
Secondary parameters which should be monitored but do not warrant the
setting of guidelines at this time are: chemical oxygen demand (COD),
total dissolved solids (TDS), suspended solids, total chromium, zinc,
iron, and nickel. The chief reason for not establishing standards for
the secondary parameters is that treatment of the primary parameters
will effect removal of these secondary parameters. Another reason is
that insufficient data exists to establish effluent limitations.
These selections are supported by the knowledge that best practicable
control technology currently available does exist to control the chosen
parameters and that improved technology is being developed and refined
to meet best available technology economically achievable and best
demonstrated technology.
Rationale^for Selecting^Identified_Parameters
Ammon ia _ Nit rog en
Ammonia nitrogen is the most prominent pollution parameter because it is
common to all four process plants. This contaminant is found mostly in
the process condensates but may also te present in cooling towers.
Although some ammonia nitrogen may be consumed in the growth of
biological organisms, the majority would probably be oxidized to
nitrites and nitrates.
Nitrate,Nitrogen
Nitrate nitrogen is found in contaminated process condensate from the
ammonium nitrate plant and spills and leaks from the nitric acid plant.
Nitrate nitrogen in waste waters can directly affect receiving waters
contributing to rapic algae growth.
Organic Nitrogen
Organic nitrogen contaminants in the waste waters consist mainly of urea
and lesser amounts of organic CO2 scrubbing solutions. Such compounds
can supply nutrient nitrogen for increased plant and algae growth in
receiving waters.
The organic scrubbing solution - monethanolamine (MEA) - can add a
slight BOD load to the effluent waste stream.
79
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EH
While nitrogen fertilizer plant effluents are normally consistent and
fall well within acceptable pH limits, abrupt changes must be avoided.
Oil & Grease
While some amounts ccme from all rotating machinery, reciprocating
compressors for process air and synthesis gas in ammonia plants are the
greatest contributors tc oil contamination of the waste water. Oil in
the receiving waters can have deleterous effects on marine life, plant
life or plummaged water fowl. Oil may also cause taste and odor
problems.
Total^chrgmium and Zinc
Cooling tower and boiler blowdown are the major sources of these metals.
Effluent standards for constituents in noncontact cooling water other
than ammonia and boiler blowdown will be established at a later date.
METHODS_OF_ANALYSIS
The methods of analysis to be used for quantitative determination are
given in the Feder.al_Rec|ister 40 CFR 130 for the following parameters
pertinent to this study:
alkalinity (and acidity)
ammonia nitrogen
arsenic
cadmium
chromium
fluoride
hardness
nitrate nitrogen
nitrogen, total kjeldahl
oxygen demand, chemical
phosphorus
solids, total
suspended nonfilterable solids, total
temperature
zinc
Organic nitrogen should be analyzed according to Standard Methods for
t^e Examination of Water and Waste Water (SMWW) (ref W) method 215.
Oil and grease should be determined by Methods for Chemical Ana.ly.sis of
Water and Wastes (ref.X), page 217.
Vanadium should be determined by SMWW method 164.
80
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SECTION VII
CONTROL AND TREATMENT TECHNOLOgY
The factors and contaminants in fertilizer process effluent streams have
for the most part been quite well identified and fairly well known for
many years. As a consequence considerable effort has been expended to
correct or nrinimize the majority of those which are particularly
detrimental to natural water receiving bodies. Much of this work has
been directed at correcting the source of the contamination or an in-
process improvement rather than an end-of-pipe type of treatment. A
large part of the motivation for such improvement has been economics
that is, improved operating efficiency and costs. Such improvements are
just plain good business and justify capital expenditure required to
achieve it. Additional cr future corrective measures are for the most
part going to require capital expenditures which will do nothing towards
improving operational economics and will, in fact, increase operational
costs.
With an appreciation of the above mentioned facts, it must be considered
that future expenditures for waste water treatment should be well
documented as to the need, the degree of water quality required, and
assurance that the specified treatment is a workable and viable
technology before the associated effluent limitation it is stipulated as
an absolute requirement. It was with these conditions in mind that the
following criteria were established as a basis for investigating
treatment technology.
to determine the extent of existing waste water control
and treatment technology
to determine the availability of applicable waste water
control and treatment technology regardless of whether
it be intra-industry transfer technology
to determine the degree of treatment cost reasonability
Based upon these stated criterion the effort was made to factually
investigate overall treatment technologies dealing with each of the
primary factors and contaminants listed in Section VI. The results of
that investigation are covered separately for phosphate and nitrogen
fertilizers.
CONTROL AND TREATMENT TECHNOLOGY
PHOSPHATE FERTILIZER INDUSTRY
Process technology does exist for treatment and reduction of the primary
factors and contaminants present in phosphate fertilizer process
effluent streams to the levels proposed. These treatment technologies
are reviewed in the following paragraphs.
81
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Sulfuric_Acid_Plant_EfJluent_Control
A sulfuric acid plant has no inherent water pollutants associated with
the actual production of acid. An indispensible part of the process,
however, is heat remcval. This heat removal is accomplished with steam
generating equipment and cooling towers. Both of these cooling methods
require blowdown and subsequent disposal to natural drainage. The
amount and degree of impurities discharged vary widely with the raw
water quality.
An inherent hazard cf any liquid handling process is the occurrence of
an occasional accidental break and operator error. In a sulfuric acid
plant the sulfuric acid cooling coils are most prone to an accidental
break. On these occasions the cooling tower water quickly becomes
contaminated. In turn, the normally acceptable practice is to take care
of that break as soon as it is discovered and protect the natural
drainage waters.
Process Description
The facilities are relatively simple. It involves the installation of a
reliable pH or conductivity continuous monitoring unit on the plant
effluent stream (preferably the combined plant effluent stream but at
least on the cooling tower blowdown). A second part of the system is a
retaining area through which non-contaminated effluent normally flows.
This retaining area can be any reasonable size but should be capable of
retaining a minimum of 24 hours of the normal plant effluent stream.
The discharge point from the retaining area requires a means of positive
cut-off, preferably a concrete abutment fitted with a valve. A final
part of the system is somewhat optional. For example, the retaining
area could be provided with lime treatment facilities for
neutralization. In addition equipment for transfering this acid water
from the retaining area to a contaminated water holding or recirculating
system could also be provided. Plants 002 and 009 provide such systems
to control process leaks.
The procedure is that an acid break is detected by the water monitoring
instrument, located at the inlet of the cooling tower, and causes an
audible alarm to be sounded. It is preferable to also have the
instrument automatically activate the positive cutoff at the discharge
of the retaining area although this can be done manually. Activation of
this system in turn necessitates a plant shutdown to locate the failure
and initiate repairs. The now contaminated water in the retaining area
must then be either neutralized in the pond or moved to a contaminated
water storage area where it can be stored or neutralized through a
central treatment system.
Figure 19 depicts a sketch of the suggested treatment facilities. Such
a system provides continuous protection of natural drainage waters as
well as means to correct a process failure. The primary factor to
control is pH. Sufficient neutralization to raise the contaminated
water pH to 6 is required. Neutralization is preferably by use of lime.
Lime serves not only to neutralize the hydrogen ion concentration (low
82
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pH) but also removes sulfate (SO4) as an insoluble calcium sulfate
according to the following reaction:
H2SOU + CaO + H20 - ^.CaSO4 .2HO
Sulfuric Lime Water Calcium Sulfate
Acid
84
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GYE§li!D_P2S^_lContajninated) Water Treatrnent_
As described in Section V, all phosphate complex process effluents
(contaminated water) are collected and impounded. The impoundment
area,ranging in size frcm 65 to 570 hectares (160 to 1400 acres) serves
two functions. One function is as a storage area for waste by-product
gypsum from the phosphoric acid process. The second is as an area for
atmospheric evaporative cooling of the contaminated water prior to its
reuse back in the various process units. This pond system functions in
a closed loop mode the majority of the time. The time interval that it
can function as a no discharge closed loop system is dependent on the
quantity of rainfall it can accept before the water storage capacity is
exceeded. Once the storage area approaches capacity it is necessary to
begin treating the contaminated water for subsequent discharge to
natural drainage bodies.
Process Description
Contaminated water can be treated effectively for control of the
pollution parameters identified in section VI, namely pH, phosphorus,
and fluorides. Treatment is by means of a "double liming" or two stage
lime neutralization procedure.
At least two stages of liming or neutralization are necessary to effect
an efficient removal cf the fluoride and phosphate contaminants.
Fluorides are present in the water principally as fluosilicic acid with
small amounts of soluble salts as sodium and potassium fluosilicates and
hydrofluoric acid. Phosphorus is present principally as phosphoric acid
with some minor amounts cf soluble calcium phosphates.
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,
to a significant degree, dependent upon the mixing efficiency at the
point of lime addition and the constancy of the pH control. At a pH
level of 3.5 to 4.0, the fluorides will precipitate principally as
calcium fluoride (CaF2) as shown by the following chemical equation.
H2SiF6 + 3 CaO + H20 >3 CaF2 + 2 H.20 + SiO2
Fluosilicic Lime Water Calcium Water Silica
Acid fluoride
This mixture is then held in a quiescent area to allow the particulate
CaF2 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 compartmented mixer. Similarly 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
85
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again treated with lime sufficient to increase the pH level to 6.0 or
above. At this pH level calcium compounds, primarily dicalcium
phosphate plus additional quantities of CaF2 precipitate from solution.
The primary reactions are shown by the following chemical equation:
2 H3PO4 + CaO
Phosphoric Lime
Acid
Ca(H2PO4)2 + CaO
Monocalcium Lime
Phosphate
H20 >Ca (H2P04) 2
Water Monocalcium
Phosphate
H 20 > 2CaHP04
Water Dicalcium
Phosphate
As before, this mixture is retained in a quiescent
CaHPOU and minor amounts of CaF2 to settle.
2 H20
Water
Water
2 H20
Water
area to allow the
After settlement, the clear, neutralized water will contain 15-30 mg/1 F
and 30-60 mg/1 P at a pH of 6-8. The reduction of the P value is
strongly dependent upcn the final pH level and quality of the
neutralization facilities, particulary mixing efficiency.
Neutralization to pH levels of 9-11 will reduce P values to 15-30 mg/1
or less. Figure 20 shows a sketch of a well designed "double lime"
treatment facility. Plants 002, 007, 008, 009, 010, 014 and 019 all
practice some degree cf liming.
Laboratory and plant data for phosphorus and fluoride removal is
presented below:
PH
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
Phosphorus (mg/1)
laboratory plant
Fluoride (mg/1)
laboratory plant
500
330
200
120
20
3
1,
42
2*4
18
1*1
12
8
6
3
1.2
13
8.5
6.8
5.8
5.2
4.8
4.6
17
14
12.
12.
12,
12.
12,
12.
12.
12,
5
5
5
5
5
5
5
5
Although the starting concentrations are either arbitrary or specific to
that plant only, the data does show significant removal at high pH,
86
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87
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Up to this point, nothing has been mentioned about the pollutant ammonia
N in contaminated water. Any phosphate complex containing an ammonium
phosphate unit will probably have NH3-N in the contaminated water
system. "Double lime" treatment alone will not reduce the N quantity,
although at high pH (greater than 9.0), significant ammonia loss to
ambient air can occur. To date there is no proven means of economically
removing NH3-N from aqueous solutions having such weak concentrations as
20-60 mg/1. The best method to keep the NH3_-N contaminant level low is
tc prevent its entry into the main contaminated water system. More
about the manner that this can be done is discussed in the DAP self-
contained process discussion.
88
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Gypsum Pond_Water_Seepage Control
The contaminated (gypsum pond) water storage areas are surrounded by
dikes. The base of these dikes are normally natural soil from the
immediate surroundings. As the need develops to increase the height of
the retaining dikes, gypsum is dug from inside the diked area and added
to the top of the earthen base. Dikes in Florida now extend to a 100-
120 ft. vertical height. These combined earth/gypsum dikes tend to have
continual seepage of contaminated water through them. In order to
prevent this seepage from reaching natural drainage streams, it is
necessary to collect and re-impound it.
Seepage collection and re-impoundment (Plant 002) is best accomplished
by construction of a seepage collection ditch all around the perimeter
of the diked area. The seepage collection ditch needs to be of
sufficient depth and size to not only collect contaminated water seepage
but to permit collection of seepage surface water from the immediate
outer perimeter of the seepage ditch. This is best accomplished by
erection of a small secondary dike as depicted on Figure 21. The
secondary dike also serves as a back-up or reserve dike in the event of
a failure of a 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. In Florida, where the largest
number of phosphate complexes are located, the soil condition is such
that little, if any, vertical water percolation occurs. The soil at 4.5
7.5 meter (15-25 ft) depths is unconsolidated ancient beach sands
which lay on top of the underlying Hawthorne matrix deposit. This
Hawthorne matrix deposit is basicly a nonporous material made up of
impervious clay-sand-phosphate pellet mixture. Surface drainage or
impounded waters percolate down to this Hawthorne layer. Then, due to
the nonporous nature of Hawthorne layer, are forced to migrate
horizontally following the interface between the unconsolidated surface
soil and the Hawthorne layer. Some data suggests that the gypsum pond
bottoms tend to be self-sealing. 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
conclusion, the design of seepage ditches must consider the area geology
and the phreatic water level of the impounding dike material to achieve
an effective seepage control system. An installation of a pump station
at the low or collection point of the seepage ditch completes this
seepage control system. The pumps serve to move the collected seepage
water back into the contaminated water storage area. Normally these
pumps are operated only a few hours per day but this is entirely
dependent upon the seepage and rainfall conditions.
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Ammonium Phgspha-tegg If-Contained Process
It was mentioned in the "double lime" treatment description that the
best means of reducing NH3-N from appearing in the contaminated water
system was to prevent its entry into the water. NH_3-N enters the
contaminated water principally through the ammonium phosphate plant gas
scrubber system. A secondary entry point is by way of washdown or water
spillage into a surface drainage system. Both of these process waste
streams can be segregated along with the ammonium phosphate scrubber
waters from the gypsuir pcnd water system and can be either introduced
back into the process cr treated for ammonia removal prior to discharge
or inection into the gypsum pond.
One means of doing this is to adjust the in-process water balance to
permit the absorption of these collected NH3-N containing waters (Plant
001). 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. Normally 30-40% P205 phosphoric acid is required to
produce ammonium phosphates. It may be necessary to increase this
concentration to as high as 54% P.2O5. This is dependent upon the water
quantity to be absorbed and the acid concentration required to produce
the specific ammoniuir phosphate product. Figure 22 is a sketch of this
procedure.
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Wet Process Phosphoric Acid - Pond Water Dilution of Sulfuric Acid
General
The need to treat phosphate fertilizer process contaminated water is
almos-t entirely dependent upon the local rainfall/evaporation ratio.
This means that barring poor water management and concentrated periods
of heavy rainfall the complex fresh water use and pond water evaporation
are essentially in balance. Therefore, any means of making an in-
process change to significantly reduce 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.
There are two different methods to make an in-process phosphoric acid
process modification to permit the use of contaminated water for
dilution of sulfuric acid. Currently, the necessity of fresh water for
this dilution step represents approximately 50% of the total fresh water
intake to a phosphoric acid plant. Not only does use of contaminated
water for sulfuric acid dilution eliminate (except for extreme weather
conditions) water effluent from a phosphate complex, but the overall
~P2Q5 recovery of the phosphoric acid complex is increased by that amount
of P2O5 in the contaminated water.
Both methods of accomplishing sulfuric acid dilution with pond water are
proprietary. One method is considered a trade secret. The other is
protected by patent. Either process can be added to existent plants or
included in the design of a new facility.
The trade secret procedure involves two points. One is the mechanical
means by which the dilution is made so as not to create a pluggage
problem. The second involves redesign of the phosphoric acid reactor
cooling system to remove the heat load formerly removed by the sulfuric
acid dilution cooler (Fig. 23) .
The patented process was developed and has been placed in commercial
operation (44) .
It involves sulfuric acid dilution by a two-step procedure in a manner
radically different from current practice. The details of process
control, vessel design, and materials construction are all proprietary
information (Fig. 24).
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CCNTPQL^AND TREATMENT TECHNOLOGY
NITROGEN FERTILIZER INDUSTRY
Proven technology exists and additional technology is being developed,
which will enable the nitrogen fertilizer manufacturer, when used
properly, to attain the proposed effluent limitations.
Most of these treatment processes are reviewed in the following
paragraphs of this Section.
Ammonia Stripping
This treatment method can be used on process condensate, boiler blowdown
or cooling tower blowdcwn from ammonia plants, urea plants and ammonium
nitrate plants for the removal of ammonia from these streams. However,
due to the large volumes of cooling tower blowdown and the presence of
scale forming contaminants in cooling tower and boiler blowdowns this
method is best suited for the treatment of process condensate or
effluent from urea hydrolysis.
The stripping medium can be either air or steam depending on the desired
end use of the overhead vapors, the availability of a low level heat
sink and the local and national air pollution regulations.
1.Steam Stripping
There are a number cf ammonia steam stripping units in operation in
nitrogen fertilizer plants in this country. (Plants 006, 011, 015, 017,
020, and 024). These range from completely integrated process units
producing boiler feed water quality condensate to separate units
treating a process ccndensate effluent before discharge. The
concentration of ammonia in the condensate feed to the stripper varies
from 100 mg/1 to 1,300 ing/1 with the stripped effluent ranging from 5
mg/1 to 100 mg/1 giving reductions in some cases of better than 95%.
However, the best consistent results frcm an ammonia stream stripper is
in the range of 20 to 30 mg/1 and this is highly dependent on the amount
of steam supplied and the pH of the contaminated feed condensate. The
stripping of ammonia frcm water depends on how the ammonia exists in the
water. In neutral solutions ammonia exists as NH^t~ while at higher pH
(11 to 12) ammonia exists as dissolved NH3 gas. The following
equilibrium prevails:
NH4+ > H+ + NH3 (g)
H+ * OH •—^ H20
As the pH is increased towards 12.0 and as the temperature is increased
the reaction proceeds further to the right. Therefore, if the stripped
condensate is to be discharged, consideration to artificially raising
the pH with caustic should be made. If the condensate is to be reused as
boiler feed water then operation of the stripper at a higher temperature
(and pressure) would te the preferred design method.
96
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The design and operation of an efficient ammonia steam stripping system
is not simple or straight forward. Due to deviations from ideal
conditions, the stripping column requires considerably more transfer
units than theoretical tc produce a low residual ammonia level in the
stripped condensate (bottoms). One example of a separated condensate
stripping system which will produce a bottom condensate with a residual
ammonia concentration of 25 to 30 mg/1 has a process condensate feed
rate of from 8.8 to 10.7 I/sec (140 to 170 gpm). The stripper column
has a diameter of 0.915 meters (3 feet) and is 12.2 m. (40 ft.) high.
The column is packed with stainless steel Pall Rings.
A second ammonia steam stripping system, operating on process condensate
from an ammonia plant, employs two columns operating in parallel with a
total contaminated condensate feed of 7.6 I/sec (120 gpm). This unit
recently operated for a 22 day period producing a stripped condensate
effluent averaging less than 20 mg/1 ammonia while using slightly in
excess of .12 kg of steam/ liter (1 Ib. of steam/gallon) of condensate
fed.
A third steam stripping unit operating satisfactorily is completely
integrated with an ammonia plant. This stripping column takes process
condensate and steam turbine vacuum condenser condensate and steam
strips the ammonia to a level that is acceptable for boiler feed water
in a 102 atm (1500 psia) steam system. The trayed stripping column is
1.37 m (4.5 ft.) in diameter and about 12.2 m (40 ft.) high. Some
recent data indicates that this unit is handling some 41 I/sec (700 gpm)
of total condensate input. The effluent from the stripper has less than
5 mg/1 ammonia (Fig. 26). A fourth amrrcnia steam stripping unit that is
completely integrated within an ammonia plant is handling process
condensate and producing a stripped effluent that is acceptable for high
pressure boiler feed water. This plant has been in operation for more
than two years.
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COOLING
WATER IN
OUT
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HOT CARBONATE SYSTEM-
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STRIPPER
CONDENSER
AMMONIA
STRIPPER
\J
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STEAM
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CONTROLLED
VESSEL-
CONDENSATE
POSSIBLE CAUSTIC
ADDITION
IF DESIRED/REQUIRED
CONDENSATE
FEEDTANK
TO COOLING TOWER ~
TO SEWER ~
TO BOILERS-
TO RAW WATER
TREATMENT SYSTEM
FIGURE 25
AMMONIA/CONDENSATE STRIPPING
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2. Air Stripping
A considerable amount of work has been done on air stripping of ammonia
from waste water, but this has been in the field of municipal waste
water treatment. Although this process does have some drawbacks, it. is
worth mentioning because of its possible use in connection with nitrogen
fertilizer plant waste waters. The major drawbacks of air stripping are
the very low efficiencies in cold weather and the deposition of calcium
carbonate scale from the water on the column packing or internals
resulting in plugging.
On the other hand, test data and installation performance to date show
that the ammonia in the effluent air will not exceed 10 mg/m3 (13 ppmv).
The threshold limit fcr odor of ammonia is 35 mg/m3 (46 ppmv). With
this type of discharge there probably would not be any air pollution
problem.
As mentioned under steam stripping, temperature and pH have an effect on
the stripping operation. However, since temperature will be controlled
by the climatic conditions, pH must be controlled to assure complete
stripping.
Although most air stripping to date has been with contaminated waste
water with less than 60 mg/1 ammonia, the results obtained by using the
proper bed depth, the proper transfer medium and the proper surface
loading rate with good control of pH have given better than 90% removal
of the ammonia. The resulting aqueous discharge can have less than 5
mg/1 ammonia (Fig. 27).
Contrary to some reports, cooling towers are not good stripping units
for ammonia contaminated waters. Due to their construction and air flow
they are actually abscrbers of air-bcrne ammonia with the result that
their blowdowns may contain up to 50 mg/1 of ammonia.
100
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FAN
AIR OUT
AIR IN
WATER IN DISTRIBUTION
I BASIN
CATCH BASIN
'TYPICAL FILL
• BAFFLE (TYPICAL)
WATER OUT
FIGURE 27
AMMONIA/CONDENSATE AIR STRIPPING
From Slechta And Gulp 1967
101
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3 • High Pressure Air/ Steam Spriggin
One engineering firm (30) has proposed -the use of the process steam
required for the primary reformer or the process air required for the
secondary reformer as the stripping mediums for process condensate. In
each case, the stripping would be performed at medium to high pressure
(pressure high enough tc get into the primary or secondary reformer) .
This would require the process condensate to be boosted up to this
pressure, but if the condensate is then an acceptable boiler feed water
make-up there would be very little energy lost since boiler feed water
would have to be boosted to the boiler pressure anyway. The overhead
vapors, whether steam/ammonia or air/ammonia, could be be injected into
the primary or secondary reformers, respectively, without any expected
problems. Ammonia wculd be dissociated into its elements in either the
primary or secondary reformers and any carbon dioxide that might be
stripped from the condensate is present in the reformers anyway. Any
organic compounds which strip over should also be dissociated in the
reformers.
If the stripped condensate is not to be used at these high pressures
then it can be flashed to lower pressures in stages to release any
additional ammonia.
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Urea_HydrolYsis
This effluent waste water treatment system is designed to process
condensate from urea plants by converting the urea through a series of
intermediate products tack to ammonia and carbon dioxide. This process
is carried out at temperatures above 100°C (212°F) and under pressures
of up to 18 atm (250 psig). Following the conversion or hydrolysis, the
ammonia and carbon dioxide are stripped off and returned to the urea
process Plants 006 and 015.
One of the proprietary (40) variations of this treatment is presented in
Fig. 28. This flowsheet depicts a unit capable of treating 4.2 I/sec
(66 gpm) of process effluent, containing 4000 mg/1 urea and 3000 mg/1
ammonia. Aqueous discharge from this treatment unit will contain 100
mg/1 and 50 mg/1 of urea and ammonia respectively. Steam requirements
for this unit are 2200 kg/hr (4840 Ib/hr) of 19 atm (265 psig) steam and
4000 kg/hr (8800 Ib/hr) of 4 atm. (44 psig) steam. It is understood
that this unit will be offered commercially with a urea plant and a
guarantee will be given that the effluent will not contain more than
42.5 kg (85 Ibs) cf Org-N and 37.5 kg (75 Ibs) of NH3-N per 1000 kkg
(1000 ton) of urea produced.
A second proprietary urea hydrolysis system is available (41, 42) This
treatment unit has been installed in a urea plant in the spring of 1973
(Fig. 29). Although cnly limited information is available to date, the
new unit has with some difficulty processed the urea plant condensate
giving very mixed, but in some cases, good results. This medium size
installation is being modified from a control instrumentation standpoint
and is then expected to operate satisfactorily. Although this unit is
not completely operative yet, it is expected that, with continued
operating experience and future design modifications, this process will
be commercially available with respectable guarantees regarding ammonia
and urea levels in the effluent.
This unit consists of a steam heated vertical tower operated under
pressure, to which the contaminated condensate is fed. A feed-effluent
heat exchanger is included to conserve energy. The contaminants are
decomposed, stripped cff and recovered in the urea synthesis section of
the main plant.
A third type of urea hydrolysis treatment system is in operation at a
fairly large urea plant. The process was developed and installed by the
owner and therefore, very little detail is available. Data obtained
from this plant, however, does show that the hydrolysis unit is
operating very well.
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Biological Treatment^-_tjitrification and Denitrifjcation
This possible -treatment is based on the reaction of ammonia nitrogen
with oxygen in an aerated pond or basin tc form nitrates via biological
oxidation. The nitrates are in turn reacted in an anaerobic pond in the
presence of carbon to form elemental nitrogen. Although there has not
been any significant industrial use of this combination, municipal
wastes have been treated in this manner for years. Recently more and
more investigations into this type of treatment for industrial use have
been made (Fig. 30).
The first step-nitrification-takes place in the presence of aerobic
bacteria which convert the ammonia nitrogen to nitrates. This reaction
is promoted by the degree of aeration and warm temperatures. This step
can be carried out ir. a lagoon, pond or a trickling filter according to
the following equations:
2NH3 + 302 > 2NO2- + 2H+ + 2H2O
2NO2- + 02 >2NO3-
The denitrification step is an anaerobic process which occurs when the
biological micro-organisms cause the nitrates and available carbon to be
broken down into nitrogen gas and carbon dioxide. A portion of this
CO2, in turn, is broken down into carbon and oxygen to supply the
essential elements tc sustain anaerobic biological growth. The initial
breakdown of the nitrates requires that some amount of organic carbon be
present. This can be in the form of methanol in which case the
following overall reaction would occur:
6N03- «• 5CH30H- > 3N2 + 5CO2 + 7H20 + 6OH~
This reaction must be carried out in a pond, lagoon or tank under
anaerobic (all dissolved oxygen must be consumed) conditions. It is
essential that complete nitrification be obtained in a previous pond,
lagoon, etc. before the denitrification process starts; this usually
requires longer retention time and lower load factors than are found in
conventional activated sludge plants. Continuous addition of organic
carbon (e.g. methancl) and inorganic carbon (e.g. bicarbinate) to
accelerate the denitrification step rate is possible, but costs are
elevated accordingly.
The overall oxidation-reduction process functions best with initial
ammonia-nitrogen concentrations around 25 mg/1 but expected removals of
90% can be achieved with carefully controlled operations.
However, there are drawbacks, with by-products and side reactions which
can give rise to odorous compounds such as hydrogen sulfide plus the
ever present sensitivity to shock loads, e.g. ammonia spills, etc.
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Ion Exchange
Ion exchange is a unique effluent waste water treatment method in that
it not only removes the contaminants from the waste water but it can
also produce a useful end product. An ion exchange system may consist
of a cation unit, an anicn unit or both, this depends on the nature of
the ions to be removed from the waste water.
1 . Cation/Anion ^ Separation Unit
The first ion exchange system that will be covered is the integrated or
combined unit containing a cation resin column and a separate anion
resin column. This unit can be used for the treatment of waste waters
containing both ammoniunr ions and nitrate ions (Fig. 31) . The ammonium
nitrate contaminated waste water first flows through a bed of strongly
acidic cation resin operating in the hydrogen form. The ammonium ion
combines with the cation while the H+ icn combines with the nitrate ion
to form nitric acid.
NH4NOJI + R2!H+ - ^R2NH4 + HNO3
The acidic waste water, minus the ammonium ion, then passes through a
bed of weakly basic anion resin where the nitrate ion combines with the
resin and water is fcrmed.
HNO3 + R2OH - > R2NC3 + H2O
The effluent water from this second bed is low in ammonia and nitrates
and can then be discharged or reused within the plant as make-up boiler
feed water, cooling tcwer make-up or recycled back to the raw water
treatment unit.
Each of the ion exchange resins must be regenerated. The cation resin
holding the ammonium ion can be regenerated using nitric acid to form
ammonium nitrate solution and a regenerated strongly acidic cation
resin. The anion resin holding the nitrate ion is regenerated using a
solution of ammonium hydroxide. This will form more ammonium nitrate
and a regenerated weakly basic anion resin. The major difference
between the incoming waste water and the regenerate by-product is that
the latter has a 10% to 20% concentration of ammonium nitrate versus a
few hundred mg/1 in the raw waste water. This means that, depending nn
available fertilizer products on site, this by-product may be used as is
or it may be concentrated for sale.
A continuous unit, similar to that above, is operating at Plant 022.
Information to date indicates that both the ammonium ion and the nitrate
ion are being removed to levels fcr ammonia-N of 12 to 50 mg/1 and for
nitrate -N of 6 to 40 mg/1 for a waste stream of one million gallons per
day.
2 • Selective Ion Ex change^f or _Ammonia Removal
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Although this treatment process has not been industrially installed
there has been enough testing to indicate that greater than 90% of
ammonia nitrogen can be removed from waste streams containing
approximately 25 mg/1 ammonia. This process (43) is based on a natural
zeolite ion exchange resin clinoptiloite. The resin can be regenerated
with lime slurry yielding an alkaline aqueous ammonia solution, that can
be air stripped to reirove the ammonia. The stripped slurry can then be
recycled to regenerate more zeolite. The regeneration of the
clinoptilolite can be improved by the addition of sodium chloride to the
recirculated lime slurry.
Qil_Separation
Oil and grease in waste water effluents from nitrogen fertilizer
complexes can be a problem especially when large rotating machinery,
such as reciprocating compressors in small ammonia and urea plants are
in use.
Oil and grease can te removed from the waste water effluents to levels
below 25 mg/1 in properly designated A.P.I. Separators (Fig. 32) . To
assist in the design of these separators, The A.P.I, in Washington,
D.C., has published "Manual on Disposal of Refinery Wastes." The
information contained in this manual is applicable to nitrogen plants
effluent waste water. Plants 003, 016 and 022 practice oil removal
treatment of their waste streams. Oil and grease from many such sources
can be kept out of the effluent by housekeeping techniques at the
source. This can be accomplished by such containment devices as drip
pans.
Ammonium Nitrate Condensate Reuse
Flashed vapors from the neutralizer carry with them ammonia, ammonium
nitrate and some oxides of nitrogen. Partial condensation of these
vapors results in a contaminated condensate that requires treatment
before discharge.
One possible "treatment" method for this condensate stream is to collect
it and use it as the absorber feed in the associated nitric acid plant.
Refer to Figure 33 for a process description of this treatment method.
Such use would create an internal recycle of streams from this
condensate waste in which both the airmonia and nitrate values would be
recovered, i.e. overall yields for both the ammonia and nitric acid
units increased in terms of product ammonium nitrate.
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SECTION VIII
COST, ENERGY AND NON-WATER QUALITY ASPECT
General
A detailed cost analysis of the various treatment methods pertaining to
the fertilizer industry have been summarized in the tables of this
section.
The costs discussed are listed under subcategories as follows:
(1) Phosphate Table 2
(2) Ammonia, urea, ammonium Table 3
nitrate and nitric acid
All investment cost figures and related annual costs have been
reported in August 1971 dollars.
The treatment technologies summarized in some cases may be utilized
in series with each ether to meet more advance levels of control.
Water Effluent Treatment_Cost Tables
An explanation of the water effluent treatment cost tables is set forth
to aid in understanding the magnitude of the figures set forth therein.
Investments
This includes the traditional expenditures, such as design; purchase of
land and materials; site preparation; construction and installation;
plus those additional expenditures necessary or required to place the
treatment method into operation including expenditures for related or
needed solid waste disposal. Because of the broad general scope,
methods and processes covered, nothing has been shown in the investments
for losses due to downtime; i.e. production halts needed to install
pollution abatement equipment. This is treated separately.
Interest on Money
This is more or less self-explanatory. It is the cost of the money used
for investments on an annual basis.
Depreciation
There are numerous methods of accounting and depreciating equipment.
Because of the nature cf the treatment technology and the way it may be
installed for utilization, all capital is depreciated over a ten year
period by the straight line method.
Maintenance costs
113
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This is exclusive of energy and power which has been covered under a
heading of its own. Costs here include materials, insurance, taxes,
solid waste disposal, operating labor and maintenance.
It is anticipated that iraintenance , as it is normally thought of in most
processes, will be lower for the add on technology to achieve pollution
abatement. Therefore, the costs are adjusted accordingly to reflect a
lower maintenance cost.
Energy_and Power Costs
Costs for energy and power include such items as electricity and steam
for pumps, agitators and evaporators/heat exchangers.
Ef f luent Qual i ty
The items covered are the expected parameters of the resulting effluent
after the pollution abatement technology has been installed and placed
into operation.
The raw waste load flew has been given in liters per second and gallons
per minute. Effluent level parameters are given in units of milligrams
per liter and kg/kkg cf product where appropriate.
Supplemental Data
This heading is for miscellaneous data that is considered useful in
understanding or using the tables. All items are identified as to their
nature or use.
Operation __ of .Treatment ^Methods
It is difficult to show exactly how much will be involved in an
installation. This is attributed to the fact that no two plants are
exactly alike nor would they require the same amount of work, equipment
and land to be installed. However, hypotheses have been made in order
to permit reasonable estimations as to the time and effort involved.
All plants are of 900 kkg/day (1000 tons/day) and for the main part,
considered to be existing plants. The explanation for these items are
covered in order for Tables 2 and 3.
Since there is so much variation in time for certain types of work to be
done and equipment to be shipped, a total possible elapsed time will be
given under each treatment method. This time span will include:
engineering, procurement and construction.
Also listed separately, as it applies, will be the amount of downtime to
make equipment tie-ins and length of time for start-up and placing the
unit(s) into operation.
114
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Phosphate Subcategory (Table 2)
Sulfuric_Acid Effluent_Control
Total elapsed time fcr engineering, procurement and construction should
be five months.
It should be possible tc arrange for this work to be accomplished and
put into service with nc downtime to the plant operations.
No start-up is required for this item. It should be noted that as an
alternate the effluent may be discharged back to a retention pond or
gypsum pond until control has been restored.
Pond Waterjrreatment
The elapsed time for this method in engineering, procurement and
construction should be about fifteen to eighteen months.
There should be no need to shut any plant down to install or make tie-
ins of this method of treatment.
For start-up and operations to be stabilized it will take approximately
one twenty-four hour day of continuous operation.
Gypsum Pond Water Seep_age_ContrQl
Since this is only a secondary dike arrangement it should not interfere
with plant operations both in construction and placing pump system into
service.
Construction time is considered the prime requirement here. The work
around a 80-100 hectare (200-250 acre) pond area should be accomplished
in ten weeks. It is not anticipated that much start-up time will be
consumed to start the pumps, so time for this effort will not be
considered.
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DAP Self Contained Process
This system is one that is considered to be existing and will require
installation of an evaporator and related auxiliaries to concentrate the
feed acid stream. This creates the negative water balance necessary, to
utilize the water from the local area.
Engineering, procurement and construction time should be about twelve
months.
The system can be pre-ccnstructed ready for tie-in. Only one eight-hour
day will be required to tie the unit in. If this work is scheduled
around a routine wash day in the phosphoric acid plant there will be no
downtime in production.
The start-up and operations should be done and the unit stabilized in
approximately twenty-four to forty-eight hours.
Operational coverage for this unit should be no more than one half a man
per shift at an annual cost of approximately $UO,000 to $46,000.
Pondwater Use For Sulfuric Acid_Dilution (Internal Method)
There are two types of costs listed here. One is for adding to an
existing system and the ether is for a new plant installation.
The time required for a new plant installation is not involved with
causing a plant shutdown for tie-in; therefore, it will not be
considered for engineering, procurement and construction. Similarly it
is not considered for start-up or operations.
Time required to revise an existing plant is rather complicated and
complex. The hard part of this job is installing a new larger flash
cooler system in place of the existing flash cooler system.
The entire elapsed time for engineering, procurement and construction
should be about six tc eight months.
After considerable pre-fabrication has been completed, the plant will
then have to be shut down for three to four weeks of intensive change
out work on the equipirert.
This type work could be planned and executed around an annual turn
around which would reduce the unproductive plant downtime to one to two
weeks.
The new system would be so similar to the existing system that there
should be no additional time required for start-up and operation of the
modified system.
One other alternative for the installation would be to set up a new
adjacent structure and pre-construct everything. The plant downtime
could be cut to about four days tie-in time.
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This again could be scheduled around an extensive maintenance program,
such as an annual turnaround. By so doing there would be no lost
production from the plant.
Sulfuric_Acid_Diluticn_With_Pond^Water
This system can be engineered, procured and constructed in about fifteen
months.
It should be possible tc have the system prefabricated and constructed
so very little time will be required to make tie-ins. The anticipated
tie-ins should be accomplished in eight to ten hours.
There will be no start-up time involved and the unit should be
stabilized in twenty-four hours of continuous operations.
It is believed that there will be no requirement or need for extra
operating personnel tc cover this method of treatment.
Nitrogen Fertilizer gubcategorjes (Table - 3)
Ammonia/Condensate_Stri£Eing
Time for engineering, procurement and construction is eight months.
The system should be completely prefabricated and constructed so that
plant shut-down time will be no more than three to four hours.
The start-up of this unit can be done very slowly and easily with no
more than twenty-four hours involved to stabilize the unit. During this
time of stabilizing operations the rest of the plant should function
normally.
There is no known need to add more operating personnel to monitor this
unit.
Integrated Ammonia/Cgndensate Stripper Unit
The only work involved here is installing the ammonia condensate
stripper and piping it to the existing points for tie-in.
Engineering, procurement and construction time should be about eight
months to have the unit prefabricated and installed prior to tie-in.
The plant will be shut dcwn about six to ten hours to make tie-ins.
The start-up and operation should be very similar to that mentioned for
ammonia/condensate stripping. There is no need for extra personnel to
give this unit coverage.
AmroiLia/Condensate Air
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The easiest way to explain this system is to say that it is very similar
to a cooling tower. To design, procure and construct such a unit can be
from twelve to fourteen months.
The tie-in to the plant will require about twelve to twenty- four hours.
Also there is no anticipated need for extra personnel to operate this
unit.
Proprietary J40} _ Ur e a H ydr gl ys is
The design engineering, equipment procurement and construction should be
completed in approximately ten months.
The plant will be shut down for equipment tie-ins for about twelve to
thirty-six hours.
This treatment method is a little more complex. Therefore, it is more
involved to start up. The unit is brought on line simultaneously as the
plant start up, but to gain positive and stable control of the unit
could vary from twelve to thirty hours.
The unit in the early stages of start-up and operation could involve one
half to one man per shift. When the unit becomes checked out and the
operators educated as to the operations of the unit the extra personnel
may be phased out. This increased need may exist for four to six weeks.
The cost of extra coverage could vary from $4,400 to $12,500.
The unit is not considered complex and should take about ten to twelve
months for design, procurement and construction .
The tie-in of the unit should involve no more than six to eight hours of
down time for the plant .
When the unit is ready it will come on line when the plant is started.
Although the operator may not become very involved during the start-up,
the unit will require increased monitoring until the operating and plant
personnel are familiar with the unit and its limitations. This could
involve one half to one man per shift for two to four weeks. After the
unit is stabilized the extra personnel may be phased out.
The increased operating surveilance could amount from $2,000 to $9,000.
Biological_Treatment __ JNitrif ication-Denitrif icationj_
Design, procurement and construction time could be twelve to fourteen
months.
There is not enough start-up time involved to be considered. However,
there will be monitoring time involved during the normal unit
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operations. It is estimated that about one quarter of a man will be
utilized at an approximate cost of $19,000 to $20,000.
Ammonium_Nitrate.Removal^by Ion Exchange
This system is somewhat more complex and involved than most of the
treatment methods discussed thus far.
To design, procure and construct the ion exchange system will take from
fourteen to sixteen months.
The start-up and operation of this unit to date has experienced some
difficulty; mainly mechanical. This makes it somewhat difficult to
delineate the exact needs for operation of future installations.
It is anticipated that two persons per shift will be required to operate
the unit. The cost of such labor will be approximately $145,000 to
$160,000 on an annual basis.
Qil/Grease_RemQval
The oil/grease removal systems may be used as1 single units or in
series. For this study they are used in series.
To design, procure and construct such a unit would take approximately
eight months.
There is no start-up and operation time involved so this is not
considered. It is not felt that these units will require additional
personnel to monitor or operate them.
Ammoniuni_Nitrate Effluent^ytilization
There is not much involved in this system. It should take about eight
to ten months to design, procure and construct the modified system.
The plants should be down not more than two to three hours for the final
equipment tie-ins.
This system is unique in its possible mode of operation. It must be so
designed to enable the ammonium nitrate and nitric acid plants to
operate independently of one another or in tandom with one another. The
start-up of either unit should require a few minutes to set up and
initiate. The switching from one unit to the other should be very easy
and quick to execute with no ill effect on the operations of the nitric
acid plant.
With the above in mind, no time is considered for start-up and operation
of the system.
There is no increase in requirements for operating labor.
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Non-Water Quality Aspects of Treatment and_Control_TechnolQgies
Phosphate Fertilizers
The treatment and control technology proposed for use by the phosphate
fertilizer industry to meet the guidelines does not have any deleterious
non-water quality aspects. There are no air pollution, noise pollution
or identifiable solid waste disposal problems associated with the
proposed waste water treatment methods.
Containment of contaminated recirculated (gypsum) water must not be
accomplished with fluorine loses from scrubbers or ponds. Nor must
containment be achieved by percolation to ground waters (or horizontal
subsurfact loses).
Nitrogen Fertilizers
There is one possible and one real air pollution control problem that
may exist with some treatment methods. At present, there are no air
pollution regulations on ammonia. When considering the ammonia
stripping process using either air or steam, one must be concerned about
where the ammonia is going, most of the time into the air. Tests have
shown that with air stripping, the off gas concentration contains less
than 10 mg/m3 (13 ppmv). Since the threshold odor for ammonia is about
35 mg/m3 (46 ppmv) there would not be any noticeable odor around the
stripping operations. The maximum allowable OSHA concentration of
ammonia in air (on a time weighted basis) is 35 mg/m3 (46 ppmv). Since
this also is greater than the expected gas effluent and surrounding air
concentration, air/steam stripping of ammonia is not expected to cause
any air pollution problems.
Although the anaerobic (without free oxygen) denitrification process has
been used for years, especially in the municipal sewage treatment
plants, it is a process that tends to be more of an art than a science.
The operations of an anaerobic treatment of denitrification pond can
take a great deal of care. The internal reaction occurring can lead to
the formation of hydrogen sulfide if there is any sulfur present that
can create an odor problem. Therefore, care should be taken when
considering the installation of a denitrification pond as to the
location of the plant site in relation to the wind direction and the
nearest town or inhabitants.
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SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
"AVAILABLE
GUIDELINES AND LIMITATIONS
INTRODUCTION
The effluent limitations which must be achieved by July 1, 1977 are
based on the degree cf effluent reduction attainable through the
application of the best practicable control technology currently
available. For the fertilizer manufacturing industry, this level of
technology is based on the best existing performance by exemplary plants
of various sizes, ages and chemical processes within each of the
industry's categories. In some cases where no truly exemplary plants
were surveyed, this level of technology is based upon state-of-the-art
unit operations commonly employed in the chemical industry.
Best practicable control technology currently available emphasizes
treatment facilities at the end of a manufacturing process but also
includes the control technology within the process itself. Examples of
in-process control techniques which are used within the industry are:
*manufacturing process controls *recycle and alternative uses of
water *recovery an/cr reuse of waste water constituents *dry
collection of airborne solids instead of (or prior to) wet
scrubbing.
Consideration was also given to:
a. The total cost of application of technology in relation to the
effluent reduction benefits to be achieved from such
application;
b. The size and age of equipment and facilities involved;
c. The process employed;
d. The engineering aspects of the application of various types of
control techniques;
e. Process changes;
f. Nonwater quality environmental impact (including energy
requirements) .
PROCESS WAgTE^WATER, GUIDELINES
Process waste water is defined as any water which during the
manufacturing process, comes into direct contact with raw materials,
intermediates, products, by-products, or gas or liquid that has
accumulated such constituents. All values of guidelines and limitations
are expressed as consecutive 30 day averages in units of kilograms of
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parameter per metric ton and pounds of parameter per 1000 pounds of
product produced except where they must be expressed as a concentration.
Maximum daily values are also presented.
Based upon the informaticn contained in Sections III through VIII of
this report, the following determinations were made on the degree of
effluent reduction attainable with the application of the best
practicable control technology currently available to the fertilizer
manufacturing industry.
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PHOSPHATE SUECATEGORY
GENERAL DESCRIPTION
The survey (described in detail under Section III) of designated
exemplary phosphate fertilizer plants was conducted to determine the
levels of contaminants being discharged together with the in-process
and/or treatment methods used. Results of this survey revealed that
isolated data from particular phosphate fertilizer plants is subject to
many interpretations. It is absolutely essential that the circumstances
and conditions surrounding effluent data be known in detail by a person
knowledgeable in the industry, if meaningful guidelines and limitations
are to be established. This point is of particular importance in the
phosphate fertilizer processes due to the only periodic need to treat
and discharge process waste waters. Such need is primarily a function
of climatic conditions ever which there is no human control. In turn
this practically prohibits a guideline or limitation which relates the
allowable amounts of contaminant discharge to plant production.
Best Practicable Control Technology_Currentlv Available includes^
A. Sulfuric Acid__Plant Effluent Control
This effluent control and treatment technology is in current
industrial use. The technology is primarily one of preventing
contamination of natural drainage water from accidental equipment
break or operator error. It provides for a monitoring system to
signal that an emergency exists followed by facilities for
contaminated water isolation and subsequent treatment. A more
detailed discussion of this technology is included in Section VII.
B. Gypsum Pond (Contaminatedj Water_Treatment
The "double liming" treatment for gypsum pond (contaminated) water
has been in common use for some 15 years. There is little that is
not known about the treatment capabilities and limitations.
C. Ammonium PhQSphate_self-Contained^Process
This technology serves to essentially remove ammonia N as a
contaminant in phosphate fertilizer process effluent. The treatment
is an in-process change which adjusts the process water balance to
permit absorption of all process effluent back into the process.
Principally, this is accomplished by a combination of reducing
process effluent quantity to a minimum followed by an increase in
the phosphoric feed acid concentration to a level which will permit
reuse of the effluent. such technology may require additional
phosphoric acid concentration facilities to maintain existing levels
of production and product mix. A limited number of production
plants are currently practicing this technology.
Even when the self-contained process is utilized, current practice is to
discharge leakage, spills, and washout wastes to the gypsum pond. This
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is considered unsatisfactory. To meet the best practicable control
technology currently available, segregation and treatment of these
additional ammonia-N waste waters will be necessary. Appropriate
technology for such ammonia removal has already been discussed in
Section VII. A possible alternative not discussed in detail is
precipitation of the ainircnia as magnesium ammonium phosphate.
Proposed Effluent Limitatipns^Guidelines
The proposed effluent limitation representing the degree of effluent
reduction attainable through the application of the best practicable
control technology currently available tc the phosphate subcategory is
no discharge of process waste water pollutants to navigable waters. A
discharge is allowed under the following conditions:
1. A process waste water impoundment which is designed,
constructed and operated so as to contain the precipation from the
10 year, 24 hour rainfall event as established by the U.S. National
Weather Service fcr the area in which such impoundment is located
may discharge that volume of precipitation that falls within the
impoundment in excess of that attributable to the 10 year, 24 hour
rainfall event, when such event occurs.
2. During any calendar month in which the precipitation exceeds
the evaporation fcr the area in which a process waste water
impoundment is located, as established by the U.S. National Weather
Service (or as otherwise determined if no monthly evaporation data
have been established by the National Weather Service) for the area
in which such impoundment there may be discharged from such
impoundment either a volume of process waste water equal to the
difference between the precipitation and the evaporation for that
month or a volume of process waste water equal to the difference
between the mean precipitation that falls within the impoundment and
the mean evaporation for that month as established by the U.S.
National Weather Service for the preceeding 10 year period,
whichever is greater.
3. Any process waste water discharged pursuant to subparagraph (2)
above shall not exceed each of the following requirements:
Parameter Maximum daily Maximum average of daily
concentration values for periods of discharge
covering 10 or more consecutive days
mg/1 mg/1
phosphorus as(P) 20 10
fluoride as (F) 30 15
nitrogen as (N) 10 5
total suspended
nonfilterable
solids 30 15
The pH of the water discharged shall be within
the range of 6.0 to 9.0 at all times.
Rationale for Best^Practicable Control Technology Currently Available
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The criteria used for selection of the treatment technology was
information obtained at each listed exemplary plant through sampling;
inspection and review of plant operations; collection of validated
historical effluent data; and direct discussions with responsible plant
operational personnel fcr positive definition of treatment methods and
analytical procedures. Additional information was gathered from
technical literature, direct contacts with experts and consultants, and
discussions with vendors of treatment equipment and services.
consideration was also given to application of industry transfer
technologies for specific contaminant treatment.
The proposed limitations are based on composite (not grab) sampling and
years of historical effluent data. These limitations represent values
which are being achieved by the better exemplary plants surveyed.
The proposed effluent limitations for fluorine, phosphate, nitrogen and
pH represent an unusual effluent situation which warrants further
discussion. Several factors need to be recognized. One is there is
only a periodic need for effluent treatment and discharge. This need
essentially always results from excessive rainfall.
Another factor is the treatment limitations. Particular reference is to
the residual P and N levels after even the second lime neutralization
step. The degree of P reduction is a function of pH level. At a pH of
6 the residual P in the treated water will range 30-60 mg/1. Additional
neutralization (third stage) to raise the treated water pH to 9-11 will
effect a P level reduction to the 15-25 mg/1 range.
Ammonia-N also is a particular problem. Even though the best
practicable control technology currently available includes the ammonium
phosphate self-contained process, there is still an N accumulation in
the contaminated gypsum pond water system. The sources of this N are
absorption from the atmosphere by contaminated water sprays in other
process units and also from a variety of non-point sources. One complex
which has been utilizing the self-contained ammonia phosphate technology
has observed N concentrations in the range of 25-66 mg/1 in the
contaminated gypsum pond water. The N concentration is a function of
the discharge frequency with the higher values observed during those
periods when no discharge of effluent is made from the contaminated
water treatment system. Such periods are normally of 8-10 months
duration per year. An ammonia N limitation is therefore still required.
The primary source of sulfate introduction to the effluent stream is
from the sulfuric acid cooling coils. Traditionally, these have been
cast iron coils which develop small cracks plus the hundreds of
connection joints which are subject to small leaks without being
detectable. New sulfuric acid cooling equipment such as stainless steel
heat exchangers with cathodic protection and teflon type heat exchangers
are now finding increased industry acceptance. Such units are
considered more reliable and less leak-prone than the cast iron units
currently in universal use.
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NITgOGEN_FEgTILIZEg_INDySTRY
GENERAL^DESCRIPTION
The survey (described in detail under Section III) of exemplary nitrogen
fertilizer plants was conducted as part of this project to determine
what level of contaminants was in the effluents from these plants and
what were the treatment methods in use to maintain these levels. The
results of this survey revealed that none of these exemplary plants were
operating within the interim guidelines established by EPA. However,
the survey also revealed that there were a number of errors in the
preliminary information used by the EPA in establishing these interim
guidelines. Therefore, a second review cf this survey data did indicate
that there were some process plants which could be considered exemplary.
Verifying the present treatment methods in use and those treatment
methods that are still being developed, the following technology is
considered to be the best practicable and currently available which is
needed to meet the 1977 requirements:
Best Practicable_Controj._TechnolQgy^Currently Ayailable^Includeg:
A. Ammonia Steam Stripping
This treatment technology is in operation today in the plants whose
effluents are within the newly proposed guidelines for ammonia-N.
Although each nitrogen fertilizer complex is different, steam
stripping of ammonia contaminated waste water is the best
practicable method of control.
B. yrea_HYdrolysi s
This type of technology is used in various forms and to various
degrees in urea plants today to give an effluent waste water that
will meet the newly proposed ammonia-N guidelines. Although some of
these hydrolysis units are company designed, commercial units that
will meet the proposed effluent limitations are available.
C. lon_
Although this treatment technology has not been proven completely on
a full scale operation, it does represent the best technology
currently available. The ammonium nitrate by-product may have to be
concentrated and sold as is, rather than blending as is presently
being tried.
D• Qil_SeparatiQn
Design technology for API oil separators has been used effectively
for years and can now be applied to the nitrogen fertilizer industry
to help meet the guidelines.
.Ef f luent_Limitations_Guidelines
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The following guidelines are recommended as the effluent waste water
limitations for the ammcnia, ammonium nitrate, nitric acid, urea and
subcategories.
Parameter
NH3-N
Organic N
N03-N
Oil & Grease
Ammonia
kg/kkg of product 0.063
(lb/1000 Ib)
kg/kkg of product
(lb/1000 Ib)
kg/kkg of product
(lb/1000 Ib)
kg/kkg of product 0.0125
(lb/1000 Ib)
Subcategory
Urea Ammonium Nitrate
0.0375
0.05*
0.0625
0.125*
0.05
0.0625
*Effluent limitations fcr urea plants that prill their product.
The above limitations apply to the maximum average of daily values for
any period of 30 consecutive days. The daily maximum average is twice
the 30 day maximum average. pH shall be within the range of 6.0 to 9.0
at all times.
recommended for the
No discharge of process waste water pollutants is
nitric acid subcategory.
Rationale S Assumptions_for Selection of Technology
The guidelines used fcr selection of the treatment technology which is
required to meet the proposed 1977 effluent limitations have been based
on material obtained through sampling, data taking, information
gathering, and direct conversation with plant operating personnel at
each and every plant contacted on the exemplary plant survey.
Additional information in the form of available literature, direct
contacts and vendor contacts was also considered. Treatment methods
which are being successfully used in other industries were analyzed for
their possible service tc the fertilizer industry.
The proposed limitation numbers are based on the best judgment of what
is reasonably obtainable after careful analysis of time weighted data
over periods of up to two years. These guideline numbers do represent
effluent levels that have been met by some of the exemplary plants and
can be conformed with by any of the nitrogen fertilizer plants which
will employ best practicable control technology currently available.
Ammonia steam stripping is one treatment method which is being used by
the fertilizer industry successfully at a number of locations. However,
ammonia steam stripping is also in use in the petroleum industry. Steam
stripping of ammonia has the drawbacks of what to do with the ammonia.
Under present circumstances, it is proposed that this ammonia be vented
to the atmosphere either through the carbon dioxide stripper, reformer
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stack, or an off site boiler stack. The ammonia concentration in the
gases from these stacks is not expected to be above 35 mg/m3 (46 ppmv)
which is the threshold odor limit for ammonia and, therefore, should not
present an air pollution problem. The urea hydrolysis units that are
operating in the industry can produce an effluent which is acceptable
for the currently proposed guidelines. Existing units have had some
mechanical problems but these problems can be solved with improved
engineering and additional operating experience. Also there are a
number of contracting companies who will offer this treatment method.
The basic ion exchange process is capable of performing the waste
treatment necessary to meet 1977 guidelines; however, further
development is necessary to completely automate and control the process.
Even though the ammonium nitrate by-product may not be completely
acceptable to each manufacturing and retailing location, it can be con-
centrated for a nominal expense and marketed at a reduced cost.
The petroleum industry for years has been using oil separators for waste
water streams. This type of treatment technology can very easily be
transferred from one industry to another. The design manual published
by the American Petroleum Institute - Manual on Disposal of Refinery
HSSi§Sx. Volume on Liquid Wastes^ gives all necessary design information
for an efficient oil separation device.
The pH of any effluent waste water stream should be between 6.0 and 9.0.
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SECTION X
BEST AVAILABLE TECHNQLOGY^ECQNOMICALLY
ACHIEVABLE
INTRODUCTION
The effluent limitations which must be achieved by July 1, 1983 are
based on the degree of effluent reduction attainable through the
application of the best available technology economically achievable.
For the fertilizer manufacturing industry, this level of technology was
based on the very best control and treatment technology employed by a
specific point source within the industrial category or subcategory, or
where it is readily transferable from one industry process to another.
Best available technology economically achievable places equal emphasis
upon in-process controls and control or treatment techniques employed at
the end of a production process.
Those plant processes and control technologies which at the pilot plant,
semi-works, or other level, have demonstrated both technological
performances and economic viability at a level sufficient to reasonably
justify investing in such facilities were also considered in assessing
best available technology economically achievable. This technology is
the highest degree cf control technology that has been achieved or has
been demonstrated to be capable of being designed for plant scale
operation up to and including nc discharge of pollutants. Although
economic factors are considered in this development, the costs for this
level of control reflect the top- of-the-line of current technology
subject to limitations imposed by economic and engineering feasibiligy.
However, best available technology economically achievable may be
characterized by some technical risk with respect to performance and
with respect to certainty of costs. Therefore, this technology may
necessitate some industrially sponsored development work prior to its
application.
The following factors were taken into consideration in determining best
available technology economically achievable:
a. The age of equipment and facilities involved;
b. The process employed;
c. The engineering aspects of the application of various types of
control techniques;
d. Process changes;
e. Cost of achieving the effluent reduction resulting from
application of best available technology economically
achievable
f. Non-water quality environmental impact (including energy
requirements).
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PROCESS WASTE WATER GUIDELINES
Process waste water is defined as any water which, during the
manufacturing process, comes into direct contact with raw materials,
intermediates, products, by-products, or gas or liquid that has
accumulated such constituents.
Based upon the information contained in Sections III through IX of this
report, the following determinations were made on the degree of effluent
reduction attainable with the application of the best available control
technology economically achievable in the various subcategories of the
fertilizer manufacturing industry.
PHOSPHATE_SUECATEGQRY
Best available technology economically achievable includes:
Wet_Process PhQSp-horic_Acid_-_JPgnd Water Dilutionmof Sulfurjc Acid
This technology serves to insure a negative water balance in a
phosphate fertilizer complex. That is, there will always be need
for fresh water addition to the process units under the assumption
that reasonable water management is practiced. With a negative
balance, no discharge is required except under extreme weather
conditions in which the recirculating water containment volume is
exceeded.
The treatment involves an in-process change in the procedure for
diluting sulfuric acid. Two different methods have been developed
to circumvent the problems of equipment pluggage formerly
experienced when contaminated (gypsum pond) water was used for such
dilution. As previously mentioned, both of these methods are
proprietary but are commercially available.
Propoged_Best_Ayailable Technology Economically Achievable
The proposed effluent limitation representing the degree of effluent
reduction obtainable by the application of the best available technology
economically achievable is no discharge of process waste water
pollutants to navigable waters. A discharge is only allowed under the
following condition. A process waste water impoundment, which is
designed, constructed and operated so as to contain the precipitation
from the 25 year, 24 hour rainfall event as established by the U.S.
National Weather Service for the area in which such impoundment is
located, may discharge that volume of precipitation that falls within
the impoundment in excess of that attributed to the 25 year, 24 hour
rainfall event, when such event occurs.
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RATIONALE FOR BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
The use of the best, available technology economically achievable on
sulfuric acid dilution in a phosphoric acid plant is to a degree not
proven commercially in the U.S. This is also true of both the described
processes. There is, however, sufficient industrial experience,
confidence, and warranty available en one of the treatment methods to
justify its incorporation into the design of three large new units which
will come on stream in 1974. The other method has had a unit very
similar to the patented method in commercial operation for approximately
two years. The unit new in operation is a more refined version of the
same process and has proven its ability to function well by use of
correct construction materials. Both methods are considered to be
technically proven and viable technologies.
The use of pond water for sulfuric acid dilution reduces fresh water
consumption by approximately 50* in a phosphoric acid plant. It also
provides an attractive financial payout on phosphoric acid operating
efficiency by reclamation of water soluble PJ2OJ5 values in the gypsum
pond water. It is also possible through better reclamation procedures
of uncontaminated steair condensate streams to make the negative fresh
water balance even more negative.
Based upon the above discussion regarding best available technology
economically achievable, it is considered practical and economical to
establish a no discharge limitation on phosphate complex effluent.
NITROGEN FERTILIZER INDUSTRY
The following technology is considered to be the best available
technology economically achievable:
A. Ammonia steam stripping followed by either high flow ammonia air
stripping or biological nitrification-denitrification. This
combination can be designed to keep the ammonia nitrogen well within
the 1983 guidelines.
B. Improved continuous ion exchange followed by denitrification. This
treatment system can provide the technology to maintain the nitrate
nitrogen within the effluent guidelines.
C. Advanced urea hydrolysis followed by high flow ammonia air
stripping. The urea hydrolysis technology is fast improving and
will be capable of meeting the proposed guidelines.
Proposed Ijest Ayailable_TechnQlQgy Econcmically^Achieyable
The following guidelines are recommended as the effluent waste water
limitations from the ammonia, nitric acid, urea and ammonium nitrate
subcategories:
133
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Parameter Units
Ammoniuin Nitrate
NH3-N kg/kkg of product 0.025 0.015 0.0075
(lb/1000 Ib)
Organic N kg/kkg of product - 0.025
(lb/1000 Ib) 0.0375*
N03-N kg/kkg of product - - 0.0125
(lb/1000 Ib)
Oil 6 Grease kg/kkg of product 0.0125
(lb/1000 Ib)
* Effluent limitations for urea plants that prill their product.
The above limitations apply to the maximum average of daily values for
any period of 30 consecutive days. The daily maximum average is twice
the 30 day maximum average. pH shall be within the range of 6.0 to 9.0
No discharge of process waste water pollutants is recommended for the
nitric acid subcategcry.
Rationale gnd Assumptions for Select ign^of_Technology
Although economics cannot be over looked, there will be considerable
changes before 1983 which will alter the economic analysis of any
treatment system proposed and therefore the selection of 1983 technology
will lean more towards the availability of processes than the detailed
economics. The possibility of new improved technology being developed
between now and 1983 can only enhance the owner -operators choice of
treatment methods capable of meeting these guidelines.
Much of the technology proposed is still in the development stage such
as high flow air and steam stripping, continuous ion exchange and
advanced urea hydrolysis. However, progress to date shows that much of
the remaining work deals with mechanical improvement, control
instrumentation and equipment modifications which should make each one
of these processes completely functional.
134
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SECTION XI
NEW SOURCE^PERFORMANCE^STANDARDS
AND PRETREATMENT~RECOMMENpATIQNS
INTRODUCTION
This level of technology is to be achieved by new sources. The term
"new source: is defined in the Act to mean "any source, the construction
of which is commenced after publication of proposed regulations
prescribing a standard of performance". New source performance
standards are to be evaluated by adding to the consideration underlying
the identification cf best practicable control technology currently
available a determination of what higher levels of pollution control are
available through the use of improved production processes and/or
treatment techniques. Thus, in addition to considering the best in-
plant and end-of-process control technology, new source performance
standards are to be based upon an analysis of how the level of effluent
may be reduced by changing the production process itself. Alternative
processes, operating methods or other alternatives are to be considered.
However, the end result of the analysis identifies effluent standards
which would reflect levels of control achievable through the use of
improved production processes (as well as control technology), rather
tahn prescribing a particular type of process or technology which must
be employed. A further determination which was to be made for new
source performance standards is whether a standard permitting no
discharge of pollutants is practicable.
The following factors were to be considered with respect to production
processes which were analyzed in assessing new source performance
standards:
a. The type of process employed and process changes;
b. Operating methods;
c. Batch as opposed to continuous operations;
d. Use of alternative raw materials and mixes of raw materials;
e. Use of dry rather than wet processes (including substitution of
recoverable solvents for water); and
f. Recovery of pollutants as by-products.
PROCESS WATER GUIDELINES
Phgsghate^Subcateggry
It is recommended that new source performance standards be identical to
the 1983 limitations for all new phosphate fertilizer plant sources.
Nitrogen Fertilizer Industry
135
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General_ Discussion
In addition to the treatment technologies listed under the 1977 and 1983
technologies the following process modifications and plant arrangements
may be considered.
Best Demonstrated^TechnclQgy jprocess Imprpyements)
A. Integration of an ammonia process condensate steam stripping column
into the condensate-boiler feed water system of an ammonia plant
with or without further stripper bottoms treatment depending on
boiler quality make-up needed.
E. Building of adequate sized urea and ammonia plants so that
centrifugal rather than reciprocating compressors can be used,
C. Designing in contaminated water collection systems so that common
contaminant streams can be segregated and treated in minor
quantities for improved efficiencies and reduced treatment costs.
D. Location of plant cooling tower up wind of the prevailing wind
direction to minimize the chance of absorbing ammonia in the tower
water.
E. Design of a low velccity air flow prill tower for urea and ammonium
nitrate to minimize the dust loss. This can reduce the yield loss
around the prill tower from 35t down to less than 0.5% with a
corresponding reduction in the raw waste load.
F. Design for a lower pressure steam level, say 41.8 atm (600 psig) to
62.2 atm (900 psig), in an ammonia plant to make process condensate
recovery easier and less costly.
G. Install air cooled condensers and exchangers where possible to
minimize cooling water circulation and subsequent blowdown.
Proposed New_Source Performance^Standards
Th,e following guidelines are recommended for new source effluent waste
water standards from the ammonia, urea, nitric acid, ammonium nitrate
and subcategories:
136
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Parameter SDiiS Subcategory
Ammonia Urea Ammonium Nitrate
NH3-N kg/kkg of product 0.055 0.0325 0.05
(lb/1000 Ib)
Organic-N kg/kkg of product - 0.0375
(lb/1000 Ib) 0.0625*
NO3-N kg/kkg of product - - 0.025
(lb/1000 Ib)
Oil & Grease kg/kkg of product 0.0125
(lb/1000 Ib)
* Effluent limitations for urea plants that prill
their product.
The above limitations apply to the maximum average of daily values for
any period of 30 consecutive days. The daily maximum average is twice
the 30 day maximum average. pH shall be within the range of 6.0 to 9.0
at all times.
No discharge of process waste water pollutants is recommended for the
nitric acid subcategory.
Rationale & Assumptigns_in_the DevelQBment of New Source
Performance Standards
One major problem in trying to treat waste water contaminants is that of
dealing with large quantities of water with very dilute contaminant
concentrations. Most existing plant complexes have very limited
facilities for keeping different waste waters separated and, therefore,
any treatment system installed has to handle large amounts of effluent
waste water. The construction of a new process plant and more
noticeably a nitrogen fertilizer complex allows the design of a
contaminated water separation/ collection system to allow more
efficient, less costly treatment of contaminants. More improved use of
plant water including recycling should also aid in treating waste
effluents.
Best available technology currently available is applicable to new
sources as it becomes available on a commercial basis; however, all best
practicable control technology currently available can be up-graded to
treat "concentrated/separated" waste water effluents from new plants to
meet the New Source Performance Standards. Therefore some effluent
limitations for new sources are less stringent than those for the 1983
standards because the technology is still being refined. Of particular
importance is the placement of cooling towers in relation to the
ammonia, air emissions sources. Downwind absorption of ammonia by
recycled cooling water can significantly contribute to the raw waste
load. New plants have the freedom of plant arrangement that existing
plants do not. Furthermore, through good engineering design, new plants
should be able to eliminate the problem at the source by minimizing air
137
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leaks. Since much of the 1983 -technology is not commercially available,
the above limitations represent engineeringing judgment as to what
improvements can be implemented beyond best practicable control
technology currently available.
PretreatJDgnt Reguirements for'New Sources
The type of waste water effluent that is discharged from a nitrogen
fertilizer complex contains compounds, such as ammonia nitrogen and
nitrate nitrogen, that would pass through a typical activated sludge or
trickling filter waste water plant and therefore this waste water at its
normal concentration levels would not be amenable to treatment by
conventional biological treatment processes. No discharge of process
waste water pollutants from new sources to publicly cwned treatment
works is recommended for the phosphate and nitric acid subcategories.
For the remaining sutcategories pretreatment and treatment provided by
the publicly owned treatment works must sum to equal the effluent
limitations for discharge to navigable waters for new sources if a
discharge to publicly owned treatment works is to be allowed.
138
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SECTION XII
ACKNOWLEDGMENTS
This study has been made possible by the following companies,
institutions, associations, laboratories, agencies, and persons. They
are to be commended for their help, assistance and cooperation in
providing information:
1. Borden Chemical Company, Piney Point, Florida
2. Royser Fertilizer company. Mulberry, Florida
3. American Cyanamid, Erewster, Florida
4. Agrico Chemical Company, South Pierce, Florida
5. W. R. Grace, Mulberry, Florida
6. Gardinier (USPP), East Tampa, Florida
7. Apple River Chemicals, East Dubuque, Illinois
8. Cooperative Farm Chemicals Association, Lawrence, Kansas
9. Phillips, Hoag, Nebraska
10. Cominco-American Hcag, Nebraska
11. Chevron Corporation, Ft. Madison, Iowa
12. North Carolina Nitrogen complex, Tunis, North Carolina
13. Central Farmers, Incorporated, Tyner, Tennessee
14. J. R. Simplot, Pocatello, Idaho
15. Valley Nitrogen, Helm, California
16. Vistron Corporation, Lima, Ohio
17. Terra Chemicals International, Inc., Sioux City, Iowa
18. National Phosphates/ Taft, Louisiana
19. Triad Chemical, Dcnaldsonville, Louisiana
20. Mississippi Chemical Corporation, Yazoo City, Mississippi
21. Mississippi Chemical Corporation, Pascagoula, Mississippi
22. Socal, Pascagoula, Mississippi
23. Freeport Chemical company, Convent, Louisiana
24. St. Paul Ammonia Products, St. Paul, Minnesota
25. Farmland Industries, Fort Dodge, Iowa
26. Thornton Labratory, Tampa, Florida
27. Serco Laboratory, Minneapolis, Minnesota
28. Harris Laboratories, Lincoln, Nebraska
29. Stewart Laboratory, Knoxville, Tennessee
30. James Engineering, Armon, New York
31. Mr. A. L. West, Lakeland, Florida
32. Dr. James A. Taylor, Lakeland, Florida
33. Mr. W. A. Lutz, fceston, Connecticut
34. The Fertilizer Institute
35. The Environmental committee, The Fertilizer Institute
36 Florida Phosphate Chemists Association
37. Davy Powergas, Inc., P.O. Box 2436, Lakeland, Florida
38. stamicarbon N.V, Dutch State Mines, Geleen, Netherlands
39. IVO MAROVIC, Consultant, New York, New York
40. Technip, Inc., 437 Wadison Avenue, New York, New York
41. Battelle Northwest, Richland Washington
42. United States Steel Agricultural Chemicals corporation, Bartow,
Florida.
Those persons, not already mentioned, who participated in the
working group/steering committee in order to coordinate the internal
EPA review are:
139
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43. Mr. Walter J. Hunt, Effluent Guidelines Division, EPA.
44. Mr. Elwood E. Martin, Effluent Guidelines Division, EPA.
45. Mr. Harry Trask, Office of Solid Waste Management Program, EPA.
46. Mr. John Savage, Office of Planning and Evaluation.
47. Mr. Srini Vasan, Region V, EPA.
48. Dr. Edmond Lomasney, Region VI, EPA,
49. Mr. Paul DesRosiers, Office of Research and Monitoring, EPA.
50. Dr. Murray Strier, Office of Permit Programs, EPA.
51. Mr. Ray McDevitt, Office of General counsel, EPA.
52. Mr. Ray Insinger, Office of Planning and Evaluation, EPA.
53. Dr. Robert R. Swank, Jr., Office of Research and Development, NERC -
Corvallis, Athens, Georgia.
54. Mr. Michael W. Kosakowski, Effluent Guidelines Division, EPA.
Special appreciation is given to the secretarial staff, especially Ms.
Sharon Ashe, Ms. Kay Starr, Ms. Chris Miller and Ms. Nancy Zrubek, for
typing and revision of this and the accompanying documents.
Appreciation is also given to Ms. Kit Krickenberger who coordinated the
secretarial staff assignments.
140
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SECTION XIII
REFERENCES
A- iHP-iStSSi?- Fertilizer and Phosphate Mining Industries - Water
P.2lil*tion and Control
prepared by Battelle Memorial Institute Richland, Washington for the
Environmental Protection Agency, Grant No. 12020FPD, September 1971,
U.S. Government Printing Office, Washington, D.C., 20402.
»
B- Advanced Wastewat6r_Treatment
by Russell L. Gulp and Gordon L. Gulp, Van Nostrand Runhold,
Environmental Engineering Series, Copyright 1971 by Litton
Educational Publishing, Inc., New York, Library of Congress, Catalog
Card Number 78-147192.
C. Ammonia Removal inja^Physical-Chemical_Wastewater Treatment_Process
by Robert A. Barnes, Peter F. Atkins, Jr. Dale A. Scherger; Prepared
for Office of Research and Monitoring, U.S. Environmental Protection
Agency, Washington, D. C., 20460, EPA-R2-72-123, November, 1972.
D. Arnmonia_and_SYnt hes is_Gas
by Robert Noyes; Noyes Development Corporation, Mill Road at Grand
Avenue Park Ridge, New Jersey, 07656.
E• Industrial Pollution Control^Handbpok
by Herbert F. Lund; McGraw Hill Publishing Co., New York, Library of
Congress Catalog Card Number 70-101164.
F• Gauging and iSampling_Industrial_Wastewater
by Joseph G. Robasky and Donald L. Koraido Calgon Corporation;
Chemical Engineering Magazine, Vol. 80, No. 1, January 8, 1973,
Pages 111-120.
G« Environmental Protection Agency Study Report Industrial Waste
v
Group 6 Fertilizers prepared by Wellman-Powergas. Inc.; Lakeland,
Florida, 33803, for Environmental Protection Agency, July, 1971,
Contract No. 68-01-0029.
The Phosphate_IndustrY_in^the_ynitedj-iStates
by E.G. Houston Tennessee Valley Authority, Office of Agricultural
and Chemical Development, Division of Chemical Development, Muscle
Shoals, Alabama, July, 1966.
141
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I. Commercial Fertilizer ^^
Walter W. Brown Publishing Co., Inc. 75 Third Street, N.W. Atlanta,
Georgia, 30308.
J- Characteristics cf the World Fertilizer Industry - Pho§£h§tic
Fertilizers
by Travis Hignett, Director of Chemical Development, Tennessee
Valley Authority, Muscle Shoals, Alabama, December 1967, TVA Peport
No. S-422.
D- World^Fertilizer Forecast 1965-1980
by Wellman-Lord, Inc. Lakeland, Florida, Copyright 1967, Paramount
Press, Inc., Jacksonville, Florida.
L. Economic Impact of Water Pollution Control Beguirements on the
Fertilizer Manufacturing Industry
by Development Planning and Research Associates, Inc., P.O. Box 727,
Manhattan, Kansas, 66502. Interim Report to Environmental
Protection Agency, Contract No. 68-01-0766, November, 1972.
1968-.1973
Chemical Products Series Report-May 1969, Stanford Research
Institute; Menlo Park, California, 94025.
N. Phospjiatic Fertilizers - Properties and^Prpcesses
by David W. Bixby, Delbert L. Rucker, Samuel L. fisdale, Technical
Bulletin No. 8, October 1966, The Sulphur Institute, 1725 "K" Street
Northwest Washington, D.C. 20006.
0. New Developments in Fluoride Emissions From Phosphate Processing
Plants ~ ~
by Frank L. Cross, Jr. and Roger W. Ross JAPCA, Volume 19, No. 1,
Page 15, January, 1969.
P. The Chemical Industry Facts _Bock by Manufacturing Chemist
Association, Inc., 5th Edition 1962, 1825 Connecticut Ave.,
Washington, D.C., Library of Congress Catalog Card No. 59-15407.
Q- Water^Quality Cr iteria
National Technical Advisory Committee, Federal Water Pollution
Control Administration, Washington, C.C., 1968.
R. Handbook_of_Dangergus_Materials
N.I Sax, Reinhold Publishing Corp. New York, New York, 1951.
142
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s • Nitra-tes in^Human_Health
C. J. Mansfield, Missouri Agricultural Experiment Station, Special
Report No. 55, Pages 37-38, 1965.
T• Industrial Water_Follutj.on_CQntrol
W. W. Ekenfelder, McGraw-Hill Publishing Co., New York, Published
1966, Library of Congress Catalog Card No.66 - 17913.
u- Phosphorus and lts_Cgmpounds
John R. Van Wazer, Interscience Publishers, Inc., New York (1961),
Library of Congress Card No. 58-10100.
V. Cadmium in Rock Phosjahate^Ores
H.P. Nicholson, PH.E., Director Southeast Environmental Research
Laboratory (6/19/73).
w- Standard Methods for the Examination of Water and Waste Water^ 13th
edition, American Public Health Association (1971).
x- M§£hods for Chemical Analy_sis of Water and Wastes^ EPA, National
Environmental Research Center, Analytical Quality Control
Laboratory, Cincinnati, Ohio (1971).
143
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SECTION XIV
GLOSSABY
All underlined numbers within a chemical formula represent normally
subscripted numbers. For example, H20 represents water. Physical
limitations of the printing device make this system necessary.
Aerobic
Living in the presence of oxygen.
Algae
A group of aquatic nonvascular plants with chlorophyll.
Anaerobic
Living in the absence of free oxygen.
Apatite
A natural calcium phosphate usually containing fluorine occuring as
phosphate rock.
Biological Process
The process by which bacteria and other micro-organisms in search of
food, breakdown complex organic materials into simple, more stable
substances.
Biuret
NH2CONHCONH2 • H2C. Also referred to as allophanamide and
cabamylurea.
Boiler Blowdown
A small amount of bciler feed water wasted to remove the build up of
contaminants frcw the boiler.
Boiler Feed Water Make-up
Water that is acceptable for steam generation in high pressure
boilers.
Contaminated Waste Water
Effluent waste water that has been contaminated due to contact with
process water (could be cooling tower, boiler blowdown or pond
water)
Cooling Water Blowdown
Small quantity of cooling water discharged from a recycling cooling
water system to remove concentrated contaminants from the tower.
Deionized Water
Water (raw, filtered or treated) that had certain ions removed by an
ion exchange unit.
Denitrification
145
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An anaerobic process which converts nitrate nitrogen to nitrogen
gas.
Dissolved Oxygen
Amount of free oxygen dissolved in water.
Exemplary
The term used for plants or units within plants that exhibit well
operated treatment schemes or in-plant techniques that qualify them
as best practicable control technclcgy currently available, best
available technology economically achievable, or best demonstrated
technology. Such plants or units may belong to another industrial
category whose technology may be transferred to the industry onder
study.
GTSP
Granulated triple superphosphate.
Nitri fication
Conversion of nitrogenous matter into nitrate by bacteria.
Pond Water
Water used in the manufacture of phosphoric acid and related
compounds to remove heat, convey gypsum and scrub contaminants.
Prills
Small round or aciciilar aggregates of a material that are
artificially prepared.
Process water
Any water which, during the manufacturing process, comes into direct
contact with any raw material, intermediate, product, by-product, or
gas or liquid that has accumulated such constituents.
Raw Water
Water that has not been treated in any way, taken from a well, a
river, a lake, or other non-contaminated source.
ROP
Run-of-pile triple superphosphate.
Single Train Plant
A plant (especially an ammonia plant) that employs a single very
large production unit with a high degree of maintenance-free
reliability. This is in contrast to ct double train plant which
employs 2 identical units run in parallel with a lesser degree of
reliability, but which has the advantage of maintaining some
production when one unit is down.
Ton
All uses of the term "ton" imply short ton equal to 2000 Ib.
Treated Water
146
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Raw water or filtered water that has been treated to make it
suitable for plant needs (such as softening).
TSP
Triple superphosphate.
T
»
147
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TABLE 4
METRIC UNITS
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)
ENGLISH UNIT ABBREVIATION
ft
acre ac
acre - feet ac
British Thermal
Unit BTU
British Thermal BTU/lb
Unit/pound
cubic feet/minute cfm
cubic feet/second cfs
cubic feet cu ft
cubic feet cu ft
cubic inches cu in
degree Fahrenheit °F
feet ft
gallon gal
gallon/minute gpm
horsepower hp
inches in
inches of mercury in Hg
pounds Ib
million gallons/day mgd
mile mi
pound/square inch . psig
(gauge)
square feet sq ft
square inches sq in
tons (short) ton
yard yd
by TO OBTAIN (METRIC UNITS)
CONVERSION ABBREVIATION METRIC UNIT
hectares
cubic me ters
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
ha
cu m
kg cal
kg cal/kg
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km •
(0.06805 psig +l)*atm
0.0929
6.452
0.907
0.9144
sq m
sq cm
kkg
m
kilogram-calories
kilogram calories/
kilogram
cubic meters/minute
cubic metcrc/ir.inntc
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
killowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres
(absolute)
square me ters
square centimeters
metric tons
(1000 kilograms)
meters
J
* Actual conversion, not a multiplier
Environcental Protection Agency
Region V, Library
£T; South Dearborn Street
Chicago, mtnols 60604
148
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