&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research EPA 600 2-79-1 86
Laboratory August 1979
Research Triangle Park NC 27711
Research and Development
An Evaluation of Control
Needs for the Nitrogen
Fertilizer Industry
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-79-186
August 1979
An Evaluation of Control Needs
for the Nitrogen Fertilizer Industry
by
Philip S. Hincman and Peter Spawn
GCA/Technology Division
Burlington Road
Bedford, Massachusetts 01730
Contract No. 68-02-2607
Task No. 12
Program Element No. 1AB604B
EPA Project Officer: Ronald A. Venezia
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
This report evaluates the pollution control needs of the nitrogen fer-
tilizer industry. It includes a description of ammonia, ammonium nitrate and
urea manufacturing processes and an evaluation of existing pollution control
equipment. In addition, this report evaluates the pollution reduction poten-
tial of alternative pollution control techniques, processes and feedstocks.
Both air emission and water effluent control techniques are examined for
each industry and its unit operations.
iii/iv
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CONTENTS
Abstract iii
Figures vi
Tables viii
1.0 Introduction 1
2.0 Conclusions and Recommendations 2
2.1 Conclusions 2
2.2 Recommendations 6
3.0 The Nitrogen Fertilizer Industry 9
4.0 Ammonia 13
4.1 Process Description 13
4.2 Emissions and Effluent Sources 18
4.3 Present and Potential Control Technology 24
5.0 Ammonium Nitrate 39
5.1 Process Description 39
5.2 Emissions and Effluent Sources 43
5.3 Present and Potential Control Techniques 46
6.0 Urea 55
6.1 Process Description 55
6.2 Emissions and Effluent Sources 57
6.3 Present and Potential Control Techniques 65
7.0 Meeting Effluent Guidelines 74
References 77
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FIGURES
Number Page
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Potential integration of a nitrogen fertilizer plant
Process flow diagram for an ammonia plant with pollutants
associated with each process
Flow diagram of an ammonia process
Incineration scheme of various air streams
Vistron's cryogenic recovery system
Percent return of a cryogenic system versus price of ammonia at
various natural gas prices
NFK-TRW burner flame reaction
Principle of SRG burner
Low NOX two-stage combustion burner
NHM plant denitrif ication process flowsheet
Reflux incineration system
Reflux condensate stripping system
Process condensate natural gas saturation process flow diagram .
A schematic view of MCC neutralizer
Brink collection unit
CFCA collection cone and Brink scrubbing unit
Joy Type D Turbulaire impingment scrubber and C&I Girdler
granulation process ,
Evaporative scrubbing system for low density ammonium nitrate
prills
Stamicarbon CCb stripping process for urea production
12
14
16
25
26
27
28
30
30
32
36
36
37
48
50
50
52
54
58
vi
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FIGURES (continued)
Number Page
20 Snamprogetti process for urea production 59
21 Toyo-Koatsu method in urea production 60
22 Stamicarbon total recycle 61
23 Evaporative scrubbing system, urea plant, prills or granules . . 68
24 Vistron pollution control system 69
25 Emission control system 70
26 Ammonium nitrate effluent utilization 73
vii
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TABLES
Number Page
1 Present and Potential Techniques to Abate Ammonia Plant
2
3
4
5
6
7
8
9
10
Present and Potential Techniques to Abate Ammonium Nitrate Plant
Present and Potential Techniques to Abate Urea Plant Emissions .
Annual U.S. Production of Ammonia, Urea, and Ammonium Nitrate
Summary of Ammonia Production Emission and Effluent Sources . .
Air Pollution Control Requirements ...... ...
Potential Water Pollutant Problems in the Nitrogen Fertilizer
Mass Balance Around the Condensate Steam Stripper — Result of
Effluent Discharge Factors for a Condensate Steam Stripper . . .
*
Trace Metal Effluent Discharge Factors from a Condensate Steam
Stripper
~*
4
5
10
19
21
ff*Jtm
22
fnf *•»
33
*J +J
33
34
11 Theoretical Conversion of Ammonia in Stripper Overhead of a 900
Metric Ton/Day Plant to NOX in Primary Reformer Stack .... 34
12 Air and Water Pollutants and Control Requirements for Ammonium
Nitrate Production 44
13 Average Effluent Parameters for Nitrogen Fertilizer Plants ... 44
14 Summary of Neutralization Emission Data 47
15 Emission from Esso Chemical Canada Spray Head with Shroud Prill
Tower Modification 51
16 Air and Water Pollutants and Control Requirements for Urea
Production 62
viii
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TABLES (continued)
Number
17 Summary of Emission Data for Prill Tower Controlled by Wet
Scrubber 67
18 Plant Treatment of Ammonia Plant Process Condensate 71
19 Representative Waste and Ion Exchange Treated Water Analysis . . 72
20 Effluent Guidelines and Standards of April 26, 1978 75
IX
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1.0 INTRODUCTION
The Industrial Environmental Research Laboratory (IERL) of the Environ-
mental Protection Agency (EPA) has the responsibility of insuring that pollu-
tion control technology is available for stationary sources. If control tech-
nology is unavailable, inadequate, and/or uneconomical, IERL may help develop
the needed control technique. Approaches to control include: process and
equipment modifications, feedstock alternatives, add-on control devices, and
complete process substitution.
This evaluation of the control needs of the nitrogen fertilizer industry
is based largely upon the results of previous EPA-sponsored source assessment
(SA) studies of the industry, and its objectives are to examine the various
processes that create the pollutants and to evaluate control technologies that
may reduce emissions to acceptable levels. Production processes are described,
emission and effluent sources are identified, present and potential control
technology are reviewed, and recommendations are made, as appropriate, for
further work to define emission rates and/or evaluate process and control
alternatives.
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2.0 CONCLUSIONS AND RECOMMENDATIONS
2.1 CONCLUSIONS
The two major emission problems associated with the nitrogen fertilizer
industry are (1) oxides of nitrogen resulting from the addition of purge gas
and overhead to primary reformer firing in ammonia synthesis and (2) particu-
lates from prilling towers in urea and ammonium nitrate production. Apart from
these two problems other emission sources within the industry are amendable to
available control techniques. Tables 1, 2, and 3 summarize present and poten-
tial emission and effluent control techniques for ammonia, ammonium nitrate,
and urea production, respectively. The following are more detailed conclusions:
1. Because the future of the United States ammonia industry is highly
dependent upon energy costs, it is important that, insofar as
practicable, the energy penalties associated with the installation
of emission controls be minimized. Hence, long-term pollution
control solutions must be considered along with those providing
immediate emission reductions.
2. Natural gas feedstock for the production of ammonia is desulfur-
ized by either an activated carbon bed or a zinc oxide bed.
Steam regeneration of the former can result in air emissions of
HC, CO, and S02- Controls have not been required on this unit by
regulatory agencies; however, a few producers have installed
thermal incinerators despite the added cost. The trend in desul-
furization is an increased utilization of zinc oxide beds. The
primary reason for this trend is that zinc oxide beds are not re-
generated which results in energy savings.
3. In the primary reformer, natural gas reacts with steam to form
carbon monoxide and hydrogen under high pressure and temperature.
The heat for the reaction is supplied by firing the primary re-
former with natural gas or fuel oil yielding typical combustion
products (HC, CO, C02, SOX, NOX, and particulates). Many ammonia
producers are now adding purge gas from the ammonia synthesis
loop and overhead from the condensate stripper to the primary
stack reformer, but while reducing emissions from these sources,
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TABLE 1. PRESENT AND POTENTIAL TECHNIQUES TO ABATE AMMONIA PLANT EMISSIONS
Source
Emissions
Present
controls
Controls/modifications Potential alternative
trends controls/processes
Testing/R&D needs
D»»ulturl»atlon
• Activated carbon
bed (95X of
producers)
HC, CO, C02
None (1) Thermal incineration
(2) Zinc oxide bed (5% of
ammonia producers -
no air emissions)
Testing carbon bed
emissions
Testing thermal
incineration of
carbon bed emission;
Primary reformer
• Natural gas/
fuel oil
NOX, SOX. CO, HC,
particulates
None (1) Combustion
modifications
(1) NOX reduction
by atninon i.rj
in jecc ion
Testing and eval-
uation of reduc-
tion processes
Natural gas or
fuel oil and
purge gas
Natural gas or
fuel oil and
purge gas and
condensate
stripper
overhead
Combustion products None
plus high NOX
levels
Combustion products
plus high NO
levels and ammonia
and methanol
None
• Vaporized fuel NOX, SO , CO, HC,
oil (VFO) particulates
Carbon dioxide removal NHs, CO, COj, HC,
MEA
None
None
Condensate stripper
(Air, ammonia
methanol, carbon
dioxide)
(Water, ammonia,
methanol)
Overhead in-
jection pri-
mary reformer
stack
Overhead in-
cineration
Condensate re-
cycled as
boiler feed
water
(1) Cryogenic recovery
of purge gas
(1) LJungstron wheel
(air preheater)
decreasing overhead
decomposition
(1) Fuel conversion
process
(1) Hoc potassium car-
bonate system
(1) Overhead cryogenic
recovery of ammonia
(2) Modified reflux and
production recovery
100% recycle
(3) Natural gas
saturation
Testing primary
reformer stack
• Testing primary
reformer stack
• Locate a higher
temperature injec-
tion point for
more efficient
decomposition
• Testing primary
reformer stack
• Hrack lent
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TABLE 2. PRESENT AND POTENTIAL TECHNIQUES TO ABATE AMMONIUM NITRATE
PLANT EMISSIONS
Source
Emissions
Present controls
Controls/modification trends
Potential alternative
controls/processes
ir needs
Neutralization
(KX03)
SH_NO= particulates
pH control
wet scrubbers
nist elininacors
condensation
1) Close process control (MCC)
None
So 1 u t ion Cone e r. c r a t ion
Solid Formatic"
Prilling
Drum granulation
Graining
(HNO;), NHi.NO; parciculates
SH-NOj particulates, H20.NH;
NHWN03 particulates, NH;
NH^NOs particulates, Ntt$
Stengel reactor/Sandvik NH^NOs particulates, N
belt
Scrubbers None
nist eliminators
None
Wet scrubbers. 1) CFCA/Monsanto cone collection
mesh pads 2) Lsso spray head redesign
Formation of low den- Further raodifi-
sity product by process cation of prill
other than prilling tower design
and testing*
Scrubbers 1) Foster-Wheeler evaporative scrubbers
Product Finishing
Drying
Cooling
Additives
Handling ar.c shipping
Coating material
NH-N'Os fines
Wet scrubbers
Wet scrubbers
None
None
Improved hand-
ling tech-
niques to avoid
dust-
Generally e-issions from all process steps appear to be inadequately defined under varying operating conditions.
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TABLE 3. PRESENT AND POTENTIAL TECHNIQUES TO ABATE UREA PLANT EMISSIONS
Source Emissions
Solution Formation
Ammonium carbamate NH3,C(>2, inert s
synthesis
Urea formation NH3,C02, urea
Solution Concentration
Crystallization NH3,C02, urea
Evaporation NH3.C02, urea
Solid Formation* Formaldehyde, particulates
Product Finishinjg*
Present controls
Scrubbers
Recycling
Condensation, wet
scrubbers, demiscers
Recycling
Wet scrubbers, modification
of production rates
Controls/modification trends
None
None
None
None
Pan granulation, Foster-Wheeler
evaporative scrubbers, cen-
trifugal scrubbers
Potential alternative
controls/processes
None
None
None
None
Vistron control
system
RiD needs
t
T
7
t
Evaluation of pan gra-
nulation for production
of low density product
These processes and chese problems are very similar to those for ammonium nitrate (see Table 2).
•4.
'Generally, emissions from all process steps appear to be inadequately quantized under varying operating conditions; in particular levels of any escaping
formaldehyde additive need further quantization.
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a substantial increase in NOX emissions from the primary reformer
stack results. A promising applicable add-on control system for
NOX abatement is the ammonia injection technique. Several Japanese
processes appear to be applicable to the primary reformer operation.
A viable alternative to firing the reformer with purge gas for NOX
reduction is a cryogenic recovery system.
4. Many ammonium nitrate producers expressed difficulty in control-
ling neutralizer pH. High pH results in excess ammonia losses.
5. Prill towers for the production of solid NH^NOg are a source of
particulate emissions. For the most part, pollution control equip-
ment is available to meet state emission requirements, and emis-
sions from ammonium nitrate production can be lowered as the
application of control technology increases.
6. Solid product urea is produced using equipment and procedures
similar to those used in the ammonium nitrate industry. The addi-
tion of pollution control equipment to the industry has been very
slow compared to the ammonium nitrate industry.
7. Emissions from the urea solution concentration process evapora-
tor may be controlled to recover ammonia and/or urea to meet state
emissions regulations. Approximately 40 percent of the urea evapor-
ators are controlled by condensation, 10 percent by wet scrubbing
and 5 percent by demisters. The remainder are operating without
controls.
8. Prill towers are the major urea particulate emission source.
Opacity limits are presently violated because a major fraction of
particulate emissions from prill towers are extremely small par-
ticles (fume).
2.2 RECOMMENDATIONS
In order to further our understanding of the environmental impact of the
nitrogen fertilizer industry, the following studies are recommended to EPA:
1. Additional research is needed to determine the pollution problems
associated with each alternative feedstock, such as coal, naptha,
etc. to natural gas for ammonia synthesis.
2. In view of its essential nature, high energy-intensive character,
and vulnerability to foreign competition, a careful examination
should be made, in light of probably increasing energy costs, of
how much regulation our domestic nitrogen fertilizer industry can
tolerate yet remain viable, including the economic impact of regu-
lation, combined with energy costs, on the industry.
3. Additional testing is needed to determine the true severity of
emissions from the steam regeneration of activated carbon ammonia
-------
production natural gas feedstock desulfurization beds. A more
definitive evaluation is needed of zinc oxide beds versus acti-
vated carbon beds plus incineration in terms of costs, energy
consumption and environmental impact (including solid waste dis-
posal as well as air pollution).
4. In-depth research and development in the form of testing and pilot
plants are still needed in order to determine NQx reduction effi-
ciencies, the proper ammonia injection point, catalyst life, and
operation stability of the ammonia production primary reformer as
applied to the process and cost of the available techniques.
Several processes developed by the Japanese applicable to pri-
mary reformer operation should be examined as well as cryogenic
recovery studies. Additional research and testing programs are
needed to determine the efficiency of overhead decomposition in
the primary stack and to evaluate injection at higher tempera-
ture locations. Other systems to abate condensate stripper over-
head which should be evaluated are reflux incineration, modified
reflux and product recovery, and natural gas saturation.
5. Because of insufficient data, the evaluation of emerging process
modifications and pollution control equipment for the formation
of ammonium nitrate by neutralization has been limited. Such
data are necessary for formulating research and development needs
for pollution control in the industry. Emissions from the ammo-
nium nitrate industry are now being measured for the purpose of
developing New Source Performance Standards (NSPS). This NSPS
program will effectively fill many of the existing gaps.
6. An in-depth evaluation of pH controls and monitoring systems for
ammonium nitrate production by neutralization is needed to deter-
mine what Best Available Control Technology (BACT) equipment is
applicable to neutralizer pH control. Mississippi Chemical Cor-
poration (MCC) has developed a two-stage neutralizer in which
emissions are reduced by process design and close pH monitoring.
Some ammonium nitrate producers use either total or partial con-
densation systems. Other methods used are mist eliminators and
wet scrubbers. These approaches should be subjected to compara-
t ive evalu at ion.
7. A research and development program is needed to develop a means
of producing low density ammonium nitrate solids in a granulator.
This would provide an alternative to prill towers. The elimina-
tion of prill towers as process equipment is desirable because
of their associated particulate pollution problem. Until such an
alternative process can be developed, conventional control equip-
ment will have to be used on existing prill towers. Approxi-
mately 50 percent of ammonium nitrate prill towers operate with-
out emission control equipment, 2 to 5 percent use the Coopera-
tive Farm Chemical Association (CFCA) cone/Monsanto high energy
(HE) system, 15 percent use wet scrubbers and the remainder use
mesh pads or similar devices. A program should be conducted to
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evaluate the collection efficiency of the CFCA cone as a function
of airflow and cost. The shrouded spray head developed by Esso
Chemical Canada also looks promising and the Foster-Wheeler eva-
porator scrubbing system for reducing particulates from prilling
and granulation should be thoroughly examined and evaluated for
BACT regarding air and water pollution.
8. Because of insufficient process and emissions data for urea pro-
duction, the evaluation of emerging process modifications and
pollution control equipment has been limited. Effort is needed
to obtain such information; however, as in the case of ammonium
nitrate production, work now being conducted by EPA to establish
NSPS should fill many existing data gaps.
9. Controlled and uncontrolled urea concentrators should be tested
to determine emission concentrations and control efficiencies.
10. The Foster-Wheeler system should be evaluated for urea as well as
NH^NOj. C & I Girdler has developed a system to abate wastewater
effluents as well as particulate emissions. Some problems have
been experienced with the system; for example, difficulty has been
experienced in removing the smaller particulates. However, addi-
tional research and development may elevate this system to BACT.
11. Urea production emission data are not sufficient to evaluate pol-
lution control research and development needs of the urea industry.
These data are essential to develop recommendations leading to
research and development programs for improving pollution control
for the nitrogen fertilizer industry.
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3.0 THE NITROGEN FERTILIZER INDUSTRY
Modern agricultural technology, sometimes called "The Green Revolution,"
is based upon three practices:
1. the massive application of artificial fertilizers,
2. the massive application of synthetic pesticides, and
3. the use of fewer but higher yield crop genetic strains
and each of these three practices has great potential of adverse environmental
impact:
1. pollution from manufacture and field run-off of fertilizers,
2. pollution from manufacture and field run-off of pesticides, and
3. increased likelihood of catastrophic crop yield reduction by
plant diesease and pest vectors
The three essential nutrient elements supplied by artificial fertilizers are
potassium, phosphorus, and nitrogen. The United States/Canada region is second
only to Europe in the intensive per capita use of these fertilizers with the
undeveloped countries lagging far behind. Artificial fertilizer production
is highly energy intensive and as energy costs rise, the situation of the de-
veloping countries will worsen.1 As for the United States, as early as 1974
it was forewarned that unless we can find supplies of cheap gas we will go
from an exporter to a progressively larger importer of nitrogen products.2
The basic nitrogenous fertilizer chemicals are ammonia (NHs), urea
(CO(NH2)2), and ammonium nitrate (NHi+NO). Urea and ammonium nitrate are made
-------
from ammonia. There are many other nitrogen fertilizers produced, however
these are formed by combinations and/or additions to these three compounds.
In 1977, 3.6 million metric tons of anhydrous ammonia were produced in
the United States.3 Based upon historical consumption trends, anhydrous
ammonia production may reach 4.5 million metric tons by 1988 (Table 4). How-
ever, imports may slow or reverse this trend. Approximately 85 percent of the
ammonia produced is used as fertilizer and in the production of urea, ammonium
nitrate, and ammonium phosphates. Other applications are the production of
nonfertilizer products.
TABLE 4. ANNUAL U.S. PRODUCTION OF AMMONIA,
AMMONIUM NITRATE, AND UREA
Ammonia (NHs)
Ammonium nitrate (NH^l
Urea (CO(NH2)2)
Annual production
1977
3.6
K>3) 6.8
4.0
in million metric tons
1988
4.5
8.5
5.0
The average capacity ammonia plant being built today is at least 900 metric
ton/day. Ammonia plant production costs range from $27 to $36 per metric ton
of ammonia produced.4 Technological advances in the ammonia industry have
been geared toward optimizing the energy requirements.
In 1977, preliminary figures indicate that the total U.S. production of
ammonium nitrate was 6.76 million metric tons (100 percent amtaonium nitrate).3
Of this quantity, approximately 77 percent was intended for fertilizer and the
remaining 23 percent for production of other products such as explosives and
nitrous oxide. Approximately 50 percent of the ammonium nitrate produced for
fertilizer use was in the solid form while the other 27 percent was sold as
liquid fertilizer.
10
-------
Preliminary figures indicate that the total U.S. production of urea was
4.03 million metric tons in 1977. Approximately 80 percent of the urea pro-
duction was used in fertilizers; urea-formaldehyde resins and livestock feed
are the other major uses. Urea fertilizer is produced in solid and liquid
form. Forty-two percent of the urea produced was consumed in direct applica-
tion as solid fertilizer, mostly in the form of granules. Livestock feed is
generally produced as prills.
The production of fertilizer very often involves a complex of more or
less integrated plants in which more than one fertilizer product is manu-
factured. To optimize production costs, many fertilizer companies may have an
arrangement similar to that shown in Figure I.5 By plant integration and ex-
change of products or byproducts, costs normally incurred by external purchases,
transportation, and energy become a savings for the company, thereby reducing
overall production costs. Moreover, this arrangement appears advantageous
relative to potential pollution problems. Advantages with respect to air and
water pollution arise from recycling and reuse. The general use of a common
outfall by integrated plants, where all process waters discharge into a
single channel, is also advantageous from a control standpoint.
11
-------
r~
K>
-- - - — — — — SOLUTION — — — SOLUTION
Figure 1. Potential integration of a nitrogen fertilizer plant.
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4.0 AMMONIA
4.1 PROCESS DESCRIPTION
Ninety-eight percent of the ammonia produced in the U.S. is by catalytic
steam reforming of natural gas. The ammonia production process basically in-
volves the production of hydrogen, synthesis gas purification, and ammonia
synthesis.
Ammonia production by catalytic steam reforming involves seven processes:
1. Feedstock desulfurization,
2. Primary reformation,
3. Secondary reformation,
4. High and low temperature carbon monoxide shifts,
5. C02 absorption,
6. Methanation, and
7. Ammonia synthesis,
several of which are designed to remove impurities such as sulfur, carbon
monoxide and carbon dioxide. Figure 2 shows a typical ammonia plant flow
diagram with pollutants associated with each process.
4.1.1 Feedstock Desulfurization
The reformer catalyst is poisoned by sulfur, therefore, the 229 to
915 yg/m3 sulfur content, mostly hydrogen sulfide, of pipeline grade natural
gas must be reduced to less than 280 yg/m3.6 For this purpose, approximately
90 percent of ammonia producers use activated carbon beds with a metallic
additive (CuO) while the remainder use zinc oxide beds.7
13
-------
t T T
NATURAL SA5
HYDROGEN
FEEDSTOCK
AIR EMISSION _,
(NHj and METHANOL)
STRIPPING AGENT
IN
C02 REGENERATION
INJECTED INTO
PRIMARY REFORMER
STACK
T:
HC
t
METHANOL
n» *
t /
AIR EMISSION
COMBUSTION
PRODUCTS
PRIMARY REFORMER
STACK
OVERHEAD
CONDENSATE
STRIPPER
(NHj OKI METHANOL)
NH, CO, HC „
r ir t /
ME A
STEAM
t_
I HYOROGEN
FEEDSTOCK
OR FUEL
PRIMARY
REFORMER
FOR FUEL
AMMONIA
CRYOSEN/C
RECOVERY
SYSTEM
t.
PURGE
GAS
AMMONIA
SYNTHESIS
HHj
NHj
Figure 2. Process flow diagram for an ammonia plant with
pollutants associated with each process.6
-------
CuO + H2S -*• CuS + H20 (1)
ZnO + H2S •*• ZnS + H20 (2)
When the feedstock sulfur concentration entering the reformer reaches
approximately 0.2 ppm and/or elemental sulfur buildup in the carbon bed reaches
13 to 25 percent by weight of the carbon, the activated carbon bed is regen-
erated, typically every 20 days, by passing super-heated steam through the bed,
and then maintaining a temperature of,. 2,30°C for 8 to 10 hours while additional
air is added which reacts with the metal sulfide regenerating the metal oxide
and elemental sulfur:
2 CuS + 02 -»• 2 CuO + 2S (3)
Sulfur, carbon monoxide and hydrocarbons are released. Normally, ammonia
producers will incorporate two desulfurizing units, with one unit operating
while the other is being regenerated.
The zinc oxide catalyst absorbs sulfur up to approximately 18 to 20 percent
by weight and is replaced about once a year rather than regenerated.
4.1.2 Primary Reformer
In the primary reformer, the desulfurized natural gas, consisting mostly
of methane, is mixed with pretreated process steam in the presence of a nickel
base catalyst to convert roughly 70 percent of the methane to carbon monoxide
and hydrogen.
CHij + H20 54°°C CO + 3H2 (4)
Figure 3 shows the primary reformer in synthesis gas production.6 The heat
(227 KJ/Mole) for the reforming reaction is supplied by firing natural gas or
fuel oil and purge gas.
15
-------
J
Figure 3. Flow diagram of an ammonia process.1
-------
4.1.3 Secondary Reformer
The process gas is next introduced into the secondary reformer, where it
is mixed with compressed air (3.4 MPa) preheated to a temperature of 540°C to
give a hydrogen to nitrogen mole ratio of 3:1, corresponding to NH3.
4.1.4 High and Low Carbon Monoxide Shifts
Cooled gas from the secondary reformer enters a high temperature CO shift
converter (330 to 550°C) filled with an iron oxide-chromium oxide catalyst to
remove carbon dioxide.
CO + H20 ->• COj + H2 (5)
The gas stream is cooled to 200°C and passes into the low temperature
shift converter for further CO removal. Unreacted steam is condensed and the
condensate separated. Approximately 90 percent of the wastewater from ammonia
production is from this process condensate. A 907 metric ton/day plant pro-
duces about 1,200 m3 per day of condensate.6 Components of wastewater conden-
sate are ammonia, methanol, sodium, iron, copper, zinc, calcium and aluminum.
4.1.5 Carbon Dioxide Removal
Carbon dioxide next must be removed since it poisons the ammonia synthesis
catalyst. About 80 percent of ammonia producers remove the C02 from the pro-
cess gas by monoethanolamine scrubbing
Monoethanolamine (MEA)
the others use hot carbonate scrubbing based on the reaction
CDs + C02 + H20^=^2HC03 (6)
Both scrubbing materials are regenerated by steam stripping.7
17
-------
4.1.6 Methanation
Finally residual C02 is removed by conversion under pressure to methane
using a nickel catalyst
2H20 (7)
to yield purified synthesis gas with a 3:1 hydrogen to nitrogen mole ratio.
4.1.7 Ammonia Synthesis
Anhydrous ammonia is synthesized directly in two stages, first by com-
pression and then by passing the purified synthesis gas over an iron oxide
catalyst at elevated temperature and pressure.
N2 + 3H2^=^2NH3 (8)
Liquid ammonia is collected from each stage for flashing to remove
impurities such as argon. Anhydrous ammonia is either stored at a temperature
of -28°C or piped to local plants to produce other products.
4.2 EMISSIONS AND EFFLUENT SOURCES
Table 5 summarizes major emission and effluent sources associated with the
overall process steps in ammonia production (see also Figure 1) -while Table 6
summarizes severities and pollution control requirements .
The source severity factor is used to evaluate the significance of an
emission. Source severity is the ratio of the ground level concentration of
each emission species to its corresponding ambient air quality standard (for
criteria pollutants) or to a reduced Threshold Limit Value (TLV) for noncriteria
emissions species. The TLV refers to the airborne concentration of a sub-
stance which represents conditions under which it is believed that nearly all
workers may be repeatedly exposed day after day without adverse effect for a
7- or 8-hour workday and 40-hour workweek.
18
-------
TABLE 5. SUMMARY OF AMMONIA PRODUCTION EMISSION AND EFFLUENT SOURCES
Process step
Air emissions (A) and water effluents (W)
DESULFURIZATION
Activated carbon bed
regeneration
PRIMARY REFORMER
Natural gas combustion
products
Fuel oil combustion products
Fuel, purge gas and
condensate stream combustion
products
(A) Oxides of sulfur
(A) Free sulfur
(A) Hydrogen sulfide
(A) Hydrocarbons
(A) Carbon monoxide
(A) Oxides of sulfur
(A) Oxides of nitrogen
(A) Carbon monoxide
(A) Hydrocarbons
(A) Particulates
(A) Oxides of sulfur
(A) Oxides of nitrogen
(A) Carbon monoxide
(A) Hydrocarbons
(A) Particulates
(A) Oxides of sulfur
(A) Oxides of nitrogen^
(A) Carbon monoxide
(A) Hydrocarbons
(A) Particulates
(A) Ammonia^
(A) Methanol*
8.4 mg/kg NH3*
3.6 g/kg NH3*
6.9 g/kg NH3t
0.0024 g/kg fuelf
2.7 k/kg fuelf
0.068 g/kg fuelf
0.012 g/kg fuelf
0.072 g/kg fuelf
1.3 g/kg fuelf
2.7 g/kg fuelf
0.12 g/kg fuelf
0.15 g/kg fuelf
0.45 g/kg fuelf
115-350 ppm
CARBON MONOXIDE SHIFTS
Condensate following low
temperature shift
(W) Ammonia
(W) Methanol
(A) Carbon dioxide
(W) Trace metalsff
(A) Ammonia
(A) Methanol
0.57 kg/hr§§
0.28 kg/hr§§
127 kg/hr§§
41.2 kg/hr§§
22,7 kg/hr§§
19
-------
TABLE 5 (cont.)- SUMMARY OF AMMONIA PRODUCTION EMISSION AND EFFLUENT SOURCES
CARBON DIOXIDE ABSORPTION
Regeneration of scrubbing
solutions (A) Carbon dioxide 1,220 g/kg NH|**
(A) Methane 0.47 g/kg NH3**
(A) Ammonia 1.0 g/kg NH3
(A) Carbon monoxide 1.0 g/kg NH3**
(A) Methanolf
(A) Monoethanolamine 0.05 g/kg NH3**
FUGITIVE SOURCES - vents, leaky seals, compressors, pumps, storage, spillage,
etc.
Monsanto Research Corporation, "worse case" estimate.
Texas Sir Control Board estimate.
Reference 6.
§
Adding the purge gas to the natural gas fuel may increase NOX levels from
approximately 35 ppmv to 115-350 ppmv. Adding overhead increases NOX
emissions in a worse case estimate over 50 percent (Reference 10).
J£
Overall plant NH3 on CH3OH emissions reduced to undetectable levels (based
on a confidential information source). Other stack tests indicate only a
59 percent and 75 percent reduction of CH3OH on NH3 emissions respectively.
**
Worse case estimate, Reference 6.
tt
If overhead from condensate stripper is used to strip regeneration.
tt
Including Na, Fe, Cu, Zn, Ca, and Al.
§ §
Calculated (Reference 5) for a 1000 metric ton/day NH3 plant.
20
-------
TABLE 6. AIR POLLUTION CONTROL REQUIREMENTS6
Source
Synthetic Ammonia Production
Desulfurization tank
Primary reformer (oil)
Carbon dioxide regenerator
Condensate stripper
^ _ . -_
Pollutant
S02
CO
HC
NOV
A.
Part.
HC
NH3
CO 2
HC
MEA
NH3
Methanol
Average
Source
severity
0.05
0.30
32.4
4.1
0.21
0.16
2.2
0.25
0.54
0.33
3.2
0.12
plant
Required
control^
percent
0.0
94.4
99.85
98.78
76.2
68.8
97.73
80.0
90.7
84.9
98.4
58.3
To achieve a Source Severity factor of 0.05
Sources and pollutants were examined on the basis of source severity
factors developed by Monsanto Research Corporation as a direct indication of a
potential pollution problem.
Wastewater originates from three general sources at nitrogen fertilizer
facilities:
• Process units
• Nonpoint sources such as leaks and spills
• General stormwater runoff
Table 7 summarizes effluent problems in the prodution of ammonia and other
fertilizer industry products.
Source severity factors for major effluent sources in Table 7 indicate low
impact of nitrogen fertilizer plant discharges on receiving waters.
21
-------
TABLE 7. POTENTIAL WATER POLLUTANT PROBLEMS IN
THE NITROGEN FERTILIZER INDUSTRY6
Product
Ammonia
Ammon iura
nitrate
Urea
Process
Condensate
stripper
Neutralizer
and evaporator
condensate
Evaporator
condensate
Crystallizer
filtrate
Effluent
specie
NH3
Methanol
Ammonia nitrogen
(NH3 + NH4)*
Nitrate nitrogen
Ammonia nitrogen
(NH3 + NHij)*
Organic nitrogen
Average
source
severity
factor
0.2
4.
0.12t
0.0004
0.09?
0.004
Effluent
factor
rag /kg product
15
7.5
860
470
760
275
Effluent
concentration
g/m3
12
6
480
120
120
90
«
Average for each plant weighted with respect to plant production.
j.
'Effluent factors include minor contribution from ammonia plant.
TAverage for receiving water pH 9.
-------
Process wastewater at modern plants originates primarily from condensation
of vapor exhaust streams which would otherwise be exhausted to the atmosphere.
Cooling tower and boiler water blowdown or wastage also contributes to process
wastewater along with regenerate solution from ion exchange systems normally
used at a plant to provide feed water. There may also be additions from wet
scrubber air pollution control devices.
Nonpoint sources, generally intermittent and highly variable, result from
accidential spills; valve and pump seal leaks; cooling tower blowdown, over-
flows, and leaks; and plant washdowns. These wastewaters either enter the
general plant wastewater treatment system for removal or recycling, or dis-
charge to receiving ponds or water courses.
New plants generally use closed loop cooling towers with periodic wasting
or blowdown, while some older plants still use once-through systems. Cooling
water may contain NH3 from absorption from ambient air (especially if cooling
towers are downwind of ammonia emission points).8 Slight leaks from process
equipment may allow NHs or NOa to contaminate cooling water, depending on de-
gree of maintenance and inspection procedures applied at any particular plant.
Both cooling tower and boiler blowdown usually contain corrosion inhibitors
which are typical of any industrial process and include hexavalent chromium
(10 mg/£) and some copper and zinc. Many plants reduce hexavalent chromium to
the less toxic trivalent species followed by liine precipitation prior to
discharge.
Stormwater runoff can contain a significant quantity of nitrogeneous com-
pounds, especially at plants with poor handling of dry product. Some state
regulatory agencies address this potential problem by requiring containment and
specifying discharge limitations for stormwater runoff from active plant areas.
23.
-------
The primary source of process wastewater in an ammonia plant is condensate
from cracking of methane for hydrogen production. For a number of plants sur-
veyed, process condensate averages about 1150 liters/metric ton of ammonia,
containing about 870 mg/£ ammonia and 520 mg/£ methanol.9
4.3 PRESENT AND POTENTIAL CONTROL TECHNOLOGY
In general, most synthetic ammonia plant emissions are within current state
compliance limitations and do not require air control equipment. The major
reason for past reduction in air emissions in the ammonia industry is more
efficient utilization of material and energy through process modification and
advanced ammonia production technology development.
4.3.1 Desulfurization
During regeneration of an activated carbon bed, carbon monoxide, hydro-
carbons, and steam are vented to the atmosphere. State air control agencies
have not considered this source to be a problem because the emission only
occurs from 10 to 20 hours once every 20 days. Hydrocarbon emission levels
appear to be quite high during regeneration reaching 3.6 g/kg of product (mea-
sured as methane). To date, the majority of ammonia producers do not have a
control device on this source.
Emissions from regeneration of the activated carbon bed can be eliminated
by incineration. Figure 4 illustrates how an incineration system may be
utilized to burn various pollutant streams in a typical ammonia plant. Air
emission from the desulfurization unit, overhead from the condensate stripper,
relief valves and vents are all routed to the incinerator. In addition, this
system allows all process condensate to be recycled.
Alternatively, the problem of regeneration emissions can be eliminated by
the substitution of zinc oxide for activated carbon desulfurization beds. This
24
-------
NATURAL -*V V* •» <
a*. £. i '
mtlMEMATO*
H5 , HCTHAMOLt
AIM EMISSION
(HC,CO,SO2)
OCSULFUHIZA
iiM'.oTU^'^l^M'r-."
"""" -*ji««TOR
"T"
[ STEAM 1
TURBINE 1
L°r
•».
„.
*
(
HIGH
0 SHIfT
WASTE
BOILER
com
Tr
CO
Figure 4. Incineration scheme of various air streams.
not only eliminates regeneration emissions but also saves energy and is a more
effective desulfurization technique.
Zinc oxide beds contain approximately 14 m3 of zinc oxide. The normal
design life of a zinc oxide bed is 1 to 2 years depending upon the sulfur
concentration of the natural gas. The spent bed is disposed by landfill or
sale for recovery as zinc oxide.10
4.3.2 Primary Reformer
To date there are no pollution control devices used to control emissions
from the primary reformer. In the past, purge gas which was vented from the
synthesis process to prevent buildup of inerts was flared. Ammonia producers
now use purge gas for 15 to 20 percent of the energy input into the primary
reformer. Firing the reformer with purge gas results in a substantial increase
in NOX concentrations (see above). If NOX emission standards are made more
stringent, it may be difficult for ammonia producers to comply. There are
several approaches to the avoidance or abatement of this problem:
• cryogenic recovery instead of use of purge gas as fuel
• modification of combustion conditions
25
-------
• low nitrogen fuel use
• removal of NOX from flue gas
4.3.2.1 Cryogenic Recovery—
While most ammonia producers fire their reformers with natural gas and
purge gas, a few ammonia producers are installing a cryogenic system for the
separation of hydrogen and to maximize production. Cryogenic recovery instead
of direct use of purge gas as fuel in the primary reformer reduces NOx
emissions.^
Figure 5 shows a flow diagram of a cryogenic hydrogen unit at Vistron
Corporation's (Cleveland, Ohio) 1360 metric ton/day ammonia plant.12 Vistron's
recovery unit costs less than $2 million with an expected system pay-back time
of approximately 2-1/2 years. Figure 6 shows the rate of return with varying
prices of ammonia and natural gas.
Rn.yclcrt hydrogen
4 26 MM 1|3/d
40° F
400 psi
91% H,
< 1 % Ar
< 1%CH4
Ammonia
put <)C'(jas
7 69 MM ft^/d
20 to 10° F
2.000 psi
62% Hj
21%N,
4% Ar *-•
11% CH,,
2% NH3
(to syngas
compressor
suction)
1
Aquec
, ammo
\ / Absor
A
(_ Rich
liquor
1
.
Waste fuel
gas -«
3.28 MM ft^/d
40° F
75 psi
28% H2
38% N2
10% Ar
21% CHa
>us
^ia^-i
ber JL
-*©*
&—
Pretreatn
X
X
X
T
nent
Vistron's recovery unit uses waste fuel-gas
(to primary reformer burners)
Treated purge gas
—xx
f \J\ Cooling
\^J water
Anhydrous
ammonia
Distillation ,
column /
Molecular
sieves-'
•«- — [Reboiler
L_^ZI_Pj~
Condensate
II
r£xt-
K
X
rr^'
LTV-L
j
A
t
R
*. ^ 1
1 cleanui
c
For
burning
For
regeneration
£
Electric
heater
for molecular-sieve regeneration
i
1
• ;
i .
H
>yoge
r--Plate-and-fin
,' heat exchanger
i
1
T Refrigeration
j system
"*
Hydrogen
Separator
Condensed
waste fuel-gas
nic section ^
Fig.
Figure 5. Vistron's cryogenic recovery system,12
26
-------
100 110 120 ISO 140
AMMONIA PRICE, $/ton
Figure 6. Percent return of a cryogenic system versus price of
ammonia at various natural gas prices.*2
4.3.2.2 Modification of Combustion Conditions—
Combustion modifications through changes in operating conditions and
burner redesign are NOx control techniques that have been successfully demon-
strated on utility boilers and other stationary combustion sources. The forma-
tion of NOx from fuel combustion takes place by two mechanism. The first
mechanism, termed thermal fixation, involves the reaction of atmospheric oxygen
and nitrogen. The second mechanism involves the oxidation of nitrogen contained
in the fuel. Reduction in the oxygen content by use of low excess air or staged
combustion reduces emissions of both fuel and thermal NOX whereas reductions in
flame zone temperature produce significant reductions only in thermal NOX.
Methods used to reduce temperature include water injection, reduced air pre-
heating and extraction of heat from the flame zone by burner modification.
The primary reformer combustion unit of most ammonia produces operates
at relatively low excess air levels (10 to 20 percent). A reduction of NOX
emissions by further reduction of excess air levels does not appear practical.
Ammonia producers feel that the only means of reducing NOX levels is through
27
-------
burner redesign.13 However, the significance of achievable, reductions will be
lowered by use of purge gas as a reformer unit fuel and the injection of the
stripper overhead into the reformer stack.
Burner modifications to reduce NOX have been classified into the following
categories: (1) mixing; (2) divided flame; (3) self-recirculation; and
(4) staged combustion.
Good mixing qualities may be achieved by burner modification by the con-
tinuous injection of air into a cylindrical stream mixing with jets of fuel in-
jected radially outward through shaped ports. In addition, the air and fuel
mixing "process is aided by a deflector plate (Figure 7). The homogenous mixture
of air and fuel produces a radial conial flame thin and flat for maximum heat
radiation and dissipation.1If The shape of the flame ensures an extremely short
nitrogen oxygen reaction time, thus reducing the production of thermal NOX-
l\\\\\\\\\\
IANT RADIATION
CYLINDRICAL AIR SHEET
FUEL
ZONE
RECIRCULATION ZONE
Figure 7. NFK-TRW burner flame reaction.14
28
-------
Another method for reducing thermal NOX is by exhaust recirculation.
Personal communications with ammonia producers indicated that retrofitting an
exhaust gas recirculation system to primary reformers would be impractical, and
would increase energy demands. Figure 8 illustrates a self-recirculating gasi-
fication (SRG) burner which has been developed by Nippon Furnace Kogyo
Corporation.11*
There are two types of staged combustion burners: the two-staged com-
bustion type and the off-stoicheometric combustion type. The two-stage com-
bustion type burner is shown in Figure 9.11* This type of burner is not yet
used commercially because of flashback problems. However, it may be applicable
as a combustion unit for the primary reformer and deserves further study.
The off-stoicheometric combustion type burner for gas firing features an
atomizer with various size holes .creating rich and lean regions of fuel under
a uniform airflow. Because of easy installation and low cost, this burner is
used widely in Japan. However, there is a tendency for the burner to increase
soot emissions resulting from low excess air regions in the combustion zone.
Water and steam injection has been found to reduce effectively NOX emis-
sions. However, water and steam injection decreases thermal efficiency re-
quiring additional heat input to produce an equivalent amount of ammonia,
increases corrosion and causes undesirable operating conditions.
4.3.2.3 Use of Low Nitrogen Content Fuels—
Other methods of reducing NOX are related to the nitrogen content of
fuels. Normally, about 30 percent of the fuel nitrogen is converted into NOX
on combustion and is emitted along with thermal NOX. Fuel NOX emissions will
decrease in the utilization of the following fuels in descending order: solid
fuels (coal and coke), liquid fuels (petroleum) and gaseous fuels. At the
29
-------
.GASIFICATION GASv
1 CO, H2 RICH ;<
RE-COWUSTIOH GAS
8ASIFICATION REACTION
C
H
C02 * C
C * HZO^
CWtn + mH
FUE
CmHn
COMBUSTION PRODUCTS
)
SECONDARY AIR
Figure 8. Principle of SRG burner.
GAS OR
GAS PREMIXED
WITH AIR
FIRST STAGE
SECOND STAGE
t
AIR
Figure 9- Low NOX two-stage combustion burner.14
30
-------
present time in the U.S., coal (-1.5 percent nitrogen by weight) is not used
as a heat source in the primary reformer. Grade C heavy oil contains about
0.35 percent nitrogen by weight, Grade B, 0.08 percent, Grade A and kerosene
0.005 to 0.08 percent. Nitrogen content will be an important consideration in
the development of alternative feed stocks (see Section 7.1).
4.3.2.4 Flue Gas Treatment to Reduce NOX—
The Japanese are>developing five techniques for denitrification of flue
gas:
1. Selective catalytic reduction (SCR) with ammonia
2. Ammonia reduction (AR) without a catalyst
3. Electron beam radiation
4. Absorption (by molecular sieve, gelatinous materials, etc.)
5. Catalytic decomposition.
Only SCR and AR systems are being used commercially in a number of plants
in Japan. The other three techniques are still in the R&D, pilot plant, and
small scale production stages with very limited data available.
The advantages of selective catalytic reduction are the consumption of
less reducing gas than nonselective catalytic reduction, less plant space re-
quired, absence of troublesome byproducts, and no requirement of reheating of
gases compared to wet NOx denitrification. The disadvantages with SCR units
vary with each system. Particulates can plug the catalyst and SOX poison it.
The Sumitona Chemical Company in Japan has five commercial plants in
operation using selective catalytic reduction of NOX. One commercial plant is
treating 200,000 m3/hr of flue gas from a reformer burning LPG at Higashi Nikon
Methanol Company (HNM). (Figure 10.)
31
-------
STACK
Figure 10. HNM plant denitrification process flowsheet.14
The advantages of HNM process are its simplicity, smooth operation, and
very low NHs emissions. However, the cost for denitrifying is quite high, about
$0.40/1000 m3.
NOX can be converted to N2 by ammonia in the presence 02. Tests by Exxon
indicated that ammonia injected into flue gas at 960°C will convert approxi-
mately 70 percent of the NO to N2,15 tests on a full scale retrofit commercial
combustion source conducted at the Kawasaki plant in Japan indicated a 60
percent conversion of NO to N2, and tests on a denitrification process developed
by Nippon Kokan indicated an 80 percent conversion of NO to N2 with residual
NHs in the treated gas less than 20 ppm. In large scale operations Nippon
Kokan expects about 50 percent NOX removal at an NHs/NO m°le ratio of 1.5 to
2.O.16
4.3.4 Carbon Monoxide Shift Condensate Stripper
Process condensate is formed while cooling synthesis gas. In order for
ammonia producers to comply with effluent standards, most have incorporated a
condensate stripper that reduces ammonia and methanol condensate by about 98
percent (Table 8) to levels in compliance with effluent standards for discharge
into receiving streams.
32
-------
TABLE 8. MASS BALANCE AROUND THE CONDENSATE STEAM
STRIPPER—RESULT OF 65 TEST MEASUREMENTS9
Stream
Process condensate
Steam
Overhead
Effluent
Stream
flow
rates
(kg/hr)
80,500
7,980
8,680
81,200
Mass
Ammonia
39.2
0
41.2
0.57
flow rate
Methanol
21.1
0
22.7
0.28
(Kg/hr)
Carbon
dioxide
1
0
1
0
Note: Mass entering the stripper does not exactly equal mass
exiting because these values are the averages from test
measurements.
An EPA-sponsored study developed effluent discharge factors for steam
strippers, shown in Tables 9 and 10.9
TABLE 9. EFFLUENT DISCHARGE FACTORS FOR A CONDENSATE
STEAM STRIPPER (mg/kg OF PRODUCT)9
Effluent species Effluent discharge factor
Ammonia 15 ± 105%
Methanol 7.5 ± 97%
Note: Uncertainty values were calculated using
the "Student t" test for 95 percent
confidence limits.
33
-------
TABLE 10. TRACE METAL EFFLUENT DISCHARGE FACTORS
FROM A CONDENSATE STEAM STRIPPER9
„ . - Average concentration
Metal f / 3\
(g/nr)
Chromium
Copper
Iron
Nickel
Zinc
< 0.2
< 0.02
< 0.1
< 0.2
< 0.02
Effluent discharge factor
(g/kg of product)
< 4 x
< 4 x
< 2 x
< 4 x
< 4 x
10~5
10~6
io-5
10~5
io-6
Stripping the ammonia from the water results in air emissions of ammonia
and methanol, termed overhead. The overhead can be injected into the furnace
inlet but this is uneconomical; for a 900 metric ton/day NHs plant an additional
2000 m3/day of natural gas is required.5
Injecting the overhead into the primary reformer stack is the most widely
used and economical abatement system. However, as discussed previously, while
this reduces overall plant emissions of NR^ and methoanol, NOX emissions are
significantly increased as shown in Table II.17
TABLE 11. THEORETICAL CONVERSION OF AMMONIA IN
STRIPPER OVERHEAD OF A 900 METRIC TON/
DAY PLANT TO NOX IN PRIMARY REFORMER
STACK9
Ammonia
mg/£
4750
0
introduced
kg/hr
38
0
NOX from stack
ppm kg/hr
261 103
172 68
34
-------
Some plants have installed a common incinerator for the thermal decom-
position of emissions from vents, overhead and polluted streams. Figure 11
illustrates a flowsheet of a reflux incineration system. The refluxing system
concentrate contaminants as an overhead vapor product which is incinerated or
the ammonia can be recovered cryogenically. Stripper bottoms may be recycled
as boiler feedwater or cooling tower makeup.18 In the latter instance, nitro-
gen compounds may be eventually discharged with blowdown to water courses or
treatment systems.
A system which has been used in conjunction with a carbon dioxide scrubbing
system and low level heat is a modified overhead reflux and product recovery
system. Figure 12 shows such a reflux condensate stripping system.6
Another scheme based on 100 percent condensate recycle utilizes a satura-
tion tower to saturate natural gas feed to the primary reformer with untreated
condensate (Figure 13).18
Hot water circulation supplies the heat required for vaporizing the con-
densate. This design utilizes the partial pressure of natural gas to facilitate
saturation. All the condensate is vaporized and serves as feed for the reformer.
This system does not require a condensate stripper. Figure 13 shows a natural
gas saturation flow diagram. Natural gas saturation has the following advan-
tages: (1) elimination of additional reforming steam, (2) reduction in boiler
feedwater, and (3) complete elimination of condensate disposal.8
4.3.5 Carbon Dioxide Removal System
The composition of emissions from the carbon dioxide removal system is
98.5 percent carbon dioxide and 1 percent water. Industry has not been re-
quired to install air control devices on such units. Approximately 70 percent
of ammonia producers use the carbon dioxide as a chemical feedstock in urea
35
-------
PROCESS
COMPENSATE
>TO INCINERATION OR
AMMONIA RECOVERY
UP STEAM
STRIPPED CONDENSATE
TO
COOLING TOWER
OR
BOILER FEEDWATER
Figure 11. Reflux incineration system
18
COMPENSATE
STRIPPER
PROCESS
CONDENSATE
TO AND FROM
COj
REGENERATOR
VENT
->| LOW
1 PRESSw*
STRIPPED
CONDENSATE
PREHEATED
NATURAL OAS
>TO PRIMARY
REFORMER AS
FEEDSTOCK
SUPERHEATED
REFORMING
STEAM
REFLUX SYSTEM
\—i
T
ENTRAINMENT
(TO STRIPPER)
DESUPERHEATER
Figure 12. Reflux condensate stripping system.6
36
-------
NATURAL GAS
SATURATOR
PREHEAT
NATURAL GAS
FEED
LOV PRESSURES-
FLASH STREAM
V
NATURAL GAS/STEAM MIXTURE
{NH3 , C02 METHANOL)
TO REFORMER FURNACE
INTERMEDIATE
PRESSURE
STEAM
/
STEAM
CONDENSATE
(TO RECOVERY)
*—WATER CIRCULATION
SYSTEM
SHIFTED GASES
TO
C02 ABSORBER
<—LOW TEMPERATURE
SHIFT EFFLUENT
PROCESS CONDENSATE
T
PROCESS.
CONDENSATE
(FROM OTHER
SOURCES)
SLOWDOWN
Figure 13. Process condensate natural gas saturation process flow diagram.18
-------
production while the other 30 percent is used in other processes. In the past,
most ammonia producers have used MEA carbon dioxide removal systems because of
their low capital investment. However, the hot potassium carbonate system
require 40 to 50 percent less energy for regeneration than the MEA system. In
addition, after decades of research and development, capital costs for the hot
potassium carbonate systems and MEA system are similar.-1^ Therefore, the
economic incentive from energy savings clearly favors an increase in hot
potassium carbonate process utilization.
Still another method of treating stripper condensate is air stripping, an
approach which has been considered in advanced municipal wastewater treatment.
The technique is costly energy-wise and has other drawbacks. No air strippers
are known to be operating or planned at nitrogen fertilizer facilities.
38
-------
5.0 AMMONIUM NITRATE
5.1 PROCESS DESCRIPTION
Ammonium nitrate is presently produced at 57 plants located in 28 states.
Present annual capacity is roughly 8.9 * l'o6 metric tons of ammonium nitrate
solution in terms of 100 percent ammonium nitrate. The industry typically
operates at 85 to 90 percent capacity. The average capacity of a low density
ammonium nitrate plant is 550 metric ton/day. A large ammonium nitrate plant
produces about 800 metric ton/day. The average high density plant produces
725 metric ton/day while a large high density plant has a capacity of about
1100 metric ton/day. Ammonium nitrate is produced by neutralizing nitric acid
directly with ammonia:
NH3 + HN03 NHHN03 (9)
The reaction is exothermic, releasing roughly 112 KJ per gram mole of
aqueous ammonium nitrate produced. This heat of reaction is used to drive off
some of the water, concentrating the product stream.20'21
The overall manufacturing process can be broken down into the following
operations:
1. solution formation
2. solution concentration
3. solids formation
4. solids drying and cooling
5. coating and/or additives
39
-------
6. screening
7. bagging, storage and bulk shipping
5.1.1 Solution Formation
Approximately 90 percent of all the ammonium nitrate produced in the U.S.
uses the same general solution formation steps. The other 10 percent is pro-
duced by the Stengel process and will be discussed later. During neutralization,
the lower the pH, the lower the ammonia losses will be. Reaction pH is usually
held either in the 1.5 to 2.5 or the 5.0 to 7.0 range.5»2l>22 Heat from the
reaction concentrates the solution to the desired 83 percent.
5.1.2 Solution Concentration
Most plants producing solid ammonium nitrate rely on falling film evap-
orators to concentrate the ammonium nitrate to the levels required for subse-
quent prilling, granulation, etc. Typically, these units operate under a vacuum
of 57 kPa. Most of these units are single stage, although two-stage evaporation
is occasionally employed. Other evaporation equipment used are air-swept fall-
ing film heat exchangers, barometric condensers, and agitated tanks (e.g.,
calandrias).
5.1.3 Solid Formation
Approximately 60 percent of the ammonium nitrate produced in the United
States is sold as a solid product. There are four methods of producing solid
ammonium nitrate:
1. prilling
2. drum granulation
3. grinding
4. Stengel Reactor and Sandvik belt process
40
-------
Eighty percent of the solid ammonium nitrate produced is by prilling;
about another 10 percent by granulation, and remaining 10 percent by graining
and Stengel and Sandvik belt processes.
In a prill tower, molten ammonium nitrate falls from the top of the tower
countercurrent to an airflow. The airflow cools the falling droplets and
allows their surfaces to crystallize before reaching the bottom of the tower.
Upon reaching the bottom of the tower, the solidified droplets or prills
are either carried away on a conveyor or held temporarily at the bottom,
fluidized by the entering air. The fluidized bed technique allows the prills
7 O Q
to cool further with minimum caking or sticking before being removed. >J Am-
f\ Q
monium nitrate prill sizes typically fall in the range 1.5 to 4.0 mm.^3 Low
density prills contain 95 to 96 percent NlfyNC^, high density prills 99 percent.
The former is used for fertilizer and explosives, the latter fertilizer.
In the granulation technique, particles are built up to granules by
accretion. The particles produced are larger with greater abrasion resistance
and two to three times the crushing strength of standard prills. These pro-
perties result in less crushing, dust formation and caking upon handling.22 »2t* >25
Graining is a costly operation, accounting for less than 2 percent of the
country's ammonium nitrate production. Ammonium nitrate grains are produced
by discharging 98 percent melt into large jacketed kettles equipped with plows
for stirring the molten material. The rate of cooling is controlled by steam
and cooling coils in the kettle jacket. The material .cools and "fudges," and
then is broken up into grains by the plow. The resulting pellets are cooled,
screened, and coated.20'21
Although the Stengel reactor process is actually a solution formation
step, it is examined here because it is normally employed in conjunction with
41
-------
a Sandvik belt to combine solution formation, concentration, and solid formation
steps.
Ammonia and 55 percent nitric acid are fed into a high temperature, high
pressure reactor packed with steel Raschig rings. The product stream is ex-
panded into a cyclone separator, and is further concentrated to about 99.8 per-
cent before exiting from the separator by a stream of hot air which enters at
the bottom of the cyclone.
The melt from the Stengel reactor and separator unit is spread onto a
water-cooled stainless steel Sandvik belt. A doctor blade removes the crystal-
line product from the belt. The material is ground, screened, coated, and
bagged.11,17,26,27,28
5.1.4 Product Finishing
Drying removes water from solids which have been formed with a high mois-
ture content melt, (< 98 percent ammonium nitrate). Typically, this step is -
performed by two rotary drum dryers in series although fluidized bed coolers
are beginning to gain some acceptance. It is common practice to use a coating
and/or an additive to enhance shelf life and to suppress dust emissions from
solid ammonium nitrate particles. Additives include magnesium oxide, calcium
oxide, and magnesium nitrate.20 »29
Product size is primarily controlled by screening. Oversize and undersize
material is removed from the product solids and recycled.
In most plants, it is common for material to be transported by conveyor
belt from one process step to another. Ammonium nitrate shipment is either
by bag or bulk. The trend has been toward bulk handling of ammoinium nitrate
solids (over 90 percent of product).20*30
42
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5.2 EMISSIONS AND EFFLUENT SOURCES
Process steps responsible for air emissions in ammonium nitrate production
are as follows: (1) neutralization; (2) evaporation and concentration;
(3) prilling; and (4) cooling. Sources of wastewater effluent in ammonium
nitrate manufacturing process are as follows: (1) neutralizer, (2) evaporator
exhaust, and (3) solutions from air pollution control equipment used on the
cooler and/or dryer. In addition, there is a potential for fugitive air emis-
sions and water effluent from vents, leaky seals, compressors, pumps, storage
facilities, relief valves and ammonia spillage. Table 12 shows pollutants,
source severity factors (see Section 5.2), and control equipment for various
processes.5 »20
Point sources of wastewater from ammonium nitrate manufacturing include
condensate from neutralizer and evaporator exhausts and solution from wet
scrubber air pollution equipment. Roughly one-half of ammonium nitrate plants
condense process exhaust, and about one-half of these plants either recycle
material to process units or combine it with fertilizer solutions. Thus, only
about 25 percent of all plants release process condensate to treatment units
or receiving waters.
EPA evaluated effluent parameters by surveying the industry prior to
setting effluent standards. Ammonia nitrogen and nitrate nitrogen were the
primary pollutants of ammonium process wastewater as summarized in Table 13.
5.2.1 Neutralizer
The vapor stream off the top of the neutralization reactor is primarily
steam with some ammonia and NHi^NOs particulates present. The lower the pH
(excess of nitric acid), the lower the ammonia emissions while the higher the
pressure the higher the ammonia emissions. Uncontrolled particulates for
43
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TABLE 12. AIR AND WATER POLLUTANTS AND CONTROL REQUIREMENTS
FOR AMMONIUM NITRATE PRODUCTION5'20
Average plant
Source
Pollutant
_ Required
Sour?e control*
severity
J percent
Air
Ammonium nitrate
Neutralizer
Evaporator /Concentrator
Prilling tower
Granulator drum
Cooler
Particulate
Particulate
Particulate
Particulate
Particulate
2.07
0.70
0.17
ND
0.06
97.6
92.9
70.6
ND
7.0
Water
*
Ammonium nitrate
(including nitric acid
and ammonia)
NH3 - N
NHq. - N
N03 - N
0.089
0.0043
0.0004
43.8
0
0
To achieve a source severity = 0.05. Sources are not
identified. Data are for combined plant effluent.
Note: ND = No Data.
TABLE 13. AVERAGE EFFLUENT PARAMETERS FOR
NITROGEN FERTILIZER PLANTS10
Parameter Ammonium nitrate Urea
Wastewater effluent flow rate, m3/s
Effluent factor, g/kg
Ammonia nitrogen (NH
Nitrate nitrogen
Organic nitrogen
Effluent concentration
Ammonia nitrogen (NH
Nitrate nitrogen
Organic nitrogen
of product
:3 + Ha**)
, g/m3:
3 + NH.+)
0.0346
0.862
0.471
0
482
121
0
0.03
0.7
0.2
1
Data on file at the Effluent Guidelines Division of the U.S.
Environmental Protection Agency, Washington, D.C., 1977.
44
-------
conventional neutralizers usually fall in the range Of 0.25 to 3.7 kg/metric
ton of 100 percent ammonium nitrate. A typical uncontrolled emission rate for
ammonia losses from a neutralizer is 1.5 kg/metric ton of NR^.
5.2.2 Evaporator/Concentrator
Approximately 75 percent of the industry utilizes film-type evaporators.
Ammonia emissions should not be a problem because of the pH range of 5.2 to 5.4.
Ammonium nitrate particulate emissions in the vapor streams off the evaporators
generally fall in the range of 0.1 to 1.0 kg/metric ton of ammonium nitrate.20
5.2.3 Prill Towers
The prilling process, which involves prills falling through a counter-
current airstream, is highly conducive to particulate entrainment. The smaller
particulates in the submicron range, referred to as "fume," resulting from the
evaporation and subsequent condensation and solidification of the material
being prilled, is particularly difficult to control. The quantity of fume pro-
duced has been found to be temperature dependent; to minimize fume formation,
melt temperature should be kept as low as possible and melt composition care-
fully controlled.28*31 Typical emissions from an ammonium nitrate prilling
tower fall in the range 0.2 to 1.5 kg of ammonium nitrate particulates per
metric ton of ammonium nitrate product.
5.2.4 Granulator
Because of the limited use of drum granulators in the ammonium nitrate
industry, there is a scarcity of data regarding emissions from this source. A
reasonable estimate for particulate emissions can be made by assuming emissions
similar to those for urea. This assumption leads to an estimate of a range of
0.05 to 1.0 kg of particulate emitted per metric ton of ammonium nitrate pro-
duced for a granulator equipped with a scrubber. Note that this range is not
for uncontrolled emissions as a scrubber is considered as an integral part of
the process.
45
-------
5.2.5 Dryers, Coolers, Additives, Coating, and Screening
Uncontrolled emissions from dryers and coolers range from 1 to 10 kg/metric
ton of product, but are readily reduced by scrubbers. Pollutants from additive
operations can be considered negligible. Emissions from coating operations are
fugitive emissions. Based on the estimate of 10 percent loss of coating ma-
terial during coating operations, there is an emission of 3 kg/metric ton of
ammonium nitrate (for a coating level of 3 percent). Most of the material
actually settles to the floor and only a small percentage of this material es-
capes to the atmosphere.20 Only a small quantity of particulates escape as
fugitive emissions from the building in which the screening is performed.
5.2.6 Product Handling
One source of emissions of airborne fines is the series of transfer points
often by conveyor belt, in the process. The severity of this emission source
will depend on the characteristics of the material.
Approximately 90 percent of all ammonium nitrate solids are handled in
bulk. Because of the small quantities of fines present in the ammonium nitrate
solid, particulate entrainment is low in these operations. One estimate is
that less than 0.1 kg of particluates per metric ton of ammonium nitrate
product is entrained in bulk handling.20
5.3 PRESENT AND POTENTIAL CONTROL TECHNIQUES
Particulates and ammonia are emphasized in this section. NOX emission
data was not available from the industry sources and equipment vendors contacted
during this study. Because there is no standard test method for ammonium
nitrate particulates, and the physical and chemical properties of ammonium
nitrate can affect sampling results when the standard EPA Method 5 is used,
there is also a paucity of information relative to the control of emissions of
this material.
46
-------
5.3.1 Neutralizer
The neutralization reaction is exothermic and produces quantities of steam
which may contain particulates, ammonia, and/or nitric acid. During normal
plant operations emissions can be eliminated by total condensation. However,
even with total condensation it is necessary to vent steam during startup,
shutdown, or upset conditions. Little information is available on the factors
affecting other control methods. Emission rates after control, as shown in
Table 14, range from 0.17 to 0.5 g/kg. Condensation, wet scrubbing, and
Monsanto high efficiency mist eliminators should be effective for ammonia.
TABLE 14. SUMMARY OF NEUTRALIZATION
EMISSION DATA17
Emissions
Emission control method
g/m3* g/kg of product
HV mist eliminator 0.50 0.42
Partial condensation 1.23 0.50
Mississippi Chemical unit 0.36 0.17
*
Grams per wet standard cubic meter.
Mississippi Chemical Corporation (MCC) has developed and patented a
neutralizer which reduces particulates and fumes and ammonia emissions to a
fraction of those emitted from most conventional neutralizers. By process
design and by close pH monitoring, particulate emissions from conventional
neutralizers typically run about 1.07 to 1.92 kg/metric ton of ammonium nitrate
while MCC neutralizers have been found to generate 0.074 to 0.247 kg/metric
ton and < 2 kg of ammonia per metric ton of ammonium nitrate produced.
The MCC neutralizer (Figure 14) has two reaction zones: (1) a nitric acid
aqueous reaction zone and (2) an ammonia aqueous reaction zone. Nitric acid
circulates into the ammonia reaction zone in such a way that the acid entering
47
-------
VAPOR
OUTLET
OVERFLOW
AMMONIUM-
NITRATE
NITRIC ACID-*
• f:
NITRIC ACID
REACTION ZONE
INLET TO
AMMONIA
REACTION ZONE
AMMONIA
ENTERS REACTION
ZONE
AMMONIA
INLET TO
VESSEL
•DEFLECTS SOLUTION
DOWNWARD INTO FIRST
REACTION ZONE
OUTLET
SPARGER
•AMMONIA REACTION ZONE
-MESH SCREEN
Figure 14. A schematic view of MCC neutralizer.32»33
48
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the zone has been diluted to less than 5 percent by weight.32'33 Figure 14
shows a schematic view of an MCC neutralizer.32'33 Existing neutralizers can
be modified at moderate costs to incorporate these features.
5.3.2 Evaporator/Concentrator
About 70 percent of particulate emissions from the neutralizer, evaporator/
concentrator and prill tower are less than 3 pm in size. Emissions from the
evaporator/concentrator are commonly controlled by a high efficiency scrubber
(99 percent) or a medium efficiency scrubber (85 percent).
In a few plants, the neutralizer and the evaporator/concentrator are ducted
to a Monsanto HE mist eliminator. Figure 15 illustrates a Monsanto HE collec-
tion unit.31f Test data indicated an efficiency of 98.6 percent cleanup on a
stream containing neutralizer evaporator/concentrator and prill tower (with a
Cooperative Farmers Chemical Association (CFCA) cone emissions. Figure 16
illustrates a CFCA cone with a Monsanto HE mist eliminator.
5.3.3 Prill Towers
Approximately 50 percent of ammonium nitrate prill towers operate without
emission control equipment, 2 to 5 percent use the CFCA cone/Monsanto HE system,
15 percent use wet scrubbers and the remainder uses mesh pads or similar devices.
Tests for uncontrolled ammonium nitrate prill towers indicated an emission rate
of 0.455 g/kg of product, at a concentration of 0.071 g/m3. The overall CFCA/
Monsanto HE system appears to reduce emissions to below 20 percent opacity.
The CFCA cone collection efficiency was 76.9 percent (0.55 g/kg) of a
total uncontrolled emissions of 0.715 g/kg of product.17 In addition, the
Monsanto HE unit with a CFCA cone achieved a control efficiency of 96 percent
(0.02 g/kg).31* The overall control efficiency for the Monsanto HE unit alone
was only 68 percent. Tests for three different CFCA cone/Monsanto HE units
indicated an emission of 0.285 to 0.55 g/kg of product.17.31*
49
-------
AMMONIUM NITRATE
SOLUTION
AIR
OUTLET^
COLLECTION
CONE
rl /i
i
it
i /
j
4
AIR
i-«
, H
\
u
1 1
4 4
SCRUBBING
LIQUOR IN-
• \
NEUTRALIZER
AND
EVAPORATOR
- i
BRINK
COLLECTION
UNIT
i
*. LIQUOR
FAN
•PRILLS
Figure 15. Brink collection unit.3"*
ATOMIZING—\.
SPRAYS ^
SCRUBBER
SOLUTION TANK
FAN
HIGH EFFICIENCY
ELEMENTS
SPRAY CATCHER
ELEMENTS
•EMISSIONS
NEUTRALIZER,
EVAPORATOR, EMISSIONS
Figure 16. CFCA collection cone and Brink scrubbing unit.34
50
-------
The performance of wet scrubbers is especially sensitive to the
particulate size distribution. Particulate size distribution for a typical
prill tower is as follows:
• 30 percent by weight: > 3 ym
• 20 percent by weight: 1 to 3 ym
• 35 percent by weight: 0.5 to .1 ym
• 15 percent by weight: < 0.5 ym
P- *
The large fraction below 1.0 ym creates a difficult control problem and a high
opacity even at low concentrations.2® A low energy scrubber reduces emissions
to 0.625 g/kg at a concentration of 0.098 g/m3.17
By replacing the 64 prill tower spray heads with two metal shroud enclosed
spray heads, thereby creating a quiescent zone which decreases fume and micro-
prill formation, ESSD Chemical, Canada, has achieved significant reductions in
ammonia and ammonium nitrate emissions (Table 15) at a cost of $25,000.35
TABLE 15. EMISSIONS FROM ESSO CHEMICAL CANADA SPRAY HEAD WITH
SHROUD PRILL TOWER MODIFICATION35
Condition
Before
modification
After
modification
Ammonium
nitrate
kg/metric ton
product
6.5
1.2
Ammonia
kg/metric ton
product
0.18
0.10
Gas
velocity
(m/sec)
2.04
4.24
Gas volume
(m3/min)
7,500
15,500
5.3.4 Granulation
Drum granulation equipment is typically controlled by a Joy Turbulaire
scrubber. Figure 17 illustrates a Type D Joy Turbulaire impingement scrubber
and C&I Girdler granulation process.36 Emission rates typically quoted in the
51
-------
Ui
JOY TYPE 0
TURBULAIRE SCRUBBER
OUTLET
AIR OUT
CRUSHER
STORAGE
Figure 17. Joy Type D Turbulaire impingment scrubber and
C&I Girdler granulation process.^6
-------
industry range from 0.05 to 0.5 g/kg of product. A high collection efficiency
is achieved because particulate size is largely greater than 10 ym.37
Foster-Wheeler developed an evaporative scrubber system (Figure 18) to
reduce or eliminate the particulate matter in the effluent airstream associated
with the production of ammonium nitrate prills or granules and to eliminate the
process condensate.38 In addition, this system makes fertilizer recovery from
effluent streams econimically viable. One disadvantage is that this type of
scrubbing does not remove the "fume" from a high density ammonium nitrate plant,
however, if high efficiency particulatevremoval systems are incorporated, such
as those mentioned earlier, submicron particles could be eliminated.
5.3.5 Predryers, Dryers, Coolers and Product Handling
Predryers, dryers and coolers are usually very similar except that warm
air is used for predryers/dryers and cold air is used for coolers. Wet
scrubbers are practically the only type of equipment used to control emissions
from predryers, dryers and coolers. Emission rates for low energy scrubbers
controlling predryers, dryers and coolers range from 0.02 to 0.145 g/kg of
product. Emissions from product handling, as discussed in Section 5.2.6, are
negligible.
53
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AMMONIUM NITRATE SOLUTION MAKE TO EVAPORATION
AMMONIUM
NITRATE
NEUTRALIZATION
VACUUM
EVAPORATION,
PRILLING,
PRILL DRYING
AND COOLING
Ui
EVAPORATOR
VAPOR FROM AMMONIUM CONDENSER
NITRATE VACUUM
EVAPORATOR @ 5 psio
CONDENSER
I
VAPOR FROM AMMONIUM '
NITRATE NEUTRA'LIZER I"
cwcK !
i "1 — •>
ABSORBERV ^ i.
WATER 7 T*
CONDENSER >
(OPTIONAL) I
N I
TO NITRIC ACID
ABSORBER
WEAK
SOLUTION
COOLER
AIR PLUS WATER
TO ATMOSPHERE
EVAPORATOR
.SCRUBBER
IO4°F
WEAK
AMMONIUM
NITRATE
SOLUTION
II7° F
TV TV
«*-
131 °F
STRONG
AMMONIUM
NITRATE
SOLUTION
AIR PLUS AMMONIUM NITRATE DUST FROM PRILL DRYING AND COOLING
Figure 18. Evaporative scrubbing system for low density ammonium
nitrate prills.38
-------
6.0 UREA
6.1 PROCESS DESCRIPTION FOR UREA PRODUCTION
Urea is presently being produced at 44 plants located in 23 states.
Present annual capacity (340 days/year at maximum daily capacity) is approxi-
mately 5.7 x 106 short tons of urea solution in terms of 100 percent urea.
The industry typically operates between 80 and 90 percent capacity.
Urea is produced by reacting ammonia (NHs) and carbon dioxide (C02) to
form ammonium carbamate (NHitC02NH2) . The carbamate is then dehydrated to yield
urea. The reactions can be represented as follows:
2NH3 + C02 . NH^COzNHa (10)
NH^O^NHa . NH2CONH2 + H20 (11)
The final product is distributed as either a urea solution having a concentration
of 70 to 75 percent urea, or a solid.39
The overall urea manufacturing process can be broken down into the
following steps:
1. solution formation
2. solution concentration
3. solids formation
4. solids cooling
5. coating and/or additives
6. screening
7. bagging, storage, bulk shipping
55
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6.1.1 Solution Formation
There are three methods for producing urea: (1) once-through processes,
(2) partial recycle processes, and (3) total recycle processes. The most im-
portant of these three classes is the total recycle process. The Snamprogetti
process and the Stamicarbon COg stripping process appear to be the best candi-
dates for new plants. A less popular method is the Mitsui Toatsu D improvement
upon the Toyo-Koatsu process, a version of conventional total recycle process.
Additional improvements could make this process competitive with the
Snamprogetti and Stamicarbon process. Figure 19 is a schematic diagram of a
typical Stamicarbon C02 stripping process, Figure 20 of the Snamprogetti process,
Figure 21 of the Toyo-Koatsu process, and Figure 22 of the Stamicarbon total
recycle process for urea solution production.
6.1.2 Solution Concentration
There are two methods of concentrating urea solution prior to solid forma-
tion: crystallization and evaporation. The method chosen depends on the
acceptable biuret (H2NCONHCONH2) level, and impurity formed by a side reaction.
To obtain technical grade urea (< 0.4 percent biuret), more expensive crystal-
lation is necessary.39
Crystallization is performed in a tank equipped with a heat exchanger to
maintain a solution temperature of 57°C, evaporation in one or two (in series)
falling film heat exchangers operated under vacuum.
6.1.3 Solids Formation
There are essentially three methods of producing solid urea: prill towers,
drum granulators, and pan granulators. About 18 drum granulators are in oper-
ation in the United Stated. Drum granulation accounts for roughly 50 percent
of the solid urea produced.tf° The remaining 50 percent is produced mainly by
56
-------
prilling with only a small percentage produced by pan granulation. Pan
granulation is a recent development and its overall cost is somewhat less than
drum granulation.
Urea prilling and drum granulation processes are similar to those for
ammonium nitrate described above in Section 5.1.3. The pan granulator consists
of a tilted, rotating, circular pan. Feed material deposited at the top falls
through a fine spray of liquid urea and the larger granules thus formed spill
- t
over the lower edge of the pan onto a conveyor belt. TVA has developed a low
temperature (100 to 107°C) and Norsk-Kydro a high temperature (113 to 121°C)
process. Cooling is typically accomplished in a rotary drum cooler.
6.1.4 Product Finishing and Handling
The principal means of product size control is screening. Oversize and
under size material is removed from the product size solids and recycled.
The primary purpose of coatings and additives is to reduce caking and dust
formation. The most common additives are formaldehyde and phosphate-based com-
pounds. In most plants, material commonly is transported by conveyors from one
process step to another. Urea shipment is either by bag or bulk. The trend
has been toward bulk handling. Solution bulk shipment of urea is in tank cars.
6.2 EMISSIONS AND EFFLUENT SOURCES
Process steps responsible for air emissions in urea production are:
(1) solution formation; (2) concentration; (3) prilling; and (4) granulation.
Sources of wastewater effluent in urea manufacturing are evaporator exhaust and
filtrate from the concentration of urea solution when a crystallizer is used.
In addition, there is a potential for fugitive air emissions and water effluents
from vents, seals, compressors, storage facilities, relief valves and spills.
Table 16 shows air and water pollutants and control requirements to reach the
acceptable severity factor of 0.05 for various process operations.
57
-------
, IKEBTS
Ln
WASTEWftTER
UMEA »ELT
Figure 19. Stamicarbon C02 stripping process for urea production.
-------
LOW
•turn
I
MEDIUM PRESSURE
AMMONIA
SCRUBBER
REACTOR
PRHE'sl!uRE
RECIPROCATING
PUMP
6 ITTI
TREATED
MASTEWkTER
UREA
MELT
Figure 20. Snamprogetti process for urea production.
-------
EXPANSION
A 1
s — *
r
X
. — '
,
/CN
ON
O
H.P. = High Pressure
M.P. = Medium Pressure
L.P. = Low Pressure
Figure 21. Toyo-Koatsu method in urea production.
-------
cof-
H.P. = High Pressure
•ASTEWkTER
STREMI
Figure 22. Stamicarbon total recycle.
-------
TABLE 16. AIR AND WATER POLLUTANTS AND
CONTROL REQUIREMENTS FOR UREA
PRODUCTION5'20
Source urea
Pollutants
Average
Source
severity
plant
Required
control
percent
Air sources
Evaporator
Prill tower
Granulator
Including
ammoniai
NHs
Part.
NHs
Part.
NHs
Part.
Water
NH3-N
NH£ -N
ORG-N
8.8
0.12
0.51
0.94
1.27
0.1 to 0.24
sources
0.161
0.0083,
0.0025
99.43
58.3
90.2
94.7
96.1
50 to 80
69.0
-
t
To achieve source severity = 0.05
Sources are not identified. Data are for combined
plant effluent.
62
-------
6.2.1 Solution Formation
Figure 19 is a schematic of a Stamicarbon C02 stripping process for urea
production. The major emission sources of the Stamicarbon C02 stripping process
are (1) the airstream from the medium pressure scrubber, (2) the wastewater
stream from the desorber, and (3) the scrubbing fluid leaving the medium pres-
sure scrubber. The air emissions and water effluents contain NH3 and C02. In
addition, the water effluent contains urea.
The emission sources of the Snamprogetti process are two airstreams,
each treated by a water scrubber and one wastewater stream leaving the
water treatment section. The primary emissions in the airstream are W.$,
C02, and urea.
The primary emissions from the Toyo-Koatsu Process are NHs, C02, and urea.
Major emission sources in the Stamicarbon total recycle process are
(1) gases vented through the NHs scrubber containing NHs and excess C02, and
(2) wastewater stream containing NHs, C02, and urea.
In summary, most solution processes have emission sources where inerts
such as unreacted N2 and H2 are vented. Usually, these are extremely minor
emission sources - low airflow and low NHs concentration. The solution for-
mation step is not one of the major sources of air contamination in this
industry.4
6.2.2 Solution Concentration
Crystallization under vacuum is maintained by a steam ejector on an over-
head vent. The system has a minor emission source which contains NH3, C02, and
water vapor. In addition, wastewater effluent from the ejector contains NH3,
C02, and urea.
63
-------
Typically, the evaporators are also operated under a vacuum; again steam
ejectors being a common method of applying vacuum. Emissions are the same as
those previously mentioned for the crystallizer. In the case of atmospheric
evaporators, the vapor stream exiting the exchanger contains NHs and €0%.
This stream is usually recycled to the solution formation process. The air-
swept evaporators produce an airstream contaminated with NHs , CQ^, and urea
particulates which is also usually returned to the process.
6.2.3 Solid Formation
Prilling of urea has emissions analagous to the prilling of
above) with the fume being particularly difficult to eliminate.41 Emissions of
NHs can result from urea decomposition. Uncontrolled emissions are typically
1.0 to 2.0 kg/metric ton of urea product for particulates and roughly 0.7 to
1.0 kg/metric ton urea for ammonia emissions.39
The cooling air passing through the drum granulator entrains 15 to 20
percent of the product, but this airstream is smaller (approximately one-third
the airflow used in prill towers) and easier to treat than corresponding prill
tower airflows.25 Scrubbers are an integral part of the process. Drum granu-
lator emissions are relatively low, generally in the range of 0.05 to 0.50 kg/
metric ton product. Ammonia emissions are 0.1 tO 0.4 kg/metric ton product.23
Emissions from pan granulators are reportedly very low- Treatment is
standard procedure. Overall emissions, therefore, are comparable to those from
drum granulators, that is to say, 15 to 20 percent of the urea melt ends up as
potential particulate emissions.22 »23 »42
6.2.4 Product Finishing
Urea product finishing covers cooling, screening, incorporation of addi-
tives, and coating. As the cooling drum rotates, particulates are entrained
64
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However, this exhaust stream from the cooling drum is typically treated.
Particulate emissions from this unit can be expected to be lower than from a
drum granulator.
Emissions from screening are difficult to assess but are believed to be
generally of a fugitive nature and low.
6.2.5 Product Handling
It is also somewhat difficult to predict or determine emissions from urea
product handling activities. A value of 0.12 kg NH3/metric ton 100 percent
urea upon loading into tank cars has been estimated on the basis of the equili-
brium vapor pressure NH3 over 70 percent urea solution.'*3 For bagging opera-
tions, a "worst case" value of 0.15 kg particulates/metric ton of urea handled
had been calculated on the basis of the fraction of fines.39
6.3 PRESENT AND POTENTIAL CONTROL TECHNIQUES
The major emission point from urea production is in the solid formation
step. Generally speaking, controls have not been applied because no state
standards are violated. However, the above examination of source severity
factors for air emissions and water effluents for urea indicates a need for
pollution control.
6.3.1 Solution Formation Process
Process vents from the solution formation process are often scrubbed to
recover ammonia and other chemicals. There are no data available regarding the
control or even the occurrence of particulate emissions from the solution pro-
duction process, and Monsanto Research Corporation appears to conclude that
O Q
there are no particulate emissions from the solution production process.
6.3.2 Solution Concentration Process
In the solution concentration process, evaporator emissions may be
controlled to recover ammonia and/or urea to meet state emission regultions.
65
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Data collected as part of this study indicate that about 40 percent of the urea
evaporators are controlled by condensation, 10 percent by wet scrubbing, and 5
percent by demisting. The remaining 35 percent of the urea evaporators are
currently operating without control equipment.
Some evaporators are controlled by Venturi scrubbers. Available data show
a particulates emissions rate, after such control, of 0.24 g/kg.17 The ex-
haust from a wet-scrubber-controlled evaporator may be recycled in some in-
stances, thus eliminating both particulate and ammonia emissions. The litera-
ture for a Wet scrubber-controlled evaporators show ammonia emission rates
reduced to 1.7 g/kg.
6.3.3 Prill Towers
Approximately 45 to 50 percent of the plants use wet scrubbers for
particulate emission control for urea prill towers. The other plants modify
production rates to meet state regulations. Many facilities can meet existing
mass emission rate regulations but have difficulty with opacity standards be-
cause of the relatively large fraction of fine particles.
Available emission data for wet scrubber-controlled urea prill towers are
presented in Table 17. For "uncontrolled" towers, data show a typical emission
rate of 1.6 g/kg.17 The ammonia emission factor for prill towers is 0.4 g/kg.
Many facilities add 0.4 g of formaldehyde per kilogram of urea to the melt
before prilling. No data on formaldehyde emissions from prill towers are
available.
6.3.5 Granulator
Emissions from drum and pan granulators are controlled by wet scrubbers.
Approximately 10 to 20 percent of the feed would be lost if the scrubber were
not used, so the scrubber may be considered as process as well as pollution
66
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TABLE 17. SUMMARY OF EMISSION DATA FOR
PRILL TOWER CONTROLLED BY
WET SCRUBBERS*17
Emissions
«
c
Df
D!
E
5/kg
0.
0.
0.
0.
product
058
43
375
425
g/m3
0.0071
0.032
0.020
0.048
g/sec
0.18
4.5
4.2
3.2
Test data not yet validated.
Fertilizer grade urea.
tFeed grade urea.
control equipment. Emission rates from granulators are 0.25 g NH3/kg and 2 g
particulates/kg.
The primary purpose of the Foster-Wheeler evaporative system (Figure 23)
is to eliminate particulate matter from prilling and granulation production
processes and to eliminate the discharge of nitrogen bearing process condensate
into receiving waters. Similarly the Vistron urea pollution control system
(Figure 24) is also designed to abate both air and water pollution.
The pan granulator is more amenable to effective particulate emission
control than prill towers and Figure 25 shows such a system incorporating a
hood to collect fume and a centrifugal scrubber.44
Urea plant process condensate can be treated by urea hydrolysis. This
reconverts the urea back to NH3 and C02 which can be vented to the atmosphere
or, preferably, recycled.
Several hydrolysis stripper units are commercially available and operating
in domestic urea plants. The Technip SD unit is designed for influent concen-
trations up to 15 percent ammonia and 3 percent urea (by weight) with effluents
67
-------
00
Urea Solution to Evaporation
Figure 23. Evaporative scrubbing system, urea plant, prills or granules.
38
-------
Urea Prill Tower
WET SCRUBBER
ATM.
L
CITY
WATER
BUSTLE
AIR TO ATM.
PRILLED
UREA
Figure 24. Vistron pollution control system.
69
-------
95 PERCENT
SOLUTION
GRANULATED
FERTILIZER
EFFLUENT
CONCENTRATED
IN SCRUBBERS
FOR REUSE
STACK
EXHAUST FAN
PAN GRANULATION
CENTRIFUGAL
SCRUBBER
Figure 25. Emission control system.
70
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of 30 g/m3 (ammonia and urea combined)>5 Vistron, also has several operating
units designed for comparable influent concentrations and effluents of 60 g/m3
urea and 30 g/m3 NH3. This system was also discussed in Section 6.3.6.
Certain approaches to abatement of water pollution are applicable or of
potential applicability to the fertilizer industry generally as well as to urea
production.
6.3.5 Predryers, Dryers, Coolers, and Product Handling
As discussed in Section 5.3.5, emission from these operations are extremely
low-
6.3.6 Other Water Effluent Treatment Approaches
Conversions of nitrogeneous compounds to nitrogen gas via biological
nitrification/denitrification has been investigated and applied to some extent
to municipal and industrial wastewaters.
Biological treatment can also reduce the methanol content of ammonia plant
wastewaters. Some plants only apply nitrification in conjunction with oxida-
tion of methanol and other organic matter. In this case, ammonia is converted
to nitrates and nitrites which are much less toxic to receiving waters.
Typical performance of this type of aeration lagoon is shown in Table 18.
TABLE 18. PLANT TREATMENT OF AMMONIA PLANT
PROCESS CONDENSATE8
Component
Ammonia
COD
BOD
PH
Process condensate
bio-pond influent
rag/a
800 - 1100
2200 - 2800
1600 - 2800
8-9
Bio-pond
effluent
mgM
100 - 650
100 - 400
150 - 250
8 - 8.5
71
-------
A continuous ion exchange process marketed by Chemical Separations Corpora-
tion (CHEM-SEPS) is currently in use at 10 or more plants for ammonium nitrate
bearing wastes. A cation exchange unit removes ammonium ions and anion ex-
changer unit the nitrate ions. Typical waste effluents and treated water
discharge are shown in Table 19.
It is technically feasible to remove nitrogeneous compounds from plant
wastewater by breakpoint chlorination or by reverse osmosis, but these systems
are not used due to high costs relative to other available treatment processes.
Total nitrogen removal for these systems is on the order of 80 to 95 percent.
When faced with stringent effluent standards, most new and existing nitro-
gen fertilizer plants first minimize the quantity of wastewater requiring treat-
ment commonly by recycling. In some cases, effluents may be recycled to an
adjacent plant as illustrated in Figure 26, showing recylce of condensed
neutralizer exhaust from an ammonium nitrate plant to a nitric acid facility.
TABLE 19. REPRESENTATIVE WASTE AND ION EXCHANGE
TREATED WATER ANALYSIS46
Component
Ammonia (NH3 )
Magnesium (Mg )
Calcium (Ca^)
Sodium (Na+)
Nitrate (N03~)
Chloride (Cl~)
Sulfate (SOp
PH
Silica (Si02)
Ammonium nitrate
Influent
(g/m3)
340
4.8
60
0
1,240
53
72
5 to 9
15
removal is 99
Effluent
(g/m3)
2 to 3
-
-
-
7 to 11
-
-
5.9 to 6.4
15
.4%
72
-------
— — •+ TAILGAS
TO VENT SCRUBBER
1
[ |« COOLING WATI
CONDENSER
f-M 1 > COOL ING WATI
1 I CONDENSED
1 WATER
AMMONIA. » r i PROCESS
REACTOR
|» TO CONCENTRA1
.
•R
;R
POR-,
SURGE
TANK
rOR
GAS FROM
AND HEAT
-£
CON
EXC
MAKE UP ACID
NITRIC ACID
A
VERTER
HANGERS ~"~*
^^
BSORPTIC
COLUMN
r
i
i
iN
< „ COOLING
,.. . » PRODUCT
•" NITRIC ACID
AMMONIUM NITRATE PLANT
NITRIC ACID PLANT
Figure 26. Ammonium nitrate effluent utilization.18
Finally, such obvious abatement precautions for preventing the escape of
washdown, storm run-off, and flushing of railcars and tank trucks waters off
the site as constructing curbs, drains and storage facilities to contain these
wastewaters for either treatment or recycle to scrubber or process solutions
should be mentioned.
A review of effluent data on file at State water pollution control agencies
in Louisiana and Texas (which accounts for about 50 percent of domestic nitro-
gen fertilizer facilities) to identify plant effluent control techniques was of
limited usefulness because many plants are located within a manufacturing com-
plex combining wastewater from a number of different plants and the uniqueness
in individual plant design. At least one-half of the plants in Texas disposed
wastewaters by either deep well injection or sale as farm irrigation water.
Several plants in both states sent wastewaters to a biological treatment pond
in conjunction with wastes from other manufacturing processes.
73
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7.0 MEETING EFFLUENT GUIDELINES
Effluent guidelines for existing urea and ammonium nitrate plants and
standards of performance for new plants were promulgated by EPA on April 26,
1978.£*7 Based on a survey of about 80 percent of all ammonium nitrate and urea
plants, effluent levels achievable by best conventional pollutant control tech-
nology CBCT) and best available technology economically available (BAT) were
identified. The BCT guidelines were first promulgated on April 8, 1974, but
were modified in 1978 to reflect industry comments and incorporate additional
data. Under the Clean Water Act of 1977, industrial point sources must achieve
effluent levels corresponding to BCT by 1 July 1977 and BAT by 1 July 1984.
These effluent guidelines and also standards for new sources are summarized in
Table 20.
Nitrogen fertilizer plants, equipment vendors, industry trade associations
and research groups were contacted to discuss the need for improved control
technology to meet the effluent guidelines. Some contacts inevitably felt the
1984 BAT guidelines were too stringent. EPA's position and response to these
comments is addressed in the effluent guidelines of April 26, 1978, in the
Federal Register.**7 Standards were relaxed somewhate from those originally
proposed in 1974.9 A few sources felt ion exchange technology for meeting am-
monium nitrate BAT provisions in 1984 was not feasible for solids-producing
plants because of disposal problems for resin regenerate solution. This issue
was also addressed by EPA in promulgating the 1978 guidelines, indicating
feasibility of concentrating regenerate for recycle to the process.
74
-------
TABLE 20. EFFLUENT GUIDELINES AND STANDARDS OF APRIL 26, 1978^7
Effluent limitations
kg/1000 kg product*
BCT
(1977)
BAT
(1984)
New sources
BCT
(1977)
'
BAT (1984) and
New sources
Type plant Effluent
parameter
Urea- solutions:^ Ammonia-N
Organic-N
PH
Urea solids: Ammonia-N
Organic-N
PH
Urea-solutions: Ammonia-N
Organic-N
Urea-solids : Ammonia-N
Organic-N
Urea-solutions: Ammonia-N
Organic-N
pH
Urea-solids: Ammonia-N
Organic-N
PH
Ammonium nitrate:? Ammonia-N
Nitrate-N
pH
Ammonium nitrate:? Ammonia-N
Nitrate-N
Maximum Maximum f°* average
daily of daily values for
30 consecutive days
0.95
0.61
6.0 - 9.0
1.18
1.48
6.0 - 9.0
0.58
0.45
0.53
0.85
0.53
0.45
6.0 - 9.0
0.53
0.86
6.0 - 9.0
0.73
0.67
6.0 - 9.0
0.08
0.12
0.48
0.33
6.0 - 9.
0.59
0.80
6.0 - 9.
0.27
0.24
0.27
0.48
0.27
0.24
6.0 - 9.
0.27
0.46
6.0 - 9.
0.39
0.37
6.0 - 9.
0.04
0.07
0
0
0
0
0
V*
Based on 100 percent product.
j,
Urea guidelines do not include discharges from shipping losses, precipitation
runoff outside of battery limits and cooling tower blowdown.
IApplies to both solids and solution plants, but excludes shipping losses,
precipitation runoff from outside of plant battery limits, cooling tower
blowdown and plants which totally condense neutralizer overheads.
75
-------
Several sources commented on problems of pH control (also addressed by
EPA) and disposal of cooling tower/boiler blowdown and regenerate solution
from feedwater ion exchange units. These latter problems are not specific to
nitrogen fertilizer facilities, but rather confront industry in general.
Overall the ability to meet EPA effluent guidelines has been demonstrated
by the plants selected as the basis for setting the standards.
76
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REFERENCES
1. Pimentil, D., L.E. Hued, A.C. Bellotti, M.J. Forster, I.N. OKa, O.D. Sholes,
and R.J. Whitman. Food Production and the Energy Crisis. Science, 182
(4111): 443-449, 1973.
2. Grace, J.P. Long-term Fertilizer Problems. Chemical and Engineering News
J., 52(7): 10, 1974.
3. Commercial Fertilizer Consumption (1977). Crop Reporting Board, Statistical
Reporting Service, U.S. Department of Agriculture, Washington, B.C.,
November, 1977. 30 pp.
4. Quartulli, O.J. Developments in Ammonia Production Technology. The M.W.
Kellogg Company, Houston, Texas, (Bulletin) 1974. 27 pp.
5. Search, W.J., J.R. Klieve, G.D. Rawlings, and J.M. Nyers. Source Assess-
ment: Nitrogen Fertilizer Industry Water Effluent. EPA-600/2-79-019b,
NTIS PB292837/AF, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina, January 1979. 80 pp.
6. Rawlings, G.D., and R.B. Reznik. Source Assessment: Synthetic Ammonia
Production. EPA-600/2-77-107m, NTIS PB276718/AS, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina, 1977. 74 pp.
7. Slack, A.V., and G.R. James. Ammonia. Marcel Dekker, Inc., 95 Madison
Avenue, New York, New York, 1973.
8. Ricci, L.J. EPA Sets Its Sights on Nixing CPl's NOX Emissions. Chemical
Engineering, 7(4): 33-36, 1977.
9- Romero, C.J. , F. Yocum, J.H. Mayes, and D.A. Brown. Treatment of Ammonia
Plant Process Condensate, EPA-600/2-77-200, NTIS PB273069/AS. U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina,
1977. 93 pp.
10. Personal Communication with B.A. Sinclair. EENatCo Combustion Engineering,
Inc., P.O. Box 1710, Tulsa, OK, August 1978.
11. Personal Communication with Dr. Roy Banks. Petrocarbon Developments, Inc.
Houston, Texas. August 1978.
12. Banks, R. Hydrogen Recovery Unit Ups NH3 - Plant Efficiency. Excerpted
by special permission from Chemical Engineering, 84(21): 90-92, 1977 by
McGraw-Hill Inc., New York, New York 10020.
77
-------
13. Personal Communication with Dr. J. Hayes, Gulf South Research Institute,
New Orleans, Louisiana. August 1978.
14. Ando, J., and T. Henchiro. NOX Abatement for Stationary Sources in Japan.
EPA-600/2-76-013b, NTIS PB-250586/5BA. U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, 1976. 116 pp.
15. Exxon Research and Engineering Company, Exxon Thermal DeNox Process.
Florham Park, New Jersey (Bulletin) April, 1978. 13 pp.
16. Ando, J., and T. Henchiro. NOX Abatement for Stationary Sources in Japan.
Stationary Sources in Japan. EPA-600/7-77-103b, NTIS PB-278373/6BE.
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina, 1977. 16e pp. .
17. Information on file at U.S. Environmental Protection Agency, Industrial
Environmental Research Laboratory, Research Triangle Park, North Carolina.
18. Quartulli, J.Q. Review of Methods for Handling Ammonia Plant Process
Condensate. Preceedings of the Fertilizer Institute Environmental
Symposium, New Orleans, Louisiana, 1976. pp. 25-44.
19. Fleming, J.B., J.R. Lambrix, and M.R. Smith. Energy Conservation in New
Plant Design, 8(12): 112-122, 1974.
20. Payne, A.J., and P.G. Gliken. Ammonium Nitrate-Process Survey. Chemical
and Processes Engineering, 49(.4): 65-68, 1968.
21. Shearon, W.H., and W.B. Dunwoody. Ammonium Nitrate. Industrial and
Engineering Chemistry, 45(3): 496-504, 1953.
22. Ruskan, R.P. Prilling Versus Granulation for Nitrogen Fertilizer
Production. Chemical Engineering, 83(12): 114-118, 1976.
23. Pelitti, E., and J.C. Reynolds. Improving Product Quality and Environmental
Control Through Drum Granulation. C&I Girdler, Inc. (Bulletin),
Louisville, Kentucky.
24. Reed, R.M. and J.C. Reynolds. The Spherodizer Granulation Process.
Chemical Engineering Progress, 69(2): 62-66, 1973.
25. McCamy, I.W., and M.W. Norton. Have You Considered Pan Granulation or
Urea. Farm Chemical (Reprint), January, 1977.
26. Palck-Muus, R. New Process Solves Nitrate Corrosion. Chemical Engineering
74(14): 108-116, 1967.
27. Dorsey, J.J. Ammonium Nitrate by the Stengel Process. Industrial and
Engineering Chemistry, 47(1): 11-17, 1955-
28. Metzger, J.R. Controlling Airborne Emissions From Ammonium Nitrate
Production, presented: Ammonium Nitrate Pollution Study Group, Sarnia
Ontario, August, 1974.
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29. Sjolin, C. Mechanism of Caking Ammonium Nitrate (NH NO Prills). J.
of Agrigultural Fool Chemistry, 20(4): 895-900, 1972.
30. Kirk, R.E., and D.F. Othmer. Encyclopedia of Chemical Technology. Wiley,
Third Avenue, New York, New York, 9: 59-67.
31. Roberts, A.G., and K.D. Shah. The Large Scale Application of Prilling.
The Chemical Engineer, 34: 748-750, 1975.
32. Cook, T.M., G.L. Tucker, and M.L. Brown. Ammonium Nitrate Neutralizer
(to Mississippi Chemical Corporation). U.S. Patent 3,758,277.
September 11, 1973.
33. Cook, T.M., G.L. Tucker, and M.L. Brown. Ammonium Nitrate Neutralizer (to
Mississippi Chemical Corporation). U.S. Patent 3,870,782. March 11, 1975.
34. Stover, J.C. Control of Ammonium Nitrate Prill Tower Emission. Proceedings
of the Fertilizer Institute Environmental Symposium, New Orleans, Louisiana.
1976. pp. 251-286
35. Unruh, W. Reduction of Ammonium Nitrate Particulate Emission from Prill
Towers. Preceedings of The Fertilizer Institute Environmental Symposium,
New Orleans, Louisana, 1976. pp. 287-292.
36, The Mcllvaine Scrubber Manual. The Mcllvaine Company, Northbrook,
Illinois. Vol. 1-4, 1974.
37. Reynolds, J.C., and R.M. Reed. Progress Report on Spherodizer Granulation.
Proceedings of The Fertilizer Institute Environmental Symposium, New
Orleans, Louisiana, 1976. pp. 193-216.
38. Bress, D.F. Eliminating Effluents From Urea and Ammonium Nitrate Plants
(Foster Wheeler Energy Corporation). Proceedings of The Fertilizer
Institute Environmental Symposium, New Orleans, Louisana, 1976.
pp. 123-136.
39. Search, W.J., and R.B. Reznik. Source Assessment: Urea Manufacture.
EPA-600/2-77-107I, NTIS PB-274367/AS, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, 1977. 94 pp.
40. Capone, S. Industry Survey - Solid Urea Manufacturing. GCA Corporation,
Bedford, Massachusetts (Unpublished Data), July, 1978.
41. Robert, A.G., and K.D. Shah. The Large Scale Application of Prilling.
Chemical Engineering (London), 304: 748-750, 1975.
42. McCam, I.W. Production of Granular Urea, Ammonium Nitrate and Ammonium
Polyphosphate - Process Review, Presented at the International Conference
on Granulated Fertilizer and Their Production, London, England, November,
197 7 •
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43. Killen, J.M. Urea Plant Pollution Control. Proceedings of the Fertilizer
Institute Environmental Symposium, New Orleans, Louisiana, 1976.
pp. 25-44.
44. Barber, J.C. Review and Analyses Pollution Control in Fertilizer
Manufacture. Environmental Quality, 59 4(1): 1-11, 1975.
45. Urea Makers can Strip Away Waste Problems. Chemical Week, 119(14):
33-34, 1976.
46. Bingham, E.G., and R.C. Chopra. A Closed Cycle Water System for Ammonium
Nitrate Production (Bulletin). Chemical Separation Corporation, Oak
Ridge, Tennessee, 1971.
47. Effluent Guidelines and Standards, Fertilizer Manufacturing Point Source
Category. Federal Register, 43(81): 17821-17828, April 26, 1978.
80
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/2-79-186
2.
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
An Evaluation of Control Needs for the Nitrogen
Fertilizer Industry
5. REPORT DATE
August 1979
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
Philip S. Hincman and Peter Spawn
8. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
GC A/Technology Division
Burlington Road
Bedford, Massachusetts 01730
10. PROGRAM ELEMENT NO.
LAB604B
11. CONTRACT/GRANT NO.
68-02-2607, Task 12
2. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 3/78 - 7/79
14. SPONSORING AGENCY CODE
EPA/600/13
5. SUPPLEMENTARY NOTESjjERL-RTP project officer R. A. Venezials no longer with EPA.
For details concerning this report, contact David Sanchez, Mail Drop 62, 919/541-
a U ft I • L .. ^ , , „ „„ „„ i..m.T....J.L.._,.._. _,_,. , ,._ _ _.,. , __ i. , -
16.ABSTRACT .j,^ repOr|- gjves results of an evaluation of pollution control needs for the
nitrogen fertilizer industry. It includes descriptions of ammonia, ammonium nitrate,
and urea manufacturing processes and evaluations of existing processes, pollution
control techniques, and emissions. It also evaluates existing and potential pollution
control techniques. processes, and alternative feedstocks as they apply to manufac-
turing ammonia, ammonium nitrate, and urea for additional pollution control and
emission reduction. Air emission and water effluent controls were examined for each
process. Source severity factors were used to evaluate the environmental signifi-
cance of emission sources. The most significant emission problems associated with
the industry are: (1) oxides of nitrogen from the addition of purge gas and overhead
to primary reformer firing in ammonia synthesis, and (2) particulates from prilling
towers in ammonium nitrate and urea production. Further work is needed to develop
adequate control techniques for these pollutant sources. All other pollutant sources
for this industry can be adequately controlled by existing technology.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pollution
Fertilizers
Ammonia
Ammonium Nitrate
Urea
Nitrogen Oxides
Dust
Aerosols
b.lDENTIFIERS/OPEN ENDED TERMS
Pollution Control
Stationary Sources
Nitrogen Fertilizers
Particulate
Prilling Towers
. DISTRIBUTION STATEMENT
19. SECURITY CLASS (ThisReport)
Release to Public
CLASS (Thispage)
Unclassified
c. COSATI Field/Group
13B
02A
07B
07C
UG
07D
22. PRICE
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