United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
EPA 600 7-79-162
August 1979
»EPA
Research and Development
Environmental
Considerations of
Selected Energy-
Conserving
Manufacturing
Process Options
Volume XX
Toxics/Organics
Interagency
Energy/Environment
R&D Program
Report
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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 INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-162
August 1979
ENVIRONMENTAL CONSIDERATIONS OF SELECTED
ENERGY-CONSERVING MANUFACTURING PROCESS OPTIONS
Volume XX. Toxics/Organics
by
Arthur D. Little, Inc.
Cambridge, Massachusetts 02140
Contract No. 68-03-2198
Project Officer
Herbert S. Skovronek
Power Technology and Conservation Branch
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
For »ale by the Superintendent of Documents, U.S. Government
Printing Office, Waihington, D.C. 20402
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory-Cincinnati, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
ii
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FOREWORD
When energy and material resources are extracted, processed, con-
verted, and used, the related pollutional impacts on our environment,
and even on our health, often require that new and increasingly more
efficient pollution control methods be used. The Industrial Environ-
mental Research Laboratory - Cincinnati (lERL-Ci) assists in developing
and demonstrating new and improved methodologies that will meet these
needs both efficiently and economically.
This report summarizes information on toxics/organics from a study
of 13 energy-intensive industries. If implemented over the coming 10
to 15 years, these processes and practices could result in more effec-
tive utilization of energy resources. The study was carried out to
assess the potential environmental/energy impacts of such changes and
the adequacy of existing control technology in order to identify po-
tential conflicts with environmental regulations and to alert the
Agency to areas where its activities and policies could influence the
future choice of alternatives.
The results will be used by the EPA's Office of Research and De-
velopment to define those areas where existing pollution control tech-
nology suffices, where current and anticipated programs adequately ad-
dress the areas identified by the contractor, and where selected pro-
gram reorientation seems necessary.
Specific data will also be of considerable value to individual
researchers as industry background and in decision-making concerning
project selection and direction.
The Power Technology and Conservation Branch of the Energy Sys-
tems-Environmental Control Division should be contacted for additional
information on the program.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
iii
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ABSTRACT
Under EPA Contract No. 68-03-2198, Arthur D. Little, Inc.
undertook a study of the "Environmental Considerations of
Selected Energy-Conserving Manufacturing Process Options."
Some 80 industrial process options were examined in 13 industrial
sectors. Results were published in 15 volumes, including a
summary, industry prioritization report, and 13 industry
oriented reports (EPA-600/7-76-034 a through o).
This present report summarizes the information regarding
toxic/organic pollutants in the 13 industry reports. Four parallel
reports treat sulfur oxides, nitrogen oxides, particulates, and
solid residues. All of these pollutant-oriented reports are
intended to be closely used with the original 15 reports.
iv
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CONTENTS
Forword iii
Abstract iv
Tables vi
English-Metric (SI) Conversion Factors vii
1. INTRODUCTION 1
BACKGROUND AND PURPOSE 1
APPROACH 2
2. FINDINGS AND R&D OVERVIEW 5
FINDINGS 5
IDENTIFICATION OF CROSS-INDUSTRY TECHNOLOGY 10
R&D AREAS 10
3. PROCESSES AND POTENTIAL TOXIC/ORGANIC DISCHARGES 14
BASES OF CALCULATIONS 14
IRON AND STEEL 15
PETROLEUM REFINING 22
PULP AND PAPER 28
OLEFINS 34
AMMONIA 39
ALUMINA/ALUMINUM 44
TEXTILE 57
CEMENT 61
GLASS 65
CHLOR-ALKALI 68
PHOSPHORUS/PHOSPHORIC ACID 73
PRIMARY COPPER 79
FERTILIZER 84
REFERENCES 89
TECHNICAL REPORT DATA (includes abstract) 90
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TABLES
Number Page
1 Projected U.S. Production in Industries Studied 4
2 Qualitative Comparison of Organic/Toxic Pollutant 29
Discharges—Petroleum Refining Industry
3 Qualitative Comparison of Organic/Toxic Pollutant 35
Discharges—Pulp and Paper Industry
4 Qualitative Comparison of Organic/Toxic Pollutant 40
Discharges—Olefins Industry
5 Qualitative Comparison of Organic/Toxic Pollutant 45
Discharges—Ammonia Industry
6 Qualitative Comparison of Organic/Toxic Pollutant 55
Discharges—Alumina/Aluminum Industry
7 Qualitative Comparison of Organic/Toxic Pollutant 62
Discharges—Textile Industry
8 Qualitative Comparison of Organic/Toxic Pollutant 69
Discharges—Glass Industry
9 Qualitative Comparison of Organic/Toxic Pollutant 85
Discharges—Primary Copper Industry
vi
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ENGLISH-METRIC (SI) CONVERSION FACTORS
To Convert From
To
Metre
Pascal
3
Metre
Joule
Pascal-second
Degree Celsius
Degree Kelvin
Metre
Metre /sec
Metre3
2
Metre
Metre/sec
2
Metre /sec
Metre3
Watt
Watt
Watt
Metre
Joule
Metre
Metre
Metre
Metre
Pascal-second
Newton
Kilogram
Kilogram
Kilogram
Kilogram
Kilogram
Kilogram
Multiply By
4,046
101,325
0.1589
1,055
0.001
t° = (t° -32)/1.8
4 - 'R'1-8
0.3048
0.0004719
0.02831
0.09290
0.3048
0.00002580
0.003785
745.7
746.0
735.5
0.02540
3.60 x 106
1.000 x 10~3
1.000 x 10~6
0.00002540
1,609
0.1000
4.448
0.4536
0.02916
1,016
1,000
907.1
1,000
Acre
Atmosphere (normal)
Barrel (42 gal)
British Thermal Unit
Centipoise
Degree Fahrenheit
Degree Rankine
Foot
Foot /minute
Foot
Foot2
Foot/sec
Foot2/hr
Gallon (U.S. liquid)
Horsepower (550 ft-lbf/sec)
Horsepower (electric)
Horsepower (metric)
Inch
Kilowatt-hour
Litre
Micron
Mil
Mile (U.S. statute)
Poise
Pound force (avdp)
Pound mass (avdp)
Ton (Assay)
Ton (long)
Ton (metric)
Ton (short)
Tonne
Source: American National Standards Institute, "Standard Metric Practice
Guide," March 15, 1973. (ANS72101-1973) (ASTM Designation E380-72)
vii
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SECTION 1
INTRODUCTION
BACKGROUND AND PURPOSE
During 1975 and the first half of 1976, under EPA Contract No.
68-03-2198, Arthur D. Little, Inc., undertook a study of the "Environ-
mental Considerations of Selected Energy-Conserving Manufacturing Process
Options" in 13 energy-intensive industry sectors for the U.S. Environmental
Protection Agency (EPA). The results of these studies were published in
the following reports:
• Volume I — Industry Summary Report (EPA-600/7-76-034a)
• Volume II — Industry Priority Report (EPA-600/7-76-034b)
• Volume III -- Iron and Steel Industry (EPA-600/7-76-034c)
• Volume IV — Petroleum Refining Industry (EPA-600/7-76-034d)
• Volume V — Pulp and Paper Industry (EPA-600/7-76-034e)
• Volume VI — Olefins Industry (EPA-600/7-76-034f)
• Volume VII — Ammonia Industry (EPA-600/7-76-034g)
• Volume VIII ~ Alumina/Aluminum Industry (EPA-600/7-76- 034h)
• Volume IX — Textiles Industry (EPA-600/7-76-034i)
• Volume X — Cement Industry (EPA-600/7-76-034J)
• Volume XI — Glass Industry (EPA-600/7-76-034k)
• Volume XII — Chlor-Alkali Industry (EPA-600/7-76-0341)
• Volume XIII — Phosphorus/Phosphoric Acid Industry
(EPA-600/7-76-034m)
• Volume XIV — Copper Industry (EPA-600/7-76-034n)
• Volume XV — Fertilizer Industry (EPA-600/7-76-034o)
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In the course of this study some 80 industrial process options were
examined, focusing on:
• Identification of any major sources and amounts of pollutants
(air, water, and solid) expected from the processes;
• Development of estimated capital and operating costs for both
production and pollution control aspects of the processes;
• Estimation of the types and amounts of energy used in both
production and pollution control for the processes;
• Assessment of the economic viability and likelihood of
implementation of those alternative process options
being studied;
• Identification of areas where EPA's activities and policies
could influence the future choice of alternatives; and
• Identification of research and development areas in both
process and pollution control technology.
Because of the industry orientation of the study, encompassing
fifteen volumes and some 1,700 pages, it was felt that pollutant-specific
information across all the 13 sectors studied should be summarized so
that environmental, energy and economic impacts can be considered from
this viewpoint. Five such pollutant types were identified as being of
particular interest:
• Nitrogen oxide (NO ) emissions,
• Sulfur oxide (SO ) emissions,
X
• Fine particulate emissions,
• Solid residues, and
• Organic and/or toxic pollutants.
A summary pollutant report in each of these areas has been prepared.
Although we did attempt some estimates and extrapolations on pollutants
where the information was readily available, in general, we did not attempt
to go beyond the contents of the 15 original reports.
APPROACH
These summary pollutant reports are intended to be used closely with
the original 15 reports. Generally, information such as detailed descrip-
tions of the processes has not been duplicated in these pollutant reports.
Sections of the previous 15 reports where this information can be found
have been extensively referenced by volume number and page number (e.g.,
Volume VII, page 20, refers to page 20 of the Ammonia Industry report).
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In Section 2 of this report (Findings and R&D Overview), summary
information on generic, cross-industry problems that emerged and suggestions
for research and development work in the areas of both pollution control
technology and process technology are presented. In Section 3 of this
report, the subject of "toxic/organic pollutants" is reviewed in relation
to the industries and processes analyzed in the original study. All
emissions are estimated unless specifically referenced, since we believe
that actual data do not exist for many of the processes described, which
are frequently still under development. The significance of pollution
in terms of specific organics and toxic constituents is a relatively new
concept and historical data simply have not been collected in most industries.
To give the reader a sense of the size of the industries for which
the pollution problems covered in these summary pollutant reports are
considered, Table 1 lists these industries, their total production in
1974 (the base case year for the study), and their projected incremental
production in 1989,15 years hence. Other than the estimates given in
this report, reliable pollutant loads, in terms of organics and/or toxics,
have yet to be developed on a parallel basis.
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TABLE 1.
PROJECTED U.S. PRODUCTION IN INDUSTRIES STUDIED
Commodity
Alumina
Aluminum
Ammonia
Cement
Chlorine
Coke
Copper
Fertilizers (HNO )
Glass (flat) J
Iron
Olefins (ethylene)
Petroleum
Pulp (kraft)
Pulp (newsprint)
Phosphoric Acid
(detergent grade)
Phosphoric Acid
(wet acid grade)
Steel
Textiles (knit)
Textiles (woven)
Total U.S.
production
in 1974
(106 tons*)
7.7
5.0
9.2
79.0
11.0
62.0
1.6
8.2
29.0
100.0
13.0
740.0**
16.0
3.9
1.4
9.0
133.0
0.32
2.1
Projected
rate
of growth
(%/yr)
6.0
6.0
6.0
2.0
5.0
2.5
3.5
4.0
2.5
2.5
8.0
1.5
5.0
2.5
2.5
2.5
2.5
2.2
2.2
Total
projected
production
in 1989
(106 tons)
18.5
12.0
22.0
106.3
22.9
89.8
2.7
14.8
42.0
144.8
41.2
925.0***
33.3
5.6
2.03
13.0
193.0
0.44
2.91
Increase ii
annual
7roduction
in 1989 ovei
that of 197'
(10 tons)
10.75
7.0
12.8
27.3
11.9
27.8
1.1
6.6
13.0
44.8
28.2
185.0****
17.3
1.7
0.63
4.0
60.0
0.12
0.81
*All tons referred to in these reports are net tons, unless otherwise
indicated.
**Approximate equivalent of 30 quads (1 quad is equal to 10
***Approximate equivalent of 37.5 quads.
****Approximate equivalent of 7.5 quads.
15
Btu).
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SECTION 2
FINDINGS AND R&D OVERVIEW
FINDINGS
So that the findings and general content of this report can be viewed
in proper perspective, it is essential that the reader fully understand
the purpose and scope of our study on "organic/toxic pollutants." Compared
to the specific areas of air and water pollution control and solid waste
disposal, the subject of "organic/toxic pollutants" is somewhat nebulous
and, indeed, often requires a consideration of the several pathways by
which pollutants enter the environment. In our original 13 industry
studies, we examined, in conventional terms, the air pollution, water
pollution, and solid waste disposal implications of energy-saving manu-
facturing process options. The subject of "organic/toxic pollutants"
was not examined as a separate entity. Since the scope of this study
largely restricts our data base to the original 13 industry studies,
much of the material on "organic/toxic pollutants" had to be inferred
from the nature of the air emissions, wastewater effluents, and solid
waste streams from the various manufacturing processes. Since this
study deals with a whole group of pollutants rather than a single pol-
lutant or waste stream, and since many of these problems are only now
being recognized, a quantitative comparison of organic/toxic pollutants
would be next to impossible. Our treatment of the subject of organic/
toxic pollutants is therefore qualitative. The main purpose of this
report is to highlight those areas where the implementation of an energy-
saving process option would result in a change in the quantity and/or
composition of the organic/toxic pollutants discharged. Since specific
identification of pollutants as "toxic" may be premature, we have used
those materials identified in the June 1976 Consent Decree* as guidance.
Our findings regarding the implications of energy-saving manufacturing
process options on the discharge of organic/toxic pollutants are presented
below.
General Findings
• There is a wide variety of organic/toxic pollutants discharged
from the base case manufacturing operations in the 13 industries
studied. Where proper air and water pollution measures are
NRDC versus EPA, June 1976.
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implemented, most of the identified organic/toxic pollutants are
eventually discharged in the form of wet sludge or solid waste.
However, since acceptable discharge levels to the environment
are frequently not yet established, the acceptability of the
final discharge is unknown.
Many of the energy-saving process options have a negligible effect
on the quantity and characteristics of the organic/toxic pollutants
discharged when compared to conventional technology. This is not
to be interpreted as no such pollutants are discharged but only
that the change appears to be small.
In those cases where there is an increase in the discharge of
organic/toxic pollutants, the most prevalent cause is the con-
version from natural gas or fuel oil to coal as the source of
process energy. When using coal, the toxic pollutants generally
of greatest concern are the large number of heavy metals contained
in the coal, as well as polyaromatic organics.
Specific Findings
Iron and Steel Industry - The base case manufacturing operations
in the iron and steel industry generate organic/toxic pollutants
that include phenol, cyanide, ammonia, sulfide, fluoride, and
trace heavy metals. Substitution of dry quenching for wet quenching
will tend to lessen discharge of organic and toxic pollutants.
Otherwise, the new process options examined have very little
effect on the discharge of organic/toxic pollutants.
Petroleum Refining Industry - A variety of organic/toxic
pollutants is found in the base case petroleum refinery dis-
charges. These pollutants, including metal catalysts of poly-
aromatics, originate largely from the crude petroleum and its
refined products.
Most of the process options would result in very little change
in the base case discharge of organic/toxic pollutants. In the
Flexicoking process option, required air pollution control measures
result in an additional small but concentrated wastewater stream
that contains a variety of organic compounds, plus vanadium, which
may require specific attention.
Pulp and Paper Industry - While the base case processes in the
pulp and paper industry generate large quantities of organic
waste which is largely composed of wood-derived chemicals and
degradation products and contains sulfur compounds, the waste
as a whole is not generally considered toxic although numerous
toxic compounds have been identified to be present in small amounts.
Most of the process options either alleviate or have a negligible
effect on the base pollution problem.
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• Olefins Industry - The base case ethylene production unit discharges
air, water, and solid waste streams that contain organic pollutants.
The waste streams are not generally considered toxic.
Both process options—naphtha cracking and gas oil cracking—will
result in an increase in the quantity of organic pollutants dis-
charged in the treated wastewater stream and in the solid waste
streams. Due to the necessity for storing liquid hydrocarbon
feedstocks, both process options will result in an increase in
the amount of hydrocarbons that escape to the atmosphere, par-
ticularly as fugitive emissions. Whether these are or will be
determined to be toxic is impossible to state without further study.
• Ammonia - The base case technology involving the production of
ammonia from natural gas has very few environmental problems.
There is a minimal discharge of organic pollutants.
The process option based on the use of coal as a feedstock greatly
increases the air, water, and solid waste pollution loads over the
base case technology. Heavy metals present in both coal and slag—
and which eventually appear in the treated wastewater and sludge
streams—create a much more serious pollution problem than the
waste streams from the base case technology. There is also a
significant increase in the amount of organic pollutants appearing
in the water and solid waste streams.
The process option based on the gasification of fuel oil also
results in a significant increase in the base case pollutional
load, but to a lesser degree than the ammonia-from-coal process
option.
• Alumina/Aluminum Industry
Alumina - The base case Bayer process for the production of
alumina from bauxite does not discharge organic pollutants.
The disposal of very large quantities of "red mud," the in-
soluble residue that remains after alumina extraction, con-
stitutes the chief environmental problem associated with
alumina production. The red mud is highly alkaline and
contains small quantities of heavy metals. However, they
are in suspended form as hydroxides/oxides which are usually
considered innocuous.
Alumina production from domestic kaolin clays by the hydro-
chloric acid and nitric acid leaching processes produces
even larger quantities of waste residues, which also contain
heavy metals. The wastes from these two processes are acidic
rather than alkaline and contain small amounts of organic
reagents used in the processing; the metals will normally be
in the less desirable soluble forms (chlorides, nitrates).
The Toth alumina process, also intended for the extraction
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of alumina from domestic clay, produces a waste similar to
that generated by the hydrochloric acid process. Unless
proper air pollution controls are used, it is possible for
volatilized titanium and silicon tetrachlorides to be emitted
to the atmosphere. Adjustments of pH to the basic side would
appear to be a necessary treatment step for all three processes.
Aluminum - Aluminum production by the base case Hall-Heroult
process discharges fluoride salts, hydrogen fluoride, and
hydrogen sulfide to the atmosphere. Wet air pollution con-
trol systems transfer some of these pollutants to wastewater
and, eventually, solid waste streams.
The Alcoa process eliminates the fluoride problem but, in
its place, discharges considerable amounts of sodium chloride.
If proper gas handling techniques are not employed, it is
possible for chlorinated hydrocarbons to be discharged to
the atmosphere. Carbon cathodes are used in the Alcoa process
but are inert and thus, if implemented, would reduce emissions
from the baking operation (prebaked or Soderberg cells) found
in Hall-Heroult practice.
Textile Industry - Dyes, dye carriers, phenols, formaldehyde,
melamines, and the chromium compounds found in certain dyes are
the major organic/toxic pollutants discharged by the base case
processes in the textile industry.
The process options mostly alleviate or do not alter the base case
waste load, although the option based on a solvent (instead of
aqueous) system has the potential for discharging significant
amounts of perchlorethylene to the atmosphere, if that becomes
the solvent of commercial systems, but could reduce discharge
of organic/toxic finishing agents.
Cement Industry - There is no discharge of organic pollutants
and virtually no discharge of toxic pollutants (small amounts
of heavy metals are sometimes present in cement dust) from the
base case cement process.
Of the process options considered, the only one that would
introduce toxic pollutants into the waste streams is the option
involving the conversion to coal fuel. Heavy metals are present
in coal ash and can appear in waste cement dust. Depending on
the ultimate use/disposal of these dusts, leaching may require
some study. The storage and handling of coal also presents
pollutional problems, which would be typical of any coal-using
industry.
Glass Industry - The base case natural gas-fired melting operation
discharges air, water, and solid waste streams containing heavy
metals originally present in the raw materials. The bulk of
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the heavy metals Is eventually discharged in the form of a solid
waste stream from air cleaning.
The coal-based process options do not alter the emissions from
the melting operation, but rather introduce additional emissions
of heavy metals from the large quantities of coal ash produced.
Chlor-Alkali Industry - The major discharge of organic/toxic
pollutants from the base case diaphragm cell process is the
solid waste from cell rebuilding that contains asbestos and
lead, plus a waste stream from chlorine purification that con-
sists of chlorinated organic compounds.
The two process options, involving the use of dimensionally
stable anodes and the use of modified diaphragms, both alle-
viate the organic/toxic pollutant problem by reducing the
amount of asbestos discharged. The use of modified diaphragms
virtually eliminates the chlorinated organic waste stream from
the chlorine purification step.
Phosphorus/Phosphoric Acid Industry - The base case process for
producing high-grade phosphoric acid generates wastewater and
solid waste streams that contain fluorides, phosphates, elemental
phosphorus, and heavy metals.
The process option involving the wet process production of phos-
phoric acid followed by chemical clean-up differs from the base
case mainly in that large amounts of wet gypsum sludge are pro-
duced. The sludge contains fluorides, phosphates, and trace heavy
metals, the latter as hydroxides/oxides.
The solvent extraction clean-up process differs from the conventional
process in that a large calcium chloride brine stream is substituted
for a large fraction of the gypsum sludge and, consequently, heavy
metals could be carried along as soluble chlorides. Pollutants
associated with the base case (namely, fluorides, phosphorus, phos-
phates, and heavy metals) are still present, plus lost solvent
consisting of normal butanol.
Primary Cooper Industry - There is no discharge of organic
pollutants from the base case conventional smelting and
refining process. Heavy metals (such as arsenic, antimony,
bismuth, mercury, lead, zinc, and tellurium), mostly in the
form of particulate matter, are present in air, water, and
solid waste streams.
From a pollutional standpoint, the pyrometallurgical process
options do not represent a significant departure from the base
case technology.
The Arbiter process, however, has major pollutional implications.
This hydrometallurgical process virtually eliminates the air
-------
pollution problems associated with conventional smelting, but
substantially increases the amount of solid waste destined for
disposal. The solid waste is in the form of a wet sludge rather
than a hard dry slag, and is therefore more prone to leaching of
the heavy metals.
• Fertilizer Industry - There is no discharge of organic/toxic
pollutants from the base case nitric acid plant or from the
various process options intended for the control of NOX emissions.
The base case mixed fertilizer plant does not discharge organic/
toxic pollutants. The process option involving the conversion
from natural gas to fuel oil will likely result in wastewater
and solid waste discharges containing phosphates, fluorides,
and ammonia.
IDENTIFICATION OF CROSS-INDUSTRY TECHNOLOGY
As specifically related to the problem of organic/toxic pollutants,
the only cross-industry, energy-conserving technology that has a signifi-
cant impact on the nature and quantity of solid waste is the conversion
from natural gas or fuel oil to coal. As noted earlier, these impacts
would be very significant.
R&D AREAS
Since organic/toxic pollutants from many of the base case manufacturing
operations and their process options are present in wastewater effluents,
solid waste streams, and air emission, R&D activity pertinent to organic/
toxic pollutants involves air pollution control, water pollution control,
and solid waste disposal.
Air Pollution Control Technology
With regard to air emissions in the new technology investigated, we
have identified the following to be deserving of R&D attention:
• Improving fine particulate removal technology. This would
include especially those particulates resulting from metallic
smokes and sublimed substances such as mercury, arsenic, zinc,
etc. Further information on the source of pollutants and nature
of the problems in new technology examined in this study is found
in the Industry Assessment reports dealing with aluminum, ammonia,
cement, copper, fertilizers, glass, iron and steel, petroleum
refining, phosphorus, and pulp and paper.
• Collection or control of fugitive emissions from process equipment.
Further information on the source of pollutants and nature of the
problems in new technology examined in this study is found in the
Industry Assessment reports dealing with aluminum, ammonia, copper,
fertilizers, iron and steel, and textiles.
10
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To a lesser extent, it is also a problem in the following industry
sectors: cement, olefins, petroleum refining, phosphorus, and
pulp and paper.
• Better definition of the environmental, health, and ecological
impacts of gaseous emissions (such as SOX, NOX, CO, HF, Cl2,
NH3> with respect to obtaining more quantitative knowledge for
establishing bases for appropriate emission regulations. Further
information on the source of pollutants and nature of the problems
in new technology examined in this study is found in the Industry
Assessment reports dealing with aluminum, ammonia, cement, chlor-
alkali, copper, glass, iron and steel, petroleum refining, and
pulp and paper.
To a lesser extent, it is also a problem in the olefins industry.
• Better definition of the environmental, health, and ecological
impacts of metallic smoke emissions with respect to obtaining
more quantitative knowledge for the purpose of establishing the
bases for appropriate emission regulations. Further information
on the source of pollutants and nature of the problems in new
technology examined in this study is found in the Industry Assess-
ment reports dealing with aluminum, ammonia, cement, copper, glass,
and iron and steel.
To a lesser extent, it is also a problem in the olefins and
petroleum refining industry sectors.
• Better definition of the environmental, ecological, and health
impacts of organic compounds that have a high smog characteristic
or potential carcinogenic properties. More quantitative knowledge
is needed for the purpose of establishing bases for appropriate
emission regulations. Further information on the source of pol-
lutants and nature of the problems in new technology examined in
this study is found in the Industry Assessment reports dealing
with aluminum, iron and steel, olefins, petroleum refining, and
textiles. To a lesser extent, it is also a problem in the pulp
and paper industry.
• Improvements in odor control. Further information on the source
of pollutants and nature of the problems (odor-causing pollutants)
in new technology examined in this study is found in the Industry
Assessment reports' dealing with petroleum refining and pulp and
paper. To a lesser extent, it is also a problem in the olefins
industry.
• Improved instrumentation for rapid monitoring and recording of
airborne emissions. Further information on the source of pol-
lutants and nature of the problems in new technology examined
in this study is found in the Industry Assessment reports dealing
11
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with aluminum, copper, glass, iron and steel, and pulp and paper.
To a lesser extent, it is also a problem in the cement and petro-
leum refining industries.
Water Pollution Control Technology
With regard to water pollution control in new technology investigated
in this study, we have identified the following as deserving consideration
for additional research and development.
• Better definition of the environmental, health, and ecological
impact of substances which cannot be removed by Best Available
Technology Economically Achievable (BATEA). This would include
principally metals and organic compounds that have long biolog-
ical half-lives or carcinogenic effects. Further information on
the source of pollutants and nature of the problems in new tech-
nology examined in this study is found in the Industry Assessment
reports dealing with aluminum, ammonia, copper, iron and steel,
petroleum refining, phosphorus, and pulp and paper.
• Removal of refractory organic compounds not achievable by tech-
nologies now designated by EPA as BATEA. Further information
on the source of pollutants and nature of the problems in new
technology examined in this study is found in the Industry
Assessment reports dealing with iron and steel, textiles,
petroleum refining, and olefins. To a lesser extent, it is
also a problem in the aluminum industry.
• Improvements in suspended solids removal from treated wastewaters.
Further information on the source of pollutants and nature of the
problems in new technology examined in this study is found in the
Industry Assessment reports dealing with ammonia, iron and steel,
petroleum refining, phosphorus, and pulp and paper. To a lesser
extent, it is also a problem in the aluminum, cement, chlor-alkali,
and copper industry sectors.
• Improvements in color removal. Further information on the source
of pollutants and nature of the color producing problems in new
technology examined in this study is found in the Industry Assess-
ment reports dealing with pulp and paper and textiles. To a lesser
extent, it is also a problem in the petroleum refining industry.
• Removal of dissolved metals or inorganic salts. Further information
on the source of pollutants and nature of the problems in new tech-
nology examined in this study is found in the Industry Assessment
reports dealing with aluminum, iron and steel, and phosphorus. To
a lesser extent, it is also a problem in the chlor-alkali, copper,
glass, and petroleum refining industry sectors.
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• Improved instrumentation for rapid monitoring and analysis of
waterborne pollutants. This is really a pressing problem for
all technologies in all industries. Further information on
the specific source of pollutants and nature of the problems
in new technology examined in this study is found in the Industry
Assessment reports dealing with iron and steel and pulp and paper.
Solid Waste Disposal
With regard to solid wastes emanating from new technology investigated
in this study, the following have been identified as deserving R&D attention:
• Demonstration of adequate landfill disposal techniques, including
control of leachate. Further information on the source of pollu-
tants and nature of the problems in new technology examined in
this study is found in the Industry Assessment reports dealing
with aluminum, cement, iron and steel, petroleum, refining, and
phosphorus.
To a lesser extent, it is also a problem in the ammonia, chlor-
alkali, copper, glass, olefins, pulp and paper, and textile
industry sectors.
• Demonstration of thermal destruction technologies. Further
information on the source of pollutants and nature of the
problems in new technology examined in this study is found
in the Industry Assessment reports dealing with aluminum,
olefins, and petroleum. To a lesser extent, it is also a
problem in the chlor-alkali, iron and steel, and pulp and
paper industry sectors.
• Additional research into the methods of categorization, regulation,
and legal methodologies for controlling the disposal of solid
wastes. Further information on the source of pollutants and
nature of the problems in new technology examined in this study
is found in the Industry Assessment reports dealing with aluminum,
ammonia, cement, copper, fertilizers, glass, iron and steel, ole-
fins, petroleum refining, and phosphorus. To a lesser extent, it
is also a problem in the chlor-alkali, pulp and paper, and textile
industry sectors.
Thus, in each case, the direction of research programs should be
viewed with the objective of attaining the maximum effectiveness for
removing or controlling pollutants at the minimum economic penalty, since
it is rarely possible to remove or control pollutants to present and
anticipated standards without entailing cost penalties. Consequently,
research programs must be examined within the framework of cost/benefits
to the environment, to health, and to the economy.
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SECTION 3
PROCESSES AND POTENTIAL TOXIC/ORGANIC DISCHARGES
BASES OF CALCULATIONS
In Volume III (page 19), describing the methodology used in this
study, we indicate that selected State air emission regulations, along
with the Federal Government's stationary source performance standards
and effluent limitation guidelines, were surveyed to:
• establish the most probable limits of air and water
emissions, and
• obtain a perspective of the types of pollution control
systems to be considered.
While there are a large number of different regulations for airborne
emissions at the State regulatory level, we found that approximately
the same type of air pollution control systems would be required,
regardless of the State or Federal regulations to be met. Generally,
these air pollution control systems included baghouses, venturi scrub-
bers, and electrostatic precipitators for particulate and chemical-based
systems for sulfur removal such as alkaline-based aqueous scrubbing for
SO .
x
For water effluents we chose the EPA's Best Available Technology
Economically Achievable (BATEA) guidelines (1983) as the effluent
limitations that would have to be met for both currently practiced
and the alternative processes considered. The rationale for this
choice was that any plant employing the technologies evaluated in these
reports should install wastewater treatment systems capable of meeting
BATEA standards, although at the time of construction the New Source
Performance Standards might be applicable. Because regulations for the
handling and disposal of solid waste are either non-specific or non-
existent, we chose various types of controlled landfill disposal methods,
where our judgment suggested potential adverse environmental impacts might
occur from uncontrolled disposal. At the time the original reports were
prepared, the RCRA had not yet issued. It can only mean more stringent
control will be needed by specific industries.
Potential toxic and organic compounds resulting from industrial
processing (e.g., slags, fumes, slimes, and so on) and the suggested
or expected treatment approach are described in the industry reports
(Volumes III through XV) and are summarized in this section.
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Recognizing that data are limited on process discharges, estimated
waste loads after treatment become even more speculative. Keeping in mind
that with nothing more than an approximation, we have generally assumed
that treated waste loads are proportional to raw waste loads.
In the following sections, each industry is addressed in the order
it was studied for the original study. Each base case technology is
synopsized, including our information concerning the organic and toxic
pollutants and their control. This is then followed by a parallel exam-
ination of the process option or options. It must be recognized, however,
that for many of these options there is a dearth of reliable information,
particularly in this nebulous area of "organics and toxics." As noted
earlier, we have attempted to make judgments where these seemed appropriate.
IRON AND STEEL
The Basic Oxygen Process (BOP) for Steelmaking
Base Case Discharge of Organic/Toxic Pollutants—
The base case BOP unit (which is described in detail in Volume III,
pages 18-28) is a complete combustion system in which the gases issuing
from the mouth of the furnace are burned and collected in a hood, with
considerable infiltration of air, and then cooled and cleaned of parti-
culates before being released to the atmosphere.
Air Emissions and Wastewater Effluents - Most BOP units employ wet
high energy scrubbers for dust collection. The dust consists mostly
of iron oxide with small amounts of lime and/or calcium fluoride
also present. If chromium-, lead-, or zinc-containing scrap is
charged to the BOP, oxides of these metals may also be present in
the dust. The dust-laden scrubber water is usually subjected to
suspended solids removal in a sedimentation basin or clarifier.
A portion of the water thus treated is recycled back to the scrubber,
while the remaining water is discharged. The treated effluent water
contains mostly suspended solids, sometimes with small amounts of
dissolved fluoride and heavy metals present. Other than uncombusted
carbonaceous particulate matter, few, if any, organic compounds are
present in the gas and thus the wastewater stream.
Solid Waste - There are two significant solid waste streams associated
with BOP operations—(1) slag and (2) wet sludge—resulting from dust
collection.
Neither the composition nor the quantity of the slag is affected by
the process changes selected for analysis in the original study;
therefore, its disposal was not a subject of comparison in the study.
The ultimate fate of BOP slag (as well as slag from other steelmaking
processes) proceeds along three routes: (1) some of the slag is re-
cycled to the blast furnaces; (2) some of it is sold to slag process-
ors, where it is made into aggregate material for construction uses;
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and (3) a portion is disposed of in landfills on or near the plant
site. The slag contains iron and other metals present in the scrap
charged to the furnace as well as calcium fluoride, all in a solid
matrix. Smaller (trace) amounts of other metals may also be present.
The wet sludge resulting from dust collection is removed from the
sedimentation basin and usually subjected to mechanical dewatering
to further reduce its volume prior to reclamation of iron values
and/or disposal. The ability to reclaim iron values depends upon
the composition of the dust, which is influenced by the nature of
the scrap charged to the BOP. If clean uncoated home scrap is used,
the dust consists primarily of iron oxides and can be recycled to
the sinter strand. If purchased scrap is used, it may not be pos-
sible to control the composition closely; as a result, the dust and
resultant sludge can contain lead, zinc, tin, and other metals,
thereby reducing the potential for recycle. Such sludge is usually
disposed of to landfill.
BOP Off-Gas Recovery—
When off-gas recovery is incorporated into a BOP unit, the carbon
monoxide containing off-gas may be collected for eventual use as an
internal plant fuel, rather than allowed to combust naturally as in
the conventional BOP (see Volume III, pages 18-28).
BOP units equipped with off-gas recovery produce lower gas volumes
than conventional BOP units, due to the marked reduction in the volume
of infiltration air. Gas-cleaning equipment in both cases consists of
high-energy venturi scrubbers. The quantity of dust is essentially the
same for conventional and off-gas recovery-equipped BOP units. The
composition of the dust, however, is slightly different. In the con-
ventional BOP operation where the carbon monoxide is burned with en-
trained air, the dust particles are largely oxidized. In BOP units
equipped with off-gas recovery, the dust is subjected to far less
oxidation and, therefore, contains a higher fraction of unoxidized
or partially oxidized species. A comparison of the dust compositions
is presented in Volume III, page 25.
The Conventional Blast Furnace for the Production of Iron
Base Case Discharge of Organic/Toxic Pollutants —
The base case process is the conventional blast furnace used in the
production of iron. Iron ore, coke, limestone, and fluorspar are charged
to the furnace which is operated under reducing conditions to convert the
iron oxide to the metallic iron. The operation of the blast furnace
results in wastewater effluents,solid wastes, and air emissions (see
Volume III, pages 64-78, for description).
Wastewater Effluents - Blast furnaces are equipped with air pollution
control systems that employ wet scrubbers for the removal of particu-
late matter. The scrubber water is subjected to gravity settling.
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Part of the effluent from the gravity settling step is recycled to
the scrubbers, while the remainder is discharged. The wastewater
effluent contains suspended solids, phenol, cyanide, sulfide, ammonia,
fluoride, and certain heavy metals. Future water pollution regulations
will require that the wastewater be subjected to further treatment
steps for the removal of large portions of many of the above pollutants.
Solid Waste - A blast furnace produces two major solid waste streams:
(1) wastewater treatment sludge and (2) slag.
• Wastewater Treatment Sludge - The particulate matter originally
present in the blast furnace gas is removed from the scrubber
water stream as a wet sludge. While the solid phase of the
sludge is relatively innocuous (containing mostly carbon and
iron particulates), the liquid fraction is similar to the
above-described wastewater stream, containing phenol, cyanide,
sulfide, ammonia, fluoride, and certain heavy metals. A por-
tion of the dewatered wastewater treatment sludge is usually
recycled back into the process for reclamation of iron values.
• Slag - A large fraction of the slag generated by blast furnaces
is sent to slag processors where it is converted into aggregate
material for construction. When the demand for the slag is
less than the supply, the excess slag must be disposed of on
land. Blast furnace slag generally contains small quantities
of heavy metals such as chromium, copper, manganese, nickel,
lead, and zinc, as well as fluoride. The materials in the
slag are fused together in a relatively inert solid matrix;
under normal conditions, they are not prone to leaching.
Air Emissions - We do not believe that air emissions from blast furnaces
will be noticeably affected by implementation of external desulfurization.
External Desulfurization—
Coke, containing some of the sulfur found in the coal used, is the
major contributor to the total amount of sulfur entering the blast furnace.
Other sources of sulfur in the blast furnace include fuel injections, the
scrap mixed with the burden, and the minerals themselves (ore, limestone).
Only a small portion of the sulfur is found in the off-gases; most of
the sulfur leaving the blast furnace appears in the liquid slag and hot
metal. The capacity of the slag to retain sulfur is generally increased
as more limestone is added. Limestone, however, increases coke consumption,
which in turn introduces more sulfur. Clearly, then, there is a limit to
the amount to which this "internal" desulfurization is viable. It may be
advantageous to tap a hot metal containing more sulfur than specified, and
to add to the process sequence a new step: the injection of desulfuriza-
tion agents into the molten iron during its transfer from the blast furnace
to the steelmaking furnace. These agents (usually calcium compounds) react
with the dissolved sulfur and form a sulfide slag that can be disposed of.
This additional step is called external desulfurization.
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External desulfurization can provide two energy-related benefits:
(1) it can reduce coke consumption, and (2) more importantly, it decreases
the dependence on low-sulfur metallurgical coal, which is becoming increas-
ingly difficult to obtain.
The external desulfurization process produces a gaseous emission
which contains particulates and possibly some cyanide (the process takes
place under reducing conditions; other organic compounds may possibly be
present). If the gas stream is subjected to wet scrubbing, a wastewater
stream will be produced which will be not unlike that of the parent blast
furnace. If the wastewater is treated in the same manner as blast furnace
wastewater, a similar type of wet sludge will be produced. The additional
wastewater treatment sludge stream from the external desulfurization step
must be balanced against the reduced volume of blast furnace gas and the
sludge that results from cleaning it.
The external desulfurization process reduces the amount of coke and
limestone used in the blast furnace, thereby reducing the amount of slag
generated in the blast furnace proper. While external desulfurization
produces a slag stream of its own, the overall effect is a net reduction
in the amount of slag generated. It appears that the external desulfuri-
zation process will not appreciably alter the overall discharge of pollu-
tants from the base, case blast furnace.
The Quenching Operation in Coke-Making
Base Case Discharge of Organic/Toxic Pollutants--
Current technology involves wet quenching of coke as described in
Volume III, page 48. In wet quenching, hot coke (at 1900-2000°F) is
delivered in a coke car to a tower where the coke is quenched with water,
thereby producing large quantities of steam which are vented to the atmo-
sphere. The coke car is designed to allow the excess water to drain.
This water is usually recirculated, thereby eliminating wastewater discharge.
If contaminated wastewater is used for coke quenching, air pollution
can result when organic contaminants in the wastewater are volatilized
into the air/steam plume that evolves during the quenching. The use of
clean water minimizes the emission of objectionable organic vapors, and
the installation of baffles in the quench tower is claimed to remove
solid particles satisfactorily (Volume III, page 48). However, at this
time, there are no regulations requiring use of clean water.
Dry Quenching of Coke—
In the dry quenching of coke, the hot coke pushed from the ovens is
cooled in a closed system, as described in Volume III, page 48. Dry
quenching uses inert gases to extract heat from incandescent coke by
direct contact. The heat is then recovered in a waste heat boiler or
by other techniques. The inert gases can be generated from an initial
intake of air which reacts with the hot coke to form a quenching gas
largely composed of nitrogen, carbon dioxide, and carbon monoxide.
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The dry quenching process eliminates the type of emissions that are
normally associated with wet quenching; however, there are still a number
of particulate emissions which must be controlled. While the amount of
emissions are largely based on the system design and no actual data are
available, it appears that the dry quenching process has a greater poten-
tial for reducing air pollution than the wet quenching process and, in so
doing, would lessen the discharge of any organic or toxic pollutants.
Conventional Iron and Steelmaking Base Case for
Comparison in the Direct Reduction of Iron Ore
Base Case Discharge of Organic/Toxic Pollutants—
Direct reduction of iron ore is designed to replace the blast furnace
along with its supporting coke plant. In the version of the direct reduc-
tion process selected for comparison (coal-based rotary kiln; see Volume III,
page 59), the reduced product iron from the direct reduction unit is sent
to an electric arc furnace (rather than a more conventional open hearth
or basic oxygen process furnace) for Steelmaking. In order to compare
direct reduction with the existing technology on an equivalent basis, it
is necessary to make the comparison all the way through the Steelmaking
process. Thus, the base case process consists of the following units:
• Byproduct coke plant,
• Blast furnace, and
A BOP furnace.
A variety of wastewater effluents, solid waste streams, and air
emissions are generated by the base case group of processes:
Wastewater - Pollutants of concern in coke plant wastewater are
phenol, ammonia, cyanide, sulfide, oil and grease, and a number
of other organic and sulfur compounds.
Blast furnace wastewater also contains the above pollutants in
addition to fluoride and heavy metals. Even after the applica-
tion of the recommended treatment steps, measurable amounts of
these pollutants are present in the treated wastewater.
Wastewater from the basic oxygen process contains mostly suspended
solids and a small amount of fluoride.
Solid Waste - The major solid waste streams from the base case
process operations are described below:
• Byproduct Coke - Solid waste includes coke dust and
wastewater treatment sludge. The water fraction of
the sludge can contain phenol, oil and grease, cyanide,
ammonia, sulfide and other organic and sulfur compounds,
many of which can be considered as toxics.
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• Blast Furnace - Solid waste includes slag and wastewater
treatment sludge. The slag is generally sold to a slag
processor for conversion into construction material. The
liquid fraction of the wastewater treatment sludge can
contain phenol, ammonia, cyanide, sulfide, fluoride, and
heavy metals. Much of the sludge is recycled back into
the process for the reclamation of iron values.
• Basic Oxygen Furnace - Solid waste includes slag and waste-
water treatment sludge. BOP slag is also reprocessed, and
the wastewater treatment sludge (containing mostly particu-
lates, iron oxides, and fluoride) is usually recycled.
Air Emissions - The base case group of processes produces air
emissions consisting mostly of particulate matter composed of
carbon, iron oxide, and a small amount of calcium fluoride.
Direct Reduction—
The direct reduction process is described in detail in Volume III,
pages 54-87. In the direct reduction process, iron oxides, coal, and
lime for desulfurization are mixed and charged into a rotary kiln. Coal
provides the reducing gas (carbon monoxide) and the heat for the reduction
of iron oxides. Air is admitted at the lower end of the kiln and along
the length of the kiln. After the reduction has taken place, the products
pass into a cooling drum where they are cooled to prevent reoxidation.
The cooler discharge, consisting of sponge iron, excess coal, coal ash,
and desulfurizing agents, is split into the individual components by
screening and magnetic separation. The excess coal is largely recycled.
There is one significant wastewater stream from the direct reduction
process: the kiln exhaust gas scrubber water. The exact composition of
the exhaust gas is not known; however, the exhaust gas and its associated
scrubber water should be similar to those of the conventional blast furnace,
and would therefore very likely contain suspended solids, phenol, cyanide,
ammonia, and sulfide. Since no fluorspar fluxing agent is used in the direct
reduction process, there would not be any fluoride in the scrubber water.
The sludge from the wastewater treatment system is expected to be
similar to blast furnace sludge in that the liquid fraction of the sludge
would probably contain cyanide, ammonia, phenol, and sulfide.
Instead of producing slag, as in the case of the conventional blast
furnace, the direct reduction process produces coal ash and a residue
consisting of the spent desulfurization agents. The electric furnace
that converts the product iron from the direct reduction step into steel
produces a slag and air pollution control dust.
Air emissions are mostly particulates.
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Overall, we do not expect that the direct reduction process option
will increase the discharge of organic/toxic pollutants, and, in fact, it
should alleviate some of the pollution problems associated with the base
case process, mainly due to the elimination of the coke oven. However,
these changes will, with the exception of CaF2, be in amounts rather
than in character.
Summary
The base case basic oxygen process for steelmaking discharges mostly
solid matter to the environment, in wastewater effluents, solid waste
streams, and air emissions. The particulates mainly consist of carbon
and iron oxide particles, with a small amount of calcium fluoride and
heavy metals also present. The process option for the basic oxygen
process is off-gas recovery, which has only a very minor effect on the
nature of the pollutants discharged.
The conventional blast furnace discharges a variety of pollutants
which are mostly in the form of wastewater effluents and solid waste
streams. The pollutants of greatest concern are phenol, cyanide, sulfide,
ammonia, fluoride, and heavy metals. While the external desulfurization
process option results in a net reduction in the overall amount of slag
produced, its incorporation into a conventional blast furnace operation
is not expected to appreciably alter the nature or quantity of the overall
discharge of pollutants.
Dry quenching of coke has at least the potential for generating a
smaller amount of air emissions than the base case wet quenching process,
and, of course, eliminates the water pollution inherent in wet quenching.
The overall conventional steelmaking process, including the basic
oxygen furnace, the blast furnace that supplies the iron, and its support-
ing coke plant discharges pollutants as wastewater effluents, solid waste
streams, and air emissions. The pollutants of concern are phenol, cyanide,
ammonia, sulfide, oil and grease, fluoride, and heavy metals. The direct
reduction process option eliminates the coke plant, substitutes the blast
furnace with a direct reduction kiln, and replaces the basic oxygen furnace
with an electric furnace. Since fluorspar fluxing agent is not used in the
direct reduction process option, fluoride will not be present in the effluent.
Mainly due to the elimination of the coke oven, the direct reduction process
should result in at least a slight decrease in the base case pollutional
load. Of course, the electric arc furnace must be considered to generate
the typical airborne, waterborne, and solid wastes at the power plant,
either on-site or at the utility, during generation of the required
electricity. Whether these wastes, after treatment by existing tech-
nology, are harmful is an unresolved point.
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PETROLEUM REFINING
The Total Petroleum Refining Process
Base Case Discharge of Organic/Toxic Pollutants—
For the purpose of performing economic and energy utilization
comparisons, three base case refineries have been established—an East
Coast refinery, a West Coast refinery, and a Gulf Coast refinery. The
base case refineries reflect differences in feedstock, process configura-
tion, and product mix. A detailed description of the process technology
and energy consumption patterns embodied by the three base case refineries
is presented in Volume IV, pages 111-133.
From an environmental point of view, there is very little difference
between the three base case refineries. The treated wastewater effluent
pollutant loadings and the rates of solid waste generation are estimated
to be the same for all three refineries. There is only a slight difference
between the three refineries in the magnitude of the air emissions. A
variety of organic (and possibly toxic) pollutants are present in the
air emissions, wastewater effluents, and solid waste streams from refin-
eries. In terms of the type of pollutants present, there is virtually
no difference between the three base case refineries.
Wastewater - The major refinery wastewater streams are process
water, cooling tower blowdown, and boiler blowdown. Many of the
organic constituents found in petroleum appear in the wastewater
for the simple reason that there is contact between water and
petroleum products during processing. Constituents present in
the process wastewater include free oil, dissolved hydrocarbons,
sulfur and nitrogen compounds (such as sulfides and ammonia), coke,
and inorganic particulates. As a result, process wastewater exerts
both a chemical (COD) and a biochemical oxygen demand. The presence
of phenols and aromatic hydrocarbons is of particular concern. The
process wastewater is usually subjected to biological treatment and
physicochemical separation processes to remove a large percentage of
the organic matter prior to discharge. The cooling tower blowdown
often contains chromium compounds which are used as corrosion
inhibitors.
Solid Waste - A petroleum refinery generates a wide variety of
solid wastes, many of which contain petroleum-derived organic
compounds identified as toxic substances (NRDC, 1976). Basically,
refinery solid waste streams fall into two main groups: those
that are intermittently generated and those that are continuously
generated.
The intermittent wastes are generally those that result from
cleaning within the process areas and off-site facilities of
the refinery. The following are typical intermittent waste
streams:
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• Process vessel sludges, vessel scale, and other deposits
generally removed during plant turnarounds;
• Storage tank sediments; and
• Product treatment wastes, such as spent filter clay and
spent catalysts from certain processing units.
Continuous wastes (those requiring disposal at less than two-week
intervals) can be further broken down into two groups: process
unit wastes and wastewater treatment wastes.
Major process unit wastes include:
• Coker wastes, such as coke fines from delayed or fluidized
cokers, and spilled coke from unloading facilities;
• Spent catalysts and catalyst fines from the fluid catalytic
cracking units; and
• Spent and spilled grease and wax wastes from lube oil
processing plants.
Wastewater treatment wastes can include:
• Waste biological sludges from activated sludge units; and
• Dissolved air flotation float.
Typically such wastes are dewatered by means of sludge thickeners,
coupled with vacuum filters or centrifuges. The dewater sludge
can then either be land-disposed or incinerated. Low concentra-
tions of heavy metals are usually present in the sludges.
A summary description of major refining solid waste streams is
presented in Table 14 (Volume IV, page 160).
Air Emissions - Petroleum refineries emit significant quantities
of pollutants to the atmosphere. In addition to particulates,
sulfur dioxide, and nitrogen oxides, there are also relatively
large emissions of organic vapors, including aldehydes and
hydrocarbons.
Process Option A-l - Direct Combustion of Asphalt
in Process Heaters —
Presently, the asphalt fraction of a refinery's output is usually
subjected to several processing steps to make it suitable for sale as a
construction material. Asphalt has characteristically been a very low
value refinery product. As a result, the processing and sale of asphalt
are more of a "least cost" means of disposal rather than an important
source of revenue.
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Internal refinery heat energy requirements are supplied by combusting
portions of the refinery output. By introducing asphalt into the total
refinery heat generation system, a greater quantity of higher value fuels
is made available to the consumer. Thus, while the direct combustion of
asphalt does not save energy in an absolute sense, it does improve the
overall form value of the refinery product mix. Direct combustion of
asphalt is considered to be most feasible for the base case East Coast
refinery.
Wastewater - It is anticipated that an East Coast refinery employing
direct combustion of asphalt will have a treated process wastewater
effluent and a treated cooling tower blowdown that will be of the
same volume and composition as that of the base case East Coast
refinery.
Solid Waste - Implementation of direct combustion of asphalt will
not appreciably alter the quantity or characteristics of the base
case East Coast refinery total solid waste stream.
Air Emissions - Asphalt contains an appreciable amount of sulfur
and ash. The direct combustion of asphalt will result in a signi-
ficant increase in the amount of sulfur dioxide emitted. Flue gas
desulfurization would be required and would convert the sulfur that
is removed from the gas stream into a sulfuric acid byproduct. It
is not clear whether the direct combustion of asphalt would have any
effect on the base case emission of hydrocarbons.
Process Option A-2 - Hydrocracking of Heavy Bottoms--
The purpose of this process is to convert heavy ends into lighter,
more usable fuels. As in the case of direct combustion of asphalt, it
is designed to improve the form value of the refinery product mix rather
than to conserve energy in absolute terms. It is intended for use in a
West Coast base case refinery.
Wastewater - It is anticipated that a West Coast refinery employing
heavy-bottoms hydrocracking will have essentially the same wastewater
volume and characteristics as the base case West Coast refinery. The
only incremental (over the base case) waste load is a small sour water
(sulfide-containing) stream which increases the total process waste-
water flow rate by only 0.25%.
Solid Waste - Implementation of heavy-bottoms hydrocracking will
slightly alter the total quantity of refinery solid waste. This
process will require the disposal of a chrome-molybdenum catalyst
which will slightly increase the base case quantity of solid waste
disposal.
Air Emissions - Due to the sulfur content of heavy bottoms, there
will be an increase in hydrogen sulfide and sulfur dioxide emissions
which will have to be controlled by using an amine scrubber and a
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Claus plant. It is not clear whether the hydrocracking of heavy
bottoms would have any effect on the base case emission of hydro-
carbons.
Process Option A - Flexicoking —
The Flexicoking process is most applicable to East Coast refineries.
Flexicoking is the combination of fluid coking with coke gasification;
it contributes to energy conservation in two ways: (1) it frees high-
Btu refinery gas for higher priority uses, and (2) it converts asphalt
feed to naphtha and gas oil intermediates which then become available
for refining. This represents a portion of crude which otherwise would
not be a salable fuel product.
Wastewater - It is anticipated that an East Coast refinery employing
Flexicoking will have a treated process wastewater stream very nearly
the same as that of the base case East Coast refinery. The total
volume of waste load will be slightly increased due to the presence
of additional sour water and increased cooling tower blowdown.
The use of Flexicoking increases the amount of sulfur that must be
removed from gaseous streams. The sulfur in the high-Btu fuel gas
is removed using an amine scrubbing system, and the exhaust from
that scrubbing system is sent to the refinery gas plant. The hydrogen
sulfide in the low-Btu "flexigas" is too low in concentration to be
economically scrubbed out, and, therefore, this process comes with
an integral Stretford unit for sulfur removal. The Stratford unit
has a liquid purge stream which contains rather high concentrations
of metallic and organic compounds. A typical composition of a Stretford
purge stream is shown below.
TYPICAL COMPOSITION OF STRETFORD PURGE SOLUTION
Constituent m/1
Sodium Anthraquinone Disulfonate
NaVO~ (sodium meta-vanadate)
Sodium Citrate
Na2SCN 6,000
Source: "Characterization of Sulfur Recovery from Refinery Fuel
Gas," U.S. Environmental Protection Agency,
EPA-450/3-74-055, p. 36.
25
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The disposal of Stretford purge solution presents a problem. It
contains compounds that could disrupt the performance of a biological
wastewater treatment system should it be discharged to the main refin-
ery wastewater system. First, it may have to be concentrated and
then disposed of in a lined disposal site, much in the manner of a
solid waste stream.
Solid Waste - In addition to the base case solid waste load, the
Flexicoking process will also produce a solid waste stream con-
sisting of coke fines that will more than double the base case
solid waste generation rate. The coke fines, however, are not
considered particularly objectionable in terms of potential
environmental problems.
Air Emissions - As discussed under the section on water pollution,
increased sulfur emissions are the major increase in the base case
level of air emissions. It is not clear whether the implementation
of Flexicoking would have any effect on the base case emissions of
hydrocarbons.
Process Option B - On-Site Electric Power by
Combustion of Vacuum Bottoms—
In this process option, electric power is generated internally within
the refinery rather than purchased from the local power utility. The
internal generation of electric power within the refinery does not con-
serve energy overall—nor does it consume more energy than when power
is purchased, assuming that the internal and external power plants would
operate at the same efficiencies. In effect, the form value of the
asphalt product is upgraded to a higher form of electric power for refin-
ery use. This process option is most applicable to the base case Gulf
Coast refinery.
Wastewater - The only water pollutional implications of a Gulf Coast
refinery employing on-site power generation via asphalt combustion
will be increased cooling tower and boiler blowdown flow rates. The
process wastewater flow rate and composition will be essentially the
same as the base case.
Solid Waste - The total solid waste stream for on-site power generation
is essentially of the same volume and composition as that of the base case.
Air Emissions - The major pollutant of concern is the sulfur dioxide
emission in the exhaust from the boiler. The emission of hydrocarbons
will be essentially the same as the base case Gulf Coast refinery.
One must also recognize that off-site electricity generation would
also produce pollutants, the nature of which will be dependent on
the fuel used by the utility.
26
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Process Option C - High Purity Hydrogen Production
via Partial Oxidation of Asphalt —
This alternative is based on the production of high-purity hydrogen
for hydrotreating from vacuum bottoms, using a partial oxidation process.
The feedstocks freed up by this approach would then be available for sale
outside the refinery in the form of pipeline gas or naphtha. This alter-
native is considered most applicable to a West Coast base case refinery.
Wastewater - It is anticipated that a West Coast refinery employing
hydrogen production via partial oxidation will have a treated process
wastewater effluent and a treated cooling water blowdown stream that
will be slightly greater than that of the base case West Coast refin-
ery and similar in composition.
Solid Waste - Implementation of hydrogen production via partial
oxidation at the base case West Coast refinery will slightly
increase the volume of the total solid waste stream due to the
slightly increased quantity of wastewater treatment sludge. In
addition there will be a small waste catalyst stream containing
iron, chromium, copper,and zinc, which are often landfilled.
Air Emissions - Increased sulfur emissions are the only change
in the base case air pollution profile.
Summary
Wastewater effluents, solid waste streams, and air emissions from
petroleum refineries contain a variety of organic (and sometimes toxic)
pollutants that originate largely from the petroleum and its products
processed within the refinery.
The treated wastewater effluent streams of the base case refinery
would not be significantly altered by the implementation of the process
options. The most significant impact on wastewater would result from
the Flexicoking process option which produces an additional wastewater
stream that is small in volume and contains high concentrations of
organic compounds as well as vanadium.
Most of the process options result in increased sulfur dioxide
emissions; however, we do not expect the base case hydrocarbon emissions
to be significantly increased by any of the process options.
Hydrocracking of heavy bottoms adds a small chrome-molybdenum catalyst
stream to the base case solid waste discharge; Flexicoking adds large
quantities of relatively inert coke fines; and the partial oxidation
process option adds to the base case a small catalyst stream that con-
tains iron, chromium, copper, and zinc.
27
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A qualitative comparison of organic/toxic pollutant discharges is
presented in Table 2. In the final analysis, it does not appear that
new organic or toxic pollutants from the several proposed process options
will influence the decisions on implementation of these processes.
PULP AND PAPER
Bleached Kraft Pulping
Base Case Discharge of Organic/Toxic Pollutants—
A detailed description of the base case Kraft process is given in
Volume V, pages 54-60. Mills employing the conventional process steps
for producing bleached Kraft pulp discharge organic pollutants into the
air, water, and solid waste streams. The organic material originates
from the wood itself. (Although pentachlorophenol was formerly used by
many mills to inhibit microbial degradation in wood storage piles, the
industry has largely eliminated this practice specifically because of
concern over the discharge of this substance to the environment.) In
the manufacture of bleached Kraft pulp, a certain fraction of the wood
undergoes a variety of complex reactions with the caustic soda/sodium
sulfide cooking liquor and the chlorine or chlorine-based chemicals
used in the bleaching step. The result is a wide array of complex
organic species in the wastes.
Both soluble and insoluble components of the original wood and the
reaction byproducts are discharged as aqueous effluents. When chlorine
bleaching is used, the reaction between the chlorine and chemicals in
the wood may result in the formation of chlorinated organic compounds,
such as chlorophenols. Wood hydrolysis products are also present.
Typically, the various wastewater streams are combined into a single
stream and treated in a central wastewater treatment plant. As in
most industries, pulp and paper mill wastewater effluents are usually
characterized by gross parameters, such as biochemical oxygen demand
(BOD), chemical oxygen demand (COD), suspended solids, and color, rather
than by the identification of specific compounds. The wastewater is
usually subjected to suspended solids removal followed by biological
treatment for the removal of biodegradable organic matter. Treated
Kraft mill effluents, although still containing significant amounts of
BOD, COD, and color, are not considered toxic, even though numerous
"toxic" components have been identified as present, at least in small
amounts.
The wastewater treatment plant produces a wet sludge which is
composed largely of wood fibers, inorganic particulate matter, and
excess micro-organisms from the biological treatment step. The sludge
is usually subjected to mechanical dewatering to reduce its volume
prior to land disposal on or near the plant site. The sludge is not
considered toxic. As with many other organic sludges, both inorganic
and organic sulfur compounds present in both the liquid and solid phases
of the sludge can be partially converted to offensive hydrogen sulfide gas
by microbial activity if the sludge is subjected to anaerobic conditions.
28
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TABLE 2. PETROLEUM REFINING INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case petroleum
refinery
Process option A-l:
direct combustion of
asphalt
Process option A-2:
hydrocracking of
heavy bottoms
Petroleum-derived organic
compounds, sulfide, and
ammonia in treated efflu-
ent.
Same as base case.
Very slight increase
over base case in quantity;
character very similar.
Emission of organic
vapors (including al-
dehydes) to the atmos-
phere.
Increased SOX emissions
but organic pollutants
expected to be similar
to base case.
Increased SOX emission
but organic pollutants
expected to be similar
to base case.
Petroleum containing pro-
cess and wastewater treat-
ment sludges. Small amounts
of heavy metals present.
Same as base case.
Base case solid waste dis-
charge plus discharge of
a chrome-moly catalyst.
Process option A-3:
flexicoking
Base case waste load plus
small wastewater stream
containing organics and
vanadium.
Increased SOX emissions
but organic pollutants
expected to be similar
to base case.
Base case solid waste dis-
charge plus major addition
to solid waste load due to
coke fines.
Process option B:
On-site electric
power by combustion
of vacuum bottoms
Process option C:
High-purity hydrogen
production via partial
oxidation of asphalt
Base case waste load plus
slight increase in cooling
tower blowdown and boiler
blowdown.
Slight increase in base
case waste load.
Increased SO emissions
v
but organic pollutants
expected to be similar
to base case.
Increased SO,, emissions
A
but organic pollutants
expected to be similar
to base case.
Same as base case.
Slight increase in base
case waste load. Additional
small catalyst stream con-
taining iron, chromium, copper,
and zinc.
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Air emissions from a conventional Kraft mill contain small (yet
odoriferous) amounts of hydrogen sulfide and organic sulfur compounds,
such as methyl mercaptan and dimethyl sulfide. Through both process
modifications and improved operational controls, the magnitude of these
emissions has been greatly reduced in recent years.
Process Option 1 - Alkaline-Oxygen (A-0) Pulping—
A process description of alkaline-oxygen pulping is provided in
Volume V, pages 84-85. In terms of pollution control considerations,
its most significant feature is that it employs a non-sulfur cooking
step that would eliminate the air pollution from malodorous sulfur
compounds and greatly alleviate the bleach plant liquid effluent
problem.
It is expected that the wastewater effluent flow rate will not be
significantly changed as a result of A-0 pulping. However, elimination
of two of the standard bleach stages should result in approximately a
50% reduction in both raw wastewater BOD and color for A-0 compared
with Kraft. If the wastewater is treated by the same means in both
cases, i.e., by biological methods, the quantity of BOD and color in
the treated effluent will also be lower for A-0 pulping. In addition,
the quantity of sulfur compounds in the treated effluent will be greatly
reduced, being the result only of the sulfur originally present in the wood.
Since the quantity of sludge produced by a biological treatment system
is proportional to the amount of BOD removed, a reduction in the total raw
waste load BOD will reduce the quantity of the biological fraction of the
wastewater treatment sludge. The sludge will contain a far smaller quan-
tity of sulfur compounds.
By eliminating malodorous sulfur compounds, the implementation of
A-0 pulping will have a beneficial effect on air pollution control. In
addition to the virtual elimination of organic sulfur compounds (measured
as total reduced sulfur), A-0 pulping is expected to result in a slightly
lower level of particulate emission (Volume V, page 9).
Process Option 2 - The Rapson Effluent-Free Kraft Process—
The Rapson effluent-free Kraft process is described in Volume V,
pages 95-97. It essentially consists of a number of modifications to
the conventional Kraft process which are designed to increase the amount
of chemical recovery and water recycle. As its name implies, the main
environmental advantage of the Rapson process over conventional Kraft
processes is the elimination of water effluent from the bleaching step.
A mill using the Rapson process would produce significantly less
wastewater than a conventional bleached Kraft pulp mill. Thus, for the
application of a given type of wastewater treatment, the Rapson process
would discharge less organic pollutants in the treatment wastewater
effluent. The type of pollutants would be very nearly the same as
those associated with the conventional Kraft process.
30
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Since the wastewater flow rate and the quantity of pollutants in
the wastewater are lower for the Rapson process as compared to the con-
ventional Kraft process, it is anticipated that the quantity of waste-
water treatment sludge would also be less. There is, however, a small
stream of salt cake (sodium sulfate) leaving the process which can either
be disposed of or sold.
Air emissions from the Rapson process are expected to be essentially
the same, both in terms of composition and magnitude, as the air emissions
from the conventional Kraft process.
Mechanical Pulping
Base Case Discharge of Organic/Toxic Pollutants—
Mechanical pulping processes are described in Volume 5, pages 98,
105-113. Mechanical pulp (i.e., wood reduced to fiber by grinding) is
typically combined with wood fiber produced by chemical means and used
primarily in the manufacture of newsprint. It is also used in combina-
tion with chemical fiber in the manufacture of catalogue paper, construc-
tion paper, and other so-called groundwood papers. Wood chips, sawdust,
and shavings from saw mills can be used as raw material.
Since no chemicals are used in mechanical pulping, the organic
materials present in the wastewater stream are those present in the
wood itself and its hydrolysis products. The wood-derived organic
material is present as both wood fiber and as dissolved chemical
species. The quantity of color and sulfur compounds are less than
in Kraft mill effluent since the only sulfur present in mechanical
pulping would be that contained in the wood. The wastewater is sub-
jected to suspended solids removal and biological treatment for the
removal of biodegradable organic matter.
Solid waste from mechanical pulping is mostly wastewater treatment
plant sludge similar to that produced by Kraft mill wastewater treatment
facilities. The sludge will, however, contain a far smaller amount of
organic sulfur compound.
Air emissions are not generally a serious problem for mechanical
pulping operations. There is virtually no emission of organic sulfur
compounds, as in the case of Kraft mills. The only organic materials
discharged to the air are small quantities of fine particulate wood
fiber from the wood preparation steps.
Process Option - Thermo-Mechanical Pulping (TMP)-~
In the TMP process, described in detail in Volume V, pages 98, 105-113,
the wood is preheated to 266°F (130°C) for a short period and then reduced
to fibers in a pressurized device. The incentive to switch to TMP has
been the improved fiber properties and resultant expansion of the wood
31
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source base, i.e., the ability to use chips and residual wood to a greater
degree than if conventional mechanical pulping were employed.
The elevated temperature of the TMP process causes slightly more
organic matter to dissolve from the wood and eventually appear in the
wastewater effluent as an additional BOD loading. Thus, for a given
type of wastewater treatment applied, the implementation of the TMP
process will slightly increase the amount of organic material discharged
to the aquatic environment. However, the composition is expected to be
essentially unchanged.
Since the amount of sludge produced is proportional to the amount
of pollutants removed, TMP will also result in a slight increase in the
quantity of wastewater treatment sludge generated. The nature is expected
to be very similar.
No significant difference between the air emissions produced by the
TMP process and the base case mechanical pulping process is expected.
The Manufacture of Newsprint
Base Case Discharge of Organic/Toxic Pollutants—
Newsprint is manufactured from blends of mechanical pulp and Kraft
pulp (described in Volume V, pages 113-119). The discharges associated
with these processes have been discussed in the preceding sections.
Other than a minimal contribution from those pollutants retained by the
pulp (particularly the Kraft), pollution would be restricted to non-toxic
surfactants, wetting agents, etc., used in the paper-making.
Process Option - The De-inking of Old News for
Newsprint Manufacture—
The de-inking of old news for newsprint manufacture is a well-established
commercial process which is described in detail in Volume V, pages 113-119.
Although the concept of blending recycled fiber with virgin mechanical
fiber is not new, it has only recently been introduced for the manufacture
of newsprint on a large scale. It was chosen for in-depth technical/economic
analysis because the production of newsprint containing de-inked news now
accounts for less than 5% of the total newsprint consumed in the United
States and its broader application could significantly reduce both energy
usage and pollution.
De-inking is carried out by washing and pulping the old news in either
a batch or continuous operation using heat, water, and de-inking chemicals,
typically consisting of sodium peroxide, sodium silicate, and detergents.
The de-inking chemicals are largely recoverable.
The de-inking operation produces a wastewater that is quite high in
suspended solids, composed largely of unrecovered fibers from the paper
itself. The wastewater will also contain ink particles and the chemicals
32
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contained within the ink. Letterpress newsprint ink is made of carbon
black particles suspended in a mineral oil vehicle that may also contain
rosin and other additives. Litho newsprint ink (used for color printing
in magazines) is composed of various dye materials suspended in a vehicle
which may contain resins dissolved in aliphatic hydrocarbon solvents.
Thus, the wastewater may contain not only natural organic material from
the wood itself, but also small quantities of synthetic and petroleum-
based hydrocarbons. Although the wastewater contains higher levels of
suspended solids than the wastewater from the various mixes of mechani-
cal pulp and Kraft pulp that constitutes the base case, the concentration
of BOD is very nearly the same, if not slightly lower.
The de-inking operation produces a wet waste sludge consisting of
paper or cellulose fiber and ink particles which is usually sent to
landfill.
Also, de-inking operations produce slightly more wastewater treatment
sludge than the base case. Although it is difficult to quantify, it is
clear that, overall, the implementation of de-inking of old newsprint will
alleviate the national solid waste disposal problem by substantially reduc-
ing the amount of old news destined for municipal landfills.
There are no significant air emissions of organic materials from the
de-inking of news for newsprint.
Summary
The base case conventional bleached Kraft pulping process discharges
wood-derived organic material into air, water, and solid waste streams.
The two options to the conventional K.raft process, alkaline-oxygen pulping
and the Rapson effluent-free Kraft process, both reduce the total amount
of organic material discharged. Neither process uses radically new chem-
istry or introduces any synthetic organic substances which could eventually
appear in effluent streams.
The base case mechanical pulping process also discharges wood-derived
organic material into water and solid waste streams. There are no signi-
ficant air emissions. The process option, thermo-mechanical pulping, while
resulting in slightly higher quantities of organic material discharged into
water and solid waste streams, allows more effective use of low-grade wood,
thereby conserving resources. No new water (or air) emission problems of
any consequence can be visualized.
The base case manufacture of newsprint is a mix of Kraft pulp manu-
facture and mechanical pulp manufacture. The process option, the de-inking
of old newsprint, while introducing small quantities of synthetic organic
material and having a slightly higher treated wastewater pollutional load,
results in a significant overall reduction in solid waste generation by
using an existing source of solid waste as the raw material. Carbon black
and dyes in the discharge may be of concern in the future.
33
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A qualitative comparison of the organic waste discharges is presented
in Table 3.
OLEFINS
Production of Ethylene by Ethane-Propane Cracking
Base Case Discharge of Organic/Toxic Pollutants—
The base case ethylene production unit discharges air, water, and
solid waste streams that contain a variety of organic and inorganic
pollutants.
There are five major sources of wastewater in the base case ethylene
production unit:
• Decoking scrubber effluent,
• Dilution steam blowdown,
• High-pressure steam blowdown,
• Acid gas scrubber water, and
• Non-contact cooling water blowdown.
Except for non-contact cooling water blowdown, the major process
wastewater streams are usually combined into a single stream and sent
to a central wastewater treatment facility. The combined wastewater
contains a variety of hydrocarbon pyrolysis products, dissolved inor-
ganic carbonates, sulfates, sulfides, and other salts, and suspended
solids (mostly carbonaceous particulates). It is quite common for non-
contact cooling water blowdown to contain chromium compounds which are
used as corrosion inhibitors. Generally, the pollutants of greatest
concern are the hydrocarbons and various sulfur compounds which are
characterized by non-specific parameters such as biochemical oxygen
demand (BOD) and chemical oxygen demand (COD). The wastewater is
typically subjected to suspended solids removal followed by biological
treatment. Even though the treated effluent still contains appreciable
amounts of organic matter, it is not generally considered toxic—certainly
not in the same degree as high-concentration synthetic organic residues.
A detailed description of wastewater effluent loadings, treatment tech-
nology, and costs is presented in Volume VI, pages 90-100.
The major solid wastes are wastewater treatment sludge and spent
dessicants. The sludge produced by the wastewater treatment processes
contains large quantities of relatively inert carbon particulate matter
("coke"), biodegradable solids from the waste micro-organisms in the
biological treatment system, and many of the previously listed pollu-
tants originally present in the raw wastewater. The sludge is often
dewatered by mechanical means prior to landfill. Spent dessicants are
34
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TABLE 3. PULP AND PAPER INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Process
Medium
Water
Air
Solid Waste
Base case
Bleached Kraft
pulping
CJ
Alkaline-oxygen
pulping
The Rapson effluent-
free Kraft process
Soluble and insoluble
wood-derived organic
material. Presence of
sulfur compounds; not
considered toxic. Major
source of organic pollu-
tants .
Soluble and insoluble
wood-derived organic
materials. Smaller
amount of sulfur com-
pounds than base case.
Quantity of total organic
pollutants somewhat less
than base case.
Soluble and insoluble
wood-derived organic
materials. Quantity of
total organic pollutants
significantly less than
base case.
Hydrogen sulfide and organic
sulfur compounds such as
methyl mercaptan and di-
methyl sulfide. Minor (but
malodorous) source of organ-
ic pollutants.
Elimination of the discharge
of malodorous sulfur com-
pounds to the air.
Air emissions expected to
be essentially the same as
the base case kraft process.
Wet sludge from biologi-
cal wastewater treatment.
Sulfur compounds present,
though not considered
toxic. Major source of
organic pollutants.
Wet sludge from biologi-
cal treatment. Smaller
amount of sulfur com-
pounds than base case.
Quantity of total organic
pollutants somewhat less
than base case.
Wet sludge from biologi-
cal treatment. Quantity^
of total organic pollu-
tants significantly less
than base case.
(continued)
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TABLE 3 (Continued). PULP AND PAPER INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case
mechanical pulping
Thermo- mechanical
pulping
LU
cr>
Base case
manufacture of
newsprint
De-inking of old
news for newsprint
Soluble and insoluble
wood-derived organic
materials. Major source
of organic pollutants.
Soluble and insoluble
wood-derived organic
materials. Quantity of
organic pollutants
slightly greater than
base case.
Discharges are a mixture
of those of the conven-
tional kraft process and
mechanical pulping.
Wood-derived organic
materials plus synthetic
and petroleum-derived
organic material from ink.
Major source of organic
pollutants.
No significant emission
of organic material.
No significant emission
of organic material.
Discharges are a mixture
of those of the conven-
tional kraft process and
mechanical pulping.
No significant emission
of organic material.
Wet sludge from biologi-
cal treatment. Major
source of organic
pollutants.
Wet sludge from biologi-
cal treatment. Quantity.
of organic pollutants
slightly greater than
base case.
Discharges are a mixture
of those of the conven-
tional kraft process and
mechanical pulping.
Wet sludge from de-ink-
ing operation and from
biological treatment.
Use of old news greatly
alleviates overall solid
waste disposal problems.
-------
solid particles typically composed of silica gel, alumina, or ceramic
molecular sieve material. The dessicants themselves are relatively
inert, but they can be contaminated with hydrocarbons. The spent
dessicant solid waste stream is many times smaller than the waste-
water treatment sludge stream. Neither is generally considered toxic.
Organic pollutants present in air emissions are mainly in the form
of carbonaceous particulate matter and hydrocarbon vapors. Particulate
matter is emitted from coking and related operations and is largely
removed by wet air pollution control devices. Hydrocarbons are dis-
charged to the air largely as the result of fugitive emissions from
the following sources:
• Compressor, valve, and pump seals;
• Emergency venting and startup;
• Periodic maintenance operations requiring the flushing
of heat exchangers, pipes, and so on; and
• Miscellaneous leaks and spills.
Although many of the hydrocarbon emissions can be piped to the plant
flame and combusted, a significant amount of hydrocarbon vapors (mainly
ethylene) do eventually escape to the atmosphere.
Process Option 1 - Production of Ethylene from
the Pyrolysis of Naphtha—
Because of the foreseeable shortage of natural gas, and hence the
declining availability of ethane and propane, more and more domestic
ethylene production is being based on heavier petroleum products. One
option is the pyrolysis of naphtha. Conceptually, naphtha cracking is
quite similar to ethylene cracking. A detailed process description is
given in Volume VI, pages 22-26. While the total energy demand for a
naphtha cracker is larger on a per-unit-ethylene basis, so much more
co-product material is produced that the energy consumption per unit
of net hydrocarbon product is smaller than for ethylene-propylene
cracking.
The production of ethylene from the pyrolysis of naphtha also
generates air, water, and solid waste streams that contain organic
pollutants. Qualitatively, the wastewater from naphtha cracking is
not unlike that from the base case technology. No different waste-
water streams are added, and no existing wastewater streams are eli-
minated. While the exact composition of the individual wastewater
streams cannot be precisely calculated on a generalized basis, the
similar process sources would be expected to result in similar com-
positions. The wastewater flow rate from an ethylene plant based on
naphtha cracking is expected to be approximately 1.7 times that of the
base case plant. It is, therefore, likely that the quantity of organic
37
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pollutants in the wastewater would be approximately 1.7 times that of
the base case plant, assuming biotreatment at the same efficiency.
As in the case of the base case technology, most of the solid waste
generated by the production of ethylene from naphtha cracking is waste-
water treatment sludge. Its composition is expected to be quite similar
to that of sludge generated by the base case technology. The quantity
of wastewater treatment sludge is expected to be 1.7 times that of the
base case plant. The quantity of spent dessicants is expected to be
the same as the base case plant. An additional solid waste stream
composed of recovered sulfur is generated by naphtha cracking. It will
probably contain small amounts of organic material.
The production of ethylene from the pyrolysis of naphtha results in
an increase in air emissions over the base case technology. More particu-
late matter is generated due to the required increase in furnace capacity
and the increased frequency of decoking. In addition to the base case
emissions of hydrocarbons, the production of ethylene from naphtha cracking
will result in hydrocarbon emissions from the storage of liquid hydrocarbon
feedstocks. (When ethane and propane are processed, the feedstocks arrive
at the plant either in pressurized storage tanks or via pipeline. On the
other hand, the heavy feedstocks may be stored in petroleum storage tanks,
which, even if equipped with floating roofs, undergo evaporative losses.)
The increase in hydrocarbon emissions IS Significant. The nature of the
volatile hydrocarbons is not considered to be toxic in the usual sense.
Process Option 2 - Production of Ethylene
from Gas-Oil Cracking --
Also a natural gas-conserving option, ethylene production from gas-oil
cracking is technically quite similar to that of naphtha cracking. A de-
tailed process description is presented in Volume VI, pages 27-31. As in
the case of ethylene production by naphtha cracking, the composition of
the combined wastewater stream is expected to be quite similar to that
of the base case ethylene plant. The wastewater flow rate, however, will
be approximately 3 times greater than the base case. We can, therefore,
expect the quantity of organic pollutants in the treated effluent to be
3 times that of the base case plant. The wastewater treatment sludge
generated by ethylene production from gas-oil cracking is similar in
composition to that of the base case ethylene plant, but will be gen-
erated at a rate that is 3 times greater. Gas-oil cracking also produces
a recovered sulfur waste stream. It is expected to be 1.8 times the size
of that produced by the naphtha cracking process option. (The base case
process essentially has no sulfur waste stream.) The composition and
size of the spent desslcant waste stream are expected to be about the
same as those of the base case ethylene plant.
As in the case of the naphtha-cracking process option, gas-oil
cracking will result in an increase in fugitive hydrocarbon emissions
over the base case ethylene plant, primarily as the result of storing
liquid hydrocarbon feedstock. However, the quantity of hydrocarbons
38
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emitted is expected to be somewhat less than that of the naphtha cracking
process option.
Summary
The base case ethylene production unit discharges air, water, and
solid waste streams that contain organic pollutants. The waste streams
are not generally considered toxic.
Both process options—naphtha cracking and gas-oil cracking—will
result in an increase in the quantity of organic pollutants discharged
in the treated wastewater stream. Also, both process options will result
in an increase in the quantity of wastewater treatment sludge and will
also introduce a new solid waste stream—namely, recovered sulfur.
Due to the necessity for storing liquid hydrocarbon feedstocks,
both process options will result in an increase in the amount of hydro-
carbons that escape to the atmosphere.
A qualitative comparison of the organic/toxic pollutants is presented
in Table 4.
AMMONIA
Manufacture of Ammonia from Natural Gas
Base Case Discharge of Organic/Toxic Pollutants^-
The manufacture of ammonia from natural gas has associated with it
very few environmental problems. A schematic representation of the
process, showing the potential air, water, and solid waste emissions,
is given in Volume VII, Figure 2.
Wastewater streams consist of cooling tower blowdown, boiler blow-
down, compressor blowdown, and process condensates. With the exception
of cooling tower blowdown, the wastewater streams are relatively small.
Cooling tower blowdown can sometimes be contaminated with corrosion
inhibitors composed of chromium compounds. In the remaining waste-
water streams, ammonia is the principal contaminant. The wastewater
contains only small amounts of organic material.
The main air pollution problem associated with the production of
ammonia from natural gas is the loss of ammonia to the atmosphere from
various sources within the plant. There are no significant emissions
of organic pollutants to the atmosphere.
There are two sources of solid waste from the manufacture of ammonia
from natural gas:
• Wastewater treatment sludge, and
• Waste catalyst.
39
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TABLE 4. OLEFINS INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case production Treated effluent contains
of ethylene by ethane- hydrocarbon pyrolysis pro-
propane cracking ducts and carbonaceous
particulate matter. Non-
contact cooling water may
contain chromium compounds.
Process Option 1:
Naphtha cracking
Process Option 2:
Ges oil cracking
Same composition as base
case. Quantity of organic
pollutants is approxi-
mately 1.7 times that of
base case.
Same composition as base
case. Quantity of organic
pollutants is approxi-
mately 3 times that of
base case.
Fugitive hydrocarbon
emissions from vents,
leaks, and spills.
Increase in fugitive
emissions over base case
due to storage of liquid
hydrocarbons.
Increase in fugitive
emissions over base case
due to storage of liquid
hydrocarbons.
Wastewater treatment sludge
containing hydrocarbon
pyrolysis products, carbon-
aceous particulate matter,
and waste microorganisms.
Small amount of hydrocarbon-
contaminated spent dessicant.
Increase in wastewater treat-
ment sludge over base case.
Introduction of a recovered
sulfur waste stream. Spent
dessicants same as base case.
Increase in wastewater treat-
ment sludge over base case
and naphtha cracking. Larger
recovered sulfur stream than
naphtha cracking.
-------
The quantity of wastewater treatment sludge is quite small. The
sludge contains inorganic particulate matter such as rust, oil and grease,
small amounts of ammonia, and chromium compounds (if chromate corrosion
inhibitors are used in the cooling water system). Waste catalyst is
composed of iron oxide. Neither can be considered a serious problem.
Process Option 1 - Manufacture of Ammonia from Coal—
Given the shortage of natural gas, and the need for the United States
to reduce its dependence on foreign petroleum, serious consideration should
be given to basing future ammonia plants on coal. Prior to World War II,
nearly all synthetic ammonia production was based on the use of coal to
produce synthetic gas for the actual ammonia production step. Since that
time only a small number of ammonia plants based on coal have been built.
A detailed description of the process is presented in Volume VII, pages 37-45,
The use of coal as a feedstock for the manufacture of ammonia results
in pollution problems that are far more serious than those associated with
the production of ammonia from natural gas.
In addition to the base case wastewater streams, an ammonia plant
based on coal will have the following wastewater streams:
• Coal pile runoff;
• Slag and ash pile runoff;
• Cooling tower blowdown (over and above the base case
cooling water blowdown) and
• Wastewater from the synthesis gas purification system.
Rainwater runoff from coal piles is slightly acidic and would contain
particulates, organic compounds, and heavy metals leached out of the coal
by the rainwater, and oxidation reaction products. Heavy metals are the
pollutants of greatest concern in this wastewater stream. A representa-
tive distribution of heavy metals in coal, slag, and fly ash is presented
in Volume VII, page 54. Many of these constituents could be leached.
The carbon dioxide and hydrogen sulfide removal system (Rectisol)
and the sulfur recovery plant tail gas cleanup system produce wastewater
streams that must be treated. The wastewater streams contain methanol
and other organic compounds as well as hydrogen sulfide. Many of the
organics are expected to be biodegradable.
The use of coal greatly increases the quantity of solid waste
generated. In addition to the base case solid waste streams previously
described, the manufacture of ammonia via coal gasification generates
the following solid waste streams:
• Slag - A waste slag, largely composed of the ash content of
the coal, is produced in the coal gasification step. An
41
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elemental analysis of the slag is presented in Volume VII,
Table 19, page 54. The slag contains leachable heavy metals
and therefore presents a disposal problem. Very large quan-
tities of slag are produced (0.182 ton/ton
• Runoff Treatment Plant Sludge - Since large quantities of coal
and slag must be stored on site, contaminated stormwater runoff
is a major water pollution problem associated with the coal gasi-
fication alternative. The primary pollutants of concern in the
runoff water are heavy metals. Therefore, the proposed waste-
water treatment system consists of precipitation (with lime)
and settling, which produces a secondary waste sludge composed
of metal hydroxides.
• Synthesis Gas Purification Wastewater Treatment Plant Sludge - The
wastewater from the synthesis gas purification step contains bio-
degradable organic material and hydrogen sulfide. If proper design
criteria are followed, it can be treated in a high detention time
biological treatment system. The biological treatment system
will produce a small sludge stream largely composed of waste
microorganisms and a small amount of unoxidized methanol and
sulfide in the liquid fraction.
• Recovered Sulfur - The sulfur removed from the coal during the
gasification step is recovered as molten sulfur. In our analysis
it was assumed that this byproduct sulfur would be marketed. If
market conditions are such that all of the sulfur cannot be sold,
it will become a solid waste stream destined for land disposal,
but it is not considered a severe problem.
The use of coal as a feedstock for ammonia production is expected
to have the following impact on air emissions:
• Coal Receiving and Storage - The use of coal will require
facilities for unloading and storage, coal grinding, and
conveying to the process — all of which generate particu-
late emissions.
• Synthesis Gas Production - The use of coal introduces a
significant amount of sulfur which must be removed from
the gas stream.
• Ammonia Production, Storage, and Unloading - The emissions
from the actual ammonia manufacturing operations are expected
to be the same as the base case.
While the air pollution problems associated with the use of coal
are quite significant, the major pollutant of concern is sulfur rather
than organic/toxic pollutants (see Sulfur Oxides report) .
42
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Process Option 2 - Production of Ammonia
from Heavy Fuel Oil —
This process option is also intended to conserve natural gas. In
the early 1950fs, industrial processes were developed for producing a
synthesis gas, carbon monoxide, and hydrogen by the partial oxidation
of hydrocarbons. In producing ammonia from heavy fuel oil, the fuel
oil is first converted into synthesis gas which is then processed (in
a. manner almost identical to that used in the coal gasification alterna-
tive) to form a feedstock for the actual ammonia-producing step. A
detailed description of the process is presented in Volume VII, pages 66-79.
The production of ammonia from heavy fuel oil results in a significant
increase in the base case air, water, and solid waste pollution problems.
However, these are less serious than the pollution problems associated
with the production of ammonia from coal.
In addition to the base case wastewater streams, the production of
ammonia from fuel oil results in a synthesis gas purification stream
that has about the same flow rate and characteristics as that produced
in the ammonia-from-coal option. There is also a wastewater stream from
the sulfur recovery unit and a stream from the soot recycle system. The
use of fuel oil instead of coal eliminates the contaminated rainwater
runoff problem from coal and slag piles. Overall, the water pollution
problems resulting from the use of fuel oil are less than those associated
with the ammonia-from-coal option.
In addition to the base case solid waste streams, the following
solid waste streams are generated in the production of ammonia from
fuel oil:
• Wastewater Treatment Sludge - The wastewater streams contain
biodegradable organic matter and therefore can be treated in
biological treatment systems. A waste sludge is produced
which contains waste micro-organisms and some of the organic
pollutants originally present in the wastewater. The amount
of sludge is far less than that produced by the ammonia-from-
coal option and does not contain appreciable amounts of heavy
metals.
• Recovered Sulfur - As in the case of the production of ammonia
from coal, sulfur is removed from the oil and presumably sold
as a byproduct in the form of molten sulfur. The rate of sulfur
generation is significantly less than for the ammonia-from-coal
process option.
The air pollution resulting from oil gasification is less than that
associated with the ammonia-from-coal process option. There is no coal-
related dust source. The only significant air emission is the sulfur-
laden exhaust from the carbon dioxide and hydrogen sulfide removal systems.
43
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Summary
The base case technology involving the production of ammonia from
natural gas has very few environmental problems. There is a minimal
discharge of organic pollutants, and the waste streams are not generally
considered toxic.
The process option based on the use of coal as a feedstock greatly
increases the air, water, and solid waste pollution loads over the base
case technology. Heavy metals present in both coal and slag, and which
eventually appear in the treated wastewater and sludge streams, create
a much more serious pollution problem than the waste streams from the
base case technology. There is also a significant increase in the
organic pollutants appearing in water and solid waste streams.
The process option based on the gasification of fuel oil also results
in a significant increase in the base case pollution load, but to a lesser
degree than the ammonia-from-coal process option. Heavy metals are not a
major problem, as they are in the coal option.
A qualitative comparison of the organic/toxic pollutant discharges
is presented in Table 5. Organic/toxic pollutants other than those
found in any use of coal do not appear to be of a magnitude that would
influence decision-making.
ALUMINA/ALUMINUM
The aluminum industry is comprised of two basic operations: (1) the
production of alumina (A1203) from aluminum-bearing minerals, and (2) the
reduction of alumina to aluminum metal. The two operations are conducted
at entirely separate locations.
Production of Alumina by the Bayer Process
Base Case Discharge of Organic/Toxic Pollutants--
At present, the sole technology used to produce alumina in the
United States is the Bayer process. It is applicable only to bauxite
as a raw material, most of which is imported from the Caribbean, northern
South America, and Australia.
In the Bayer process (which is described in detail in Volume VIII,
pages 106-118), finely ground bauxite is digested at elevated tempera-
tures under pressure. The digesting liquor contains sodium aluminate
and free caustic. After the digestion step, the insoluble components
of the bauxite, primarily the oxides of iron, silica, and titanium, are
removed by thickening and filtration. The aluminum-containing liquor
is then subjected to a series of precipitation, separation, and calcina-
tion steps to yield the final product—alumina.
44
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TABLE 5. AMMONIA INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case production
of ammonia from
natural gas
Process Option 1:
Production of ammonia
from coal
Process Option 2:
Production of ammonia
from heavy fuel oil
Cooling tower blowdown
sometimes contaminated
with chromium plus small
ammonia-contaminated pro-
cess streams. Virtually
no organic pollutants.
Base case discharge plus
heavy metal-containing
coal and slag pile run-
off, plus process waste-
water streams containing
organic pollutants.
Major increase in base
case organic/toxic pollu-
tant discharge.
Base case discharge plus
process wastewater con-
taining organic pollutants.
Major increase in base
case organic/toxic pollu-
tant discharge, but less
than that of the coal
process option.
Losses of ammonia from
storage and processing
facilities. No signifi-
cant discharge of organic
pollutants.
Base case discharge plus
particulate matter from
coal handling, plus sul-
fur emissions from syn-
thesis gas production.
No significant discharge
of organic pollutants.
Base case discharge plus
sulfur emissions from
synthesis gas production.
No significant discharge
of organic pollutants.
Small quantities of waste-
water treatment sludge and
waste catalyst. Very minor
source of organic/toxic
pollutants.
Base case discharge plus
very large quantities of
heavy metal-containing slag
and runoff treatment sludge,
plus wastewater treatment
sludge containing organic
pollutants. Very large
increase in base case organic/
toxic pollutant discharge.
Base case discharge plus
wastewater treatment sludge
containing organic pollutants.
Very large increase in base
case organic/toxic pollutant
discharge, but less than
coal process option.
-------
Solid Waste - The separated solids, known as "red mud," are discarded,
usually into large tailing ponds. The quantity of red mud removed
from the caustic slurry following digestion varies with the bauxite
used and can range from 0.33-2.0 tons (dry basis) per ton of alumina
produced. About 0.8 ton per ton of alumina is typical in U.S. plants.
The composition of red mud is presented in Volume VIII, Table 1,
page 121. The solid fraction, in addition to containing the oxides
of iron, silicon, and titanium, also contains undissolved alumina,
phosphates, lime, and manganese oxide. Various trace heavy metals
may also be present and would constitute the only "toxic" waste.
The liquid fraction of the red mud is highly alkaline (typically
pH 12.5) and contains high concentrations of caustic, soda ash,
sodium chloride, and dissolved alumina. The disposal of red mud
constitutes the largest environmental impact associated with
alumina production.
Wastewater - While the flow rate of the red mud stream is quite
large, most of the water fraction is recycled after the red mud
is deposited. Other wastewater streams consist of spent alkaline
process liquors, condensates, cooling water, and stormwater runoff.
Many of these streams can be used as red mud transport water if the
overall water balance of the plant is favorable. In fact, a major
segment of the industry operates its wastewater systems in essen-
tially a zero-discharge mode. Small quantities of heavy metals
may also be present in the wastewater streams of those plants
that occasionally or continuously discharge wastes.
Air Emissions - Particulates, originating from the bauxite ore
and evolved during the various grinding and calcining steps, con-
stitute the major air emission from alumina production.
Process Option 1 - Production of Alumina from Domestic
Clays via Hydrochloric Acid Leaching —
The impetus for employing this process is not energy conservation
(it actually uses more energy than the base case Bayer process), but
rather to reduce the dependence on foreign sources of raw material. The
hydrochloric acid and other alternatives to the Bayer process are based
on the extraction of alumina from the large reserves of kaolin clay in
Georgia and South Carolina.
The hydrochloric acid process is described in detail in Volume VIII,
pages 23-30. Briefly, in the hydrochloric acid process, clay is dehydrated,
leached with hydrochloric acid, and then settled to separate the residue
from the aluminum chloride/iron chloride solution. This solution is then
purified with an amine ion exchange system operation to remove the iron
chloride, while leaving the aluminum chloride in solution. The aluminum
chloride is crystallized from the solution and decomposed to alumina, and
the acid value is recovered.
-------
Solid Waste - The primary waste material from this process is the
underflow from the series of thickeners, which consists of the
acid-insoluble clay fraction and a dilute aluminum chloride aqueous
solution. The composition of this solid waste stream is given below
(Volume VIII, page 28):
Constituent Weight percent
Alumina (undissolved) 12.8
Silica 33.5
Aluminum chloride (soluble) 0.6
Other soluble chlorides (mostly iron) 1.5
Other impurities (Mg, Ti, P, V, SO^) 2.7
Water 48.9
Total 100.0
This waste material will also very likely be contaminated with small
quantities of kerosene, alcohol, and amines, all of which originate
from the ion exchange loop.
On a dry basis, this waste is generated at a rate of approximately
3.35 tons per ton of alumina, which is about 4 times greater than
the typical 0.8 ton per ton rate for conventional bauxite refining
plants. The main reason for this tremendous increase in solid waste
is the low alumina content of kaolin clay as compared to bauxite.
The characteristics of the waste are also quite different. Instead
of the liquid fraction of the waste being highly alkaline, it is
acidic and contains high concentrations of chlorides. This chemical
environment is far more conducive to the dissolution of many trace
heavy metals than the alkaline conditions present in red mud from
bauxite refining.
Wastewater - As in the case of the base case alumina process, most
if not all of the water will be recycled through the solid waste
impoundments. If a water discharge is unavoidable, it will very
likely contain chlorides, small quantities of the above listed
organic materials, and the heavy metals contained in the clay as
soluble chlorides.
Air Emissions - Since grinding and calcination operations are
involved, this process will generate particulate matter in much
the same way as bauxite refining. In addition, the acid recovery
plant generates a tail gas stream that may contain HC1. It will
most likely have to be controlled by wet scrubbing, with the spent
scrubber water discharged to the tailings pond.
47
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Process Option 2 - Production of Alumina from
Domestic Clays via Nitric Acid--
Also intended for the extraction of alumina from domestic kaolin
clay, the nitric acid process (described in detail in Volume VIII,
pages 30-38) involves the following basic steps:
• Calcining the kaolin clay to make the contained alumina
selectively available for extraction with nitric acid.
• Leaching the calcined clay with hot nitric acid at atmospheric
pressure to produce a solution of aluminum nitrate and a sus-
pension of clay insolubles.
• Separating the clay insolubles from the aluminum nitrate
liquor in thickeners.
• Removing the iron and other impurities from the clarified
aluminum nitrate liquor by use of a liquid ion-exchange
medium.
• Removing the remaining impurities from the iron-free
aluminum nitrate liquor by means of vacuum crystalliza-
tion of aluminum nitrate nonohydrate.
• Recovering the alumina by hydrolysis of the aluminum nitrate
under controlled conditions so that the nitrate values are
recovered largely as nitric acid rather than as nitric oxides.
• Recovering the nitric acid and nitrogen oxide values in the
form of nitric acid for recycle.
• Calcining the product alumina.
Solid Waste - The primary waste material from this process is the
underflow wet sludge from the series of thickeners, which consists
of the acid-insoluble clay fraction and a dilute aluminum nitrate
aqueous solution. The composition of this waste stream is given
below (Volume VIII, page 37):
Constituent Weight percent
Alumina ( und i s s o1ved) 1.5
Silica 45.0
Aluminum nitrate (soluble) 1.9
Other soluble nitrates 2.2
Water 47.2
Other impurities (Mg, Ti, P, V, 804) 2.2
Total 100.0
48
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On a dry basis, this waste is generated at a rate approximately
1.9 tons per ton of alumina, which, although lower than that for
the hydrochloric acid process, is still about double that of con-
ventional bauxite refining.
The waste is acidic, and the pollutants of major concern are the
soluble nitrates, which, in general, pose more of a threat to
groundwater than either the chlorides from the hydrochloric acid
process or the alkaline solutions from the conventional bauxite
refining process. In addition, the waste will be contaminated
with small amounts of kerosene and organic phosphate ion-exchange
liquid, as well as trace heavy metals from the clay itself.
Wastewater - As in the base case bauxite refining process and the
hydrochloric acid process, it will be possible to recycle the bulk,
if not all, of the wastewater generated. If a wastewater discharge
is unavoidable, it will be contaminated with small quantities of
the previously mentioned organic matter, heavy metals, and nitrates.
Air Emissions - The calcination of beneficiated clay pellets would
not generate as much particulate matter as the calcination of bauxite,
but dust emission controls will still be required for clay particulate
as well as for fly ash removal, since coal could be used in the calci-
nation kiln. This process also generates several waste gas streams
containing oxides of nitrogen. Control of these streams is part of
the total process.
Process Option 3 - Clay Chlorination (Toth
Alumina) Process—
The Toth Aluminum Corporation (TAG) has been developing a process
for the production of alumina and byproducts from clays and other alumina-
containing minerals. The process involves the chlorination of alumina-
containing raw materials in the presence of carbon to produce aluminum
chloride vapor and other volatile chlorides. These are subsequently
purified to remove other metal chlorides and then oxidized to produce
alumina and chlorine for recycle. Based on kaolin clays, the steps in
the process involve: (1) ore drying and calcination; (2) chlorination
in which the aluminum, titanium, and iron present in the ore are carried
overhead as volatile chlorides; (3) separation of the other chlorides
from the aluminum chloride by fractional condensation and distillation;
and (4) separate oxidation of the iron, silicon, and titanium chlorides
to their respective oxides for recovery of chlorine for recycle. Finally,
the aluminum chloride, after separation, is also oxidized to produce
alumina and to regenerate chlorine for recycle. A detailed description
of the process is given in Volume VIII, pages 37-49.
Solid Waste - The process produces a waste stream which contains
the gangue materials present in the clay. An estimated composi-
tion of the waste stream is given as follows:
49
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Constituent Weight percent
Aluminum (insoluble) 6.0
Silica 73.7
Iron (ferric) oxide 0.8
Soluble chlorides 2.2
Other impurities 6.8
Water 10.5
Total 100.0
The rate at which this waste is generated is estimated to be
approximately 1.5 tons (dry basis) per ton of alumina.
Although the solid waste streams are produced in an essentially
dry state, water is used in the process, and liquid waste control
will very likely involve the recycling of wastewater through the
disposal lagoon, so the same type of wet tailings pond situation
will be created as in HC1 leaching. As in the case of the hydro-
chloric acid process, the pollutants of greatest concern are
soluble metal chlorides.
Wastewater - The only anticipated wastewater actually discharged
is cooling tower blowdown, which is often contaminated with chromium
corrosion inhibitors.
Air Emissions - Three potential emission streams (described below)
are apparent from this technology:
(1) The exhaust from the chlorinator, after cooling and
scrubbing to remove the chlorides, will contain CO,
C02, and probably traces of HC1, if moisture, chlorine,
and the more volatile titanium and silicon tetrachlo-
rides are present. We expect that some chlorinated
hydrocarbons would result from the chlorination of
heavy volatile material remaining in the coke. We
would also expect that these materials would be
removed in the low-temperature condensation step
required to remove the titanium and silicon tetra-
chlorides. When these materials are oxidized at
high temperature to recover the chlorine values
for recycle, the chlorinated hydrocarbons are also
destroyed.
(2) The dry residue from the chlorinator contains the
ash from the clay and coke, alumina, and non-volatile
chlorides of the alkali and alkali earth metals present
in the clay and coke ash.
(3) In separating alumina from A1C13 vapor and chlorine
following oxidation, residual chlorine and A1C13 may
50
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be present in the solid alumina. The same may also occur
in the oxidation of silicon and titanium tetrachlorides.
We have assumed that the sources of chlorine emission
would be controlled because there is a real economic
incentive to conserve it and to prevent escape of this
hazardous gas, although it is not one of the criteria
pollutants.
The emission rates for this process depend upon purge
and exhaust rates which, for the most part, are unknown
at present.
Aluminum Production by the Hall-Heroult Electrolytic
Reduction Process
Base Case Discharge of Organic/Toxic Pollutants—
The Hall-Heroult electrolytic reduction process is presently used
to produce all of the primary aluminum throughout the world. A detailed
process description is presented in Volume VIII, pages 112-118. Basically,
the alumina is dissolved in molten cryolite (Na3AlFg) in an electrolytic
cell wherein aluminum is liberated at the cathode and oxygen at the anode.
The oxygen liberated at the anode reacts with the carbon anode to produce
CC>2 and CO. Modern Hall-Heroult electrolytic cells are largely steel
boxes lined with insulating refractory and carbon. Carbon blocks at
the bottom of the cell serve as the cathode in the electric circuit.
The anodes are also carbon suspended in the electrolyte from above.
Wastewater - The main sources of wastewater from primary aluminum
production are the wet scrubbers used to control air emissions
from the various in-plant operations and the cooling water blow-
down. The following chemical constituents were found to be present
in wastewater from primary aluminum production:
Suspended solids,
Dissolved solids,
Chemical oxygen demand (COD),
Oil and grease,
Fluoride,
Chloride,
Sulfate,
Free cyanide, and
Trace metals (including zinc, copper, and nickel).
Fluoride is generally considered the pollutant of greatest concern
with respect to wastewater treatment. Lime neutralization/precipi-
tation, which is standard treatment, is only partially successful
in its removal.
51
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Solid Waste - Minor amounts of solid wastes originate from the
handling, storage, and feeding of raw and consumable materials
(alumina, calcined coke, cryolite, and aluminum fluoride) brought
into the smelter. Emissions of these materials are largely in
the form of dust from handling and feeding to the cells and the
anode-making operations.
However, the rebuilding of cells is a major source of solid waste
from an aluminum smelter. When a cell reaches the end of its use-
ful life and has to be rebuilt, it is removed, dismantled, and
rebuilt. This operation generates a good deal of solid rubble
and waste solid materials. Most of the refractory internals are
impregnated with cryolite and aluminum fluoride. These materials
are typically leached to recover the fluorides for reuse. The
quantity of this waste varies greatly from plant to plant,
depending on the procedures used.
Another major solid waste stream from aluminum production is the
result of air pollution control intended for the collection of
particulate matter and fluorides. If wet air pollution devices
are used, the scrubber water must be treated for the removal of
suspended solids and fluorides. Lime treatment is typically
used to precipitate the fluorides as calcium fluoride.
Air Emissions - The electrolytic reduction of aluminum produces a
CO exhaust at the anode of the cell. As the exhaust leaves the
cell, it entrains particulates including fluoride salts. The
exhaust also contains noxious gases, such as hydrogen fluoride
and hydrogen sulfide. The manufacture of carbon anodes and
their subsequent degradation produce emissions of hydrocarbons,
sulfur, compounds, and particulates. These are removed as part
of the air emission control system and then become wastewater
constituents.
Process Option 1 - Production of Aluminum by the New Alcoa Process—
Precise details concerning this process are not available. Basi-
cally, the feed alumina is converted to aluminum chloride by chlorina-
tion in the presence of carbon to form volatile aluminum chloride. This,
in turn, is purified and fed to an electrolytic cell to produce molten
aluminum at the cathode and chlorine at the anode. The chlorine is
recycled to the chlorination step. A description of the process is
given in Volume VIII, pages 57-64.
Wastewater - Since alumina is the basic raw material for both the
Hall-Heroult process and the ALCOA chloride process, those water-
borne pollutants (such as heavy metals) emanating directly from
the alumina itself will be substantially the same. However, the
ALCOA process eliminates the use of the fluoride-containing fluxing
agent. Therefore, fluoride will not be present in the scrubber
52
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wastewater stream. On the negative side, the ALCOA process will
introduce large amounts of sodium chloride into the wastewater
discharge.
The ALCOA process uses very large amounts of cooling water. If
chromium corrosion inhibitors are used in the cooling water
circuits, they will also appear in the cooling tower blowdown.
Solid Waste - A number of solid waste streams are discharged by
the ALCOA process. A waste sludge periodically removed from the
electrolyte would be predominantly composed of sodium aluminate
contaminated with NaCl/LiCl, and would be quite soluble. There
is also a purge stream composed of unchlorinated alumina. Since
the process involves coke-making to supply the carbon, it is quite
possible that sulfur dioxide will have to be controlled. If so, a
calcium sulfate/sulfite sludge would be produced.
Air Emissions - During the chlorination part of the process, alumina,
carbon (from cracked No. 6 fuel oil), and chlorine are contacted in
a fluidized state. It is possible that chlorine could react with
certain residual hydrocarbon compounds to form chlorinated hydro-
carbons, many of which are considered toxic pollutants. If indeed
this phenomenon does occur and is found to be a serious problem,
one possible solution is the installation of a combustion chamber
to incinerate the chlorinated hydrocarbons.
The coke-making process produces an exhaust gas which contains
sulfur dioxide and will very likely have to be subjected to
sulfur dioxide removal. The exhaust gas from the HC1 absorber
contains carbon monoxide, carbon dioxide, minor amounts of HC1,
and perhaps traces of chlorine.
The ALCOA cells use inert carbon cathodes which means that no
significant amount of carbon oxide gases is released at the
anode. With inert ALCOA cathodes, we expect that emissions
in the baking process are significantly reduced when compared
to conventional technology using consumable cathodes (Hall-
Heroult prebaked cathodes or Soderberg cathodes).
Process Option 2 - Refractory Hard Metal Cathodes —
Refractory hard metal cathodes, made from zirconium and titanium
carbides and borides and mixtures thereof, have been considered as
potential replacements for the conventional carbon cathodes. They
exhibit operational and energy conservation advantages. A description
of this process innovation is presented in Volume VIII, pages 68-77.
We expect that the use of such cathodes will not appreciably change
the nature or size of the base case water, air, and solid waste discharges.
53
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Summary
The base case technology for producing alumina is the Bayer process
which uses bauxite as the alumina-containing raw material. The Bayer
process does not discharge any organic pollutants in water, air, or
solid waste streams. The disposal of very large quantities of red mud,
the insoluble residue that remains after alumina extraction, constitutes
the chief environmental problem associated with alumina production. The
red mud is highly alkaline and contains small quantities of heavy metals.
Alumina production from domestic kaolin clays by the hydrochloric
acid and nitric acid leaching processes results in even larger quantities
of waste residues, which also contain heavy metals. The wastes from these
two processes are acidic rather than alkaline and contain small amounts
of organic reagents used in the processing. The disposal of these wastes
will pose even more of a problem than the red mud produced by the Bayer
process. Heavy metals would be the major problem, both in sludges and
in wastewater discharges. Nitrate is another problem of some potential
concern.
The Toth alumina process, also intended for the extraction of alumina
from domestic clay, produces a dry residue not unlike the solid fraction
of the waste produced by the hydrochloric acid leaching process. The
waste would probably be slurried and disposed of in a tailings pond in
much the same manner as the other processes. Unless proper air pollution
controls are used, it is possible for volatilized titanium and silicon
tetrachlorides to be emitted into the air.
Aluminum production by the base case Hall-Heroult process discharges
fluoride salt dust as well as hydrogen fluoride and hydrogen sulfide to
the atmosphere. Wet air pollution control systems transfer some of these
pollutants to the wastewater streams. When wastewater is treated for the
removal of fluoride and suspended solids, a waste sludge is generated.
The new ALCOA process eliminates the use of fluoride-containing
fluxing agents, but introduces large quantities of sodium chloride.
The ALCOA process also produces a highly soluble waste sludge. In
this process, a possibility exists for chlorinated hydrocarbons to
be formed. If proper gas-handling techniques are not employed, they
could be discharged to the atmosphere.
The use of refractory metal cathodes is expected to have little
effect on the base case discharge of organic/toxic pollutants.
A qualitative comparison of the organic/toxic pollutants associated
with the various process options is shown in Table 6.
54
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TABLE 6. ALUMINA/ALUMINUM INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case production Many plants operate in a
of alumina by the
Bayer process
Hydrochloric acid
leaching of domestic
clays
Nitric acid leach-
ing of domestic
clays
zero-discharge mode.
When water is discharged,
its composition is simi-
lar to the liquid frac-
tion of the red mud.
May possibly be operated
in a zero-discharge mode.
If not, wastewater will
have composition similar
to liquid fraction of
solid waste residue, i.e.,
acidic and containing
chlorides, heavy metals
and organics.
May possibly be operated
in a zero-discharge mode.
If not, wastewater will
have composition similar
to liquid fraction of
solid waste residue, i.e.,
acidic and containing
nitrates, heavy metals,
and organics.
Particulates originating
from the bauxite ore.
Particulates originating
from the clay, plus small
stream containing HC1.
Particulates originating
from the clay, plus some
oxides of nitrogen.
Large quantitites of "red
mud," the insoluble residue
from the bauxite ore.
Highly alkaline and con-
tains small quantities of
heavy metals.
Acid-insoluble residue
generated at a rate over 4
times that of the base
case. Waste is acidic and
contains chlorides, heavy
metals, and small quanti-
ties of organic reagents.
Acid-insoluble residue
generated at a rate of al-
most twice that of the
base case. Waste is acid-
ic and contains nitrates,
heavy metals, and small
quantities of organic
reagents.
(continued)
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TABLE 6 (Continued). ALUMINA/ALUMINUM INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Process Option 3:
The Toth alumina
process
Base case aluminum
^production by the
•^Hall-Heroult process
Process Option 1:
The new ALCOA
process
Process Option 2:
Refractory hard
metal cathodes
Cooling tower blowdown.
May contain chromium
corrosion inhibitors.
Wastewater streams from
wet scrubbers contain
some organics, cyanide,
and fluoride.
Little or no fluoride
present due to elimination
of fluoride-containing
fluxing agents, introduc-
tion of large quantities
of sodium chloride. Cool-
ing tower blowdown may
contain chromium.
No appreciable change
from base case.
Unless proper air pollu-
tion controls are used,
possibility of discharg-
ing titanium and silicon
tetrachlorides, which will
probably hydrolyze to
oxides and HC1.
Particulates containing
fluoride salts, plus
gaseous hydrogen fluoride
and hydrogen sulfide,
plus hydrocarbons.
S02, small amounts of HC1,
and possibly chlorine gas.
The possible formation of
chlorinated hydrocarbons
may require the use of
exhaust gas combustion
chambers.
No appreciable change
from base case.
Solid waste composed of the
rejected materials present
in the clay, generated at a
rate 1.5 times that of the
base case. Contains solu-
ble metal chlorides.
Fluoride-contaminated cell
rebuilding material plus
fluoride-containing dust
and wastewater treatment
sludge.
S02 control sludge, plus
soluble sludge composed of
NaCl/LiCl, purge stream of
unchlorinated alumina,
chromium hydroxide sludge
if cooling tower blowdown
is treated.
No appreciable change from
base case.
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TEXTILE
Integrated Knit Fabric Mills
Base Case Organic/Toxic Pollutants Discharge—
The base case mill produces polyester doubleknit using purchased
texturized yarn. It includes the following sequence of operations
(which is described in detail in Volume IX, pages 33-35): (1) yarn is
first knitted into fabric in the greige mill; (2) the greige (undyed,
unbleached) fabric then goes through a scouring operation to remove
knitting oil, followed by dyeing, washing, and spin-drying to remove
as much water as possible before hot-air drying; (3) a finish (soft-
ener/lubricant) is then applied to the fabric, which is dried and
heat set. Process water is required for the scouring, dyeing, and
washing operation, and this is combined into one wastewater effluent.
Most of the organic or toxic pollutants discharged from the base
case integrated knit fabric mill are in the treated wastewater effluent.
A major source of organic material is the removal of knitting oil
with detergent/water solutions. Knitting oils are generally based on
mineral oils and certain vegetable oils. Although knitting oils do not
biodegrade rapidly, they are not considered toxic.
The other major sources of organic material in the wastewater stream
are the disperse dyes and dye carriers. Many dyestuffs are closely analo-
gous in molecular structure to known carcinogenic substances, often being
polycyclic, unsaturated, and highly substituted hydrocarbons. Disperse
dye carriers, such as butyl benzoate, biphenyl, and others, are organic
pollutants of more than moderate concern. Chromium compounds are also
present in certain dyes. Disperse dyes are minute solid particles rather
than in solution, and are therefore more readily removed by conventional
wastewater treatment processes than water-soluble dyes.
There is a lack of quantitative data on the presence of organic
materials in the treated effluents from textile mills. Organic mate-
rial is usually measured indirectly in terms of gross parameters, such
as biochemical oxygen demand (BOD), chemical oxygen demand (COD), and
color. To provide at least an indirect measure of the amount of organic
material present in treated effluents, the proposed 1983 BATEA (Best
Available Technology Economically Achievable) effluent limitations
guidelines are presented as follows:
57
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Average daily value for
30 consecutive days shall
not exceed
(lb/1000 Ib of product)
Biochemical oxygen demand (BOD) 1.7
Chemical oxygen demand (COD) 10-16.7
Total chromium 0.05
Phenol 0.05
Sulfide 0.10
Color 300 (color units)
Air pollution from textile mills is relatively minor and consists
of low levels of particulates, such as lint, and a small amount of
organic material from the finishing chemicals used.
Due to the nature of textile mill wastewater treatment systems,
very little organic wastewater treatment sludge is generated. Aside
from accumulated lint, the only other significant solid waste stream
is the tarry residues that accumulate in the equipment used in certain
hot finishing operations. The residues consist of finishing chemical
degradation products, and are periodically removed and sent to landfill.
Process Change 1 - Advanced Processing—
"Advanced processing," as applied to integrated knit fabric mills,
is a term referring to a collection of process changes, plant modifica-
tions, and general operational improvements which are designed to con-
serve both energy and water. Advanced processing consists of the following
measures: use of water-soluble size, water conservation, processing at
low liquor/fabric ratio, vacuum impregnation and extraction, and improved
finishing techniques. These are described in detail in Volume IX, pages 28-31.
While advanced processing reduces the volume of wastewater that must
be treated, it does not necessarily reduce the net pollutional loads (in
terms of Ib per 1000 Ib of product) because approximately the same amounts
of the same or very similar chemicals are used. While the lower water
volumes may enable textile mills to achieve the 1983 effluent limitations
more easily and at lower costs, the total quantity of pollutants discharged
in the treated effluent is expected to remain very nearly the same as the
base case.
prganic/toxic pollutants present in the air and solid waste streams
are expected to be the same as the base case.
Process Change 2 - Solvent Systems—
A solvent-based integrated knit fabric mill is described in detail
in Volume IX, pages 37-39, and would employ an organic solvent (typically
perchlorethylene) instead of water for the various scouring, dyeing, and
finishing operations. The contaminated solvent streams are collected and
58
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recovered in a central solvent still. The use of solvent systems virtually
eliminates wastewater effluents. A small amount of condensate from the
finishing operation and from the still represents the only wastewater
effluent that may contain traces of solvent and other chemicals.
Although solvent systems are currently being used for scouring
synthetic knit fabrics prior to dyeing and finishing, practicable
methods for complete processing, even for synthetic fibers, have not
yet been developed. Thus, the various waste streams emanating from
a totally solvent-based mill are not well quantified.
The escape of hydrocarbon vapors from the process poses a serious
air pollution problem, and for this reason the solvent processing units
are surrounded by an enclosure maintained at a negative pressure by ex-
hausting air continuously. Exhausted air containing solvent vapors passes
through an activated carbon vapor recovery system before discharge to the
atmosphere. Periodically, the activated carbon is stripped with steam
and the solvent vapors are returned to the solvent recovery still.
According to manufacturers' data, solvent losses are about 3% of the
fabric weight in present solvent-scouring systems, both as fugitive
emissions and as losses within the fabric. We believe that solvent
losses will have to be reduced to less than 1% to meet air quality
regulations (Volume IX, page 39). Long-term losses from stored fabric
may present an unexpected air pollution source.
Thus, there is a distinct possibility that implementation of solvent
systems will result in a significant increase in the discharge of organic/
toxic pollutants to the atmosphere. By largely eliminating the discharge
of dye and dye carriers in the wastewater effluent, the amount of organic/
toxic materials discharged to the aquatic environment will be greatly
reduced. If the small wastewater stream from solvent finishing is in-
cinerated, it will be eliminated altogether.
Knitting oils removed in scouring and chemicals from dyeing and
finishing remain as residues in the solvent still and are removed as a
solid waste for disposal. Although we have no data on either the quantity
or composition of this stream, it is quite reasonable to assume that it
will contain a certain amount of organic solvent. Since chlorinated
organic solvents are far more environmentally objectionable than rela-
tively inert waste textile fibers (constituting most of the base case
solid waste), the possibility exists that the implementation of solvent
systems will have a negative effect on the base case solid waste disposal
problem.
Integrated Woven Fabric Mill
Base Case Organic/Toxic Pollutants Discharge—
Woven fabrics require a much larger sequence of processing operations
than knit fabrics. Although more complex, the major processes include
various combinations of scouring, washing, bleaching, dyeing, and finishing.
59
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As in the case of the integrated knit fabric mill, most of the
organic/toxic pollutants discharged from the base case integrated woven
fabric mill are in the treated wastewater effluent. The combined waste-
water stream from the entire manufacturing operation contains natural
and processing impurities removed by hot alkaline detergents, dye mate-
rial, oil and grease, and inorganic and dissolved solids. A major source
of organic material is the sizing (typically polyvinyl alcohol) applied
prior to weaving operations. Although polyvinyl alcohol is marginally
biodegradable, it is not considered toxic. The wastewater is basically
treated in the same way as wastewater from knit fabric mills, although
the wastewater flow rates and concentrations are somewhat different.
The proposed 1983 BATEA effluent limitations guidelines for integrated
woven fabric mills are presented below (from Volume IX, page 65):
Average daily value for
30 consecutive days shall
not exceed
(lb/1000 Ib of product)
Biochemical oxygen demand (BOD) 2.2
Chemical oxygen demand (COD) 10-20.2
Total chromium 0.05
Phenol 0.05
Sulfide 0.10
Color 300
Air pollution and solid waste disposal problems for the base case
woven fabric mill are basically the same as those associated with the
base case knit fabric mill.
Process Change - Advanced Processing—
Advanced processing for woven fabrics is similar to advanced processing
for knit fabrics in that it consists of a collection of process changes,
plant modifications, and general operational improvements. The most
important process change is the inclusion of a polyvinyl alcohol (PVA)
recovery loop which takes the effluent stream from the desizing step
and (after ultrafiltration) recycles the concentrated PVA solution
back to sizing, and the hot water back to the desizing operation. A
process flow diagram of the advanced processing steps for an integrated
woven fabric mill is presented in Volume IX, page 50. This operation
both conserves energy (in the form of heated water) and reduces the
volume of the effluent wastewater stream. Although the raw waste
loading is also somewhat reduced due to the recovery of PVA, one can
expect that the net quantity of pollutants in the treated effluent
would be more or less the same as that of the base case, i.e., the
amount of pollutants that will satisfy the effluent guidelines
limitations.
The implementation of advanced processing is not expected to have
a significant effect on either the base case air pollution or solid
waste disposal problem.
60
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Summary
Of the processes examined here, solvent processing of knit fabrics
can be expected to have the most significant impact on the generation
and discharge of organic/toxic pollutants. Significant waterborne wastes
may be replaced by solvent emissions of chlorinated hydrocarbons. The
relative importance of both streams is difficult to quantify, but will
undoubtedly have some impact on the industry's decisions concerning
implementation of the newer technology.
A qualitative comparison of the organic/toxic pollutant discharges
is presented in Table 7.
CEMENT
Manufacture of Portland Cement by the Dry
Process, Long Rotary Kiln
Base Case Discharge of Organic/Toxic Pollutants—
Hydraulic cement is a powder made by burning lime, silica, alumina,
iron, and magnesia together in a kiln and then pulverizing the product.
The processing of raw materials into finished cement follows four steps:
• Crushing,
• Grinding,
• Clinkering, and
• Finishing grinding,
which are described in detail in Volume X, pages 8A-89. The crushing,
grinding, and finishing grinding are merely size reduction and material
preparation steps. The heart of the process, and the operation which
consumes about 70-80% of the total energy used in cement manufacturing,
is the clinkering step. In the clinkering step, the accurately con-
trolled mixture of raw materials reacts chemically at high temperatures
(over 2000°F) in the kiln to produce "clinker," which is subsequently
ground into cement.
Since the changes in Portland cement technology and cement industry
practices examined in this study have an effect only on the clinkering
operation, the analysis of organic/toxic pollutant implications have
also been restricted to the clinkering operation.
No organic pollutants are present in any of the water, air, and
solid waste streams associated with the clinkering step of the base case
gas-fired cement manufacturing process. The chief pollutant discharged
in any of the waste streams is cement dust. While small amounts of lead
and chromium have been reported in wastewater streams from some cement
61
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TABLE 7. TEXTILE INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case integrated
knit fabric mills
Knitting oils, dyes and
dye carriers. Major
source of organic/toxic
pollutants.
Advanced processing Essentially the same as
base case.
Solvent systems
Drastic reduction or
possible elimination of
wastewater discharge.
Base case integrated
woven fabric mills
Sizing material, dyes,
and dye carriers. Major
source of organic/toxic
pollutants.
Lint, organic materials
from finishing chemicals.
Minor source of organic/
toxic pollutants.
Essentially the same as
base case.
Introduction of organic
solvents will very likely
increase air pollution
problems. Major source of
organic/toxic pollutants.
Same as knit fabric mills.
Wastewater treatment
sludge, lint, residues
from finishing operations.
Minor source of organic
toxic pollutants.
Essentially the same as
base case.
Possible solvent contami-
nation of solid waste
streams. Some increase
over base case. Minor
source of organic/toxic
pollutants.
Same as knit fabric mills.
Advanced processing Same as base case.
Same as base case.
Same as base case.
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plants, the cement dust usually is virtually free of trace heavy metals
(Volume X, page 106). As a result, the effluent limitations guidelines
for the cement industry place restrictions only on pH and total suspended
solids. Air emission and solid waste (dust) are certainly generated, but
they would not normally be considered "toxic."
Process Option 1 - Equipping the Rotary Kiln with
a Suspension Preheater—
A suspension preheater is a modification to or an addition to a
cement rotary kiln. It is attached to the raw feed inlet end of the
kiln, totally replacing the preheating zone of the rotary kiln. A
detailed process description is given in Volume X, pages 16-34. Essen-
tially, suspension preheating conserves energy by improving heat and
mass transfer and making better use of the waste heat in the combustion
gases.
As in the case of the base case cement plant, the suspension pre-
heater option will produce a waste dust, which probably will also be
stored in large piles or holding ponds. The cement dust is expected
to have a composition quite similar to that of the base case plant,
although the fraction of soluble inorganic salts is expected to be
somewhat higher. Since the same basic raw materials are used and
since no organic or toxic pollutants are introduced into the process,
it is reasonable to expect the waste streams to be virtually free of
organic pollutants and trace heavy metals.
Process Option 2 - Installation of a Flash Calciner—
The flash calciner is a process operation intended for installation
between a rotary kiln and a suspension preheater. Its use has a number
of operational and energy conservation benefits, which are described in
detail in Volume X, pages 34-40.
The quantity and composition of pollutants discharged from a cement
operation equipped with a flash calciner are expected to be essentially
the same as those of the suspension preheater option, i.e., no organic
pollutants and virtually no heavy metals.
Process Option 3 - Fluidized Bed Process—
The difference between the fluidized bed cement-making process and
the conventional processes is in the high-temperature clinkering step.
All of the other steps are essentially identical. The fluidized bed
process has many mechanical, operational, economic, and energy-related
advantages over the rotary kiln manufacturing process. Of particular
note is that practically any form of carbonaceous fuel can be used in
the fluidized bed reactor. Also, current studies indicate that the
cement process employing the fluidized bed cement reactor, with proper
heat recovery, requires significantly less total energy than the con-
ventional dry, long rotary kiln. A detailed description of the fluidized
bed process is presented in Volume X, pages 40-54.
63
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A plant using the fluidized bed process is expected to generate
one-fifth of the cement dust produced by the base case plant. As in
the case of the base case, no organic pollutants will be discharged,
and the dust will be virtually free of trace heavy metals. An impor-
tant difference, though, is that the cement dust from the fluidized bed
process will consist of high-grade potassium and sodium sulfate, both
of which are highly soluble and would require more careful disposal.
Process Option 4 - Conversion to Coal Fuel from
Oil and Natural Gas—
The energy conservation potential of the use of coal fuel is
primarily one of form rather than quantity of energy. A variety of
material handling steps and process modifications are required to
convert a conventional oil or natural gas-fired rotary kiln to coal.
These measures are discussed in detail in Volume X, pages 60-66.
The pollutional implications associated with the use of coal in the
manufacture of cement have to do with the ultimate fate of the ash content
of the coal. Most of the organic air pollutants can be expected to have
been oxidized by the high temperature of the clinkering. Typical bitumi-
nous coal contains approximately 10% ash by weight. Between 50% and 100%
of all of the coal ash produced by the combustion of coal in a rotary
cement kiln contacts and chemically combines with the clinkering raw
materials, thereby losing its identity as coal ash and becoming Portland
cement clinker. When using coal, however, the composition of the raw
materials must be adjusted to incorporate the coal ash.
A portion of the coal ash escapes the rotary kiln with the cement
dust and is eventually disposed of with the cement dust. It alters the
composition of the combined waste, principally due to the presence of
heavy metals in coal ash. (A composition of West Virginia coal ash is
presented in Volume X, Table 22, page 73.)
The relative fractions of the coal ash which leave the plant as
cement versus solid waste are highly dependent on the raw material
composition, process configuration, and other site-specific factors.
It is therefore not possible to quantify the overall toxic pollutant
implications of using coal as a fuel in cement manufacturing. However,
since the base case plant discharges virtually no toxic heavy metals,
it follows that the use of coal must necessarily result in an increase
in the discharge of toxic heavy metals. Since the cement dust is alkaline,
it is reasonable to expect that the metals from the coal ash will not be
prone to a high degree of leaching when the cement dust is exposed to
water. It is very likely that more serious pollutional problems will
result from the storage and handling of coal rather than from the actual
process wastes. Leaching of heavy metals from concrete made with a coal-
fired kiln cement has not been studied.
-------
Summary
There is no discharge of organic pollutants and virtually no discharge
of toxic pollutants (a small amount of heavy metals is sometimes present
in cement dust) from the base case cement process.
The only process option that would introduce toxic pollutants into
the waste streams is the one involving the conversion to coal fuel. Heavy
metals are present in coal ash and can appear in waste cement dust. The
storage and handling of coal also presents pollutional problems. Never-
theless, the incorporation of a portion of the coal ash into the clinker
and the cement dust reduces the pollution. Consequently, use of coal, if
possible, in cement clinkering would allow transfer of higher forms of
energy (gas and oil) to other industries and utilities where such advan-
tage would not be gained.
GLASS
Glass Melting
Base Case Discharge of Organic/Toxic Pollutants—
Since glass melting is by far the most energy-intensive portion of
the entire glass manufacturing process, downstream finishing operations
have not been included in the analysis.
The conventional glass-melting furnace is presently fired by natural
gas. The major raw materials which make up a soda-lime glass (the most
common type of glass) are silica sand, feldspar, dolomite, limestone, and
soda ash. Small amounts of fluorspar are often added as a fluxing agent.
A description of the base case glass-melting process is given in Volume XI,
pages 17-32.
The escape of raw materials into air, water, and solid waste streams
constitutes the major source of pollutants from the glass-melting opera-
tion. Air emissions are controlled by a two-stage process consisting of
a wet scrubber followed by a bag filter. Soda ash is added to the scrub-
ber water to remove sulfur oxides as calcium sulfate/sulfite. The scrub-
ber water is recycled and a small purge stream discharged. It is likely
that the purge stream will have to be treated with lime to precipitate
fluorides and heavy metals, thereby producing a wet sludge. The bag
filter collects fine particulate matter not captured by the scrubber.
Aside from carbonaceous particulates resulting from incomplete
combustion of gas, there is no discharge of organic pollutants from the
base case glass-melting operation. Particulate matter emitted from the
furnace, and eventually introduced into wastewater and solid waste streams,
contains heavy metals such as arsenic, antimony, selenium, and lead. The
composition of glass-melting furnace emissions is given in Volume XI,
page 27. Most of the heavy metal-containing particulates are eventually
discharged from the plant as a solid waste.
65
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Process Option 1 - Melting Energy Supplied by a
Coal Gasification System—
In this process option, an on-site coal gasification system is
designed to supply the entire fuel gas requirements for the melting
operation, thus eliminating the dependence on natural gas. Generally,
coal gasification processes include, in some variation, the following
steps:
• Coal handling and storage,
• Coal preparation,
• Gasification,
• Oxidant feed facilities, and
• Gas cleaning.
The details of the process are described in Volume XI, pages 32-45.
When coal gasification is used to generate a gaseous fuel for the
glass-melting furnace, the major environmental difference is not in the
glass-melting process, but rather in the fuel-generating process for
the furnace. The coal gasification unit generates considerable air,
water, and solid waste emissions.
The fuel gas produced in the coal gasifier will contain sulfur,
mainly in the form of H2S. To prevent excessive SC>2 emissions, the
sulfur is removed prior to the burning of the fuel in the glass furnace.
Elemental sulfur recovery via the Stretford process is a highly applicable
means of sulfur removal for the type and size of coal gasifier that would
be used in a glass plant. Since the quantity of elemental sulfur recov-
ered is too small to warrant an attempt at marketing it as a byproduct,
it will very likely have to be disposed of as a solid waste. The Stretford
process also produces a small wastewater stream containing many of the
reagents used in the sulfur recovery process. The stream contains
sodium anthraquinone disulfonate, sodium meta-vanadate, sodium citrate,
sodium thiosulfate, and sodium thiocyanate. Due to the small and inter-
mittent nature of this waste stream, it would probably be removed from
the plant via contract disposal.
The disposal of very large quantities of coal ash constitutes the
major addition of toxic pollutants to the base case process for it results
in a four-fold increase in the quantity of solid waste generated. Coal
ash contains a variety of heavy metals, the concentrations of which are
highly dependent on the type of coal used. A representative composition
of coal is presented in the Cement Industry Report, Volume X, page 73.
66
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Process Option 2 - Melting Energy Supplied by
Direct Coal Firing--
Direct coal firing has the advantage over other coal-firing process
options in that it uses all of the heating value of the coal. To use coal
directly in burners, a coal storage area is needed as well as a live coal
storage bin, a pulverizer, screens, a feeder, and the pulverized coal
burner(s). A coal storage area capable of storing about one month's
supply appears reasonable.
Since coal is a high-sulfur fuel, a direct coal-fired glass-melting
facility will require a sulfur dioxide scrubbing system. Alkaline-based
SO 2 scrubbers generate solid waste in the form of calcium sulfate/sulfite
sludges which also contain some of the ash content of the coal. Thus,
the SO2 scrubber sludge will contain some of the heavy metals present in
the ash. As in the coal gasification alternative, large quantities of
heavy metal-containing coal ash will have to be disposed of, in addition
to the solid waste streams emanating from the base case glass-melting
operation.
Process Option 3 - Coal-Fired Hot Gas
Generation (COHOGG)—
In this process (which is described in detail in Volume XI, pages
48-53), coal is pyrolyzed to produce a combustible gas for the glass-
melting operation. Sulfur is removed directly from the process by the
addition of limestone. In addition to the ash from the coal and the
base case solid waste stream, this alternative generates a calcium
sulfate solid waste stream. The primary increase in toxic pollutants
over and above base case discharge is due to the heavy metals present
in the coal ash.
Process Option 4 - All-Electric Melting—
Molten glass can be heated by the passage of an electric current.
Both the design and the operation of an all-electric glass-melting furnace
differ greatly from the typical natural gas-fired regenerative furnace.
A detailed description of the design and operational differences is
given in Volume XI, pages 53-55.
All-electric melting is based on the use of purchased electrical
power, and therefore there is a shift of some of the environmental
problems from the glass-manufacturing plant to the electric power
generating station. This process change generates solid waste in the
form of coal ash (at the power plant) and dust from the glass-melting
air pollution control system (as in the base case process but probably
in smaller quantity). As in the case of the other coal-based process
options, the heavy metals present in the coal ash represent the major
discharge of toxic pollutants to the environment.
67
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Process Option 5 - Batch Agglomeration Preheating—
This process, still in the developmental stage, is designed to
pretreat the batch ingredients rather than to conserve energy. A
variation of the process proposes to use waste heat for preheating
the materials. The preheating step, in itself, does not produce any
waste discharges (although it does slightly alter the volume of com-
bustion gases discharged).
If natural gas is the energy source, the nature and quantity of
pollutants will be the same as the base case. If one of the coal-based
alternatives is used, the previously described solid waste streams will
be generated. In either case, no organic pollutants are expected and
toxic pollutants would be limited to the heavy metals noted earlier.
Summary
The base case natural gas-fired melting operation discharges air,
water, and solid waste streams containing heavy metals originally present
in the raw materials used to manufacture the glass. The heavy metals
are present in particulate form. The bulk of the heavy metal-containing
particulates is eventually discharged to the environment in the solid
waste stream.
The coal-based process options do not alter the emissions from the
melting operation, but rather introduce additional emissions of heavy
metals from the large quantities of coal ash produced. The various
desulfurization steps required by the coal-based alternatives produce
either either a calcium sulfate/sulfite residue (which also contains
coal ash) or an elemental sulfur stream. If the Stretford process for
elemental sulfur recovery is employed, a small and intermittent waste-
water stream containing high concentrations of organic reagents will be
produced.
A qualitative comparison of the organic/toxic pollutant discharges
is presented in Table 8.
Other problems inherent in a shift away from natural gas in the
glass industry, such as capital cost and product quality, are expected
to play a larger role in decision-making concerning the alternative
processes than would the question of organic and toxic pollutants.
CHLOR-ALKALI
Chlorine Production via the Graphite Anode Diaphragm Cell
Base Case Discharge of Organic/Toxic Pollutants—
A detailed description of the diaphragm cell process is given in
Volume XII, pages 21-28. In this process, a nearly saturated solution
of sodium chloride is subjected to electrolysis to yield chlorine,
sodium hydroxide, and hydrogen.
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TABLE 8. GLASS INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case natural
gas-fired glass
melting
Coal gasification
Direct coal firing
Coal-fired hot gas
generation
Heavy metals from par-
ticulates collected by
air pollution control
system. Minor source of
organic/toxic pollutants.
Base case emissions plus
small, high organic con-
centration wastewater
stream from Stretford
sulfur-removal process.
Minor source of organic/
toxic pollutants.
Base case emissions plus
additional coal ash con-
taining scrubber water.
Minor source of organic/
toxic pollutants.
Same as base case.
Heavy metal-containing
particulates. With pro-
per air pollution con-
trol, minor source of
organic/toxic pollutants,
Base case emissions plus
S0~ and particulate-con-
taining emissions from
coal gasification unit.
Minor source of organic/
toxic pollutants.
Essentially the same as
the coal gasification
process option.
Similar to coal gasifica-
tion process option.
Heavy metal-containing par-
ticulates removed from air
and water streams. Major
jsource of organic/toxic
pollutants.
Base case emissions plus
elemental sulfur stream and
large volumes of heavy metal-
containing coal ash. Major
j>ource of organic/toxic
pollutants.
Base case emissions plus cal-
cium sulfate sludge from SCL
control plus coal ash. Major
source of organic/toxic
pollutants.
Base case emissions plus cal-
cium sulfate solid waste
from S02 control system plus
coal asn. Major source of
organic/toxic pollutants.
(continued)
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TABLE 8 (Continued). GLASS INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
All electric melting
Same as base case.
Batch agglomeration
o preheating
Same as base case.
Reduction in pollutants
at the glass plant.
Air emissions of the
electric power plant
must be taken into
account.
Same as base case, or
slightly less.
Base case emissions plus
S02 control sludge plus
coal ash at the power plant.
Major source of organic/
toxic pollutants.
Same as base case.
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Wastewater - The base case diaphragm cell chlor-alkali plant
generally has the following wastewater discharges (Volume XII,
pages 23, 29):
• A solution of sodium hypochlorite and sodium bicarbonate
from the scrubbing of chlorine tail gas;
• Weak caustic and brine solution from the caustic
evaporators that use barometric condensers;
• Weak caustic and brine solution from the caustic
filter washdown; and
• Intermittent wastes from general housekeeping
operations and equipment cleaning.
Lead and copper are used in the cell construction and are sometimes
present in the wastewater effluents as the result of cracks around
the protective resin seals which encase the lead portion of the cell.
Solid Waste - Prior to electrolysis, calcium, magnesium, and heavy
metals are removed from the raw brine by adding sodium carbonate
to precipitate the metals as hydroxides and carbonates. The pre-
cipitates are removed as a wet sludge and usually sent to landfill
(or lagoon).
During normal processing the graphite anodes are consumed and form
tiny particles which clog the diaphragm cathode. As a result, cells
must be periodically rebuilt. Since the diaphragm contains asbestos,
and lead is present in the cell bottoms, the debris from cell rebuild-
ing contains lead and asbestos weighing approximately 0.04 and <0.4 lb/
1000 lb, Cl2 respectively. It is disposed of through landfill dumping.
The reactions between chlorine and organic material in the graphite
anode result in the formation of volatile chlorinated organic mate-
rial of rather indefinite composition. It is removed from the
chlorine in a final purification step, drummed, and disposed of
either by incineration or landfill. This waste amounts to 0.45 lb/
1000 lb Cl2-
Typical solid waste generation rates are given in Volume XII, page 23.
Air Emissions - Atmospheric emissions of chlorine, carbon dioxide,
carbon monoxide, residual gas,or hydrogen occur from diaphragm cell
plants in amounts that depend largely upon plant operation. Chlorine
and other gases can escape to the atmosphere from various vents and
leaks throughout the plant. Since emissions of chlorine to the
atmosphere represent an economic loss, strong efforts are made
to control such emissions.
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When a chlorine-cell gas is compressed and cooled to produce liquid
chlorine, non-condensable gases saturated with chlorine vapor are
produced at the discharge of the condenser. These gases are commonly
called blow gas. The value of the chlorine contained in the blow gas
is significant and, for this reason, all but the smallest plants have
for many years recovered chlorine by either burning it with hydrogen
to make hydrochloric acid or by caustic scrubbing to produce bleach.
Process Option 1 - Dimensionally Stable Anodes (DSA)--
To eliminate the problems associated with the graphite anode, the
industry has long worked on developing a non-consumable anode for use
in the diaphragm cell. The dimensionally stable anode consists of an
expanded titanium metal substrate coated with precious metal/rare earth
oxides. The DSA has numerous advantages which result in power savings
and reduced pollutional loads. The DSA leads to a major reduction in
the formation of chlorinated organics as well as eliminating the need
for handling and disposing of waste graphite anodes. The amount of
asbestos destined for land disposal is also reduced.
The use of dimensionally stable anodes does not, in any way, alter
the sludge produced from brine purification, nor does it appreciably
alter air emissions or wastewater discharges.
Process Option 2 - Modified Diaphragms—
In addition to the significant changes in anodes, some major
improvements are being introduced for diaphragms which have beneficial
effects on both power consumption and pollution control. The three
most significant modified diaphragms are: (a) polymeter modified
asbestos; (b) polymer membranes; and (c) ion exchange membranes.
These are described in detail in Volume XII, pages 48-52.
Polymer Modified Asbestos - Use of the polymer modified asbestos
diaphragm has a minor environmental advantage over conventional
asbestos diaphragms in that the discarded material, at the time
of cell rebuilding, is in stabilized pieces instead of loose
asbestos fibers. Thus, disposal is easier and safer because
the fibers resist dispersion. The amount of brine sludge gen-
erated would be the same as in the base case, and the quantity
of cell rebuilding waste would be approximately the same as in
the case of the dimensionally stable anode. Air emissions and
wastewater discharges would not be appreciably different from
those of the base case.
Polymer Membranes and Ion Exchange Membranes - While the quantity
of brine purification sludge would remain the same, the use of
polymer membranes and ion exchange membranes would eliminate
the graphite and asbestos rubble associated with the rebuilding
on conventional diaphragm cells. Also, the generation of chlori-
nated hydrocarbon waste material would be virtually eliminated.
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As in the case of the other process options, there would be no
appreciable change in the base case air emissions or wastewater
discharge.
Summary
The major discharge of organic/toxic material from the base case
diaphragm cell process is the solid waste from cell rebuilding that
contains asbestos and lead, and a waste stream from chlorine purifi-
cation that consists of chlorinated organic compounds.
Two process options, the use of dimensionally stable anodes and the
use of modified diaphragms, both alleviate the organic/toxic pollutant
problem by reducing the amount of asbestos discharged. The use of modi-
fied diaphragms also virtually eliminates the chlorinated organic waste
stream from the chlorine purification step. The process options do not
appreciably alter the base case brine purification sludge stream, air
emissions, or wastewater discharges. With the great concern over asbestos
in the environment, these two processes will offer benefits in addition
to the energy conservation aspect and should be encouraged. Long-term
operating efficiencies and cost must still be established.
PHOSPHORUS/PHOSPHORIC ACID
Furnace Acid-Electric Furnace Production of Phosphorus
and Conversion of Phosphorus to Phosphoric Acid
Base Case Discharge of Organic/Toxic Pollutants—
Phosphate rock is mined in Florida, Tennessee, and North Carolina,
and in the Mountain States of the West. It is converted to commercial
end-products either by digestion with sulfuric acid to produce phosphoric
acid (the "wet process") or by reduction to elemental phosphorus in an
electric furnace. Most of the phosphorus from the electric furnace is
burned in air and the oxides absorbed in water to form phosphoric acid.
Although phosphoric acid is the principal commercial end-product
of each of the two methods, there is an important difference in the
purity of the acid obtained. Phosphoric acid produced via the electric
furnace process is essentially a pure chemical that is suitable for
detergent, food, and fine chemical uses. Wet process phosphoric acid
is not pure; it is suitable for fertilizer manufacture, but, without
cleanup, not for most other purposes.
The key issue in this whole analysis is the fact that the manufacture
of phosphoric acid via the electric furnace process has an energy consump-
tion per unit of product that is approximately 5 times that of the wet
process. There is, therefore, an incentive to modify the wet process
in order to produce phosphoric acid that has a level of purity equiva-
lent to that produced by the electric furnace process.
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In the electric furnace process (which is described in detail in
Volume XIII, pages 22-34), the phosphate rock is first fed to a direct-
fired rotary kiln where it is heated to a temperature of incipient fusion.
It is then processed through a screening operation to a suitable size
range. The kiln gases must be scrubbed to remove dust and fluorides
present in the phosphate rock. The other raw materials, coke and silica,
are also dried before they are fed, along with the prepared phosphate
rock, into the electric arc furnace. The phosphorus is produced as
gaseous P^ and is then condensed as a liquid. The production of phos-
phorus and its conversion to phosphoric acid usually occur at different
geographic locations. The most common practice is to ship the liquid
phosphorus to the point of end-use where it is converted to phosphoric
acid by oxidation and dissolution in water.
A number of toxic pollutants are present in the air emissions,
wastewater effluents, and solid waste streams from the manufacture of
phosphorus/phosphoric acid via the electric furnace process.
Wastewater - There are three major wastewater streams generated by
the electric furnace production of elemental phosphorus:
• Nodulizer Scrubber Water Slowdown - Gaseous emissions from
the phosphate rock nodulizer are dusty and contain hydrogen
fluoride and silicon tetrafluoride; therefore, they must be
controlled by means of a wet scrubber. The scrubber water
is recycled. The necessary purge stream from the recycle
system is acidic, contains phosphates, sulfates, fluorides,
and suspended solids, and must be treated prior to discharge.
• Slag Quench Water - Furnace slag is cooled by means of
quenching witn a water stream. The slag quench water is
slightly alkaline, contains phosphates, sulfates, fluorides,
and suspended solids,and also must be treated.
• "Phossy" Water - A notoriously difficult stream is the so-
called "phossy" water. This stream results from the un-
avoidable contact of liquid phosphorus with water in the
condenser and in the phosphorus transfer lines. Water is
also used as a seal in storage and transport to prevent
exposure of the phosphorus to air. The result is that
water discharged from these operations contains a small
amount of very finely divided phosphorus in suspension.
The "phossy" water also contains significant amounts of
phosphates and fluorides.
The usually recommended method of treatment for the above wastewater
streams consists of the addition of lime for the neutralization of
acidity and the precipitation of fluorides and phosphates followed
by coagulation and settling for the removal of suspended solids
(including particles of elemental phosphorus) and precipitates.
With proper treatment the wastewater should contain relatively
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low concentrations of fluorides, phosphates, and phosphorus, although
improvements in fluoride removal are still being sought.
Solid Waste - There are a number of solid waste streams produced
by the overall production of phosphoric acid via the electric
furnace process.
• Slag - Large quantities of slag are produced. The slag
contains silica, iron oxide, calcium oxide, calcium
fluoride, alumina, and the oxides of trace heavy metals.
It is sold as a construction material and therefore does
not become a waste stream destined for disposal.
• Wastewater Treatment Sludge - The treatment of the
wastewater stream, as described in the preceding
sections, produces a waste sludge containing calcium
fluoride, calcium phosphate, calcium sulfate, elemental
phosphorus, and the hydroxides of trace heavy metals
(including arsenic).
Care should be taken to dispose of the sludge in an environmentally
acceptable manner. The presence of elemental phosphorus and trace
arsenic compounds can result in low-level emissions of volatile
species, such as the phosphorus oxides and arsine. Leaching from
landfill lagoons must be avoided.
Air Emissions - Air pollution control is a significant problem in
a phosphorus plant. Large amounts of dust originating from the
phosphate rock are generated by the various processing steps.
A variety of air pollution control devices is used. However,
no air pollution control system is 100% effective, and the par-
ticulates that do escape contain fluorine compounds, phosphates,
and other constituents originally present in the phosphate rock.
Process Option 1 - Wet Process Production of Phosphoric
Acid Followed by Chemical Cleanup—
As previously stated there are a number of impurities in wet process
phosphoric acid which make it unsuitable for use as detergent phosphate.
These impurities include calcium chloride, iron and aluminum salts, carbon
and organic matter, and small quantities of a number of heavy metals, such
as magnesium, chromium, titanium, manganese, copper, zinc, arsenic, vanadium,
and uranium. The acid is saturated in calcium sulfate and has a high content
of fine suspended solids. It is difficult to remove these impurities to
the degree necessary to meet specifications for food grade or fine chemical
phosphate use. A major outlet for phosphoric acid, however, is in the form
of sodium tripolyphosphate (STPP). Wet process acid can be purified to
the degree necessary for this product by a two-stage neutralization
cleanup process, as described in Volume XIII, pages 48-60.
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This alternative produces a variety of wastewater effluents, solid
waste streams, and air emissions, which are described below:
Wastewater - The main wastewater stream from the wet process production
of phosphoric acid remains the overflow from the gypsum ponds (the
large impounded areas containing the acid-insoluble fraction of the
phosphate rock). The liquid fraction of this residue contains sodium
silicofluoride, phosphates, free phosphoric acid, and a number of
trace heavy metals, such as cadmium. When the recommended treatment
(consisting of lime addition followed by precipitation and sedimenta-
tion) is applied, the treated effluent should contain relatively low
concentrations of the above pollutants, although further improvements
are still desired.
Solid Waste - The following solid waste streams are generated:
• Gypsum Sludge - The wet process produces very large amounts
of gypsum sludge from the reaction of sulfuric acid with
the phosphate rock. The sludge is stored in large impound-
ments which also serve as water recirculation reservoirs.
A large amount of the fluorine originally present in the
phosphate rock is discharged, along with the gypsum, as
sodium silicofluoride. The gypsum sludge contains free
phosphoric acid and trace heavy metals, and is slightly
acidic.
• Wastewater Treatment Sludge - When gypsum pond overflow is
treated with lime, a waste sludge containing calcium fluoride,
calcium phosphate, and the hydroxides of trace heavy metals
is produced.
• Impurities From the Two-Stage Neutralization Cleanup Step -
The impurities from the two-stage cleanup step consist of
filter cakes containing sodium silicofluoride in both the
aqueous and solid phases, phosphoric acid, calcium sulfate,
ferric phosphate, aluminum phosphate, and trace quantities
of heavy metals.
Air Emissions - Air emissions associated with the production of
phosphoric acid via the wet process are generated by both the
digestion and evaporation systems. The uncontrolled air emissions
contain hydrogen fluoride and silicon tetrafluoride. Wet scrubbers
remove most of these contaminants, and, in turn, produce a contami-
nated wastewater stream which, itself, must be neutralized.
The chemical cleanup of wet process phosphoric acid produces a
number of small air emissions which are relatively uncontaminated.
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Process Option 2 - Wet Process Production of Phosphoric
Acid Followed by Solvent Extraction Cleanup—
In this process (which is described in detail in Volume XIII, pages
60-71), phosphate rock is dissolved in hydrochloric acid rather than in
sulfuric acid. The crude phosphoric acid thus produced is subjected to
a solvent extraction step in which the phosphoric acid is transferred
from solution in an aqueous phase to solution in an organic phase, such
as normal butanol, leaving behind the undesirable impurities, such as
calcium chloride, in the aqueous phase. The organic phase can then be
contacted in a separate unit with fresh water to yield a pure solution
of phosphoric acid. The calcium chloride brine initially separated from
the extraction step also contains hydrochloric acid and solvent which
must be recovered.
Since the process is still in the developmental stage at this time,
it is only possible to speculate as to the nature of the wastewater
effluents, solid waste streams, and air emissions.
With respect to wastewater effluents and solid waste disposal, the
most significant difference between this process and the conventional
wet process followed by chemical cleanup is that a large concentrated
calcium chloride brine stream is substituted for a large fraction of
the gypsum sludge stream. Undissolved inorganic solids separated from
the digestor liquor would be impounded in much the same way as in the
conventional process. Since much of the solid waste would be replaced
by calcium chloride brine, the size of the impoundments would be con-
siderably smaller.
The impoundment overflow would have to be treated in much the same
way as in the conventional process, i.e., via lime treatment to neutra-
lize acidity and to precipitate fluoride, phosphate, and metals. It
should be noted that solvent (normal butanol) losses within the process
will eventually appear in the liquid fraction of the sludge. If solvent
losses are severe, the liquid fraction of the sludge could exert a signi-
ficant biochemical oxygen demand. This entire process presents serious
water pollution control problems, since chloride salts of metals tend
to be soluble.
Air emissions are similar to those of the conventional wet process,
with the exception of the anticipated losses of the normal butanol solvent.
However, butanol is not considered a toxic material.
Process Option 3 - The Use of Byproduct Sulfuric Acid—
A conventional wet process plant for phosphoric acid consists of
two distinct process units. In the first, sulfur is converted to sul-
furic acid; in the second, sulfuric acid is used as a reagent to convert
phosphate rock to phosphoric acid. Sulfur is a major element of the
production of phosphoric acid, and, at the right price, a phosphoric
acid producer would be tempted to use byproduct sulfuric acid (obtained
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largely from electric power plant sulfur dioxide control systems) in
place of the sulfur.
While the use of byproduct sulfuric acid will eliminate that part
of the pollution problem associated with an on-site sulfuric acid plant,
it will have a negligible effect on both the quantity and characteris-
tics of the waste streams (and the presence of organic/toxic pollutant)
associated with the overall manufacture of phosphoric acid.
Process Option A - Strong Phosphoric Acid Processes —
Although these processes (which are described in detail in Volume
XIII, pages 73-75) provide certain operational and economic advantages,
it is not apparent that they influence the discharge of organic/toxic
pollutants one way or another.
Summary
The base case process for producing high-grade phosphoric acid via
the electric furnace production of elemental phosphorus and subsequent
conversion to phosphoric acid generates: (1) a wastewater stream con-
taining fluorides, phosphates, and elemental phosphorus; (2) solid waste
streams consisting of fluoride-containing slag, and wastewater treatment
sludge that contains fluorides, phosphates, elemental phosphorus, and
heavy metals; and (3) air emissions containing fluorine compounds, phos-
phates, and other constituents originally present in the phosphate rock.
The slag is sold as a construction material.
The process option involving the wet process production of phosphoric
acid followed by chemical cleanup differs from the base case, mainly in
that large amounts of wet gypsum sludge (as opposed to dry slag) are
produced. The gypsum sludge contains fluorides, phosphates, and trace
heavy metals. The cleanup step produces a solid residue which also
contains fluorides, phosphates, and heavy metals.
The process option involving the hydrochloric acid-based wet process
followed by solvent extraction cleanup differs considerably from the con-
ventional process in that a large calcium chloride brine stream is substi-
tuted for a large fraction of the gypsum sludge stream. Pollutants associated
with the base case, i.e., fluorides, phosphates, and heavy metals, are also
present, as well as lost solvent consisting of normal butanol. The water
pollution problems associated with this process option are considered
quite serious, and are certainly worse than those of the base case. In
view of these observations, the chemical cleanup processes will require
careful evaluation and assessment to assure proper environmental protection
in spite of the attraction of significant energy conservation which they offer.
The process option involving the use of byproduct sulfuric acid and
the option based on the strong phosphoric acid process have a negligible
impact on the discharge of organic/toxic pollutants.
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PRIMARY COPPER
Manufacture of Copper by Smelting and Refining
of Concentrates
Base Case Discharge of Organic/Toxic Pollutants—
Copper extraction from sulfide ores is traditionally divided into
four segments:
• Mining - where ore containing 0.6% to 2% copper is mined;
• Beneficiation - where the copper-containing minerals are
separated from the waste rock to produce a concentrate
containing about 25% copper;
• Smelting - where concentrates are melted and reacted to
produce 98% pure "blister" copper or "anode" copper (copper
98% to 99% pure requiring further refining); and
• Refining - where blister copper is refined electrolytically
to produce 99.9% pure "cathode" copper.
The energy-related process changes described in Volume XIV affect
only the smelting and refining portions of copper extraction; therefore,
conventional smelting and refining represent the base case against which
potential process options have been compared in order to evaluate pollu-
tional and energy consequences of these process alternatives.
Conventional smelting of sulfide concentrate involves the smelting
of concentrates in a reverberatory furnace either directly (green charge
smelting) or after roasting (calcine smelting). The mixture of molten
sulfides from the reverb is converted to blister copper in converters.
Conventional electrorefining purifies the smelter output to cathode
quality copper. A detailed description of the conventional smelting and
refining processes is presented in Volume XIV, Appendix A.
Although the conventional smelting and refining of copper concentrates
do not involve the discharge of organic pollutants, metals such as arsenic,
antimony, bismuth, mercury, lead, zinc, and tellurium can be present in
air, water, and solid waste streams. The heavy metals are not externally
introduced into the process, but rather originate from the copper ore itself.
Most of the heavy metals removed from the copper ore during the
refining process are in the form of a slag containing low solubility
metal oxides. Although very large quantities of slag are produced, it
is a rather inert, rock-like material, and in itself would not generally
be considered any more toxic than the original ore.
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A number of wastewater streams are produced in the smelting and
refining of copper. The wastewater is acidic, contains high amounts
of suspended solids, and also contains low levels of soluble heavy
metals. The recommended means of treatment for meeting the proposed
1983 effluent guidelines include neutralization and sedimentation, both
of which produce a waste sludge. The sludge would contain calcium sulfate
and a variety of metal hydroxides. Although the quantity of wastewater
treatment sludge that would be produced is far less than the quantity of
slag, the finely divided precipitates composed of metal hydroxides would
be more subject to the leaching of heavy metals than would the slag. When
properly treated, the wastewater stream should contain heavy metals in
concentrations no greater than several parts per million.
The smelting of copper produces large quantities of dust composed
of fractions of the ore itself and therefore containing heavy metals.
Most of the dust is collected by air pollution control devices and then
recycled to the reverberatory furnace. To prevent the buildup of impuri-
ties, it is necessary to purge a portion of the recycled dust from the
system. Depending on the composition of the feed, a fraction of the
dust may either be sold to other specialized smelters or disposed of
as a solid waste.
Since no air pollution control device is 100% effective in removing
particulate matter, it is inevitable that copper smelters will discharge
a certain amount of heavy metal-containing particulate matter to the
atmosphere. Metals that are easily volatilized, such as arsenic, lead,
and zinc, tend to form very fine condensation particles that are not
easily removed by many conventional air pollution control devices. Al-
though the quantity of metals discharged to the atmosphere is many times
less than the amount discharged as a solid waste, it still constitutes a
not insignificant pollutional problem, particularly since it will be
emitted as extremely fine particulates. Sulfur oxides, of course, are
another problem requiring attention.
Process Option 1 - Outokumpu Flash Smelting —
Flash smelting (which is described in detail in Volume XIV, pages
41-44) combines the separate roasting and smelting operations of con-
ventional copper extraction into a combined roasting-smelting process.
The heat generated by the exothermic roasting reactions can be used for
smelting so that little or no extraneous fuel is needed. A characteristic
of this method is that fine-grained concentrates are used and the smelting
takes place in suspension, which allows for rapid reaction rates. The
major advantages of the method are a reduction in fuel used for smelting
and the production of a stream of gas high in S02 which is suitable for
sulfuric acid manufacture.
The Outokumpu flash smelting process produces the same quantity of
slag and bleed dust as the conventional smelting and refining of copper.
Since the water pollution control problems are similar to those of a
conventional smelter, it is reasonable to assume that if the same
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recommended treatment technology is applied to the Outokumpu process,
the same quantity of wastewater treatment sludge will be generated.
While the Outokumpu process has several advantages regarding S02
control, it is not apparent that the emission of heavy metal-containing
particulates would be substantially different from that of the base case
smelting process.
Process Option 2 - The Noranda Process—
The Nornnda process combines the three operations of roasting,
smelting, and converting of copper concentrates in a single reactor.
The heat losses suffered during the transfer of concentrate from the
roaster to the reverberatory furnace are suppressed, as well as the
heat losses occurring during the transfer of matter from the reverbera-
tory furnace to the convertor. In addition, the net heat of oxidation
is used for smelting. A detailed process description is presented in
Volume XIV, pages 55-70. Other than expected reductions in SOX emissions,
the air, water, and solid wastes generated by the process are not expected
to be significantly different in heavy metal levels from those generated
by conventional smelting.
Process Option 3 - The Mitsubishi Process--
The Mitsubishi process consists of three metallurgical stages, each
of which is carried out in a separate furnace. Thus, there is a smelting
furnace for concentrates, a converting furnace to oxidize iron in the
matte and make blister copper, and a slag cleaning furnace. Intermediate
products in the molten state move continuously among the respective furnaces
which are thus functionally connected with each other. A detailed process
description is presented in Volume XIV, pages 71-81. The Mitsubishi process
has many of the same energy-conserving advantages as the Outokumpu and
Noranda processes. The air, water, and solid waste streams are expected
to be quite similar to those from the Outokumpu process.
Process Change 4 - The Use of Oxygen in Smelting-^-
Copper smelting by any of the foregoing base or new processes can
be conducted with pure oxygen or by using oxygen-enriched air. Reasons
for using oxygen or oxygen enrichment include:
• Increasing processing temperatures and process heat rates;
• Decreasing the nitrogen content of the flue gases (when high
S02 concentrations are needed) and increasing fuel efficiency
(particularly where waste heat is not recovered); and
• Increasing the specific capacity of furnaces so that production
of metal is increased for a given size reactor.
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We do not believe that the use of oxygen in smelting will signifi-
cantly alter the base case air, water, or solid waste discharges. The
on-site oxygen plant would require large volumes of water which, if
recycled through a cooling tower, would very likely contain small
quantities of corrosion inhibitors such as chromium compounds. The
oxygen plant consumes electricity, and the generation of this elec-
tricity at a central power station has associated pollutional loads,
such as the disposal of coal ash and SC^ removal sludge which should
also be considered.
Process Option 5 - Metal Recovery from Slag--
In conventional copper smelting, converter slag is recycled to the
reverberatory furnace, and all of the slag tapped from the furnace is
discarded. The copper contained in this discarded slag is lost. The
amount of copper lost with the slag is quite significant—about 1.5% to
3% or more of the copper in the feed materials.
Slag can be recovered by two methods: (1) flotation, or (2) slag
cleaning the electric furnaces.
Flotation - In flotation, the slag is acid ground and the copper
is recovered via froth flotation (see Volume XIV, pages 89-93).
This process converts the slag into fine particles which are then
disposed of as a wet slurry into a tailings pond. The water from
the tailings pond is recycled. This process has no effect on the
base case air emissions or wastewater effluent loadings. While
the overall quantity of slag is not radically different from that
of the base case conventional smelter, and its copper content will
be lower, it will be in the form of very fine particles mixed with
water rather than large dry particles. Consequently, concern over
leachability of trace heavy metals should be greater.
Slag Cleaning in Electric Furnace - The mechanism by which slag
can be recovered in an electric furnace is discussed in Volume XIV,
pages 93-95. The fumes coming off the electric furnace must be
collected, and the dusts are further processed for recovery of
metallic values (zinc, cadmium, etc.). The volume of the cleaned
gas is insignificant and can be easily merged with other air streams.
Aside from reducing the metal content of the slag, this practice does
not alter the quantity or nature of the base case solid waste streams.
Process Option 6 - The Arbiter Process —
The Arbiter process is one of several potentially applicable
hydrometallurgical copper extraction techniques.
The basic process (which is described in detail in Volume XIV,
pages 95-106) consists of five separate stages for the treatment of
copper concentrates. The copper concentrate slurry is first leached
with ammonia and oxygen. The pregnant solution is then separated from
82
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the leached solids. From there it is sent to a solvent extraction step
where copper is selectively extracted with an organic reagent to form a
copper-loaded electrolytic solution. Copper is recovered from the solu-
tion via conventional electro-winning. The actual process entails a
large number of rather complex material recycle circuits and purification
steps.
The Arbiter process, like most hydrometallurgical processes, causes
little direct air pollution. The major emissions from the process are
associated with the ammonia recovery system, which would contain traces
of ammonia and fugitive emissions of sulfuric acid mist from the electro-
winning tank house. Unlike the base case technology, there are no major
emissions of heavy metal-containing particulates.
The process is energy-intensive and mainly uses electricity and
steam. Some pollution would be associated with the boiler plant in both
cases whether on- or off-site.
The Arbiter process can be operated so that there is no wet aqueous
discharge to the environment in areas where solar evaporation is high,
such as Arizona, the location considered for this study. In areas where
evaporation is insufficient, it might be necessary to bleed water from
the process and treat it in a manner similar to that recommended for
conventional copper smelters.
The Arbiter process produces two major solid waste streams:
Gypsum Sludge - During the process, ammonia is recovered from spent
ammonium sulfate streams by boiling with lime to yield ammonia and
gypsum (calcium sulfate). The gypsum sludge forms a major solid
waste stream.
Leach Residue - The process produces a leach residue containing
iron oxide, silica, pyrites, bismuth, sulfides, lead, arsenic,
and other metals.
These two waste streams would require storage in lined ponds with
a wet top surface to prevent dust emissions during the period the pond
is in use and proper cover after the pond is abandoned.
The total solid waste stream is substantially greater than that of
the base case process, although the quantity of heavy metals present
would be roughly the same. The extent to which byproduct metals can
be recovered when using the Arbiter process is not well established.
The wet sludge and leach residue are probably more subject to the
leaching of heavy metals than the relatively inert slag from the base
case process.
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Summary
There is no discharge of organic pollutants from the base case
conventional smelting and refining process. Heavy metals, mostly in
the form of particulate matter, are present in air, water, and solid
waste streams. By far, the solid waste—in the form of slag, dust, and
wastewater treatment sludge—constitutes the major source of heavy metals
discharged to the environment.
The discharge of heavy metals into the air, water, and solid waste
streams of the Outokumpu, Noranda, and Mitsubishi processes is essen-
tially the same as that of the base case technology.
Aside from an incremental pollutional load associated with off-site
power generation and the use of cooling towers, the use of oxygen in
smelting does not alter the base case pollutional load.
The only major pollutional implication of recovering metal from
slag is that the slag destined for disposal will have a lower concen-
tration of copper and certain other metals.
The Arbiter process has major pollutional implications. It virtually
eliminates the air pollution problem associated with conventional smelting,
but substantially increases the amount of solid waste destined for dis-
posal. The solid waste is in the form of a wet sludge rather than a hard
dry slag and is, therefore, more subject to the leaching of heavy metals.
This process will need careful evaluation of pollution potential in con-
junction with its progress through development.
A qualitative comparison of the organic/toxic pollutant discharges
for the several processes is presented in Table 9.
FERTILIZER
The Manufacture of Nitric Acid
Base Case Discharge of Organic/Toxic Pollutants—
Of the major fertilizer production activities (excluding the
production of ammonia which is covered as a separate industry in
Volume VII), the manufacture of nitric acid poses the greatest number
of possible conflicts between energy conservation and pollution control.
The problem areas are in the control of gaseous nitrogen oxide emissions
rather than in the manufacturing process itself. The basic process and
the several control technologies now being considered are described in
Volume XV, pages 24-42.
Nitric acid is an important material in the manufacture of fertilizer-
grade ammonium nitrate and explosives. The acid is produced by the oxida-
tion of ammonia, usually under high pressure and temperature over a platinum
catalyst, forming nitric oxide (NO). The gaseous products from the reactor
and oxygen are cooled to form N02, and are then sent to an absorption tower
to form the acid product.
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TABLE 9. PRIMARY COPPER INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
Base case conventional
smelting and refining
of concentrates
Outokompu flash
smelting
The Noranda process
CD
Ul
The Mitsubishi
process
The use of oxygen in
smelting
Metal recovery
from slag
Low levels of soluble
heavy metals in treated
wastewater effluent.
Minor source of organic/
toxic pollutants.
Similar to base case.
Similar to base case.
Similar to base case.
Base case waste load
plus cooling tower
blowdown (possibly
containing chromium)
and external pollution
loads associated with
fossil fuel-burning
control power station.
Similar to base case.
Fine particulates con-
taining heavy metals.
With adequate air pollu-
tion control, minor
source of organic/toxic
pollutants.
Similar to base case.
Similar to base case.
Similar to base case.
Base case waste load
plus air pollution
associated with fossil
fuel-burning central
power station.
Similar to base case.
Very large quantities of
heavy metal-containing slag,
dust, and wastewater treat-
ment, sludge. Metals, mostly
in solid phase. Major source
of organic/toxic pollutants.
Similar to base case.
Similar to base case.
Similar to base case.
Base case waste load plus
solid waste stream (coal
ash and S02 control sludge)
associated with fossil fuel-
burning central power station.
Lower concentration of copper
and certain other heavy metals
in waste slag.
(continued)
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TABLE 9 (Continued). PRIMARY COPPER INDUSTRY
QUALITATIVE COMPARISON OF ORGANIC/TOXIC POLLUTANT DISCHARGES
Medium
Process
Water
Air
Solid Waste
The Arbiter process
Depending on site speci-
fic conditions, treated
effluent loads very
likely to be similar to
base case.
oo
Virtual elimination of
air pollution problems
associated with base
case.
Substantial increase in quan-
tity of solid waste. Solid
waste is in the form of a wet
sludge and contains heavy
metals in a form more likely
to be leached than that of
the base case. Major source
of organic/toxic pollutants.
-------
The only significant pollutional problem resulting from the production
of nitric acid is the discharge of unabsorbed oxides of nitrogen in the
absorption tower tail gas.
While each of the several processes available for the control of
nitrogen oxide emissions has significant energy and NOX air control
implications, none produces waste streams containing organic/toxic
pollutants.
Mixed Fertilizer Plants
Base Case Discharge of Organic/Toxic Pollutants—
The base case plant used in this analysis is an ammoniation granula-
tion plant (ammoniation of normal super phosphate) equipped with a natural
gas-fired dryer and bag house filter to control particulate emissions.
There are no contaminated wastewater streams or solid waste streams, and
the collected particulates actually consist of product material and are
recycled back into the process. No organic/toxic pollutants are dis-
charged from the base case process.
Process Option - Conversion from Natural Gas to Fuel Oil and
Installation of a Wet Scrubber for Air Pollution Control—
Due to the impending shortage of natural gas, there is an incentive
to convert drying operations from natural gas to fuel oil. When using
fuel oil, however, there ±s a tendency for bag house filters to become
clogged with products of incomplete combustion. While it may be possible
to alleviate this problem by modifying the combustion process, it is likely
that many plants would require a wet scrubber.
Even though it is possible to recycle scrubber water to a high degree,
a certain amount must be purged to prevent the excessive buildup of dis-
solved solids. The scrubber water would contain ammonia, chloride, fluoride,
phosphate, and suspended solids. It would most likely have to be treated
with lime to precipitate the fluoride and phosphate as calcium fluoride
and calcium phosphate, and to convert ammonium ions to ammonia gas so
that it could be stripped from the wastewater by aeration. The waste-
water treatment system would produce a waste sludge composed of calcium
phosphate and calcium fluoride. The liquid fraction of the sludge would
contain small amounts of dissolved phosphate, fluoride, and possibly
some ammonia, which would represent the most environmentally objection-
able constituents. Although the pollutional problems associated with
this process option are clearly greater than the base case, the waste
streams do not contain pollutants now considered toxic.
Summary
There is no discharge of organic/toxic pollutants from the base
case nitric acid plant, nor from the various process options intended
for the control of NOX emissions. This aspect will not play a role
in the industry's selection of control technology.
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The base case mixed fertilizer plant has no discharge of organic/
toxic pollutants. The process option involving the conversion from
natural gas to fuel oil will likely result in wastewater and solid
waste discharges containing phosphates, fluorides, and ammonia, but
no organic/toxic pollutants.
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REFERENCES
U. S. Environmental Protection Agency, "Characterization of Sulfur
Recovery from Refinery Fuel Gas," EPA-450/3-74-055.
National Resources Defense Council (NRDC), Settlement Agreement with
Environmental Protection Agency, United States District Court for the
District of Columbia, June 7, 1976.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79- 162
2.
4. TITLE AND SUBTITLE
Environmental Considerations of Selected Energy-
Conserving Manufacturing Process Options
Volume XX Toxics/Organics
6. PERFORMING ORGANIZATION CODE
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
August 1979
7. AUTHOR(S)
Arthur D. Little, Inc.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Arthur D. Little, Inc.
20 Acorn Park
Cambridge, MA 02140
10. PROGRAM ELEMENT NO.
1NE 624B
11. CONTRACT/GRANT NO.
68-03-2198
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Arthur D. Little, Inc. undertook a study of the "Environmental Considerations
of Selected Energy-Conserving Manufacturing Process Options." Some 80 industrial
process options were examined in 13 industrial sectors. Results were published in
15 volumes, including a summary, industry prioritization report, and 13 industry
oriented reports (EPA-600/7-76-034 a through o).
This present report summarizes the information regarding toxic/organic
pollutants in the 13 industry reports. Four parallel reports treat sulfur oxides,
nitrogen oxides, particulates, and solid residues. All of these pollutant
oriented reports are intended to be closely used with the original 15 reports.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Energy, Pollution, Industrial Wastes
b.IDENTIFIERS/OPEN ENDED TERMS c. COS AT I Field/Group
Manufacturing Processes,
Energy Conservation
68D
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
98
20. SECURITY CLASS (Thispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
90
6US. K>WroMBnpR»«mGOFFICM979 -657-060/5408
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