Industrial Manufacturing Process Quality Control
'valuation Series • 02/78-03
E
Toxic Pollutant
Identification:
ACRYLONITRILE MANUFACTURING
^V~O\\ /D^' tS ~—— ~=~
iW '^^M'
U.S. ENVIRONMENTAL PROTECTION A
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02/78-03
February 1978
EPA - IMPQE Series
TOXIC POLLUTANT IDENTIFICATION:
ACRYLONITRILE MANUFACTURING
by
W. LOWENBACH
J. SCHLESINGER
J. KING
The MITSE Corporation
METREK Division
McLean, Virginia 22101
Grant No. 805-6201-01
Contract No. 68-01-3188 Task 64
Project Officers: Paul E. desRosiers
David L. Becker, IERL-CI
U.S. ENVIRONMENTAL PROTECTION AGENCY
INDUSTRIAL AND EXTRACTIVE PROCESSES DIVISION
OFFICE OF ENERGY, MINERALS AND INDUSTRY
OFFICE OF RESEARCH AND DEVELOPMENT .
WASHINGTON, D.C. 20460
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ACKNOWLEDGMENT
The authors wish to acknowledge those who gave so generously
of their time and patience during the compilation of this document.
Special thanks in particular go to Dr. Alan Goldfarb of The MITRE
Corporation for his'valuable contributions to this study. Finally,
the many helpful suggestions- and technical assistance of the following
individuals are greatly appreciated: Mr. Paul des Rosiers
EPA-ORD-Washington; Dr. Barbara B. Fuller, Dr. Paul R. Clifford,
Mr. John A. King, Mr. Joginder S. Bhutan!, and Dr. Elbert C. Herrick,
all of The MITRE Corporation; and Dr. Ronald Barbaro, Project
Consultant.
iii
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TABLE OF CONTENTS
EXECUTIVE SUMMARY ' xi
I. INTRODUCTION 1
Legislative and Regulatory Background 1
Objectives and Approach 3
Overview of Acrylonitrile Manufacture 7.
Process Technology 7
Market Outlook 9
II. ACRYLONITRILE MANUFACTURE 13
Reaction Conditions 13
Feedstock Composition 14
Ammoxidation of Propene 16
Reaction Mechanism 19
Mechanism of Catalysis 24
By-Product Formation 32
Pollutants from Feedstock Impurities 32
Significant Side Reactions . 35
Process Configuration for Acrylonitrile Manufacture • 46
The Generic SOHIO Process 46
Significant Modifications to the SOHIO Process 58
III. WASTEWATER TREATMENT ' 69
Introduction . 69
Industrial Wastewater Treatment Practices 69
Current Treatment of Wastewater from Acrylonitrile
Manufacture 72
Wastewater Characteristics 72
Federal and State Discharge Requirements 73
Current Industrial Practices 80
Future Regulatory Concerns 83
IV. ALTERNATIVE METHODS OF TREATMENT 87
Introduction 87
Biological Treatment 89
Chemical Pretreatment 100
Chemical Oxidation 103
Ozonation 104
Treatment with a Peroxide Compound 105
Wet-Air Oxidation and Incineration 109
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TABLE OF CONTENTS (Continued)
Page
IV. ALTERNATIVE METHODS OF TREATMENT (Continued)
Adsorption and Catalytic Oxidation on
Granular Activated Carbon 115
Treatment with Formaldehyde 117
Hydrolysis • 119
Chemical Precipitation " . 120
Physical Pretreatment . 120
Separation Practices 121
Ammonium Sulfate Recovery 121
Combination and^ Alternative Techniques • . 125
Wet-Oxidation with Biophysical Treatment 125
Other Combination Systems 128
V. RECOMMENDED TREATMENT ALTERNATIVES 131
Introduction 131
Point Sources of Potential Pollutants . 132
Point No. 1 132
Point No. 2 • 135
Point No. 3 : . 136
Point No. 4 . • . • 137
Point No. 5 137
Point No. 6 . 138
Point No. 7 138
Point No. 8 139
Point No. 9 139
Non-Point Source Emissions 139
VI. SUMMARY AND CONCLUSIONS 141
REFERENCES 147
APPENDIX I TOXIC POLLUTANTS TO BE REGULATED UNDER AI-1
SECTION 307 OF THE FEDERAL WATER POLLUTION
CONTROL ACT
APPENDIX II INDUSTRIAL CATEGORIES DEFINED BY THE CLEAN AII-1
WATER ACT OF 1977
APPENDIX III THE EPA LIST OF PRIORITY POLLUTANTS AIII-1
APPENDIX IV CONSULTANT REPORT AIV-1
vi
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LIST OF FIGURES
Figure Number Page
1 Acrylonitrile and By-Product Markets 11
2 Mechanism of Propane Oxidation and 20
Ammoxidation
3 Overall Reaction Mechanism of Ammoxidation ' 21
of Propene
4 A Formal Kinetic Scheme of Acrylonitrile 21
Synthesis
5 Representation of Ligand ut-Molecular Orbitals 26
and Their Possible Interactions with Metal
Orbitals
6 Proposed Bonding of Chemisorbed Allylic . 27
Species
7 Reactive Intermediates Formed in 29
Acrylonitrile Synthesis
8 Proposed Bonding at the Catalyst Surface of 31
C3Hs and €3!!^ Species
9 The SOHIO Process for Acrylonitrile 47
. Manufacture
10 Cross Section of a Representative Catalytic 49
Fluidized Bed Reactor
11 Acetonitrile Purification 55
12 Hydrocyanic Acid Purification 57
13 Erdolchemie-Bayer Process Modification for 61
Acrylonitrile Manufacture
14 Badger Process Modifications for Acrylonitrile 64
Manufacture
15 Significant Pollutants from Acrylonitrile 67
Manufacture
vii
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LIST OF FIGURES (Concluded)
• Figure- Number Page
16 Oxidation of AcetonitrUe in Ohio Elver 91
Water • • •
17 Oxidation of Acrylonitrile In Ohio River 91
Water
18 Flowsheet for Waatewater Treatment Using in
Wet-Oxidation (Wet-Ox)
19 Recovery of Annnonium Sulfate from 124
Acrylonitrile Manufacture
20 Wet-Oxidation with Biophysical Treatment 126
21 Potential Treatment Options for 143
Acrylonitrile Wastewaters by Point Source
viii
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LIST OF TABLES
Table Number . Page
1 Consumption Pattern of Acrylonitrile 10
2 Analysis of Propene Impurities -15
3 Specifications of Ammonia Used in 16
Acrylonitrile Synthesis and Degradation
4 Relative Reaction Rates of Acrylonitrile , .23
Synthesis and Degradation
5 Summary of Pollutants from Acrylonitrile 44
Manufacture
6 Analysis of the Reactor Effluent Gases 50
7 Principal Species Present in Quench Column 53
Bottoms and Wastewater Stripper Overhead
8 Composition of Crude Acetonitrile . 56
9 . Wastewater Characterization of Major Process 74
Streams from Acrylonitrile Manufacture
10 BPT and BAT Effluent.Limitations for 78
Acrylonitrile Manufacture
11 U.S. Acrylonitrile Manufacturers 82
12 Biological Treatment of Nitrile Containing 101
Wastewaters
13 Summary of Foreign Applications of Physical- 113
Chemical Treatment to Acrylonitrile/Cyanide
Containing Wastewaters
14 Combination Systems Applied to Acrylonitrile 130
Wastewater by Foreign Researchers
15 Representative Composition of the Quench 133
Column Bottoms • ""
16 ' Representative Composition of the Waste- 137
water Stripper Bottoms
ix
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LIST OF TABLES (Concluded)
Table Number Page
17 Representative Composition of the Waste- 133
water Streams from Acetonitrile Purifica-
tion
18 Representative Composition of Surface 140
Runoff
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EXECUTIVE SUMMARY
The discharge of a toxic substance to the environment by an organic
chemical manufacturer, depending on the persistence and mobility of the
compound, may have irreversible effects on the environment. Under the
Clean Water Act of 1977, the EPA must establish effluent limitations
for 65 toxic pollutants (and/or classes of chemicals) in terms of the
best available technology. (As the law under Section 53 does not pre-
clude consideration of other pollutants, the EPA is currently working
from a list of 129 chemicals (See Appendix III).) However, the estab-
lishment of such standards for specific toxic species that are not
only equitable to industrial manufactures, but more importantly that
will prevent further deterioration of the environment, is an exceedingly
difficult task. As a first step, EPA must thoroughly understand the
manufacturing process and available control technologies so that,
ultimately, attainable standards may be set.
Because acrylonitrile is a major organic intermediate (over one
and one-half billion pounds were produced in the United States in 1977)
and in light of current toxicity data, acrylonitrile manufacture
potentially represents a significant hazard to both man and his envir-
ment. For the above reasons, this study is specifically directed
toward the assessment of toxic pollutant generation from the manu-
facture of acrylonitrile and possible methods of control.
Currently, acrylonitrile production throughout the world is based
on the catalytic oxidation of propene and ammonia:
CH2=CH-CH3 + NH3 + 3/202 Catalyst ,. CH2=CH-C=N + 3H20
xi
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The prevailing technology is licensed by The Standard Oil Company of
Ohio and is generally referred to as the SOHIO process, although
European manufacturers may use somewhat different catalyst and reactor
systems. Current domestic producers of acrylonitrile are American
Cyanamid Company (New Orleans, Louisiana), E.I. duPont deNemours &
Company, Inc. (Beaumont, Texas and Memphis, Tennessee), Monsanto Com-
pany (Chocolate Bayou and Texas City, Texas) and The Standard Oil
Company (OHIO)(Lima, Ohio).
In Section II, a detailed description of acrylonitrile manufacture
has been presented. Included is a comprehensive discussion of the reac-
tion mechanism, with a summary of potential pollutants generated from
feedstock impurities and significant side reactions. The catalytic
ammoxidation of propene over bismuth molybdate involves the abstraction
of hydrogen from a methyl group of propene to yield an allylic inter-
mediate; abstraction of a second hydrogen atom to yield a carbenoid
system (C^B.,); and reaction of this species with either ammonia adsorbed
at the site, to eventually yield acrylonitrile, or with oxygen to yield
acrolein. Alternatively, the allylic radical may upon abstraction of a
second hydrogen, dissociate to adsorbed C2B.^ an-ci CH species, and, in
reactions analogous to the above, react with ammonia and oxygen to
yield acetonitrile, hydrocyanic acid, acetaldehyde, and formaldehyde
respectively.
A generic process configuration for acrylonitrile manufacture has
been formulated, identifying nine point source discharges. Specifi-
cally, two major process waste streams are generated: the quench
xii
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minimi bottoms and the recovery column stripper bottoms. Other signi-
ficant point sources include the still bottoms from the purification
of acrylonitrile, and if by-product recovery is practiced, the column
bottoms from the purification of acetonitrile and hydrogen cyanide.
Also discussed are two distinct in-process modifications to the SOHIO
process: the first, specific to ammoniam sulfate recovery, is reportedly
used by European manufacturers; the second configuration involves
selective absorption of acrylonitrile allowing for complete combustion of
waste by-products.
A review of current wastewater treatment and disposal practices
is presented in Section III,in light of current discharge requirements
and future regulatory concerns. At this time, there are no effluent
limitations specific to point source discharge from acrylonitrile
manufacture. All U.S. acrylonitrile manufacturing facilities deep well
their wastewater, with the exception of duPont's Memphis operation,
where segregated streams are pretreated by alkaline hydrolysis prior
to discharge to a publicly owned treatment facility. As deep well
disposal is not a long term solution to the pollution problem, altern-
nate treatment technologies were investigated.
Section V consists of a detailed discussion of pollution abatement
alternatives for acrylonitrile manufacture. As the waste is character-
ized by high loadings of hydrogen cyanide, organic nitriles, heavy
polymeric material and inorganic salt, the discussion focuses on means
of chemically detoxifying the waste stream prior to biological treat-
ment by acclimated, activated sludge. Included is a review of
xiii
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alternative means of destroying cyanides/organic nitriles, such as,
chemical oxidation procedures (ozonolysis, treatment with a peroxide
compound, wet-air oxidation, adsorption and catalytic oxidation on
granular activated carbon), treatment with formaldehyde, and alka-
line hydrolysis. As the high salt content of the waste precludes
direct treatment by biological processes or incineration practices,
ammonium sulfate recovery practices are discussed in detail.
Section VI presents a point source-by-point source summary of
potential pollutants from acrylonitrile manufacture using the SOHIO
process and recommends treatment alternatives for each stream. Recommen-
dations (which are based solely on the efficiency of a process to treat
a waste stream, and exclude any analyses of capital, operation and
maintenance, and energy costs) focus on treatment and disposal of
the quench column bottoms and the bottom stream from the wastewater
stripper. Treatment options include incineration of a concentrated
organic stream and biological treatment of a detoxified (chemically
pretreated) stream.
In summary, this report outlines some of the steps that must
be taken before BAT effluent limitations can be rationally promulgated
for acrylonitrile-containing wastewaters. Recommendations for
further study include:
• EPA verification, from sampling of actual process wastewaters,
of all pollutant predictions and concentrations.
• Extension of this pollution prediction and abatement
methodology to other unit processes such as nitration,
chlorination, oxidation, etc.
xiv
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EPA funding of pilot scale studies for determination of
the technical practicability of the recommended treatment
alternatives.
An economic analysis of viable treatment alternatives
(with regard to best available technology economically
achievable).
Demonstration of BAT in an EPA-industry Jointly funded
project.
xv
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SECTION I
INTRODUCTION
LEGISLATIVE AND REGULATORY BACKGROUND
While the hazards of certain toxic water pollutants have long
been recognized, the Environmental Protection Agency has histori-
cally placed priority on improving traditional water quality param-
eters such as pH, suspended solids, and biochemical oxygen demand.
Yet specific toxics are coming increasingly into prominence; head-
lines tell of widespread Kepone contamination of the James River in
Virginia, carbon tetrachloride spills in the Ohio River, and con-
tamination of the Hudson River from dumping of polychlorinated bi-
phenyls. Furthermore, seventy-eight cities have found significant
quantities of industrial chemicals such as FCB's, cyanides, phenols,
and carcinogenic chlorinated hydrocarbons in drinking water sup-
plies (Becker, 1977).
There is no single comprehensive water pollution control stat-
ute; indeed, toxic substances are generally regulated under no less
than six different federal laws - the Clean Water Act of 1977;* the
Safe Drinking Water Act; the Marine Protection, Research, and Sanc-
tuaries Act (also known as the Ocean Dumping Act); the Resource
Conservation and Recovery Act (also known as the Solid Waste Act);
the Federal Insecticide, Fungicide, and Rodenticide Act; and the
*This act supercedes the Federal Water Pollution Control Act of
1972.
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Toxic Substances Control Act. Since each of these lavs take a some-
what different approach to regulation of water quality, areas of
•
jurisdiction often overlap or intersect.
Undoubtedly, the Federal Water Pollution Control Act was ini-
tially intended as EPA1a primary regulatory tool for control of
toxic discharges to the aquatic environment. Section 307(a) spe-
cifically requires that a list of toxic pollutants be published and
limits for the discharge of those pollutants be established, taking
only into account the substance's impact on the environment. How-
ever, nearly four years after the passage of the Act, Section
307(a) had yet to be implemented. Thus, in June of -1976 as a re-
sult of civil actions brought by three environmental interest '
groups, the EPA signed a consent agreement which required the im-
mediate establishment of Section 307(a) limitations for six partic-
ularly toxic chemicals (four pesticides - aldrin/dieldrin, DDT/DDD/
DDE, endrin, and toxaphene, plus benzidine and polychlorinated bi-
phenyls). Additionally the EPA agreed to write effluent limita-
tions for 65 other chemicals (and/or classes of chemicals) into
best-available-technology (BAT) effluent guidelines for NPDES*
permits (authorized under Section 302 and 304 of P.L. 92-500) for
21 industries (see Appendices I and II); these limitations are to
go into effect by 1983.
^National Pollutant Discharge Elimination System.
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As a result of the shortcomings of P.L. 92-500 for the control
of toxic discharges to public waters,* Congress has sought to cor-
rect these deficiencies by the Clean Water Act of 1977 which em-
bodies the major points of the consent agreement. Specifically
under Section 53 of this legislation, the Administrator must esta-
blish effluent limitations for 65 toxic pollutants in terms of the
best available technology economically achievable for the appli-
cable category or class of point sources established in accordance
with sections 301(b)(2)(A) and 304(b)(2) as soon as practicable,
but no later than July 1, 1980 (see appendix I and II for the list
of toxic pollutants and applicable categories respectively). The
law, under Section 53, does not preclude consideration of other
pollutants and currently the EPA is working from a list of 129
chemicals (see appendix III). However, to be able to promulgate
these regulations the EPA must at a minimum;
• Predict or otherwise measure discharge rates for each
pollutant;
• Provide supporting data on each pollutant's health and
ecological effects;
• Evaluate control technology capabilities; and
• Recommend ambient water quality criteria levels.
OBJECTIVES AND APPROACH
Much of the information required by the EPA for promulgation
of practicable regulations in accordance with the Clean Water Act
*For a brief review of the difficulties encountered by EPA in im-
plementing Section 307(a) of P.L. 92-500 see Ward, 1977.
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of 1977 does not yet exist. Pollutant discharge rates for each of
the hundreds of processes in the 21 targeted Industries is not
readily available; indeed, general analytical protocols have yet
to be developed for a substantial number of the specified pollutants.
Moreoever, effective methods of wastewater treatment for each of
the 65 pollutants have yet to be defined, much less demonstrated as
BAT.
Thus, the first task in meeting the requirements of the Clean
Water Act of 1977 is to develop the data necessary to promulgate
.practicable regulations. Nonetheless, any data gathering system,
whether it is a complex sampling and analysis program or simply a
collection of existing wastewater data, must, within the existing
budgetary constraints, be designed to be both cost and information
effective. The current procedures for collecting this pollutant
Information focus on the list of 65 classes or compounds known to
be hazardous to the environment and, as such, involve only a cur-
sory review of manufacturing processes. While this method is prob-
ably cost effective, the risk of bypassing unsuspected hazardous
materials is rather high. An alternate solution is to directly
analyze and evaluate in some manner, all streams for an entire
spectrum of all possible processes individually; though this scheme
is obviously Information effective, it is also likely to be
prohibitively, expensive.
Yet another approach to this problem, which represents a
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compromise between the above extremes, is to identify prior to
sampling and analysis in the field, which species are likely to
occur at each point source within a process from consideration of
the reactants and reaction pathway. Thus the advantages of work-
Ing from a limited list of discrete species is retained in addi-
tion to examining, in detail, each process for potentially toxic
emissions to the environment. Because toxic species formation
is derived solely from the reaction chemistry (and feedstock im-
purities) this method represents a multimedia approach to this
problem.
Acrylonitrile is an explosive, flammable liquid which has a
boiling point of 77°C at atmospheric pressure and a vap.or pressure
of SO mm (20°C). The acute toxic effects of acrylemitrile are
similar to.those of cyanide poisoning. More importantly, recent
evidence furnished by E.I. duFont de Nemours & Company, Inc. (du
Font) in May 1977, indicates an excess of cancer among workers ex-
posed to acrylonitrile at a textiles fibers plant. Additionally,
in on-going ingestion and inhalation studies of acrylonitrile, labo-
ratory rats developed a variety of tumors, including carcinomas.
As acrylonitrile is a major organic intermediate (over one and one-
half billion pounds were produced in the United States in 1977)
and in light of the above toxicity data, acrylonitrile manufacture
potentially represents a significant hazard to both man and his en-
vironment. For the above reasons, this study is specifically
5
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directed toward the assessment of toxic pollutant generation within
the manufacture of acrylonitrile and possible methods of control.
The objectives are fivefold:
• Identify the toxic chemicals likely to be present in
the aqueous effluent from each process;
• Identify the point sources of these pollutants;
• Identify current treatment practices;
• Survey alternate treatment technologies; and
• Indicate practicable methods of pollutant reduction
where current treatment has been deemed Inadequate.
Information has been gathered in the following manner;
(1) Through a thorough search of the chemical literature,
the reaction mechanism (and thus the reaction inter-
mediates) for the formation of acrylonitrile has been
identified. From a .knowledge of the reaction inter-
mediates, significant by-products formed during .acrylo-
nitrile manufacture have been predicted. Additionally
the effect of feedstock impurities were considered.
(27 From an extensive patent search, a generic process
configuration for acrylonitrile manufacture has been
formulated. Included in this process description are
specific point sources for various process operations.
In general, pollutant discharges are considered from
a multimedia viewpoint and not restricted solely to
aqueous effluents.
(3) Manufacturers of acrylonitrile provided summaries of
their current wastewater treatment and discharge prac-
tices (see Appendix IV). In addition to this survey,
applicable NPDES permits have been gathered.
(4) From a thorough literature review, "state-of-the-art"
wastewater treatment technology for acrylonitrile manu-
facture has been identified. Both patented technologies
and relevant theoretical studies have been included in
this review.
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OVERVIEW OF ACRYLONITRILE MANUFACTURE
Process Technology
Though a large number of procedures might conceivably be used
for the manufacture of acrylonitrile, relatively few have proved to
be of commercial interest. These processes include:
• Reaction of ethyl ene oxide with hydrogen cyanide followed
by catalytic dehydration of ethylene cyanohydrin,
C2H40 + HCN - -C3H3NO
catalyst
C3H5NO - ;
Addition of hydrogen cyanide to acetylene using a cuprous
chloride catalyst, _ _
CuCl
C2H2 + HCN • C3H3N
Catalytic reaction of propene with nitric oxide,
catalyst
4C3Hg + 6NO - -4C3H3N + N2 + 6H20
Catalytic oxidation of propene and ammonia,
catalyst
C3flg + NH3 + 1 1/2 02- - — C3H3N + 3H20
which also yields acetonitrile and HCN as recoverable by-
products, and
Catalytic oxidation of propane and ammonia.
catalyst
NH3 + 202 - • Cs^N + 4H20
Though each of the first four processes has been used to pro-
duce acrylonitrile on a commercial scale, ^current production through-
out the world is based exclusively on the catalytic Oxidation of
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propene and ammonia. The last process has been studied only on a
pilot scale (Horn and Hughes, 1977).
World demand for acrylonitrile approached 5 billion pounds in
1976 of which approximately one and one-half billion pounds were
manufactured .in the United States. The prevailing technology is
licensed by the Standard Oil Company of Ohio and is generally re-
ferred to as the SOHIO process, although European manufacturers may
use somewhat different catalyst and reactor systems. However, in
the United States, for the foreseeable future at least, it does not
appear as though there is any other process that will be able to
economically compete with the SOHIO process. Current domestic pro-
ducers of acrylonitrile are American Cyanamid Company (New Orleans,
Louisiana), E.I. duFont de Nemours & Company, Inc. (Beaumont, Texas
and Memphis, Tennessee), Mpnsanto Company (Chocolate Bayou and
Texas City, Texas), and The Standard Oil Company (Ohio) (Lima,
Ohio).
A major weakness of the acrylonitrile market is the total de-
pendence of the SOHIO process on propene which in recent years has
been in tight supply. However the future availability of propene
promises to be much brighter, due, in large part, to an expected
switch to naptha and/or gas oil cracking for production of ethane,
which yields propene as a co-product.
Potentially competing with, propene as a feedstock is propane.
Although at first glance propane appears to Be a less expensive raw
8
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material than propene, the yield of acrylonitrile from propane is
substantially less than that from propene. Thus at present, the
cost of recovery and recycle more than offset the low initial cost
of propane. In the future, however, the relative cost and avail-
ability of propane versus propene could alter this situation.
Market Outlook
The backbone of acrylonitrile demand lies in the production
of acrylic and modacrylic fibers by copolymerization with methyl
acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, or
vinylidene chloride. Acrylic fibers, marketed under tradenames in-
cluding Acrilan, Cresland, Orion, and Zefran, are used in the manu-
facture of apparel, carpeting, blankets, draperies, and upholstery.
' During the period from 1966 to.1976, demand for acrylonitrile has
averaged better than 6 percent per year. Though, this rate may not
be equalled in the future, an increase of about five percent over
the next five years seems assured.
The second ranking use for acrylonitrile is acrylonitrile-
butadiene-styrene (ABS) resins. Styrene-acrylonitrile (SAN) resins
also constitute another major end product of acrylonitrile. Com-
bined demand for ABS and SAN resins has, over the past 10 years,
averaged a twelve percent growth rate. However the recent decision
by the Food.-and Drug Administration to ban the use of acrylonitrile
in plastic beverage containers makes the growth potential of this
market uncertain at this time. The largest of the remaining uses
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for acrylonitrile is the manufacture of adiponitrile, which in
turn is used to make hexamethylenediamine and eventually Nylon 66.
Demand for this use is expected to grow at least as fast as the
average for the above mentioned acrylonitrile outlets. Current
market outlets for acrylonitrile, together with the process by-
products, hydrogen cyanide and acetonitrile are delineated in Fig-
ure 1, while the consumption pattern of acrylonitrile is listed
In Table 1.
TABLE 1
CONSUMPTION PATTERN OF ACRYLONITRILE1
Market • Consumption, percent
Acrylic Fibers" 42.0
ABS and SAN Resins ' 19.0
Nitrile Elastomers 4.0
Miscellaneous Applications 17.5
Exports 17.5
•'•Based on production of 1.52 billion pounds in 1977.
Source: Lawler (1977)
10
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ACRYLONITRILE
ACRYLIC FIBERS
MODACRYLIC FIBERS
ACRYLONITRILE-BUTADIENE-STYRENE (ABS) RESINS-
STYRENE-ACRYLONITRILE (SAN) RESINS-
NITRILE ELASTOMERS
PIPE AND PIPE FITTINGS
AUTOMOTIVE PARTS
APPLIANCE PARTS
ELECTRICAL AND ELECTRONIC PARTS
PACKAGING
LUGGAGE
TOYS AND SPORTS EQUIPMENT
FURNITURE
HOUSEWARE ITEMS
AUTOMOBILE INSTRUMENT
PANEL WINDOWS
INSTRUMENT LENSES
ADIPONITRILE-
"HEXAMETHYLENEDIAMINE (HMDA)-
I NYLON 66
-I NYLON 610.
FFILMS
-I FIBERS
RESINS
ACRYLAMIDE
NITRILE BARRIER RESINS
GRAIN FUMIGANT
DIACETONB ACRYLAMIDE-*-
REACTIVE CROSS-LINKING
AGENT IN UNSATURATED
POLYESTER RESINS
POLYACRYLAM1DES
DRILLING MUD ADDITIVES
TEXTILE TREATMENT
SURFACE COATINGS
WASTE AND WATER TREAT-
MENT FLOCCULANTS
PAPERMAKING STRENGTHENERS
BY-PRODUCTS
ACETONITRILE-
I VITAMIN B
~ PERFUMES
I SOLVENT
HYDROGEN CYANIDE-
ACETONE CYANOHYDRIN
ADIPONITRILE
ACRYLONITRILE
AMINOPOLYCARBOXYLIC ACIDS-
:HELATING AGENTS
SODIUM CYANIDE -
CYANURIC CHLORIDE-
OIERBICIDES
:RIALLYL CYANURATE
TERTIARY ALKYL AMINES
LACTIC ACID
(3-AMINES
METHIONINE
DIAMINOMALEONITRILE —
BARIUM CYANIDE "-ELECTROPLATING
ADIPONITRILE
CHELATING AGENTS
CASE-HARDENING AND HEAT
TREATMENT OF STEEL
SODIUM THIOCYANATE
EXTRACTION OF GOLD AND
SILVER FROM ORES
ELECTROPLAflNG
ORE SEPARATION
DYES
PHARMACEUTICALS
PLASTICS
HYDROGEN CYANIDE (FOR
SPECIALTY CHEMICALS)
POLYESTERS
FLUORESCENT BRIGHTENING AGENTS
DYES
PHARMACEUTICALS
I SPECIALTY POLYMERS
+-1 PHARMACEUTICALS
AGRICULTURAL CHEMICALS
Source: Chemical Origins and Markets, SRI, 1977.
FIGURE 1
ACRYLONITRILE AND BY-PRODUCT MARKETS
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SECTION II
ACRYLONITRILE MANUFACTURE
REACTION CONDITIONS
The stoichiometric equation for the reaction of propene,
ammonia, and air (subsequently referred to as ammoxidation),
400 - 510°C
135 - 310kPa
CH2=CH-CH3 + NH3 + 3/2 02 catalyst l CH2«CH-C=N + 3 H20 (1)
although an obvious oversimplification, has too often been consid-
ered as a sufficient description of the industrial synthesis of
acrylonitrlle. Any reaction in which a large number of bonds are
broken will usually require passage through a number of distinct
intermediates. Thus the above equation, although describing the
overall reaction, does not describe the formation of hazardous by-
products such as acetonitrile, acrolein, and hydrogen cyanide.
Only from careful consideration of (1) reaction conditions,
(2) feedstock composition, (3) the reaction mechanism, and (4) the
most probable manufacturing configuration, can formation of such
by-products be logically explained and the environmental impact
adequately assessed.
While a large number of mixed oxide catalysts have been evalu-
ated and patented for ammoxidation of propene, apparently only two
different types have been used commercially. The first of these is
a silica supported antimony-uranium oxide mixture of which the
active phases are represented as USb30lO and USbOs. The second
13
-------
system is a silica supported bismuth phosphomolybdate composition
described in the patent literature as 70 percent by weight
•
P205:Bi203:Mo03 in a molar ratio of 1:9:24 (Callahan, 1965).
Though the yield of acrylonitrile over either catalyst is reported
to be about 65 percent (based on moles of propene), the latter sys-
tem is more effective (i.e., operating nearer the stoichiometric
requirements) in terms of ammonia and air utilization. Thus, the
following discussion is predicated upon the use of a bismuth phos-
phomolybdate system operating at a propene/ammonia/air molar ratio
of approximately 1:1.1:8, pressures only slightly greater than
atmospheric, and temperatures in the range of 400-510°C.
FEEDSTOCK COMPOSITION
To accurately predict the formation of reaction by-products
from acrylonitrile manufacture, significant (in terms of chemical
reactivity, potential toxicity, and quantity present) impurities
in the starting materials must be identified. Unfortunately, a
truly representative analysis of the propene feedstock is diffi-
cult to obtain due to the nature of its manufacture (either re-
finery produced or as a by-product of olefin production with steam
crackers which use a heavy liquid feedstock)* A typical propene
feedstock, however, is likely to contain propane as the principal
*Propene is produced either from refineries, or steam crackers
which are located near each plant site. The current ratio of
refinery to that of steam cracker co-product is approximately
50-50; by 1985, however, Sanders (1977) has forecast that 70
percent of propene will be from steam crackers.
14
-------
contaminant with smaller amounts of other Impurities such as
ethane, ethene, benzene, water, and €4 hydrocarbons as"shown in
Table 2.
TABLE 2
ANALYSIS OF PROPENE IMPURITIES1
Component Mole %
Methane > 0.01
H20 > 0.01
Ethane 0.05
Ethene . > 0.01
Propane 2.85
C, Hydrocarbons > 0.01
Nickel carbonyl . N/A
Allene N/A
Methyl acetylene N/A
•'•Propane Produced from catalytic cracking of propane.
Source: Dunn (1976)
Refrigeration grade ammonia of the composition shown in Table
3 is used in the manufacture of acrylonitrile (Considine, 1974).
Although specific impurities other than water are not Identified,
the small amount of oil and non-condensable gases (probably nitro-
gen or hydrogen) present are unlikely to lead to significant by-
product formation.
15
-------
i TABLE 3
SPECIFICATIONS OF AMMONIA USED IN ACRYLONITRILE MANUFACTURE
COMPONENT %, BY WEIGHT1
99.8 (Minimum)
Water 0.015 (Maximum)
Oil 3 ppm (Maximum)
Non-condensable gas 0.0002 or/Kg (Maximum)
^Percent by weight unless otherwise noted.
Source: Considine (1974)
.The oxygen required for acrylonitrile manufacture is supplied as
air which is filtered and compressed prior to use. Impurities pres-
ent in the feed air are of course site specific and their effect on
by-product formation is difficult to predict.
AMMOXIDATION OF PROPENE
An understanding of the reaction mechanism, specifically the
identification of those reactive intermediates which describe the
reaction pathway, results in a complete, although qualitative,
description of by-products.* Only a limited number of by-products
have been explicitly associated with or identified from acrylo-
nitrile manufacture in the chemical literature, though a large num-
ber of species have been found in the wastewater at such facilities.
Known by-products of acrylonitrile manufacture include acetonitrile,
acrolein, carbon monoxide, carbon dioxide, hydrogen cyanide, and
*This is actually the reverse of a more traditional approach, where
the existence of minor products is used to validate a mechanism.
16
-------
nitrogen. A detailed examination of the reaction mechanism will
provide an indication of which minor side reactions may generate other
hazardous or toxic compounds.
To facilitate the discussion of ammoxidation of propene, it is
useful to first consider the significant features of heterogeneous
catalysis. Whereas simple gas phase reactions are characterized by
radical rather than ionic mechanisms, heterogeneous reactions, such
as those which take place partly in the gas phase and partly on a
surface, are considerably more complex. In the latter case, radical
species need not exist explicitly and indeed ionic species may pre-
dominate at the solid-gas Interface. Regardless of the specific
species involved, a reaction occurring on a surface may usually be
regarded as involving the following five consecutive steps:
1. Diffusion of the reacting molecules to the surface;
2. Adsorption of the gases on the surface;
3. Reaction on the surface;
4. Desorption of the products;
5. Diffusion of the desorbed products into the main body of the
gas.
For reactions such as the ammoxidation of propene which occur
over porous catalysts, the diffusion process, 1, may be the slowest
process and, thus, the rate determining step (Lankhuyzen, 1976).
Generally, however, either, adsorption or desorption, is likely
to be rate determining in teterogeneous reactions, since both
commonly have appreciable activation energies. Desorption
17
-------
energies are particularly high and may, for a large number of re-
actions, be the slow step. In practice, separation of steps 3 and
4 is difficult since product desorption rates are not generally
known; therefore, the reaction on the surface, giving the gaseous
products, is most often regarded as a single step.
While identification of the rate limiting step of ammoxidation
of propene is necessary to reconcile empirical data with a proposed
reaction mechanism, it is more important, for the purposes of this
document, to first identify and discuss the reaction intermediates
which lead to the formation of products and by-products. Though it is
difficult to ascertain with absolute certainty the nature of the re-
acting species, available experimental evidence is best accounted for
In terms'of several radical-like intermediates derived from.propene.
Less attention has been given to the nature of the absorbed reactants
«
ammonia and oxygen. Thus, the specific identity of absorbed ammonia
is not known with certainty and for convenience is identified only as
NHabs but again is assumed to exist as a radical-like species.
Oxygen, on the other hand, appears to be supplied 'by the catalyst
rather than directly from the oxygen feed; thus the reactive form of
oxygen during acrylonitrile synthesis may be of an ionic rather than
radical nature. Where the identity of the reacting oxygen species is
unknown, oxygen is simply shown as [0],
So that the following discussion of the reaction mechanism will be
Intelligible to a reader with a limited knowledge of organic chemistry,
18
-------
the basic features of the reaction mechanism which lead to the forma-
tion of important reaction intermediates (i.e., lead directly to
acrylonitrile or significant by-products) are outlined first. The
more difficult question of the specific mode of catalysis is dis-
cussed in a separate subsection entitled "Mechanism of Catalysis" and
may be omitted without serious loss of continuity.
Reaction Mechanism
The mechanism of catalytic ammoxidation of propene over bismuth
molybdate catalysts has been intensively studied (Lankhuyzen at al.,
1976; Callahan et al., 1970; Ghenassia and Germain, 1975; Cathala and
Germain, 1970; Shelsted and Chong, 1969; Adams and Jennings, 1963;
Adams, 1965). By means of isotopic labeling, Adams and Jennings (1963)
have shown, as illustrated in Figure 2, that the first step of the over-
all reaction is the abstraction of hydrogen from a methyl group leading
to formation of an allylic intermediate.1" This step is then followed
by a second abstraction of hydrogen. Ammoxidation then proceeds In a
series of fast steps.
*For the purposes of this discussion, organic reaction intermedi-
ates are illustrated as radicals. Though the true structure of
these species is not known with certainty, a better description
is radical-like intermediate.
19
-------
1st H Abstraction
2nd H Abstraction
Aerolain
3rd H Abstraction
• Acrylonitrile
Figure 2. Mechanism of Fropene Oxidation and Ammoxidation
The above mechanism, however, does not account for formation
ef signficant by-products such as hydrogen cyanide, acetonitrile,
acetaldehyde, etc. Cathala and Germain (1970) in a more recent
study of the ammoxidation of propene over bismuth phosphomolybdate
have refined the basic mechanism of Adam and Jennings as follows:
(1) abstraction of hydrogen from propene to yield an allylic radi-
cal; (2) abstraction of a second hydrogen atom to yield a carbenoid
system (CoH,); (3) reaction of this species with either ammonia
adsorbed at the site, to eventually yield acrylonitrile, or with
oxygen to yield acrolein. Alternatively, the allylic radical may
upon abstraction of a second hydrogen, dissociate to C£H3 and CH
species, and, in reactions analogous to the above, react with
ammonia and oxygen to yield acetonitrile, hydrocyanic acid, acetal-
dehyde, and formaldehyde respectively. This mechanism is illus-
trated in Figure 3.
20
-------
5—[C3H4.]
C3H4NH]—C^CHCN*
[2CHCHO
r-»HCN ,.-
[OH]
CO
Figure 3. Overall Reaction Mechanism of Ammoxidation of Propene
To be able to discuss the above mechanism in terms of empiri
cal data, development of a formal kinetic scheme is useful as a
framework within which the principal reactions may be considered.
Thus, Cathala and Germain (1970) have suggested the following
series of successive and parallel reactions shown in Figure 4.
- • • H CaN
:o,co2
Figure 4. A Formal Kinetic Scheme of Acrylonitrile Synthesis
21
-------
Each of the above reactions has been studied in some detail.
Ghenassia and Germain (1975), for example, have investigated the
ammoxidation of acroleln. Other reactions as shown (i.e., 7, 8,
9) may be regarded as the processes of primary oxidation and sec-
ondary combustion which in this scheme are relatively slow. These
reactions may be represented by the following equations:
(2) C3Hg + NH3 + 3/2 02 -»• CH2-CH-CN + 3H20
(3) C3H6 + 1/2 02 ->• CH2-CH-CHO + H2
(4) C3H6 + NH3 + 202 -»• CHaCN + CO + 3H20
or
C3H$ + NH3 + 5/2 02 •»• CH3CN + C02 + 3H20
(5) C3He + 302 •* 3CO + 3H20
or
C3He + 9/2 02 -*• 3C02 + 3H20
(6) CH2-CH-CHO + NH3 + 1/2 02 -»• CH2=CH-CN + 2H20
(7) 2CH2=CH-CN + 11/2 02 •*• 6CO + 3H20 + 2NO
or
2CH2=CH-CN + 17/2 02 -* 6C02 + 3H20 + 2N02
(8) CH2=CH-CHO + 202 •*• SCO + 2H20
or
CH2-CH-CHO + 7/2 02 * 3C02 + 2H20
(9) 2CH3CN + 9/2 02 -»• 4CO + 3H20 + 2NO
or
2CH3CN + 15/2 02 -»• 4C02 + 3H20 + 2N02
22
-------
Making the assumption that the system may be approximated by
pseudo first order kinetics in the presence of excess oxygen,
Cathala and Germain (1970) derived the following relative veloci-
ties for each reaction as shown in Table 4. It is of particular
interest to note that, while acroleln is formed during ammoxidatlon
and is facilely converted to acrylonitrile under these reaction
conditions, acrolein is not an important intermediate in this se-
quence (see Figure 3) as has been previously suggested. • Table 4
also illstrates the effects of steam injection (as known to be
practiced during commercial manufacture) on the reaction rates.
Steam injection, although decreasing the overall reaction rate by
about 13 percent, has two practical consequences: (1) by decreas-
ing the rates of degradation (k5»kg), the yield of acrylonitrile
is Increased and (2) the heat of the reaction is reduced. (That
this last result is not simply one of dilution, is demonstrated by
the addition, without effect, of an inert gas.)
TABLE 4. RELATIVE REACTION RATES OF ACRYLONITRILE
SYNTHESIS AND DEGRADATION
Rate Constant Relative
Without Steam
k2 100
k3 3.3
k4 3.3
ks 2.0
kfi 535
k? 18
k8 0
kg 37
Velocity
With Steam
100
2.4
4.3
0
1680
40
0
18
Source: Cathala and Germain (1970)
23
-------
In theory, were kinetics of this type available for all inv.
mediate species, quantification of reaction by-products would be
relatively straight-forward. Though such calculations are beyond
the scope of this document, this data does clearly indicate that
there are two distinct routes to acrylonitrile via the same reactive
intermediate. (The first goes through an inline intermediate and
the second through acrolein—see Figure 4.) Additionally the data
is consistent with the reaction mechanism shown in Figure 3. Thus,
by further examination of reaction intermediates, i.e., C3Hs, C3H4,
C2H3, and CH radicals, together with consideration of their sub-
sequent reactions, additional by-products may be predicted.
Mechanism of Catalysis (Optional Section)
By further examining the reactive intermediates at the catalyst
surface, a mechanism for the catalysis of the ammoxidation of pro-
pene over bismuth molybdate may be postulated. To do this, however,
necessarily requires detailed consideration of the bonding between
metallic (i.e., bismuth and molybdenum, inorganic (i.e., oxygen
and nitrogen), and organic species in terms of molecular orbital
theory. Once understood, the formation of significant by-product
(in terms of quantity) may be examined.
Before discussing the catalytic mechanism, however, a brief
review of bonding in organometallic TT complexes is in order. Con-
sideration of the symmetry of a molecule followed by the application
of group theory permits determination of which orbitals of the metal
24
-------
end of the ligand(s) are available to combine and form molecular
orbitals, though significant bonding results only when these orbi-
tal a are of suitable and similar energy. Frequently the ligand and
metal orbitals are classified as cr-, IT, or 6-orbitals, which are
defined by the rotational axis of symmetry perpendicular to the
plane containing the organic ligand and passing:through the metal
atom. (By convention this axis is called the z axis.) Thus, the
wave function of a-orfaital does not change sign on rotation through
180° about the axis of symmetry, while for a ir-orbital the wave
function changes once, and for a 6-orbital twice upon such rotation
(see Figure 5). Unfortunately, symmetry considerations alone do
not give any information concerning the energies of the molecular
orbitals formed from metal and ligand orbitals, or even their rela-
tive orders. However, a large overlap between orbitals of similar
energy will lead to strong bonding, and the closer in energy the
interacting orbitals are, the more stable the bonding molecular
orbital will be.
The bonding of allylic Uganda (a 3-electron ligand) to molybdenum
can be treated by the above molecular orbital approach. As a first
approximation, the electrons involved in the Internal a-bonding of
the carbon and hydrogen framework are assumed to play no part in
the bonding of the allylic group to the metal. Thus, after the
a-bonds are formed, there remains a 2pz orbital on each carbon atom
which can interact with the two other 2pz orbitals to form 3
25
-------
NJ
3-electron
ir-ally!
Metal atomic orbital*
with correct symmetry
to overlap with the
M0,» ol ligandj
Classified'
at
a-«ymmet>y
Classified at
IT-symmetry
(n-l)dix
(n-l)d,,
Clatiilied at
S-tymmitry
in-\}dxt-tt
(n-l)dxy
FIGURE 5
REPRESENTATION OF LIGAND Tr-MOLECULAR ORBITALS AND THEIR POSSIBLE
INTERACTIONS WITH METAL ORBITALS
-------
TT-molacular orbitals. Again these molecular orbitals are classi-
fied as having cr-, IT-, or 6-aymmetry. Another significant feature
of allylic systems is their dynamic Behavior. From nuclear mag-
netic resonance studies, certain allylic complexes (notably tr-allyl
triphenyl phosphine palladium chloride) are suggested to be unsym-
metrically bound using both a a and ethylenic, 2 -electron ir-bond
rather than a symmetrical IT allyl system. With the rudiments of
allylic molecular orbital systems thus defined, specific reactive
Intermediates may be discussed.
As was proposed in the previous section, the first step in the
ammoxidation of propene is suggested to be irreversible associative
chemisorption of propene leading to an allylic Intermediate bonded
to a molybdenum ion. Formally this may be written as
H2C=CH-CH3 + Mb6+ + 02~ -f [C3Hs..Mo]6+ + OH" + e" (10)
where the electron may be localized on another metal ion. The bond-
Ing between the allylic species is uncertain but is suggested by
Peacock et al." (1969) to be best represented as an equilibrium be-
tween a ir-allyl complex and a a, TT system as shown in Figure 6,
where the a, IT system is the reactive intermediate.
H H
Mo Mo
Figure 6. Proposed Bonding of Chemisorbed Allylic Species
27
-------
The four centered cr-molecular orbital of the a, TT system is formed
from the filled IT bonding orbital of the allylic species and the
o
initially empty dz atomic orbital of the molybdenum. The three
centered IT molecular orbital may be formed from the empty dX2 orbi-
tal of the molybdenum cation and the non-bonding orbital of the
allyl ligand. Of these two molecular orbitala, the a orbital is
filled, whereas the ir ligand-molybdenum bonding orbital contains a
single electron. Thus, this scheme predicts a partial positive
charge on the chemisorbed allyl species and allows for reduction of
a neighboring Mo"™ cation to Mo+^ by the electron set free in re-
action (10). The alternate explanation, that is, full occupation
of both the a and IT molecular orbitals (i.e., with the electron in
equation (10) localized in the complex) does not allow for the ex-
perimentally observed paramagnetic nature of the complex. Existence
of a bonded complex, rather than a a, IT system, with the accompany-
ing electron transfer from the ligand to the molybdenum ion, leads
to the species - -
(0^5+) •• Mo+5
which, though accounting for the production of Mo , requires the
allylic ligand to be a carbenium ion; if this were the case, then
the relative oxidation rates for alkenes of differing structures
would span many more orders of magnitudes than is observed in prac-
tice (Adams, 1965).
28.
-------
_ _Subsequent reaction steps are not well understock but the
r
following pathway has been suggested by Cathala and Germain (1970);
H H
Mo Mo
[NH]
-2H
Figure 7. Reactive Intermediates Formed in Acrylonitrile Synthesis
This oxidation of the allylic species,, though conceivably leading
to further reduction of Mo^+ to Mo*+, most likely involves bismuth.
Bismuth oxide is not by i'tself an active catalyst nor is it reduced
rapidly by propene (Peacock et al,, 1969)i Yet in its absence the
yield is decreased to approximately 12 percent (Aykan, 1968). One
explanation of this data is that reduction of Bi3+ occurs either
subsequent to, or is connected with, the reduction of Mo as shown
in equation 11.
Mo5+ + B13+ * Mo6* + Bi2+ (11)
Thus the further reaction of the allylic species may be associated
by coupled reactions with the reduction of Bi3"1" as indicated in
equation 12.
29
-------
(C3H5..Mo)5H" + [N^abs) + °2~ + B13+ ** C3H3N + ^^ + Bi2+
An alternate scheme, which also assumes Mo^+ to be the active
catalyic species, proposed by Kuczynski and Carberry (1974) assumes
that the selective ammoxidation to acrylonitrile is a function of a
specific oxidation state of molybdenum, where the yield is a func-
tion of the redox process -involving oxidation of Bi3+ to Bi*+ with
concomitant reduction of Mb^+ to Mo^+. The small (VL2%) but signifi
cant yield of acrylonitrile observed over pure Mo03 is attributed
to Mo^+ which is produced thermally. This model further assumes
that reaction of ammoxidation of propene involves electron exchange
between the adsorbed propene and Mo^+. Notably, reinterpretation
of earlier experimental data (Aykan, 1968) is in 'excellent agree-
ment with this mechanism.
Oxidation, however, need not occur exclusively at a primary
carbon, and may lead to other reactive species such as C^B.^ anc^
CH. This carbon-carbon bond scission is thought to occur at the
third step of the reaction (as shown in Figure 7) at the level of
the 03114 species. Indeed, Cathala and Germain (1970) suggest,
from the symmetry of the molecular orbital, this species to be
intrinsically unstable. Formation of molybdenum-carbon double bond
at the primary carbon, aside from the obvious requirement of a
hydrogen abstraction, must also involve 90° rotation of the IT or-
bital at this carbon, as shown in Figure 8. This implies the for-
mation of a conventional 2c-2e bond at this carbon (c) with a
30
-------
z
P
p
I
J—-H
Figure 8. Proposed Bonding at the Catalyst Surface of CgH^ and
CjH^ Species
concurrent weakening of the carbon (b)-carbon (c) bond. This
species may further react in two possible ways: (1) the IT bond
between the €314 species and the catalyst is broken to yield a
single doubly-bonded species which leads to formation of acrylo-
nitrile or (2) the carbon (b)-carbon (c) bond is broken to yield
two adsorbed species, €21^3 and CH. The latter species must react
with oxygen or adsorbed ammonia to yield by-products such as
HCN, CH3CN, H2CO, and CH-jCHO.
With the propene-catalyst bonding scheme thus described, it
would be well to discuss the chemisorption of the remaining re-
actants, 02 and NH.,. Unfortunately the nature of these chemi-
sorbed species have not been studied in this system. However,
chemisorption (i.e., abstraction from propene and ammonia) of
hydrogen at the catalyst surface must certainly be on oxide ions
rather than on Mo****" cations. Thus, the hydrogen system will bear
little resemblance to the propene system as there can be no rea-
sonable intermediate other than OH~. Recent studies (Lankhuyzen,
1976) have suggested the principal role of oxygen to be the main-
tenance of the catalyst in a high oxidation state rather than a
31
-------
direct interaction of molecular oxygen with adsorbed organic inter-
mediates. Thus, evidence indicates that-oxygen is supplied by the
catalyst and subsequently the reduced catalyst is reoxidized. More-
over, this process of oxygen diffusion through the lattice of the
catalyst during catalyst reoxidation together with product inhibi-
tion (i.e., desorption of acrolein) may be rate determining.
BY-PRODUCT FORMATION
Thus far, the two principal routes of pollutant formation have
been identified: (1) impurities which are present in the feedstock
and (2) the existence of more than one reaction pathway for interme-
diate species. In the case of the former, it is pertinent to note" that
impurities, regardless of whether reactive or not, may still appear
in process effluents as pollutants. Additionally, the identity and
quantity of such impurities- are difficult to obtain in many cases
because feedstock sources may vary from day to day, irregardless of
the supplier. Prediction of pollutant formation from the second
route is even more difficult and necessarily qualitative rather than
quantitative. For convenience, the following discussion is broken
into two subsections; the first will consider pollutants arising from
feedstock contamination wtjile the second will consider deviations
from the main reaction pathway.
Pollutants From Feedstock Impurities
The principal feedstock impurities are (in approximate order
of concentration) assumed to be propane, ethane, €4 hydrocarbons,
32
-------
methyl acetylene, allene and nickel carbonyl. Accordingly, a number
of significant side reactions may arise from feestock contamination.
In reactions analogous to the ammoxidation of propene, butenes may
react to produce species such as crotonitrile,
NH3 NH3
H3C-CH=CH-CH3 ——-*• H3C-CH=CH-CN — + CN-CH=CH-CN (13)
U2 02
methacrylonitrile,
NH3
H2C=CH(CH3)2 02 » H2C=CH(CH3)CN (14)
and methacrolein or methacrylic acid,
NH3 -Q2
H2C=CH(CH3)2 Q » H2C=CH(CH3)CHO »• H2C=eH(CH3)COOH (15)
While allene is probably inert to ammoxidation, it may be hydrolyzed
to form acetone.
H2C=C=CH2
H20+ 0
H2C=C(OH)CH3—-*• H3C-(!;-CH3 - (16)
Methyl acetylene may cyclize to form 1, 2, 4-trimethylbenzene. Though
this reaction generally requires a nickel catalyst the possibility of
such a reaction should not be precluded.
33
-------
\
3CH3-CHCH
CH3
A . p" rr d7)
Ltlj ..... .. - - .
The fate of other hydrocarbon species is difficult to ascer-
tain. There are conflicting claims as to the reactivity of propane
over bismuth phosphomolybdate catalysts in the patent literature.
However, the direct ammoxidation of propane to acrylonitrile is
well known. Based on'the similarities of the catalysts used for
either feedstock, it appears unlikely that propane would be com-
pletely inert. Thus, in addition to acrylonitirile, propionitrile
and propionaldehyde may be produced.
C3H +CH84O2 * H3C-CH2-CN (18)
C3H8-K)2 > H3C-CH2CHO + H3C-CH2-COOH (19)
NH3
H3C-CH2-CN (20)
02
> H3C-CH2-CHO 4- H3C-CH2-COOH (21)
Other hydrocarbon impurities, such as ethane and ethene, probably
do not undergo ammoxidation to form the nitrile but rather are oxi-
dized to a variety of products.
34
-------
°2
C2H6 »• H3C-CHO + H3C-COOH + CO (22)
Nickel carbonyl, Chough presumed to be inert under these reaction
conditions, nevertheless represents an important emission because
of its extreme toxicity.
Significant Side Reactions
Examination of intermediate species (i.e., €3115, €3114, €2113,
and CH) together with consideration of the subsequent reactions of
these initial products, provides a logical basis for prediction of
additional by-products. However, this discussion is based on probable
rather than demonstrated reaction pathways and, as such, the existence
»
of predicted pollutant species must be verified experimentally.
While the mechanism postulated has assumed the allylic species
to yield principally an absorbed [€3114] species, oxygen may
react directly with [03115] .in the following way:*
[C3H5] + [OH] - f CH2=CH-CH2OH ' (23)
[C3H5] + [OH] - »• (CH3)2CO (24)
[C3H5] + [0] - -* CH2=CH-CHO (25)
Acrolein may also result from oxidation of allyl alcohol. Further
oxidation of acrolein yields acrylic acid.
CH2=CH-CHO + [0] — - = - »• CH2=CH-COOH (26)
*Adsorbed intermediates are denotated by enclosure within
brackets.
35
-------
The primary reaction, i.e., a second hydrogen abstraction, produces
a [03(14] species adsorbed at a catalytic site which may react in
a variety of ways with adsorbed oxygen and ammonia.
[C3HiJ + [0] - — - »• CH2-CH-CHO C27)
[C3H,J + [NH] - - + [CsH^NH] ~ - ^ CH2=CH-CN (28)
Alternatively, a carbon bond of the allylic radical may be cleaved
at the catalyst surface to yield two additional adsorbed species,
[€2115] and [CH] , which may further react with adsorbed oxygen and
nitrogen species :
[C2H3]+ [NH] - »• [C2H3NH] "H > CH3CN (29)
[C2H3] + [OH] »• CH3CHO .- (30)
[CH] + [NH] » [HCNH] —— »• NCH (31)
[CH] + [OH] > CH20 (32)
Moreover, in reactions (26), (28) and (30) each species might
reasonably react further with an adsorbed NH species or oxygen to
yield the following compounds:
+ [NH] f CH2(CN)2 (33)
CH3CHO - - > CH3COOH (34)
CH20 - - + HCOOH (35)
Succinonitrile, which has been identified in acrylonitrile wastewater
might be formed from either dimerization of the intermediate shown in
reaction (36) or from addition of hydrogen cyanide
36
-------
2[C2H3NH]
NC(CH2)2CN
(36)
to acrylonitrile (reaction 37).
HCN + H2C-CH-CN
* NC(CH2)2CN
(37)
A wide variety of heterocycles are formed from condensation
of the adsorbed species, [€3114], ^^NH] , [02^1, [C2H3NH], [CH],
and [HCNH] . Pyridine, for example, may be produced by the following
type of reaction:
[C2H3] + [C3H4NH]
[C2H3NH] + [C3HiJ
or
(38)
CH3
In a similar fashion, cyclic compounds containing two heteroatoms,
specifically pyrazine, pyrazole, oxazole, and isoxazole, may be
synthesized:
37
-------
[C2H3NH]
(42) [
Pyrazoles are suggested to result from the following types of
reactions:
[C2H3NH] + [HCNH]
[C3Hi»] + [NH]2
V
or
(43)
Oxazole and its isomer, isoxazole are formed by condensation of
oxygen containing species, in this instance an aldehyde, with an
adsorbed intermediate containing nitrogen. Thus isoxazole is sug-
gested to result from a reaction similar to the following.
0 _ »
[NH]
-u
(44)
The formation of the isomeric oxazole may result from the following
sequence.
38
-------
r N
* Q
CH2=CHCHO + [NCNH] *> II (45)
There are numerous other reactions occuring in the aqueous
phase (i.e., after the gaseous reactor effluent is quenched with
sulfuric acid), which may. lead to formation of additional by-products.
(Trivial examples of acid-base reactions, for example the reaction of
ammonia with formic acid to produce ammonium formate, need not be
considered further.) The most important and significant of these,
from the standpoint of pollution, are the reactions of nitriles,
aldehydes, and amines in aqueous solution.
Nitriles can be hydrolyzed to give either amides or carboxylic
acids as shown below:.
JT+ II TT+ II
CH3-C=N —=^7; * CH3-C-NH2 -~ »• CH3-C-OH (46)
"
The amide is the initial product, but because amides are also
hydrolyzed under, these conditions, the acid is the more common
product. Hydrocyanic acid (HCN) also may add to nitriles and imines
(formed by reaction of amines and carbonyl compounds) to give (initially)
iminonitriles or a- amino malononitriles.
39 '
-------
CH3CN
HCN
CN
H
'•
CH3-C=NH
CN
CN
CN
'
CH3-C-NH2
CN
(47)
In acid solution, these species are unstable and hydrolyze to a-amino
carboxylic acids.
CH3CHO + CN
CN
CH3CH
NH2
(48)
Where ammonia, aldehydes, and cyanides are present, a wide
variety of compounds may be expected. Probably the best known
of these reactions is the Strecker synthesis. This reaction
CN
CH3-C-NH2
CN
i
COOH
I
CH3-C-NH2
COOH
H
i
CH3-C-COOH
(49)
is broad in scope and is often used for preparation of a -ami no acids
as the cyanide is easily hydro lyzed.
CH3-CH
j
NH2
CH3CH(NH2)COOH
(50)
In the absence of ammonia, hydrocyanic acid adds to aldehydes to
yield or-hydroxy acids.
40
-------
CH3CHO + HCN *• RCH(OH)CN -~- „ RCH(OH)COOH (51)
Aldehydes and amines (in this case ammonia) also may react
to form additional species. Generally, the addition of ammonia to
aldehydes or ketones does not give useful products. Initial products
would be expected to be hemiaminals and/or imines which are generally
not stable. Indeed, imines with an a-hydrogen on the nitrogen
NH NH . .
» ii Amino
>• CHs-C + CHs-CH *• Polymers (52)
I
. OH •
spontaneously polymerize and have never been isolated in this
reaction. When stable compounds are prepared by this reaction, they
are the result of combinations and/or condensations of imines, and/or
hemiaminals with each other, or with additional molecules of ammonia
or carbonyl compound. The most important example of such a product
is hexamethylene tetramine.
^ /-YI
HCHO + NH3 +• ^ L'N (53)
Alkylpyridines may also be prepared by this reaction. Thus,
acetalydehyde, acrolein, and ammonia yield 5-ethyl-2-picoline.
41
-------
.c*H5
CH3CHO + CH2CHCHO + NHs + \ \\ (54)
A particularly interesting example of this general reaction is
the tricyclization of a, p-unsaturated aldehydes with ammonia.
Fitzgibbons et al., (1973) reports the presence of 0.4 percent
acrolein-ammonia sulfate reaction product in a primary wastewater
stream. While not identified within the general body of acrylo-
nitrile literature, this compound is most likely to be a tri-
oxaazatricyclodecane (Fritz et al., 1976).
3 H2C=C-CHO + (NHithSOi* *• °^^s^/ (55)
A reaction similar to those shown above is the condensation of
ketones, aldehydes, and ammonia.
HCH + m + CH3CCH3 - + H2NCH2CH2CCH3 (56)
' -
0
The cyanide ion in aqueous solution can also form inorganic
complexes with transition metals. In particular, molybdenum forms
42
-------
complexes of Che type [Mo(CN)s] . Mixed complexes, particularly
of the type [Mo(CN>5X], where X represents H20, NH3, or a halogen,
are also well known. The bonding of these complexes is generally
well accounted for by postulating M-CN bonding. Aside from having
possible implications as to the degradation of cyanide in natural
aquatic systems, the most important aspect of these complexes is the
increased solubility of molybdenum species.
From the foregoing discussion, by-products from the manufacture
of acrylonitrile have been predicted. However, the reactions shown
should be regarded primarily as examples rather than as a complete
predicted list of all possible reactions. The by-products from the
preceding reactions, together with feedstock impurities, are sum-
marized in Table 5.
43
-------
TABLE 5
SUMMARY OF POLLUTANTS FROM
ACRYLONITRILE MANUFACTURE
Pollutant
Reaction
Number^
Acetaldehyde
Acetaldehyde cyanohydrin
Acetic acid
Acetone
Acetone cyanohydrin
Acetonitrile
Acrylamide
Acrolein
Aerolain cyanohydrin
Acrylic acid
Acrylonitrile
Allene
Allyl alcohol
Ammonia
Ammonia acetate
Ammonium acrylate
Ammonium formate
Ammonium methacrylate
Ammonium sulfate
(3-Aminopropionitrile
P,P" - Iminiopropionitrile
P,P',P" - Nitrilotripropionitrile
Benzene
Bismuth (II)
Bismuth(lll)
Carbon dioxide
Carbon monoxide
Crotonitrile (E and Z)
Cyanides
Cyanopyrazine
Ethane
Ethene
Formaldehyde
Formic Acid
30
51
22,34
16
51
29
46
25
51
15,26
1
F
23
F
N
48
47
47
F
C
C
I
I
14
31
41
F
F
32
35
44
-------
TABLE 5 (Concluded)
SUMMARY OF POLLUTANTS FROM
ACRYLONITRILE MANUFACTURE
Pollutant
Reaction
Number*
Furonitrile
Glyconitrile
Hydrogen cyanide
Isoxazole
Lutidine isomers
Malononitrile
Methacrylonitrile
Methacrylic acid
Methyl acetylene
Methyl pyrazine isomers
Molybdenum (IV)
Molybdenum (V)
Molybdenum (VI)
Nickel carbonyl
Nicotinonitrile
Nitrogen oxides
Oxazole
Propane
Propionaldehyde
Propionic acid
Propionitrile
Pyrazine
Pyrazole
Pyridine
Succinonitrile
Sulfur dioxide
Sulfur trioxide
Toluene
Trimethyl benzene
13
51
31
44
39
33
14
15
F
41,42
F
54
C
45
F
19,27
19
18
40-42
43
38
36,37
I
I
F
17
The following notations are used for brevity:
F
C
I
P
N
feedstock impurity
species results from catalyst attrition
species resulting from incineration of waste
products.
product
neutralization product.
45
-------
PROCESS CONFIGURATION FOR ACRYLONITRILE MANUFACTURE
Although a large number of different process configurations
are described in the patent literature, only the general features
of the SOHIO process and two particularly promising process modifi-
cations will be considered explicitly. Furthermore, since the
process in actual practice is likely to be somewhat different than
as described in SOHIO patents, the following description must be
regarded as generic rather than specific to a given plant. The
reaction and crude extraction portions of the process are shown in
Figures 9 and 10, while further product separation and purification
steps are shown in Figure 11 and 12.
The Generic SOHIO Process
Approximately stoichiometric quantities of propene, ammonia,
and air are typically, fed to fluidized bed catalytic reactor*
(see Figure 10) at pressures and temperatures between 135 to 310 kpa
and 400 to 500°C, respectively. Additionally, steam is injected,
together with the above reactants, to increase both the selectivity
*For reasons discussed previously, a silica supported bismuth
phosphomolybdate catalyst composition is assumed Co be in current
use; however, other compositions might reasonably be used. The
principal modification of bismuth molybdate catalysts, is the
presence of an additional promoter(s) selected from the following
groups: alkali, metals, alkaline earth metals, the third period
transition metals, group I and II b metals, tin, lead, and antimony
(Grasselli et al., 1976).
46
-------
Propene »
Ammoniar
Steam -
"2S04
Volatile Impurities Co Flare
2
u o
4) U
03
Steam -
Acetonltrile •
» P. 0
5 P. i
*J -H 13
U M iH
q) H O
PC M O
Azeotropic
Reagent
Steam*
. M 00
;*3
01 M fH
U U O
•< « O
Volatile »,9
Impurities
',3,33
Purified
Acrylonltrlle'
Waste Treatment
IjL:
^ To Wastewater Treatment
To Acetonltrlle
Purification.
T
i 7,!8
To Uasteuater Treatment
To Wastewater Treatment
Source: after r-ilzgiblxjiH el a\. cl 971
FIGURE 9
THE SOHIO PROCESS FOR ACRYLONITRILE MANUFACTURE
-------
for, and yield of, acrylonitrile. Because the reaction is highly
exothermic* (&H = -150 kcal/mole), the active catalyst zone is
equipped with heat transfer coils to maintain reaction temperature
which generates high pressure steam for process use. Indeed, under
normal operating conditions essentially all steam requirements are
met internally.
Although the theoretical amount of ammonia required is one
mole per mole of propene, excess ammonia is used to suppress the
formation of oxygenated compounds (e.g., acetone, acrolein); fur-
thermore, about 20 percent of the ammonia fed reacts with the
catalyst to form nitrogen and water. A large excess, however,
decreases the conversion of propene to acrylonitrile. Thus, the
optimum NH3/C3H6 ratio is reported to lie between 1:03 to 1:07:1
(Dunn, 1976). Excess oxygen (approximately 4 to 7 mole percent)
is necessary to replace the oxygen consumed at the catalyst and
further to maintain a high state of oxidation (e.g., Mo°+) in the
catalyst. An analysis of the hot gaseous reactor effluent is shown
in Table 6.
*The heat of reaction for propene to acrylonitrile is ~123 k cal/
mole in the gas phase at 25°C. Oxidation and combustion of acrylo-
nitrile and other side products, together with the heat of reaction
of these products, have the net effect of increasing the exother-
micity to over 150 kcal/mole.
48
-------
OLEFIN . ,
FEED
DISENGAGING
ZONE
REGENERATION
ZONE 8
Source: Sheely (1976).
FIGURE 10
CROSS SECTION OF A REPRESENTATIVE CATALYTIC
FLUIDIZED BED REACTOR
49
-------
TABLE 6
ANALYSIS OF THE REACTOR EFFLUENT GASES
Component Mole %
Non-condesible Gases 62.59
(CO, C02, N2, 02)
H20 18.10
NH3 3.77
HCN 3.77
Acetonitrile 0.38
Acrylonitrile 11.31
Acetone
Acrolein . 0.08
Propionitrile
Polymeric By-products Trace
Source: Sheely (1975).
While there are some variations, the fluidized bed catalytic
reactor (Figure 10) is equipped with a series of sieve trays which effec-
tively create catalyst zones within the reactor. 3y introducing air to
the lowest zone of the catalyst bed upstream of the propene and
ammonia inlets, catalyst deactivation is minimized; moreover, if
a portion (10 to 30 percent) of the ammonia is introduced to the
regeneration zone as above, formation of carbon monoxide and dioxide
50
-------
is minimized (Sheely, 1976). A space is provided at the top of the
reactor to allow for catalyst disengagement from the effluent gases
which then must pass through one or more cyclone collectors (in
series) before exiting from the reactor. Entrained catalyst particles
in the effluent gases are removed by the cyclones and returned to the
regeneration zone by a dip leg of the cyclone which extends into the
bottom of the reactor.
Inevitably, a certain portion of the catalyst, which accumu-
lates on the surface of the structural components of the cyclone, is
reduced by prolonged contact with the effluent gases. Aside from
causing catalyst deactivation, the particles tend to agglomerate,
break loose, fall into the catalyst bed, and disrupt fluidization. A*
simple modification to prevent this is the fitting of a perforated
plate around the structural components above the cyclone inlet, thus
isolating the catalyst bed from the- top of the reactor. Addition-
ally, an inert gas (e.g., €02).may be continuously fed to this
section to minimize catalyst reduction (Callahan, 1972).
Another cause of catalyst deactivation is the loss of molybdenum,
possibly as a result of either particle attrition or formation of a
volatile organo-metallic compound (e.g., MoCCO^), during the course
of the reaction. The traditional approach is either to remove the
catalyst from the reaction zone for subsequent reactivation or to
maintain a continuous bleed and fresh catalyst make-up. Another
51
-------
'solution, however, is to reactivate the catalyst in situ without
disruption of the reaction by adding molybdenum ( 50 percent by
weight) on a silica support.* Using this method, the catalyst may
be reactivated within a period of 48 hours (Callahan et al., 1975).
After a mean residence time of 1 to 15 seconds the hot gaseous
effluent is quenched and scrubbed in a counter-current manner in the
quenching column with an ammonium sulfate/sulfuric acid solution to
remove excess ammonia. The resultant solution, which contains, aside
from ammonium sulfate and sulfuric acid, significant quantities of
catalyst fines, cyanides, and a wide variety of organic compounds, is
split into two streams. The first of these streams is recycled to
the quenching column, while the second is conventionally distilled in
the wastewater stripping column to recover low boiling organic com-
pounds which are combined with the gaseous effluent of the quenching
column. The recycle ratio is adjusted to maintain an ammonium sul-
fate concentration of approximately 15 to 30 percent (maximum). The
bottoms from the wastewater stripping column represent the largest
single pollutant load within the acrylonitrile manufacturing process;
included among the numerous species typically present are significant
*0ther supports such as alumina, boron phosphate, silica-aluminum,
silicon carbide, titania, or zirconia may be used. However, that
the support material have some degree of physical instability, after
the molybdenum is transferred to the oxidation catalyst, is parti-
cularly useful. When the molybdenum concentration falls to a low
level, the support material disintegrates and is carried out in the
reactor effluent. Thus, the effective concentration of catalyst is
not decreased by an inert support remaining after regeneration.
52
-------
amounts of ammonium sfulfate, acetaldehyde, acetic acid, acrylamide,
acrylic acid, fumaronitrile, succinonitrile, polyacrylonitrile,
polyacrylamide, and ammonia-hydrogen cyanide-carbonyl condensation
products. To minimize the fouling of the distillation column by this
polymeric material, acetonitrile is added to the feed stream of the
wastewater stripper (Ohashi et al., 1972). Table 7 lists the ;
concentrations of typical components of the quenching column bottoms
and the wastewater striping column overhead product.
TABLE 7
PRINCIPAL SPECIES PRESENT IN QUENCHING COLUMN
BOTTOMS AND WASTEWATER STRIPPING COLUMN OVERHEAD PRODUCT
Compound
Acrylonitrile
Acetonitrile
Hydrocyanic Acid
Ammonium Sulfate
Water
%, by
Quenching Column
Bottom Product
1.0
0.15
0.70
15.00
balance
Weight
Wastewater
Overhead
6.0
20.0
6.0
-
68.0
Stripper
Product.
Source: Ohashi et al.; 1972.
The ammonia free gaseous product is next counter-currently
extracted with a conventional scrubber (i.e., the recovery column)
using water to recover condensable organic products as an aqueous
53
-------
solution.. Noncondensable reaction products,' for example nitrogen,
excess oxygen, and unreacted propene, are vented to a flare. The
now aqueous product stream is separated by extractive distillation
(extractive distillation column) using water as a solvent and yields
an acrylonitrile rich stream overhead and a dilute solution of
acetonitrile as a bottoms product. The acrylonitrile rich overhead
stream, containing water, hydrogen cyanide, and volatile impurities,
is first azeotropically distilled (azeotropic distillation column)
with a suitable reagent to separate volatile components from acrylo-
nitrile. Acrylonitrile is subsequently purified by conventional
distillation (acrylonitrile distillation column).
The acetonitrile rich bottom product'from the extractive distil-
lation column can be further concentrated to approximately 60 to 70
weight percent acetonitrile by recycling a portion of this stream to
the recovery column. Acetonitrile is further separated by steam-
stripping (acetonitrile stripping column) where the acetonitrile,
together with hydrogen cyanide and water, is removed overhead. A
portion of this stream is returned to the stripper as a reflux, while
the remainder is, first, azeotropically distilled and second, conven-
tionally distilled for final purification as shown in Figure 11.
The composition of crude acetonitrile is shown in Table 8. During
this distillation, hydrogen cyanide is also removed as a relatively
"clean" gas which may be further purified, along with hydrogen cyanide
recovered from the azeotropic distillation column, for reuse or sale
54
-------
1 en
Crude
Acetonitrile
Azeotropic
Reagent
'
/
§
O T
O r-
M r-
*J T
8*.
0
V
1
1
1
1
}l
1 3
) H
1 t?
) CJ
/
-x'
r^
Decanter ? ;
Y'
l»i
^Volatile Decomposition
A. Products
:3 j
;ti
k iJ ^Purified :
F ! g §! r Acetonitrile
' 4J 91
-------
TABLE 8 i
COMPOSITION OF CRUDE ACETONITRILE
Compound %, mole
Hydrocyanic Acid 6.01
Acetonitrile 70.43
Acetone 1.94
Water 20.03
Polymeric Material 1.59
Source: Sheely, 1969
(see Figure 12). It is important to note that because limited
•
markets exist for both acetonitrile and hydrogen cyanide, these
by-products may be treated as wastes and incinerated.
As indicated in Figures 12 and 13, stabilizers may be employed
to inhibit product polymerization; either acetic or sulfuric acid is
added to the hydrogen cyanide, while pyrogallol or hydroquinone are
used to stabilize 'the purified acrylonitrile. Small amounts of
cyanohydrins which may co-distill with acrylonitrile are reported to
be stabilized by the addition of oxalic acid which prevents dissocia-
tion to the parent carbonyl compound and hydrogen cyanide (Idol,
1964). Heterocyclic nitrogen bases, notably oxazole, may impart an
undesirable color to acrylonitrile polymers. Oxazole which is not
56
-------
Acetic-
Acid
Concentrated
Sulfuric Acid"
Anhydrous
HCN
•>" Purified HCN
To Wastewater Treatment
FIGURE 12
HYDROCYANIC ACID PURIFICATION
Source: Scherhag and Hansweiler (1972).
57
-------
easily removed by distillation may be removed by: (1) complexation
with metals such as cadmium (Hall and Francis, 1970), zinc, cobalt,
or nickel (Maute, 1972); (2) adsorption on cationic ion exchange
resins (Darcas and Tcherkawsky, 1971), silica, alumina, or decoloriz-
ing clay (Allirot et al., 1972); or (3) further fractional distil-
lation (Hadley, 1970).
Significant Modifications to the SOHIO PROCESS
Not surprisingly, there are numerous "improvements" of the
SOHIO process to be found in the patent literature; the economic
feasibility of many of these modifications is, however, dubious.
The following discussion addresses, in a general context only,
those procedures which may significantly reduce the waste load from
acrylonitrile manufacture.
As noted previously, the effluent stream from the wastewater
stripping column represents the major pollutant load of the manufac-
turing process. This results from two basic features of the ammoxi-
dation reaction: (1) HCN is a major by-product ( 0.07 mole HCN/
mole of C3H$); and (2) ammonia is used in excess (typically 10 to
20 percent) to favor acrylonitrile over oxygen containing by-products.
Unreacted ammonia must then be removed from the reactor effluent to
minimize condensation of ammonia and hydrogen cyanide'to form com-
pounds such as p-aminopropionitrile, (3, p'-iminodipropionitrile, or
(3,(3' , p"-nitrilotripropionitrile.
58
-------
An ideal solution for Che reduction of this waste load (parti-
cularly 'for the polymeric portion which is most troublesome) would be
the total elimination of ammonia and/or hydrogen cyanide from the
reactor effluent without a concomittant decrease in the yield of
acrylonitrile. Though these goals appear to be mutually exclusive,
the presence of excess ammonia in the effluent gas, in fact results
from the competition between ammonia and hydrogen cyanide for
propene (Sheely, 1974). By recycling hydrogen cyanide to the reactor
above the ammonia feed port and concurrently decreasing the ammonia/
propene ratio, ammonia becomes the limiting reactant. Unreacted
propene and acrolein then further react to yield acrylonitrile.
Thus, both the concentration of ammonia and hydrogen cyanide in the
reactor effluent are claimed to be significantly reduced by this
procedure.
Another approach for reduction of the waste load from the
wastewater stripper is the recovery of ammonium sulfate. Within
this general context, however, there are several specific methods
which might be used. These methods can be conveniently subdivided
into two groups: those which represent an extensive modification of
the SOHIO process, and those which are directed primarily to "end-of-
pipe" recovery. In the following discussion only process modifications
will be considered; all other recovery techniques are classified as
physical pretreatment of a waste stream and accordingly are discussed
in Section IV.
59
-------
s f
the only acrylonitrile manufacturing process specific to ammonium
sulfat'e recovery believed to be commercially used is described in
patents jointly held by two large European chemical manufacturers,
Erdolchemie Ltd. and Farben Fabriken Bayer (Erdolchemie-Bayer).
While the basic details of the fluidized catalytic reactor are
similar to those of the SOHIO process (see Figure:10), recovery and
the- subsequent purification of acrylonitrile are substantially
different, as indicated in Figure 13 (Hausweiller, 1970). The
gaseous reactor effluent is first washed with water to remove organic
polymers and catalyst fines which are removed as a bottom stream.
The concentration of polymers and catalyst in the washer-effluent may
reach 40 percent. Approximately one-half to three-quarters -of this
waste is organic- material, and after separation of the catalyst, may
be conveniently incinerated. The gas leaving the washer is next
divided into two streams: the first is scrubbed with an ammonium
sulfate/sulfuric acid solution to neutralize all ammonia present.
Upon saturation, ammonium sulfate cyrstallizes and is removed as a
slurry for subsequent drying. Small amounts of organic polymers are
removed in a circulation vessel, though their accumulation is claimed
to be minimal. The second gas stream is washed in a separate scrubber
with an unsaturated solution of ammonium sulfate and 3 to 5 percent
sulfuric acid (i.e., sufficient to neutralize all ammonia). The
resulting solution (or slurry) of ammonium sulfate is withdrawn and
60
-------
Propene-
. Ammonia^
Air
! Steam
Waste Gas
To Incineration
Acrylonltrlle
aVd HCN
Source: Uausvxttir €l al. 11970.
Steam
Acetonltrile
>Steam
Crystalline
Ammonium
Sulfate
FIGURE 13
ERDOLCHEMIE BAYER PROCESS MODIFICATION FOR
ACRYLONITRILE MANUFACTURE
-------
fed to the first washer. Subsequent evaporation of a portion of this
•; ;'
water yields additional ammonium sulfate of fertilizer grade purity.
Upon recombination of the ammonia free gas streams, the condens-
able organic compounds (i.e., acrylonitrile) are recovered in a
conventional scrubber (recovery column). The resultant aqueous
solution is then extractively distilled to yield an overhead product
of hydrogen cyanide and acrylonitrile. Both products may be separated
and purified by procedures similar to those of the SOHIO process (see
Figures 9 and 12, respectively). A portion of the bottom stream
from the extractive distillation column is recycled as wash water to
the first column. The acetonitrile and other volatile components are
thus removed as a gaseous overhead product, which is subsequently
incinerated (Hausweiller, 1970).
Perhaps the best method of all for elimination of waterborne
pollutants, at least from acrylonitrile manufacture, would be the
combustion of all major waste streams; however, the high salt con-
centration together with low fuel values of major waste streams
(i.e., Point No. 1 and 3) in the generic SOHIO process render incin-
eration impractical. Therefore, yet another process modification is
based upon the selective absorption of acrylonitrile- in a hydrocarbon
solvent; unreacted ammonia and by-products such acetonitrile and
hydrogen cyanide are not condensed but remain with absorber off-gas
for ultimate disposal by incineration (Sheely, 1975).
62
-------
i
f
'Again the basic reaction conditions and catalytic reactor design
! ' '
are the same as the SOHIO process; significant differences .only
appear in the recovery and disposition of waste materials (see Figure
14). The reaction effluent is first adiabatically quenched (hot
quench column) with water and a high boiling organic solvent (e.g., a
kerosene boiling between 250 to 400°C) to condense polymeric by-products.
The condensed polymers and any catalyst present in the reactor effluent
are subsequently bled from the quench column in a small stream of un—
vaporized solvent. The partially quenched effluent is next extracted
in a conventional column (hot absorber) in a counter-current manner
at temperatures sufficient to prevent condensation of water* At this
temperature practically none of the ammonia and only a minor amount
of hydrogen cyanide are ab'sorbed because of their high vapor 'pressures;
• "
additionally, only a portion of by—products such as acetonitrile,
propionitrile, and water are extracted because of the non ideal
behavior of the solvent. To minimize solvent losses, the overhead
vapors are scrubbed with a high boiling oil.* Acrylonitrile and
the hydrocarbon solvent are removed as a bottom stream while the hot
absorber off-gases are incinerated. (Ammonia, hydrogen cyanide,
*The choice of the solvent and scrubbing oil will be determined in
part by their boiling points. Preferably the solvent should have a
boiling point of at least 40°C higher than acrylonitrile (b.p. 77°C)
and approximately 100°C less than that of the scrubbing oil. The
choice of scrubbing oil and solvent, insofar as their boiling points
are concerned, is also influenced by how much oil and solvent overhead
loss is sufficient to provide fuel values for the incinerator.
63
-------
Propylene
Ammonia
Makeup
Scrubbing
Oil
XII
kxiiBi.ai.ui
•
rJ -
Vacuum.
To Vacuum
.Reactor Hot Quench Hot Oil Recovery Lights Product
. Column Absorber • Column Column ' Column
Source: Sheely (1975). FIGURE 14 *
BADGER PROCESS MODIFICATIONS FOR ACRYLONITRILE
MANl^JTURE
-------
.acetonitrile, propionitrile, and vaporized solvent furnish the
necessary fuel values.) Volatile by-products are removed in the
"lights" column overhead for recycle to the absorber while acrylo*-
•
nitrile and the solvent are removed as column bottoms. This product
is distilled in the product column to recover substantially pure
•
acrylonitrile overhead. Any inert gases present are withdrawn under
vacuum for subsequent incineration. The solvent, removed as a bottom
stream from the bottoms column, is recycled to the hot quench column.
The mixture of scrubbing oil and solvent removed from the absorber is
vacuum distilled for solvent purification and oil recovery, The
solvent recovered overhead is recycled to the absorber and lights .
column, while the scrubbing oil is recycled to the absorber.
Although the economic practibility of this method has yet to
be evaluated in the open literature, such a system does appear to
warrant further investigation for the following reasons: (1) the
polymeric by-products are almost completely removed from the reactor
effluent in the quench column in a form easily incinerated; (2) the
remaining reaction by-products are also disposed of by incineration.
Thus, both the wastewater stripper and corrosion problems attendant
to handling of sulfuric acid, in the generic SOHIO process are elimi-
nated. Furthermore, recovery of ammonium sulfate, only a marginally
economic operation at best, based on current demand, is eliminated.
Though incineration is not without some problems - formation of
65
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carbon monoxide and nitrogen oxides, in the case at hand - the Badger
process appears to be potentially the "cleanest" procedure for the
manufacture of acrylonitrile.
Effluent species have been previously identified and summarized
in Table 5. This information, together with the generic SOHIO
process configuration previously formulated, is presented in Figure
15.
66
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POINT 1 I
Acetaldehyde
Acetic acid
Acetonltrlle
Acroleln
Acrylamide
Acrylic acid
Acrylonltrlle
Ammonium Sulfate
Catalyst fines
Cyanides
Cyanohydrins
Fumaronitrile
Hydrogen cyanide
Succinonitrile
Trioxaazatrlcyclotrldecanes
POINT 2 |
Acetonltrlle
Acrylonltrlle
Allyl alcohol
Benzene
Butenes
Ethane
Ethene'
Furan
Hydrogen cyanide
Methane
Propane
Propene
Proplonaldehyde
Toluene
POINT 3 |
Acetaldehyde
Acetic acid
Acetonltrlle
Fumaronitrlle
Maleonltrlle
Nlcotlnonitrile
Succinonitrile
Hydrogen cyanide
Propene— — +
AaBonU— ^^
«r=:
r
"2^4 Volatile
A A
Volatile iBpurlttt-fl
V
Purified
Acr,lo,,ll,llc
Acetonlcrlle
POINT 4 i
Acetone
Acetaldehyde
Acrolein
Hydrogen cyanide
Propionaldehyde
. POINT 6:
Acrylonitrile
Pyrazlne iaomers
Pyrazole Isomers
Pyrldine Isomers
Cyanohydrins
POINTS
Acrylonitrile
Isoxazole
Oxazole
Nitrogen containing bases
POINT?
Acetonltrlle
Acetone
Benzene
Cyanides
POINT 8
Acetonitrile
Polymeric material
Salts
POINTS
Acetaldehyde
Acrylonitrile
Benzene
Butenes
Furan
Propene
Pyridines
FIGURE 15
SIGNIFICANT POLLUTANTS FROM
ACRYLONITRILE MANUFACTURE
67
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SECTION III
WASTEWATER TREATMENT
INTRODUCTION
In the first half of this report, potential pollutants from the
manufacture of acrylonitrile were identified. The remainder of the
report will discuss specific industrial wastewater practices for
handling those waste streams identified, and evaluate alternative
treatment practices for removing toxic contaminants from the process
effluents prior to discharge to the environment.
INDUSTRIAL WASTEWATER TREATMENT PRACTICES
In selecting the appropriate mode of treatment for an industrial
waste stream, factors other than just the simple reduction of standard
wastewater parameters should be examined. Specifically, the following
areas merit consideration.
• The origin of toxic pollutants, in terms of both reaction
chemistry and process configuration;
• The identification of inhibitory or refractory components of
the waste stream;
• The acceptability of current disposal practices;
• The adequacy of current treatment practices; and
• The compatability of treatment processes in achieving the
effluent requirements.
Wastewater management of toxic effluent streams involves both
in-plant control technology and end-of-pipe treatment practices.
Procedures to reduce the strength and volume of the final effluent
69
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stream may include improved housekeeping practices, waste stream
segregation, and reuse or recycle of process streams. End-of-pipe
treatment technology which, for purposes of this report, refers to
both pretreatment and final treatment practices, may involve physical-
chemical treatment techniques, biological treatment, or a'combination
of the above. Waste disposal by subsurface injection, although widely
accepted in the past, is being more closely regulated by Federal and
State agencies, and is generally discouraged when alternate treatment
and disposal systems are available.
The selection of the mode of treatment is largely dependent on
the volume of waste to be treated and the pollutants present.
Traditionally, the efficiency of a treatment method is measured by
the percent removal of 5-day biochemical oxygen demand (BOD5) and
total suspended solids (TSS). Chemical oxygen demand (COD), or
total organic carbon (TOC) are commonly used to measure the strength
of industrial waste. Discharge standards commonly include specific
restrictions on the level of ammonia-nitrogen, total Kjeldahl nitro-
gen (TKN), and where applicable, free cyanide. A brief, general
review of biological and physical treatment methods follows.
Biological-treatment involves the breakdown and stabilization
of organic material by aerobic or anaerobic microorganisms. Treatment
processes available for industrial applicati.on include: variations
of the activated sludge process, aerated lagoon systems, oxidation
ponds, trickling filters, rotating biological discs, and anaerobic
70
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lagoons or digesters. Historically, the activated sludge process,
in which aerobic microorganisms are mixed with the influent waste-
water and subsequently removed as a sludge, has had the broadest
application to industrial wastes. Detention periods and process
configurations may be modified to achieve the desired level of BOD
removal, nitrification, and in some cases, denitrification. The
toxicity of the waste, the biodegradability of the waste (typically
judged by the BOD/COD ratio), and the metabolic rate of the micro-
organisms (i.e., the effective removal rate) all influence process
efficiency.
Physical-chemical treatment techniques may be used alone or in
combination with biological processes to-achieve effluent standards.
Neutralization and equalization, for example, are commonly used as
pretreatment steps prior to activated sludge treatment. Soluble
organic compounds not effectively removed by biological treatment may
be separated from waste streams by adsorption (generally on either
carbon or an ion exchange resin), stripping techniques, distillation,
solvent extraction, or membrane processes (i.e., ultrafiltration,
reverse osmosis, electrodialysis). Oxidat'ion, acid or alkaline
hydrolysis, photolysis, chlorinolysis, or incineration have also been
used to degrade organic species in process wastewater streams.
The selected mode of treament is determined by the availability
of different treatment operations and processes to economically
71
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achieve the desired effluent. The design criteria for a specific
treatment facility will vary with the strength and volume of the
wastewater stream and the final means of"effluent disposal. In
each case, the process configuration and plant layout should be
examined to identify point source discharges and pollutant loadings.
Where possible, in-process changes, stream segregation, and solvent
reuse should be implemented to reduce the process waste load.
CURRENT TREATMENT OF WASTEWATER FROM ACRYLONITRILE MANUFACTURE
Wastewater Characteristics
Two major process waste streams are generated during the manu-
facture of acrylonitrile: the quench column bottoms (Point No. 1)
and the recovery column stripper bottoms (Point No. 3) (See Figure
9). Other point sources, such as, Point No. 5, the still bottoms
•
from the purification of acrylonitrile (and if present, wastes from
the purification acetonitrile and hydrogen cyanide, Points No. 7, 8,
and 9) and "surface runoff"* represent substantially smaller waste-
loads. Table 9 lists typical concentrations of selected pollutants
found in these streams, and may be regarded as representative of the
waste loads from any plant using the SOHIO process (see Appendix IV),
Unfortunately, a typical analysis of the distillation column bottoms
is unavailable; however, the gross composition of each of these
* Surface runoff is defined as wastewater resulting from process
spills, leaks, cleanup, and other general maintenance operations.
72
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streams (Points No. 5, 7, and 8) are presented in Figure 15, which
provides a summary, point source-by-point source, of all significant
pollutants predicted from acrylonltrile manufacture.
Data characterizing the combined waste load from an acrylo-
nitrile manufacturing facility have been previously published by EPA
as part of support material for the development of effluent limita-
tions (Train, 1975). However, as those effluent limitations were
remanded in 1976, (questionable prodedures were claimed to have been
used for the measurement of wastewater parameters) these data are not
*
provided within this report. Further details concerning the sampling
of raw waste loads at acrylonitrile plants may be found in Appendix
IV, as correspondence from duPont and SOHIO to the EPA, date.d 4
.February 1976 and 2 February 1976, respectively.
Federal and State Discharge Requirements
The Federal Water Pollution Control Act Amendments of 1972
(PL 92-500) further extended the scope of the.Federal Water Pollution
Control Act of 1965, as previously amended in 1966 and 1970. The
major objective of the Act is to restore and maintain the chemical,
physical, and biological integrity of the Nation's waters. Among the
goals and policies set forth by the Act, the following address
industrial point source discharges to navigable streams:
• It is the national goal that the discharge of pollutants
into the navigable waters be eliminated by 1985.
73
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TABLE 9
WASTEWATER CHARACTERIZATION OF MAJOR PROCESS STREAMS
FROM ACRYLONITRILE MANUFACTURE1.2
Flow, gals /rain.
pH, units
Alkalinity
NH3-N
TKN-N
N03-N+N02-N
Wastewater
Column
Bottoms
155
5.1
15,000
Recovery Column
Stripper
Bottoms
180
7
220
Surface
Runoff3
150
9
275
60
65
4
Clean
Water4
225
9.5
190
5
13
17
CN~
Sulfate
Acrylonitrile
Acetonitrile
Total Solids
Dissolved Solids
Suspended Solids
Volatile Suspended
Solids
BOD
COD
7.0006 225
32,000 500
500(or less) -<10
3,000 35
95,000 10,000
95,000 10,000
<500 <100
80,000
17,000
30
17
400
500
65
25
30
75
1 See Appendix IV. Provided by SOHIO, from acrylonitrile manufacture at the
Vistron Plant, Lima, Ohio.
2 Units in mg/1, unless otherwise indicated.
3 Represents a constant flow rate, as pumped from an equalizing/storage basin and
is associated with just .acrylonitrile manufacture. The waste load is attributed
to general housekeeping practices.
4 Composed primarily of cooling tower blowdown.
5 Reported as 4780 mg/1 in a later correspondence with SOHIO, dated
18 January 1978.
-------
• It is the national goal that wherever attainable, an
interim goal of water quality which provides for the
protection and propagation of fish, shellfish, and
wildlife and provides for recreation in and on the
water be achieved by July 1, 19B3.
• It is the national policy that the discharge of toxic
pollutants in toxic amounts be prohibited.
• It is the national policy that a major research and
demonstration effort be made to develop technology
necessary to eliminate the discharge of pollutants
into the navigable waters, waters of the contiguous
zone, and the oceans.
In committing the nation to meeting these goals and policies, the Act
established an implementatin schedule for compliance. To this end,
Section 301(b) of the Act requires the following:
(1) Not later than July 1, 1977, effluent limitations for
point sources, other than'publicly owned treatment works,
shall require the implementation of the best practicable .
control technology currently available (BPT) as defined by
Section 304. Those discharges to publicly owned treatment
works shall comply with any applicable pretreatment stand-
ards defined under Section 307 of the Act.
(2) Not later than July 1, 1983, all categories and classes
of point sources, other than publicly owned treatment works
will require application of the best available technology
economically achievable (BAT), which will result in reason-
able further progress toward the national goal of eliminating
pollutant discharge. In the case of the discharges of a
pollutant into a publicly owned treatment works, compliance
with applicable pretreatment standards is required.
Additionally, the Administrator of the EPA, under Section 304(b)
of the Act, is directed to promulgate regulations which identify in
terms of wastewater characteristics, the degree of effluent reduction
attainable through the application of BPT and BAT for classes and
categories of point sources (other than publicly owned treatment
75
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works). These regulations, or effluent limitation guidelines, are to
specify those factors related to the establishment of BPT and BAT
control measures and practices, such as, the process employed, the
age of equipment, process changes, the engineering aspects of the
application of various types of control techniques, non-water quality
impacts, and[the cost of achieving such effluent reduction.
The organic chemicals industry is_highly complex, covering
two Standard Industrial Classification (SIC) Groups in which 260
product-process segments have been identified. Thus, for the
purpose of developing effluent regulations, the EPA has categorized
selected segments of the industry into two phases. On April 25,
1974, Part 414 was added to Title 40 of the Code of Federal Regula-
tions, establishing final effluent limitations for existing sources
in 40 product-process segments (Phase I). Additionally, performance
and pretreatment standards for new sources in the organic chemical
manufacturing point source category were defined. Interim final
regulations for Phase II were published on January 5, 1976, amending
40 CFR to include 27 additional product-process segments and a new
subcategory. Chemicals were grouped within four subcategories on the
basis of similarities of process operations. The manufacture of
acrylonitrile by the ammoxidation of propene is included as part of
"Subcategory C - Aqueous Liquid Phase Reaction Systems."
In establishing Phase I and Phase II regulations, the Agency
acknowledged the toxicity of certain organic chemical manufacturing
76
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wastewaters and the potential hazard to the environment; however,
faced with a mammoth task and rapidly approaching deadlines, effluent
limitations were written in terms of the conventional parameters
of 6005, TSS, COD, and pH. Furthermore, since biological treatment
was the identified BPT for the organic chemicals point source cate-
gory, effluent limitations were established for specific pollutants
known to be inhibitory to biological treatment and detected in
significant concentrations in given waste streams. Thus, as shown in
Table 10, an additional effluent limitation was imposed for the
discharge of cyanide from acrylonitrile manufacturing efluent.
Concurrent with the promulgation of BPT regulations, EPA pro-
posed effluent limitations and guidelines for existing sources to be
achieved by the application of BAT, and standards of performance for
new point sources (See Table 10). BAT for the organic chemicals
manufacturing category has been defined as biological treatment
followed by adsorption with activated carbon. Notably, wastewaters
from the manufacture of acrylonitrile were not included in the
development of pretreatment unit operations, as listed in the "Develop-
ment Document for Interim Final Effluent Limitations and New Source
Performance Standards for the Significant Organic Products Segment of
the Organic Chemicals Manufacturing Point Source Category" (issued by
the Agency as a support document for setting interim final regulations)
(Train, 1975). As such, no limitations were proposed as pretreatment
standards for existing sources that discharge to publicly owned
treatment works.
77
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TABLE 10
BPT and BAT Effluent Limitations for Acrylonitrile Manufacture
Effluent
Characteristic
Effluent Limitations kg/kkg (lb/1000 Ib) of Product
BPT - BAT
Daily 30-J)ay Daily 30-Day
Maximum Average Maximum Average
COD
BOD.
TSS
Cyanide
pH
-
1.6
0.51
0.0045
6.0-9.0
-
0.82
0.27
0.0022.
-
42
0.18
0.26
0.0022
6.0-9.0
22
0.095
0.14
0.0011
-
Source: Federal Register, Vol. 41, No. 2, January 5, 1976.
As part of the rule making process, the EPA is required to gather
information and comments pertinent to proposed and established regu-
lations. Acrylonitrile manufacturers, in particular, took issue with
the sampling and analytical techniques used by the EPA contractor in
developing effluent limitations. Indeed, the EPA eventually conclu-
ded that the contractor retained by the Agency had used procedures to
measure certain parameters of the industry wastewaters "which may
have been, in certain instances, faulty" (Federal Register, April 1,
1976). Thus, in accordance with the U.S. Court of Appeals, the EPA
revoked all of 40 CFR 414 regulations concerning organic chemicals
with the exception of those concerning butadiene manufacture. At
this time, there are no existing federal regulations under PL 92-500,
78
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Title III governing the point source discharges from the manufacture
of acrylonitrile.
Under Title IV of PL 92-500, however, any discharger to naviga-
ble waters must be certified by the State in which the discharge
orginates and issued a permit under the National Pollutant Discharge
Elimination System (NPDES). Each NPDES permit defines effluent
limitations and monitoring requirements, as well as a schedule of
compliance. In the absence of effluent limitation regulations,
discharge limitations have been established on a case-by-case basis,
as authorized by the State agency and approved by the Regional Water
Enforcement Board of the EPA. NPDES permits are to be "revised or
modified in accordance with toxic effluent standards or prohibition"
under Section 307(a) of the Act."
While injection wells are not specifically addressed by the
*
NPDES legislation, EPA has established rules and regulations govern-
ing waste disposal wells within the framework of the NPDES system.
Industrial dischargers are typically required to monitor flow rate,
injection and annulus pressure for each well; moreover, no new wells
may be put into operation without re-application and subsequent NPDES
permit modification. Deep well disposal is no longer considered to be
a "viable" disposal method by EPA (Federal Register, January 6,
1977). Thus, in an effort to control such practices (though short of
outlawing deep well injection), the EPA has required permit holders to
submit engineering summaries of disposal practices and "practicable
79
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alternatives" to subsurface disposal including evaluation of: (1)
process changes and in-plant reductions to alter the nature of the
wastes; (2) incineration; (3) biological treatment methods; (4)
physical-chemical treatment methods, and (5) combinations of the
above.
Current Industrial Practices
There are four U.S. manufacturers of acrylonitrile with facili-
ties at six locations. Table 11 lists these manufacturers together
with their current methods of waste disposal. With the exception of
the E.I. duFont de Nemours & Co. facility (duPont) in Memphis,
Tennessee, all of the sites inject acrylonitrile wastewaters (or the
toxic portions thereof) into deep wells. According .to the Standard
Oil Company of Ohio (SOHIO), the wastewater column bottoms and
stripper bottoms "are settled, sand-filtered, and injected into
disposal wells."* Surface runoff, which is composed of miscel-
laneous streams from leaks and spills from routine maintenance
operations is treated biologically in an aerated lagoon (see Appendix
IV.) SOHIO, which regards subsurface injection as 100 percent
efficient, claims 99.4 percent COD removal, "because so much of the
raw waste load is contained in process wastewater."
In general, proper site selection (i.e., geological conditions
suitable for the emplacement of fluids), well design, and construction
techniques used in injection well systems, make contamination of
*Deep well disposal systems specific to acrylonitrile manufacture
are further described in a SOHIO patent, "Deep Well Disposal Process
for Acrylonitrile Process Waste Water," Fitzgibbons et al., 1973.
80
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fresh water aquifers remote. la certain States, such as, Texas and
Louisiana, where there are 124 and 85 permitted injection wells,
respectively, deep wells have proved a popular and economic means
for disposal of difficult to treat waste streams. However, deep
well disposal is not without hazards for extremely toxic and persis-
tent wastes. A serious threat to nearby groundwater supplies is
potentially posed by either the failure of the well system or
migration of the wastes. Specifically, in the case of deep well
disposal of acrylonitrile waste streams, acrolein and cyanides are
deemed "hazardous for deep well injection in any system" (Reeder et
al., 1977; Water Pollution Control Federation, 1977 and Appendix IV).
The duPont Memphis facility pretreats a segment of the acrylo-
nitrile wastes by alkaline hydrolysis and disposes of the biodegra-
dable effluent in a publicly owned treatment works (POTW). While the
pretreatment process is considered proprietary information, a des-
cription of the process along with a sampling and treatability study
conducted during July of 1975 and January of 1976 has been submitted
to EPA"3 Office of Water and Hazardous Materials, Effluent Guidelines
Division. As underscored in a letter dated 20 January 1976 from
duPont to Walter J. Hunt, a composite of all acrylonitrile waste
streams is toxic and should not be introduced into a POTW; however,
"based on two years operating experience...segregated, pretreated
wastewaters are readily biodegradable." (See Appendix IV).
duPont, however, "has not found it possible to biodegrade
all of the acrylonitrile wastes" and, because of this, recommends
81
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TABLE 11
U.S. ACRYLONITRILE MANUFACTURERS
Acrylonitrile Manufacturers
Name Plate Capacity
(metric tons/year)
NPDES No.3
Means of Wastewater
Disposal^
oo
American Cyanamid Company
Porsches, Louisiana
Monsanto Corporation
Alvin, Texas
Monsanto Corporation
Texas City, Texas
The Vistron Corporation
Lima, Ohio
E.I. duPont de Nemours & Co.
Beaumont, Texas
E.I. duPont de Nemours & Co.
Memphis, Tennessee
91,000
180,000
140,000
113,000
LA 0004367 Subsurface disposal
TX 0003875 Subsurface disposal
TX 0005762 Subsurface disposal
OH 0002615 Subsurface disposal
TX 0004669 Subsurface disposal
TN 0001091
Incineration^
Alkaline hydrolysis
of segregated waste
stream, followed by
discharge to munici-
pal sewer
Monsanto's production capacity is reported as 430,000 metric tons of acrylonitrile/year (Orrell, 1978),
2
Horn and Hughes, 1977.
3
Appendix IV.
Effluent Guidelines, EPA Headquarters (Personal communications with J. Schlesinger).
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that deep well injection or incineration be considered as alternate
disposal procedures. Furthermore, duPont is known to be incinerating
a portion of its wasteload at their Memphis facility. Portions of
the recoverable by-products, hydrogen cyanide or acetonitrile, which
exceed market demand are typically incinerated at acrylonitrile plant
sites (Horn and Hughes, 1977). (Such a high strength (near pure)
organic stream would be logically incinerated, rather than impose an
additional burden on a future wastewater treatment system.)
Alkaline hydrolysis is one means of destroying cyanide com-
pounds, generally at moderate temperatures and pressures. Under
these conditions, cyanides are converted to the more easily biode-
gradable cyanates; under extreme conditions the reaction yields
nitrogen and carbon dioxide. Without a further description of the
duPont process, it is generally pointless to attempt to specify the
hydrolysis conditions and what end-products are formed.
Future Regulatory Concerns
In recent years, through court and congressional action, tighter
restrictions have been placed on the discharge of hazardous or toxic
materials. The four laws which directly affect the manufacture of
acrylonitrile are: (1) The Clean Air Act; (2) The Toxic Substances
Control Act; (3) The Resource Recovery and Conservation Act; and (4)
The Clean Water Act of 1977.
• The Clean Air Act, PL 91-604, (passed in 1970, and
subsequently amended in 1977) requires regulation of
specific pollutants under a permit system for point
83
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source emissions. Air emissions for acrylonitrile manu-
facture have been studied in detail (Horn and Hughes, 1977
and Schwartz et al., 1975) as a result of legislation con-
trolling'hazardous pollutant emissions.
• The Toxic Substances Control Act (TOSCA), PL 94-469,
which was signed into law in October of 1976, gives
authorization to the EPA to regulate the manufacturing,
processing, distribution, use, and disposal of chemical
substances or mixtures deemed to represent an "unreasonable
risk of injury to health or the environment." The
Administrator is directed to control hazardous emissions
or discharges to the environment under the Clean Air Act
and Federal Water Pollution Control Act, as necessary,
unless, it is in the public interest to enforce addi-
tional protective measures under TOSCA.
• The Resource Recovery and Conservation Act (PL 94-580)
signed into law in October of 1976, will control the
transportation and disposal of solid wastes designated
as toxic or hazardous.
• The Clean Water Act of 1977 (PL 95-217) which embodies
the major points of the "consent agreement" (signed itj
1976 by EPA and environmental interest groups), re-
quires stricter regulation of toxi-c discharges. Aside
from establishing effluent limitations for 65 toxic
pollutants in terms of BAT, pretreatment standards
are required for wastes discharged to publicly owned
treatment works (POTW). However, if the treatment by
such POTW removes all or any part of the toxic pollutant
in question (and discharge of the pollutant does not pre-
vent prescribed sludge use or disposal), the pretreat-
ment requirements for the sources may now be so modified
as to reflect the removal rate achieved by the POTW.
Although the Safe Water Drinking Act (PL 93-523) enacted in
1974 is not explicitly directed toward point source discharges, the
EPA is empowered by this legislation "to promulgate regulations which
contain minimum requirements for effective programs to prevent
underground injection practices which endanger potential or present
drinking water sources" (Federal Register, August 31, 1976). The
84
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responibility of enforcement is left to State agencies under a
federally approved permit program. Thus, the proposed regulations
are intended to give maximum flexibility to the States in designing
underground injection control programs, in recognition of the large
degree of variation in geological conditions, ground water use, and
existing deep well injection operations. While key provisions of
this Act have yet to be defined, regulations will, at the very least,
require the routine monitoring and inspection of subsurface injection.
systems (Federal Register, August 1976).
However, as was the case with Section 307(a) of PL 92-500 and
the resulting "consent agreement," judicial interpretation of the
laws will undoubtedly play a major role in their enforcement. It is •
clear, however, that with the passage of The Clean Water Act of 1977,
effluent guidelines promulgated by EPA will strike a balance between
controlling the classic water quality parameters (i.e., BOD5, COD,
TSS) and specific toxic pollutants.
85
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SECTION IV
ALTERNATIVE METHODS OF TREATMENT
INTRODUCTION
The quantity and quality of the pollutant waste load from a
manufacturing facility is dependent on the degree of product puri-
fication, by-product separation and recovery, solvent reuse and re-
cycle, and stream segregation practiced. Ideally, the treatment
system best suited for a particular manufacturing operation should
be approached on an individual basis, point source-by-point source.
However, from a historical perspective, treatment of industrial
effluents has been limited, in most cases, to the application
of "end-of-pipe" technologies to combined waste streams.
Typically, the treatability of such a stream is described in
terms of its biodegradability, as biological treatment usually
provides the most cost-effective means of treating a high volume,
high (organic) strength industrial waste (i.e., minimum capital and
operating costs). Thus, in presenting a general discussion and
literature review of wastewater treatment from acrylonitrile manu-
facture, this section of the report is divided into three major
subsections: (1) biological treatment; (2) physical-chemical pre-
treatment; and (3) combinations of selected treatment technologies.
Furthermore, with the exception of specific treatment processes,
such as the recovery of ammonium sulfate, the discussion within
87
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this section will not be specific to individual process waste
streams*
Of the 63 potential pollutants from acrylonitrile manufacture
(see Table 5), six* compounds are present in the EPA list of 129
priority pollutants (See'Appendix III). In addition, many other
pollutants (e.g., imides, imines, nickel carbonyl, to name but a ;
few) represent_toxic discharges to the environment. However, only
those pollutants that were repeatedly cited in the literature
as contributing to the refractory, inhibitory, or toxic nature of the
waste load (that is acrylonitrile, acetonitrile, ammonium sulfate,
hydrogen cyanide, and polymeric material) are considered explicitly
in evaluating wastewater treatment alternatives. This decision was
based on two major considerations:
(1) It is impractical from an engineering standpoint to
discuss treatment options on a pollutant-by-pollutant
basis.' Treatment operations and processes are
selected on the basis of their effectiveness in
treating a particular wastewater, with ma'ny con-
stituents.
(2) Without laboratory or pilot test data, a ranking of
each treatment operation and process, based on its
ability to remove each of the 63 pollutants, would be
speculative.
It is not unreasonable to assume, however, that a treatment method
capable of detoxifying the high concentrations of extremely refractory
*Acrolein, acryclonitrile, benzene, cyanide, hydrogen cyanide and
toluene.
88
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organic nitriles and the inorganic cyanide compounds found in acrylo-
nitrile wastewater, might also be effective for the treatment of other
toxic pollutants present in low, or trace, concentrations.
Because of the large number'of citations, a complete review
of conventional practices for removing cyanides and metal cyanide
complexes from an aqueous waste is beyond the scope of this report.
Where the potential for technology transfer does exist, however,
detoxification of cyanide-containing wastewaters from other manu-
facturing processes (i.e., the metal plating industry) will be
discussed.
BIOLOGICAL TREATMENT
Water and soil organisms naturally found in the environment
have only a limited ability to assimilate synthetic organic chemicals
found in an industrial waste stream. However certain compounds which
may appear to be resistant to biological degradation in natural
waters, may be readily oxidized by a microbial population adapted to
the waste. Thus, the successful application of biological processes
to the treatment of hazardous organic wastes is largely dependent on:
(1) the ability to acclimate biological organisms to the waste stream
(e.g., activated sludge); (2) the operation of the treatment system
at a practicable removal rate (throughout seasonal changes); and (3)
the stability of the treatment system during variations in the waste
loading (i.e., operation near toxic or inhibitory concentrations).
89
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Shortly after the importance of acrylonitrile as a monomer basic
in the manufacture of many synthetic fibers and resins was recognized,
researchers began to study the biodegradability of organic nitriles
and their toxicities to aquatic organisms. (For historical review
see Cherry et al., 1956 and Ludzack et al., 1958). Early research
focused, on the assimilative capacity of biota found in the environ-
ment to metabolize organic nitriles and the ability of conventional
biological processes to treat these pollutants.
Cherry et al., (1956) demonstrated through stream assimilation
studies that biota found in* river water samples are capable of
degrading an acrylonitrile feed (100% COD removal) after an initial
acclimation period. Similar conclusions were reached by Ludzack et
al., (1958) in a later and more sophisticated study of the biochemical
oxidation of six nitriles in river water and aged sewage feed.
Biochemical oxidation of organic nitriles is marked by CO. produc-
tion, as shown below:
CH2=CH-CN + 302 *• 3C02+NH3 (57)
Thus, by measuring carbon dioxide production (over time and in
comparison with a control), Ludzack et al., were able to study the
acclimization of the microorganisms found in the Ohio River to the
waste feed. Figures 16 and 17 represent oxidation of acetonitrile
and acrylonitrile during an initial compound dosing of 10 mg/1 at
20°C and at serial redosings of 10 mg/1 and 40 mg/1; temperature
conditions are as noted on the graphs. More slowly metabolized than
90
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I
«
5
100 -
H
1
W
«N
O
O
a
-20
•FIGURE 16
OXIDATION OF ACETONITRILE IN OHIO RIVER WATER
to 100
o
§
u
VJ
CO
O
u
80
60
40
20
-20
T
T
\
I
I
I
20° C
5°C
.60
10 20
30
_L
_L
I
60 70 80
DAYS
90
100 110
FIGURE 17
OXIDATION OF ACRYLONITRILE IN OHIO RIVER WATER
Source: Ludzack et al. (1958).
91
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acetonitrile, the acrylonitrile curve illustrates "a marked inhibition"
during the first week of study. After a few days of rapid acryloni-
trile assimilation, a plateau was reached, during which time little
activity took place. The metabolism rate accelerated after 10 days
of "apparent inactivity" to reach about 60 percent of the theoretical
CO. production on the 25th day. Furthermore, once a healthy, accli-
mated population was established, the biological systems easily
adapted to variations in feed concentrations and oxidized 40 to 50 mg/1
doses in the same time period as the initial dosing of 10 mg/1. As
expected, the microorganisms are susceptible to temperature changes
and metabolism rates slowed in response to a significant drop
in temperature (simulated winter conditions).
In view of their test results, Ludzack et al., (1958) concluded
that the cyano-group undergoes enzymatic hydrolysis to ammonia,
organic acids, or associated material. In an acclimated system,
nitrification proceeds in two steps as the ammonium ion is converted
by nitrifying bacteria first to the nitrite, and subsequently to the
nitrate ion:
NH3 + H20 « NHit"1" + OH~ (58)
3/202
1/202 , N03- (60)
92
-------
An early increase in ammonia-nitrogen'occurs in an acclimated system
as the nitrifying population is not completely established.
In an extension of their surface water studies, Ludzack et al.,
(1959) investigated the treatment of organic cyanides by acclimated,
activated sludge. Their study was designed to investigate the
effect of system variables, such as nitrile concentrations and
load ratios, on the general performance characteristics of nitrile-
activated sludge (plus sewage feed). The authors examined the
resulting nitrogen balance during a period of acclimation, normal
operation, and overloading. For example, during normal loading
of an acrylonitrile acclimated activated sludge*, where nitrile-
nitrogen represented 60 percent of the feed nitrogen, the effluent
contained approximately 70 percent oxidized nitrogen. The remainder
of the influent-nitrogen was found in the sludge or was attributed
to ammonia and organic-nitrogen in the effluent; furthermore, at no
time was acrylonitrile present in the effluent. The acrylonitrile
activated sludge was sensitive to change, in particular overload.
Minor variations resulted in a significant reduction in treatment
efficiency, and the recovery period from an overload was frequently
"as long ... as for acclimation of a new sludge." Cross acclimation
of acrylo- and acetonitrile acclimated activated sludge was success-
ful within a one week adjustment period.
* Load ratio: 32-43 parts of influent BOD/100 parts of circu-
lating solids; 90-97% BOD removed.
93
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Marion and Malaney (1962) studied the ability of a pure culture
of Alcaligenes faecalis. a bacterial species typically found in
activated sludge flora, to degrade selected aliphatic compounds. In
tests on mono- and dinitrile substrates, A. faecalis oxidized all of
the nitriles containing a single cyanide group. However, acryloni-
trile and acetonitrile were not among the tested compounds.
In unpublished work performed by B. F. Goodrich Chemical Company,
Lank reports that a pilot activated sludge plant treating high
strength industrial waste continued to operate at a level of 90 to 95
percent COD removal after introduction of 200 mg/1 of acrylonitrile.
No acrylonitrile was found in the effluent; however, some of the
nitrile may have been lost by aeration (Lank and Wallace, 1970).
Lutin (1970) also studied the efficiency of activated sludge
for removal of organic nitriles from wastewaters. Whereas Ludzack et
al., (1959) studied the possibility of acclimatizing activated
sludge to organic nitriles using a semicontinuous feed (of nitriles
and supplementary sewage) to bench scale units, Lutin exposed
the substrate (500 mg/1) to each sludge for a 72 hour incubation
period. The toxicity of each substrate was then measured in terms
of oxygen uptake, as compared to a control. Acrylonitrile was found
to be toxic to all sludges, while acetonitrile was toxic to two
sludges and caused no significant oxidation or inhibition to the
third. Thus, from the results of his research, Lutin suggests "that
94
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treatment by unacclimated activated sludge cannot be relied on to
produce any significant removal of organic cyanides from wastewater
in conventional detention times," and methods other than the oxida-
tive mechanism should be investigated. Although these experiments
were carried out with a very high concentration of nitrile loading,
the use of biological oxidation as.the sole treatment process for
acrylonitrile wastes appears to be impractical.
A patented biological process (Fujii, 1973) for treating nitrile-
containing wastewaters recommends treatment with acclimated, acti-
vated sludge containing microorganisms from the genera Alcali-
genes and Achromobacter. In particular, the strains Alcaligenes
viscolactis S-2 ATCC 21698 (FERM-P No. 759) and Achromobacter
nitriloclastes S-10 ATCC 21697-(FERM-P 760) were isolated as two
»
strains capable of degrading nitriles and cyanides. The patent
claims total cyanide reduction of 89.0 to 99.7 percent with loadings
of 10 to 50 mg/1 CN~ and 1,000 to 2,500 mg/1 COD; the retention
time was 24 hours. According to the patent, the same waste effluents
were unsuccessfully treated (even when diluted) by unacclimated
activated sludge, and an acclimation period of three to six months
was required to acclimate "ordinary" activated sludge to the waste
and achieve similar removal efficiencies. These results should be
compared to the limited success reported by Marion and Malaney
(1963) in the oxidation of aliphatic compounds by Alcaligenes
faecalis.
95
-------
Another related patent describes the treatment of wastewaters
containing nitriles and cyanides by an acclimated, activated sludge
to which a pure culture of the genus Nocardia, specifically Nocardia
rubropertincta, ATCC 21930, has been added. (A coagulant, such as
ferric chloride, may be required to successfully add the pure culture
cells to the activated sludge.) Acclimation and propagation of the
activated sludge requires a period of approximately one week. Acrylo-
nitrile influent concentrations were reduced from 106 to 224 mg/1 to
less than 20 mg/1; and reduction of total CN~ is reported as greater
than 99 percent*(Kato and Yamamura, 1976).
Ludzack et al., (1959) briefly studied the effect of nitriles on
the anaerobic digestion of organic material (dog food). Although
the results suggest that acrylonitrile was toxic to the batch digester
systems under shock loadings, the study results were largely inconclu-
sive. Thus, in 1970 Lank and Wallace designed a more sophisticated
reactor system to evaluate the anaerobic treatment of sludge contain-
ing acrylonitrile. Under the test conditions, the bacterial popula-
tion appeared capable of acclimatizing up to 20 mg/1 of acrylonitrile.
The study, however, did not determine the acrylonitrile concentration
toxic to the digestion process (i.e., resulting in digester failure,
indicated by a cessation of gas production, etc.).
A patented process for the disposal of toxic chemical wastes
having a high concentration of cyanide involves anaerobic diges-
tion of the waste followed by aerobic biological treatment (Howe,
96
-------
1964). In the recommended procedure, an anaerobic fermentation
sludge is added to the aeration tank to adsorb toxic materials,
thereby enhancing bio-oxidation.
In a series of experiments, Raef et al., (1977) studied several
mechanisms for cyanide removal by aerobic biological treatment. As
noted by Ludzack et al., (1960) cyanide loss due to aeration (strip-
ping) may be significant. As vapor-liquid equilibrium data for low
concentration cyanide solutions is limited, the authors designed
stripping experiments in which temperature, air flow rate and mixing
were controlled. Cyanide solutions ( CN) were added to a starved
14
heterogenous culture in an aerated microfermenter, and CN and
14
. CO. were measured. From the test.-results, Raef et al., concluded
that "cyanide stripping is an important removal mechanism."
Continuing their studies, Raef et al., (1977) conducted cyanide
adsorption experiments with a nonflocculating culture of Bacillus
megaterium and a flocculant culture of heterogeneous bacteria. Up to
15 percent adsorption occurred in the tests done with flocculant
bacteria, while no significant reduction of cyanide was evident in
the tests with nonflocculating B_. megaterium. The authors concluded
that the surface characteristics (extracellular composition) of the
bacterial cells appear to influence cyanide adsorption. Furthermore,
the results suggest that the addition of anaerobic digested sludge to
an aeration tank during treatment of cyanide wastes does not detoxify
the wastewater solely by the adsorption mechanism, as hypothetized by
97
-------
Howe (1964). Most likely, stripping and chemical reactions are also
contributing to the detoxification process.
As a possible method of detoxifying cyanide containing waste-
waters, Raef et al., (1977) investigated the reaction between
cyanide and aldoses, specifically glucose, and found the reaction of
cyanide with glucose to be pseudo-first order and highly pH dependent,
with an optimum pH near 11.0. In a series of experiments, starved,
acclimated heterogeneous cultures in an aerated microf ermenter were
fed an initial solids concentrations of 483 to 1963 mg/1, an initial
glucose substrate between 100 to 600 mg/1, and a cyanide concentra-
tion of 10 mg/1 (K CN solution). The cyanide metabolism was moni-
14
tored by recovery of C from the reactor and gas washers. However,
14
because of the complexity of separating C successfully from the
soluble reactor contents and caustic gas washer, only 50 to 78 percent
of the labeled carbon was recovered.
The formation of cyanohydrin, and their subsequent hydrolysis
is shown in equations (61) and (62).
RCHO + CN" „, RCH(CN)0" (61)
H20 +
RCH(CN)0~ - * RCH(OH)C02~ + NHi, ' (62>
At pH's above 11, the cyanide removal rate decreased, and the
authors hypothesized that cyanide was polymerizing, rather than
reacting with glucose.
98
-------
HCN CN '
2HCN * HC=NH *• H,N-CH (63)
i i
CN CN
Dimer Trimer
The cyanide glucose reaction products were found to be biode-
gradable by acclimated cultures. Thus, the combination of a cyanide
contaminated waste stream with an aldose carbohydrate waste (cannery,
textile, pulp and paper) may be useful as a pretreatment step
prior to biological treatment. This pretreatment step would also
eliminate the pollutant emission of HCN to the atmosphere during
aeration of the waste. The application of this approach to waste
streams containing more than 10 mg/1 of cyanide is still untested.
Significantly, Raef et al., (1977) went beyond the scope of
earlier studies .to.examine the relative importance of cyanide strip-
ping, cyanide adsorption, cyanide reaction with substrates, and
cyanide metabolism in aerobic biological treatment systems. These
experimental results, while not specific to acrylonitrile wastewaters,
do aid in the interpretation of biological studies performed by other
investigators. Problems with sampling and analytical techniques
experienced by Raef et al., (1977) appear to be inherent in the
design of aerobic microbial test systems, and were experienced by all
the researchers reviewed in this section (to a greater or lesser
degree, depending on the sophistication of the study).
The major objective of this subsection has been to examine the
biodegradability of organic nitriles and hydrogen cyanide found in
• 99
-------
process wastewaters; in no way has any one of Che above described
biological treatment schemes been suggested to yield effluents
suitable for direct discharge to natural waterways.* Studies per-
tinent to biological treatment of acrylonitrile-containing waste
streams are summarized in Table 12. Included in this table are
several studies for which only English abstracts were available for
review.
CHEMICAL PRETREATMENT
Chemical pretreatment is a means of rendering wastewaters more
amenable to treatment by biological processes. Typically, pretreat-
ment steps consist of flow equalization, neutralization, chemical
coagulation, and in some cases, carbon adsorption to remove soluble
organic compounds.
In treating a high strength, toxic- industrial waste, such as
*
from the manufacture of acrylonitrile, the definition of chemical
pretreatment is broadened to include methods of destroying cyanides
and organic nitriles. However, it is important to differentiate
between the properties of organic cyanides (nitriles) and inorganic
cyanides in solution. For example, cyanide anions may be readily
*In point of fact, some form of denitrification would most likely
be required in order for the effluent from an acrylonitrile manufac-
turing facility to meet an NPDES imposed ammonia-nitrogen limitation.
For a general discussion of the principles of biological denitrifica-
tion, the reader is referred to EPA-TT(1975); for a description of
biological denitrification at an industrial waste treatment facility,
see Climenhage and Stelig (1973).
100
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BIOLOGICAL TSEATMENT OP NITRILE CONTAINING WASTEWATERS
Investigator
et al.,
Type of Treatment
Activated sludge ad-
sorption, followed by
activated sludge
treatment.
Cyanide
Concentration.
61,7 ppm acryloni-
trile
Supplementary
Nutrients
Petroleum
vastevater
(containing
phenol and
formaldehyde)
Detention Time—
Aerobic incubation of
activated sludge suspension
(30 C); filtrate subjected
to activated sludge process.
Comments
Acrylonitrile concentration
reported as <1 ppm after ad-.
sorption and activated
sludge treatment; and <1 ppo
aftej: activated sludge treat-
ment^ alone. '"
Chekhovskaya
et al., 1966
Bio-oxidation by
saprophytic micro-
organism.
£150 mg/1 acrylo-
nitrile
3.000 mg/1 ___.
acetonitrile
<5 mg/1 acrolein
50 mg/1 of acrylonitrile and
100 mg/1 of acetonitrile in-
hibited nitrification; 5 mg/1
of acrolein stopped ammonifi-
cation.
Chekhovskaya
et al., 1972
Activated sludge
Phosphorus
tfastewater neutralized:
pH 7 to 8
Cherry
et al., 1956
Assimilation of or-
ganic nitriles by
microorganisms found
in river water.
Acetonitrile or
acrylonitrile in
concentrations up
to 50 mg/1.
Inorganic Initial acclimation period
salts -20 oaySj reduced, for sub-
sequent redpsings.
Fujii, 1973
Acclimated, activat-
ed sludge containing
microorganisms from •
the genera Alcall-
genes and Achromo—
bacter.
10 to 60 ppm
as HCN
Nutrients,
as necessary
24 hours
98 to 99.6 percent nitrile
removal
pH 8 to 8.5
Kato and Acclimated, activat-
Yamamura, ed sludge with mi-
1976 croorganisms from
the genus Jfocardia.
50 to 250 ppm
nitriles.
Nutrients,
as necessary
7 to 24 hours
pH 6.9 to 7.3
COD loadings of
500 to 2,000 ppm
^V and
tfaTlace, 1970
Anaerobic digestion
of acrylonitrile con-
taining domestic
sludge.
1 to 20 mg/1 of
acrylonitrile
Raw digested
sludge
Loading: .107 to .155 Ib
volatile 3olids/ft3 of
reactor/day.
-pH 7
Ludzack et
al., 1958
Bio-oxidation of
organic nitriles.
Acrylonitrile or
acetonitrile in
concentrations of
10 mg/1 and
40 ng/1.
Sewage feed -10 days to reach 60 per-
cent of theoretical COD
production >
Effluents contained high
nitrate concentrations •
Ludzack et ' Activated sludge 89 mg/1 acrylo- Sewage feed " 32 to 43 parts of influent (See above)
al., 1959 nitrile during BOD/100 parts circulating
normal operation . volatile solids .
Anaerobic digestion
of nitrile contain-
ing sludge.
Acrylonitrile and
acetonitrile dosed
at 10 mg/1 and
40 mg/1.
Dog food
1 month operation of
digester
pH 6.6 to 7.1
Ludzack et
»,al., 1960
Activated sludge
treatment of cyanide,
cyanate and
thiocyanate.
Varied with test;
10 to 75 mg/1 CN~
dosage.
Loading varied with
experiment
CN removal >99 percent
a, 1970 Treatment of organic
nitriles with three
domestic activated
sludges.
500 mg/1 of Municipal 72 hours incubation period Acrylonitrile toxic to
substrate (mono— wastes unacclimated sludge;
and dinitriles) suspended solids adjusted
to 2500 mg/1.
Marion and
aey,
Oxidation by
Alcaligenes faecalis.
500 og/1 of sub-
strate (selected
aliphatic com-
pounds, including
nitriles)
Mineral salt 144 hours incubation period Acrylonitrile not one of
solution test nitriles.
-------
TABLE 12 (concluded)
Investigator Type of Treatment
Cyanide
Concentration
Supplementary
Nutrients
Dentention Time
Comments
et Activated sludge
al., 1974
Mlmura Assimilation by
et al., 1969 Corynebacterium
nitrilophilua (C-42)
60 ppm cyanides
In acrylonitrile
vastevater
Approximately
1 to 3 percent
acetonitrile
diluted 2-
fo'ld with
seawater
After 20 days all cyanide
removed, but only 50 per-
cent of ammonia-nitrogen
converted to nitrate-
nitrogen.
Aeration continued an add!-.
tional 7 days to achieve 94
percent nitrification.
Applied to petrochemical
wastes.
Raef et al., Starved, acclimated
1977 heterogeneous
cultures
10 ng/1 KCK
Glucose
Tests performed in shake
flasks, BOD bottle systems,
and aerated micrpfermeiiter.
Also Investigated cyanide
removal as a result of
stripping, adsorption onto
biological floe, and chemical
reaction of CN~ in solution .
with substrate.
Rueffer, Activated sludge
1975
140 mg/1
acrylonitrile
No acrylonitrile detected in
effluent.
Seiichi Activated sludge
et al., 1966
1001 ppm of Peptone or 95 to 99 percent CN
Ctr phosphate removal at 0.2 to 0.25
kg/m - day of CN loading.
Seed sludge acclimated in
2 to 3 weeks.
Slave Fseudomonas sludge
et al., 1973 acclimated to
acrylonitrile
Adapted to vary-
ing concentra-
tions of acrylo-
nitrile, up to
500 mg/1.
Inhibited by presence of
polymers in treating waste-
water from an acrylonitrile
plant.
-------
precipitated as metallic salts. Nitriles, on the other hand, which
are covalently bonded cyanides, are not easily removed from solution
as insoluble metal complexes. Furthermore "cyanide" refers to the
anion (a single species), whereas, there are literally thousands of
nitriles with widely varying properties (e.g., toxicity, biodegrad-
ability).
Chemical Oxidation
Cyanide-containing waste streams may be detoxified by chemical
oxidation under alkaline conditions. Degradation of cyanide or
nitriles results from the partial oxidation to the cyanate; total
degradation to carbon dioxide and nitrogen gas results from sub-
sequent acid hydrolysis. Traditionally, cyanide solutions from
manufacturing processes, particularly from the metal plating indus-
try, have been treated by alkaline chlorination. This is accom-
plished by the direct addition of sodium hypochlorite to the waste-
water, or alternatively by the addition of of chlorine gas under
basic conditions. Electrolytic decomposition is also commonly used
to oxidize very concentrated cyanide wastewaters (~10,000 mg/1); at
lower concentrations «200 mg/1), sodium chloride is generally added
to the solution to improve the process efficiency.
To effectively treat acrylonitrile manufacturing wastewater,
however, not only must hydrogen cyanide be destroyed, but also
high concentrations of organic contaminants (in particular, nitriles)
must be reduced. Conventional techniques have generally been found
103
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to be either inadequate or undesirable; alkaline chlorination, for
example, is unsuitable because of the formation of chlorinated
organic compounds. (The carcinogenesis of alkyl halides has been
well documented; for example, see Searle, 1976). Alternative
approaches to oxidizing the nitrile waste load that merit further .
•' discussion include: (1) ozonation; (2) treatment with a peroxide;
(.3) wet-air oxidation and incineration; and (4) copper-catalyzed
adsorption and oxidation on granular activated carbon.
Ozonation
A stronger oxidant than chlorine, ozone (03) may be used
for disinfection, removal of taste, odor, color, and oxidation of
compounds which are difficult to treat by other means. At pH 9 to
12, noncatalytic oxidation of cyanide to cyanate by ozone is rapid
(i.e., minutes); moreover, in the presence of a copper catalyst, the
reaction rate is substantially increased. Subsequent oxidation of
the cyanate is a much slower process,"however, and generally is not
practical unless a catalyst system is employed (Patterson, 1975).
Although ultraviolet radiation in combination with ozone has also
been suggested to be an effective technique for cyanide removal from
industrial wastewaters, this method has had only limited application
in the United States (Prengle, 1975). Currently, two commercial
organizations in the U.S., Houston Research, Inc. of Houston, Texas
and Westgate Research Corporation of Marine Del Ray, California have
been studying the practicability and economics of UV catalyzed
ozonation.
104
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In general, ozone has not been widely used for wastewater
treatment in the U.S. because of energy or operating costs, the
requirement of on-site generation, and general lack of experience
with 0-j . Currently, ozone is being employed successfully by
Boeing Corporation for the treatment of plating wastes (Lederman,
1977). Other applications of ozone to cyanide-containing wastewaters
(concentrations typically ranging from 20 to 60 mg/1) include a
plating operation in the northeastern U.S. and a Michelin tire
factory in France treating a 90 gpm waste stream (Arthur D. Little,
1977). Additionally, Hughes Tool of Texas employs UV/ozonation for
cyanide removal from their plating wastes and a chemical manufacturer
in France is completing a UV/ozonation treatment facility for
ferrous cyanide removal (Arthur D.-Little, 1977; Miller, 1977).
Treatment With a Peroxide Compound
An alternative to alkaline chlorination or ozonation, is the
use of peroxy compounds to detoxify cyanide-containing wastewaters.
Under alkaline conditions, cyanide is converted initially to cyanate
and subsequently degraded to carbonate and ammonia as shown:
— — OH n —
CN + H202 : »• OCN + H20 — + C0$ + NH3 (64)
Catalysts (e.g., copper II) are commonly used to increase the rate of
cyanide destruction and may be required in concentrations of as much
105
-------
as 1000 mg/1 (Mathre, 1971). Although Che use of a copper catalyst
greatly enhances the rate of cyanide removal, it has the drawback of
also reacting with peroxy acids to form highly soluble copper tetra-
mine complexes (i.e., copper not removed by precipitation would be
present in the effluent).
To avoid the use of hydrogen peroxide-catalyst systems, Zumbrunn
(1973) suggests oxidizing organic cyanides to amides using peroxy
compounds. Under alkaline conditions (pH>9), organic nitriles are
rapidly degraded into amides as follows:
NE „ n °
— n 11202 ii
RCN + H202 °H > RC-OOH-QJp " RC-NH2+ 02+H20 (65)
The amide is then hydrolyzed into salts of the organic acid (RCOO~)
and NH3.
0
R-C-NH2+(OH~) > RCOCf + NH3 (66)
The reaction is run with a 2 to 10 fold stoichiometric excess of
peroxides selected from the following compounds: (1) hydrogen
peroxide; (2) a member of the group consisting of mineral and organic
peroxyacids; or (3) a member of the group consisting of ammonium
dispersulfate, sodium dispersulphate, monopersulphuric acid, potas-
sium monopersulphate. While the reaction rate is dependent upon both the
specific nitrile and reaction temperatures, most wastes are degraded
106
-------
within 30 minutes to five hours. Wastewaters containing 50 mg/1
acrylonitrile were reduced to a residual content less than 0.5 mg/1.
The "Kastone process"*, commercialized "by duPont for applica-
tion to electroplating rinse water, involves the treatment of
cyanide containing wastewater with hydrogen peroxide and formaldehyde.
The process is recommended for cyanide concentrations ranging from
100-1000 ppm and is carried out at elevated temperatures under basic
conditions.
The primary and secondary reaction products which are dependent
upon cyanide concentration, the pH, and temperature of solution are
shown below:
*• CNO" + H20
(67)
CN~ + HCHO + H20 - >•' HOCH2CN + OH~ (68)
HDCH2CN + H202 - > HOCH2COONH2 + H20 (69)
H2°2 +
CNO~ + 2H20 - »• NHu + C032~ (70)
H202
CN~ + 2H20 - > HCOO + NH3 (71)
The concentration of cyanates in the treated effluent is dependent
on the pH of the stream as the cyanates are oxidized to the carbonate
and ammonium ion by acid hydrolysis. Glycolonitrile then rapidly
*Kastone is a marketed proprietary water based formulation containing
41 percent hydrogen peroxide with trace amounts of stabilizers and
catalytic compounds.
**This species was reported in Environmental Science and Technology,
1971; however, the reaction most likely stops at
107
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hydrolyzes to glycolamide, and subsequently to the acid and ammonium
ion. As both the acid and amide are biodegradable, the pretreated
waste could be either treated biologically at a plant site, or
possibly, be discharged directly to a publicly owned treatment works
(Environmental Science and Technology, 1971).
Another approach to detoxifying cyanides and organic nitriles
with peroxygen compounds is offered by Fischer (1976). The detoxi-
fication requires oxidation of wastewater with a peroxygen compound
(e.g., hydrogen peroxide) in the presence of iodide and silver cations
as catalysts. At alkaline pH, elevated temperatures, and 'in the
presence of excess of peroxide, the hydrolysis of organic nitriles
.proceeds as follows:
••• or o '
H202 „ H202 „ _ .
R-CN QH- .»• R-C QH- > R-C + N03 (72)
NH2 OH
i
The progress of the detoxification is monitored potentiographically
and effluent cyanide concentrations are reported as less than
0.1 mg/1.
Colin has patented a process for converting cyanohydrins to
biodegradable oxamides by treatment with hydrogen peroxide. The
oxidation of cyanohydrins to oxamides,
(73)
R'
i
2R-C-CN H
i
OH
R'
i
0 0
II II
u u_\r_rl_r' wn~
P ri2iN— c» o iNn2
108
-------
favored in the pH range of 9 to 10 and at elevated temperatures,
forms the basis of another treatment technique (Colin, 1974).
Hydrogen cyanide may be reacted with a carbonyl to form a cyano-
hydrin, before undergoing treatment with peroxide. Reduction of
• acrolein cyanohydrin to less than 0.01 mg/1 (as CN~) was reported.
Degussa markets several proprietary processes for the detoxi-
fication of cyanide wastewaters using peroxy compounds. The
recommended compounds have been mentioned in patented procedures
discussed earlier, (e.g., Lawes and Mathre, 1971 and Zumbrunn, 1970)
and include: hydrogen peroxide (and in combination with formaldehyde),
sodium peroxide, sodium persulfate potassium, persulfate, calcium
peroxide, potassium monopersulfate, and monopersulfuric acid).
In summary, these systems have generally addressed cyanide removal in
- plating wastes, but in many cases, with suitable modification, might
be used for oxidation of organic wastes.
Wet-Air Oxidation and Incineration
Most organic compounds, including nitriles, may be oxidized
under high temperature and pressure conditions .(i.e., in an auto-
clave). One application of this fact is the wet-air oxidation
(wet-ox) process, marketed by Zimpro, Inc. where organic material is
oxidized in aqueous solution or suspension, under high pressure and
at temperatures of 350-700°F. At lower temperatures, effluent
process gases, while free of sulfur and nitrogen oxides, may contain
significant amounts of low molecular weight organic compounds (Environ-
mental Science and Technology, 1975). Thus, temperatures above 600°F
109
-------
and pressures above 200 psig are normally required to achieve essen-
tially complete oxidation of a waste stream (i.e., carbon dioxide and
*
nitrogen gas). Figure 18 presents a flowsheet for wet-oxidation of
a concentrated waste stream. The waste is pumped into the system,
mixed with air from a compressor, and passed to the reactor, where
oxidation occurs. The gas and liquid phases are separated after
oxidation; the liquid phase is typically passed through a heat
exhanger for heating incoming waste. As the oxidation reaction is
exothermic and evaporation of all the water is undesirable, the water
condensed in the reboiler is recirculated back to the reactor. Gas
and liquid streams are discharged from the system as shown (Pradt,
1976). " ' .
Niigata Zimpro Co., Ltd. has designed five plants in Japan to
treat arcylonitrile wastes with wet-air oxidation; and currently a
sixth plant is under construction for Monsanto in England (Wilhelmi,
1977). Reductions of total cyanides from 2,000 mg/1 in the raw waste
to 6 mg/1 in the oxidized waste have been reported at on-line facilities
(Pradt, 1976). COD removal may be increased from 70 to 75 percent to
95 to 98 percent plus by the addition of a homogeneous, recoverable
catalyst at the front end of the unit. With the removal of organic
material, ammonium sulfate may be recovered from the concentrated
effluent (Wilhelmi and Ely, 1976).
Thermal oxidation, or incineration, is commonly used for the
disposal of organic waste streams that are toxic, hazardous, or
110
-------
INDUSTRIAL
WASTE
STORAGE
TANK
NO. 1
SEPARATOR
f
,A
1
¥
if *7T7T\
IIZED
ITITrv .
UJ.U
A
REACTOR
NO. 2
SEPARATOR
EXHAUST GAS
MAKE-UP
AIR"
RECYCLED
LIQUID
Source: Prodi. 1976
FIGURE 18
FLOWSHEET FOR WASTEWATER TREATMENT USING WET-OXIDATION (WET-OX)
-------
otherwise difficult to treat; furthermore, concentrated streams may
have substantial fuel value. Indeed, at acrylonitrile production
sites, the manufacturing by-products, acetonitrile and hydrogen
cyanide are routinely incinerated.* Foreign research, employing
wet-oxidation, autoclaving, or catalytic oxidation as a means of
treating acrylonitrile or cyanide containing waste streams, are
summarized in Table 13.
Catalytic, Inc. (1975), has recommended the incineration of
organic pollutants found in acrylonitrile wastewaters as an alter-
native to deepwell disposal. However, incineration of a large
volume stream high in inorganic salts (e.g., Point No. 1) is imprac-
tical and typically requires pretreatment for salt removal and volume
reduction. However, Miller and Keiffer (1968) claim that the addition
of an alkyl amine to the wastewater column bottoms (to prevent
separation of organic material during subsequent evaporation) will
render a concentrated waste stream suitable for incineration. (No
reference is made to required air pollution control equipment to
lower NOX and SOX emissions.)
Recovery of ammonium sulfate as discussed in a later section,
necessitates the separation of heavy organic tars and polymers which
may then be incinerated. Additionally, the organic portion of the
*For a more detailed description of current incineration practices
at acrylonitrile facilities, see Horn and Hughes, 1977.
112
-------
SUBMART OF TOKBUar APPLICATIONS OF PHTSICAI. - CHEMICAL TREATMENT TO ACBTLONITRILE/CTiNIDE CONTADHHG WAST2WAIEHS
Treatment
Process/
^
CHEMICAL OXIDATION
Autoclave (180°C,
2 hr) wastewater
column bottoms,
fallowed by
evaporation
(100°C) .
Autoclave (180 ,
i hr.) wastewater
column bottoms nixed
with urea,
melamine, or for-
mamide; fallowed
by distillation.
Autoclave waste-
water with NH.KO,
Investigators
Mbrishita et al.,
1975
Mbrishita et al.,
1976
Van Gool, 1973
or
at
elevated tempera-
tures (300°C) for
approx. 30 minutes.
Combustion at
2700°C and excess
air; SO. scrubbed
from mixture.
Obana and Matsuyama,
1974
ic oxida-
tion of wastewater
in the presence of
Cu and ammonia.
Iwai et al., 1977
Oxidation of waste- Hoshikums, 1972
cv-ater with oxygen at!
elevated tempera- i
cures and pressures
in. the presence of
Ca or Me carbonates,
oxides, or hydrox-
ides. I
Waste
Characteristics
Dark brown_ color
337 ppm CN~
20,100 ppm COD
pH 6.72
Dark brown color
167.4 ppm CN"
18,510 ppm COD
pH 5.98
27,500 ppm COD
27,400 ppm SO.-N
37,400 ppm TKN
By weight:
12 percent
5 percent
or ganics,
83 percent HjO
51,200 ppm COD
pH 8.3
HCN
organic compounds
Treated
Effluent
Colorless
0.08 ppm CN~
1082 ppm COD
pH 8.2
Distillater
.06 ppm CH~
952 ppm COD
pH 9.91
Liquid phase:
100 ppm N03-N
10,400 ppm TKN
Emissions: CO ,
N2' H2°' vapor>
and S02
5320 ppm COD
After copper
recovery, .
0.56 ppm Cu
in effluent.
After filtra-
tion:
0.4 ppm CN
4132 ppm COD
5.69 wt percent
Special Conditions Comments
NH4 added to initial A dark brown residue,
waste. containing 783 ppm CN~
and 71,200 ppm COD, re-
i suits upon evaporation*
I
i
Addition of urea isr- Dark brown bottom,
proves process similar in character-
efficiency, istics to above.
Autoclaved under N N,CO,C02, N,0,
gas phase. X 3 on3
S0_ absorbed into Absorption of SO-
dilute H2S04 to yield > 95 percent '
H2SO , catalytically
oxidized to H_S04
NH, in concentration Catalyst recovered by
25 fold of.Cu2+ ions. chelate resia-
157 C, 24.5 atm oxygen CaO added, corresponding
pH 10 to sulfate content.
Catalytic wet-
oxidation of
acrylonitrile
wastes.
Akitsune, 1976
Oxidation by
chlorine, chlorite,
or hypochlorite
in the presence of
an alkaline earth
aetal.
Hushizumi, 1974
Oxidizing agent re-
quired for CN~
destruction.
Chlorlnation not recom-
mended for synthetic
organic wastes.
Electrolytic oxida-
tion of cyanide
wastes.
Ueki, 1973
30 ppm CN
99.5 percent
removal
0.1N
added to waste
Zn (C?02
collected at cathode.
of CN
witinydro gen
peroxide and
sodium hypochlorite.
Bakes and Daude-
Lagrave, 1976
pH. 1; H202 is added
before SaOCl
Cyanide oxidized to
cyanate.
113
-------
TABLE 13 (concluded)
Treatment
Process/
Description
Investigators
Waste
Characteristics
Treated
Effluent
Special Conditions
Comments
AMMONIUM STJLFATE
RECOVERY OR REMOVAL
Wastewater contain- Tsuruta, 1976
ing (NH4)2S04
treated by addition-
of Ca(OH)2 to
precipitate CaSO,;
after ammonia strip-
ping waste burned
with fuel. .
4.5 wt percent
(NH4)2S04
0.4 wt percent
NH4+
0.5 wt percent CN~
3.1 wt percent
organic com-
pounds
Overhead
recovered as
crude NH.
After CaSO, removal.
4
residue burned with
kerosiue at 800-1100 C.
SO generation avoided
(HH4)2 S04 waste is Ochi et al., 1973
Created with excess
CaO or Ca(OH). at
>75°C.
Precipitate
removed
Solution neutralized
by CO..
TREATMENT WITH LIME/
ADDITION TO CEMENT
Column bottoms
wastewater is used
as cement addi-
tives : treatment
with lime and addi-
tion to a concrete
mixture.
Kawamura et al.,
1975
Lime treatment to
decompose ammonium
sulfate.
Addition of waste
improves strength and
workability of cement.
ALKALINE HYDROLYSIS
Alkaline hydrolysis
at elevated temper-
atures to purify
nitrile containing
wastes.
Serebryakov.et al.,
1966
Hydrolysis conditions:
140 to 160 C, and
16 to 20 atm.
Elevated temperature
and pressure reduce
alkali consumption.
TREATMENT WITH
FORMALDEHYDE
Treatment of a.
cyanide containing
wastewater with a
HCHO - containing
agent, and then
with a cement
mixture.
Okita and
1977
Ohbori,
After hardening of
cement, no cyanide
leachate detected.
Cyanide removal
from acrylonitrile
wastewater by
treatment with a
HCHO solution of
pH 3.
Ellscher and Metz,
1973
27 ppm CN~
pH 8.7
0.7 ppm CN
40 minute detention
time; dosage ratio
of HCHO to HCN is 2:1.
pH affects cyanide
removal rate.
CONCENTRATION OF
HASTE FOR DISPOSAL
Treatment of Hausweiler, et al.
acrylonitrile strip-
per bottoms with an
organic amine at
temperatures of 100
to 125°C; followed
by addition of more
amine to the treated
waste and a second
evaporation.
200 to 1000 ppm
HCN
400 to 3000 ppm
organic nitriles
<2000 ppm uni-
dentified com-
pounds
Concentrate from
the evaporator
contains up to
60 wt percent
high boiling and
resinous organic
compounds.
Water vapor is re-
cycled.
Concentrated solution may
be further dried for
incineration, or adsorbed
onto coal ashes for
solid waste disposal.
-------
bottoms from the acetotiitrile purification stripping column (Point
No. 3), the bottoms from the acrylonitrile distillation column (Point
No. 5), and the waste streams from the acetonitrile distillation
(Points No. 7 and 8) could also be incinerated.
Another approach to treatment of wastes by incineration,
involves a modification of the unsaturated nitrile (acrylonitrile)
manufacturing procedures (as discussed in Section II) where unreacted
ammonia, waste materials, and by-products (e.g., HCN and acetonitrile)
"are not condensed but remain with absorbed off-gas for ultimate
disposal by incineration" (Sheely, 1975). Thus, this procedure
eliminates altogether the need for ammonium sulfate recovery equip-
ment and enables complete combustion of waste loadings (i.e., no
biological treatment required), while complying with air pollution
requirements.
Adsorption and Catalytic Oxidation on Granular Activated Carbon
The oxidation of cyanide to cyanate under alkaline conditions
by oxygen (e.g., air) may be catalyzed by activated carbon.
CN~ + 1/2 02 - " CNO~ (74)
CNO" + 2H20 - + H0>3 + NH3
Not surprisingly, this reaction is even more effective under pres-
sure (Kuhn, 1971). Furthermore, cyanide removal is further cata-
lyzed by copper. Bernardin (1973) has theorized that the formation
115
-------
of copper cyanides leads to increased adsorption capacity of the
carbon (copper cyanides have a higher affinity for the carbon
than cyanide ions) and thus permit higher flows. While copper
may be initially impregnated-onto the carbon or dosed in a 1:1 ratio
i
2+ ~
(weight basis of Cu /CN ), a continuous feed of copper does lead
to the further degradation of cyanate to ammonia and carbon dioxide.
Some clogging of the bed may occur from precipitation of malachite
(CuC03*Cu(OH)2) as shown below:
HC03" + OH~ t C032~ + H20 (76)
2Cu2+ + 20H~ + C032~ »• CuC03' + Cu(OH)2 (77)
However, the precipitates may be removed and recovered by an acid
wash.
Using this method, cyanide concentrations of 100 mg/1 in the
influent were-reduced to less than 0.05 mg/1 in the effluent.
Efficiency is maximized by a low suspended solids loading and a
sufficient oxygen feed. Thus, Hager and Rizzo (1972) recommend
maintaining a dissolved oxygen (DO) concentration at least equi-
valent to the CN~ concentration in solution, with a minimum DO of
6 mg/1. The presence of copper in the effluent is of obvious
concern; but during treatment of metal plating rinse waters, effluent
Cu+2 concentrations were generally below .05 mg/1. Initial
*
116
-------
studies suggest copper may be routinely recovered by acid treatment
of the carbon.
After a review of previous investigations of cyanide treatment
with activated carbon, Prober and Kidon (1976) completed a differen-
tial bed study of sorption rates under high cyanide loadings, reaching
the following conclusions: (1) precipitation occurred outside the
— 2+
carbon bed for CN /Cu molar ratios of less than or equal to 3;
(2) no correlation was found between rate data for oxygen and copper
and the calculated rates for cyanides; and (3) further research is
needed to clarify .the effects of temperature, particle size, long-
term effects, and the general reaction mechanism. A significant
disadvantage of any adsorption system, however, is the need for
pretreatment of streams which contain large amounts of polymeric
material to prevent plugging of adsorption columns or beds. Thus,
because the major pollutant load during acrylonitrile manufacture
(Point No. 1) contains both cyanides and polymeric material, such
systems have only limited applicability without extractive pretreat-
ment to remove organic compounds.
Treatment with Formaldehyde
Hydrogen cyanide may be removed from gaseous waste streams
as cyanohydrin by reaction with formaldehyde, generally at pH _>. 8
(Karchmer and Walker, 1958).
HCN + HCOH *• HOCH2CN (78)
117
-------
Similarly, cyanide-containing waste solutions (specifically, cyanide-
metal complexes) may be treated with an aldehyde and/or a water-
soluble bisulfite reaction product (Morico, 1970) or by formaldehyde
(H-CO/CN* >^ 1) under alkaline conditions (Csuros et al., 1973).
Glycolic acid may be recovered from the solution in the form of a
metal glycolate, as in:
NaCN + CH20 + 2H20 *• HOCH2COONa + NH3 (79)
That formaldehyde reacts with cyanide to form glyconitriles, and
subsequently condenses to form a non-toxic polymer is well known.
RCH(CN)0~ + RCH(CN)0"~ > polymer (80)
The polymerization was found to be a psuedo first-order reaction,
with increased rates- at temperatures greater than 60°C and a pH be-
tween 9 and 10 (Shen and Nordquist, 1974). The presence of ammonium
sulfate increases the reaction rate (as measured by the disappear-
ance of cyanide) since ammonia may also react with glyconitrile
to form aminoacetonitrile or with hydrogen cyanide to form adenine.
While removal by polymerization may lead to solids formation, Shen
and Nordquist have found that the amount of solids formed is roughly
proportional to the initial HCN content. In fact, precipitation will
continue to occur at a very slow rate, at room temperature, in a
waste that initially contained more than 1 percent HCN. Thus, by
diluting wastewater to less than 1 percent cyanide concentration
before treatment with formaldehyde, precipitation of highly colored
solids can be avoided.
«
118
-------
N
Although rapid degradation of a 0.14 M (approximately 3600 mg/1)
cyanide solution was reported by Shen and Nordquist (1974) (the
reaction time was roughly 30 minutes to an hour depending on the
specific conditions), the rate slows appreciably as cyanide concen-
tration decreases. In the presence of a bisulfite catalyst (Cavender,
1977), detoxification of a less concentrated cyanide waste stream
(~*200 mg/1) .still requires approximately one hour at a pH of prefer-
ably 9 to 10 and temperatures of 80 to 135°C. Among the wastes
treated, perhaps significantly, is "paving run-off water" from an
acrylonitrile production site, which had bees adjusted to a cyanide
concentration of 200 mg/1 by the addition of potassium or hydrogen
cyanide. As a typical example, a cyanide waste solution of 200 mg/1
plus was reduced to 0.8 mg/1 in a period of 1 hoor (at a pH of 9 and
120°C) using this system. While solids formation or coloration of the
effluent are not explicitly discussed by Cavender (1977), the cyanide
concentrations encountered in acrylonitrile waste « 10,000 mg/1) most
likely preclude this problem.
Hydrolysis
Hydrolysis of hydrogen cyanide is favored at temperatures over
100°C:
HCN + 2H20 - > HCOO
and is further increased under high temperatures and pressures.
Heating cyanide containing wastewater to approximately 180°C in a
pressure, vessel is reported to result in the complete hydrolysis of
«
119
-------
cyanide within 5 minutes (Schindewolf, 1972 and 1977). duPont uses
a proprietary process involving alkaline hydrolysis to pretreat a
segregated waste stream at their acrylonitrile production site in
Memphis (see Appendix IV).
Chemical Precipitation
Ferrous salts have been used to remove cyanide from aqueous
solutions in the form of an iron-cyanide complex. This treatment has
limited application to acrylonitrile wastewaters, as the cyanide
concentration in the effluent is reduced to only 5 to 10 mg/1. Fur-
thermore, the cyanide ion is not degraded by the procedure but merely
precipitated and still presents a subsequent disposal problem
• (Patterson, 1975). As noted earlier, this technique would have
limited application to the treatment of organic nitriles.
PHYSICAL PRETREATMENT
Physical unit operations are commonly used by industrial manu-
facturers as in-process purification steps, for separation of streams
(e.g., a decanter), or for removal of constituents "from liquid phases
for recovery or disposal. Such unit operations include: solvent ex-
traction, stripping, aeration, absorption into an aqueous solution
or solvent, adsorption on silica, alumina, or activated carbon, and
azeotropic or extractive distillation. These techniques may be
combined or repeated in sequence, as required, to achieve the
desired level of pretreatment of the waste effluent. The effluent
is generally then chemically and/or biologically treated prior to
120
-------
discharge. Wherever practical, solvents are recovered and recycled
for reuse.
Separation Practices
Acrylonitrile manufacturers use many physical separation
techniques to purify the product and by-product streams, such as,
(1) separation of acrylonitrile and acetonitrile; (2) recovery of
hydrogen cyanide; and (3) purification of acetonitrile (Hausweiler
et al., 1970; Scherhag and Hausweiler, 1972; Lovett and Rambin,
1972; Bitners et al., 1970; Allirot et al., 1972; Ohashi et al.,
1972; Breda, 1972; Mahler et al., 1976; Sheely, 1969; Carlson, 1973).
Many of these procedures, specifically those patents assigned to
Erdolchemie-Bayer, are believed to be currently in use in European
acrylonitrile plants. Employment of such techniques result in an
overall reduction of the plant wastewater load, as concentrated
organic streams may then be disposed of by incineration. Table 13
summarizes various physical-chemical treatment schemes investigated
by foreign researchers in the last ten years for treating acrylonitrile
manufacturing wastes.
Ammonium Sulfate Recovery
The bottom stream from the wastewater stripping column (Point
Source No. 1) typically contains 8 to 12 percent ammonium sulfate
(Fitzgibbons et al., 1973, Guttmann and Grigsby, 1971), but may
be as high as 30 percent (Schwartz et al., 1975 and Heath, 1972).
This stream also contains substantial quantities of water-soluble
*
121
-------
and suspended organic material from the quenching column, and as
noted previously, represents the major wastewater load from the
manufacturing facility. By recovering ammonium sulfate, the total
dissolved solids (IDS) of the wastewater is greatly reduced, making
portions of the waste more amenable to biological treatment (i.e.,
TDS > 10,000 mg/1 is considered inhibitory to biological organisms).
Furthermore, if this waste is to be concentrated and incinerated,
recovery greatly reduces pollutant emissions of sulfur oxides and
lowers fuel requirements to a feasible range. Moreover, some
positive gain may be. realized by sale of recovered ammonium sulfate.
SOHIO and duPont hold U.S. patents specific to the recovery
of ammonium sulfate from acrylonitrile manufacture. Basically,
two approaches to the problem have been taken: (1) the ammonium
sulfate is extracted from the column bottoms with a solvent or,
«
(2) ammonia or an alkyl amine is added to the column bottoms, after
concentration, to saturate the solution and precipitate ammonium
sulfate. The latter approach, patented by Miller and Salehar
(1969), while not requiring the addition of a solvent, may lead to
equipment fouling from organic tars.
One extraction! procedure for recovering the ammonium sulfate
from solution employs a water-miscible solvent such as a glycol (up
to 6 carbons), diglycol ether, triglycol ether, or glycerol (Guttmann
and Konicek, 1971). The solvent-wastewater mixture is concentrated
122
-------
by distillation, and the ammonium sulfate is separated by filtration.
The solvent may be subsequently recovered by distillation and recycled.
A particularly attractive recovery system involves extraction
with a liquid nitrile; thus, acetonitrile (which is generated and
recovered in process) is added to the waste stream, after concen-
tration by distillation to at least 30 percent by weight ammonium
* .
sulfate (Smiley, 1971). The temperature during extraction is held
just below the boiling point of the mixture. The organic phase
(containing the organic impurities) may be distilled as shown
in Figure 19; and the nitrile extractant may be subsequently reused.
The non-volatile organic impurities may be disposed of by incinera-
tion. The ammonium sulfate solution is then crystallized using
conventional techniques. The patent procedures produce fertilizer
grade ammonium sulfate (i.e., greater than 96 percent purity).
Erdolchemie-Bayer, a jointly held European chemical company, is
believed to be recovering ammonia as crystalline ammonium sulfate
from the reaction gas mixture at their plant site in Dormagen,
Germany (Hausweiler et al., 1971). This procedure does, neverthe-
less, apparently require substantial in-process modifications to
acrylonitrile manufacture (discvussed in Section II). Additionally,
marketable ammonium sulfate is a by-product of the wet-oxidation of
acrylonitrile wastewater (Wilhelmi and Ely, 1976).
123
-------
CONTAMINATED
SOLUTION
ACETONITRILE
lEXTRACTANT
EXTRACTION
ORGANIC PHASE
•CONTAINING IMPURITIES
DISTILLATION
EXTRACTANT IMPURITIES
(RECIRCULATE)
Source: Smiley, 1971
AQUEOUS PHASE"
CONTAINING
CRYSTALLIZATION
MOTHER CRYSTALLINE
LIQUOR (NH.) SO,
! (RECIRCULATE)
FIGURE 19
RECOVERY OF AMMONIA SULFATE FROM ACRYLONITRILE MANUFACTURE
124
-------
In summary, fertilizer grade ammonium sulfate may be recovered
v
from Point No. 1 by a variety of extraction and separation tech-
niques. The practicality of such recovery is largely dependent
on ammonium sulfate yields, solvent losses and problems related
to equipment fouling. The principal advantages of ammonium sulfate
recovery is that toxic wastes may be disposed of by incineration,
and the hazard of environmental contamination from effluent disposal
is removed. At the present time, however, no U.S. manufacturer is
known to be recovering ammonium sulfate (Horn and Hughes, 1977).
COMBINATION AND ALTERNATIVE TECHNIQUES
From the preceding review of biological processes and physical-
chemical treatment techniques, it is .obvious that no single treat-
*
ment operation or process will achieve the reduction in total
pollutant loading from all acrylonitrile waste streams necessary
for discharge to navigable waters. Thus, the next step in evaluating
this wastewater problem is to assess the technical feasibility of
combining certain treatment techniques for application to combined
and/or segregated waste streams.
Wet-Oxidation with Biophysical Treatment
Wet-oxidation, as described earlier; may be combined with
biological treatment in the presence of powdered carbon in a two-
step process for treating acrylonitrile wastewater as shown in Figure
20. The raw waste load is first partially degraded by catalytic
125
-------
Raw Waste
NJ
ON
Wet!
Oxidation!
Carbon!
Make-upj
Source: Wtthelm and Ely. 1976
(Pradt and Meidl. 1976)
Aeration Basin
Polymer
.Treated Effluent
Recycle
Carbon
Regeneration
'larifier
FIGURE 20
WET-OXIDATION WITH BIOPHYSICAL TREATMENT
-------
oxidation (at 270°C and 200 psi); subsequently, the partially
oxidized stream is fed to an aeration tank containing acclimated
activated sludge. Powdered carbon is added to the aeration contact
basin to enhance bio-oxidation and reduce color and odor. Addition-
ally, flocculating agent may be required to achieve proper settling
in the clarifier of the biomass-carbon mixture. The spent carbon-
excess biomass sludge collected in the clarification step undergoes
further wet-oxidation in order to dispose of the excess biomass and
regenerate the spent carbon. This may be accomplished by (1)
providing a separate wet-ox unit solely for carbon regeneration (as
illustrated in Figure 20); or (2) mixing the biomass-carbon mixture
with the raw wastewater; or (3) providing a carbon-biomass s-torage
s
tank for intermittent treatment. A 99.9 percent reduction in total
cyanides is claimed for treatment of acrylonitrile wastewaters
(Pradt, 1976). Marketed by Zimpro, Inc., this two-step treatment
process is believed to provide a greater than 99 percent reduction
in BOD and COD. The final effluent typically contains 275 to
325 mg/1 COD, 10 to 20 mg/1 BOD, and 0.4 to 1.0 mg/1 total cyanides
(Wilhelmi and Ely, 1976 and Pradt, 1976).
A treatability and design study performed by Zimpro, Inc. on a
high flow waste stream known to be difficult to treat biologically
(high organic, as well as a high dissolved solids content) serves
to compare conventional activated sludge systems, to the biophysical
127
-------
(carbon/ wet-ox) system. Nitrification was found to be enhanced in
the latter system, with a 95.5 percent TKN removal, as opposed to
13.8 percent for the activated sludge. Furthermore, with some
modifications and the judicious addition of a carbon source (e.g.
methanol, molasses), denitrification of the waste will occur
(Frohlich et al., 1976).
5CH3OH + 6H+ -I- 6N03~ * 5C02 + 3N2 + 13H20 (82)
For a list of other powdered carbon/wet oxidation applications and
their comparative costs, the reader is referred to Environmental
Science and Technology (February), 1977.
Other Combination Systems
In theory, there are many different approaches in which treat-
ment techniques may be selected and combined to attain the desired
level of pollutant reduction. However, a critical factor in adopting
any treatment practice is the economics of the operation. Although
an economic analysis of each alternative treatment scheme (e.g., a
comparison of capital investment, operation and maintenance costs,
materials, and energy requirements) is beyond the scope of this
report, it is, nevertheless, important to acknowledge that biological
treatment processes are the most economical means of treating a high
volume, as well as high strength (but still biodegradable) organic
waste. Thus, the ideal scheme would combine an economical pretreat-
ment steR, to improve the biodegradability of the waste load, with an
128
-------
acclimated, activated sludge process. Depending on the strength of
the effluent for the pretreatment step, the waste could be biologi-
cally treated at the manufacturing plant site or, better still,
discharged to the local sewer system for treatment at a publicly owned
treatment works.
Aside from wet-oxidation (as detailed above), there are several
other means of detoxifying cyanide containing waste streams, such
as, treatment with a peroxide compounds, treatment with formaldehyde,
or alkaline hydrolysis, which enable biological organisms to degrade
the major portion of acrylonitrile manufacturing wastes. Such
pretreatment techniques could,be selectively employed in combination
•
with stream segregation practices, ammonium sulfate recovery, and
incineration. Other treatment operations or processes, such as,
ammonia stripping or polishing of the final effluent with activated
carbon would be dependent on dilution prior to discharge (many plants
are capable of combining treated streams with non-contact cooling
water, etc.) and binding effluent limitation requirements. A summary
of alternative treatment systems investigated by foreign researchers
appears in Table 14, and a more detailed discussion of practicable
alternatives follows in Section V, Recommended Treatment Alternatives.
129
-------
TABLE 14
COMBINATION SYSTEMS APPLIED TO ACRYLONITRILE WASTEWATERS BY FOREIGN RESEARCHERS
Treatment
Process/
Description
Waste
Investigator(s) Characteristics Treated Effluent
Special Conditions
Comments
Alkaline hydrolysis
by addition of NaOH
to the waste (.25
percent by wt)
at elevated tempe'fa"-
tures and pressure,
followed by biolog-
ical treatment.
Chekhovskaya•et
al., 1969
Waste is biodegradable Hydrolysis carried out Nitrification inhibited
after treatment and a at 150-160 C for 15 by acrylonitrile pre-
3-fold dilution.
minutes.
sent £50 ppm.
Oxidation with air or
0, to remove organic
* i
matter.
(NH4)2S0
Removal of
by
evaporative crystall-
ization .
Catalytic oxidation
with oxygen in the •
24- •
presence of Cu ions
and NH,+,
followed
by dilution and ion
exchange.
Hara et al.,
1976
Kasai et al.,
1976
6.1 wt percent COD
12.5 wt percent
24,600 ppm COD
- 5 wt percent
Removal of:
90 percent of COD
. - 100 percent
After ion exchange:
£250 ppm COD
SO.l ppm Cu
Conditions: 260 C and
85 kg/cm in presence
of 0.01 percent Cu
catalyst.
Mother liquor is re-
cycled to oxidation
step.
Oxidation at 250°C and 500 ppm Cu added with
70 kg/cm ; dilution of
waste 25-fold prior to
ion exchange.
99 percent recovery.
Pretreatment with a
gel-type polymer,
followed by activated
carbon treatment.
Kuyama, 1973
Synthetic waste-
water containing
5400 ppm acrylon-
itrile.
Capacity of carbon sig-
nificantly improved by
pretreatment.
• Oxidation with 0.
or an Or containing
gas under pressure
and high temperature,
followed by.ga.s-
' liquid separation.
^firnfth'-fi^ anl f afria
crystallizes from
liquid concen-
trate; mother liquor
is recycled.
Sakakihara et
al., 1976
2 percent
30,000 ppm COD
Concentrate:
45 percent
100,000 ppm COD
Oxidized at 260 C and Gas emissions
60 kg/cm2
/
Wet high pressure
treatment In the
presence of Cu , or
Cu2+ and-NH* ,
folio-wed by ion ex—
. change.
Wet oxidation, gas-
liquid separation
followed by reverse
oenosis (BO).
Tagashura et 24,000 ppn COD. After oxidation:
al., 1975 ~5 percent 240 ppm COD
.(HH4)2S04 mixed 886 ppn Cu2+
with resin regenera- 5.43 wt percent
tlon solution con- ^ , SQ
taining'CuSO4, ' 42 4
, . ; . '' (CNH4)2S04.: andX . - '-:..:'.
Takagi et al.
1974
25,000 ppm COD 2500 ppm COD (After
wet-ox)
50 ppn COD (after
BO)
Acrylonitrile waste-
water mixed with ion-
exchange regeneration
water.
Reactor.condltions:
. 220-250 C and
50 kg/«m2;
BO pressure:
49.5 kg/cm2
CuS04 recovered from
resin and recycled.
98 percent desalted
acetate film used for
RO.
,130
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SECTION V
RECOMMENDED TREATMENT ALTERNATIVES
INTRODUCTION
As was discussed in Section I, the major objective of this study
is to assess pollution control practices from the manufacture of
acrylonitrile with regard to toxic pollutant generation. Whereas
Section II provided the process chemistry and manufacturing configu-
ration necessary for the prediction of toxic pollutants (identifying
point source discharges of specific pollutants), Sections III and IV
reviewed -current wastewater practices and alternative"control technol
ogies largely in terms of the combined wasteload from acrylonitrile
manufacture. Thus, it is the purpose of this section to examine the
treatability of the process wastewater in terms of segregated point
source discharges. As shown in Figure 15, the most refractory of the
waste streams is Point No. 1, characterized by high loadings of hydro
gen cyanide, organic nitriles, heavy polymeric material and inorganic
salts. Detoxification of this stream represents the major obstacle
to successful treatment of acrylonitrile wastewaters and must be the
focal point of any future treatability studies.
The discussion that follows will present: (1) a point source-by
point source summary of potential pollutants from acrylonitrile manu-
facture using the SOHIO process; and (2) recommend treatment alterna-
tives for each stream. Recommendations will be based solely on the
efficiency of a process to treat a waste stream, and exclude any
»
131
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analyses of capital, operation and maintenance, and energy costs.
Thus, included in this section are treatment options which may be
only practicably applied to new sources (i.e., existing facilities
might require extensive repiping in order to implement a recommended
treatment). Furthermore, it is assumed throughout the section that
conventional treatment practices (e.g., equalization, neutraliza-
tion, separation) will be employed, as required.
POINT SOURCES OF POTENTIAL POLLUTANTS
Point No. 1
The bottom stream from the quench column, with an approximate
flow of 155 gpm and a chemical oxygen demand (COD) of 80,000 ppm,
represents the largest,.single waste load from the manufacture of
acrylonitrile. The stream, similar to tea or coffee in color, is
moderately acidic (pH ^5) and has a high dissolved solids content
(M.O percent); the wastewater contains catalyst fines and probably
all of the non-volatile organic species generated by the process
(see Table 5). Rather than reiterate all potential pollutants,
Table 15 presents a summary of the major compounds found in the
quench column bottoms.
After reviewing current treatment practices and available treat-
ment technologies for acrylonitrile-containing wastewaters, two
alternatives for treating Point No. 1 appear practicable and worthy
of further consideration: biological treatment of a detoxified
wastewater or incineration. With either treatment option, however,
132
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TABLE 15
REPRESENTATIVE COMPOSITION OF THE QUENCH COLUMNS BOTTOMS
Component %, by Weight
Acetaldehyde ,0.1
Acetic acid 0.2
Acetonitrile 0.3
Acrolein ' 0.02
Acrylamide 0.1
Acrylic acid 0.03
Acrylonitrile • >O.Q5
Ammonia 1.5
Ammonium sulfate 10-15
Fumaronitrile 0.08
Hydrogen cyanide 7.0
Maleonitrile 0.2
Polymeric material ^ 6
Trioxaazatricylodecane 0.4
Source:Miller and Salahar (1969)
the high inorganic salt content of the waste stream is undesirable:
biological treatment processes are inhibited by high dissolved solids
loading (e.g., 10 percent by weight ammonium sulfate contributes
100,000 mg/1 to dissolved solids loading), and efficient combustion
of the waste is likewise precluded by such a high salt concentration.
Ammonium sulfate may be recovered from the wastewater stripping
column bottoms by separation of inorganic and organic species (i.e.,
extraction of organic species with an organic solvent),.and subse-
quent crystallization of ammonium sulfate. While the mother liquor
is recirculated, the organic impurities, now concentrated in an or-
ganic phase, are conveniently disposed of by combustion. Typically,
the extractant would be purified for recirculation by 'distillation
and the non-volatile organic pollutants incinerated.
133
-------
Alternatively, the raw waste could be detoxified by chemical pre-
treatment, prior to biological treatment with acclimated, activated
sludge. Although several potential chemical pretreatment techniques
for detoxifying a cyanide/nitrile-containing waste were discussed
earlier (e.g., ozonation, treatment with a peroxide compound, ad-
sorption and catalytic oxidation on .granular activated carbon, and
polymerization with formaldehyde), oxidation of the waste stream at
elevated temperatures and pressures (under alkaline conditions) ap-
pears to be the most promising option. This technology (i.e., wet-
oxidation) has been demonstrated (and is in operation) at several
acrylonitrile facilities outside of the United States (Wilhelmi and
Ely, 1976). Furthermore, and of significance, this type of catalytic
oxidation of the waste will provide a concentrated aqueous liquid
phase from which crystalline ammonium sulfate may be recovered. After
detoxification (i.e., significant removal of cyanides and organic ni-
triles from the waste), the waste is subjected to biological or bio-
physical (activated, sludge combined with powdered activated carbon)
treatment for further reduction of conventional wastewater parameters.
duPont, at their Memphis acrylonitrile manufacturing site is reportedly
using alkaline hydrolysis to pretreat segregated process waste, prior
to discharge to a publicly owned treatment facility. (In addition, a
portion of the plant waste is disposed of by incineration.) Alkaline
hydrolysis of cyanide-containing wastes, like wet-ox, normally re-
quires high temperatures and/or pressures; however, details of this
»
134
-------
pretreatment operation are considered proprietary and, as such, are
not available to the public (see Appendix IV).
As described in Section II, significant reduction in the pollu-
tant loading from Point No. 1, as well as the entire process waste-
load, nay-be accomplished by extensive modification to the SOHIO
process. Such modifications (the "Badger process") would allow for
complete combustion of all by-products (Sheely, 1975). On a smaller
scale, but still requiring substantial in-process modifications to
existing U.S. acrylonitrile manufacturing plants, the "Erdolchemice-
Bayer process" allows for recovery of crystalline ammonium sulfate
from the reactor. (This modification involves removal of ammonia
directly from the reactor effluent with an ammonium sulfate/sulfuric
acid solution (Hausweiler, 1970).)
Point No.' 2
The vent gas consists of reactor product which has been cooled,
quenched, and scrubbed with water for acrylonitrile recovery. The
specific composition is dependent on reaction conditions, absorber
overhead temperature, feed rates, and the feedstock composition.
This point has been studied in considerable detail as part of an air
emissions source assessment of acrylonitrile manufacture (Horn and
Hughes, 1977). Significant pollutants (in the approximate order of
concentration) are as follows: carbon monoxide, propane, propene,
acrylonitrile, acetonitrile, hydrogen cyanide, ethane, methane, acetal-
dehyde, acetone, acrolein, and propionitrile. Incineration of this
«
135
-------
stream, which is believed to be the current practice at all U.S.
acrylonitrile manufacturing plant sites, is recommended.
Point No. 3
The bottom stream from the wastewater stripper, which represents
another important point source of pollution, is qualitatively similar
to the quench column bottoms, Point No. 1. In terms of conventional
water quality parameters, this waste stream is characterized by a
moderate flow (180 gpm), a neutral pH, a chemical oxygen demand of
17,000 ppm, and a dissolved solids content of 1 percent. Table 16
lists the representative concentration of species found in the strip-
per bottoms.
Removal of polymeric deposits from the heat transfer surfaces in
this unit may also generate significant quantities of solid waste.
Reportedly these surfaces must be intermittently cleaned when 40 kg
and 80 kg of deposits accumulate on the reboiler and condenser re-
spectively (Ohashi et al., 1972).
Treatment options for this waste stream are similar to those
discussed under Point No. 1. The organics in the waste stream could
be extracted, concentrated and subsequently incinerated. Alterna-
tively, this stream could be detoxified by a chemical pretreatment
step, and then, undergo biological treatment. However, as the dis-
solved solids content (^1 percent) of the stream is significant, di-
lution of the stream would most likely be required prior to biologi-
cal treatment.
<«
' 136
-------
TABLE 16
REPRESENTATIVE COMPOSITION OF THE WASTEWATER
STRIPPER BOTTOMS
Component mg/1
Acetic acid • 120
'.Acetonitrile ' .., 35
Acrylonitrile <10
Ammonia 220
Fumaronitrile 500
Hydrogen cyanide 225
Maleonitrile 300 '
Nicotinonitrile 500
Succinonitrile 5400
Sulfate 500
Source: Halvorsen and Vines (1972)
Point No. 4 '
-This point is comprised of the volatile components removed over-
* '
head from the azeotropic distillation column. The major component
of this stream is hydrogen cyanide with lesser amounts of volatile
impurities such as acetaldehyde, acetone, acetonitrile, butane,
ethene, and propene. By-product HCN may either be recovered (see
Point No. 9) for resale or reuse, or incinerated.
Point No. 5
This point represents the still bottoms from the final purifi-
cation of acrylonitrile. Aside from a certain amount of polymeric
material, suspected pollutants include methacrylonitrile, acrylamide,
acrylic acid, cyanohydrins, and heterocyclic, nitrogen containing
137
-------
bases, such as nicotinonitrile. Because this stream is largely
organic in nature, disposal by incineration is recommended.
Point No. 6
This point, if indeed present in current manufacturing configu-
rations, represents a solid waste discharge. Heterocyclic, nitrogen
containing bases, in particular oxazole and isoxazole, together with
acrylonitrile are the major contaminants of this waste. Landfill
disposal, at a site designed specifically for hazardous organic
wastes, is recommended.
Point No. 7
This effluent, together with Point No. 8, represent the waste
streams from acetonitrile purification. Not surprisingly, the prin-
cipal contaminant is acetonitrile with smaller amounts of benzene
(the presumed azeotropic reagent), acetone, polymeric material and
inorganic salts (see Table 17).
TABLE 17
REPRESENTATIVE COMPOSITION OF WASTEWATER STREAMS FROM
ACETONITRILE PURIFICATION
Component
Decanter
Wash Water
%, by weight
Column
Bottoms
Acetonitrile
Acetone
Benzene
Polymeric material
Inorganic salts
Water
12.5
1.5
0.4
—
15.4
70.3
86.2
6.9
6.9
Source: Tyler (1969)
138
-------
The organic pollutants should be separated by extraction techniques,
concentrated and incinerated.
Point No. 8
This point represents the column bottoms from the purification
of acetonitrile. Again the principal contaminant is acetonitrile
with- smaller amounts of polymeric material and inorganic salts.
Because of the high salt content together with the relatively small
volume of this stream, dilution followed by biological treatment is
recommended. Incineration of,this stream, however, should not be
totally precluded without further tests. (It must be noted that
acetonitrile may well be disposed of directly, rather than be
purified.) .
Point No. 9
This stream, if present, results from the purification of hydro-
gen cyanide. The principal contaminants are unsaturated hydro-
carbons and heterocyclic compounds which either have boiling points
close to that of hydrogen cyanide (b.p. 26°C) or form azeotropic mix-
tures which are difficult to separate by conventional distillation.
Suspected pollutants include propene, butenes, pentenes, small
amounts of sulfuric acid, together with their hydrated products.
This waste should be diluted and biologically treated.
Non-point Source Emissions
An additional waste stream results from surface runoff (and non-
point source discharges) from the acrylonitrile manufacturing process.
139
-------
Waste loading Includes miscellaneous leaks from process equipment
(e.g., valves, flanges), process upsets, and routine sampling and
maintenance operations (I.e., general housekeeping practices). The
flow rate, unless pumped from an equalization basin, fluctuates with
rainfall. The stream Is further characterized as moderately alka-
line (pH 9), low chemical oxygen demand (500 ppm), and low bio-
chemical oxygen demand (400 ppm). Table 18 lists the representative
composition of such a stream.
TABLE 18
REPRESENTATIVE COMPOSITION OF SURFACE RUNOFF
Component . mg/1
Alkalinity 225
Ammonia 6 0
Nitrates
4
Nitrites
Suspended Solids 30
Volatile Suspended Solids 17
Source: Simonsen (1977). See Appendix IV.
This waste should be neutralized and biologically treated.
140
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SECTION VI
SUMMARY AND CONCLUSIONS
The discharge of a toxic substance to the environment by an
organic chemical manufacturer, depending on the persistence and
mobility of the compound, may have irreversible effects on the
environment. Under the Clean Water Act of 1977, EPA must regulate
such industrial discharges by the establishment of effluent limita-
tions, defined in terms of the best available technology economically
achievable. However, the establishment of such standards for specific
toxic species that are not only equitable to industrial manufacturers,
but more importantly that will prevent further deterioration of the
environment, is an exceedingly difficult task. As a first step, EFA
•
must thoroughly understand the manufacturing process and available
control technologies so that, ultimately, attainable standards may be
set.
To this end, a detailed description of acrylonitrile manufacture
and pollution control technology has been presented. Included is
a comprehensive discussion of the reaction mechanism, with a sum-
mary of potential pollutants generated from feedstock impurities
and significant side reactions. Additionally, a generic process
configuration for acrylonitrile manufacture has been formulated,
identifying specific point source discharges (see Figure 15). From
this information, current wastewater treatment and disposal pract-
tices, as well as alternative methods of treatment, were reviewed.
141
-------
Currently, there are no effluent limitations specific to the
point source discharge from acrylonitrile manufacture. All U.S.
acrylonitrile manufacturing facilities deep well their wastewater,
with the exception of duPont's Memphis operation, where segregated
streams are pretreated by alkaline hydrolysis prior to discharge to
_3L publicly owned treatment facility. In the short term, it is
obvious that deep well disposal is far less expensive than any
treatment scheme previously disussed. However, deep well disposal
must be regarded as an underground storage system rather than a
treatment system, and as such, not a long term solution to the
pollution problem. In light of future regulatory concerns, it is
propitious to evaluate alternate treatment technologies.
As discussed in detail in Section V, pollution abatement
from acrylonitrile manufacture may be accomplished by in-process
modifications or end-of-pipe technologies. Practicable methods for
pollutant reduction are best examined with regard to the treatability
of segregated waste streams, as presented in Figure 21. An economic
analysis of the costs of implementing such in-process changes or
wastewater treatment options, has not been performed, and furthermore,
remains beyond the scope of this report.
This study has provided, however, a framework for approaching a
difficult industrial wastewater treatment problem. As such, it has
outlined some of the steps that must be taken before BAT effluent
limitations can be rationally promulgated for acrylonitrile-containing
142
-------
POINT 1
Concentration of Stream
• Recovery of Ammonium Sulfate
- In Process Modifications
- End-of-Pipe-Treatment
Extraction of Organic Material
Incineration of Concentrated Organic Stream
Pre reatment with Biological Treatment of Detoxified Stream
Chemical Oxidation
Polymerization
Alkaline Hydrolysis
Recovery of Ammonium Sulfate
POINT 2 {
Incineration
POINTS;
Concentration of Stream
• Extraction of Organic Material
• Incineration of Concentrated Organic Stream
Biological Treatment of Detoxified Stream
POINT 4 |
Incineration
Recovery of Hydrogen Cyanide for Reuse or Resale
POINT 6 |
Incineration '
POINTS |
Landfill '
POINT 7 j
Concentration of Stream
• Extraction of Organic Material
• Incineration of Concentrated Stream
Propene fc
Ste«n »
janic Stream
ream
r
if
A
J
3
, I
V
cetonlt
k
i
3
J
rll.
-»
X
W
\
^N
" fi
ty
S3
ol.l
J
8
V
i
tile I-porltles 1 iwll,it|e.
" uo k^7\ r | —*•';•:;;
>v 1 x \ 2-S 1 ^ ° 1 »>s^
( s SSB s3
tf.-L.fc ?Tl ou3 . fcr.T
§ »3 3o3 53 | 1 6
a . a? § r*vV Us *"uw
Sss 1 1 V y
y \ ^/ Azeoiroplc | 6
Ht"Rr"1 * ai.i li
^ Tu Acetonltrile
I ' Purification
/p\ j
* s s >*•
las
POINT 8 .
Dilution and Biological Treatment
Incineration
POINT e '
Dilution and Biological Treatment
FIGURE 21
POTENTIAL TREATMENT OPTIONS FOR
ACRYLONITRILE WASTEWATERS BY
POINT SOURCE
143
-------
wastewaters. Recommendations for further studies (to validate the
conclusions reached in Section V) include:
• EPA verification, from sampling of actual process wastewaters,
of all-pollutant predictions and concentrations.
• Extension of this pollution prediction and abatement
methodology to other unit processes such as nitration,
chlorination, oxidation, etc.
• EPA funding of pilot scale studies for determination of
the technical practicability of the recommended treatment
alternatives.
• An economic analysis of viable treatment alternatives
(with regard to best available technology economically
achievable).
• Demonstration of BAT in an EPA-industry jointly funded
project.
145
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•
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«
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159
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REFERENCES (Concluded)
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160
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APPENDIX I
TOXIC POLLUTANTS TO BE REGtJLATED UNDER SECTION 307 OF THE FEDERAL WATER
; POLLUTION CONTROL ACT
LIST OF CHEMICALS
1. Acenaphthene
2. Acrolein
3. Acrylonitrile
4. Aldrin/Dieldrin
5. Antimony and compounds*
6. Arsenic and compounds*
»
7. Asbestos
8. Benzene
9. Benzidine
10. Beryllium and compounds*
11. Cadmium and compounds*
12. Carbon tetrachloride
18. Chlorinated phenols (other than
those listed elsewhere)
trichlorophenols
chlorinated cresols
19. Chloroform
20. 2-chlorophenol
21. Chromium and compounds*
22. Copper and compounds*
23. Cyanides
24. DDT-and metabolites
25. Dichlorobenzenes
1,2-dichlorobenzenes
1,3-dichlorobenzenes
1,4-dichlorobenzenes
26. Dichlorobenzidine
13. Chlordane (technical mix- 27. Dichloroethylenes
ture and metabolites)
14. Chlorinated benzenes
(other than dichloro-
benzenes)
15. Chlorinated ethanes
16. Chloroalkyl ethers
chloromethyl
chloroethyl
mixed ethers
17. Chlorinated naphthalene
1,1-dichloroethylene
1,2-dichloroethylene
28. 2,4-dichlorophenol
29. Dichloropropane and
dichloropropene
30. 2,4-dimethylphenol
31. Dinitrotoluene
*As used throughout the term "compounds" shall include organic and
inorganic compounds.
AI-1
-------
APPENDIX I (Continued)
32. Diphenylhydrazine 45. Mercury and compounds
33. Endosulfan and metabolites 46. Naphthalene
34. Endrin and metabolities 47. Nickel and compounds
35. Ethylbenzene 48. Nitrobenzene
36. Fluoranthene 49. Nitrophenols
2,4-dinitrophenol
37. Haloethers (other than dinitrocresol
those listed elsewhere)
50. Nitrosamines
chlorophenylphenyl ether
bromophenylphenyl ether 51. Pentachlorophenol
bis (dichloroisopropyl)
ether 52. Phenol
bis (chloroethoxy)
methane 53. Phthalate esters
polychlorinated diphenyl
ether 54. Polychlorinated biphenyls
• (PCBs)
38. Halomethanes ('other .than
those listes elsewhere) 55. Polychlorinated biphenuyls
hydrocarbons
methylene chloride
methylchloride benzanthracenes
methylbromide benzppyrenes
bromoform benzofluoranthene
dichlorobromethane chrysenes
trichlorofluoremethane dibenzanthracenes
dichlorodifluoromethane indenopyrenes
39. Heptachlor and metabolites 56. Selenium and compounds
40. Hexachlorobutadiene 57. Silver and compounds
41. Hexachlorocyclohexane (all 58. 2,3,7,8-Tetrachloro-
isomers) dibenzo-p-dioxin (TCDD)
42. Hexachlorocyclopentadiene 59. Tetrachloroethylene
43. Isophorone 60. Thallium and compounds
44. Lead and compounds 61. Toluene
AI-2
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APPENDIX I (Concluded)
62. Toxaphene 64. Vinyl Chloride
63. Trichloroethylene 65. Zinc and compounds
AI-3
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APPENDIX II
INDUSTRIAL CATEGORIES DEFINED BY THE CLEM WATER ACT OF 1977
LIST OF INDUSTRIES
1. TIMBER PRODUCTS PROCESSING
2. AUTO AND OTHER LAUNDRIES
3. ORGANIC CHEMICALS MANUFAC-
TURING
4. IRON AND STEEL MANUFACTURING
5. PETROLEUM REFINING
6. INORGANIC CHEMICALS MANU-
FACTURING
7. TEXTILE MILLS
8. LEATHER TANNING AND FINISHING
9. NONFERROUS METALS MANUFAC-
TURING
10. PAVING AND ROOFING MATERIALS
(TARS AND ASPHALT)
11. PAINT AND INK FORMULATION
AND PRINTING
12. SOAP AND DETERGENT MANUFAC-
TURING
13. STEAM ELECTRIC POWER PLANTS
14. PLASTIC AND SYNTHETIC
MATERIALS MANUFACTURING
15. PULP AND PAPERBOARD MILLS;
AND CONVERTED PAPER
PRODUCTS
16. RUBBER PROCESSING
17. MISCELLANEOUS CHEMICALS
18. MACHINERY AND MECHANICAL
19. ELECTROPLATING
20. ORE MINING AND DRESSING
21. COAL MINING
AII-1
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APPENDIX III
THE EPA LIST OF PRIORITY POLLUTANTS
Compound Name
1, *acenaphthene
2. *acrolein
3. *acrylon±trile
4. *benzene
5. *benzidine
6. *carbon tetrachloride (tetrachloromethane)
^Chlorinated benezenes (other than dichlorobenzenes)
7. chlorobenezene
8. 1,2,4-trichlorobenzene
9. hexachlorobenzene
*Chloririated ethanes (including 1,2-dichloroethane,
1,1,1-trichloroethane and hexachloroethane)
10. 1,2-dichloroethane
11. 1,1,1-trichloroethane
12. hexachloroethane
13. 1,1-dichloroethane
14. 1,1,2-trichloroethane
15. 1,1,2,2-tetrachloroethane
^Specific compounds and chemical classes as listed in the consent
decree.
AIII-1
-------
16. chloroethane
*Chloroalkyl ethers (chloromethyl, chloroethyl and mixed
ethers)
17. bis(chloromethyl) ether
18. bis(2-chloroethyl) ether
19. 2-chloroethyl vinyl ether (mixed)
*Chlorinated naphthalene
20. 2-chloronaphthalene
^Chlorinated phenols (other than those listed elsewhere;
includes trichlorophenols and chlorinated cresols)
21. 2,4,6-trichlorophenol
22. parachlorometa cresol
23. ^chloroform (trichloromethane)
24. *2-chlorophenol
*Dichlorobenzenes
25. 1,2-dichlorobenzene
26. 1,3-dichlorobenzene
27. 1,4-dichlorobenzene
"*Dichlorobenzidine
28. 3,3'-dichlorobenzidine
*Dichloroethylenes (1,1-dichloroethylene and
1,2-dichloroethylene)
29. 1,1-dichloroethylene
^Specific compounds and chemical classes as listed in the consent
decree.
AIII-2
-------
30. 1,2-trans-dichloroethylene
31. *2,4-dichlorophenol
*Dichloropropane and dichloropropene
32. 1,2-dichloropropane
33. 1,2-dichloropropylene (1,3-dichloropropene)
34. *2,4-dimethylphenol
*Dlnitrotoluene
35. 2,4-dlnitrotoluene
36. 2,6,-dinitrotoluene
37. *1,2-diphenylhydrazine
38. *ethylbenzene
39. *fluoranthene
*Haloethers (other than those listed elsewhere)
40. 4-chlorophenyl phenyl ether
41. 4-bromophenyl phenyl ether
42. bis(2-chloroisopropyl) ether
43. bis(2-chloroethoxy) methane
*Halomethanes (other than those listed elsewhere)
44. methylene chloride (dichloromethane)
45. methyl chloride (chloromethane)
46. methyl bromide (bromomethane)
47. bromoform (tribromomethane)
^Specific compounds and chemical classes as listed in the consent
decree.
AIII-3
-------
48. dichlorobromomethane
49. trichlorofluorome thane
50. dichlorodifluoromethane
51. chlorodibromomethane
52. *hexachlorobutadiene
53. *hexachlorocyclopentadiene
54. *isophorone
55. *naphthalene
56. ^nitrobenzene
*Nitrophenol3 (including 2,4-dinitrophenol and dinitrocresol)
57. 2-nitrophenol
58. 4-nitrophenol
59. *2,4-dinitrophenol
60. 4,6-dinitro-o-cresol
61. N-nitrosodimethylamine
62. N-nitrosodiphenylamine
63. N-nitrosodi-n-propylamine
64. *pentachlorophenol
65. *phenol
*Phthalate esters
66. bis(2-ethylhexyl) phthalate
^Specific compounds and chemical classes as listed in the consent
decree.
AIII-4
-------
67. butyl benzyl phthalate
68. di-n-butyl phthalate
69. di-n-octyl phthalate
70. diethyl phthalate
71. dimethyl phthalate
*Polynuclear aromatic hydrocarbons
72. benzo(a)anthracene (1,2-benzanthracene)
73. benzo (a) pyrene (3,4-benzopyrene)
74. 3,4-benzof luoran.th.ene
75. benzo(k)fluoranthane (11,12-benzofluoranthene)
76. chrysene
77. acenaphthylene
78. anthracene
79. benzo(ghi)perylene (1,12-benzoperylene)
80. fluorene
81. phenathrene
82. dibenzo (a,h)anthracene (1,2,5,6-dibenzanthracene)
83. indeno (1,2,3-cd)pyrene (2,3-o-phenylenepyrene)
84. pyrene
. 85. *tetrachloroethylene
86. *toluene
87. *trichloroethylene
^Specific compounds and chemical classes as listed in the consent
decree.
AIII-5
-------
88. *vinyl chloride (chloroathylene)
Pesticides .and Metabolites
89. *aldrin
90. *dieldrin
91. *chlordane (technical mixture & metabolites)
*DDT and metabolites
92. 4,4'-DDT
93. 4,4'-DDE (p,pT-DDX)
94. 4,4'-DDD (p,p'-TDE)
*endoaulfan and metabolites
95. a-endosulfan-Alpha
96. . (3 -endosulf an-Beta
97. endosulfan sulfate
*endrin and metabolites
98. endrin
99. endrin aldehyde
*heptachlor and metabolites
100. heptachlor
101. heptachlor epoxide
*hexachlorocyclohexane (all isomers)
102. ff-BHC-Alpha
103. p-BHC-Beta
^Specific compounds and chemical classes as listed in the consent
decree.
AIII-6
-------
104. Y-BHC (lindane)-Gamma
105. 6-BHC-Delta
*polychlorinated biphenyls (PCS'a)
106. PCB-1242 (Arochlor 1242)
107. PCB-1254 (Arochlor 1254)
108. PCB-1221 (Arochlor 1221)
109. PCB-1232 (Arochlor 1232)
110. PCB-1248 (Arochlor 1248)
111. PCB-1260 (Arochlor 1260)
112. PCB-1016 (Arochlor 1016)
113. *Toxaphene
114. *Antimony (Total)
115. *Arsenlc (Total)
116. *Asbest03 (Fibrous)
117. *Berylllum (Total)
118. *Cadm±um (Total)
119. *Chromium (Total)
120. *Copper (Total)
121. *Cyanidc (Total)
122. *Lead (Total)
123. *Mercury (Total)
124. *Nickel (Total)
^Specific compounds and chemical classes as listed In the consent
decree.
AIII-7 ,
-------
125. *Selenium (Total)
126. *Silver (Total)
127. *ThaT!ium (Total)
128. *Zlnc (Total)
129. **2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
^Specific compounds and chemical classes as listed in the consent
decree.
**This compound was specifically listed In the consent decree
because of the extreme toxicity (TCDD). We are recommending
that laboratories not acquire analytical standard for this
compound.
AIII-8
-------
APPENDIX IV
CONSULTANT REPORT
Available Data on Waste water Treatment
Currently Practiced in U, S. Plants
Table B-l shown below lists the six major domestic plants
which produce acrylonitrile.
American Cyanimid Co.
(1) Porsches, LA
•Monsanto Co.
(2; Alvin, Texas
(3) Texas City, Texas
SQHlU/Vistran Corp.
(U.) Lima, Uhio
DuPont
(5) Beaumont, Texas
(6) Memphis, Tennessee
NPDES Permit
or other source
LA OOC4367
TX 0003675
Not known
UH 00261$
TX 00014.669
Telecon with
DuPont
Deep Well
Deep Well
Not known
Deep Well
Deep Well
Deep Well
plus bio
• treatment
The attached letters confirm these findings.
and discharge
to PuTW for
segregated
wastes
AIV-1
-------
Evaluation of Currently Practiced
Treatment Technologies
As Table B-l indicates, the technology currently
practiced in most plants involves direct discharge to deep
well. This practice to be regulated ultimately under the
Drinking Water Act is currently controlled under N?DES
permits until a new permit system can be implemented.
Volume 1 of KtfA Document 600/2-77-029a (June, 1977),
"Review and Assessment of Deep Well Injection of Hazardous
Wastes," indicates that wastes containing acrolein and.
nitrites are:
"potentially hazardous and have very high human
and ecological hazard ratings. Long storage
time is necessary for all of these chemicals.
They either do not degrade or have a long per-
sistence time and would, therefore, pose a long-
term potential hazard to underground water
supplies. The actual persistence time is not
generally available except for some rough
estimates for a few compounds."
The total list of pollutants predicted to occur by
W. Lowenbach in the acrylonitrile total-plant mixed waste
streams includes:
AIV-2
-------
(1) Acetaldehyde
(2) Acrolein
(3) Hydrogen cyanide
(i|.) Acetic acid
(5) Fumaronitrile
(6) Acrylic acid
(7) Acrylamide
(8) Acrylonitrile
(9) Acetonitrile
(10) Fropionitrile
(11) Ammonium formate
(12) Ammonium acetate
(13) Ammonium methacrylate
(li|.) Ammonium acrylate
(15) Acetone
(16) Acetaldehyde cyanohydrin
(17) Acetone cyanohydrin
(16) Acrolein cyanohydrin
(19) Fyrazole
' (20) Tiethyl pyrazine •
(21) Cyanopyrazine
(22) - Fyrazine
(214.) Methacrylonitrile
(25) Allyl cyanide
(26) Toluene
One main concern here is for acrolein and the alliphatic
nitrile compounds. The refractory nature and toxicity of the
nitrile group are serious problems.
Concern focuses on the compounds such as acrolein, which
appears to occur in high concentrations in one waste stream.
According to Kirk-uthaner1s Encyclopedia of Chemical Technology
(2nd ed, 1971) and the monograph, published by Union Carbide
and Carbon Chemical Co. on Acrolein- in 1955,
AIV-3
-------
"Acrolein is a clear, colorless, volatile liquid,
soluble in many organic liquids; it is a powerful
lacrimator and is highly toxic. It is also one of
the most reactive organic chemicals available to
industry. The extreme chemical reactivity of
acrolein is attributed to the conjugation of a
carboxylic group with the vinyl group within its
structure. Because of its toxic nature and because
both the liquid and the vapor are flammable, acrolein
must be handled with extreme care."
The OSHA limit falls less than TWA 0.1 ppm and the
of lj.6 mg/Kg (oral-cat) (Am. Med. Assoc. Arch. Ind. Hyg. and
Oce. Med, Vol. Uj., No. 17, 195D:
"Exposure to one part per million of acrolein
in air produces detectable eye and nose irritation
in 2 or 3 min., moderate eye irritation with
lachrymation in ij. min. and is tolerable in 5 min.
The Threshold Limit Value (1Uf) quoted in the
current Occupational Safety and Health Standards
(Fed. Reg. 1971) of 0.1 ppm is sufficiently low
to minimize, but not entirely prevent, irritation
to all exposed individuals. The ThW assessment of
the toxicological information recommends a limit
in air of .0.001 ppm ( 0.0025 mg/MJ) for
-------
treatment). Low molecular weight oligomers containing
hydroxyl and aldehyde functionalities are formed in base
catalyzed reactions. These structures are generally bio-
degradable. The waste acrolein streams are too dilute to
be amenable to incineration, therefore, secondary treatment
or deep well disposal is presently used.
Acrolein appears in tne subject acrylonitrile waste
streams in varied forms and compositions, due to varying
plant feedstock and conditions. A typical organic liquid
waste stream containing acrolein has the following com-
position: light naphtha containing 1 to 5 percent acrolein;
up to 5 percent acrolein dimers and trimers.
A private source confirms that acrolein appears as
waste in water at concentrations above the order oi' parts
per billion from the manufacturing process. Methods for
adequately handling the disposal of such aqueous solutions
of acrolein have been under study by js. D. Suthard of
Union Carbide Corporation under the partial sponsorship of
KPA.
Acrolein/Nitrile Treatment Technique Evaluation
(Current and Studied)
Option No. 1 - Secondary Treatment. Secondary treatment
procedures comprised of neutralization and subsequent lagooning
have been used by Union Carbide Corp. Sufficient information
is .not available at this time to make a recommendation as to
its adequacy based on their work and the efforts of others.
(See Attachment E)
Option No. 2 - Deepwell Disposal. Although deep well
disposal is extensively utilized as a means of waste disposal,
the method is judged to be inadequate. This judgement is
based primarily on three factors. First, the problem of
assuring that a deep well will operate satisfactorily over
a long period of time is extremely complex and costly, and
AIV-5
-------
therefore proper methods of assurance are seldom followed.
Secondly, there has been little research In the area of
long term effectiveness of this form of disposal and thirdly,
deep well injection really represents a form of relatively
unaccessable long-term storage for most organic materials,
as opposed to conversion to a nonhazardous material*
Option No. 3 - Combustion. Submerged combustion is
a direct combustion method used by the petrochemical industry.
A specially designed burner has been used successfully for
total or partial evaporation of waste streams and for con-
centrating dissolved solids. A detailed description of _.._
both the Uhde Combustion Process and the Pluor Submerged
.".
Combustion Process has been provided by Jones. The con-
centrated effluent from this process might then be treated
as a concentrated waste.
SOHIO Process. It is obvious that the SOHIO propylene-
ammoxidation process prevails in U. S. acrylonitrile manu-
facture. Use of acetylene technology is outmoded. SOHIO
* •
admits in the letter attached herewith (Attachments P-l.l
and P-1.2) that initial reactor wastewa'ter column bottoms
contain:
- high nitriles
- high HCN
- low pH
- 80,000 COD
- 38.7/1000 Ib BOD loading
- high NH^SO^
Due to the high BOD loading in the waste stream, the
prospective toxicity and resistance to bio-degradation of
"""Jones, H. R. Environmental control in the organic and
petrochemical industries. New Jersey, Noyes Data Corporation,
1971.
AIV-6
-------
nitrile compounds in the wastes, it is clear that pre-
treatraent is necessary prior to FOTW discharge. It is not
clear whether or not SOHIO is discharging waste water to
t
the FOTW or if SOHIO has tested and/or is using pretreatment
plus biological treatment at its Vistron plant.
However, DuPont's disclosures (See Attachment F-2.1,
2.2, 2.3) show that acrylonitrile plants can pretreat
propylene amraoxidation waste streams and biologicalhtreat
prior to discharge into POTW.
There are two waste water sources of concern for the
SOHIO process: (1) the acetonitrile column bottoms (which
are sometimes incinerated or constitute the main wastewater
stream (according to the EFA Effluent Guidelines Development
Document) and (2) the acrylonitrile azotropic distillation
columns bottoms.
The reported high j^jw ratio indicates that the acetonitrile
waste is not totally toxic-.-but certainly inhibitory to
biological degradation processes. This fact and the success-
ful studies on decomposition of biological resistant nitro-
benzene waste indicate that proper adaptation and control of
environmental conditions may offer effective biological j^-Vn.
to process waste water treatment. Fre and post treatmentoie
will be necessary to condition the waste and then to polish
waste for compliance to effluent standards.
Deep well injection is the prevalent disposal technology
.&
applied to waste water from acrylonitrile production. In
this system, wastes are sent to ponds for removal of suspended
solids, pH adjustment, if necessary, and are then injected
Powers, P. W. "How to dispose of toxic substances and
Industrial Waste" Environmental Technology Handbook No. 14.
Noyes Data Corp. Park Ridge, N. J. 1976.
Private Communications
(a) Mr. H. M. Keating, Monsanto Corp. 9/9/77
(b) Mr. R. N. Simonsen, Standard Oil Company of Ohio
(letter of 9/7/77)
AIV-7
-------
Often under pressure to large areas or porous strata
(limestone or sandstone sands) that are isolated from
groundwater by an impervious layer. Deep well disposal
offers an attractive waste management alternative to
industries which are fortunate enough to be located in
£.
areas that are deemed suited to deep wells.
The success of any deep well is dependent upon
(a) the formation which is ideally large, porous, and
isolated from ground water horizons, and (b) the corapatability
of components of the liquid in the formation and injected
thereto.
The suitability of a given waste for deep well injection
varies, generally the more persistent and toxic a material,
the less suited it is for deep well injection. This is
simply because the deep well must be deemed as a long term-
storage facility—much as is considered suited for disposal
of radioactive wastes. The well system is environmentally
acceptable if properly located, and pending the development
of equally cost effective means of surface systems.or until
such time as the risk of loss of the injected materials
becomes unacceptable. This risk is maximized with highly
toxic/persistent materials, such as acrolein, found in
waste water from acrylonitrile manufacture. The cessation
of use of deep wells for such materials and development'of
alternate surface treatment and disposal systems is inevitable.
•&
Heview and Assessment of Deep Well Injection of
Hazardous Wastes, Vol. 1. pg. 13. EPA - 600/2-77-029a June 1977,
AIV-8
-------
Alternative Technologies
Plan One: Biological treatment subsequent to some
hydrolysis or oxidation process, e.g., modified simple
process to the biological unit (system) used should.be
studied to determine the most effective technique e.g.,
biofiltration, activated sludge, biodisc, or other system.
Wastes from such a treatment process could be dis-
charged either to navigable waters or the local POTW.
Plan Two: The physical removal of organic constituents
based upon solubility and/or attraction to adsorbent materials
such as activated carbon.
In this process^ sedimentation process would be followed
by mixed media filtration to remove solids. Then the liquid
would either be:
(a) Passed through an adsorbent column (act. carbon)
or:
(b) Passed through multi-stage evaporator/or solvent
extractor to concentrate organics. (Solvent/
Recovery costs may limit extraction technology)
Then, the organic component or carbon would be incinerated.
AI7-9
-------
Plan Three; A third, perhaps less promising alternative,
would involve coagulation to neutralize the wastes and to
reduce the BOD, followed by biptreatraent.
Plan Pour; The fourth alternative would involve high-
energy oxidative breakdown of nitrile groups followed by
biological treatment, (chlorination requires less energy,
.but is ruled out due to its potential for formation of
toxic chlorocarbons in the treatment.)
AIV-10
-------
R & D Requirements
Plan Number One is the only approach views! to be
ly competitive with deep well disposal. An
approach to this treatment procedure is herein provided:
Plan One; Biological Treatment (Adaptation & Treatahi 1 ity)
The following steps must be executed:
(1) Sequential increasing additions of waste to sewage
carrier resulting in adaptation of microbial population.
(2} If adaptation is successful, determine extent of removal,
detention times, dilution requirements, if any,
nature of wastewater treatment process. Consider
staged treatments because of strength characteristics.
(3) To firm up data from treatability studies, consider
activated carbon a^i-Hon in powdered form to
remove color, if any. Add powdered carbon to
activated sludge basin if selected as final stage.
(This is the method used to treat nitrobenzene -
bearing wastewater s.)
(4) It will probably be necessary to otherwise polish
effluents if carbon addition is not feasible.
AIV-11
-------
'ioHioj
THE STANDARD OIL COMPANY
MIDLAND BUILDING, CLEVELAND, OHIO 44115
R. E. FARREU.
DIRECTOR
ENVIRONMENTAL Af FAIRS
September 7, 1977
Dr. Ronald Barbaro
7036 Lee Park Court
Falls Church, Virginia 22042
Dear Dr. Barbaro:
>
This is in response to the questions as numbered in the attached
letter from Mr. desRosiers following Mr. Farrell's phone conversation with
you.
1) There are two process wastewater streams from the acrylonitrile
manufacturing process itself at the Vistron plant at Lima, Ohio,
and these are segregated from the wastes from other manufactur-
ing processes. The waste streams are "wastewater column
bottoms" and "recovery column stripper bottoms". In addition,
there is a waste stream we call "surface runoff", which is
what the name implies, and contains a contaminant load made
up of miscellaneous leaks and spills from routine and mainte-
nance operations. Finally, there is another water discharge
which isga "clean water" stream, comprised primarily of cooling
tower blowdown.
2) The approximate composition of these streams is:
Flow, gals/min.
PH
Alkalinity
NH.
TKK
N03-N02
HCN
Sulfate
Acrylonitrile
Ac et on it rile
Total Solids
Dissolved Solids
Suspended Solids
Volatile Susp. Solids
BOD
COD
Wastewater
Column
Bottoms
mg/1
155
5.1
15,000
Recovery Column
Stripper
Bottoms
180
7
220
Surface
Runoff
mg/1
150
9
275.
60
65
4
7,000 225
32,000 500
500(or less) <10
3,000 35
95,000 10,000
95,'000 10,000
<500 {100
225
9.5
190
5
13
17
80,000
17,000
30
17
400
500
65
25
30
75
AIV-12
-------
THE STANDARD. OJL COMPANY
Dr. Ronald Barbaro
September 7, 1977
Page Two
3) The two process waste streams (wastewater column bottoms and
stripper bottoms) are settled, sand-filtered, and injected into
disposal wells. Surface runoff is treated biologically, along
with refinery wastewater at an adjacent petroleum refinery.
4) The waste treatment efficiency is not measured. The great bulk
of the waste load goes to disposal wells, which are 100 percent
efficient. Treatment efficienty for surface runoff cannot be
determined)since it is mixed with refinery waste.
5) With respect to COD, overall efficiency is better than 99.4 per-
cent because so much of the raw waste load is contained in
process wastewater streams put to disposal wells.
6) As noted earlier, all process waste goes to disposal wells
after pretreatment. Surface runoff is treated with refinery
wastewater in an aerated lagoon-type of biological treatment
plant. Clean water is discharged directly to the river.
Please call me in Cleveland .at 216/575-5120 if you have any questions.
?
Very truly yours,
R. N. Simonsen
Senior Environmental Consultant
RSN/k
Attach.
cc: Mr. J. M. Killen, Vistron
Mr. R. D. Presson, Sohio
P.S. Identical copies of Mr. desRosiers letter were addressed to me and
to Mr. J. M. Killen at the Vistron plant in Lima.
AIV-13
-------
^tojr%
? tf^ \
I 5S\H2.1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
V v^ WASHINGTON. D.C. 20460
'<< wtn*-4'
OFFICE OF
RESEARCH AND DEVELOPMENT
Mr. Robert Farrell
Director of Environmental Affairs
Standard Oil of Ohio
Cleveland, OH 44155 ,
Dear Mr. Farrell:
This will confirm the conversation with Dr. Ronald Barbaro, regarding
his request for the following data:
1. Is the wastewater from acrylonitrile manufacture at your
facilities segregated from waste streams for other
manufacturing processes?
2. What is. the volume/chemical composition of .this raw
waste stream?
.3. Is the waste stream from the acrylonitrile manufacturing
process afforded any treatment prior to disposal? Please
describe all unit processes.
4. How is the efficiency of this process measured?
5. What is. the efficiency of the overall treatment?.
6. How is this effluent (with or without treatment) disposed
of, i.e., what disposal.process is used? (e.g., discharged
to municipal facility without treatment, or deep well in-
jection, etc.)
The data gathered'in this survey will be used for a "state-of-the-art"
report on waste stream treatment practices associated with chemical pro-
duction. Please send your responses directly to our consultant, Dr. Ronald
Barbaro, 7036 Lee Park Court, Falls Church, VA 22042. Your cooperation
will be greatly appreaciated.
Paul desRosiers
Senior Staff Engineer
AIV-14
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• THE STANDARD OIL COMPANY
MIDLAND BUILDING, QEVEUND. OHIO, 44115
fctlWU FeblMIy 2> "76
DMCTO*
Environmental Protection Agency
401 M Street, S.W.
Washington, B.C. 20460
Attention: Distribution Officer, WH-552
Dear Sir:
Re: Significant Organic Products Segment
of the Organic Chemicals Manufacturing
Point Source-Category — Notice of
Interim Final Rulemaking _
The Vistron Corporation, the wholly-owned chemical manufacturing subsidiary
of The Standard Oil Company of Ohio (Sohio) wishes to make the comments
which follow on the effluent guidelines and standards for "Significant
Organics Products Segment of the Organic Chemicals Manufacturing Point
Source Category," as they appeared in the Notice of Interim Final-
Rulemaking in the Federal Register of January 5, 1976.
In particular, our concern is with the guidelines for the manufacture of
acrylonitrile, one of the Phase II products covered in Subcategory C
(Aqueous Liquid — Phase Reaction Systems). Vistron is a major manufacturer
of acrylonitrile at its plant In Lima, Ohio, employing the process for the
direct oxidation of ammonia and propylene developed by Sohio. Practically
all of the U.S. and world production of acrylonitrile is plants licensed
to use the Sohio process.
We have reviewed the interim final guidelines for acrylonitrile, and have
reviewed the Development Document (EPA-440/1-75/045) on which they are
based. The Vistron plant is one of three in the Document from which
guidelines have been- developed. We find nothing in the Development Document
to support the guidelines as promulgated. Based upon our experience,
there is no way by which the effluent guidelines and limitations promulgated
can be achieved by the BPCTCA technology specified, i.e., biological
treatment.
AIV-15
-------
THE STANDARD OIL COMPANY
-2-
In addition, there are a number of errors in the Development Document,
particularly in the data it uses from the Vistron plant — data that was
obtained by the EPA contractor. In the following paragraphs, we will
expand upon these points starting with the Development Document data.
1. The aerylonitrile flow sheet, Figure 4-32, is wrong. It does not
properly depict the ammoxidation of propylene process or its
process wastes. Vistron had suggested to the contractor use of
the attached flow diagram from "Chemical Engineering."
2. The Raw Waste Load Data for Plant 3 on page 159 (which we have
been told is the Vistron Plant) is Incorrect. Our research
department, which is highly experienced in acrylo waste sampling
and analysis, made analyses on split samples (from the contractor)
of the individual point sources of process waste from which the
page 159 raw waste loads were calculated. The table below compares
the raw waste loads and flow rates for Vistron shown in the
Development Document versus the same values determined by Sohio
from the same samples:
Plant 3 (Vistron)
Development Document Sohio Research
Process flow
Liter/kkg 2,820 .4,587
gal/10000 338 550
BOD RWL
mg/liter - -
kg/kkg
GOD RHL
mg/liter 41,100 31,580
kg/kkg 116 145
TOC RWL
mg/liter 15,300 13,380
kg/kkg 61.2 61
In the first place, note the wide flow discrepancy. Flow data for
the point sources comprising RWL for the sampling period were
as follows:
AIV-16
-------
THE STANDARD OIL COMPANY
-3-
Gallons/Minute of Process Waste
Waste Water Column Recovery Column Stripper
Date Tine Bottoms (WWCB) Bottoms (RCSB)
10-8-73 1200 120 171
1600. 132 171
2000 129.5 165
2400 132 . 174
10-9-73 0400 132 174
0800 138 159
Average 131 169
Production was 786,056 9 for October 8 and for October 9 when it
dropped to 631,961 9 because of a reactor shutdown at 1400 hours
on October 9. Thus 786,000 ff acrylo/day is clearly the production
figure that should be.used. Process flow thus calculates to be
550 gal/1000# acrylo.
f-^7 * 1440 7 786 - 550 gal/1000# AN
It is suspected that the contractor may have used flows of 67 gpm
for WWCB and 120 gpm for RCSB obtained October 10 (after production
had been reduced). If these low flows had been used with the
786,000 #/day production figure, process flow would calculate out
at 338 gal/1000# as shown in the Development Document — incorrectly.
The implication of this sizable difference in flows is, of course,
that the loadings, calculated from measured concentration and
flow rates, are incorrect and should be higher. The table shows how
the COD RWL for example instead of being 116 mg/kkg would be 145 kg/kkg
based on Sohio analyses of split samples and the correct flow rates.
And if the contractor's analyses were correct, waste J.oadings would
be even higher. The figures below compare raw waste loads as listed
in the Development Document, as determined from Sohio data, and as
calculated from contractor's analyses with corrected flow rates:
Vistron Waste
Development Doc By Sohio Research By Contractor Anal}
(p. 159) Analyses & Flows & Sohio Flows
mg/1 kg/kkg
COD 41,100 116
TOG 19,100 53.9
Flow, gal/10001? 338
AIV-17
-------
THE STAKDARD O»L COMPANY
3. Table 5-3, "Major Subcategory C Process Raw Waste Loads" is .
in error. This table 'is based upon the average of data from
Plants 2 and 3 on page 159. Since data for Plant 3 is in error
for the reasons stated above, Table 5-3 must be in error.
4. Table 6-4, "Miscellaneous RWL for Subcategory C" is inconsistent.
We are uncertain of the implications of rate here, but suspect
the 338 gal/1000# for one of the acrylo plants should be 550.
The point of most significance here, however, is that for both
plants the 504- concentrations are not consistent with the loadings.
We'believe the loadings are about right. If so, the concentrations
of SO A should be much higher — in the 20,000 rag/1 range. This is
significant because of the inhibitory effect of high SO^ concentrations
on biological treatment.
Although the above points are of concern, they are relatively unimportant
in comparison with the way the data has been used — or more correctly,
not used in establishing the promulgated guidelines. The following comments
deal with the promulgated BPCTCA interim final guidelines:
1. The effluent guidelines cannot be achieved by application of the
assumed biological treatment technology to acrylonitrile plant raw
waste loads. For example, even if the appropriate- raw waste loadings
for acrylonitrile .were as shown on Table 5-3 of the Development
Document, compliance with the guidelines in Section 414-72(g) of
the Federal Register would require a reduction of 97.9%.
RWL BPCTCA % Reduction
(Table 5-3 of Limitation Required
Development Document) (30 day _ave._3_ _______
BOD, 0/1000* 38.7 0.82 97.9
This is a very high percent reduction even for.a waste that is
very amenable to biological treatment. The problem is that the
acrylo raw wastes are not even amenable to bio-treatment and it
is an inappropriate treatment method. The IDS levels of 57,200
and 37,500 mg/1 shown on Table 6-4 of the Development Document are
well above the 10,000 limit usually considered inhibitory to the
biological process. Acrylo plant raw wastes are extremely toxic
to the bio-organism even when highly diluted with clean waters.
Our own experience has indicated this to such an extent that the
biological approach to effluent control was abandoned long ago
even after attempts to pre-treat cyanides. We know of no case
where biological treatment of such wastes is successful.
2. Variability factors are suspect. Since we are convinced biological
treatment is not a viable technology, we must conclude the variability
factors are without basis.
AIV-18
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THE STANDARD OIL COMPANY
.5.
3. Deep well disposal of point source acrylonitrile wastes, and
incineration — separately or in combination — are the most
effective waste treatment techniques, although neither is
'appropriate in all locations.
Our primary concern is that although we believe the promulgated guidelines
can be met as long as deep well disposal and/or incineration remain viable
alternate disposal techniques, we are deeply concerned that those same
guidelines could not be met if deep well disposal and incineration were
to become unacceptable.
We appreciate this opportunity to express our views.
- , Very truly yours,
. R. E. Farrell
REFrjmd
Attachment
AIV-19
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-------
E. I. DU PONT DE NEMOURS & COMPANY
ATCa
WILMINGTON, DELAWARE 19898
'OLYMER INTERMEDIATES DEPARTMENT
January 20, 1976
Mr. Walter J. Hunt
Environmental Protection Agency
Office of Water & Hazardous Materials
Effluent Guidelines Division
401 M Street, S.W.
Washington, D.C. 20460
PRETREATMENT OF ACRYLONITRILE WASTSWATERS TO
PUBLICLY OWNED TREATMENT WORKS
Ref:J. R. Cooper to W. J. Hunt, 8/25/75
•
Dear Mr. Hunt:
Du Pont submitted information to EPA on acrylonitrile
effluents and their treatment, including a description of a pro-
prietary Du Pont process for waste pretreatment, in April 9 and
July 22, 1975'meetings and in a preliminary report. transmitted
to you on July 17. At the July 22 meeting, EPA asked for further
information on waste treatment and suggested how the data could be
developed.
Pursuant to your request, we conducted the following
studies:
A one-month sampling study at our acrylonitrile
•plant in Memphis, Tennessee.
A three-month laboratory study of biological
treatability at our Engineering Test Center
in Newark, Delaware. The treatability study
was run on segregated wastewater, pretreated
by alkaline hydrolysis at Memphis to destroy
cyanides in order to make the waste amenable
to biological treatment.
The Federal Register published on January 5, 1976 requested
information which would be considered in establishing pretreatment
standards for users of publicly owned treatment works for the Organic
Chemicals Manufacturing Point Source Category.
-------
Mr. Walter J. Hunt -2- January 20, 1976
The enclosed final report is a technical response to your
request and that made in the "Federal Register". The report in-
cludes data on raw waste loads from acrylonitrile manufactured at
our Memphis plant, treatment of- the raw wastes, and biotreatability
of pretreated wastes. The biotreatability study supports our posi-
tion that segregated, pretreated wastewaters are readily biodegradable.
The draft report, "Development Document for Effluent
Limitations Guidelines and Standards of Performance, Organic Chemicals
Industry Phase II," by R. F. Weston,, dated February 1974, and the
EPA report, "Pretreatment of Pollutants Introduced into Publicly
Owned Treatment Works," dated October 1974, state that acrylonitrile
wastes are toxic and infer that such wastes should not be introduced
into municipal treatment systems. This may be considered-a valid
conclusion for the composite of all acrylonitrile wastes,<.but not
for those wastewaters which can be segregated and pretreated. Based
on two years operating experience and the results of our two studies,
it is our position that segregated, pretreated wastewaters are readily
biodegradable and that the outright exclusion of all acrylonitrile
wastewaters from municipal systems is not justified nor required.
We have forwarded a copy of the report to the contractor
in order that he may have the benefit of the data that was generated
in this study.. •• .
A corollary benefit of pretreatment at Memphis is the
savings in fuel which would otherwise be required to incinerate these
wastes—the equivalent of 500,000 barrels of oil annually.
After you have had an opportunity to digest the contents
of this letter, we will contact you for a meeting to discuss the
report in detail. As requested in the "Federal Register", detailed
comments on the proposed rules will be forwarded to EPA, Attention
of Distribution Officer, WH-552, under separate cover.
Yours truly,
J. R. Cooper
JRC:vb
Enclosure
cc: W. Lamar Miller
Environmental Protection Agency
AI7-22
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f ft-tilt
E. I. DU PONT DE NEMOURS & COMPANY
INCWmMUTtO •
WILMINGTON, DELAWARE 19898
POI.Y.VI-.V INTERMEDIATES DEPARTMENT
REGISTERED MAIL -
RETURN RECEIPT REQUESTED
1976
U.S. Environmental Protection Agency
401 M Street, S.W.-
Washington, D.C. 20460
Attention: Distribution Officer (WH-552)
Dear Sir:
ORGANIC CHEMICALS MANUFACTURING
POINT SOURCE CATEGORY EFFLUENT GUIDELINES (PHASE II)
In the-January 5, 1976, Federal Register, the EPA published
Interim Final Rulemaking and Proposed Rules covering effluent guide-
lines for Organic- Chemicals Manufacturing Point Source Category
(Phase II). For both the' Interim Final Rulemaking and the Proposed
Rules, the EPA requested comments. In accordance with that request,
we would like to make comments on the following products covered in
the subject guidelines.
Acrylonitrile
Adiponitrile - by chlorination of butadiene
Hexamethylene diamine - by hydrogenation of
adiponitrile
Specific comments on these products are set out below.
Because the Development Documents were only recently made available
by the EPA, we may need to supplement these comments after completion
of our review of the Development Documents.
Acrylonitrile
Several acrylonitrile manufacturers dispose of their wastes
by deep well injection. We feel that this is an environmentally
sound method of disposal and take exception with the statement made
in the preamble to the interim final regulations on page 904:
AIV-23
-------
Distribution" Officer - 2 - February 4, 1976
Recent regulations are tending to limit
the use of ocean discharge and deep-well injec-
tion because of the potential long-term detri- .
mental effects associated with these disposal
procedures. Therefore/ these disposal methods
are not considered to be viable alternates at
this time.
We have not found it possible to biodegrade all of the
acrylonitrile wastes and strongly feel that deep well disposal,
which has been safely practiced for a number of years, should be
considered along with incineration as a viable alternate.
Interim Final Rulemaking
The raw waste load back-calculated from the guideline
number for BODg discharge is much lower than what we believe is
actually experienced by most acrylonitrile manufacturers. For
example, EPA's limit for- maximum one-day•BOD5 BPTCA discharges
(p. 903, Method 3) is calculated by:
0.01 (RWL) (3.9) = 1.6
The implied long-term average RWL for an acrylonitrile plant is
therefore 41 Kg./KKg. acrylonitrile. After reading the Development
Document, we believe that EPA used this low number for RWL based on
the following questionable procedures:
• The contractor did not use acclimated seed in
obtaining the BOD data. This fact, in addition
to the inherent toxicity of the overall wastes, •
makes BOD values on the raw wastes highly ques-
tionable .
After segregation of wastes and hydrolysis of
the cyanide as practiced at our Memphis site,
BOD can be determined and a BOD/COD ratio estab-
lished. If this ratio is applied to the COD
values of the' raw waste in order to calculate
BOD, a raxv waste BOD of 118 Kg./KKg. is obtained
vs. the 41 Kg./KKg. used by EPA to establish the
discharge guideline.
* Acetonitrile is one of the waste products made
in the manufacture of acrylonitrile. Acetonitrile
can be recovered and sold. However, the nation-wide
AIV-24
-------
Distribution Officer - - 3 - February 4, 1976
market for it is less than the industry produc-
tion capacity. Therefore, every, producer cannot
recover it for sale, and alternate disposal
techniques are required.
The Development Document makes no provisions for
disposal of acetonitrile as a waste stream and
for the by-products purged from the process with
the acetonitrile waste. This purge stream will
exist even if the by-product acetonitrile is sold.
• One of our plants was one of the manufacturing
sites sampled by the contractor. Three samples
were analyzed and reported in the Development
Document. However, the data from these three
samples were ignored in the establishment of the
guidelines. This plant, during the past year,
has taken weekly samples for analysis which sub-
stantiate, with the exception-of flow and BOD,
the numbers reported in the Development Document.
The Development Document understates the plant's
flow for the acrylonitrile plant, and the BOD
values are" meaningless as discussed previously.
We believe that our plant is representative of
any other plant using the SOHIO process. The
data .from this plant corresponds very closely
with data from our other plant site. We there-
fore take exception with EPA on exclusion of the
Du Pont data.
We would be happy to share with EPA the data we
have collected to date.
A cyanide limitation is established for acrylonitrile pro-
duction which is set such that the effluent will have a cyanide con-
centration of 1 ppm. We "disagree with the limitation that has been
set because:
• The waste flow rate in the Development Document
is approximately 25% lower than what we experience
at either of our plant sites. If the correct flow
. had been employed, the 1 ppm effluent limitation
that EPA wants to achieve would have been reached
with a corresponding increase in the allowable
cyanide discharge.
• This technique of setting a guideline does not
provide for mixing with other waste to reduce
toxicity effects before discharge.
AIV-25
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Distribution Officer - 4 - • February 4, 1976
• By setting the 1 ppra discharge limitation in
these guidelines, EPA is essentially estab-
lishing a 1 ppra limit on.cyanides for the
toxic substances regulations. We feel a cyanide
limitation should not be included in these guide-
lines but would be more properly covered by the
regulation on toxic substances.
• It should be pointed out that the cyanide con-
tent o£ the raw waste in the Development Document
—- is understated by a factor of 4-20 compared to
our plants' data. We bring this to your attention
even though the RWL values for cyanide had no bear-
ing on the establishment of the guideline limitation.
Economics - We believe that the investment and operating
costs for meeting BPTCA limits are understated. If you desire, we
would be happy to review our economic evaluation with you.
Proposed Regulations
(1) BATEA - The comments made concerning RWL for the
interim final regulations apply. In addition, t;he
BATEA limit for BOD5 is only 11% of the BPTCA value.
This is a significantly greater reduction than.
specified for other industries covered by the
guidelines.
• The comments made concerning cyanide, for the
interim final regulations apply. In this case,
the CN limitation is based on a discharge con-
centration of 0.5 ppm instead of the 1 ppra for
the BPTCA case.
*
• Economics - The .comments made concerning the
interim final regulations apply.
(2) New Source - The comments made concerning the
interim final regulations apply.
(3) Pretreatment Standards - EPA has requested informa-
tion that could be used in helping to establish pre-
treatment standards. Attached are three copies of
a report from our Memphis plant which was previously
submitted to EPA (Letter to Walter Hunt, 1/20/76,
enclosed). These reports are sent in response to
EPA's request made in the January 5, 1976, publica-
tion of the Federal Register.
AIV-26
-------
Distribution Officer - 5 - February 4, 1976
The data in the report show that certain of the
acrylonitrile wastes after suitable pretreatment
are readily biodegradable. We strongly suggest
that any pretreatment limitations should contain
enough flexibility such that if suitable technology
is developed such that additional waste streams in
the process can be detoxified, these streams may
also be treated, after detoxification, in a POTW. .
Adiponitrile (ADN)
Adiponitrile is manufactured by the chlorination of
butadiene route at two of our sites.
There is no serious disagreement between RWL parameters
expressed in the Development Document and those experienced in our
ADN operation with the exception of BODg. We did not run an analysis
for BODg since we have no acclimated seed and past attempts indicate
that the ADN waste streams are not biodegradable, either as is or at
reasonable dilutions.
RWL BOD5 levels.as determined in the Development Document
must have been run at a dilution of. at least 100 to 1. At this
dilution rate, the accuracy of the results are somewhat suspect.
The inhibitory effect from NaCl and CN also promote question of BOD
accuracy.
4
The dilution of ADN waste required to obtain a concentration
that will not inhibit bio-treatment is depicted in the following
table.
RWL Inhibitory* Required
Constituent Concentration ' Concentration Dilution
NaCl 124,000 mg/1 10,000 rag/1 12.4 X
HCN 187 mg/1 . 1 mg/1 187 X
x CN 48 mg/1 1 mg/i 48 X.
Weston sampled one of our adiponitrile plants and in his
report* he suggests that with suitable dilution bio-treatment might
be feasible. He suggested that. 424,000 liters of cooling water per
KKg. of product would be available for dilution at the plant site.
* Section IV pp. 276-277 "Draft Report Development Document for
Effluent Limitation Guidelines and Standards of Performance,
Organic Chemicals Industry, Phase II," Roy F. Weston, Feb., 1974.
AIV-27
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Distribution Officer - 6 - February 4, 1976
In reality, 83% or more of this cooling water is recirculated for
reuse, thus only about 72,000 liters per KKg. are available for
dilution. This is not sufficient even for the NaCl toxicity.
Even if ADN waste were biodegradable, the required BODc
reduction of 95% to meet the proposed BPTCA guidelines exceeds tne
capability of EPA's exemplary -plants .
It is therefore our conclusion that bio-treatment is not
a feasible control method for ADN waste.
Again, we disagree with EPA's statement that ocean dis-
charge and deep well injection disposal methods are not considered
to be viable alternatives at this, time. We believe they are the
only viable means for disposal of ADN wastes. We therefore feel
they should be permitted when carried out in an environmentally
sound fashion.
Hexamethylene diamine (HMD)
•
. ' Hexamethylene diamine (HMD) is manufactured by. the hydro-
genation of adiponitrile at two of our plant site's.
With suitable adjustments and reasonable dilurtion, HMD
waste is biodegradable; however, we have currently not seen estab-
lished data that indicates specifically what will be required to
obtain biodegradability. Furthermore, the RWL BOD5 level requires
a 98% reduction to meet the proposed BPTCA limits. This reduction
exceeds the capacity of EPA's exemplary plants.
The proposed BATEA limits require a 99+% reduction for
BODc. Back-calculation assuming 90% reduction indicates that only
about 160 Ibs./day of waste could be discharged or that a spill of
40 gallons could cause an excursion. Spills, rainwater runoff,
and equipment washdowns occurring during normal operation would
almost surely result in excursions, and provisions in the guidelines
should be made for these occurrences.
We again believe that well injection should be open as a
viable alternative for HMD waste disposal at this time and should
continue to be permitted if operated in an environmentally sound
manner.
Sincerely,
J. R. Cooper
JRC : kwc AIV-28
Enclosure
-------
E-. I. DU PONT DE NEMOURS & COMPANY
INCOIWOMATCD
WILMINGTON, DELAWARE 19898
POLYMER INTERMEDIATES DEPARTMENT
September 15, 1977
Dr. Ronald Barbaro
7036 Lee Park Court
Falls Church, Virginia 22042
Dear Dr. Barbaro:
Mr. Robert F. Rocheleau of our Engineering Department was
contacted by Paul desRosiers (letter attached) of the Environmental
Protection Agency requesting information concerning the treatment of
waste water from our acrylonitrile operations. Our company'operates
two acrylonitrile plants, one in Memphis, Tennessee, and the other
in Beaumont, Texas. The plants previously supplied the information
you seek to tlm iDim'LLUi -UJ! Llie iLUiilULiiL auiaullii, i Dl»iu'luu uI"EJJi
in Jiamuai'yji'107^, in response to a Section 308 request for informa-
tion on the organic chemical industry. In addition, I supplied a
T*»F»Ma--iJi-'iiip»i i*m,^m^s_^a^l^t-~m*^ma*^mmmsaa^ayaBmi^*f^^ describing a
process for pretreatment of a segment of the acrylonitrile wastes
prior to their disposal in publicly owned treatment works.
If, after review of this information, you have additional
questions, please feel free to contact me.
JRC:kwc
Attachment
AIV-29
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THE STANDARD OIL COMPANY
MIDLAND BUILDING. CLEVELAND, OHIO <
R. E.FARREU
DIPfCTCR
January 18, 1978
Ms. Joyce Schlesinger
The Mitre Corporation
Metrek Division
1820 Dolley Madison Blvd.
McLean, Virginia 22101
Dear Ms. Schlesinger:
The following comments are in answer to the question you
asked about wastewater from acrylo manufacture in your
January 3, 1978 letter.
1) The values- shown for nitrogen-containing compounds are
•for nitrogen and. should have-been listed as NHj-N,
TKN-N, and N03-N02-N.
2) The values shown for HCN are CN"". Incidentally, I was
told that later data for wastewater column bottoms was
4780 mg/1 instead of 7000 ag/1.
3) Surface run-off varies from a low of around 20 gpm to
perhaps 1000 gpm during rains. The 150 gpm figure re-
presents the average, but continual flow that is pumped from
an equalizing/storage basin. -The flow is associated just
with the acrylo manufacture and does not include run-off
from the agricultural chemical manufacturing facilities.
Please call if you have additional questions.
Very truly yours.
/
R. N. Simonsen
RNS:kk •— -
AIV-30
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