United States
Environmental Protection
Industrial Environmental
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-120  July 1984
Project  Summary
Process Modifications  Toward
Minimization  of Environmental
Pollutants in the  Chemical
Processing  Industry
L.L Tavlarides
  Eight industries employing chemical
processes were surveyed to develop a
matrix of significant pollution problems
and attendant process modifications
which would have an impact on the
reduction or elimination of generic
pollutants shared by the eight diverse
process industries surveyed: non-
ferrous metals refining, electroplating,
coal conversion, specialty chemical,
iron and steel, paper and pulp, primary
aluminum, and phosphate fertilizer.
  The study concluded that the follow-
ing areas of research are the most
promising for minimizing pollutants
from the  industries surveyed:  solvent
extraction, catalyst deactivation, leach-
ing, gas absorption and gas-liquid-solid
  This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory, Cincinnati, OH. to
announce key findings of the research
project that  is fully documented in a
separate report of the same title (see
Project Report ordering information at

  This planning project suggests funda-
mental  research studies which could
result  in  the reduction of industrial
pollutants in the chemical  process
industry. Eight industries are surveyed to
develop a matrix of significant pollution
problems and attendant process modifi-
cations which would effect the reduction.
The eight industries are listed below.
  1. Refining of nonferrous metals
  2. The electroplating industry
  3. Coal conversion processes
  4. Specialty chemicals
  5. The iron and steel industry
  6. The paper and pulp industry
  7. The primary aluminum industry
  8. Phosphate fertilizer industry
  These diverse industries  showed
generic pollution problems; the study
identifies process pollution modification
strategies which are  also generic in

Refining of Nonferrous Metals

  This chapter concentrates on the refin-
ing of nonferrous metals from mineral ore
by three processes:
 1. Copper production  by pyrometallur-
   gical processes
 2. Copper production by hydrometallur-
   gical processes
 3. Uranium production by hydrometal-
   lurgical processes.

Copper Production by Pyro-
metallurgical Processes
  The following areas are recommended
for further research:
 • Optimization of the communition of
   dry mineral ore to redu,ce the amount
   of water used in froth flotation
 • Recover value-bearing products by
   dissolving the metals from particulates
   collected in the electrostatic precipi-
   tators and use solvent extraction
   procedures to  extract the desired
 • Use solvent  extraction to recover
   copper or other metals from effluent

    streams before the water is sent to
    the tailing ponds
  • Improve smelter design to contain
    and eliminate the release of SC>2 and
    other hazardous flue gases into the

Copper Production by
Hydrometallurgical Processes
  The following areas are recommended
for further research:
  • Recover trace metals in the effluent
    streams by using solvent extraction.
    Conduct research  in the area of
    simultaneous extraction of several
    metals that are considered hazardous
  • Recover entrained solvents by filtra-
    tion, flotation, centrifugal separation,
    etc.  Study  the various methods of
    separating liquid-liquid mixtures and
    determine the best process to use.
  • Solvents tend  to  degrade due to
    temperature, pH,  or radiation  ex-
    tremes.  Analyze the byproducts of
    this  degradation and determine  the
    best way to eliminate these byproducts
    either in the recycle stream or  the
    exit stream.
  • Evaluate new techniques for leaching
    sulphide ores or develop new tech-
    niques  to  improve selectivity in
    leaching mineral ores.

Uranium Production by
Hydrometallurgical Processes
  The following areas are recommended
for further research:
  • Evaluate new leaching solutions that
    may offer  improvement in leaching
    selectivity and/or efficiency.
  • Determine  the best  solvent  for
    solvent  extraction of uranium salts
    with minimal degradation.
  • Divert recycle streams into additional
    process circuits to remove trace

Electroplating of Common
  Electroplating  is a series of process
steps that involves the preparation of the
part  in addition to the plating operation.
The sequence and/or the process steps
may vary from plant to  plant because of
the many variables involved with electro-
  There are  numerous methods of treat-
ment for dissolved materials that exist in
effluent streams. They  include substitu-
tion  of low  concentration  solutions in
place of high concentration baths; use of
non-cyanide solutions  in  place  of  the
cyanide  treatments; use counter-flow
rinses; adding a wetting agent to rinse
waters;  installing air or  ultrasonic
agitation; recovery and reuse of  metals
in effluent streams by solvent extraction;
and recycling used rinse waters into the
make-up solutions of  their respective
treating baths.
  Each method has advantages and dis-
advantages that must be considered with
respect to the specific electroplating

Coal Conversion Processes
  The unpredictability of the international
energy market and the very real danger of
global oil  shortages  in  the next few
decades  have  necessitated a  rapid
expansion in the domestic energy base in
the U.S. Consequently, the  commercial
production of synthetic fuels from the
abundant reserves of  coal  is a  major
objective of the nation's energy research
and  development programs. Coal lique-
faction and coal gasification technologies
have received renewed interest  in this
regard.  Economic viability and environ-
mental impact will be the limiting factors
in the commercialization of such process-

Lurgi Coal Gasification Process
  The following areas are recommended
for further research:
  • Stabilization of gasifier and  boiler
    ash to decrease or prevent leachabil-
  • Operating data and composition on
    spent methanation guard, shift and
    methanation  catalyst  to determine
    possible  extraction of valuable and
    toxic metals.
  • Studies on the use of spent methana-
    tion catalyst as sulfur guard.
  • Development of solvent extraction
    systems to remove non-phenolic
    organics and determination of distri-
    bution coefficients for existing sol-
  • Engineering data  on various sulfur
    recovery, SC>2 and  tail gas pretreat-
    ment processes.

SRC Coal Liquefaction Process
  The following areas are recommended
for further research:
  • The applicability of electrostatic and
    magnetic filters to control emissions
    of coal dust particles in the submicron
  • Leachability of gasifier slag  and fly
    ash to determine  treatment  and/or
    disposal  methods.
  • Extraction of valuable metals  (Ni, Co,
    Mo, etc.)  from  spent shift and
    hydrogen generation catalysts.
  • Studies on the absorption of SOx and
    CC"2 in Stretford process leading to
    process modification to  reduce CO2
    emissions in tail gas.
  • Modification  of steam  generation
    operation to reduce NO* emissions.

Explosives Industry
  The processes involved in manufactur-
ing of high explosives are discussed in the
final report. The purpose of  the discus-
sion is to provide an insight into process
modification  as a method to reduce
pollutants arising from these processes.
The final report discussion includes the
two  most produced high  explosives,
trinitrotoluene and nitrocellulose. Both
explosives are generated by  nitration
processes to yield nitrocompounds.

TNT Product/on
  The following areas are recommended
for further research:
  • Research on kinetics of the nitration
    reactions which will permit alleviation
    of  pollutants by  adoption of a low-
    temperature denitration stage.
  • Material balances to find the optimal
    design for the fume recovery system
    in the nitration-separation process.
  • Recovery of TNT in the "pink water"
    by application of foam separation to
    an aqueous solution.

Nitric Acid Production
  The following areas are recommended
for further research:
  • Studies on kinetics and mass transfer
    process for heterogeneous catalysis
    to improve the catalytic bed design
    which will reduce  NO  dissociation
    and increase NHs consumption.
  • Studies on heat and  mass transfer
    with reaction in absorption towers to
    optimize HNOa production by finding
    the optimal parameters for adsorp-
    tion tower operation.
  • Consideration  of nitric acid produc-
    tion by means of a super azeotropic
    mixture  which  may  be useful  in
    modification of the present process.

Nitrocellulose Production
   The following areas are recommended
for further research:
  •  Better understanding of the kinetics
     of the cellulose nitration will indicate
     methods  of operation to minimize
     NOx and SOx formation.
  • Better understanding of absorption
     of SO, and addition of an absorption
     tower to  the  acid concentrator to
     recover NOX.

  • Research on filtration operations and
    filtration units for effective recovery
    of NC fines from boiling tub, Jordan
    beater and poacher houses.
  • Reexamine and  modify flow streams
    to optimize water usage by recycle
    and other techniques in the purifica-
    tion process.

Iron  and Steel Industry
  The manufacture of  steel  involves
many processes  which  require  large
quantities of raw materials and  other
resources. Due to  the wide variety  of
products and processes, operations vary
from  plant to plant. However, the steel
industry can  be  segregated into two
major components; raw steel making, and
forming  and finishing operations. An
overview of the iron and steel process is
given in the final report and is summarized
  In  the  first major process,  coal  is
converted to coke. Nearly all active coke
plants are byproduct plants which pro-
duce, in addition to coke, byproducts such
as  coke  oven gas,  coal tar, crude  or
refined light oils,  ammonium sutfate  or
anhydrous ammonia, and napthalene.
Less  than  1%  of  domestic  coke  is
produced in beehive coke making.
  The coke from coke making operations
is then supplied to the blast furance pro-
cess where  molten  iron  is produced.  In
the blast furnace, iron ore, limestone and
coke are placed into the top of the furnace
and air is blown  countercurrently from
the bottom. The combustion  of coke
provides heat which produces metallurgi-
cal  reactions. The limestone forms a fluid
slag which combines with unwanted im-
purities in the ore. Molten iron  from the
bottom of the furnace and molten slag,
which floats on top of the iron, are period-
ically  withdrawn.

Iron  and Steel Industry
  The following areas are recommended
for  further research:
  • Use of refined or cleaned coal in coke
  • Study of the  formation of  cyanides
    and carbonyls during coking in order
    to prevent or reduce pollutant for-
  • Dry coke quenching of U.S. coals to
    eliminate quench water contamina-
  • The effect of process variables such
    as coal grinding and coking time on
    coke  produced. This information
    would be used to improve the quality
    of coke stability in order to enhance
    blast furnace  performance.
  • Development of biological oxidation
    systems to remove HCN from bypro-
    duct coke making wastewaters.
  • Absorption  of H2S from coke oven
    gases by Glaus or  Stretford process.
  • Development of better  CN removal
    systems from blast furnace waste-
    waters by using additives such as
    Caros acid (H2SOs) and polyphosphate,
    and by aeration.
  • Optimization of pH and contact time
    to improve alkaline chlorination and
    ozonation to upgrade blast furnace
  • Solvent extraction of zinc or dezinci-
    fication by Walez process to remove
    zinc from blast furnace dusts. Such
    zinc removal can facilitate the use of
    treated dusts in the sintering process.
  • Study of kinetics  of H2S and SO2
    formation during blast furnace slag
    quenching  to develop  methods by
    which  H2S formation  can be de-
  • Study the  kinetics of formation and
    oxidation of cyanides in the blast
    furnace to optimize the design and
    operation of the  stack in  order to
    oxidize the cyanide.
  • Development of solvent extraction
    and sulfide precipitation methods to
    remove toxic metals from the recycled
    steel plant wastewaters.
  • Study the effect of temperature and
    agitation in order to optimize pickling

Paper  and Pulp Industry
  The pulping process, kraft (or sulfate)
pulping  in particular, is fully discussed in
the final report. Pulping wood is an initial
process in the manufacture of paper and
paper products. The  pulping process
consists  of  conversion of  fibrous raw
material, wood, into a material suitable
for use in paper, paperboard, and building
materials. Pulp is  the fibrous  material
ready to be made into  paper.
  There are four major chemical pulping
techniques: (1) kraft or sulfate, (2) sulfite,
(3)  semichemical, and (4) soda. Of the
major pulping  techniques,  the kraft or
sulfate process produces over 80% of the
chemical pulp produced annually in the
United States.  In 1970, there were 116
mills producing 29.6 million tons of pulp
by the kraft process.  During the  same
year, the pulp and paper board consump-
tion was 56.8 million tons.

Paper  and Pulp Industry
  The following areas are recommended
for further research:
  • Research on digestion of wood chips
    to determine optimal sulfidity, pH,
    and temperature to reduce pollution.
  • Studies on control of fiber carryover
    from the blow tank by cyclone and/or
    reduction of relief pressure and
    selection of  wood-to-liquor ratio to
    prevent TRS emission.
  • Comparative studies on design and
    application of diffusion and displace-
    ment washers to minimize TRS.
  • Effect of black liquor oxidation and
    pH control on weak and strong black
    liquor to reduce TRS emission.
  • Studies  on the  direct and non-
    contact evaporation in the recovery
    furnace system to determine capabil-
    ity  and  merits of each  unit  in
    reducing the TRS emission.
  • Research on combustion of strong
    black liquor to prevent  black out
    conditions and stick dust formation
    by optimizing the design and opera-
    ting conditions  in the recovery
  • Research and application of scrub-
    bing  techniques to  reduce TRS

The Primary Aluminum
  The primary aluminum industry consists
of processing bauxite ore to produce
alumina (and occasionally aluminum
hydroxide) and processing the alumina to
produce aluminum. Approximately, 7.6 x
106 tons of alumina were produced in
U.S. from processing  about  15.4 x  106
tons of  bauxite  in  1972,  94% of  the
alumina was  utilized to make aluminum.

Primary Aluminum  Industry
  The following areas are recommended
for further research:
  • Leaching and extraction of red mud
    to recover mineral values.
  • Improving the mechanical strength,
    adsorption capacity and particle size
    distribution of  calcined alumina  by
    optimizing precipitation and calcina-
    tion of alumina.
  • Optimizing the temperature for and
    stripping of high silica U.S. Bauxite
  • Enrichment of high silica U.S. Bauxite
    using bacterial action.
  • Improving calcination of AI2O3 to
    reduce its moisture content, thereby
    reducing formation  of  HF from
    electrolytic cells.
  • Optimization of the cryolite bath
    (NaF/AIF3)  ratio,  alumina  content
    and  temperature  of cell to  reduce
    flouride emissions.
  • Increasing the adsorption capacity of
    AbOs to remove HF in the fumes from

  • Understanding the interaction of HF
    and S0« on AI203 to improve dry
    scrubbing  of  SO* gases from the
    electrolytic cell.
  • The effect  of various additives in
    removing sulfur in coal as slag.
  • Effect  of  adding lithium  on  cell
    operating temperature and HF emis-
  • Leaching of cathode linings to
    remove flourides and cyanides.

Phosphate Fertilizer Industry
  Fertilizers in general can be categorized
by their composition of plant nutrients.
The fertilizers differ in their composition
of plant nutrients of nitrogen, phospho-
rous, and potassium. Normal superphos-
phate contains only one nutrient, phos-
phorous. Generally,  the solid and liquid
mix fertilizers contain all three nutrients
in varying amounts.
  Over 44 million metric tons of phos-
phate rock  were  mined  in the United
States during 1975. Approximately 22.75
million metric tons were consumed by the
fertilizer industry during the same period.
  The phosphate based  fertilizers are
produced by conversion of  unsoluble
phosphate  ore into the  soluble  form
necessary for plant consumption.  The
phosphoric  acid, backbone of phosphate
fertilizer, is formed by mixing phosphate
rock with sulfuric acid.
  The final  report fully describes the
effect of concentrates on the production
of phosphoric acid,  normal superphos-
phate, and ammonium phosphate.

Wet Process Phosphoric Acid
  The following areas are recommended
for further research:
  • Studies on purification of phosphate
    feed to reactor to reduce impurities
    which cause byproduct formation.
  • Comparative studies  on  adsorption
    and absorption  of flourme to deter-
    mine the most efficient technique to
    alleviate flourine emission.
  • Research on the design and opera-
    ting parameters of the scrubber to
    reduce  plugging and increase the
    rate of flourine transfer from the vent
    gases to scrubbing medium.

Ammonium  Phosphate
  The following areas are recommended
for further research:
  • Research on  kinetics of  reaction of
    ammonia  with  phosphoric  acid to
    enhance this reaction, either cataly-
    tically or by increasing the residence
    time  in  the  reactor vessel, which
    would reduce the emission.
 • Studies  on design of the reactor
    vessel and granulators to minimize
    the ventilation rate which would lead
    to smaller volumes of gaseous emis-
 • Research on the design and selection
    of optimal operating parameters for
    the scrubbing  unit to  reduce the
    ammonia, flouride,  and particulate

Superphosphate Production
  The following area is recommended for
further research:
  • Studies  on the scrubber design and
    optimal operating parameters to
    reduce flourine emissions.

Conclusions and
  This project identified  the following
areas of research as most promising for
minimizing pollutants from eight chemical
processing industries studied.

Solvent Extraction
  Modification  of solvent extractor
designs and  operations  should minimize
metal ions or non-phenolic organics in
process streams leaving extractor batteries
in hydrometallurgical and coal liquefac-
tion processes,  respectively. Studies
could include modelling of selective ion
extraction in multiple  metal systems,
characterization of  liquid dispersion
properties such as  surface area and
droplet mixing as a  function of  power
consumption,  extraction  kinetics, and
separation of liquid-liquid  dispersions.

Catalyst Deactivation
  Modification of catalyst  reactor bed
operation and studies on catalyst deactiva-
tion will increase catalyst life and reduce
the volume  of spent  catalyst from coal
gasification  operations. Studies could
include modelling catalyst deactivation
phenomena  as affected by temperature,
pressure, feed gas composition, catalyst
structure, and  catalyst type. Optimal
reactor operation studies for sulfur guard
catalysts  (ZnO),  shift catalysts (cobalt-
molybdate),  and  methanation catalysts
(nickel) can be conducted.

Leaching Processes
  Modification  and improvement  of
leaching  processes for  sulfide or oxide
ores will  reduce  ground water contami-
nation and  dissolved metal salts in
process streams in  hydrometallurgical
processes. These results  also apply to
recovery of metals  from particulates
(smelting dust),  coal liquefaction ash,
spent catalysts in coal gasification, and
coal liquefaction  residues. Studies could
include vat leaching using ammonial or in
organic  acid solutions. Characterization
of kinetics  of  leaching  as  affected by
particle size, temperature, concentra-
tions and  particle structure can be
explored. Minimum power requirements
to suspend particles and maximize
particle-liquid mass transfer can  be

Gas Absorption
  Modification and improvement of gas
absorption processes such as the Stret-
ford absorption process will  reduce
emissions of Hz, HCN, and CO2 in tail
gases from coal  liquefaction  processes
and  H2S and S02 for  smelter  off gas
recovery operations. Studies could
include gas-liquid mass transfer and gas-
liquid reactions  in  absorption  liquids
(sodium metavanadate,  sodium carbo-
nate,  sodium bicarbonate, and ADA) as
affeced  by  temperature, pressure, and
gas-liquid contacting.

Gas-Liquid-Solid Reactions
  Modification  and improvement of
reactors for contacting and reacting gas-
liquid-solid dispersions would minimize
particulate emissions in coal liquefaction
reactions as well  as vat leaching process-
es. Studies could include coal dissolution
rates, gas dispersion, particulate agglom-
eration, dissolved gas-particle reactions,
and  determination of the rate  limiting
steps as affected by mechanical agitation,
temperature, pressure and compositions.

L. L Tavlarides is with the Illinois Institute of Technology. Chicago, IL 6O616.
W. A. Cawley is the EPA Project Officer (see below).
The complete report, entitled "Process Modifications Toward Minimization of
  Environmental Pollutants in the Chemical Processing Industry," (Order No. PB
  84-133 347; Cost: $17.50, subject to change) will be available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
        Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
        Industrial Environmental Research Laboratory
        U.S. Environmental Protection Agency
        Cincinnati, OH 45268
                                                                                           •USGPO:  1984-759-102-10613

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