United States
Environmental Protection
Agency
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
reactions.
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
back).
Introduction
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
nature.
Refining of Nonferrous Metals
Introduction
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
products
• 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
atmosphere.
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
pollutants.
• 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
metals.
Electroplating of Common
Metals
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-
plating.
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
industry
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-
es.
Lurgi Coal Gasification Process
The following areas are recommended
for further research:
• Stabilization of gasifier and boiler
ash to decrease or prevent leachabil-
ity.
• 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-
vents.
• 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
range.
• 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
here.
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
making.
• Study of the formation of cyanides
and carbonyls during coking in order
to prevent or reduce pollutant for-
mation.
• Dry coke quenching of U.S. coals to
eliminate quench water contamina-
tion.
• 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
wastewaters.
• 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-
creased.
• 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
operations.
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
furnace.
• Research and application of scrub-
bing techniques to reduce TRS
emission.
The Primary Aluminum
Industry
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
ores.
• 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
electrolysis.
-------
• 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-
sions.
• 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
Production
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
Production
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-
sion.
• Research on the design and selection
of optimal operating parameters for
the scrubbing unit to reduce the
ammonia, flouride, and particulate
emissions.
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
Recommendations
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
studied.
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
-------
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use S300
*
------- |