EPA 440/1-75/038
GROUP I, PHASE II
Development Document for Interim
Final Effluent Limitations Guidelines
and Proposed New Source
Performance Standards
for the
CALCIUM CARBIDE
Segment of the
FERROALLOY MANUFACTURING
Point Source Category
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
FEBRUARY 1975
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"JH
DEVELOPMENT DOCUMENT
for
INTERIM FINAL EFFLUENT LIMITATIONS GUIDELINES
and
PROPOSED NEW SOURCE PERFORMANCE STANDARDS
for the
CALCIUM CARBIDE SEGMENT
of the
FERROALLOY MANUFACTURING POINT SOURCE
CATEGORY
Russell E. Train
Administrator
James L. Agee
Assistant Administrator for
Water and Hazardous Materials
Allen Cywin
Director, Effluent Guidelines Division
Patricia W. Diercks
Project Officer, Ferroalloys
Elwood E. Martin
Project Officer, Inorganic Chemicals
February, 1975
Effluent Guidelines Division
Office of Water and Hazardous Materials
U.S. Environmental Protection Agency
Washington, D.C. 20460
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ABSTRACT
For the purpose of establishing effluent limitations and
standards of performance for the calcium carbide industry,
the industry has been categorized on the basis of the types
of furnaces, air pollution control equipment installed, raw
materials and water uses. The categories are as follows:
II
Covered Calcium Carbide Furnaces with Wet Air
Pollution Control Devices; and
Other Calcium Carbide Furnaces
Effluent limitations guidelines contained herein set forth
the degree of effluent reduction attainable through the
application of the best practicable control technology
currently available (BPCTCA) and the degree of effluent
reduction attainable through the application of the best
available technology economically achievable (BATEA) which
must be achieved by existing point sources by July 1, 1977
and July 1, 1983, respectively. The standards of
performance for new sources contained herein set forth the
degree of effluent reduction which is achievable through the
application of the best available demonstrated control tech-
nology, processes, operating methods, or other alternatives.
Based upon best practicable technology currently available
the covered furnace calcium carbide category may discharge a
treated wet scrubber effluent. Based upon BPCTCA the other
furnaces calcium carbide category is required to achieve no
discharge of process wastewater.
Based on the application of best available technology
economically achievable, the covered furnace category may
discharge a treated wet scrubber effluent, while the other
category is required to achieve no discharge of process
wastewater.
The new source performance standards require no discharge of
process wastewater for the other furnaces category, but
allow a discharge of treated scrubber blowdown from the
covered furnaces category.
Promulgated regulations for discharges from uncovered (open)
calcium carbide furnaces appeared in the Federal Register on
March 12, 1974 at page 9612 as part of the inorganic
chemicals industry category. Although the subcategorization
contained in this document does include open furnaces as
part of the other carbide furnaces subcategory, the
regulation to be published as part of the ferroalloys
category will not duplicate the coverage of the inorganic
chemicals regulation, but will be complementary to that
regulation.
111
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CONTENTS
Section
I Conclusions
II Recommendations
III Introduction
IV Industry Categorization
V Waste Characterization
VI selection of Pollutant Parameters
VII Control and Treatment Technology
VIII Cost, Energy and Non-Water Quality
Aspects
IX Best Practicable control Technology
Currently Available, Guidelines and
Limitations
X Best Available Technology Economically
Achievable, Guidelines and Limitations
XI New Source Performance Standards and
Pretreatment Standards
XII Acknowledgements
XIII References
XIV Glossary
1
3
7
17
21
35
41
49
55
61
67
73
75
77
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FIGURES AND TABLES
Figure 1 Cross Section of Open Furnace
Table 1 Calcium carbide Producers
Figure 2 Open Furnace Calcium Carbide Process Flow
Diagram
Figure 3 Covered Furnace Calcium Carbide Process Flow
Diagram With Dry Collection Device
Figure H Covered Furnace Calcium Carbide Process Flow
Diagram With Wet Air Pollution Device
Table 2 Water Effluent Treatment Costs-Category I
Table 3 Conversion Factors
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26
-27
28
29
53
79
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SECTION I
CONCLUSIONS
For the purpose of establishing effluent limitations
guidelines and standards of performance for the calcium
carbide industry, the industry has been categorized on the
basis of types of furnaces, air pollution control equipment,
raw materials and water uses. The categories are as
follows:
I Covered Calcium Carbide Furnaces with Wet Air
Pollution Control Devices; and
II Other Calcium Carbide Furnaces
The effluent limitations guidelines for covered furnaces
with wet scrubbers allow for a treated discharge of scrubber
effluent with restrictions on suspended solids, pH and total
cyanide. The proposed new source performance standards
allow a discharge of treated blowdown from scrubber
recirculation systems.
The proposed effluent limitations guidelines for other
carbide furnaces is no discharge of process wastewater. 100
percent/ of this industry category is currently achieving
this limitation. Covered furnaces which use evaporative
coolers and dry bag collectors, or which have no air
pollution control have no discharge of process wastewater.
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SECTION II
RECOMMENDATIONS
It is recommended -that the effluent limitations guidelines
and new source performance standards be adopted as suggested
herein for the calcium carbide industry. These suggested
guidelines and performance standards have been developed on
the basis of an intensive study of the industry, including
plant surveys, and are believed to be reasonable and
attainable from the standpoints of both engineering and
economic feasibility.
It is recommended that the industry be encouraged to develop
or adopt such pollution reduction methods as the recovery
and reuse of collected airborne particulates for recycle to
smelting operations and the use or sale of by-products. The
development or adoption of better wastewater treatment
controls and operating methods should also be encouraged.
The best practicable control technology currently available
for existing point sources is as follows, by category:
Category I,
Covered Furnaces with Wet Air Pollution Control
Devices - physical/chemical treatment to reduce
suspended solids and harmful pollutants; and
Category II, Other Furnaces - use of dry air pollution
devices.
The effluent limitations to be achieved by July 1, 1977 are
based on the pollution reduction attainable using those
treatment technologies as presently practiced by the average
of the best plants in the categories. The 30 day average
effluent limitations corresponding to BPCTCA are as follows
for category I:
pollutant parameter
kg/kkg (lb/1000 Ib)
suspended solids
total cyanide
PH
0.190
0.0028
6.0-9.0
For category II, the effluent limitation is no discharge of
process wastewater.
The best available technology economically achievable
existing point sources is as follows, by category:
for
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I Scrubber effluent -treated by physical/chemical
treatment to reduce harmful pollutants followed by
clarification and polish filtration to reduce
suspended solids; and
II Same as BPCTCA
The effluent limitations to be achieved by July 1, 1983 are
based on the pollution reduction attainable using those
treatment technologies as presently practiced by the best
plants in the categories along with transfer of technology
from the inorganic chemicals industry. The 30 day average
effluent limitations corresponding to BATEA are as follows
for category I:
pollutant parameter
kg/kkg (lb/1000 Ib)
suspended solids
total cyanide
PH
0.11
0.0028
6.0-9.0
For category II, the effluent limitation is no discharge of
process wastewater.
The best available demonstrated control technology
sources is as follows, by category:
for new
I Recirculation of scrubber waste water, blowdown treated
by physical/chemical treatment to reduce harmful
pollutants followed by clarification and polish
filtration to reduce suspended solids; and
II Same as BPCTCA
The new source performance standards are based upon the best
available demonstrated control technology, process,
operating methods, or other alternatives, which, are
applicable to new sources. For category I, the 30 day
average effluent limitations for new sources are as follows:
pollutant parameter
kg/kkg (lb/1000 Ib)
suspended solids
total cyanide
PH
0.020
0.0005
6.0-9.0
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For category II, the effluent limitation is no discharge
process wastewater.
of
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SECTION III
INTRODUCTION
PURPOSE AND AUTHORITY
The United States Environmental Protection Agency (EPA) is
charged under the Federal Water Pollution Control Act
Amendments of 1972 with establishing effluent limitations
which must be achieved by point sources of discharge into
the navigable waters of the United States.
Section 301(b) of the Act requires the achievement by not
later than July 1, 1977, of effluent limitations for point
sources, other than publicly owned treatment works, which
are based on the application of the best practicable control
technology currently available as defined by the
Administrator pursuant to Section 304(b) of the Act.
Section 301(b) also requires the achievement by not later
than July lr 1983, of ,effluent limitations for point
sources, other than publicly owned treatment works, which
are based on the application of the best available
technology economically achievable which will result in
reasonable further progress toward the national goal of
eliminating the discharge of all pollutants, as determined
in accordance with regulations issued by the Administrator
pursuant to Section 304 (b) to the Act. Section 306 of the
Act requires the achievement by new sources of a Federal
standard of performance providing for the control of the
discharge of pollutants which reflects the greatest degree
of effluent reduction which the Administrator determines to
be achievable through the application of the best available
demonstrated control technology, processes, operating
methods, or other alternatives, including, where
practicable, a standard permitting no discharge of
pollutants. Section 304 (b) of the Act requires the
Administrator to publish within one year of enactment of the
Act, regulations providing guidelines for effluent
limitations setting forth the degree of effluent reduction
attainable through the application of the best practicable
control technology currently available and the degree of
effluent reduction attainable through the application of the
best control measures and practices achievable including
treatment techniques, process and procedure innovations,
operating methods and other alternatives. The regulations
herein set forth effluent limitations guidelines pursuant to
Section 304 (b) of the Act.
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Section 306 of the Act requires the Administrator, within
one year after a category of sources is included in a list
published pursuant to Section 306 (b) (1) (A))' of the Act, to
propose regulations establishing Federal standards of
performances for new sources within such categories. The
Administrator published in the Federal Register of January
16r 1973 (38 F.R. 1624), a list of 27 source categories.
Publication of the list constituted announcement of the
Administrator's intention of establishing, under Section
306, standards of performance applicable to new sources
within the ferroalloy manufacturing point source category,
which was included within the list published January 16,
1973.
SUMMARY OF METHODS USED FOR DEVELOPMENT OF EFFLUENT
LIMITATION GUIDELINES AND STANDARDS OF PERFORMANCE
•""—"' i> '- •I...... ... ,— . — — .•—.,,— .. ^ I, i
The Environmental Protection Agency has determined that a
rigorous approach including plant surveys and verification
testing is necessary for the promulgation of effluent stand-
ards from industrial sources. A systematic approach to the
achievement of the required guidelines and standards
includes the following:
a) categorization of the industry and determination of
those industrial categories for which separate effluent
limitations and standards need to be set;
b) characterization of the waste .loads resulting from dis-
charges within industrial categories;
c) identification of the range of control
technology within each industrial category;
and treatment
d) identification of those plants having the
technology currently available (exemplary plants); and
best
e) generation of supporting verification data for the
exemplary plants including actual sampling of plant
effluents by field teams.
The culmination of these activities is the development of
the guidelines and standards based on the best practicable
current technology and best available technology.
Categorization and Waste Load Characterization
The effluent limitations and standards of performance
proposed herein were developed in the following manner. The
point source category was first categorized for the purpose
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of determining whether separate limitations and standards
are appropriate for different segments within a point source
category. Such categorization was based upon type of
furnace, air pollution devices, treatment technology and
other factors. The raw waste characteristics for each
category were then identified. This included an analysis of
(1) the source and volume of water used in the process
employed and the sources of waste and waste waters in the
plant; and (2) the constituents of all waste waters
including harmful constituents and other constituents which
result in degradation of the receiving water. The
constituents of waste waters which should be subject to
effluent limitations and standards of performance were
identified.
Treatment and control Technologies
The full range of control and treatment technologies
existing within each category was identified. This included
an identification of each control and treatment technology,
including both in-plant and end-of-process technologies,
which are existent or capable of being designed for each
category. It also included an identification of the amount
of constituents and the characteristics of pollutants
resulting from the application of each of the treatment and
control technologies. The problems, limitations and
reliability of each treatment and control technology were
also identified. In addition, the non-water quality
environmental impact, such as the effects of the application
of such technologies upon other pollution problems,
including air, solid waste, noise and radiation were also
identified. The energy requirements of each of the control
and treatment technologies were identified as well as the
cost of the application of such technologies.
Data gase
Cost information contained in this report was obtained
directly from industry during, plant visits, f-rom engineering
firms and equipment suppliers, and from the literature.
The information obtained has been used to develop capital,
operating and overall costs for each treatment and control
method. Costs have been put on a consistent industrial
calculation basis of ten year straight line depreciation
plus allowance for interest at six percent per year
(pollution abatement tax free money) and inclusion of
allowance for insurance and taxes for an overall fixed cost
amortization of fifteen percent per year. This cost data
plus the specific information obtained from plant visits was
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then used for cost effectiveness estimates in Section
and wherever else costs are mentioned in this report.
VIII
The data for identification and analyses were derived from a
number of sources. These sources included EPA research
information, published literature, qualified technical con-
sultation, on-site visits - and interviews at plants
throughout the U.S., interviews and meetings with trade
associations, and interviews and meetings with regioneil
offices of the EPA. All references used in developing the
guidelines for effluent limitations and standards of
performance for new sources reported herein are included in
Section XIII of this report.
Exemplary Plant Selection
The following exemplary plant selection criteria were
developed and used for the selection of exemplary plants.
a) Discharge effluent Quantities
Plants with low effluent quantities or the ultimate of no
discharge of process waste water pollutants were preferred.
This minimal discharge may be due to reuse of water, rciw
material recovery and recycling, or to use of evaporation.
The significant parameter was minimal waste added to
effluent streams per weight of product manufactured. The
amount of wastes considered here were those added to waters
taken into the plant and then discharged.
*>) Effluent contaminant level
Preferred plants were those with lowest effluent contaminant
concentrations and lowest total quantity of waste discharge
per unit of product.
c) Watermanagement practices
Use of good management practices such as water re-use, plan-
ning and in-plant water segregation were considered.
3) Land utilization-
The efficiency of land use was considered.
e) Air pollution and solid waste control
Exemplary plants must possess overall effective air and
solid waste pollution control where relevant in addition to
water pollution control technology. Care was taken to
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xnsure that all plants chosen have minimal discharges into
the environment and that exemplary sites are not those which
are exchanging one form of pollution for another of the same
or greater magnitude.
f) Effluent treatment methods and their effectiveness
Plants selected have in use the best currently available
treatment methods, operating controls, and operational
reliability. Treatment methods considered included basic
process modifications which significantly reduce effluent
loads as well as conventional treatment methods.
9) Plant facilities
All plants chosen as exemplary had all the facilities
normally associated with the production of the specific
material in question. Typical facilities generally were
plants which have all their normal process steps carried out
on-site.
n) Geographic location
Factors which were considered include plants operating in
close proximity to sensitive vegetation or in densely
populated areas. Other factors such as land availability,
rainfall, and differences in state and local standards were
also considered.
i) Raw materials
Differences in raw material purities were given strong con-
sideration in cases where the amounts of wastes are strongly
influenced by the purity of raw materials used.
General Description of Calcium. Carbide^Manufacturing
There is only one process used in the United States for the
manufacture of calcium carbide. This process involves the
thermal reduction of calcium oxide (lime) and coke in a sub-
merged arc electric furnace. The calcium oxide and dried
coke are conveyed to a mix-house where they are weighed and
blended. After the batch has been formulated it is moved by
conveyor to the hoppers above the furnace, where it flows by
gravity through chutes to the furnace.
Electricity is passed through carbon electrodes extending
below the surface of the charge so that a thermal reduction
zone lies in the center of the charge. The molten calcium
carbide from the carbon reduction of lime accumulates at the
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base of the electrodes in the furnace. The molten alloy is
periodically removed through the tap-hole to drain the mate-
rial from the hearth of the furnace. The calcium carbide is
cooled in air in chill cars or hoppers, then crushed,
screened and packaged for shipment. Quality control tests
are made on batches to determine the volume of acetylene
produced by a known quantity of calcium carbide.
The basic design of the submerged-arc furnace for the
production of calcium carbide is the same throughout the
industry with the notable exception of open versus covered
furnaces. In the open furnaces the carbon monoxide reaction
qas is combusted with air at the surface of the charge, and
the large quantities of gases flow into a hood built above
the furnace. The gases are discharged through a stack to
the atmosphere or are passed through air pollution control
devices such as a baghouse or venturi scrubber. Due to the
open configuration, the parts above the furnace charge are
exposed to the radiant heat of the furnace and the hot
furnace gases. These components, along with the electrical
transformers are cooled through the use of non-contact
cooling water. Figure 1 shows a schematic of an open
furnace.
Covered furnaces have water cooled covers extending over the
top of the furnace crucible with openings for the electrodes
and gas removal dusts. The openings around the electrodes
are generally used for charging raw materials. In covered
furnaces, raw materials such as metallurgical coke and lime
chunks are used that do not tend to bridge or block the flow
of gas so that furnace eruptions are minimized.
The crucible of the submerged-arc furnace consists of a
metal shell adequately supported on foundations with
provisions for cooling the bottom of the steel shell. The
bottom interior of the steel shell is lined with two or more
layers of carbon blocks and tightly sealed with a carbon
compound packed between the joints. The interior walls of
the furnace shell are lined with refractory or carbon brick.
One or more tap-holes are provided through the shell; In
some cases, provisions are made for the furnace to rotate
slowly. Submerged-arc furnaces generally operate
continuously except for periods of power interruption or
mechanical breakdown of components. Operating time varies
from 90 to 98 percent, with 95 percent a good average.
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CD
1
0.
o.
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Although furnaces may be changed from production of one
product to another, such as from calcium carbide to ferro-
alloys, this almost always entails rearrangement of
electrode spacing and involves different power loads arid
voltage requirements.
In the production of calcium carbide by the electric-arc
furnace process, the only source of process water pollutants
is the use of wet air pollution control devices such as
scrubbers. The sources of air pollution are thus of
importance. Particulates are emitted from coke drying,
crushing, grinding and sizing and furnace operations. The
particulate emissions from the drying, crushirig and sizing
operations are generally handled in dry collectors such as
baghouses or cyclones. Dry collection is also used for the
fumes from the furnace tapping and emissions from the
electrode areas in a covered furnace. Wet scrubbers may be
used to handle the gases from the furnace reaction.
Since the emissions from the furnace have a major impact
upon the potential for water pollution in those plants using
wet air pollution control devices, some discussion of such
emissions is appropriate. The submerged-arc furnace
utilizes carbon reduction of lime, and continuously produces
large quantities of hot carbon monoxide. The CO gas venting
from the top of the furnace carries fumes from high-
temperature regions of the furnace and entrains the finer
sized constituents of the mix.
In an open furnace, all CO and other combustibles in the
furnace gas burn with induced air at the top of the charge,
resulting in a large volume of high-temperature gas. ; In a
covered furnace, most or all of the CO and other gases are
withdrawn from the furnace without combustion.
Except for ejected mix particles from the furnace the fume
size is generally below two microns. Grain loadings and
flowrates are dependent upon the furnace type and hooding.
Open submerged-arc furnaces have high flowrates and moderate
grain loadings, while closed furnaces have moderate
flowrates and generally high grain loadings.
The quantity of emissions from calcium carbide submerged-arc
furnaces will vary up to several times the normal emission
level over a period of one to three percent of the operating
time due to major furnace interruptions and, to a lesser
extent, because of normal interruptions. The quantity and
type of emissions are also dependent on the presence of
fines in the feed. Fine materials promote bridging and non-
uniform descent of the charge which may cause gas channels
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to develop. The collapse of a bridge causes a momentary
burst of gases.. A porous charge will promote uniform gas
distribution and decrease bridging. For some locations
economics dictates the use of raw materials with more fines
or with more volatile matter than desirable. An example of
this is the operation of an open furnace when using
petroleum coke as a raw material which has a greater amount
of fines than metallurgical coke. Use of an open furnace
however, allows the charge to be •stoked', thereby breaking
up bridges.
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SECTION IV
INDUSTRY CATEGORIZATION
INTRODUCTION
The development of effluent limitations guidelines and
recommended standards of performance for new sources for a
particular industry must give consideration to whether the
industry can be treated as a whole in the establishment of
uniform and equitable guidelines or whether there are
sufficient differences within the industry to justify its
division into categories. For the calcium carbide segment
of the ferroalloy industry, the following categorization is
believed to yield the least number of groups having
significant differences in water pollution control and
treatment.
The proposed categories are:
I - Covered Calcium Carbide Electric Furnaces With Wet
Air Pollution Control Devices; and
II - Other Calcium Carbide Electric Furnaces
In developing the above categorization, the following
factors were considered as a possible basis:
1) Production Processes
2) Furnace Types
a) Open
b) Covered
3) Raw Materials
4) Product Produced
5) Size & Age of Facilities
6) Wastewater Constituents
7) Water Uses
8) Air Pollution Control .
Equipment
9) Treatment Technology
Production Processes
Since there is only one production process used for the pro-
duction of calcium carbide, this is not a basis for
categorization.
Furnace Types
The types of electric furnaces used to produce calcium
carbide were found to provide a basis for categorization in
conjunction with raw materials, water uses and air pollution
control equipment. The differences between open and covered
furnaces are significant as they relate to the raw waste
loads from the process, particularly the presence or absence
of carbon monoxide in the furnace gases. The furnace gas
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volumes from the two types of furnaces may vary by a factor
of 20 and the water used for wet air pollution control
devices varies significantly in terms of hydraulic load due
to the differences in gas volumes. In general, covered
furnace operations tend to recover and utilize the carbon
monoxide in the furnace gas, while open furnace operations
burn the carbon monoxide to carbon dioxide in the process.
Raw Materials
The types of raw materials used to produce calcium carbide
were found to provide a basis for categorization in con-
junction with furnace types, water uses and air pollution
control equipment. The basic differences in raw materials
are the use of metallurgical coke versus petroleum coke.
The choice of these two raw materials is based partly on
economics and geographical location. The plants located in
the western part of the U.S. use petroleum coke while those
in the east and midwest use metallurgical coke. The use of
a specific type of coke dictates the type of furnace used
for the process. When petroleum coke is used, the
production of calcium carbide is carried out in an open
furnace due to the small sized particles characteristic of
the raw material. The use of an open furnace is necessary
due to the amount of particle emissions and eruptions from
the furnace charge. On the other hand, all of the furnaces
using metallurgical coke are covered and, therefore, must
handle the problem of carbon monoxide in the furnace off-
gas.
Product Produced
Since only one product is produced, there is no basis for
further categorization. However, it should be pointed out
that it is possible to produce other products such as ferro-
alloys in a furnace now producing calcium carbide, but the
production processes are not readily interchangeable and a
furnace will not be used one week for calcium caroide, and
the next for ferroalloy production. The furnace is always
committed to the production of one product at a time. It is
not felt that the possible convertability of a carbide
furnace to a ferroalloy furnace provides an adequate basis
for categorization.
gi_y-e and Age of Facilities
The size and age of facilities does not provide a basis for
categorization. Plant ages range from 5 to 46 years with
sizes ranging from 20,000 to 150,000 tons per year. This
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type of range
categori zation.
does not provide adequate justification for
Waste Water Constituents
The waste water constituents do not provide an independent
basis for categorization. With the exception of non-contact
cooling water, the only water used in the process is for wet
air pollution devices. Suspended solids are the largest
single constituent of the process wastewater, and result
from removal of particulates from the furnace gases.
Cyanides are generated in significant concentrations only in
covered furnaces. The wastewater constituents are due to
the differences between open and covered furnaces together
with wet air pollution control devices and, therefore, are
not a basis for categorization.
Water Uses
Water uses were found to provide a basis for categorization
in conjunction with furnace types, raw materials and air
pollution control equipment. Water is used in the process
for two purposes — cooling water and air pollution control
devices. The cooling water is non-contact and can be once-
through or recirculated via a cooling tower. Associated
with this water there may be water used for water treatment
regeneration and cooling tower blowdown. Water is also used
for air pollution control equipment for wet scrubbing.
Air Pollution Control Equipment
Air pollution control is the primary pollution problem in
this industry. The water pollution problem is created by
solving air pollution problems with wet air pollution
control devices. When a dry air pollution control system
(such as a baghouse) is used, or when emissions are
uncontrolled, there is no process waste water discharge.
For this reason, the categorization selected is partially
based upon "type of air pollution equipment; i.e., wet or
djry. Although the type of wet scrubber used for air
pollution control was considered for further categorization,
it was felt that the type of process furnace used would
provide a better basis.
Tr eatment T echnolpgy
The only plant in the other carbide furnaces category which
utilizes a wet air pollution control device is recycling all
wastewater and therefore has no discharge. However, the
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only plant in the covered furnaces category presently using
wet scrubbers does discharge treated scrubber wastewater.
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SECTION V
WATER USE AND WASTE CHARACTERIZATION
INTRODUCTION
This section discusses the specific water uses in the
calcium carbide industry^ and the amounts of process waste
materials contained in these waters. The process wastes are
characterized as raw waste loads emanating from the
manufacturing process and are given in terms of kilograms
per metric ton of product (pounds per thousand pounds). The
specific water uses and amounts are given in terms of liters
per metric ton (gallons per ton) for each of the plants
contacted in this study. The treatments used by the plants
studied are specifically described and the amount and type
of water-borne waste effluent after treatment is
characterized.
SPECIFIC WATER USES
Water is used in calcium carbide plants for three principal
purposes falling under three major characterization
headings. The principal water uses are:
1) cooling — non-*contact cooling water
2) process water — scrubber water
3) auxiliary processes water.
Non-contact cooling water is defined as that cooling water
which does not come into direct contact with any raw
material, intermediate product, by-product or product used
in or resulting from the production process. Process water
is defined as that water which, during the manufacturing
process comes into direct contact with any raw material,
intermediate product, by-product or product used in or
resulting from the production process. ^Auxiliary processes
water is defined as that used for processes necessary for
production but not contacting the process materials. For
example, water treatment regeneration is an auxiliary
process.
The quantity of water usage for plants in this industry
generally ranges from 50,000 to 100,000 liters per metric
ton (12,000 to 24,000 gallons per ton). In general, the
plants using large quantities of water use it for once-
through cooling.
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Non-Contact Cooling Water
The non-contact cooling water in the industry is generally
of two types. The first type is recycled cooling water
which is cooled by cooling towers or spray ponds. The
second type is once^through cooling water whose source is
generally a river, lake or tidal estuary, and this water is
usually returned to the source from which it was taken. The
quantity of cooling water for plants in this industry ranges
from 40,000 to 80,000 liters per metric ton (9600 to 19,200
gallons per ton) , or about 8056 of the total water usage.
Limitations for non-contact cooling water will be
established for all industries in the future. At the
present time, there is believed to be no excessive thermal
load resulting from ferroalloys plants.
Air Scrubber and Contact Wash Water ;
This water comes under the heading of process water because
it comes into direct contact with the raw material,
reactants and product when used for wet scrubbing the
furnace gases. The water usage varies in volume depending
on the type of scrubber employed. A jhigh energy vejituri
scrubber on an open furnace uses approximately 357~OTF07ln/ters
of water ; per metric ton (8,40*0" gallons per "ton)". "A high
energy venturi scrubber oh a covered fjarnace uses as little
as 1300 liters of water per, metric__tojn2~O^222g^l,ions per
ton). Another form of contact wash water is thatfound in
use in evaporative coolers, which are sometimes used to cool
the burned furnace gas before entering a bag house. All of
this water is consumed in evaporation and none would be
discharged.
t
Miscellaneous Water Uses
These water uses vary widely among the plants with general
usage for safety showers and eye wash stations, sanitary
uses, and storm run-off. The resultant streams are either
not contaminated or only slightly contaminated with wastes.
The general practice is to discharge such streams without
treatment except for sanitary waste. In instances where
process residues collect where they can be washed away by
storm waters, as for example dusts on the exterior of
process buildings, storm run-off can constitute a
contamination problem.
Auxiliary Processes Water
This water is used in moderate quantities by the typical
plant for auxiliary operations such as ion
22
-------
cooling towers with a
resultant cooling tower blowdown. The watereffluents from
these operations are gejnera^Lly, lpw_,,in_ quantity"
.concentrated in waste materials. =^» „
The waste effluent from recycled cooling water would be
water treatment chemicals and the cooling tower blowdown
which generally is discharged with the cooling water. The
only waste effluent from once-through cooling water would be
water treatment chemicals which are generally discharged
with the cooling water. The cooling water tower blowdown
may contain phosphates, nitrates, nitrites, sulfates, and
chromates.
The water treatment chemicals may consist of alum, hydrated
lime, or alkali metal ions (sodium or potassium) arising
from ion exchange processes. Regeneration of the ion
exchange units is generally accomplished with sodium
chloride or sulfuric acid depending upon the type of unit
employed. At the present time there is insufficient data
upon which to base a regulation for auxiliary process water.
Additionally, it is not directly related to production and
is relatively small in quantity. Limitations for these
discharges should be established on a case-by-case basis,
with the weight of the proof on the permit applicant, at
least until such time as a national standard is established.
PROCESS WASTE CHARACTERIZATION
In this section the following information is given:
— a short description of the differences in the
processes at the plants studied and pertinent
flow diagrams:
— raw waste load data
— water consumption data
— specific plant waste effluents found and the post-
process treatments used to produce them;
— significant differences from plant data where found
in verification measurements.
Plants Surveyed
The four producers of calcium carbide constituting 100
percent of the United States production of this chemical
were contacted and plant visits were made to all five
23
-------
currently producing locations. The producers, locations,
capacities and furnace type are listed in Table 1.
Process Description
Calcium oxide and dried metallurgical or petroleum coke are
reacted in an electric-arc furnace. The calcium carbide
product is tapped as a liquid from the furnace, then air
cooled, crushed, screened, packaged and shipped. The
process wastes are airborne dusts from the coke drier,
screening and packaging operations and the furnace off-
gases. The process reaction is:
CaO * 3C —> CaC2 + CO
For every metric ton (1.1 short tons) of carbide produced,
about 310 cubic meters (11,000 cubic feet) (15°C) of furnace
gas is evolved; the gas analyzes 75-85 percent carbon
monoxide, 5-12% hydrogen and the remainder is nitrogen,
oxygen, carbon dioxide and methane.
There are two basic types of furnaces used for the process
— open and covered; the types of coke used,, either
metallurgical or petroleum, are dependent on furnace -type.
The open furnaces use petroleum coke for reaction and burn
the furnace gases with air at the surface of the charge.
These furnaces have a large volume of burned gases which
must be handled by an air pollution control system. The
covered furnaces use metallurgical coke for reaction and
either burn the furnace off-gases in a combustion chamber to
eliminate the carbon monoxide or scrub the gases and pipe
the carbon monoxide to another operation to recover the fuel
value. In all cases, particulate emissions are the major
pollution problem from the coke drier, furnace and crushing-
screening operations. The coke drying and crushing-
screening operations dust .emissions are handled by bag-
filter collectors from which 15 to 50 percent of the dusts
can be recycled and the remainder goes to land storage.
Four of the five plants are currently operating in this
fashion. The fifth plant uses dry collection on the
crushing-screening operations and does not operate a coke
drier at the present time. When coke drying is practiced at
this plant, it is planned to combine the drier vent gases
with furnace gases and control the emissions with the
existing venturi scrubbers.
The major source of particulate emissions are from the
furnace gases. The types of air pollution control equipment
used for the furnace gases vary with the type of furnace and
whether or not carbon monoxide is recovered. The types of
-------
air pollution control systems used in the calcium carbide
plants are listed below. Figure 2 shows the process flow
diagram for an open furnace operation, while Figures 3 and 4
show the process flow diagram for covered furnaces with and
without wet scrubbers.
Types of Air Pollution Control Systems
Used On Calcium Carbide Furnace Stack Gases
1. Open furnaces with withdrawal and cleaning of
burned gases
Control.devi ce
Wet scrubbers
Cloth type filters (baghouse)
2. Covered furnaces with withdrawal and cleaning of
unburned gases
Control devices
Wet scrubbers
3. Covered Furnaces with withdrawal and cleaning of
burned gases
Control devices
Evaporative cooler and baghouse
25
-------
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Type
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26
-------
PET COKE
LIME
i
SILO
*
Bb
COAL COKE
v
DRYER
^ DRY
""" COLLECTOR
1
SILO
i
FURNACE
1
AIR COOL
i
CRUSH
1
SCREEN
1
PACKAGF
1
SHIP
VENT
^COOLING WATER
i \
DRY COLLECTOR
OR SCRUBBER
{ [RECY
POND
•
^^
^ DRY
1 *. COLLECTOR
:LE
FIGURE 2
OPEN FURNACE CALCIUM CARBIDE PROCESS
FLOW DIAGRAM
27
-------
LIME
1
SILO
METALURGICAL
COKE
1
DRYER
I
SILO
i
FURNACE
1
AIR COOL
_ DRY
m COLLECTOR
r *
COMBUSTION
CHAMBER
AND EVAPORATION
COOLER
A- 1 T
CRUSH
BAGHOUSE
1
SCREEN
i1 •* DRY
, », COLLECTOR
PACKAGE
1
SHIP
FIGURE 3
COVERED FURNACE CALCIUM CARBIDE PROCESS
FLOW DIAGRAM WITH DRY COLLECTION DEVICES
-------
LIME
1
SILO
METALURGICAL
COKE
DRYER
i
SILO
I
FURNACE
I
AIR COOL
I
CRUSH
SCREEN
PACKAGE
I
SHIP
DRY
COLLECTOR
-^NON-CONTACT
COOLING WATER
1
SCRUBBER
SCRUBBER
WASTE
CO GAS
TO OTHER
PROCESSES
DRY
COLLECTOR
FIGURE 4
COVERED FURNACE CALCIUM CARBIDE PROCESS
FLOW DIAGRAM WITH WET AIR POLLUTION DEVICE
29
-------
Raw Waste Loads
The main process reaction generates no by-product raw waste
material. Process raw wastes are generated by the coke
drier, furnace gas scrubbing, and packaging operations. The
average values are given for the two open furnace plants
below:
waste material
plant 454 P.lant_4J55
kg/kkg lib/1000 IbL kg/kka (lb/1000 Ib)
coke dust
furnace stack dust
packing dust
hydrated lime and coke
none
135
unknown
112.5
50
85
10
Plant 454 does not operate a coke drier but does landfill
some coke spillage along with off grade calcium carbide
after "airslaking" to hydrated lime. Plant 455 recycles up
to 50 percent of the fines to the furnace and landfills the
remainder.
The average raw waste loads from the covered furnace plants
are given below:
waste material
coke dust
furnace stack dust
packing dust
cyanide (total)
-The packing dusts from these three plants are recycled to
the operation and go out with the product.
Wet Scrubber Raw Waste Loads
Samples of scrubber raw wastes were analyzed by the
contractor with the following results:
plant 451
kg/ (Ib7
kka 1000 Ib)
20
23
unknown
0.203
plant 452
kg/ lib/
30.3
28
unknown
none
plant 453
kg/ (Ib/
3.9
37.5
3i.;
none
30
-------
constituent:
TSS
TDS
Cyanide (total)
Iron
Silica (SiO2)
Calcium ""
Flow (gal/ton)
plant 451
concentration
_ (213/11- _
3750
302
27
14.2
2.9
397
1800
calculated
kg/ (lb/
kkg___1000_lbl
28.2
2.3
0.203
0.11
0.02
2.98
TSS
TDS
Cyanide
Iron
Silica (Si02)
Calcium
Flow (gal/ton)
4740
2640
22.7
0.24
2570
8400
166.
92.5
0.80
0.0084
90.1
Air_gQllution Control Equipment
The following is a summary of the types of air pollution
equipment found in use -or planned for furnace off-gas
emission control. The use of wet scrubbers is more
prevalent with covered furnaces than with open.
Open Furnace Operation
furnace gas
air pollution equipment
dry bag filters
venturi high energy
wet scrubber
installed and
operating
none
pJLant 454
none in use but
considering for
future
presently in use
31
-------
furnace
gas air
pollution
equipment:
venturi wet
scrubber
evaporative
cooler and
dry bag filter
disintegrator
scrubbers
Covered Furnace_OEeratign
plant 451
none
none
presently
in use
planned
installation
1974
presently in
use
none
p_lant_453
none
planned
installation
1974
none •
Plant 453 currently wents and flares all furnace gases.
The Airco plant at Calvert City, Kentucky which is currently
not operating, is a covered furnace operation which
presently uses no air pollution control equipment, but Airco
sources indicate that a venturi wet scrubber installation is
projected for that plant when it comes back on stream.
The venturi high energy scrubbers have been the most recent
wet scrubbers to be installed in the calcium carbide plants.
A high energy venturi scrubber on an open furnace uses
approximately 35,000 liters of water per metric ton (8400
gallons per ton) . The same installation on a covered
furnace uses as little as 1300 liters of water per metric
ton (312 gallons per ton). Most venturi designs allow
recirculation of scrubbing solutions, such that the water
consumption is reduced to that evaporated plus that
contained in the blowdown of the concentrated solids stream.
A disintegrator type of scrubber is used by one of the
plants surveyed. This type of scrubber has the advantage of
producing only a slight pressure head in the off-gas line,
but capacity limitations and large water and . power
consumption make it uneconomical for most new furnace
installations.
The use of an evaporative cooler and dry bag collector has
definite advantages in that there is no waste water effluent
from the system. The water sprays used to cool the gas are
totally evaporated. The main disadvantage of this system is
32
-------
-that the carbon monoxide must be burned before entering
system.
Plant Water Use
the
Water is used in these plants for non-contact cooling and
gas scrubbing. The various modes of water consumption at
the plants are:
consumption
non-contact cooling
scrubbers
Open Furnace Operation
liters/metric ton (gal/ton)^
Plant_454 ~"" Plant 455
41,700(10,000)
35,000(8,400)
49,900(12,000)
none
Plant 455 recirculates water through a cooling tower, while
plant 454 uses once through cooling water.
consujryotion
non-contact
cooling
scrubbers
Covered Furnace Operation
plant 451 plant 452
40,000(9,600) 54,600(13,100)
7,500(1,800)
plant 453
80,000 (19,000)
Plants 452 and 453 recirculate water through a cooling
tower, while plant 451 uses cooling water for other
operations in the complex before discharging. Plant 452 is
currently installing a wet scrubber which will have a
planned water consumption of 1300 liters per metric ton (312
gal/ton).
Waste Water Treatment
Plant 455 has no process waste water due to dry collection
methods. Plant 454 totally recycles the venturi scrubber
water through two settling ponds. This system has been in
operation for over two years. Plant 452 has no process
waste water because it is presently cleaning only burned
gases by dry methods. Plant 452 is currently installing a
wet scrubber and is planning to treat the blowdown from the
recycled scrubber water by clarification and neutralization.
Plant 453 has no scrubber waste water, since no gases are
cleaned. Plant 451 is a ferroalloy complex which treats its
33
-------
waste water in a treatment system using chlorinatiori,
clarification, and neutralization.
Plant Effluents
Plants 452, 453, 454, and 455 presently do not discharge
process waste water. They do discharge non-contact coolxng
water and water treatment streams. Plant 454, using total
recycle of the venturi scrubber water, indicated some
discharge of pond water during periods of unusual rain fall.
Plant 452 is planning to discharge the blowdown of its
proposed scrubber along with cooling tower blowdown to a
municipal sewer.
The average combined discharges
complex) are given as follows:
of plant 451 (ferroalloy
waste water
constituents
TSS
TDS
BOD
COD
pH
cyanide
phenols
hardness (total)
chloride
fluoride
sulfate
iron
copper
chromium
manganese
arsenic
mercury
lead
outfall_001
24
255
none
15
8.3
0.065
0.100
139
47
0.70
26
2.331
0.090./
0.030v
0.176
0.010^
0.001^
0.005/"
concentration_lmc[/lL.
outfall 002
25
324
none
18
8.3
0.005
0.050
147
•90
0.52
45
2.565
0.090
0.030
0.166
0.010
0.001
0.005
intake
29
247
none
12
8.3
0.005
0.050
130
36
0.22
22
1.863
0.090
0.030
0.166
0.010
0.001
0.005
These discharges, on a gross basis, are from a combined
series of plant operations and are presently diluted with
cooling water prior to discharge.
34
-------
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
INTRODUCTION
The wastewater constituents of significance for this segment
of the industry are based upon those parameters which have
been identified in the untreated wastes from each category
of this study. The waste water constituents are further
divided into those that have been selected as pollutants of
significance, with the rationale for their selection, and
those that are not deemed significant, with the rationale
for their rejection.
SIGNIFICANCE AND RATIONALE FOR SELECTION OF POLLUTION
PARAMETERS
The basis for selection of the significant pollutant
parameters was:
1) toxicity to humans, animals, fish and aquatic organisms;
2) substances causing dissolved oxygen depletion in streams;
3) soluble constituents that result in undesirable tastes
and odors in water supplies;
4) substances that result in eutrophication and stimulate
undesirable algae growth;
5) substances that produce unsightly conditions in receiving
water; and
6) substances that result in sludge deposits in streams.
Selected as pollutant parameters were:
Cyanide;
Total Suspended Solids; and
pH.
Cyanide-T Total
Cyanides in water derive their toxicity primarily from
undissolved hydrogen cyanide (HCN) rather than from the
cyanide ion (CN~). HCN dissociates in water into H+ and CN~
in a pH-dependent reaction. At a pH of 7 or below, less
than 1 percent of the cyanide is present as CN-; at a pH of
8, 6.7 percent; at a pH of 9, 42 percent; and at a pH of 10,
87 percent of the cyanide is dissociated. The toxicity of
cyanides is also increased by increases in temperature and
reductions in oxygen tensions. A temperature rise of 10°C
produced a two- to threefold increase in the rate of the
lethal action of cyanide.
35
-------
Cyanide has been shown to be poisonous to humans, arid
amounts over 18 ppm can have adverse effects. A single dose
of about 50-60 mg is reported to be fatal.
Trout and other aquatic organisms are extremely sensitive to
cyanide. Amounts as small as .1 part per million can kill
them™ Certain metals, such as nickel, may complex with
cyanide to reduce lethality, especially at higher pH values,
but zinc and cadmium cyanide complexes are exceedingly
toxic.
When fish are poisoned by cyanide, the gills become
considerably brighter in color than those of normal fish>,
owing to the inhibition by cyanide of the oxidase
responsible for oxygen transfer from the blood to the
tissues.
EH
The term pH is a logarithmic expression of the concentration
of hydrogen ions. At a pH of 7, the hydrogen and hydroxyl
ion concentrations are essentially equal and the water is
neutral. Lower pH values indicate acidity while higher
values indicate alkalinity.
Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing
fixtures and can thus add such constituents to drinking
water as iron, copper, zinc, cadmium and lead. The hydrogen
ion concentration can affect the "taste" of the water. At a
low pH water tastes "sour". The bactericidal effect of
chlorine is weakened as the pH increases, and it is
advantageous to keep the pH close to 7. This is very
significant for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress
conditions or kill aquatic life outright. Dead ; fish,
associated algal blooms, and foul stenches are aesthetic
liabilities of any waterway. Even moderate changes from
"acceptable" criteria limits of pH are deleterious to some
species. The relative toxicity to aquatic life of many
materials is increased by changes in the water pH.
Metallocyanide complexes can increase a thousand-fold in
toxicity with a drop of 1.5 pH units. Ammonia is: more
lethal with a higher pH. ;
The lacrimal fluid of the human eye has a pH of
approximately 7.0 and a deviation of 0.1 pH unit from the
norm may result in eye irritation for the swimmer.
Appreciable irritation will cause severe pain. !
36
-------
Solids, Suspended
Suspended solids include both organic and inorganic
materials. The inorganic components include sand, silt, and
clay. The organic fraction includes such materials as
grease, oil, tar, animal and vegetable fats, various fibers,
sawdust, hair, and various materials from sewers. These
solids may settle out rapidly and bottom deposits are often
a mixture of both organic and inorganic solids. They
adversely affect fisheries by covering the bottom of the
stream or lake with a blanket of material that destroys the
fish-food bottom fauna or the spawning ground of fish.
Deposits containing organic materials may deplete bottom
oxygen supplies and produce hydrogen sulfide, carbon
dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional
agencies generally specify that suspended solids in streams
shall not be present in sufficient concentration to be
objectionable or to interfere with normal treatment
processes. Suspended solids in water may interfere with
many industrial processes, and cause foaming in boilers, or
encrustations on equipment exposed to water, especially as
the temperature rises. Suspended solids are undesirable in
water for textile industries; paper and pulp; beverages;
dairy products; laundries; dyeing; photography; cooling
systems, and power plants. Suspended particles also serve
as a transport mechanism for pesticides and other substances
which are readily sorbed into or onto clay particles.
Solids may be suspended in water for a time, and then settle
to the bed of the stream or lake. These settleable solids
discharged with man's wastes may be inert, slowly
biodegradable materials, or rapidly decomposable substances.
While in suspension, they increase the turbidity of the
water, reduce light penetration and impair the
photosynthetic activity of aquatic plants.
Solids in suspension are aesthetically displeasing. When
they settle to form sludge deposits on the stream or lake
bed, they are often much more damaging to the life in water,
and they retain the capacity to displease the senses.
Solids, when transformed to sludge deposits, may do a
variety of damaging things, including blanketing the stream
or lake bed and thereby destroying the living spaces for
those benthic organisms that would otherwise occupy the
habitat. When of an organic and therefore decomposable
nature, solids use a portion or all of the dissolved oxygen
available in the area. Organic materials also serve as a
37
-------
seemingly inexhaustible food source for sludgeworms and
associated organisms.
SIGNIFICANCE AND RATIONALE
REJECTION OF POLLUTION
PARAMETERS ;
A number of pollution parameters besides those selected were
considered, but had to be rejected for one or several of the
following reasons:
1) insufficient data on degradation of water quality;
2) not usually present in quantities sufficient to cause
water quality degradation;
3) treatment does not "practicably" reduce the parameter;
and
H) simultaneous reduction is achieved with another
parameter which is limited.
Acidity/Alkalinity
Acidity and/or alkalinity, reported as calcium carbonate,
are quantitative measurements of the amount of
neutralization to be required in the receiving stream.
There does not appear to be any need for their determination
in effluent wastewaters where the pH is between 6.0 and 9.0.
Calcium2*
Although calcium does exist in some quantity in the
wastewaters, there is no treatment to practicably reduce it.
Phosphates
Phosphates contribute to eutrophication in receiving bodies
of water. However, they were not found in quantities
sufficient to cause water quality degradation.
Potassium* .,
Although potassium does exist in quantity in the
wastewaters, there is no treatment to practicably reduce it.
Silica
Silica may be present in the wastewaters but it is
simultaneously reduced with another parameter which is
limited.
38
-------
SodiunrJ;
Although sodium does exist in quantity in the wastewaters,
there is no treatment to practicably reduce it.
Solids, Dissolved
The total dissolved solids is a gross measure of the amount
of soluble pollutants in the wastewater. It is an important
parameter in drinking water supplies and water used for
irrigation. A total dissolved solids content of less than
500 mg/1 is considered desirable. From the standpoint of
quantity discharged, TDS could have been considered for
selection as a pollutant parameter. However, energy
requirements (especially for evaporation) and solid waste
disposal costs are usually so high as to preclude limiting
dissolved solids at this time.
Temperature
Temperature is a sensitive indicator of unusual thermal
loads where waste heat is involved in the process. Excess
thermal load has not been and is not expected to be a signi-
ficant problem in scrubber wastewater.
39
-------
-------
SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
INTRODUCTION
The majority of water-borne wastes from the calcium carbide
industry are suspended solids, primarily calcium hydroxide,
calcium oxide and coke. The other component of the
industry's water-borne waste load is dissolved solids,
mainly as low valued materials such as calcium chloride, but
containing small quantities of hazardous substances such as
cyanides.
Specific Treatment and Control Practices
Cooling water, either once-through or recycled by means of a
cooling tower, should be relatively free of wastes. Any
contaminants present would come from leaks or recycle
buildups (cooling tower) which are handled as ancillary
water blowdown. in either event, cooling waste
contributions are small and treatment should not normally be
needed.
Process and ancillary water-borne wastes usually require
treatment. The type, degree and costs involved will depend
upon specific circumstances unique for each chemical.
Suspended Solids^Removal
Suspended solids occur as part of the water-borne
load, as a result of air pollution abatement.
waste
Many of the suspended materials are relatively inert. Most
of the suspended solids removed prior to wastewater
discharge eventually wind up as land-disposed solid waste.
Settling Ponds
Settling ponds are the major mechanism used for reducing the
suspended solids content of water waste streams. Their
performance depends primarily on the settling
characteristics of the solids suspended, the flow rate
through the pond and the pond size. Settling ponds can be
used over a wide range of suspended solids levels. Often a
series of ponds is used, with the first ponds collecting the
heavy load of easily settleable material and the following
ones providing final polishing to reach a desired final
suspended solids level. Sludge removal and disposal from
U1
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settling ponds is often a major solid waste problem. Rarely
is there any suspended solids treatment after the'final
settling pond. In most cases, the suspended solids level
from the final pond ranges from 10 to 30 mg/liter, but for
some, the values range up to 100 mg/liter.
Clarifiers and Thickeners
An alternate method of removing suspended solids is through
the use of clarifiers and thickeners. Commercially, these
units are listed as clarifiers or thickeners depending on
whether they are light or heavy duty. Clarifiers arid
thickeners are essentially tanks with internal baffles,
compartments, sweeps and other directing and segregating
mechanisms to provide efficient concentration and removal of
suspended solids in one effluent stream and clarified liquid
in the other. Usually the stream containing most of the
suspended solids is either sent to a second thickening
vessel or sent directly to a centrifuge or filter for
further concentration to sludge or cake solids. Another
alternative is to send the slurry stream to settling ponds.
Filtration
Filtration is the most versatile method for removal of
waterborne suspended solids, being used for applications
ranging from dewatering of sludges to removal of the last
traces of suspended solids to give clear filtrates.
Filtration is accomplished by passing the wastewater stream
through solids —- retaining screens, cloths, or particulates
such as sand, gravel, coal or diatomaceous earth using
gravity, pressure or vacuum as the driving force. ;
Filtration equipment is of various designs, including plate-
and-frame, cartridge and candle, leaf, vacuum rotary, and
sand or mixed media beds. All of these types are currently
used in the treatment, of water-borne wastes in the inorganic
chemical industry.
Centrifuqing
When the force of gravity is not sufficient to separate
solids and liquids to the desired degree or in the desired
time, centrifugal force can be utilized. Although there are
many types of centrifuges, most industrial units can be
broken down into major categories — solid bowl; and
perforated bowl. The solid bowl centrifuge consists of a
rapidly rotating bowl into which the waste stream is
introduced. Centrifugal action of the spinning bowl
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separates the solids from the liquid phase and the two are
removed separately. The perforated bowl centrifuge has
holes in the bowl through which the liquid escapes by
centrifugal force. The solids are retained inside the bowl
and removed either continuously or in batch fashion.
Centrifuges are not widely used for ferroalloys or inorganic
chemical waste streams when compared to settling ponds,
thickeners, or filters.
Suspended solids may settle slowly or not at all due to
their small particle size and electrical charges. Addition
of a flocculant or coagulant neutralizes these charges,
promotes coagulation of particles and gives faster settling
rates and improved separation,
Coagulants, such as alum, ferric chloride and polymeric
electrolytes, also aid in the settling of other suspended
solids that may be present.
Dissolved Materials Treatment
Treatment for dissolved materials consists of either
modifying or removing the undesired materials. Modification
techniques include chemical treatment such as neutralization
and oxidation-reduction reactions. Cyanides are examples of
dissolved materials modified in this way. Removal of
dissolved solids is accomplished by methods such as chemical
precipitation, ion exchange, carbon adsorption, reverse
osmosis and evaporation.
Chemica 1 Tre atment
Chemical treatments for abatement of water-borne wastes are
widespread. Included in this overall category are such
important subdivisions as neutralization, pH control, oxida-
tion-reduction reactions, coagulation, and precipitation.
Neutralization
Water-borne wastes may be either acidic or alkaline. Before
disposal to surface water or other medium, this acidity or
alkalinity needs to be controlled. The most common method
is to treat acidic streams with alkaline materials such as
limestone, lime, soda ash, or sodium hydroxide. Alkaline
streams are treated with acids such as sulfuric. .Whenever
possible, advantage is taken of the availability of acidic
waste streams to neutralize basic waste streams and vice
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versa. Neutralization often produces suspended solids which
must be removed prior to waste water disposal.
Oxidation
Cyanides
The two most common methods of treating cyanides are: (1)
single or two-staged alkaline chlorination and (2)
hypochlorite oxidation.
Alkaline Chlorination
Stage 1 (fast)
11.5 pH
NaCN + C12 + 2NaOH = NaCNO + 2NaCl + H2O
Stage 2 (slow)
7.5 to 9.0 pH
2NaCNO + 3C12 + 4NaOH = N2 + 2CO2 + 6NaCl + 2H2.O
The stage 1 cyanates are stable and less toxic than
cyanides. Stage 2 completes the destruction to nitrogen and
carbon dioxide, but considerably more chlorine and caustic
are required for the overall 2-stage process than for the
single-stage oxidation to cyanate. The reaction is also
slower.
Hypochlorite Oxidation
2NaCN + Ca(OCl)2 = 2NaCNO + CaCl2
2NaCN + 2NaOCl = 2NaCNO + 2NaCl
Either calcium or sodium hypochlorite can be used depending
on economics and availability. For small plants or small
cyanide wastewater loads, the recently developed electrical
hypochlorite generators may be useful.
Both alkaline chlorination and hypochlorite treatments nor-
mally reduce oxidizable cyanide to essentially zero
concentration. ;
Ozone has also been used for oxidation of cyanides. Other
methods include boiling and peroxide decomposition. ;
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Complex cyanides are more resistant to oxidation or removal
than simple cyanides. Soluble complex cyanides may often be
removed by chemical precipitation with iron salts (such as
ferrous sulfate) or other heavy metal ions (zinc or
cadmium).
Evaporation
The industrial use of evaporation in treating wastewater has
been minimal. As the cost of pure water has increased in
portions of the United States and the world, however, it has
become increasingly attractive to follow this approach.
Almost always, the treatment of waste water streams by
evaporation has utilized the principle of multi-effects to
reduce the amount of steam or energy required. Thus, the
theoretical limitation of carrying out the separation of a
solute from its solvent is the minimum amount of work
necessary to effect the particular change, that is, the free
energy change involved. A process can be made to operate
with a real energy consumption not greatly exceeding this
value. The greater the concentration of soluble salts, the
greater is the free energy change for separation, but, even
for concentrated solutions, the value is much lower than the
550 kg-cal per kilogram value to evaporate water. Multi-
effect evaporators use the heat content of the evaporated
vapor stream from each preceding stage to efficiently (at
low temperature difference) evaporate more vapor at the
succeeding stages. Thus, the work available is used in a
nearly reversible manner, and a low energy requirement
results. However, a large capital investment in heat
transfer surface and pumps is required.
prying
After evaporative techniques have concentrated the dissolved
solids to high levels, the residual water content must still
be removed for either recovery, sale or disposal. Water
content will range from virtually zero up to 90 percent by
weight. Gas or oil fired dryers, steam heated drum dryers
or other final moisture-removing equipment can be used for
this purpose. Since this drying operation is a common one
in the production of inorganic chemicals, technology is well
known and developed. Costs are mainly those for fuel or
steam.
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Containment ;
Rainwater Runoff :
Rainwater runoff of suspended or dissolved wastes is of
concern for a number of plants. Ore piles, ore residues,
and solid wastes as well as airborne wastes which settle as
dusts and mists on buildings and grounds are contributors.
Pond Containment
Unlined ponds are the most common treatment facility used by
the ferroalloys and inorganic chemicals industries. Pond.s
are often used in closed loop or zero discharge systems. In
dry climates the ponds may serve as disposal basins.
Containment failures of ponds occur because they are
unlined, or they are improperly constructed for containment
in times of heavy rainfall. ;
Unlined ponds may give good effluent control, if dug in
impervious clay areas, or poor control, if in porous, sandy
soil. The porous ponds will allow effluent to diffuse into
the surrounding earth and water streams. Plastic pond
linings are being increasingly used to avoid this problem.
In times of heavy rainfall, many ponds overflow and much of
the pond content is released into either the surrounding
countryside or, more likely, into the nearest body of water.
Good effluent control may be gained by a number of methods,
including:
1) Pond and diking designed to take any anticipated rainfall
— smaller and deeper ponds used where rainfall is heavy.
2) Construct ponds so that drainage from the surrounding
area does not inundate the pond and overwhelm it.
3) Substitution of smaller volume (and covered) treatment
tanks, coagulators or clarifiers to reduce rainfall influx
and leakage problems.
Disposal Practices
Disposal of the water-borne wastes from manufacturing
represents the final control exercised by the waste
producer. A number of options are available, some at zero
or low cost, others at high cost.
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Low-cost options include discharge to surface water —•
river, lake, bay or ocean — and where applicable, land
disposal by running effluent out on land and letting it soak
in or evaporate.
At somewhat higher costs, wastes may be disposed of into the
municipal sanitary system or an industrial waste treatment
plant. Treatment and reuse of the waste stream can also be
practiced. In dry climates unlined evaporation ponds, if
allowed, would involve moderate costs.
High-cost disposal systems include lined evaporation ponds,
deep well disposal, and ocean barging. Such methods are
used for wastes which cannot be disposed of otherwise.
These wastes contain strong acids or alkalies, harmful
substances, and/or high dissolved solids content.
Unlined^Eyaporation Ponds
Two requirements must be met for an unlined evaporation pond
to be successfully utilized. First it must be located in an
area in which unlined ponds are allowed, and secondly, the
rainfall in that area must not exceed the evaporation rate.
This second requirement eliminates most of the heavily
industrialized areas. For the low rainfall areas,
evaporation ponds are feasible with definite restrictions.
Ponds must be large in area for surface exposure. The
volume of water evaporation per year can be determined by
the following formula:
Volume = 0.00274 x D x area
Where D = difference between meters of water
evaporated per year and meters of rainfall
per year.
Evaporation of large amounts of waste water requires large
ponds. The availability and costs of sufficient land place
another possible restriction on this approach.
|jiQ.eci_EvapQration Ponds
The lined evaporation ponds now required in some sections of
the country have the same characteristics as developed for
the unlined ponds — large acreage requirements and a
favorable evaporation rate to rainfall balance. They are
significantly higher in cost than an unlined pond.
Reduction of the evaporation load prior to its ponding is a
significant advantage. For this reason, plus the short
supply and high cost of water in much of the southwestern
47
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United States, distillation and membrane processes, are
beginning to be used — either alone or in conjunction with
evaporation ponds — in these regions.
Municipal Sewers
Although the water-borne wastes from some plants were
treated on-site, the study revealed one plant that plans to
dispose of their wastes to a municipal sewer system.
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SECTION VIII
COST, ENERGY AND NON-WATER QUALITY ASPECTS
COST AND REDUCTION BENEFITS OF
TREATMENT AND CONTROL TECHNOLOGIES
INTRODUCTION
In general, plant size and age have only a nominal effect in
influencing the waste effluents and the costs for their
treatment and disposal. Although large plants and complexes
have lower treatment costs per unit of product when the same
methods are used, the small plants can often use municipal
sewers, land seepage, commercial disposal and other methods
not available or economic to the larger producers. Plant
age indirectly influences treatment and disposal costs
through the effects of isolation and control of wastes and
space limitations and cost. If treatment and disposal space
is available and waste streams are isolable then age usually
makes little difference.
Removal of dissolved solids may be expensive. The disposal
of soluble solids once they have been removed from the
wastewater is another problem. New plants have more options
in solving these problems economically than do existing
plants. New source facilities with heavy dissolved solids
effluents and/or heavy solid waste loads may avoid costly
wastewater treatment by geographical location. A favorable
balance of climatic evaporation to rainfall eases these
problems. Land storage or landfill space should be
available for solids disposal.
New plants being built can avoid major future waste
abatement costs by inclusion of: (1) piping, trenches,
sewers, sumps, and other isolation facilities to keep leaks,
spills and process water separate from cooling and sanitary
water, (2) efficient reuse, recycling and recovery of all
possible raw materials and by-products, (3) closed cycle
water utilization whenever possible. Closed cycle operation
eliminates all water-borne wastes to surface water.
COST DATA
Cost information contained in this report was obtained
directly from industry, from engineering firms, equipment
suppliers, government sources, and available literature.
Whenever possible, costs are based on actual industrial
installations or engineering estimates for projected
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facilities as supplied by contributing companies. In the
absence of such information, cost estimates have been
developed from either plant-supplied costs for similar waste
treatment installations or general cost estimates for treat-
ment technology. Costs were calculated for every'plant
surveyed. In the treatment cost table the values of
invested capital and annual costs given are the maximum for
the industry category, and are incremental costs. Thus, the
maximum investment for a plant to attain Level C would be a
total of $14.09 per metric ton. Land costs are not included
due to the variability with location.
Costs have been uniformly calculated based on 10 percent
straight line depreciation. There is an additional amount
of interest at 6 percent of the depreciated value per year
(pollution-abatement tax-free money). These plus the costs
of insurance and taxes yield a total overall annualized
fixed cost of 15 percent per year. ;
All costs have been adjusted to 1971 values and are quoted
as such unless otherwise noted.
Definition of Levels of Treatment and Control
""* Cost Development
Costs are developed for several levels of applied
technology:
Minimum {or Basic) Level - practices followed by all of the
involved.plants. Usually money for this treatment level has
already been spent (in the case of capital investment) or is
being spent (in the case of operating and overall costs).
1 and C Levels - Successively greater degrees of treatment
with respect to critical pollutant parameters.
Treatment and Disposal Rationales Applied to
Cost Developments
The following treatment rationales are employed in the cost
development:
1) All non-contact cooling water is exempted from treatment
(and treatment costs) provided that no harmful pollutants
are introduced.
2) Water treatment, cooling tower and boiler blowdown dis-
charges are not treated provided they contain no harmful
pollutants.
50
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3) Disposal considerations are covered in cost development,
including evaporation ponds, land spoilage and solid wastes
handling.
Wastewater Treatment and Control Costs
Category I Covered Furnaces with Wet Air Pollution Control
Devices
The wastes from the production of calcium carbide in covered
furnaces are primarily furnace dusts and carbon monoxide
gas. In order to recover the carbon monoxide for fuel
value, several plants are now using or are planning to
install wet scrubbers. One plant currently operates an
evaporative cooler and dry bag collector, but also flares
some of the furnace gases. This plant will incur additional
costs for the installation of piping and clarification
equipment to treat the blowdown from a new wet scrubber
installation. This plant will also incur costs for
discharge to a municipal treatment system. This plant is
going to wet scrubbing to eliminate an air pollution problem
and recover furnace gas fuel value. A second plant operates
disintegrator scrubbers with once through water usage and
treats the scrubber waste in a total plant treatment system.
A cost summary for this category is given in Table 2. Level
A costs are estimated to be $0.18 per metric ton of calcium
carbide for investment. $0.07 has already been spent by one
plant and $0.03 per metric ton is projected to be spent in
1974 by another plant. Annual costs are estimated to be
$0.06 per metric ton. Capital and operating costs for plant
451 were estimated on a prorated basis for the total complex
treatment system apportioned to the percentage of calcium
carbide furnaces in the complex. Level B costs for
additional treatment of scrubber wastewater by polish
filtration are estimated to be $0.88 per metric ton for
investment and $0.26 per metric ton for annual costs. With
a selling price of $110 per metric ton, the maximum
investment cost is 0.8 percent of the selling price while
the annual cost is 0.2 percent. Level C costs for recycle
of the scrubber wastewaters are estimated to be $13.03 per
metric ton for investment and $3.90 per metric ton for
annual costs.
Category II Other Furnaces
The wastes from the production of calcium carbide in open
furnaces are primarily furnace dusts. One plant in the
category collects all dusts in a dry bag-filter system and,
therefore, has no process water effluent. A second plant in
51
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this category operates a venturi scrubber to treat the
furnace dusts. The water from the scrubber is sent to two
settling ponds and totally recycled to the scrubber. A
third plant currently flares all gases from covered
furnaces, but is installing an evaporative cooler and dry
bag collector. This category has 100 percent of the plants
presently operating at zero discharge of pollutants in
process waste water, and therefore, there is no additional
cost to meet a no discharge limitation for the entire
category.
Solid Waste
For those waste materials considered to be non-hazardous
where land disposal is the choice for disposal, practices
similar to proper sanitary landfill technology may be
followed. The principles set forth in the EPA's Land
Disposal of Solid Wastes Guidelines (CFR Title 40, Chapter
1; Part 241) may be used as guidance for acceptable land
disposal techniques.
For those waste materials considered to be hazardous,
disposal will require special precautions. In order to
ensure long-term protection of public health and the
environment, special preparation and pretreatment may be
required prior to disposal. If land disposal is to be
practiced, these sites must not allow movement of pollutants
such as fluoride and radium-226 to either ground or surface
water. Sites should be selected that have natural soil and
geological conditions to prevent such contamination or, if
such conditions do not exist, artificial means (e.g.,
liners) must be provided to ensure long-term protection of
the environment from hazardous materials. Where
appropriate, the location of solid hazardous materials
disposal sites should be permanently recorded in the
appropriate office of the legal jurisdiction in which the
site is located.
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TABLE 2
WATER EFFLUENT TREATMENT COSTS
FERROALLOY INDUSTRY
CALCIUM CARBIDE
Covered Furnaces with Wet Air Pollution Control Devices
Treatment or Control Technologies:
Investment ($/annual metric ton)
Annual Costs: ($/metric ton)
Capital
Depreciation-
Operation & Maintenance
Energy & Power
TOTAL
0.18
0.88
13.03*
0.01
0.02
0.02
0.01
0.06
0.05
0.09
0.09
0.03
0.26
0.65
1.30
1.30
0.65
3.90*
Effluent Quality
kg/kkg (lb/1000 Ib)
Parameters
Suspended Solids
Cyanide
pH
0.03-0.19
0.0028
8.3-9.0
0.11 max
0.0028
8.3-9.0
0.020 max
0.0005
8.3-9.0
Level Descriptions:
•/
Level A—Treatment of wet scrubbing effluent by chlorination, clarification
and neutralization.
Level B—Same as Level A plus polish filtration.
Level C—Recycle of scrubber water.
*Costs include replacement of scrubbers where necessary for recycle.
53
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SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE
APPLICATION OF THE BEST PRACTICABLE CONTROL
TECHNOLOGY CURRENTLY AVAILABLE
The effluen-t limitations which must be achieved by July 1,
1977, are based on the degree of effluent reduction attain-
able through the application of the best practicable control
technology currently available. For the calcium carbide
industry, this level of technology was based on the average
of the best existing performance by plants of various sizes
and ages, within each of the industry categories. Each
category will be treated separately for the recommendation
of effluent limitations guidelines and standards of
performance.
Best practicable control technology currently available
emphasizes treatment facilities at the end of a
manufacturing process but also includes the control
technology within the process itself when it is considered
to be normal practice within an industry. Examples of waste
management techniques which are considered normal practice
are:
a) manufacturing process controls;
b) recycle and alternative uses of water; and
c) recovery and/or reuse of wastewater constituents.
Consideration was also given to:
a) The total cost of application of technology in relation
to the effluent reduction benefits to be achieved from such
applications;
b) The size and age of equipment and facilities involved;
c) The process employed;
d) The engineering aspects of the application of various
types of control techniques;
e)
Process changes; and
f) Non-water quality environmental
energy requirements).
impact (including
55
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The following is a discussion of the best practicable
control technology currently available for each of the
categories, and the proposed limitations on the pollutants
in their effluents.
General Water Guidelines
Process water is defined as any water contacting the
reactants, intermediate products, by-products or products of
a process including contact cooling water. All values of
the guidelines and limitations presented below for total
suspended solids (TSS) and harmful pollutants are expressed
as a maximum 30 day average in units of kilograms of
pollutant per metric ton (pounds of pollutant per thousand
pounds) of product. The daily maximum limitation is double
the 30 day average, except for pH. All process water
effluents are limited to the pH range of 6.0 to 9.0 unless
otherwise specified.
Based on the application of best practicable technology cur-
rently available, the recommendations for the discharge of
cooling water are as follows.
An allowed discharge of all non-contact cooling waters
provided that the following conditions are met:
a) Thermal pollution be in accordance with standards to be
set by EPA policies.
b) All non-contact cooling waters should be monitored to
detect leaks from the process. Provisions should be made
for treatment to the standards established for process waste
water discharges prior to release.
c) No untreated process waters be added to the cooling
waters prior to discharge.
The above non-contact cooling water recommendations should
be considered as interim, since this type of water plus
blowdown from water treatment, boilers and cooling towers
will be regulated by. EPA at a later date as a separate
category.
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PROCESS WASTE WATER GUIDELINES AND LIMITATIONS
Category I - Covered Calcium Carbide Furnaces With Wet Air
Pollution Control Devices
Based upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent reduction attainable through the application of the
best practicable control technology currently available is:
Effluent Characteristic
TSS
cyanide (total)
pH
Effluent Limitation
kg/kkg qb/1000 Ib)
0.190
0.0028
6.0-9.0
an average process
metric ton (1800
The above limitations were based on
wastewater discharge of 7,500 liters per
gallons per ton).
Identification_gf BPCTCA
"""" i
Best practicable control technology currently available for
the manufacture of calcium carbide in covered furnaces with
scrubbers is treatment of all scrubber wastes by chlorine
oxidation to reduce total cyanide followed by clarification
to reduce suspended solids and neutralization to pH 6 to 9.
To implement this technology at plants not already using the
recommended control techniques would require the
installation of chlorine treatment systems, clarifiers or
settling ponds, and acid neutralization plus the necessary
piping and pumps.
wastewater is
Reason^for Selection
The only plant presently discharging process
using this technology.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, the category as a whole would have to invest an
estimated maximum of $10,000 to achieve limitations pre-
scribed herein. There is also an anticipated increase in
the operating cost equivalent to approximately 0.02 percent
of the 1971 selling price of this product.
57
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It is concluded that the benefits of the reduction of the
discharge of pollutants by the selected control technology
outweigh the costs. All of this industry category is
presently achieving this level of pollutant discharge,
Age and Size of Equipment and Facilities
The best control technology currently available is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors. Also, the similarities in the process used and
wastewater characteristics in this production category
substantiate the practicality of these technologies.
Process Employed
The process used by the plants in this category are very
similar in nature and their raw wastes are also quite
similar. These similarities will enhance the application of
the recommended treatment technologies.
Engineering^Aspects
From an engineering standpoint, the implementation of the
recommended best control technologies currently available is
practicable in this production category because it is
presently used in plants discharging process waste water.
Process Changes
The recommended control technologies would require no major
changes in the manufacturing process. These control tech-
nologies are presently being used by plants in this pro-
duction category.
Non-Water Quality Environmental Impact
The single major impact on non-water quality factors of the
environment is the potential effect of land disposal of the
solids removed from the process wastewaters. These solids
may sometimes contain harmful constituents which could be
detrimental to the soil system in the area of disposal or
possibly contaminate ground waters due to rainwater run-off
and percolation through the soil. There appear to be no
major energy requirements for the implementation of the
recommended treatment technologies.
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II - Other Calcium Carbide Furnacgs
Basad upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent reduction attainable through the application of the
best practicable control technology currently available is
no discharge of pollutants in process wastewater.
Pollutants for this category are defined as: total
suspended solids and pH above 9.0,
Identification of BPCTCA
Best practicable control technology currently available is
to settle scrubber wastes in ponds and recycle to scrubber
for those plants using wet scrubbing. Those plants using
dry or no dust collection have no process waste water
discharge.
Reason for Selection
One hundred percent (100%) of
presently achieving this level.
Total Cost of Application
the industry category is
Based upon the information contained in Section VIII of this
report, the category as a whole would not have any addi-
tional investment to achieve the limitations prescribed
herein. There is also no anticipated increase in the
operating cost.
It is concluded that the benefits of the total elimination
of the discharge pollutants by the selected control
technology outweigh the costs. All of this industry
category is presently achieving this level of pollutant
discharge.
The best control technology currently available is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors.
Engineerinq_Aspects
From an engineering standpoint, the implementation of the
recommended best control technologies currently available is
practicable in this category because it is currently in use.
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Process Changes
The recommended control technologies would not require
changes in the manufacturing process. These control
technologies are presently being used by plants in this
category.
Non-Water Quality Environmental Impact
The single major impact of non-water quality factors on the
environment is the potential effect of land disposal of the
solids removed from the process wastewaters. These solids
may sometimes contain harmful constituents which could be
detrimental to the soil system in the area of disposal or
possibly contaminate ground waters due to rainwater run-off
and percolation through the soil. There appear to be no
major energy requirements for the implementation of the
recommended treatment technologies.
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH
THE APPLICATION OF THE BEST AVAILABLE
TECHNOLOGY ECONOMICALLY ACHIEVABLE
The effluent limitations which must be achieved by July 1,
1983 are based on the degree of effluent reduction attain-
able through the application of the best available
technology economically achievable. For the calcium carbide
industry, this level of technology was based on the best
control and treatment technology readily transferable from
one industry process to another.
The following factors were taken into consideration in
determining the best available technology economically
achievable:
a) the age of equipment and facilities involved;
b) the process employed;
c) the engineering aspects of the application of various
types of control techniques;
d)
process changes;
e) cost of achieving the effluent reduction resulting from
application of BATEA; and
f) non-water quality environmental impact (including
energy requirements).
In contrast to the best practicable control technology
currently available, best available technology economically
achievable assesses the availability in all cases of in-
process controls as well as control or additional treatment
techniques employed at the end of a production process. In-
process control options available which were considered in
establishing these control and treatment technologies
include the following:
a) alternative water uses
b) water conservation
c) waste stream segregation
d) water reuse
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e) cascading water uses
f) by-product recovery
g) reuse of wastewater constituents
h) waste treatment
i) good housekeeping
j) preventive maintenance
k) quality control (raw material, product, effluent)
1) monitoring and alarm systems.
Although economic factors are considered in this
development, the costs for this level of control are
intended to be for the top-of-the-line of current technology
subject to limitations imposed by economic and engineering
feasibility. However, this technology may necessitate some
industrially sponsored development work prior to its
application.
Based upon the information contained in Sections III through
IX of this report, the following determinations were made on
the degree of effluent reduction attainable with the
application of the best available control technology
economically achievable in the various categories of this
industry.
GENERAL WATER GUIDELINES
Process water is defined as any water contacting the react-
antSy intermediate products, by-products or products of a
process including contact cooling water. All values of
guidelines and limitations presented below are for total
suspended solids (TSS) and harmful pollutants are expressed
as a maximum 30 day average in units of kilograms of
pollutant per metric ton (pounds of pollutant per thousand
pounds) of product. The daily maximum limitation is double
the 30 day average, except for pH. All process water
effluents are limited to the pH range of 6.0 to 9.0 unless
otherwise specified.
Based on the application of best available
economically achievable, the recommendations
discharge of such cooling water are as follows.
technology
for the
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An allowed discharge of all non^contact cooling waters pro-
vided that the following conditions are met:
a) Thermal pollution be in accordance with standards to be
set by EPA .policies.
b) All non-contact cooling waters should be monitored to
detect leaks from the process. Provisions should be made
for treatment to the standards established for the process
wastewater discharges prior to release.
c) No untreated process waters be added to the cooling
waters prior to discharge.
The above non-contact cooling water recommendations should
be considered as interim, since this type of water plus
blowdowns from water treatment, boilers and cooling towers
will be regulated by EPA at a later date as a separate
category.
PROCESS WASTE WATER GUIDELINES AND LIMITATIONS
The other calcium carbide furnaces category was required to
achieve no discharge of process wastewater pollutants to
navigable waters based on best practicable control
technology currently available. The same limitations are
required based on best available technology economically
achievable.
Category I - Covered Calcium Carbide Furnaces with
Pollution Control Devices '
Wet Air
Based upon the information contained in Sections III through
VIII, a determination has been made that the degree of
effluent reduction attainable through the application of the
best available control technology economically achievable
is:
Effluent Characteristic
TSS
Cyanide (Total)
pH
Effluent Limitation
jcg/kkg (lb/1000 lb)
0.11
0.0028
6.0 to 9.0
The above limitations were based on an average process
wastewater discharge of 7,500 liters per metric ton (1,800
gallons per ton).
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Identification of BATEA
Best available control technology economically achievable
for the manufacture of calcium carbide by the covered
furnace process is the treatment of wet scrubbing effluent
by chlorination, clarification, neutralization, and polish
filtration where scrubbing is used.
To implement this technology at plants not already using the
recommended control techniques would require the addition of
chlorination equipment, clarifier-thickeners, neutralization
facilities, sand filters, and the necessary piping and
pumps.
Reason for Selection
Most of the recommended technology is presently being used
in the plants within the category. The polish filtration
technology is presently being used in the inorganic chemical
and ferroalloys industries for treating waste water and the
technology is transferable.
Total Cost of Application
Based upon the information contained in Section VIII of this
report, the category as a whole would have to invest up to
an estimated maximum of $168,000 to achieve limitations
prescribed herein. There is also an anticipated increase in
the operating cost equivalent to approximately 0.2 percent
of the selling price of this product. ;
It is concluded that the benefits of the elimination/re-
duction of the discharge pollutants by the selected control
technology outweigh the costs.
Age and Size of Equipment and Facilities
The best available technology economically achievable is
practicable regardless of the size or age of plants since
the use of existing technologies is not dependent on these
factors. Also, the similarities in processes used and
wastewater characteristics in this production category
substantiate the practicality of these technologies.
Process Employed
The processes used by the plants in this category are very
similar in nature and their raw wastes are also quite
similar. These similarities will enhance the application of
the recommended treatment technologies.
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Engineering Aspects
From an engineering standpoint, the implementation of the
recommended best available technology economically
achievable is practicable in this category because all of
the technology is in use in one plant of the category with
the exception of polish filtration. This technology is
readily available and transferable to "treatment of calcium
carbide scrubber wastes.
Process Changes
The recommended control technologies would not require major
changes in the manufacturing process. These control
technologies are presently being used by plants in both the
ferroalloys and chemicals industries,
Non-Water Quality Environmental^Impact
The single major impact on non-water quality factors of the
environment is the potential effect of land disposal of the
solids removed from the process wastewaters. These solids
may sometimes contain harmful constituents which could be
detrimental to the soil system in the area of disposal or
possibly contaminate ground waters due to rainwater run-off
and percolation through the soil. There appear to be no
major energy requirements for the implementation of the
recommended treatment technologies.
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SECTION XT
NEW SOURCE PERFORMANCE STANDARDS
AND PRETREATMENT STANDARDS
This level of technology is to be achieved by new sources.
The term "new source" is defined in the Act to mean "any
source, the construction of which is commenced after the
publication of proposed regulations prescribing a standard
of performance". This technology is evaluated by adding to
the consideration underlying the identification of best
available technology economically achievable, a determina-
tion of what higher levels of pollution control are
available through the use.of improved production processes
and/or treatment techniques. Alternative processes,
operating methods or other alternatives were considered.
The end result of the analysis identifies effluent standards
which reflect levels of control achievable through the use
of improved production processes (as well as control
technology).
The following factors were considered with respect to
production processes which were analyzed in assessing the
best demonstrated control technology currently available for
new sources:
a) the type of process employed and process changes;
b) operating methods;
c) use of alternative raw materials and mixes of raw
materials;
d) use of dry rather than wet processes; and
e) recovery of pollutants as by—products.
In addition to the effluent limitations covering discharges
directly into waterways, the constituents of the effluent
discharge from a plant within the industrial category which
would interfere with, pass through, or otherwise be
incompatible with a well designed and operated publicly
owned activated sludge or trickling filter wastewater
treatment plant were identified.
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EFFLUENT REDUCTION ATTAINABLE BY THE APPLICATION OF THE
BEST AVAILABLE DEMONSTRATED CONTROL TECHNOLOGIES,
PROCESSES, QPElATiNG METHODS OR OTHER ALTERNATIVES
Based upon the information contained in Sections III through
X of this report, the following determinations were made on
the degree of effluent reduction attainable with the
application of new source standards.
The other calcium carbide furnaces category was required to
achieve no discharge of process wastewater pollutants to
navigable waters based on best practicable control
technology currently available. The same limitations are
required for new source performance standards.
Category 1^ - Covered CaJLcium Carbide Furnaces With Wet Air
Pollution Control Devices '
The only process water pollution involved in the manufacture
of calcium carbide is that contributed by wet air pollution
devices. For those covered furnaces operating with
withdrawal and cleaning of unburned gas, the use of a
baghouse collector is not considered practicable technology.
However, these furnaces can operate with scrubbers and
recycle the scrubber effluent. This technology is currently
being practiced by one plant in the industry and another
plant plans to install this treatment technology. Therefore
the recommendations for new source performance standards are
as follows:
Effluent Characteristic
TSS
Cyanide (Total)
pH
Effluent Limitation
kq/kkg (lb/1000 Ib)
0.020
0.0005
6.0 to 9.0
The above limitations were based on an average process
wastewater blowdown for discharge of 1350 liters per metric
ton (325 gallons per ton) .
Identification of BADCTCA
Best available demonstrated control technology currently
available for the manufacture of calcium carbide in covered
furnaces with scrubbers is the treatment of wet scrubbing
effluent by chlorination, clarification, neutralization,
polish filtration and partial recirculation.
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Reason fpreselection
Most of the recommended technology is presently being used
in plants within the ferroalloys industry. The polish
filtration technology is presently being used in the
inorganic chemical industry for treating waste water and the
technology is transferable.
Age and Size of Equipment and Facilities
The best available demonstrated control technology currently
available is practicable regardless of the size or age of
plants since the use of existing technologies is not
dependent on these factors. Also, the similarities in
processes used and wastewater characteristics in this
production category substantiate the practicality of these
technologies.
Process Employed
The processes used by the plants in this category are very
similar in nature and their raw wastes are also quite
similar. These similarities will enhance the application of
the recommended treatment technologies.
Engineering Aspects
From an engineering standpoint, the implementation of the
recommended best available demonstrated control technology
currently available is practicable in this category because
all of the technology is in use in the industry with the
exception of polish filtration. This technology is readily
available and transferable to treatment of calcium carbide
scrubber wastes.
Process Changes
The recommended control technologies would not require major
changes in the manufacturing process. These control
technologies are presently being used by plants in both the
ferroalloys and chemicals industries.
Non-Water Quality Environmental Impact
The single major impact on non-water quality factors of the
environment is the potential effect of land disposal of the
solids removed from the process wastewaters. These solids
may sometimes contain harmful constituents which could be
detrimental to the soil system in the area of disposal or
possibly contaminate ground waters due to rainwater run-off
69
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and percolation through the soil. There appear to be no
major energy requirements for the implementation of the
recommended treatment technologies.
PRETREATMENT STANDARDS FOR NEW SOURCES
Recommended pretreatment guidelines for discharge of |plant
wastewater into public treatment works conform in general
with EPA Pretreatment Standards for Municipal Sewer Works as
published in the July 19, 1973 Federal Register and "Title
40 - Protection of the Environment, Chapter I
Environmental Protection Agency, Subchapter D - Water
Programs, Part 128 - Pretreatment Standards", a subsequent
EPA publication. The following definitions conform to these
publications:
a) Compatible Pollutant '•
The term "compatible pollutant" means biochemical oxygen
demand, suspended solids, pH and fecal coliform bacteria,
plus additional pollutants identified in the NPDES permit if
the publicly owned treatment works was designed to treat
such pollutants, and, in fact, does remove such pollutants
to a substantial degree. Examples of such additional
pollutants may include:
chemical oxygen demand
total organic carbon
phosphate and phosphorus compounds
nitrogen and nitrogen compounds
fats, oils, and greases of animal or vegetable origin
except as defined below under Prohibited Wastes.
b) Incompatible Pollutant
The term "incompatible pollutant" means any pollutant which
is not a compatible pollutant as defined above,
cj Joint Treatment Works
Publicly owned treatment works for both non-industrial arid
industrial wastewater.
d) Major Contributing Industry
A major contributing industry is an industrial user of the
publicly owned treatment works that: has a flow of 50,000
gallons or more per average work day; has a flow greater
than five percent of the flow carried by the municipcil
system receiving the waste; has in its waste, a toxic
70
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pollutant in toxic amounts as defined in standards issued
under Section 307(a) of the Act; or is found by the permit
issuance authority, in connection with the issuance of an
NPDES permit to the publicly owned treatment works receiving
the waste, to have significant impact, either singly or in
combination with other contributing industries, on that
treatment works or upon the quality of effluent from that
treatment works.
e] Pretreatment
Treatment of wastewaters from sources before introduction
into the joint treatment works.
PROHIBITED WASTES
No waste introduced into a publicly owned treatment works
shall interfere with the operation or performance of the
works. Specifically, the following wastes shall not be
introduced into the publicly owned treatment works:
a) Wastes which create a fire or explosion hazard
publicly owned treatment works;
in the
b) wastes which will cause corrosive structural damage to
treatment works, but in no case wastes with a pH lower than
5.0, unless the works are designed to accommodate such
wastes;
c) Solid or viscous wastes in amounts which would cause
obstruction to the flow in sewers, or other interference
with the proper operation of the publicly owned treatment
work s, and
d) Wastes at a flow rate and/or pollutant discharge rate
which is excessive over relatively short time periods so
that there is a treatment process upset and subsequent loss
of treatment efficiency.
PRETREATMENT FQRmrINCOMPATIBLE POLLUTANTS
In addition to the above, the pretreatment standard for in-
compatible pollutants introduced into a publicly owned
treatment works by a major contributing industry shall be
best practicable control technology currently available;
provided that, if the publicly owned treatment works which
receives the pollutants is committed, in its NPDES permit,
to remove a specified percentage of any incompatible
pollutant, the pretreatment standard applicable to users of
such treatment works shall be correspondingly reduced for
71
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that pollutant; and provided further that the definition of
best practicable control technology currently available for
industry categories may be segmented for application to
pretreatment if the Administrator determines that the
definition for direct discharge to navigable waters is not
appropriate for industrial users of joint treatment works.
RECOMMENDED PRETREATMENT GUIDELINES
In accordance with the preceding Pretreatment Standards for
Municipal Sewer Works, the following are recommended for
Pretreatment Guidelines for the wastewater effluents:
a) No pretreatment required for removal of compatible
pollutants - biochemical oxygen demand, suspended solids
(unless hazardous), pH and fecal coliform bacteria;
b) Suspended solids containing hazardous pollutants (such
as heavy metals, cyanides and chromates) should be
restricted;
c) Pollutants such as chemical oxygen demand, total
organic carbon, phosphorus and phosphorus compounds,
nitrogen and nitrogen compounds and fats, oils and greases
need not be removed provided the publicly owned treatment
works was designed to treat such pollutants and will accept
them. Otherwise levels should be at or below BPCTCA
Guideline levels;
d) Dissolved solids such as sodium chloride, sodium
sulfate, calcium chloride and calcium sulfate should be
permitted provided that the industrial plant is not a "major
contributing industry".
e) Plants covered under the "major contributing industry"
definition should not be permitted to discharge large
quantities of dissolved solids into a public sewer. Each of
these cases would have to be considered individually by the
sewer authorities, and,
f) Discharge of all other incompatible hazardous or toxic
pollutants from the chemical plants of this study to
municipal sewers should conform to BPCTCA guidelines for
discharge to surface water.
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SECTION XII
ACKNOWLEDGEMENTS
This report was prepared by the Environmental Protection
Agency on the basis of a comprehensive study performed by
General Technologies Corporation under contract # 68-01-
1513. Dr. Robert Shaver, Project Manager, assisted by Mr.
Lee McCandless, prepared the original (Contractor's) report.
This study was conducted under the supervision and guidance
of Elwood E. Martin, Project Officer for inorganic
chemicals, assisted by Patricia W. Diercks, Project Officer
for ferroalloys.
Overall guidance and assistance was provided by the author's
associates in the Effluent Guidelines Division, particularly
Messrs. Allen Cywin, Director, Ernst P. Hall, Deputy
Director, and Walter J. Hunt, Branch Chief.
The cooperation of the carbide producers who offered their
plants for survey and contributed pertinent data is
gratefully appreciated. The operations and the plants
visited were the property of the following companies:
Airco Alloys and Carbide
Midwest Carbide Corporation
Pacific Carbide Corporation
Union Carbide Corporation
Acknowledgement and appreciation is also given to Ms. Patsy
Williams of the EGD secretarial staff and to the secretarial
staff of General Technologies Corporation for their efforts
in the typing of drafts, necessary revisions, and the final
preparation of this and the contractor's draft document.
Thanks are also given to the members of the EPA Working
Group/Steering Committee for their advice and assistance.
They are: Messrs. D. Fink, Ms. N. Speck, Dr. H. Durham and
Walter J. Hunt.
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SECTION XIII
REFERENCES
1. compilation of Air Pollutant Emission Factors, U.S.
Environmental Protection Agency, Office of Air Programs,
February, 1973 (N.T.I.S. No. PB-209 559).
2. Test Number 72-PC-07 at Union Carbide Corporation
Ferroalloys Division, Ashtabula, Ohio, June 1972, Resources
Research, Inc. McLean, Va. 22101 (Contract CPA 70-81).
3. Sherman, P. R. & Springman, E. R., "Operating Problems
with High Energy Wet Scrubbers on Submerged Arc Furnaces", a
paper presented at the American Institute of Metallurgical
Engineers Electric Furnace Conference, Chicago, Illinois
December, 1972.
4. "Encyclopedia of Chemical Technology", 3rd ed., R. Kirk
and D.F. Othmer, eds. McGraw-Hill Book Company, New York,
N.Y. (1965).
5. "Current Industrial Reports - Inorganic Chemicals,
1971", Bureau of the Census, U.S. Department of Commerce,
Series: M28A(71)-14 (October, 1972).
6. "Detection and Measurement of Stream Pollution,"
Contained in Biology of Water. Pollution. Federal Water
Pollution Control Administration, 1967.
Lund, Herbert
Industrial Pollution Control
Handbook, McGraw Hill Book Co., New York, N.Y.
8- Trace Metals in Waters of the United States,
Water Pollution Control Administration, 1967.
Federal
9. Handbook for Monitoring Industrial Wastewater, U.S.
Environmental Protection Agency, August 1973.
10. Unpublished Communications, Calgon corporation, Pitts-
burgh, Pa. - Cyanide Treatment.
11. "Development Document for Proposed Effluent Limitations
Guidelines and New Source Performance Standards - Smelting
and Slag Processing Segments of the Ferroalloy Point Source
Category", Effluent Guidelines Division Report EPA-440/1-73-
008 (August, 1973), Office of Air and Water Programs, U.S.
Environmental Protection Agency, Washington, D.C. 20460.
75
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12. "Development Document for Proposed Effluent Limitations
Guidelines and New Source Performance Standards
Significant Inorganic Products Segment of the Inorganic
Chemicals Manufacturing Point Source Category". Effluent
Guidelines Division Contract No. 68-01-1513 (December,
1973), Office of Air and Water Programs, U.S. Environmental
Protection Agency, Washington, D.C. 20640.
13. Oil, Paint, and Drug Reporter, December 15, 1969 and
February 22, 1971.
76
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SECTION XIV
GLOSSARY
Covered furnace - An electric furnace with a water-cooled
cover over the top to limit the introduction of air which
would burn the gases from the reduction process. The
furnace may have sleeves at the electrodes (fixed seals or
sealed furnaces) with the charge introduced through ports in
the furnace cover, or the charge may be introduced through
annular spaces surrounding the electrodes (mix seals or
semi-closed furnace).
Ferroalloy - An intermediate material, used as an addition
agent or charge- material in the production of steel and
other metals. Historically, these materials were ferrous
alloys, hence the name. In modern usage, however, the term
has been broadened to cover such materials as silicon metal,
which are produced in a manner similar to that used in the
production of ferroalloys.
Open furnace - An electric submerged-arc furnace with the
surface of the charge exposed to the atmosphere, whereby the
reaction gases are burned by the inrushing air.
Reducing Acjent - Carbon bearing materials, such as
metallurgical coke, low volatile coal, and petroleum coke
used in the electric furnace to provide the carbon which
combines with oxygen in the charge to form carbon monoxide,
thereby reducing the oxide to the metallic form.
Self^baking electrode - The electrode consists of a sheet
steel~casing filled with a paste of carbonaceous material
quite similar to that used to make prebaked amorphous carbon
electrodes. The heat from the passage of current within the
electrode and the heat from the furnace itself, volatilize
the asphaltic or tar binders in the paste to make a hard-
baked electrode.
Sintering - The formation of larger particles, cakes, or
masses from small particles by heating alone, or by heating
and pressing, so that certain constituents of the particles
coalesce, fuse, or otherwise bind together. This may occur
in the furnace itself, in which case the charge must be
stoked to break up the agglomeration.
Submerged-arc furnace - In ferroalloy reduction furnaces,
the electrodes usually extend to a considerable depth into
the charge, hence such furnaces are called "submerged-arc
77
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furnaces". This name is used for the furnaces whose load is
practically entirely of the resistant type.
Tapping - This term is used in the metallurgical industries
for the removal qf molten metal from furnaces, usually by
opening a taphole located in the lower portion of the
furnace vessel.
78
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