vvEPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA600/S-92/006 April 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of
Metal-Cutting Wheels and Components
F. William Kirsch and J. Clifford Maginn"
Abstract
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small- and medium-size manufacturers
who want to minimize their generation of hazardous waste but
who lack the expertise to do so. Waste Minimization Assess-
ment Centers (WMACs) were established at selected universi-
ties and procedures were adapted from the EPA Waste Minimi-
zation Opportunity Assessment Manual (EPA/625/7-88/003, July
1988). The WMAC team at the University of Tennessee
performed an assessment at a plant manufacturing metal-
cutting wheels and components — approximately 6,000,000
units/yr. Tungsten carbide inserts for metal cutting are pressed,
sintered, shaped by grinding, and ultrasonically cleaned. About
half are coated with titanium nitride by chemical vapor deposi-
tion. Premolded ceramic inserts are ground to specifications
and ultrasonically cleaned. Steel disks for diamond-plated
cutting wheels are machined, cleaned, treated with sulfuric
acid, coated with a diamond abrasive compound in a nickel
lattice (plated from a nickel sulfamate solution) and given a
final electroless plating of nickel. Aluminum and aluminum-
resin disks for diamond cutting wheels are machined to work-
ing specifications, a diamond abrasive compound is applied,
and the wheels are machined to final specifications. The
team's report, detailing findings and recommendations, indi-
cated that most waste, other than treated wastewater, consists
of sludge filtered from machine coolant, and that the greatest
savings could be obtained by recycling treated water from the
plant's wastewater treatment facility to the gas/water separa-
tors of the chemical vapor deposition units.
This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
* University City Science Center, Phlladefchia, PA 19104
nati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the
same title available from the authors.
Introduction
The amount of hazardous waste generated by industrial plants
has become an increasingly costly problem for manufacturers
and an additional stress on the environment. One solution to
the problem of hazardous waste is to reduce or eliminate the
waste at its source.
University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small- and medium-size manufacturers
who want to minimize their formation of hazardous waste but
who lack the in-house expertise to do so. Under agreement
with EPA's Risk Reduction Engineering Laboratory, the Sci-
ence Center has established three WMACs. This assessment
was done by engineering faculty and students at the University
of Tennessee's (Knoxville) WMAC. The assessment teams
have considerable direct experience with process operations in
manufacturing plants and also have the knowledge and skills
needed to minimize hazardous waste generation.
The waste minimization assessments are done for small- and
medium-size manufacturers at no out-of-pocket cost to the
client. To qualify for the assessment, each client must fall
within Standard Industrial Classification Code 20-39, have gross
annual sales not exceeding $50 million, employ no more than
500 persons, and lack in-house expertise in waste minimiza-
tion.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, reduced
waste treatment and disposal costs for participating plants,
s£> Printed on Recycled Paper
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valuable experience for graduate and undergraduate students
who participate in the program, and a cleaner environment
without more regulations and higher costs for manufacturers.
Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the
procedures outlined in the EPA Waste Minimization Opportu-
nity Assessment Manual (EPA/625/7-88/003, July 1988). The
WMAC staff locates the sources of hazardous waste in the
plant and identifies the current disposal or treatment methods
and their associated costs. They then identify and analyze a
variety of ways to reduce or eliminate the waste. Specific
measures to achieve that goal are recommended and the
essential supporting technological and economic information is
developed. Finally, a confidential report that details the WMACs
findings and recommendations (including cost savings, imple-
mentation costs, and payback times) is prepared for each
client.
Plant Background
The plant manufactures metal-cutting wheels and components.
The plant operates 8,400 hr/yr to produce approximately
6,000,000 units.
Manufacturing Process
The plant makes tungsten carbide metal cutting inserts, ce-
ramic metal cutting inserts, diamond-plated cutting wheels and
diamond cutting wheels. Raw materials include tungsten car-
bide powder, premolded baked ceramic pieces, steel disks,
aluminum-resin mixture, forged and cast aluminum disks, sol-
vents, and chemical reagents.
• Tungsten Carbide Metal-Cutting Inserts
Tungsten carbide powder with binder is pressed into
insert shapes, sintered, and shaped by grinding. After
ultrasonic cleaning, 50% of the parts are packaged,
45% are coated with titanium nitride (by chemical
vapor deposition) and packaged, and 5% are
electropolished (chemically etched), coated with tita-
nium nitride and packaged. Wastes generated are
spent solvent (trichloroethane) used to clean press
and die parts, spent solutions from ultrasonic clean-
ing, spent acid hydrite (a commercial mixture of sulfu-
ric and phosphoric acids) from electropolishing, efflu-
ent water from chemical vapor deposition furnace
exhaust scrubbing, and spent rinse water. Spent
trichloroethane and spent acid hydrite are shipped to
an offsite recycler, and the spent cleaning solutions,
scrubber effluent, and rinse waters are piped to the
plant's wastewater treatment system. Grinding cool-
ant is filtered and recirculated.
« Ceramic Metal-Cutting Inserts
Premolded inserts are ground to specifications. After
ultrasonic cleaning, the ceramic inserts are marked
with ink and packaged. Grinding coolant is filtered
and recirculated.
• Diamond-Plated Cutting Wheels
Steel disks are machined, cleaned with acetone,
cleaned further in a detergent bath, given surface
treatment in sulfuric acid, coated with a diamond abra-
sive compound in a nickel lattice (plated from nickel
sulfamate solution), and given a final "electroless plat-
ing" of nickel. Wastes generated are scrap from
machining, spent solvent (acetone), spent cleaning
rags, and spent detergent and reagent solutions. Spent
acetone is sent to a recycler, the spent rags are
laundered offsite, and spent detergent and reagent
solutions are piped to the plant's wastewater treat-
ment system.
• Diamond Cutting Wheels
Purchased aluminum disks and aluminum-resin disks
manufactured in the plant are used. Both forged and
cast aluminum disks and the aluminum-resin disks
are machined to working specifications. A diamond
abrasive compound (including hexavalent potassium
chromate) is then applied in a press, and the wheels
are machined and ground to final specifications.
Wastes generated are aluminum and aluminum-resin
scrap from machining and grinding, and spent chro-
mate solution. Scrap aluminum is shipped to a scrap
metal dealer, waste aluminum-resin mixture is dis-
carded in municipal trash, hexavalent chromate solu-
tion is converted to the less toxic trivalent by treat-
ment with sodium bisulfate and hydrated lime and
piped to the plant's wastewater treatment system, and
grinding coolant is filtered and recirculated.
• Wastewater Treatment
Spent solutions and rinse waters are pH adjusted and
pumped to a floe tank before settling in a clarifier.
Decanted water is discharged to the municipal sewer
system, and sludge is partially dewatered in a sand
bed filter and shipped for disposal as hazardous waste.
• Coolant Filtering
Spent machine coolant is filtered under pressure
through diatomaceous earth. The coolant is
recirculated to the process, and sludge, which con-
tains tungsten carbide, synthetic diamonds and diato-
maceous earth, is shipped offsite for reclamation.
Existing Waste Management Practices
• Spent hexavalent chromate solution is converted to a
less toxic trivalent form by treatment with sodium
bisulfate and hydrated lime.
• Process wastewater is treated in the plant by pH
adjustment and flocculation before discharge to the
municipal sewer.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity of the waste, and the annual treat-
ment and disposal costs are given'in Table 1.
Table 2 shows the opportunities for waste minimization and
cost savings that the WMAC recommended to the plant. The
minimization opportunities, the possible waste reduction and
associated savings, and the implementation cost with payback
time are listed in the table. The quantities of waste generated
and possible waste reduction depend on the production level of
the plant. The values shown should be considered in that
context.
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It should be noted that the economic savings of the WMOs
address only the raw material cost avoidance and reduction of
present and future costs associated with waste treatment and
disposal. Other savings not quantifiable by this study include
possible future costs related to changing emission standards,
liability, and employee health. It should also be noted that the
savings given for each opportunity reflect the savings achiev-
able when implementing each waste minimization opportunity
independently and do not reflect duplication of savings that
would result when the opportunities are implemented in a
package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, two additional measures were considered.
These measures were not completely analyzed because of
insufficient data or minimal savings as indicated below. They
were brought to the plant's attention for future reference, how-
ever, since these approaches to waste reduction may increase
in attractiveness with changing plant conditions.
« Reduce the flows of cleaning solution and rinse water
to the solution and rinse tanks used in the ultrasonic
cleaning process. (The WMAC team noted that the
flows appeared to be high compared to the size of the
tanks.) Test runs would be needed to obtain data on
the feasibility of this measure. Without that data, the
measure is not formally recommended.
• The sludge obtained from the wastewater treatment
sand bed filter has a 63% water content, and vibration
during shipment to a landfill might cause "free water"
to separate. Because of a ban on landfill disposal of
Table 1. Summary of Current Waste Generation
Waste Generated
Spent solvent
(trichloroethane)
Spent solvent
(acetone)
Spent acid hydrite
Spent beeswax
Furnace exhaust gases
Source of Waste
Spent trichloroethane from cleaning press rams and dies is removed
from the plant by an outside recycler. Solvent vapors are lost from
cleaning troughs.
Spent acetone from diamond-plated wheel cleaning is decanted from
marking paint solids and shipped off site to a recycler. Vapors are lost
from a holding tank.
Spent sulfuric/phosphoric acid solution from electropolishing tungsten
carbide metal-cutting inserts is shipped offsite to a recycler.
Molten beeswax binder, drained from tungsten carbide insert sintering
furnaces, is cooled and discarded in municipal trash.
Sintering furnace exhausts are vented. Exhaust gases from chemical
Annual Quantity
Generated
605 gal
165 gal
324 gal
1,200 Ib
(Unknown)
Annual Waste
Management Cost
$3,335
825
7,595
75
(Unknown)
Steel scrap and
aluminum scrap
Aluminum-resin mixture
Spent cleaning rags
Machining coolant sludge
Treated wastewater
Water treatment sludge
Waste oil
Masking paint residua
vapor deposition furnaces, used for titanium nitride coating of tungsten
carbide cutting inserts, contain titanium chloride and chlorine. These are
scrubbed with water and the effluent water piped to the plant's wastewater
treatment system.
Waste from machining of steel and aluminum cutting wheel disks is 10,000 Ib '
shipped to a scrap dealer at no charge to the plant. 4,100 Ib *
Waste from machining of pressed aluminum-resin cutting wheel 4,500 Ibs
disks is discarded with municipal trash.
Acetone-soaked rags from spot cleaning of cutting wheel disks 480,000 rags
are laundered offsite and reused in the process.
The coolant, mainly from grinding operations, is filtered through 180,000 Ib
a diatomaceous earth filter. The sludge obtained (72% tungsten
carbide) is reclaimed offsite. The filtered coolant is recirculated.
Rinse water from process operations and effluent water from 5,498,000 gal
chemical vapor deposition furnace exhaust scrubbers are
treated with caustic soda and calcium chloride forpH adjustment.
After flocculation and settling of sludge the water is discharged to
the sewer.
Sludge from wastewater flocculation is partially dewatered in a sand 20,000 Ib
bed filter and shipped offsite for disposal as hazardous waste.
Spent oil from maintenance is removed for off-site disposal as 2,000 gal
hazardous waste.
Dried masking paint is manually stripped from completed (Unknown)
diamond-plated cutting wheels and discarded in municipal
trash.
225
225
225
325
3,000
10,996
15,875
150
225
1 Steel
2 Aluminum
•U.S.Government Printing Office: 1992—648-080/60078
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free liquids, landfill operators may require costly addi-
tion of cement kiln dust to soak up the free water. If
recommended oven drying of the sludge were imple-
mented, free water with the sludge would be reduced
or eliminated.
This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmen-
tal Protection Agency. The EPA Project Officer was Emma
Lou George.
T»blo 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction
Quantity Percent
Net Annual Implementation Payback
Savings Cost Years
Spent scrubber water
Sludge from the plant's
wastowater treatment
system
Spent acidic degreaser
solution
Spent trichohroethane
and acetone from cleaning
presses, maintenance
cleaning, and cleaning
cutting wheel disks
Use water from the plant's 5,292,000 gal
wastewater treatment system
in place of fresh water to scrub
the chemical vapor deposition
furnace exhaust gases.
Install a gas-fired drying oven 15,000 Ib
for dewatering the sludge.
Preclean the tungsten carbide 0
inserts with a hot water rinse
before they enter the acidic
degreaser tank. The quantity of
degreaser solution needed will be
reduced by about 50%.
Install a batch distillation unit 493
to recover the solvents for reuse.
100
75
$21,1681 $31,500
9,906 16,200
12,333' 1,196
1.5
1.6
0.1
90
3,542' 15,740
4.4
Includes savings on raw materials.
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S-92/006
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