vyEPA
United States
Environmental Protection
Agency
Research and Development
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
EPA/600/S-92/037 Sept. 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer of Penny Blanks and Zinc Products
Richard J. Jendrucko* and J. Clifford Maginn, Jr.**
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 waste but who lack the expertise to do
so. Waste Minimization Assessment Centers (WMACs) were es-
tablished at selected universities and procedures were adapted from
the EPA Waste Minimization 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
penny blanks, dry cell battery cans, and other zinc products—
approximately 120 million Ib/yr. Zinc ingots and scrap zinc are
melted in an electric furnace. The molten zinc is formed into coils of
strip for further processing or sale to industrial customers. The
circular penny blanks are formed in a press, upset to form a rim on
the edge, copper plated, and visually inspected. Battery can blanks
are pressed from the strip, drawn into can shape, cleaned, and
dried. The team's report, detailing findings and recommendations,
indicated that the most waste was generated as dross in melting the
zinc and that the greatest savings could be obtained by reducing
drag-out from the plating tanks to reduce downstream sludge for-
mation and installing driers to dewater the sludge before shipment
for disposal.
This Research Brief was devebped by the principal investigators
and EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH,
to announce key findings of an ongoing research project that is fully
documented in a separate report of the same title available from
University City Science Center.
Introduction
The amount of waste generated by industrial plants has become an
increasingly costly problem for manufacturers and an additional
University of Tennessee, Department of Engineering Science and Mechanics
" University City Science Center, Philadelphia, PA
stress on the environment. One solution to the problem of 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 waste but who lack the inhouse expertise
to do so. Under agreement with EPA's Risk Reduction Engineering
Laboratory, the Science 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 operatbns
in manufacturing plants and also have the knowledge and skills
needed to minimize waste generatbn.
The waste minimizatbn 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 Classificatbn Code 20-39, have gross annual sales not
exceeding $75 millbn, emptay no more than 500 persons, and lack
inhouse expertise in waste minimizatbn.
The potential benefits of the pibt project include minimizatbn of the
amount of waste generated by manufacturers, reduced waste treat-
ment and disposal costs for partbipating plants, valuable experience
for graduate and undergraduate students who partbipate in the
program, and a cleaner environment without more regulatbns 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 pro-
cedures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The
WMAC staff locate the sources of waste in the plant and
identifies the current disposal or treatment methods and their
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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 WMAC's findings and
recommendations (including cost savings, implementation costs,
and payback times) is prepared for each client.
Plant Background
The plant produces penny blanks, dry cell battery cans, zinc
roll stock, and other zinc products. The raw materials include
zinc ingots, caustic soda, chlorine, potassium cyanide, copper
anodes, sodium metal sulfide, sulfuric acid, iron sulfide, phos-
phate cleaner, electro-cleaning solution, active carbon, and
solvents.
Manufacturing Process
The following steps are involved in making the penny blanks:
• The circular blanks are formed from zinc strip in a press.
Scrap zinc is recycled to the electric melting furnace.
• The blanks are upset to form a rim on the edge.
• The blanks are cleaned in a non-alkaline cleaner solution
and a heated electro-cleaning solution, rinsed in water,
and treated in a copper strike tank (containing copper
cyanide and copper anodes), where a thin copper film is
formed on the zinc surface.
• The blanks are copper plated in a solution containing
potassium cyanide, copper cyanide, tartar, and brighten-
ers. Spent solution is filtered, treated with active carbon
and hydrogen peroxide, and returned to the plating tank.
Carbon slurry and decanted liquids are sent to a wastewa-
ter treatment system.
• The blanks are rinsed in water, washed in a water spray
washer with an anti-tarnishing agent added, and dried in a
steam-heated drier. Rinse water is sent to the wastewater
treatment system.
The following steps are involved in making the dry cell
battery cans:
• Blanks are formed from zinc strip in a press. Scrap zinc is
washed and returned to the melting furnace.
• The can shape is formed from the blanks in a draw-redraw
machine.
• The cans are cleaned in a drum washer and dried.
An abbreviated process flow diagram is shown in Figure 1.
Existing Waste Management Practices
A batch system is used for lime treatment of spent cleaning
solutions and filter media, with alkaline chlorination to destroy
residual cyanide. Spent plating solutions and rinse waters are
handled in a continuous flow water treatment system with
electrolytic metal recovery for solutions with high copper content
and an alkaline chlorination system to break down residual
cyanide. Effluents from these treatment systems are treated
with a flocculant to precipitate insoluble copper compounds as
a sludge. Remaining soluble copper is reacted with iron sulfide
and precipitated as copper sulfide sludge. The sludges are
dewatered for disposal, and the effluent water is filtered and
discharged to a creek.
Spent cleaner solutions (nonhazardous) from battery can production
are treated with a flocculant to trap insolubles, which settle as a
Scrap
Zinc
Zinc Ingots
Zinc Strips
to Packaging/Shipping
^J Scrap Zink
to Melting
Penny Blanks
to Inspection/Shipping
^ Battery Cans
to Packaging/Shipping
Figure 1. Abbreviated process flow diagram.
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sludge. Effluent water is filtered and discharged to a creek. Sludge is
dried in a vacuum filter and disposed of as landfill.
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 manage-
ment costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The type of waste, the
minimization opportunity, the possible waste reduction and as-
sociated savings, and the implementation cost along with the
payback times are given in the table. The quantities of hazard-
ous waste currently generated by the plant and possible waste
reduction depend on the production level of the plant. All values
should be considered in that context.
It should be noted that, in most cases, the economic savings of
the minimization opportunities result from the need for less raw
material and from reduced present and future costs associated
with hazardous waste treatment and disposal. Other savings
not quantifiable by this study include a wide variety of possible
future costs related to changing emissions standards, liability,
and employee health. It should also be noted that the savings
given for each opportunity reflect the savings achievable when
implementing each waste minimization opportunity indepen-
dently and do not reflect duplication of savings that would result
when the opportunities are implemented in a package.
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.
Table 1. Summary of Current Waste Generation
Waste Generated Source of Waste
Annual Quantity
Generated
Zinc dross
Spent cleaner (a solvent mixture)
Cleaner solvent vapor loss
Spent phosphate cleaner and
spent electrocleaner solutions
Spent copper strike solution
Spent copper plating solution
Spent filter paper
Spent active carbon slurry
Plating solution drag-out
Processed waste water
Copper-rich sludge
Iron su I fide/cleaner sludge
Battery can wastewater sludge
Zinc ingots are melted in an electric furnace. Dross,
periodically raked from the surface of the molten zinc
and sold to a reclaimer, contains about 45% zinc metal.
Zinc strip, after slitting, is cleaned in a cold cleaner tank.
The spent cleaner is shipped offsite for disposal as
hazardous waste.
Solvent vapor loss occurs when slit zinc strip is cleaned
with a cold cleaner solvent mixture.
A non-alkaline phosphate cleaner solution and a low-foaming
electro-cleaning solution used to clean penny blanks before
plating, when spent, are treated with hydrated lime and
combined with other aqueous effluents in the plant's
wastewater treatment system.
Copper dissolved in spent copper strike solution is recovered
by plating it onto zinc anodes for recycle to the zinc melting
furnace. The effluent solution is diluted with rinse waters
and treated by alkaline chlorination (to break down residual
cyanide) in the wastewater treatment system.
Copper plating solution is continuously treated with hydrogen
peroxide and active carbon, filtered, and recirculated to the
plating tanks. Spent solution is decanted and treated by
electrolytic metal recovery and alkaline chlorination in the
wastewater treatment system.
Filter paper from filtration of copper plating solution is pulverized
and, with the spent plating solution, is treated by hydrated lime
and alkaline chlorination in the water treatment system.
Spent active carbon used in treating recirculated plating solution
is transferred to the wastewater treatment system for
alkaline chlorination
Drag-out from the plating tanks is collected in a drip tank and
pumped to the wastewater treatment system for recovery
of dissolved copper and alkaline chlorination.
Spent aqueous solutions and rinse waters, after treatment in
the wastewater treatment system, are discarded to a local creek.
Sludge filtered from recirculated copper plating solution
is sold to a reclaimer.
Wastewater treatment clarifier effluent is treated with iron sulfide
to remove copper. Effluent from treatment of the aqueous cleaner
solutions is added, and the sludge is removed by filtration
and disposed of as hazardous waste.
Drum washer wastewater is treated with a flocculant. The resulting
sludge, with a filter aid, is removed by vacuum filtration and
disposed of in a landfill.
2,000,000 Ib
3,500 Ib
12,400 Ib
98,400 gal'
2,200 gar
14,400 gal'
900 Ib'
200 gal'
60,000 gal*
80,000,000 gar
816,000 Ib
183,600 Ib
384,000 Ib
Annual Waste
Management Cost
$221,200
24,225
5,178
0
0
0
319,140
111,340
97,775
* Water is obtained by the plant without charge and after treatment, is discarded without charge in a local creek. Charges for waste materials accumulated
in the plant's wastewater treatment system are listed here
'U.S. Government Printing Office: 1992 — 648-080/60064
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Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction
Quantity Percent
Net
Annual Savings
Implementation
Costs
Payback
Years
Zinc dross
Copper-rich sludge
and iron sulfide sludge
Copper-rich sludge,
iron sulfide/cleaner
sludge
Spent cold cleaner
(a solvent mixture)
Copper-rich sludge,
iron sulfide/cleaner
sludge, and battery
can wastewater sludge
Solvent vapor loss
(cold cleaner) in
cleaning the slit
zinc strip
Install a small furnace to bleed 630,000 Ib
zinc metal contained in the dross,
and recharge it to the zinc melting
furnace.
Install rinse spray nozzles abo ve 30,000 Ib
stations where penny blanks are
transferred from plating baths to
rinse tanks. The spray mist will
reduce solution drag-out, which
causes sludge formation down-
stream. Circulate air over the
bath to increase the water evap-
oration rate and compensate for
the added water.
Install gas-fired driers to dewater 403,500 Ib
the sludge. It is estimated that 50%
of the contained water can be re-
moved, reducing the weight of haz-
ardous sludge by 25% and that of
nonhazardous sludge by 40%.
Use an aqueous cleaner (nonhaz- 0
ardous) instead of a solvent-based
cleaner for cleaning slit zinc coils.
(There is no net reduction in waste
generated, but raw material and
disposal costs are reduced.)
A void excess copper plating thick- 30,000 Ib
ness by injecting plating solution
into the barrels of penny blanks and
increasing barrel rotating speed to
improve solution circulation. Plating
to a more uniform and lower thick-
ness will consume a lesser amount
of plating reagents and generate
lesser amounts of sludge downstream.
Tight enclosure of the zinc coil clean- 9,900 Ib
ing station will reduce cleaner solvent
vapor loss.
32
$75,310
53,652
$86,160
5,800
1.1
10.8
29
41,093
29,725
9,539
81,880
20,000
32,740
2.0
0.7
3.4
80
4,118
1,250
0.3
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-92/037
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