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Bouquet Enterprises
Outsources Process to Reduce Hazardous Waste and Employee
Exposure
Best Alternative to Using Selenius Acid
is Outsourcing
Process Background
Bouquet Enterprises manufactures over 600 different decorative
products and gifts. Some of their products require the metal
parts to have a rustic appearance. Sheet metal is given this
aged look through an antiquing or blackening process which
uses selenious acid.
Incentives for Change
The selenium-based acid is hazardous to employees and must
be disposed of as a hazardous waste. The sewer system in Kellogg
cannot handle heavy metals, including selenium from Bouquet.
The overall efficiency of the blackening process needed to
be improved.
Options
The MnTAP intern identified three main options to improve
Bouquet’s blackening operation.
Option 1: Optimizing use of selenium-based
acid
The first step is to use a more appropriate selenium-
based acid solution. The chemical solution identified by the
intern is specifically designed for the type of sheet metal
that Bouquet blackens. The concentrate is diluted in water
and used at room temperature to produce the desired appearance.
Optimize concentrations. The
current process can be optimized by keeping the chemical concentration
of the process bath at the lowest possible operating level.
This minimizes losses from dragout—chemical clinging
to the part and being removed from the bath. By optimizing
the chemical ratio, Bouquet would reduce their chemical consumption
by five to ten percent, saving $5,600 annually on chemicals.
A few procedures would need to be added, including testing
the solution concentration periodically, having a schedule
for adding more solution to the bath and filtering the solution
bath on a regular basis.
Withdrawal and drain times.
Increasing withdrawal and drain times allows more solution
to remain in the bath and minimizes the amount of solution
contaminating following stages.
Spray rinse and a racking system.
A spray rinse system would replace the current rinsing dip
tank. Bouquet could reduce waste by 75 percent, saving $6,000
to $11,000 annually in off-site disposal fees.
A racking system would allow up to thirty
sheets to be blackened at one time. The rate of production
would triple; even greater efficiencies could be attained
with more racks.
The cost of the spray rinse tub was too
high, making this option unfeasible.
Ion exchange system. Having
an ion exchange system for the rinse water will eliminate
the stage’s hazardous waste and its disposal fees. The
deionized water could be reused in the rinsing process instead
of sewered, reducing overall water use.
Potential savings: Reduces waste by 660
gallons and saves 180 gallons of raw material a year. Estimated
savings of $14,300 a year.
Option 2: Substituting
a non-selenium based acid
A non-selenium based acid
could be used to blacken iron and steel. This system uses
no U.S. Environmental Protection Agency regulated chemicals,
making sewer disposal a potential option. Hazardous waste
and the need for an ion exchange system would be eliminated.
This option posed two problems. A stronger
acid was required, raising concerns about employee safety.
Also, tests of this product indicate that the appearance of
the metal from this process is not acceptable. Instead of
looking rustic, the metal looks shades of red, purple or blue.
Option 3: Outsourcing
Outsourcing may be the most economical way for Bouquet to
manage their blackening process. They would not have to worry
about spent chemical from the solution bath, the risks to
employees and the liability of handling the acid. A facility
with a high production rate will have better economies of
scale than Bouquet, resulting in a lower cost per part for
blackening.
Potential savings: Reduces waste by nearly 1,000 gallons
and saves an estimated $6,000 a year.
| Table: Comparison of Options |
| Optimizing |
Substituting |
Outsourcing |
Advantages
Low cost for chemicals
Larger coverage per gallon
Solution bath only needs replenished periodically |
Advantages
Reduced liability
Larger coverage per gallon
Low capital investment
Disposal costs eliminated |
Advantages
Lower cost per sheet
Eliminates liability
No capital investment
Disposal costs eliminated |
Disadvantages
Capital investment
Liability
Disposal costs
Regulations |
Disadvantages
Final appearance
Cost of solution
Solution bath needs dumped periodically |
Disadvantages
Final appearance could vary
Scheduling |
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Results
As a result of the project, Bouquet decided that outsourcing
the process is the most effective way to handle this hazardous
material problem. They are currently outsourcing half of the
products requiring blackening. Bouquet plans to outsource
the entire process once they have worked out all the issues
related to quality.
When considering outsourcing, Bouquet had
to work with the service provider to match their color requirements
and make the process more efficient. Initially the parts were
batch processed, resulting in an inconsistent appearance.
They worked with a vendor to develop a racking system to keep
parts separate when dipped into the bath. As a result, quality
is acceptable and consistent, and costs decreased by 75 percent.
Because Bouquet still has half of the process
in-house they optimized their acid baths and developed clear
instructions to let employees know when recharging the baths
is necessary.
More Information
MnTAP has a variety of technical assistance services available
to help Minnesota companies reduce and better manage their
industrial waste. If you would like assistance or more information
about MnTAP’s Intern Program, call 612.624.1300 or 800.247.0015
from greater Minnesota.
This project was conducted
in 1997 by MnTAP intern Tony Smook, a composite materials
engineering student at Winona State University.
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