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Source Recovery of
Isopropyl Alcohol at an Electronic Equipment Manufacturer
Process Background
Zytec Corporation manufactures
and services computer power units. The production process
includes the building, soldering and testing of electronic
circuit boards; assembling of units; packaging; and shipping.
As a part of the soldering process, solder fluxes are used
to chemically clean and deoxidize the copper circuit surface
in preparation for soldering.
In 1989, Zytec successfully implemented
a low-solids foam soldering flux (LSF) process. The flux solution
contains about 93 percent isopropyl alcohol (IPA), which acts
as a thinner and a solvent for the flux. Circuit boards are
wetted with this solution prior to soldering. After a predetermined
number of production runs, the spent solution is removed and
disposed of as hazardous waste.
In addition to the high IPA content
in the LSF, virgin IPA is used extensively throughout the
Zytec facility. Hand- soldering, testing and inspection areas
rely heavily on IPA for removing residual fluxes from circuit
boards and for general cleaning. IPA is applied to returned
parts and boards to prepare them for re-work. IPA is also
used to clean computer chassis before final assembly of the
power units.
Incentive for Change
Zytec hoped to save money by reducing the volume of IPA
waste by setting up an IPA recovery system. During a six-month
period, about 700 gallons of flux solution was shipped off-site
as hazardous waste and 440 gallons of fresh IPA was purchased
for cleaning purposes. The total annual cost for purchase
and disposal of IPA was $5,100.
Intern Activities
The purpose of the intern project was to study the recovery of IPA from the flux-thinner waste and reuse it in Zytec's general cleaning areas. During the project, the intern:
- inventoried fresh IPA consumption and spent IPA-flux disposal;
- distilled and assessed samples of spent flux by comparing them with fresh IPA and noting employee's comments; and
- acquired information on distillation equipment size and selection, fire code issues, safety operating procedures and economic feasibility.
Results
For most cleaning purposes, distilled IPA performed as
well as virgin IPA.
For Zytec's current usage, a distillation
unit with a 7.5-gallon capacity was deemed adequate since
it recovered 90 percent of the IPA. Through discussions with
the local fire department, city inspector and insurance agency,
it was determined that the distillation equipment must be
explosion-proof and located in an area with adequate ventilation
(up to six air changes per hour).
The cost for the distillation equipment
would be $5,600. Costs for equipment operation and maintenance,
and disposal of still bottoms costs total $2,100 per year.
Annual savings due to reduced amounts of IPA purchased and
decreased disposal costs are estimated at $4,800, with a payback
period of 14 months. Zytec expects to purchase and install
the recovery equipment during 1994.
Additional Information
For more information about recovering and reusing isopropyl
alcohol, or to receive technical assistance to prevent, reduce
or manage your industrial waste, contact MnTAP at 612.624.1300
or 800.247.0015 from greater Minnesota.
This project was conducted in 1993 by MnTAP
intern Janelle Valdez, a civil engineering student at the
University of Minnesota.
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