distillation of water/IPA will result in an azeotropic mixture (88%IPA & 12% water). This is the most concentrated the IPA can be if you start off with no more than 88%IPA initially. So you can not get industrial grade IPA without a lot of expense to break the azeotrope. However, since they are using an IPA/water mixture, it seems like the most important thing is a change in perception of what they need - they need a clean IPA-water mixture, not clean, dry IPA. If that is acceptable, IPA distillation is straightforward.
The other issue Mike Callahan raised is whether there are volatile components in the emulsitone product and whether their presence in the cleaning solution would have a negative effect. If they have the same boiling range as IPA and water, those components should have similar drying properties and leave no residue - they would simply function as another solvent component. Mike's idea of a second stage, pure IPA rinse would be a way of eliminating real or imagined contamination issues if process validation is an issue.
oxide solids separation - measuring a particle size distribution would be useful in identifying a separation scheme.
tin-nickel rinse - a first question is what is the quality of effluent from the ion exchange column? If it is equivlent to the second rinse feed - cascade the 2nd rinse to the 1st, treat overflow from rinse 1, return treated water to the 2nd rinse with some makeup.
If the quality is worse, ask whether the 2nd rinse flow rate was set arbitrarily. Can the second rinse feed rate be reduced to the point it can serve as makeup? What constitutes rinse contamination that will cause product failure and what safety margin is needed?
If needed flow is still too high, is there space to add a 3rd rinse? Rinse 2 & 3 can be cascaded with flow reduced by a factor of 3 to 10, with no reduction in final rinse quality. If space does not exist, can the 2nd rinse be divided into 2 cascaded sumps, with the water applied to product via sprays to allow better rinsing on the existing footprint?
Manufacturing Team Leader/Senior Engineer
Minnesota Technical Assistance Program
University of Minnesota
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of Callahan, Mike
Sent: Friday, February 10, 2006 1:31 PM
To: Lockwood, Paul; P2Tech
Subject: RE: Looking for some P2 process change ideas
Ceramic chip fab for electronic parts? Sounds like chip capacitors. Takes me back about 20 years to one of my first P2 assessments. Here are some thoughts on your problem.
1. I'm not familiar with the emulsitone product but it might be difficult to recover "clean" alcohol. I'm guessing that some of the volatile components will carry over with the alcohol. However, do you actually need clean alcohol? You might be able to recover an acceptable product that can be used for bulk cleaning. You would then follow this by a final rinse with fresh alcohol to rinse off the recycled alcohol. The still must be explosion proof and equipped with a microfilter to remove particles. You might want to consider filtering the dirty alcohol before the still so you don't have to worry about particulate carry-over and because recyclers will likely pay for the dirty filters.
Can the chips be washed in DI water? Is there an aqueous version of emulsitone available? If you can wash the chips with water then you might be able to reduce alcohol use to a minimum (this assumes alcohol is used for drying). You would then filter the dirty water (to recover $ solids) and discharge to sewer (if acceptable).
2. Ultrafilitration or porous metal/ceramic filters should be able to remove most of the particulates from the water stream. To make sure that you're not dealing with soluble metals, pass the water through a 0.5 micron lab filter and test for Ni/Cr. If you find Ni/Cr, then some form of chemical treatment will likely be required. And why do they need DI water to wash the belt? Is it being cleaned at high temp? The use of DI water avoids solids formation on the hot belt but it may also solubilize some oxides. It may be possible to reduce the aggressiveness of the DI water by relaxing the spec but detailed study would be required.
Also, does the process require an oxygen atmosphere or just high temp? If you're just dealing with thermal effect, then you might want to look into flushing the oven with an inert atmosphere. This will prevent oxide formation on the belt. It should also lengthen the life of the belt. Again, detailed study is required.
3. Evaporation is a relatively easy and simple approach to concentrating waste streams for recycling. Membranes are becoming more common, but the systems are a little more complex and prone to fouling (membrane selection is major key to success). But the simplest approach might be to use conductivity control to reduce rinse water use and to then raise the temperature of the first bath. In essence, you use the rinse tank as an evaporator. Just be sure you don't exceed the operating temp of the IX system. Or you might want to consider raising the temp of the second rinse so that the parts flash dry upon removal. Just be sure to use DI water for the second rinse. Adding air agitation is another way to increase evaporation and achieve water balance.
Good luck in your efforts. Have a great weekend!
From: firstname.lastname@example.org [mailto:email@example.com]On Behalf Of Lockwood, Paul
Sent: Friday, February 10, 2006 9:20 AM
Cc: Abbt, James S
Subject: Looking for some P2 process change ideas
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