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RE: Looking for some P2 process change ideas



Hi Paul,
 
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!
 
-----Original Message-----
From: owner-p2tech@great-lakes.net [mailto:owner-p2tech@great-lakes.net]On Behalf Of Lockwood, Paul
Sent: Friday, February 10, 2006 9:20 AM
To: p2tech@great-lakes.net
Cc: Abbt, James S
Subject: Looking for some P2 process change ideas

P2 Tech – 

 

NH’s looking for a little e-brainstorming help:

 

We are working with a high-tech electronics parts manufacturer that has a zero-discharge policy.  They have three waste steams that ought to be recycled/reused that they’re presently drumming up and shipping as a hazardous waste.  We’ve looked through our “P2 for metal finishing guides” and Googled filtration and distillation unit vendors, but we were hoping someone might have run into any of these situations, before:

 

1.  The company uses a water/isopropyl alcohol solution to clean an “emulsitone” paste coating (alpha terpineol, ethyl cellulose, and other low vapor organics) from ceramic chips, along with some ceramic powder from laser-cutting the chips.  Can the alcohol easily be distilled and reused?

  • 50-75 gallons used per month.
  • Alcohol also contains metals (silver, platinum, gold, and palladium metal and aluminum nitride particles in the solution).
  • The alcohol needs to end up “industrial grade.”

 

 

2. The company fires ceramic-based chips at high temperature (850 degrees) on a continuous-feed nickel/chrome mesh belt that develops a black, Ni/Cr oxide coating.  The belts run through a tank of DI water that washes off the black oxide.  They want to filter and reuse this water.

  • Waste water contains Nickel/Chrome Oxides (very fine particles suspension)
  • Water needs to be cleaned of particles
  • Water needs to end up (preferably) 12 megohm DI

 

 

3.  The company has small Nickel and Tin plating line.  The contaminated rinse from the first rinse tanks runs through an ion exchange unit that pulls out the Nickel and Tin and returns the water to the primary rinse tanks.  The secondary rinse tanks have a lower metals concentration and are not worth running though the exchanger.  We suggested using this water as make-up water in the primary rinse tank but they generate more than they need.  They are considering evaporation or membrane filtration and want to know what equipment would work best or if there are any other options.

 

P2 Tech has always come up with some good, creative suggestions to our postings and we’re open to any suggestion.

 

Paul L. Lockwood

NH Dept. of Environmental Services

29 Hazen Drive

Concord, NH 03301

(603) 271-2956

 

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