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Re: Recycling ideas for perchloroethylene?



Bill - 

The P2 option is to find a better cleaning method, of which there are many.
What about CO2? It's a great degreaser in liquid state, and can be enhanced
with ultrasonic techniques. At super-critical stage, CO2 provides chemical
extraction and solvent cleaning of organic compounds. It's dry, non-toxic,
and is ideal for complex parts and penetrating small pores and crevices.
Target contaminants include silicon oils, dielectric oils, machine oils,
plasticizers, damping fluids, and fluorinated oils. SC-CO2 is in fact used
often in aircraft maintenance for such applications as aerospace parts,
bearings, cables, o-rongs, seals and gyroscopes. 

Down side of SC-CO2 is high initial cost and an inability to clean
inorganics (lint, scale, rust, fluxes). 

One treatment option for perc is azeotropic distillation. I don't think
this is any less labor intensive than straight distillation, but they could
definitely beef up their recovery efficiency by adding water to the still
following the final boil down to form an azeotrope. The water combines with
the perc, to lower the boiling point from about 250 degrees to 190. Just
one extra water addition can decrease the average prec content from 54% to
3.4%. After a second, the perc level can drop below 0.5%.

The down side of azeotropic distillation is that one generates more contact
water, which is generally hazardous. Many drycleaners evaporate their
contact water and capture some of the perc vapor with carbon. 

Just some thoughts. Good luck.

Todd MacFadden
Montana P2 Program


At 01:39 PM 4/8/98 -0700, you wrote:
>Perchloroethylene in aircraft parts cleaning:
> 
>An aircraft part inspection facility switched from
>TCA to perchloroethylene because perk is not a
>HAP (does not deplete ozone).  They had tried to
>find aqueous solvent substitutes but they do not
>do the job well enough.  They did look into new dry
>solvent products but the cost was outrageous
>$3500.00 and way too expensive for them.  The
>facility had researched a variety of aqueous type
>cleaners but found none that worked.  They have
>invested money in systems that have not cleaned
>the parts to specification.  They will continue to
>look for a solution but Perk is a stop gap measure
>for now. 
>
>What do they use Perc for?
>They use Perc to clean aircraft parts for
>inspection.  They need to make sure the parts do
>not have any cracks.  The parts usually have oil or
>wax on them.   They inspect the parts for cracks
>and it is very important that the parts are throughly
>cleaned. They cannot take any chances that they
>will miss a crack by not having the part thoroughly
>cleaned.  They are responsible for the safety of
>the aircrafts.
>
>How do they use the Perc?
>Perc is used in a hot vapor degreaser application,
>chilled freeboard, 110 gallon capacity.  At 60 days
>they add about 30 gallons of Perk.  Estimated at
>90 days they will have to dump 110 gallons
>because it will become too dirty.  Every 3 months
>they would like to send out for recycling.    Some
>metal chips (aluminum) will be in the cleaning
>solution. 55 gallon drum cost about $300. 
>$500.00 estimated cost of disposal of 110 gallons.
>
>What are they looking for?
>1.  Information on recycling Perc.  Looking for an
>economical way to recycle Perc.  What types of
>systems are available?  They do not want to
>dispose of it and would like some information on
>how to recycle it, perhaps closed loop recycling
>system.  (They do have a 5 gallon still but it is slow
>and labor intensive.)
>
>and/ or
> 
>2.  Looking for someone to take used Perk off
>hands (exchange or reuse).
>also,
>
>3.  Any suggestions on a replacement.
>
>Any information in this regard would be most
>appreciated.
>
>Bill Quinn
>Az DEQ
>Pollution Prevention Unit
>Phoenix, AZ 
>
>
>
******************Montana P2 Program*******************

Todd MacFadden
Pollution Prevention Technical Specialist
MSU Extension Service
Taylor Hall				(406) 994-3451
Box 173580				(fax) 994-5417
Bozeman, MT 59717-3580	      toll-free (888) MSU-6872

toddm@montana.edu
http://www.montana.edu/wwwated

*******Pollution Prevention Makes Business Sense*******