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topic 6633



How does one go about determining if one needs an exhaust scrubber for a ventilation system from a particular finishing process, as opposed to a simple overboard exhaust. Is there a listing by process, or by chemical to use as a reasonable guide. My question specifically pertains to passivation of stainless steel IAW QQ-P-35C [link is to free spec at Defense Logistics Agency,].

Robert M. Wilson
aerospace - Wichita, Kansas

"The Opinions Expressed herein are my own and not those of my employer"


Hi Robert !

For the U.S. of A one goes, I'd imagine, to the local EPA (in Canada it's the Ministry of the Environment) who will surely tell you if your process needs scrubbing.

It all depends on the acid or alkali, the temperature, the process ... and then, were you to go to a good source of mass transfer packing (i.e., Tripack comes to mind) they'll really get you going by asking what removal efficiency you want ... as that determines the neutralizing gpm rate and the amount of packing for a given diameter (sic. velocity).

In B.C. they demand a field test. In Ontario, they are pretty damn sticky, they want to see the design and will 'computer check it out' and will tell YOU what to do.

Had you given some more information re your process, maybe I could have helped ... my background being in the capture of low micron mists and ALL ambient emissions of acids contain 'invisible' droplets with the exception mainly of some of the many nitric compounds.

That tome of knowledge, the Ventilation Manual, will generally point you in the right direction as far as emissions are concerned. You should get it. Useful book if higgeldy-piggeldy and conservative in outlook.

I hope that helps you. Cheers !

Freeman Newton
Freeman Newton
White Rock, British Columbia, Canada

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