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Scrubber on top of fume hood




Hi My customer asking for a Perchloric Fume hood and their concern is scrubber location. From what we have study the space above false ceiling is very constraint. Hope I can get some information.

Yuva
- Singapore
2006



2006

Hi Yuva,

Once and once only was I forced to put a so-called scrubber on top of the hood ... in this case it was a l2 micron inertial type... and I didn't like doing it... and I bet it wasn't too successful, either.

Having designed very, very many Perchloric systems (hoods, scrubbers, fans & ducting for multiple acids, too) I do NOT recommend this approach.

Why? One of the reasons is that the airflow in the hood will perforce have to vector to one end in order to 'turn' into the scrubber. Another reason is that the flow distribution, due to the great lack of space will be very
poor.

The scrubbers I'm talking about are the inertial type not the mass transfer designs which would need even more room. Hit LMITS on Google for an idea.

Having recently done designs for similar problem areas, the solution was to use the adjacent next room (or further down the line for that matter) for the scrubber ... and then one must consider accessibility (which at Noranda was not the case) because sooner or later, but perhaps many years later, one may well have to clean spray jets, etc.etc.etc.

Perchloric is my favourite assay acid ! But don't put a so-called scrubber on the top of the fume hood and is someone else says Why Not ... accept what they say with a great pinch of salt !

freeman newton portrait
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).




2006

Hi Yuva once again.

Vertical space.... which you say is at a premium.

Assume that the countertop is at 2'-6". Assume, too, that the hood is 5 feet high, that the ducting is l2" Ø ... then you'd need an overall height of 10 feet allowing for some minimal clearance, 6" or so.

What about having the fume hood exhaust laterally, i.e., sideways. That then would reduce the overall height by at least 2 feet.

Another point ...you said 'Perchloric' but the hoods I designed were for ALL the Assay acids with Perchloric being, of course, the last one. Construction was from a PVC: FRP dual laminate. But for straight HCl04, then stainless would be OK but that's a waste of energy and space and still need scrubbing.

Food for thought.

freeman newton portrait
Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).





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