RogueRose
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Filtration - any issue with using positive pressure instead of vacuum?
I was devising some improvised filtration devices and was wondering if I increase the pressure above the media to be filtered to like 30-60 PSI, would
that work to help increase speed of filtering?
Also, if I have a container that is 12" diameter where the air-space is and then a reduction down to 6" where the filter is located. There is more
surface area where the air pressure is, so would that increase the pressure over the filter medium? So would I get more pressure with what I just
explained vs a 6" straight pipe?
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Magpie
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yes, no, no.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Fulmen
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Short and to the point, Magpie :-)
Using high pressure rather than vacuum is a valid approach and has some benefits over vacuum as well. Filtering saturated solution with vacuum can be
a challenge as the pressure drop causes evaporation and cooling that can cause the solute to precipitate out in the filter. You can also achieve far
greater pressure differences than vacuum will permit.
We're not banging rocks together here. We know how to put a man back together.
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subsecret
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Keep in mind that it's much easier to keep an apparatus together if it's under vacuum, rather than under pressure.
Fear is what you get when caution wasn't enough.
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aga
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Pressure instead of Vacuum kinda makes it hard to do any washing.
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Xenoid
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Pressure filtering works wonderfully well, and is commonly used on an industrial scale.
Check out this thread, http://www.sciencemadness.org/talk/viewthread.php?tid=9630 a pressure filter built from PVC plumbing parts! Note the WARNING.
Cheers, Xenoid
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Mesa
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Flow rates are a hell of a lot slower with positive pressure in my experience. I had the same idea in the past but quickly abandoned it.
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Pumukli
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Once I tried applying a bit of pressure over a diethyl-ether containing solution/solid particles mixture, although not for filtering purposes, by a
hand bicycle pump. Could not even finish the first "stroke", the ether vapour "detonated" in the pressurized chamber - a plastic hypodermic syringe in
this case!
(We all know that it was not a real detonation, but this word seems to be the most accurate to describe the emotional effect it had on me.) 
Based on this experince I would avoid pressurizing anything flammable with air. Maybe with inert gas it would be different.
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