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compressed air dryer newbie question

compressed air dryer newbie question

compressed air dryer newbie question

(OP)
(ALSO POSTED IN MFG PLANT ENGRG)

In a typical mfg facility, what is the advantages / disadvantages of a refrigerated air dryer versus a dessicant air dryer?  Why would I choose one over the other?

Thanks in advance...

TygerDawg

RE: compressed air dryer newbie question

tygerdawg:

In a refrigerated air dryer:

1) You are accepting a much higher dew point than that achievable by an adsorption dryer; i.e., your product air will have considerably more moisture.  An adsorption dryer can easily produce air with only ppm(v) of moisture.

2) You will inherit maintenance costs and spare parts inventories that outstrip those of an adsorption dryer (which doesn't require any mechanical moving parts).

3) The amount of energy expended to remove a unit of water moisture is far greater than the energy required for an adsorption unit; the removal efficiency is relatively poor.

4) The foot print (or space required) is greater than that for the adsorption dryer.

5) An electric motor is a prerequisite for the refrigeration compressor, while the adsorption dryer needs no motor; at most, the adsorption unit would need an electric heater for regeneration - in the event waste steam is not available.

6) The adsorption unit inherently puts out a superior, purer air product because the adsorption bed filters out and removes any compressor oils or vapors that your air compressor might emit.

In an industrial environment, where one is concentrating on producing energy-efficient product at the lowest competitive price and at the highest quality, I consider the refrigerated dryer to be far inferior in performance than the adsorption dryer.  I would consider a refrigerated dryer only at the insistance of the owner-operator and where the applicationis a commercial one - as opposed to an industrial one.

I hope this addresses your questions directly.

Art Montemayor
Spring, TX

RE: compressed air dryer newbie question

(OP)
Thanks for cutting through the fat, Art!  After reviewing the designs of both, I had to ask myself "why would anybody NOT choose dessicant drying?...it seems like the better choice for a variety of reasons".  But I didn't find any kind of definitive YEA/NAY discussions on the vendor websites.

TygerDawg

RE: compressed air dryer newbie question

Art went quickly past the only drawback to an adsorption unit (or mole sieve for that matter) and that is regeneration.  

I've seen a couple of folks use a refrigerated unit because they simply couldn't come up with a way to cook the water out of the bed.  Electric heaters can work if carefully designed, but a poor design will create hot spots that can change the characteristics of the bed and even destroy the ceramic matrix of a mole sieve.  It's best if you can use a waste-heat source to regenerate the bed, but you have to be careful of how you do that as well.

If you can lick the regeneration issues, a bed is far superior.

David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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