Blower or Compresor

[hyposmurf]

I have this facts.
To supply air at 2m3/min at 1.5 bar abs to a fermentation vessel.
Air shall be filtered to 99.99 % particulate < 0.2 micron.

Air supply could be
1.-
A roots type blower at 1.5 bar absolute
2._
A screw or piston compressor rated at 8 bar absolute.

Cons for roots type
I can not find filters to such pressure and flow.


Pros for compressor at 8 bar
No problem with filters .
Cons ; to use reduction pressure stages to downward the pressure from 8 to 1.5 bar abs .

My question , what would be the flow capacity of the screw or piston compressor to choose??

Thanks in advance.

 

[zdas04]

Your question seems to be indeterminate, either technology can be sized for just about any capacity.

The specs I see for Roots blowers have a maximum discharge pressure that is closer to 2 bara than 1.5 bara which should give you plenty of extra pressure capacity to duct the suction to a HVAC drop-in filter, and put a piped high-efficiency filter on the discharge.

The screw compressor seems to be very wasteful of energy. Taking air from 1 bara to 2 bara requires about 30 kW/ thousand Sm^3. Going up to 8 bara requires 97 kW/ thousand Sm^3. Unless you have a specific use for the high pressure air this would be pretty hard to justify.

David

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[dcasto]

You can set the optimum ratio for a screw at 2.2 and get the same results. I think I'd look at which one works best dry or with no oil in it so you won't have that to deal with.

 

[crjones]

Haven't you asked this same question already?

 

[hyposmurf]

yes, in other way , but yes.
sorry

 

[quark]

1.5 bara may be the overlay pressure for the fermentor. In this case, you have to generate air at 1.5bara + pressure drop in the piping system. We use either oil less reciprocating or screw compressors for the fermentors. Your flowrate is pretty low and a single stage non lubricated reciprocating compressor will do.

 

[hyposmurf]

Hi Quark , can you tell me how do you filter the air to be it sterile?

 

[quark]

Contact Pall, Millipore, Sartorius and Domnick Hunter etc for 0.22 micron sterile filters. Better to take a sterilizable grade filter (so that you can sterilize it). You should validate the filtered air for sterile quality. Just note that, the pressure drop across the filter for your flowrates is about 0.12bar. You can operate at lower inlet pressures if you increase the surface area of filtration. Talk to the filter manufacturers.