How about a CO2 Capture system?

[Jesse17]

I just want a cheaper version of one of these....

http://cgi.ebay.com/HOOKAMAX-hookah...ryZ16056QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


I'd say maybe a hobby airbrush compressor might be the best bet. They're generally oilless and will make upwards of 40 PSI. Just need a way to restrict their intake so they aren't collecting the surrounding air...

Oh wait... no you don't. I think I have an idea.... I use plastic carboys as an example as I know they will hold some pressure. I am not suggesting they actually be used to develop high pressures... it's just for the visual...

Two plastic carboys, one higher than the other, connected airtight by a tube. Each carboy has an airtight valve on top. Fill the lower carboy with 5 gallons of star-san, the upper carboy filled with air. Open the valve on the upper carboy to the atmosphere.

The lower carboy's valve is connected to the fermenter. As the fermentation occurs, it displaces the starsan solution until you have 5 gallons of pure CO2 in the lower carboy. No purging is necessary because the entire headspace is consumed by water. So it will be very pure CO2.

Once the lower carboy is full of CO2, it will start bubbling, just like a giant airlock. At this time, hook the compressor (doesn't even have to be oilless) up to the high side. Connect the lower side (full of CO2) to your collection vessel (which will have to get purged in this process). Now start the pump on the high side, which will compress the water back into the lower container, in the process, compressing the CO2 into your collection vessel.

When done, close the valve on your collection vessel and release the pressure from the top of the upper carboy.

Hey we think alike. I don't know if you read my post on the green board or not, but I came up with practically the same idea. I swear I didn't see this post first.

 

[Jesse17]

Yeah, me too.

The beer staying at serving pressure is a tough one to think through since the regulator won't work at such low back pressures.

What about the regulator from an air compressor. I can set the low pressure gage on mine to 10 psi, and it will stay there until the pressure on the high side drops below 10 psi. And the high side pressure never starts over 128 psi.

 

[Sir Humpsalot]

What about this pump? I sincerely doubt it'd actually get anywhere close to 250psi, but if it did, that'd be right where we need it to be...

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4077

 

[david_42]

I had a 12v "truck" air compressor. Paid around $60 for it. It was rated at 250 psi, but never managed to get past 70. And then the power cord melted. Not the copper, just the insulation.