How To Compress Methane Gas?

by Joe
(Craig, US)

Hi, do you have any information on the type and size of compressor that we would need to safely compress and store the methane gas that we already have available(not associated with animal waste). We would want to use this for our home, ie. heating, cooking etc., if you have any diagrams to help us we would greatly appreciate it,

thanks and good day!!

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Feb 15, 2017
Water compressor?
by: Hojo

While reading on this topic, I wonder if it would be effective to do a diaphragm system like standby/relief water tanks use. The basic premiss of these, as one can easily look up, is a diaphragm with air on one side and water on the other. As water flows in the air compresses so the water is backed by pressure so it can return to the system as the water pressure drops.

I'm thinking that the actual water pressure tanks might not be directly suitable but it'd be easy to put an inner tube into an enclosure that can be filled with water. Fill the tube with gas then fill the chamber with water and it should compress the gas as water is pumped in. If you need to achieve high compression, you're leveraging water rather than trying to compress gas through a machine.

Heck, just taking the tube and sinking it in a pond with a weight would achieve compression. With enough depth you could get some rather high temps. If you did use a pond, if the gas were to combust under pressure due to too much O2 in the mix, the results would be less incendiary to surrounding things and people and stuff!

And, just so you know, my captcha below is "blowup" which is apt for this thread ;)

Sep 08, 2015
Using Refrigertion Compressors
by: DancingCrow

Hi all. I am a refrigeration engineer with 30 years field experience, and I have a few comments. I, too, am looking for a good way to compress methane from a digester. As for using a refrigerator compressor, we should consider:
1.) Refrigeration compressors do not have piston rings, and therefore allow oil from the sump to 'blow by' the piston and exit with the discharge gas. In a refrigeration system, this is not an issue, usually (there are exceptions) as the system is sealed and the oil eventually returns to the compressor in the return gas stream. So trapping and returning this oil could be an issue. Else you risk compressor lock-up due to lack of oil.
2.) I have, of course, considered using this method, but there appear to be too many risks for me to be comfortable with. Unless you are SURE there is no O2 in the gas, any small spark or heat source can blow you to hell. Refrigerator compressors have the motor winding IN THE GAS STREAM FOR COOLING. They require the return gas stream to be about 40F to cool the motor or it will burn out. When that happens, you get a spark. When you get a spark, you blow yourself up. Don’t blow yourself up.
3.) Almost ALL compressors, from pancake air compressors down to small 12v tire pumps, use a reciprocating piston in a sleeve like cylinder. Usually there is steel on steel contact. Which presents the possibility of a spark. Again…."big-bad-a-boom".
4.) Compressor start up under pressure. True. But these compressors will safely and easily start with head pressures as high as 125 psi or there abouts. So, if you’re pressing to 50? No worries, mate. In their usual environment, these puppies are pushing about 250psi when running. Compressor stops, and within 5 minutes, the pressure has equalized (again , it’s a closed system) to about 50 – 100 psi of head pressure and the compressor can handle that.
5.) Pressure switches. There ARE pressure switches that can sense down to 0psig, but they are expensive. A cheap, reliable low pressure switch can be made from a piece of PVC pipe, a little rubber from an inner tube, and a microswitch that can be scavenged out of any of a number of things. After all, it’s just a diaphragm that presses something that moves a contact.
Aaannnnnddddd back over to you in the studio. Paul?

Jan 28, 2013
Compress with wieghts.
by: Accumulator tank

Use your accumulator tank as a compressor. Put weights on your accumulator until your line pressure is at the perscribed psi. This will require a much larger accumulator.

Sep 04, 2012
Gas compressor
by: Cor.

When you want a gastight compressor you should look at the back of an old refrigiater. The compressor there is suitable to bring gas up to 20 bar. Only downside of this compressor is that it wont start under pressure. So you need some sort of pressure relief valve which opens after the compressor has stopped, and closes again when it starts. All of this without losing to much gas.
Hope you have some benefits from this post and sorry for the misspelling's, I'm Dutch.
Bye Cor.

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