Carbon Dioxide Liquefaction

[zzz0507]

Hello everyone!
I'm looking for an answer to this question:

What equipment do we use to liquefy carbon dioxide?
The carbon dioxide is at initial temperature and pressure of 125 degree Celsius and 120 bar respectively. The liquefied CO2 product is required to have a temperature of 25 degree Celsius and pressure of 200 bar.

I've read some articles (

http://www.ccivalve.com/pdf/429.pdf)

on the net regarding the natural gas liquefaction but still could not extract enough information. Maybe I need some guidance from the expert to make me understand more about the gas liquefaction process. Thanks for helping!

 

[MortenA]

I think that co2 at 200 barg/25 deg C is in the critical phase - but thats splitting hairs i guess.

Try talking to these guys - they make co2 plants all the time

http://www.union.dk/

Best regards

Morten

PS: They also have a free and very excellent co2 handbook:

http://www.union.dk/media/CO2-GB.pdf

 

[zzz0507]

Thanks MortenA for your response. You thought at 200bar/25 deg C it is in critical phase but actually it is not. I've drawn a line at 25 deg C/298K on the phase diagram and it fell just slightly into the liquid phase region. However that's not the important point here. What important is how do I actually liquefy the CO2 from gaseous phase? And what equipment should be used to achieve the given temperature and pressure? At first I thought that could be done by first compressing the gas from 120 bar to 200 bar and then use heat exchanger to decrease(and I assume it will be liquefied as well) the temperature to 25 deg C. But then I was told that I need to use some sort of 'chiller' or refrigerant to cool down and condense it to liquid form. And furthermore, I've found another option after reading this (

http://www.powermag.com/coal/Capturing-CO2-Gas-Compression-vs-Liquefaction_1939.html)

which gave me the idea of liquefying the gas to liquid and maintain the temperature at 25 deg C and then use pumps to increase the pressure of liquefied CO2 to 200 bar. I'm not sure though if this is possible. Anyway thanks again for the links up there.I'll try asking them later. Cheers!

 

[dcasto]

You are in the temperature range where I'd use a propane refrig cycle. Even a freon would work. Liquify it and then pump it to 200 bar, then use the cold CO2 at 200 barr and prechill the original stream befor a chiller.

I say this without looking at the moliier diagram to see if you go through a solid phase during the chilling.

 

[zzz0507]

Thanks dcasto. Pretty helpful info. now I got the rough idea. But I would highly appreciate if you could provide me with some sample or diagrams about this propane refrigeration cycle.. which contain explanations on how it works etc.

 

[MortenA]

I still think that you should go for a packaged solution.

Best regards

Morten

 

[dcasto]

google refrigeration cycle. propane is the refrigerant. go to the nist webbook and get the mollier diagram for it.

I'll second Mortens suggestion, but, all good engineers responsible for the solution should be able to understand what the package solution does.

 

[BenThayer]

we recovered CO2 from an ammonia plant. amazingly enough, we used ammonia as the refrigerant.

we had a centrifugal compressor take it up to ~300 psig and go through a set of mole sieve dryers to remove any water and then went to the ammonia evaporator that was running ~ -28°F.

the liquid CO2 was stored at about -10°F and ~ 250 psig. this was over 10 years ago so the nominal temperatures/pressure of the storage might be a bit off.

+1 on the package design but make sure you have something to remove any water that might be present.