Supercritical compressor

[Sabergg1981]

Hi guys.
I'm not process engineer and I don't have any knowledge about reservoir. But in our last study we find that our off gases for injecting into well heads stand in supercritical regime. In other word we want to compress our off gases to inject into well heads. But as we compress the gas in stands in supercritical regime. We don't hear about compressor for gases in sepurcritical regime. Do you? Do you have any guidance or reference about it?
Thanks

 

[TD2K]

It's not an issue in itself. Any air compressor for example is handling a supercritical fluid.

 

[EmmanuelTop]

See

http://www.eng-tips.com/viewthread.cfm?qid=222118

Dejan IVANOVIC
Process Engineer, MSChE

 

[Sabergg1981]

@TD2K
Dear can you explain more? I don't have any understanding about that. Does an air compressor work in supercritical region? What about a natural gas in supercritical region?

 

[Sabergg1981]

I want to know for these compressors how can we obtain property of fluid? What about adiabatic compression ? How can I calculate cp,cv and ... In what pressure and temperature?

 

[TD2K]

A supercritical fluid is any fluid that is above its critical temperature. O2 has a critical temperature of -118.6C and nitrogen has a critical temperature of -147C. So at most temperatures that you would encounter air at,it's going to be a supercritical fluid. You can't just take room and and liquefy it by increasing the pressure, no matter how much, because it's above its critical temperature.

How do you get properties? For most applications today process simulators and an equation of state is used to generate properties.

 

[rotw]

quote
A supercritical fluid is any fluid that is above its critical temperature. O2 has a critical temperature of -118.6C and nitrogen has a critical temperature of -147C.
unquote

I think what the OP meant is dense phase see link below, otherwise the OP question would be a "non-issue".

[URL unfurl="true"]http://www.eng-tips.com/viewthread.cfm?qid=366131[/url]

 

[rotw]

or even here; please see attached.

 

[georgeverghese]

It is not usual to see that a multicomponent gas mix for associated or non associated gas from a subterranean hydrocarbon resevoir to be in the supercritical region - it may be due to poor characterisation of the heavy ends(C6+) in the gas mix. Poor resolution of these heavy ends can lead to misconception of the "dryness" of this mix.

 

[CostasV]

IMHO the diagramm attached in rotw's message is not telling the truth. For example, we know that natural gas is 100% gaseous at 0 degC and 5 MPa, but the diagramm says it is mixture of gas and liquid. What am I missing?

And I think that superctirical area is where the substance has both pressure and temperature above critical values. So, unless air compressor discharge pressure is higher than critical pressure 38 bar, compressed air is not supercritical.