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Jt Effect During Compressor Recycle Control

compressor recycle control jt effect reciprocating

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#1 rs20170808@gmail.com

rs20170808@gmail.com

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Posted 21 October 2018 - 02:00 AM

Hello, 

 

I am a recent graduate engineer and wanted to share some queries regarding a reciprocating compressor.

I have a reciprocating compressor for natural gas which compresses it from 40 psig to 2000 psig with a 4-stage reciprocating compressor. There are a total of 4 compressors in parallel and each has a capacity of 4 mmscfd. 

There is a common recycle valve for capacity control which tries to maintain the suction header pressure. However, I see that when recycling there is a drop from 2000 psig to 40 psig across control valve and temp. drops from 120F to 7F. Is this a cause of concern? I do not see any liquid dropout. Do we need any heat tracing after control valve to bring up the temperature? Or can be depend on heating from the ambient to increase temperature?

rs



#2 fallah

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Posted 21 October 2018 - 04:50 AM

rs,

 

Do a simulation for the process parameters conversion across the control valve to see if any liquid would be performed. 



#3 rs20170808@gmail.com

rs20170808@gmail.com

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Posted 21 October 2018 - 11:29 AM

hello fallah,

 

thanks for your reply.  From hysys simulation, there seems to be no liquid dropout..vap fraction remains 1 downstream of control valve.  However, there is a drop in temperature.  In general practice, is there something needed to be done for increasing the temperature with heater or heat trace or its generally assumed that ambient heat transfer will increase the temperature.

 

rs



#4 rs20170808@gmail.com

rs20170808@gmail.com

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Posted 21 October 2018 - 11:29 AM

hello fallah, 

 

thanks for your reply. From hysys simulation, there seems to be no liquid dropout..vap fraction remains 1 downstream of control valve. However, there is a drop in temperature. In general practice, is there something needed to be done for increasing the temperature with heater or heat trace or its generally assumed that ambient heat transfer will increase the temperature. 

 

rs



#5 fallah

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Posted 21 October 2018 - 12:31 PM   Best Answer

rs,

 

If the MOC (material of construction) of the piping system at control valve downstream is even to be CS, it can tolerate the low temperature not lower than -20 F which is highly lower than the temperature you reported i.e. 7 F.  Hence, if the liquid droplet wouldn't be formed after passing the gas through the valve, appears there would be no problem regarding the material tolerability and no need to consider heat tracing facility...



#6 rs20170808@gmail.com

rs20170808@gmail.com

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Posted 23 October 2018 - 08:35 PM

Thank you, Fallah 






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