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Compressor Discharge Flow Control


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#1 x127127@hotmail.com

x127127@hotmail.com

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Posted 25 September 2018 - 04:06 PM

I am trying to design an upgrade project for a client. Please refer to the attached PFD. The existing compressor is 180 mmscfd and a new reciprocating compressor is going to be added. The discharge gas 240 mmscfd will be routed to 140mmscfd amine system and 100 mmscfd bypass.  Right now I am planning to have two FIC for flow control respectively.

 

Below are my questions:

  1. The control scheme: there are flow control for the amine system (140 mmscfd), and another flow control on the bypass (100 mmscfd). Will this control scheme work well? Or is there a better option for flow control?  The 140 mmscfd and 100 mmscfd bypass will operate at the same time.
     
  2. The anti-surge valve: the existing 180 mmscfd centrifugal compressor has an anti-surge valve PV-5. The new compressor will be reciprocating comp and a recycle valve is included in the compressor package already. Is it okay to keep the anti-surge valve in the common discharge header and I know This will reduce the availability of the two compressors. And does this work for centrifugal and reciprocating combination? For now I prefer dedicated recycle for each compressor. If the recycle line is dedicated from the discharge side, is it okay to send them back to one common separator in the suction side?

Thank you in advance for your help.

 

Attached File  PFD.pdf   22.67KB   24 downloads



#2 Bobby Strain

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Posted 25 September 2018 - 05:30 PM

We can't really answer your query without knowing more about the supply to the compressors.

 

Bobby



#3 x127127@hotmail.com

x127127@hotmail.com

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Posted 25 September 2018 - 06:15 PM

Thank you for your reply. I don't have the compressor information. What kind of information is required? 



#4 Bobby Strain

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Posted 25 September 2018 - 06:52 PM

Usually such an operation would be supplied gas in a varying amount. Unless the supplier is somehow regulating the pressure to your compressors, one of your controllers will have to control the compressor inlet pressure.

 

Bobby



#5 x127127@hotmail.com

x127127@hotmail.com

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Posted 27 September 2018 - 01:56 PM

Thank you Bobby for your help. 

I don't understand that why such an operation usually supplied with varying amount of gas?

The inlet gas is from a pipeline (driven by another set of compressors). Client told me that the suction pressure is pretty stable, althrough  I doubt it because the surge happen very often in the past. 

Should I put a pressure control valve in the suction header?

 

Thank you for your help. Any advised will be appreciated.



#6 Bobby Strain

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Posted 27 September 2018 - 05:15 PM

You need to control the compressor inlet pressure with one or both of the flow control valves on the discharge. If the flow is erratic enough you may also need an inlet control valve, too. It sounds like you need to enlist the services of a professional to design a proper control system.

 

Bobby






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