3 replies to this topic

[look4siva]

Process Summary: Flare gas is recovered from Refinery Flare Stack through new Seal Drums and diverted to two trains of Dry Screw Compressor. Adequate coolers and KO Drums are provided .Flare gas is compressed and treated in an Amine Absorber and is sweetened to Fuel gas.

 

Query: For Start up of Compressor below is my query

1. There is a 2” tapping in a 16” Compressor Suction line for fuel gas purge. Is it possible to start the Compressor by purging fuel gas in the whole suction and discharge line filling the volume and after required suction pressure is attained we can start the Compressor in recycle mode ? Battery limit valve of the FEEDinlet (Flare gas) and outlet battery limit valve(Fuel gas system) will be in closed condition. After  stabilisation of Compressor running battery limit valves can be opened and more flow can be provided to the system.Else should I purge only suction line for pressurising the suction and open the FEED battery limit valve and start the Compressor?

2. My limitation is without treating the flare gas I cannot give the gas to the refinery fuel gas system.Hence Can I start the Compressor initially with discharge battery limit valve (Fuel gas system) in closed condition and the recycle valve back to suction in open condition so that Compressor will be running in recycle mode.Then after Amine circulation is established I can open the discharge valve.

 

Note: If I run in recycle mode I will ensure that suction flow & pressure does not rise by manually controlling PCV’s in Seal Drum.

 

Need experts review on this. It would be helpful if people who have done Commissioning/Start up of Compressors in gas sweetening unit provide their feedback. Thank You.

[look4siva]

Any Experts , Please provide your views . . 

[saeed.s]

Dear look4siva

According to your explanation, I will do these:

 

1-Purge the Compressor with N2 & pressurize it ( inlet & outlet  valve of compressor are closed)

2-Steam out suction line

3-pressurize with natural gas ( or slowly open the FEED battery limit valve to pressurize FEED line)

4- close steam to feed line & drain steam condensate from feed line is there any.

5- Step 2 to 4 for discharge line (and  also for all the unit !!! )

 

Now feed & discharge battery limit valve are open.

 

6- open inlet & recycle ( or spill back)   valve of compressor

7-start compressor ( electrical motor or turbine driver ,no  difference)

 

Now, recycle gas after cooling in inter cooler, come back to inlet KO drum.As you mentioned, after Amine circulation is established, open the compressor discharge valve and slowly close recycle valve to increase discharge pressure. It s done!!!

 

Note: If I run in recycle mode I will ensure that suction flow & pressure does not rise by manually controlling PCV’s in Seal Drum.

I could nt understand what you mean of manual control. It should  work in auto mode also.

In these step its better to check it in auto mode & tune the recycle control valve. but do it slowly please.  wrong tuning parameters ( PID ) make surge in control valve operation and  discharge pressure.

 

Good luck

Edited by behnam, 13 October 2016 - 01:51 PM.

[Bobby Strain]

Looks like you got one answer without cost to you. Do you know if it is correct? Or safe?

 

Bobby