3 replies to this topic

[pawanhbti]

We have 2 stage four cylinder reciprocating compressor. It is used to compress Boil off Gas for LNG tank. Its rated discharge pressure is 9.6 BarA. and its capacity is 12000 ton/hr . we have three such compressor. For power saving in the compressor we want to reduce discharge header pressure from 9.5 BarA (Existing) to 6 BarA. Suction pressure is 1.11 BarA . 

What will be its effect on the compressor. Can we do this . Can it affect balancing of the compressor.

We have simulated other process parameter in ProII , everything is OK.

Please help !!

[fallah]

Hi,

 

You should submit all info about the BOG compressing and relevant refrigeration cycle...then it should be thermodynamically and hydrolically evaluated if lowering compressor discharge pressure is possible without any other change in VCU performance...  

[ankur2061]

pawanhbti,

 

You are supposed to call up your compressor manufacturer and discuss the proposed modifications with him. He is supposed to guide you on the modalities of such changes. ProII simulation cannot substitute the guidance and instructions of the manufacturer and any engineer who claims that based on simulation results he can manipulate the operating parameters is either naive or just a computer geek (not a real process engineer).

 

Regards,

Ankur.

[Art Montemayor]

Our Forum members don't know what you are doing with the compressed boil-off gas.  As such, we can't comment on what will happen in your process when you "reduce" the compressors" discharge pressure.  Additionally, just exactly HOW do you propose to reduce the discharge pressure?  Normally, a recip will easily take a discharge pressure reduction.  But how does this affect your remaining process?   I just can't know that without further information.

 

I've operated LNG tanks and the boil-off gas was either inserted into the send-out gas pipeline, or refrigerated.

As Fallah states, it could affect your refrigerating ability.  ....we just can't be expected to guess what it is that you have.

As Ankur also remimds you, why don't you consult with the designer, fabricator of the boil-off system?  That would probably be simpler.

 

If our Forum is to contribute helpful, accurate, and safe responses, it must receive accurate and detailed data regarding what you are doing,  It is called Basic Data and should include a COMPLETE description of the process - including a PFD and P&ID as well as a Data Sheet on the compressors.