1 reply to this topic

[shan]

Hi Everybody,

 

We are considering a centrifugal compressor with LP section and HP section driven by a single turbine. 

 

LP suction is from a 150 psig production separator and discharges 450 psig.  HP suction is from LP discharge joined by a 450 psig production separator gas and discharges at 1100 psig.  The design capacity is 50 MMSCFD for both LP section and HP section. 

 

The problem is there are not much LP gas (about 2 MMSCF) at the early production phase. The question is if and how much we have to letdown gas from 450 psig to 150 psig for balancing the compressor LP section and HP section operation.

[prengr]

Dear shan,

 

It seems that the LP gas capacity(2 MMSCFD) at early production phase is too limited based on normarl operation phase(50 MMSCFD). This compressor's minimum turndown ratio is 2:50(=1:25). In my opinion for this wide turndown ratio, it is better that you should install a total recycle by-pass valve that can cover from 0% load to 100% load of compressor capacity.

 

For your reference, i explain my experience as below.

1) Theoretical turndown ratio = 1:34

2) Max capacity = 14,000 Nm3/hr(12 MMSCFD), Single stage compressor

3) Differential pressure = 9 bar(130 psi)

During start-up, this compressor should be operated at almost no load and our experienced engineering team and operating team made a decision that is installing a total recycle by-pass valve for easy and stable start-up and nomal operation.

 

Thanks.