Q & A > Question Details
One of our centrifugal compressors in recycle gas service (93% H2; 6% CH4) was designed to perform for 4 cases, SOR; EOR conditions, H2 service and only N2 service. However, during the design phase the differential pressure data given the vendor was uniform and corresponded to that envisaged for N2 service. During commissioning, the actual DP obtained across the system is way less and the compressor is operating on a very low RPM and more towards the stonewall, even though gas molecular weight and the operating parameters have reached their near design values. What are the probable solutions to this problem, so that we can push the machine towards its normal operating envelope and increase the flexibility of plant operation? Will trimming of impellers help?
11/09/2019 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
You could trim impellers but you may wish you had the extra DP when the unit has been operating a while and system DP has increased. Better options are to either use the spillback valve (install one if the unit was designed without one) or just run higher H2 circulation than you need. Running extra recycle hydrogen doesn't normally have any negative effects other than some extra energy consumption and it can cause a modest improvement in catalyst life.