COMPRESSOR STATION RECYCLE SYSTEM DYNAMICS DURING EMERGENCY SHUTDOWN

Transient phenomena associated with gas recycling during compressor em ergency shutdown (ESD) have been studied both experimentally an numeri cally. A scaled-down laboratory test rig has been constructed to study the influence of various underlying parameters on ESD operation. Thre e different configurations representing different design scenarios wer e tested. The first configuration has a long recycle system with a vol ume capacitance representing an air-cooled heat exchanger in the recyc le loop, and the recycle valve located close to the discharge side. Th e second one is the same as the first except the recycle valve is plac ed close to the suction side. In the third configuration, the cooler c apacitance was removed from the recycle loop and the piping capacitanc e on the discharge side was further reduced. Shutdown tests were carri ed out from different steady-state initial conditions varying the recy cle valve opening time, and the synchronization time between the compr essor ESD signal and valve opening signal. Numerical simulations based on the solution of the full one-dimensional conservation equations us ing the method of characteristics were also conducted for the above co nfigurations. Good agreement was obtained between measurements and sim ulation results. Numerical simulations were used to analyse other case s, which were not investigated experimentally, to further investigate the interaction between equipment and flow parameters. Results indicat e that the valve prestroke time is more crucial than the stroke time a nd that it should be made short to avoid surging the compressor during ESD. Locating the recycle valve as close as possible to the suction o r discharge of the compressor helps reduce unit surge during shutdown.