Performance research on a power generation system using twin-screw expanders for energy recovery at natural gas pressure reduction stations under off-design conditions

Abstract This paper has focused on the performance study of a power generation system for energy recovery at natural gas pressure reduction stations under off-design conditions. First, an experiment was carried out to test the off-design performance of a twin-screw expander prototype. Two empirical models based on the experimental data were built and validated to predict the inlet volume flow rate and the isentropic efficiency of the expander, separately. Then, a case study was presented at a natural gas pressure reduction station located in Jinan, China. The method of selecting the optimal inlet volume flow rate was presented and the thermodynamic analysis of the power generation system was performed, based on the operating data in a typical day. The results indicated that the total power output of the system based on the twin-screw expander prototype was around 147.33 kW·h in a typical day. Interestingly, high-pressure gas produced about 0.16 kW·h of electricity per cubic meter. Meanwhile, a very superior cold energy resource with a minimum temperature of −72 °C could be obtained incidentally. Moreover, the power generation system ran with high efficiency for most of the time, and the average energy and exergy efficiency of the system reached 96.09% and 66.00% respectively.