Energy destruction in Iran's natural gas pipe line network

Abstract

Natural gas is transported from production sites to end users through high pressure (5-7 MPa) transmission pipelines. At a consumption point or when passing into a lower pressure pipeline, the pressure of the gas must be reduced. This pressure reduction takes place at City Gate Stations (CGS). Currently in all of Iran's CGSs, valuable pressure exergy (potential, energy) contained by the high-pressure natural gas is lost to the environment in throttling valves (expansion valves). In this study, based on a comprehensive program, the inlet and outlet properties and daily flow rates of natural gas through Khorasan province (Iran) CGSs were measured and recorded for a whole year. Based on these data, the amount of energy lost to the environment was calculated. It was found that the yearly average mass flow rate in Khorasan CGSs is 90.5 kg/s, and average energy destruction is 13,240 kW. Assuming a conversion efficiency of 75%, one can extract 9,930 kW of electrical power. Based on Iran's average daily natural gas consumption of 336 × 106 m3/day and assuming the same conditions at all CGSs as at Khorasan, 762 MW of electrical power could be generated by capturing the lost pressure exergy flowing through all of Iran's CGSs.