AbstractNatural gas is transported through transit pipeline at high pressures (5–7 MPa) from production sites to end users. In a place of consumption or at passing into a lower pressure pipeline, the pressure of the gas must be reduced. This pressure reduction takes place in places which are called city gate stations (CGSs). Currently, in all Iran's CGSs, valuable pressure exergy (potential energy) of natural gas flow is destroyed in throttling valves. In the current study, based on a comprehensive programme, inlet and outlet properties of natural gas flow and daily flow rate through seven Khorasan Province (Iran) CGS were measured and recorded for a whole year. Based on these data, the amount of energy which could be generated using a combined heat and power system was calculated. The combined heat and power system consists of a preheat section, a turbo expander and an additional prime mover. The amount of electricity generation for the system has been calculated. The results show that 20˙5 MW electrical...