To prevent Natural Gas (NG) frozen during pressure reduction process, a heater is contrived for preheating NG. In this study, a novel system is suggested to supply part of heat demand of a NG City Gate Station (CGS). The system consists of a heat pump in which the compressor input work is supplied by the turbo-expanders. In the proposed system, pressure reduction is carried out by turbo-expanders instead of Regulator Valve (RV) to recover the energy of high pressure NG. The recovered energy by turbo-expanders meets the heat pump cycle work demand. A CGS is selected as a case study, and the suggested system is assessed in terms of energy, exergy, and economics. The amount of the annual fuel savings is calculated 2.42×106 kg (70.08%). Exergy analysis shows that the most exergy destruction occurs in the RV and heater. The exergy factor of the proposed system in the days that the system works, is about 2.2 to 5.1%. Based on the economic analysis, the value of simple payback period and discounted payback period are calculated 2.63 and 3.08 years, respectively. The annual revenue that comes from saving fuel is 310,000 $/year based on the current price of NG.

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