In this paper, a gas pressure regulating station is mentioned. In order to generate power, the throttling valve system has been replaced with turbo expanders. Also, heat exchangers are utilized after expansion process with the purpose of producing refrigeration. Furthermore, a computer code has been developed based on Matlab software and an exergy analysis of this system has been conducted. To have a better insight of this study, the effects of key parameters such as 1st turbine pressure ratio (R), 1st turbine inlet temperature (T2), 2nd turbine inlet temperature (T4), turbine isentropic efficiency, and heat exchanger efficiency on the total exergy destruction and total exergy efficiency have been performed. The exergy analysis revealed that the preheater is the most exergy destructor in comparison to other components. This is due to the high temperature difference between working fluid and combustion temperature. In addition, it was found that an increase in T2 causes a reduction in the total exergy efficiency of the system, while an increase in T4 has a converse effect. Variation of R shows that for a specific value the system exergy efficiency has a maximum amount. Also, an optimization using a genetic algorithm has been conducted to find the optimal solution of the system. Due to the optimization results, the mean exergetic efficiency of the system is 78%. The optimized decision variables are R≈2, T4 ≈ 2-5 ºC and T2=T1. After optimization procedure for the mentioned cases, because of inappropriate effects of preheater utilization, expressed above, the turbines pressure ratio are set to values which finally lead to preheater omitting by the genetic algorithm.

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