Abstarct: Abstract Turbines have played a fundamental role in electrical energy generation for a long time, and today, expansion turbines can significantly contribute to the recovery of energy and exergy lost in gas pressure reduction stations, as well as to electrical energy production. In this research, the waste heat from the constant blowdown of steam boilers in the power plant was used to preheat the gas entering the expansion turbine. Initially, the system was modeled using the SRK equation of state and solved using MATLAB and EES software. The results of the analysis were then compared and validated against the actual results of the installed expansion turbine at the Shahid Salimi Thermal Power Plant in Neka. The comparison showed that under nominal operating conditions of the expansion turbine, the modeling results had a 1% error compared to the actual data. Once the results were validated, we examined the effects of three variables—gas inlet pressure, gas outlet pressure, and inlet gas temperature—on the recoverable power from the expansion turbine. The results indicate that as the inlet gas temperature increases, both the useful work and the turbine output power increase significantly. Since changing the inlet gas temperature is more accessible and controllable, this method is the most suitable for increasing the recoverable power from the expansion turbine. Furthermore, if all required heating can be obtained from the waste heat of the plant (in this study, from the constant blowdown of the steam boiler), the total power output of the expansion turbine can be generated without consuming any additional energy, solely by recycling some of the waste heat and exergy lost in the pressure control valves of the gas reduction station. The analysis, using EES and MATLAB software, showed that the power output in the optimized state increased by 15.62% and 15.85% with changes in the inlet and outlet gas pressures, respectively, and by 78.5% with an increase in the inlet gas temperature. Finally, the results were generalized to the Shazand Arak Thermal Power Plant, where a design consisting of two 9 MW expansion turbines was proposed. It was found that without additional gas consumption and by recycling some of the energy and exergy lost in the plant, 17 MW of electrical power could be generated.