Simulation and Economic Analysis of Combined Desalinated Water and Power Generation from Associated Gases of Cheshmeh Khosh

Flaring of gases often having a high heating value results in considerable economic and energy losses in addition to significant environmental impacts. Power generation through combined gas and steam turbine cycles may be considered as a suitable flare gas recovery process. Thermal desalination of seawater is a process that requires a considerable amount of heat; hence, it may be used in the downstream section of power generation cycles. Energy is the largest part of the cost of the water generation of all desalination processes. The energy cost of the thermal distillation of seawater is close to 50%–60% of the water generation costs. In the current study, the generation of power and desalinated water through the gas turbine cycle, steam cycle, and multistage flash (MSF) method using the flare gases of Cheshmeh Khosh is investigated. The economic parameters related to the different scenarios considered for the production of power and water are evaluated in this work. According to the economic evaluation carried out, the most economically profitable scenarios for the investigated cogeneration plant is generating as much as possible power in the steam turbine and using the remaining heat in the low-pressure outlet steam for the MSF desalination process. The results show that by increasing the steam turbine outlet pressure from 3 to 78 bar, the power generation and the water generation change from 697 to 581 MW and from 1557 to 2109 m3/h respectively. Also, by increasing the outlet pressure of the steam turbine from 3 to 78 bar, the total capital cost increases from 1177 to $1192 million, and the operating cost changes from 117.85 to $117 million per year. Finally, the operating profit decreases from 300 to $50 million per year, and the payback period extends from 3.92 to 4.75 years.