Innovative modification process of a natural gas power plant using self-sufficient waste heat recovery and flue gas utilization for a CCHP-methanol generation application: A comprehensive multi-variable feasibility study

Waste heat recovery holds significant importance in the context of natural gas power plants, as it facilitates the utilization of energy loss, leading to enhanced overall performance and mitigating adverse environmental effects. By harnessing and employing waste heat, power plants possess the capability to modify and optimize their operation, making a substantial contribution toward sustainable power/energy generation. Therefore, this study proposes a novel and eco-friendly approach to utilizing the flue gas emitted by a natural gas power plant. In addition to recovering waste heat, this method involves harnessing the flue gas for methanol production. The proposed system consists of an organic Rankine cycle, and absorption chiller, heating provider units, an electrolyzer for hydrogen generation, and a methanol synthesis unit. The novel method is implemented through computer -aided simulation using the Aspen HYSYS software and is subjected to an extensive analysis encompassing energy, exergy, environmental, and economic viewpoints. The simulation results exhibit producing 2712 kg/h of methanol with a purity of 99.97 mol%, 395.67 kg/s of hot water, 378 kg/s of chilled water, and 12253.57 kW of power. In this process, the energy and exergy efficiencies are 94.35% and 31.74%, respectively. Parametric study results demonstrate that reducing the gas turbine pressure and increasing the working fluid temperature in the evaporator of the absorption chiller cycle leads to improved exergy efficiency. Moreover, the multigeneration scenario shows a carbon dioxide footprint of 0.1564 kg/kWh and a total unit cost of product of 0.0485 $/GJ.