Exergoeconomic analysis of natural gas fired and biomass post-fired combined cycle with hydrogen injection into the combustion chamber

A natural gas firing and biomass post-firing combined cycle is proposed and analyzed with thermodynamics and exergoeconomics. To enhance performance, hydrogen is produced in a proton exchange membrane electrolyzer and when there is temporarily no market for hydrogen is injected into the combustion chamber of the natural gas firing and biomass post-firing combined cycle with hydrogen injection. Advantages and disadvantages are reported for the cycle with hydrogen injection (NFBPC-HI) relative to the cycle without hydrogen injection (NFBPC-H) with an equivalent biomass flow rate. In this case, the natural gas flow rate reduces by 46% through hydrogen injection. The plant energy efficiency with hydrogen injection decreases by 36% and the exergy efficiency by 37%. The exergy destruction rate decreases and the exergy loss rate becomes slightly lower with hydrogen injection. Regarding environmental impact, hydrogen injection decreases the plant CO2 emission rate by 27%. Also with hydrogen injection, the exergy destruction cost rate decreases and the exergy loss cost rate declines slightly. The product cost using hydrogen injection decreases by up to 9% point as does the exergoeconomic factor for the biomass integrated post-firing combined cycle with hydrogen injection, especially at higher gas turbine inlet temperatures and lower compressor pressure ratios. Overall, the plant with hydrogen injection exhibits some better facets of thermodynamic and economic performance and cleaner production, e.g. lower exergy destruction and loss rates and CO2 emissions and lower total unit product economic costs, although it has lower energy and exergy efficiencies.