Advanced exergy and advanced exergoeconomic analyses of biomass and natural gas fired combined cycles with hydrogen production

A biomass integrated co-fired combined cycle is proposed, in which hydrogen is produced using steam turbine output power. The product hydrogen, when there is temporarily no market for it, is injected into the combustion chamber to raise efficiency and lower fossil fuel consumption. Advanced exergy and advanced exergoeconomic analyses are applied for the first time to this plant. The following benefits are obtained: hydrogen injection results in 67% less fossil fuel consumption and 19% less CO2 emissions, while the energy efficiency decreases by almost 37% and the exergy efficiency by 39%. Also hydrogen injection decreases the plant's total exergy destruction and, more importantly, total exergy loss. Similarly, the exergy destruction cost and exergy loss cost rates are lowered by hydrogen injection into the combustion chamber of the co-fired combined cycle. The total unit product cost for the combined cycle with hydrogen injection is lower than for the cycle without hydrogen injection. Finally, the relative cost difference and exergoeconomic factor both increase with hydrogen injection. This demonstrates that there are higher component purchase and maintenance costs relative to the exergy destruction costs for the corresponding components in a biomass integrated co-fired combined cycle with hydrogen production and injection into the combustion chamber. Advanced exergy and advanced exergoeconomic analyses yield some contradictory results relative to common analyses.