Thermo-ecological evaluation of biomass integrated gasification gas turbine based cogeneration technology

Biomass integrated gasification combined cycle cogeneration is nowadays considered as one of the most attractive technology for CO₂ emission reduction and non-renewable fuel savings. Different criterions such as primary energy savings or emission reduction are usually taken into account in order to evaluate potential energy and environmental benefits resulting from the technology. On the other hand investment decision is in most cases based on financial profitability of a project. Nowadays the biomass energy conversion plants, especially the integrated gasification ones, cannot compete effectively with fossil fuel fired technologies without an effective financial support. Therefore in many countries, in order to satisfy political priorities, there have been established supportive mechanisms that are based on different forms of financial subsidies. The subsidies are usually allocated between projects according to the amount of electricity generated, therefore promoting rather power generation than its efficiency or the influence on the depletion of non-renewable resources. In the face of growing scarcity of non-renewable natural resources, it seems to be reasonable that additional criterion is applied to evaluate biomass conversion technologies. The Thermo-Ecological Cost (TEC), which expresses the cumulative consumption of non-renewable exergy, seems to be an appropriate indicator in this matter. Moreover, to express the total effect of considered energy conversion systems the TEC should be supplemented with the data resulting from Life Cycle Analysis (LCA). In this paper the proposed methodology has been applied to the analysis of a gas turbine based cogeneration plant integrated with gasification of biomass. There are investigated different gasification technologies and configurations of CHP plant. There are taken into account atmospheric fluidized bed gasification (AFB), pressurized fluidized bed gasification (PFB) and allothermal gasification using pure steam as gasification agent (FICFB) as well as simple and combined power cycles based on a recuperated gas turbine. The performance of the plant has been investigated using the combined model developed using Engineering Equation Solver and GateCycle software. The results reveal that simple cycle with gas turbine and waste heat recovery water boiler offers better effects than combined cycle configuration. The best performance has been reported for pressurized gasification technology.