Abstract
The aim of this work is to evaluate the energy and exergy efficiencies at the system and subsystem level of different Integrated biomass Gasification coupled to Fischer-Tropsch synthesis (IGFT) configurations. The combination of the first and second law analysis provides a comprehensive understanding of the different analyzed systems and, in particular, of the peculiarities of hot gas cleaning. Four Aspen Plus models were developed: 1) air-based gasification, cold gas cleaning (CGC), FT synthesis; 2) air-based gasification, hot gas cleaning (HGC), FT synthesis; 3) steam-based gasification, CGC, FT synthesis; 4) steam-based gasification, HGC, FT synthesis. The results highlight the higher energy and exergy efficiency of the configurations that use hot gas cleaning system or steam as gasification agent, with the highest values (52.0% and 55.5%) achieved by the fourth configuration. The gasification part of the process shows the highest exergy irreversibilities, both in terms of exergy destruction and exergy loss, due to the large chemical exergy degradation and to the char production. The results of this work provide further evidence towards the feasibility of renewable biofuels production. Moreover, this analysis gives a more comprehensive understanding of the optimal IGFT technologies to maximize the energy and exergy efficiency.