A numerical investigation of CO2 gasification of biomass particles - analysis of energy, exergy and entropy generation

Much attention has been recently paid to biomass CO2 gasification as a means of CO2 utilisation and mitigation. In this study, a novel low-cost theoretical tool based on thermodynamic equilibrium, and a computational fluid dynamics model are developed to analyse gasification of biomass particles in a CO2 atmosphere. It is shown that increases in C/CO2 enhances the production of hydrogen and results in improving energy and exergy efficiencies of the process. In keeping with that reported for air gasification, increasing the moisture content of biomass intensifies hydrogen production and reduces the yield of CO. The effects of particle temperature on the gasification process are further explored through a spatiotemporal analysis of the gaseous chemical species. In particular, the results reveal that higher initial temperatures of biomass at the entrance of the reactor lead to stronger generation of chemical entropy. Also, the time trace of entropy generation is found to be affected significantly by the initial temperature of the biomass particle. Importantly, the relation between the particle temperature and total entropy generation is observed to be highly nonlinear. Further, it is found that the irreversibility of chemical reactions is the most significant contributor to the total entropy generation in the process