Thermodynamic analysis of a biomass anaerobic gasification process for hydrogen production with sufficient CaO

Abstract

Based on CO 2 acceptor gasification technology, a biomass anaerobic gasification technology for H 2 production was proposed. Utilizing thermodynamic equilibrium calculation software FactSage 5.2, the rules of biomass/CaO/H 2O and C/CaCO 3/air reaction system involved in this H 2 production technology were studied. The results show that the increase of CaO can obviously increase H 2 mole fraction in C/H 2O reaction products. When the mole ratio of CaO to carbon ([Ca]/[C]) is 1, H 2 concentration may achieve the maximum value. The H 2 amount obviously increases, and H 2 mole fraction decreases slightly with increasing reaction pressure in a specific range. Higher reaction temperature obviously decreases the amount and mole fraction of H 2. There are different maximum temperatures which are suitable for H 2 production under various pressures. Increasing of the mole ratio of H 2O to carbon of biomass ([H 2O]/[C]) is helpful for H 2 production. But the H 2 mole fraction is reduced with the increasing of [H 2O]/[C] when it exceeds 1.5. The calculations of linear sensitivity coefficient show that [H 2O]/[C] has the greatest influence on H 2 production efficiency, the influence of reaction pressure and temperature are also obvious. Compared with the coal gasification for H 2 production, the excess of H 2O in biomass anaerobic gasification system is relatively obvious. Lower reaction pressure is helpful for CaO regeneration in the C/CaCO 3/air reaction system, and there are different minimum temperatures which CaO regeneration needs under various reaction pressures.