Exergy analysis of biomass gasification process

Based on an equilibrium RGibbs reactor model, the gasification processes of pine, straw and sawdust were simulated under the conditions of biomass containing 10%, 20% and 30% moisture content and the gasification agent temperature being 25°C and 250°C. The maximum gasification exergy efficiency and the optimum temperature increased with the increase of biomass heating value and the decrease of moisture content. For 30% moisture content biomass and 25°C gasification agent, the maximum gasification exergy efficiency of pine was 71.06%, which was higher than that of 69.87% of straw and that of 63.15% of sawdust. The optimum gasification temperatures of pine, straw and sawdust were respectively 627°C, 601°C and 544°C. The maximum gasification exergy efficiency of pine with 10% moisture content was 73.73%, which was 1.45% and 2.67% higher than that of pine with 20% and 30% moisture content. The maximum gasification exergy efficiencies of pine, straw and sawdust increased respectively 0.87%, 1.09% and 0.03% when gasification agent temperature increased from 25°C to 250°C. The results show that the biomass type, moisture content and gasification agent temperature have great effects on gasification exergy efficiency, synthesis gas composition and its low heating value. The gasification performances can be improved by reducing biomass moisture content and increasing gasification agent temperature.