Exergy Analysis of Biomass Gasification with Steam/Air: A Comparison Study

Biomass gasification with steam/air is compared from an exergetic aspect. The comparison details include the exergy efficiencies of the product gases, tar, char and the lost part from the same biomass of both steam gasification and air gasification. Some conclusions can be obtained from the results. In the temperature range from 800°C to 1200°C analyzed in this paper, exergy efficiencies of both steam gasification and air gasification have the same changing tendency: gas exergy efficiency increases, while exergy efficiencies of tar and char decline. On the while, the exergy efficiencies of gases, tar and char of steam gasification are higher than that of air gasification. From this aspect, steam gasification is a better technology, especially when the tar and char can be efficiently used. When the gasification temperature increases, both these two technologies improve.