Deactivation and Energy Analysis of Char Catalysts in Biomass Gasification Systems

One of the major barriers to gasification is the need for elimination of tars that are generated in thermochemical conversion processes. While metal catalysts can be used for tar decomposition, and cheaper alternative is char. Deactivation of char catalysts has been studied and these deactivation rates have been applied to a model for a gasification system. The calculations and experimental data presented here show that if the char from a gasifier is recycled to a tar reformer then some char deactivation will take place, but the activity will not fall below 40% of its initial activity. The energy penalty for diverting char, a potential heat source, to a catalytic reactor has been accounted for. This was done by comparing the heating value of char to the heating value of syngas generated from reforming tar using the char as a catalyst. At high gasification temperatures, when tar production in the gasifier was low, the char had a higher heating value than the syngas that was produced from tar reforming. At low temperatures, the heating value of the syngas exceeded that of the char combustion, which implies an overall energy benefit.