Quasi-equilibrium thermodynamic model with empirical equations for air–steam biomass gasification in fluidized-beds

Abstract

Gasification is one of the most promising technologies for converting biomass into a fuel. This study presents a simple and practical biomass gasification model based on thermodynamic equilibrium to find effective operating conditions of the air–steam gasification system in fluidized-beds. The carbon conversion fraction empirically obtained was involved in a global gasification reaction. Two empirical equations as the non-equilibrium factor expressing the deviation from equilibrium were derived as the function of the equivalence ratio (ER) from 43 experimental data sets of various operating conditions and different feedstocks. One energy balance was also solved for determining the gasification temperature (T). After the producer gas composition with respect to ER and steam to biomass ratio (SBR) was obtained from the air–steam biomass gasification (ASBG) model, process performances such as lower heating value, heat efficiency, net heat efficiency, and H2/CO molar ratio were evaluated. An effective operating area was suggested from the contour plot of the process performances with respect to ER and SBR in the auto-thermal gasification temperature from 700 to 830°C.