BIOMASS CATALYTIC STEAM GASIFICATION - Thermodynamics Analysis and Reaction Experiments in a CREC Riser Simulator

A thermodynamic equilibrium model based on evaluations involving C, H and O element balances and various product species up to C6 hydrocarbons is reported in this study. This model establishes the effects of biomass composition, temperature, and steam on the various gas product molar fractions. On this basis, most significant parameters determining the chemical interconversions and distribution of chemical species are identified. Based on the proposed equilibrium model and using glucose as model biomass species [C6 H12 O6], an optimum gasification temperature close to 800 °C and a steam/biomass ratio between 0.5 and 0.7 g/g is established.

This study has the special value of comparing thermodynamic equilibrium predictions with experimental data obtained in a CREC Riser Simulator using a fluidizable Ni-Al2O3 catalyst. Results are relevant for scaled-up gasifiers. They show that for reaction times longer than 30 seconds chemical species are essentially equilibrated and that the proposed model does provide adequate description of various product fractions. Data obtained also demonstrate the shortcomings of equilibrium models for gasifiers with reaction times shorter than 10 seconds and the need of non-equilibrium models to describe gasifier performance at such conditions.