Modelling of biomass gasification with steam

Abstract

A model of biomass steam gasification in a dual fluidised bed (DFB) reactor has been developed. The model involves two stages: pyrolysis of feedstock and gasification of pyrolysis products. The biomass pyrolysis stage is described according to the multiple reactions of first-order kinetics. The model allows one to compute 8 gas species as well as char, tar and BTX yields. Gasification reactions as the second stage of the conversion process are described according to the pseudo-equilibrium approach and include the steam gasification of unreacted char and tar and secondary gas phase reactions. Based on the compositions of products, the mass and heat balances of the described process are calculated. The developed model allows for the prediction of gasification product yields and gas composition and for the calculation of heat demand for the entire process. In addition, the model enables one to predict key parameters of process performance, e.g., cold gas efficiency and steam- and fuel-related conversion rates. The model was validated with experimental results of three gasification test runs conducted with a 100 kW DFB pilot plant based at TU Wien.