Modelling and simulation of the biomass fired dual fluidized bed gasifier at Guessing/Austria

Abstract

l steady state model of the gasification reactor of a dual fluidized bed biomass steam gasification system has been developed. The gasification reactor is operated in bubbling regime. The model distinguishes two zones: dense zone and freeboard zone. The dense zone is the bubbling bed and is modelled with modified two phase theory while freeboard is modelled as a plug flow reactor. The main fuel is biomass (wood) and is introduced into the dense zone. Biomass is modelled as a homogeneous matrix of C, H, and O. The solids within the dense zone are considered to be well mixed while the gases are in plug flow regime. Energy balance is solved globally in each zone. Results show that the wood is only partly converted in the gasifier. The gas composition profile and temperature profile predicted by the model is in good agreement with the values measured at 8 MW (fuel power) plant in Guessing/Austria.