Numerical Simulation Research Of Co-Gasification Of Biomass And Coal In A Fluidized Bed

Biomass energy is a abundant reserves of renewable energy. Gasification is one ofthe most effective way for the usage of biomass energy. Biomass is taken as a populartechnical route to produce fuel gas. But biomass gasification alone have manyshortcomings such as supply changes with the seasons, fluidized difficult inside thefluidized bed and high tar content in the syngas. Co-gasification of coal and biomasscan improve the biomass supply problem, increase the gasification temperature topromote tar crack and also improve the fluidization characteristic inside the fluidizedbed. This paper take co-gasification experimental fluidized bed as a subject for study,use CFD software Fluent to establish the fluidized bed gasification model, performcold-state simulation and hot-state simulation for the co-gasification fluidized bed.In the part of cold-state simulation, we study the effect of different structure ofdistributor to the airflow uniform distribution, then we study the flow characteristic ofparticles in the fluidized bed. The results indicate that the best structural distributorwhose holes are equilateral triangle arrangement and0.5mm in diameter in thisexperimental model and operating condition. The particles present a “upper-dense andlower-dilute” flow. The particles near the wall move downward, got a low velosity and ahigh concentration. The particles in the furnace central move upward, got a highvelosity and a low concentration. The particles present “center-wall-center” and“core-annular” flow pattern.In the part of hot-state simulation, we carry a major study of gasificationcharacteristics about biomass gasification and co-gasification of biomass and coal.Through the simulation results, the effects of equivalence ratio and lignite blend radioon the temperature distribution and concentration of major component in syngas havebeen studied. The reliability of model have been confirmed through the comparisonbetween the experimental value and the simulation value. The final results shows that:the model in this paper is suitable to predict the gasification characteristics of biomass gasification and co-gasification of coal and biomass satisfactorily. The results canprovideus theoretical references to the further research of fluidized bed gasification.