Theory And Computation On The Optimal Gasification Of Biomass In The Fluidized Bed Gasifier

The thesis describes kinds of physical chemical model and numerical methods that predict the gasification process in the fluidized bed gasifier of the biomass, such as haulm and wood. The simulation of the biomass gasification in the fluidized bed is modeled through thermodynamics and kinetics methods. The fluidized bed gasifier is predigested as an axis-symmetrical emulational reactor according as its geometry configuration. The complex chemical reactions are expressed by a set of coupling partial-differential governing equations. The governing equations which are based on the Navier-Stokes equation are solved with SIMPLE/SIMPLEC algorithm in finite volume way. According to the simulation result, the factors affecting the component of product gas are discussed such as the input velocity of biomass, air and steam and the diameter of biomass particle. Some phenomena such as the tracks of the biomass particle are also discussed.The thesis tries hard to give advices for experimentation from the optimization of the fluidized bed gasifier and the adjusting of reaction parameter. The aid is to realize the optimal gasification of biomass in the fluidized bed gasifier. Considering practicability, the thesis focuses on the kinetic behave of pine sawdust in the columned reactor and the flow and radiation of air, steam and product gas under the influence of air and steam.In thermodynamics field, the thesis makes an assumption of "Four Regions". The program named of FBGB (Fluidized Bed Gasification of Biomass) is compiled based on language C and DELPHI. The program can offer fifteen values such as the component of product gas, the heat value of product gas and tar. The thesis gives the affecting rules of each parameter by analyzing the simulation results with experimental results.In kinetic field, the thesis uses FLUENT which is the CFD commercial software, and builds the non-premixed combustion model. κ-ε-g model and Six Flux radiation model are used considering of buoyancy effect. And the thesis analyzes the particle track. It helps proving the "Four Regions" assumption, and offering mensurable evidence for the partition of each area.