Modeling of an experimental updraft countercurrent moving bed biomass gasifier



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Texas Tech University


A steady-state model of a countercurrent, updraft, biomass gasifier was developed and verified against pilot-plant data. The gasifier was modeled in two parts: a combustion-fasification (CG) and a pyroiysis model. Development of the CG model demonstrated that the combustion reaction was mass transfer controlled, and the water-gas shift reaction was approximately at equilibrium. The CG model was studied for sensitivity to the particle diameter, air-to-steam ration, oxygen mass transfer coefficient, and the chemical reaction activation energies. THe pyroiysis model was based on the assumption that the pyroiysis process was heat transfer limited. The linearized results for a moving-boundary, phase-change model were used to develop the rate of the pyroiysis process.