| A small type downflow fluidized bed reactor for biomass fast pyrolysis suitable for research in laboratory leval was designed. The calefaction of this device was divided into tow structures, the pyrolysis was considered occurring in the upper oven, and the second thermal cracking occurred in the lower oven with the tar content diminishing. This paper deals with fast pyrolysis of sawdust and peanut shells in the down flow fluidized bed reactor. The effect of pyrolysis temperature, carrier gas flowrate, the particles diameter and the residue nature on the fast pyrolysis characteristics was studied in detail, and test for the purpose of optimization of operational parameters. The experimental results showed that the increasing temperature is specially important to increase the production of gas, the raw gas second thermal cracking technology could improve substantially the gasification process. The tar content in the gas producer was diminished to 10.35%, and gas production rate was increased to75.62%. The pyrolysis products were analyzed, and the influences of the heat and mass transfer properties of the porous structure of biomass were elementarily discussed as well. A one step-multi pyrolysis model was proposed. The kinetic parameters of biomass pyrolysis were obtained according to the experimental data and lines. All the results are very useful to design and develop a new biomass pyrolysis device.
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