Method and device for preparing synthesized gas by biomass step-wise rich oxygen gasification

This invention relates to a technique for producing synthetic gas by using biomass as raw material and oxygen-rich gas as gasification agent. First, the biomass is proceeded low temperation pyrogenicdecomposition under the condition of isolated from air. All the products are delivered into a gasification furnace, in which they react with high temperation oxygen-rich gas; so forming a high temperation oxidization zone; the heavy hydrocarbons are decomposed; after that ,the products, thus produced, are proceeded reduction by the bottom hot carbon. The tar oil in the product is less than 20mg/m3; the volume ratio of H2 and CO is (1-2):1, the synthetic gas contains H2 and CO high upto 70%, the efficiency of gasification is higher than 80%, the high quality synthetic gas can be used as fuel inchemical plant. The carbon residue from the furnace ash can be used as fuel for combustion furnace.