Two-stage fluidized bed gasification enhanced with oxidative pyrolysis for low-tar producer gas from biomass

Oxidative pyrolysis of fuel was adopted to configure an advanced two-stage fluidized bed gasification system, aiming to produce low-tar producer gas efficiently. A series of tests were carried out to investigate the effect of oxygen allocation in supply on gasification of pine chips in terms of both efficiency and producer gas quality. Compared with the case without pre-oxidation, coupling oxidative pyrolysis increased gas volume fraction of CO, CH4, and CnHm while decreasing that of CO2 and H2 in the produced gas. Further analysis showed that adopting oxidative pyrolysis reduced fuel gas yield, but the tar in the produced gas was lighter. The generated tar is easily transformed into small-molecule combustible gas by the catalytic action of hot char, thus increasing the calorific value of product gas. The long-term operation of the pilot plant presents a great steady continuous running with a minimum tar content in the producer gas of 1.3 g/Nm3. The above-mentioned results thus well verified the technical advantage and feasibility of the two-stage fluidized bed gasification with oxidative pyrolysis.