A moving-bed gasifier with internal recycle of pyrolysis gas

A co-current moving bed gasifier with internal recycle and separate combustion of pyrolysis gas has been developed with the aim of producing a design suitable for scaling-up downdraft gasifiers while maintaining a low tar content in the producer gas. Using wood chips with a moisture content of 7–9 wt% (db) as a fuel at a rate of 20 kg h−1, this system produced a gas with a heating value of 4500 kJ ms−3 and a very low tar content of < 0.1 gms−3.