Design and experimental study of a two-stage pilot scale biomass fixed bed gasifier

Abstract

Two stage biomass fixed bed gasifier has the advantage of lower tar content and higher calorific value of producer gas. This paper presented design and experimental investigation of a 190KWe (nominal) pilot scale biomass fixed bed gasifier using a double air stage downdraft approach. Wood chips were used as feedstock. The results demonstrated that due to the secondary air supply, a temperature as high as 900oC in the oxidation zone for a better tar cracking. Use of both stirrer and reciprocating grate avoided bridging and channeling. A direct connection of the gasification chamber and charcoal cooling chamber could minimize gas storage space to avoid deflagration. The average value of the composition was about 16.6% (CO), 2.3% (CH4), 16.1% (H2), 13.8% (CO2) and 0.4% (O2) whereas the average calorific value was 4.7MJ/ Nm3. The maximal LHV was 5.28 MJ/ Nm3 when the frequency of draft fan and secondary air supply were 45 Hz and 54 Nm3/h respectively.