Study On Biomass Gasification In Fixed Bed

With the shortage of fossil fuels and severe environmental pollution, biomass, as a clean, storable and transmittable renewable energy resource, has been attached to great attention around the world.In this paper, the pyrolysis characteristics of biomass, coal and their blending were studied by thermal gravimetric analysis (TGA). The effects of biomass species, heating rates and mixed proportions were studied. The results show that, comparing with coal, the ignition temperature of devolatilization and complete pyrolysis temperature of biomass are lower, the occurring time of exothermic peak was earlier, and the complete pyrolysis time was shorter. The blending of biomass and coal has lower ignition temperature of devolatilization than coal, with the increasing of biomass proportion to coal, the ignition temperature of devolatilization and complete pyrolysis temperature decrease. This thesis discussed product distribution in various temperature ranges using the fixed-bed pyrolyser.Two sets of biogas processing unit were designed, they are fixed-bed updraft gasifier, fixed-bed downdraft gasifier and gas cleaning system. The gasification test of biomass (cotton stalk and wheat stalk) and co-gasification test of biomass and coal were carried out on the two sets of biogas processing unit. By means of gas chromatogram and other equipments, this paper tested and verified main technical performances, such as hearth temperature distribution, gas ingredient, net calorific value, impurity content, etc., and analyzed influences on gasification effect of different biomass, granularity, hearth temperature, air flow rate and other factors. The comparison experiment results show that, the co-gasification of biomass and coal has higher gasification intensity and gas rate than the gasification of biomass, but has more tar.This thesis realized the fixed-bed updraft biogas processing unit large-scalization, and the syngas was used to space heating. Using cotton stalk as stock feed, the gasification intensity of the large-scale biogas processing unit is about 120 kg/(m²Â·h), the syngas rate is about 3.0 m³/kg, LHV of biogas is 4413 kJ/m3, the ratio of H₂ to CO is at the range of 1:2.48～1.17:1, and gasification efficiency is about 77%. The syngas was used to make heat for the field of 2600 m² in winter, and the room temperature can reach above18℃.