Solid Biomass to Medium CV Gas Conversion With Rich Combustion

Abstract

Abstract A modified cone calorimeter for controlled atmosphere combustion was used to investigate the gases released from fixed bed rich combustion of solid biomass. The cone calorimeter was used with 50 kW/m2 of radiant heat that simulated a larger gasification system. The test specimen in the cone calorimeter is 100mm square and this sits on a load cell so that the mass burn rate can be determined. Pine wood was burned with fixed air ventilation that created rich combustion at 1.5–4 equivalence ratio, Ø. The raw exhaust gas was sampled using a multi-hole gas sample probe in a discharge chimney above the cone heater, connected via heated sample lines, filters and pumps to the heated Gasmet FTIR. The FTIR was calibrated for 60 species, including 40+ hydrocarbons. The hydrogen in the gas was computed from the measured CO concentration using the water-gas shift reaction. The exhaust gas temperature was also measured so that the sensible heat from the gasification zone was included in the energy balance. The GCV of the pine was 18.8 MJ/kgpine and at the optimum Ø the energy in the rich combustion zone gases was 14.5 MJ/kgpine, which is a 77% energy conversion from solid biomass to a gaseous fuel feed for potential gas turbine applications. This conversion efficiency is comparable with the best conventional gasification of biomass and higher than most published conversion efficiencies for coal gasifiers. Of the energy in the gas from the rich combustion 35% was from the CO, 20% from hydrogen, 35% from hydrocarbons and 10% sensible heat. Ash remained in the rich burning gasification zone. As the biomass is a carbon neutral fuel there is no need to convert the gasified gases to hydrogen, with the associated energy losses.