Gasification Burning of Biomass

Biomass combustion for heat applications uses two stage combustion with a gasification first stage followed by oxidation of the gases in a second stage combustion, where most of the heat release occurs. These type of combustion system are gasification or log boilers. However, there has been little study of the optimisation of the gasification stage for biomass applications and this was the objective of this research.
The cone calorimeter was used in its controlled atmosphere configuration. A 180oC gas sample line was used to sample the raw gases from the rich burning gasification zone and transfer them via a heated pump and filter to the heated Gasmet FTIR, which was calibrated for 60 species. Hydrogen was computed from the CO measurements. The test facility was also operated on nitrogen in order to measure the composition of the gases evolved under heating with no combustion. were H2O, CO2, CO, formic acid, xylene, trimethylbenzene, acetic acid, formaldehyde, acrolein, acetone, furfural, methyl tertiary butyl ether (MTBE) and propanol were the major gases with other hydrocarbons. The energy in the devolatilised gases from the heated biomass in nitrogen was determined from the gas composition and flow rate and a very high conversion of energy from solid biomass into gaseous products was demonstration for a range of biomass.
The Chemical Equilibrium and Applications (CEA) software was used to predict the adiabatic equilibrium gas composition as a function of equivalence ratio for the range of biomass compositions. The predicted optimum equivalence ratios for the maximum yield of CO was in good agreement with the experimental measurements. The experimental optimum equivalence ratio for pine was 2.7. The total energy in the gases from the gasification zone showed a thermal efficiency of 80%. Major components were H2O, CO2, CO with hydrocarbons benzene, acetylene, ethylene and naphthalene.