Mathematical modelling of biomass thermal degradation in a fixed bed reactor

Sammanfattning: A mathematical model of biomass thermal degradation in afixed bed has been developed. Theoretical analysis of drying,pyrolysis and char combustion has been carried out. The basicequations ofbiomass degradation kinetics, heat and masstransfer differential equations are formulated and detailedanalysis of the relevant parameters and biomass characteristicsare done and the equations of transport phenomena in a fixedbed are solved both analytically and numerically.Pyrolysis and drying kinetics (paper I), theoreticalanalysis and mathematical modeling of char combustion problemsin a fixed bed of biomass reactor (paper II), mathematicalmodelling of heat and mass transfer during drying (paper III),pyrolysis (paper IV) and char combustion (paper V) have beendone.This final work analyzes the above mentioned papers and adetailed theoretical analysis is given. The study focuses onheat and mass transfer mathematical modelling, especiallyemphasis being given to the thermal non-equilibrium conditiondeveloped due to the difference in temperature of solid fueland gas phase which lead to the formulation of differentequations for solid and gas phase separately. The mathematicalmodel results are compared with some experimental results.Keywords:Pyrolysis, fixed bed, gasification, drying,combustion, biomass, kinetic.©Gemechu Bitima, 1999