Study On Simulation Of Biomass Gasification In Fixed-bed

Base on biomass gasification of the theory, A transient model has been developed fora fixed-bed wood gasifier by applying a two-step pyrolysis mechanism in which primarytars are initially formed and the cracked into secondary tars and other combustible gases.The model describes the complex physical and chemical processes tacking place in thereactor by the use of mass and energy balances, together with lot of information about ratesof chemical reactions and physical transport processes. The computer model is capable ofpredicting the gas composition profile and temperature profile along with the axis of thegasifier. Programming written by Fortran language,data processing with softwareTecplot360.Study on the updraft fixed-bed wood gasifier with air, Air supply rate7kg/h, theconditions of the gasification medimum air temperature form300K to750K, predicting thegas composition profile and temperature profile along with the axis of the gasifier and thegasification medium temperature affect on gasification parameters. Simulation resultsshow that Gasification efficiency increased with the temperature of the gasificationmedium.Air temperature is450K,CO mole fraction is15.46%,H2mole fraction is5.27%,Net heating value of gas4.31MJ/m3,Total Energy out37.95MJ/h,Cold gasefficiency48.55%, Higher the concentration of tar in the gas produced3.68%. Adowndraft fixed-bed wood gasifier with air, The results show that a higher air supply rateincreases the combustion zone temperature and reduces outlet tar levels.Air supply rate9kg/h, Net heating value of gas5.89MJ/m3，Total Energy out88.59MJ/h,Cold gasefficiency64.58%, the concentration of tar in the gas produced reduced to:0.89%. Aupdraft fixed-bed wood gasifier using high temperature steam, study on high temperaturesteam temperature form1200K to1500K, Simulation results show that the efficiency ofgasification, gas calorific value and the output power with the temperature of gasificationmedium increased. When steam temperature is1500K,Net heating value of gas11.35MJ/m3,High the concentration of hydrogen in the drying gas produced35.0%, So canbe used for the preparation of high concentrations of hydrogen.In the self-heating system,downdraft fixed bed gasification to the updraft fixed-bed gasification efficiency improve8%-15%.