Thermal Plasma Gasification Of Biomass Tar To Syngas

The tar produced in the process of biomass gasification not only corrodes the pipelines and equipments,pollutes the environment,but also reduces the efficiency of biomass gasification.The thermal plasma,which has its special characteristic of high temperature,can also produce activated particles with high energy density and high reactivity.We used thermal plasma with CO2 to gasify biomass tar compounds and real sample for the first time,which could provide a new choice for improving biomass gasification efficiency and innocent treatment of tar.Toluene and benzene were selected as the substitutes of biomass tar.The effects of CO2 flow rate and input power on the gasification process were investigated.The experimental results showed that the main production gases of thermal plasma with CO2 were CO and H2,including a small amount of CO2.The carbon conversion efficiency was 79.74%and the specific energy consumption was 6.17 kWh/Nm3 when the toluene feed rate was 9.70 g/min,CO2 flow rate was 0.96 Nm3/h and the input power was 12.60 kW.The maximum of carbon conversion was 92.84%and the specific energy consumption was 5.73 kWh/Nm3 in the gasification process of benzene when the benzene feed rate was 9.88 g/min,CO2 flow rate was 0.96 Nm3/h and the input power was 12.96 kW.It could be deduced indirectly from thermodynamic equilibrium calculation that the temperature of gasifying toluene is 1840 K-2600 K and the temperature of gasifying benzene is 1580 K-2850 K.The mixture of benzene and naphthalene was applied as biomass tar surrogate.Experiments were carried out to investigate the influences of CO2 flow rate,naphthalene mass fraction and input power.The results demonstrated with the increase of naphthalene mass fraction,the gasification efficiency of the mixture,the carbon conversion efficiency and the gas yield decreased gradually,while the specific energy consumption of the syngas increased gradually.As a result,the carbon conversion efficiency was up to 90.92%and the specific energy consumption was 6.87 kWh/Nm3,with a naphthalene mass fraction of 10.2%,CO2 flow rate of 0.96 Nm3/h and the input power of 14.73 kW.It could be deduced indirectly from thermodynamic equilibrium calculation that the temperature of gasifying the mixtures of benzene and naphthalene is 1500 K-3034 K.The physical and chemical properties of biomass tar were analyzed.In addition,experiments were performed on the variables which included CO2 flow rate,input power and water content of raw material.The experimental results showed that the water content of biomass tar was 74.2%and the relative amount of naphthalene in its cormponents was the highest,up to 31.52%.Integrated yields of H2 and CO and specific energy consumption,the optimum condition of gasifying mixture of biomass tar and benzene was CO2 flow rate of 0.69 Nm3/h and the input power of 11.95 kW,and the maximum production of H2 and CO were 62.71 g/kg and 754.03 g/kg and the specific energy consumption was 7.63 kWh/Nm3.The water in the tar mixtures could promote the gasification reaction to some extent.Nevertheless,too much water would lead to the worse gasification effect.