Simulation Study On Biomass Gasification In Entrained Flow Gasifiers

With the deterioration of energy and environmental situation, biomass has attracted increasingly great attention from the world. Bomass high-temperature entrained flow gasification is regarded as the best choice for biomass indirect liquefaction technology for the high efficiency, low tar yield and good adaptability of raw materials.In this paper, a kinetics model of biomass entrained flow gasification was established based on the characteristics of the process and then simulated the gasification process in detail. The results demonstrate that:under the given conditions in this paper, the optimum operation data is the temperature of1300℃, residence time of2s, H2O/biomass of0.1and O2/biomass of0.2. Under the optimum conditions, the carbon conversion of biomass gasification canbe higher than95%and the effective gas composition can be more than70%; Residence time and temperature affects the gasification extend a lot that finally affects the composition of the produced gas. While O2/biomass and H2O/biomass is the key factor to the carbon combustion reaction and water-gas shift reaction which affect the gasfication process a lot.In order to solve the low carbon convertion rate and the unsuitable H2/CO of the traditional gasification mode, a new type of gasification mode was proposed based on the separation of thermal crack products and division of gasification process. The former kinetics model was used to simulate the new mode and find that the new mode can improve the carbon conversion rate and H2/CO a lot; the distribution of residence time between the two of the division gasification processes affects the results a lot; the time of the medium addition is another factor that affect the produced gas composition.In order to confirm the reliability of simulation results, a bench-sacle entrained flow biomass gasification system was built and the experiment of biomass steam gasification was performed on the system, different gasification temperature and H2/CO was studied and the results was compared with the simulation results. It’s proved that the simulation results get from the mode of this paper agree well with the experiment and the gasification model in this paper isreliable except for some deviation. The key factor of the deviation of the simulation is the assume that the thermalcrack process finishied in a flash moment. Ignoring the tar producing in the thermalcrack process and the secondary cracking of tar is the main reason causing the yield of CH4from the simulation result far less than the experiment result.