Numerical Simulation Of The Technology Of The Biomass And Coal On Co-gasification In A Fluidized Bed

In the process of renewable energy systems transition from fossil fuel-based to sustainable energy-based, biomass gasification technology is one of the important methods. The co-gasification of coal and biomass are based on biomass gasification, biomass mixed with coal as a raw material for the gasification reaction in the process. Compared with the separate gasification of biomass, co-gasification of coal and biomass solved the instability fluidizing and seasonality of biomass and improved the vaporization temperature so that the tar cracking was promoted and the efficiency of gasification was improved.Gasification technology was concentrated in the process with a fluidized bed gasifier as a reactor. In the dual fluidized bed gasifier of the gasification process and the combustion process were carried out in two fluidized bed through the circulatory system so that the endothermic gasification and exothermic combustion reaction was carried out in the same apparatus, the synthesis gas of high purity can be obtained to achieve a highly integrated and energy of the apparatus proper coordination. However, due to heat transfer achieved only with flow of material in the circular between the burners and the gasifier, the efficiency of direct heat radiation or convection heat transfer was low. In addition, there are many problems in the independent gasifier and combustion furnace, such as foreign cooling, large radiating area and system heat loss.Existing dual fluidized bed gasifier improvements proposed a raw material and coal in fluidized bed gasification process, not only using the high-temperature recyclable materials to provide heat for the gasification reaction, but also reducing the heat loss through the combustion chamber and the gasification chamber direct heat exchange of thermal radiation and convection, while improving the production efficiency. Based on this process, the co-gasification of biomass and coal model was established with CFD software, optimized by numerical simulation. The transfer effect and gasification effect of pine sawdust and bituminous coal blending ratio and inlet temperature of air and steam the heat were analyzed, which provides a theoretical basis for the optimization of biomass and coal in fluidized bed gasification process.The results showed that: biomass and coal fluidized bed of the gasification reactor can maintain gasification chamber gasification reaction by the heat transfer in combustion chamber. When the reactor reached thermal equilibrium, the reaction temperature of the gasification chamber increased100-150K compared to the steam inlet temperature. Biomass and coal fluidized bed had good heat transfer effect and utilized the thermal energy efficient. High-quality gas can be obtained by biomass and coal fluidized bed. H2+CO content was high in gas, calorific value of gas could achieved13.7MJ·m-3, gasification efficiency can reach82.5%. The carbon conversion rate was slightly lower due to not take the material cycle into account. Compared to the direct heat supplied to the gasification chamber, biomass and coal in fluidized bed supplied to the gasification reactor the heat required to achieve the same effect by the heat exchange between the combustion chamber and the gasification chamber. Compared with separate gasification, appropriate blending ratio of pine sawdust and bituminous coal were conducive to gasification in the gasification chamber. When the operating temperature at1200K and the content of pine sawdust at20%, the synthesis gas heat value achieves13.78MJ-Nm-3, carbon conversion rate achieves85.8%, the efficiency of gasification achieves87%, H2volume content achieves80%, which is the best gasification results. With the combustion chamber air inlet temperature was increased, the combustion chamber and the gasification chamber temperature increased, the gas concentration of gasification chamber is increased, the calorific value of gas, carbon conversion rate and efficiency of gasification are substantially rise which is conducive to the gasification reaction carried out. When the air inlet temperature is increased from800K to1000K, very small changes in the temperature of the gasification chamber, gasification reaction process substantially unchanged. With the improvement of the steam inlet temperature of the gasification chamber, the combustion chamber and the gasification indoor temperature rise, the gas component in the combustion chamber unchanged, the gasification chamber gas concentration increased, the calorific value of gas, carbon conversion rate and the gasification efficiency increased significantly, which was conducive to the gasification reaction. However, when the steam inlet temperature increased from800K to1000K, the gasification changed slightly flat.