基于CPFD方法的流化床生物质气化数值模拟

Numerical simulation of 3D fluidized bed biomass gasification based on CPFD

基于计算颗粒流体动力学(CPFD)建立了三维鼓泡流化床水蒸气-空气混合气化的数值模型,并进行了模型验证,结果表明模拟和实验具有良好的一致性。在该模型的基础上,研究了气化炉内气体分布以及温度分布;同时探究了生物质属性(颗粒粒径、含水率、种类)以及操作条件(气化温度、床料高度)对气化特性的影响。结果表明,生物质颗粒粒径对气化性能的影响存在一个最优值,平均粒径为0.6 mm是最佳的;较高的含水率会降低可燃气体产量,不利于气化反应的进行;四种生物质中,锯末气化的效率最高、可燃气体产量最大、气体热值最高,稻壳仅次于锯末但其碳转化率高于锯末;提高气化温度可以增加可燃气体的比例、提高气化效率;而初始床层高度的变化可以改变H2/CO的比例。本实验为生物质水蒸气/空气气化提供了理论参考,有助于生物质原料的选取和处理,也有助于气化炉的放大和优化。

Based on computational particle fluid dynamics(CPFD),a three-dimensional bubbling fluidized bed steam-air mixed gasification numerical model was established,and it was verified with experiment trials.The results show that the simulation and experiment have good consistency.Based on the model,the gas distribution and temperature distribution in the gasifier were studied;meanwhile,the biomass properties(particle size,water content,types)and operating conditions(gasification temperature,bed height)were investigated.The results show that there is an optimal value for the impact of biomass particle size on gasification performance,with an average particle size of 0.6 mm being the best;a higher water content will reduce the output of combustible gas and is not conducive to the gasification reaction.Among the four types of biomass,sawdust gasification has the highest efficiency,the largest combustible gas production,and the highest gas calorific value.Rice husk is second only to sawdust but its carbon conversion rate is higher than that of sawdust;increasing the gasification temperature can increase the proportion of combustible gas and increase gasification efficiency;while the change of initial bed height can change the ratio of H2/CO.This experiment provides a theoretical reference for biomass steam/air gasification,which is helpful for the selection and processing of biomass raw materials,and also facilitates the amplification and optimization of the gasifier.