气流床气化炉中,颗粒停留时间分布是反映物料混合的重要特性,研究其规律对于改进炉内流场结构,优化运行参数和气化炉的宏观建模都具有重要的意义.通过建立三维CFD模型,研究了进口气速、颗粒粒径和密度等因素对颗粒停留时间分布规律的影响.模拟结果显示出与实验结果相同的规律.结果表明,在研究范围内,颗粒平均停留时间随着气速的增加,呈现出先增大后减小的趋势,在一定气速下达到峰值,这是颗粒和气体停留时间分布规律的重要区别.达到这一峰值所需的气速,只受到颗粒粒径的影响,而不受密度的影响.进口气速一定时,颗粒密度和粒径的增加,均导致颗粒平均停留时间减小.此外,随着颗粒密度、粒径以及进口气速的增加,颗粒最短停留时间始终减小.%Particle residence time distribution (RTD) is a key factor used to characterize the mixing degree of the gas-solid mixture in an entrained-flowed gasifier. Thus, the investigation of particle RTD has great significance for comprehending and optimizing the entrained-flow gasifier. In this study, a 3-D CFD model was established and was employed to study the influences of inlet gas velocity, particle diameter and density on particle RTD in the entrained-flow gasifier. The simulation results agree with the experimental data reasonably well. The results show that the particle mean residence time increases firstly and then decreases with the increase of the inlet gas velocity. Then, for a certain size particle, with the increase of inlet gas velocity, a peak of particle mean residence time can be obtained under a certain inlet gas velocity, and the inlet gas velocity under this peak is only related to the particle diameter. With increasing inlet gas velocity, the particle mean residence time curve appears to have a peak, which is the greatest difference between the RTD of gas and particle. It was found that, when the gas inlet velocity is constant, both the greater particle diameter and density could make the particle mean residence time shorter. Meanwhile, the particle lag time decreases constantly with the increases of inlet gas velocity, particle diameter and density.
展开▼
