预提升气对循环流态化气力输送的影响

发布时间：2018-12-28 07:09

【摘要】：在循环流化床冷态模拟实验装置上,对预提升气在气力输送过程中的作用进行了研究,详细分析了气力输送中的压力平衡,考察了底部气体返混及操作流型对颗粒循环速率的影响,同时描绘了提升管预提升段内微观气固流动结构。实验结果表明,提升管底部通入预提升气可避免颗粒在床层底部的积累,增大颗粒向前输送的推动力,从而提高系统循环量。其中,喷嘴进料气体积流量的增加将加剧气体返混,底部气体内循环和局部涡流导致气流夹带增多,颗粒循环速率逐渐提高,一定程度上可削弱预提升气对循环量的影响;随预提升气体积流量的增加,底部气固流动结构由密相流态化为主向气力输送为主转变,瞬时颗粒浓度信号波动减弱,颗粒浓度显著降低。概率密度分析结果表明,预提升气体积流量的增大致使预提升段内气固两相分布相对更均匀,有利于气固相的混合及接触。
[Abstract]:In this paper, the role of pre-lift gas in pneumatic conveying is studied in a circulating fluidized bed cold simulation experimental device, and the pressure balance in pneumatic conveying is analyzed in detail. The effects of bottom gas backmixing and operating flow pattern on particle circulation rate were investigated, and the microscopic gas-solid flow structure in the pre-lifting section of the riser was described. The experimental results show that the accumulation of particles at the bottom of the bed can be avoided and the propelling force of the particle forward transportation can be increased by adding the pre-lifting gas to the bottom of the riser thus increasing the circulation of the system. The increase of the volume flow rate of the inlet gas will aggravate the gas backmixing, the inner circulation of the bottom gas and the local eddy current will lead to the increase of the entrainment of the gas flow and the increase of the particle circulation rate, which can weaken the effect of the pre-lifting gas on the circulation rate to a certain extent. With the increase of volume flow rate of pre-lifting gas, the flow structure of gas-solid at the bottom changes from dense phase fluidization to pneumatic transport, and the fluctuation of instantaneous particle concentration signal weakens, and the particle concentration decreases significantly. The results of probability density analysis show that the increase of volume flow of pre-lifting gas leads to a more uniform distribution of gas-solid two phases in the pre-lifting section, which is advantageous to the mixing and contact of gas-solid phase.
【作者单位】：中国石油大学(华东)重质油国家重点实验室;
【分类号】：TQ051.13

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