MP-PIC simulation of the gas-solid full-loop flow characteristics in a dual fluidized bed and validation with experimental data
MP-PIC simulation of the gas-solid full-loop flow characteristics in a dual fluidized bed and validation with experimental data
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DOI：
10.1016/j.cej.2021.129835
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发表时间：
2021
影响因子：
15.1
通讯作者：
Q. Tu;Zhan Luo;Haigang Wang
中科院分区：
文献类型：
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作者：
Q. Tu;Zhan Luo;Haigang Wang
研究和了解气固两相流动特性对于化学环流燃烧反应器等涉及双床系统的化工过程的设计和优化操作是十分必要的。为了了解气固两相流动特性，本研究在实验室规模的冷态三维全循环双床模型上进行了基于颗粒单元(MP-PIC)方法的计算流体力学模拟。模拟结果与压力和电容层析成像(ECT)测量结果进行了分析和验证。结果表明，用文宇/尔贡阻力模型预测该DFB系统的气固两相流动是可行的。模拟的颗粒体积分数与ECT结果吻合较好。在鼓泡床(BFB)中，根据气泡和颗粒的行为，可以识别出四个流动区域。在各个区域中，气泡主要集中在中间区域。此外，溜槽内的流态化空气起到了BFB的二次风的作用，有利于颗粒的运动。BFB和下U形阀作为一个部件工作，并起到颗粒缓冲区的作用。因此，整个系统的平衡取决于立管达到稳定状态的时间。提升管的进气速度越高，系统达到稳定运行的时间越早。此外，在仿真结果的基础上，研究了提升管、BFB和U型阀之间的启动特性。结果表明，当提升管和鼓泡床达到稳定状态时，两者之间存在启动时滞。
It is necessary to investigate and understand the gas-solid flow characteristics for the design and optimized operation for chemical looping combustion reactors and other chemical process which involves dual fluidized bed (DFB) system. In this research, computational fluid dynamics simulation was performed in a lab-scale cold three-dimensional full-loop dual fluidized bed model based on the Particel-In-Cell (MP-PIC) method to understand its gas-solid flow characteristics. The simulated results were analyzed and validated with the pressure and electrical capacitance tomography (ECT) measurements. It has been shown that Wen-Yu/Ergun drag model is feasible for the prediction of the gas-solid flow dynamics of this DFB system. The simulated particle volume fraction and ECT results have a good agreement. In the bubbling fluidized bed (BFB), four flow zones are identified based on the bubble and particle behaviors. In each zone, bubbles are mainly concentrated in the middle region. Moreover, the fluidizing air in the chute functions as a secondary air of the BFB to facilitate the particle movement. The BFB and the lower U valve are working as one component and function as a particle buffer region. Therefore, the balance of the whole system is determined by the time when the riser reaches steady state. The higher the air inlet velocity of the riser, the sooner the system reaches steady operation. In addition, the start-up characteristics among the riser, the BFB and U-valve are investigated based on the simulation results. The results indicated that there is a start-up time lag between the riser and bubbling fluidized bed when they each reach steady state.