微膨胀床反应器内气液分布设备性能数值模拟

Numerical simulation of the hydrodynamics of a gas-liquid distributor used in an upward slightly expanded bed reactor

用VOF数值模型方法,对适用于上流式微膨胀床反应器内的气液分布设备进行了数值模拟研究,并与实验结果进行了对比。考察了气液分布设备对气液两相的分布作用,包括分布器内的动态流动特征和流动形态。同时考察了气泡的大小、上升速度、压力降随着表观气液速的变化规律。结果表明:(1)选用VOF数学模型,可以清晰准确的模拟出气液分布器的动态流动特性和气液分界面,可以指导气液分布器的优化设计;(2)气泡的上升速度随着表观气速和表观液速的增大而增大;气液分布器出口气泡的直径随着表观气速的增大而增大,随着表观液速的增大而减小;截面平均气含率随着表观气速的增大而增大,随着表观液速的增大而减小;气液分布器的压降则随着表观气速的增大而减小,随着表观液速的增加而增大;(3)相对于表观液速的变化,气液分布器对表观气速的变化敏感度更高,表观气速更影响分布器的工作负荷。

Two-phase flow through an upward gas-liquid distributor in an upward slightly expanded bed reactor has been numerically studied. Three-dimensional computational fluid dynamics( CFD) simulations using the volume of fluid( VOF) approach have been used to compute the flows for similar flow conditions to those used in the experiments. It has been shown that agreement between experiments and calculations is good for small gas and liquid superficial velocities. Based on the simulations,the relationships between inlet gas and liquid velocities and flow patterns,gas,gas bubble size,gas bubble rising velocity,phase holdup and pressure drop are discussed. The results show that( 1) the VOF model is suitable for simulating the fluid dynamics of the gas-liquid distributor,this model can exactly simulate the interface of gas and liquid,so that CFD enables the design of gas-liquid distribution devices to be optimized;( 2) With increasing gas and liquid superficial velocities,the gas bubble rising velocity increases,with an increase in gas superficial velocity or decrease in liquid superficial velocity,the gas bubble size and average gas holdup increase,and the pressure drop increases with increased liquid superficial velocity or decreased gas superficial velocity;( 3) The gas-liquid distributor is more sensitive to changes in gas superficial velocity than changes in liquid velocity.