环管反应器内液固两相流的数值模拟

Numerical Simulation of Liquid-Solid Two-Phase Flow in Tubular Loop Reactor

为了对环管反应器内液固两相的流动形态进行研究,建立了以颗粒动力学为基础的Euler-Euler双流体模型。在浆液流速远大于自由沉降速度的情况下,模拟了不同浆液入口速度时的环管反应器上升段压力降,同时对管道内液固两相流中的一些重要参数进行了数值研究:在入口液固两相体积分布均匀的情况下,环管反应器上升段、弯管段以及下降段液固两相体积分布和液固两相速度均不一样,在弯管段由于离心力存在而引起管道内二次流,使得固相颗粒甩向弯管的外侧壁,引起固相体积分数在弯管外侧壁明显增大,管道内固体颗粒相分布不均。在浆液速度v=3m·s-1时,液相和固相的速度有一定的速度差,随着入口速度增大,速度差变小;当浆液速度v=7m·s-1时,固体颗粒相速度分布与液相速度基本相同,两者之间的滑移速度可以忽略。计算结果与传统经验公式的比较表明模型能有效地描述环管反应器内压力降和反应器内浆液流动形态。

Based on the granules kinetics, an Euler-Euler two-fluid model was established for studying the flow patterns of liquid-solid two-phase flow in the tubular loop reactor. The mean pressure gradients in the up-section of the tubular loop reaction were simulated for different slurry inlet velocities when these velocities are much higher than the free setting velocity of the solid particles. The flow pattern simulations show that the volume fractions and velocity distributions of liquid-solid two-phase are different in the up-section, curve-section and down-section of the tubular loop reactor. The secondary flow occurs when the liquid and solid particles enter the curve-section of the tubular loop reactor and the solid particles flow towards the tube wall by the push of centrifugal force, which leads to the un-uniform distribution of solid volume fraction. The slip velocity between the liquid and solid particles exists when the slurry inlet velocity v=3 m.s^-1, and the magnitude of the slip velocity reduces with the increase of slurry inlet velocity. When the slurry inlet velocity v≥7 m.s^-1, the slip velocity between the liquid and the solid particles can be neglected. The comparison of the numerical results calculated by the Euler-Euler two-fluid model presented and the traditional empirical equation for liquid-solid two-phase flow shows that the presented model is available to describe the pressure gradients and slurry flow pattern in the tubular loop reactor.