Abstract

Airlift reactors (ALRs) are widely used in the chemical, petrochemical biological industry. A fundamental understanding of the flow field in these airlift reactors are necessary for efficient design and scaling up. In this work, the behavior of the flow field is investigated using the Euler–Eulerian approach. The liquid phase is modeled as continuous and the gas phase is dispersed in the form of bubbles. Three dimensional (3 D) transient computational fluid dynamics (CFD) simulations are performed to characterize flow behavior in ALR. The spatio-temporal variations in the flow field are quantified and an optimum liquid level in the ALR is determined. Various gas source locations are chosen and their effects on bubble plume motion are analyzed to find an optimum gas injection point that supports plume oscillation. Further, CFD simulations are performed to identify the prevailing flow regime in ALR for various gas source locations, and it is compared with experimental observations. The homogeneous and heterogeneous flow regimes are observed at lower and higher flow rates, respectively. The bubble size distribution is predicted using population balance equations through bubble coalescence and breakage models with interphase force formulations. This is computed through the discrete method of moments. The bubble size distribution is found to be narrow at lower gas flow rates and wider at higher gas flow rates. These predictions provide a unified description to characterize flow regimes in ALR.

摘要

气升式反应器(ALRs)广泛应用于化学、石化生物工业。对这些气升式反应器中的流场有一个基本的了解对于有效的设计和放大是必要的。在这项工作中，使用欧拉-欧拉方法研究了流场的行为。液相被建模为连续的，气相以气泡的形式分散。执行三维 (3 D) 瞬态计算流体动力学 (CFD) 模拟以表征 ALR 中的流动行为。对流场中的时空变化进行量化，并确定 ALR 中的最佳液位。选择各种气源位置并分析它们对气泡羽流运动的影响，以找到支持羽流振荡的最佳气体注入点。更远，执行 CFD 模拟以确定 ALR 中各种气源位置的主要流态，并将其与实验观察结果进行比较。分别在较低和较高流速下观察到均匀和非均匀流态。通过具有相间力公式的气泡聚结和破裂模型，使用总体平衡方程预测气泡尺寸分布。这是通过矩的离散方法计算的。发现气泡尺寸分布在较低的气体流速下较窄，而在较高的气体流速下较宽。这些预测提供了一个统一的描述来表征 ALR 中的流态。分别在较低和较高流速下观察到均匀和非均匀流态。通过具有相间力公式的气泡聚结和破裂模型，使用总体平衡方程预测气泡尺寸分布。这是通过矩的离散方法计算的。发现气泡尺寸分布在较低的气体流速下较窄，而在较高的气体流速下较宽。这些预测提供了一个统一的描述来表征 ALR 中的流态。分别在较低和较高流速下观察到均匀和非均匀流态。通过具有相间力公式的气泡聚结和破裂模型，使用总体平衡方程预测气泡尺寸分布。这是通过矩的离散方法计算的。发现气泡尺寸分布在较低的气体流速下较窄，而在较高的气体流速下较宽。这些预测提供了一个统一的描述来表征 ALR 中的流态。发现气泡尺寸分布在较低的气体流速下较窄，而在较高的气体流速下较宽。这些预测提供了一个统一的描述来表征 ALR 中的流态。发现气泡尺寸分布在较低的气体流速下较窄，而在较高的气体流速下较宽。这些预测提供了一个统一的描述来表征 ALR 中的流态。