Study on the Flow Field Characteristics of a Liquid–Solid–Solid Three-Phase System and the Influence of a Draft Tube in a Stirred Reactor

The liquid–solid–solid three-phase flow field was established in a stirred reactor with a draft tube and baffles. The solid concentration distribution, mixing time, velocity distribution, flow pattern, and power consumption of the flow field were systematically studied by means of a cold model experiment and computational fluid dynamics (CFD) simulation. The CFD model was based on the Euler multiphase flow model and the RNG k–ε turbulence model. Different momentum exchange coefficient models were taken into account for each phase. It was found that at the same stirring speed, the solid distribution was more uniform and the mixing time was less when the draft tube was equipped. The flow pattern of the flow field was more regular and the velocity distribution of the solid phase was more uniform in the reactor with the draft tube. According to the Nagata correlation, a power consumption formula was derived, and its applicability was verified by comparison of the experimental results.