Study on the Flow Field Characteristics of a Gas–Liquid–Solid Three-Phase Combined Impeller Agitator Based on CFD

Abstract

To address the issues of mixing efficiency and impeller configuration in the gas–liquid–solid three-phase system during CO₂ mineralization and sequestration using coal-based solid waste, a numerical investigation of the internal flow characteristics in a three-phase stirred reactor was carried out using computational fluid dynamics (CFD). A reactor model was established using Fluent simulation software. The multiple reference frame (MRF) method was adopted to construct the stirring flow-field model, and the Navier–Stokes equations were employed as the governing equations. The standard k–ε turbulence model was applied to solve the fluid flow in the stirred tank. Under a stirring speed of 100 r/min, the flow-field characteristics of different impeller combination schemes were simulated and analyzed. By examining the axial, radial, and tangential velocity distributions at specific cross-sections of the reactor, and combining velocity contours with the distributions of solid volume fraction and gas volume fraction, the flow characteristics and mixing performance of different impeller combinations were comparatively studied. The results show that different impeller combinations have significant effects on the internal flow-field structure and multiphase distribution in the reactor. Among the investigated configurations, the combination of an upper double-helical ribbon impeller and a lower pitched-blade turbine impeller can generate a more pronounced axial circulation flow, promoting the suspension of solid particles and the dispersion of gas bubbles. This configuration results in a more uniform distribution of the three phases within the reactor and improves the overall mixing efficiency of the system. The findings provide a theoretical reference for the structural optimization of three-phase stirred reactors and the design of impeller combinations in the CO₂ mineralization and sequestration process using coal-based solid waste.