Numerical simulation of flow regions in red mud separation thickener’s feedwell by analysis of residence-time distribution
(1. School of Energy Science and Engineering, Central South University, Changsha 410083, China;
2. Hunan Key Laboratory of Energy Conservation in Process Industry,
Central South University, Changsha 410083, China;
3. Department of Mechanical Engineering, Purdue University Calumet, Hammond 46323-2094, United States)
2. Hunan Key Laboratory of Energy Conservation in Process Industry,
Central South University, Changsha 410083, China;
3. Department of Mechanical Engineering, Purdue University Calumet, Hammond 46323-2094, United States)
Abstract: The residence-time distribution (RTD) and the compartment model were applied to characterizing the flow regions in red mud separation thickener’s feedwells. Combined with the experimental work, validated mathematical model as well as three-dimensional computational fluid dynamics (CFD) model was established to analyze the flow regions of feedwells on an industrial scale. The concept of RTD, although a well-known method for the characterization of mixing behavior in conventional mixers and reactors, is still a novel measure for the characterization of mixing in feedwells. Numerical simulation results show that the inlet feed rate and the aspect ratio of feedwells are the most critical parameters which affect the RTD of feedwell. Further simulation experiments were then carried out. Under the optimal operation conditions, the volume fraction of dead zone can reduce by10.8% and an increasement of mixing flow volume fraction by 6.5% is also observed. There is an optimum feed inlet rate depending on the feedwell design. The CFD model in conjunction with the RTD analysis then can be used as an effective tool in the design, evaluation and optimization of thickener feedwell in the red mud separation.
Key words: computational fluid dynamics; residence-time distribution; compartment model; feedwell