Numerical Simulation And Optimization On Solid-liquid Separation In The Red Mud Thickener

The red mud thickener is the main equipment in the sedimentation process of the alkaline alumina production. Taking a deep cone efficient thickener as the research object, based on the reasonable assumption and the simplification, a physical model and a mathematical model is established in this paper.The velocity field, solid concentration distribution and the turbulent kinetic energy distribution in the feed-well are simulated to compare the solid-liquid separation between the straight pipe and the jet pipe thickener. The results show that the jet pipe thickener have stronger diluting effect, more uniform and reasonable distribution of turbulent kinetic energy, etc.Thereafter, the paper puts forward an index of60-70g/L solid concentration distribution percentage to evaluate the solid-liquid separation efficiency of the thickener. The orthogonal experimental design method, combined with range analysis and variance analysis method, is used to study the factors affecting the efficiency of the thickener, such as the diameter of the feed-well, the depth of feed-well, type of jet pipe, the height of the blocking flow ring plate away from feed pipe, distance of mixing pipe to nozzle. It shows that the effect levels of above factors successively are the type of the jet pipe, the height of the blocking flow ring plate away from feed pipe, the distance of mixing pipe to nozzle, the diameter and depth of the feed-well; The height of the blocking flow ring plate away from feed pipe, distance of mixing pipe to nozzle and the type of the jet pipe influence that solid concentration distribution range of60-70g/L and that the effect of the type of the jet pipe is most significant.Research also concluded that the best structure parameters of the thickener are:feed-well diameter3000mm, feed-well depth5000mm, jet pipe type5#, the height of the blocking flow ring plate away from feed pipe220mm, distance of mixing pipe to nozzle180mm. After the optimization, the turbulent kinetic energy distribution in the feed-well of thickener is more uniform and reasonable; With the feed solid concentration being110g/L, the solid concentration of the slurry in the feed-well is59.3g/L after get through the jet pipe, and the volume fraction of solid concentration60～70g/L is up to12.5%, which increased by15.1%and128%respectively compared with the basic condition, and it can play a greater efficiency flocculant flocculation.In addition, according to numerical simulation and the results of various analysis approaches, the structural optimization is done to the thickener and the industrial test is taken to the red mud thickener in the cooperated corporation. The result of the industrial test shows that the power of two circulating pumps of the thickener is saved, which greatly saving the power consumption; the dry red mud flocculants consumption is17.8%reduced (from an average of103.4g/t to85g/t). It brings large economic and social benefits that the optimization method based on the research of this paper.