Researches On Bauxite Desilicating Hydraulic Separating Equipment

In order to solve the problems of low efficiency and productive capacity of the equipments used for the removal of silicates from bauxite by settlement, a new type of bauxite desilicating hydraulic separating equipment was made, and the laboratory and pilot tests on a variety type of bauxite ores were carried out. The effects of structural parameters, processing parameters and flowsheet on the separating efficiency of equipment were systemly studied. The influence rules of the structural and processing parameters on the performance of hydraulic separating equipment had been confirmed. FLUENT software was used to simulate the internal flow field and the particle movement inside the hydraulic equipment, and the reasons for good separation performance of the hydraulic separating equipment were explained intuitively.The results of experiments show that a concentrate with Al₂O₃ recovery of 70.38% and Al-Si ratio of 4.61 was obtained from the No.2 sample of Henan Huiyuan with Al-Si ratio of 3.31 and particle size under 0.038mm, and its tailings has Al-Si ratio of 1.98 by one stage separation. A concentrate with Al₂O₃ recovery of 90.64% and Al-Si ratio of 6.34 was also obtained from the No.1 sample of Henan Huiyuan with Al-Si ratio of 4.70 and the -0.074mm fraction of 90%, and its tailings has Al-Si ratio of 1.75 by one stage separation. A concentrate with Al₂O₃ recovery of 85.01% and Al-Si ratio of 5.45 was obtained from the sample of Xiaoyi with Al-Si ratio of 3.95 and the -0.074mm fraction of 90% by two stage separation.A concentrate with Al₂O₃ recovery of 87.18% and Al-Si ratio of 5.90 was obtained from the pilot sample of Henan with Al-Si ratio of 4.18 and the -0.074mm fraction of 70～75%, and its tailings has Al-Si ratio of 1.50 by one stage separation. These results indicate that the new hydraulic separating equipment shows good separation and adaptation performance on different ores.Height of inclined plate, stirring speed, location of agitator and height of cylinder are the main structure parameters influence the performance of equipment. Flow flux of feed, the ratio of overflow and underflow are main processing parameters influence the performance of equipment. Speed of agitator must be changed according to the change of height of inclined plates, so that a good separation index can be reached. Low height of inclined plates is matched to the slow speed of agitator, and high height of inclined plates is needed for high speed of agitator. Fast speed of agitator and high height of inclined plates are responsibility for the good performance of the equipment. The separating performance of equipment is good while the agitator is positioned inside the cone zone not inside the cylinder zone. Besides, the increase of height of cylinder is also benefit to the good performance of equipment.Results of the flow field simulation based on the fluid dynamics software of FLUENT show that the turbulence caused by agitating is responsibility for the change of volume distribution of different solid phases. The agitating decreases the settling velocity of low density and fine particle of silicates and causes the good dispersion and suspension of silicates, but the agitation shows little influences on the settlement of alumina minerals with larger particle size and density, this is benefit for the separation of Diaspora from silicates. Agitation makes the distribution of velocity and energy more uniform, and it also makes the feed dispersing quickly and the maximum usage of the settle surface area. Agitation can also cause the turbulence of flow near the discharge zone, and it makes the settled particles dispersing again and then the larded gangue minerals can be released. Inclined plates can decrease the velocity and turbulence of the flow clearly, this is good for the settlement of mineral particles at the upper position of the equipment.