Technology Of Iron Recovery From Iron Tailings Residue By Continuous Centrifugal Concentration

Centrifugal concentration, which can separate materials quickly at a low cost and in an environment friendly manner, is an effective method for recovering micro iron values from iron tailings residue. However, Chinese traditional intermittent centrifugal concentrator can not be efficiently applied to concentrate iron tailings residue, due to its incapability of working continuously and its very low processing capacity; and centrifugal concentrators available abroad, e.g., Knelson and Falcon concentrators, which are efficient in treating very lean metallic materials, can also not be used to concentrate rich metallic materials such as iron tailings residue. In view of this, continuous centrifugal concentration by reciprocating water sprays to remove the settled bed of heavy particles was theoretically analyzed, and studied for the recovery of iron values from iron tailings residue on the development of continuous centrifugal concentrators. The technology was tested for iron recovery from iron tailings residue both in experimental and in industrial conditions.Discharging experiments were carried out using the pilot continuous centrifugal concentrator developed in the study to treat iron tailings residue. It was found that continuous centrifugal concentration can be achieved only when the water sprays have both a high enough impacting pressure and adequate enough impacting energy. The threshold impacting pressure of water sprays increases with the increase in drum rotation speed proportionally, and it is around 0.55 MPa when the drum roates at the highest speed of 700 r/min; it is therefore concluded that a relatively low impacting pressure of water sprays is needed for achieving continuous concentration of the concentrator. The threshold impacting energy of water sprays increases with the increase in drum roation speed and in concentrate mass; the impacting angle of water sprays has a significant influence on the discharging efficiency of water sprays.The pilot continuous centrifugal concentrator was also used to concentrate iron tailings residue assaying 52.42% Fe from magnetic pretreatment to study the effect of the most important variables on performance of the pilot concentrator. The experimental results show that the optimum values of the variables are feed volume flow rate around 25 L/min, feed % solids 20%, drum rotation speed 450 r/min, drum inclination 5°and reciprocation of water sprays 36 mm/s. When all the variables were kept optimum, an iron concentrate assaying 62.32% Fe with 65.02% recovery at a solid recovery of 54.69% was achieved, with processing capacity, with electric and water consumptions of the concentrator being 0.3525 t/h, 2.57 Kwh and 1.30 t a ton of the residue, respectively; it is therefore concluded that the concentrator is effective and energysaiving in concentrating iron tailings residue. It was found during the experiments that the change in reciprocation of water sprays from 36 mm/s to 60 mm/s causes a drastic deterioration in concentrate grade from 62.32% Fe to 59.16% Fe but a neglectable drop in iron recovery from 65.02% to 64.75%; it is concluded that the impacting of water sprays at an optimum reciprocating velocity do not destroy the thin film flow, besides, it improves concentration performance of the concentrator.Continuous and intermittent centrifugal concentrations of the iron tailings residue were comparatively performed using the pilot concentrator to analyze superiority of the continuous centrifugal concentration over the intermittent one. The results of the comparison indicate that the continuous centrifugal concentration is capable of achieving a higher iron recovery but a lower concentrate grade, with the overall performance near to each other. However, the continuous centrifugal concentrator is much higher in processing capacity and much lower in failure rate and energy consumption in comparison with the intermittent one, which makes it easy to achieve industrialization in treating iron tailings residue combined with other methods such as high gradient magnetic separation.High gradient magnetic separation can be used to concentrate iron tailings residue efficiently at a very high processing capacity, but generally it cannot be used to produce a high grade qualified concentrate. Therefore, a high gradient magnetic pretreamtent-continuous centrifugal concentration method was used to treat iron tailings residue assaying 28.76% Fe; it obtained an efficient recovery of iron values, with a qualified concentrate assaying 62.32 % Fe with 23.94% recovery at a solid recovery of 11.05% achieved.To apply the technology in industry, a full-scale recovering plant by the technology was built and tested for recovering iron values from a currently discarding iron tailings residue. The results of the test of three months show that it can obtain a marketable concentrate assaying 58.48% Fe with 21.66% recovery at a solid recovery of 10.42% from the residue assaying 28.12% Fe; the test reduces 10.42% by weight of the residue and achieves significant environmental and economic benefits. However, the quality of concentrate achieved by the technology in industry is relatively inferior to that achievable in experimental condition; this may be mainly due to the lower efficiency of the full-scale concentrator in industry. It is therefore vitally important for the full-scale concentrator to improve efficiency if the technology is meant to achieve effective applications in industry.In summary, continuous centrifugal concentration is proven effective for recovery of iron values from iron tailings residue and can achieve significant environmental and economical benefits; it has an important industrial application worth. The continuous centrifugal concentrator, which can be used to concentrate iron tailings residue of high iron content, may be an important supplementary for the centrifugal concentrators available domestic and abroad, which are effective in the treatment of very lean metallic materials.