Selective flocculation, iron ore fines, coagulant, magnetic seed with the rapid development of China's steel industry, demand for finished products of iron ore increasing exploitation of iron ore can be easy to choose the amount gradually reduce, mineral processing Objects are not only increasingly depleted, but the granularity of useful minerals is becoming finer and finer. The weak magnetic iron ore with micro-fine particles embedded in the fine grinding process is easy to be muddy and has a serious mud covering phenomenon. It is difficult to obtain satisfactory results by conventional re-election, magnetic separation and flotation processes. From the 1970s to the present, after several decades of trial and error research, it has been shown that the treatment of fine-grained mud iron ore, selective flocculation and its combined process is a promising sorting process. Selective flocculation mainly includes three processes: slurry dispersion, that is, by adding a dispersant, preventing the ore particles having opposite sign charges from coagulating, so that the ore particles are in a suspended dispersion state; selective flocculation, after the slurry is dispersed, by adding a polymer selective The flocculating agent utilizes the bridging action of the selective flocculant and the surface of the ore particles to cause the target mineral to form a floc sinking, while the non-target mineral is still in a suspended state; the slime is removed, the target mineral is formed into a floc sinking, and suspended. The slime becomes overflowed. First, the factors affecting the selective flocculation effect (1) Effect of flocculant on selective flocculation effect In order to make the ore group in suspension and dispersion state, it is a common practice in practice to use mechanical agitation with a certain intensity to impart certain kinetic energy to the ore particles. However, in order to make the fine-grained slime in the slurry in a fully effective suspension state without agglomeration, practice has shown that the addition of a certain amount of dispersant is an effective basic measure. Since the fine-grained hematite is sufficiently dispersed, it is difficult to settle. At this time, it is necessary to add a selective flocculant to flocculate the hematite while maximally keeping the other components fully dispersed. The selective flocculant is different from ordinary flocculant in that it must not only have flocculation property, but also must be selective. Otherwise, it is impossible to sort a certain mineral from a stable suspension. The selectivity of the flocculant is selective flocculation. key. CRIMM NaOH and a pH adjusting agent in a humic acid Ammonium hematite Hunan Fine Particle performed, NaOH and sodium silicate dispersants, NaOH and sodium hexametaphosphate dispersant combination, NaOH and sodium silicate and the DTY It was found in the experimental study that DTY can effectively achieve selective flocculation of hematite. The amount of fixed NaOH and water glass, DTY selective flocculant dosage test results are shown in Figure 1. Figure 1 DTY selective flocculant dosage test results ▲-mineral iron loss rate; ■-grit sand iron grade; ○-sludge yield; △-sludge iron content It can be seen from Figure 1 that increasing the amount of DTY is beneficial to the reduction of the iron content of the slime and the increase of the iron recovery rate. When the dosage of DTY is 36g/t, the yield of slime is 32.79%, the content of mineral iron is 12.55%, the grade of grit iron is 33.97%, the loss rate of slime iron is 15.27%, and the selective flocculation effect is quite obvious. However, it should also be noted that when the amount of flocculant is excessive, flocculation will increase, resulting in aggravation of encapsulation and entrainment during selective flocculation, and the selectivity of flocculation will be deteriorated, which is not conducive to the removal of slime. (II) Effect of magnetic species on the selective flocculation effect Magnetic species are added during the selective flocculation separation process, and the magnetic species is selectively adhered to the target mineral by a physical or physical chemical process to form a magnetic cover, and the target mineral is thereby obtained by adding a polymer selective flocculant. The synergistic effect of magnetic flocculation and chemical flocculation, so as to achieve the purpose of optimizing the selective flocculation sorting effect. Related studies have shown that magnetic agglomeration-polymer flocculation combined treatment of hematite has good selectivity and high recovery rate, and the obtained floc is more dense than the single magnetic species agglomeration and the floc obtained by polymer flocculation only. It provides favorable conditions for the separation between the floc and the dispersed phase in the subsequent work. The Changsha Research Institute of Mining and Metallurgy found in a selective flocculation test of a fine-grained iron ore in Hunan (Fig. 2) that the increase in the proportion of magnetic species is conducive to the reduction of the iron content of the slime in the selective flocculation and the increase of the recovery rate of the grit. However, it is not conducive to the improvement of grit iron grade. This is mainly due to the increase in the proportion of magnetic species, and the magnetic flocculation ability also increases, resulting in aggravation of magnetic inclusions. Therefore, the magnetic species addition ratio should be determined by comprehensively considering the iron recovery rate and the iron concentrate grade. Figure 2 Effect of magnetic species on the effect of selective flocculant ▲-mineral iron loss rate; ■-grit sand iron grade; ○-sludge yield; △-sludge iron content (3) Effect of slurry temperature, concentration and external magnetic field on selective flocculation effect Xu Jianben of Changsha Research Institute of Mining and Metallurgy conducted selective flocculation and beneficiation tests on Jidong Iron Mine. It has been found that the slurry temperature has a great influence on the sedimentation time of flocculation and desliming. To maintain the same de-sludge effect, the settlement time should be adjusted according to the slurry temperature. For example, the settling time is 4 min at 25 °C and 6 min at 10 °C to maintain the same desliming effect. The concentration of pulp is more suitable at 30%, and too high and too low will reduce the flocculation and desliming effect. The external magnetic field can effectively improve the flocculation and desliming process before de-mudging, which not only shortens the settlement time from 6min to 2min, but also reduces the grade of slime iron from 12% to 10.5% when the yield of demineralized sludge is similar. (4) Influence of settlement time on selective flocculation effect After the dispersant is added, the slurry in a suspended state, before the flocculant is added, if the particle size of each component of the slurry is uniform, and the levitation force is in equilibrium with gravity, theoretically no sedimentation will occur. This requires the formation of flocculation of the target mineral by adding a polymer selective flocculant and breaking the balance between the forces, thereby causing the formation of the target mineral. At this time, the settling time of the target mineral will have an important effect on the selective flocculation effect. The Changsha Research Institute of Mining and Metallurgy found in the selective flocculation test of hematite in a section of the Jidong Iron Mine (Fig. 3) that prolonging the sedimentation time of the slurry is conducive to reducing the iron content of the slime, but it is not conducive to the removal of the slime. That is not conducive to improving the grade of de-sanding sand. Therefore, the determination of the settlement time needs to be comprehensively considered from the iron recovery rate and the desalination iron grade. Figure 3 Effect of sedimentation time on the effect of selective flocculant ▲-mineral iron loss rate; ■-grit sand iron grade; ○-sludge yield; △-sludge iron content Second, the application of selective flocculation in fine iron ore beneficiation The selective flocculation process has been studied for decades and is relatively mature, and there have been successful industrial practice precedents in fine-grain iron ore beneficiation. With the establishment of the Tilden concentrator in the United States in 1974, the selective flocculation process for the treatment of refractory iron oxide porphyrites, the application of selective flocculation of iron ore, has been widely used both at home and abroad. Pay attention to it. The Tilden Concentrator in the United States treats the original ore as a non-magnetic inclusion of fine-grained non-magnetic iron-bearing rocks. The main iron minerals are hematite and imaginary hematite; the gangue minerals are mainly quartz , vermiculite and other silicate minerals. The average embedding grain size of iron minerals is 10~25μm, and the ore needs to be ground to -25μm to account for 85%, in order to achieve sufficient dissociation. The plant handles 10 million tons of raw ore annually, 36% of original ore grade, and can produce 4 million tons of pellets containing 65% iron. In 1979, it expanded to an annual processing capacity of 21 million tons of ore, with an annual output of 8.1 million tons. The scale of the mine. The concentrating plant uses tapioca starch as a selective flocculant for hematite. After selective flocculation treatment, 15% to 30% of the slime can be removed from the ore, and the iron loss is only 5%. The main iron mineral of the Kelton Iron Mine in Canada is hematite, followed by magnetite. The hematite has a size of 5 to 30 μm, the magnetite is coarse, and the inlaid grain size is 20 to 200 μm; the gangue minerals are mainly quartz, silicate and chloride. The process of the concentrator is a selective flocculation-de-sludge process, using two-stage grinding, four selective flocculation-de-sludge, and corn starch as a selective flocculant for magnetic and hematite. In the semi-industrial test, The concentrate rate is 34.10%, the iron grade is 65.00%, the iron recovery rate is 74.60%, and the iron content of the slime is only 11.40%. The Mindong iron deposit in Hunan Province is a sedimentary metamorphic deposit. It is an acidic siliceous fine-grained inlay and difficult to select iron ore. It is a typical representative of China's fine-grained complex refractory iron ore. Its iron minerals are mainly hematite, followed by magnetite and a small amount of pseudo-hematite; the hematite has a size of 2 to 30 μm; the magnetite has a particle size of 10 to 300 μm; the gangue mineral is quartz. , followed by a sericite, chlorite, feldspar, actinolite, tremolite, calcite, dolomite and zoisite. Changsha Research Institute of Mining and Metallurgy has carried out research on the ore dressing technology of this mine for many years since the 1970s. In 2006, the experimental study and comparison of the multi-program of the Jidong iron ore was carried out, and finally the selective flocculation de-sludge-reverse The flotation process successfully completed the expansion of the re-election test, and achieved technical indicators of 31.91% concentrate yield, 64.16% iron grade and 70.67% iron recovery rate. In 2007, an industrial test plant with an annual processing capacity of 300,000 tons was built. In 2008, the industrial commissioning stable operation stage achieved a production technical index of 63.02% concentrate iron grade and 65.83% iron recovery rate. Third, the development direction of selective flocculation With the deepening of the research and development of fine-grained and fine-grained iron ore in China, the selective flocculation process and theory have been widely applied and developed. In practical applications, the selective flocculation process has also exposed some problems, and it is necessary for the mineral processing scientists to carry out further technical research to promote the process in industrial practice. The next step should be to focus on the deeper research from the following aspects. (1) Develop more selective flocculants to reduce encapsulation and magnetic entrainment during selective flocculation. (2) Develop a magnetic (pulse)-heavy composite force field high-efficiency desilting device to solve the problem that the removal amount of the slime and the iron content cannot be unified. (3) Solving the problems of sedimentation clarification, recycling and recycling, and environmental protection of high-dispersion suspended slurry produced by mud removal. Coil Form is special designed for coil bending with L , C,U, G shape according to different application Coil Form Coil Form, Coil Bending Machine, Coil Bender Satis Products Co., Ltd. , https://www.satismachinery.com