Our lean ore iron ore resources, mixed ore, less high-grade ore, iron ore grade of more than about 30%, and ore disseminated fine grain size, beneficiation process more complicated. In recent years, with the development of the steel industry, the demand for iron concentrate powder has increased year by year. Although the domestic production of iron concentrate is increased every year, it still cannot meet the production needs of the steel industry, and can only rely on a large number of imported foreign iron ore to make up for the lack of 1:1. At the same time, the iron ore resources with better domestic selectivity are depleting. Therefore, the full development and utilization of lean, miscellaneous and fine iron ore has become an effective way to alleviate the contradiction between domestic iron ore supply and demand. There is a large-scale reserves of magnetite-hematite in the eastern part of Hunan Province. The total reserves are nearly 500 million tons. The majority of ore iron grades are concentrated between 27% and 31%. The iron minerals in the ore are very fine. Currently, there are a few selected plant has been built using a single weak magnetic separation process magnetite ore, hematite ore, martite and other metal minerals can not be effectively recycled. The yield of concentrates in the whole production process is low, all below 20%, and the recovery effect of iron metal is also poor, resulting in serious waste of resources. In order to comprehensively develop and utilize the iron ore resources in the region, in recent years, the selected plant has selected the iron ore in the eastern part of the country by the phase-grinding, weak magnetic separation-strong magnetic separation-centrifuge magnetic weight combined process, and obtained good selection indicators. . First, the nature of the ore (1) Multi-element analysis of raw ore. The results of multi-element chemical analysis of raw ore are shown in Table 1. From Table 1, this part of the ore containing sulfur oxidizing acidic phosphorus ore gangue mainly of SiO 2 based. (2) Mineral composition of ore, see Table 2. It can be seen from Table 2 that the main metal minerals of the ore are magnetite, hematite, and imaginary hematite. These three types of minerals are the target minerals for process research and recovery. In addition, limonite, pyrite, and pyrrhotite have a small proportion in the mineral composition. Some of the iron concentrate grades have a certain reduction effect after recycling, so they can not be recovered as the main purpose metal minerals. (3) Particle size characteristics of iron mineral inlays. The iron ore in the eastern part of the territory is a typical fine-grained ore-selected ore. It is determined that the granular composition and distribution characteristics of iron minerals in the ore are beneficial to determine the reasonable grinding fineness and to formulate a reasonable beneficiation process. Therefore, the iron mineral inlay size in the ore was counted under a microscope, and the results are shown in Table 3. It can be seen from Table 3 that the size of the iron mineral inlay in the ore is fine, and the grinding fineness is selected to be -0.037mm, which can make the ore dissociated more than 95% of the ore. In general, the iron ore material composition in the eastern part of the country is relatively simple. It is a typical low-sulfur phosphorus-containing acid micro-embedded iron ore. The ore iron grade does not change much, and the deposit is a sedimentary metamorphic deposit. The ore is a gray-black block and partially has a striped structure. Through microscopic observation and x-ray diffraction analysis, the iron minerals in the ore are mainly magnetite and hematite, imaginary hematite, and a small amount of limonite, and occasionally the distribution of siderite. Metal sulfides are mainly pyrrhotite and pyrite, which are often interspersed in the gangue and are distributed along the pores or edges of the magnetite. Gangue of quartz majority, followed by sericite, chlorite, feldspar, actinolite, tremolite, calcite, dolomite, biotite, muscovite, zoisite. Trace minerals include tourmaline , rutile, zircon , apatite and epidote. Second, the beneficiation test (1) Magnetic separation process tailing test 1. The target iron ore mineral in the ore is finely sized, and the continuous grinding, weak magnetic separation-strong magnetic separation process can be used in the production process. If the grinding fineness of this process directly reaches -0.037mm, not only the grinding cost is high, but also muddy phenomenon is easy to occur. In order to reduce the grinding cost and prevent the occurrence of over-grinding and muddy phenomenon, the test process adopts a stage grinding and weak magnetic separation and a strong magnetic separation process (Fig. 1). The original ore section is ground to -0.074 mm, accounting for 75%. 1 weak magnetic separation, 1 strong magnetic separation and tailing, 1 weak magnetic separation, 1 strong magnetic separation coarse concentrate and then grinding to -0.037 mm, 2 weak magnetic separation, 2 strong magnetic separation tail. According to the process test, the weak magnetic separator is a common magnetic induction intensity 0.16 T magnetic separator, and the strong magnetic separator adopts a SLon vertical ring pulsation high gradient magnetic separator. The test results of one section of grinding are shown in Table 4. It can be seen from Table 4 that the original ore is tailed by one section of grinding, one weak magnetic separation, and one strong magnetic separation. The comprehensive iron concentrate grade can reach 44.02%, the yield is 59.16%, the recovery rate is 85.89%, and 40.84 can be thrown away. The tailings of % greatly reduce the amount of re-grinding in the second stage, and the tailing effect is better. 2. After a period of grinding, weak magnetic separation (0.16T)-strong magnetic separation (0.70T) tailing process, the grade of coarse iron powder reaches 44.02%, and the second stage is re-grinded according to the granularity of ore inlay. The grinding fineness reaches -0.037mm, accounting for 95%. Under the same magnetic induction intensity, different magnetic separation media have different ore recovery rates. Considering the fineness of grinding fineness, two strong magnetic separation tests are compared with fine magnetic media. The test results are shown in Table 5. It can be seen from Table 5 that the second-stage re-grinding, the second weak magnetic separation, and the second strong magnetic separation test, the effect of selecting the fine-grained iron ore by the 1.5 mm magnetic medium is better than that of the 2 mm magnetic medium. Weak magnetic separation concentrates can obtain qualified iron concentrates with a concentrate grade of 66.52%. With 1.5mm magnetic media sorting, the grade of strong magnetic working iron concentrate can only reach 50.84%, which can not be qualified iron concentrate. Consider using centrifuge to improve the concentrate grade. (2) Centrifuge selection test The intensity of iron concentrate powder in 50 times of strong magnetic separation operation is 50.84%. The main iron minerals are hematite, imaginary hematite and a small amount of magnetite. The reason for the lower iron grade is that the impurities contain gangues such as quartz, actinolite, tremolite, zoisite, sericite and chlorite. In the past, some concentrating plants were selected by flotation process, but the flotation process required higher production conditions, and the flotation process easily caused environmental pollution. In recent years, some plants have adopted the centrifuge re-election process to replace the flotation selection process, and have achieved good selection indicators and economic benefits. The new-generation SLon centrifuge automatic control system is composed of programmable PLC and touch screen peripheral circuits. It is used for the feeding sequence of the centrifuge beneficiation process, the swinging of the mine, and the automatic control of the action sequence and time of the pneumatic valve. The control system is also equipped with a detection device that can track the working state of the centrifuge drum, the swing bucket and the pneumatic valve, and perform logical judgments, and can alarm in time when there is an abnormal situation. According to the requirements of the beneficiation process, the feeding time, the time of the mine, the flushing time and the reset time of the centrifuge can be corrected to achieve the best ore recovery index. At present, many manufacturers in China have used centrifuge re-election operations instead of flotation operations [1] . Centrifuge re-election operation, drum rotation speed is an important parameter affecting the selection effect. This test compares the different drum speeds. The test results are shown in Table 6. It can be seen from Table 6 that the centrifuge selection operation can obtain an excellent index of 73.11% of the iron concentrate operation yield, 61.33% of the concentrate grade, and an operation recovery rate of 88.20%. (III) Stage grinding, weak magnetic separation-strong magnetic separation-centrifuge magnetic weight combined process test The mass flow process using phase grinding, weak magnetic separation-strong magnetic separation-centrifuge magnetic weight combined process is shown in Fig. 2. It can be seen from Fig. 2 that a poor iron ore refractory iron ore in the eastern part of the country can obtain a comprehensive iron concentrate yield of 33.05% using a phase grinding, weak magnetic separation-strong magnetic separation-centrifuge magnetic weight combined process. 63.51%, a good indicator of a recovery rate of 69.24%. Third, the conclusion (1) Single weak magnetic separation-strong magnetic separation process for sorting a poor and difficult refractory iron ore in Jidong, using 1 weak magnetic separation (0.16 T), 1 strong magnetic separation (0.70 T) The iron concentrate grade reached 44.02%, the operating yield was 59.16%, and the recovery rate was 85.89%. 40.84% ​​of the tailings could be thrown away, and the tailing effect was better. (2) The experimental study shows that the coarse concentrate obtained by one section of grinding, one weak magnetic separation and one strong magnetic separation is subjected to two-stage grinding, two weak magnetic separation, two strong magnetic separation, and the second stage grinding. With a fineness of -0.037 mm and 95%, the SLon type high gradient magnetic separator adopts 1.5 mm magnetic medium. The strength of iron concentrate in 2 strong magnetic separation operations can only reach 50.84%. It is still necessary to use SLon centrifuge. Selected to improve the grade of iron concentrate. (III) The process test shows that a poor iron ore refractory iron ore in the eastern part of the country can obtain a comprehensive iron concentrate yield of 33.05% through the phase grinding, weak magnetic separation-strong magnetic separation-centrifuge re-election process. The ore grade is 63.51%, and the good recovery rate of 69.24% is higher than the iron concentrate yield in the production process of single magnetization recovery magnetite by more than ten percentage points, and the recovery rate is greatly improved. (4) The production cost of the centrifuge selection process is lower than that of the flotation process. No ore dressing agent is added in the whole production process, and the surrounding water environment is minimized. Undoubtedly, the mature magnetic separation-centrifuge reselection combined process is an important choice to replace the magnetic separation-flotation process. references [1] Chen Luzheng, Ren Nanqi, Xiong Dahe. Experimental study on strong magnetic-centrifugal separation of Haigang tailings [J]. Metal Mine, 2006 (10): 75-77. [2] Wang Jianmin, Yang Qinglin, Zheng Chuanwen, et al. Selective industrial test and production practice of coarse concentrate in ф1600×900 centrifugal concentrator [C]. Metal Mine Magazine, 2008 National Metal Mine Difficult Mineral Separation and Low Grade Dressing Proceedings of New Technology Academic Discussion and Technical Achievements Exchange and Equipment Exhibition. Ma Anshan: Metal Mine Magazine, 2008: 427-430. Flat Face Mask Making Machine Flat Face Mask Making Machine,Automatic Mask Machine,Robot Surgical Machines,Mask Earloop Welding Machine Dongguan Pailade Machinery Equipment Co.,Ltd , https://www.pailade.com