Grading is an extremely important preparation task during the beneficiation process. Grading can effectively separate the coarse and fine particles, thus avoiding the excessive pulverization of the fine-grained minerals, reducing unnecessary energy consumption, and enabling the granular minerals to be effectively crushed by the returning sand returning mill. The quality of the grade directly affects the level of technical and economic indicators such as the production capacity of the mill, the quality of the products and the concentrate grade and recovery rate of the subsequent sorting operations.
1 grading equipment large-scale and wear-resistant components development
  The world's largest spiral classifier 2FC38 developed by China North Heavy Industry Co., Ltd. is a double helix busy Φ3 800m m . It is used well in mines such as Yunnan Jingdong and Φ3. 6m ball mill .
  The large-diameter hydrocyclone is mainly used for forming a closed-circuit grinding with a large ball mill due to the coarse separation d 50 . The largest foreign hydrocyclone (excluding the heavy medium cyclone) is Φ8 38mm (33 inches) from Krebs, USA . The domestic Weihai Haiwang Cyclone Company has a maximum specification of Φ8 5 Omm, its maximum feed size is 22mm, and the feed rate is 0.03-0.15MPa, the processing capacity can reach 500-900 m 3 /h .
  Due to the limitation of the principle of centrifugal force, the hydrocyclone has reached the limit. At the same time, the smaller the radius of gyration, the larger the centrifugal force, the smaller the separation particle size d 50 , and the enhanced grading of the small diameter cyclone is more important. For example, Φ 150mm hydrocyclone, the maximum feed size is 1.5mm, the feed pressure is 0.05~0.4MPa, the treatment amount is 11~20m 3 /h, but the separation particle size is fine, 0.020～0.074mm. Φ5 Omm small and Φ 25mm diameter polyurethane hydrocyclone in non-metallic mineral beneficiation get the application. In order to increase the throughput, a plurality of small diameter cyclones are usually used in the unit.
  At present, the total area of ​​the single screen of the largest fine screening equipment in China can reach about 18m 3 . There are many fine screen apparatus, wherein the main types representative :( 1) the screen frame and the screen at the same time the vibration type, such as laminate Derrick U.S. sieve of Hubei Xin Eagle HGZS sieve stack; (2) Electromagnetic Vibrator vibration network type, such as China's GPS high-frequency vibrating screen, MVS high-frequency vibrating screen.
  There are many types of fine screens. The high-frequency vibrating fine screens for domestic main applications are : (1) GPS-900-3 high-frequency fine screen developed by Changsha Research Institute of Mining and Metallurgy ; (2) Developed by Guangzhou Nonferrous Metal Research Institute GYX type high frequency vibration fine screen ; (3) MVS type electromagnetic vibration high frequency vibrating screen developed by Tangshan Lukai Technology Co., Ltd .; (4) HGZS type laminated high frequency vibrating fine screen developed by Hubei Xinying Company. The main application of US foreign Drake (De r rick) high-frequency vibration fine sieve, Derrick fine sieve in the domestic tungsten tin mining applications are also popular acclaim.
  Wear-resistant materials in the grading apparatus, Zhaixiao Wei et al. Reported of spiral classifier vanelets cast wear-resistant iron, manganese, chromium added high-alloy cast iron can be significantly extended service life. The small blade of polyurethane is used in the Yunfu pyrite mine in Guangdong Province, and the service life is more than 300% higher than that of the original cast iron . The CZ-type cyclone lining produced by the Mining and Metallurgical Equipment Company of Changsha Mining and Metallurgy Research Institute uses CNU wear-resistant materials developed in cooperation with Ukraine. Hubei Xin Eagle developed anti-blocking and abrasion resistant urethane screen, Jane shaped aluminum alloy electric vibrator, pangang group Mining Co. Midi Concentrator Drake sieve comparative test, the good results.
2 hierarchical process control
  The stability and automation of the grading process is an important factor in determining efficiency. Therefore, the automatic and stable control of the grading process is also an important development direction of grading operations. Yu Qingqiang introduced the slurry flow of the hydrocyclone to the mine pump using the frequency converter. Zhao Jing et al. conducted research on the automatic control system of hydrocyclone. By introducing an adjustable grit diameter diameter cyclone, a closed loop control loop of the cyclone grit size is realized. Liu Weisheng researched and developed the digital control system of electromagnetic vibration high-frequency vibration mesh screen. It adopts embedded integrated software and Client / Serv e r structure to communicate with the control board through Modbus protocol to realize the control and data processing of high-frequency vibration mesh screen.
3 new classification equipment
  In recent years, there developed a new grading equipment: Compound round sieve spiral classifier, a spiral classifier bilateral discharge, flows obliquely narrow spiral classifier, fixedly connected to spiral classifier, centrifugal classifier cyclone pre volute. America's new K rebs g MAX hydraulic rotary flow. DXFDZS complex vibration frequency fine sieve, a sieve classification efficient secondary flow.
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