1 Purpose and significance of grinding The grinding is the continuation of the crushing process and the last processing of the ore before the sorting. The purpose of grinding is to make all or most of the useful components in the ore reach the monomer separation, and at the same time, to avoid the "over-grinding" phenomenon, and to achieve the particle size required for the sorting operation, in order to effectively recycle the sorting operation. The useful ingredients in the ore create conditions. A lot of grinding work and sorting operations, good or bad sorting index (concentrate taste and metal recovery), and depends largely on the quality of grinding minerals. If the fineness of the grinding product is not sufficient and the minerals do not reach sufficient monomer separation from each other, the selection index will not be too high. The slime produced by overgrinding is difficult to recover effectively. For example, a strong magnetic separator can effectively recover a particle size lower limit of 30 microns. Slime less than 30 microns is difficult to recycle. The lower limit of the particle size of the electrostatic concentrator can be effectively recovered. The lower limit of the particle size is 25 microns, and the less than 25 microns is the slime, which is difficult to recycle. For froth flotation, the lower limit of the effective recovery is 3-10 microns. If a large amount of slime (ie, less than 3-10 microns of ore) is produced due to grinding, the consumption of flotation chemicals will increase, the selectivity of the flotation process will be lost, and the recovery rate and concentrate grade will be affected. In severe cases, it may even make flotation difficult to proceed normally. In addition, the grinding products are also required to meet the concentration required for the sorting operation. Various sorting operations have their appropriate concentration ranges, which are not suitable for too high or too low. Grinding operations also have a lot to do with the economic indicators of beneficiation. Grinding is one of the most power-consuming operations of the concentrator. Only crushing and grinding accounts for about 45-65% of the power consumption of the plant. At the same time, the grinding operation is also a large operation that consumes metal. According to statistics, when grinding a ton of ore, the total loss of grinding media (such as steel balls or steel bars) and liners is 0.4-3.0 kg. Therefore, in the entire ore dressing cost, grinding costs account for a large proportion. It can be seen that improving grinding operations, improving the quality of its products, reducing grinding costs, and increasing the productivity of the grinding machine can not only improve concentrate quality and metal recovery rate. It is also important to reduce the total cost of dressing and increase the productivity of the concentrator. 2 Main factors affecting grinding efficiency 2.1 Influence of ore properties The composition and physical properties of ore have a great influence on the grinding effect. When the useful mineral in the ore is coarser and the structure is loose and brittle, it is easier to grind. When the useful mineral has a finer grain size, a dense structure, and a higher hardness, it is more difficult to grind. In the production, under the premise of the technical requirements of the beneficiation process, reasonable ore distribution can be carried out, the ore size can be made as uniform as possible, and the ratio of the block and powder minerals is reasonable and stable. 2.2 Influence of equipment factors Equipment factors have a certain impact on the grinding effect. For example, the overflow ball mill has a slower discharge rate, and the large density of the ore is not easily discharged, and it is easy to cause excessive pulverization. In addition, the classifier which constitutes a closed circuit with the grinding machine, when the classification efficiency is low, is easy to be pulverized, thereby reducing the efficiency of the grinding technology. 2.3 Influence of operational factors Operational factors undoubtedly affect the grinding effect. The ability to effectively control the return sand ratio, grinding concentration, grinding machine speed and ball loading system during grinding operations directly determines the quality of the final grinding product. 3 How to improve the grinding and grinding operation 3.1 When closed-circuit grinding, the appropriate cyclic load production practice shows that the productivity of the ball mill increases with the increase of the sand-return ratio within a certain range, under the condition of large return-to-sand ratio The fluctuation of the classification efficiency has little effect on the productivity of the mill. When the sand return ratio is too small, it shows the superiority of closed-circuit grinding. Therefore, it is advantageous to appropriately increase the sand return ratio. Usually, the amount of sand returned by the rod mill is smaller than that of the ball mill because the rod mill has a small volume in the medium volume and contains less material. 3.2 The speed of the mill should be controlled when the appropriate speed is slightly higher, although higher productivity can be obtained. However, since the relative motion is intensified and the grinding medium has a large energy, it is easy to over-crush the material. For example, after a certain plant increased the rotational speed of the rod mill from 27 rpm to 29.7 rpm, the productivity increased by 3.7%; but the yield of less than 19 micron increased from 10.64% to 14.73%, and the corresponding metal possessed The rate increased from 3.18% to 4.57%. 3.3 Ball loading system The ball loading system should include the quality (density, hardness, wear resistance) of the steel ball, the size of the steel ball, the filling rate of the steel ball and the reasonable addition. When the large-density and large-diameter steel balls fall, the impact force is large, and the hardness of the steel ball is large, and the wear resistance is good, and the grinding and peeling force is strong. Therefore, for hard and coarse ores, steel balls of large density and large diameter are required. However, in order to effectively grind fine ore particles and increase the number of hits of steel balls per unit time, steel balls with smaller diameters are required. When the filling rate is constant, the smaller the ball diameter, the more the number of balls, and the more the number of hits per unit time. The filling rate increases and the number of balls increases, thereby increasing the grinding effect. However, when the filling rate is increased, the centrifugal speed of the ball mill is correspondingly reduced, and the grinding effect is also reduced. At the same time, the effective volume of the grinding machine is also reduced due to the increase of the ball filling rate, thereby reducing the production capacity. In production practice, the filling rate is mostly 40-50%. The size of the ball is determined by factors such as the density of the ball, the particle size composition of the ore, the required product fineness, and the physical properties of the ore. According to general experience, the larger the nugget, the harder the ore, and the larger the ball diameter. When the ore size is small and the grinding product is required to be fine, some small balls should be installed. At present, many factories in China add 100 mm diameter steel balls regardless of the size of the ore. This is unreasonable. Adding unnecessary oversized steel balls, in addition to increasing the over-grinding of the grinding, increases the consumption of the steel balls. The larger the ball diameter, the faster the wear. A steel ball that is too small is basically not grinding. Instead, it occupies the volume of the mill, consumes electricity, and affects the production capacity of the mill. Generally, the ball grinding effect of less than 10 mm is small. In addition, the ball mill will continuously wear the steel ball in continuous work. In order to maintain the ball filling rate and the reasonable ratio of the ball and maintain the stable operation of the ball mill, it is necessary to make a reasonable ball to compensate for the wear. (4) Grinding concentration should be appropriate, too high and too low are not good, the actual operation should pay attention to the adjustment of water volume. Grinding concentration has a great influence on the grinding effect. Because the grinding concentration directly affects the grinding time, the concentration is too large, the material flows slowly in the mill, the grinding time increases, and it is easy to over-crush. In addition, in the high concentration of the slurry, the coarse particles are not easy to sink, and it is easy to flow away with the slurry, resulting in "running rough". If the concentration of the slurry is too thin, the material flow rate will increase. The time of grinding is shortened. There will also be “running roughâ€, and large-density ore particles will easily deposit on the bottom layer of the slurry, which will also cause over-grinding. Therefore, proper grinding concentration should be mastered during operation, which requires strict control of water consumption. Generally, the coarse grinding concentration is usually 75-85%, and the fine grinding concentration is generally 65-75%. Machining Steel is the use of CNC machining out,and the machining services including drilling, boring, cutting,meatl bending/metal bending, machining Steel Product material: carbon steel, 20#, 45#, A3, Q235,35Cr2MnMo and other series. In the high-speed machining out of the workpiece has a good finish. But machining Steel of the workpiece is easy to rust, so it will do heat treatment, surface nickel plating, chromium plating, surface black heat treatment, etc.. We have a special inspection department to carry out inspection, ensure the material aging hardness and each size to meet the requirements of the drawings, including the machining steel parts application in various industries: automotive, marine, communications, medical equipment, industrial automation equipment.Except them,we supply the sheet metal operations. Machining Steel, CNC Machining Steel, Machining Steel Parts, Metal Machining Hong Kong RYH CO., LTD , https://www.szcncmilling.com