How to improve the efficiency of the grinding machine?

In the grinding operation, improving the efficiency of grinding technology is of great significance for improving the mineral processing index. How can we improve the efficiency of grinding technology? According to the above questions, we can consider the following aspects.

(1) The grinding process with reasonable closed-circuit grinding process should be that the mineral particles should be quickly discharged from the grinding machine once they are ground to the monomer separation. In this way, over-grinding can be avoided, and on the other hand, the grinding medium can be completely applied to the coarse ore particles, so that the energy can be used to the maximum extent. However, it is very difficult to classify the material in the existing grinding machine. For this reason, a classifier or fine sieve is used to separate the qualified fractions of the grinding products, and the coarse particles are returned to the grinding machine for re-grinding (also called returning). sand). It can be seen that in the closed-circuit grinding, the ore feeding of the grinding machine is added to the new ore, so the grinding machine passes more materials, the speed of the material passing through the grinding machine is accelerated, and the grinding time is short. In closed-circuit grinding, it is necessary to force unqualified coarse particles to pass through the grinding machine repeatedly until the grinding is qualified. Secondly, in the case of closed-circuit grinding, the coarse fraction of the mill feedstock is increased due to the large amount of coarse sand fed. According to the principle of grinding dynamics, energy is maximized to be useful, so the grinding speed is increased and the productivity of the grinding machine is increased. In addition, due to the presence of an appropriate amount of sand return, it can eliminate the fluctuation of the new ore of the mill and produce an influence on the particle size of the product.

It can be seen that closed-circuit grinding can effectively avoid excessive smashing and â€œrunning roughâ€ phenomenon. It enables the grinding operation to obtain a uniform and coarser narrower level of product under the premise of ensuring the qualified particle size, which is advantageous for the next sorting operation.

(2) The practice of using different grinding machines has proved that the rod mill with peripheral discharge can reduce over-grinding, especially for brittle minerals. Due to the faster discharge rate of these grinding machines, the large-density ore particles that are deposited on the bottom layer of the slurry are easy to be discharged, and the rod mill also reduces the excessive pulverization phenomenon by using parallel long steel bars as the grinding medium. In addition, due to the shallow slurry surface of these grinding machines, the buffering effect of the slurry on the grinding medium is small, so that the grinding medium can fully exert the crushing effect, so the production capacity of these grinding machines is large.

In the selection of grading equipment , the use of fine screen and mill closed circuit, or pre-grading has certain advantages. When using a fine sieve as a sorting device. It can strictly control the particle size of the grinding machine, so that the coarse particles can not be discharged, effectively avoiding the phenomenon of â€œrunning roughâ€. Secondly, the screening efficiency of the sieve is high, about 80% to 90%, while the spiral classifier and the jaw classifier usually have a classification efficiency of only 40% to 60%. This easily leads to the re-grinding of the qualified fine-grained grade, resulting in over-grinding.

(3) The following aspects should be noted in the operation of the grinding machine.

1 When closed-circuit grinding, the appropriate cyclic load production practice shows that, within a certain range, the productivity of the grinding machine increases with the increase of the sand-return ratio, and the fluctuation of the classification efficiency under the condition of large return-to-sand ratio The impact on the productivity of the mill is small. When the sand return ratio is too small, the superiority of closed-circuit grinding is not exhibited, and 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.

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 selection 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 Î¼m increased from 10.6% to 14.73%, corresponding to the gold. The share of genus increased from 3.18% to 4.57%.

3 ball loading system to properly fill the ball system including the quality of the steel ball (density, hardness, wear resistance), steel ball size, steel ball filling rate and 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 hits per unit time. The filling rate increases and the number of balls increases, thereby increasing the grinding effect, which is an advantageous aspect of improving the filling rate. However, the optimum speed of the grinding machine is related to the filling rate of the ball. When the filling rate is large, 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, and the production capacity is correspondingly reduced, which is an unfavorable aspect. The above factors are contradictory. At present, there is no universal theoretical formula for calculating the optimum filling rate of the grinding machine. Usually, the appropriate filling rate is determined according to the test. In production practice, the conversion rate is 76% to 88%, and the filling rate is 40% to 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. However, when the ore size is small and the grinding product is required to be fine, the large ball is too much and not suitable, and some small balls should be installed.

At present, the steel balls used in many factories in China are too large, and some have added 120 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. Tests show that the larger the ball diameter, the faster the wear. When the grinding machine rotates at a higher speed, the wear rate of the steel ball is proportional to the cube of the ball diameter. When the rotational speed is low, the wear rate of the steel ball is proportional to the square of the ball release.

However, a steel ball that is too small is basically unable to grind, but instead occupies the volume of the grinding machine, consumes electric energy, and affects the production capacity of the grinding machine. Generally, the ball grinding effect of less than 10 mm is small.

After correctly correcting the size of the ball, it is also necessary to solve the appropriate ratio of the ball. In addition, the ball mill will continuously wear the steel ball in continuous work. In order to maintain the proper filling rate and ball ratio of the ball, it is necessary to make a reasonable ball for the grinding machine.

4 The concentration of grinding should be too high or too low. In actual operation, attention should be paid to the adjustment of water quantity.

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