In recent years, semicontinuous mining technology has been widely used in large open-pit coal mines. In this mining process, the mobile (semi-mobile) mineral sizers are the key equipment. Since 1970s, many coal mines in China have had to change the mining technology due to the lack of such equipment, which has increased the mining cost. Developing large-scale mobile mineral sizers with double-tooth roller can not only provide reliable and efficient equipment in the open-pit coal mine, meet the requirements of semi-continuous mining technology, but also provide the gap in designing and manufacturing mobile (semi-mobile) mineral sizers in our country, thus leading to manufacturing crushing equipment level to rise to a new level. With its light weight, small size, low machine height, large feeding size and high crushing ratio, the new double-tooth roller mineral sizers are ideal for semi-continuous mining processes in various open-pit mines. The study of the new double-toothed roller mineral sizers is just begun in our country and is still in the stage of profiling design. Power calculation is a key part of mineral sizers design. It directly concerns the success of the subsequent design. Theoretical and experimental studies have been conducted in this paper on the calculation method of mineral sizers with a new double-tooth roller.
In 1957, Charles proposed a general formula of crushing energy consumption, dA=-C 1), where dA is the energy consumed when the particle size reduces dx; C,a is a constant; x is the particle size. Integrate the above equation, then A= cg=c score) In equation a, D is the average particle size of the material before crushing; d is the average particle size of the material after crushing. By substituting a2,al and a0.5 into the above formula respectively, R ittinger, K ick-K irp ichev,.Bond formula recognized by the mineral processing industry is obtained. Theoretically speaking, R ittinger formula only considers the energy consumption of surface area increase during crushing, K ick K irp ichev formula only considers the deformation energy before crushing, and Bod formula is exactly the geometric average of the previous two formulas. In fact, the actual energy consumption is the sum of the surface area plus the deformation energy. The feeding size is different, and the proportion is different. In coarse crushing, due to the large volume of materials, deformation energy consumption accounts for a large proportion, and relatively speaking, from before crushing to after crushing, due to the increase of surface area, the required power consumption will increase sharply. Therefore, the above three formulas have different ranges in application. R ittinger. Formula is suitable for fine grinding, K ick-K irp ichev formula is suitable for coarse crushing, and Bond formula is in between. As mineral sizers is a new model, no empirical formula can be used. For example, wn=c-)=1om(zai -)(kw.h) according to the universal formula proposed by Charles, where m is the Bond work index kWh); d is the particle size (μm) of the component that accounts for more than 80% of the discharge particle size;) Is the particle size (μm) of the component accounting for more than 80% of the feeding particle size: is the constant exponent.
It is difficult to determine the size of an exponent using this formula. Let's calculate the range of values. The Bond work index of some rocks and coal in Yuanbaoshan open-pit coal mine is 8.72kWh for coal, 12.40 kWh for inner sandstone and 17.52kWh for coarse sandstone. mineral sizers of the new 1250 double-tooth roller: production Q=2100th, discharge size d=2×105μm, feed size D=5×105μm. For three different materials, the power N' N'=WHQ) can be calculated according to formula 3). The relationship between N' and i is shown in Figure 1. As can be seen from the figure, when < When 0.45, N will increase sharply, and the power required by the three materials is very different, and when > At 0.5, the power obtained will be smaller than the actual situation. Therefore mineral sizers of the double-toothed roller are preferred: 0.45< i< 0.5. Take 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, separately obtained by the power of N 'as you can see: when take 0.48 and transmission efficiency of N take 0.85, motor power N = N'/N = 3720.85 = 437.6 kW. This calculation result is in good agreement with the actual situation of the prototype. Based on this, we can determine the mineral sizers power formula of the new 1250 double-tooth roller
Since many parameters of mineral sizers are related, mineral sizers are built with double-toothed rollers on the principle of similarity. The mineral sizers can be simulated with two types of tooth rollers: a four-tooth roller and a six-tooth roller. The center distance of the tooth rollers can be adjusted. The bench test of the experimental machine can determine which formula is used to calculate the power of mineral sizers of the new double-toothed roller and the coefficients in the formula. The installation of experimental system equipment is shown in Figure 2. Each crushing test material 200kg, material composition: D=025mm material 40kg; D=25~40mm material 60kg; D=4080mm material 60kg; D> 80mm material 40 kg. Manually pour the prepared material into mineral sizers bin, place the receiving box under the machine, start mineral sizers, adjust the frequency converter to the given speed, open the ram under the bin quickly while the test system is open, start the timing, test and record the speed, power, torque and other parameters, stop after 1 hour. Weigh the broken product. The tooth roller was replaced and the center distance of the two rollers was adjusted for the second test. A total of 9 tests were carried out.