Iron ore crushing technology (2)

Second, the transformation of the crushing system equipment
During the transformation process of the crushing process, the transformation of the crushing and screening equipment compatible with the system was carried out at the same time.
The equipment modifications carried out in the crushing process of the above three plants mainly include the following items.
1. Reconstruction of crushing equipment The Donganshan plant selected the technical research in the early 1970s to transform the mine-type mining machine used for rough crushing into the belt conveyor. After the transformation, it overcomes the problem of the chain-type mining opportunity, the yellow mud mine affects the production, and makes the coarse and broken products unimpeded. In the case of ensuring the particle size of the crushed product, the annual crushing output is increased to more than 5 million tons.
Fine crusher liner geometry: After the annual crushing output reaches 5 million tons, the lack of fine crushing capacity becomes a prominent weak link. In 1975, the geometry of the fine crusher liner was modified: First, the replacement method of the fine crusher liner was changed, and the original replacement method was changed to the same fine crusher. The plate is replaced at the same time. The second is to enlarge the vertical part of the lower part of the original moving cone lining outward, 30° with the vertical part, so that the diameter of the cone is gradually increased to ø2160mm; the third is the outer circle of the fixed cone lining. Take about 30mm in a circle (see the picture below).

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After the transformation, the curling phenomenon of the wear of the fixed cone liner is eliminated. The parallel belt of the liner is extended from 350mm to 500mm in the later stage of wear, and the moving and fixed cone liners are simultaneously replaced, and the contact gap size of the parallel belt is adjusted and improved. Therefore, it has played a significant role in improving the efficiency of the fine crusher and reducing the particle size of the crushed product, so that the particle size of the fine crushed ore-cut product with a particle size of -12 mm is increased from 35% before the change to 44.5%.
In 1977, the middle crusher lining was rebuilt, and the crusher of the first and third crushers in the three medium crushers was changed from the original crushing fixed cone liner to the fine crushed fixed cone liner (see the following figure). ).

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After the transformation, the parallel belt of the lining plate is extended from the original length of 170mm to 220mm, the inlet is reduced from 350mm to 285mm, and the feeding and discharging ports can be adjusted at any time, and the DC motor is steplessly regulated. Therefore, the medium crushing effect is exerted. Under the same conditions of the crusher discharge port, the product size of -12mm is increased from 16.82mm to 25.35%, which is 8.25%. The fine crushing load is reduced, and the closed loop load is reduced from 220% to 180%.
In 1986, the two selected plants of Dashihe and Shuichang successively replaced the crushing wall of the crusher with the crushing wall of the fine crusher to extend the crushing zone of the crusher, increasing the content of -75mm, and reducing the load of fine crushing operations. , to create conditions for reducing the size of finely divided products. The beneficiation plant water statistics, since the broken crusher with an extension, increasing grain size -75mm content, resulting in crushing system power consumption increases 0.852kW • h / t, but the entire concentrator has decreased power consumption 1.44kW • h / t And reduce the grinding steel and iron ball consumption by 0.04kg/t and 0.10kg/t respectively.
According to the situation of the Yankou iron ore mine, in recent years, the system has been carried out with the transformation of the crushing chamber as the core, taking into account the uniform fabric, feeding control, improving the material of the lining, changing the number of oscillating times and eccentricity of the moving cone, and improving the screening equipment. Transformation plan.
The following measures are proposed for the transformation of the fine crusher structure:
(1) Shorten the parallel zone to ensure that the ore is broken once in the parallel zone, increase the length of the fracture zone, and improve the utilization of the entire cavity shape.
(2) The fixed cone is changed from a straight line segment to a curved link, and the broken wall and the rolling wall joint point are staggered to reduce the possibility of blockage.
(3) The cavity shape is changed from two corner regions to four corner regions.
The shape of the cavity after modification according to the above three aspects is shown in the figure below.

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The parts of the auxiliary transformation include:
(1) Adding a single-machine driven rotary distributor: There is no separate feeder for the existing fine crushers in China. The current feeding method is that the material flows directly from the funnel to the cloth tray on the moving cone. Due to the flow direction of the material, the material scattered on the periphery of the crushing chamber is unevenly mixed, which is not conducive to crushing. In addition, the material also has an impact on the cloth tray, causing troubles and uneven wear and deterioration of working conditions. Referring to the structure and form of the disc crusher and some hydraulic cone crusher distributors, a single-machine driven rotary distributor is designed and installed above the feeder feed port.
(2) Feeding automatic control: mainly adopts power control scheme, the control parameters are taken from the crusher motor load, and the adjustment amount is the ore supply amount.
(3) Number of swinging of the moving cone and eccentricity: Increasing the number of swinging of the moving cone can increase the number of crushing of the material, which is beneficial for improving productivity and reducing product granularity. This has been practiced in China and has achieved certain effects. The intention of strengthening the crushing is limited by the strength of the power and the equipment itself, and cannot be arbitrarily improved. According to the analysis and calculation, while increasing the rotational speed, the eccentricity is correspondingly reduced to ensure that the machine strength basically meets the requirements of use, and the number of cone swings is increased by about 20%, and the eccentricity is reduced by 15%.
(4) Improved vibrating screen: Screening is an important part in the crushing system. At present, most of the vibrating screens in China's mine fine crusher have some problems, such as low screening efficiency and short life of the screen. The improved measures are: 1 increase the length of the screen surface; 2 increase the vibration frequency; 3 reduce the installation angle of the screen surface; 4 improve the feeding mode; 5 improve the screen structure and materials.
The industrial test of the crushing chamber and the distributor was carried out on the No. 5 crusher of the Yankou Iron Mine. The test results are shown in the table below. From the test results, the particle size of the improved fine crusher is significantly reduced, especially in the case of a small discharge port. When the discharge port is 6 mm, the particle size of -12 mm accounts for 60%, and the treatment capacity and before the transformation. The crushers are basically the same.

2. Reconstruction of screening equipment After the crushing system of Donganshan Concentrator is changed to closed-circuit process, the vibrating screen load is increased, the screening efficiency is reduced, the wear of the sieve plate is accelerated, and the particle size of the product is directly affected. Therefore, five kinds of iron sieve plates have been used successively, and the above drawbacks still exist. Therefore, in 1978, a rubber sieve plate was used, the specification was 600×600 mm, the thickness was 20 mm, the upper opening of the mesh hole was 15.5 mm wide, and the lower opening was 17.5 mm wide. The transformation effect is better, the inspection and installation is convenient, the service life is 3.4 times longer than the iron sieve plate, and the equipment operation rate is increased by 2%. The original vibrating screen has a small amplitude and insufficient vibration force, which causes the material to move at a slow speed. The surface of the material is thickened and the screen is often pressed and the sieve plate is affected by the mud ore, so that the screening efficiency is lowered. To this end, the flywheels on both sides of the original vibrating screen are increased in weight, and the center-to-center eccentricity is changed from 21° to 23°, thereby increasing the amplitude and increasing the vibration force, improving the working conditions of the sieve and improving the screening efficiency. . The original vibrating screen is concentrated in the middle part of the sieve plate, and the plow type miner is modified and welded in the feeding funnel. As a result, the original concentrated sieve plate is changed to a uniform distribution to the ore, which improves the utilization of the screen surface. Screening efficiency plays a major role in stabilizing and controlling product particle size.
The water mill iron ore dressing plant and the Dashihe iron ore dressing plant also carried out the transformation of the vibrating screen equipment. In 1984, the sieve material was changed from Q235A grade steel to 20MnV round steel, and its life span was extended from 14 days to 27 days. The screen is changed from a flat surface to an upwardly convex curved screen surface to make the material evenly distributed. From 1985 to 1987, the sieve hole of the 1/3 sieve was changed from 12mm to 10mm.
3. Speed ​​up the feeder speed water plant and Dashihe plant to increase the speed of the ZBC2400×1200mm heavy-duty plate feeder from 0.065m/s to 0.07m/s. In addition, replace the conveyor belt to slow down. The machine and the addition of a fluid coupling (protecting the main motor) to accelerate the belt conveyor.
Third, the explosion hardening of the coarse crusher cone bushing

A cone bushing is so symmetrically divided into two patches, which can be detonated, so that each side has a "diarrhea" surface on each side, so as not to cause the jacket to crack. Under normal circumstances, a coat can be detonated twice and put two shots to complete an explosion hardening. If the jacket is subjected to two explosive hardening treatments, it can be repeated as described above.
The test was subjected to two explosion hardening treatments (four batches). The initial hardness of the jacket was HB175 on average, and the average hardness of HBB was 306 after one explosion hardening; the average was HB389 after two explosion hardenings. The two hardness increases were 74.8% and 122.3%, respectively.
The rough crusher cone jacket after two explosion hardening treatments was installed in the waterworks iron ore mine in December 1987. The results showed that the service life was increased by 28.5% (see table below).

The annual production of Shougang Mining Company's plant is about 720 tons of broken wall and rolled wall. If the increase is 25%, the whole company can save 180 tons/a of high-quality high-manganese steel castings and machined parts.

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