The high pressure grinding rolls technology originated from the coal forming technology of the early 20th century. In 1979, Professor Schonert patented the high pressure grinding rolls. In the mid-1980s, the high pressure grinding rolls began to be used in the crushing work in the cement field to process fragile materials. The huge economic benefits have revolutionized the energy saving and productivity improvement of the cement industry. Since then, with the advent of new wear-resistant roll faces, high pressure grinding rolls have been used to process harder, tougher, more abrasive minerals and are now widely used in diamond, iron ore, limestone, copper ore and gold. Fine crushing and ultra-fine crushing of ore.
Compared with the traditional grinding process, the high pressure grinding rolls process is mainly reflected in energy saving, pre-tailing to reduce the amount of subsequent grinding, and to improve the subsequent processing index.
1.1 Energy saving advantages
Compared to conventional crushers and mills, the main technical advantage of high pressure grinding rolls is energy savings. According to the application experience of domestic and foreign selection plants, the high-pressure roller grinding process saves 15% to 30% compared with the traditional grinding process. Compared with the traditional crushing and grinding equipment, the high-pressure roller mill acts differently on the material, and exerts a relatively slow force on the material particles, so that the internal structure of the material is destroyed and the energy utilization rate is high.
The energy-saving advantage of the high pressure grinding rolls is also reflected in the fact that after the material is rolled, micro-cracks are generated inside, which reduces the ball-grinding index of the subsequent grinding, so that the unit power consumption of the subsequent grinding is reduced. In addition, compared with the conventional crusher, the high-pressure roller mill will increase the fine powder content and reduce the unit power consumption of subsequent grinding.
1.2 Pre-spinning reduces the amount of subsequent grinding
If the high pressure grinding rolls is used as a superfine crushing device after the third-stage crusher, it can be called a quasi-grinding process, and the particle size is close to the self-grinding/semi-self-grinding grinding effect, which can meet the requirements of the conventional rough grinding and early tailing operations. The requirements of particle size, dissociation and other characteristics, combined with wet coarse-grain tailing, can significantly reduce the subsequent grinding amount and increase system capacity.
For some ultra-poor magnetite ore (TTe < 15%) with a coarser grain size, the advantages of high pressure grinding rolls are even more pronounced. After the rolling product is classified, magnetic pre-concentration is carried out, which can throw away a large number of gangue, improve the grade of grinding ore, reduce the subsequent grinding treatment, reduce the cost of ore dressing, and improve the utilization value of the super-poor magnet deposit.
1.3 Selecting processing advantages
The crushing of the high pressure grinding rolls is quasi-static crushing. The material layer is pulverized. After the material between the rolls is squeezed, the material and the material are pulverized with each other, and a large number of cracks are generated inside the particles to make useful minerals in the subsequent grinding. Dissociation in advance can reduce the feed size and drug consumption of subsequent selection within a certain range. At the same time, the generation of micro-cracks in the rolled product can reduce the over-grinding and muddy phenomenon of subsequent grinding and improve the subsequent processing index.
There are a large number of micro-cracks inside the high-pressure roll mill product, which makes it uniquely advantageous in the heap leaching process, allowing the leachate to penetrate faster and deeper, increasing the leaching speed and leaching rate of useful minerals, and reducing the heap leaching process. Complexity, reducing upfront investment and operating costs.
The high-pressure roller mill can be broken as the third stage after being crushed, or it can be used as the fourth-stage superfine operation after the fine crushing operation. The high-pressure roller grinding process can be divided into three types: open-circuit crushing, edge material return crushing and vibrating screen closed-circuit crushing.
2.1 Open circuit crushing process
The high-pressure roller mill open-circuit crushing process refers to the high-pressure roller mill product directly entering the next working process, and no longer returns to the crushing process of the high-pressure roller mill. The open roll product can be directly fed into the ball mill for grinding, or it can be classified first, and the coarse product enters the ball mill for grinding. This process has obvious advantages when the fine powder content of the rolled product is high.
The advantage of the open circuit crushing process is that the process flow is simple and smooth, the system is stable, and the operation and management are convenient. However, due to the non-grading operation, the product granularity is uneven, and the rolled product will be mixed with a little large particle material, which is bad for subsequent grinding. Impact, the actual operation of the plant can be added to the appropriate amount of large balls to alleviate such problems.
2.2 Edge material return crushing process
The high-pressure roller mill edge material returning crushing process refers to the process in which the high-pressure roller grinding intermediate product directly enters the next working process, and the material is returned to the high-pressure roller mill to be broken again. After rolling, the intermediate product can directly enter the ball mill for grinding, or it can be classified first, and the coarse product enters the ball mill for grinding. This process has obvious advantages when the fine powder content of the rolled product is high.
The process also has the advantages of simple and smooth process, stable system and convenient operation and management. The proportion of edge material can be adjusted within the range of 0 to 50%, but it is not possible to return all the coarse minerals that have not been rolled by the high pressure roller mill. . Compared with the open circuit system configuration, the proportion of coarse-grained products has dropped sharply, but the crushing is still incomplete. There are also a lot of large-grain materials in the rolled products, which will have adverse effects on subsequent grinding.
2.3 closed circuit crushing process
The high-pressure roller grinding closed-circuit crushing process is divided into dry screening and wet screening according to the different classification methods.
The dry screening of the high-pressure roller mill needs to be equipped with a dispersing machine to break up the rolling cake, otherwise the screening efficiency will be greatly reduced. In addition, since the whole process adopts dry grinding, dry screening and dry sorting, the moisture content of the material is required to be high, and it is not suitable to treat materials with high water content. At the same time, attention should be paid to dustproof work, and dust removal is required. Equipment, etc. The process is mainly applied to non-metallic minerals and ore containing less mud, as well as water-deficient and arid areas.
(1) The high-pressure roller mill must be densely fed during use. If the feed is loose, the uneven force on the roll surface will reduce the life of the roll surface.
(2) The high-pressure roller mill must have proper powder in the feed, not only the material on the screen, otherwise the life of the roll surface will be greatly reduced.
(3) The high-pressure roller mill should be evenly fed, otherwise it will cause the squeeze roller to deflect and reduce the extrusion effect. In severe cases, the host will jump.
3.2 Iron treatment
If there is metal in the feed of the high-pressure roller mill, the life of the roll surface will be reduced. If the metal near or larger than the roll gap size is fed into the high-pressure roll mill, the partial roll surface load will be too large, resulting in damage to the stud or roll surface. If there is metal in the feed to the high pressure roller mill, the following measures can be taken to protect the roll surface.
(1) Install metal detectors and iron removers on the feed belt of the high pressure roller mill.
(2) If it is closed-circuit screening, the iron remover can be installed above the discharge end of the material on the sieve. At this time, the material on the sieve is in a loose state, which can effectively remove the magnetic metal minerals therein.
(3) In the self-grinding/semi-self-grinding machine process, if the cone crusher and the high-pressure roller mill are combined as a hard stone crushing device, a curved iron remover can be installed at the discharge end of the mill (only for non-magnetic and weak magnetic properties) Mineral), de-ironing the self-grinding/semi-self-grinding machine, and installing metal detectors and iron removers on the subsequent return belt to ensure that all metal materials in the return material are removed.
(4) In the iron removal system, the iron remover should be used in combination with the metal detector, because the iron remover can only remove the magnetic metal in the feedstock, and for the non-magnetic metal, it should be manually removed by the metal detector.
3.3 Bypass system
At present, many conditional mines have set up a bypass system in the high-pressure roller mill system, which can not delay production when the high-pressure roller mill fails, periodically repairs and replaces the roller surface. The bypass system is suitable for three-stage closed-circuit crushing + high-pressure roller mill ultra-fine crushing process, in high-pressure roller mill parking or under certain special conditions (such as continuous rain, excessive air humidity, high-pressure roller mill running poorly), materials It can be directly fed into the subsequent ball mill to make the production continuous.
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