Research progress in grinding process

Grinding is an indispensable process in the processing of minerals. The purpose is to decompose the valuable mineral components and gangues in the ore from the granules into relatively independent monomers, or multiple kinds of valuables. The components are separated from the gangue into relatively independent monomers, and the useful components are separated into individual concentrates by physical beneficiation . Therefore, the research and application of different minerals and mine grinding processes have always been valued.

In recent years, the grinding process mainly includes stage grinding process, self-grinding and semi-self-grinding process, high-pressure roller mill-ball milling process, etc., and development and application promotion are faster.

1. Selective grinding grade pre-selection process

Feng Qiming et al describes the development of "selective grinding bauxite - Flotation desilication agglomeration." Process and its effect in industrial applications of Zhongzhou Aluminum Company. The process fully utilizes the selective disintegration characteristics of bauxite for selective grinding, so that the ratio of coarse-grained aluminum to silicon in grinding products is increased, and the coarse-grained grade is directly used as concentrate, and then by selective agglomeration flotation Processing fine-grained grades, producing fine-grained flotation concentrates, combined with coarse-grained concentrates.

Wang Cuihua et al. reported a selective grinding classification pre-selection process for a quartz - fluorite ore. Since the difference in hardness between the target mineral and the gangue mineral is large, by simply setting the screening equipment in the middle of the grinding classification, the difficult-to-grind, low-grade gangue is removed in advance, and the amount of minerals entering the flotation is reduced. Improve the processing capacity of the ball mill to achieve energy saving.

2. A section of grinding process

Western Mining Company iron tin lead zinc ore mountains because disseminated grain size of minerals fairly thick lead, disseminated relations with other minerals is relatively simple, using ore period of closed-circuit grinding process. Yuntianhua International Chemical Furui Branch Grinding System uses a closed-circuit grinding.

In a closed-circuit grinding process, control grading is sometimes added once to achieve acceptable monomer dissociation to meet subsequent sorting operations. Shandong Jinjin Mining Jinruiling Gold Mine transformed the original grinding process from a closed-circuit grinding system into a closed-stage grinding grading system with one section of grinding, one section of inspection and classification, and one section of controlled classification.

3. Two-stage grinding process

When the size of the ore inlay is fine, the ore fineness is required to reach -0.074mm, and the ore with a higher content of more than 75% can obtain a better selection index. Usually, a two-stage grinding process is required. The outstanding advantage of the two-stage grinding is that it can obtain a finer product, can be coarsely ground and finely ground in different grinding sections, and the product has a uniform particle size composition and less over-grinding. The two-stage closed-circuit ball milling process is currently the most widely used grinding process in the concentrator. Under normal circumstances, a section of grinding uses a lattice ball mill and a spiral classifier to form a closed circuit, and the second section of the grinding uses an overflow ball mill and a cyclone to form a closed circuit.

Liu Shixu introduced the Yunnan Red Hill copper mine contrasting study period of grinding and grinding of two. For the same size mill, when processing medium-hard ore materials, the unit production capacity of the two-stage grinding is 0.1-0.2t/(m ³ .h) higher than that of one-stage grinding, and the system production capacity can be increased by 7%. The product granularity characteristics of the closed-circuit grinding are better than that of a closed-circuit grinding.

4. Rod mill + ball milling process

The rod grinding + ball milling process belongs to a two-stage grinding process. The first section of the grinding uses an open rod mill, or a rod mill + a ball mill, and the second section uses an overflow ball mill.

The processing capacity of the second ore dressing plant of the largest copper- nickel mine in Gansu Jinchuan Nonferrous Metals Co., Ltd. in China is 9000t/d. The current principle process is two-stage grinding and stage flotation. One section of grinding is composed of a rod mill and a ball mill. The 1000t/d concentrating plant of Shizhuyuan tungsten- molybdenum- bismuth polymetallic ore uses rod grinding + ball milling technology. One section of grinding uses a spiral classifier as the inspection grading of the rod mill and the pre-classification of the ball mill. An overflow ball mill is used. Lu Chaobo introduced the technical measures for the fluctuation of the original tin grade in the Huahe Concentrator of Guangxi Huaxi Group. The grinding process consists of rod grinding + ball milling.

5. Stage grinding stage selection

The commonly used stage grinding and floating process is a two-stage grinding and floating process. There are three possible solutions: coarse concentrate regrind process, medium mine regrind process and tailings regrind process. With the reduction of rich mineral resources, in order to effectively separate and enrich useful minerals from lean mineral resources, the stage grinding process is increasingly valued. Such as coarse concentrate regrind process, medium mine regrind process, tailings regrind process.

6. Self-grinding process and semi-self-grinding process

A single self-grinding process

The autogeneous mill is a grinding machine which uses the pulverized material itself as a grinding medium. Compared with the ball (rod) mill, the self-grinding machine has a large ore feeding size, generally 200-300 mm, and the crushing ratio is large. It can replace medium, fine crushing and a length of grinding, simplifying the grinding process. When the wet self-grinding machine treats the ore with high water content, it can eliminate the washing operation and simplify the crushing and screening process, which has obvious superiority.

B Semi-grinding + ball milling process

Semi-autogenous grinding + ball milling process, also known as SAB process (SA: semi-autogenous mill; semi-autogeneous mill;

B: ball mill). In 2006, the 4th International Self-grinding/Semi-self-grinding Conference was held in Vancouver, Canada, and four volumes of essays were published. The 116 essays of the conference proceedings have been translated and published in the second issue of Foreign Metal Ore Dressing Magazine in 2007. The collection has introduced a large number of development and application status of foreign semi-self-grinding processes. The 5th International Self-grinding/Semi-self-grinding Conference in 2011 was held in Vancouver, Canada, and the sixth session was held in 2015.

In order to solve the problem of difficult-to-grind particles in the self-grinding machine and improve the grinding efficiency, a small number of steel balls (ball diameter 80-180 mm) are added to the self-grinding machine, which is called a semi-autogenous grinding machine. The filling rate of the steel ball of the semi-autogenous mill is generally 6%-12%, and the total material filling rate is not more than 30%-40%. The speed rate is 70%-80%, and the crushing ratio can reach 100-150. Because the semi-autogenous grinding process has the advantages of large processing capacity, saving energy consumption of crushing and grinding, reducing dust pollution, and simple process, the foreign semi-self-grinding process has developed rapidly. Most of the large-scale concentrators built in the 1980s have adopted semi-self-grinding. The process has become a routine process in the field of mineral processing.
C    Semi-grinding + closed ball milling + hard stone crush
Semi-autogenous grinding + closed ball milling + hard stone crushing process, also known as SABC process (SA: semi-autogeneous mill; B: ball mill, ball mill; C: cone crusher , cone crusher). The SABC process also uses two kinds of intensive grinding measures, namely semi-self-grinding and the removal of gravel from the mill for crushing, which can effectively solve the problem of accumulation of difficult-grain critical particle size materials. It is currently a popular process and has been used in many large metal mines in the world in recent years, such as the Cadia gold mine in Australia, the Escondida copper mine in Chile (fourth phase), the Sossego copper mine in Brazil and the Kennecott copper mine in the United States (reconstruction). Etc., is currently the process of promotion and application of large foreign concentrators.

7. High-pressure roller mill-ball milling process

The application of high-pressure roller press conforms to the principle of “multi-breaking and less grinding”, and the high-pressure roller mill has been widely used in China's cement industry. Wenping introduced the transformation of the Φ4.8m×9.5m ball mill and roller press combined cement grinding system. In August 1995, Krupp Polgsius's Φ2.4m×1.4m PoLycom high-pressure roll mill was used in the Cyprus Sierita copper mine in the United States and began to be popular in the metallurgical industry.
attention. In recent years, Australia's One steel magnetite ore dressing plant, Russia's Zapadnoye gold ore dressing plant, Australia's Boddington Gold Mine gold mine, etc. have used high-pressure roller mill to crush ore. At the beginning of 2007, China took the lead in introducing a German high-pressure roller mill to crush iron ore at the Hongshan Concentrator of Mashan Iron and Steel Group Nanshan Mining Company. In August 2013, the high-pressure roller mill project of the alumina plant of Chinalco Henan Branch was put into operation. After the actual production inspection, the high-aluminum ore milled by the high-pressure roller mill has a particle size of less than -8mm and the pass rate is over 85%. After production, the productivity of the lattice type ball mill and tube mill can be increased by 20%, and the energy consumption can be greatly reduced. High-pressure roll-grinding—The economics of the ball-milling process can compete with the semi-self-grinding-ball milling process. High-pressure roller mill-ball milling process is also the development direction of the mineral processing industry.

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