Selective Dissociation Enhanced Sorting Technique for Fine Minerals

For the development and utilization of mineral resources tend to lean, thin, heteroaryl, wherein the fine particle size lot disseminated gold ore, silver ore, molybdenum ore, copper ore, nickel ore, lead ore and zinc ore iron. For example: Shanxi Taigang Yuanjiacun iron ore, to achieve 90% mineral dissociation, grinding fineness needs to reach -38μm 95%; Hunan Mindong iron ore, Dongkou iron ore grinding fineness needs to reach -38μm 98% or more Fine; while the high- phosphorus hematite to be developed, the inlaid grain size is up to 25μm. Due to the fine particle size of such mineral inlays, the energy consumption of the ball mill increases sharply when the dissociation particle size is reached, and the fine-grained mineral has a high specific surface area, which is prone to magnetic flocculation during the magnetic separation process, and consumes more during the flotation process. A large amount of medicament, therefore, it is very important to achieve dissociation of the target mineral at the coarsest particle size. Fine grinding equipment with suitable stress mode and strain strength can enhance the selective dissociation of fine-grained minerals, increase the monomer dissociation degree of the target mineral under the same grinding particle size, and significantly reduce the grinding energy consumption.

I. Current status of selective dissociation and enhanced sorting technology for fine-grained minerals

(I) Improvement and optimization of traditional horizontal ball mill

Prof. Duan Xixiang from Kunming University of Science and Technology, China, and other researches on the improvement of traditional horizontal ball mill equipment and the optimization of grinding process, carried out a series of coarse-grained selective grinding theory and technology research, aiming to use the difference of mineral crushing rate to make the target mineral in a certain These grain-level ranges are enriched, thereby increasing the technical specifications of minerals and achieving a series of results.

By optimizing the control of the media ball ratio, diameter, material, shape, mill speed and inlet and outlet structure, the technical indicators of the plant are effectively improved. The semi-theoretical formula of the ball diameter is proposed and continuously revised, so that the ball diameter semi-theoretical formula can accurately calculate the ball diameter in the rough grinding, medium grinding and fine grinding operations, which provides a basis for the selection of the steel ball size. Improve the precision of the ball filling method, improve the grinding and sorting process, the mill productivity is significantly improved, the grinding power consumption and ball consumption are significantly reduced, and the dissociation degree of useful mineral monomers is significantly improved (5% to 6%). In particular, the concentrate grade and recovery rate are both improved. Replace the steel ball with a cast iron segment to reduce the excessive pulverization of the mineral and make the product evenly distributed.

Researchers relevant for bauxite, molybdenum ore, copper, tin, iron ore and other metal minerals, carried out a series of selective grinding work, has made some achievements in the coarse-grained mineral processing. However, due to the structure limitation of the conventional horizontal ball mill, it is only suitable for the dissociation of coarse minerals. In the grinding equipment, the selective crushing/dissociation of the ball mill is poor. Therefore, on the basis of selective grinding/dissociation of ball mills, it is important to use new fine grinding/ultrafine grinding equipment to enhance the dissociation of fine-grained minerals.

(2) Fine grinding/ultrafine grinding technology and its strengthening of selective dissociation of minerals

From the energy point of view, when the grinding particle size is 20 ~ 40μm, the Tower mill (vertical spiral stirring mill) is the most suitable grinding equipment. In fact, the column mill has a suitable particle size range of 20 to 65 μm. Abroad, the tower grinding technology is mainly provided by Metso, and its tower mill (now renamed as Vertimill) has been widely used in the mining industry to obtain minerals with a P ₈₀ of 15-30 μm. Grinding circuit; domestic, Changsha Research Institute of Mining and Metallurgy has developed a high-efficiency micro-fine ball mill-vertical spiral agitating ball mill with independent intellectual property rights, and realized serialization and large-scale, and formed the key technology of mixing fine grinding. At present, this technology has become the key technology for the re-grinding of coarse concentrates in the domestic molybdenum ore dressing industry, and has been extended to lead or zinc, copper, copper and molybdenum, gold, iron ore and other mineral processing applications. In addition, Australia Xstrata (Xstrata) produced by Isaac horizontal stirring mill (Isamill), developed since 1994, has been successfully used in lead, zinc, copper, molybdenum, gold, platinum group metals such as finely ground ore, The maximum power of the mill is up to 3.0MW, which is mainly used in the re-grinding circuit of P80 for 7~20μm concentrate, medium mine and tailings.

In order to take advantage of the mineral interface in the ore and the structural properties of different minerals, the selective dissociation of minerals is achieved under relatively coarse particle size, the mineral sorting effect is improved and the energy consumption is greatly reduced. Some researchers have done a lot of work. And achieved some results.

Andreatidis found in the experiments of ball milling and agitating mills on mineral fragmentation and dissociation that the dissociation of minerals varies depending on the type of mineral. When ball milling a relatively simple zinc concentrate, the particle size-dissociation relationship is independent of the type of mill. However, when the coarse ore of the low-grade medium particle size is ball milled to P ₈₀ 8 μm, the dissociation degree of the agitated mill mineral Above the ball mill, the degree of dissociation of the SiO ₂ and sphalerite at -10 μm is increased due to the low energy grinding of the agitator mill, which causes the SiO _{2 on the} surface of the zinc blende to detach. Isa Mill improves mineral dissociation by selectively grinding coarse particles. When Jennifer re-grinded the sphalerite coarse concentrate, it was found that the use of agitating mill significantly improved the dissociation degree of quartz , and the dissociation degree of sphalerite was also improved. When the author used the vertical stirring mill developed by Changsha Research Institute of Mining and Metallurgy to re-mill fine-grained iron ore, it was also found that the stirring mill mainly selectively grinds quartz, which significantly improves the monomer dissociation degree of quartz, thereby improving the concentrate. Iron grade. Table 1 shows the agitating mill in and out and the new-500 mesh iron grade and Fe/Si ratio.

Table 1 Stirring mill in and out and new-500 mesh iron grade and Fe/Si ratio

(3) Strengthening of mineral dissociation by pretreatment methods such as microwave

Microwave pretreatment is to use different minerals that make up the ore to increase the heating rate in the microwave field. Under the same conditions, different minerals in the ore will be heated by microwave to different temperatures, forming cracks at the mineral boundary, thus strengthening the mineral boundary. broken.

Amankwah et al. conducted microwave pretreatment of gold ore containing quartz, silicate, iron oxide ore, etc., and found that microwave pretreatment improved the grindability of the ore, and its crushing strength and Bond work index decreased by 31.2% and 18.5, respectively. %. At the same time, gold is also dissociated from the gangue minerals at a coarser particle size, thereby increasing the recovery of monomer gold by 12%.

Harrisont et al found that the specific surface area of ​​ore, such as porphyrite, sphalerite, magnetite, and pyrite, increased after microwave/heat treatment, and the work index decreased. After the microwave pretreatment of the Palabara copper mine in South Africa by Kingman et al., the copper work index was greatly reduced, the chalcopyrite was separated from the gangue, and the other minerals remained in the gangue matrix. The SEM image shows the boundary cracking of the chalcopyrite/gangue induced by microwave treatment. Walkiewiczt et al. used 3kW and 2.45GHz for microwave irradiation of iron ore (temperature 840 ~ 940 °C), the work index decreased by 10% to 24%, and SEM showed that it broke along the mineral grain boundary through the gangue matrix.

At present, microwave pretreatment is limited to laboratory research and is not economically feasible.

In addition to microwave pretreatment, heating, freezing, and chemical pretreatment are also commonly used to improve the pretreatment of mineral dissociation.

Second, the fine particle mineral dissociation analysis technology

The determination of the degree of dissociation has always been a concern, and the process mineralogy uses image analysis of the grinding disc or sheet to qualitatively/quantitatively analyze the composition of the continuum particles. The traditional ordinary optical image analysis technology is very useful in the research and dissociation measurement of coarse-grained mineral inlay structure, but its accuracy is greatly reduced when the mineral inlay particle size is <20μm. In recent years, the use of scanning electron microscopy for dissociation analysis has been rapidly developed and commercialized, which not only automates the determination of dissociation, but also makes the accuracy and reproducibility of the dissociation measurement very large. improve.

QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electronic Microscopy) has been developed by the Commonwealth Scientific and Industrial Research Organization (CSIRO) and has been commercialized. The system consists of a Zeiss EVO50 scanning electron microscope, 1 to 4 energy spectra with a light element Gresham X-ray probe, its own developed scanning electron microscope control system, and an energy spectrum control system and software. The phase can be distinguished by X-ray energy spectrum and backscattered electron images, and the minerals are automatically identified by software. QEMCSCAN can automatically determine the process mineralogy parameters such as dissociation degree, mineral inlay particle size, mineral relative content, mineral embedding complexity, and can be programmed to obtain parameters of interest to researchers.

MLA (Mineral Liberation Analyser) was developed by Dr. Gu Ying from the Julius Kruttschnitt Mineral Research Center (JKMRC). It consists of FEI scanning electron microscopy, 1 or 2 EDAX spectra and software. The resulting backscattered electron image is very clear, the mineral identification is accurate and reliable, and the X-ray energy spectrum analysis can solve the possibility of creating a false "boundary phase" between the two minerals. It is efficient to process data and form reports automatically. At present, several research institutions in China have introduced the system and successfully put it into use.

Third, the conclusion

(1) The selective dissociation and enhanced mineral separation technology has achieved certain results. The parameters such as the proportion, diameter, material, shape, mill speed and inlet and outlet structure of the ordinary horizontal ball mill are optimized. The dissociation degree of the target mineral is improved, and the technical indicators of the plant selection are improved. However, due to the structure and stress mode of the horizontal ball mill, it is difficult to generalize to fine-grain minerals.

(2) The agitating mill not only has the energy efficiency advantage, but also can improve the monomer dissociation degree of the target mineral, and will become the key equipment for fine grain mineral re-grinding. It is expected to be in bauxite and fine-grained iron. It is widely used in minerals such as mines, copper, molybdenum, lead and zinc. The development of large-volume, high-selective agitating mills will become the focus of future work.

(3) Microwave pretreatment and chemical treatment can promote the selective dissociation of fine-grained minerals, thereby improving the grindability and dissociation degree, and finally reducing the cost of fine grinding and grinding. Safe and economical microwave pretreatment technology and low-cost, adaptable drug development will be the focus of attention.

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