Application of preselection technology in iron ore beneficiation

With China's rapid economic development, the demand for steel in the national economy into the high growth period, the rapid development of the iron and steel industry, steel production in 2000 128 500 000 t, an increase of 349 million in 2005 t, greatly stimulated the iron Ore production, domestic iron ore production in 2000 produced 245 million tons, increased to 370 million tons in 2005, a large number of gaps filled by imported iron ore. China's iron ore demand has led to an overall increase in global iron ore prices, bringing prosperity to domestic mine production. China's iron ore resources are poor, fine and miscellaneous. The scale of iron ore production is small and scattered, and the quality of finished ore should be improved. Longer ore processing and complex processes are required, which are destined to produce higher iron ore concentrates. The overall increase in iron ore prices has made it possible to exploit uneconomical ore and mining methods in the past. It should be noted that with the intensification of competition among steel companies and the increase in the salaries of mine personnel and the increase in the prices of auxiliary materials, the production cost of iron ore will increase accordingly. The profit margin of ore production will certainly be compressed. Improving the efficiency of mineral processing and applying new technologies and processes for mineral processing is an effective way to improve the economic profits of the mining industry.

First, the role of ore pre-selection

A mineral processing tradition followed by a mineral processing worker: can take early, can lose early. The ore is pre-enriched before the grinding operation, and some of the waste rock is discarded early. This is the pre-selection. Domestic and foreign plants have more successful examples in the application of pre-selection process technology, such as the treatment of low-grade ore abandoned by a large iron ore mine in Australia, and the pre-selection application of tin mines and tungsten mines in China. Pre-selection applications such as concave mountain beneficiation and Meishan mineral processing, the lead scrap yield in advance is 10% to 40%. Pre-selected applications can usually be reflected in the following aspects: 1. Restoration of geological grades. In the mining process, there are always some waste stones to be mixed into the ore. The mixing rate of different waste rock in mining methods is also different. Generally, the mixed rate of open-pit mining waste rock is 3% to 5%, and underground mining is generally 10% to 20%. Higher. 2. Simplify mining methods. For relatively thin ore belts or interlayers, in order to prevent the loss of resources or the low grade of mined ore, the miners usually have to selectively separate the mining or stratified mining, or discard them. 3. Effectively utilize the poor ore resources and extend the service life of the mine. In the past, low-grade ore that was economically and technically considered to be unexploitable, because of the better pre-selection method, improved the selected grade and reduced the amount of grinding, and became a resource that can be utilized; for mines with difficult ore grades, the mine can be improved. Economy, extending production service period. 4. Reduce ore transportation costs. For the long-distance transportation of the mine, the economic effect of throwing money in advance is obvious. For general mines, the delivery of tailings to the tailings pond can be greatly reduced. 5. Reduce the processing capacity of the largest operation grinding of ore dressing. According to the energy consumption statistics of traditional mines used for ore crushing, ore mining accounts for 3% to 5%, crushing operations are about 5% to 7%, and grinding operations are about 85% to 90%. Reducing the grinding consumption and reducing the amount of grinding is the most direct. 6. It is conducive to the stable operation index after grinding. The ore grade of iron ore usually has large fluctuations. Some mines have a grade fluctuation of 5% to 10% a day. After pre-selection, the selected grade is stable, which is conducive to improving the quality index. From the formal point of view, as far as possible under the conditions of large-grained, coarse-grained conditions, the largest amount of waste, no or less ineffective work and consumption, to improve the technical and economic indicators of the mine.

Second, the conditions of pre-selection application

Economic rationality is the starting point for the application of pre-selection process. It not only considers the cost of the waste rock that can be discarded in the subsequent grinding operation, but also considers whether the minerals thrown away by the waste cause the loss of resources. There is no clear economic model to define the throwing. The waste boundary, each beneficiation process is determined by experiment and practice. In order to realize the application of the pre-selection process in production, it is necessary to find a suitable pre-selection process and process equipment. The nature of ore is the basis for the selection of processes and equipment. People usually pay attention to the concentrate grade and recovery rate of beneficiation, study the relationship between the dissociation degree of useful minerals and the fineness of ore, and the “dissociation” of gangue minerals and useful mineral aggregates. Neglect, in fact, many of the selection plants are cumbersome and complicated for the grinding process, and there are not many inputs under the coarse grain conditions before grinding. Whether the pre-selection can be achieved under coarse-grained conditions depends on whether the ore can produce a large number of gangue aggregate "monomers" under coarse-grained conditions, that is, "dissociation" of gangue minerals and useful mineral aggregates. The particle size of the ore is an important factor. After the crushing, it is still finely divided, and different process equipments are selected for different particle sizes. Another factor is to determine a reasonable level of waste. Generally, the grade of magnetite is 5% to 10% or less. The refractory ore such as hematite or mixed ore is generally higher, and some even 16%. ~18%.

Third, iron ore pre-selection new process application examples

The iron ore mined in China's mines is mainly magnetite. The majority of magnetite grades are 20% to 30%, which are lean iron ore. In recent years, due to domestic iron ore demand, some low-grade magnets. The mine is also being developed and utilized. For example, the grade of Gaocun iron ore developed by Maanshan Iron & Steel Co., Ltd. is 18%-20%, and the grade of a vanadium- titanium magnetite in Hebei is only about 16%. The increase in the cost of selecting low-grade ore will offset the increase in ore price. Most of the profits. The pre-selection process of magnetite is widely used in dry magnetic separators and magnetic pulleys. The process is generally simple and the configuration is easy to do. Compared with the pre-selection of ferromagnetic ore, the pre-selection process of weak magnetic ore is more complicated, and there are more practical methods. This is because the ore is more difficult to choose and has to apply complex processes. Therefore, the pre-selected cost is relatively weak. high. In recent years, many domestic mines have been pre-selected and creatively formed energy-saving and efficient new technologies. Some new equipments have been developed or introduced in China. The application and experimental studies of several mines are described below.

(1) Application in Maanshan Group Nanshan Mining Company

The Nanshan Mine Concave Mountain Concentrator handles the ore mining and Gaocun ore. The main target mineral is magnetite. The iron grade of the concave mountain mining site is about 30%. If the mining resources of the concave mountain in 2008 are dry, the pit is closed. The Gaochang Mine, which has a processing capacity of only about 20%, not only does the concentrate grade not meet the requirements of Maanshan Iron and Steel, but also the concentrate production will fall below 1.2 million tons under the same annual processing capacity. According to the experimental research, the pre-selection effect of the magnetic separation and tailing of the 10mm grain size of Gaocun Mine is very poor, and the ore is rolled to below 3mm. Under this fineness, the wet magnetic separation can throw a large amount of tailings, and the trial production results also prove that The process is reasonable and the effect is obvious. The application of roller press-sieving ultra-fine crushing-wet magnetic separation and tailing new process has been successful. The wet-type magnetic separation of 3~0mm rolling products can pre-grow the coarse-grain tailings with a yield of 50% and a grade of 7.81%. The grade of the ore after the tailing is increased to more than 40%. Due to the reduction of the grinding grain size and the drastic reduction of the amount of grinding, the energy consumption of the grinding can be greatly reduced, and the production capacity of the main plant is greatly improved, which is equivalent to the construction of a grinding plant of the same scale. The pre-selection process is shown in Figure 1.

Figure 1 Process flow chart of high-pressure roller superfine pre-selection principle

(II) Application in Gushan Mining Company of Maanshan Iron and Steel Group Co., Ltd.

The Gushan ore is dominated by hematite, which is a domestic “difficult to collect, difficult to grind, difficult to select” red mine. The original design process is coarse grain (-12～+6mm) jigging pre-selection operation and jigging medium mine (- 12~+6mm) and the original mine-6mm merge into the ball milling operation. The production application proves that the coarse grain pre-selection makes full use of the ore characteristics and achieves good economic results. Because the trapezoidal jig has a large water consumption (260m ³ /h stage), Difficulties in operation adjustment (stroke, rushing ore thickness, ore level, ore supply, etc.), poor adaptability to fluctuations in raw ore properties, large maintenance and large spare parts consumption, which bring great difficulties to tissue production, while using advection sedimentation The water quality of the pool ring water operation area is poor, the environment is poor, and the pollution is serious. For many years, Gushan research applied the dry magnetic separation pre-selection process, and cooperated with the Changsha Research Institute of Mining and Metallurgy to conduct two laboratory tests and install a φ300×1000 permanent magnet strong Magnetic Separator in the jig plant. Industrial tests, 72-hour continuous production tests and equipment assessments have all achieved better than the jigs in production. It can extract about 35% of the concentrates in advance and discard about 10% of the tailings. After the transformation of the project, four sets of 155KW ring water pumps and other ancillary equipment were stopped, saving 3.022 million kWh per year, saving electricity costs of 1.403 million yuan and reducing material consumption by 626,000 yuan.

After the success of the dry strong magnetic separation and the selection of -12~+6m ore, the particle size analysis of the fine crushed back ore belt ore has been “dissociated” from some iron aggregates and gangue. Crushing operations return ore is mounted under the belt 2 φ600 × 1000 permanent magnet machine strong magnetic separator, selected from finely divided ore -30 ~ + 10mm qualified lump ore in advance, reducing the subsequent job through pulverization, help to improve the metal recovery . The process of pre-selection of Gushan is shown in Figure 2 and Figure 3.

Figure 2 30 ~ 15mm lump ore process

Figure 3 Dry magnetic preselection process

(III) Pre-selection test study on the 6mm grain size of Gushan Red Mine

After the three sections and one closed-circuit crushing mine, the Gushan Red Mine has about -6mm grain size of about 35%. It has not been treated for a long time and the +6mm selected medium ore is sent to the grinding and selection. In the 1980s, fine-grained jigging was applied. Due to the poor production index of the bed, the CS-1 electromagnetic induction roller magnetic separator was used, and it was stopped due to equipment and other reasons. The -6mm grain size beneficiation has become a blank. Professor Cao Zhiliang of the 2003 Changsha Research Institute of Mining and Metallurgy has developed a new type of equipment for generalized space immersion permanent magnet strong magnetic separator, which brings high-efficiency and low-cost selection of -6mm grain grade hematite. Breakthrough, after a rough sweep of the Gushan Red Mine, a product with a crude powder concentrate yield of 34% and an iron grade of about 53% can be obtained. At the same time, the tailings with a yield of 15% and an iron grade of about 17% can be discarded. Although the process has not been applied due to the shrinkage of the red mines in the Gushan open pit, as a pre-selection of new processes and new equipment, technical reserves have been made for the future beneficiation of the Gushan mining open pit.

(4) WISCO Jinshandian Iron Ore Concentrator

Due to the continuous grinding process, a large number of gangues that should be pre-selected and thrown into the ore have entered the grinding operation, which brings about high energy consumption, low quality of iron concentrate products, unstable production, etc. The -15mm ore after grinding is subjected to an optimization test of the iron selection process. Self-grinding and grading, a weak magnetic preselection and tailing, classifying -15mm self-grinding ore samples, and different kinds of -5mm, -3mm, -2mm and -1mm under the condition of magnetic field strength of 79.58kA/m The pre-selected tailing test of the granular sample is carried out. The results show that it is not only feasible to use the grading-preselection tailing process for -15mm self-grinding and discharging, but it is also necessary to pre-deliver the pulse with the operating yield of 43.66%-44.23%. Stone, tailings iron grade 9.68% ~ 9.39%, iron loss rate of only about 11%, which will greatly reduce the amount of human grinding during ball milling, effectively reduce ball wear and improve the ball mill processing capacity.

Fourth, the conclusion

Economic development is inseparable from resources. The development of iron ore resources is conditional on the economy. Pre-selection technology is an effective means to achieve efficient and economical mines. Studying pre-selected new technologies, new processes and new equipment is one of the effective ways to save energy and reduce consumption in mines. It is one of the ways to expand and reproduce mines, and it is also a way to improve mine competitiveness. Resources are the source of life for mining companies. Mineral resources are dynamic concepts. Off-balance meters that were considered unusable many years ago have become non-disposable resources. How to effectively exploit and maximize the use of existing mineral resources, not only in mining methods. On top, mineral processing will be more important, and pre-selection technology application is one of the most economical means.

references

1. Yan Songshan, Nanshan Mining Company's practice of making full use of ore resources [J]. Metal Mine, 200618.

2. Li Dapei, Qian Shihu, Ding Boxun 1 Review and Prospect of Mineral Processing Technology Reform of Gushan Mining Company [J]. Mining Express, 200318.

3, Mai Xiaoyu, Yan Chaoying, Peng Wenbin 1 Experimental study on optimization of iron selection process in Jinshandian Iron Mine [J]. Metal Mine, 200618.

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