3 Completion of main indicators and tailings output
In 2003, the average ore grade of the above-mentioned mines in Shandong Province was 34.88%, the ore grade was 40.22%, the concentrate grade was 65.27%, and the tailings grade was 13.4% (see Table 2). The total output of tailings is nearly 2.6 million tons, of which 650,000 tons of tailings are used for underground goaf filling and open pit mining, and the stocking capacity is 1.95 million tons. At the end of 2003, the cumulative output of tailings was 33.5 million tons, and the tailings pond covers an area of ​​1.33km ² .

Table 2 Main technical indicators for ore dressing of iron ore mines in Shandong Province in 2003

Note: Due to the processing of purchased ore by the Lanshi Mine and the Mazhuang Small Plant, the output is low and the index is unstable. [next]

4 The main results are the first, and achieved remarkable results in the research and application of the wet magnetic separation process before grinding. On the basis of 15% dry and medium-breaking dry magnetic separation, the pre-grinding wet magnetic separation technology developed by Weihai Xinshan Metallurgical Company and the production practice of three mines such as the economic Nangangcheng Mining Company were promoted. The results have been remarkable, with an average reduction of grinding capacity of nearly 7% and an annual reduction of grinding costs of more than 3 million yuan (see Table 3).

Table 3 % wet magnetic separation effect before grinding

At present, the average ore dressing ratio of domestic magnetite ore is around 2.6, and the tailings amount accounts for about 50% of the total metal mine tailings. Therefore, it is necessary to conduct in-depth research and discussion on how to improve the ore recovery rate of iron ore resources, comprehensively utilize iron ore tailings, and protect the natural environment. [next]
Second, a lot of work has been done on the re-election of tailings, and remarkable results have been achieved. Luzhong Metallurgical Mining Group Co., Ltd. cooperated with Maanshan Mining Research Institute to carry out tailings re-election process test. The combination of strong magnetism and re-election can improve the recovery rate by 4 percentage points and reduce the tailings grade by 8 percentage points. Construction of tailings re-election project. Lunan Mining Company invested more than 700,000 yuan in 2001 to build a tailings re-election line. It uses a two-stage magnetic separation process. The grade of iron ore fines is 32%, the yield is about 5%, and the grade of tailings is reduced by 2.5 percentage points. The tailings of Steel City Mining Company are re-elected, the grade of iron ore fines is more than 55%, and the annual output is more than 1,500 tons. Shimen Iron Mine entrusted Qingdao Institute of Construction and Engineering to carry out tailings re-election test, using tailings to re-grind to -0.074mm to reach 75%, first weak magnetic separation, and then two strong magnetic separation, and the product can be 53.41% iron ore. Powder, yield 9.5%, tailings grade decreased by 3.5 percentage points.
Third, preliminary results have been achieved in the comprehensive utilization of tailings. At present, the main utilization route of iron ore tailings is to fill underground mined areas, open pits and low-lying areas. Jinan Gangcheng Mining Company completed the complete tailings cement filling system in 1994. It uses cementation filling mining method, which not only solves the tailings discharge problem, but also improves the ore recovery rate by more than 20%. Laiwu Mining Company used tailings to fill the open pit of Zhaozhuang Iron Mine, recreated the land and treated the environment; used the full tailings horizontal filling mining method in Mazhuang Iron Mine, and filled the original goaf and ground with tailings. The subsidence area solved the problem of tailings storage in the Mazhuang plant.
5 major problems exist
First, the recovery rate of ore dressing is low and the tailings grade is high. Except for Jinling Iron Mine, the tailings grade of other mines is above 10%, the highest is close to 19%, with an average of 13.4%. Compared with the national advanced level, there is a certain gap. In 2003, the average grade of selected iron ore mines in China was 30.77%, the grade of iron concentrate was 67.56%, the grade of tailings was 8.86%, and the recovery rate of ore dressing was 83.56%. The statistics included Panzhihua Mining Company and Baotou Steel Baiyun Obo. The proportion of sedimentary metamorphic lean ore is higher than that of Shandong Province. It can be seen that there is still a certain gap in the technical indicators of iron ore dressing in Shandong Province.
Second, the equipment is in a backward state. The performance is large, new types of equipment, small equipment, low degree of automation, resulting in high energy consumption, production management difficulties, restricting the improvement of mineral processing technical indicators. The grinding capacity of individual plants is 250,000 t/a, while the length of one grinding is 5 series. At present, the world's largest ball mill reaches φ6.7m×13.1m, the largest ball mill in China is φ3.6m×6m, and the largest ball mill in Shandong iron mine is φ2.7m×3.6m, which shows that there is a big gap in equipment status.
In addition, from the analysis of the actual situation of the tailings pond of the mine, at present, the tailings storage service of many mines in the seven iron mines is very short, facing the problem of tailings discharge, and necessary measures must be taken as soon as possible. [next]
6 improvement measures
Strengthen technical management and actively adopt new technologies and equipment
In specific mineral processing methods and processes, technical management work directly affects mineral processing technical indicators. Since the geological bodies are heterogeneous, the ore properties of different ore deposits are different, and the ore properties of different ore bodies are different. The parameters of the ore dressing operation such as grinding grain size, feed rate, number of magnetic separation sections and magnetic field strength, etc. Appropriate adjustments should be made based on changes in the nature of the ore. In the production practice, Lunan Mining Company has pre-mastered the selectivity of different sections of ore through the beneficiation test, appropriately adjusted the beneficiation parameters or matched the selection, and the ore recovery rate and concentrate grade increased by 1.0.3 percentage points respectively.
Actively adopting advanced mineral processing equipment is an important means to improve the recovery rate of mineral processing. In recent years, the development of magnetic materials has promoted the development of magnetic separation equipment in China. New high-efficiency magnetic separation equipment has emerged, such as magnetic field magnetic separator in ZC and NCT series, permanent magnet magnetic separator in LP series, and SQC series. Magnetic separator, Slon series vertical pulsation high gradient magnetic separator, JLCW type moment ring bare magnetic waterless discharge permanent magnet recovery machine. The application of the midfield strong and high field strength magnetic separator has significantly improved the recovery rate of iron ore resources. The application of high-efficiency pulverizing equipment improves the beneficiation efficiency. The application of advanced sampling, analysis and measuring instruments reduces the fluctuation range of beneficiation indicators.
Pre-selection before grinding to reduce tailings output
Because the inside of the ore body contains stones of different sizes, the waste rock will inevitably be mixed in the mining process. Before the ore is put into the mill, if the waste rock can be removed as much as possible, not only the grinding amount can be reduced, but also the output of the fine-grained tailings can be reduced. The waste rock that has been pre-extracted has a large particle size and has a large comprehensive utilization value. The dry magnetic separation and tailing technology of coarse-grained ore has been widely used in iron mines in China, but the pre-selection problem of fine ore has once become a technical problem. At present, the wet magnetic separation technology before grinding has been successfully applied. If it can be fully promoted in the above-mentioned iron ore mines, it can reduce the grinding capacity by more than 400,000 tons and the direct economic benefit is more than 8 million yuan.
Do a good job in iron ore tailings re-election
The re-election of iron ore tailings is an important measure to improve resource utilization and reduce tailings emissions. According to the geological data of the deposit, the iron content in the iron ore is generally around 5%. The tailings above this index still contain iron ore resources that can be further recovered. How to further recycle these available resources, still It is the focus of the future research. On the basis of studying the type of iron minerals in tailings, it is possible to select suitable beneficiation methods such as strong magnetic separation, weak magnetic separation, flotation, re-election, or use of combined beneficiation methods for tailings re-election; for hematite, brown For tailings with high iron ore content, the possibility of re-election after roasting can be explored. If the average tailings grade of the above-mentioned iron ore mines can reach the national average level, that is, 4.5 percentage points lower, it can comprehensively recover more than 300,000 tons of iron ore fines (used for cement production) with a grade of 35%, direct and indirect economy. The benefits are very obvious. [next]
The lead-zinc ore Jiangxi Hill silver recovered from the tailings sericite success for the rubber filler, there may be other useful integrated components can be recovered iron ore tailings. According to the survey, the mica content in some iron mine tailings in Shandong Province is high, and its type and recycling value are worth further exploration.
Broaden the use of tailings
At present, the channels for comprehensive utilization of tailings are mainly: First, the filler used for cementing and filling mining. The use of full tailings cement filling mining method not only solves the problem of tailings storage, avoids environmental pollution, but also prevents geological disasters such as ground collapse caused by mining, and can greatly improve the recovery rate of ore. Second, it is used to fill the open air. Reclaim land by mining pits or low-lying areas. After some open pit mining, the open pit mining is also a good way to change the tailings pond. However, the protection of deep ore bodies should be done. When the bottom of the pit is tailed, technical analysis and demonstration should be carried out to take the tailings solidification measures to avoid giving In the future, underground mining will cause accidents and unnecessary ore losses; the third is to develop and produce building materials. For example, the production of glass ceramics, ceramic tiles, lawn bricks, hollow bricks, river sand, etc.; fourth is the production of fertilizer.
Further improve relevant policies
The state has always adopted incentive policies for the comprehensive utilization of resources and wastes, such as tax reductions for some mineral resources comprehensive utilization products. However, overall, policy support is still insufficient. The comprehensive utilization of mine waste is a systematic project. It requires the joint efforts of government departments and enterprises. The government departments should do a good job in two aspects. First, improve relevant regulations and do a good job in supervision and management. Second, improve relevant policies and do Good guidance and support work. Although some comprehensive utilization projects can create certain economic benefits, they often have large social benefits and low economic returns. At present, there are not many successful technologies in the comprehensive utilization of tailings in iron ore mines. Technical research work is difficult and long-term, and enterprises are difficult to undertake. Relevant technologies should be included in the national basic research topics, and should be promoted and applied after successful experience.

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