Shandong iron ore resource recovery and tailings usage

1 Resource reserves and production situation Shandong Province currently has 8 iron ore mines at or above the provincial level, including 1 central enterprise. In 2003, the total mining (stripping) volume completed was 10.09 million tons, the raw ore output was 6.204 million tons, and the finished ore output was 3.325 million tons (including 2.941 million tons of iron concentrate output). As of the end of 2003, 19 mining areas were mined, accounting for 22% of the total number of identified mining areas in the province, with resource reserves of 46.1 billion tons, basic reserves of 361 million tons, and reserves of 249 million tons. ​

2 Ore dressing process

Among the 8 iron mines, 7 mines have 10 mineral processing plants, a total of 20 jaw crushers of various types, 3 autogenous grinders, 5 hammer crushers, 9 cone crushers, and 44 ball mills. 68 magnetic separators. The raw ore processing capacity is 6.62 million t/a, and the actual processing capacity in 2003 was 6.44 million t of raw ore (excluding Lai Mine Wenshibu and Mazhuang Small Processing Plant).

3 Completion status of main indicators and tailings output

In 2003, the average grade of raw ore selected from provincial-level or above mines in Shandong Province was 34.88%, the ore grade for grinding was 40.22%, the concentrate grade was 65.27%, and the tailings grade was 13.4% (see Table 2). The total tailings output is nearly 2.6 million tons, of which 650,000 tons are used for filling underground goafs and open pits, and 1.95 million tons are stockpiled. By the end of 2003, the cumulative output of tailings was 33.5 million tons, and the tailings reservoir covered an area of 1.33km2.

Note: Because the Wenshibu dressing plant and Mazhuang small dressing plant of Lai Mine process purchased ore, their output is small and their indicators are unstable, so they are not included in the calculation.

4 Main Achievements

First, remarkable achievements have been made in the research and application of wet magnetic separation technology before grinding. On the basis of dry magnetic separation of 15% after coarse and medium crushing, the pre-mill wet magnetic separation technology developed by Weihai Xinshan Metallurgical Company’s iron ore and the production practice of three mines including Economic Nangangcheng Mining Company were promoted. The results are remarkable, with the average grinding volume reduced by nearly 7% and the annual grinding cost reduced by more than 3 million yuan.

At present, the average beneficiation ratio of domestic magnet ore is around 2.6, and the tailings account for about 50% of the total metal forging mineral tailings. Therefore, it is necessary to conduct in-depth research and discussion on how to improve the 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 tailings reprocessing and significant results have been achieved. Luzhong Metallurgical Mining Group Co., Ltd. and Ma’anshan Mining Research Institute cooperated to carry out a tailings re-selection process test. The mineral processing process combining strong magnetism and gravity separation can increase the recovery rate by 4 percentage points and reduce the tailings grade by 8 percentage points. Now it is Construction of tailings re-selection project. Lunan Mining Company invested more than 700,000 yuan to build a tailings re-selection production line in 2001. It adopted a two-stage magnetic separation process. The iron ore powder grade was 32%, the yield was about 5%, and the tailings grade was reduced by 2.5 percentage points. The tailings of Gangcheng Mining Company are reprocessed, and the grade of iron ore powder reaches over 55%, with an annual output of more than 1,500 tons. Shimen Iron Mine commissioned Qingdao Institute of Architectural Engineering to carry out a tailings re-selection test. The tailings were reground to -0.074mm to reach 75%. First, weak magnetic separation, and then two stages of strong magnetic separation, can produce iron ore with a grade of 53.41%. powder, the yield is 9.5%, and the tailings grade is reduced by 3.5 percentage points. ​

Third, preliminary results have been achieved in the comprehensive utilization of tailings. At present, the main utilization method of iron ore tailings is to fill underground goafs, open pits and low-lying areas on the ground. Jinan Gangcheng Mining  Company News built a full tailings cementing and filling system in 1994. It adopted the cementing and filling mining method, which not only solved the tailings emission problem, but also increased the ore recovery rate by more than 20 percentage points. Laiwu Mining Company uses tailings to fill the open-pit pits of Zhaozhuang Iron Mine, regenerating the land and improving the environment; at Mazhuang Iron Mine, it adopts the full tailings horizontal filling mining method and uses tailings to fill the original goaf and ground The subsidence area solves the tailings storage problem of the Mazhuang dressing plant. ​

5 main problems

First, the ore dressing recovery rate is low and the tailings grade is high. Except for Jinling Iron Mine, the tailings grade of other mines is above 10%, with the highest being close to 19% and the average reaching 13.4%. Compared with the national advanced level, there is a certain gap. In 2003, the average selection grade of major iron ore mines in the country was 30.77%, the iron concentrate grade was 67.56%, the tailings grade was 8.86%, and the ore dressing recovery rate was 83.56%. The statistics include Panzhihua Mining Company, Baotou Steel Co., Ltd., Bayan Obo and other difficult-to-benefit mineral areas. , the proportion of sedimentary metamorphic lean ores is higher than that of Shandong Province. It can be seen that there is still a certain gap in the mineral processing technical indicators of iron mines in Shandong Province.

Second, the equipment condition is backward. The performance is as follows: there are few large-scale and new-type equipment, more small-scale equipment, and a low degree of automation, resulting in high energy consumption and difficult production management, which restricts the improvement of mineral processing technical indicators. The grinding capacity of individual dressing plants is 250,000 t/a, while the grinding capacity of one section reaches 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 Province Iron Mine is φ2.7m×3.6m. It can be seen that there is a big gap in the condition of the equipment. ​

In addition, based on the analysis of the actual situation of the tailings ponds in mines, at present, among the seven iron mines, the service life of the tailings ponds in many mines is very short. Faced with the problem of tailings discharge, necessary measures must be taken as soon as possible. [next] 6 Improvement Measures Strengthen technical management and actively adopt new processes and new equipment. In specific mineral processing methods and processes, technical management work directly affects mineral processing technical indicators. Since the geological body is inhomogeneous, the ore properties of different deposits are different, and the ore properties of different sections of the same ore body are also different. The parameters of the ore dressing operation such as grinding particle size, feeding speed, number of magnetic separation sections and magnetic field strength, etc., Appropriate adjustments should be made according to changes in ore properties. In the production practice of Lunan Mining Company, through mineral processing experiments, the selectivity of ores in different sections was mastered in advance, and the mineral processing parameters were appropriately adjusted or selected. The mineral processing recovery rate and concentrate grade were increased by 1 and 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 my country. New high-efficiency magnetic separation equipment continues to appear, such as ZC and NCT series medium-field magnetic separators, LP series vertical disk permanent magnet magnetic separators, and SQC series ring-type magnetic separators. Magnetic separator, Slon series vertical slow pulsating high gradient magnetic separator, JLCW type rectangular ring type bare magnetic water-free discharge permanent magnet recovery machine, etc. The application of midfield strength and high field strength magnetic separators has significantly improved the recovery rate of iron ore resources. The application of high-efficiency crushing equipment improves the efficiency of mineral processing. The application of advanced sampling, analysis, and measuring instruments has reduced the fluctuation range of mineral processing indicators. ​

Pre-selection before grinding to reduce tailings output

Since the interior of the ore body contains rocks of varying sizes, waste rocks will inevitably be mixed in during the mining process. If these waste rocks can be removed as much as possible before the ore is milled, it will not only reduce the amount of grinding, but also reduce the output of fine-grained tailings. The waste rock thrown out in advance has a larger particle size and has greater comprehensive utilization value. The dry magnetic separation and tailing technology of coarse-grained ores has been widely used in iron ore mines in my country, but the problem of pre-selection of finely crushed ores once became a technical problem. At present, the wet magnetic separation technology before grinding has been successfully applied. If it can be fully promoted in iron mines above the provincial level, it can reduce the grinding volume by more than 400,000 tons and generate direct economic benefits of more than 8 million yuan. ​

Do a good job in re-selection of iron ore tailings

Carrying out iron ore tailings reprocessing is an important measure to improve resource utilization and reduce tailings emissions. According to the geological data of the ore deposit, the unusable iron content in iron ore is generally around 5%. Tailings higher than this indicator still contain iron ore resources that can be further recycled. How to further recycle these available resources is still This is the focus of future research. On the basis of studying the types of iron minerals in tailings, suitable mineral processing methods such as strong magnetic separation, weak magnetic separation, flotation, and gravity separation can be selected, or a combined mineral processing method can be used to re-select the tailings; for hematite, brown For tailings with high iron ore content, the possibility of re-selection after roasting can be explored. If the average tailings grade of iron ore mines at or above the provincial level can reach the national average, that is, reduced by 4.5 percentage points, more than 300,000 tons of iron ore powder (used for cement production) with a grade of 35% can be comprehensively recovered, which is directly and indirectly economical. The benefits are very obvious. [next] Based on the successful experience of recovering sericite from tailings at Jiangxi Yinshan Lead-Zinc Mine for use as rubber filler, there may be other useful components in iron ore tailings that can be comprehensively recovered. According to surveys, mica content in some iron mine tailings in Shandong Province is relatively high, and its type and recycling value deserve further exploration. ​

Expand tailings utilization channels

At present, the main channels for comprehensive utilization of tailings are: First, filling materials used for cemented filling mining. The use of full tailings cemented filling mining method not only solves the problem of tailings storage and avoids environmental pollution, but also prevents geological disasters such as ground collapse caused by mining, and can also greatly increase the ore recovery rate; second, it is used to fill open pits Mining pits or low-lying areas to regenerate the land. After the open-pit mining in some mines is completed, it is also a good way to convert the open-pit mining pit into a tailings pond, but the protection of the deep ore body should be done well. When tailings are discharged at the bottom of the mine, technical analysis and demonstration should be carried out, and tailings solidification measures should be taken to avoid causing damage to the mine. Underground mining will cause accident risks and unnecessary ore losses in the future;

The third is to develop and produce building materials products. For example, the production of crystallized glass, ceramic tiles, lawn tiles, hollow bricks, river sand, etc.; the fourth is the production of fertilizers.

Further improve relevant policies

The state has always adopted policies to encourage the comprehensive utilization of resources and waste, such as tax exemptions and reductions for some products that utilize comprehensive mineral resources. But overall, policy support is still insufficient. The comprehensive utilization of mine waste is a systematic project that requires the joint efforts of government departments and enterprises. Government departments should do a good job in two aspects.

First, improve relevant laws and regulations and do a good job in supervision and management;

The second is to improve relevant policies and provide guidance and support. Although some comprehensive utilization projects can create certain economic benefits, the social benefits are often large but the economic benefits are not high. At present, there are not many successful technologies for comprehensive utilization of iron ore mine tailings. The technical research work is difficult and takes a long time, which is difficult for enterprises to undertake. The relevant technologies should be included in the national basic research topics and be promoted and applied after successful experience is obtained.