After years of sustained high-intensity development, many of the metal mines has entered the stage of deep mining. With the implementation of the "three deep and one soil" strategy, strengthening the exploration and development of deep resources has become the main direction of future development.
The current situation of metal mineral resources in China
China's total mineral resources are abundant. At present, China has discovered 171 kinds of mineral resources and found 168 kinds of minerals with reserves. The potential value of proven mineral resources reserves accounts for about 14.6% of the total value of world mineral resources, ranking the third in the world. However, the per capita possession of mineral resources in China is far below the world average. With 45 major mineral resources, China's per capita reserves rank 80th in the world, only 58% of the world average.
Economy requires bulk strut mineral species, such as metallic minerals iron, manganese, copper, lead, zinc, bauxite and the like, can not meet the demand. More than 60% of iron concentrates, more than 70% of copper concentrates and 50% of bauxites must be imported from abroad each year. The high foreign dependence of major metal mineral resources poses a potential serious threat to China's national economic development. More importantly, the advantages of China's dominant minerals are also weakening and even losing, such as tungsten, tin , molybdenum , antimony , fluorite , barite, etc., and the reserves available for reserves in 2020 are only 89%. 35%, 85%, 55%, 15%, 26%.
Mining Status and Problems of Metal Mineral Resources in China
After more than 60 years of mining since the founding of New China, China's shallow mineral resources have been reduced and depleted year by year. The exploitation of mineral resources, especially metal mineral resources, is in the stage of comprehensive promotion to the deep. Before 2000, there were only two metal mines in China with a depth of 1000 meters. Since the beginning of the 21st century, the development speed has been very fast. At present, 16 underground metal mines have reached or exceeded 1000 meters. Among them, Jilin Jiapigou Gold Mine, Yunnan Huize Lead-Zinc Mine and Liuyu Copper Mine, and Henan Lingbao Busin Gold Mine are all over 1,500 meters.
At present, there are 112 metal mines with a depth of more than 1,000 meters. Ranked by number, the top countries are: Canada 28, South Africa 27, Australia 11, USA 7 and Russia 5. China has surpassed Australia and ranks third in the world. However, according to the current development speed, the number of deep mines in China will rank first in the world in a relatively short period of time.
Among the 112 deep well mines abroad, there are 16 deep mining depths over 3,000 meters, 12 of which are located in South Africa, all of which are gold mines. Among the 16 deep mines in China, there are 8 gold mines and 7 non-ferrous metal mines. The situation at home and abroad is basically similar. In the deep mines, the number of gold mines is the largest.
Recently, a large gold deposit with a gold metal reserve of 400 tons was discovered at a depth of 1600 m to 2600 m in the Xiling Mining Area of ​​Sanshan Island Gold Mine, which pointed out the direction for China to find a larger gold deposit in a similar mining area in the deep Jiaodong Peninsula. . With the implementation of the "three deep and one soil" strategy and the advancement of exploration technology and equipment, it is entirely possible for China to find a large number of large gold deposits in the depths of 3,000 meters to 5,000 meters. According to statistics, in the next 10 years, more than one third of metal mines in China will reach a depth of 1,000 meters or more. Deep mining is the most important problem facing the development of metal mineral resources in China. Among them, gold mines bear the brunt.
The future development of mineral resources involves three major themes of green mining, deep mining and intelligent mining. Deep mining is the theme of overall leadership. In deep mining, all new mining concepts, new models and new technologies, including green development and intelligent mining, must be innovatively developed to ensure the safe and efficient mining of deep.
Deep mining will face many key problems: First, deep high stress problems. Deep high stresses can lead to destructive ground pressure activities, including rockbursts, landslides, roof collapses, water inrush, and other dynamic disasters caused by mining excavation. The second is the problem of deterioration of lithology. The shallow hard rock turns into soft rock in the deep, and the elastic body becomes the latent plastic body, which imposes a great burden on the support and mining safety, which seriously affects the mining efficiency and efficiency. The third is the high temperature environment in deep wells. The rock formation temperature increases with a gradient of 1.7 ° C / 100 m ~ 3.0 ° C / 100 m deep. The high temperature environmental conditions of deep wells seriously affect the labor productivity of workers. In order to effectively cool down, it will definitely increase mining costs. At the same time, with the increase of mining depth, the lifting height of ore and various materials has increased significantly, the difficulty of upgrading and the cost of raising are greatly increased, and the production safety is a threat.
Constraints to achieve safe and efficient mining of deep mineral resources
In order to solve a series of key technical problems in deep mining, it is necessary to extensively absorb the high and high technology of various disciplines, develop advanced non-traditional mining processes and technologies, and create mining models with higher efficiency, lower cost, least environmental pollution and best safety conditions. .
First, rockburst prediction and prevention and control under deep stress conditions in deep wells. Before the excavation, the stratum is in a natural equilibrium state. The excavation causes the excavation to release the ground stress to the excavation space, forming a “release loadâ€, which leads to deformation and stress concentration of the surrounding rock and generates disturbance energy. When the disturbance energy accumulated in the rock mass reaches a very high level and is suddenly released in the case of cracking of the surrounding rock, impact damage, that is, rock explosion occurs. This is an accurate understanding of the rockburst mechanism. Based on the above-mentioned rockburst induction mechanism, the rockburst prediction should be closely integrated with the mining process. According to the future mining plan, numerical simulation and other methods are used to quantitatively calculate the magnitude, time and spatial distribution of the disturbance energy in the future. With the change law in the mining process, the relationship between seismic energy and magnitude in seismology can be used to predict the development trend and magnitude law of rockburst induced by future mining. Based on the induced mechanism of rockburst, rockburst prevention and control should start from optimizing mining methods, mining layout and mining sequence, reducing and controlling the accumulation of disturbance energy during mining, thus reducing and controlling the occurrence of rockburst. At the same time, take measures to absorb energy and prevent shocks to prevent and reduce the impact damage of rock bursts.
The second is high temperature environmental control and cooling treatment in deep wells. The temperature of the subterranean formation increases with the increase of the depth. Generally, the temperature of the deep well above 1000 meters will exceed the human body temperature. According to our latest survey, there are more than 100 deep metal mines in China over 700 meters. After more than 700 meters, the rock temperature generally exceeds 35 °C. High temperatures cause severe deterioration of working surface conditions, labor productivity and equipment operation efficiency are greatly reduced, and serious disasters can occur. The mine cooling technology commonly used at home and abroad has two categories: non-manual refrigeration and artificial refrigeration. Mine ventilation is the main non-artificial refrigeration cooling technology, but after the well depth exceeds kilometer, conventional ventilation can not meet the safety requirements of the underground working face. Artificial cooling and cooling include water cooling and ice cooling. Water cooling is to produce cold water on the ground or underground to the underground station. After the air is cooled by the high and low pressure heat exchangers and the air cooler, the cold air is sent to the working surface to cool down. Ice-cold ice or muddy ice is produced on the well, sent to the underground ice-melting pool to melt ice, and the cold water formed by melting ice is sent to the working surface for spray cooling.
Both artificial and non-artificial cooling are passive cooling techniques. In order to effectively solve the problem of deep well cooling, it is necessary to play an active cooling technology, focusing on the following two aspects: First, the deep well high temperature rock layer insulation technology. Research and development of new and efficient new insulation materials, new technologies and new processes to isolate the high temperature of the rock formation. On this basis, the artificial cooling and cooling technology will be used to achieve a good cooling effect on the underground roadway and mining face. The second is the deep well geothermal development technology. Geothermal is a natural energy source and current energy systems are using geotechnical research for geothermal mining. If the combination of deep well mining and deep geothermal development is combined, it will find a subversive technical approach for deep cooling of mining projects, which can achieve a win-win situation in deep energy development and resource development.
Therefore, in terms of current mining technology and mining costs, it is not very economical to develop mineral resources below 3,000 meters underground. EGS/E deep geothermal mining technology uses mining technology for geothermal development, which can greatly improve the efficiency of deep geothermal development, and can greatly reduce the cost of deep mining, to solve future energy problems and economic problems of deep mining. Open up an effective way. The ideal combination and win-win situation of the two will be a major breakthrough in technological innovation in the energy and mining sectors, with subversive effects. Our country hopes to achieve breakthrough progress in the leading world with Chinese marks in these two aspects.
Progress in non-traditional mining technology
The traditional blasting mining technology not only destroys the stability of surrounding rock, but also the mining of ore and waste rock, which greatly increases the workload and cost of upgrading and beneficiation . From the long-term goal, it is an important direction to use mechanical excavation and mechanical rock drilling methods to replace mining and mining technology with traditional blasting mining technology. The mechanical cutting mining space does not need to implement blasting to significantly improve the stability of the surrounding rock, and is not restricted by the blasting safety boundary to expand the mining boundary; mechanical cutting can accurately mine the target ore, so that the mining loss rate and the ore depletion rate are minimized. However, the operation of mining machines is limited by the variety of metal deposits and complex geological conditions. The life and cost of cutting heads are the key issues to be solved in implementing this technology. Here, we will introduce several non-traditional mining technologies and their progress.
High-pressure water jet rock breaking and mining technology: High-pressure water jet technology is a new cleaning and cutting technology developed in the 1970s. The high-speed water jet from the high-pressure nozzle has a large amount of energy, and can generate a huge impact force on the target to cut rocks, crush rocks, and the like. At present, the technology has been used for soft rock and hard rock medium, large number of applications water jet technology developed by coal mining machine, cutting machine and cleaning machine after another, and industrial test and application. However, when crushing hard ore, it is necessary to use higher water jet pressure, and the current water jet launcher system cannot withstand such high pressure. In order to solve the problem of hard rock breaking, high-pressure water jets need to be developed in the direction of ultra-high pressure and high power. It is necessary to further develop and improve ultra-high pressure water jet components and equipment to create conditions for the application in metal ore hard rock.
Laser rock breaking and mining technology: laser rock breaking is the rapid heating of the rock by the heat generated by the high energy laser beam. When the temperature is high enough, a series of complex physical and chemical reactions are generated, and the crushing is sequentially performed with the increase of temperature. , decomposition, melting and vaporization of three types of rock breaking. As long as the mining rock breaks down, when the high-energy laser acts on the rock surface, the rock locally expands rapidly and causes local thermal stress to rise. When the thermal stress is higher than the ultimate strength of the rock, the rock will undergo thermal fracture to achieve cutting and rock breaking. The micro-cracks and pores on the surface of the rock reduce the ultimate strength and thus exacerbate this thermal fracture.
Plasma rock breaking and mining technology: This technique first drills into the rock body, then tightly fits the coaxial electrode into the borehole and fills the electrode tip with an electrolyte solution. The capacitor group connected to the coaxial electrode is turned on, and under the action of high electric energy, the electrolyte is quickly converted into a high temperature and high pressure plasma gas. The high temperature and high pressure ionic gas rapidly expands to form a powerful shock wave, which results in a blasting effect similar to that produced by chemical explosives, which can generate pressures exceeding 2 GPa, enough to break hard rock.
Green mining mode of green mine
First, there is no waste mining mode. The goal of non-waste mining is to minimize the output and discharge of waste, improve the comprehensive utilization of resources, and reduce or eliminate the ecological and environmental damage caused by the exploitation of mineral resources. The mine-free mining model follows the viewpoint of industrial ecology. It focuses on mining activities and links the mine ecological environment, resource environment and economic environment to an organic industrial system to obtain maximum resources and economic benefits with minimum emissions. After the mining activity is completed, the mine environment and the ecological environment are integrated by the minimum end treatment. In order to achieve waste-free mining, we should vigorously improve the level of mining technology, greatly reduce the depletion rate of ore, minimize waste production, and control the rate of waste rock production from the source. At the same time, the recovery rate of ore dressing should be increased as much as possible, and the tailings emissions should be reduced. The components in the ore resources that cannot be utilized due to the low level of smelting and smelting should be minimized. Strengthen comprehensive recycling, realize the recycling of waste, improve the overall utilization level of waste, and strive to achieve zero discharge and zero stock of mine waste.
The second is the in situ leaching mining mode. This is a technology that integrates mining and selection, and forms a liquid injection channel in the ore body by drilling or blasting, and directly injects the leaching liquid into the ore body. The leaching solution leached by the leaching solution is recovered and sent to the surface for treatment through the collecting channel. This method eliminates the mining operation and directly recovers the metal from the leaching solution, which can greatly reduce the mining operation and the increased workload. It is an ideal and relatively non-waste mining method for large-scale field application, and has a deeper mining method for deep deposits. Strong adaptability. However, at present, there are too few large-scale metals that can be recycled in this process, only uranium , copper and gold. It is necessary to vigorously study the technology of recovering more metal minerals by this process.
The third is the integrated mode of underground mining and selection. Before the ore raises the ground, pre-selection and pre-enrichment are carried out downhole, and most of the waste rock is thrown away, which can significantly reduce the amount of ore lifting. In addition, Western countries are experimenting with the use of hydraulic lifting methods to replace traditional lifting methods such as buckets and cages. The ore is crushed and ground after underground pre-selection, and then pumped to the ground dressing site. Since there is no need to excavate the shaft, the investment in the roadway engineering can be greatly reduced, and the safety of the mining project can be greatly improved. The ore dressing platform is built underground, and the concentrate is directly transported to the ground after underground ore dressing, which can greatly reduce the amount of waste rock lifting, which is an important way to solve the lifting problem. At the same time, waste rock and tailings remain in the underground for filling in the goaf, achieving in situ utilization and reducing pollution and damage to the ecological environment after discharge to the ground. Moreover, the non-concentration plant and tailings pond on the ground eliminates the cost of land acquisition and construction of tailings ponds and management of tailings ponds.
The fourth is the remote control intelligent unmanned mining mode. This is the best, most effective, and most reliable way to cope with deteriorating deep mining conditions and environmental conditions, maximizing mining efficiency and ensuring mining safety. At present, the domestic and international are still in the initial stage of building “unmanned minesâ€. At this stage, the core technology of unmanned mining is still the automation and intelligence of mining process and production organization management. A new generation of advanced unmanned mining technology will inevitably involve changes in the mining process and the production process itself.
The gap between China's mining technology and western countries
In the 1980s, Western countries began to implement unmanned mining in underground working faces. At present, many mines in China cannot even do full-scale mechanization. But on the whole, China's mining technology has approached or reached the international advanced level in many aspects. The overall gap in the mine is mainly reflected in the backwardness of mining equipment in a large number of mines. The advanced mining equipment is mainly imported from abroad and the price is expensive. This is a key issue that restricts the progress of mining in China.
In order to solve the above problems, China must increase investment in science and technology, based on introduction-digestion and absorption-re-innovation, based on independent innovation. First, breakthroughs were made in the development of automated mining equipment to achieve localization of large-scale automated mining equipment in a relatively short period of time. This has created reliable conditions for accelerating the promotion and application of China's automated intelligent mining technology. At the same time, a large number of newly-built large-scale underground metal mines have been put into high starting from the beginning of design, and automated remote-controlled intelligent mining operations can be realized after production. After the completion of these batches of mines, the output will account for a large part of the production of underground metal mines in China, which can drive the level of automation and remote-controlled intelligent mining in China as a whole. In addition, China is engaged in mining technology research and mines engaged in engineering technology application and management. The number of people and strength is strong. As long as they concentrate their efforts, they can make breakthroughs in mining new technologies and new process research and application. "Create conditions for the transition to the "advanced stage." Therefore, compared with the western mining developed countries, China's mining engineering technology in the near future, to achieve "curve overtaking" is promising.
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