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(1) Leaching mining technology
Leaching mining is a mining method based on physical and chemical principles and chemical processes, using certain chemical solvents and microorganisms to selectively dissolve, leach and recover useful components in mineral deposits, ores or waste rock. Geology, mining Science, hydrometallurgical, physical chemistry, fluid mechanics multidisciplinary interdisciplinary. According to different leaching processes and methods, leaching mining can be divided into three main methods: in-situ leaching, heap leaching, and in-situ leaching.
The in-situ leaching method is referred to as “ground leachingâ€, and its remarkable feature is that the leaching solution is used to selectively leach the useful components from the heterogeneous ore under natural burial conditions, and to extract, select, and smelt the combined ore. Method; heap leaching method refers to the mining of ore by traditional mining methods, transported out of the original place and stacked in the underground empty space or roadway, or transported to the surface yard or waste rock field, and then leached and processed into commercial products. Method; the local crushing leaching method is to use the open space or underground crushing compensation space, crush the ore in situ by blasting or ground pressure, then carry out leaching, and send the leaching liquid to the extraction workshop through the liquid collecting system. The method of qualifying products.
With the development of modernization, the contradiction between China's surge in demand for ore and most of China's mineral resources, which are characterized by “one poor, two mixed and three poorâ€, has become increasingly prominent. Leaching mining can better recover by conventional low-grade ore mining methods can not be recovered, it is difficult ore bodies, waste rock and hard dressing stone useful components broadens the use of underground mineral resources, increased ore reserves to meet China Industry has opened up new avenues for the growing demand for ore products. Moreover, compared with traditional mining methods, leaching mining has obvious advantages such as low environmental pollution and low production cost. Therefore, leaching mining technology has shown broad application prospects in low-grade ore mining.
For a long time, domestic and foreign scholars have paid great attention to the theory and practice of leaching mining. Especially since the 1970s, the United States, Canada, the former Soviet Union, Australia and other countries have carried out a large number of research in the field of leaching and mining. According to incomplete statistics, copper metal produced by the leaching method in foreign countries accounts for about 30% of the total output, uranium metal accounts for 20% of the total output, and gold production accounts for about 25%.
At present, domestic and foreign leaching mining technology has become increasingly mature. In the production of several major metals such as uranium, copper, gold and silver , the proportion of leaching mining technology production has increased year by year. Innovative and breakthrough in theory and technology, mainly in the following aspects:
1. After years of practice and continuous reform, the process technology has been perfected, such as improvement of drilling engineering; control of leaching range and protection and restoration of ecological environment; optimal selection and preparation of leaching solution; Numerical simulation; formation of various control and monitoring systems; bacterial culture and preparation of bacterial liquid; cloth liquid and liquid collection process; process facility and anti-corrosion of conveying and pumping pipeline; technology for preventing leakage; Control, leaching and improvement of extraction process have accumulated rich experience.
2. The latest achievements of multidisciplinary research have been closely integrated. Such as the new theory of mineral deposits, hydrometallurgical ion exchange, solvent extraction; oil drilling, cementing, completion technology; hydrogeology and hydrodynamics and seepage theory. Leaching mining is rapidly developed under the influence of mineralization, geology, geochemistry, hydrogeology, oil recovery technology, hydrometallurgy, mineral processing and conventional mining.
3, the study of leaching mining theory, in the leaching of thermodynamic conditions and kinetic mechanism, bacterial leaching mechanism, porous media fluid dynamics, computer simulation and other aspects have achieved a lot of results.
(II) Key technologies for leaching mining
1. Extrusion blasting technology controlled by underground leaching ore block
In the underground crushing and leaching process, the blasting and crushing effect of the ore will directly affect the underground leaching rate. How to study and design a practical and effective blasting technology to control the leaching block degree is one of the key points of underground leaching according to the specific conditions and conditions. The self-slotting small compensation space primary extrusion comprehensive collapse technology has successfully realized the ore block control of tens of thousands of tons of blasting, which satisfies the requirement of the underground leaching process for the explosive block. The detonation scheme is: millisecond differential non-conducting squib and detonating cord double detonation. The specific blasting network design scheme is: double-row same-segment multi-row differential extrusion blasting.
2. Hole mesh liquid and static liquid flow system control technology
The design is to statically permeate the liquid to the vertical fan-shaped hole to ensure uniform liquid distribution without leaving a dead angle. Design a new underground leaching liquid flow system simulation test method, investigate the influence of different liquid distribution methods, different liquid strength, different spray system, different ore blockiness on the leaching liquid flow, and finally the various processes of industrial leaching production. The determination of the parameters provides a basis for design. Industrial production shows that the designed liquid solution is correct, the liquid flow system is balanced, no leaching runoff is formed, and the leaching effect is good. The leaching solution concentration is up to 5.6g/L.
3. Comprehensive liquid collection technology combined with grouting anti-seepage and drainage
Liquid collection is the key link in underground leaching. If the leaching rich liquid is not effectively collected, it will not only cause the loss of copper metal, but also cause pollution to groundwater. On the one hand, the drainage of the leachate is carried out through the diversion hole, and on the other hand, the anti-seepage grouting is carried out through the grouting hole. Grouting uses a semi-circulating grouting process in which the orifice is circulated. Industrial production shows that the technology has a good application effect and the liquid collection rate is 92.18%. Groundwater environmental monitoring data also confirmed that since the underground leaching production, the pH value of groundwater, S042-, Cu2+, Fe3+ concentrations are in line with the three standards of groundwater environmental assessment (GB/T14848-93) “Groundwater Quality Standardsâ€.
(III) Application of leaching mining in the development of low grade deposits
1. Low grade copper ore
In order to develop a large number of rare and difficult-to-select low-grade oxidized ore resources that have been used in the copper ore-bearing copper deposits, the Beijing Mining and Metallurgical Research Institute, Zhongtiaoshan Nonferrous Metals Corporation and the Changsha Mine Research Institute cooperated in 1997-2000. The research on the underground leaching test of the key scientific and technological projects of the Ninth Five-Year Plan, which is difficult to recover and difficult to select low-grade copper ore, has formed a set of underground leaching extractions with the technical characteristics of “hole mesh liquid, static penetration, grouting and sealing, comprehensive liquid collectionâ€. For the first time, copper technology successfully realized the application of in-situ broken leaching mining technology in China's non-ferrous mines, and achieved good economic benefits and significant social benefits.
From 1997 to 2001, through the joint efforts of the Beijing Research Institute of Mining and Metallurgy and the Shouwangfen Copper Mine, the Ministry of Finance's resource compensation fund-funded project “Study on the in-situ bacterial leaching technology and industrialization of the Shouwangfen Copper Mine Empty Deposit†was completed. For low-grade mixed copper ore, the leaching rate is 68.11%, and the liquid collection rate is 93.48%, which is an excellent indicator. It has realized the first domestic copper mine resources of tens of thousands of tons of on-site bacterial leaching industrial production, and achieved annual direct economic benefits and significant social benefits of 9,142,200 yuan. In addition, the Duobaoshan Copper Mine in Heilongjiang Province achieved the first heap leaching of the first cold region in China for underground low-grade copper oxide ore. In the aspect of antifreezing, the drip tube liquid method embedded in the ore heap is used, and the effect is very good.
The research on biological copper extraction technology of Zijinshan Copper Mine carried out on-site 300t·Cu/a and 1000t·Cu/a industrial tests on the basis of the small test and expansion test of the laboratory. The indium immersion copper grade is 0.42%~0.88%, the leaching period is 180~240 days, and the copper leaching rate is 75.68%~80.84%. The quality of copper is up to the national A-grade copper standard. The technical innovations include: (1) Improvement and application of indigenous microorganisms, obtaining domesticated bacteria and mutagenizing bacteria, improving acid resistance and leaching efficiency; 2 Research succeeded in biological heap leaching engineering technology suitable for high S/Cu ratio copper ore characteristics, ferric balancing techniques and cleaning techniques; ③ the successful development of high temperature and rainy areas heap bioleaching process water balance technology; Purple for containing arsenic grade copper ore characteristics, the traditional dressing - compared to pyrometallurgical copper process, the technology The problem of arsenic pollution is better solved. The developed technologies and indicators are leading domestically and reach the international advanced level. Zijinshan Copper Mine has formed the first underground mining-bio-pile-extraction-electricity kiloton production line in China, which has produced 3209t of cathode copper and obtained economic benefits of 25.9 million yuan. The Zijinshan 10,000-ton biological copper-raising mine constructed with the results of this technology has been basically completed, and the large-scale low-grade copper sulfide mine of Zijinshan with a copper reserve of 1.46 million tons has been developed on a large scale. The annual economic benefit is expected to reach 184 million yuan. The technology is low in cost, environmentally friendly, and has significant economic benefits. It can be applied to the development of copper resources in low-grade and remote areas in China.
2. Ionic rare earth
The ionic rare earth ore is mined by the local controlled speed leaching mining method, which basically does not destroy the mine vegetation, and does not produce the stripping and tailings pollution. Since the leaching electrolyte solution is injected from the upper part of the weathered layer and enters the lower part of the weathering layer, it can also penetrate into the semi-weathered layer and the micro-weathered layer until the granite bedrock, thereby greatly improving the utilization rate of the rare earth resources. The in-situ leaching area is as small as several thousand square meters, and tens of thousands of square meters. It participates in leaching of tens of thousands of tons to hundreds of thousands of tons of rare earth, and the production of rare earths is several tens of tons to several hundred tons. Double growth has not only greatly improved the working conditions of workers, but also greatly reduced production costs. Due to the precipitation of ammonium bicarbonate, the supernatant liquid is recovered and treated. After closed-circuit circulation, the consumption of leaching electrolyte is lower than that of the pool leaching process. In addition, it is not necessary to construct a series of leaching tanks with higher cost, so the cost of ton rare earth is better than that of the pool. The process has been greatly reduced. Xunwu rare earth ore production company has been exploring the development of ionic rare earth deposits by leaching mining method for the past ten years, and some of them have achieved certain success.
Second, the situation faced by low-grade ore mining
In recent years, although the non-ferrous industry in China has achieved certain results in the use of low-grade ore, there are still many problems.
First, the development of low-grade ore mining is uneven. The use of low-grade ore mines in non-ferrous mines has been carried out in most mines, but the development is slow and unbalanced. The use of low-grade ore mines is often a social benefit greater than economic benefits, and is a cause of "work in the present, benefiting the future." Secondly, the depth and breadth of relevant experimental research on the use of low-grade ore is insufficient. Many mines do not form a systematic scientific management system for the use of low-grade ore mines, so that the use of the work can not be graded, can not scale. Therefore, in the ore mining process, the main process should be improved while improving the process to improve the comprehensive utilization rate. Third, low-grade ore utilization has a low recovery rate. According to reports, at present, the total recovery rate of China's total and associated components is more than 70%, and the recovery rate of associated gold in non-ferrous mines is generally only 50% to 60%, and the recovery rate of associated silver is 60% to 70%. Compared with foreign indicators, the difference is about 10%. Fourth, China’s current mining taxes and fees are too heavy. Since January 1994, a new tax and fee system has been implemented. The taxes and fees of non-ferrous mining enterprises have increased by about 15%. This has made it necessary for most enterprises to abandon poverty and temporarily reduce excessive taxes.
Third, strengthen the countermeasures for the development of low-grade deposits
(1) Further changing concepts and raising awareness of the use of low-grade ore. Mining enterprises should establish a long-term strategic concept and use low-grade ore mining as a necessary measure to achieve sustainable development of mining industry. Under the premise of economic rationality, gradually improve the comprehensive utilization rate of low-grade ore.
(2) Strengthen the intensity of geological exploration and reasonably determine the boundary grade of the mine and the lowest grade of the industry. The state should organize its forces to further explore the country's mineral resources. While searching for new mines, it should strive to tap the potential of old mines, redefine its boundary grades, and turn waste stones that have been abandoned in the past into low-grade mines that can be utilized, especially It is a comprehensive recovery of residual copper and gold resources in the old airspace and the collapse zone.
(3) Improve the scientific and technological content of mines and increase the intensity of scientific and technological research. First of all, we must strengthen the investigation of low-grade ore resources, find out the quantity, type and quality of low-grade ore resources, do a good job in economic evaluation according to the different characteristics of different types of low-grade ore, and find advanced equipment for low-grade ore use in accordance with local conditions. New technologies, new processes, especially the study of enhanced leaching mining methods: 1 Further strengthen the research on the leaching and mining technology of refractory minerals; 2Expand the experimental research on the use range of leaching mining, so that more varieties of metals can be dissolved Leaching mining technology recovery, and strengthen research, so that leaching mining for large-scale industrial production; 3 focus on strengthening in-situ leaching process technology research, in-situ leaching is the most effective method for low-grade metal deposit recycling, especially not allowed under the surface This is especially true when it collapses.
(4) Strengthen management and formulate relevant management regulations. Low-grade mine utilization work should organize a special team to carry out the responsibility, from research, economic evaluation, scientific and technological research to final development and utilization of comprehensive management, each link is controlled by experts, the management team should be coordinated and mutually restricted. At the same time, the specific implementation rules for the utilization of low-grade ore mines will be formulated, so that the development and utilization of low-grade ore mines will be truly incorporated into the normal production track of mining enterprises.
(5) Reducing taxes and relieving pressure. In order to encourage mining enterprises to use low-grade ore, the state should give some preferential policies and give the mine more preferential policies.
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