introduction Since China entered the stage of rapid industrialization, the consumption of resources has increased rapidly. On the other hand, the growth of China's mineral resources reserves has been slow, resulting in a sharp decline in the level of resource guarantee. Several major non-ferrous metal reserves of life assurance were about 10 years. Copper ore, for example, in 1999, an annual amount of copper metal mine 520 100 t, satisfying only 44.29% of smelting capacity, in 2008 China's copper concentrate self-sufficiency rate to 30%. Bioleaching technology can be economical to develop low-grade ore, hard ore bodies, hard rock and mineral processing waste rock, broaden the scope of utilization of mineral resources, improve the utilization of mineral resources. At the same time, the technology has the advantages of low cost, low investment, simple process and mild working conditions, and has good environmental value. I. Current status of low grade mineral resources in China One of the salient features of China's mineral resources is low grade. For example, the average grade of copper mines in China is only 0.87%, and the grades of super-large copper mines above 2 million tons are basically less than 1%; nickel- cobalt leans account for the total 30% to 40% of reserves; iron ore accounts for 95% of the overall lean ore reserves, manganese ore lean ore accounts for 93% of the total reserves. In addition, China's total resource recovery rate is low, and mineral solid waste discharge is large, which contains many useful ingredients. According to statistics, the tailings stockpiles produced by metal mines in China have reached more than 5 billion tons, and 2 to 3 per year. The speed of billions of t is increasing. For example, since the discharge of waste rock in the Dexing Copper Mine in 1994, the waste rock has been discharged about 70 million tons, the final emission of the design is 680 million tons, and the amount of copper metal in the waste rock is estimated to exceed 600,000. t. Second, the application status of low-grade ore microbial leaching technology Microbial leaching technology is based on chemical reactions and physicochemicals. It uses some leaching agents that dissolve the useful components in the ore and selectively dissolves them by the action of certain microorganisms, catalysts, or ore surfactants. The purpose of mining ore is achieved by leaching the useful metal components in the ore or ore body, converting it from a solid state to a liquid state and recovering it. At present, microbial leaching technology is mainly divided into waste rock heap leaching, ore heap leaching and in situ leaching. It is widely used in the mining of copper, gold, nickel, uranium and rare earth ore. (1) Review of microbial leaching history of mineral resources Microbial leaching technology is a process of human conscious use of the already existing biogeochemical processes in nature. As early as the 16th century, the Harz region of Germany and the Rio Tinto mine in Spain used leaching methods to treat sulfide ore. At the end of the 19th century, the Russians proposed the idea of ​​leaching gold deposits in situ. In 1922, Waksman and Joffe isolated Thiobacillus oxidans from the soil. In 1947, Colmer and Hinkle separated Thiobacillus ferrooxidans from acid waste water. People began to understand and use the role of bacteria in sulphide leaching. In the 1960s, the United States and the Soviet Union began trials of in-situ leaching to extract uranium. In the 1970s, the United States Kennecott Mining Company built the world's largest microbial heap leaching site, processing 3.6 billion tons of ore, with an annual output of 72,000 tons of copper metal. In 1976, BHP began the experimental study of gold leaching technology in gold mines. In 1986, the Fairview mine in South Africa was built into the world's first gold leaching plant, and the gold concentrate was treated 10 tons a day. In the past 20 years, leaching technology has been promoted in the United States, Chile, Australia and other countries. In the mid-1980s, China's in-situ leaching of sandstone -type uranium, ionic rare earth ore and copper was successful. Currently, 25% of the world's copper and 20% of uranium are from leaching. (II) Current status of microbial leaching at home and abroad With the wide application of leaching technology, ultrasonic technology, high temperature bacteria, granulation technology, thin layer building method, forced gas filling and nuclear blasting technology have made the microbial leaching technology have a greater development. In the 1970s, ultrasonic waves were used to accelerate the growth and reproduction of microorganisms, strengthen the leaching process, and increase the leaching rate. Ultrasonic technology can improve the in-situ leaching recovery rate of lateritic nickel ore from 40% to 50%, and make copper in tailings. The leaching rate increased from 60% to 80%. In 1993, the Gi. ralambone copper mine in Australia first imposed forced gas filling on the leaching ore heap to provide 02 and CO2 for the growth and reproduction of bacteria in the heap. The high temperature bacteria leaching test of copper concentrate began in 1995, and the Chilean Chuquicamata copper mine was completed in 1997. Copper concentrate high-temperature leaching plant, designed with an annual output of 20,000 tons of copper. In addition, Chile's Quebrada Blanca copper mine is leached with sulphuric acid and hot water to overcome the unfavorable factors such as high altitude, cold and oxygen deficiency. Treatment of sulfide ore of 17,300 tons; in 2004, the Escondida copper mine in Peru built a large-scale microbial heap leaching field by layered pile-up technology. The heap covers an area of ​​100,000 km2 and is built in 7 layers, each layer is 17 m high, with an planned annual output. 180,000 tons of electric copper. Since the 1980s, there have been 19 factories in the world that have extracted copper and cobalt from bioleaching technology. (III) Current status of research on microbial leaching theory The successful application of microbial leaching technology has ignited the research physics of leaching mining, the basic theory of "three-pass" (heat, solute, momentum transfer) and microbial leaching mechanism. 1. Physical and chemical principles of the leaching process. The physical chemistry of leaching mining mainly involves the problem of reaction equilibrium and reaction rate. The former belongs to the thermodynamics of leaching process, mainly studies the direction of leaching reaction process and the maximum possible yield of product; the latter belongs to leaching kinetics, mainly studies the leaching reaction rate and Its influencing factors. G. Heisbourg et al. combined the x-ray photoelectron spectroscopy and x-ray absorption spectroscopy techniques to analyze the thermodynamics of Th1-XUX02 leaching by leaching experiments. King et al. studied the effects of temperature, leaching ion composition and ore particle geometry on leaching kinetics; Shu Rongbo et al. conducted a low-potential bioleaching experiment for chalcopyrite and found that the presence of high concentrations of Fe2+ ions contributes to the dissolution of oxygen to yellow. Oxidative leaching of copper ore. 2. The law of heat, solute and momentum transfer in the leaching system. Temperature is a key factor affecting the leaching process. MJ Leahy et al. established a heat balance model of mesophilic and moderately thermophilic leaching of chalcopyrite. It was found that the bottom-up leaching front movement of the mixed bacteria moved faster than the immersion front of the mesophilic bacteria. Chen Tong et al. established a dissolution-infiltration coupling mathematical model for in-situ water-soluble mining of glauberite deposits. Metodiev et al. simulated fluid flow and ferrous ion concentration around bacteria; Mousavi used fluid volume method to flow velocity field of solution. The volume fraction distribution of fluid in the heap was simulated. The results show that the liquid distribution is mainly affected by the surface tension and turbulence of the ore. Li Guobin et al. added a certain proportion of framework materials to the refractory gold ore, which solved the problem of poor permeability of the heap. . 3. Mechanism of microbial leaching. Since the discovery of leaching bacteria in the 1950s, the mechanism of microbial-mineral interaction has been the basic problem that people have tried to solve. At present, there are three hypotheses of direct action, indirect action and complex action. Direct action means that the surface of the ore-impregnated bacteria adheres to the sulfide minerals in the ore, and a series of secreted polysaccharide compounds and minerals act to oxidize and dissolve the minerals. Indirect action refers to the process of dissolving ore and releasing metal ions through bacterial metabolites. The complex action refers to the case where the direct action of bacteria and the indirect action of chemical oxidation coexist. Liu Hui et al. used hard rock uranium ore as the research object and compared the effects of bacterial leaching and acid leaching through column leaching experiments. Third, the theory and development trend of microbial leaching Although there has been a lot of research work on refractory microbial leaching of copper, nickel and gold mines at home and abroad, and successful in industrial applications of secondary copper, gold, uranium and other bioleaching, biological heap leaching technology still exists. The following key technical problems: high ore content and poor permeability; leaching system physical, chemical, biological and other factors coupling mechanism and leaching kinetics research is not comprehensive and in-depth; lack of efficient and exclusive strains suitable for primary sulfide ore leaching; difficult Effective control of the leaching range, the problem of leaching solution loss is serious; the number of bioleaching minerals is limited. Therefore, the following theoretical research work should be strengthened in the future. (1) Breeding and basic biology of leaching microorganisms The low-grade complex sulfide ore leaching rate is slow and the leaching rate is low, which is an unsolvable problem in the world. The microbial metallurgical technology of low-grade complex sulfide ore such as copper, nickel, cobalt and zinc has not been applied in industry. The discovery, collection and screening of leaching bacteria with high activity, adaptability and selectivity are natural in nature, and this method is blind and has a huge workload. Improve the various qualities of the leaching bacteria by means of directed breeding, mutation breeding, cross breeding, genetic engineering and other domestication methods, such as growth and reproduction rate, ability to oxidize and degrade ore, high temperature resistance, and resistance to heavy metal ions. It is possible to achieve the goal faster. (2) Ore-solution-microbial mechanism There are three main factors affecting the bio-implementation system, namely physical factors (such as ore mineral composition, particle size distribution and porosity, osmotic pressure, etc.), chemical factors (pH, Fe3+/Fe2+ concentration and solution potential, etc.). Biological factors (such as microbial species, bacterial concentration, O2 and CO2, supply mechanisms, etc.). The interaction of these three factors directly determines the distribution characteristics and variation of the temperature field, concentration field and seepage field of the leaching system, and affects the transfer of heat, mass and momentum in the system, and ultimately relates to the effect of mineral leaching. . The bio-implementation system is a complex multi-phase biochemical reaction and physical chemical reaction system. The core of it is the interaction between microorganisms and minerals. Understanding the mode of action of microorganisms and minerals, the mechanism of ore biooxidation and degradation will help to effectively control. The leaching process improves the efficiency of leaching. (III) Seepage characteristics and mass transfer laws of ore bodies When the ability of microorganisms to oxidize, degrade and etch minerals is certain, the success of bio-dump leaching technology mainly depends on the penetration effect of leaching solution in the heap and the law of solute migration. The size of the ore particles determines the pore size and specific surface area of ​​the heap and affects the seepage characteristics of the solution; the development of ore fissures, the accumulation of ore particles and the pore network and geometry formed directly affect the multi-stage seepage of the solution in the heap. status. During the leaching process, as the solution seepage, chemical reaction and solute migration progress, the ore particles are gradually dissolved, the fine particles migrate downward and deposit at the bottom, and the permeability coefficient decreases with the leaching time. (4) Microbial heap leaching technology The leaching reaction process research is carried out in order to select an effective and economically feasible leaching scheme, develop a reliable leaching system and optimize the leaching process conditions, and design an efficient and economical bioleaching reaction equipment. Fourth, the conclusion Microbial leaching technology can economically and reasonably recover valuable elements in complex low-grade ore, mining waste rock and beneficiation tailings, reduce the economic exploitation grade of mineral resources, improve the utilization rate of proven geological reserves, and have broad application prospects. However, the current basic theory of this technology is still very weak, and further theoretical research is needed on the effects of multi-factors on the seepage dynamics of the bulk, the cultivation of high-efficiency strains, and the leaching process. In order to solve the use of high-efficiency strains and improve the seepage field of the immersion reactor The technical problems such as the uniformity, the artificial control of the temperature field of the immersion pile and the strength of the concentration field lay the foundation, thus changing the problems of long leaching period and low leaching rate in the leaching mining technology. Vending Machine,Smart Vending Machine,Toy Vending Machine,Food Vending Machine Dongguan Kaisijin Intelligent Technology Co., Ltd , https://www.dgsmartlockoems.com