Bacterial oxidation pretreatment of refractory gold ore
I. Status of industrial applications at home and abroad Bacterial oxidation pretreatment of refractory gold ore was first proposed by the French in 1964. For the first time, the French attempted to use bacteria to leach gold from laterite minerals and achieved encouraging results. In 1977, the Soviet Union first published the test results. After many years of theoretical research, the bio-preoxidation technology of refractory gold ore began to enter the industrial application stage, and gradually developed two technical directions: concentrate tank leaching and lean ore heap leaching. In 1986, South Africa's Fairview Gold Mine established the world's first bacterial oxidation gold extraction plant, the first commercial application of oxidative pretreatment of refractory gold ore in the world; after that, Brazil, Australia, the United States, Plants for biological pretreatment of gold mines such as Ghana and Peru have been put into operation. The world's first large-scale bacterial treatment plant is the Ashanti biooxidation system in Ghana, which was expanded in 1995 with a design scale of 960 t/d. The most important feature of this technology is that the leaching process of fine flotation gold concentrate is carried out in an aerated stirred leaching tank, which is typically a BIOX process using medium temperature bacteria. On the basis of the industrialization of BIOX process, the adoption of high-temperature bacteria and the simultaneous extraction of basic metals have developed rapidly, and the process of biotechnology from development to industrialization has become shorter and shorter. In recent years, Australia and South Africa have successively introduced Bactech and MINBAX processes; in 1990-1995, five bacterial oxidation plants such as San Bento, Harbour lights, Wiluna, Ashanti and Youal-i-mi were built and achieved considerable economic success. benefit. Subsequently, GeoBiotics launched the Geobiotics process based on the advantages of the first three processes (BIOX, Bactech and MIN-BAX) and built a bio-dip immersion plant in Newmont, USA, which greatly promoted the development of bio-immersion gold technology. Bacterial metallurgy has occupied a very important position in the mining and metallurgical engineering in the United States. One-third of the total US gold production is produced by biopile leaching. In the past ten years, the domestic bacterial oxidation-cyanide gold extraction process has developed rapidly and some breakthroughs have been made. In 1998, Shaanxi Zhongkuang Company built China's first 10 t/d scale bacterial oxidation gold extraction test plant; in 2000, China's first 50 t/d scale refractory gold concentrate bio-oxidation-cyanide leaching The gold-plating workshop was officially put into operation at the Yantai Gold Smelting Plant, marking that the process of extracting gold from difficult-to-treat gold mines in China has shifted from the scientific research stage to the industrial production stage; in 2001, the Laizhou gold smelter introduced 100 t/d from abroad. The bacterial oxidation-cyanide leaching process is put into production. In the next few years, China has become the country with the most bio-oxidation-cyanide leaching and gold extraction process. Second, the main problems and possible solutions The bio-oxidation-cyanide leaching process has a long production cycle and a low leaching rate, which limits its application. In actual production, to achieve the necessary oxidation rate of sulfurized minerals (65% to 95%), heap leaching time generally takes several days, months or even years, and the tank immersion time is generally 4 to 5 days, while other wet methods Metallurgical technology takes only a few hours. The increase in operating costs caused by long-term reactions has offset the economic advantages of this process to a considerable extent, thus constraining the progress of its industrial application. Metallurgical and biological researchers have been working on bioleaching mechanisms and processes, and aim to adopt various methods and means to increase the leaching rate of gold and shorten the production cycle. Compared with normal temperature bacteria, the heat-resistant medium and high temperature bacteria (working temperature (45 ° C) tend to leaching minerals several times higher. The reason for the analysis: First, at higher temperatures, the chemical leaching speed is faster; One is that the metabolism of medium and high temperature bacteria is fast, and the rate of formation of Fe 3 + and sulfuric acid is faster, which accelerates the progress of the reaction and promotes the increase of the leaching rate. Therefore, Yao Guocheng and others have invested in the enhanced leaching of medium and high temperature bacteria. In the applied research, it is expected that the breeding and domestication of medium-temperature bacteria will provide more suitable bacterial resources for the development of refractory gold mines. In addition, genetic recombination technology has begun to be used in the development of excellent strains. During the leaching process, the re-incorporation of various new ions into the insoluble coating on the ore surface is also one of the important reasons for the low efficiency of leaching. Wherein the sulfur coating layer can be solved by a multi-species polyculture; jarosite or acidity of the solution can be controlled by changing the nutrient solution and the formulation adopted ways to reduce leaching segment generates. In industrial production, bioleaching of metal sulfide ore is mainly carried out by tank immersion. Under these conditions, high-efficiency bacteria are difficult to adhere to the surface of the ore, or are easily damaged by the impact of the ore. Current research on solutions has focused on the improvement of immobilized cell technology and reactors. Domestic research at this stage is less likely to be carried out from the perspective of the nutritional conditions required for microbial growth. Russian scientists have applied the formulation of the degraded collagen in the feed industry to the process of bacterial leaching, which has a good effect on the leaching effect of metallurgical microorganisms; the nutrient solution of BIOX process contains 5% yeast hydrolysate; There is a significant positive correlation between the biomass of the bacteria and the leaching rate and leaching rate. Therefore, the study of leaching microbial nutrition has the potential to promote the effective solution of the problem of low biometallurgy efficiency. Third, the conclusion The bio-oxidation pretreatment refractory gold mine technology is environmentally friendly, low in cost and simple in processing. It is one of the feasible means to deal with large-scale low-grade gold-bearing ore and some tailings. With the development of refractory gold mines and low-grade mines, bio-oxidation technology will have a profound impact on the sustainable development of China's gold industry and the transformation of production methods. Judging from the application effect of this technology, there is still a large research space for bacterial oxidation technology, and it is waiting for the metallurgical workers to further carry out their work. Plywood production line is one of the most common machine in woodworking field . plywood production machine includes veneer peeling machines, veneer peeling production line , Veneer Dryer , veneer slicing machine, Veneer Glue Spreader, plywood veneer hot press machine , plywood veneer cold press machine ,sanding machine and etc. plywood production machines are more and more popular nowadays! Plywood Production,Plywood Production Line,Plywood Production Machines,Plywood Veneer Production Line Shandong Shine Machinery Co.,Ltd , https://www.shinewoodmachine.com