First, the domestic distribution of refractory gold ore resources and features
China's refractory gold resources are relatively abundant. Among the proven gold geological reserves, about 1,000 tons are refractory gold resources, accounting for about 1/4 of the proven reserves. Such resources are widely distributed and are distributed in various gold producing provinces. Among them, Guizhou, Yunnan, Sichuan, Gansu, Qinghai, Inner Mongolia, Guangxi, Shaanxi and other western provinces account for a large proportion, Liaoning, Jiangxi, Guangdong, Hunan and other provinces also have large reserves. The main resource mining areas are: Guangxi Jinya Gold Mine (30 tons), Guizhou Lengmugou Mining Area (52 tons), Guizhou Zimu Coal Mine Area (26 tons), Guizhou Yuta Mining Area (16 tons), Yunnan Zhenyuan Winter Melon Mining Area (10 tons), Zhouqupingding Mining Area (15 tons) in Gansu, Luerba Mining Area (30 tons) in Gansu County, Fengcheng (38 tons) in Liaoning, Changkeng Mining Area (25 tons) in Guangdong, Mashan Mining Area in Anhui 14 tons) and so on. The reasons for the difficulty in dealing with these ores are various. The occurrence and mineral composition of gold in the ore are the most fundamental reasons. According to the characteristics of process mineralogy, the domestic refractory gold resources can be divided into three types. The main type.
The first type is gold ore with high arsenic , carbon and sulfur type. In this type, it contains more than 3% arsenic, 1-2% carbon, 5-6% sulfur, and gold leaching rate by conventional cyanidation gold extraction process. Generally, it is 20-50%, and a large amount of Na2CN is consumed. When the flotation process is used for enrichment, although a high gold concentrate grade can be obtained, the concentrate contains high levels of harmful elements such as arsenic, carbon and antimony . It will have an impact on the next gold extraction process.
The second type is gold containing fine ore and microscopic inclusions in gangue minerals and harmful impurities. In this type, the metal sulfide content is small, about 1-2%, embedded in gangue mineral crystals. The fine-grained gold accounts for 20-30%, is floated by conventional cyanidation, or floated by flotation, and the gold recovery rate is very low.
The third type is a gold ore with gold and arsenic and sulfur intercalation. It is characterized by the main carrier mineral of arsenic and sulfur as gold, and the arsenic content is medium. This type of ore is extracted by a single cyanide gold extraction process. Lower, if the flotation method is used for enrichment, gold can also obtain a higher recovery rate index, but it is difficult to sell due to excessive arsenic content.
In view of the above characteristics, solving the difficult problem of domestic refractory gold resources still needs to start from the following three aspects:
First, prior to cyanide gold extraction, the pretreatment is carried out to oxidize and decompose the main minerals associated with the gold ore, so that the encapsulated gold is dissociated and exposed, and at the same time, some harmful components that interfere with cyanide leaching are also removed;
Second, by adding certain chemicals or reagents to inhibit or eliminate the interference of harmful components on the cyanidation gold leaching process to achieve the purpose of enhanced leaching;
Third, look for new high-efficiency or non-toxic immersion gold solvents to replace cyanide to completely solve environmental pollution problems.
The above three technical measures should be the main direction of our research and development of difficult metallurgical technology in the future. However, from the perspective of technological development trends at home and abroad, the pretreatment technology for difficult gold ore processing will be developed and applied in the coming period. The important goal.
two. Regulations and prospects for the utilization of domestic refractory gold resources
For the development and utilization of domestic refractory gold resources, we have carried out a lot of research work in the past ten years, from the gold industry research plan during the “Eighth Five-Year Plan†to the national scientific and technological research of the “Ninth Five-Year Planâ€, plus enterprises and mines. All aspects of investment have made the difficult resources to be exploited to a certain extent. However, the overall situation is not optimistic. The proportion of gold that is effectively and reasonably, safely and environmentally extracted from the difficult gold resources is not high. From the way of development and utilization, it can be roughly divided into two categories. One is the resource mine that is difficult to handle gold mines. The real estate gold method is realized by adopting pretreatment technology or strengthening immersion gold measures, such as the Hunan Golden Cave Gold Mine. Treatment of high arsenic gold concentrate by two-stage oxidative roasting process, Lufeng gold deposit in Ganyu County, Gansu Province, using raw ore roasting process to treat raw ore containing arsenic, carbon and low sulfur, and gold concentrate of Wulayu gold deposit and Jinshan gold deposit in Jiangxi Cyanide process, etc. The resource utilization status of this part of the mine is that the gold recovery rate is generally not high or has caused a certain degree of pollution and damage to the environment. It is urgent to solve the problem fundamentally from the process technology. Another type of mine that is difficult to handle gold ore resources uses flotation or other process enrichment methods to produce gold concentrates that are difficult to be smelted and concentrate on sales to smelters. The resource utilization rate of this method is mainly determined by the smelter. The technical level of the pretreatment process.
At present, there are 34 designated enterprises in China that have approved the smelting and processing of gold-containing materials for the whole country, including 22 gold smelters and 12 non-ferrous smelters. These smelting enterprises include Yantai Gold Smelter, Laizhou Gold Smelter and Shaanxi. The three smelters of the mining bio-mining engineering limited liability company have begun to use the bacterial cyanidation pretreatment process to treat some of the arsenic-containing gold concentrates. The majority of the remaining smelting enterprises still use the gold cyanide direct cyanidation process or roasting – The cyanidation process, which is limited by the “poor, fine and miscellaneous†diversity of the current refractory gold resources in China.
Therefore, the current status of development and utilization of difficult-to-handle gold resources in China is that although the proportion of difficult-to-handle gold resources is large, the degree of development and utilization is relatively low. Smelting enterprises have a large demand for single gold-containing materials, and the raw materials market is highly competitive. The technical level of processing technology for refractory gold concentrates is relatively low, and the production of complex gold concentrates is difficult to produce, thus limiting the development of refractory gold resources. This has also caused a passive situation in the domestic gold industry production. On the one hand, the easy-to-handle gold resources are becoming more and more exhausted; on the other hand, a large amount of geological exploration funds have been invested and the proven refractory resources are not developed or exploited. low. The more favorable aspect is that many smelting enterprises have turned their attention to the development and utilization of arsenic-containing, carbon-containing, fine-grain-wrapped refractory gold-containing materials, and have sought their own channels and methods to break through the difficulties of technology and preemption. potential market. Therefore, it can be foreseen that with the industrialization and application of pretreatment technology, the production of difficult-to-smelt materials will become larger and larger, and the prospect of difficult to handle the development and utilization of gold resources will be broader.
three. Application status and development trend of foreign difficult metallurgy technology
The research and development of difficult smelting technology has been valued by the United States, South Africa, Australia, Canada and other countries. The pretreatment process currently applied is basically developed and researched abroad and used in the industry. These process development and application also enable most of the foreign refractory resources that have been proven to be economically rational, safe and environmentally friendly. Except for the extremely small carbon refractory gold mines, there is still no effective treatment. At present, about one third of the world's total gold production is produced from refractory gold mines.
It can be seen from the research route and application effect of difficult smelting technology in foreign countries that the main key of difficult smelting technology is the “robbery†of pre-oxidation or pre-selection of carbonaceous minerals. Therefore, the so-called difficult smelting technology is mainly Refers to pretreatment techniques. The pretreatment technologies that have been developed or are currently being studied include roasting process, pressure oxidation process, bacterial oxidation process, chemical oxidation process, and chlorination process and sulfur-containing reagent oxidation process. The development trend and application of foreign pretreatment process Degree analysis, roasting oxidation, pressure oxidation process and bacterial oxidation will become the basic process technology for future difficult gold processing.
Calcination is the oldest and traditional pretreatment method for refractory gold ore. It is like the early use of multi-hearth roasting, rotary kiln roasting, muffle furnace roasting, and with the advancement of technology and market demand, it has been developed in the past decade. The two-stage boiling roasting and raw ore circulating boiling furnace roasting bring new life to the industrial application of this traditional process. In the past ten years, more than ten new roasting and oxidation plants have been built around the world. More representative applications such as Jerritt Canyon and Big Spring in the United States and New Consort in South Africa.
The advantage of the roasting process is that it is relatively adaptable (can handle gold-bearing refractory gold ore), and the operating cost is relatively low. (When the sulfur content is above 80%, it is easy to carry out naturally), and when it is contained in the ore In the case of copper , the copper can be recovered by a immersion immersion process. The disadvantage of this process is that it is sensitive to changes in operating parameters and feedstock composition, and it is easy to cause over-burning or under-burning. When it is not burned, the sulfur and arsenic-containing minerals in the ore are not fully decomposed. The pores of the sand are closed to find a secondary coating of the particles, resulting in a decrease in the leaching rate of gold. In addition, sulfur dioxide and arsenic trioxide will be produced during roasting, and when the comprehensive recovery is unfavorable, the atmosphere and the environment will be seriously polluted. From the current point of view, as environmental protection requirements become more stringent, the cost of flue gas treatment associated with the process will be greatly improved. Therefore, the process will be challenged by the wet pretreatment process. In order to better solve environmental protection requirements, reduce energy consumption, increase roasting intensity and increase leaching rate, the technology of roasting process has also been improved and developed. In recent years, foreign research institutions are developing pyrolysis-oxidation roasting method. More efficient calcination techniques, such as flash calcination and microwave roasting, are still in the experimental research stage, but like the microwave roasting process, it has shown good industrial application prospects.
Hot-pressure oxidation is considered to be the most effective pretreatment process in Latin America. It is divided into acidic hot pressure oxidation and alkaline hot pressure oxidation. Alkaline hot-pressure oxidation is applicable only to refractory gold ore with high carbonate content and low sulfide content (<20%). Therefore, the application of acid hot-pressure oxidation process is relatively extensive.
Based acidic pressure oxidation at high temperature and pressure, pyrite, and other sulphide minerals arsenopyrite reacts with oxygen, so that the mechanism changes mineral structure, a high temperature in an acidic medium, of a series of reactions under high pressure, so that the The gold of the package is exposed. The purpose of cyanide leaching gold is achieved. In 1985, after the first application of the acid hot-pressure oxidation pretreatment process in the McLaughlin gold factory in the United States, the United States, Canada, Brazil and Babiya and other countries have established nearly 10 gold extraction plants applying the process. Most of them are large-scale raw ore hot-pressure oxidation processes that process more than 1,000 tons per day. Such as the US Gold Strike Getchell. This process is also ineffective for refractory gold concentrates, such as Sao Renton in Brazil, Olypias in Greece, Porgora in Papua New Guinea, and the Campbell gold mine in Canada as a representative of gold concentrates.
The advantage of the hot-pressure oxidation process is that the oxidation products of pyrite and arsenopyrite are both soluble. Therefore, no matter how fine the gold particles are, they will be dissociated, so the recovery rate of gold is high, and many difficult gold concentrates are added. After leaching, the leaching rate is as high as 98%. At the same time, the process can directly treat the ore, which is more effective for gold ore that is not easy to float and enrich. Because of the wet process, no smoke pollution is caused. problem. The disadvantages are: the design and material requirements of the equipment are very high; due to the pressure operation and the anti-corrosion problem of the equipment, it will bring certain safety hazards; compared with the biological oxidation method, the operation and maintenance level is higher; in addition, the capital investment cost is higher. High, it is generally believed that only the construction of large-scale treatment plants is economically reasonable. It is suggested in the literature that the daily processing capacity should be above 1200 tons.
Recently, the ultra-fine grinding technology (Activex) proposed by Dominion Minerals of Australia has improved the surface activity of minerals by ultra-fine grinding (5~15μm), reducing the oxidation temperature and pressure of the process, and making the reactor material. The anti-corrosion problem has become smaller. Therefore, it is foreseeable that the process will become more broad after the breakthrough of equipment pressure and anti-corrosion problems.
The bacterium oxidation technology is a kind of pretreatment process with strong vitality after hot pressing oxidation and roasting oxidation. It is currently applied to both tank leaching oxidation and heap leaching oxidation. The latter is mainly used to recover gold from low-grade refractory gold mines. The pretreatment technique is either BIOX or BacTech. The BIOX method is a technology developed by Gencor in South Africa. It began research and development in 1975. Since the first 10 t/d bacterial oxidation pretreatment plant was built in Fairview Gold Mine in South Africa in 1986, Gencor has begun to transfer the project to foreign gold mines. Technology, and since 1991, five bacterial oxidation plants have been built to deal with difficult-to-select concentrates, namely Fairvew (40t/d) in South Africa and Sao Bento (150t/d) in Brazil. Harbour Light (40t/d) in Australia. ) and Wiltuna (157t/d), Ashanti (960t/d) in Ghana, where the size of Ashanti in Ghana is currently the largest, and the ore it treats is a carbonaceous sulphide gold deposit with a direct liquefaction gold leaching rate of only 5 ~40%, the leaching rate of gold cyanide after bacterial oxidation pretreatment can be increased to more than 94%. Recently, Uzbekistan's Navoi has also purchased the technology to deal with the refractory gold ore of the Kokpntas gold mine, which is currently in production.
The BacTech method is a technology developed by BacTech in Australia. Bactech is the first to successfully use thermophilic bacteria (suitable temperature range 45~55 °C) for production practice, successfully produced in the Yonanmi gold mine in Australia. For more than two years, the processing capacity is 120t/d.
Bacterial oxidation technology has many advantages from foreign application practice analysis: compared with hot pressing and roasting process, the capital investment is lower, the production cost is lower, and the complexity of production operation is relatively low; the final generation of arsenic iron is arsenic Compounds are safer and more environmentally friendly than gas generation; bacteria can selectively oxidize arsenic pyrite. When gold in ore is mainly associated with arsenic pyrite, minerals mixed in arsenic pyrite and pyrite In the middle, only arsenic oxide pyrite can dissociate the gold without oxidizing all the sulfides.
However, this process also has certain disadvantages: long oxidation time, low slurry concentration, large volume and agitation tank are required, and the oxidation process is completed in the acidic interlayer, so the anti-corrosion material is required to be an outer material; in normal work, cooling is generally required. There is a need to consume extra energy. Lastly, there is a disadvantage that if there is a "misoperation" in the operation, the bacteria may die, which takes several weeks to recover the biomass of the bacteria.
Although there are not many factories that use the bacterial oxidation process at present, as a relatively new process, it has shown a very good development prospect compared with other pretreatment processes.
In addition to the above three pretreatment processes, the chemical oxidation process has also been applied industrially, and the Carlin-type carbonaceous ore has been treated by a flash chlorination process. At present, countries are still researching and developing various more effective and easy-to-industrial pretreatment technologies, such as nitric acid as a catalyst for nitric acid catalytic oxidation, simultaneous completion of pretreatment and immersion gold HMC processes, sulfuric acid, carbonic acid, sodium hydroxide, In the chloride oxidation medium electrochemical oxidation process, various chemical oxidation methods have achieved good results in laboratory research and semi-industrial test research, but many engineering technical problems still need to be solved. From the development trend of difficult smelting technology in foreign countries, the research and development operating conditions are relatively mild, the reaction speed is fast, the process investment cost and production cost are appropriate, and the pretreatment technology with small environmental pollution is the main development direction.
Fourth, the status quo and development prospects of domestic difficult smelting technology
The development of domestic difficult smelting technology began in the early 1990s. During the "Eighth Five-Year Plan" period, domestic scientific research institutions carried out many insightful experimental research work on the refractory gold resources discovered in China. But most of them stayed at the level of results obtained in the laboratory. Industrial applications are almost blank. The concentrate roasting and gold extraction plant in Danzhai, Guizhou Province has tried industrialized utilization of refractory gold resources, which has only been operated for several years for various reasons.
The more systematic research began in the national scientific and technological research in the "Ninth Five-Year Plan". The Changchun Gold Research Institute, Beijing Nonferrous Metals Research Institute and other research institutes conducted a systematic study on the oxidative roasting process, alkaline hot-pressure oxidation process and bacterial oxidation process with the help of the national “Ninth Five-Year†scientific and technological research plan. And achieved phased results, laying a solid technical foundation for the development and utilization of difficult-to-treat mineral resources in China.
The Beijing Nonferrous Metals Research Institute completed the three research stages of the system's small test, pilot test and industrial test relying on the Hunan Golden Cave Gold Mine. The research project is aimed at the high arsenic refractory gold concentrate of the Golden Cave Gold Mine. The research focused on solving the technical conditions and parameters of the two-stage roasting process, and completed the two-stage roasting-cyanide industrial test at 20t/d scale. The process removes arsenic in the absence of oxygen, desulfurization in an oxidizing atmosphere, and produces loose porous calcine. Under laboratory conditions, the cyanidation leaching rate is increased from 60-70% before roasting to about 93%. The arsenic in the flue gas is recovered in the form of chalk, the comprehensive recovery rate is 99.9%, and the SO2 in the flue gas is 6%~10%, which is in accordance with the acid-making conditions, and is treated by absorption method, and the absorption rate is over 90%. The process test shows that the treatment of arsenic-containing gold concentrate by two-stage roasting process not only improves the leaching rate of gold, but also comprehensively recovers the associated elements such as arsenic and sulfur. At present, the process production plant is in the commissioning stage, and after the normal production, it can provide more comprehensive industrial parameters for the domestic roasting process plant.
In addition to the Golden Cave Gold Mine, there are currently four smelters in the domestic roasting cyanidation process with a total production capacity of 1,100 tons/about, but the processes used are all a calcination and oxidation gold extraction process. Complex gold mines are not yet able to meet technical and environmental requirements. In addition, the Lufeng gold mine in Ganyu County, Gansu Province uses raw ore boiling roasting technology to treat raw ore containing arsenic, antimony and carbon, but the current process is still in the commissioning stage.
As far as the domestic application status of the roasting process is concerned, the pretreatment process of oxidizing roasting as a refractory gold ore is not widely used at present, because many smelters have adopted a oxidative roasting process to deal with relatively complicated Gold materials, therefore, have a basis for a certain technological transformation. The NUS Gold Smelter is currently working with the Nanhua Institute and the Beijing Research Institute of Mining and Metallurgy to carry out a technical transformation of the two-stage roasting process. Therefore, the oxidative roasting pretreatment process should have a broad development prospect in China.
The industrial application of hot-pressure oxidation process is still blank in China. However, after systematic research on the “Ninth Five-Year†scientific and technological research, we have obtained a large number of research data on process technology from the small-scale experiment to the large-scale work of expanding the continuity test. It laid the foundation for the next industrial application. Especially between 1997 and 1999, Changchun Gold Research Institute cooperated with the Nuclear Industry Beijing Metallurgical Research Institute to raise gold for the refractory ore in Jilin Minjiang Gold Mine by using alkaline hot-pressure oxidation – rapid cyanidation in the kettle. The process technology effectively oxidizes and decomposes gold-bearing sulfides, increasing the gold leaching rate from less than 47% of direct cyanidation to over 92%. And the expansion test of 800-1000kg/d was completed. The process research, due to the use of alkaline hot pressing process, the temperature and pressure of the oxidation process is lower than the foreign acid hot pressing technology, so it is more suitable for our national conditions, easier to promote and apply in China. Shandong Jinyiling Gold Mine is preparing to build a hot-pressure oxidation---cyanide gold extraction plant.
Although the bacterial oxidation process is a relatively new process, it is the fastest-developing process in China. Its current industrial application level and the degree of acceptance in the country have far exceeded the former two processes, which is entirely due to the fact that A large number of experimental research and exploration work done by various research institutes, at present, no less than ten scientific research units engaged in the research of bacterial oxidation process, such as Changchun Gold Research Institute, Northeastern University, Jilin Metallurgical Research Institute and Shaanxi Zhongmei Biological Mining Engineering Responsibility Ltd., these research units have done a lot of experimental research work on domestic refractory gold concentrates. Among them, Changchun Gold Research Institute has formed a relatively complete process research system. From the selection, cultivation and domestication of strains to continuous tests of 1kg/d, 5kg/d and 100kg/d, it has basically reached the extended industrial test. The scale of the research provides a systematic and detailed technical consultation and technical service for the engineering application of the process. In December 2000, they successfully built the first 50t/d scale bacterial oxidation-cyanide-carbon slurry process gold demonstration plant in Yantai Gold Smelter, and has experienced 8 months of production practice. Now the process is smooth and the technical indicators are stable. In the gold concentrate, the grinding is -0.038 mm, 90%, the oxidation temperature is 40-50 °C, the oxidized pulp concentration is 18%, and the oxidation time is 6 days. The cyanide leaching rate is over 95%, which has created a good situation for the domestic industrial application of the bacterial oxidation process.
While developing and applying domestic bacterial oxidation technology, paying attention to the introduction and absorption of technology is also an important way to realize the engineering application of the process. Laizhou Gold Smelter cooperates with Australia and South Africa, and introduces foreign advanced technology and equipment for the whole process. Promote applications and provide a broader choice.
The self-developed research and the industrialization practice of introduction and absorption have laid a technical foundation for the popularization and application of bacterial oxidation technology in China. At present, more mines and enterprises have begun to pay attention to the application of this technology, and some enterprises are preparing to build a production plant. . From the current development trend, the bacterial oxidation process is bound to become the mainstream of difficult metallurgy technology in the future.
From the application and development trend analysis of difficult metallurgical technology at home and abroad, the roasting process, hot pressing process and bacterial oxidation process will become the basic pretreatment process for the difficult gold ore resources in the 21st century. The reason is that all three processes have oxidative decomposition into gold sulfide minerals, destroying the crystal structure of the sulfide minerals to expose the encapsulated gold to facilitate the common characteristics of chlorination and gold extraction. At the same time, they are all tested by the practice of application and have Deep technical research foundation. However, each process has its own characteristics, environmental characteristics and economic characteristics. Therefore, when choosing a pretreatment process, we should be based on the ore physical properties of the ore, the mining area, environmental requirements, economic benefits, etc. The situation is systematically and comprehensively analyzed, especially for the smelting enterprises that are processing materials. Due to the wide range of gold-bearing gold materials and the complex mineral types, the market and process suitability of raw materials should be fully considered in the process selection. Only in this way can China's difficult selection and smelting technology be able to move toward a benign development track.
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