Comprehensive utilization of tin tailings

The world's tin resources are rich and concentrated. In 2007, the world's tin reserves and reserves were 6.1 million tons and 11 million tons respectively. China's total proven tin metal of about 5.6 million t, 2007 tin reserves of 1.7 million t, accounting for 28% of world reserves, ranking first in the world, mainly distributed in Yunnan, Guangxi, Guangdong, Hunan, Inner Mongolia, Jiangxi In other provinces, only Yunnan Gejiu and Guangxi Dachang have accounted for about 40% of China's reserves.

The long-term development and utilization of tin resources has greatly promoted the development of the world economy, but it has also piled up hundreds of millions of tons of tin tailings around the world, occupying a large area of ​​land and becoming one of the environmental hazards. These tailings were then stored as waste. According to tests, so-called wastes in such a large amount contain a large amount of valuable components, which have been called "artificial deposits". With the passage of time, tin resources are increasingly depleted, the grades are getting lower and lower, and some are close to or even lower than the old tailings. Therefore, whether old tailings can be used as replacement resources or tin mine tailings can be used as secondary The development of resources has attracted great attention. At the same time, the price of tin has risen (although although the price has dropped by a large margin, it has more than doubled compared with more than 10 years ago) and the progress of modern metallurgy technology, especially the fine progress of fine grain dressing and low tin material smelting technology, It also accelerated the process of recycling mine tailings. At present, at home and abroad, there has been a lot of practical experience in the re-election of old tailings in tin mines. The comprehensive recycling of valuable metals in tin tailings has also become a hot topic of research.

I. Analysis of comprehensive utilization potential of tin mine tailings

Like other non-ferrous minerals, there are many associated components in tin mines. Tin ore in a single form accounts for only 12% of China's total reserves, tin is the main metal of 66%, and tin as a co-associated component accounts for 22%. And symbiotic associated metals copper, lead, zinc, tungsten, antimony, molybdenum, bismuth, silver, niobium, tantalum, beryllium, indium, gallium, germanium, chromium, and iron, sulfur, arsenic, and fluorite. According to relevant statistics, the average tin deposit per ton of tin in the old tin mine is associated with more than 2 tons of lead, zinc, copper, antimony, tungsten, molybdenum and other metals, and the per ton of tin reserves in the Tongchangzhuang and Manjiazhai sections of the Maguandu Longxi Zinc Mine. Associated with zinc, copper, sulfur, arsenic and other 21t, Guangxi Dachang tin mine is associated with a large number of minerals such as lead, zinc, antimony, copper, tungsten, mercury . However, the comprehensive recovery level of the associated valuable elements in China is still very low. The concentrating plant with a comprehensive utilization rate of beneficial components of 75% only accounts for 2% of the total, and a large number of valuable components remain in the tailings.

At the same time, sand-tin ore in China's tin ore resources only accounts for 10%, and sand-tin ore is dominated by refractory residual sand-tin ore with high iron content, while 95% of the tin-bearing ore with 90% of reserves is polymetallic. Sulphide deposits are a kind of comprehensive ore containing a variety of companion useful elements or components. Compared with the world's similar ores, the average grade of tin is low, the size of cassiterite is fine, the associated minerals are numerous, the components are complex, and the symbiosis is closely related. The difficulty in the development and utilization of mines is generally greater than that in foreign countries (the major foreign tin producing countries are still mainly based on the selection of sand and tin mines). In addition, the level of mining and mining in China's tin mines is uneven, and the utilization rate of associated metal resources is low. Some small and medium-sized tin mines are “single development, discarding others”, and only recovering conventional, high-value tin, lead, zinc, etc. Minerals that are difficult to recycle or of low value are lost in the tailings. Therefore, China's tin mine tailings contain more valuable metals, and the potential value is huge. Only Yunxi Company has more than 200 million tailings stored in more than 30 tailings ponds, containing about 0.18% tin, and the iron content is also very rich. It is more than 100 times the amount of tin metal. According to the current production capacity, The accumulated tailings can be produced by Yunxi Company for more than 25 years; and Yunxi Tailings is also associated with certain useful components such as copper, silver, lead, zinc, arsenic and antimony, and the comprehensive utilization value is very large. In the past 50 years, Nandan in Guangxi has also accumulated tens of millions of tons of tailings, mainly concentrated in the three areas of Dachang, Chehe and Mang. Due to the low recovery index of most selected plants, the fine-grained metal is seriously lost in the tailings. The tailings still contain tin, lead, zinc, antimony, arsenic, sulfur and other minerals that can be recycled. Only the tin metal in the tailings of Dachang has 100,000 tons, and the zinc and antimony metal is 500,000 tons. 120,000 tons, as well as pyrrhotite, pyrite, poisonous sand and so on. Hunan Shizhuyuan Mine is known as the “World Nonferrous Metals Museum”. The mine is called tungsten-tin polymetallic ore, but it does not produce tin in the early stage. The No. 3 ore body it is producing, the comprehensive utilization of symbiotic ore is also Very unsatisfactory, the previous research on the research only considered how to reduce the tin in the tungsten concentrate, and did not consider the use of difficult tin resources. The metal tin of 100,000 tons entered the tailings pond. The Dongcheng lead-zinc-tin polymetallic ore, which is affiliated to the Shizhuyuan Mine, has a tin content of up to 2.5% after the selection of lead and zinc, and has not been comprehensively recycled.

It can be seen that the comprehensive utilization potential of tailings resources in tin mines in China is huge. Under the background of increasingly depleted mineral resources, in order to ensure the sustainable development of China's tin industry, it is necessary to mine valuable metals in tin mine tailings in China under the current new situation. The recycling carries out objective and realistic analysis and research, and takes corresponding countermeasures.

2. Research progress on comprehensive recovery of valuable metals from tin mine tailings

In recent years, China has made great progress in the recycling of non-ferrous metal resources. However, compared with the rich mine tailings resources, the utilization level of tailings in China is still quite low, far lower than that of developed countries. In 1997 the State Planning Commission report on "comprehensive utilization of resources potential research report" that the 1996 national comprehensive utilization of industrial solid waste amount to 28,364 million t, the comprehensive utilization rate averaged 43%, smelting slag, powder coal ash, The utilization rate of coal shale is 83.7%, 47.9% and 38%, respectively, but the utilization rate of metal tailings is less than 10%, far lower than the utilization level of fly ash and coal shale. Statistics from the National Development and Reform Commission show that mine tailings and red mud accounted for 30.9% of the country's industrial solid waste in 2000, but its utilization rate was only 3.2%.

The research on the re-election of tailings in tin mines in China began in the early 1960s, and there are many selected factories for production practice. However, due to various reasons, the production cost is high and the economic benefits are very low. Large-scale tailings re-election still needs further improvement in the level of mineral processing technology .

(I) Research status of re-election of polymetallic tin tailings

Since the 1960s, the state has given great support to large-scale tin mining enterprises. Some ore dressing equipment and achievements with independent property rights have been well promoted and applied. However, due to technical and economic conditions, metal recycling indicators tend to be low. A large amount of valuable metals are lost in the tailings. Therefore, many studies tend to focus on how to improve the overall recovery rate. For example, in the 1980s, the collector salicyl hydroxamic acid was developed and used in the Chehe and Xianghualing plant. The tin concentrate grade and operation recovery rate of Chehe Concentrator was 28% and 93%, respectively, and re-election. In comparison, the recovery rate of fine-grained cassiterite has increased by 40% to 50%; in recent years, the new collector of GY-C series has been developed, which is lower in price than salicylhydroxamic acid, and is used in combination with P86. it is good. At present, some tin ore dressing plants use heavy medium cyclones to treat tin tailings, and the effect is good. The specific selection indicators are shown in Table 1.

Table 1 Selection index of heavy medium cyclone in a tin mine in Guangxi

In the recovery of valuable metals in polymetallic tin tailings, Liu Jin et al. used open-circuit flotation research on calcium hypochlorite, sodium humate and its mixed agents in Dachang tailings, and obtained a zinc concentrate grade of 45.90%. The recovery rate is a good indicator of 52.62%. Gao Likun and others used a re-election-flotation combined process for the large-scale sulfur-arsenic-tin mixed mine. The sulfur and arsenic were effectively separated, which provided ideas for the tailings to recover tin. Wang Yajing et al. conducted a pre-selection tail-splitting test on Dachang tailings. The results show that the pre-selected tailings are effective for the tailings and can abandon the tailings with a yield of 44.66%, which not only improves the selected grade but also reduces the dressing. Cost, and through the study of appropriate processes and rational pharmaceutical systems, comprehensive recovery of zinc minerals in tailings. Zhou Zongyi and others designed a self-flow beneficiation process to recover the tin, tungsten and other valuable metals in the re-selected tailings by using a carpet chute to obtain a hair concentrate containing 0.5% to 2.0% tin. Jin Yunhong, through the study of the process mineralogy of Yunxi old tailings, found out the mineral composition of the old tailings and related mineral processing characteristics, and provided a theoretical basis for formulating the principle process of tin selection and increasing the graded regrind operation. Li Cunqian pointed out that the development of pre-selected equipment with multiple force fields and multiple functions, and the use of these new equipment to form a new process of re-election, is expected to push the development and utilization of Yunxi old tailings resources to a new level. The instrument clearly believes that outdated equipment and technology have been economically difficult to adapt to the re-election of tailings, reducing the smashing, improving the recycling effect of the shaker, introducing new equipment for re-election in foreign gold fields, and improving the overall recovery rate. An important research direction of ore dressing. On the basis of the study of tailings properties, Yan Kefei et al. carried out tailings desulfurization and cassiterite enrichment tests, and found that it is difficult to float qualified lead-zinc mixed concentrate or tin concentrate from tailings, but using flotation method. It is feasible to first remove the sulfur-containing components from the tailings, and then use a shaker to select tin, and obtain a qualified tin concentrate. Ren Liujing carried out research on the recovery of tin from a tin tailings. After desulfurization, he obtained 48.76% tin concentrate, and the total tin recovery was 49.88%.

Between 1979 and 1984, nine foreign companies from the United States Gulf Company, the British CJB, the German Lurgi company, and five countries in Japan and Australia conducted a beneficiation test on the old tailings of Yunnan old card houses. They used re-election, magnetic separation, and floatation. Selection, acid leaching and other methods, even using some secret technology to test, but have not obtained the results of practical use. T. Sleinias other developed by flotation from a low grade tin reselection pulse collecting tin tailings flow, using three different test results show that collector, using one alkyl phosphate vinegar - Si A pharmaceutical system of sodium fluoride-industrial grade sulfuric acid and citric acid obtained a flotation product of 7% tin, with a recovery rate of 55%. India recovering tungsten and tin and the like from the mixing Sreenivas wolframite a Central Mine a scheelite ore a cassiterite, three kinds of very fine mineral particles to each package, each of the degree of dissociation varies greatly mineral used is selected from In the combined process of smelting, the recovery rates of tungsten and tin reached 80% and 90%, respectively.

(II) Research status of recovery of fine-grained cassiterite and tin ore in tin tailings

The recycling technology of coarse-grained cassiterite in China is at the international leading level, but there are still some shortcomings in the recycling of fine-grained cassiterite. Due to the brittleness of the cassiterite, it is particularly prone to pulverization and muddy during the grinding process, and a large amount of secondary slime is difficult to recover and enters the tailings. The re-election of Yunxi Tailings was listed as a national scientific and technological project in 1983, and passed the technical appraisal in 1985. It is believed that this breakthrough has broken through the recovery of -19μm fine-grained smectite, which is technically advanced, but later Due to the limitations of the technical conditions of the smelting and smelting at the time, the benefits were poor and could not be industrialized for a long time. In addition, the cassiterite in the old areas of Yunnan also has the characteristics of fine crystal grain size, dense symbiosis with iron-manganese minerals or being wrapped by it, especially difficult to choose. For example, Yunxi Daxuan Plant, the recovery rate of -37+10μm grade cassiterite is only From 11% to 13%, and -10 μm, the re-election is almost ineffective, and most of the fine-grained cassiterite is discharged into the tailings. The loss of fine-grained metal of Guangxi Dianxi polymetallic sulfide ore in tailings is also very serious. Therefore, the re-election of tin tailings is largely a recovery of fine-grained cassiterite or tin ore.

At present, the recovery of fine cassiterite is still mainly by re-election methods, such as fine mud shaker, disc concentrator, vibrating spiral chute, Mozley type multi-gravity concentrator (MGS), Kelsey centrifugal jig, Nelson and Falcon centrifugal concentrator and so on.

Compared with the re-election of fine-grained cassiterite, the recovery rate is relatively high. Chen Chuqiang discussed the changes in the structure and equipment configuration of the mine re-election process in tin mud and the relationship between the products with different quality and the recovery rate of ore dressing, and re-election with the swollen acid collector. The results show that the minerals in the slime The technical index for flotation re-election of concentrates after centrifuge selection is much higher than that with belt chute re-election. The comparison between the advantages and disadvantages of several flotation cassiterites in Dachang Changpo Concentrator is: swollen acid>phosphonic acid>A-22>oleic acid>alkyl sodium sulfate (flow: floating tin after floatation, a thick Two sweeps two fine).

The increase in demand for tin in recent decades has also stimulated the flotation research of fine-grained cassiterite to some extent. Qiu Guanzhou et al. investigated the adsorption state of sodium oleate on the surface of fine-grained cassiterite and quartz , studied the coagulation of cassiterite and quartz, and the phenomenon of mutual condensation between cassiterite and quartz. It is believed that the extended DLVO theory can predict and explain the state of the system. Wu Bozeng et al studied the agglomeration behavior of -10μm fine-grained cassiterite in the sodium oleate hydrophobic system, and investigated the effect of macromolecular flocculant polyacrylamide on the flocculation of cassiterite by sedimentation test. It is believed that sodium oleate can strengthen the cassiterite. Flocculation and the application of extended DLVO theory explain the hydrophobic agglomeration and flocculation of cassiterite. Dai Shaotao et al studied the agglomeration and dispersion of fine-grained cassiterite, determined the surface potential and contact angle of cassiterite, calculated the energy constant of the polar interaction of fine smectite surface, and provided an important basis for sillimanite sorting. JM Hargrave performs an image analysis of the color and structure of the fine-grained cassiterite flotation foam to determine the quality of the concentrate and the working state of the entire flotation unit. This method is not only useful for sulphur flotation, but also for other applications. Flotation of minerals. Central South University has developed a new flotation technology for fine-grained copper-lead-zinc-tin ore by using “pharmaceutical regulation” and “granularity adjustment”, that is, using the coarse-grained effect and carrier effect of similar ore particles in the flotation system, using conventional coarse-grain flotation The equipment realizes the recovery of fine-grained cassiterite, solves the problem of flotation separation of complex tin slime, and improves the selectivity of flotation separation. Liang Rulu et al. conducted a deep research on the theory of coarse particle effect in fine-grained smectite carrier flotation and fine-grain flotation system, systematically investigated the process factors affecting carrier flotation, and promoted the development of fine-grained smectite flotation technology. .

Third, the characteristics of tin mine tailings and the reasons for refractory

Although the research on re-election of tin mine tailings has been carried out extensively in recent years, the industrial application of re-election of tin tailings is still rare. After the re-election of tin mud, after the combination of horizontal centrifuge and belt chute has been eliminated, there has not been a successful combination of equipment that can be widely used. At home and abroad, the re-election of fine-grained cassiterite still exists. Technical problem. Taking Yunnan Dulong Zinc-tin Mine as an example, due to the complex and variable ore nature, more than 70% of the cassiterite particle size is less than 15μm, and the recovery rate of fine cassiterite single re-election is only 30% to 40%. Similar problems exist in Mengzi and Wenshan, Guangxi, Hunan, Jiangxi, Inner Mongolia, Sichuan and Xinjiang. The recovery of fine-grained cassiterite, especially tin tailings, is still considered to be the current worldwide problem of mineral processing. Compared with re-election, although the flotation recovery rate of fine-grained cassiterite is relatively improved, the flotation index is still not ideal, and the high cost of flotation, large environmental pollution, and many influencing factors hinder the widespread use of this method.

In order to facilitate the in-depth study, systematically summarize and analyze the tailings of tin mines in China, and obtain the following characteristics of tin mine tailings and the reasons for their difficulty in re-election for reference.

(1) The mineral inlay of tin mine is fine in size and complex in symbiosis. In order to obtain a variety of concentrates of higher grade, it is generally selected after fine grinding. Therefore, the valuable metals such as tin in the tailings discharged are mostly fine. The presence of fine particles and non-monomeric dissociated continuum, after fine grinding or even ultra-fine grinding, is still difficult to dissociate, and fine grinding will cause further deterioration of the sorting process. At present, the sorting effects and indicators of fine-grained cassiterite, silt shaker, centrifugal concentrator, belt chute and disc concentrator such as -37μm or ～19μm are still not satisfactory, and the cost of dressing is also high. , can not be comprehensively recovered for polymetallic sulfide minerals.

(2) Tailings are post-election wastes, and the valuable components are relatively poor, especially rare, rare and precious metals. This increases the difficulty of comprehensive utilization, and the residual flotation reagents have a greater impact on recycling.

(3) The high content of slime and fine particles seriously interferes with the recovery of valuable metals.

(4) There are relatively many types of valuable metals in tailings, and the selection conditions are not the same. It is difficult to obtain high-efficiency recovery in the same process. In addition, due to the different conditions and genesis of tin ore deposits, the tailings are complex in nature. There are also large differences in the main associated elements, which puts higher requirements on the universality of the process and theory of valuable metal recovery. However, in general, the cost of mining, selection, and metallurgy is limited, and it is impossible to significantly increase the grade of tailings re-election products. Therefore, to achieve comprehensive utilization of tailings, the key is to improve tin. Recycling rate and efficient recovery of various valuable metals in the same process as much as possible.

(5) Most of the old tailings in the Yunxi area are tailings for the treatment of oxidized ore. The iron grade is 12% to 25%. Most of the cassiterite is densely symbiotic with limonite, and a small amount is associated with the gangue. Separation.

Fourth, thinking and suggestion

Based on field research and research, we believe that in order to achieve the recovery of valuable metals in tin tailings, we must strengthen the following aspects of research, or seriously consider and solve the following key issues.

(1) It is necessary to remove sulfide minerals which are similar to the density and floatability of cassiterite, which are densely symbiotic with cassiterite and which are easily floated by the smectite collector. They consume both the collector and the tin concentrate grade. Therefore, the effective separation of sulfides is one of the keys to re-election and flotation of tin.

(2) Iron-manganese minerals that are similar in density to the cassiterite and interfere with and affect the re-election and flotation of tin concentrate grades must be removed. They also consume large amounts of tin-selecting agents. The density of cassiterite and iron-manganese minerals is not much different, and it is difficult to re-separate, but there is a certain difference between the two magnetization coefficients. It is possible to separate by magnetic separation. In addition, most of the cassiterite in the tailings is densely symbiotic with limonite, and a small amount is associated with the gangue. In order to improve the recovery rate of tin, it is necessary to increase the classification and regrind operation.

(3) -10μm mineral mud, talc , mica , calcite , fluorite, tremolite and other calcium-containing and easy-floating minerals, which seriously affect the selection of useful elements such as cassiterite, and at the same time, the difficulty of different grain size selection is different. The recycling methods are also different. Therefore, it is possible to recover the useful metals to the greatest extent by appropriately classifying and removing the slime and eliminating the interference of the floating gangue and muddy minerals on the flotation. At present, it is better to use the cyclone to remove mud. The cyclone can be installed in the tailings field, and the mud is removed on the spot. Only the ore is sent to the plant for selection, which can increase the processing capacity of the sorting equipment and improve the points. Choosing the candidate's taste for the equipment plays a pre-selection role, which is an effective way to reduce costs.

(4) In the aspect of flotation reagents, the research on collectors in cassiterite plays a very important role. From the development process of cassiterite flotation, almost every progress is closely related to the research of cassiterite collectors. relationship. However, only good collectors can not solve all the separation problems encountered in the cassiterite flotation process. The gangue mineral inhibitors are as important as the cassiterite collectors in the tin flotation flotation. significance. At the same time, since cassiterite is generally floated under acidic conditions, and polymetallic sulphide ore is often separated and enriched under alkaline conditions, research on flotation reagents under low alkali conditions should be strengthened to improve the selection of processes and medicaments. Sex, expand the difference in the planktonic properties of the target minerals and gangue minerals, and improve the efficiency of beneficiation.

(5) In terms of flotation technology, carrier flotation shows a good application prospect in the recovery of fine-grained cassiterite, which deserves further study. In addition, flotation concentrate products often contain a large number of easy-floating gangue mineral talc, illite, mica, kaolinite, hornblende, montmorillonite, etc., and the natural floatability of these gangue minerals with cassiterite Similar, so that in the process of floating tin with the cassiterite up, resulting in a low grade of tin concentrate. However, there is a large difference in density between these gangue minerals and cassiterite, and the separation of cassiterite and gangue minerals can be achieved by utilizing the difference in density between minerals. Therefore, for the re-election of tin tailings, the research on the joint process of different metallurgical methods should also be strengthened.

(6) The selection of fine-grained cassiterite is one of the key factors determining the beneficiation efficiency of tin tailings. When sorting fine-grained ore particles, the viscous resistance increases, the sedimentation velocity decreases, and the speed difference of light and heavy minerals decreases. Therefore, the fine particle sorting under the gravity field is inefficient; if the Bayern force is selected by various shearing motions, the processing capacity per unit area is unsatisfactory; therefore, the composite force should be strengthened. Research on field beneficiation equipment to strengthen the re-election process. The Nelson and Falcon concentrators that have appeared in the past 20 years have been working with a composite force field and are currently mainly used for the recovery of precious metals, which is expected to be extended to the re-election of tin mine tailings.

In addition, due to the low grade of tailings, the cost of mineral processing products will inevitably be high. Coupled with the impact of the current economic crisis, the plant has basically no longer dealt with tin tailings. Therefore, for tin tailings, it is also necessary to create benefits with economies of scale, and to choose re-election methods such as low processing costs and environmental advantages. However, the existing flow film re-election equipment capable of solving the sorting problem of fine-grained materials has a small processing amount, and therefore, the research on the fine-grain re-election equipment of the "deep water layer" should be strengthened.

V. Conclusion

(1) China's tin mine tailings have a large stockpile, and there are many types of valence metals, and the comprehensive utilization potential is huge. However, the utilization level of tailings in China is still very low.

(2) The re-election of tin mine tailings has been mentioned on the agenda, but there are many studies on tin-containing polymetallic ore at home and abroad, and there are still many technical problems in the re-election of fine-grained cassiterite. Although the flotation recovery rate is relatively high, the indicators are still not ideal, and the high cost of flotation, environmental pollution, and many influencing factors hinder the widespread use of this method. For tin mine tailings, due to its characteristics of “poor, fine, miscellaneous, difficult”, the starting point of research is relatively low, the research content and results are few, and the key issues still need to be resolved.

(III) Inductively analyzed the characteristics and difficult factors of tin mine tailings, and proposed the key issues to be solved from the comprehensive recovery of valuable metals from tin mine tailings and the key points for further research in the future. It is believed that after extensive research and development of new pharmaceuticals, equipment and metallurgical processes, the industrialization of tin tailings re-election will be widely implemented in the near future.

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