1 Introduction

Tin is one of the earliest discovery and use of metals in human history. Tin has many advantages such as low melting point, good plasticity, corrosion resistance, fatigue resistance, non-toxicity, etc. Tin has a wide range of uses in various fields of national economy and national defense construction. Formerly used to produce a large number of tin horse iron, solder and alloys. With the development of science and technology, the application field of tin is expanding, which leads to the world's growing demand for tin. With the reduction of easy-to-select sand and tin resources, the selection of fine-grained and fine-grained tin resources and the search for new beneficiation methods have important practical significance for the development and prosperity of tin mining.

2 Types and distribution of tin ore

2. 1 Types of tin ore

There are about 60 kinds of tin minerals, and the existence form in the ore is mainly cassiterite. Such as cassiterite - sulphide ore and skarn tin ore, these two types of tin ore is the main mineral resource industry; tin lead zinc mine, such as XITIESHAN mine; iron tin, such as Mianning County Yantie mine, Huanggang iron tin mine in Keshiketengqi, Inner Mongolia, iron tin deposit in Nanling area; marble type polymetallic deposit, such as Hunan Shizhuyuan mining area.

2. 2 Distribution of tin ore at home and abroad

2. 2. 1 Domestic tin ore distribution

China's tin mine resources are abundant. By the end of 2007, the amount of resources identified was 4,836,600 tons, of which the basic reserves were 1,152,500 tons, accounting for 31.5%. It is mainly concentrated in Yunnan, Guangxi, Hunan, Inner Mongolia, Guangdong and Jiangxi provinces. The tin mine resources in these six provinces accounted for 97.89% of the nationally identified resource reserves.

Iron-iron ore has a large reserve in China. The iron-tin ore is rich in tin-contacting iron ore or iron-based tin ore. The comprehensive development and utilization of iron-iron ore is of great practical significance for the development of the national economy. Iron-iron ore is often in the form of large-sized super-large deposits. The fine particles of cassiterite and the distribution of tin in the ion state of magnetite and other mineral crystal lattices are relatively high, which makes it difficult to comprehensively recover tin and other valuable elements. Therefore, the selectivity is poor. Most of these mines either only sort out a single iron concentrate with a higher tin content, or they are not effectively recycled due to the difficulty of mineral processing, making the overall utilization rate of such resources not high.

2. 2. 2 Distribution of foreign tin ore

Foreign tin mines are mainly concentrated in a few areas. The world's largest tin belt is in Southeast Asia, with Malaysia, Indonesia and Thailand being the most important tin producers in Southeast Asia. This is followed by Central South America, Australia's Tasmania and the former Soviet Union's Far East, Central and South Africa and western Europe on the Atlantic.

3 Status of research on tin selection at home and abroad

Due to the different types of tin deposits and ore properties in different countries, historical conditions and development conditions are different, so the tin beneficiation status of different countries is very different. Some of the mineral processing methods are very simple; some are more complicated, and the other metals are combined with the same selection of tin. In recent years, due to the advancement of science and technology, the tin beneficiation process and technology have been improved in various countries. Among them, heavy medium pre-selection, flotation of cassiterite, fine mud sorting, re-election of old tailings, and comprehensive recovery are worth mentioning.

3. 1 Study on the preparation of cassiterite-polymetallic sulfide ore

The ore dressing method of tin ore is determined by its own characteristics. Since the density of cassiterite is larger than that of symbiotic minerals, the traditional beneficiation process of tin ore is gravity beneficiation. At the same time, due to the presence of other useful metal minerals and gangues in the cassiterite polymetallic sulphide ore, there will be auxiliary processes such as flotation, magnetic separation and electrification during the sorting of such tin ore. These auxiliary processes are re-elected together with re-election. A joint process is formed to sort the cassiterite.

The Jianfengpo tin deposit in Jiangxi belongs to the cassite polymetallic sulfide ore type deposit. The ore contains a large amount of sulfide ore and a considerable amount of iron oxide minerals and iron carbonate minerals. The size of the cassiterite is fine and the dispersion rate is high. For the refractory cassiterite polymetallic sulphide ore, the process of "pre-desulfurization of floating zinc 2 flotation tailings re-election and tin selection" is carried out, and in the case of the raw ore Sn grade of 0.70%, finally obtained The grade is 54.38%, the recovery rate is 54.28% tin concentrate; at the same time, the high grade zinc product is obtained. Both tin and zinc are effectively recovered.

Beneficiation process of the Lu Xinyi silver rock tin were studied, the mine belongs porphyry tin deposit, in addition to tin-containing ores, but still contains a small amount of tungsten, molybdenum, bismuth, copper and other valuable elements. The first flotation sulphide ore is used to recover the cassiterite from the sulphur sulphur tailings by re-election 2 fine mud flotation 2 re-election process, and obtain a tin concentrate with a tin content of 56.11% and a recovery rate of 74.20%. The molybdenum concentrate product having a molybdenum content of 47.22% and a recovery rate of 67.65% was recovered. The process technology is feasible, economical, simple, and reliable.

Li Zhenghui also adopted a flotation and re-election joint process in the ore dressing test of the old plant cassite polymetallic oxygen-sulfur mixed mine. The use of fine crushing, pre-selection waste, flotation de-mixing, enhanced float washing and other processes to improve tin beneficiation recovery rate of 1.28 percentage points.

Yin Wenxin et al. used the refining and reverse flotation test method after re-election and flotation to improve the quality and recovery rate of tin concentrate. Since the mineral contains cassiterite and sulfide ore, the concentrate obtained by re-election contains a large amount of sulfide ore which cannot be separated, which affects the quality of the tin concentrate. The flotation is then selected by flotation, and the remaining in the flotation cell is the enriched tin concentrate.

Zhang Jie et al. conducted a comprehensive recovery process for a certain cassiterite polymetallic sulphide ore in Yunnan. The cassiterite polymetallic sulfide ore is a complex refractory polymetallic ore. In addition to Sn and Zn, it is also accompanied by components such as Cu, S, Fe, and As, and also contains Ge, Ga, Cd, In, Ag, etc. Rare and precious metal elements. Through the study of the mineralogical analysis and sorting process of the mineral, the principle process of first selecting the copper-sulfur 2 and then selecting the zinc-magnetically-selected iron-re-electing tin was carried out, and the raw ore coarse grinding, the ore fine grinding and the ore were carried out. The coarse-milled 2 sulphur concentrate was re-grinded into a small closed-circuit test of various grinding conditions, and the shaker re-election process of the flotation tailings and the test of the selection process of the tailing 2 shaker of the composite force field re-election equipment were carried out. The obtained beneficiation effect was obtained, and the tin concentrate grade was 49.64% and the recovery rate was 54.03%; the zinc concentrate grade was 42.79%, the recovery rate was 88.41%, and other rare and precious metals were also enriched.

As can be seen from the above examples, re-election is the most important method for the selection of cassiterite polymetallic sulphide ore. At present, an important development trend is the combination of single gravity ore dressing to heavy, floating, magnetic and electric beneficiation technologies , from the recovery of single tin concentrate products to the comprehensive recovery of a variety of useful concentrate products.

3. 2 Beneficiation of iron tin ore

Iron tin ore is a type of skarn tin ore. Because iron ore contains iron minerals such as magnetite, limonite, and hematite, these iron minerals have a great influence on the separation of cassiterite, so that cassiterite cannot be effectively separated from iron minerals. Therefore, the iron should be removed before the sorting, and then the iron tailings should be shaken and re-selected to obtain tin concentrate. The general principle flow for this mineral sorting is shown in Figure 1.

Li Guangtao and other researches on the beneficiation of a certain tin-iron mine in Yunnan laid the foundation for the development and utilization of the iron-tin deposit. The lower part of the deposit is tin ore and the upper part is tin-containing magnetite. The tin-bearing magnetite has a relatively high grade of iron, and the tin grade is relatively low. In addition to the presence of magnetite, iron has a small amount of hematite and limonite. The minerals with recoverable value in the ore are mainly magnetite and cassiterite. According to the difference between the two properties, the iron ore concentrate is obtained by weak magnetic separation, and then the magnetic separation tailings are re-elected to obtain qualified tin concentrate. .

When Guan Zezheng conducted a sorting test on a tin-iron ore, the process of re-election after magnetic separation was adopted, and the ideal effect was obtained. The main minerals recovered in the ore are iron minerals and tin minerals, iron minerals are mainly magnetite and shale magnetite, and tin minerals are mainly cassiterite. First, the magnetic iron mineral is selected by weak magnetic separation, and then the magnetic coarse concentrate is re-grinded and then selected. The two-stage magnetic separation tailings are merged into re-election, and the magnetic or heavy process is selected. When the original ore grade is 31.10 %, tin grade 0. 6%, after two-stage grinding, two-stage magnetic separation, the iron concentrate grade 63.45%, the recovery rate of 74.66%; the tin-selected ore is magnetic separation tailings, the second section The shaker was selected to obtain an index of 48.35% of tin concentrate and a recovery rate of 57.84%.

Niu Fusheng conducted a study on the optimization of the beneficiation process of a concentrator in a tin-iron mine in Inner Mongolia. The mine is a low-slung tin ore with the main recoverable elements being iron and tin. The original production process grinding product has too coarse particle size, insufficient dissociation of mineral monomers, and simultaneous recovery of tin and iron during sorting, resulting in low quality of iron and tin products. After the transformation of the ore beneficiation process, the process of weak magnetic separation and strong magnetic separation of iron was carried out, and the process of re-election of the magnetic concentrate tailings to recover the tin concentrate was finally realized, and the recovery of iron and tin was finally realized.

Inner Mongolia Keshiketengqi Huanggang Mining Co., Ltd. cooperated with Beijing Research Institute of Mining and Metallurgy to carry out research on iron-tin separation technology. The study is based on the high grade of iron in the Huanggang iron tin mine, and the iron mineral is mainly the process mineralogy of magnetite. The “magnetic separation-flotation-re-election” process was developed to flotation of the magnetic separation tailings. Zinc and arsenic concentrates simultaneously remove impurities that have a great influence on the recovery of tin. Finally, re-election is used to obtain tin concentrates, and the valuable elements iron, tin, tungsten, zinc and arsenic in the ore are comprehensively recovered, thereby improving the comprehensive recovery of resources. And the development and utilization of unresolved ore mines for many years.

Iron-iron ore has a wide distribution in China. The size of the cassiterite particles in the ore is fine, and the proportion of the cassiterite in the mineral crystal lattice such as magnetite is high, which makes the separation of iron and tin difficult. Therefore, magnetic separation operation occurred during the sorting of iron-iron ore. This magnetic separation operation was mainly for the separation of tin-iron. The re-election process of the magnetic separation tailings is followed to obtain qualified products, which is the more commonly used technology. With the deteriorating situation of China's iron and tin resources, strengthening the research on mineral processing technology of such resources has important theoretical significance and practical application value.

3. 3 Tin-bearing tailings beneficiation research

Tin ore is brittle and produces a large amount of fine-grained cassiterite and tin slime during the grinding process. In the process of sorting these fine-grained tin minerals and tin ore mud, the tailings were discharged into the tailings stock due to the limitation of recycling technology at that time. The stored tailings cause both waste of resources and environmental pollution. With the increasing demand for tin metal in the world and the reduction of easy-to-select tins, it has become a top priority for the comprehensive recycling of tin in tailings ponds.

When the particle size of the cassiterite is less than 19 μm, the efficiency of the re-election recovery is greatly reduced, and the sulphur flotation is an effective method for recovering the fine cassiterite. The flotation process of tin mud in tailings is shown in Figure 2.

He Mingfei et al. conducted a floating tin study on tailings in the lead-zinc flotation process of a Bainiuchang mining area of ​​a mining and metallurgical company. First, the tailings were re-elected to recover tin. Due to the fine grain size of the tin in the tailings, the recovery rate of the shaker is low, and the effect is not satisfactory. It is considered to recover the tin ore by flotation. BY-9 is the collector , P86 is the auxiliary collector, BY-5 and sodium carbonate are the gangue inhibitors. Once the tin is floated, the tin grade 8.56% and the recovery rate of 61.61% tin concentrate can be obtained. The concentrate re-floats, the grade of tin concentrate reaches 53.58%, and the operation recovery rate is 81.35%. High-grade tin concentrate was obtained twice in floating tin, and the total tin recovery was 50.12%.

Yan Wujin studied the fine cassiterite of the Chehe Concentrator, which is a graded overflow of two re-election tailings. Due to the large amount of mud in the flotation to the mine, the difficulty of floating tin is increased. Therefore, the process of desliming-floating tin and desulfurization-de-sludge-floating tin is compared. The process is more economical and reasonable, and the quality of the concentrate is higher. The foam concentrate produced in the desulfurization-de-sludge-floating tin process can be directly floated without deliming, and a tin concentrate with a grade of 50% and a recovery rate of more than 90% can be obtained.

Yan Kefei et al. conducted an experimental study on tailings in the tailings reservoir of the Xianghualing mining area in Hunan Province. The main metal minerals contained in the tailings in the Xianghualing tailings reservoir are minerals such as cassiterite, sphalerite, pyrite, and chalcopyrite. Gangue minerals as quartz, illite, mica, topaz, chlorite, calcite, dolomite and fluorite. Except for cassiterite, most of the other elements are present in the tailings with sulfide ore. It is difficult to obtain tin concentrate from tailings by flotation, but the sulfur-containing components in the tailings can be removed by flotation to create conditions for the enrichment and sorting of the cassiterite. Finally, a cassiterite concentrate with a grade of 53% to 55% and a recovery of more than 52% is obtained.

Ren Liujun et al. explored the flotation conditions and chemical systems of tin minerals in the study of the comprehensive recovery of tin minerals in a certain cassiterite-polymetallic sulphide tailings, and proposed a comprehensive recovery of tin in the tailings. Selection process. Since the content of sulfur in the ore is very high, in order to separate the tin, sulfur is first removed by using sulfuric acid. According to the study of mineral properties, cassiterite is mainly present in the fine-grain grade, and the tin grade in the coarse-grained grade is low. The coarse fraction should be removed first to improve the recovery of fines. During the floating tin experiment, several drugs were compared and selected, and finally BY-9 was used as a collector, and sodium carbonate was used as an inhibitor for the float tin experiment. The crude concentrate obtained from the primary float tin is subjected to secondary floatation, and the secondary float is directly added to the solid agent. The tin concentrate contains 48.76% of tin, and the operation recovery rate is 81.35%. The total recovery of tin from the first and second stages of tin is obtained. 49.88%.

It can be seen from the above that due to the finer grain size of tin in the tailings, the re-election has certain limitations on the recovery of fine-grained tin, and the lower-order particle size of the flotation specific gravity is more fine, so the recovery of tailings Tin is mainly based on flotation process. Flotation plays a large role in the separation, recovery and removal of associated minerals, as well as the separation and recovery of various useful minerals from the crude tin concentrate. With the development of high-efficiency flotation reagents, the use of flotation technology to treat tailings to obtain high-grade tin concentrate is a good choice.

3. 4 Other ore dressing methods for tin ore

There are many types of tin ore, which are sorted according to the nature of different tin ore. Due to the existence of various iron oxide minerals in tin ore, these minerals cannot be separated from the cassiterite by flotation and re-election. Therefore, magnetic separation operation occurs in the tin beneficiation process. The main purpose is to separate tin and iron. Wet strong magnetic separators play an important role in the tin beneficiation process. Magnetic separation operations are generally used for the separation of raw ore, secondary concentrates and concentrates. For the study of fine-grained and fine-grained cassiterite, there are electroflotation, carrier flotation, flocculation and selective flocculation, liquid-liquid extraction, and centrifuge beneficiation. The high-temperature chlorination method of rotary kiln jointly researched by Yunxi Company, Kunming Metallurgical Research Institute and Beijing Research Institute of Mining and Metallurgy, etc., is used for refractory tin ore of low-tin high-speed iron to comprehensively recover valuable metals such as tin and lead. It can increase the recovery rate of existing tin ore dressing by 6 to 7 percentage points, and recover a large amount of tin and other metals from the tailings accumulated over the years. In foreign countries, this technology is still a frontier topic in the research of tin metallurgy, and China has taken the lead in the world of tin metallurgy.

4 Conclusion

Tin is a very versatile metal. The composition of tin ore is complicated, and it is difficult to sort. It is often necessary to use one or two or more methods in magnetic separation, re-election, flotation re-election, flotation, electro-election, chemical treatment, etc. to obtain concentrate. The actual selection of cassiterite is mostly re-election method. The stage grinding and stage selection are the main processes of cassiterite re-election. When the re-election method is used to treat the cassiterite fine mud, the obtained index is low, and a considerable part of the useful mineral is lost in the fine mud. The flotation method is one of the effective ways to recover the cassiterite fine mud. Iron-iron ore is widely distributed in China, and it is aimed at the current situation of less and less sand and tin resources that are easy to be selected and easy to choose.

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