A method for pre-enrichment, sorting, and recovery of tin and iron from tin tailings.

Abstract

This invention relates to a method for pre-enrichment and sorting of tin tailings to recover tin and iron, belonging to the field of tailings processing technology. The invention first separates tin tailings into different particle size grades. After grading, different methods are used to separate and process tailings of different particle sizes, enabling precise separation of cassiterite and hematite. This achieves the separation of tin and iron, which are difficult to separate in tin tailings, thus recovering not only tin but also iron. This invention can obtain tin concentrate with a tin grade higher than 3% and a recovery rate higher than 65%, and iron concentrate with an iron grade higher than 60% and a recovery rate higher than 70%. The method of this invention also has the advantages of strong operability, low cost, and excellent tin-iron separation indicators.

Description

Technical Field

[0001] This invention belongs to the field of tailings processing technology, specifically, it relates to a method for pre-enrichment, sorting and recycling of tin and iron from tin tailings. Background Technology

[0002] Tin is an important strategic metal in my country, mainly used in aerospace, spacecraft, atomic energy, and electronics. In 2020, my country's tin concentrate production reached 81,000 tons and refined tin production reached 170,000 tons, both ranking first in the world. Due to the long-term mining of tin resources, the recycling value of tin tailings has gradually become apparent. In particular, the successful application of smelting technology for low-grade, high-impurity tin-containing materials has accelerated the process of redeveloping and utilizing tin tailings resources.

[0003] Over 80% of tin tailings consist of fine-grained cassiterite, which not only wastes resources but also pollutes the environment surrounding the mine. The trajectory of fine-grained cassiterite in traditional single gravity separation operations is similar to that of gangue minerals, making it difficult to obtain high-quality tin concentrate using conventional gravity separation techniques. Furthermore, ordinary flotation processes are no longer suitable for processing fine-grained minerals, primarily due to factors such as the high surface energy of fine-grained cassiterite, severe particle agglomeration, high reagent consumption, significant entrainment, and low probability of particle-bubble collisions.

[0004] Cassiterite in tin tailings is often associated with iron-bearing minerals such as hematite, limonite, and magnetite. Cassiterite exists as fine-grained or micro-fine-grained inclusions embedded in or along the edges of iron minerals, with some iron existing isomorphously within the cassiterite lattice. Due to the dense symbiosis of tin and iron, conventional beneficiation techniques suffer from drawbacks such as single metal recovery, long process flows, and low tin-iron recovery rates, making efficient separation of tin and iron difficult. This results in severe tin-iron intermingling in the concentrate, thus affecting the recovery and utilization of tin and iron from tin tailings. Therefore, there is an urgent need to develop a key technology for the coordinated separation and simultaneous recovery of tin and iron in beneficiation and smelting to achieve low-cost, green, and efficient separation of tin and iron from tin-iron ore and the comprehensive utilization of tin and iron resources. Summary of the Invention

[0005] To overcome the problems existing in the background technology, this invention provides a method for pre-enrichment and sorting of tin tailings to recover tin and iron. This invention uses a combined graded gravity and magnetic field technique to separate the closely associated tin and iron minerals in the tin tailings from the hematite with a high degree of individual liberation. Then, a combined beneficiation and metallurgical technique is used to obtain tin-rich middlings ore and iron concentrate that can be recovered separately. This invention also has the advantages of strong operability, low cost, and excellent tin and iron separation performance.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: The method for pre-enrichment, sorting, and recovery of tin and iron from tin tailings includes the following steps: (1) The tin tailings are screened into coarse-grained tailings, medium-grained tailings and fine-grained tailings.

[0007] (2) Medium-sized tailings are separated by shaking table; fine-sized tailings are separated by suspended cone concentrator.

[0008] (3) The medium-sized shaking table tailings and the fine-sized suspension shaking tailings are recovered by strong magnetic separation; the strong magnetic separation tailings are the final tailings.

[0009] Furthermore, the strong magnetic separation concentrate obtained in step (3) is subjected to roasting-weak magnetic separation to obtain iron concentrate II, and the weak magnetic separation tailings are the final tailings.

[0010] Furthermore, after roasting the concentrate from the strong magnetic separation in step (3), the concentrate is first ground and then subjected to weak magnetic separation. The roasting is carried out by reduction roasting, and the reducing agent is one or more of lignite, bituminous coal or anthracite.

[0011] Furthermore, the coarse-grained tailings from step (1) are ground and then separated by a shaking table to obtain coarse-grained shaking table concentrate and coarse-grained shaking table tailings; the coarse-grained shaking table tailings are mixed with the medium-grained shaking table tailings and fine-grained suspension tailings obtained in step (3).

[0012] Furthermore, the medium-grained shaking concentrate and medium and fine-grained suspension concentrate obtained in step (2) are mixed with the coarse-grained shaking concentrate to obtain tin-iron co-existing minerals.

[0013] Furthermore, the tin-iron associated minerals were subjected to roasting-grinding-weak magnetic separation to obtain iron concentrate I and tin-rich middlings.

[0014] Furthermore, the tin-iron associated minerals are roasted using reduction roasting, with the reducing agent being one or more types of lignite, bituminous coal, or anthracite.

[0015] Furthermore, the coarse-grained tailings refer to tin tailings with a particle size greater than 0.15 mm, the fine-grained tailings refer to tin tailings with a particle size less than 0.05 mm; the remaining tin tailings are medium-grained tailings.

[0016] Furthermore, the grading method used in step (1) is sieving or hydrocyclone.

[0017] The beneficial effects of this invention are: This invention employs a pretreatment technology combining grading, coarse regrinding, and medium-fine particle shaking / suspended cone beneficiation gravity separation-intense magnetic separation. This technology enables the pre-enrichment of hematite closely embedded with cassiterite and hematite with a high degree of liberation, thereby reducing the processing volume and cost of subsequent tin-iron separation.

[0018] This invention classifies and processes the pre-enriched tin-iron rough concentrate and hematite rough concentrate using a "roasting-grinding-weak magnetic separation" technique to obtain iron concentrate I, tin-rich middlings, and iron concentrate II, respectively. This achieves the classification and separation of closely associated tin-iron minerals and single hematite, and obtains iron concentrate that can be directly recycled while recovering cassiterite from tin tailings.

[0019] This invention has the advantages of being easy to operate, low cost, and having excellent tin-iron separation indicators. It can obtain tin rough concentrate with a tin grade of over 3% and a recovery rate of over 65% and iron concentrate with an iron grade of over 60% and a recovery rate of over 70%. Attached Figure Description

[0020] Figure 1 This is a simplified process flow diagram of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0022] The method for pre-enrichment, sorting, and recovery of tin and iron from tin tailings includes the following steps: (1) The tin tailings are classified into coarse-grained tailings, medium-grained tailings and fine-grained tailings.

[0023] The grading adopts any particle size classification method that can be used for solids, such as screening or hydrocyclone. The grading standard is as follows: tin tailings with a particle size greater than 0.15 mm are coarse-grained tailings; tin tailings with a particle size less than 0.05 mm are fine-grained tailings; and the middle part is medium-grained tailings.

[0024] Most of the cassiterite in tin tailings exists as fine tin mud, with a small portion of cassiterite and other minerals occurring together in coarse and medium-grained ore. Directly grinding all the tailings not only increases production costs but also easily leads to over-grinding and severe mud formation of the cassiterite, thus significantly reducing its recovery rate. This invention, through screening, treats tin tailings of different particle sizes using different methods, which can significantly improve the cassiterite recovery rate.

[0025] (2) Grind and shake table separate the coarse-grained tailings; shake table separate the medium-grained tailings; and shake table separate the fine-grained tailings.

[0026] Through numerous experiments and analyses, it was found that it is difficult to achieve efficient recovery of cassiterite and iron-bearing minerals in tailings using only magnetic separation or gravity separation. However, by screening tin tailings into three different particle sizes, it was discovered that the enrichment of cassiterite in the concentrate and middlings of the shaking / suspension cone concentrator differs at different particle sizes. Therefore, tin tailings were divided into three particle size levels as described in step (1) and processed separately.

[0027] (3) The coarse-grained shaking table tailings, medium-grained shaking table tailings and fine-grained suspension tailings are combined and recovered by strong magnetic separation; the strong magnetic separation tailings are the final tailings.

[0028] Single gravity separation cannot completely separate tin and iron-bearing minerals. The tailings still contain a large amount of iron-bearing minerals, which are iron minerals that are not associated with cassiterite (it was also found that the tin and iron grades in the gravity separation concentrate are high, and most of the tin and iron are associated). Process mineralogy has proven that most of the iron-bearing minerals in the tin tailings are hematite. Mixing the gravity separation tailings with strong magnetic separation can further and better recover this type of iron-bearing mineral.

[0029] The coarse-grained shaking table concentrate, medium-grained shaking table concentrate and middlings, and fine-grained suspension vibratory concentrate were combined and subjected to reduction roasting-grinding-weak magnetic separation to obtain iron concentrate I and tin-rich middlings.

[0030] The symbiotic tin and iron are reduced to magnetite through reduction roasting, while cassiterite is non-magnetic. Tin and iron are then separated by weak magnetic separation.

[0031] (4) The strong magnetic separation concentrate from step (3) is subjected to reduction roasting-grinding-weak magnetic separation to obtain weak magnetic separation concentrate and weak magnetic separation tailings. The weak magnetic separation concentrate is iron concentrate II, which is combined with iron concentrate I for recovery. The weak magnetic separation tailings are combined with the strong magnetic separation tailings from step (3) to form the final tailings.

[0032] Strong magnetic separation of tailings can only produce hematite concentrate with 40%-50% iron content, which cannot be sold as iron concentrate product alone. The iron rough concentrate produced by strong magnetic separation is upgraded by reduction roasting-weak magnetic separation to meet product standards. The recovered iron can be sold directly as iron concentrate product.

[0033] In this process, the reduction roasting in steps (3) and (4) is carried out in different systems. The reducing agent is one or more types of lignite, bituminous coal, or anthracite.

[0034] To illustrate the present invention more clearly, the following embodiments will be described in detail. Example 1

[0035] A tin tailings deposit in Yunnan Province contains 0.19% tin and 12.20% iron. The gangue minerals are mainly calcite, dolomite, and quartz. The beneficiation process for this tin tailings is as follows: (1) The tin tailings are divided into +0.15mm coarse-grained tailings, 0.15~0.05mm intermediate-grained tailings and -0.05mm fine-grained tailings; (2) Grind the +0.15mm coarse tailings from step (1) to a fineness of -0.074mm accounting for 75%, and then proceed to the shaking table gravity separation operation. At the same time, the 0.15~0.05mm intermediate tailings from step (1) are subjected to shaking table gravity separation operation, and the -0.05mm fine tailings are processed by a suspended vibrating cone surface concentrator.

[0036] (3) Mix the coarse-grained gravity concentrate, medium-grained gravity concentrate, and medium and fine-grained suspension concentrate from step (2) to form a mixed concentrate, and then enter the reduction roasting operation. The roasting temperature is 650℃, the amount of reducing agent is 10% of lignite, and the holding time is 40min.

[0037] (4) The roasted product in step (3) is subjected to weak magnetic separation with a magnetic field strength of 0.29T to obtain iron concentrate I with an iron grade of 61.16% and a comprehensive recovery rate of 23.00% (23.00% is the recovery rate calculated based on the iron in all tin tailings. Unless otherwise specified, the tin recovery rate or iron recovery rate mentioned below is the recovery rate obtained based on the total tin tailings) and tin-rich medium ore with a tin grade of 3.53% and a recovery rate of 67.1%.

[0038] (5) The coarse-grained gravity separation tailings, medium-grained gravity separation tailings and suspension tailings from step (2) are mixed and fed into a high-gradient magnetic separator for strong magnetic separation. The magnetic field strength is 1.4T and the pulse is 21Hz to obtain hematite rough concentrate.

[0039] (6) The strong magnetic separation concentrate from step (5) is subjected to reduction roasting at a temperature of 700℃, with a reducing agent of 15% lignite, and a holding time of 1h. The roasting product is then ground to a fineness of -0.05mm accounting for 70%, and the ground product is subjected to weak magnetic separation at a magnetic field strength of 0.20T to obtain iron concentrate II with an iron grade of 60.34% and a comprehensive recovery rate of 48.02%.

[0040] Comparative Example 1 (except for the fine-particle tailings which were separated by shaking table gravity separation, all other aspects were the same as in Example 1).

[0041] The tin tailings were treated in the same manner as in Example 1, and the specific procedures are as follows: (1) The tin tailings are divided into +0.15mm coarse-grained tailings, 0.15~0.05mm intermediate-grained tailings and -0.05mm fine-grained tailings; (2) Grind the +0.15mm coarse tailings from step (1) to a fineness of -0.074mm accounting for 75%, and then proceed to the shaking table gravity separation operation. At the same time, the 0.15~0.05mm intermediate tailings and the -0.05mm fine tailings from step (1) are respectively subjected to shaking table gravity separation operation.

[0042] (3) Mix the coarse-grained gravity concentrate, medium-grained gravity concentrate, and medium and fine-grained shaking table concentrate from step (2) to form a mixed concentrate, and then enter the reduction roasting operation. The roasting temperature is 650℃, the amount of reducing agent is 10% of lignite, and the holding time is 40min.

[0043] (4) The roasted product in step (3) is subjected to weak magnetic separation with a magnetic field strength of 0.29T to obtain iron concentrate I with an iron grade of 60.74% and a comprehensive recovery rate of 25.32% and tin-rich medium ore with a tin grade of 1.94% and a comprehensive recovery rate of 39.35%.

[0044] (5) The coarse-grained gravity separation tailings, medium-grained gravity separation tailings and fine-grained gravity separation tailings from step (2) are mixed and fed into a high-gradient magnetic separator for strong magnetic separation. The magnetic field strength is 1.4T and the pulse is 21Hz to obtain hematite rough concentrate.

[0045] (6) The strong magnetic separation concentrate from step (5) is subjected to reduction roasting at a temperature of 700℃, with a reducing agent of 15% lignite, and a holding time of 1h. The roasting product is then ground to a fineness of -0.05mm accounting for 70%, and the ground product is subjected to weak magnetic separation at a magnetic field strength of 0.20T to obtain iron concentrate II with an iron grade of 56.32% and a comprehensive recovery rate of 29.38%.

[0046] Comparative Example 2 (no classification, all ore was directly ground and then subjected to gravity separation using a shaking table) Similar to Example 1, the tin tailings were beneficiated using the following method: the tin tailings were ground to below 0.15 mm and then subjected to unclassified shaking table gravity separation to obtain shaking table concentrate 1, shaking table concentrate 2, shaking table concentrate 3, shaking table middlings, and shaking table tailings. The tin and iron grades in concentrate 1 were 0.345% and 28.19%, respectively, with recoveries of 28.02% and 34.90%. In concentrate 2, the tin and iron grades were 0.27% and 16.80%, respectively, with recoveries of 5.03% and 4.78%. In concentrate 3, the tin and iron grades were 0.143% and 11.13%, respectively, with recoveries of 25.67% and 30.46%. In the middlings, the tin and iron grades were 0.173% and 8.29%, respectively, with recoveries of 31.86% and 23.26%. Overall, the tin and iron enrichment effect was poor.

[0047] Results of shaking table gravity separation test of tin tailings Example 2

[0048] A tin tailings deposit in Yunnan Province contains 0.25% tin and 24.38% iron. The gangue minerals are mainly quartz, feldspar, sericite, and tremolite. The beneficiation process for this tin tailings is as follows: (1) Tin tailings are divided into +0.15mm coarse-grained tailings, 0.15~0.05mm intermediate-grained tailings and -0.05mm fine-grained tailings.

[0049] (2) The +0.15mm coarse-grained tailings from step (1) are ground to a fineness of -0.074mm, accounting for 70%, and then subjected to shaking table gravity separation. At the same time, the 0.15~0.05mm intermediate-grained minerals from step (1) are subjected to shaking table gravity separation, and the -0.05mm fine-grained minerals are processed by a suspended conical surface concentrator.

[0050] (3) Mix the coarse-grained gravity concentrate, medium-grained gravity concentrate, and medium and fine-grained suspension concentrate from step (2) to form a mixed concentrate, and then enter the reduction roasting operation. The roasting temperature is 600℃, the amount of reducing agent is 8% lignite, and the holding time is 80min.

[0051] (4) The roasted product in step (3) is subjected to weak magnetic separation with a magnetic field strength of 0.20T to obtain iron concentrate I with an iron grade of 62.52% and a recovery rate of 19% and tin-rich medium ore with a tin grade of 4.03% and a recovery rate of 65.5%.

[0052] (5) The coarse-grained gravity separation tailings, medium-grained gravity separation tailings and suspension vibration tailings from step (2) are mixed and fed into a high gradient magnetic separator for strong magnetic separation. The magnetic field strength is 1.6T and the pulse is 21Hz to obtain hematite rough concentrate.

[0053] (6) The strong magnetic separation concentrate from step (5) is subjected to reduction roasting at a temperature of 750℃, with a reducing agent of 20% lignite, and a holding time of 100 min. The roasted product is then ground to a fineness of -0.05 mm (75%). The ground product is then subjected to weak magnetic separation at a magnetic field strength of 0.25T to obtain iron concentrate II with an iron grade of 60.52% and a recovery rate of 52%. Example 3

[0054] A tin tailings ore from Guangxi Province, containing 0.15% tin and 16.65% iron, was subjected to beneficiation. The specific procedures are as follows: (1) The tin tailings are screened into +0.15mm coarse tailings, 0.15~0.05mm intermediate tailings and -0.05mm fine tailings; (2) The +0.15mm screen feed from step (1) is subjected to grinding operation, and the grinding fineness is -0.074mm accounting for 80%. Then it enters the shaking table gravity separation operation. At the same time, the 0.15~0.05mm intermediate particle size minerals from step (1) are subjected to shaking table gravity separation operation, and the -0.05mm fine particle size minerals are processed by a suspended vibrating cone surface mineral concentrator. (3) Mix the coarse-grained gravity concentrate, medium-grained gravity concentrate, and medium and fine-grained suspension concentrate from step (2) to form a mixed concentrate, and then enter the reduction roasting operation. The roasting temperature is 750℃, the amount of reducing agent is 12% lignite, and the holding time is 50min.

[0055] (4) The roasted product in step (3) is subjected to weak magnetic separation with a magnetic field strength of 0.20T to obtain iron concentrate I with an iron grade of 60.66% and a recovery rate of 22.88% and tin-rich medium ore with a tin grade of 3.21% and a recovery rate of 65.89%.

[0056] (5) The coarse-grained gravity separation tailings, medium-grained gravity separation tailings and suspension tailings from step (2) are mixed and fed into a high-gradient magnetic separator for strong magnetic separation. The magnetic field strength is 1.2T and the pulse is 21Hz to obtain hematite rough concentrate.

[0057] (6) The strong magnetic separation concentrate from step (5) is subjected to reduction roasting at a temperature of 650℃, with a reducing agent of 10% lignite, and a holding time of 1h. The roasting product is then ground to a fineness of -0.05mm accounting for 80%, and the ground product is subjected to weak magnetic separation at a magnetic field strength of 0.25T to obtain iron concentrate II with an iron grade of 61.75% and a recovery rate of 50.28%.

[0058] Note: Unless otherwise specified, all percentage contents mentioned in this invention are mass percentage contents.

[0059] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for pre-enrichment, sorting, and recovery of tin and iron from tin tailings, characterized in that, Includes the following steps: (1) The tin tailings are classified into coarse-grained tailings, medium-grained tailings and fine-grained tailings; the coarse-grained tailings refer to tin tailings with a particle size greater than 0.15 mm, the fine-grained tailings refer to tin tailings with a particle size less than 0.05 mm; the remaining tin tailings are medium-grained tailings. (2) Coarse-grained tailings are separated by shaking table after grinding; medium-grained tailings are separated by shaking table; fine-grained tailings are separated by suspended cone concentrator. (3) The medium-sized shaking table tailings and the fine-sized suspension shaking tailings are recovered by strong magnetic separation; the strong magnetic separation tailings are the final tailings; Among them, the strong magnetic separation concentrate obtained in step (3) is roasted and weak magnetic separation to obtain iron concentrate II, and the weak magnetic separation tailings are the final tailings.

2. The method according to claim 1, characterized in that, Step (3) After roasting the strong magnetic separation concentrate, it is first ground and then weak magnetic separation is performed. The roasting is reduction roasting.

3. The method according to claim 1 or 2, characterized in that, The coarse-grained shaking table tailings from step (2) are mixed with the medium-grained shaking table tailings and fine-grained suspension tailings from step (3) and then recovered by strong magnetic field.

4. The method according to claim 3, characterized in that, The medium-grained shaking table concentrate and the medium, fine-grained suspension vibrating concentrate and coarse-grained shaking table concentrate obtained in step (2) are tin-iron co-existing minerals.

5. The method according to claim 4, characterized in that, The tin-iron associated minerals were processed by roasting, grinding and weak magnetic separation to obtain iron concentrate I and tin-rich middlings.

6. The method according to claim 5, characterized in that, The roasting is a reduction roasting.

7. The method according to claim 1, characterized in that, The grading method used in step (1) is sieving or hydrocyclone.

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