Method for recovering cassiterite by flotation from tin-containing polymetallic tailings coarse sand and fine particles

Abstract

This invention discloses a method for the flotation recovery of fine-grained cassiterite embedded in coarse sand of tin-containing polymetallic tailings, relating to the field of mineral processing technology. It introduces microwave pretreatment technology into the recovery of fine-grained cassiterite embedded in coarse sand at the tailings dam head, employing a combined process of "microwave pretreatment-grinding-intense magnetic separation for iron removal-fine-grained cassiterite flotation" to improve cassiterite recovery efficiency. This method utilizes the differences in microwave absorption capacity between cassiterite, iron-bearing minerals, and gangue to generate selective thermal stress and microcracks at the mineral interface, achieving efficient and selective dissociation of cassiterite from the intergrowth of iron-bearing minerals and gangue. Intensive magnetic separation then removes iron-bearing minerals, eliminating their interference with flotation. Finally, a ternary combined collector composed of SN01-1-hydroxyoxime acid, SN02-1-hydroxyoxime acid, and a flotation defoaming agent is used for cassiterite flotation. This method achieves efficient recovery of difficult-to-process cassiterite resources from coarse sand in tailings dams, providing an effective technical path for the resource utilization of historically inherited tailings.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and in particular to a method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite. Background Technology

[0002] my country has abundant tin resources, but they are characterized by being poor, fine, and complex. In particular, the recovery of fine-grained cassiterite, which is associated with polymetallic tailings, has always been a technical challenge for the industry.

[0003] Tailings stored in different areas of the tailings dam exhibit significant differences: the tailings at the dam tail are mainly fine-grained, with the -0.038mm cassiterite particles largely liberated and directly recoverable through flotation; while the coarse sand at the dam head has a high proportion of coarse particles due to hydraulic classification, where the cassiterite is mainly in a fine-grained disseminated state, closely associated with iron-bearing minerals (such as limonite, goethite, and other pyrite oxidation products) and silicate gangue, forming a complex intergrowth structure. Due to the brittle nature of cassiterite, conventional grinding presents a dilemma: to liberate the finely disseminated cassiterite, the ore needs to be ground finely, but this grinding process easily leads to over-grinding, producing a large number of ultrafine particles of -0.01mm or even -0.005mm. These ultrafine cassiterite particles, due to their extremely fine size and large specific surface area, are also lost in the tailings during flotation due to high reagent consumption and poor selectivity. Existing gravity separation processes are extremely ineffective at recovering fine-grained cassiterite from coarse sand, resulting in the waste of large amounts of tin resources along with the coarse sand and causing a serious waste of strategic metal resources.

[0004] For refractory ores with fine particle size and complex symbiotic relationships, conventional grinding processes struggle to achieve selective liberation of cassiterite and gangue minerals, often resulting in a technical dilemma: insufficient grinding leads to inadequate liberation, while excessive grinding results in severe over-grinding. Research indicates that microwave heating pretreatment technology can leverage the differences in microwave absorption capacity among different minerals to rapidly raise the temperature of metallic minerals (including cassiterite and iron-bearing minerals), while the gangue minerals show only a slight temperature increase. This generates a significant temperature gradient and thermal stress, forming microcracks at the mineral interface. This effectively reduces grinding energy consumption, promotes selective liberation of the target mineral, and minimizes over-grinding. Summary of the Invention

[0005] To address the above shortcomings, this invention provides a method for the flotation recovery of fine-particle cassiterite embedded in coarse sand from tin-containing polymetallic tailings. This method introduces microwave pretreatment technology into the recovery of fine-particle cassiterite embedded in coarse sand, combined with strong magnetic separation for iron removal and a high-efficiency fine-particle cassiterite flotation process, thereby improving the recovery rate of fine-particle cassiterite embedded in coarse sand. The specific technical solution is as follows:

[0006] A method for flotation recovery of cassiterite embedded in coarse sand from tin-containing polymetallic tailings, comprising the following specific steps:

[0007] S1 Microwave Pretreatment: The coarse sand feed from the tailings dam head is fed into the microwave pretreatment equipment. Microwave irradiation is performed under microwave power of 1~5kw and processing time of 1~10min. This causes the metallic minerals such as cassiterite and iron-bearing minerals in the coarse sand to selectively absorb microwave energy and heat up rapidly, while the gangue minerals heat up slowly. A temperature gradient is formed between the metallic minerals and the gangue minerals. Thermal stress and microcracks are generated at the mineral interface of the metallic minerals such as cassiterite and iron-bearing minerals. Selective dissociation of cassiterite from the intergrowth of iron-bearing minerals and gangue minerals occurs.

[0008] S2 grinding: The microwave pretreated coarse sand obtained in S1 is fed into the grinding equipment for grinding, and the grinding fineness is controlled at -0.074mm, accounting for 80%~95%;

[0009] S3 desulfurization flotation: After adding water to adjust the slurry obtained from S2, sulfide flotation reagents are added for desulfurization flotation. One roughing, three scavenging, and two cleaning processes are carried out. The middlings are returned sequentially to remove residual sulfides and obtain desulfurized tailings.

[0010] S4 hydrocyclone group desliming: The desulfurized tailings obtained from S3 are sent to the hydrocyclone group for desliming under appropriate pressure conditions to remove -0.005mm fine mud and obtain deslimed sand.

[0011] S5 High-Intensity Magnetic Separation for Iron Removal: The sand obtained from S4 is sent to a high-intensity magnetic separation device for high-intensity magnetic separation. Under the condition of magnetic field strength of 0.8~1.5T, iron oxide minerals are removed to obtain magnetic tailings.

[0012] S6 Cassiterite Flotation: After adjusting the slurry of the magnetic separation tailings obtained from S5, cassiterite flotation ternary collector is added for flotation, which involves one roughing, three scavenging, and three cleaning processes. The middlings are returned sequentially to obtain tin concentrate.

[0013] Preferably, the microwave pretreatment equipment in S1 adopts an industrial-grade microwave mineral modification furnace with a microwave frequency of 2450MHz, a processing time of 60~90s, and the moisture content of the coarse sand feed is controlled at 5%~10%.

[0014] Preferably, the sulfide flotation reagent in S3 includes an activator, a xanthate collector, and a frother, and the flotation pH range is 5.5 to 6.5.

[0015] Preferably, the activator is copper sulfate or sulfuric acid.

[0016] Preferably, the hydrocyclone group in S4 consists of 2 to 4 hydrocyclones connected in series, and the desliming particle size is controlled at 0.005 mm.

[0017] Preferably, the strong magnetic separation equipment in S5 is a periodic high gradient magnetic separator with a magnetic field strength of 0.8~1.2T.

[0018] Preferably, the ternary combined collector in S6 is composed of SN01-1 hydroxamic acid collector, SN02-1 hydroxamic acid collector and flotation defoaming aid in a mass ratio of 1:0.8~1.2:0.2~0.3.

[0019] Preferably, the SN01-1 hydroxamic acid collector is an alkylamine-modified C6~C10 alkyl hydroxamic acid, which introduces an amino functional group into the original alkyl hydroxamic acid molecule.

[0020] Preferably, the SN02-1 hydroxamic acid collector is a sulfonated modified aryl hydroxamic acid derivative, in which a sulfonated group is introduced into the aryl hydroxamic acid molecule.

[0021] Preferably, the flotation defoaming aid is a composite system formed by ester-modified C8~C12 fatty acids and polyether-modified silicone oil in a mass ratio of 3:1.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention provides a method for the flotation recovery of finely embedded cassiterite in coarse sand of tin-containing polymetallic tailings. Microwave pretreatment technology is introduced into the recovery of finely embedded cassiterite in coarse sand at the dam head. Utilizing the differences in microwave absorption capacity between cassiterite, iron-bearing minerals, and gangue minerals, selective thermal stress and microcracks are generated at the mineral interfaces. Experiments show that after microwave pretreatment, the grindability of the ore is significantly improved, the Bond work index decreases, the selective liberation effect between cassiterite and gangue is enhanced, grinding energy consumption is reduced by 15%~25%, and over-grinding is also reduced.

[0024] 2. This invention achieves efficient and selective dissociation of cassiterite from iron-bearing minerals and gangue intergrowths in coarse sand through the synergistic effect of microwave pretreatment and grinding, creating ideal conditions for subsequent magnetic separation and flotation. Compared with conventional grinding, the degree of dissociation of cassiterite monomers is increased by 10 to 15 percentage points after microwave pretreatment.

[0025] 3. This invention employs strong magnetic separation to pre-remove iron-containing minerals, eliminating the interference of these poorly floatable iron oxide minerals on subsequent cassiterite flotation.

[0026] 4. The innovative ternary combined collector in this invention achieves functional upgrades and dual-site adsorption. The hydrogen bonding + chelation dual-site adsorption of SN01-1 significantly improves the selectivity of cassiterite. The sulfonation modification of SN02-1 enhances the collection ability of ultrafine cassiterite. The multifunctional auxiliary defoaming component has both defoaming and weak gangue suppression functions. The three work together to improve the efficiency of the collector by more than 15% and reduce the dosage by 10%~15%.

[0027] 5. Compared with the prior art, the present invention can achieve a recovery rate of 75%~85% for fine-grained cassiterite in coarse sand at the tailings dam, and a tin concentrate grade of 6%~8%. This is a significant improvement over conventional gravity separation (recovery rate less than 20%) and conventional flotation (recovery rate 40%~60%), and realizes efficient recovery of difficult-to-process cassiterite resources in coarse sand of tailings dam. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0029] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. Where the terms "first," "second," and "third" are used for descriptive purposes and to distinguish technical features, they should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the sequential relationship of the indicated technical features.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Example

[0035] like Figure 1 As shown, this invention provides a method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite. The specific steps of this recovery method are as follows:

[0036] S1 Microwave Pretreatment: The coarse sand feed from the tailings dam head is fed into a microwave pretreatment device. Microwave irradiation is performed at a power of 1-5 kW and a processing time of 1-10 min. This causes cassiterite, iron-bearing minerals, and other metallic minerals in the coarse sand to selectively absorb microwave energy and rapidly heat up, while gangue minerals heat up slowly. A temperature gradient is formed between the metallic minerals and gangue minerals. Thermal stress and microcracks are generated at the mineral interfaces of cassiterite, iron-bearing minerals, and other metallic minerals. Selective dissociation occurs between cassiterite and the intergrowth of iron-bearing minerals and gangue. The microwave pretreatment device uses an industrial-grade microwave mineral modification furnace with a microwave frequency of 2450 MHz (commonly used in industry). Preferably, the processing time is 60-90 s, and the moisture content of the coarse sand feed is controlled at 5%-10%.

[0037] S2 grinding: The microwave pretreated coarse sand obtained in S1 is fed into the grinding equipment for grinding, and the grinding fineness is controlled at -0.074mm, accounting for 80%~95%;

[0038] S3 Desulfurization Flotation: After adding water to adjust the slurry obtained from S2, sulfide flotation reagents are added for desulfurization flotation. One roughing, three scavenging, and two cleaning processes are performed, and the middlings are returned sequentially to remove residual sulfides, resulting in desulfurized tailings. The sulfide flotation reagents include activators, xanthate collectors, and frothers. The flotation pH range is 5.5 to 6.5. Further, the activator is copper sulfate or sulfuric acid, and the removed sulfur concentrate can be recovered separately.

[0039] S4 hydrocyclone group for desliming: The desulfurized tailings obtained from S3 are fed into the hydrocyclone group for desliming under appropriate pressure conditions to remove -0.005mm fine mud and obtain deslimed sand. The hydrocyclone group consists of 2 to 4 hydrocyclones connected in series. The desliming particle size is controlled at 0.005mm. The removed fine mud has a high mud content and low tin grade and can be disposed of as tailings.

[0040] S5 Strong Magnetic Separation for Iron Removal: The sand obtained from S4 is fed into a periodic high-gradient magnetic separator for strong magnetic separation. Under the condition of magnetic field strength of 0.8~1.5T, preferably 0.8~1.0T, iron oxide minerals are removed, including limonite, goethite, etc., to obtain non-magnetic product magnetic separation tailings. If these iron oxide minerals are not removed, they will compete for the adsorption of collectors and deteriorate the foam after entering the flotation system, which will seriously affect the quality of the concentrate.

[0041] S6 Cassiterite Flotation: After adjusting the slurry of the magnetic separation tailings obtained from S5, cassiterite flotation ternary collector is added for flotation, which involves one roughing, three scavenging, and three cleaning processes. The middlings are returned sequentially to obtain tin concentrate.

[0042] Preferably, the ternary collector is composed of SN01-1 hydroxamic acid collector, SN02-1 hydroxamic acid collector, and flotation defoaming aid in a mass ratio of 1:0.8~1.2:0.2~0.3, wherein:

[0043] The SN01-1 hydroxamic acid collector is an alkylamine-modified C6~C10 alkyl hydroxamic acid. An amino functional group is introduced into the original alkyl hydroxamic acid molecule. The amino group can form hydrogen bonds with the hydroxyl groups on the surface of cassiterite after microwave modification. At the same time, the original hydroxamic acid group forms a five-membered ring chelate with tin ions, realizing hydrogen bond + chelate dual-site adsorption, which greatly improves the selective adsorption capacity of cassiterite. Moreover, it has no adsorption effect on iron-containing minerals with reduced hydrophobicity after microwave modification, further reducing gangue interference.

[0044] The SN02-1 hydroxamic acid collector is a sulfonated modified aryl hydroxamic acid derivative. A sulfonated group is introduced into the aryl hydroxamic acid molecule. The sulfonated group can enhance the dispersibility of the agent in the slurry, making it suitable for the dispersion system of ultrafine cassiterite after microwave dissociation. At the same time, it retains the strong chelating and collecting ability and moderate foaming property of aryl hydroxamic acid, enhances the adhesion efficiency of ultrafine cassiterite to bubbles, and solves the problem of easy loss of ultrafine cassiterite after microwave dissociation.

[0045] The flotation defoaming aid is a composite system formed by ester-modified C8~C12 fatty acids and polyether-modified silicone oil in a mass ratio of 3:1. By replacing the original single fatty acid / modified vegetable oil with the flotation defoaming aid, the ester-modified fatty acids can moderately suppress excessive foam without reducing the collection effect. The polyether-modified silicone oil is a non-ionic defoamer with high defoaming efficiency and good compatibility with the pulp. At the same time, it can form an adsorption film on the surface of silicate gangue, which has the dual functions of defoaming and weak gangue suppression, realizing the synergistic effect of "defoaming + impurity reduction" and further improving the concentrate grade.

[0046] This example uses historical heavy metal tailings waste from Nandan area in Guangxi Zhuang Autonomous Region, my country, as a case study, and analyzes samples from different areas of the tailings pond:

[0047] The coarse sand sample from the dam head: 63% of the particles are +0.074mm, with a tin content of 0.18%. Tin metal is mainly found in the +0.074mm particles. Cassiterite is found in a fine-grained intergrowth. Cassiterite is closely associated with limonite, goethite and silicate gangue, with a single-unit liberation degree of only 18%.

[0048] Fine mud samples from the dam tail: 68% were of -0.038mm size, with a tin content of 0.22%. The cassiterite was basically in a monomeric dissociation state, with a dissociation degree of over 78%.

[0049] The results show that the coarse sand at the dam head and the fine mud at the dam tail have significantly different characteristics, requiring a differentiated treatment approach.

[0050] I. Microwave Pretreatment

[0051] Coarse sand samples were taken from the dam head and pretreated under different microwave powers and processing times to investigate the effect on grinding efficiency. A fixed grinding time of 10 min was used to determine the -0.074 mm content and the degree of cassiterite liberation in the ground product.

[0052] Microwave power (kW) Treatment time (s) -0.074 mm content (%) Cassiterite monomer dissociation degree (%) Remarks 0 (control) 0 72.5 56.3 No pre-treatment 1 30 76.3 65.5 - 2 30 79.8 72.6 - 2 60 82.2 75.8 Preferred 2 90 83.6 76.7 Preferred 2 120 84.2 77.3 Limited improvement 3 60 83.1 76.2 - 3 90 84.5 77.5 High energy consumption 3 120 84.8 78.4 High energy consumption

[0053] Table 1 Results of microwave pretreatment experiments

[0054] Taking into account both the dissociation effect and energy consumption, a microwave power of 2kW and a processing time of 60-90s were optimally selected. After microwave pretreatment, the content of -0.074mm particles increased by nearly 10% and the degree of dissociation of cassiterite monomers increased by 17% under the same grinding conditions.

[0055] II. Strong Magnetic Separation for Demagnetization

[0056] The coarse sand product was pretreated by microwave (microwave power 2kW, treatment time 60s) and then selectively ground (grinding fineness -0.074mm accounted for 82%). The sand slurry that had undergone flotation desulfurization and hydrocyclone desliming was subjected to strong magnetic separation under different magnetic field intensities to investigate the iron removal effect and tin loss.

[0057] Magnetic field strength (T) Magnetic separation tailings yield (%) Magnetic separation tailings iron content (%) Magnetic separation tailings tin grade (%) Tin loss rate (%) Iron removal rate (%) 0.6 91.50 6.10 0.20 4.25 58.60 0.8 86.30 4.35 0.23 5.83 76.44 1.0 85.20 4.22 0.23 6.28 78.60 1.2 81.60 3.80 0.24 7.84 79.50 1.5 80.70 3.50 0.26 9.30 82.60

[0058] Table 2. Effect of strong magnetic field on iron removal

[0059] Taking into account both the iron removal effect and tin loss, a magnetic field strength of 0.8~1.0T is preferred.

[0060] III. Cassiterite Flotation

[0061] Flotation tests were conducted on magnetic separation tailings (iron content 4.35%, tin grade 0.23%) using a ternary combined collector. Fixed conditions: pulp concentration 30%, total collector dosage 900 g / t, to investigate the effects of different ratios.

[0062] SN01-1 : SN02-1 Auxiliary defoaming ratio Concentrate tin grade (%) Operation recovery rate (%) Foam condition 1:0.5 0.2 8.27 74.56 Foam slightly less 1:0.8 0.2 7.81 78.81 Foam stable 1:1 0.25 6.50 80.75 Foam good 1:1.2 0.3 5.74 81.25 Foam slightly more 1:1.5 0.3 5.22 81.64 Foam too much

[0063] Table 3. Cassiterite Flotation Results

[0064] Conventional process (without microwave pretreatment)

[0065] A sample of coarse sand from the dam head was directly ground to -0.074 mm (82%) without microwave pretreatment, and then subjected to flotation desulfurization-desliming-intense magnetic separation-cassiterite flotation under the same conditions. Results: The tin grade in the magnetic separation tailings was 0.20%, the tin grade in the flotation concentrate was 6.25%, and the flotation recovery rate was 62.3%, significantly lower than that of the embodiment of this invention.

[0066] Direct flotation (without magnetic separation) of coarse sand at the dam head.

[0067] Coarse sand samples were taken from the dam head, pretreated with microwaves, ground, and then directly floated without strong magnetic separation. Results: The tin grade in the floated tin concentrate was only 2.26%, with a recovery rate of 82.8%, and the iron content in the tin concentrate was as high as 18%. This indicates that strong magnetic separation for iron removal is crucial for improving concentrate quality.

[0068] Industrial applications

[0069] This invention relates to the recovery of fine-grained cassiterite from coarse sand at the tailings pond head in the Nandan area. The tin grade of the coarse sand feed at the tailings pond head is 0.18%~0.20%, of which +0.074mm particles account for 63%. Cassiterite in the coarse particles is finely intercalated, closely associated with iron-bearing minerals and gangue. A combined process is employed: microwave pretreatment (2kW, 90s) - grinding (-0.074mm particles account for 80~82%) - flotation desulfurization - hydrocyclone desliming - strong magnetic separation (1.0T) - fine-grained cassiterite flotation, accompanied by an innovative ternary combined collector (SN01-1:SN02-1: auxiliary defoaming component = 1:1:0.25).

[0070] During industrial commissioning, the system operated stably. Microwave pretreatment improved grinding efficiency by approximately 20% and reduced power consumption. Magnetic separation achieved an iron removal rate of 75%–80%, with tin loss less than 6%. The tin grade in the flotation concentrate was 6%–8%, and the cassiterite flotation recovery rate was 79%–82%, while the tin recovery rate relative to coarse sand feed reached 65%–68%.

[0071] The successful implementation of this project provides a feasible technical approach for the efficient recovery of refractory cassiterite resources in the coarse sand area of ​​historical tailings ponds, and significantly improves the comprehensive utilization level of tailings resources.

[0072] In summary, this recovery method improves the recovery rate of fine-particle cassiterite in coarse sand by introducing microwave pretreatment technology into the recovery of fine-particle cassiterite in coarse sand, combined with strong magnetic separation for iron removal and efficient flotation of fine-particle cassiterite.

[0073] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for flotation recovery of cassiterite embedded in coarse sand from tin-containing polymetallic tailings, characterized in that, The specific steps are as follows: S1 Microwave Pretreatment: The coarse sand feed from the tailings dam head is fed into the microwave pretreatment equipment. Microwave irradiation is performed under microwave power of 1~5kw and processing time of 1~10min. This causes the metallic minerals such as cassiterite and iron-bearing minerals in the coarse sand to selectively absorb microwave energy and heat up rapidly, while the gangue minerals heat up slowly. A temperature gradient is formed between the metallic minerals and the gangue minerals. Thermal stress and microcracks are generated at the mineral interface of the metallic minerals such as cassiterite and iron-bearing minerals. Selective dissociation of cassiterite from the intergrowth of iron-bearing minerals and gangue minerals occurs. S2 grinding: The microwave pretreated coarse sand obtained in S1 is fed into the grinding equipment for grinding, and the grinding fineness is controlled at -0.074mm, accounting for 80%~95%; S3 desulfurization flotation: After adding water to adjust the slurry obtained from S2, sulfide flotation reagents are added for desulfurization flotation. One roughing, three scavenging, and two cleaning processes are carried out. The middlings are returned sequentially to remove sulfides and obtain desulfurized tailings. S4 hydrocyclone group desliming: The desulfurized tailings obtained from S3 are sent to the hydrocyclone group for desliming under appropriate pressure conditions to remove -0.005mm fine mud and obtain deslimed sand. S5 High-Intensity Magnetic Separation for Iron Removal: The sand obtained from S4 is sent to a high-intensity magnetic separation device for high-intensity magnetic separation. Under the condition of magnetic field strength of 0.8~1.5T, iron oxide minerals are removed to obtain magnetic tailings. S6 Cassiterite Flotation: After adjusting the slurry of the magnetic separation tailings obtained from S5, cassiterite flotation ternary collector is added for flotation, which involves one roughing, three scavenging, and three cleaning processes. The middlings are returned sequentially to obtain tin concentrate.

2. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 1, characterized in that, The microwave pretreatment equipment in S1 uses an industrial-grade microwave mineral modification furnace with a microwave frequency of 2450MHz, a processing time of 60~90s, and the moisture content of the coarse sand feed is controlled at 5%~10%.

3. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 1, characterized in that, The sulfide flotation reagents in S3 include activators, xanthate collectors, and frothers, with a flotation pH range of 5.5 to 6.

5.

4. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 3, characterized in that, The activator is copper sulfate or sulfuric acid.

5. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 1, characterized in that, The hydrocyclone group in S4 consists of 2 to 4 hydrocyclones connected in series, and the desliming particle size is controlled at 0.005 mm.

6. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 1, characterized in that, The high-intensity magnetic separator in S5 is a periodic high-gradient magnetic separator with a magnetic field strength of 0.8~1.2T.

7. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 1, characterized in that, The ternary combined collector in S6 is composed of SN01-1 hydroxamic acid collector, SN02-1 hydroxamic acid collector and flotation defoaming aid in a mass ratio of 1:0.8~1.2:0.2~0.

3.

8. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 7, characterized in that, The SN01-1 hydroxamic acid collector is an alkylamine-modified C6~C10 alkyl hydroxamic acid, which introduces an amino functional group into the original alkyl hydroxamic acid molecule.

9. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite as described in claim 7, characterized in that, The SN02-1 hydroxamic acid collector is a sulfonated modified aryl hydroxamic acid derivative, in which a sulfonated group is introduced into the aryl hydroxamic acid molecule.

10. The method for flotation recovery of tin-containing polymetallic tailings coarse sand with finely embedded cassiterite according to claim 7, characterized in that, The flotation defoaming aid is a composite system formed by ester-modified C8~C12 fatty acids and polyether-modified silicone oil in a mass ratio of 3:1.

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