DESCRIPTION

RECOVERY METHOD FOR TIN MINERAL BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a recovery method for tin mineral, and particularly to a recovery method capable of increasing a recovery rate of tin mineral from tailings.

Priority is claimed on Japanese Patent Application No. 2013-180673, filed August 30, 2013, the content of which is incorporated herein by reference.

Description of Related Art

[0002] In the related art, gravity concentration has been mainly used in the

concentration of tin ore. However, it is difficult to separate fine-grained tin concentrate particles from tin ore by gravity concentration. As a recovery method for the fine-grained tin concentrate particles, flotation concentration is suitable. Here, in order to improve the recovery rate of tin mineral in the concentration of tin ore, both gravity concentration and flotation concentration can be used, as required.

In addition, as a recovery method for high-grade tin concentrate particles, flotation concentration performed under the presence of at least one of sulfurous acid and sulfite is proposed (for example, refer to Patent Document 1 as mentioned below).

[0003] However, in the related art, tin mineral remains in the tailings separated from the tin concentrate particles by the concentration of the tin ore without being recovered.

In recent years, the tin mineral remaining in the tailings separated from the tin ore has attracted attention. Thus, a recovery method for tin mineral from tailings separated from tin ore has been investigated.

PRIOR ART DOCUMENT

Patent Document

[0004] Patent Document 1 : Japanese Examined Patent Application, Second Publication No. S55-17627

SUMMARY OF THE INVENTION

Technical Problem to be solved

[0005] For example, as a recovery method for tin mineral from tailings separated from tin ore, flotation concentration in the related art can be used similarly to when tin mineral is mined from a tin mine. However, even when there is an attempt to concentrate the tailings separated from tin ore by flotation, tin concentrate particles hardly float, and thus the problem of a low recovery rate arises. Specifically, when using flotation

concentration of the tin mineral, even when a sulfonic acid-based reagent typically used as a collector is used under an acidic condition where pH value is 2 to 3, the tin concentrate particles are rarely separated from the tailings separated from tin ore.

[0006] Further, due to the improvement of a concentration technique, the recovery rate of tin mineral from the tin ore is gradually improved and the tin content in the tailings is gradually decreased with the improvement of the recovery rate. Therefore, as the tailings are stocked in a tailing dam for a longer period of time, the tin content becomes higher. Thus, it is preferable to recover tin mineral from the tailings stocked in the tailing dam for a long period of time in order to increase the recovery rate of tin mineral.

[0007] However, in a case where the tailings separated from tin ore are concentrated by flotation, as the tailings are stocked in the tailing dam for a longer period of time, the separation of the tin concentrate particles become more difficult. Therefore, the tin mineral cannot be effectively recovered by flotation concentration even from the tailings considered to have been stocked in the tailing dam for a long period of time and having a high tin content.

[0008] Further, a recovery method for tin mineral by concentrating tailings separated from tin ore by gravity can be considered. However, even when gravity concentration is used, tin mineral cannot be effectively recovered from tailings separated from tin ore.

[0009] An object of the present invention is to provide a recovery method for tin mineral capable of effectively recovering tin mineral from tailings separated from tin ore.

Solution to the Problem

[0010] In order to solve the above problems, the inventor has focused on the properties of tailings, and the differences between tailings and tin ore to obtain the following findings.

That is, the ratio of fine-grained tin concentrate particles is high in tailings since coarse-grained tin concentrate particles are removed from the tailings during

concentration. Therefore, it is difficult to increase the recovery rate of tin mineral only by the gravity concentration.

In addition, as the tailings are stocked in the tailing dam for a longer period of time, a large amount of slime (fine particles) separated from the tin concentrate particles during concentration or a large number of ions resulting from a reagent used during concentration adhere to the tin concentrate particles. Thus, the tin concentrate particles are oxidized in many cases.

[0011] Although oxidized minerals and slime are contained in the tin ore, the amount of oxidized minerals and slime adhering to the tailings is small compared to the tin ore. Thus, it is assumed that the slime and the ions adhering to the tin concentrate particles hinder adhesion of a reagent to the tin concentrate particles in the tailings in flotation concentration.

[0012] As a result of various repeated investigations, the inventor has found that before the flotation concentration is performed, the tailings have only to be washed using hydrofluoric acid to remove slime or ions adhering to tin concentrate particles, and thus the present invention has been devised.

[0013] According to a first aspect of the present invention, a recovery method for tin mineral is provided including adding hydrofluoric acid to tailings separated from tin ore, and flotation-concentrating the tailings after the adding of the hydrofluoric acid to separate tin concentrate particles from the tailings.

The recovery method for tin mineral according to the first aspect may further include gravity-concentrating the tailings before the flotation-concentrating of the tailings.

According to a second aspect of the present invention, a recovery method for tin mineral is provided including removing at least one of ions and slime from surfaces of particles of cleaner tailings separated from tin ore, and flotation-concentrating the tailings after the removing of at least one of ions and slime to separate tin concentrate particles from the tailings.

In the recovery method for tin mineral according to the second aspect, the tailings may be washed with a water solution including hydrofluoric acid to remove at least one of ions and slime. Effects of the Invention [0014] The recovery method for tin mineral includes adding hydrofluoric acid to tailings separated from tin ore, and flotation-concentrating the tailings after the adding of the hydrofluoric acid. Inhibitory substances such as slime or ions adhering to the tin concentrate particles included in the tailings separated from tin ore are removed by hydrofluoric acid. Accordingly, the reagent used in the flotation-concentrating of the tailings easily adheres to the tin concentrate particles. As a result, the tin mineral can be effectively recovered from the tailings separated from the tin ore by the flotation concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a flowchart describing an example of a recovery method for tin mineral of the present invention.

FIG. 2 is a flowchart illustrating an example of a method for obtaining cleaner concentrates from tailings separated from tin ore using the recovery method for tin mineral illustrated in FIG. 1.

FIG. 3 is a flowchart illustrating an example of the method for obtaining cleaner concentrates from tailings separated from tin ore using the recovery method for tin mineral illustrated in FIG. 1.

FIG. 4 is a flowchart illustrating an example of the method for obtaining cleaner concentrates from tailings separated from tin ore using the recovery method for tin mineral illustrated in FIG. 1.

FIG. 5 is a flowchart describing a recovery method for tin mineral of Example 1 in which cleaner concentrates are obtained from tailings separated from tin ore.

FIG. 6 is a flowchart describing the recovery method for tin mineral of Example 1 in which cleaner concentrates are obtained from tailings separated from tin ore. FIG. 7 is a flowchart describing a recovery method for tin mineral of Example 2 in which cleaner concentrates are obtained from tailings separated from tin ore.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a recovery method for tin mineral of the present invention will be described in detail referring to examples. Embodiments described below are representative examples of the present invention and the scope of the present invention is not to be interpreted as being limited thereby.

FIG. 1 is a flowchart describing an example of a recovery method for tin mineral of the present invention. In the recovery method for tin mineral of the embodiment, first, tailings separated from tin ore and transferred from a tailing dam as feed material are classified and further ground (classification/grinding step SI).

[0017] Next, as illustrated in FIG. 1, tailings having a predetermined particle size in the classification/grinding step SI are desulfurized by flotation (desulfurization step S2). Sulfides included in the tailings are removed from the tailings by the

flotation-desulfurization in the desulfurization step S2.

[0018] Next, as illustrated in FIG. 1, the desulfurized tailings are concentrated by gravity (first gravity concentration step S3).

In the first gravity concentration step S3, first, the desulfurized tailings are roughly concentrated by gravity. Accordingly, the desulfurized tailings are separated into rougher concentrates and rougher tailings. Coarse-grained tin concentrate particles that are hardly recovered by the flotation concentration are included in the rougher concentrates.

[0019] Thereafter, as required, the rougher concentrates are classified and separated into first rougher concentrates having low specific gravity and a large particle size and second rougher concentrates having high specific gravity and a small particle size. The first rougher concentrates are preferably added to the tailings before the tailings are roughly concentrated by gravity while being ground.

On the other hand, the second rougher concentrates are cleanly concentrated by gravity. Accordingly, the second rougher concentrates are separated into cleaner concentrates including tin mineral having high specific gravity and a high concentration and cleaner tailings having low specific gravity.

In addition, the rougher concentrates may not be classified but may be cleanly concentrated by gravity.

[0020] Next, as illustrated in FIG. 1 , the tailings (rougher tailings and cleaner tailings) separated from the concentrates in the first gravity concentration step S3 are washed (washing step S4).

In the embodiment, before the washing step S4 is performed, the tailings separated from the concentrates in the first gravity concentration step S3 are preferably classified using a cyclone separator or the like. Thus, some of the fine particles (slime) included in the tailings separated from the concentrates in the first gravity concentration step S3 can be removed. Accordingly, the tin content in the tailings separated from the concentrates in the first gravity concentration step S3 is increased.

[0021] Next, the tailings (or tailings from which some of the slime is removed) separated from the concentrates in the first gravity concentration step S3 are washed with a water solution including hydrofluoric acid. For example, the washing step S4 may be performed by conditioning a slurry obtained by mixing the tailings with the water solution including hydrofluoric acid and storing and stirring the slurry in a tank for washing. By performing the washing step S4, the recovery rate of tin mineral from the tailings separated from the concentrates in the first gravity concentration step S3 is improved.

[0022] Next, as illustrated in FIG. 1 , the washed tailings are concentrated by flotation (flotation concentration step S5).

In the flotation concentration step S5, the tin concentrate particles included in the tailings are floated in the solution and concentrated, and the tin concentrate particles included in the washed tailings are recovered as first flotation concentrates. For example, the flotation concentration step S5 may be performed by storing the slurry including the washed tailings in a tank for flotation concentration, adding a reagent thereto, and blowing air into the tank to generate bubbles.

[0023] In the embodiment, in order to improve the recovery rate of tin mineral, the concentrated tailings from which the first flotation concentrates are separated by performing the flotation concentration step S5 may be washed again with a water solution including hydrofluoric acid (washing step S4), and the washed tailings may be concentrated by flotation again. That is, the washing step S4 and the flotation concentration step S5 may be repeatedly performed.

[0024] Next, as illustrated in FIG. 1 , in order to increase the tin content in the first flotation concentrates, the first flotation concentrates separated from the concentrated tailings in the flotation concentration step S5 are concentrated by gravity as required (second gravity concentration step S6). By performing the second gravity concentration step S6, the first flotation concentrates are separated into concentrated tailings and second flotation concentrates including tin mineral having a high concentration.

[0025] The second flotation concentrates separated from the concentrated tailings by the second gravity concentration step S6 are mixed with the cleaner concentrates separated from the concentrated tailings in the first gravity concentration step S3.

Next, a liquid is separated from the mixture of the second flotation concentrates and the cleaner concentrates separated from the concentrated tailings in the first gravity concentration step S3 and the mixture is concentrated using a thickener. Then, the mixture concentrated by the thickener is dehydrated using a drum filter, a disk filter, or the like, and dried (dehydration step S7).

Through the above steps, cleaner concentrates including tin mineral having a high concentration can be obtained.

[0026] The recovery method for tin mineral illustrated in FIG. 1 includes the washing step S4 of washing the tailings separated from tin ore with hydrofluoric acid, and the flotation concentration step S5 of flotation-concentrating the tailings after the washing step S4. Accordingly, even when slime or ions adhere to the tin concentrate particles included in the tailings separated from tin ore, the slime or ions are removed in the washing step S4 with the water solution including hydrofluoric acid. Therefore, the reagent used in the flotation concentration step S5 easily adheres to the tin concentrate particles without hindrance of the slime or the ions. As a result, the tin mineral can be effectively recovered from the tailings separated from tin ore in the flotation

concentration step S5.

[0027] Further, in the recovery method for tin mineral illustrated in FIG. 1 , the first gravity concentration step S3 is performed before the flotation concentration step S5. Thus, the coarse-grained tin concentrate particles which are not easily recovered in the flotation concentration step S5 can be effectively recovered. Accordingly, in the recovery method for tin mineral illustrated in FIG. 1 , the recovery rate of tin mineral from the tailings can be further improved compared to a case in which the first gravity concentration step S3 is not performed.

When a desired recovery rate can be obtained without performing the first gravity concentration step S3, the first gravity concentration step S3 may be omitted. [0028] In addition, in the recovery method for tin mineral illustrated in FIG. 1, the second gravity concentration step S6 is performed even after the flotation concentration step S5, and thus high-grade cleaner concentrates including tin mineral having a high concentration can be obtained.

When high-grade cleaner concentrates can be sufficiently obtained without performing the second gravity concentration step S6, the second gravity concentration step S6 may be omitted.

Further, in the recovery method for tin mineral illustrated in FIG. 1, the desulfurization step S2 is performed before the flotation concentration step S5.

Therefore, high-grade cleaner concentrates including tin mineral having a higher concentration can be obtained.

When high-grade cleaner concentrates can be sufficiently obtained without performing the desulfurization step S2, the desulfurization step S2 may be omitted.

[0029] Next, a method for obtaining cleaner concentrates from the tailings separated from tin ore using the recovery method for tin mineral illustrated in FIG. 1 will be described in more detail referring to specific examples.

FIGS. 2 to 4 are flowcharts illustrating an example of a method for obtaining cleaner concentrates from the tailings separated from tin ore using the recovery method for tin mineral illustrated in FIG 1.

First, as illustrated in FIG. 2, tailings separated from tin ore mined in the tailing dam of a mine are excavated. Next, the excavated tailings (feed material) separated from tin ore are loaded in, for example, a 20t truck or the like, transferred, and received by feed material receiving equipment.

[0030] It is preferable to prepare machines such as an excavator for tailings, and a shovel loader and a back hoe loader for loading tailings onto a truck, effluent treatment facilities, a tire washer, and a lighting system in the tailing dam of the mine.

In addition, it is preferable to construct a spare tailing dam as a place for receiving and storing the tailings. Moreover, it is preferable that the tailings can be put into the feed material receiving equipment from the spare tailing dam using a loading machine or the like as required.

Classification/Grinding Step SI

[0031] Next, as illustrated in FIG. 1, the tailings received into the feed material receiving equipment are classified and further ground in the classification/grinding step SI. That is, the tailings received by the feed material receiving equipment include a large number of particles having a particle size of substantially 5 μηι to 400 μπι, and the tailing particles having such a size are suitable for recovering tin concentrate particles by flotation concentration. The tailings to be treated which are concentrated from tin ore before being stocked in the tailing dam have a particle size falling within the above range, and include a relatively large number of small particles. Accordingly, the tailings do not need to be ground unlike a case in which tin mineral is directly recovered from tin ore.

[0032] In the classification/grinding step SI, as illustrated in FIG. 2, first, the tailings are washed with water using a drum scrubber. Next, the washed tailings are screened using a rotary siever (that is called "trammel") having a mesh size of 24 mm. Tailings having a particle size exceeding 24 mm, which cannot pass through the mesh of the siever, are transferred to a new tailing dam. On the other hand, tailings having a particle size of 24 mm or less, which can pass through the mesh of the siever, are introduced to a two-stage Akins classifier.

[0033] Subsequently, as illustrated in FIG. 2, the tailings are classified using the two-stage Akins classifier. The coarse particles (sand) of the tailings classified by the two-stage Akins classifier are ground using, for example, a ball mill having lifting blades. The ground coarse particles are introduced to the two-stage Akins classifier again.

On the other hand, the fine particles (overflow) of the tailings that are classified by the two-stage Akins classifier and have a predetermined particle size are sent to a desulfurization step S2 as illustrated in FIGS. 1 and 2.

Desulfurization Step S2

[0034] The conditions of flotation desulfurization in the desulfurization step S2 are not particularly limited as long as sulfides included in the tailings can be removed. In order to effectively remove sulfides included in the tailings, the desulfurization step is preferably performed under the following conditions.

[0035] In the desulfurization step S2, first, as illustrated in FIG. 2, tailing slurry is conditioned for performing the flotation desulfurization. The average particle size of the tailings included in the slurry is preferably 100 μηι or less, and the percentage of particles having a particle size of 200 μηι or less is preferably substantially 85% with respect to the total amount. In addition, the content of the tailings (pulp concentration) in the slurry is preferably 25 mass% to 30 mass%.

[0036] Next, as illustrated in FIG. 2, the conditioned tailing slurry is desulfurized (first flotation desulfurization). That is, the conditioned tailing slurry is stored in a tank for first flotation desulfurization, a reagent is added thereto, and air is blown into the tank to generate bubbles. A period during which the first flotation desulfurization is performed (conditioning time) may be, for example, substantially 10 minutes. Here, the

conditioning time in the desulfurization step S2 refers to a temporary staying time from the introduction of the tailing slurry into the tank for desulfurization to the discharge of the tailing slurry in a case in which the tailing slurry is continuously supplied to the tank for desulfurization in which bubbles are generated.

[0037] As the reagent used in the first flotation desulfurization, well-known reagents used in flotation desulfurization during the concentration of tin ore in the related art can be used.

Specifically, for example, CuS0 ₄ -5H ₂ 0 or the like can be used as an activator, as required. When being used as the activator, CuS0 ₄ -5H ₂ 0 is preferably added at a ratio of 300 g to 500 g per ton of feed material. As a frother, D.F. 250# (product name, produced by The Dow Chemical Company) or the like can be preferably used. When being used as the frother, D.F. 250# can be added at a ratio of 50 g to 300 g per ton of feed material.

In addition, when the first flotation desulfurization is performed, the pH value of the tailing slurry is preferably 4.5 to 5.

[0038] Next, as illustrated in FIG. 2, in order to improve the recovery rate of tin mineral, the slurry including the tailings from which sulfides are removed by the first flotation desulfurization is desulfurized again (second flotation desulfurization). That is, the tailing slurry from which sulfides are removed is stored in a tank for second flotation desulfurization, a reagent is added thereto, and air is blown into the tank to generate bubbles.

[0039] A period during which the second flotation desulfurization is performed

(conditioning time) may be, for example, substantially 10 minutes as in the first flotation desulfurization. As the reagent used in the second flotation desulfurization, well-known reagents used in flotation desulfurization during the concentration of tin ore in the related art can be used as in the first flotation desulfurization. As for the reagent used in the first flotation desulfurization, the reagent may be the same as the reagent used in the second flotation desulfurization or maybe different from the reagent used in the second flotation desulfurization. Further, the pH value of the tailing slurry when the second flotation desulfurization is performed is preferably 4.5 to 5 as in the first flotation desulfurization.

[0040] As illustrated in FIG. 2, the slurry including the tailings from which sulfides are removed by the second flotation desulfurization is sent to a first gravity concentration step S3 illustrated in FIG. 3.

In addition, liquid content is separated from the sulfides separated from the tailings by performing the first flotation desulfurization and the second flotation desulfurization, the sulfides are concentrated using a thickener as illustrated in FIG. 2 and then transferred to a new tailing dam. The overflow water recovered by the thickener is preferably recycled as recycling water.

In the desulfurization step S2 illustrated in FIG. 2, flotation desulfurization is performed twice. However, flotation desulfurization may be performed only once or may be performed three times or more.

Second Gravity Concentration Step S3

[0041] In the second gravity concentration step S3, as illustrated in FIG. 3, first, the desulfurized tailings are roughly concentrated by gravity (table roughing). Accordingly, the desulfurized tailings are separated into rougher concentrates including coarse-grained tin concentrate particles and rougher tailings.

[0042] Thereafter, as illustrated in FIG. 3, the rougher concentrates are classified using a vibration screener having a mesh size of 200 μπι. Thus, the rougher concentrates are separated into first rougher concentrates having high specific gravity and a particle size of 200 μηι or less and second rougher concentrates having low specific gravity and a particle size exceeding 200 μηι.

As illustrated in FIG. 3, the first rougher concentrates having a particle size of 200 μηι or less are cleanly concentrated by gravity (table cleaning). Thus, the first rougher concentrates are separated into cleaner concentrates including tin mineral having high specific gravity and a high concentration and cleaner tailings having low specific gravity.

On the other hand, as illustrated in FIG. 3, the second rougher concentrates having a particle size exceeding 200 μηι are ground to have a particle size of 200 μιη or less and then added to the tailings before being roughly concentrated by gravity.

The cleaner tailings are sent to a washing step S4 illustrated in FIG. 4 and the cleaner concentrates are sent to a dehydration step S7 illustrated in FIG. 4.

Washing Step S4 and Flotation Concentration Step S5

[0043] In the embodiment, as illustrated in FIG. 4, the tailings (rougher tailings and cleaner tailings) separated from the concentrates in the first gravity concentration step S3 are classified using a cyclone separator before the washing step S4 is performed. Thus, the tailings separated from the concentrates in the first gravity concentration step S3 are separated into fine particles having a particle size of 6 μπι or less including slime, and coarse-grained tailings having a particle size of 6 μηι or more.

[0044] As illustrated in FIG. 4, a liquid is separated from the fine particles having a particle size of 6 μηι or less including slime and the fine particles are concentrated using a thickener and then flow into a new tailing dam. Here, the overflow water recovered by the thickener is preferably recycled as recycling water.

In the washing step S4, as illustrated in FIG. 4, the tailings from which the fine particles (slime) are removed during the classification are washed with a water solution including hydrofluoric acid (first washing step). For example, the first washing step may be performed by conditioning a slurry obtained by mixing the tailings with the water solution including hydrofluoric acid and storing and stirring the slurry in a tank for washing.

[0045] When the first washing step is performed, the content of the tailings (pulp concentration) in the slurry is preferably 25 mass% to 30 mass%.

In addition, a period during which the first washing step is performed

(conditioning time) is preferably substantially 10 minutes. Here, the conditioning time in the first washing step refers to a temporary staying time from the introduction of the tailing slurry to the discharge of the tailing slurry when the tailing slurry is continuously supplied to the tank for washing.

[0046] The water solution used in the first washing step may include hydrofluoric acid. The water solution may also include sodium silicate (Na ₂ Si0 ₃ ) with the hydrofluoric acid.

Further, the water solution including hydrofluoric acid may include a

pH-adjusting agent such as sulfuric acid or sodium hydroxide, as required. The pH value of the slurry obtained by mixing the tailings with the water solution including hydrofluoric acid is preferably 4 to 5.5. When the pH value of the water solution including hydrofluoric acid is 4 to 5.5, the tailings can be more effectively washed.

[0047] The amount of hydrofluoric acid used in the first washing step is preferably 0.5 kg to 2 kg per ton of feed material of the tailings. When the ratio of the hydrofluoric acid is 0.5 kg to 2 kg per ton of feed material, the tailings can be effectively washed. When the ratio of the hydrofluoric acid is less than 0.5 kg per ton of feed material, the tailings may fail to be effectively washed in some cases. In addition, when the ratio of the hydrofluoric acid exceeds 2 kg per ton of feed material, the washing effect on the tailings is not improved.

When the water solution including hydrofluoric acid includes sodium silicate, unnecessary substances can be precipitated, and thus it is preferable to include sodium silicate in the water solution.

[0048] Next, in the flotation concentration step S5, as illustrated in FIG. 4, the concentrated tailings after the first washing step are concentrated by flotation (first flotation concentration). By performing the first flotation concentration, the tin concentrate particles included in the washed concentrated tailings are floated in the solution and concentrated, and then the tin concentrate particles are recovered as first flotation concentrates. For example, the first flotation concentration may be performed by, for example, storing the slurry including the washed tailings in a tank for flotation concentration, adding a reagent thereto, and blowing air into the tank to generate bubbles.

[0049] When the first flotation concentration is performed, the content of the tailings (pulp concentration) in the slurry is preferably 25 mass % to 30 mass%.

A period during which the first flotation concentration is performed

(conditioning time) may be, for example, 5 minutes to 10 minutes. The conditioning time in the first flotation concentration refers to a temporary staying time from the introduction of the tailing slurry into the tank for flotation desulfurization to the discharge of the tailing slurry from the tank in a case in which the tailing slurry is continuously supplied to the tank for flotation desulfurization in which bubbles are generated.

[0050] As the reagent used in the first flotation desulfurization, well-known reagents used in flotation desulfurization during the concentration of tin ore in the related art can be used. Specifically, for example, hydrofluoric acid or the like can be used as an activator, as required. When being used as the activator, hydrofluoric acid is preferably added at a ratio of 500 g to 800 g per ton of feed material. As a collector, sodium oleate or the like can be preferably used. When being used as the collector, sodium oleate can be added at a ratio of 500 g to 800 g per ton of feed material. As a frother, D.F. 250# (product name, produced by The Dow Chemical Company) can be added.

In addition, when the first flotation desulfurization is performed, the pH value of the tailing slurry is preferably 4.5 to 5.

[0051] In the embodiment, even when slime or ions adhere to the tin concentrate particles included in the concentrated tailings, the slime or ions are removed using a water solution including hydrofluoric acid in the washing step S4. Accordingly, a hydrophilic group included in the collector in the first flotation concentration easily adheres to the surface of the tin concentrate particles without hindrance of the slime or the ions. Therefore, the tin concentrate particles included in the tailing slurry are easily floated with the bubbles. As a result, the tin mineral can be effectively recovered in the first flotation concentration.

[0052] Next, as illustrated in FIG. 4, in the washing step S4, the concentrated tailings separated from the first flotation concentrates by the first flotation concentration are washed with the water solution including hydrofluoric acid as in the first washing step (second washing step). The first washing step and the second washing step may be performed under the same conditions or different conditions.

Next, as illustrated in FIG. 4, in the flotation concentration step S5, the concentrated tailings after the second washing step are concentrated by flotation (second flotation concentration). By performing the second flotation concentration, the tin concentrate particles included in the concentrated tailings are floated in the solution and concentrated, and then tin concentrate particles are recovered as second flotation concentrates.

[0053] In the embodiment, as illustrated in FIG. 4, a combination of a single washing step S4 and a single flotation concentration step S5 is performed twice. However, the number of times of performing the washing step S4 and the flotation concentration step S5 is not limited to that in the example. For example, in the combination of the washing step S4 and the flotation concentration step S5, plural flotation concentration steps S5 may be performed after a single washing step S4 is performed, or a single or plural flotation concentration steps S5 may be performed after plural washing steps S4 are performed. In addition, the number of times of performing the combination of the washing step S4 and the flotation concentration step S5 may be one or may be three or more.

[0054] Further, when the washing step S4 is performed plural times, grinding is preferably performed before the second and subsequent washing steps S4 are performed. Accordingly, the washing effect on the tailings is improved in the second and subsequent washing steps S4, and thus the tin mineral can be recovered from the tailings separated from tin ore in the following flotation concentration step S5 with a higher recovery rate.

Second Gravity Concentration Step S6

[0055] Next, as illustrated in FIG. 4, the flotation concentrates (first flotation concentrates and second flotation concentrates) separated from the concentrated tailings in the flotation concentration step S5 are concentrated by gravity (second gravity concentration step S6). It is preferable that the second gravity concentration step S6 be accurately performed using a fine particle table in which the flow velocity is suppressed to treat the flotation concentrates including fine tin concentrate particles. By performing the second gravity concentration step S6, the flotation concentrates are separated into concentrated tailings and high-grade second flotation concentrates including tin material having a high concentration. The concentrated tailings separated from the second flotation concentrates are preferably added to the concentrated tailings separated from the cleaner concentrates in the first gravity concentration step S3 before the concentrated tailings are classified using the cyclone separator.

Dehydration Step S7

[0056] As illustrated in FIG. 4, third flotation concentrates separated from the concentrated tailings in the second gravity concentration step S6 are mixed with the cleaner concentrates separated from the cleaner tailings by gravity concentration in the first gravity concentration step S3.

Next, as illustrated in FIG. 4, liquid content is separated from the mixture of the third flotation concentrates and the cleaner concentrates separated from the cleaner tailings in the first gravity concentration step S3 and the mixture is concentrated using the thickener. Then, the concentrated mixture is dehydrated using a drum filter, a disk filter, or the like, and dried. The overflow water recovered by the thickener is preferably recycled as recycling water.

Through the above steps, high-grade cleaner concentrates including tin mineral having a high concentration can be obtained.

EXAMPLES

Example 1

[0057] FIGS. 5 and 6 are flowcharts describing a recovery method for tin mineral of Example 1 in which cleaner concentrates are obtained from tailings separated from tin ore. Hereinafter, Example 1 will be described in detail using FIGS. 1, 5 and 6.

In the recovery method for tin mineral in Example 1, tailings separated from tin ore mined from the tailing dam of a mine in Bolivia were used as feed material. Here, 1 kg of feed material was used each time.

Classification/Grinding Step SI

[0058] As illustrated in FIG. 5, 1 kg of feed material, 1000 mL of water, and 5 kg of iron balls were put into a ball mill container, rotated for 50 minutes, and ground. Desulfurization Step S2

[0059] As illustrated in FIG. 5, a slurry including tailings having a predetermined particle size by grinding was desulfurized by flotation (first flotation desulfurization in FIG. 5, that is desulfurization step S2 in FIG. 1). Specifically, the tailing slurry was stored in a tank for first desulfurization, a reagent was added thereto, and air was blown into the tank for 5 minutes to generate bubbles.

In the first flotation desulfurization, ACC #208 (product name, produced by Cytec Industries Inc.) as a collector and D.F. #250 (product name, produced by The Dow Chemical Company; D.F. was an abbreviation of Dow Froth) as a frother were used as the reagents. Further, the collector was added at a ratio of 200 g per ton of feed material, and six drops of the frother were added using a syringe (at a ratio of 300 g per ton of feed material).

The pH value of the tailing slurry when the first flotation desulfurization started was 4.63 and the pH value of the tailing slurry when the first flotation desulfurization ended was 4.65.

[0060] Next, a slurry including tailings (Tl) from which sulfides (CI) were removed by the first flotation desulfurization was desulfurized by flotation again (second flotation desulfurization). Specifically, the tailing slurry from which sulfides were removed was stored in a tank for second desulfurization, a reagent was added thereto, and air was blown into the tank for 7 minutes to generate bubbles.

In the second flotation desulfurization, an activator, a collector, and a frother were used as the reagents. CuS0 ₄ -5H ₂ 0 was used as the activator, the ACC #208 was used as the collector, and the D.F. #250 was used as the frother. The activator and the collector were added at a ratio of 200 g per ton of feed material, and three drops of the frother were added using a syringe (at a ratio of 150 g per ton of feed material).

In addition, the pH value of the tailing slurry when the second flotation desulfurization started was 4.31 and the pH value of the tailing slurry when the second flotation desulfurization ended was also 4.31.

[0061] Next, the reagents were further added to the slurry, from which sulfides (C2) were removed by the second flotation desulfurization, in the tank for second

desulfurization, and air was blown into the tank for 5 minutes to generate bubbles.

Then, third flotation desulfurization was performed.

In the third flotation desulfurization, an activator, a collector, and a frother were used as the reagents. CuS0 ₄ -5H ₂ 0 was used as the activator, the ACC #208 was used as the collector, and the D.F. #250 was used as the frother. The activator and the collector were added at a ratio of 100 g per ton of feed material, and three drops of the frother were added using a syringe (at a ratio of 150 g per ton of feed material).

First Gravity Concentration Step S3

[0062] In a first gravity concentration step S3, first, as illustrated in FIG. 5, tailings (T2) from which sulfides were removed were roughly concentrated by gravity. Thus, the desulfurized tailings were sorted into rougher concentrates (RC) including coarse-grained tin concentrate particles and rougher tailings (RT) concentrated by gravity.

[0063] Then, as illustrated in FIG. 5, the rougher concentrates (RC) were classified using a vibration screener having a mesh size of 200 μηι. Thus, the rougher

concentrates (RC) were separated into rougher concentrates (RC1) having high specific gravity and a particle size of 200 μηι or less, and rougher concentrates (RC2) having low specific gravity and a particle size exceeding 200 μηι.

As illustrated in FIG. 5, the rougher concentrates (RC1) having a particle size of 200 μηι or less were cleanly concentrated by gravity. Thus, the rougher concentrates (RC1) were separated into cleaner tailings having low specific gravity and cleaner concentrates including tin mineral having high specific gravity and a high concentration. Further, each of the cleaner tailings and the cleaner concentrates were cleanly

concentrated by gravity, and the resultants were separated into cleaner tailings having low specific gravity and cleaner concentrates including tin mineral having high specific gravity and a high concentration (CC1 or CC2).

On the other hand, as illustrated in FIG. 5, the rougher concentrates (RC2) having a particle size exceeding 200 μιη were ground again to have a particle size of 200 μηι or less and then added to the rougher concentrates (RC) before being classified. Washing Step S4 and Flotation Concentration Step S5

[0064] As illustrated in FIG. 6, the tailings (rougher tailings and cleaner tailings) separated from the concentrates in the first gravity concentration step S3 were classified using a cyclone separator before a washing step S4 was performed. Thus, the tailings separated from the concentrates in the first gravity concentration step S3 were separated into fine particles (OF) having a particle size of 6 μηι or less including slime and coarse-grained tailings (UF) having a particle size of 6 μηι or more.

First Time Treatment

[0065] Next, as illustrated in FIG. 6, the tailings (UF) from which fine particles (OF) were removed during the classification were washed with a water solution including hydrofluoric acid (first washing step in FIG. 6, that is washing step S4 in FIG. 1).

Specifically, a slurry obtained by mixing the tailings with the water solution including hydrofluoric acid was conditioned and the slurry was stored in a tank for washing and stirred. The first washing step was performed for 10 minutes (conditioning time).

[0066] In the first washing step, a solution including hydrofluoric acid and sodium silicate (Na ₂ Si0 ₃ ) was used as the water solution including hydrofluoric acid. The amount of hydrofluoric acid in the first washing step was adjusted to a ratio of 800 g per ton of feed material.

In addition, the pH value of the slurry in the first washing step was adjusted using sulfuric acid. The pH value of the slurry when the first washing step started was 4.60 and the pH value of the slurry when the first washing step ended was 4.00.

[0067] Next, as illustrated in FIG. 6, the concentrated tailings after the first washing step were concentrated by flotation (first flotation concentration, that is flotation concentration step S5 in FIG. 1). By performing the first flotation concentration, the tin concentrate particles included in the concentrated tailings after the first washing step were floated in the solution and concentrated, and then tin concentrate particles were recovered as first flotation concentrates (SnC). Specifically, the slurry including the washed tailings was stored in a tank for flotation concentration, a reagent was added thereto, and air was blown into the tank to generate bubbles. The first flotation concentration was performed for 5 minutes (conditioning time).

[0068] In the first flotation concentration, sodium oleate, AP #845 (product name, produced by Cytec Industries Inc.) as a collector, and D.F. #250 (product name) as a frother were used as the reagents.

Further, the collector and sodium oleate were respectively added at a ratio of 300 g per ton of feed material, and two drops of the frother were added using a syringe (at a ratio of 100 g per ton of feed material).

Second Time Treatment

[0069] Next, as illustrated in FIG. 6, the concentrated tailings (SnRT) from which the first flotation concentrates were separated by the first flotation concentration were washed with a water solution including hydrofluoric acid (second washing step in FIG. 6, that is washing step S4 in FIG. 1) as in the first washing step. The second washing step was performed for 10 minutes (conditioning time).

In the second washing step, a solution including hydrofluoric acid and sodium silicate (Na ₂ Si0 ₃ ) was used as the water solution including hydrofluoric acid. The amount of hydrofluoric acid in the second washing step was adjusted to a ratio of 500 g per ton of feed material.

In addition, the pH value of the slurry in the second washing step was adjusted using sodium hydroxide. The pH value of the slurry when the second washing step started was 3.77 and the pH value of the slurry when the second washing step ended was 4.00.

[0070] Next, as illustrated in FIG. 6, the tailings after the second washing step were concentrated by flotation again (second flotation concentration, that is flotation concentration step S5 in FIG. 1). By performing the second flotation concentration, the tin concentrate particles included in the concentrated tailings after the second washing step were floated in the solution and concentrated, and then tin concentrate particles were recovered as second flotation concentrates (SnC). Specifically, the slurry including the washed tailings was stored in a tank for flotation concentration, a reagent was added thereto, and air was blown into the tank to generate bubbles. The second flotation concentration was performed for 5 minutes (conditioning time).

[0071] In the second flotation concentration, a collector and a frother were used as the reagents. AP 845# and sodium oleate were used as the collector, and the D.F. 250# was used as the frother.

The AP 845# and sodium oleate as the collector were respectively added at a ratio of 200 g per ton of feed material, and one drop of the frother was added using a syringe (at a ratio of 50 g per ton of feed material).

Third Time Treatment

[0072] Next, as illustrated in FIG. 6, the concentrated tailings (SnRT) from which the second flotation concentrates were separated by the second flotation concentration were ground using a 1 kg pot mill. The pH value of the slurry including the ground tailings was 5.58.

[0073] Next, as illustrated in FIG. 6, the ground tailings were washed with a water solution including hydrofluoric acid as in the first washing step (third washing step in

FIG. 6, that is washing step S4 in FIG. 1). The third washing step was performed for 10 minutes (conditioning time).

In the third washing step, a solution including hydrofluoric acid and sodium silicate (Na ₂ Si0 ₃ ) was used as the water solution including hydrofluoric acid. The amount of hydrofluoric acid in the third washing step was adjusted to a ratio of 800 g per ton of feed material.

In addition, the pH value of the slurry in the third washing step was adjusted using sulfuric acid. The pH value of the slurry when the third washing step started was 4.33 and the pH value of the slurry when the third washing step ended was 4.00.

[0074] Next, as illustrated in FIG. 6, the tailings after the third washing step were further concentrated by flotation again (third flotation concentration, that is flotation concentration step S5 in FIG. 1). By performing the third flotation concentration, the tin concentrate particles included in the tailings after the third flotation concentration were floated in the solution and concentrated, and then tin concentrate particles were recovered as third flotation concentrates (SnC). Specifically, the slurry including the washed tailings was stored in a tank for flotation concentration, a reagent was added thereto, and air was blown into the tank to generate bubbles. The third flotation concentration was performed for 5 minutes (conditioning time).

[0075] In the third flotation concentration, a collector and a frother were used as the reagents. AP 845# and sodium oleate were used as the collector, and the D.F. #250 was used as the frother. The AP 845# and sodium oleate as the collector were respectively added at a ratio of 300 g per ton of feed material, and two drops of the frother were added using a syringe (at a ratio of 100 g per ton of feed material). Fourth Time Treatment

[0076] Next, as illustrated in FIG. 6, the concentrated tailings (SnRT) from which the third flotation concentrates are separated by the third flotation concentration were washed with a water solution including hydrofluoric acid as in the first washing step (fourth washing step in FIG. 6, that is washing step S4 in FIG. 1). The fourth washing step was performed for 10 minutes (conditioning time). In the fourth washing step, a solution including hydrofluoric acid and sodium silicate (Na ₂ Si0 ₃ ) was used as the water solution including hydrofluoric acid. The amount of hydrofluoric acid in the fourth washing step was adjusted to a ratio of 500 g per ton of feed material.

In addition, the pH value of the slurry in the fourth washing step was adjusted using sulfuric acid. The pH value of the slurry when the third washing step started was 4.33 and the pH value of the slurry when the third washing step ended was 4.00.

[0077] Next, as illustrated in FIG. 6, the tailings after the fourth washing step were further concentrated by flotation again (fourth flotation concentration, that is flotation concentration step S5 in FIG. 1). By performing the fourth flotation concentration, the tin concentrate particles included in the tailings after the fourth flotation concentration were floated in the solution and concentrated, and then tin concentrate particles were recovered as fourth flotation concentrates (SnC). Specifically, the slurry including the washed tailings was stored in a tank for flotation concentration, a reagent was added thereto, and air was blown into the tank to generate bubbles. The fourth flotation concentration was performed for 5 minutes (conditioning time).

[0078] In the fourth flotation concentration, a collector and a frother were used as the reagents. AP 845# and sodium oleate were used as the collector, and the D.F. #250 was used as the frother. The AP 845# and sodium oleate as the collector were respectively added at a ratio of 200 g per ton of feed material, and one drop of the frother was added using a syringe (at a ratio of 50 g per ton of feed material).

[0079] On the other hand, as illustrated in FIG. 6, the fine particles (OF) having a particle size of 6 μηι or less including slime, which was classified using the cyclone separator, were concentrated by gravity. Thus, the fine particles were separated into tailings (OFT) and cleaner concentrates (OFC). Second Gravity Concentration Step S6

[0080] Next, as illustrated in FIG. 6, the first to fourth flotation concentrates (SnC) separated from the concentrated tailings in the first to fourth flotation concentration were concentrated by gravity (gravity concentration after flotation, that is second gravity concentration step S6 in FIG. 1). Thus, the flotation concentrates were separated into concentrated tailings (SnCT) and high-grade cleaner concentrates (SnCC) including tin mineral having a high concentration.

[0081 ] In the above-described recovery method for tin mineral of Example 1 , the mass of the cleaner concentrates or the tailings, the grade of Sn0 ₂ , the distribution rate of Sn0 ₂ , and the tin content, in each stage were investigated. The results are shown in Table 1. Here, the results of Table 1 are average values of values from two batches of 1 kg each.

[0082]

[Table 1]

[0083] The symbols shown in Table 1 correspond to symbols illustrated in FIGS. and 6. In addition, mass% in Table 1 is mass in which the mass of feed material is converted to 100%.

As shown in Table 1, it was found that the recovery rate of tin mineral is improved by performing the washing step S4 and the flotation concentration step S5 after the first gravity concentration step S3 is performed.

Example 2

[0084] FIG. 7 is a flowchart describing a recovery method for tin mineral of Example 2 for obtaining cleaner concentrates from tailings separated from tin ore. Hereinafter, Example 2 will be described in detail using FIGS. 1 and 7.

In the recovery method for tin mineral of Example 2, tailings separated from tin ore mined from the tailing dam of a mine in Bolivia were used as feed material. Here, 1 kg of each feed material was used. Desulfurization Step S2

[0085] As illustrated in FIG. 7, a slurry including tailings (feed material) was desulfurized by flotation. Specifically, the tailing slurry was stored in a tank for first desulfurization, a reagent was added thereto, and air was blown into the tank to generate bubbles.

In the flotation desulfurization, ACC #208 (product name) as a collector and D.F.

#250 (product name) as a frother were used as the reagents. Further, the collector was added at a ratio of 400 g per ton of feed material, and nine drops of the frother were added using a syringe (at a ratio of 450 g per ton of feed material).

First Gravity Concentration Step S3 [0086] In a first gravity Step S3, as illustrated in FIG. 7, first, tailings from which sulfides were removed by the flotation desulfurization were roughly concentrated by gravity. Thus, the desulfurized tailings were separated into rougher concentrates including coarse-grained tin concentrate particles and rougher tailings concentrated by gravity.

Then, as illustrated in FIG. 7, the rougher concentrates were cleanly

concentrated by gravity. Thus, the rougher concentrates were separated into cleaner tailings having low specific gravity and cleaner concentrates including tin mineral having high specific gravity and a high concentration.

Washing Step S4 and Flotation Concentration Step S5

First Time Treatment

[0087] Next, as illustrated in FIG. 7, rougher tailings from which rougher concentrates were separated by rough gravity concentration by gravity and cleaner tailings from which cleaner concentrates were separated by clean concentration by gravity were washed with a water solution including hydrofluoric acid (first washing step in FIG. 7, that is washing step S4 in FIG. 1). Specifically, a slurry obtained by mixing the tailings with the water solution including hydrofluoric acid was conditioned and the slurry was stored in a tank for washing and stirred. The first washing step was performed for 10 minutes

(conditioning time).

[0088] In the first washing step, the amount of hydrofluoric acid included in the water solution in the first washing step was adjusted to a ratio of 800 g per ton of feed material.

Next, as illustrated in FIG. 7, the tailings after the first washing step were concentrated by flotation (first flotation concentration, that is flotation concentration step S5 in FIG. 1). By performing the first flotation concentration, tin concentrate particles included in the tailings after the first washing step were floated in the solution and concentrated, and then tin concentrate particles were recovered as flotation concentrates. Specifically, the slurry including the washed tailings was stored in a tank for flotation concentration, a reagent was added thereto, and air was blown into the tank to generate bubbles. The first flotation concentration was performed for 5 minutes (conditioning time).

[0089] In the first flotation concentration, AP #845 (product name) as a collector and Dow #250 (product name, produced by The Dow Chemical Company) as a frother were used as the reagents. Further, the collector was added at a ratio of 300 g per ton of feed material, and two drops of the frother were added using a syringe (at a ratio of 100 g per ton of feed material).

Second Time Treatment

[0090] Next, as illustrated in FIG. 7, the tailings from which the flotation concentrates were separated by performing the first flotation concentration were washed with a water solution including hydrofluoric acid as in the first washing step (second washing step, that is washing step S4 in FIG. 1). The second washing step was performed for 10 minutes (conditioning time).

The amount of hydrofluoric acid contained in the water solution in the second washing step was adjusted to a ratio of 500 g per ton of feed material.

[0091] Next, as illustrated in FIG. 7, the tailings after the second washing step were concentrated by flotation again (second flotation concentration, that is flotation concentration step S5 in FIG. 1). By performing the second flotation concentration, the tin concentrate particles included in the tailings after the second washing step were floated in the solution and concentrated, and then tin concentrate particles were recovered as flotation concentrates. Specifically, the slurry including the washed tailings was stored in a tank for flotation concentration, a reagent was added thereto, and air was blown into the tank to generate bubbles. The second flotation concentration was performed for 5 minutes (conditioning time).

[0092] In the second flotation concentration, AP #845 (product name) as a collector and Dow #250 (product name) as a frother were used as the reagents. Further, the collector was added at a ratio of 200 g per ton of feed material, and one drop of the frother was added using a syringe (at a ratio of 50 g per ton of feed material).

As described above, as illustrated in FIG. 7, the flotation concentrates were separated from the tailings in the first and second flotation concentration.

Comparative Example

[0093] A recovery method for tin mineral was performed in the same manner as in Example 2 except that the washing step S4 was not performed.

[0094] In the above-described recovery methods for tin mineral of Example 2 and in the Comparative Example, the mass of the cleaner concentrates or the tailings (mass in which the mass of feed material was converted to 100%), the tin content (mass%), the recovery rate (%), and the flotation/concentration ratio in each stage were investigated. The results are shown in Table 2.

[0096] As shown in Table 2, the flotation/concentration ratio of Example 2 is higher than that of the Comparative Example. In addition, the recovery rate of the flotation concentrates in the first flotation concentration of Example 2 is higher than that of Comparative Example. The reason can be assumed to be that the reagent used in the flotation concentration step S5 easily adheres to tin concentrate particles by performing the washing step S4.

[0097] While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

EXPLANATION OF REFERENCES

[0098] SI : Classification/grinding step, S2: Desulfurization step, S3: Gravity

concentration step, S4: Washing step, S5: Flotation concentration step, S6: Gravity concentration step after flotation.

INDUSTRIAL APPLICABILITY

[0099] The present invention relates to a recovery method for tin mineral including adding hydrofluoric acid to tailings separated from tin ore, and flotation-concentrating the tailings after the adding of the hydrofluoric acid. According to the present invention, the tin mineral can be effectively recovered from the tailings separated from the tin ore.