Efficient tin ore grinding process

Abstract

According to the efficient tin ore grinding process, the pressure of a hydrocyclone is accurately controlled within the pressure range of 0.02-0.04 MPa, coarse particles are effectively separated and enter sand setting, it can be effectively ensured that the content of particles with the particle size of + 0.35 mm in overflow of the first-section hydrocyclone is strictly smaller than 5%, and the purpose that coarse particles do not run in the overflow is achieved; meanwhile, the ore feeding concentration is controlled to be 30%-40%, it is guaranteed that the flow state of ore pulp in the hydrocyclone is stable, the hydrocyclone can conduct grading operation more accurately, the sand setting concentration of the first-section hydrocyclone is reduced, it is guaranteed that ore entering a ball mill is basically + 1 mm in size fraction through efficient screening, and therefore the over-grinding phenomenon of the ball mill is reduced, and the quality of the ball mill is improved. According to the method, materials with the flotation feeding particle size of-0.074 mm are stabilized between 50% and 55%, the proportion of materials with the particle size of-0.01 mm is about 18%, and therefore the tin recovery rate is increased, and the economic benefits and the resource utilization rate of tin ore dressing are improved.

Description

Technical Field

[0001] The invention relates to the technical field of ore dressing, and in particular to a high-efficiency grinding process for tin ore. Background Art

[0002] Tin is an important nonferrous metal, which is widely used in many fields such as electronics, chemical industry, machinery, etc. The development and utilization of tin ore resources are of key significance to meet industrial needs and promote economic development. As an important link in the tin ore beneficiation process, the grinding process is to use the impact of steel balls, steel rods or gravel in mechanical equipment and the ore itself to further reduce the particle size of the mined tin ore until it is ground into powder. The purpose is to maximize the separation of useful minerals that make up the ore from other minerals, provide selected materials of suitable particle size for subsequent separation operations, and thus achieve efficient recovery and utilization of tin ore resources.

[0003] One of the most common grinding process combinations used by existing 2500t / d concentrators is the SAB grinding process, which is a combination of semi-autogenous grinding and ball milling. Specifically, the raw ore is firstly subjected to the first stage of coarse grinding by the semi-autogenous mill, and then the discharge of the semi-autogenous mill is passed through a cylindrical screen. The screened product is sequentially processed through a first-stage cyclone, a linear vibrating screen, a second-stage cyclone, a high-frequency vibrating screen, and a ball mill for fine grinding. Finally, the overflow of the first-stage cyclone, the overflow of the second-stage cyclone, and the screened product of the high-frequency vibrating screen are used as ore for flotation operations. However, this process has many defects:

[0004] On the one hand, after the material enters the first stage of the cyclone, the feed pressure is controlled at above 0.05MPa for a long time, making the sand concentration in the first stage as high as about 70%, resulting in low screening efficiency of the linear vibrating screen. The screening efficiency of -1mm is only 42.58%, and the screening efficiency of -0.5mm is only 48.14%. In addition, the products on the linear vibrating screen are seriously fine, and a part of the fine particles that should have fallen through the sieve holes did not pass through the sieve holes normally, but remained in the products on the screen. Among the products on the screen, -1mm accounts for 79.87%, and -0.5mm accounts for 53.76%. When these fine ores enter the ball mill for re-grinding, they are very likely to cause over-grinding, which deteriorates the grinding effect.

[0005] On the other hand, the existing second-stage cyclone has a sand concentration as high as 70%, which not only leads to low screening efficiency of the high-frequency vibrating screen and serious fine particles on the screen, with -0.3mm accounting for 47.49%, but also easily causes blockage or slippage of the high-frequency vibrating screen, seriously interfering with the normal operation of the entire grinding process and reducing production efficiency and mineral processing quality.

[0006] Based on the above-mentioned existing SAB grinding process, the grinding fineness is difficult to control. When the final grinding products enter the flotation operation, the material with a particle size of -0.074mm accounts for 63% of the total material, and the material with a particle size of -0.01mm accounts for 30% of the total material. The standard for flotation feeding is that the material with a particle size of -0.074mm accounts for 50-55%, and the material with a particle size of -0.01mm is as little as possible, that is, the actual over-grinding phenomenon is serious, which greatly affects the tin recovery index, resulting in a large fluctuation of the tin recovery rate at only about 40%, and also damaging the benefits of the enterprise. Summary of the invention

[0007] The main purpose of the present invention is to provide a high-efficiency tin ore grinding process, aiming to solve the technical problem that the grinding fineness of the existing tin ore grinding process is difficult to control, resulting in serious over-grinding phenomenon.

[0008] In order to achieve the above object, the first aspect of the present invention provides a tin ore efficient grinding process, comprising the following steps:

[0009] (1) Pre-screening: The raw ore is passed through a multi-layer vibrating screen, and the product on the screen is the raw ore with a particle size greater than 0.074 mm;

[0010] (2) SAG: The pre-screened oversize product is fed into a SAG mill for the first stage of grinding. The particle size composition of the SAG discharge is monitored to dynamically adjust the operating parameters of the SAG mill. The SAG discharge is screened through a cylindrical screen, and the oversize product is returned to the feed end of the SAG mill.

[0011] (3) One-stage hydrocyclone treatment: The undersize product of the semi-autogenous grinding mill is fed into a one-stage hydrocyclone for classification. The hydrocyclone pressure is controlled at 0.02-0.04 MPa, and the feed concentration is 30-40%. The first-stage hydrocyclone sand settling and the first-stage hydrocyclone overflow are obtained.

[0012] (4) Screening: The sand settling in the first stage cyclone enters the linear vibrating screen, and the product under the linear vibrating screen enters the high-frequency screen;

[0013] (5) Ball milling: The products on the linear vibrating screen and the high-frequency screen enter the ball mill for secondary grinding;

[0014] (6) Subsequent treatment: The ball mill discharge enters a first-stage cyclone for re-classification to obtain a re-classified cyclone overflow, wherein the multi-layer vibrating screen undersize product, the first-stage cyclone overflow, the re-classified cyclone overflow and the high-frequency screen undersize product are used as feed for flotation operation.

[0015] Furthermore, the multi-layer vibrating screen includes multiple layers of screen surfaces, and the diameter of the screen holes of each layer of the screen surface gradually decreases from top to bottom.

[0016] Furthermore, the multi-layer vibrating screen includes a first screen surface layer, a second screen surface layer and a third screen surface layer, the screen hole diameter of the first screen surface layer is 80 mm, the screen hole diameter of the second screen surface layer is 20 mm, and the screen hole diameter of the third screen surface layer is 0.074 mm.

[0017] Furthermore, the vibration frequency of the multi-layer vibrating screen ranges from 800 to 1200 times per minute, and the amplitude ranges from 3 to 6 mm.

[0018] Furthermore, the operating parameters in the semi-autogenous grinding step include rotation speed and filling rate, the rotation speed ranges from 15 to 20 r / min, and the filling rate ranges from 25% to 35%.

[0019] Furthermore, the rotation speed of the second-stage grinding is 15-20 r / min, and the filling rate of the second-stage grinding is in the range of 25%-35%.

[0020] Furthermore, the diameter of the sieve holes of the cylindrical sieve is 12 mm.

[0021] Furthermore, the diameter of the mesh of the linear vibrating screen is 1 mm, and the diameter of the mesh of the high-frequency screen is 0.35 mm.

[0022] Furthermore, the screen surface of the linear vibrating screen is made of polyurethane.

[0023] Furthermore, in the ball mill, steel balls with a diameter of 60 to 80 mm account for 30% to 40%, steel balls with a diameter of 40 to 60 mm account for 40% to 50%, and steel balls with a diameter of 20 to 40 mm account for 10% to 30%.

[0024] Beneficial effects:

[0025] The invention provides a high-efficiency tin ore grinding process, which eliminates the second-stage cyclone and optimizes the parameters of the first-stage cyclone. By accurately controlling the cyclone pressure within the pressure range of 0.02-0.04MPa, the cyclone can effectively separate the coarser particles and make them enter the sand settling, so as to avoid the coarse particles from entering the overflow too early and affecting the subsequent flotation operation, and can effectively ensure that the content of particles with a diameter of +0.35mm in the overflow of the first-stage cyclone is strictly less than 5%, so as to achieve the goal of overflow without coarse particles. At the same time, the feed concentration is controlled to be 30-40%, so as to ensure the stability of the slurry flow state in the cyclone, so that the cyclone can perform classification operations more accurately under a given pressure, further ensure the stability of the cyclone overflow, and significantly reduce the sand settling concentration of the first-stage cyclone, thereby creating favorable conditions for subsequent linear vibrating screen screening.

[0026] Due to the optimization of the above-mentioned cyclone parameters, after the sand from a first stage of the cyclone enters the linear vibrating screen, the screening efficiency of the linear vibrating screen (-1mm) reaches more than 91%, and the screening efficiency of the linear vibrating screen (-0.5mm) reaches more than 69%. Through efficient screening, it is ensured that the ore entering the ball mill is basically +1mm particle size ore, thereby reducing the over-grinding phenomenon of the ball mill, improving the working efficiency and grinding effect of the ball mill, and making the flotation feed material with a particle size of -0.074mm stable at 50-55%, and the material with a particle size of -0.01mm accounts for about 18%, thereby increasing the tin recovery rate by about 13%, significantly improving the economic benefits and resource utilization of tin ore dressing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a process flow chart of an embodiment of the present invention;

[0028] Figure 2 This is the process flow chart of Comparative Example 1.

[0029] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The experimental methods in the following examples of the present invention, where no specific conditions are specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0031] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0032] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to these processes, methods, products or equipment.

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0034] The present invention is further described in the following examples, but the examples are not intended to limit the scope of protection of the present invention.

[0035] An embodiment of the present invention provides a method comprising the following steps:

[0036] (1) Pre-screening: The raw ore is passed through a multi-layer vibrating screen, and the product on the screen is the raw ore with a particle size greater than 0.074 mm;

[0037] (2) SAG: The pre-screened oversize product is fed into a SAG mill for the first stage of grinding. The particle size composition of the SAG discharge is monitored to dynamically adjust the operating parameters of the SAG mill. The SAG discharge is screened through a cylindrical screen, and the oversize product is returned to the feed end of the SAG mill.

[0038] (3) One-stage hydrocyclone treatment: The undersize product of the semi-autogenous grinding mill is fed into a one-stage hydrocyclone for classification. The hydrocyclone pressure is controlled at 0.02-0.04 MPa, and the feed concentration is 30-40%. The first-stage hydrocyclone sand settling and the first-stage hydrocyclone overflow are obtained.

[0039] (4) Screening: The sand settling in the first stage cyclone enters the linear vibrating screen, and the product under the linear vibrating screen enters the high-frequency screen;

[0040] (5) Ball milling: The products on the linear vibrating screen and the high-frequency screen enter the ball mill for secondary grinding;

[0041] (6) Subsequent treatment: The ball mill discharge enters a first-stage cyclone for re-classification to obtain a re-classified cyclone overflow, wherein the multi-layer vibrating screen undersize product, the first-stage cyclone overflow, the re-classified cyclone overflow and the high-frequency screen undersize product are used as feed for flotation operation.

[0042] In the above embodiment, by accurately controlling the cyclone pressure within the pressure range of 0.02-0.04MPa, the cyclone can effectively separate the coarser particles and make them enter the sand settling, so as to avoid the coarse particles from entering the overflow too early and affecting the subsequent flotation operation, and can effectively ensure that the content of particles +0.35mm in the overflow of the first stage cyclone is strictly less than 5%, so as to achieve the goal of overflow without coarse particles; at the same time, the feed concentration is controlled to be 30-40%, so as to ensure the stability of the slurry flow in the cyclone, so that the cyclone can perform classification operations more accurately under a given pressure, further ensure the stability of the cyclone overflow, and significantly reduce the sand settling concentration of the first stage cyclone, thereby creating favorable conditions for subsequent linear vibrating screen screening.

[0043] Due to the optimization of the above-mentioned cyclone parameters, after the sand from a first stage of the cyclone enters the linear vibrating screen, the screening efficiency of the linear vibrating screen (-1mm) reaches more than 91.10%, and the screening efficiency of the linear vibrating screen (-0.5mm) reaches more than 69.56%. Through efficient screening, it is ensured that the ore entering the ball mill is basically +1mm particle size ore, thereby reducing the over-grinding phenomenon of the ball mill, improving the working efficiency and grinding effect of the ball mill, and making the flotation feed grinding particle size of -0.074 particle size material stable between 50 and 55%, and the -0.01mm particle size accounts for about 18%, thereby increasing the tin recovery rate by about 13%, significantly improving the economic benefits and resource utilization of tin ore dressing.

[0044] The high-efficiency tin ore grinding process of the present invention breaks through the limitation of the traditional process of simply pursuing "improving the classification efficiency of the cyclone", and innovatively clarifies the dual working purposes of "overflow without coarseness and reducing the concentration of sedimentation" of a cyclone.

[0045] In one embodiment, the multi-layer vibrating screen includes multiple layers of screen surfaces, and the diameter of the screen holes of each layer of the screen surface gradually decreases from top to bottom. The multi-layer vibrating screen includes two or more layers of screen surfaces, and the diameter of the screen holes of the bottom layer is 0.074 mm. Fine-grained ore smaller than 0.074 mm is screened out in advance to avoid over-grinding in the subsequent semi-autogenous grinding and ball milling process; and the size of the screen holes of the remaining layers of the screen surface increases from bottom to top, and the raw ore is pre-divided into different particle sizes for subsequent processing, thereby significantly improving the efficiency of semi-autogenous grinding, while laying a good foundation for subsequent separation operations and effectively reducing the risk of over-grinding.

[0046] In the above embodiment, the multi-layer vibrating screen includes a first screen surface, a second screen surface and a third screen surface, wherein the diameter of the screen hole of the first screen surface is 80 mm, the diameter of the screen hole of the second screen surface is 20 mm, and the diameter of the screen hole of the third screen surface is 0.074 mm. The first screen surface is used to screen out larger-sized particulate matter in the raw ore, which may contain a large amount of gangue minerals or tin ore that has reached the monomer dissociation level and does not need to be further ground; the second screen surface separates the ore with a particle size between 20 mm and 80 mm, so as to perform differentiated treatment on ores of different particle sizes and optimize the material distribution of the entire grinding process; the third screen surface can separate the fine-grained ore in the raw ore, and screen out the fine-grained ore less than 0.074 mm in advance, which can avoid excessive grinding in the subsequent semi-autogenous grinding and ball milling process, reduce over-grinding, and thus improve the overall recovery efficiency of tin ore.

[0047] In one embodiment, the vibration frequency of the multi-layer vibrating screen is in the range of 800 to 1200 times / minute, and the amplitude is in the range of 3 to 6 mm. A vibration frequency that is too low or an amplitude that is too small may result in insufficient movement of the ore on the screen surface, affecting the screening efficiency; while a vibration frequency that is too high or an amplitude that is too large may cause the ore to jump too violently on the screen surface, causing part of the ore to pass through the screen hole, also reducing the screening accuracy. By setting the vibration frequency to 800 to 1200 times / minute and the amplitude range to 3 to 6 mm, the efficiency and accuracy of the pre-screening are guaranteed.

[0048] In one embodiment, the operating parameters in the step of semi-autogenous grinding include a rotation speed and a filling rate, the rotation speed ranges from 15 to 20 r / min, and the filling rate ranges from 25% to 35%. By monitoring the particle size composition of the semi-autogenous grinding discharge during the semi-autogenous grinding process, the operating parameters of the semi-autogenous mill are dynamically adjusted to make the rotation speed range between 15 and 20 r / min, so that larger particles of ore can have enough time and space to grind in the semi-autogenous mill, and the filling rate ranges from 25% to 35%, so that there is a certain probability of collision between the steel ball and the ore and the fluidity of the material is moderate, thereby ensuring the grinding effect.

[0049] In one embodiment, the rotation speed of the second-stage grinding is 15-20 r / min, and the filling rate of the second-stage grinding is in the range of 25%-35%. Similarly, the rotation speed and filling rate of the ball mill used in the second-stage grinding ensure the grinding effect.

[0050] In one embodiment, the diameter of the mesh of the cylindrical screen is 12 mm.

[0051] In one embodiment, the diameter of the mesh of the linear vibrating screen is 1 mm, and the diameter of the mesh of the high-frequency screen is 0.35 mm, which can avoid the problems of clogging and slipping that often occur in the 0.2 mm high-frequency screen in the prior art.

[0052] In one embodiment, the screen surface of the linear vibrating screen is made of polyurethane material. The screen surface of polyurethane material has good wear resistance and elasticity, can adapt to long-term high-load screening working environment, reduce the wear and deformation of the screen, and extend the service life of the screen.

[0053] In one embodiment, the steel balls with a diameter of 60 to 80 mm account for 30% to 40% of the ball mill, the steel balls with a diameter of 40 to 60 mm account for 40% to 50%, and the steel balls with a diameter of 20 to 40 mm account for 10% to 30%. The adjustment of the steel ball ratio based on the particle size of the tin ore can maximize the grinding capacity of the ball mill. The large steel balls firstly perform strong impact crushing on the larger particles of ore during the rotation of the ball mill. As the particle size of the ore gradually decreases, the medium steel balls and the small steel balls play a role in turn, further grinding and refining the ore, so that the uniformity of the particle size of the ball-milled product is significantly improved, over-grinding and under-grinding are reduced, and materials with suitable particle size and good uniformity are provided for subsequent flotation operations, which is conducive to improving the flotation recovery rate and concentrate grade of the tin ore.

[0054] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0055] Embodiment 1:

[0056] Taking a silver-tin polymetallic mine in Yunnan as the research object, a high-efficiency grinding process for tin ore is proposed. Figure 1 , the specific steps are as follows:

[0057] (1) Pre-screening: A certain amount of tin ore is selected and transported to a multi-layer vibrating screen, the vibration frequency of which is set to 800 times / minute and the amplitude is 3mm. The ore first passes through the first layer of screen (screen hole 80mm), which removes and collects about 20% of large-particle impurities and dissociated large-particle ore; then, it passes through the second layer of screen (screen hole 20mm), and about 30% of medium-particle ore is separated; finally, it passes through the third layer of screen (screen hole 0.074mm), and about 15% of fine-particle ore is screened out;

[0058] (2) Semi-autogenous grinding: The pre-screened raw ore is fed into a semi-autogenous mill. The speed of the semi-autogenous mill is set to 15r / min, and the filling rate is 25%. During the semi-autogenous grinding process, the particle size composition of the ore discharge is monitored every 30 minutes. Through the detection of the laser particle size analyzer, it was found that the proportion of -0.074mm particles in the semi-autogenous ore discharge was about 25% of the total material, of which -0.025mm accounted for about 20% of the total material. According to the monitoring results, the mill speed was appropriately increased to 16r / min to further optimize the ore discharge particle size. After adjustment, the proportion of -0.074mm particles in the semi-autogenous ore discharge was stabilized at about 28%, which met the preliminary requirements for material particle size in subsequent processes;

[0059] (3) One-stage cyclone treatment: The ore discharged from the semi-autogenous mill passes through a 12 mm cylindrical screen, and the product on the screen is returned to the feed end of the semi-autogenous mill through a belt conveyor for re-grinding; the product under the screen enters a first-stage cyclone for classification. The feed concentration of the cyclone is monitored and controlled at 30% by an online concentration meter. The cyclone pressure is set to 0.02 MPa. At this time, the content of particles +0.35 mm in the overflow of the first stage is 3%, and the concentration of the first stage sediment is 50%. The particle size analysis of the first stage sediment shows that its particle size distribution is relatively uniform, which is suitable for entering the linear vibrating screen for screening treatment;

[0060] (4) Screening: The sand from a cyclone is sent to a 1mm linear vibrating screen, which uses a polyurethane screen with an aperture error of ±0.03mm. After screening, the screening efficiency of the linear vibrating screen (-1mm) reaches 92%, and the screening efficiency (-0.5mm) reaches 70%. The particle size of the product on the linear vibrating screen is tested, and it is found that the +1mm particle size accounts for about 95%, and the product under the screen enters a 0.35mm high-frequency screen; the screening efficiency of the high-frequency screen (-0.35mm) reaches 84%. The particle size of the product on the high-frequency vibrating screen is tested, and it is found that the +0.35mm particle size accounts for about 87%,

[0061] (5) Ball milling: The products on the linear vibrating screen and the high-frequency screen enter the ball mill for secondary grinding. The steel balls in the ball mill are filled with steel balls with a diameter of 60-80 mm accounting for 30%, steel balls with a diameter of 40-60 mm accounting for 40%, and steel balls with a diameter of 20-40 mm accounting for 30%. During the ball milling process, the filling rate of the ball mill is controlled to be 30% and the rotation speed is 18r / min;

[0062] (6) Subsequent treatment: The ball mill discharge enters the first hydrocyclone for re-classification, and the multi-layer vibrating screen under-screen products, the first hydrocyclone overflow, the re-classified hydrocyclone overflow and the high-frequency screen under-screen products are used as the feed for flotation operation. According to the test, the flotation feed grinding fineness is 50%, the -0.01mm particle size accounts for 17%, and the tin recovery rate is increased by 12%.

[0063] Embodiment 2:

[0064] Taking a cassiterite polymetallic sulfide ore in Guangxi as the research object, a high-efficiency grinding process for tin ore is proposed. The specific steps are as follows:

[0065] (1) Pre-screening: A certain amount of tin ore is selected and transported to a multi-layer vibrating screen, the vibration frequency of which is set to 1000 times / minute and the amplitude is 4mm. The ore first passes through the first layer of screen (screen hole 80mm), which removes and collects about 22% of large-particle impurities and dissociated large-particle ore; then, it passes through the second layer of screen (screen hole 20mm), and about 28% of medium-particle ore is separated; finally, it passes through the third layer of screen (screen hole 0.074mm), and about 13% of fine-particle ore is screened out;

[0066] (2) Semi-autogenous grinding: The pre-screened raw ore is fed into the semi-autogenous grinding machine. The initial mill speed of the semi-autogenous grinding machine is set to 18r / min, and the filling rate is 30%. During the semi-autogenous grinding process, the particle size composition of the ore discharge is monitored every 25 minutes. Through the detection of the laser particle size analyzer, it was found that the proportion of -0.074mm particles in the semi-autogenous grinding ore was about 26% of the total material, of which -0.025mm accounted for about 22% of the total material. According to the particle size in the monitoring results, the filling rate was fine-tuned to 28%. After adjustment, the proportion of -0.074mm particles was stabilized at about 30%, ensuring that the particle size of the semi-autogenous grinding ore discharge met the subsequent process requirements;

[0067] (3) One-stage cyclone treatment: The SAG mill discharge passes through a 12 mm cylindrical screen, and the screened product is returned to the SAG mill feed end through a belt conveyor for re-grinding; the screened product enters a first-stage cyclone for classification. The cyclone feed concentration is monitored and controlled at 35% by an online concentration meter. The cyclone pressure is set to 0.03 MPa. At this time, the content of particles +0.35 mm in the first-stage overflow is 2%, and the first-stage sediment concentration is 45%. The first-stage sediment is analyzed for particle size, and the results show that its particle size distribution is relatively uniform, which is suitable for entering the linear vibrating screen for screening treatment;

[0068] (4) Screening: The sand from a cyclone is sent to a 1mm linear vibrating screen, which uses a polyurethane screen with an aperture error of ±0.04mm. After screening, the screening efficiency of the linear vibrating screen (-1mm) reaches 93%, and the screening efficiency (-0.5mm) reaches 72%. The particle size of the product on the linear vibrating screen was tested, and it was found that the +1mm particle size accounted for about 96%, and the product under the screen entered a 0.35mm high-frequency screen; the screening efficiency of the high-frequency screen (-0.35mm) reached 85%. The particle size of the product on the high-frequency vibrating screen was tested, and it was found that the +0.35mm particle size accounted for about 88%,

[0069] (5) Ball milling: The products on the linear vibrating screen and the high-frequency screen enter the ball mill for secondary grinding. The steel balls in the ball mill are filled with steel balls with a diameter of 60-80 mm accounting for 35%, steel balls with a diameter of 40-60 mm accounting for 45%, and steel balls with a diameter of 20-40 mm accounting for 20%. During the ball milling process, the filling rate of the ball mill is controlled to be 32% and the rotation speed is 19r / min;

[0070] (6) Subsequent treatment: The ball mill discharge enters the first hydrocyclone for reclassification, and the multi-layer vibrating screen undersize product, the first hydrocyclone overflow, the reclassified hydrocyclone overflow and the high-frequency screen undersize product are used as the feed for flotation operation. According to the test, the flotation feed mill -0.074mm particle size accounted for 53%, the -0.01mm particle size accounted for 19%, and the tin recovery rate was increased by 14% compared with the comparative example 1.

[0071] Embodiment 3:

[0072] Taking a silver-tin polymetallic mine in Hunan as the research object, a high-efficiency grinding process for tin ore is proposed. The specific steps are as follows:

[0073] (1) Pre-screening: A certain amount of tin ore is selected and transported to a multi-layer vibrating screen, the vibration frequency of which is set to 1200 times / minute and the amplitude is 6mm. The ore first passes through the first layer of screen (screen hole 80mm), which removes and collects about 25% of large-particle impurities and dissociated large-particle ore; then, it passes through the second layer of screen (screen hole 20mm), and about 32% of medium-particle ore is separated; finally, it passes through the third layer of screen (screen hole 0.074mm), and about 18% of fine-particle ore is screened out;

[0074] (2) Semi-autogenous grinding: The pre-screened raw ore is fed into the semi-autogenous grinding machine. The initial mill speed of the semi-autogenous grinding machine is set to 20r / min, and the filling rate is 35%. During the semi-autogenous grinding process, the particle size composition of the ore discharge is monitored every 20 minutes. Through the detection of the laser particle size analyzer, it was found that the -0.074mm particles in the semi-autogenous grinding ore accounted for about 28% of the total material, of which -0.025mm accounted for about 25% of the total material. According to the particle size in the monitoring results, the speed was appropriately reduced to 19r / min. After adjustment, the proportion of -0.074mm particles was stabilized at about 32%, ensuring that the particle size of the semi-autogenous grinding ore discharge met the subsequent process requirements;

[0075] (3) One-stage cyclone treatment: The SAG mill discharge passes through a 12 mm cylindrical screen, and the screened product is returned to the SAG mill feed end through a belt conveyor for re-grinding; the screened product enters a first-stage cyclone for classification. The cyclone feed concentration is monitored and controlled at 40% by an online concentration meter. The cyclone pressure is set to 0.04 MPa. At this time, the content of particles +0.35 mm in the first-stage overflow is 4%, and the first-stage sediment concentration is 40%. The particle size analysis of the first-stage sediment shows that its particle size distribution is relatively uniform, which is suitable for entering the linear vibrating screen for screening treatment;

[0076] (4) Screening: The sand from a cyclone is sent to a 1mm linear vibrating screen, which uses a polyurethane screen with an aperture error of ±0.05mm. After screening, the screening efficiency of the linear vibrating screen (-1mm) reaches 91%, and the screening efficiency (-0.5mm) reaches 69%. The particle size of the product on the linear vibrating screen was tested, and it was found that the +1mm particle size accounted for about 94%, and the product under the screen entered a 0.35mm high-frequency screen; the screening efficiency of the high-frequency screen (-0.35mm) reached 82%. The particle size of the product on the high-frequency vibrating screen was tested, and it was found that the +0.35mm particle size accounted for about 84%,

[0077] (5) Ball milling: The products on the linear vibrating screen and the high-frequency screen enter the ball mill for secondary grinding. The steel balls in the ball mill are filled with steel balls with a diameter of 60-80 mm accounting for 40%, steel balls with a diameter of 40-60 mm accounting for 50%, and steel balls with a diameter of 20-40 mm accounting for 10%. During the ball milling process, the filling rate of the ball mill is controlled to be 35% and the rotation speed is 20r / min;

[0078] (6) Subsequent treatment: The ball mill discharge enters the first hydrocyclone for reclassification, and the multi-layer vibrating screen undersize, the first hydrocyclone overflow, the reclassified hydrocyclone overflow and the high-frequency screen undersize are used as the feed for flotation operation. According to the test, the flotation feed ore with a grinding particle size of -0.074mm accounts for 55% of the total material, and the -0.01mm particle size accounts for 18%. The tin recovery rate is increased by 13% compared with Comparative Example 1.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the existing SAB grinding process is adopted. Figure 2 .

[0081] When the grinding products entered the flotation operation, the material with a particle size of -0.074mm accounted for 63% of the total material, the -0.01mm particle size accounted for 30.27%, and the tin recovery rate was 40.51%.

[0082] Comparative Example 2

[0083] Different from Example 1, the feed pressure of the first stage cyclone is set to 0.05 MPa, and the feed concentration is controlled to be 50%.

[0084] When the grinding products entered the flotation operation, the material with a particle size of -0.074mm accounted for 64.84% of the total material, the -0.01mm particle size accounted for 28.67%, and the tin recovery rate was 41.38%.

[0085] Comparative Example 3

[0086] Different from Example 1, there is no pre-screening step, and the tin ore is directly fed into the semi-autogenous mill. When the ground products enter the flotation operation, the material with a particle size of -0.074 mm accounts for 62.12% of the total material, the -0.01 mm particle size accounts for 32.51%, and the tin recovery rate is 38.92%.

[0087] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A tin ore efficient grinding process, characterized in that: The following steps are involved: (1) Pre-screening: The raw ore is passed through a multi-layer vibrating screen, and the product on the screen is the raw ore with a particle size greater than 0.074 mm; (2) SAG: The pre-screened oversize product is fed into a SAG mill for the first stage of grinding. The particle size composition of the SAG discharge is monitored to dynamically adjust the operating parameters of the SAG mill. The SAG discharge is screened through a cylindrical screen, and the oversize product is returned to the feed end of the SAG mill. (3) One-stage hydrocyclone treatment: The undersize product of the semi-autogenous grinding mill is fed into a one-stage hydrocyclone for classification. The hydrocyclone pressure is controlled at 0.02-0.04 MPa, and the feed concentration is 30-40%. The first-stage hydrocyclone sand settling and the first-stage hydrocyclone overflow are obtained. (4) Screening: The sand settling in the first stage cyclone enters the linear vibrating screen, and the product under the linear vibrating screen enters the high-frequency screen; (5) Ball milling: The products on the linear vibrating screen and the high-frequency screen enter the ball mill for secondary grinding; (6) Subsequent treatment: The ball mill discharge enters a first-stage cyclone for re-classification to obtain a re-classified cyclone overflow, wherein the multi-layer vibrating screen undersize product, the first-stage cyclone overflow, the re-classified cyclone overflow and the high-frequency screen undersize product are used as feed for flotation operation.

2. The high-efficiency grinding process for tin ore according to claim 1, characterized in that: The multi-layer vibrating screen comprises multiple layers of screen surfaces, and the diameter of the screen holes of each layer of the screen surface gradually decreases from top to bottom.

3. The high-efficiency grinding process for tin ore according to claim 2, characterized in that: The multi-layer vibrating screen includes a first screen surface layer, a second screen surface layer and a third screen surface layer. The diameter of the screen holes of the first screen surface layer is 80 mm, the diameter of the screen holes of the second screen surface layer is 20 mm, and the diameter of the screen holes of the third screen surface layer is 0.074 mm.

4. According to any one of claims 1 to 3, the efficient grinding process for tin ore, the vibration frequency range of the multi-layer vibrating screen is 800 to 1200 times / minute, and the amplitude range is 3 to 6 mm.

5. The high-efficiency grinding process for tin ore according to claim 1, characterized in that: The operating parameters in the semi-autogenous grinding step include rotation speed and filling rate. The rotation speed ranges from 15 to 20 r / min, and the filling rate ranges from 25% to 35%.

6. The high-efficiency grinding process for tin ore according to claim 1, characterized in that: The rotation speed of the second-stage grinding is 15-20 r / min, and the filling rate range of the second-stage grinding is 25%-35%.

7. The high-efficiency grinding process for tin ore according to claim 1, characterized in that: The diameter of the sieve hole of the cylindrical sieve is 12 mm.

8. The high-efficiency grinding process for tin ore according to claim 1, characterized in that: The diameter of the mesh of the linear vibrating screen is 1 mm, and the diameter of the mesh of the high-frequency screen is 0.35 mm.

9. The high-efficiency grinding process for tin ore according to claim 1 or 8, characterized in that: The screen surface of the linear vibrating screen is made of polyurethane.

10. The high-efficiency grinding process for tin ore according to claim 1, characterized in that: In the ball mill, steel balls with a diameter of 60 to 80 mm account for 30% to 40%, steel balls with a diameter of 40 to 60 mm account for 40% to 50%, and steel balls with a diameter of 20 to 40 mm account for 10% to 30%.

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