Iron separation and impurity removal process in granulated blast-furnace slag grinding process

Abstract

The invention discloses an iron separation and impurity removal process in a granulated blast furnace slag grinding process, and belongs to the field of solid waste resource utilization. The process comprises the following steps that (1) coarse particle materials in a vertical mill serve as external circulation materials to enter a bucket elevator; (2) the materials enter an iron separation and impurity removal chute through a bucket elevator, an iron removal magnetic drum is arranged in the iron separation and impurity removal chute, the external circulation materials are separated through the iron removal magnetic drum, and iron-removed materials and iron-rich materials are obtained; (3) the iron-removed material is screened through a vibrating screen, undersize slag powder is returned to the vertical mill, and oversize low-activity hard particles are discharged; (4) slag powder carried in the iron-rich material is sucked back to the vertical mill under the action of negative pressure; and (5) carrying out magnetic separation on the iron-rich material from which the slag powder is removed, directly recycling iron particles subjected to magnetic separation, and returning the residual material to the iron separation and impurity removal chute for circular treatment. According to the method, the recovery rate and quality of the slag are improved, and the purity of iron particles can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of solid waste resource utilization, and in particular relates to an iron separation and impurity removal process in the process of external circulation of granulated blast furnace slag grinding. Background Art

[0002] Granulated blast furnace slag (slag for short) is a by-product produced during the smelting of pig iron, with a chemical composition similar to that of silicate cement clinker (mainly CaO, SiO2, MgO and Al2O3). Usually, 400 to 600 kg of slag will be produced for every ton of pig iron smelted. Due to the sudden cooling treatment during discharge, the slag is mostly an amorphous glassy structure, and at the same time stores a large amount of chemical energy and has good volcanic ash activity. After processing, it can be widely used in cement admixtures, concrete admixtures, high-performance building materials and other fields. It can not only generate good economic benefits, but also play an important role in promoting the implementation of the "dual carbon" strategy and the "two mountains" concept.

[0003] According to the requirements of GB / T 18046-2017 Granulated blast furnace slag powder for cement, mortar and concrete, the specific surface area of ​​slag should reach 300m 2 / kg or more can be used as an admixture. At present, vertical mill grinding is the most commonly used slag grinding process, which has the advantages of small footprint, simple process flow, and low energy consumption. In addition to the performance of the grinding equipment itself, the effective removal of iron particles in slag is the key to improving its comprehensive performance such as grinding efficiency and activity index. It is also an important measure to protect the grinding disc and roller of the mill. At the same time, it can achieve efficient recovery of iron materials in slag.

[0004] The iron removal process involved in the production process of slag powder is mainly divided into two methods: iron removal before grinding and iron removal after grinding. Iron removal before grinding is to remove iron particles in the slag by installing an iron removal device on the feed conveyor belt before the slag enters the mill. For example, the Chinese invention patent with publication number CN107469997A proposes a circulating slag crushing and iron selection device, which filters the crushed slag by setting a screen, and at the same time, the incompletely crushed slag is circulated and crushed by a spiral elevator to ensure the crushing quality of all slag. The patent realizes the collection and reuse of iron powder in the slag by setting a rotating drum and a cylindrical magnet. Iron removal after grinding is carried out after the slag is ground, including iron removal of the circulating material outside the mill and iron removal of the finished material of the powder separator. Common iron removal equipment includes belt self-unloading iron removers, pipeline self-unloading iron removers, and strong magnetic drum iron removers.

[0005] In general, the iron removal process before grinding can only remove large pieces of iron mixed in the slag raw materials, but it is greatly affected by the thickness of the material layer and the material conveying speed, and it cannot effectively remove the weakly magnetic iron mixed in and the iron particles wrapped in the slag. The main problem of the iron removal process after grinding is the difficulty of incomplete separation of iron particles and slag powder. The quality of the separated iron particles is low, and the loss of slag powder is high. The survey found that the external circulation iron removal operation after grinding is the key process affecting the iron removal of slag. The existing improvement plan still has problems such as complex process flow, low quality of iron particles and high loss rate of slag powder. Summary of the invention

[0006] Based on the above technical problems, the present invention proposes a process for iron separation and impurity removal in the process of granulated blast furnace slag grinding.

[0007] The technical solution adopted by the present invention is:

[0008] A process for iron separation and impurity removal in a granulated blast furnace slag grinding process comprises the following steps:

[0009] (1) After the slag raw materials are ground and dried in the vertical mill, the particles that reach the qualified fineness are selected by the powder concentrator connected to the vertical mill and collected as qualified products; the coarse particles in the vertical mill fall to the bottom of the vertical mill under the action of centrifugal force and enter the bucket elevator as external circulation materials;

[0010] (2) The bucket elevator is connected to the iron separation and impurity removal chute, and an iron removal magnetic drum is arranged in the iron separation and impurity removal chute. After the external circulating material is sorted by the iron removal magnetic drum, iron-removed material and iron-rich material are obtained;

[0011] (3) The iron-removing materials are screened through a vibrating screen, and the slag powder under the screen is returned to the vertical mill under negative pressure, while the low-activity hard particles on the screen are discharged;

[0012] (4) The slag powder entrained in the iron-rich material is sucked back into the vertical mill under the action of negative pressure;

[0013] (5) After removing the slag powder, the iron-rich material is subjected to magnetic separation. The iron particles after magnetic separation are directly recycled, and the remaining material is returned to the iron separation and impurity removal chute for recycling.

[0014] Preferably, the iron selection and impurity removal chute comprises a first pipeline, a second pipeline and a third pipeline, the first pipeline is arranged vertically, the second pipeline and the third pipeline are bifurcated and connected to the bottom end of the first pipeline, and the iron removal magnetic drum is arranged at the connection between the first pipeline, the second pipeline and the third pipeline;

[0015] The external circulation material enters the iron separation and impurity removal chute through the first pipeline, and the iron particles of the external circulation material are separated by the iron removal magnetic drum;

[0016] The iron-removed materials obtained by sorting fall into the second pipe, on which a vibrating screen is arranged, and a fourth pipe is connected to the second pipe and located above the vibrating screen; the second pipe is connected to the vertical mill, and after the iron-removed materials are screened by the vibrating screen, the slag powder under the screen returns to the vertical mill under the action of negative pressure, and the low-activity hard particles on the screen are discharged through the fourth pipe;

[0017] The end of the third pipeline is connected to the fifth pipeline and the sixth pipeline, the fifth pipeline is arranged vertically, the third pipeline and the sixth pipeline are bifurcated and connected to the top of the fifth pipeline, and the sixth pipeline is connected to the vertical mill;

[0018] The iron-rich material is transported through the third pipeline, and the slag powder entrained in the iron-rich material is sucked back to the vertical mill through the sixth pipeline by relying on the negative pressure in the vertical mill;

[0019] A conveyor belt is arranged below the fifth pipeline, and the iron-rich material after the slag powder is removed is transported to the magnetic separator for magnetic separation via the conveyor belt.

[0020] Preferably, the slag raw material is first subjected to the steps of grating impurity removal and pre-grinding iron removal before entering the vertical mill.

[0021] Preferably, a distribution baffle group for dispersing external circulating materials is arranged inside the first pipeline; the distribution baffle group includes a plurality of distribution baffles, which are arranged to extend obliquely downward, with upper and lower adjacent distribution baffles arranged in parallel and left and right adjacent distribution baffles arranged in a staggered manner.

[0022] Preferably, the magnetic field strength of the iron removal drum is 3000-5000 Gs, the magnetic wrap angle of the iron removal drum is 180°, and the drum linear speed is 150-200 m / min.

[0023] Preferably, a receiving plate is further provided in the second pipeline, the receiving plate is arranged obliquely and extends toward the middle area of ​​the vibrating screen, and the receiving plate is located above the fourth pipeline.

[0024] Preferably, the receiving plate is a corrugated chute structure, including a plurality of corrugated bodies, each of which includes a first strip slide and a second strip slide, and one side of the first strip slide and the second strip slide are connected; adjacent corrugated bodies are connected end to end to form a chute; the mesh size of the vibrating screen is 1 to 5 mm.

[0025] Preferably, the third pipeline, the fifth pipeline and the sixth pipeline together constitute a Y-shaped pipeline, and the bottom end of the fifth pipeline is sealed and connected to the conveyor belt through a rubber sheet; a valve for controlling the negative pressure in the Y-shaped pipeline is also provided on the sixth pipeline.

[0026] Preferably, the magnetic separator adopts an upward suction magnetic separator, and its magnetic rollers include a first-stage magnetic roller, a second-stage magnetic roller and a third-stage magnetic roller arranged from bottom to top; a blanking plate is arranged on one side of the upward suction magnetic separator, and the blanking plate is arranged at an angle, and a high-quality iron particle discharge port is arranged at the top of the blanking plate, and a discharge port for residual materials after magnetic separation is arranged at the bottom of the blanking plate.

[0027] Preferably, the magnetic induction intensity of the first-level magnetic roller is 8000-10000Gs, the magnetic induction intensity of the second-level magnetic roller is 5000-8000Gs, the magnetic induction intensity of the third-level magnetic roller is 3000-5000Gs, the vertical height difference between the first-level magnetic roller and the second-level magnetic roller is 5-10cm, and the vertical height difference between the second-level magnetic roller and the third-level magnetic roller is 5-10cm.

[0028] The beneficial technical effects of the present invention are as follows:

[0029] Aiming at the problems that the low efficiency of iron particle removal in the slag grinding process affects the service life of the mill, and the poor separation effect of slag powder and iron particles affects the value of iron particles and the activity of slag, the present invention takes the external circulation material of the vertical mill as the processing object, and designs an iron selection and impurity removal process in the external circulation process of granulated blast furnace slag grinding. The iron selection and impurity removal process includes the efficient separation of iron particles and slag powder, the purification of iron particles and the removal of low-activity hard particles. The main equipment is a bucket elevator, an iron selection and impurity removal chute, a vibrating screen and a three-stage magnetic separator. The process obtains high-quality iron particles from the external circulation material by a two-stage sorting method. In addition, the low-activity hard particles in the external circulation material are effectively removed by the sorting of the pipeline high-frequency vibrating screen, thereby improving the quality of the slag powder. The entire iron selection and impurity removal process adopts a cyclic and closed mode, and the slag powder is continuously circulated in the system until it is finally selected by the powder selector connected to the vertical mill. This design not only improves the recovery rate and quality of the slag, but also greatly improves the purity of the iron particles. The present invention also has the advantages of simple process flow, low equipment operation and maintenance cost, and effectively reduces the wear of the vertical mill grinding disc and grinding roller caused by iron particles, thereby increasing the service life of the vertical mill. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a process flow chart of iron separation and impurity removal in the process of granulated blast furnace slag grinding;

[0031] Figure 2 The schematic diagram of the overall structure principle of the device used in the iron separation and impurity removal process of the present invention;

[0032] Figure 3 This is a schematic diagram of the structural principle of the iron separation and impurity removal chute in the device used in the present invention;

[0033] Figure 4It is a structural schematic diagram of the material receiving plate in the device adopted by the present invention;

[0034] Figure 5 This is a schematic diagram of the connection between the fifth pipeline and the conveyor belt in the device adopted by the present invention.

[0035] Figure 6 It is a numerical flow chart of the iron selection and impurity removal process in the slag grinding process in a specific application example of the present invention.

[0036] In the figure: 1-vertical mill, 2-bucket elevator, 3-iron separation and impurity removal chute, 4-iron removal magnetic drum, 5-receiving plate, 6-vibrating screen, 7-conveyor belt, 8-rubber plate, 9-three-stage magnetic separator;

[0037] 301-first pipeline, 302-second pipeline, 303-third pipeline, 304-fourth pipeline, 305-fifth pipeline, 306-sixth pipeline, 307-valve; 3011-material baffle;

[0038] 501-corrugated body, 502-chute;

[0039] 901-first level magnetic roller, 902-second level magnetic roller, 903-third level magnetic roller. DETAILED DESCRIPTION

[0040] The present invention takes the slag in the external circulation process of the vertical mill as the treatment object, and designs an iron selection and impurity removal process in the external circulation process of granulated blast furnace slag powder grinding, which mainly includes the efficient separation of iron particles and slag powder, the purification of iron particles and the removal of low-activity hard particles. The main equipment is a bucket elevator, an iron selection and impurity removal chute, a high-frequency vibrating screen and a three-stage magnetic separator. Based on the process method proposed by the present invention, the iron particles and low-activity hard particles in the external circulation material of the vertical mill can be effectively separated, and at the same time, by adding a purification process, the quality of the iron particles is effectively improved and the loss rate of the slag is reduced.

[0041] like Figure 1 As shown, a process for iron separation and impurity removal in the process of granulated blast furnace slag grinding mainly includes the following steps:

[0042] (1) After the slag raw materials are ground and dried in the vertical mill, the particles that reach the qualified fineness are selected by the powder concentrator connected to the vertical mill and collected as qualified products; the coarse particles in the vertical mill fall to the bottom of the vertical mill under the action of centrifugal force and enter the bucket elevator as external circulation materials.

[0043] (2) The bucket elevator is connected to the iron selection and impurity removal chute, which includes a first pipeline, a second pipeline and a third pipeline. The first pipeline is arranged vertically, and the second pipeline and the third pipeline are forked and connected to the bottom end of the first pipeline. An iron removal magnetic drum is arranged at the connection between the first pipeline and the second pipeline and the third pipeline.

[0044] The external circulation material enters the iron separation and impurity removal chute through the first pipeline, and is sorted by the iron removal magnetic drum to obtain iron-removed material and iron-rich material.

[0045] (3) The iron-removed material falls into the second pipe, on which a vibrating screen is arranged, and a fourth pipe is connected to the second pipe and above the vibrating screen; the second pipe is connected to the vertical mill, and after the iron-removed material is screened by the vibrating screen, the slag powder under the screen returns to the vertical mill under the action of negative pressure, and the low-activity hard particles on the screen are discharged through the fourth pipe.

[0046] (4) The end of the third pipeline is connected to the fifth pipeline and the sixth pipeline, the fifth pipeline is arranged vertically, the third pipeline and the sixth pipeline are forked and connected to the top of the fifth pipeline, and the sixth pipeline is connected to the vertical mill.

[0047] The iron-rich material is transported through the third pipeline, and the slag powder entrained in the iron-rich material is sucked back to the vertical mill through the sixth pipeline by relying on the negative pressure in the vertical mill.

[0048] (5) A conveyor belt is arranged below the fifth pipeline. The iron-rich material after the slag powder is removed is transported to the magnetic separator for magnetic separation via the conveyor belt. The iron particles after magnetic separation are directly recycled, and the remaining material is returned to the iron separation and impurity removal chute for recycling.

[0049] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0050] like Figure 2 As shown, the slag raw material first passes through the grid to remove impurities and remove iron before grinding, and then enters the vertical mill 1 for grinding. After the slag raw material is ground and dried in the vertical mill 1, the particles that reach the qualified fineness are selected by the high-efficiency powder concentrator connected to the vertical mill and collected as qualified products. The coarse particles in the vertical mill 1 fall to the bottom of the vertical mill 1 under the action of centrifugal force and enter the bucket elevator 2 as external circulation materials.

[0051] (1) First-stage separation of iron particles in the external circulation material;

[0052] The bucket elevator 2 is connected to the iron separation and impurity removal chute 3, such as Figure 3 As shown, the iron selection and impurity removal chute 3 includes a first pipeline 301, a second pipeline 302 and a third pipeline 303, wherein the first pipeline 301 is arranged vertically, and the second pipeline 302 and the third pipeline 303 are bifurcated and connected to the bottom end of the first pipeline 301. The iron removal drum 4 or the magnetic drum type iron remover is arranged at the connection between the first pipeline 301, the second pipeline 302 and the third pipeline 303.

[0053] A distribution baffle group for dispersing external circulating materials is arranged inside the first pipe 301; the distribution baffle group includes a plurality of distribution baffles 3011, which are arranged to extend obliquely downward, with upper and lower adjacent distribution baffles arranged in parallel and left and right adjacent distribution baffles arranged in a staggered manner.

[0054] The external circulation material enters the iron separation and impurity removal chute 3 through the first pipeline 301. A distribution baffle 3011 is provided in the first pipeline 301 to disperse the external circulation material and make it more evenly distributed. An iron removal magnetic drum 4 is installed at the end of the first pipeline 301, and its main function is to perform a first-stage sorting of the iron particles of the external circulation material.

[0055] The magnetic field strength of the iron removal drum 4 is 3000-5000Gs, preferably 3500-4500Gs, which is used to sort out the iron particles in the external circulation material. The magnetic wrap angle of the iron removal drum 4 is 180°, and the drum linear speed is 150-200m / min, preferably 160-180m / min, so that the iron-rich material and the mixed ore powder are thrown away from the drum surface as much as possible by the centrifugal force. After the external circulation material is separated by the iron removal drum 4, the iron-removed material falls into the second pipe 302, and the iron-rich material falls into the third pipe 303.

[0056] (2) Primary recovery of slag powder and removal of low-activity hard particles in the external circulation material;

[0057] After the external circulation material is sorted by the iron removal drum 4, the iron-removed material falls into the second pipe 302. The second pipe 302 is connected to the fourth pipe 304, and a material receiving plate 5 is arranged above the connection, and a vibrating screen 6 is arranged below. The material receiving plate 5 is arranged in an inclined manner and extends toward the middle area of ​​the vibrating screen. The material receiving plate is located above the fourth pipe. Figure 4 As shown, the receiving plate is designed as a corrugated chute structure, including a plurality of corrugated bodies 501, each of which includes a first strip slide and a second strip slide, and one side of the first strip slide and the second strip slide are connected. Adjacent corrugated bodies are connected end to end to form a chute 502. This arrangement allows the iron-removing material in the second pipe 302 to fall evenly into the vibrating screen 6 through the receiving plate 5. The vibrating screen 6 can be vibrated at a high frequency, and the mesh size is 1 to 5 mm, preferably 2 to 3 mm. After the iron-removing material is screened by the vibrating screen 6, the slag powder falls into the lower part of the second pipe 302 through the screen and returns to the vertical mill 1 under the action of negative pressure, while the low-activity hard particles enter the fourth pipe 304 from the screen and are discharged from the external circulation of the grinding, thereby realizing the first-stage recovery of the slag powder in the external circulation material and the removal of the low-activity hard particles.

[0058] (3) Secondary recovery of slag powder in the external circulation material;

[0059] After the external circulation material is sorted by the iron removal drum 4, the iron-rich material falls into the Y-shaped pipe composed of the third pipe 303, the fifth pipe 305 and the sixth pipe 306. When the external circulation material passes through the iron removal drum 4, due to the large amount of slag powder passing through, the iron particles will carry some non-magnetic slag powder during iron selection, resulting in the loss of slag powder and reducing the quality of the iron particles. Therefore, the present invention designs a two-stage slag powder recovery process for iron-rich materials. The specific method is:

[0060] The third pipeline 303, the fifth pipeline 305 and the sixth pipeline 306 form a Y-shaped pipeline. The end of the third pipeline 303 is connected to the fifth pipeline 305 and the sixth pipeline 306. The fifth pipeline 305 is arranged vertically. The third pipeline 303 and the sixth pipeline 306 are forked and connected to the top of the fifth pipeline 305. The sixth pipeline 306 is connected to the vertical mill. The slag powder entrained in the iron-rich material is sucked back to the vertical mill 1 by relying on the negative pressure in the vertical mill 1. In order to ensure the formation of a stable negative pressure in the Y-shaped pipeline, the fifth pipeline 305 is connected to the conveyor belt 4 by a rubber plate 8, and a closed or semi-closed state is formed by relying on the accumulation of materials, such as Figure 5 As shown, the second stage recovery of slag powder in the iron-rich material is realized. A valve 307 is installed on the sixth pipeline 306. By changing the opening of the valve 307, the negative pressure in the Y-shaped pipeline is controlled to adjust the recovery rate of slag powder.

[0061] (4) Purification of iron-rich materials in the external circulation material and three-stage recovery of slag powder;

[0062] After the iron-rich material completes the second-stage recovery of slag powder in the Y-shaped pipeline, the remaining iron-rich material falls into the conveyor belt 7 through the fifth pipeline 305, and is then transported to the tertiary magnetic separator 9. The tertiary magnetic separator 9 is an upward suction magnetic separator, and its magnetic rollers are arranged from bottom to top in a primary, secondary and tertiary structure, the magnetic induction intensity of the first-stage magnetic roller 901 is 8000-10000Gs, the magnetic induction intensity of the second-stage magnetic roller 902 is 5000-8000Gs, and the magnetic induction intensity of the third-stage magnetic roller 903 is 3000-5000Gs, the vertical height difference between the first-stage magnetic roller 901 and the second-stage magnetic roller 902 is 5-10cm, and the vertical height difference between the second-stage magnetic roller 902 and the third-stage magnetic roller 903 is 5-10cm.

[0063] The design of three-stage magnetic separation and gradually decreasing magnetic roller induction intensity can effectively ensure the quality of iron particles, realize three-stage recovery of slag powder, and avoid dust problems when iron particles are discharged. The high-quality iron particles after the third-stage magnetic roller separation can be directly recycled, and the remaining materials are returned to the iron separation and impurity removal chute 3 through the bucket elevator 2 for recycling.

[0064] The process of the present invention obtains high-quality iron particles from the external circulation material by two-stage sorting. Through the sorting of the pipeline high-frequency vibrating screen, the low-activity hard particles in the external circulation material are effectively removed, and the quality of the slag powder is improved. The entire iron selection and impurity removal process adopts a circular and closed mode. The slag powder is continuously circulated in the system until it is finally selected by the powder selector connected to the vertical mill. This design not only improves the recovery rate and quality of the slag, but also greatly improves the purity of the iron particles.

[0065] The present invention will be further described below in conjunction with specific application examples.

[0066] 1. Physical and chemical properties of slag;

[0067] The main chemical composition of slag is shown in Table 1.

[0068] Table 1

[0069]

[0070] 2. Example of iron separation and impurity removal process in slag grinding;

[0071] The slag with a moisture content of 13.26% enters the vertical mill 1 at a feed rate of 50.00t / h for grinding. The slag is ground, dried and selected in the vertical mill 1. After the 50.00t slag is circulated externally, the final qualified 42.73t product will be selected and taken away by the powder selector in the vertical mill, while the coarse particles fall into the bucket elevator 2 below the vertical mill 1 due to the centrifugal force.

[0072] 3. One-stage separation of iron particles in the external circulation material;

[0073] The bucket elevator 2 is connected to the iron selection and impurity removal chute 3, which includes a magnetic drum iron remover, a high-frequency vibrating screen and a Y-shaped pipe. The external circulation material enters the iron selection and impurity removal chute 3 through the first pipe 301. An iron removal magnetic drum 4 is installed at the end of the first pipe 301, and its main function is to sort the iron particles of the external circulation material. After the external circulation material is sorted by the iron removal magnetic drum 4, 0.62t of iron-rich material and 41.00t of iron-removed material are obtained respectively. The magnetic field intensity of the iron removal magnetic drum 4 is 5000Gs. The magnetic wrap angle of the magnetic drum roller is 180°, and the linear speed of the magnetic drum roller is 180m / min, so that the iron-rich material and the mixed ore powder are thrown away from the drum surface as much as possible by centrifugal force. After the external circulation material is separated by the iron removal magnetic drum 4, the obtained 41.00t of iron-removed material falls into the second pipe 302, and 0.62t of iron-rich material falls into the third pipe 303.

[0074] 4. Primary recovery of slag powder and removal of low-activity hard particles in the external circulation material;

[0075] After the external circulation material is sorted by the iron removal drum 4, the obtained iron-free material falls into the vibrating screen 6 through the second pipe 302. The mesh size of the high-frequency vibrating screen is 3 mm. After the iron-free material is screened by the high-frequency vibrating screen, 40.47 tons of slag powder falls into the lower part of the second pipe 302 through the screen and returns to the vertical mill 1, while 0.53 tons of low-activity hard particles enter the fourth pipe 304 from the screen and are discharged from the external circulation of the grinding mill.

[0076] 5. Secondary recovery of slag powder in external circulation materials;

[0077] After the external circulating materials are sorted by the iron removal drum 4, the iron-rich materials fall into the Y-shaped pipeline. In the Y-shaped pipeline, the sixth pipeline 306 sucks the 0.14t slag powder entrained by the iron particles back to the vertical mill 1 through negative pressure.

[0078] 6. Purification of iron-rich materials in the external circulation materials and three-stage recovery of slag powder;

[0079] After the iron-rich material completes the second-stage recovery of slag powder in the Y-shaped pipeline, the remaining iron-rich material falls into the conveyor belt 7 through the fifth pipeline 305, and is then transported to the tertiary magnetic separator 9. The magnetic rollers of the tertiary magnetic separator 9 are arranged from bottom to top as a primary, secondary and tertiary structure, the magnetic induction intensity of the first-stage magnetic roller is 10000Gs, the magnetic induction intensity of the second-stage magnetic roller is 8000Gs, the magnetic induction intensity of the third-stage magnetic roller is 5000Gs, the vertical height difference between the first-stage magnetic roller and the second-stage magnetic roller is 8cm, and the vertical height difference between the second-stage magnetic roller and the third-stage magnetic roller is 8cm.

[0080] The iron-rich materials are magnetically separated in the three-stage magnetic separator 9. During the magnetic separation process, the iron-rich materials are separated by magnetic fields of different strengths. The iron grade of 0.38t of iron particles after the third-stage magnetic separation reaches 88.54%, while the 0.10t of materials that are not enough to be attracted by the field strength of the third stage and below are returned to the bucket elevator 2 through the channel for further circulation.

[0081] Finally, after the iron removal process, 50.00 tons of slag with a moisture content of 13.26% was dried, iron selected and impurity removed to obtain 42.73 tons of slag powder products and 0.38 tons of iron particles. 0.53 tons of low-activity hard particles that affect the activity of slag grinding and finished products were discharged from the slag grinding system.

Claims

1. A process for removing impurities from iron during the grinding of granulated blast furnace slag, characterized in that The following steps are involved: (1) After the slag raw materials are ground and dried in the vertical mill, the particles that reach the qualified fineness are selected by the powder concentrator connected to the vertical mill and collected as qualified products; the coarse particles in the vertical mill fall to the bottom of the vertical mill under the action of centrifugal force and enter the bucket elevator as external circulation materials; (2) The bucket elevator is connected to the iron separation and impurity removal chute, and an iron removal magnetic drum is arranged in the iron separation and impurity removal chute. After the external circulating material is sorted by the iron removal magnetic drum, iron-removed material and iron-rich material are obtained; (3) The iron-removing materials are screened through a vibrating screen, and the slag powder under the screen is returned to the vertical mill under negative pressure, while the low-activity hard particles on the screen are discharged; (4) The slag powder entrained in the iron-rich material is sucked back into the vertical mill under the action of negative pressure; (5) After removing the slag powder, the iron-rich material is subjected to magnetic separation. The iron particles after magnetic separation are directly recycled, and the remaining material is returned to the iron separation and impurity removal chute for recycling.

2. The iron separation and impurity removal process in the granulated blast furnace slag grinding process according to claim 1, characterized in that: The iron selection and impurity removal chute comprises a first pipeline, a second pipeline and a third pipeline, the first pipeline is arranged vertically, the second pipeline and the third pipeline are bifurcated and connected to the bottom end of the first pipeline, and the iron removal magnetic drum is arranged at the connection between the first pipeline, the second pipeline and the third pipeline; The external circulation material enters the iron separation and impurity removal chute through the first pipeline, and the iron particles of the external circulation material are separated by the iron removal magnetic drum; The iron-removed materials obtained by sorting fall into the second pipe, on which a vibrating screen is arranged, and a fourth pipe is connected to the second pipe and located above the vibrating screen; the second pipe is connected to the vertical mill, and after the iron-removed materials are screened by the vibrating screen, the slag powder under the screen returns to the vertical mill under the action of negative pressure, and the low-activity hard particles on the screen are discharged through the fourth pipe; The end of the third pipeline is connected to the fifth pipeline and the sixth pipeline, the fifth pipeline is arranged vertically, the third pipeline and the sixth pipeline are bifurcated and connected to the top of the fifth pipeline, and the sixth pipeline is connected to the vertical mill; The iron-rich material is transported through the third pipeline, and the slag powder entrained in the iron-rich material is sucked back to the vertical mill through the sixth pipeline by relying on the negative pressure in the vertical mill; A conveyor belt is arranged below the fifth pipeline, and the iron-rich material after the slag powder is removed is transported to the magnetic separator for magnetic separation via the conveyor belt.

3. The iron separation and impurity removal process in the granulated blast furnace slag grinding process according to claim 1, characterized in that: Before the slag raw materials enter the vertical mill, they first go through the grate to remove impurities and remove iron before grinding.

4. The iron separation and impurity removal process in the granulated blast furnace slag grinding process according to claim 2, characterized in that: A distribution baffle group for dispersing external circulating materials is arranged inside the first pipeline; the distribution baffle group includes a plurality of distribution baffles, which are arranged to extend obliquely downward, with upper and lower adjacent distribution baffles arranged in parallel and left and right adjacent distribution baffles arranged in a staggered manner.

5. The iron separation and impurity removal process in the granulated blast furnace slag grinding process according to claim 2, characterized in that: The magnetic field intensity of the iron removal drum is 3000-5000 Gs, the magnetic wrap angle of the iron removal drum is 180°, and the drum linear speed is 150-200 m / min.

6. The iron separation and impurity removal process in the granulated blast furnace slag grinding process according to claim 2, characterized in that: A material receiving plate is also arranged in the second pipeline. The material receiving plate is arranged obliquely and extends toward the middle area of ​​the vibrating screen. The material receiving plate is located above the fourth pipeline.

7. The process for removing impurities from iron during granulated blast furnace slag grinding according to claim 6, characterized in that: The receiving plate is a corrugated chute structure, including a plurality of corrugated bodies, each of which includes a first strip slide and a second strip slide, and one side of the first strip slide and the second strip slide are connected; adjacent corrugated bodies are connected end to end to form a chute; the mesh size of the vibrating screen is 1 to 5 mm.

8. The process for iron separation and impurity removal in the process of granulated blast furnace slag grinding according to claim 2, characterized in that: The third pipeline, the fifth pipeline and the sixth pipeline together form a Y-shaped pipeline, and the bottom end of the fifth pipeline is sealed and connected to the conveyor belt through a rubber sheet; a valve for controlling the negative pressure in the Y-shaped pipeline is also arranged on the sixth pipeline.

9. The iron separation and impurity removal process in the granulated blast furnace slag grinding process according to claim 2, characterized in that: The magnetic separator adopts an upward suction magnetic separator, and its magnetic rollers include a first-stage magnetic roller, a second-stage magnetic roller and a third-stage magnetic roller arranged from bottom to top; a blanking plate is arranged on one side of the upward suction magnetic separator, and the blanking plate is arranged at an angle. A high-quality iron particle discharge port is arranged at the top of the blanking plate, and a discharge port for residual materials after magnetic separation is arranged at the bottom of the blanking plate.

10. The process for iron separation and impurity removal in the process of granulated blast furnace slag grinding according to claim 9, characterized in that: The magnetic induction intensity of the first magnetic roller is 8000-10000Gs, the magnetic induction intensity of the second magnetic roller is 5000-8000Gs, the magnetic induction intensity of the third magnetic roller is 3000-5000Gs, the vertical height difference between the first magnetic roller and the second magnetic roller is 5-10cm, and the vertical height difference between the second magnetic roller and the third magnetic roller is 5-10cm.

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