A method of treating hard stone for a semi-autogenous iron ore grinding process

Abstract

The application provides a method for processing hard stone for a semi-autogenous grinding process of iron ore, comprising the following steps: (1) hard stone grading, (2) primary iron removal, (3) secondary iron removal, (4) thin layer spreading, and (5) tertiary magnetic separation and waste rejection. The method makes the slurry discharged from the semi-autogenous grinding machine pass through the primary magnetic drum iron removal, the secondary magnetic drum iron removal, the open circuit crushing of the cone crusher, the uniform spreading of the scraper device, and the tertiary magnetic drum magnetic separation and waste rejection in sequence, and recycles the broken steel balls, the ordinary iron pieces, the partial magnetite and the fine iron pieces, and the partial high-magnetic mineral, thereby avoiding the metal foreign matters from entering the cone crusher, reducing the failure risk of the cone crusher, reducing the equipment wear, improving the safety and the continuous stability of the system operation, fully crushing the hard stone, improving the dissociation degree of the useful mineral and the gangue mineral, being beneficial to improving the recovery rate of the magnetic mineral and the separation effect of the waste stone, and realizing the recycling of the broken steel balls and the valuable mineral and improving the comprehensive utilization rate of resources.

Description

Technical Field

[0001] This invention relates to a processing method, particularly a method for treating stubborn rocks in a semi-autogenous grinding process of iron ore, belonging to the field of mineral processing. Background Technology

[0002] With the large-scale development and utilization of low-grade iron ore resources, the semi-autogenous grinding (SAG) process has been widely applied in iron ore beneficiation due to its advantages such as simple process, large processing capacity, and wide adaptability to ore particle size range. After the raw ore is ground in a semi-autogenous grinding mill, the resulting slurry is usually classified by a vibrating screen. The slurry with qualified particle size under the screen enters subsequent separation processes such as magnetic separation and flotation, while the oversize is returned to the semi-autogenous grinding mill for further grinding, forming a closed-loop grinding process. However, in actual production, the oversize of the vibrating screen usually contains a large amount of coarse ore particles with a particle size of about 8-80 mm and high hardness. This part of the material is usually called "pebble". Because pebble particles are large and have poor grindability, they need to be returned to the semi-autogenous grinding mill for repeated grinding in traditional processes.

[0003] While the above-mentioned treatment methods can maintain the closed-circuit grinding process, as production operation time increases, the accumulated waste rock continuously circulates between the semi-autogenous mill and the vibrating screen. This can easily lead to a continuous increase in the circulating load of the semi-autogenous mill, with a large amount of waste rock occupying the effective volume of the mill, reducing the grinding efficiency after the new feed enters the mill, resulting in a decrease in system processing capacity, and in severe cases, even affecting the stable operation of the entire mineral processing production line. On the other hand, the circulating waste rock usually contains a high proportion of waste rock, surrounding rock, and low-grade intergrowths. These materials have low iron content, are difficult to liberate, and have poor grindability. Repeated grinding in the semi-autogenous mill not only fails to effectively improve the degree of liberation of valuable minerals, but also causes a large amount of ineffective energy consumption, increases the wear of grinding media and liners, increases production costs, and reduces the energy utilization efficiency of the entire mineral processing system.

[0004] To reduce the circulating load of ore, existing processes involve drawing the ore out for open-circuit crushing before returning it to the grinding system. However, the ore contains steel balls, forged steel, and other metallic foreign objects generated during the grinding process. If these are not effectively removed before entering crushing equipment such as cone crushers, over-iron accidents are highly likely to occur, leading to damage to critical components such as the main shaft, moving cone, and liners. This results in equipment downtime for maintenance, affecting production continuity and increasing equipment maintenance costs and safety risks.

[0005] Furthermore, most existing waste rock treatment processes are designed only for crushing and recycling waste rock, lacking the pre-identification and effective removal of low-grade waste rock. This makes it difficult to achieve synergistic optimization of multiple stages such as waste rock reduction, pre-disposal of waste rock, iron removal protection, and regrinding utilization. Consequently, the entire semi-autogenous grinding system still suffers from problems such as high circulating load, high energy consumption, high equipment operation risk, and low resource utilization. Therefore, it is necessary to improve the existing technology. Summary of the Invention

[0006] To address the problems of high circulating load of stubborn rocks in existing semi-autogenous grinding mills, high grinding energy consumption, easy iron overload failure of crushing equipment, and inability to pre-dispose of stubborn rocks, this invention provides a method for treating stubborn rocks in semi-autogenous grinding processes of iron ore.

[0007] This invention is achieved through the following technical solution: a method for treating stubborn rocks in a semi-autogenous iron ore grinding process, comprising the following steps: (1) Grading of stubborn rocks: The ore in the ore bin is transported to the semi-autogenous mill by the first and second conveyors and mixed with water for grinding and slurry treatment before being discharged. The discharged slurry is sent to a linear vibrating screen with a screen size of 8×16mm for screening. The undersize material is qualified slurry and is sent to the slurry pump pool; the oversize material is stubborn rocks with a particle size of 8 to 80mm. (2) Primary iron removal: When the ore obtained in step (1) is transported to the output end by the third conveyor, it passes through the primary magnetic drum with a magnetic field strength of 2000-3000 Gs, 360° rotation and circumferential linear velocity of 1.2-1.6 m / s set at the output end of the third conveyor. This causes more than 90% of the broken steel balls, ordinary iron parts and some magnetite mixed in the ore to be adsorbed on the primary magnetic drum by the magnetic field. After leaving the magnetic field area, it falls to the fourth conveyor under the action of gravity. Then it returns to the first conveyor through the fourth and fifth conveyors and enters the semi-autogenous mill together with the new feed to continue grinding, realizing the recycling of grinding media. The ore that is not adsorbed by the primary magnetic drum is transported by the sixth conveyor. (3) Secondary iron removal: When the stubborn rocks that were not attracted by the primary magnetic drum in step (2) are transported to the output end by the sixth conveyor, they pass through the secondary magnetic drum with a magnetic field strength of 3000-4000Gs, 360° rotation and circumferential linear velocity of 1.2-1.6m / s set at the output end of the sixth conveyor 7. The residual fine iron parts and some high magnetic ores mixed in the stubborn rocks are attracted to the secondary magnetic drum by the magnetic field. After leaving the magnetic field area, they fall to the seventh conveyor under the action of gravity. The stubborn rocks that were not attracted by the secondary magnetic drum 8 are sent to the cone crusher with a discharge port of 17-25mm and a driving power of 130-200kW for open-circuit crushing, so that the particle size of the crushed stubborn rocks is controlled below 40mm, and then sent to the seventh conveyor. (4) Thin layer spreading: The stubborn stones with a particle size of less than 40mm, as well as residual fine iron parts and some high magnetic ores fed into the seventh conveyor are evenly spread into a material layer with a thickness of less than 10cm by the scraper device set on the seventh conveyor. (5) Three-stage magnetic separation and waste disposal: When the material layer in step (4) enters the output end of the seventh conveyor, it passes through a three-stage magnetic drum with a magnetic field strength of 4000-7000Gs, 360° rotation, and a circumferential linear velocity of 1m / s set at the output end of the seventh conveyor. The magnetic material in the material layer is attracted to the three-stage magnetic drum by the magnetic field. After leaving the magnetic field area, it falls to the eighth conveyor under the action of gravity. It returns to the first conveyor through the eighth conveyor and enters the semi-autogenous mill together with the new ore to continue grinding. Waste rock and extremely poor intercalary ore with an iron grade of less than 14% are sent into the waste rock chute due to their weak magnetic properties and finally enter the waste rock bin.

[0008] Furthermore, the scraper device includes columns respectively located on both sides of the seventh conveyor, with a crossbeam fixedly connected between the upper ends of the two columns. The crossbeam is provided with two lifting adjustment mechanisms spaced apart along the width direction of the seventh conveyor. A scraper is fixedly connected between the lifting ends of the two lifting adjustment mechanisms so that the material on the conveyor can be spread evenly by the scraper, and the height of the spreading scraper can be adjusted by the lifting adjustment mechanism to adjust the thickness of the material layer.

[0009] Furthermore, the top edge of the scraper is connected to the lifting and adjusting mechanism, and the bottom edge of the scraper is provided with a serrated structure that is continuously distributed along the length direction, so as to use the serrated structure to evenly spread the material on the seventh conveyor, thereby making the material layer thickness consistent and improving the subsequent magnetic separation waste removal effect.

[0010] Furthermore, the lifting and adjusting mechanism includes a mounting bracket fixedly mounted on the crossbeam and a vertical screw rotatably mounted on the mounting bracket. A horizontal handwheel is fixedly connected to the upper end of the vertical screw. A nut threadedly connected to the vertical screw is provided inside the mounting bracket. The lower end of the nut is connected to the upper end of a connecting rod. The lower end of the connecting rod passes through a vertical guide hole on the crossbeam and is connected to a scraper. Rotating the horizontal handwheel drives the vertical screw to rotate, causing the nut, connecting rod, and scraper on the vertical screw to rise or fall, thereby adjusting the distance between the scraper and the seventh conveyor to adapt to different material thicknesses.

[0011] The present invention has the following advantages and effects: (1) The present invention sets up a primary iron removal process and a secondary iron removal process before the stubborn stone enters the cone crusher. Through the primary magnetic drum and the secondary magnetic drum respectively set at the output end of the third conveyor and the fifth conveyor, the broken steel balls, ordinary iron parts, some magnetite, residual fine iron parts and some high magnetic ores mixed in the stubborn stone are separated step by step, which effectively avoids a large number of metal foreign objects from entering the cone crusher. This not only reduces the risk of failure of the cone crusher caused by the entry of iron parts, but also reduces equipment wear and improves the safety and continuous stability of system operation.

[0012] (2) The present invention adopts a treatment method that combines two-stage iron removal and open-circuit crushing. After removing the metal foreign objects that affect the operation of the crushing equipment, the cone crusher is used to open-circuit crush the stubborn rock, so that the stubborn rock is fully crushed, which improves the degree of dissociation between useful minerals and gangue minerals, and creates good material conditions for subsequent magnetic separation and waste disposal, which is conducive to improving the recovery rate of magnetic minerals and the separation effect of waste rock.

[0013] (3) The present invention sets up a scraper spreading device before the three-stage magnetic separation. By spreading the material before entering the three-stage magnetic drum evenly, the thickness of the material layer on the conveyor belt is controlled to be less than 10cm, which reduces the magnetic field shielding phenomenon caused by material accumulation and improves the effect of the magnetic field on each layer of material. This effectively improves the separation efficiency of the three-stage magnetic drum for magnetic minerals and waste rock, and ensures a more stable waste disposal effect.

[0014] (4) This invention returns the crushed steel balls, ordinary iron parts and part of the magnetite recovered by the first-stage magnetic drum to the semi-autogenous mill via the fourth and first conveyors, and returns the magnetic minerals recovered by the third-stage magnetic drum to the semi-autogenous mill via the eighth conveyor. This achieves the recycling of grinding media and useful minerals, while timely discharge of waste rock and extremely lean intergrowths with an iron grade of less than 14% from the system. This effectively reduces the circulating load of the semi-autogenous mill system, improves the system processing efficiency, and increases the new feed processing capacity of the semi-autogenous mill system to more than 650t / h. While ensuring the recovery rate of useful minerals, it achieves the simultaneous improvement of system processing capacity and production efficiency. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a structural diagram of the process equipment of the present invention; Figure 3 This is a structural diagram of the scraper paving device of the present invention. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings. Example 1

[0017] like Figure 1As shown, the method for treating stubborn rocks in a semi-autogenous iron ore grinding process provided by the present invention includes the following steps: (1) Grading of stubborn rocks: The ore in the ore bin is conveyed to the semi-autogenous mill 3 by the first conveyor 1 and the second conveyor 2 and mixed with water for grinding and slurry treatment before being discharged. The discharged slurry is sent to the linear vibrating screen 4 with a screen size of 8×16mm for screening. The undersize material is qualified slurry and is sent to the slurry pump pool; the oversize material is stubborn rocks with a particle size of 8 to 80mm. (2) Primary iron removal: When the stubborn stone obtained in step (1) is transported to the output end by the third conveyor 5, it passes through the primary magnetic drum 6, which has a magnetic field strength of 2000-3000 Gs, rotates 360°, and has a circumferential linear velocity of 1.2-1.6 m / s at the output end of the third conveyor 5. This causes more than 90% of the broken steel balls, ordinary iron parts, and some magnetite mixed in the stubborn stone to be adsorbed on the primary magnetic drum by the magnetic field. After leaving the magnetic field area, it falls to the fourth conveyor 14 under the action of gravity. Then, it returns to the first conveyor 1 through the fourth conveyor 14 and the fifth conveyor 15, and enters the semi-autogenous mill together with the new feed ore to continue grinding, realizing the recycling of grinding media. The stubborn stone that is not adsorbed by the primary magnetic drum 6 is transported by the sixth conveyor 7. (3) Secondary iron removal: When the stubborn rocks that were not attracted by the primary magnetic drum in step (2) are conveyed to the output end by the sixth conveyor 7, they pass through the secondary magnetic drum 8, which has a magnetic field strength of 3000-4000Gs, rotates 360°, and has a circumferential linear velocity of 1.2-1.6m / s at the output end of the sixth conveyor 7. The residual fine iron pieces and some highly magnetic ores mixed in the stubborn rocks are attracted to the secondary magnetic drum 8 by the magnetic field. After leaving the magnetic field area, they fall to the seventh conveyor 13 under the action of gravity. The stubborn rocks that were not attracted by the secondary magnetic drum 8 are sent to the cone crusher 9 with a discharge port of 17-25mm and a driving power of 130-200kW for open-circuit crushing, so that the particle size of the crushed stubborn rocks is controlled below 40mm, and then sent to the seventh conveyor 13. (4) Thin layer spreading: The stubborn stones with a particle size of less than 40mm, as well as residual fine iron parts and some high magnetic ores fed into the seventh conveyor 13 are evenly spread into a material layer with a thickness of less than 10cm by the scraper device 12 set on the seventh conveyor 13. (5) Three-stage magnetic separation and waste disposal: When the material layer in step (4) enters the output end of the seventh conveyor 13, it passes through the three-stage magnetic drum 11 with a magnetic field strength of 4000~7000Gs, 360° rotation and circumferential linear velocity of 1m / s set at the output end of the seventh conveyor 13. The magnetic material in the material layer is attracted to the three-stage magnetic drum 11 by the magnetic field. After leaving the magnetic field area, it falls to the eighth conveyor 10 under the action of gravity. It returns to the first conveyor 1 through the eighth conveyor 10 and enters the semi-autogenous mill together with the new ore to continue grinding. Waste rock and extremely poor intercalary ore with an iron grade of less than 14% are sent into the waste rock chute due to their weak magnetic properties and finally enter the waste rock bin.

[0018] The scraper device includes columns 121 respectively located on both sides of the seventh conveyor 13. A crossbeam 122 is fixedly connected between the upper ends of the two columns 121. Two lifting adjustment mechanisms 123 are provided on the crossbeam 122, which are spaced apart along the width direction of the seventh conveyor 13. A scraper 124 is fixedly connected between the lifting ends of the two lifting adjustment mechanisms 123, so that the material on the conveyor can be spread evenly by the scraper 124, and the height of the spreading scraper can be adjusted by the lifting adjustment mechanism 123, thereby adjusting the thickness of the material layer.

[0019] The top edge of the scraper 124 is connected to the lifting and adjusting mechanism 123. The bottom edge of the scraper 124 is provided with a serrated structure that is continuously distributed along the length direction, so as to use the serrated structure to evenly spread the material on the seventh conveyor 13, thereby making the material layer thickness consistent and improving the subsequent magnetic separation waste removal effect.

[0020] The lifting and adjusting mechanism 123 includes a mounting bracket 127 fixedly mounted on the crossbeam 122 and a vertical screw 125 rotatably mounted on the mounting bracket 127. A horizontal handwheel 126 is fixedly connected to the upper end of the vertical screw 125. A nut 128 threadedly connected to the vertical screw 125 is provided inside the mounting bracket 127. The lower end of the nut 128 is connected to the upper end of a connecting rod. The lower end of the connecting rod passes through a vertical guide hole on the crossbeam 122 and is connected to a scraper 124. Rotating the horizontal handwheel 126 drives the vertical screw 125 to rotate, causing the nut 128, connecting rod, and scraper 124 on the vertical screw 125 to rise or fall, thereby adjusting the distance between the scraper 124 and the seventh conveyor 13 to adapt to the adjustment of material layers of different thicknesses.

[0021] In this embodiment 1, the particle size of the hard rock discharged from the semi-autogenous mill 3 is 8-80mm, and the hard rock processing capacity is more than 650t / h.

[0022] When operating with the above-mentioned process parameters of this invention, the primary magnetic drum 6 can recover more than 90% of broken steel balls, ordinary iron parts, and some magnetite. The secondary magnetic drum 8 further recovers residual fine iron parts and some highly magnetic ores. The tertiary magnetic drum 11 achieves effective separation of magnetic minerals and waste rock, ensuring the recovery rate of valuable minerals while allowing for the early disposal of waste rock. Long-term production operation has verified that this invention has a processing capacity of over 650 t / h, significantly reduces wear on the cone crusher, effectively improves the circulating load of the semi-autogenous grinding system, and makes the system operation more stable.

Claims

1. A method for treating stubborn rocks in a semi-autogenous iron ore grinding process, characterized in that... Includes the following steps: (1) Grading of stubborn rocks: The ore in the ore bin is transported to the semi-autogenous mill by the first and second conveyors and mixed with water for grinding and slurry treatment before being discharged. The discharged slurry is sent to a linear vibrating screen with a screen size of 8×16mm for screening. The undersize material is qualified slurry and is sent to the slurry pump pool; the oversize material is stubborn rocks with a particle size of 8 to 80mm. (2) Primary iron removal: When the ore obtained in step (1) is transported to the output end by the third conveyor, it passes through the primary magnetic drum with a magnetic field strength of 2000-3000 Gs, 360° rotation and circumferential linear velocity of 1.2-1.6 m / s set at the output end of the third conveyor. This causes more than 90% of the broken steel balls, ordinary iron parts and some magnetite mixed in the ore to be adsorbed on the primary magnetic drum by the magnetic field. After leaving the magnetic field area, it falls to the fourth conveyor under the action of gravity. Then it returns to the first conveyor through the fourth and fifth conveyors and enters the semi-autogenous mill together with the new feed to continue grinding, realizing the recycling of grinding media. The ore that is not adsorbed by the primary magnetic drum is transported by the sixth conveyor. (3) Secondary iron removal: When the stubborn rocks that were not attracted by the primary magnetic drum in step (2) are transported to the output end by the sixth conveyor, they pass through the secondary magnetic drum with a magnetic field strength of 3000-4000Gs, 360° rotation and circumferential linear velocity of 1.2-1.6m / s set at the output end of the sixth conveyor 7. The residual fine iron parts and some high magnetic ores mixed in the stubborn rocks are attracted to the secondary magnetic drum by the magnetic field. After leaving the magnetic field area, they fall to the seventh conveyor under the action of gravity. The stubborn rocks that were not attracted by the secondary magnetic drum 8 are sent to the cone crusher with a discharge port of 17-25mm and a driving power of 130-200kW for open-circuit crushing, so that the particle size of the crushed stubborn rocks is controlled below 40mm, and then sent to the seventh conveyor. (4) Thin layer spreading: The stubborn stones with a particle size of less than 40mm, as well as residual fine iron parts and some high magnetic ores fed into the seventh conveyor are evenly spread into a material layer with a thickness of less than 10cm by the scraper device set on the seventh conveyor. (5) Three-stage magnetic separation and waste disposal: When the material layer in step (4) enters the output end of the seventh conveyor, it passes through a three-stage magnetic drum with a magnetic field strength of 4000-7000Gs, 360° rotation, and a circumferential linear velocity of 1m / s set at the output end of the seventh conveyor. The magnetic material in the material layer is attracted to the three-stage magnetic drum by the magnetic field. After leaving the magnetic field area, it falls to the eighth conveyor under the action of gravity. It returns to the first conveyor through the eighth conveyor and enters the semi-autogenous mill together with the new ore to continue grinding. Waste rock and extremely poor intercalary ore with an iron grade of less than 14% are sent into the waste rock chute due to their weak magnetic properties and finally enter the waste rock bin.

2. The method for treating stubborn rocks in a semi-autogenous iron ore grinding process according to claim 1, characterized in that... In step (5), the scraper device includes columns respectively located on both sides of the seventh conveyor. A crossbeam is fixedly connected between the upper ends of the two columns. Two lifting adjustment mechanisms are provided on the crossbeam at intervals along the width direction of the seventh conveyor. A scraper is fixedly connected between the lifting ends of the two lifting adjustment mechanisms so that the material on the conveyor can be spread evenly by the scraper. The height of the spreading scraper can be adjusted by the lifting adjustment mechanism to adjust the thickness of the material layer.

3. The method for treating stubborn rocks in a semi-autogenous iron ore grinding process according to claim 2, characterized in that... The top edge of the scraper is connected to the lifting and adjusting mechanism, and the bottom edge of the scraper is provided with a serrated structure that is continuously distributed along the length direction, so as to use the serrated structure to evenly spread the material on the seventh conveyor, thereby making the material layer thickness consistent and improving the subsequent magnetic separation and waste removal effect.

4. The method for treating stubborn rocks in a semi-autogenous iron ore grinding process according to claim 2 or 3, characterized in that... The lifting and adjusting mechanism includes a mounting bracket fixed on the crossbeam and a vertical screw rotatably mounted on the mounting bracket. A horizontal handwheel is fixedly connected to the upper end of the vertical screw. A nut threadedly connected to the vertical screw is provided inside the mounting bracket. The lower end of the nut is connected to the upper end of a connecting rod. The lower end of the connecting rod passes through a vertical guide hole on the crossbeam and is connected to a scraper. Rotating the horizontal handwheel drives the vertical screw to rotate, causing the nut, connecting rod, and scraper on the vertical screw to rise or fall, thereby adjusting the distance between the scraper and the seventh conveyor to adapt to different material thicknesses.

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