A microwave roasting equipment and process flow for iron extraction from red mud

Abstract

This invention provides a microwave roasting equipment and process flow for iron extraction from red mud, relating to the field of red mud iron extraction technology. It includes a fixed base frame with a rotary kiln mounted on top. The rotary kiln comprises a furnace shell, furnace tubes, a discharge end pipe, a feeding assembly, a preheating assembly, a retention assembly, and a drive assembly. By incorporating the preheating and retention assemblies, this invention achieves effective preheating of the red mud particles, reducing the energy consumption required for roasting. Simultaneously, the retention assembly ensures uniform microwave action on the red mud particles, effectively improving the heating and roasting efficiency. The combined effect significantly reduces energy consumption during red mud roasting, and through this novel red mud iron extraction process, the iron grade of the obtained iron concentrate is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of red mud iron extraction technology, specifically a microwave roasting equipment and process flow for red mud iron extraction. Background Technology

[0002] Red mud, a typical bulk waste from the aluminum industry, has a comprehensive utilization rate of less than 6%, with an annual consumption of less than 7 million tons. To achieve the goal of a 60% comprehensive utilization rate for newly added bulk solid waste and an orderly reduction in existing bulk solid waste by 2025, the annual comprehensive utilization of red mud needs to reach over 60 million tons. Currently, the scale and rate of red mud utilization are far from the target value, and iron recovery is one of the important ways to reduce red mud volume. Domestic and international scholars have conducted extensive research on iron ore beneficiation from red mud, with the main beneficiation methods including physical separation, pyrometallurgy, and iron ore extraction.

[0003] Physical methods are simple, have low investment costs, and cause less pollution, but the iron concentrate obtained is of relatively low quality.

[0004] In summary, the physical iron extraction technology from red mud has the advantages of low energy consumption and relatively small investment, and it has been industrialized in China. However, the physical method still has the problem of low iron concentrate grade, and there is still room for optimization in the energy consumption of red mud iron extraction using the physical method.

[0005] In summary, the present invention provides a microwave roasting equipment and process for iron extraction from red mud to solve the above problems. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a microwave roasting equipment and process flow for iron extraction from red mud, which is achieved by the following specific technical means:

[0007] A microwave roasting device for iron extraction from red mud includes a fixed base frame, on top of which a rotary kiln is mounted. The rotary kiln comprises:

[0008] The furnace shell is equipped with a microwave generator, and the inner wall of the furnace shell is lined with heat insulation material to reduce heat loss during the red mud roasting process.

[0009] The furnace tube is installed inside the furnace shell and is arranged in an inclined shape. It consists of three parts: the middle part is made of a special ceramic segment that can be penetrated by microwaves, the two ends are metal segments that pass through the two ends of the furnace shell respectively, and each of the three parts of the furnace tube is equipped with a turning plate. The red mud is heated by microwaves and roasted as it passes through the microwave section of the furnace tube.

[0010] The discharge end pipe is fixedly connected to the fixed base frame. The bottom of the discharge end pipe is provided with a discharge pipe, and the metal section at the lower end of the furnace tube passes through the discharge end pipe.

[0011] The feeding assembly is used to feed red mud into the furnace tube from the inlet of the higher metal section of the inclined furnace tube;

[0012] A preheating component is installed in the metal part at the higher end of the furnace tube to preheat the red mud during its entry into the furnace tube, thereby reducing the energy consumption required for the red mud during the microwave roasting process.

[0013] The retention component is connected at one end to the preheating component and at the other end through the microwave section into the metal section at the lower end of the furnace tube. The retention component is used to make the red mud stagnate in the furnace tube, improve the uniformity of the distribution of the red mud inside the furnace tube, and enable the microwave to act evenly on the red mud particles.

[0014] A drive assembly for driving the furnace tube to rotate.

[0015] Furthermore, the preheating component includes an external fixed tube and a heat conduction component. One end of the external fixed tube extends out of the furnace tube and is provided with an air outlet. A mud inlet pipe is provided at the top of the portion of the external fixed tube extending out of the furnace tube and is connected to the feeding component. Both ends of the portion of the external fixed tube located inside the metal section of the furnace tube are provided with sealing ring plates, and the bottom of the sealing ring plate near the special ceramic section of the furnace tube is provided with an opening for allowing red mud to enter the special ceramic section from the metal section of the furnace tube. A mud inlet is provided at the top of the external fixed tube between the two sealing ring plates, and a mud outlet is provided at the bottom.

[0016] Furthermore, the heat conduction component is installed inside the outer fixed pipe, including a front fixed cover, a rear fixed cover, and a heat-conducting strip tube. There are multiple heat-conducting strip tubes, which are arranged between the front fixed cover and the rear fixed cover to connect the front fixed cover and the rear fixed cover. Hot air in the furnace tube passes through the heat-conducting strip tube and conducts heat to the red mud to achieve preheating. The front fixed cover is arranged inside the outer fixed pipe and is located below the mud inlet pipe. The rear fixed cover is arranged inside the outer fixed pipe near one end of the special ceramic section of the furnace tube. The front fixed cover and the rear fixed cover are used to isolate a closed area between the front fixed cover and the rear fixed cover in the outer fixed pipe for the red mud to pass through.

[0017] Furthermore, the retention component includes a fixed crossbar and two hollow support rods. The fixed crossbar is disposed inside the discharge end pipe and fixedly connected to the discharge end pipe. The two hollow support rods are symmetrically arranged between the fixed crossbar and the preheating component, and both ends of the hollow support rods are fixedly connected to the fixed crossbar and a nearby sealing ring plate, respectively. Multiple rotating shafts 1 and 2 are arranged in an array between the two hollow support rods. The number of rotating shafts 1 and 2 is the same, and the multiple rotating shafts 1 and 2 are staggered between the two hollow support rods. A fixed half-box 1 is fixedly connected between the two hollow support rods by rotating shaft 1, and a fixed half-box 2 is fixedly connected between the two hollow support rods by rotating shaft 2. The fixed half-box 1 and fixed half-box 2 can form a fixed box with an open top for containing red mud.

[0018] Furthermore, each of the hollow support rods has a connecting rod fixedly connected inside the rotating shaft, and a linkage rod is installed inside the hollow support rod. The ends of the multiple connecting rods away from the rotating shaft are rotatably connected to the linkage rod.

[0019] The rotating shaft 2 is fixedly connected to the connecting rod 2 inside another hollow support rod, and the hollow support rod is equipped with a linkage rod 2 inside. The ends of the multiple connecting rods 2 away from the rotating shaft 2 are rotatably connected to the linkage rod 2.

[0020] In addition to the first and second rotating shafts located at both ends, each of the adjacent first and second rotating shafts is provided with a sector gear inside the hollow support rod, and the sector gear of the first rotating shaft meshes with the sector gear of one of the adjacent second rotating shafts.

[0021] A fixing pin is provided on one side of the linkage rod, and a fixing pin is provided above the linkage rod in the hollow support rod where the linkage rod is located. The fixing pin is connected to the fixing pin by a tension spring.

[0022] Furthermore, a slider is slidably mounted on the outer side of the hollow support rod. A strip groove is vertically provided on the slider. A movable groove is provided on the surface of the hollow support rod at the slider position. A movable pin is inserted through the movable groove and the strip groove. One end of the movable pin is inserted into the hollow support rod and fixedly connected to the linkage rod one / two. A guide pin is also provided on one side of the slider. A guide ring is provided on the inner wall of the metal section at the lower end of the furnace tube. A plurality of trapezoidal blocks are evenly arranged on one side of the guide ring to push the guide pin and move the slider on the hollow support rod.

[0023] Furthermore, the drive assembly includes a motor and support wheels. The support wheels have two pairs for supporting the furnace tube and reducing the rotational resistance of the furnace tube. The motor is fixedly connected to the fixed base frame and drives the furnace tube to rotate via a belt.

[0024] Furthermore, the feeding assembly includes a fixed bracket, on which a feeding pipe is fixedly installed, and the bottom end of the feeding pipe is connected to the mud inlet pipe.

[0025] A microwave roasting process for iron extraction from red mud includes the following steps:

[0026] S1: Add sodium carbonate to the red mud tailings and mix them. The mixing ratio is red mud: sodium carbonate = 10: 1.5. After mixing, granulate to obtain red mud particles.

[0027] S2: Preliminary drying of red mud particles to achieve a moisture content of ≤2%, thereby increasing the strength of red mud particles and preventing them from pulverizing.

[0028] S3: Add the pre-dried red mud particles into the above-mentioned red mud iron extraction microwave roasting equipment for a first roasting. The roasting temperature is 850℃-1000℃ and the roasting time is 1-2 hours to oxidize and reduce the iron in the red mud particles.

[0029] S4.1: Mix the red mud particles obtained after S3 with coal at a ratio of red mud particles:coal = 10:1. After mixing, add the mixture back into the microwave roasting equipment for red mud iron extraction for secondary roasting at a temperature of 600℃-700℃.

[0030] S4.2: Mix the red mud particles obtained after S3 with coke particles in a ratio of red mud particles:coke particles = 10:1. After mixing, add the mixture back into the microwave roasting equipment for red mud iron extraction for secondary roasting at a temperature of 600℃-700℃.

[0031] S5: The red mud obtained from S4.1 or S4.2 is subjected to high-temperature water quenching;

[0032] S6: The water-quenched red mud is subjected to wet ball milling for 30-60 minutes to achieve a red mud particle size of -200 mesh ≥85%;

[0033] S7: Magnetic separation is performed on the ball-milled red mud to obtain high-iron grade iron concentrate.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. This invention preheats the red mud particles before they enter the furnace tube for roasting by setting up a preheating component, thereby reducing the power consumption of the equipment in the subsequent roasting process. At the same time, the red mud and flue gas are separated to preheat the red mud particles, which effectively prevents the small amount of water vapor in the flue gas from condensing after contacting the red mud particles and then re-entering the furnace tube for roasting, further reducing the energy loss in the red mud roasting process.

[0036] 2. The present invention effectively improves the uniformity of red mud particle distribution in the furnace tube by setting the retention component, so that microwaves can be applied evenly to the red mud particles, thereby improving the overall efficiency of red mud particle roasting. At the same time, it allows the red mud particles to fully contact the high-temperature flue gas in the furnace tube, thereby increasing the temperature rise rate of the red mud particles and greatly reducing the overall power consumption of the equipment.

[0037] 3. This invention improves the existing iron extraction process from red mud tailings, resulting in a significant increase in the iron grade of the obtained iron concentrate. Attached Figure Description

[0038] Figure 1 This is a three-dimensional schematic diagram of the present invention;

[0039] Figure 2 This is a schematic cross-sectional view of the present invention;

[0040] Figure 3 This is a three-dimensional schematic diagram of the furnace tube and its internal components in this invention;

[0041] Figure 4 This is a schematic diagram of the installation of the preheating component inside the furnace tube in this invention;

[0042] Figure 5 This is a three-dimensional schematic diagram of the preheating component in this invention;

[0043] Figure 6 This is a three-dimensional schematic diagram of the heat conduction component in this invention;

[0044] Figure 7 This is a three-dimensional schematic diagram of the retention component in this invention;

[0045] Figure 8 This is a cross-sectional schematic diagram of one side of the retention component in this invention;

[0046] Figure 9 This is a cross-sectional schematic diagram of the other side of the pre-retention component in this invention;

[0047] Figure 10 This is the present invention. Figure 3 A magnified view of part A in the diagram.

[0048] In the picture:

[0049] 1. Fixed base frame; 2. Rotary kiln; 201. Furnace shell; 202. Furnace tube; 2021. Special ceramic section; 2022. Metal section; 2023. Tilting plate; 203. Discharge end pipe; 204. Discharge pipe; 3. Feeding assembly; 301. Fixed bracket; 302. Feeding pipe; 4. Preheating assembly; 401. External fixed pipe; 402. Air outlet; 403. Mud inlet pipe; 404. Sealing ring plate; 405. Opening; 406. Mud inlet; 407. Mud outlet; 408. Heat conduction component; 409. Front fixed cover; 410. Rear fixed cover; 411. Heat-conducting strip pipe; 5. Retention assembly; 501 502. Fixed crossbar; 503. Hollow support rod; 504. Rotating shaft one; 505. Rotating shaft two; 506. Fixed half box one; 507. Fixed half box two; 508. Connecting rod one; 509. Connecting rod two; 510. Connecting rod two; 511. Sector gear; 512. Fixed pin one; 513. Fixed pin two; 514. Tension spring; 515. Slider; 516. Strip groove; 517. Movable groove; 518. Movable pin; 519. Guide pin; 520. Guide ring; 521. Trapezoidal block; 6. Drive assembly; 601. Motor; 602. Support wheel; 603. Belt. Detailed Implementation

[0050] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. Example 1

[0051] like Figure 1-10 As shown, the present invention provides a microwave roasting device for iron extraction from red mud, including a fixed base frame 1, on the top of which a rotary kiln 2 is installed. The rotary kiln 2 includes:

[0052] The furnace shell 201 is integrally welded from 304L stainless steel, which not only meets the structural strength requirements but also prevents microwave leakage. A microwave generator is installed on the furnace shell 201. The microwave generator is evenly distributed axially along the side wall of the furnace tube 202, corresponding to the ceramic section of the furnace tube 202. The inner wall of the furnace shell 201 is lined with heat insulation material, which is microporous ceramic heat insulation brick, to reduce heat loss during the red mud roasting process.

[0053] Iron oxides (Fe2O3) have strong microwave absorption properties (microwave absorption coefficient ≥100 S / m), rapid heating rate (up to 10-15℃ / min), and significant grain growth; while Al2O3 and TiO2 have weak microwave absorption properties (absorption coefficient ≤10 S / m), slow heating rate (3-5℃ / min), and almost no grain growth, forming a structural difference between the iron-rich region and the aluminum-titanium gangue region, which facilitates subsequent separation.

[0054] The furnace tube 202 is installed inside the furnace shell 201 and is inclined at an angle of 3-5° to the horizontal plane. It consists of three parts: the middle part is made of a special ceramic section 2021 that can be penetrated by microwaves; the two ends are metal sections 2022 that extend from the two ends of the furnace shell 201 respectively; and each of the three parts of the furnace tube 202 is provided with a turning plate 2023. Under the action of the inclined furnace tube 202, the red mud is continuously conveyed by the gravity of the red mud itself and the synergistic effect of the turning plate 2023. The red mud is heated by microwaves and roasted as it passes through the microwave section of the furnace tube 202.

[0055] The discharge end pipe 203 is fixedly connected to the fixed base frame 1. The bottom of the discharge end pipe 203 is provided with a discharge pipe 204. After roasting, the red mud is discharged through the discharge pipe 204. The metal section 2022 at the lower end of the furnace tube 202 is inserted into the discharge end pipe 203.

[0056] Feeding assembly 3, the feeding assembly 3 is used to feed red mud into the furnace tube 202 from the inlet of the higher metal section 2022 of the inclined furnace tube 202;

[0057] The preheating component 4 is located in the metal part at the higher end of the furnace tube 202 and is used to preheat the red mud during the process of the red mud entering the furnace tube 202, thereby reducing the energy consumption required for the red mud in the microwave roasting process.

[0058] The retention component 5 is connected at one end to the preheating component 4, and at the other end passes through the microwave section and enters the metal section 2022 at the lower end of the furnace tube 202. The retention component 5 is used to make the red mud stagnate in the furnace tube 202, improve the uniformity of the distribution of red mud inside the furnace tube 202, and make the microwave evenly act on the red mud particles.

[0059] The drive component 6 is used to drive the furnace tube 202 to rotate. The drive component 6 drives the furnace tube 202 to rotate continuously, so that the red mud is continuously lifted and then falls under the action of the tipping plate 2023. Since the furnace tube 202 is inclined, the red mud will move a certain distance towards the discharge end pipe 203 (lower end) during each passing process, thus completing the continuous conveying of the red mud from the feeding component 3 to the discharge end pipe 203.

[0060] The preheating component 4 includes an external fixed pipe 401 and a heat conduction component 408. One end of the external fixed pipe 401 extends out of the furnace tube 202, and an outlet 402 is provided at the exit end. The high-temperature exhaust gas generated during the roasting process passes through the external fixed pipe 401 and is discharged from the outlet 402 to the exhaust gas treatment equipment for treatment. A mud inlet pipe 403 is provided at the top of the portion of the external fixed pipe 401 extending out of the furnace tube 202, and the mud inlet pipe 403 is connected to the feeding component 3. Sealing ring plates 404 are provided at both ends of the portion of the external fixed pipe 401 located inside the metal section 2022 of the furnace tube 202. The material turning plate 2023 on the inner wall of the metal section 2022 of the furnace tube 202 is located between the two sealing ring plates 404, and the external fixed pipe 401 is circular. The distance between the outer surface of the arc section and the inner wall of the furnace tube 202 is equal to the length of the turning plate 2023. An opening 405 is provided at the bottom of the sealing ring plate 404 near the special ceramic section 2021 of the furnace tube 202 for allowing red mud to enter the special ceramic section 2021 from the metal section 2022 of the furnace tube 202. The top of the outer fixed tube 401 is provided with a mud inlet 406 between the two sealing ring plates 404, and the bottom is provided with a mud outlet 407. A guide plate is provided inside the mud inlet 406. The guide plate is used to guide the red mud particles falling into the mud inlet 406 to between the heat-conducting strip tubes 411, so that after the red mud particles pass between the heat-conducting strip tubes 411, they fall back from the mud outlet 407 to between the turning plates 2023 of the metal section 2022.

[0061] Furthermore, the heat conduction element 408 is installed inside the outer fixed pipe 401, including a front fixed cover 409, a rear fixed cover 410, and a heat-conducting strip pipe 411. There are multiple heat-conducting strip pipes 411, which are arranged between the front fixed cover 409 and the rear fixed cover 410 to connect the front fixed cover 409 and the rear fixed cover 410. Hot air in the furnace tube 202 passes through the heat-conducting strip pipe 411 and conducts heat to the red mud to achieve preheating. The front fixed cover 409 is arranged inside the outer fixed pipe 401 and is located below the mud inlet pipe 403. The rear fixed cover 410 is arranged inside the outer fixed pipe 401 near one end of the special ceramic section 2021 of the furnace tube 202. The front fixed cover 409 and the rear fixed cover 410 are used to isolate a closed section between the front fixed cover 409 and the rear fixed cover 410 in the outer fixed pipe 401 for the red mud to pass through.

[0062] The function of the preheating component 4 is as follows: When the red mud particles enter the preheating component 4 from the mud inlet pipe 403, they fall between the heat-conducting strips 411. At the same time, the high-temperature exhaust gas generated during roasting passes through the inside of the heat-conducting strips 411. The heat is conducted to the red mud particles through the heat-conducting strips 411, achieving preliminary preheating of the red mud particles. This reduces the energy consumption required for roasting the red mud particles. The parallel arrangement of multiple heat-conducting strips 411 can evenly distribute the red mud particles entering from the mud inlet 406, ensuring the smooth fall of the red mud particles. At the same time, it can effectively improve the red mud preheating efficiency, effectively reduce the heat loss caused by exhaust gas emissions, and reduce the overall power consumption of the equipment. The purpose of separating the red mud particles from the exhaust gas for heat conduction is to prevent the high-temperature water vapor in the exhaust gas generated during roasting from condensing due to direct contact with the lower-temperature red mud particles, thereby avoiding repeated heating of the water vapor and further reducing the power consumption of the red mud roasting equipment.

[0063] The retention component 5 includes a fixed crossbar 501 and two hollow support rods 502. The fixed crossbar 501 is disposed inside the discharge end pipe 203 and fixedly connected to the discharge end pipe 203. The two hollow support rods 502 are symmetrically arranged between the fixed crossbar 501 and the preheating component 4, and both ends of the hollow support rods 502 are fixedly connected to the fixed crossbar 501 and the adjacent sealing ring plate 404, respectively. Multiple rotating shafts 503 are arranged in an array between the two hollow support rods 502. The number of rotating shafts 503 and 504 is the same, and multiple rotating shafts 503 and 504 are staggered between two hollow support rods 502. A fixed half-box 505 is fixedly connected between the two hollow support rods 502 for each rotating shaft 503. A fixed half-box 506 is fixedly connected between the two hollow support rods 502 for each rotating shaft 504. The fixed half-boxes 505 and 506 can form a fixed box with an open top for containing red mud.

[0064] The function of the retention component 5 is as follows: when the red mud particles fall from the tilting plate 2023 after being lifted inside the furnace tube 202, they are trapped in the middle of the furnace tube 202 by the fixing box. The fixing box will rotate and open every once in a while, pouring the red mud particles inside back to the bottom of the furnace tube 202. After closing again, the red mud particles can be trapped again. The design of the fixing box makes the red mud particles distributed in the furnace tube 202 in the upper (lifted but not yet fallen), middle (inside the fixing box), and lower (not lifted) positions, which effectively improves the uniformity of the distribution of red mud particles inside the furnace tube 202. On the one hand, it reduces the accumulation of red mud particles, so that microwaves can act on the red mud particles evenly. On the other hand, the red mud particles can fully contact the hot air inside the furnace tube 202, so that the temperature of the red mud particles can rise more efficiently and reduce the overall power consumption of the equipment.

[0065] In this configuration, each of the rotating shafts 503 has a connecting rod 507 fixedly connected inside one of the hollow support rods 502, and a linkage rod 508 is installed inside the hollow support rod 502. The ends of the multiple connecting rods 507 that are away from the rotating shaft 503 are rotatably connected to the linkage rod 508.

[0066] The rotating shaft 504 is fixedly connected to the connecting rod 509 inside another hollow support rod 502, and the hollow support rod 502 is equipped with a linkage rod 510. The ends of the multiple connecting rods 509 away from the rotating shaft 504 are rotatably connected to the linkage rod 510.

[0067] In addition to the first rotating shaft 503 and the second rotating shaft 504 located at both ends, the adjacent first rotating shaft 503 and the second rotating shaft 504 are each provided with a sector gear 511 in the hollow support rod 502, and the sector gear 511 of the first rotating shaft 503 is meshed with the sector gear 511 of one of the adjacent second rotating shafts 504.

[0068] A fixing pin 512 is provided on one side of the linkage rod 508, and a fixing pin 513 is provided above the linkage rod 508 in the hollow support rod 502 where the linkage rod 508 is located. The fixing pin 512 and the fixing pin 513 are connected by a tension spring 514.

[0069] When the first linkage rod 508 moves, it drives each of the first rotating shafts 503 to rotate synchronously. When the second linkage rod 510 moves, it drives each of the second rotating shafts 504 to rotate synchronously, thus allowing each of the fixed half-boxes 505 and 506 to rotate synchronously. Through the setting of the sector gear 511, when the rotation of the first rotating shaft 503 drives the fixed half-box 505 to rotate and open, the first connecting rod 507 rotates, driving the first linkage rod 508 to move. The movement of the first linkage rod 508 drives each of the first connecting rods 507 to rotate, causing each of the first rotating shafts 503 and the fixed half-box 505 to rotate synchronously. The first rotating shaft 503 drives the sector gear 511 connected to it to rotate, and... The sector gear 511 connected to the first rotating shaft 503 drives the sector gear 511 connected to the second rotating shaft 504 to rotate, thereby causing the second rotating shaft 504 to rotate. The rotation of the second rotating shaft 504 drives the second connecting rod 509 to rotate, and the rotation of the second connecting rod 509 drives the second linkage rod 510 to move, thereby causing each second connecting rod 509 to rotate synchronously, which in turn causes each second rotating shaft 504 and the second fixed half box 506 to rotate synchronously. At the same time, due to the meshing action of the sector gear 511, the rotation directions of the first fixed half box 505 and the second fixed half box 506 are opposite (clockwise and counterclockwise), so that each first fixed half box 505 and the second fixed half box 506 can rotate synchronously to pour out the red mud particles located inside.

[0070] The hollow support rod 502 has a slider 515 slidably mounted on its outer side. The slider 515 has a vertically arranged strip groove 516. The surface of the hollow support rod 502 has a movable groove 517 at the position of the slider 515. A movable pin 518 is inserted through the movable groove 517 and the strip groove 516. One end of the movable pin 518 is inserted into the hollow support rod 502 and fixedly connected to the first linkage rod 508 and the second linkage rod 510. A guide pin 519 is also provided on one side of the slider 515. A guide ring 520 is provided on the inner wall of the metal section 2022 at the lower end of the furnace tube 202. A plurality of trapezoidal blocks 521 are evenly arranged on one side of the guide ring 520 to push the guide pin 519 to move the slider 515 on the hollow support rod 502.

[0071] During the calcination of red mud particles, the furnace tube 202 rotates continuously, causing the guide ring 520 to rotate as well. As the guide ring 520 rotates, the trapezoidal block 521 on one side continuously presses and pushes the guide pin 519. The guide pin 519 drives the slider 515 to move. When the slider 515 moves, it drives the movable pin 518 to move through the vertically arranged strip groove 516. The movement of the movable pin 518 can drive either the first linkage rod 508 or the second linkage rod 510 to move, thereby causing the first connecting rod 507 or the second connecting rod 509 to rotate, thus controlling the rotation of the fixed box. Since the movement of the first linkage rod 508 or the second linkage rod 510 is... The movable groove 517 is formed by the rotation of the first linkage 507 or the second linkage 509. Therefore, the shape of the movable groove 517 is an arc that matches the moving path of the first linkage rod 508 or the second linkage rod 510. When the guide pin 519 passes the trapezoidal block 521, the tension spring 514 pulls the linkage rod to reset, thereby resetting the slider 515. The guide pin 519 re-engages with the guide ring 520. The purpose of setting the trapezoidal block 521 is that when the guide pin 519 passes through the inclined part of the trapezoidal block 521, the guide pin 519 will be held in position for a period of time, that is, the fixed box will be held in a tilted state for a period of time, so that the red mud particles in the fixed box have enough time to be poured out.

[0072] The drive assembly 6 includes a motor 601 and support wheels 602. The support wheels 602 have two pairs for supporting the furnace tube 202 and reducing the rotational resistance of the furnace tube 202. The motor 601 is fixedly connected to the fixed base frame 1 and drives the furnace tube 202 to rotate through the belt 603.

[0073] The feeding assembly 3 includes a fixed bracket 301, on which a feeding pipe 302 is fixedly installed. The bottom end of the feeding pipe 302 is connected to the mud inlet pipe 403. The feeding pipe 302 is used to feed red mud particles from the mud inlet pipe 403 into the preheating assembly 4. Example 2

[0074] A microwave roasting process for iron extraction from red mud includes the following steps:

[0075] S1: Add sodium carbonate to the red mud tailings and mix them. The mixing ratio is red mud: sodium carbonate = 10: 1.5. After mixing, granulate to obtain red mud particles.

[0076] S2: Preliminary drying of red mud particles to achieve a moisture content of ≤2%, thereby increasing the strength of red mud particles and preventing them from pulverizing.

[0077] S3: Add the pre-dried red mud particles into the above-mentioned red mud iron extraction microwave roasting equipment for a first roasting. The roasting temperature is 850℃-1000℃ and the roasting time is 1-2 hours to oxidize and reduce the iron in the red mud particles.

[0078] S4.1: Mix the red mud particles obtained after S3 with coal at a ratio of red mud particles:coal = 10:1. After mixing, add the mixture back into the microwave roasting equipment for red mud iron extraction for secondary roasting at a temperature of 600℃-700℃.

[0079] S4.2: Mix the red mud particles obtained after S3 with coke particles in a ratio of red mud particles:coke particles = 10:1. After mixing, add the mixture back into the microwave roasting equipment for red mud iron extraction for secondary roasting at a temperature of 600℃-700℃.

[0080] S5: The red mud obtained from S4.1 or S4.2 is subjected to high-temperature water quenching;

[0081] S6: The water-quenched red mud is subjected to wet ball milling for 30-60 minutes to achieve a red mud particle size of -200 mesh ≥85%;

[0082] S7: Magnetic separation is performed on the ball-milled red mud to obtain high-iron grade iron concentrate.

[0083] In S1, the ratio of red mud tailings to sodium carbonate is determined based on the AL2O3 content in the red mud tailings. Since the conventional AL2O3 content in red mud tailings is 10%-15%, adding 15% sodium carbonate can ensure that the AL2O3 in the red mud tailings reacts completely.

[0084] In S2, the moisture content of the dried red mud particles is controlled to ≤2%, which can effectively reduce the energy loss (energy consumption of water vapor evaporation) in the subsequent roasting process.

[0085] During the initial calcination of S3, the finely dispersed hematite (Fe2O3) and goethite (α-FeOOH) in the red mud particles undergo further oxidation and crystallization at high temperatures of 850°-1000° (2FeOOH → Fe2O3 + H2O↑), increasing the grain size from 1-5μm to 10-20μm. This produces larger-grained iron oxides that are easier to reduce and more easily separated by magnetic separation. At the same time, the reaction between the red mud particles and sodium carbonate (AL2O3) is completely carried out at high temperatures, generating NaAlO2. The reaction formula is: Al2O3 + Na2CO3 → 2NaAlO2 + CO2↑.

[0086] In S4.1 or S4.2, Fe2O3 in the red mud particles after primary roasting is reduced to Fe3O4 through the weak reducing effect of coal or the high-efficiency reducing characteristics of coke particles. The reaction formula is: 3Fe2O3 + C → 2Fe3O4 + CO↑. Compared with coal as a reducing agent, the ash content in coke particles is ≤10%, which is much smaller than the 20%-30% of coal. The reducing activity is stronger. At 600℃, the reaction rate is 30% faster than that of coal. At the same time, there is no release of volatile organic compounds. When users have higher requirements for the purity of iron concentrate, they can choose to use coke particles as a reducing agent according to production needs.

[0087] In step S5, the reduced red mud particles obtained from secondary roasting (600℃-700℃) are fed into a water quenching tank (80℃-90℃), with the water volume being 5-8 times the material mass and the residence time ≤5s. Water quenching yields fragmented red mud. Inside the reduced red mud particles, the thermal expansion coefficients of Fe3O4 grains and aluminum-titanium gangue differ significantly (the thermal expansion coefficient of Fe3O4 is 12×10⁻⁶). -6 / ℃, Al2O3 is 8×10 -6 When high-temperature particles at 600℃-700℃ suddenly come into contact with water at 80℃-90℃, a drastic temperature difference (instantaneous temperature difference exceeding 500℃) is generated between the surface and the interior, resulting in enormous stress within the crystal lattice. This leads to the formation of numerous microcracks (crack width 5-10μm), reducing the Mohs hardness of the red mud particles from 5-6 to 3-4, facilitating subsequent ball milling and reducing ball milling energy consumption by 40-50%. At the same time, the formation of microcracks facilitates water penetration, accelerating the dissolution of NaAlO2 within the reduced red mud particles. Furthermore, it can prevent the re-oxidation of Fe3O4 during the slow cooling process of the reduced red mud.

[0088] Among them, the fragmented red mud in S6 is ground to obtain red mud slurry with a particle size of -200 mesh ≥85%. During the ball milling process, NaAlO2 in the red mud dissolves in the water flow and particle collision, forming an aluminum-containing solution.

[0089] In S7, Fe3O4 in the red mud slurry is separated by magnetic separation equipment to obtain high-quality iron concentrate with Fe≥65%, Al2O3≤1.5%, and TiO2≤0.5%, which is much higher than that obtained by traditional physical methods (45 iron powder, 42 iron powder).

[0090] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A microwave calcination apparatus for extracting iron from red mud, characterised in that: Includes a fixed base frame (1), on the top of which a rotary kiln (2) is mounted, the rotary kiln (2) comprising: The furnace shell (201) is equipped with a microwave generator and the inner wall of the furnace shell (201) is provided with heat insulation material to reduce heat loss during the red mud roasting process. Furnace tube (202), the furnace tube (202) is installed inside the furnace shell (201), the whole is inclined and consists of three parts, the middle part is made of a special ceramic section (2021) that can be penetrated by microwaves, the two ends are metal sections (2022) and they pass out from the two ends of the furnace shell (201) respectively. Each of the three parts of the furnace tube (202) is provided with a turning plate (2023). The red mud is heated by microwaves and roasted as it passes through the microwave section of the furnace tube (202); The discharge end pipe (203) is fixedly connected to the fixed base frame (1). The bottom of the discharge end pipe (203) is provided with a discharge pipe (204). The metal section (2022) of the lower end of the furnace tube (202) is inserted into the discharge end pipe (203). The feeding assembly (3) is used to feed red mud into the furnace tube (202) from the inlet of the higher metal section (2022) of the inclined furnace tube (202); The preheating component (4) is located in the metal part at the higher end of the furnace tube (202) and is used to preheat the red mud during the process of the red mud entering the furnace tube (202) to reduce the energy consumption required for the red mud in the microwave roasting process. The retention component (5) is connected at one end to the preheating component (4) and at the other end through the microwave section into the metal section (2022) at the lower end of the furnace tube (202). The retention component (5) is used to make the red mud stagnate in the furnace tube (202), improve the uniformity of the distribution of red mud in the furnace tube (202), and make the microwave evenly act on the red mud particles. A drive assembly (6) is used to drive the furnace tube (202) to rotate; The preheating component (4) includes an external fixed pipe (401) and a heat conduction component (408). One end of the external fixed pipe (401) extends out of the furnace tube (202) and is provided with an air outlet (402). A mud inlet pipe (403) is provided at the top of the portion of the external fixed pipe (401) extending out of the furnace tube (202), and the mud inlet pipe (403) is connected to the feeding component (3). The external fixed pipe (401) is located in the metal section (2) of the furnace tube (202). 022) Both ends of the inner part are provided with sealing ring plates (404), and the bottom of the sealing ring plate (404) near the special ceramic section (2021) of the furnace tube (202) is provided with an opening (405) for allowing red mud to enter the special ceramic section (2021) from the metal section (2022) of the furnace tube (202). The top of the outer fixed tube (401) is provided with a mud inlet (406) between the two sealing ring plates (404), and the bottom is provided with a mud outlet (407). The retention component (5) includes a fixed crossbar (501) and two hollow support rods (502). The fixed crossbar (501) is disposed inside the discharge end pipe (203) and fixedly connected to the discharge end pipe (203). The two hollow support rods (502) are symmetrically arranged between the fixed crossbar (501) and the preheating component (4), and the two ends of the hollow support rods (502) are fixedly connected to the fixed crossbar (501) and the adjacent sealing ring plate (404) respectively. A plurality of rotating shafts (503) and rotating... are arranged in an array between the two hollow support rods (502). Shaft 2 (504), the number of shaft 1 (503) and shaft 2 (504) is the same, and multiple shaft 1 (503) and shaft 2 (504) are staggered between two hollow support rods (502). Shaft 1 (503) is fixedly connected to fixed half box 1 (505) between two hollow support rods (502). Shaft 2 (504) is fixedly connected to fixed half box 2 (506) between two hollow support rods (502). Fixed half box 1 (505) and fixed half box 2 (506) can form a fixed box with an open top for containing red mud.

2. The red mud iron extraction microwave calcination apparatus of claim 1, wherein: The heat conduction element (408) is installed inside the outer fixed tube (401) and includes a front fixed cover (409), a rear fixed cover (410), and a heat-conducting strip tube (411). There are multiple heat-conducting strip tubes (411), which are arranged between the front fixed cover (409) and the rear fixed cover (410) to connect the front fixed cover (409) and the rear fixed cover (410). The hot air in the furnace tube (202) passes through the heat-conducting strip tube (411) and conducts heat to the red mud. Preheating is now underway. The front fixing cover (409) is located inside the outer fixing pipe (401) and below the mud inlet pipe (403). The rear fixing cover (410) is located inside the outer fixing pipe (401) near one end of the special ceramic section (2021) of the furnace tube (202). The front fixing cover (409) and the rear fixing cover (410) are used to isolate a closed section between the front fixing cover (409) and the rear fixing cover (410) inside the outer fixing pipe (401) for the red mud to pass through.

3. The red mud iron extraction microwave calcination apparatus of claim 2, wherein: The rotating shaft (503) has a connecting rod (507) fixedly connected inside one of the hollow support rods (502), and a linkage rod (508) is installed inside the hollow support rod (502). The ends of the multiple connecting rods (507) away from the rotating shaft (503) are rotatably connected to the linkage rod (508). The rotating shaft 2 (504) is fixedly connected to the connecting rod 2 (509) inside another hollow support rod (502), and the hollow support rod (502) is equipped with a linkage rod 2 (510). The ends of the multiple connecting rods 2 (509) away from the rotating shaft 2 (504) are rotatably connected to the linkage rod 2 (510). Except for the first (503) and the second (504) of the two ends, the adjacent first (503) and second (504) of the hollow support rod (502) are each provided with a sector gear (511), and the sector gear (511) of the first (503) of the rotating shaft is meshed with the sector gear (511) of one of the adjacent second (504) of the rotating shaft. A fixing pin 1 (512) is provided on one side of the linkage rod 1 (508), and a fixing pin 2 (513) is provided above the linkage rod 1 (508) in the hollow support rod 1 (502) where the linkage rod 1 (508) is located. The fixing pin 1 (512) and the fixing pin 2 (513) are connected by a tension spring (514).

4. The red mud iron extraction microwave calcination apparatus of claim 3, wherein: A slider (515) is slidably mounted on the outer side of the hollow support rod (502). A vertically oriented slot (516) is provided on the slider (515). A movable groove (517) is provided on the surface of the hollow support rod (502) at the position of the slider (515). A movable pin (518) is inserted through the movable groove (517) and the slot (516). One end of the movable pin (518) is inserted into the hollow support rod (502) and engages with the slider. The first linkage rod (508) and the second linkage rod (510) are fixedly connected. A guide pin (519) is also provided on one side of the slider (515). A guide ring (520) is provided on the inner wall of the metal section (2022) at the lower end of the furnace tube (202). A plurality of trapezoidal blocks (521) are evenly provided on one side of the guide ring (520) for pushing the guide pin (519) to move the slider (515) on the hollow support rod (502).

5. The red mud iron extraction microwave calcination apparatus of claim 1, wherein: The drive assembly (6) includes a motor (601) and support wheels (602). The support wheels (602) have two pairs for supporting the furnace tube (202) and reducing the rotational resistance of the furnace tube (202). The motor (601) is fixedly connected to the fixed base frame (1) and drives the furnace tube (202) to rotate through a belt (603).

6. The microwave roasting equipment for iron extraction from red mud as described in claim 2, characterized in that: The feeding assembly (3) includes a fixed bracket (301), on which a feeding pipe (302) is fixedly installed, and the bottom end of the feeding pipe (302) is connected to the mud inlet pipe (403).

7. A microwave roasting process for iron extraction from red mud, characterized in that: The microwave roasting equipment for iron extraction from red mud as described in any one of claims 1-6 includes the following steps: S1: Add sodium carbonate to the red mud tailings and mix them. The mixing ratio is red mud: sodium carbonate = 10: 1.

5. After mixing, granulate to obtain red mud particles. S2: Preliminary drying of red mud particles to achieve a moisture content of ≤2%, thereby increasing the strength of red mud particles and preventing them from pulverizing. S3: The pre-dried red mud particles are added to the red mud iron extraction microwave roasting equipment as described in any one of claims 1-6 for a first roasting. The roasting temperature is 850℃-1000℃ and the roasting time is 1-2h, so that the iron in the red mud particles is oxidized and reduced. S4.1: The red mud particles obtained after S3 are mixed with coal at a ratio of red mud particles:coal = 10:

1. After mixing, the mixture is added again to the red mud iron extraction microwave roasting equipment as described in any one of claims 1-6 for secondary roasting at a roasting temperature of 600℃-700℃. S4.2: Mix the red mud particles obtained after S3 with coke particles in a mixing ratio of red mud particles:coke particles = 10:

1. After mixing, add the mixture to the microwave roasting equipment for iron extraction from red mud as described in any one of claims 1-6 for secondary roasting at a roasting temperature of 600℃-700℃. S5: The red mud obtained from S4.1 or S4.2 is subjected to high-temperature water quenching; S6: The water-quenched red mud is subjected to wet ball milling for 30-60 minutes to achieve a red mud particle size of -200 mesh ≥85%; S7: Magnetic separation is performed on the ball-milled red mud to obtain high-iron grade iron concentrate.

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