Medium gangue magnetic tail high value coal recovery system based on multi-section flotation and synergistic regulation

Abstract

This invention relates to the field of tailings flotation technology and discloses a high-value clean coal recovery system based on multi-stage flotation and synergistic control of mid-gangue magnetic tailings. The system includes a classification pretreatment unit employing a high-efficiency thickening and classifying hydrocyclone, a feed pump, and a pressure transmitter to separate mid-gangue magnetic tailings into coarse and fine particles. It also features a multi-stage gradient flotation unit composed of multiple flotation tanks connected in series. Each flotation tank is equipped with an independent stirring drive device, an aeration system, a liquid level adjustment mechanism, and a reagent dosing device. Furthermore, by setting different aeration volumes and stirring linear velocities, multi-gradient flotation operations including roughing, primary cleaning, secondary cleaning, and intermediate cleaning can be achieved. This multi-stage flotation and synergistic control system for high-value clean coal recovery of mid-gangue magnetic tailings simultaneously achieves efficient extraction of clean coal and upgrading and utilization of tailings slime through a systematic architecture of classification pretreatment, multi-stage gradient flotation, and closed-loop control.

Description

Technical Field

[0001] This invention relates to the field of tailings flotation technology, specifically to a high-value clean coal recovery system based on multi-stage flotation and synergistic control of middlings magnetic tailings. Background Technology

[0002] Against the backdrop of my country's ongoing "dual-carbon" strategy and the green transformation and upgrading of the coal industry, coking coal preparation plants in regions such as Wuhai are generally facing the challenge of handling mid-gum magnetic tailings. Mid-gum magnetic tailings are characterized by a wide particle size distribution (0-3mm), high ash content (45%-65%), severe mudification, and significant differences in floatability. Traditional processes either directly incorporate them into the tailings slurry system or discard them, resulting in a serious waste of resources. This is mainly because the fine particles (<0.1mm) in the mid-gum magnetic tailings are actually rich in low-ash clean coal (ash content can be as low as around 28%). Direct disposal leads to the loss of scarce coking coal resources and huge economic losses. Statistics show that the yield of such materials in some coal preparation plants can reach 3%-5%, with huge potential economic value. However, the quality of tailings sludge deteriorates and disposal is difficult. High-ash fine mud mixed into the tailings sludge system results in tailings sludge with low ash content (usually <50%) and high calorific value (>1500 kcal), which does not meet the standards for low-calorific-value fuels and is difficult to use as building material raw materials. Stockpiling causes the risk of spontaneous combustion and environmental pollution. Moreover, the external sales price is low and disposal fees may be required. Traditional technical routes have failed. Single gravity separation, magnetic separation or simple flotation cannot simultaneously achieve the recovery rate of clean coal and ash content indicators. Problems such as high ash content or low yield of clean coal, large reagent consumption, and low separation efficiency exist. The industry generally regards it as a material "unsuitable for flotation" and lacks mature, efficient and stable proprietary technology.

[0003] Therefore, based on the problems existing in the above-mentioned technologies, there is an urgent need to develop a system that can simultaneously optimize the efficient recovery of clean coal and the upgrading of tailings slime. Summary of the Invention

[0004] Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a high-value clean coal recovery system based on multi-stage flotation and synergistic control of mid-gangue magnetic tailings. This system solves the problems of resource waste, poor quality of tailings slime, and failure of traditional technologies in existing technologies. It also addresses the inability to achieve efficient recovery of scarce coking coal resources and resource utilization of tailings slime, as well as the inability to reduce reagent consumption and operating costs.

[0006] Technical solution To achieve the above objectives, the present invention provides the following technical solution: a mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control, comprising: The classification pretreatment unit includes a high-efficiency concentrating and classifying hydrocyclone, a feed pump and a pressure transmitter, used to separate the medium gangue magnetic tail into coarse particles with a particle size >0.1mm and fine particles with a particle size ≤0.1mm. The multi-stage gradient flotation unit consists of multiple flotation cells connected in series. Each flotation cell is equipped with an independent stirring drive device, an aeration system, a liquid level adjustment mechanism, and a dosing device. It can achieve multi-gradient flotation operations of roughing, primary cleaning, secondary cleaning, and intermediate cleaning by setting different aeration volumes and stirring linear velocities. The intelligent control unit includes a PLC controller, an online ash analyzer, a flow meter, a concentration meter, a level gauge, a pressure sensor, and actuators. The actuators include a variable frequency dosing pump, an electric regulating valve, and a variable frequency fan. The PLC controller has a built-in expert algorithm model and a redundant backup module. The product dewatering unit includes a quick-opening diaphragm filter press and a clean coal conveyor belt; The tailings sludge control unit includes a thickener, a filter press, and an online ash content detection device. The tailings sludge control unit also includes a diversion regulating valve, which is interlocked with the online ash content detection device and is used to return unqualified tailings sludge to the flotation tank for re-selection.

[0007] As a further description of the above technical solution, the upper end of the flotation tank is provided with an opening, and a horizontal plate is fixedly connected to the opening. The lower end of the horizontal plate is rotatably connected to a hollow shaft through a sealed bearing. A drive motor is fixedly connected to the upper end of the horizontal plate. The drive motor is provided with a reduction gearbox, and the output shaft of the reduction gearbox is fixedly connected to the upper end of the hollow shaft. A flotation rotor is fixedly connected to the lower end of the hollow shaft. The hollow shaft, drive motor, reduction gearbox, and flotation rotor constitute a stirring drive device. A feed inlet is provided on one side of the flotation tank, and a sealing ring is installed at the feed inlet. An overflow outlet is provided on the other side of the flotation tank at the same height, and an electric regulating valve is fixedly installed at the overflow outlet. A discharge valve and a variable frequency dosing pump are installed at the lower end of the flotation tank. A foam discharge mechanism is provided inside the flotation tank, and the foam discharge mechanism is coaxially arranged with the hollow shaft.

[0008] As a further description of the above technical solution, the flotation rotor includes an upper circular plate, the center of which is coaxially fixed to a hollow shaft through a fixing hole. A trumpet-shaped gas distribution box is provided at the lower end of the upper circular plate. An annular groove is provided between the gas distribution box and the lower end of the upper circular plate. A first aeration hole is provided on the side wall of the annular groove. Multiple evenly distributed stirring blades are provided on the outer side of the gas distribution box, and an arc-shaped load reduction notch is provided at the edge of the stirring blade. Multiple inclined exhaust holes are opened at the edge of the stirring blade. The inclined exhaust holes are connected to the interior of the gas distribution box to discharge inclined airflow. Multiple transversely arranged second aeration holes are opened circumferentially on the side wall of the gas distribution box to discharge transverse airflow.

[0009] As a further description of the above technical solution, the side wall of the air distribution box is fixedly connected with multiple baffles, and the multiple baffles and multiple stirring blades are distributed alternately on the periphery of the air distribution box. The side wall of the stirring blade is provided with a longitudinal exhaust hole, and the longitudinal exhaust hole is connected to the interior of the air distribution box for discharging longitudinal airflow.

[0010] As a further description of the above technical solution, both the first aeration hole and the second aeration hole are two-section structures, one section being a straight hole of the same diameter and the other section being an enlarged hole structure with a gradually changing opening diameter. The inclined exhaust hole and the longitudinal exhaust hole are both straight hole structures with a diameter of 0.8mm-1.2mm.

[0011] As a further description of the above technical solution, the foam discharge mechanism includes an upper pipe and a lower pipe. The upper end of the upper pipe is provided with a collection hopper. The upper pipe and the lower pipe are sleeved at opposite ends. The lower end of the lower pipe is fixedly connected with a conical cover. The lower end of the conical cover is provided with an inclined constriction portion. The constriction portion is fixedly connected with multiple evenly distributed guide pipes. One end of the guide pipe extends to the outside of the flotation tank. The lower end of the horizontal plate is fixedly connected with a guide pipe. The lower end of the guide pipe is provided with a flared pipe. The lower end of the flared pipe is a sealed structure and is rotatably connected to the wall of the hollow tube through a sealed bearing. The guide pipe is rotatably connected to the wall of the hollow tube through multiple ball bearings. An air inlet pipe is fixedly connected to one side of the guide pipe. An air inlet is opened on the shaft wall of the hollow shaft.

[0012] Two electric push rods are fixedly connected to the side wall of the horizontal plate. The output end of the electric push rod passes through the horizontal plate and is fixedly connected to the edge of the hopper, which is used to adjust the overflow height of the upper opening of the hopper.

[0013] As a further description of the above technical solution, a circular ring is fixedly connected to the edge of the collection hopper, and multiple arc-shaped guide plates are fixedly connected to the side wall of the circular ring. The multiple arc-shaped guide plates together form multiple guide channels to assist the foam in entering the collection hopper and being discharged. A bottom box is fixedly connected to the lower end of the flotation tank, and a foam conveying pipe is fixedly connected to the lower end of the bottom box. One end of the foam conveying pipe is provided with a plug-in part.

[0014] As a further description of the above technical solution, each of the four corners of the flotation tank is fixedly connected with an arc-shaped partition. A sealing plate is fixedly connected between the upper end of each of the four partitions and the inner wall of the flotation tank, forming a gas distribution chamber at each corner. A gas distribution channel is fixedly connected to the bottom inner wall of the flotation tank. Multiple gas distribution holes are laterally opened on the side wall of the gas distribution channel. One end of the gas distribution channel is sealed, and the other end communicates with the gas distribution chamber. An air-filling network is installed at the upper end of the flotation tank. An air inlet pipe and an air inlet control valve are installed on the side wall of the air-filling network. The side wall of the sealing plate is connected to the joint of the air-filling network via an air supply pipe, thereby enabling the air-filling system to deliver airflow into the air-filling network.

[0015] As a further description of the above technical solution, the high-efficiency concentration and classification hydrocyclone of the classification pretreatment unit has a classification particle size of 0.1 mm and a classification efficiency of ≥85%. The flotation tank has a volume of 20-30 m³, a stirring linear velocity control range of 2-7 m / s, and an aeration rate control range of 0.3-2.0 m³ / m²·min. The aeration rate control range for the intermediate flotation is 1.0-1.5 m³ / m²·min. The dosing device configured in the flotation tank includes at least three independent reagent tanks, which store collectors, frothers, and inhibitors respectively. Each reagent tank is equipped with a weighing sensor and is added via a variable frequency dosing pump.

[0016] As a further description of the above technical solution, the PLC controller of the intelligent control unit adopts a dual-machine hot standby redundancy architecture, including a main controller and a standby controller, which are connected by synchronous optical fiber, and the fault switching time is ≤50ms. The intelligent control unit also includes a foam image analysis module, which includes a high-resolution industrial camera and an image recognition processor, used to analyze the foam color, size, stability and flow rate in real time, and output the results to the PLC controller as auxiliary adjustment parameters.

[0017] Beneficial effects Compared with existing technologies, this invention provides a high-value clean coal recovery system based on multi-stage flotation and synergistic control of middlings magnetic tailings, which has the following beneficial effects: 1. This invention proposes a synergistic system of "grading pretreatment" + "multi-stage gradient flotation." It precisely separates fine-particle, combustible-rich materials using a high-efficiency thickening and grading hydrocyclone, avoiding interference from coarse particles. Then, it employs a four-stage flotation process with clearly defined functions: "roughing, primary cleaning, secondary cleaning, and mid-stage flotation." Each stage has a clear division of labor and works in concert to achieve integrated operations of rapid collection, deep purification, and residue recovery. This fundamentally changes the processing technology of middlings magnetic tailings, making materials previously considered ineffectively separable readily available. Grading pretreatment significantly improves the properties of the flotation feed, creating favorable conditions for subsequent separation. Furthermore, multi-stage gradient flotation successfully resolves the contradiction between recovery rate and product quality, greatly improving resource recovery while ensuring the quality of clean coal. It also provides a replicable and scalable path for similar complex and difficult-to-separate coal slimes.

[0018] 2. This technical solution designs differentiated operating strategies and functional positioning for roughing, primary cleaning, secondary cleaning, and intermediate flotation. Roughing employs strong agitation, moderate aeration, and compound collectors to achieve high-efficiency initial enrichment. Primary and secondary cleaning utilize low aeration, low agitation, slow flow rates, and the addition of inhibitors to create a stable separation environment for deep purification. Intermediate flotation employs enhanced aeration and supplemental collectors to achieve complete recovery of residual clean coal. Each stage independently controls agitation intensity, aeration volume, liquid level, and reagent formulation, allowing each flotation stage to perform its specific function and complement each other's strengths. The roughing stage efficiently recovers the main clean coal, the secondary cleaning stage precisely removes gangue, and the intermediate flotation stage fully utilizes residual resources. Overall separation efficiency is significantly improved, clean coal quality is stable and controllable, and resource recovery is maximized.

[0019] 3. This technical solution also constructs an intelligent control platform based on a dual-machine hot-standby PLC, integrating a multi-dimensional sensing system including an online ash analyzer, flow meter, concentration meter, level gauge, pressure sensor, and foam image analysis module. It incorporates an expert algorithm model combining fuzzy PID and neural network in parallel to achieve feedforward compensation for changes in feed properties and feedback correction closed-loop control for product ash content. Key detection instruments employ dual-probe redundancy, and actuators are equipped with manual bypasses to ensure high system reliability. This represents a leap from "experience-based operation" to "data-driven, precise control," significantly improving product quality stability, markedly reducing reagent consumption, and achieving near-unattended operation.

[0020] 4. Through precise front-end sorting, the ash content and calorific value of the final tailings slime are actively controlled to the range required for resource utilization. An online ash content detection device is interlocked with the diversion regulating valve, automatically returning substandard tailings slime to the flotation machine for re-selection, ensuring stable and compliant product quality. This transforms tailings slime from "hazardous waste" into a stable resource. The proactive control of tailings slime quality allows it to be directly supplied to power plants for co-firing or used as raw material for cement, bricks, and other building materials, realizing a green production model of "replacing disposal with utilization and turning burden into resource." Attached Figure Description

[0021] Figure 1 This is the main material flow diagram of the high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention; Figure 2 This is a schematic diagram of the material flow direction and functional division of labor within the multi-stage gradient flotation unit of the high-value clean coal recovery system based on multi-stage flotation and coordinated control of gangue magnetic tailings proposed in this invention. Figure 3 This is a diagram of the intelligent control unit architecture in the high-value clean coal recovery system based on multi-stage flotation and synergistic control of mid-gangue magnetic tailings proposed in this invention. Figure 4 This is a schematic diagram of the flotation cell in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 5 This is a cross-sectional view of the flotation cell in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 6 This is a top view of the flotation cell, baffle, and gas distribution channel in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 7 This is a schematic diagram of the arc-shaped guide plate, the collecting hopper, and the upper pipe in the high-value clean coal recovery system based on multi-stage flotation and synergistic control of gangue magnetic tailings proposed in this invention. Figure 8 The present invention relates to a high-value clean coal recovery system based on multi-stage flotation and synergistic control of middlings magnetic tailings. Figure 7 Top view; Figure 9 This is a schematic diagram of the conical hood, flared pipe, guide pipe, and flotation rotor in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 10 This is a schematic diagram of the hollow tube and flotation rotor in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 11 The image shows a bottom view of the hollow tube and flotation rotor in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 12 This is a cross-sectional view of the hollow tube and flotation rotor in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention. Figure 13 The present invention relates to a high-value clean coal recovery system based on multi-stage flotation and synergistic control of middlings magnetic tailings. Figure 12 Enlarged view of the structure at point A in the middle; Figure 14 The present invention relates to a high-value clean coal recovery system based on multi-stage flotation and synergistic control of middlings magnetic tailings. Figure 12 Enlarged view of the structure at point B; Figure 15 This is a schematic diagram of a flotation machine consisting of multiple flotation cells in the mid-gangue magnetic tail high-value clean coal recovery system based on multi-stage flotation and synergistic control proposed in this invention.

[0022] In the diagram: 1. Flotation tank; 2. Baffle plate; 3. Horizontal plate; 4. Electric push rod; 5. Drive motor; 6. Arc-shaped guide plate; 7. Electric regulating valve; 8. Sealing plate; 9. Conduit; 10. Air inlet pipe; 11. Sealing ring; 12. Foam conveying pipe; 13. Guide pipe; 14. Bottom box; 15. Upper circular plate; 16. Lower pipe; 17. Circular ring; 18. Collection hopper; 19. Air supply network; 20. Upper pipe; 21. Hollow shaft; 22. Conical hood; 23. Air distribution channel; 24. Flared pipe; 25. Stirring blade; 26. Baffle plate; 27. Annular groove; 28. Air distribution box; 29. ​​First aeration hole; 30. Second aeration hole; 31. Inclined exhaust hole; 32. Longitudinal exhaust hole; 33. Variable frequency dosing pump; 34. Discharge valve. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example: See attached document Figures 1-3 and Figure 15 As shown, the multi-stage flotation and synergistic control system for recovering high-value clean coal from mid-gum magnetic tailings provided by this invention mainly comprises five units: a staged pretreatment unit, a multi-stage gradient flotation unit, an intelligent control unit, a product dewatering unit, and a tailings slime control unit, as detailed below: The classification pretreatment unit includes a high-efficiency concentrating and classifying hydrocyclone, a feed pump and a pressure transmitter, used to separate the medium gangue magnetic tail into coarse particles with a particle size >0.1mm and fine particles with a particle size ≤0.1mm. The medium-sized gangue magnetic tailings are fed into the hydrocyclone at a pressure of 0.10-0.15 MPa via a feed pump, where centrifugal force is used to achieve classification to a size of 0.1 mm. The underflow (>0.1 mm coarse particles) is returned to the gravity separation system or used as raw material for building materials, while the overflow (≤0.1 mm fine particles) is used as flotation feed. Classification efficiency ≥85%. The multi-stage gradient flotation unit consists of multiple flotation cells 1 connected in series. Each flotation cell 1 is equipped with an independent stirring drive device, an aeration system, a liquid level adjustment mechanism, and a dosing device. It can achieve multi-gradient flotation operations of roughing, primary cleaning, secondary cleaning, and intermediate cleaning by setting different aeration volumes and stirring linear speeds. The specific functions are as follows:

[0025] The flotation machine is a mechanically agitated flotation machine with a tank volume of 20-30 m³. It is equipped with an independent dosing device. The dosing device in the flotation tank 1 includes multiple independent reagent tanks, which store collectors, frothers, and depressants respectively. If additional reagents are needed, additional independent reagent tanks can be added. Each reagent tank is equipped with a weighing sensor and is added via a variable frequency dosing pump 33. The agitation linear velocity of the flotation machine is controlled within the range of 2-7 m / s, and the aeration rate is controlled within the range of 0.3-2.0 m³ / m²·min. The aeration rate for the intermediate flotation is controlled within the range of 1.0-1.5 m³ / m²·min. All of the above equipment can be independently adjusted to complete roughing, primary cleaning, secondary cleaning, and intermediate flotation. The sediment at the bottom can be controlled by the discharge valve 34 at the bottom of the flotation tank 1. If necessary, a sludge pump can be configured.

[0026] The intelligent control unit includes: Controller: A certain brand's S7-1500 series dual-machine hot standby system, with the main and backup controllers connected via a fiber optic synchronization module, and a fault switching time of ≤50ms.

[0027] Testing instruments: online ash analyzer (measuring range 0-70%, accuracy ±0.5%), electromagnetic flowmeter (accuracy ±0.2%), ultrasonic concentration meter (accuracy ±1%), radar level gauge (accuracy ±2mm), pressure transmitter (accuracy ±0.065%). All testing instruments are installed in the corresponding positions in flotation tank 1 according to the construction requirements.

[0028] Actuators: Variable frequency dosing pump (flow rate adjustment range 0-200 L / h, control accuracy ±1%), electric regulating valve (response time ≤2s), variable frequency fan (air volume adjustment range 0-100%).

[0029] Foam Image Analysis Module: Includes a high-resolution industrial camera and image recognition processor, used to analyze foam color, size, stability and flow rate in real time, and output to PLC as auxiliary adjustment parameters.

[0030] The host computer monitoring system connects to the PLC via industrial Ethernet to display the process flow, historical data trends, alarm records, and parameter settings. The PLC controller has a built-in expert algorithm model and a redundant backup module. Product dewatering unit: includes a quick-opening diaphragm filter press (filtration pressure 0.6~0.8 MPa) and a clean coal conveyor belt, used for dewatering flotation clean coal, with filter cake moisture content ≤22%.

[0031] The tailings slime control unit includes a thickener, a filter press, and an online ash content detection device. The tailings slime control unit also includes a diversion regulating valve, which is interlocked with the online ash content detection device. This valve is used to return unqualified tailings slime to the flotation tank 1 for re-selection. The final tailings slime has an ash content of ≥60% and a calorific value of ≤500 kcal / kg.

[0032] The control process of the intelligent control unit is as follows: 1. Hardware architecture redundancy backup The controller features dual-machine hot standby; when the main controller fails, the backup controller automatically takes over, and all I / O states are synchronized. Key testing instruments (online ash analyzer and concentration meter) employ dual-probe redundancy, and the signals are used after median filtering.

[0033] The actuators (dosing pumps, regulating valves) are equipped with a manual bypass, which can switch to manual operation when automatic operation fails.

[0034] 2. Software and Control Algorithms Expert algorithm model: Employs a parallel structure of fuzzy PID and BP neural network. Fuzzy PID is used for rapid response under normal operating conditions; the neural network is used for feedforward compensation when the feed properties change abruptly. The neural network model has three layers (input layer: feed ash content, concentration, flow rate; hidden layer: 10 nodes; output layer: dosage, aeration rate, and liquid level setpoints for each stage). The model is updated online every 24 hours based on actual production data.

[0035] Control logic: Main circuit: The deviation between the set value (e.g., 8.0%) of the ash content of the clean coal and the actual value is calculated by fuzzy PID, and the output is the secondary selection of the aeration volume and the inhibitor dosage correction.

[0036] Secondary loop: When the ash content, concentration, and flow rate of the feed change, the neural network feedforward model directly provides the pre-adjustment amount of the coarse collector dosage.

[0037] Liquid level control: The liquid level of each flotation machine adopts cascade control. The main loop controls the deviation between the set liquid level and the actual liquid level, and the secondary loop controls the opening degree of the tailings discharge valve.

[0038] Key parameter table (stored in the PLC recipe data block):

[0039] 3. Dosing device It includes at least three separate reagent tanks, which store collectors, foaming agents and inhibitors respectively, and each reagent tank is equipped with a variable frequency metering pump 33 and a weighing sensor.

[0040] This invention is the first to propose a synergistic system of "gradual pretreatment + multi-stage gradient flotation". It precisely separates fine-particle combustible-rich materials using a high-efficiency concentrator-classifying hydrocyclone, avoiding interference from coarse particles. Then, it employs a four-stage flotation process with clearly defined functions: "roughing, primary cleaning, secondary cleaning, and mid-stage flotation". Each stage has a clear division of labor and works in concert to achieve integrated operation of rapid collection, deep purification, and residue recovery. This fundamentally changes the processing technology of middlings magnetic tailings, making materials that were previously considered ineffectively separable readily available for efficient utilization. The pre-treatment of graded flotation significantly improved the properties of the flotation feed, creating favorable conditions for subsequent separation. Moreover, multi-stage gradient flotation successfully resolved the contradiction between recovery rate and product quality, greatly improving the resource recovery level while ensuring the quality of clean coal. At the same time, it provided a replicable and scalable path for similar complex and difficult-to-separate coal slimes. This solved the problems of existing technologies that directly perform single-stage flotation or simple gravity separation on the mid-gangue magnetic tail without targeted classification of materials, resulting in coarse high-ash gangue entering the flotation system, seriously interfering with separation and increasing ineffective load; and the contradiction that single-stage flotation cannot simultaneously take into account the clean coal recovery rate and ash content index, resulting in "high recovery rate leads to excessive ash content, and ash reduction leads to a sharp drop in yield".

[0041] Furthermore, this technical solution designs differentiated operating strategies and functional positioning for roughing, primary cleaning, secondary cleaning, and intermediate flotation. Roughing employs strong agitation, moderate aeration, and a compound collector to achieve high-efficiency initial enrichment; primary and secondary cleaning utilize low aeration, low agitation, slow flow rate, and the addition of inhibitors to create a stable separation environment for deep purification; intermediate flotation employs enhanced aeration and supplementary collectors to achieve complete recovery of residual clean coal. Each stage independently controls agitation intensity, aeration volume, liquid level, and reagent formulation, allowing each flotation stage to perform its specific function and complement each other's strengths. The roughing stage efficiently recovers the main clean coal, the secondary cleaning stage precisely removes entrained gangue, and the intermediate flotation stage fully utilizes residual resources. Overall separation efficiency is significantly improved, clean coal quality is stable and controllable, and resource recovery is maximized. This effectively solves the problems of conventional flotation systems where the operating parameters of each stage are similar and lack functional differentiation for different separation tasks. This leads to the following issues: the roughing stage excessively pursues purification and loses yield; the cleaning stage is entrained with gangue minerals due to excessive aeration or stirring; and the intermediate stage misses residual clean coal due to improper parameter settings, resulting in low overall separation efficiency.

[0042] This technical solution also constructs an intelligent control platform based on a dual-machine hot-standby PLC, integrating a multi-dimensional sensing system including an online ash analyzer, flow meter, concentration meter, level gauge, pressure sensor, and foam image analysis module. An expert algorithm model combining fuzzy PID and neural network in parallel is built-in to achieve feedforward compensation for changes in feed properties and feedback correction closed-loop control for product ash content. Key detection instruments employ dual-probe redundancy, and actuators are equipped with manual bypasses to ensure high system reliability. This represents a leap from "experience-based operation" to "data-driven, precise control," significantly improving product quality stability, reducing reagent consumption, and achieving near-unattended operation. The foam image analysis module further enhances the system's ability to perceive changes in flotation status and accelerates response speed. The dual-machine hot standby and redundancy design ensures high system availability, avoiding production interruptions due to single-point failures and providing reliable technical support for the intelligent upgrading of coal preparation plants. It solves the problems of traditional flotation control relying on manual experience, resulting in delayed response to changes in feed properties, high reagent consumption, significant product quality fluctuations, and a lack of redundancy backup in the control system, making it prone to production interruptions in case of failure.

[0043] By precisely sorting the tailings at the front end, the ash content and calorific value of the final tailings are actively controlled to the range required for resource utilization. An online ash / calorific value detection device is interlocked with the diversion regulating valve, automatically returning substandard tailings to the flotation machine for re-selection, ensuring stable and compliant product quality. This transforms tailings from "hazardous waste" into a stable resource. The proactive control of tailings quality allows them to be directly supplied to power plants for co-firing or used as raw materials for cement, bricks, and other building materials, realizing a green production model of "using utilization instead of disposal, turning burden into resource." This solves the problem of traditional processes directly mixing high-ash fine mud into the tailings system, resulting in tailings with low ash content and high calorific value, making them unsuitable as low-calorific-value fuel for power plant co-firing or as qualified building material raw materials, thus creating "inferior waste" and a disposal dilemma.

[0044] Example 2: The difference from Example 1 is that; See attached document Figure 4-14 The present invention also provides a modular flotation machine that can be assembled from multiple flotation cells 1, and each flotation cell 1, including its configuration, can be used as an independent flotation machine. The specific technical solution is as follows: The upper end of the flotation cell 1 is provided with an opening, and a horizontal plate 3 is fixedly connected to the opening. The lower end of the horizontal plate 3 is rotatably connected to a hollow shaft 21 through a sealed bearing. The upper end of the horizontal plate 3 is fixedly connected to a drive motor 5. The drive motor 5 is provided with a reduction gearbox, and the output shaft of the reduction gearbox is fixedly connected to the upper end of the hollow shaft 21. The lower end of the hollow shaft 21 is fixedly connected to a flotation rotor. The hollow shaft 21, the drive motor 5, the reduction gearbox and the flotation rotor constitute a stirring drive device. The drive motor 5 can directly drive the hollow shaft 21 to make the flotation rotor work and stir the mid-gangue magnetic tail slurry in the flotation cell. A feed inlet is provided on one side of the flotation tank 1, and a sealing ring 11 is installed at the feed inlet. An overflow outlet is provided on the other side of the flotation tank 1 at the same height, and an electric regulating valve 7 is fixedly installed at the overflow outlet. Figure 15 As shown, when multiple flotation tanks 1 are spliced ​​together, the feed inlet on one side is attached to the overflow port by the sealing ring 11, and the overflow flow can be adjusted by the electric regulating valve 7. The lower end of the flotation tank 1 is equipped with a discharge valve 34 and a variable frequency dosing pump 33. The discharge valve 34 is used to discharge the sediment in the flotation tank. The variable frequency dosing pump 33 is connected to a storage tank and is used to draw different reagents into the flotation tank 1 as needed to mix with the medium gangue magnetic tailings slurry. The flotation tank 1 is equipped with a foam discharge mechanism, which is coaxially arranged with the hollow shaft 21.

[0045] Unlike traditional scraping discharge, this technical solution adopts a central overflow discharge technology, using the middle part of the flotation tank 1 as a foam removal channel. This effectively reduces the flow distance of the foam, allowing it to enter the foam discharge mechanism in the shortest possible time after rising to the liquid surface. The specific technical solution is as follows: The foam discharge mechanism includes an upper pipe 20 and a lower pipe 16. The upper end of the upper pipe 20 is provided with a collection hopper 18. The upper pipe 20 and the lower pipe 16 are connected at opposite ends. The lower end of the lower pipe 16 is fixedly connected with a conical cover 22. The lower end of the conical cover 22 is provided with an inclined constriction section. The constriction section is fixedly connected with multiple evenly distributed guide pipes 13. One end of the guide pipe 13 extends to the outside of the flotation tank 1. The lower end of the horizontal plate 3 is fixedly connected with a guide pipe 9. The lower end of the guide pipe 9 is provided with a flared pipe 24. The lower end of the flared pipe 24 is a sealed structure and is rotatably connected to the wall of the hollow tube through a sealed bearing. The guide pipe 9 is rotatably connected to the wall of the hollow tube through multiple ball bearings. An air inlet pipe 10 is fixedly connected to one side of the guide pipe 9. An air inlet is opened on the shaft wall of the hollow shaft 21.

[0046] Two electric push rods 4 are fixedly connected to the side wall of the horizontal plate 3. The output end of the electric push rod 4 passes through the horizontal plate 3 and is fixedly connected to the edge of the collecting hopper 18, used to adjust the overflow height of the upper opening of the collecting hopper 18. Figure 5 and Figure 9As shown, the uppermost end of the collecting hopper 18 serves as an overflow weir, and its height can be directly adjusted by the electric push rod 4, so that the generated foam can be discharged efficiently.

[0047] A circular ring 17 is fixedly connected to the edge of the collection hopper 18. Multiple arc-shaped guide plates 6 are fixedly connected to the side wall of the circular ring 17. The multiple arc-shaped guide plates 6 together form multiple guide channels to assist the foam in entering the collection hopper 18 and being discharged. A bottom box 14 is fixedly connected to the lower end of the flotation tank 1. A foam conveying pipe 12 is fixedly connected to the lower end of the bottom box 14, and one end of the foam conveying pipe 12 is provided with a plug-in part. The flotation rotor is always rotating, and the slurry in the flotation tank 1 also generates swirling flow (clockwise). At this time, the foam above the liquid surface also generates swirling flow with the water flow. Therefore, under the guiding action of multiple arc-shaped guide sections 6, the foam can smoothly enter the collection hopper 18, then enter the upper pipe 20 and the lower pipe 16, and finally be discharged into the bottom box 14 through the guide pipe 13, and finally discharged into the dewatering equipment through the foam conveying pipe 12 for dewatering.

[0048] This technical solution also redesigns the flotation rotor, employing a combination of agitation and degassing for aeration, allowing the gas to form microbubbles in the slurry. The specific technical solution is as follows: The flotation rotor includes an upper circular plate 15, which is coaxially fixed to a hollow shaft 21 at its center via a fixing hole. A trumpet-shaped gas distribution box 28 is provided at the lower end of the upper circular plate 15. An annular groove 27 is provided at the lower end of the gas distribution box 28 and the upper circular plate 15. A first aeration hole 29 is provided on the side wall of the annular groove 27. Multiple evenly distributed stirring blades 25 are provided on the outer side of the gas distribution box 28. An arc-shaped load reduction notch is provided at the edge of the stirring blade 25. Multiple inclined exhaust holes 31 are provided at the edge of the stirring blade 25. The inclined exhaust holes 31 are connected to the interior of the gas distribution box 28 to discharge the inclined airflow. Multiple transversely arranged second aeration holes 30 are provided on the circumferential side wall of the gas distribution box 28 to discharge the transverse airflow.

[0049] like Figures 9-11 The gas distribution box 28 and the upper circular plate 15 form a closed space, through which compressed gas can be injected only through the hollow shaft 21 (the compressed gas can be provided by a Roots blower or an air compressor, selected according to the required air pressure). When the flotation rotor is driven, the first aeration hole 29 and the second aeration hole 30 can both achieve scattering by utilizing their variable diameter hole structure, thereby completing transverse aeration. The inclined exhaust hole 31 on the stirring blade 25 and the longitudinal exhaust hole 32 on the baffle plate 26 can both discharge airflow in different directions. Thus, by exhausting in multiple directions, the area of ​​bubble generation can be increased, and under the pushing action of the stirring blade 25 and the baffle plate 26, the bubbles can quickly diffuse at the bottom of the flotation tank 1.

[0050] Multiple baffles 26 are fixedly connected to the side wall of the air distribution box 28. The multiple baffles 26 and multiple stirring blades 25 are distributed alternately around the periphery of the air distribution box 28. The side wall of the stirring blades 25 is provided with longitudinal exhaust holes 32, which are connected to the interior of the air distribution box 28 to discharge longitudinal airflow.

[0051] like Figure 10 As shown, the structure of the stirring blade 25 has a load reduction notch, which can effectively reduce the resistance of the stirring blade 25. The baffle 26 adopts a smaller area and a narrow structure, which can supplement the agitation of the slurry passing through the load reduction notch, and can also further release compressed gas using the baffle 26. The first aeration hole 29 and the second aeration hole 30 are both two-sectioned, one section is a straight hole of the same diameter, and the other section is an enlarged hole structure with a gradually changing opening diameter. The inclined exhaust hole 31 and the longitudinal exhaust hole 32 are both straight hole structures with a diameter of 0.8mm-1.2mm.

[0052] Arc-shaped partitions 2 are fixedly connected to the four corners of the flotation tank 1. Sealing plates 8 are fixedly connected between the upper ends of the four partitions 2 and the inner wall of the flotation tank 1, forming gas distribution chambers at the four corners of the flotation tank 1. A gas distribution channel 23 is fixedly connected to the bottom inner wall of the flotation tank 1. Multiple air distribution holes are laterally opened on the side walls of the gas distribution channel 23. One end of the gas distribution channel 23 is sealed, and the other end connects to the gas distribution chamber. An air filling network 19 is installed at the upper end of the flotation tank 1. Ten air inlet pipes and an air inlet control valve are installed on the side walls of the air filling network 19. The side walls of the sealing plates 8 are connected to the joints of the air filling network 19 via air delivery pipes, thereby enabling the air filling system (Roots blower or air compressor) to deliver airflow into the air filling network 19. Figure 5 and Figure 6 As shown, the gas in the aeration pipeline 19 can directly transport the gas generated by the aeration system to the gas distribution chamber, and then discharge it through the air distribution holes on both sides of the bottom gas distribution channel 23. This effectively replenishes the air volume in the slurry and improves the flotation efficiency of foam during flotation. Figure 15 As shown, the flotation machines, from left to right, consist of: scavenging, roughing, primary cleaning, and secondary cleaning. A booster pump is added to return the slurry that needs to be recycled back to the scavenging tank. See the attached diagram for details. Figure 2 The reflux order in the process is as follows; 1. The tailings slurry is pumped into the roughing tank for roughing. The foam after roughing is then passed through the primary and secondary cleaning tanks for cleaning. The cleaned coal foam is then sent to a quick-opening diaphragm filter press for dewatering. The product is clean coal. 2. Secondary scavenging of tailings: After roughing and secondary cleaning, the tailings are refluxed to the intermediate separation tank by a reflux pump for further ore beneficiation. The foam after secondary scavenging is sent to the roughing tank for roughing. After mixing with the tailings slurry, it enters the subsequent scavenging process. The final tailings after intermediate scavenging enter the coal slime control.

[0053] The reflux pump and related pipelines required for the system are not shown in the diagram. In actual assembly, they are configured according to the flow direction of foam and tailings in each scavenging tank. It should be noted that since the middlings tank produces middlings foam, this foam cannot be directly dewatered and needs to be returned to the roughing tank for roughing. Therefore, the middlings tank cannot be connected in series with the other three tanks and must be configured independently so that the collected middlings foam is returned to the roughing tank. The produced tailings are pumped out by a special pump and sent to the roughing tank. The final tailings are concentrated, filtered, and then tested online for ash content. If they pass the test, they are further processed into tailings resource products. If they fail the test (high clean coal content), they are returned to the middlings flotation tank through the waste regulating valve for secondary middlings flotation.

[0054] Experimental Example 1: Raw material properties: The raw material used is the gangue magnetic tailings from a coking coal preparation plant; The total ash content of the sample was 52.78%. Grain size distribution: +0.1 mm accounted for 76.74% and 58.21% of the ash content; -0.1 mm accounted for 23.26% and 28.67% of the ash content. XRD analysis showed that the main minerals were quartz, kaolinite and illite, with a high content of vitrinite in the fine-grained fraction.

[0055] System Configuration: Classification pretreatment unit: φ150mm high-efficiency concentrator and classifier hydrocyclone, feed pressure 0.12 MPa.

[0056] Multi-stage gradient flotation unit: roughing, primary cleaning, secondary cleaning and intermediate cleaning all adopt the flotation machine in the technical solution of Example 2. Each flotation machine is independently controlled, the parameters are set according to the key parameter table, and a dedicated booster pump and related conveying pipelines are configured according to actual requirements.

[0057] Intelligent control unit: A certain brand S7-1500 dual-machine hot standby PLC, equipped with an online ash analyzer, electromagnetic flow meter, concentration meter, radar level gauge, and pressure transmitter; the actuators are a variable frequency dosing pump, an electric regulating valve, and a variable frequency fan host computer.

[0058] Product dehydration unit: quick-opening diaphragm filter press, filtration pressure 0.7 MPa.

[0059] Tailings slime control unit: thickener + filter press, online ash content detection device, interlocking diversion regulating valve.

[0060] Operation process: The medium-sized gangue magnetic tailings are fed into the classifying hydrocyclone via a feed pump. The overflow (fine particles) enters the flotation feed buffer tank, while the underflow (coarse particles) is returned to the gravity separation system. The flotation feed sequentially undergoes roughing, primary cleaning, secondary cleaning, and intermediate separation. The aeration rate, stirring speed, liquid level, and reagent dosage of each flotation stage are automatically adjusted by the PLC based on feedback from the ash content and concentration of the feed and the ash content of the product. The clean coal froth product enters the quick-opening filter press for dewatering, and the tailings sludge is concentrated and filtered before its ash content is tested. Any unqualified products are returned to the intermediate flotation stage for further selection via a diversion valve.

[0061] Operating results: After 72 hours of continuous operation, the reagent consumption was as follows: collector 1.5 kg / t dry ore, frother 0.4 kg / t dry ore, and depressant 0.2 kg / t dry ore; this was 18% lower than that of traditional single-stage flotation. The average data are shown in the table below.

[0062]

[0063] Experimental Example 2: The difference from Experiment 1: This experiment processed three types of medium-grain gangue magnetic tailings raw materials with different ash contents (A, B, and C), with automatic parameter adaptation by the system. The properties of the raw materials are as follows:

[0064] Results: Under the same operating parameters (key parameter table), the system automatically adjusts the dosage through intelligent control, as shown in the table below.

[0065]

[0066] Conclusion: The system can stably produce qualified products with clean coal ash content ≤8.3% and tailings slurry ash content ≥62% within a wide range of feed ash content (45%-65%), demonstrating good adaptability.

[0067] Experiment Example 3: The Impact of Staged Efficiency on System Performance Experimental objective: To investigate the impact of hydrocyclone classification efficiency in the classification pretreatment unit on the overall system performance and to determine the optimal range of classification efficiency.

[0068] Experimental Method: Based on Experiment 1, different classification efficiencies (75%-92%) were obtained by changing the feed pressure of the classifying hydrocyclone (0.08-0.18 MPa). Keeping other operating parameters constant, the overall clean coal yield, clean coal ash content, and tailings slurry ash content were recorded under each operating condition.

[0069] Experimental results:

[0070] Experimental conclusion: When the classification efficiency is ≥85%, the overall clean coal yield can reach over 65%, and the clean coal ash content is consistently ≤8.2%. Further increasing the classification efficiency to 92% results in limited improvement in clean coal yield (only an increase of 0.5 percentage points), but significantly increases equipment energy consumption (increased feed pressure leads to approximately 15% increase in pump power consumption). Therefore, this invention preferably controls the classification efficiency between 85% and 90%.

[0071] Experiment Example 4: Performance Comparison between Intelligent Control System and Manual Control Experimental objective: To verify the advantages of the intelligent control system of this invention (including PLC closed-loop control, expert algorithm model, and foam image analysis module) over traditional manual operation.

[0072] Experimental Methods: Under the same raw material conditions as in Experiment Example 1, the intelligent control system of this invention (automatic mode) and manual control by an experienced operator were used respectively, each running continuously for 7 days (8 hours per day). The average and standard deviation of clean coal ash content, overall clean coal yield, average collector dosage, and number of operator interventions (in automatic mode, the number of times manual confirmation was performed after system alarms) were recorded. Simultaneously, the foam image analysis module was enabled and disabled in automatic mode to examine its contribution.

[0073] Experimental results:

[0074] Experimental conclusion: Compared with manual operation, the intelligent control system of this invention reduces the standard deviation of ash content in clean coal from 0.45% to 0.14%, significantly improving product quality stability; the overall clean coal yield increases by 2.7 percentage points, and the amount of collector used decreases by 17.6%, achieving near-unmanned operation.

[0075] The activation of the foam image analysis module further reduced the ash standard deviation to 0.08% and saved approximately 12% of the foaming agent usage (from 0.40 kg / t to 0.35 kg / t).

[0076] It should be noted that the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-value clean coal recovery system based on multi-stage flotation and synergistic control of mid-gum magnetic tailings, characterized in that, include: The classification pretreatment unit includes a high-efficiency concentrating and classifying hydrocyclone, a feed pump and a pressure transmitter, used to separate the medium gangue magnetic tail into coarse particles with a particle size >0.1mm and fine particles with a particle size ≤0.1mm. The multi-stage gradient flotation unit consists of multiple flotation cells (1) connected in series. Each of the multiple flotation cells (1) is equipped with an independent stirring drive device, an aeration system, a liquid level adjustment mechanism and a dosing device. It can achieve multi-gradient flotation operations of roughing, primary cleaning, secondary cleaning and intermediate selection by setting different aeration volume and stirring linear speed. The intelligent control unit includes a PLC controller, an online ash analyzer, a flow meter, a concentration meter, a level gauge, a pressure sensor, and an actuator. The actuator includes a variable frequency dosing pump (33), an electric regulating valve (7), and a variable frequency fan. The PLC controller has a built-in expert algorithm model and a redundant backup module. The product dewatering unit includes a quick-opening diaphragm filter press and a clean coal conveyor belt; The tailings sludge control unit includes a thickener, a filter press and an online ash content detection device. The tailings sludge control unit also includes a diversion regulating valve, which is interlocked with the online ash content detection device and is used to return unqualified tailings sludge to the flotation tank (1) for re-selection.

2. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control as described in claim 1, characterized in that: The flotation tank (1) has an opening at its upper end, and a horizontal plate (3) is fixedly connected to the opening. The lower end of the horizontal plate (3) is rotatably connected to a hollow shaft (21) through a sealed bearing. The upper end of the horizontal plate (3) is fixedly connected to a drive motor (5). The drive motor (5) is equipped with a reduction gearbox, and the output shaft of the reduction gearbox is fixedly connected to the upper end of the hollow shaft (21). The lower end of the hollow shaft (21) is fixedly connected to a flotation rotor. The hollow shaft (21), the drive motor (5), the reduction gearbox, and the flotation rotor constitute a stirring drive device. A feed inlet is provided on one side of the flotation tank (1), and a sealing ring (11) is installed at the feed inlet. An overflow outlet is provided on the other side of the flotation tank (1) at the same height, and an electric regulating valve (7) is fixedly installed at the overflow outlet. A discharge valve (34) and a variable frequency dosing pump (33) are installed at the lower end of the flotation tank (1). A foam discharge mechanism is provided inside the flotation tank (1), and the foam discharge mechanism is coaxially arranged with the hollow shaft (21).

3. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 2, characterized in that: The flotation rotor includes an upper circular plate (15), the center of which is coaxially fixed to a hollow shaft (21) through a fixing hole. The lower end of the upper circular plate (15) is provided with a trumpet-shaped gas distribution box (28). The lower end of the gas distribution box (28) and the upper circular plate (15) are provided with an annular groove (27). The side wall of the annular groove (27) is provided with a first aeration hole (29). The outer side of the gas distribution box (28) is provided with multiple evenly distributed stirring blades (25), and the edge of the stirring blades (25) is provided with an arc-shaped load reduction notch. The edge of the stirring blades (25) is provided with multiple inclined exhaust holes (31). The inclined exhaust holes (31) are connected to the inside of the gas distribution box (28) to discharge the inclined airflow. The side wall of the gas distribution box (28) is provided with multiple horizontally arranged second aeration holes (30) to discharge the horizontal airflow.

4. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 3, characterized in that: The side wall of the air distribution box (28) is fixedly connected with multiple baffles (26). The multiple baffles (26) and multiple stirring blades (25) are distributed alternately on the periphery of the air distribution box (28). The side wall of the stirring blades (25) is provided with longitudinal exhaust holes (32). The longitudinal exhaust holes (32) are connected to the interior of the air distribution box (28) to discharge longitudinal airflow.

5. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 4, characterized in that: The first aeration hole (29) and the second aeration hole (30) are both two-section structures, one section being a straight hole of the same diameter and the other section being an enlarged hole structure with a gradually changing opening diameter. The inclined exhaust hole (31) and the longitudinal exhaust hole (32) are both straight hole structures with a diameter of 0.8mm-1.2mm.

6. The middlings magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 2, characterized in that: The foam discharge mechanism includes an upper pipe (20) and a lower pipe (16). The upper end of the upper pipe (20) is provided with a collection hopper (18). The upper pipe (20) and the lower pipe (16) are connected at opposite ends. The lower end of the lower pipe (16) is fixedly connected with a conical hood (22). The lower end of the conical hood (22) is provided with an inclined constriction portion. The constriction portion is fixedly connected with a plurality of evenly distributed guide pipes (13). One end of the guide pipes (13) extends to the flotation stage. Outside the pool (1), the lower end of the horizontal plate (3) is fixedly connected to a conduit (9), the lower end of the conduit (9) is provided with a flared pipe (24), the lower end of the flared pipe (24) is a sealed structure, and is rotatably connected to the wall of the hollow tube through a sealed bearing. The conduit (9) is rotatably connected to the wall of the hollow tube through multiple ball bearings. An air inlet pipe (10) is fixedly connected to one side of the conduit (9), and an air inlet is opened on the shaft wall of the hollow shaft (21). Two electric push rods (4) are fixedly connected to the side wall of the horizontal plate (3). The output end of the electric push rod (4) passes through the horizontal plate (3) and is fixedly connected to the edge of the hopper (18) to adjust the overflow height of the upper opening of the hopper (18).

7. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 6, characterized in that: A ring (17) is fixedly connected to the edge of the collection hopper (18). Multiple arc-shaped guide plates (6) are fixedly connected to the side wall of the ring (17). The multiple arc-shaped guide plates (6) together form multiple guide channels to assist the foam in entering the collection hopper (18) and being discharged. A bottom box (14) is fixedly connected to the lower end of the flotation tank (1). A foam conveying pipe (12) is fixedly connected to the lower end of the bottom box (14), and one end of the foam conveying pipe (12) is provided with a plug-in part.

8. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 1, characterized in that: The flotation tank (1) is fixedly connected to four corners with arc-shaped partitions (2). The upper ends of the four partitions (2) are fixedly connected to the inner wall of the flotation tank (1) with sealing plates (8), so that the four corners of the flotation tank (1) form gas distribution chambers. The bottom inner wall of the flotation tank (1) is fixedly connected with a gas distribution channel (23). The side wall of the gas distribution channel (23) is horizontally provided with multiple air distribution holes. One end of the gas distribution channel (23) is a sealed structure. The other end of the gas distribution channel (23) is connected to the gas distribution chamber. The upper end of the flotation tank (1) is provided with an air filling pipe network (19). The side wall of the air filling pipe network (19) is provided with an air inlet pipe (10) and an air inlet control valve. The side wall of the sealing plate (8) is connected to the joint of the air filling pipe network (19) through an air supply pipe, thereby realizing the air supply system to deliver airflow into the air filling pipe network (19).

9. The middlings magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 1, characterized in that: The high-efficiency concentration and classification hydrocyclone of the classification pretreatment unit has a classification particle size of 0.1 mm and a classification efficiency of ≥85%. The volume of the flotation tank (1) is 20-30 m³, the stirring linear velocity is controlled within the range of 2-7 m / s, and the aeration volume is controlled within the range of 0.3-2.0 m³ / m²·min. The aeration volume of the intermediate flotation is controlled within the range of 1.0-1.5 m³ / m²·min. The dosing device configured in the flotation tank (1) includes at least three independent reagent tanks, which store collectors, frothers and inhibitors respectively. Each reagent tank is equipped with a weighing sensor and is added by a variable frequency dosing pump (33).

10. The mid-gum magnetic tailings high-value clean coal recovery system based on multi-stage flotation and synergistic control according to claim 1, characterized in that: The PLC controller of the intelligent control unit adopts a dual-machine hot standby redundancy architecture, including a main controller and a backup controller, which are connected by synchronous optical fiber, and the fault switching time is ≤50ms. The intelligent control unit also includes a foam image analysis module, which includes a high-resolution industrial camera and an image recognition processor, used to analyze the foam color, size, stability and flow rate in real time, and output the results to the PLC controller as auxiliary adjustment parameters.

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