A method and system for stone coal negative pressure conveying, sorting and recycling of a medium-speed coal mill

Abstract

The application provides a method and system for negative pressure conveying and sorting of stone coal of a medium-speed coal mill, and belongs to the technical field of stone coal recycling in a pulverizing system of a thermal power plant, which can alleviate or solve the problems of large artificial transfer dust, difficult to balance coal particle recovery and stone removal in single sorting, and difficult to recycle combustible components in existing stone coal disposal. The method obtains operation parameters of a stone coal treatment process, and negative pressure conveys stone coal discharged from a medium-speed coal mill to a stone coal bin and dedusts the conveying airflow, adjusts the discharging state of the stone coal bin to make the stone coal spread, sequentially performs particle size screening, projectile sorting and stone identification and removal, and separates coal particles and stone particles, and returns the coal particles to a raw coal bin or an inlet of the medium-speed coal mill after regrinding. The method and system can improve the recovery rate of coal particles and the accuracy of stone removal, reduce dust escape, stone coal discharge and fuel waste, and realize continuous and automatic internal recycling of stone coal.

Description

Technical Field

[0001] This invention belongs to the technical field of stone coal recycling in thermal power pulverizing systems, specifically relating to a method and system for negative pressure conveying, sorting and recycling of stone coal from a medium-speed coal mill. Background Technology

[0002] In coal-fired power generating units, the pulverizing system is a crucial system affecting boiler combustion stability, unit economy, and operational safety. The medium-speed coal mill, as a key piece of equipment in the pulverizing system, is responsible for crushing, grinding, and conveying raw coal to the combustion system. During the operation of the medium-speed coal mill, stones, gangue, pyrite, and some insufficiently ground coarse coal particles mixed in with the raw coal are usually difficult to enter the boiler combustion system with qualified pulverized coal. Instead, they are discharged as coarse coal at the bottom of the mill. Because coarse coal contains both stones and gangue with low or no calorific value, as well as coal particles and fine pulverized coal with calorific value, direct discharge or simple stockpiling not only wastes fuel resources but also increases the pressure on on-site cleanup, transportation, dust control, and waste disposal.

[0003] Existing thermal power plants typically handle the coking coal discharged from medium-speed coal mills using manual transfer, mechanical conveying, negative pressure conveying, or centralized collection. Some systems use negative pressure pneumatic conveying to centrally transport coking coal from each mill to a coking coal bunker to reduce on-site spillage and dust. Other systems perform simple processing using vibrating screens, conveyor belts, or crushing and grinding equipment after the coking coal is collected. However, the composition of coking coal is complex, with different particles varying in particle size, density, hardness, color, shape, and calorific value. Relying solely on a single conveying, screening, or crushing method makes it difficult to effectively distinguish recoverable coal particles from impurities such as stones and gangue. Especially when coal quality fluctuates, coking coal discharge volume changes, or particle composition changes, single screening equipment is prone to problems such as fluctuating screening load, screen blockage, mis-discharge of coal particles, and stone entrainment, making it difficult to simultaneously achieve coal particle recovery rate and stone removal accuracy.

[0004] Furthermore, in existing methods for handling stone coal, the processes of negative pressure conveying, bottom feeding, screening and separation, visual recognition, and regrinding are often independent of each other, lacking a continuous processing flow that is interconnected. Negative pressure conveying systems typically only address the centralized collection of stone coal, without fully considering the stable feeding and material spreading state before it enters the sorting process. Ordinary vibrating screens primarily rely on particle size differences for screening, making it difficult to further separate coal particles, stones, and gangue with similar particle sizes but different densities. While ordinary conveyor belts and visual recognition devices can identify material color differences, without positioning, delay, and separation control relationships with the sorting actuators, it is difficult to accurately remove residual stones. When a ball mill is used for grinding, without a return path between it and the raw coal bunker or the inlet of the medium-speed coal mill, it is difficult to establish an internal circulation system for the re-entry of combustible components from the stone coal into the pulverizing system.

[0005] Therefore, existing technologies have at least the following shortcomings: First, the stone coal processing flow mostly remains at the collection or single-stage screening level, failing to form a continuous closed loop encompassing negative pressure conveying collection, stable feeding, particle size screening, ball milling, visual stone removal, ball milling regrinding, and return to the pulverizing system; Second, the lack of a synergistic structure that simultaneously utilizes differences in particle size, density, ball milling distance, and color for multi-path sorting limits the effectiveness of coal particle recovery and stone removal; Third, the lack of feedback regulation between the stone coal bunker feeding speed, trapezoidal guide chute spreading state, screen aperture, ball milling adjustment chute angle, separation height adjustment baffle height, visual recognition threshold, and sorting execution lever response parameters makes it difficult to adapt to different coal qualities and particle compositions; Fourth, the unusable coal particles obtained from sorting lack effective connection with the ball milling regrinding and pulverizing system return path, making it difficult to fully recover and utilize the combustible components in the stone coal.

[0006] Therefore, there is an urgent need for an internal circulation treatment method and system that can combine centralized negative pressure collection of stone coal, multi-stage sorting, regrinding, and return to the pulverizing system. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method and system for negative pressure conveying, sorting and recycling of stone coal in a medium-speed coal mill.

[0008] This invention provides a method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill, comprising the following steps: S1: Obtain the operating parameters of the stone coal processing process; S2: According to the operating parameters, the stone coal discharged from the medium-speed coal mill is transported to the stone coal bunker under negative pressure, and the conveying airflow is treated for dust removal. S3: Adjust the feeding state of the stone and coal bunker so that the stone and coal are spread out before entering the sorting process; S4: The spread-out stone coal is sequentially subjected to particle size screening, ballistic sorting and stone identification to separate coal particles and stone particles. S5: The coal particles are refmilled and then sent back to the raw coal bunker or the inlet of the medium-speed coal mill.

[0009] Furthermore, the operating parameters include at least one of conveying operating parameters, sorting operating parameters, and reuse evaluation parameters; the conveying operating parameters include the stone and coal discharge status, stone and coal bunker level, or conveying negative pressure; the sorting operating parameters include the feeding amount, the spreading thickness, or the sorting load; the reuse evaluation parameters include the coal particle recovery rate, the stone entrainment rate in the coal particles, the coal content in the stone discharge, the stone identification and removal error rate, or the stone identification and removal miss rate.

[0010] Specifically, the step of conveying the stone coal discharged from the medium-speed coal mill to the stone coal bunker under negative pressure includes: Based on the stone coal discharge status and conveying negative pressure of the medium-speed coal mill, the connection status of the corresponding conveying branch is controlled. The gravel and coal are transported to the gravel and coal bunker using negative pressure airflow; and The conveying airflow is discharged after being cleaned by the dust removal structure.

[0011] Specifically, adjusting the feeding state of the stone and coal bunker includes: adjusting the feeding amount of stone and coal according to the material level and sorting load of the stone and coal bunker; and adjusting the feeding angle or feeding speed according to the spreading thickness before entering the sorting process, so that the stone and coal can be spread out.

[0012] Preferably, the particle size sieving includes: The screening aperture is determined based on the particle size distribution of the stone coal, the target sorting accuracy, and the regrinding capacity; fine particles that pass through the screening area are directed to the fine particle recycling path or the fine particle temporary storage path; and particles that do not pass through the screening area are directed to the ballistic separation.

[0013] Specifically, the projectile sorting includes: The critical separation position is determined based on the landing point distribution of the coal particles and the stone particles; and the projection angle or height of the baffle is adjusted to allow the coal particles to enter the coal particle collection path and the stone particles to enter the stone discharge path.

[0014] Furthermore, the method also includes: adjusting at least one control parameter among the negative pressure conveying, feeding status adjustment, particle size screening, ballistic sorting, or stone identification and removal based on the coal particle recovery status, stone removal status, or conveying blockage status.

[0015] Another aspect of the present invention provides a medium-speed coal mill stone coal negative pressure conveying, sorting and recycling system, comprising: The negative pressure conveying unit is used to transport the stone coal discharged from the medium-speed coal mill to the stone coal collection unit; The stone and coal collection unit is connected to the negative pressure conveying unit and is used to collect stone and coal and to remove dust from the conveying airflow. The material screening unit is connected to the stone and coal collection unit and is used to adjust the stone and coal feeding state and to screen the stone and coal by particle size. The projectile sorting unit is connected to the cloth screening unit and is used to separate coal particles and stone particles according to the differences in particle projection. The stone-removing unit is connected to the ballistic sorting unit and is used to identify and remove residual stones from the coal particles. The regrinding and return unit is connected to the material screening unit and the stone identification and removal unit. It is used to regrind the coal particles obtained from the sorting and return the regrinding product to the raw coal bunker or the inlet of the medium-speed coal mill. An adjustment and control unit is connected to the negative pressure conveying unit, the stone and coal collection unit, the material screening unit, the projectile sorting unit, the stone identification and removal unit, and the regrinding and return unit, respectively, and is used to adjust the control parameters according to the sorting and recycling effect.

[0016] Furthermore, the negative pressure conveying unit includes a conveying branch, a conveying main pipe, and a negative pressure generating device; the stone and coal collection unit includes a stone and coal bunker and a dust removal structure; the material distribution and screening unit includes a material feeding adjustment structure, a material distribution structure, and a screening structure; and the projectile sorting unit includes a projectile adjustment structure, a height adjustment baffle, a coal particle collection path, and a stone discharge path.

[0017] Specifically, the stone-removing identification unit includes a conveyor belt, a spectral recognition device or an image recognition device, and a stone-removing actuator; the adjustment and control unit is used to adjust the negative pressure conveying parameters, feeding parameters, material distribution parameters, screening parameters, throwing parameters, or stone-removing parameters according to the coal particle recovery rate, the stone entrainment rate in the coal particles, the coal content in the stone discharge, the negative pressure conveying blockage status, the stone-removing error rate, or the stone-removing missed rate.

[0018] The beneficial effects of this invention are as follows: This invention uses a negative pressure conveying method to centrally transport the stone coal discharged from the medium-speed coal mill to the stone coal bunker, and performs dust removal treatment on the conveying airflow, which can reduce manual handling, on-site scattering, and dust escape. By spreading the material before sorting, the stone coal is diffused, which helps to reduce the risk of material accumulation and screening blockage, and improves the stability of subsequent sorting. The progressive separation of coal particles and stone particles is carried out by successively using particle size screening, ballistic separation, and stone identification and removal, which can improve the coal particle recovery rate and the accuracy of stone removal. The sorted coal particles are refmilled and then sent back to the raw coal bunker or the inlet of the medium-speed coal mill, so that the combustible components in the stone coal can re-enter the pulverizing system, reducing fuel waste and stone coal discharge. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the steps of a medium-speed coal mill stone coal negative pressure conveying, sorting, and recycling method according to a specific embodiment of the present invention. Figure 2 This is a connection block diagram of a medium-speed coal mill stone coal negative pressure conveying, sorting and recycling system according to a specific embodiment of the present invention.

[0020] The components include: 1. Raw coal bunker; 2. Coal feeder; 3. Medium-speed coal mill; 4. Stone and coal hopper; 5. Wear-resistant pipe; 6. Stone and coal bunker; 7. Slide valve; 8. Trapezoidal guide trough; 9. Screen trough; 10. Throwing adjustment trough; 11. Height adjustment baffle; 12. Fine powder silo; 13. Small and medium particle silo; 14. Stone silo; 15. Hyperspectral industrial camera; 16. Parallel sorting and separating actuator; 17. Conveyor belt; 18. Stone collection trough; 19. Ball mill; 20. Bag dust collector; 21. Roots blower. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown in the figure, a method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill, provided by a specific embodiment of the present invention, includes the following steps: S1: Obtain the operating parameters of the stone coal processing process; S2: According to the operating parameters, the stone coal discharged from the medium-speed coal mill 3 is transported to the stone coal bunker 6 under negative pressure, and the conveying airflow is treated for dust removal. S3: Adjust the feeding state of the stone and coal bunker 6 so that the stone and coal are spread out before entering the sorting process; S4: The spread-out stone coal is sequentially subjected to particle size screening, ballistic sorting and stone identification to separate coal particles and stone particles. S5: The coal particles are refmilled and then sent back to the raw coal bunker 1 or the inlet of the medium-speed coal mill 3.

[0023] In one embodiment, the stone coal processing process involves the continuous treatment of stone coal discharged from the stone coal discharge port of a medium-speed coal mill through negative pressure conveying, centralized collection, feeding and distribution, multi-stage sorting, regrinding, and return to the pulverizing system. The operating parameters are used to reflect the state of the stone coal during conveying, sorting, and reuse, ensuring that the negative pressure conveying capacity, feeding capacity, sorting capacity, and regrinding and return capacity are matched.

[0024] Specifically, the "stone coal" refers to a coarse particle mixture discharged from the stone coal discharge port during the operation of the medium-speed coal mill 3, including at least one of stones, gangue, pyrite, coal particles, and fine coal powder. The "coal particles" refer to particles with combustion and reuse value after sorting, including coal particles, fine coal powder, and coal-containing particles that meet reuse conditions; the "stone particles" refer to stones, gangue, or mineral particles with combustion and reuse value lower than preset requirements that need to be discharged from the reuse path.

[0025] Furthermore, the stone coal processing process does not require all operating parameters to be controlled simultaneously. Under different operating conditions, one or more operating parameters are selected for control based on actual detection conditions. For example, during the negative pressure conveying stage, the stone coal discharge status, conveying negative pressure, and stone coal bunker level 6 are the key parameters; during the material feeding and distribution stage, the stone coal bunker level 6, feeding amount, and spreading thickness are the key parameters; and during the sorting and recycling stage, the coal particle recovery rate, stone entrainment rate, coal content in stone discharge, and stone identification error rate or stone identification missed rate are the key parameters.

[0026] Based on the above basic implementation method, the operating parameters include at least one of conveying operating parameters, sorting operating parameters, and reuse evaluation parameters; the conveying operating parameters include the stone and coal discharge status, the stone and coal bunker level 6, or the conveying negative pressure; the sorting operating parameters include the feeding amount, the spreading thickness, or the sorting load; the reuse evaluation parameters include the coal particle recovery rate, the stone entrainment rate in the coal particles, the coal content in the stone discharge, the stone identification and removal error rate, or the stone identification and removal miss rate.

[0027] Furthermore, the stone coal discharge status includes whether the medium-speed coal mill 3 is in discharge state, the amount of stone coal discharged, or the frequency of stone coal discharge; the conveying negative pressure is obtained by a pressure detection component installed on the negative pressure conveying pipeline; the material level of the stone coal bunker 6 is obtained by a material level detection component; the sorting load is characterized by the load of the vibrating screen equipment, the load of the conveyor belt 17, the material flow rate, or the driving current.

[0028] Furthermore, the coal particle recovery rate is used to characterize the proportion of coal particles entering the regrinding and return path to the reusable coal particles entering the stone coal processing process; the stone entrainment rate in the coal particles is used to characterize the degree of stone particles mixed in the coal particle collection path; the coal content in the stone discharge is used to characterize the degree of mis-discharged coal particles in the stone discharge path; the stone identification and rejection error rate is used to characterize the degree to which coal particles are misidentified as stone particles and rejected; the stone identification and rejection miss rate is used to characterize the degree to which residual stones are not identified and rejected and enter the coal particle recycling path; the stone identification and rejection error rate and the stone identification and rejection miss rate can be obtained by comparing the identification results with the sampling inspection results; the coal particle recovery rate, the stone entrainment rate in the coal particles, and the coal content in the stone discharge are obtained by at least one of the following methods: sampling and weighing, image recognition statistics, calorific value detection, or manual sampling inspection. The above evaluation parameters are used to characterize the sorting and recycling effect and are not limited to using the same detection method.

[0029] In one specific embodiment, the step of conveying the stone coal discharged from the medium-speed coal mill 3 to the stone coal bunker 6 under negative pressure includes: Based on the stone coal discharge status and conveying negative pressure of the medium-speed coal mill 3, the connection status of the corresponding conveying branch is controlled. The gravel and coal are transported to the gravel and coal bunker 6 using negative pressure airflow; and The conveying airflow is discharged after being cleaned by the dust removal structure.

[0030] In this embodiment, the negative pressure conveying process generates a negative pressure airflow within the negative pressure conveying pipeline through a negative pressure generating device, pointing from the stone coal discharge port of the medium-speed coal mill to the stone coal bunker 6. The negative pressure conveying pipeline includes conveying branches connected to multiple medium-speed coal mills 3 respectively, and a main conveying pipe connected to each conveying branch. Each conveying branch is equipped with an isolation valve or a switching valve to receive the stone coal discharged from the corresponding medium-speed coal mill 3 in a predetermined sequence.

[0031] Furthermore, the negative pressure generating equipment includes a Roots blower 21, a wear-resistant induced draft fan, or a pneumatic conveying device with negative pressure suction capability. The negative pressure conveying pipeline uses wear-resistant pipes 5, and wear-resistant linings, inspection ports, or purging interfaces are provided at bends, diameter changes, or locations prone to material accumulation. After the gravel and coal enter the gravel and coal bunker 6, they settle inside the bunker. The conveying airflow is discharged after being dusted by at least one of the following: a bag filter 20, a cartridge filter, or a combination of a cyclone separator and a filter, in order to reduce the risk of dust escape.

[0032] In another specific embodiment, adjusting the feeding state of the stone and coal bunker 6 includes: adjusting the feeding amount of stone and coal according to the material level and sorting load of the stone and coal bunker 6; and adjusting the feeding angle or feeding speed according to the spreading thickness before entering the sorting process, so that the stone and coal can be spread out.

[0033] In this embodiment, the discharge port of the stone and coal bunker 6 is equipped with a discharge adjustment structure, which includes a gate valve 7, a star-shaped discharge valve, an electric gate valve, or a frequency conversion feeding mechanism. By adjusting the opening degree, rotation speed, or operating frequency of the discharge adjustment structure, the amount of stone and coal entering the material distribution and screening area per unit time is changed, thereby avoiding excessively fast discharge leading to screening accumulation, or excessively slow discharge leading to insufficient utilization of the sorting capacity.

[0034] Specifically, the fabric placement angle is adjusted via the trapezoidal guide trough 8, the oscillating guide trough, or the angle of the inclined fabric placement plate; the fabric placement speed is adjusted via the feed rate, the guide trough inclination angle, the vibration intensity, or the conveying speed. After the gravel and coal are discharged from the feed port of the gravel and coal bunker 6, they first enter the fabric placement structure and spread along the width direction, forming a relatively uniform layer of material before entering the screening area. The material placement state includes at least one of the following: material placement width, material placement thickness, and material continuity.

[0035] In another specific embodiment, the particle size sieving includes: The screening aperture is determined based on the particle size distribution of the stone coal, the target sorting accuracy, and the regrinding capacity; fine particles that pass through the screening area are directed to the fine particle recycling path or the fine particle temporary storage path; and particles that do not pass through the screening area are directed to the ballistic separation.

[0036] Furthermore, the particle size screening is achieved through a screen groove 9, a vibrating screen plate, or a rolling screen structure. The screening aperture serves as the particle size separation threshold. Fine particles with a diameter smaller than the screening aperture pass through the screening area and enter the fine particle recycling path or the fine particle temporary storage path, while particles with a diameter greater than or equal to the screening aperture continue to move along the screening area and enter the projectile separation.

[0037] Specifically, when the fine particles meet the preset coal content, preset calorific value, or preset reuse particle size requirements, the fine particles enter the fine particle reuse path and are then fed back into the regrinding process. When the fine particles do not meet the preset coal content, preset calorific value, or preset reuse particle size requirements, the fine particles enter the fine particle temporary storage path for subsequent sampling, temporary storage, or external discharge. The screening aperture is determined based on the coal quality, the particle size distribution of the gravel coal, the processing capacity of the ball mill 19, and the reuse particle size requirements, to balance fine particle recovery and the risk of screening blockage.

[0038] In another specific embodiment, the projectile sorting includes: The critical separation position is determined based on the landing point distribution of the coal particles and the stone particles; and the projection angle or height of the baffle is adjusted to allow the coal particles to enter the coal particle collection path and the stone particles to enter the stone discharge path.

[0039] Furthermore, the projectile sorting is achieved through the cooperation of a projectile adjustment structure and a height adjustment baffle. After the particles on the screen enter the projectile adjustment structure, they form different landing point distributions under the combined effects of gravity, rolling and sliding state, particle shape, particle density, and launch angle. The critical separation position is the boundary between the main landing point area of ​​coal particles and the main landing point area of ​​stone particles, used to determine the separation boundary between the coal particle collection path and the stone discharge path.

[0040] Specifically, the projection adjustment structure includes a projection adjustment trough 10 or an inclined projection plate, and the height adjustment baffle is disposed between the coal particle collection path and the stone discharge path. By adjusting the trough angle, discharge height, discharge speed of the projection adjustment trough 10, or the height of the height adjustment baffle, particles with a projection distance less than the critical separation position enter the coal particle collection path, and particles with a projection distance reaching or exceeding the critical separation position enter the stone discharge path. The projection sorting here is not limited to separation based solely on density differences; it also includes differences in landing point caused by particle size, shape, surface condition, and rolling / slipping states.

[0041] In another specific embodiment, the stone identification and removal includes: acquiring image or spectral information of the residual mixture entering the conveyor belt 17 after ballistic sorting; determining the position of the residual stones based on the image or spectral information; and controlling the stone removal actuator to remove the residual stones based on the position of the residual stones, the running speed of the conveyor belt 17, and the stone removal execution position of the stone removal actuator. Further, the spectral information is acquired by a hyperspectral industrial camera 15, and the image information is acquired by an industrial camera; the stone removal actuator is a paddle, push rod, pneumatic removal device, or electromagnetic removal device in the parallel sorting and separating actuator 16. Specifically, when the residual stones reach the stone removal execution position, the stone removal actuator pushes the residual stones into the stone collection trough 18, and the removed coal particles continue to enter the regrinding return path.

[0042] In another specific embodiment, at least one of the control parameters of the negative pressure conveying, the feeding state adjustment, the particle size screening, the ballistic sorting, or the stone identification and removal is modified according to the coal particle recovery status, the stone removal status, or the conveying blockage status.

[0043] Furthermore, the coal particle recovery status includes coal particle recovery rate, regrinding product yield, or regrinding product particle size; the stone removal status includes stone entrainment rate in coal particles, coal content in stone discharge, stone identification error rate, or stone identification missed rate; the conveying blockage status includes negative pressure conveying pipeline blockage, stone and coal bunker 6 blockage, screening area blockage, or conveyor belt 17 overload. The control parameters include negative pressure conveying parameters, feeding parameters, material distribution parameters, screening parameters, projection parameters, or stone removal parameters.

[0044] Specifically, when the conveying negative pressure is lower than the preset conveying requirements or the negative pressure conveying pipeline shows a tendency to blockage, the operating frequency of the negative pressure generating equipment is increased, the material feed rate is reduced, or a purging operation is initiated; when the coal particle recovery rate is lower than the target value, the screening aperture, material distribution angle, or projection angle is adjusted to increase the proportion of coal particles entering the reuse path; when the coal content of the stone discharge increases, the height of the height adjustment baffle or the projection angle is adjusted to reduce the proportion of coal particles mistakenly entering the stone discharge path; when the stone identification and rejection rate increases, the image recognition threshold or spectral recognition threshold is adjusted, or the response time of the stone removal actuator is shortened; when the stone identification and rejection error rate increases, the stone identification sensitivity is reduced or the action range of the stone removal actuator is adjusted.

[0045] In one specific implementation, such as Figure 2 As shown, a medium-speed coal mill stone coal negative pressure conveying, sorting and recycling system is provided, comprising: The negative pressure conveying unit is used to convey the stone coal discharged from the medium-speed coal mill 3 to the stone coal collection unit; The stone and coal collection unit is connected to the negative pressure conveying unit and is used to collect stone and coal and to remove dust from the conveying airflow. The material screening unit is connected to the stone and coal collection unit and is used to adjust the stone and coal feeding state and to screen the stone and coal by particle size. The projectile sorting unit is connected to the cloth screening unit and is used to separate coal particles and stone particles according to the differences in particle projection. The stone-removing unit is connected to the ballistic sorting unit and is used to identify and remove residual stones from the coal particles. The regrinding and return unit is connected to the material screening unit and the stone identification and removal unit. It is used to regrind the coal particles obtained from the sorting and return the regrinding product to the raw coal bunker 1 or the inlet of the medium-speed coal mill 3. An adjustment and control unit is connected to the negative pressure conveying unit, the stone and coal collection unit, the material screening unit, the projectile sorting unit, the stone identification and removal unit, and the regrinding and return unit, respectively, and is used to adjust the control parameters according to the sorting and recycling effect.

[0046] In one embodiment, the raw coal bunker 1 is connected to the coal feeder 2, and the coal feeder 2 is connected to the medium-speed coal mill 3. The coal feeder 2 is used to transport the raw coal in the raw coal bunker 1 to the medium-speed coal mill 3 at a set feed rate, so that the medium-speed coal mill 3 obtains a stable input of raw coal. After the regrinding product output from the regrinding and return unit is returned to the raw coal bunker 1, it can re-enter the medium-speed coal mill 3 via the coal feeder 2, thereby allowing the sorted coal particles to re-enter the pulverizing process.

[0047] Furthermore, the height adjustment baffle 11 is disposed on the discharge side of the ejection regulating trough 10 and located in the separation area between the small and medium particle hopper 13 and the gravel hopper 14. The height adjustment baffle 11 is used to form a critical separation position between the coal particle collection path and the gravel discharge path. By adjusting the height of the upper edge of the height adjustment baffle 11, the separation boundary corresponding to the particle ejection landing point can be changed, allowing coal particles with shorter ejection distances to enter the small and medium particle hopper 13, and gravel particles with longer ejection distances to enter the gravel hopper 14.

[0048] Specifically, the fine powder hopper 12 is located below the screen groove 9 and is used to receive fine particles that pass through the screen groove 9. The fine particles include fine coal powder, small coal particles, and fine fragments that fall off during screening. The fine powder hopper 12 is connected to the regrinding and return unit or to the fine particle temporary storage path; when the fine particles meet the reuse conditions, the fine particles in the fine powder hopper 12 enter the ball mill 19 for regrinding; when the fine particles do not meet the reuse conditions, the fine particles in the fine powder hopper 12 enter the temporary storage or discharge path.

[0049] Furthermore, the small and medium-sized particle hopper 13 is located below the projectile adjustment trough 10 and in the main landing area of ​​the coal particles, for receiving the small and medium-sized coal particles obtained after projectile separation, as well as a small amount of residual mixture. The small and medium-sized particle hopper 13 is connected to the conveyor belt 17, so that the material entering the small and medium-sized particle hopper 13 can continue to be transported to the identification and stone removal area for further identification and removal of residual stones.

[0050] Specifically, the parallel zoning and sorting actuator 16 is arranged on the conveying path of the conveyor belt 17 and is communicatively connected to the hyperspectral industrial camera 15. The parallel zoning and sorting actuator 16 includes multiple stone-removing actuators arranged in sections along the width direction of the conveyor belt 17, each corresponding to a different identification area on the conveyor belt 17. After the hyperspectral industrial camera 15 collects the spectral information of the material on the conveyor belt 17 and determines the position of the residual stones, the control unit determines the action time of the corresponding stone-removing actuator based on the position of the residual stones, the running speed of the conveyor belt 17, and the distance between the hyperspectral industrial camera 15 and the parallel zoning and sorting actuator 16, so that the corresponding stone-removing actuator performs a removal action when the residual stones reach the removal position.

[0051] Furthermore, the stone collection trough 18 is located on one side or below the conveyor belt 17 and corresponds to the stone-removing output position of the parallel sizing and sorting actuator 16. The stone collection trough 18 is used to receive the residual stones removed from the conveyor belt 17 by the parallel sizing and sorting actuator 16 and guide the residual stones into the stone discharge path. By setting the stone collection trough 18, it is possible to prevent the removed residual stones from being re-mixed into the coal particle conveying path, thereby improving the purity of the coal particles after stone removal.

[0052] Furthermore, in the process of processing coal with stones, the fine powder silo 12, the small and medium particle silo 13, the stone silo 14, and the stone collection trough 18 respectively serve the functions of temporary storage and diversion of different sorting results. The fine powder silo 12 is used to receive fine particles obtained from particle size screening, the small and medium particle silo 13 is used to receive coal particles and residual mixtures obtained from ballistic separation, the stone silo 14 is used to receive stone particles obtained from ballistic separation, and the stone collection trough 18 is used to receive residual stones removed during the identification and stone removal process. The above structures cooperate with each other to form a continuous sorting path for particle size screening, ballistic separation, and identification and stone removal.

[0053] In this embodiment, the negative pressure conveying unit, the stone and coal collection unit, the material screening unit, the projectile sorting unit, the stone identification and removal unit, and the regrinding and return unit are connected sequentially along the flow direction of the stone and coal material, so that the stone and coal discharged from the medium-speed coal mill 3 enters the processing flow from the collection end, and the sorted coal particles are re-grinded and then re-enter the pulverizing system.

[0054] Specifically, the adjustment and control unit includes at least one of a PLC controller, a DCS control module, an industrial computer, or an edge controller. The adjustment and control unit receives detection signals from a pressure detection component, a material level detection component, a load detection component, an image recognition device, or a spectral recognition device, and outputs control commands to the negative pressure generating device, the material feeding adjustment structure, the material spreading structure, the screening structure, the throwing adjustment structure, the height adjustment baffle, and the stone-removing actuator.

[0055] In one specific embodiment, the negative pressure conveying unit includes a conveying branch, a conveying main pipe, and a negative pressure generating device; the stone and coal collection unit includes a stone and coal bunker 6 and a dust removal structure; the material distribution and screening unit includes a material feeding adjustment structure, a material distribution structure, and a screening structure; and the projectile sorting unit includes a projectile adjustment structure, a height adjustment baffle, a coal particle collection path, and a stone discharge path.

[0056] Furthermore, each conveying branch is connected to the stone and coal discharge port of the corresponding medium-speed coal mill 3, and the main conveying pipe is connected to the stone and coal bunker 6. The negative pressure generating device is located at the end of the main conveying pipe, on the exhaust side of the stone and coal bunker 6, or at the rear end of the dust removal structure. The stone and coal bunker 6 includes a gas-solid separation space and a material collection space. The dust removal structure is located on the exhaust path of the gas-solid separation space, and the material discharge adjustment structure is located at the discharge port of the material collection space.

[0057] Furthermore, the fabric distribution structure includes a trapezoidal guide trough 8, an inclined guide trough, or a vibrating fabric distribution plate; the screening structure includes a screen trough 9, a screen plate, or a screening drum; the projection adjustment structure includes a projection adjustment trough 10 or a projection guide plate; the height adjustment baffle is a height-adjustable baffle and is located between the coal particle collection path and the stone discharge path. The coal particle collection path is connected to the stone identification and removal unit or the regrinding and return unit, and the stone discharge path is connected to the stone temporary storage bin, the stone silo 14, or the stone external discharge conveying mechanism.

[0058] In one specific embodiment, the stone-removing identification unit includes a conveyor belt 17, a spectral recognition device or an image recognition device, and a stone-removing actuator; the adjustment and control unit is used to adjust the negative pressure conveying parameters, feeding parameters, material distribution parameters, screening parameters, throwing parameters, or stone-removing parameters according to the coal particle recovery rate, the stone entrainment rate in the coal particles, the coal content of the stone discharge, the negative pressure conveying blockage status, the stone-removing error rate, or the stone-removing missed rate.

[0059] Specifically, the spectral recognition device includes a hyperspectral industrial camera 15, a supplementary lighting component, and a spectral processing component; the image recognition device includes an industrial camera, a supplementary lighting component, and an image processing component. The spectral recognition device identifies residual stones based on the differences in the reflectance spectra of coal particles and stone particles at different wavelengths; the image recognition device identifies residual stones based on color differences, grayscale differences, texture differences, or contour differences between coal particles and stone particles. The stone-removing actuator includes an electric paddle, a pneumatic paddle, an electromagnetic paddle, or a zoned removal mechanism.

[0060] Furthermore, the adjustment and control unit determines the timing of the stone-scraping actuator's action based on the location of the residual stones, the operating speed of the conveyor belt 17, the distance between the identification device and the stone-scraping actuator, and the response time of the stone-scraping actuator. The stone-scraping actuator performs a scraping action when the corresponding residual stone reaches the scraping position, pushing the residual stone into the stone discharge path, and resets after the scraping action is completed to reduce the impact on subsequent coal particle conveying. The sorted coal particles and fine particles meeting the reuse conditions enter the regrinding and return unit, where they are processed by the ball mill 19 or other regrinding equipment to form regrinding products. These products are then returned to the raw coal bunker 1 or the inlet of the medium-speed coal mill 3 via a return pipeline, screw conveyor, belt conveyor, or pneumatic conveyor.

[0061] In one specific embodiment, the method and system of the present invention will be further explained by taking the centralized treatment of stone coal discharged from multiple medium-speed coal mills 3 in a coal-fired unit as an example.

[0062] Each medium-speed coal mill 3 has its stone and coal discharge port connected to a corresponding stone and coal hopper 4. Each stone and coal hopper 4 is connected to a conveying branch of the negative pressure conveying unit, and all conveying branches converge into the main conveying pipe. The main conveying pipe uses a wear-resistant pipe 5 with an inner diameter of 150mm. A Roots blower 21 is installed at the end of the main conveying pipe as a negative pressure generating device. During operation, the regulating control unit controls the switching valve on the corresponding conveying branch to open according to the stone and coal discharge status of each medium-speed coal mill 3 and the conveying negative pressure in the main conveying pipe, allowing the stone and coal to be conveyed to enter the main conveying pipe. The Roots blower 21 generates a negative pressure airflow of -15kPa to -40kPa in the main conveying pipe, and the negative pressure airflow carries the stone and coal into the stone and coal bunker 6.

[0063] After the coke and stones enter the coke and stones bunker 6, the solid particles settle within the bunker. The conveying airflow enters the exhaust path at the top of the bunker and is discharged after being cleaned by the bag filter 20. A circular pipe section with a diameter of 400mm is installed at the bottom of the coke and stones bunker 6, and a slide valve 7 is installed at the outlet as a feeding adjustment mechanism. The adjustment and control unit adjusts the opening of the slide valve 7 according to the material level in the coke and stones bunker 6 and the processing load of the subsequent feeding and screening unit, ensuring a stable feed rate of coke and stones into the feeding and screening unit.

[0064] After being discharged from the feed inlet, the gravel and coal enter the trapezoidal guide chute 8. The feed end of the trapezoidal guide chute 8 corresponds to the feed inlet of the gravel and coal bunker 6, the discharge end is 1.0m wide, and the inclined length is 1.0m. The lower end of the trapezoidal guide chute 8 connects to the screen trough 9. The trapezoidal guide chute 8 is connected to an angle adjustment mechanism, which allows the angle between the trapezoidal guide chute 8 and the horizontal plane to be adjusted within the range of 30° to 45°. As the gravel and coal roll down the trapezoidal guide chute 8, they spread along the width direction, changing the material from a concentrated falling state to a spread-out state before entering the screen trough 9, thereby reducing the impact of local accumulation on the screening effect.

[0065] Specifically, the screen trough 9 is 1.0m wide and 0.5m long, and a screen structure is installed inside the screen trough 9. The screen aperture is determined based on the particle size distribution of the gravel and coal, the target sorting accuracy, and the processing capacity of the ball mill 19. After the gravel and coal enter the screen trough 9, fine particles with a diameter smaller than the screen aperture pass through the screen structure and enter the fine particle collection path; particles with a diameter greater than or equal to the screen aperture continue to move along the screen trough 9 and enter the projectile sorting unit. Fine particles that meet the coal content or calorific value requirements after testing enter the regrinding and return unit; those that do not meet the requirements enter the fine particle temporary storage path.

[0066] The particles passing through the sieve enter the projection regulating trough 10. The projection regulating trough 10 is 1.0m wide and 0.2m long, and is connected to a projection angle adjustment mechanism. The angle between the projection regulating trough 10 and the horizontal plane is adjustable within the range of 0° to -45°. The discharge end of the projection regulating trough 10 faces the separation area between the coal particle collection path and the stone discharge path. A height-adjustable baffle is installed within the separation area, serving as a height adjustment baffle 11 located between the coal particle collection path and the stone discharge path. The adjustment control unit determines the critical separation position based on the drop point distribution of the coal and stone particles, and adjusts the angle of the projection regulating trough 10 and the height of the height adjustment baffle. This ensures that coal particles with shorter projection distances fall into the coal particle collection path, while stone particles with longer projection distances pass over or around the height adjustment baffle before entering the stone discharge path.

[0067] Residual mixture in the coal particle collection path enters the conveyor belt 17. A spectral identification device is installed above the conveyor belt 17, which includes a hyperspectral industrial camera 15, a supplementary lighting component, and a spectral processing component. The hyperspectral industrial camera 15 continuously scans the residual mixture on the conveyor belt 17, and the spectral processing component identifies the residual stones based on the difference in reflectance spectra between coal particles and stone particles, and outputs the location of the residual stones. Downstream of the conveyor belt 17, multiple stone-removing actuators are arranged in sections along the width direction. The adjustment and control unit determines the action time of the corresponding stone-removing actuator based on the location of the residual stones, the running speed of the conveyor belt 17, the distance between the hyperspectral industrial camera 15 and the stone-removing actuators, and the response time of the stone-removing actuators. When a residual stone moves to the stone-removing position, the corresponding stone-removing actuator actuates, pushing the residual stone into the stone discharge path; after removal, the stone-removing actuator resets.

[0068] Further, the coal particles after stone removal enter the ball mill 19. Fine particles that meet the reuse conditions in the fine particle collection path also enter the ball mill 19. The ball mill 19 regrinds the coal particles and fine particles to obtain regrinded products with particle sizes that meet the regrinding requirements. The regrinded products are transported to the raw coal bunker 1 via a return conveying mechanism, or directly returned to the inlet of the medium-speed coal mill 3, so that the coal components in the stone coal can re-enter the pulverizing system.

[0069] During operation, the control unit adjusts control parameters based on the coal particle recovery status, stone removal status, and conveyor blockage status. When the conveying negative pressure decreases and blockage occurs, the operating frequency of the Roots blower 21 is increased or the opening of the gate valve 7 is decreased; when material accumulates above the screen trough 9, the feed rate is reduced or the angle of the trapezoidal guide trough 8 is increased; when the coal content of the stone discharge increases, the angle of the throwing adjustment trough 10 is adjusted or the height of the height adjustment baffle is decreased to reduce the number of coal particles accidentally entering the stone discharge path; when the stone entrainment rate in the coal particles increases, the height of the height adjustment baffle is increased, the spectral recognition threshold is corrected, or the response time of the stone removal actuator is shortened; when the stone removal error rate increases, the stone recognition sensitivity is reduced or the action range of the stone removal actuator is decreased. Through the above processing, the negative pressure conveying, feeding and distribution, particle size screening, throwing sorting, stone removal, and regrinding return form a continuous processing flow.

[0070] In summary, this embodiment has at least the following technical effects: This invention achieves centralized collection and closed conveying of stone coal by negative pressure conveying the stone coal discharged from the medium-speed coal mill 3 to the stone coal bunker 6 and by dust removal treatment of the conveying airflow, thereby reducing the problems of manual transfer, material falling and dust, and on-site scattering, and reducing the impact of the stone coal discharge disposal process on the on-site environment and operation and maintenance. This invention adjusts the feeding state of the stone coal bin 6 before the stone coal enters the sorting process, so that the stone coal is spread out before entering the subsequent sorting process, avoiding material accumulation that leads to insufficient screening, local blockage or sorting load fluctuation, and improving the stability of subsequent particle size screening, ballistic sorting and stone identification processes. This invention employs a multi-stage separation process involving particle size screening, projectile sorting, and stone identification and removal. By utilizing differences in particle size, projectile landing point, and image or spectral characteristics, coal particles and stone particles are progressively separated, thereby improving the coal particle recovery and stone removal efficiency and reducing the problems of misplacement of coal particles and stone entrainment caused by a single screening method. The present invention re-grinds the coal particles obtained from the sorting and sends them back to the raw coal bunker 1 or the inlet of the medium-speed coal mill 3, so that the particles with combustion value in the stone coal can re-enter the pulverizing system, forming a stone coal sorting and reuse path, reducing fuel waste and the amount of stone coal transported out, and improving the utilization rate of coal resources. This invention modifies the control parameters of the stone coal processing process based on the sorting and reuse effect, so that negative pressure conveying, feeding and distribution, particle size screening, ballistic sorting and stone identification can be adjusted according to changes in coal quality, stone coal discharge and sorting results, thereby improving the system's adaptability to different stone coal compositions and different operating conditions. This invention integrates negative pressure conveying, stone coal collection, material screening, ballistic sorting, stone identification and removal, and regrinding and return into a continuous processing flow, which enhances the automation and continuity of stone coal processing, reduces the degree of manual intervention, and is conducive to the reduction, resource utilization and internal recycling of stone coal in thermal power plants.

[0071] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill, characterized in that, Includes the following steps: S1: Obtain the operating parameters of the stone coal processing process; S2: According to the operating parameters, the stone coal discharged from the medium-speed coal mill is transported to the stone coal bunker under negative pressure, and the conveying airflow is treated for dust removal. S3: Adjust the feeding state of the stone and coal bunker so that the stone and coal are spread out before entering the sorting process; S4: The spread-out stone coal is sequentially subjected to particle size screening, ballistic sorting and stone identification to separate coal particles and stone particles; S5: The coal particles are refmilled and then sent back to the raw coal bunker or the inlet of the medium-speed coal mill.

2. The method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill according to claim 1, characterized in that, The operating parameters include at least one of conveying operating parameters, sorting operating parameters, and reuse evaluation parameters; the conveying operating parameters include the stone and coal discharge status, stone and coal bunker level, or conveying negative pressure; the sorting operating parameters include the feeding amount, the spreading thickness, or the sorting load; the reuse evaluation parameters include the coal particle recovery rate, the stone entrainment rate in the coal particles, the coal content in the stone discharge, the stone identification and removal error rate, or the stone identification and removal miss rate.

3. The method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill according to claim 1, characterized in that, The process of conveying the stone coal discharged from the medium-speed coal mill to the stone coal bunker under negative pressure includes: Based on the stone coal discharge status and conveying negative pressure of the medium-speed coal mill, the connection status of the corresponding conveying branch is controlled. The gravel and coal are transported to the gravel and coal bunker using negative pressure airflow; and The conveying airflow is discharged after being cleaned by the dust removal structure.

4. The method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill according to claim 1, characterized in that, The adjustment of the feeding state of the stone and coal bunker includes: adjusting the feeding amount of stone and coal according to the material level and sorting load of the stone and coal bunker; and adjusting the feeding angle or feeding speed according to the spreading thickness before entering the sorting process, so that the stone and coal can be spread out.

5. The method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill according to claim 1, characterized in that, The particle size sieving includes: The screening aperture is determined based on the particle size distribution of the stone coal, the target sorting accuracy, and the regrinding capacity; fine particles that pass through the screening area are directed to the fine particle recycling path or the fine particle temporary storage path; and particles that do not pass through the screening area are directed to the ballistic separation.

6. The method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill according to claim 1, characterized in that, The projectile sorting includes: The critical separation position is determined based on the landing point distribution of the coal particles and the stone particles; and the projection angle or height of the baffle is adjusted to allow the coal particles to enter the coal particle collection path and the stone particles to enter the stone discharge path.

7. The method for negative pressure conveying, sorting, and recycling of stone coal in a medium-speed coal mill according to any one of claims 1 to 6, characterized in that, The method further includes: adjusting at least one of the following parameters based on the coal particle recovery status, stone removal status, or conveying blockage status: negative pressure conveying parameters, feeding status adjustment parameters, particle size screening parameters, projectile sorting parameters, or stone identification parameters.

8. A negative pressure conveying, sorting, and recycling system for stone coal in a medium-speed coal mill, characterized in that, include: The negative pressure conveying unit is used to transport the stone coal discharged from the medium-speed coal mill to the stone coal collection unit; The stone and coal collection unit is connected to the negative pressure conveying unit and is used to collect stone and coal and to remove dust from the conveying airflow. The material screening unit is connected to the stone and coal collection unit and is used to adjust the stone and coal feeding state and to screen the stone and coal by particle size. The projectile sorting unit is connected to the cloth screening unit and is used to separate coal particles and stone particles according to the differences in particle projection. The stone-removing unit is connected to the ballistic sorting unit and is used to identify and remove residual stones from the coal particles. The regrinding and return unit is connected to the material screening unit and the stone identification and removal unit. It is used to regrind the coal particles obtained from the sorting and return the regrinding product to the raw coal bunker or the inlet of the medium-speed coal mill. An adjustment and control unit is connected to the negative pressure conveying unit, the stone and coal collection unit, the material screening unit, the projectile sorting unit, the stone identification and removal unit, and the regrinding and return unit, respectively, and is used to adjust the control parameters according to the sorting and recycling effect.

9. The medium-speed coal mill stone and coal negative pressure conveying, sorting, and recycling system according to claim 8, characterized in that, The negative pressure conveying unit includes a conveying branch, a conveying main pipe, and a negative pressure generating device; the stone and coal collection unit includes a stone and coal bunker and a dust removal structure; the material distribution and screening unit includes a material feeding adjustment structure, a material distribution structure, and a screening structure; the projectile sorting unit includes a projectile adjustment structure, a height adjustment baffle, a coal particle collection path, and a stone discharge path.

10. The medium-speed coal mill stone and coal negative pressure conveying, sorting, and recycling system according to claim 8, characterized in that, The stone-removing identification unit includes a conveyor belt, a spectral recognition device or an image recognition device, and stone-removing actuators; the adjustment and control unit is used to adjust the negative pressure conveying parameters, feeding parameters, material distribution parameters, screening parameters, throwing parameters, or stone-removing parameters according to the coal particle recovery rate, the stone entrainment rate in the coal particles, the coal content of the stone discharge, the negative pressure conveying blockage status, the stone-removing error rate, or the stone-removing missed rate.

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