Pebble coal recycling pulverizing system for ultra-supercritical coal-fired power plant and working method

Abstract

The invention provides an ultra-supercritical coal-fired power plant pebble coal recycling pulverizing system and a working method, and belongs to the technical field of coal-fired power plant pulverizing. A pneumatic conveying mode is adopted, pebble coal generated by a plurality of coal mills can be uniformly and hermetically conveyed to a pebble coal bunker through a centralized recovery network consisting of an air compressor, a main gas transmission pipeline, a branch recovery pipeline and a valve, and a traditional manual clearing and conveying or mechanical carrying mode is replaced. The system and a main coal mill are in linkage control, and discharging and feeding are achieved; by arranging an independent secondary pulverizing loop composed of a ball mill, a separator and the like, pebble coal which is discharged by a traditional medium-speed coal mill and is high in heat value is deeply ground, qualified coal powder is prepared and sent back to a boiler to be combusted, resource reutilization of solid waste is achieved, heat energy contained in the solid waste is effectively recycled, and energy conservation and emission reduction are achieved. The fuel consumption and the fuel cost of a power plant are directly reduced, and meanwhile, the disposal cost and the environmental pressure of the solid waste are reduced.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power plant pulverizing technology, specifically relating to a pulverizing system and working method for the recovery and reuse of gravel coal in an ultra-supercritical coal-fired power plant. Background Technology

[0002] Ultra-supercritical coal-fired power plants are among the most efficient and technologically advanced commercial coal-fired power generation technologies in the world. Their high steam parameters place stringent demands on the stability and economy of unit operation. To ensure efficient and stable combustion in the boiler, power plants typically employ a pulverizing system consisting of multiple (usually 4-8) medium-speed coal mills to meet the need for a continuous and sufficient supply of qualified pulverized coal under high loads. During the operation of the medium-speed coal mills, while the raw coal is ground into fine powder in the grinding zone, the gangue, pyrite, hard coal particles that are difficult to grind, and other mineral impurities contained within are separated and discharged under centrifugal force and gravity, forming what is known as "stone coal." This is an unavoidable byproduct of medium-speed coal mill operation.

[0003] Currently, the mainstream treatment method for coal ash in the industry remains a linear "collection-discharge-waste" model, meaning that the coal ash discharged from the coal mill is collected and directly transported to designated locations for open-air stockpiling or landfill disposal. This simple and inefficient method has revealed increasingly serious and numerous problems in practice: 1. Severe Waste of Energy Resources: The discharged coal ash is not entirely inert; it contains a considerable proportion (usually 30%-50%, and in some cases as high as 60%-80%) of combustible coal components, and its calorific value is not negligible. Based on the calculation that the coal ash emissions from a single medium-speed coal mill account for approximately 1%-3% of the raw coal processed, a large power plant equipped with multiple medium-speed mills could generate tens of thousands of tons or even more of coal ash annually. Long-term direct disposal is essentially equivalent to discarding a large amount of usable fuel energy, resulting in severe resource waste and running counter to the current energy development policy of energy conservation, emission reduction, and efficiency improvement.

[0004] 2. Significant Environmental and Safety Pollution Risks: Open-air stockpiling of coal and stone generates dust, affecting air quality in and around the plant area. The small amounts of heavy metals and sulfur they contain may migrate under rainwater leaching, posing a long-term environmental risk of soil and groundwater pollution. Landfill disposal, on the other hand, requires valuable land resources and also carries the potential problem of leachate pollution. This does not comply with increasingly stringent environmental regulations and the requirements for clean power plant development.

[0005] 3. Increased operating costs and disposal burden: The daily collection, transfer, storage site maintenance and final landfill disposal of coal stone require additional manpower, equipment (such as dedicated transport vehicles) and management costs, which increases the power plant's operation and maintenance costs and solid waste disposal burden.

[0006] 4. Difficulties in Upgrading Existing Power Plants: For existing ultra-supercritical units, implementing stone coal recycling upgrades faces severe physical space constraints. Power plant coal bunkers are compactly laid out with dense equipment and piping. Traditionally envisioned centralized recycling and regrinding systems are typically large and complex, making it difficult to find suitable installation and layout space without affecting the safe and stable operation of existing pulverizing and conveying systems. This "hard constraint" means that even if most existing power plants recognize the problem, they struggle to implement effective stone coal recycling upgrades.

[0007] Although some technological explorations have been undertaken for the recovery of coking coal, such as equipping individual coal mills with small crushing or grinding devices, these solutions are mostly decentralized and isolated processing models, suffering from drawbacks such as low recovery efficiency, high unit energy consumption, numerous operation and maintenance points, and difficulty in centralized control. More importantly, these technologies often fail to be organically integrated with the main combustion system, lacking a complete technological chain from off-site collection to deep processing and then to qualified feed into the furnace. This prevents the achievement of a true closed-loop utilization of "recovery-fine grinding-efficient recombustion," resulting in low resource utilization rates.

[0008] Therefore, a key bottleneck that urgently needs to be overcome in the current technological field is the development of a highly integrated and modular stone coal recycling system. This system needs to be compatible with multiple medium-speed coal mills to achieve centralized and efficient processing; it needs a compact design to maximize the use of the limited space between existing coal bunkers, minimizing interference with the original pulverizing and combustion systems; and ultimately form a complete, fully enclosed, automated, and resource-efficient solution. The lack of such a systematic solution has become a significant obstacle to further improving fuel utilization, reducing solid waste emissions, and achieving green and low-carbon upgrades in ultra-supercritical coal-fired power plants. Summary of the Invention

[0009] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a pulverizing system and working method for the recovery and reuse of gravel coal in ultra-supercritical coal-fired power plants.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a pulverizing system for recovering and reusing gravel in an ultra-supercritical coal-fired power plant, comprising several coal mills and air compressors. Each coal mill is sequentially connected to a weighing gravel hopper and a branch recovery pipeline. The air compressor is connected to the branch recovery pipeline through a main air supply pipeline. The end of the branch recovery pipeline is connected to a gravel bunker. The gravel bunker is sequentially connected to a coal feeder and a ball mill. The ball mill is connected to a separator. The separator transports pulverized coal to the boiler burner through a pulverized coal pipeline.

[0011] An electric valve is installed on the main gas pipeline.

[0012] The branch recovery pipeline is equipped with a pneumatic quick-closing valve.

[0013] A bag filter is installed at the end of the branch recovery pipeline. The bottom of the bag filter is connected to the stone and coal bunker, and an exhaust pipe is installed at the top of the bag filter.

[0014] The stone and coal bunker is equipped with a material level detection module to monitor the material level in real time. When the material level reaches a preset threshold, a start signal is sent to the coal feeder.

[0015] A quantitative feeding unit is installed at the connection between the stone coal bunker and the coal feeder. The quantitative feeding unit adopts a speed-regulating feeding structure of the coal feeder.

[0016] The feeding speed of the variable-speed feeding mechanism of the coal feeder can be adjusted within the range of 2-15t / h.

[0017] The ball mill is equipped with a current sensor to monitor the grinding load in real time. The current sensor is electrically connected to the quantitative feeding unit, and the feeding speed of the quantitative feeding unit is controlled by the grinding load.

[0018] The system includes a control system, which is electrically connected to the coal mill, air compressor, electric valves, pneumatic quick-closing doors, material level detection module of the stone and coal bunker, quantitative feeding unit, and current sensor of the ball mill, to realize the linkage and closed-loop control of the entire system.

[0019] Secondly, this invention provides a working method for a pulverizing system for recycling and reusing coke in an ultra-supercritical coal-fired power plant. When any pulverizer is running, the coke discharged from it falls into the corresponding weighing coke hopper for weighing. Compressed air from the air compressor forms a high-speed airflow at the purging node below the weighing coke hopper through the main air supply pipeline and the corresponding branch recovery pipeline. This airflow blows up the falling coke and carries it along the branch recovery pipeline and the converging pipeline. The coke sequentially enters the coke bunker, the coal feeder, and the ball mill. Under the action of the ball mill, it is ground into fine powder. The ground fine powder enters the separator for sorting. The qualified fine powder is carried by the airflow and directly transported to the boiler burner through the pulverized coal pipeline for combustion in the furnace, thus realizing the recycling and reuse of coke. The unqualified coarse particles are returned to the ball mill for further grinding.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a pulverizing system and operating method for recovering and reusing coke from ultra-supercritical coal-fired power plants. Utilizing pneumatic conveying, a centralized recovery network consisting of air compressors, main pneumatic pipelines, branch recovery pipelines, and valves can uniformly and securely transport coke from multiple coal mills to a coke silo, replacing traditional manual or mechanical handling methods. The system is linked to the main coal mill for immediate discharge and delivery. By setting up an independent secondary pulverizing circuit consisting of ball mills and separators, the high-calorific-value coke discarded by traditional medium-speed coal mills is deeply ground into qualified pulverized coal, which is then returned to the boiler for combustion. This achieves resource-based reuse of solid waste, effectively recovering its inherent heat energy, directly reducing fuel consumption and costs for power plants, while also reducing solid waste disposal costs and environmental impact.

[0021] Furthermore, it is equipped with a shutdown delay purging function, which effectively prevents pipeline blockage, ensures the continuity and reliability of long-distance, multi-node recovery, greatly reduces the intensity of manual labor, and improves the working environment.

[0022] Furthermore, by setting up a stone and coal bunker with material level detection as a buffer, the flow fluctuation and matching problem between the recycling and grinding processes was solved. An innovative closed-loop control strategy based on the ball mill's grinding current was adopted to monitor the load in real time and dynamically adjust the feeding speed of the upstream coal feeder, ensuring the ball mill always operates automatically within its optimal load range. This avoids energy waste due to insufficient load and prevents the risk of decreased grinding efficiency, equipment overload, or even mill blockage due to excessive load, thus optimizing energy consumption while ensuring grinding effect and output. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the system structure of the present invention; The following are the labels in the attached diagram: 1. Coal mill; 2. Stone and coal hopper; 3. Air compressor; 4. Electric valve; 41. Main air conveying pipeline; 5. Pneumatic quick-closing valve; 51. Branch recovery pipeline; 6. Bag filter; 61. Exhaust pipe; 7. Stone and coal bunker; 8. Coal feeder; 9. Ball mill; 10. Separator; 11. Pulverized coal pipeline; 12. Boiler burner. Detailed Implementation

[0025] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0031] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0032] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] Example 1 A pulverizing system for recovering and reusing gravel coal in an ultra-supercritical coal-fired power plant has the following structural components: like Figure 1 As shown, a pulverizing system for recovering and reusing coal from an ultra-supercritical coal-fired power plant includes several coal mills 1 arranged in parallel. The outlet of each coal mill 1 is sequentially connected to a weighing coal hopper 2, and a branch recovery pipeline 51 connected downstream of the weighing coal hopper 2. The system is equipped with an air compressor 3, the outlet of which is connected to a main air supply pipeline 41. An electric valve 4 is installed on the main air supply pipeline 41 to control the on / off state of the air supply. The main air supply pipeline 41 is connected to each branch recovery pipeline 51, and a pneumatic quick-closing valve 5 is installed on each branch recovery pipeline 51 to control the on / off state of the corresponding branch.

[0035] The ends of each branch recovery pipeline 51 converge and connect to the inlet of the bag filter 6. The bag filter 6 is used to achieve gas-solid separation. Its bottom outlet is connected to the top inlet of the stone and coal bunker 7, and its top exhaust port is connected to an exhaust pipe 61 for discharging filtered clean air.

[0036] Preferably, the stone and coal bunker 7 constitutes the buffer storage part of the system, and a material level detection module is installed inside it to monitor the material level height of the stone and coal in the bunker in real time.

[0037] A coal feeder 8 is connected to the bottom outlet of the stone and coal bunker 7, and a quantitative feeding unit is installed at this connection. The quantitative feeding unit adopts a speed-adjustable feeding structure, and its feeding speed can be adjusted within the range of 2-15 t / h to control the flow rate of stone and coal from the stone and coal bunker 7 to subsequent equipment. The outlet of the coal feeder 8 is connected to the inlet of the ball mill 9, forming a secondary grinding section. The ball mill 9 is used for deep crushing and grinding of the stone and coal. It is equipped with a current sensor to monitor the motor operating current and reflect the material load (i.e., grinding load) in the grinding chamber in real time. The outlet of the ball mill 9 is connected to the inlet of the separator 10. The separator 10 is used to sort the ground material. The coal powder outlet of the separator 10 is connected to the boiler burner 12 through the coal powder pipeline 11, thereby sending the processed coal powder back to the boiler for combustion.

[0038] The core of the system is the control system, which is electrically connected to the coal mill 1, air compressor 3, electric valve 4, each pneumatic quick-closing door 5, the material level detection module of the stone coal bunker 7, the quantitative feeding unit, and the current sensor of the ball mill 9, to realize the linkage and closed-loop control of the entire system.

[0039] Example 2 A pulverizing system for recovering and reusing gravel from an ultra-supercritical coal-fired power plant, the working method of which is as follows: When any one of the coal mills 1 is running, the discharged coal stones first fall into the corresponding weighing coal hopper 2 for weighing. When any coal mill 1 starts, the control system starts the air compressor 3 in conjunction with it, and opens the electric valve 4 on the main air conveying pipeline 41 and the pneumatic quick-closing valve 5 on the branch recovery pipeline 51 corresponding to the running coal mill. Compressed air is output from the air compressor 3, passes through the main air conveying pipeline 41 and the corresponding branch recovery pipeline 51, and forms a high-speed airflow at the purging node below the weighing coal hopper 2, blowing up the falling coal stones and carrying them along the branch recovery pipeline 51 and the converging pipeline. When all coal mills 1 have stopped running, the control system controls the air compressor 3 and the electric valve 4 to close after a delay of 20-30 minutes, during which purging continues to ensure that all residual coal stones in the pipelines are completely transported to the bag filter 6, effectively preventing pipeline blockage.

[0040] The gas-solid two-phase flow carrying stones and coal enters the bag filter 6, where the stones and coal are filtered out and fall into the stone and coal bin 7 below for storage, thus achieving material collection and buffering. The filtered air is discharged through the exhaust pipe 61 at the top of the bag filter 6.

[0041] The material level detection module inside the stone and coal bunker 7 continuously monitors the material level. When the material level reaches the preset upper limit threshold, the control system sends a start signal to the coal feeder 8 and its quantitative feeding unit. The unloading device at the bottom of the stone and coal bunker 7 opens, and the stones and coal fall into the coal feeder 8. After the flow rate is controlled by the quantitative feeding unit, they are fed evenly and stably into the ball mill 9. The current sensor inside the ball mill 9 monitors its operating current in real time, and this current value reflects the current grinding load. The control system receives this current signal and compares it with the preset rated current value to form a closed-loop control: when the grinding current exceeds 80%-85% of the rated value, it indicates that the load is too high, and the control system automatically reduces the feeding speed of the quantitative feeding unit; when the grinding current is lower than 55%-60% of the rated value, it indicates that the load is insufficient, and the control system automatically increases the feeding speed of the quantitative feeding unit. Through this closed-loop adjustment, the ball mill 9 always operates within the optimal load range, balancing grinding efficiency and energy consumption. When the material level in the stone and coal bunker 7 drops to the preset lower limit threshold (e.g., 15%-20% of the bunker volume), the control system controls the quantitative feeding unit and ball mill 9 to continue running for 10-15 minutes before stopping, to ensure that the material in the grinding chamber and connecting pipes is completely processed.

[0042] The coarse coal entering the ball mill 9 is deeply ground into fine powder under the impact and extrusion of grinding media such as steel balls. The ground material enters the separator 10 for sorting. The qualified fine coal powder is carried by the airflow and directly transported to the boiler burner 12 through the coal powder pipeline 11, and sent into the furnace for combustion, realizing the recycling of coarse coal; the unqualified coarse particles are returned to the ball mill 9 for further grinding.

[0043] In addition, the system is equipped with comprehensive safety protection logic, including overload protection and over-temperature protection for the ball mill 9, as well as dust leakage monitoring for pipelines and equipment. When situations such as abnormally excessive grinding current, excessive bearing temperature, or detected dust leakage occur, the control system will automatically trigger an emergency shutdown procedure and issue audible and visual alarm signals to ensure safe system operation.

[0044] The entire system, from recycling to powder production and conveying, features a compact structure and a smooth process. The control system integrates multiple logics, including equipment linkage, material level control, and closed-loop load regulation, achieving fully automated and intelligent operation and reducing human intervention. Furthermore, the system is equipped with multiple safety monitoring and protection devices for overload, over-temperature, and dust leakage, enabling timely detection of potential faults and automatic protective measures, significantly improving the operational stability and safety of the entire recycling system.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A pulverizing system for recovering and reusing gravel from an ultra-supercritical coal-fired power plant, characterized in that, It includes several coal mills (1) and air compressors (3). Each coal mill (1) is connected in sequence to a weighing stone coal hopper (2) and a branch recovery pipeline (51). The air compressor (3) is connected to the branch recovery pipeline (51) through the main air supply pipeline (41). The end of the branch recovery pipeline (51) is connected to the stone coal bunker (7). The stone coal bunker (7) is connected in sequence to a coal feeder (8) and a ball mill (9). The ball mill (9) is connected to a separator (10). The separator (10) transports pulverized coal to the boiler burner (12) through a pulverized coal pipeline (11).

2. The ultra-supercritical coal-fired power plant stone coal recovery and reuse pulverizing system according to claim 1, characterized in that, An electric valve (4) is installed on the main gas pipeline (41).

3. The ultra-supercritical coal-fired power plant stone coal recovery and reuse pulverizing system according to claim 1, characterized in that, A pneumatic quick-closing valve (5) is installed on the branch recovery pipeline (51).

4. The ultra-supercritical coal-fired power plant stone coal recovery and reuse pulverizing system according to claim 1, characterized in that, The end of the branch recovery pipeline (51) is provided with a bag filter (6), the bottom of the bag filter (6) is connected to the stone coal bunker (7), and the top of the bag filter (6) is provided with an exhaust pipe (61).

5. A pulverizing system for recovering and reusing gravel coal in an ultra-supercritical coal-fired power plant according to claim 1, characterized in that, The stone coal bunker (7) is equipped with a material level detection module for real-time monitoring of material level height. When the material level height reaches a preset threshold, a start signal is sent to the coal feeder (8).

6. A pulverizing system for recovering and reusing gravel coal in an ultra-supercritical coal-fired power plant according to claim 5, characterized in that, A quantitative feeding unit is provided at the connection between the stone coal bunker (7) and the coal feeder (8). The quantitative feeding unit adopts a coal feeder speed-regulating feeding structure.

7. A pulverizing system for recovering and reusing gravel coal in an ultra-supercritical coal-fired power plant according to claim 6, characterized in that, The feeding speed of the variable-speed feeding mechanism of the coal feeder can be adjusted within the range of 2-15t / h.

8. A pulverizing system for recovering and reusing gravel coal in an ultra-supercritical coal-fired power plant according to claim 7, characterized in that, The ball mill (9) is equipped with a current sensor to monitor the grinding load in real time. The current sensor is electrically connected to the quantitative feeding unit, and the feeding speed of the quantitative feeding unit is controlled by the grinding load.

9. A pulverizing system for recovering and reusing coke from an ultra-supercritical coal-fired power plant according to claim 8, characterized in that, The system includes a control system, which is electrically connected to the material level detection module of the coal mill (1), air compressor (3), electric valve (4), each pneumatic quick-closing door (5), stone coal bunker (7), quantitative feeding unit, and current sensor of ball mill (9) to realize the linkage and closed-loop control of the entire system.

10. A working method for a pulverizing system for recovering and reusing coke from an ultra-supercritical coal-fired power plant, based on the pulverizing system for recovering and reusing coke from an ultra-supercritical coal-fired power plant as described in any one of claims 1 to 9, characterized in that... When any coal mill (1) is running, the coal stones discharged from it fall into the corresponding weighing coal hopper (2) for weighing and measurement. The compressed air from the air compressor (3) passes through the main air supply pipeline (41) and the corresponding branch recovery pipeline (51) to form a high-speed airflow at the purging node below the weighing coal hopper (2), which blows up the falling coal stones and carries them along the branch recovery pipeline (51) and the converging pipeline. The coal stones enter the coal hopper (7), the coal feeder (8) and the ball mill (9) in sequence. Under the action of the ball mill (9), they are ground into fine powder. The ground fine powder enters the separator (10) for sorting. The qualified fine powder is carried by the airflow and directly transported to the boiler burner (12) through the coal powder pipeline (11) and sent into the furnace for combustion, realizing the recycling of coal stones. The unqualified coarse particles are returned to the ball mill (9) for further grinding.

Images