Coal-fired unit powder supply control system and method based on small powder bin

Abstract

The invention belongs to the technical field of coal-fired unit powder making and pulverized coal conveying systems, and particularly relates to a coal-fired unit powder supply control system and method based on a small powder bin. According to the invention, by setting a plurality of powder supply modes of powder taking through a powder pipe, powder taking through a grinding outlet and combined switching of the powder taking through the powder pipe and the grinding outlet, and providing a matched powder taking amount adjusting, branch balancing, material level interlocking, backflow preventing, blockage clearing and online switching operation control method, intelligent and controllable powder supply online switching, blockage powder disposal and backflow protection are realized; and the safety, the reliability and the engineering applicability of powder supply of the coal-fired unit are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of coal-fired power unit pulverization and pulverized coal conveying system, specifically relating to a coal-fired power unit pulverized coal supply control system and method based on a small pulverized coal silo. Background Technology

[0002] With the increasing demand for deep peak shaving and flexible operation of thermal power units, traditional direct-fired pulverizing systems are struggling to meet the requirements of rapid load changes due to issues such as slow response and poor low-load stability. To improve the dynamic adjustment capability of the fuel supply system, the industry has widely explored adding small pulverizer silos as a buffer to decouple the pulverizing and combustion processes. Chinese patent CN121338910A discloses a highly flexible pulverizing system and its control method based on the addition of small pulverizer silos. This system uses a small pulverizer silo system as an intermediate buffer, with a diversion pipeline downstream of the primary air-coal mixing pipe. By combining the opening and closing of direct-fired valves and silo inlet valves, three modes of pulverizing—direct-fired, intermediate-storage, or dual-source—are achieved. This decouples the pulverizing process of the coal mill from the boiler's pulverizing demand, and utilizes the rapid adjustment capability of the pulverizer to compensate for the slow response of the coal mill system, thereby improving the overall fuel supply system's response speed to boiler load changes. Simultaneously, this scheme introduces a waste gas recirculation system, which maintains the internal air velocity by adjusting the recirculation air volume, improving low-load operation stability. However, this existing technical solution still has the following three shortcomings:

[0003] (1) Lack of general logic for online powder supply switching: Although it supports switching between dual-source powder supply modes, the valve position operation sequence, rate control and disturbance suppression strategy during the switching process are not defined, which may easily lead to powder interruption or sudden pressure change at the mill outlet / powder pipe.

[0004] (2) Passive handling of powder blockage: The system is not equipped with a powder blockage diagnosis mechanism and active unblocking methods. Once the powder intake pipeline is blocked, it can only be stopped to deal with the problem, which affects continuous operation.

[0005] (3) High risk of coal powder backflow: When the small coal silo is filled or the pressure fluctuates, a reverse pressure difference may be formed, which may cause coal powder to flow back into the coal mill or primary air system. The existing technical solution does not set backflow protection measures, which poses a safety hazard. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, the technical problem to be solved by this invention is to provide a coal-fired power unit coal supply control system and method based on a small coal silo. Through standardized structural design and intelligent control logic, it realizes intelligent and controllable online switching of coal supply, coal blockage handling and backflow protection, so as to improve the safety, reliability and engineering applicability of coal-fired power unit coal supply.

[0007] The core idea of ​​this invention is to set up multiple powder supply modes, including powder pipe intake, mill outlet intake, and combinations thereof, and to provide matching powder intake adjustment, branch balancing, material level interlocking, backflow prevention, blockage clearing, and online switching operation control methods. The technical solutions adopted are as follows:

[0008] A coal-fired power unit coal pulverizing control system based on a small coal silo includes a coal mill, a small coal silo, a controller, a coal pulverizing pipe extraction module, a coal mill outlet extraction module, a combination switching module, and a return coal pulverizing and mixing access module.

[0009] The controller is a DCS or auxiliary controller, used to execute mode management, closed-loop regulation, interlock protection, blockage clearing and online switching logic;

[0010] The powder pipe powder collection module includes a powder pipe powder collection interface, a powder pipe powder collection branch, a branch isolation valve, a branch regulating valve, a branch differential pressure measuring point, a branch check valve, a branch powder collection main pipe, a branch flow equalization structure, a purging interface, and a small powder hopper powder inlet connection section.

[0011] Preferably, the powder intake interface of the powder pipe is located in the horizontal stable section of the powder pipe, with a wear-resistant inner lining, and the powder intake direction is consistent with the main flow; the branch powder intake main pipe is used to collect coal powder from the branch powder intake pipe, and the inner wall is lined with a wear-resistant inner lining; the branch flow equalization structure is located in the merging section of the branch powder intake main pipe to equalize the velocity field entering from each branch; the purging interface is located between the branch isolation valve and the branch regulating valve, connected to a compressed air or steam source, and equipped with a purging valve and a check valve; the powder inlet connection section of the small powder bin includes a quick-closing isolation valve, a check valve, and a differential pressure measuring point before the bin.

[0012] The coal mill outlet powder extraction module includes a common powder extraction interface, a common powder extraction branch, a common powder extraction isolation valve, a common powder extraction regulating valve, a common powder extraction differential pressure measuring point, a common powder extraction check valve, a common powder extraction flow equalization structure, and a common powder extraction main pipe;

[0013] Preferably, the common powder intake interface is located in the pressure-stable section between the coal mill outlet and the powder pipe distributor, avoiding bends and abrupt changes in cross-section; the common powder intake flow equalization structure is located at the common powder intake interface to improve the uniformity of air-powder distribution; the common powder intake main pipe is used to receive coal powder from the common powder intake branch and connects to the powder inlet of the small powder bin.

[0014] The combined switching module includes a switching valve group, a switching monitoring differential pressure measuring point, and a connection section between the common powder intake main pipe and the powder inlet of the small powder hopper.

[0015] Preferably, the switching valve group is respectively set at the powder pipe intake interface and the common powder intake interface, including a switching isolation valve and a regulating valve; the switching monitoring differential pressure measuring point is arranged before and after the switching valve group to monitor the stability of the switching process; the connection section between the common powder intake main pipe and the powder inlet of the small powder silo is used as the confluence and conveying channel of the two powder intake paths corresponding to powder pipe intake and powder intake at the coal mill outlet.

[0016] The feed back and mixing access module includes a metering feed device, a feed back pipeline, a feed back isolation valve, a regulating valve, a check valve, a feed back differential pressure measuring point, a mixing access point, a mixing section flow equalization structure, and a dual anti-backflow structure.

[0017] Preferably, the metering and feeding device is located downstream of the small pulverized coal silo to precisely control the amount of pulverized coal discharged; the mixing access point is located in the mixing section before the primary air main pipe enters the pulverized coal pipe distributor; the return pipeline connects the outlet of the metering and feeding device to the mixing access point; the flow equalization structure of the mixing section is used to promote thorough and uniform mixing of the returned pulverized coal and the primary air; the dual anti-backflow structure includes a check valve on the return pipeline and a check valve on the side of the small pulverized coal silo to prevent backflow of primary air or pulverized coal.

[0018] The working principle of the above-mentioned powder supply control system is as follows:

[0019] (1) Powder extraction stage:

[0020] According to the operating mode (powder pipe powder collection, mill outlet powder collection, or a combination switch), the controller activates the corresponding powder collection path;

[0021] Each powder extraction branch achieves closed-loop control of powder extraction volume through regulating valves and differential pressure measuring points, while check valves and differential pressure interlocks prevent backflow.

[0022] When multiple branches collect toner, the flow equalization structure and differential pressure feedback ensure that the toner collection of each branch is balanced, avoiding disturbance to the original toner distribution.

[0023] (2) Clearing congestion and switching assurance:

[0024] The purge port will initiate backflushing or pulse clearing when the differential pressure rises abnormally;

[0025] During combination switching, the switching valve group operates in the order of "open first, then close, open slowly and close slowly", and is coordinated with the differential pressure monitoring before and after to ensure continuous powder extraction without interruption;

[0026] (3) Storage and recovery stage:

[0027] Powdered coal enters a small powder silo for temporary storage via a shared powder intake manifold. A quick-closing valve and check valve structure at the silo entrance prevent back pressure risk.

[0028] When pulverized coal is required, the metering and feeding device outputs pulverized coal according to the instruction, which is then transported to the mixing access point via the return pipeline;

[0029] (4) Mixing and backflow prevention:

[0030] The returned pulverized coal is fully mixed with the primary air under the action of the flow equalization structure in the mixing section, ensuring uniform coal supply to the burner;

[0031] The return pipeline check valve and the small pulverized coal silo side check structure provide double protection, preventing backflow of primary air or backflow of pulverized coal during shutdown.

[0032] The present invention also provides a coal-fired power unit coal-fired power supply control method based on a small coal silo, which is implemented based on the above-mentioned coal-fired power unit coal-fired power supply control system based on a small coal silo, and includes the following steps:

[0033] Step S1: System initialization and status monitoring;

[0034] The system collects and processes the following input signals in real time: small powder silo level, differential pressure of the common powder intake main pipe, differential pressure of each powder intake branch, coal mill operating status, mill outlet pressure fluctuation, powder pipe differential pressure, purge valve status, opening degree and status feedback of all valves, check valve status, and return path differential pressure; the system initially enters the "shutdown isolation" or "standby preparation" state.

[0035] Step S2: Determine and select the operating mode;

[0036] Based on the current working conditions and equipment status, the controller selects one of three modes: powder intake from the powder pipe, powder intake from the mill outlet, and combination switching.

[0037] Preferably, in step S2,

[0038] If the following conditions are met simultaneously: the coal mill is stable, the differential pressure of the powder pipe is normal, the powder extraction direction is correct, the material level is lower than the target value, and the selected branch valve and measuring point are normal, the powder extraction mode will be entered.

[0039] If the following conditions are met simultaneously: the coal mill is stable, the differential pressure at the mill outlet is normal, the common powder extraction direction is correct, the material level is lower than the target value, and the common powder extraction path is normal, then the mill outlet powder extraction mode will be entered.

[0040] If both pathways are available, a switching command is received, and pressure fluctuations are within acceptable limits, then the combined switching mode is entered.

[0041] Step S3: Perform powder dispensing amount adjustment and material level closed-loop control;

[0042] If the powder silo level is below the lower limit H low Increase the opening of the corresponding powder-collecting regulating valve to improve powder collection capacity until the powder level in the small powder silo is higher than H. low ;

[0043] If the powder silo level is higher than the upper limit H highReduce the opening of the regulating valve until it is closed to stop powder extraction, or until the material level in the small powder silo is lower than H. high ;

[0044] If the material level is within the target range [H] low H high Maintain the current valve position and fine-tune the valve position according to the differential pressure of the common powder intake manifold to stabilize it at the set value DP. set ;

[0045] All regulating valve opening changes are limited by amplitude (u) min ≤u≤u max The slope constraint (du / dt≤Ru) and the slope limit constraint prevent the powder extraction mutation from disturbing the main system.

[0046] Step S4: Perform equalization control when collecting powder from multiple branches;

[0047] When using powder collection via a powder pipe or when multiple branches are in operation:

[0048] Using the differential pressure of each branch as feedback, the regulating valves of each branch are independently fine-tuned: if the differential pressure is too high, the valve is closed; if it is too low, the valve is opened, so as to keep the differential pressure within the set range.

[0049] The total amount of fans collected is maintained by a shared fan collection main pipe or the main control logic, and the branch is only responsible for the allocation ratio.

[0050] If a branch valve position has reached its upper limit but still cannot meet the standard, it will be marked as "insufficient capacity" and its allocation weight will be reduced.

[0051] If the differential pressure on a branch road rises abnormally, it will be marked as "suspected blockage" and the process will be initiated to clear the blockage.

[0052] Step S5: Monitor backflow risk in real time and implement interlock protection;

[0053] Preferably, in step S5, if any of the following fault conditions occur: abnormal differential pressure direction at the powder extraction point, reverse pressure at the silo opening, check valve malfunction, or reverse differential pressure in the return path, the anti-backflow interlock is immediately triggered:

[0054] (1) Close the regulating valve of the faulty branch;

[0055] (2) Close the isolation valve of the faulty branch;

[0056] (3) Close all quick-closing isolation valves on the powder collection main pipe;

[0057] (4) Issue an alarm and record the event;

[0058] Simultaneously execute powder retrieval and return interlock: if the warehouse pressure, return differential pressure, or check valve exceeds the limit, both are prohibited from running in parallel, and exit in the order of stopping return first, then stopping powder retrieval.

[0059] Step S6: Diagnose the blockage and initiate the clearing strategy;

[0060] Preferably, in step S6, when the blockage criterion is met: the branch differential pressure continues to exceed the limit, the material level does not increase, and the valve position and response do not match, the unblocking sequence is executed:

[0061] S6.1, restrict the powder dispensing valve position to a safe position;

[0062] S6.2, Open the branch purge valve and perform pulse purging;

[0063] S6.3, Periodically disturb the regulating valve to remove powder buildup;

[0064] S6.4 After clearing the blockage, restore the original valve position and observe the differential pressure drop and the material level rise;

[0065] S6.5 If the differential pressure remains high and the material level has not recovered, it indicates that the unblocking has failed. In this case, the branch is shut down and the backup branch is switched to. If there is no backup branch, the powder collection mode at the mill outlet is switched to and an abnormal alarm state is entered.

[0066] Step S7: Perform online switching, converting the powder tube powder collection mode to the mill outlet powder collection mode;

[0067] Preferably, in step S7, the mode conversion is premised on the simultaneous satisfaction of the two corresponding passages of powder intake from the powder pipe and powder intake from the coal mill outlet being in normal condition, pressure fluctuation within the allowable range, material level being safe, and valve feedback being effective.

[0068] The switching process is as follows:

[0069] S7.1, Open the new passage isolation valve and slowly open the regulating valve to the pre-open position;

[0070] S7.2, increase the powder-collecting capacity of the new pathway by adjusting the slope;

[0071] S7.3, simultaneously reduce the powder-collecting capacity of the old path according to the slope to maintain the continuity of the total powder-collecting volume;

[0072] S7.4 After the old passage is completely closed, its isolation valve is closed, and the new passage enters stable operation;

[0073] S7.5 records key parameters throughout the entire switching process.

[0074] If any monitored quantity in the two-channel status, pressure fluctuation, material level, or valve feedback exceeds the limit during the switching process, the switching will be immediately stopped, the valve position combination before the switching will be returned, the "abnormal reversal" state will be entered, and an alarm will be triggered.

[0075] Step S8: Exception handling and system recovery;

[0076] In abnormal conditions, the system isolates the fault path, maintains safe shutdown or switches to standby mode; after the fault is eliminated, manually confirmed or automatically reset, it returns to the "standby" state and re-enters the normal control cycle.

[0077] The beneficial effects obtained by adopting the above technical solution are as follows:

[0078] (1) The present invention designs an online switching control strategy. When switching between powder taking from the powder pipe and powder taking from the mill outlet, the controller first opens the isolation valve of the target path and adjusts the powder taking valve to the preset opening. After the differential pressure and silo pressure stabilize, the valve of the original path is closed. The mill outlet pressure, powder pipe differential pressure and small powder silo pressure are monitored in real time throughout the process. If the limit is exceeded, the switching is automatically stopped and the system returns to a safe state. The continuous and stable transition of powder taking volume is achieved, avoiding the interruption of coal powder supply or the violent fluctuation of system pressure, and ensuring the stable operation of the main pulverizing system.

[0079] (2) This invention sets differential pressure measuring points in each powder extraction branch and the main pipe, and constructs a powder blockage diagnosis logic based on abnormal increase in differential pressure, decrease in powder extraction volume, or abnormal silo pressure. Once the diagnosis is triggered, a blockage clearing strategy is automatically started, including backflushing, pulse purging, or high-frequency small-amplitude disturbance of the regulating valve. If the blockage clearing is ineffective, it automatically switches to the backup branch or switches the powder extraction mode and issues an alarm. This realizes early identification and online handling of powder blockage faults, greatly reduces unplanned downtime, and improves system availability and self-healing capability.

[0080] (3) This invention integrates check valves (hardware protection) in each powder intake branch and the main pipe, and sets up anti-backflow interlocks in the control logic. When an abnormal pressure difference direction is detected (such as the silo pressure being higher than the powder pipe pressure) or the backflow risk criterion is met, the controller immediately closes the corresponding regulating valve and isolation valve and prohibits related operations. In addition, a check structure is also set in the small powder silo return pipeline to prevent backflow. By blocking the coal powder backflow path from both hardware and software levels, the backflow of coal powder is effectively prevented from flowing back into the coal mill or primary air system, significantly improving operational safety. Attached Figure Description

[0081] Figure 1 This is a block diagram of a coal-fired power unit pulverized coal supply control system based on a small pulverized coal silo, according to the present invention.

[0082] Figure 2 This is a flowchart of a coal-fired power unit pulverized coal supply control method based on a small pulverized coal silo, according to the present invention. Detailed Implementation

[0083] The technical solution of the present invention will now be described more clearly and completely with reference to the accompanying drawings.

[0084] I. System Composition and General Component Description (Applicable to all embodiments)

[0085] The present invention discloses a coal-fired power unit coal supply control system based on a small coal silo, which includes a coal mill, a coal pipe, a primary air coal powder conveying section, a small coal silo, each coal powder intake branch / each coal powder intake main pipe, valve groups and measuring points, and a controller (preferably a DCS or auxiliary controller) for realizing operation control.

[0086] For ease of description, the following general component numbers are used in the embodiments:

[0087] Small powder hopper: S; Material level measuring points: LH (high material level), LL (low material level), which can be switch quantities or continuous quantities; Hydrant pressure measuring point: PS;

[0088] Powder pipe intake branch valve group: isolation valve Vi, regulating valve Vci, check valve Vri; branch differential pressure measuring point: DPi;

[0089] Coal mill outlet powder intake valve assembly: isolation valve V0, regulating valve Vc0, check valve Vr0; differential pressure measuring point DP0;

[0090] Common powder collection main pipe: H; Main pipe differential pressure measuring point: DPH; Purge / backflush interface: B;

[0091] Switching valve groups: Vs1, Vs2 (used for combined switching structures);

[0092] Controller: C, used for execution mode management, closed-loop regulation, interlock protection, blockage clearing and online switching logic.

[0093] II. Example 1: Powder Pipe Powder Picking Connection Structure and Operation Control

[0094] 1. Connection structure

[0095] like Figure 1 As shown, one or more powder pipes corresponding to the same coal mill are selected to set up powder intake branches. Each powder intake branch includes a powder intake interface, an isolation valve Vi, a regulating valve Vci, and a differential pressure measuring point DPi, and preferably a check valve Vri is installed to reduce the risk of backflow. All branches converge into the common powder intake main pipe H and then enter the small powder silo S.

[0096] To reduce the risk of wear and dust accumulation, wear-resistant pipe fittings and reasonable elbow radii should be used in the dust extraction branch, and purging / backflushing interfaces B should be arranged in the main pipe or at key low points.

[0097] 2. Operation mode and control logic

[0098] Controller C provides powder collection mode M1 via the powder pipe. Its operation control includes:

[0099] (1) Powder collection and valve position establishment

[0100] Before commissioning, the controller is checked to ensure that the material level in the small powder silo is not higher than the upper limit (LH is not triggered), the valve is in an operable state, the differential pressure measuring point is valid, and the silo pressure PS is within the allowable range.

[0101] For initial commissioning, it is preferable to first open one powder pipe branch: first open the isolation valve Vi, then open the regulating valve Vci according to the slope, so that the powder intake is gradually established and avoids sudden changes in the resistance of the original powder pipe.

[0102] (2) Adjustment of powder output (mainly based on material level, supplemented by differential pressure)

[0103] The controller uses the powder silo level as the main control variable: when the powder level is below the lower limit of the target range, the opening of the powder dispensing valve is increased; when the powder level is close to the upper limit, the opening is decreased; when the upper limit is reached, powder dispensing is stopped or the minimum powder dispensing is maintained.

[0104] At the same time, differential pressure DPi is introduced as a constraint: if DPi rises abnormally (indicating blockage or increased resistance), Vci is limited to increase further and a blockage clearing diagnosis is triggered.

[0105] (3) Multi-branch balancing (when powder is collected in parallel)

[0106] When two or more powder pipes need to be connected in parallel to collect powder, the controller uses the differential pressure DPi of each branch or the estimated powder collection amount as feedback to perform balanced control:

[0107] The goal is to distribute powder from each branch according to a preset ratio (e.g., equal distribution or distribution according to branch capacity).

[0108] When the DPi of a certain branch deviates significantly or the torrent-collecting capacity decreases, the contribution of that branch is automatically reduced and the total torrent-collecting demand is made up by other branches.

[0109] (4) Backflow prevention and interlock protection

[0110] When an abnormal differential pressure direction, an abnormal increase in silo pressure, or a backflow risk criterion is detected, the controller can quickly reduce or close the corresponding branch's regulating valve Vci. If necessary, it can also close the isolation valve Vi and issue an alarm. If a check valve Vri is installed, the probability of abnormal backflow can be further reduced.

[0111] III. Example 2: Pulverizer Outlet Connection Structure and Operation Control

[0112] 1. Connection structure

[0113] like Figure 1As shown, a common powder intake interface is installed in the primary air conveying section or separator outlet section between the coal mill outlet and the powder pipe distributor. This interface is connected to a common powder intake manifold H via an isolation valve V0, a ​​regulating valve Vc0, and a differential pressure measuring point DP0. The common powder intake manifold leads into the small powder silo S. Preferably, a flow equalization structure and / or a wear-resistant powder intake structure are installed at the common powder intake interface to improve powder intake uniformity and reduce wear.

[0114] 2. Operation mode and control logic

[0115] Controller C provides mill outlet powder collection mode M2. Its operation control includes:

[0116] (1) Powder collection, operation and stability establishment

[0117] Before commissioning, verify the material level, silo pressure, valve status, and DP0 validity.

[0118] First, open the isolation valve V0, then open the regulating valve Vc0 according to the slope to establish powder collection; and monitor the fluctuations of DP0 and the mill outlet pressure to ensure that the disturbance of powder collection to the original system is within the allowable range.

[0119] (2) Closed-loop method for powder intake

[0120] The material level in the small powder silo is the main control, and Vc0 is the execution quantity.

[0121] DP0 is used to determine the boundary between resistance change and powder collection capacity. When DP0 reaches the boundary, Vc0 is limited or its speed is limited to avoid over-extraction that would aggravate disturbances in the conveying section.

[0122] (3) Blockage diagnosis and clearing

[0123] When DP0 continues to rise and the material level increase does not meet expectations, or when the silo pressure PS fluctuates abnormally, the controller triggers the unblocking process:

[0124] Perform purging / backflushing (if configured B), or perform valve position disturbance (small, rapid opening and closing) to remove powder buildup;

[0125] If the blockage is not cleared, powder collection will stop and an alarm will sound, prompting you to check for wear at the powder collection port, powder accumulation, or the condition of the flow equalization structure.

[0126] IV. Example 3: Combined switching structure and online switching of powder pipe powder collection + mill outlet powder collection

[0127] 1. Connection structure

[0128] like Figure 1 As shown, a powder intake branch group from the powder pipe and a common powder intake branch from the mill outlet are simultaneously set up, and selective connection of the two powder intake paths corresponding to the powder intake from the powder pipe and the powder intake from the mill outlet is achieved through switching valve groups Vs1, Vs2 or equivalent structures. This structure allows:

[0129] Powder is collected using a separate powder tube;

[0130] Powder is collected solely from the mill outlet;

[0131] When constraints allow, short-term parallel toner acquisition is performed (for transition or toner replenishment capability).

[0132] 2. Online switching control method

[0133] When the controller C performs online switching, it adopts the principle of "open first, then close, open slowly and close slowly" to avoid sudden changes in the amount of powder taken, which may cause disturbances in the mill outlet or powder distribution.

[0134] (1) Switch from powder collection at the mill outlet to powder collection via the powder pipe.

[0135] First, open the isolation valve Vi of the target powder pipe branch, and open the regulating valve Vci to the pre-open position according to the slope, and observe the stability of DPi;

[0136] Subsequently, the contribution of the powder pipe to powder collection was gradually increased, while the opening of the powder collection valve Vc0 at the mill outlet was reduced according to the slope.

[0137] Once the powder intake through the powder pipe reaches the target total intake, close the powder intake valve Vc0 at the mill outlet and, if necessary, close the isolation valve V0 to complete the switching.

[0138] (2) Switch from powder pipe to powder outlet.

[0139] First open V0 and establish Vc0 to the pre-open position according to the slope, then monitor the fluctuations of DP0 and the mill outlet.

[0140] Then gradually reduce the Vci opening of each powder pipe branch until it is discontinued; if necessary, the branch lines will be discontinued in sequence.

[0141] Finally, close the isolation valve Vi of the powder intake branch of the powder pipe to complete the switching.

[0142] (3) Switch monitoring and rollback

[0143] During the switching process, continuously monitor the following: DP0, DPi, silo pressure PS, and related fluctuation signals at the mill outlet / powder pipe. If any critical quantity exceeds the limit, the switching will be aborted and the system will revert to the safety valve position combination before the switching, with an alarm issued.

[0144] V. Example 4: Operation Control Method Flow

[0145] like Figure 2 As shown, the operation control method of the present invention can be solidified into the following process:

[0146] 1) Mode determination: Select M1 / M2 / M3 based on equipment availability, historical congestion, maintenance status, and operational requirements;

[0147] 2) Powder collection setup: Powder collection is established according to the valve position sequence and slope control;

[0148] 3) Closed-loop powder extraction: The powder extraction rate is adjusted by controlling the material level and using differential pressure as a constraint.

[0149] 4) Branch balancing (only activated when powder pipes in M1 or M3 are connected in parallel): Balances are achieved based on DPi or estimated flow rate;

[0150] 5) Interlock protection: High material level stops powder taking, low material level restricts related actions; abnormal differential pressure direction or abnormal silo pressure triggers anti-backflow action;

[0151] 6) Unblocking and clearing: abnormal differential pressure, purging / valve position disturbance, effect judgment; if it fails, switch branches or switch modes;

[0152] 7) Online switching: Follow the "open first, then close, slow open, slow close" strategy and monitor for over-limit rollback;

[0153] 8) Event logging and alarms: Record events such as blockage, backflow risk, valve failure, and sensor malfunction to facilitate maintenance and optimization.

Claims

1. A pulverized coal supply control system for a coal-fired power unit based on a small pulverized coal silo, characterized in that, Includes a coal mill, a small powder silo, a controller, a powder pipe powder collection module, a coal mill outlet powder collection module, a combination switching module, and a return powder supply and mixing access module; The controller is a DCS or auxiliary controller, used to execute mode management, closed-loop regulation, interlock protection, blockage clearing and online switching logic; The powder pipe powder collection module includes a powder pipe powder collection interface, a powder pipe powder collection branch, a branch isolation valve, a branch regulating valve, a branch differential pressure measuring point, a branch check valve, a branch powder collection main pipe, a branch flow equalization structure, a purging interface, and a small powder hopper powder inlet connection section. The coal mill outlet powder extraction module includes a common powder extraction interface, a common powder extraction branch, a common powder extraction isolation valve, a common powder extraction regulating valve, a common powder extraction differential pressure measuring point, a common powder extraction check valve, a common powder extraction flow equalization structure, and a common powder extraction main pipe; The combined switching module includes a switching valve group, a switching monitoring differential pressure measuring point, and a connection section between the common powder intake main pipe and the powder inlet of the small powder hopper. The feed back and mixing access module includes a metering feed device, a feed back pipeline, a feed back isolation valve, a regulating valve, a check valve, a feed back differential pressure measuring point, a mixing access point, a mixing section flow equalization structure, and a dual anti-backflow structure.

2. The powder supply control system according to claim 1, characterized in that, The powder intake interface of the powder pipe is located in the horizontal stable section of the powder pipe, with a wear-resistant inner lining, and the powder intake direction is consistent with the main flow. The branch powder intake main pipe is used to collect coal powder from the branch powder intake pipes, and its inner wall is lined with a wear-resistant inner lining. The branch flow equalization structure is located in the merging section of the branch powder intake main pipe to equalize the velocity field entering from each branch. The purging interface is located between the branch isolation valve and the branch regulating valve, connected to a compressed air or steam source, and equipped with a purging valve and a check valve. The powder inlet connection section of the small powder bin includes a quick-closing isolation valve, a check valve, and a differential pressure measuring point before the bin.

3. The powder supply control system according to claim 2, characterized in that, The common powder intake interface is located in the pressure-stable section between the coal mill outlet and the powder pipe distributor; the common powder intake flow equalization structure is located at the common powder intake interface to improve the uniformity of air and powder distribution; the common powder intake main pipe is used to receive coal powder from the common powder intake branch and connects to the powder inlet of the small powder bin.

4. The powder supply control system according to claim 3, characterized in that, The switching valve group is respectively installed at the powder pipe intake interface and the common powder intake interface, including a switching isolation valve and a regulating valve; the switching monitoring differential pressure measuring point is arranged before and after the switching valve group to monitor the stability of the switching process; the common powder intake main pipe and the powder inlet of the small powder silo are connected to serve as the confluence and conveying channel for the two powder intake paths corresponding to powder pipe intake and powder intake at the coal mill outlet.

5. The powder supply control system according to claim 4, characterized in that, The metering and feeding device is located downstream of the small pulverized coal silo and is used to precisely control the amount of pulverized coal discharged. The mixing access point is located in the mixing section before the primary air main pipe enters the pulverized coal pipe distributor. The return pipeline connects the outlet of the metering and feeding device to the mixing access point. The flow equalization structure of the mixing section is used to promote the full and uniform mixing of the returned pulverized coal and the primary air. The dual anti-backflow structure includes a check valve on the return pipeline and a check valve on the side of the small pulverized coal silo, which is used to prevent the backflow of primary air or pulverized coal.

6. A coal-fired power unit coal pulverizer supply control method based on a small coal silo, implemented based on the coal pulverizer supply control system described in claim 5, characterized in that, Includes the following steps: Step S1: System initialization and status monitoring; The system collects and processes the following input signals in real time: small powder silo level, differential pressure of the common powder intake main pipe, differential pressure of each powder intake branch, coal mill operating status, mill outlet pressure fluctuation, powder pipe differential pressure, purge valve status, opening degree and status feedback of all valves, check valve status, and return path differential pressure; the system initially enters either "shutdown isolation" or "standby preparation" state. Step S2: Determine and select the operating mode; Based on the current working conditions and equipment status, the controller selects one of three modes: powder intake from the powder pipe, powder intake from the mill outlet, and combination switching. Step S3: Perform powder dispensing amount adjustment and material level closed-loop control; If the powder silo level is below the lower limit H low Increase the opening of the corresponding powder-collecting regulating valve to improve powder collection capacity until the powder level in the small powder silo is higher than H. low ; If the powder silo level is higher than the upper limit H high Reduce the opening of the regulating valve until it is closed to stop powder extraction, or until the material level in the small powder silo is lower than H. high ; If the material level is within the target range [H] low H high Maintain the current valve position and fine-tune the valve position according to the differential pressure of the common powder intake manifold to stabilize it at the set value DP. set ; All regulating valve opening changes are limited by amplitude (u) min ≤u≤u max ) and slope constraint (du / dt≤Ru); Step S4: Perform equalization control when collecting powder from multiple branches; When using powder collection via a powder pipe or when multiple branches are in operation: Using the differential pressure of each branch as feedback, the regulating valves of each branch are independently fine-tuned: if the differential pressure is too high, the valve is closed; if it is too low, the valve is opened, so as to keep the differential pressure within the set range. The total amount of fans collected is maintained by a shared fan collection main pipe or the main control logic, and the branch is only responsible for the allocation ratio. If a branch valve position has reached its upper limit but still cannot meet the standard, it is marked as "insufficient capacity" and its allocation weight is reduced. If the differential pressure on a branch road rises abnormally, it will be marked as "suspected blockage" and the blockage clearing and handling process will begin. Step S5: Monitor backflow risk in real time and implement interlock protection; Step S6: Diagnose the blockage and initiate the clearing strategy; Step S7: Perform online switching, converting the powder tube powder collection mode to the mill outlet powder collection mode; Step S8: Exception handling and system recovery; In abnormal conditions, the system isolates the fault path, maintains safe shutdown or switches to standby mode; after the fault is eliminated, manually confirmed or automatically reset, it returns to the "standby" state and re-enters the normal control cycle.

7. The powder supply control method according to claim 6, characterized in that, In step S2 If the following conditions are met simultaneously: the coal mill is stable, the differential pressure of the powder pipe is normal, the powder extraction direction is correct, the material level is lower than the target value, and the selected branch valve and measuring point are normal, the powder extraction mode will be entered. If the following conditions are met simultaneously: the coal mill is stable, the differential pressure at the mill outlet is normal, the common powder extraction direction is correct, the material level is lower than the target value, and the common powder extraction path is normal, then the mill outlet powder extraction mode will be entered. If both pathways are available, a switching command is received, and pressure fluctuations are within acceptable limits, then the combined switching mode is entered.

8. The powder supply control method according to claim 7, characterized in that, In step S5, if any of the following fault conditions occur: abnormal differential pressure direction of powder extraction, reverse pressure at the silo opening, check valve failure, or reverse differential pressure in the return path, the anti-backflow interlock will be triggered immediately: (1) Close the regulating valve of the faulty branch; (2) Close the isolation valve of the faulty branch; (3) Close all quick-closing isolation valves on the powder collection main pipe; (4) Issue an alarm and record the event; Simultaneously execute powder retrieval and return interlock: if the warehouse pressure, return differential pressure, or check valve exceeds the limit, both are prohibited from running in parallel, and exit in the order of stopping return first, then stopping powder retrieval.

9. The powder supply control method according to claim 8, characterized in that, In step S6, when the blockage criterion is met: the branch differential pressure continues to exceed the limit, the material level does not increase, and the valve position and response do not match, the unblocking sequence is executed: S6.1, restrict the powder dispensing valve position to a safe position; S6.2, Open the branch purge valve and perform pulse purging; S6.3, Periodically disturb the regulating valve to remove powder buildup; S6.4 After clearing the blockage, restore the original valve position and observe the differential pressure drop and the material level rise; S6.5 If the differential pressure remains high and the material level has not recovered, it indicates that the unblocking has failed. In this case, the branch is shut down and the backup branch is switched to. If there is no backup branch, the powder collection mode at the mill outlet is switched to and an abnormal alarm state is entered.

10. The powder supply control method according to claim 9, characterized in that, In step S7, the mode conversion is premised on the simultaneous satisfaction of the two corresponding passages of powder pipe powder intake and coal mill outlet powder intake being normal, pressure fluctuation within the allowable range, material level safety, and effective valve feedback. The switching process is as follows: S7.1, Open the new passage isolation valve and slowly open the regulating valve to the pre-open position; S7.2, increase the powder-collecting capacity of the new pathway by adjusting the slope; S7.3, simultaneously reduce the powder-collecting capacity of the old path according to the slope to maintain the continuity of the total powder-collecting volume; S7.4 After the old passage is completely closed, its isolation valve is closed, and the new passage enters stable operation; S7.5 records key parameters throughout the entire switching process; If any monitored quantity in the two-channel status, pressure fluctuation, material level, or valve feedback exceeds the limit during the switching process, the switching will be immediately stopped, the valve position combination before the switching will be returned, the "abnormal reversal" state will be entered, and an alarm will be triggered.

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