Coal-fired unit deep peak regulation stable combustion control system and method based on small powder bin

Abstract

The invention belongs to the technical field of coal-fired power unit deep peak regulation operation and combustion powder preparation cooperative control, and particularly relates to a coal-fired power unit deep peak regulation stable combustion control system and method based on a small powder bin. Based on flame signals, CO, hearth negative pressure, pulverized coal concentration equivalent quantity and the like, combustion side and powder making side multi-parameter fusion combustion stability criteria are constructed, measurable parameters and clear criteria are used for driving, low-load stable combustion is actively intervened, and preventive stable combustion is achieved; according to the method, a complete six-step control process is defined, an automatic state transition mechanism is formed, a complete closed loop of pre-commissioning, emergency switching and smooth back-switching is provided, and implementation, popularization and application in a DCS are facilitated; meanwhile, a powder supply redundant path is provided, dual redundancy of a gas source and a powder source is established, and the risk of stable combustion control failure is reduced.

Description

Technical Field

[0001] This invention belongs to the field of deep peak shaving operation and combustion pulverizing coordinated control technology of coal-fired power generating units, specifically involving a deep peak shaving and stable combustion control system and method for coal-fired power generating units based on a small pulverizing silo. Background Technology

[0002] With the increasing proportion of new energy sources in the power system, coal-fired power units need to adjust rapidly and frequently over a wider load range, and deep peak shaving and long-term low-load operation are gradually becoming the norm. Under low-load conditions, the furnace heat load decreases and the combustion stability margin becomes smaller. The unit is more sensitive to the continuity of pulverized coal supply and the stability of pulverized coal concentration. Once there is a fluctuation in pulverized coal supply, it can easily cause flame swaying, deterioration of burnout, and even the risk of fireout. Existing coal-fired power units usually use coal mills and pulverized coal feeding systems as the main pulverized coal supply channels. Under deep peak shaving and low-load conditions, coal mills are often in a state of low output, low ventilation, or frequent start-stop, which can easily lead to mill skipping or pulverized coal interruption. This may cause drastic fluctuations in the fuel supply of coal-fired power units and thus lead to boiler fireout.

[0003] To address the aforementioned issues, Chinese patent CN110645588B discloses a boiler system comprising a boiler and a pulverizing unit. The boiler has at least one burner, and the pulverizing unit includes at least one coal mill. Each separator outlet of the coal mill is connected to at least one pulverized coal feeding pipeline leading to the burner. Each separator outlet of the coal mill is also connected to an auxiliary pulverized coal pipe, which is connected to a pulverized coal storage bin. When the coal mill trips or experiences a coal shortage, a control device connects the pulverized coal storage bin to the pulverized coal feeding pipeline, enabling the storage bin to begin supplying pulverized coal. The pulverized coal feeding pipeline acts as an air duct, blowing pulverized coal to the burner to maintain the burner's fuel supply, thereby preventing boiler flameout. Chinese patent CN117109024A discloses a pulverizing system and control method for stable operation of a coal-fired unit under ultra-low load. It modifies a medium-speed mill direct-fired pulverizing system by connecting a pulverized coal silo in series with the pulverized coal outlet pipe of a mill connected to the bottom burner, transforming it into an intermediate storage pulverizing system. Under ultra-low load, only this system is used for pulverized coal supply, increasing the air-coal concentration and improving the uniformity of air-coal distribution, reducing the impact of mill pulverization instability on stable combustion at low loads; simultaneously, other mills are retained for direct-fired operation, accommodating full load operation. Chinese patent CN117190170A discloses an intermediate pulverized coal silo combustion and feeding system for stable combustion at low loads in boilers, including a mill, a feeding unit, and a furnace. It is equipped with an intermediate pulverized coal silo, a feeder, and a mixer, and can independently supply pulverized coal to the burner, supporting both pulverized coal silo storage and silo-only supply modes. Path isolation is achieved through a gate switching mechanism.

[0004] The aforementioned existing technologies introduce pulverized coal storage bins or intermediate pulverized coal bins in their structure, providing a certain degree of pulverized coal supply buffering or independent pulverized coal supply capability. This reduces the coupling between the coal mill and the boiler, enabling emergency pulverized coal supply during mill trips or improving the boiler's low-load stable combustion capability. However, in practical applications, some shortcomings still exist. First, existing technical solutions lack comprehensive combustion stability criteria, passively responding to coal mill trip signals or switching based on manual judgment of operating conditions. They cannot proactively improve the stable combustion margin before pulverized coal supply is cut off, easily causing combustion fluctuations or response delays. Second, the stable combustion control of existing technical solutions is based on a single mill trip trigger to start the pulverizer, or manual switching of operating conditions via the gate valve, or pulverized coal level control. This does not form a complete control logic and closed-loop control process, making it impossible to integrate with existing DCS systems. Third, existing technical solutions heavily rely on the main and primary air ducts as conveying channels, failing to form dual redundancy for air and pulverized coal sources. Under extreme conditions, such as primary air fan failure or duct blockage, the small pulverized coal bins will also be unable to supply pulverized coal, resulting in a significant risk of stable combustion control failure. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, the technical problem to be solved by this invention is to provide a deep peak-shaving and stable combustion control system and method for coal-fired power units based on a small pulverized coal silo. Based on comprehensive combustion stability criteria, a complete closed-loop control logic is formed and embedded in the DCS system to actively intervene in low-load stable combustion and achieve preventive stable combustion. At the same time, redundant pulverized coal supply paths are provided to establish dual redundancy of gas source and pulverized coal source, reducing the risk of stable combustion control failure.

[0006] The technical solution adopted in this invention is as follows:

[0007] A deep peak shaving and stable combustion control system for coal-fired power units based on small pulverized coal silos includes a burner, a main pulverized coal supply path, a small pulverized coal supply path, a switching and isolation component, a measurement unit, and a controller.

[0008] The main coal supply path includes a coal mill, a coal feeding device, a main coal supply pipeline, and a primary air duct. A mixing point is provided on the primary air duct. The coal powder enters the burner through the primary air duct along with the primary air.

[0009] The powder supply path of the small powder hopper includes the small powder hopper, the powder outlet and metering feeding device, the small powder hopper conveying device, and the branch pipeline; the branch pipeline is connected to the mixing point set on the burner or the primary air duct.

[0010] Preferably, the small powder hopper conveying device is a pneumatic conveying device or an ejector device.

[0011] The switching and isolation components include electric valves, pneumatic valves, check valves, and quick-opening valves installed at the outlet of the small powder silo branch pipeline and before and after the mixing point; to meet the response requirements in case of mill jump or powder interruption emergency.

[0012] The measurement unit is used to provide feedback on the material level in the small powder silo, the operation of the powder discharge actuator in the small powder silo, the main powder supply or feed rate, the primary air volume, the operation or tripping status of the coal mill, and the combustion stability parameters; the combustion stability parameters include flame detection signal, furnace temperature, furnace negative pressure, O2 and CO parameters;

[0013] The controller is used to perform state machine control of standby preparation, commissioning, emergency supply, coordinated combustion stabilization, smooth back-off, and reset based on load, coal supply status, combustion stability parameters, and interlock status.

[0014] Preferably, the controller is a unit DCS or an auxiliary control system.

[0015] A deep peak-shaving and stable combustion control method for coal-fired power units based on small pulverized coal silos, implemented based on the aforementioned deep peak-shaving and stable combustion control system for coal-fired power units based on small pulverized coal silos, includes the following steps:

[0016] Step S1: Pre-charging and verification, and before the coal-fired unit enters the deep peak shaving low load condition or during low load operation, the controller triggers the standby preparation logic of the small powder silo.

[0017] Preferably, step S1 includes:

[0018] S1.1, Pre-filling powder ensures that the powder level in the small powder silo reaches the set target;

[0019] S1.2, Availability verification, availability includes that the material level in the small powder silo is not lower than the lower limit, the powder discharge valve is in an operable state, the powder feeding actuator provides normal feedback, the differential pressure or blockage diagnosis of the conveying pipeline is normal, and the interlock meets the commissioning conditions.

[0020] S1.3, Self-check and setting: Set the small powder silo control status to standby, and record the available inventory and maximum continuous powder supply capacity.

[0021] Step S2, Monitoring Criterion Acquisition: The controller acquires the following indicators at fixed intervals of 1s-5s:

[0022] (1) Main powder supply status: coal mill operation or trip signal, main powder supply quantity, main powder supply fluctuation range, and main powder supply lower limit margin;

[0023] (2) Combustion stability parameters: flame stability indicator, furnace temperature or burner outlet temperature, furnace negative pressure fluctuation, O2 and CO parameters;

[0024] (3) Equivalent index of primary air pulverized coal concentration.

[0025] Preferably, in step S2, the formula for calculating the equivalent index of primary air pulverized coal concentration is:

[0026]

[0027] Where C eq It is a single-pass powder concentration, Q 主 Main powder supply, Q 小粉仓 V is the amount of powder supplied to the small powder silo. PA This refers to the primary air volume. If the primary air volume cannot be stably obtained on-site, equivalent quantities can be constructed using the supply fan / primary air fan load, primary air damper opening, etc.

[0028] Step S3, Commissioning: The controller will commission the powder supply path of the small powder hopper when any of the following criteria are met:

[0029] (1) Combustion side stable combustion demand criteria: flame stability indicator is below the threshold, furnace temperature rises beyond the limit, furnace negative pressure fluctuation increases, CO rises, or burner outlet temperature fluctuation exceeds the limit.

[0030] (2) Risk criteria for main coal supply on the pulverizing side: the main coal supply reaches the minimum stable coal supply, the main coal supply fluctuation exceeds the limit, the coal mill operation stability margin is insufficient, and the unit load is lower than the set threshold.

[0031] (3) Tripping criterion: A tripping signal of the coal mill is detected;

[0032] Preferably, in step S3, the operation of the powder supply path for the powder storage unit includes:

[0033] (1) Open the small powder silo branch valve to the pre-open position;

[0034] (2) Start the powder feeding and metering actuators;

[0035] (3) The powder supply of the small powder bin is increased from 0 to the target powder supply according to the slope limit to avoid combustion fluctuations caused by sudden changes in powder supply;

[0036] (4) Record the commissioning time and enter the "low load auxiliary" state.

[0037] Step S4, Emergency Mill Trip: When a mill trip signal is detected, the controller executes the emergency mill trip supply strategy.

[0038] Preferably, in step S4, the emergency power supply strategy for mill skipping includes:

[0039] (1) Rapid switching: The coal supply in the small coal bin is rapidly increased from the current value to the emergency target coal supply, and the coal supply on the burner side is guaranteed to be no less than the minimum stable combustion coal supply within the set response time;

[0040] (2) Powder shortage judgment and closed-loop correction: If the flame stability indicator continues to decline or the CO rises abnormally, the powder supply in the small powder bin will be further increased or stronger stabilization measures will be triggered. The stronger stabilization measures include limiting the rise of primary air and temporarily increasing the amount of stabilizing fuel oil.

[0041] Step S5, Coordinated stable combustion: During the coal supply from the small coal hopper, the controller performs coordinated control of primary air and coal supply;

[0042] Preferably, in step S5, the coordinated control of primary air and powder supply includes:

[0043] (1) Under the premise of ensuring that the primary air volume meets the lower safety limit of the burner, priority should be given to increasing the coal supply to achieve the desired C. eq It will either rise or remain within the target range;

[0044] (2) If C eq If the primary air volume is below the safety lower limit but still above the minimum lower limit, reduce the primary air volume or limit the increase in primary air volume; if the primary air volume has already reached the lower limit, increase the C only by increasing the powder supply of the small powder hopper. eq ;

[0045] (3) Using the flame stability indicator as the outer loop feedback, when the flame stability indicator returns to the safe range and remains stable for a set time, the powder supply of the small powder bin is controlled to drop back to the economic target value.

[0046] Step S6, Smooth Back-off and Reset: When the main powder supply path is restored and the back-off conditions are met, the controller performs a smooth back-off and reset.

[0047] Preferably, in step S6, the cut-back conditions are: the coal mill resumes operation, the main coal supply is restored to the target margin, and the combustion stability parameters are continuously and stably maintained for a set time of 30 s-300 s;

[0048] The smooth back-cut reset includes:

[0049] (1) Smooth handover: The main powder supply increases at a set slope, and the powder supply from the small powder silo decreases at a set slope, ensuring that the sum of the main powder supply and the powder supply from the small powder silo is smooth and does not change abruptly.

[0050] (2) Exit and reset: When the powder supply of the small powder silo drops to the exit threshold and stabilizes at the set time, close the branch valve of the small powder silo and stop the powder feeding actuator; restore the small powder silo to standby inventory and return to the status of "hot standby or standby".

[0051] The beneficial effects obtained by adopting the above technical solution are as follows:

[0052] (1) This invention is based on the equivalent quantities of flame signal, CO, furnace negative pressure, and pulverized coal concentration (C). eq The combustion stability criteria, which integrates multiple parameters on the combustion and pulverizing sides, are constructed. Driven by measurable parameters and clear criteria, active intervention is carried out on low-load stable combustion, achieving "preventive stable combustion" and improving the stable operation capability of coal-fired units under deep peak shaving conditions.

[0053] (2) The stable combustion control method of the present invention defines a complete six-step control process, forming an automated state transition mechanism, and has a complete closed loop of pre-operation, emergency switching and smooth return, which is convenient to implement and promote in DCS;

[0054] (3) The small powder bin in the stable combustion control system of the present invention provides a redundant path for powder supply, forming a dual redundancy of gas source and powder source, reducing the risk of stable combustion control failure, and can quickly and continuously supply powder after the mill jumps; and through the powder supply of the small powder bin and the primary air adjustment, the primary air pulverized coal concentration can be increased, the low load stable combustion margin can be improved, and the stable ignition and stable combustion capabilities under low load can be enhanced. Attached Figure Description

[0055] Figure 1 This is a block diagram of a deep peak-shaving and stable combustion control system for coal-fired power units based on a small powder silo, according to the present invention.

[0056] Figure 2 This is a flowchart of a deep peak shaving and stable combustion control method for coal-fired power units based on a small powder silo, according to the present invention. Detailed Implementation

[0057] The technical solution of the present invention will now be described more clearly and completely with reference to the accompanying drawings.

[0058] like Figure 1 As shown, a deep peak shaving and stable combustion control system for coal-fired power units based on a small pulverized coal silo includes a burner, a main pulverized coal supply path, a small pulverized coal supply path, a switching and isolation component, a measurement unit, and a controller.

[0059] Based on the above-mentioned stable combustion control system, the present invention also provides a corresponding stable combustion control method, such as... Figure 2 As shown, the specific workflow is as follows:

[0060] (1) Preparation and availability check of small powder silo: Before the unit enters deep peak shaving and low load or during low load operation, the small powder silo is pre-filled with powder, and the material level, powder outlet channel, conveying / feeding actuator, sealing and interlocking signals are checked to ensure that it has emergency powder supply capability and can support the duration.

[0061] (2) Status monitoring and risk identification: Real-time acquisition of pulverizing system status parameters and combustion stability parameters. Pulverizing system parameters include pulverizer operation / trip status, coal / pulverized coal feed rate, differential pressure, primary air volume, etc.; combustion stability parameters include flame detection signal, furnace temperature or burner outlet temperature, furnace negative pressure fluctuation, oxygen content, CO, etc., used to identify low-load stable combustion requirements and pulverized coal supply interruption risks.

[0062] (3) Small pulverized coal bin commissioning criteria and pulverized coal supply establishment: When the low load stable combustion criteria are met (such as flame stability indicator decline, furnace temperature rise, combustion fluctuation increase, etc.) or the pulverizing system disturbance risk criteria are met (such as insufficient coal mill stability margin, excessive pulverized coal supply fluctuation, etc.), the small pulverized coal bin is commissioned and the pulverized coal supply path from the small pulverized coal bin to the burner is established, and the target pulverized coal supply amount and adjustment rate are determined at the same time.

[0063] (4) Emergency continuous coal supply for mill jump / coal supply interruption: When mill jump, coal supply interruption or insufficient main coal supply is detected, the emergency strategy is triggered: the small coal silo switches to continuous coal supply mode within the set response time and quickly increases the coal supply in the climbing manner to avoid coal supply interruption on the burner side.

[0064] (5) Air-coal synergy to improve primary air pulverized coal concentration: During the pulverized coal supply in the small pulverized coal bin, coordinate the primary air volume and the pulverized coal supply: Under the premise of meeting the minimum safe ventilation constraints of the burner, improve or maintain the primary air pulverized coal concentration in the target range through the strategy of "prioritizing pulverized coal supply and matching air volume", enhance the low-load stable combustion capability and reduce flame fluctuation;

[0065] (6) Smooth back-cut and small powder bin reset after main powder supply is restored: When the coal mill is restored and the main powder supply meets the combustion stability constraint, smooth back-cut is performed: the main powder supply increases at the set slope and the small powder bin supply decreases at the set slope, so as to achieve seamless switching under the condition of no furnace shutdown and no fire extinguishing; after the back-cut is completed, the small powder bin is replenished and reset, and the standby state is restored.

[0066] The stable combustion control method is described in detail below in three implementation scenarios:

[0067] (1) Specific implementation scenario A: Low load stable combustion improvement (no mill jumping)

[0068] The unit load decreased, entering the deep peak-shaving low-load sensitive zone. While the main coal supply remained stable, the flame stability indicator showed a downward trend. Simultaneously, the primary air volume was constrained by the safety lower limit and could not continue to decrease, leading to C... eq Low; the controller triggers the stable combustion demand criterion, puts the small coal silo into operation for coal supply, and increases the coal supply from the small coal silo at a small slope, so that C eq Once the flame returns to the target range, the flame stability indicator recovers and stabilizes; subsequently, the powder supply from the small powder bin is maintained at a low level or withdrawn as needed.

[0069] The effect of the implementation is to improve the stable combustion capability under low load without relying on a significant increase in oil input.

[0070] (2) Specific implementation scenario B: Emergency grinding without powder interruption

[0071] During low-load operation, the coal mill experiences a sudden drop in the main coal supply, which rapidly decreases to near zero within a short period. If the main coal supply is relied upon directly for recovery, a coal supply interruption will occur on the burner side. Upon detecting the mill jump signal or an excessive drop in the main coal supply, the controller immediately enters emergency mode within milliseconds: it opens the branch valve to the emergency position, increases the coal supply from the small coal bin to the target supply, and performs air-coal coordination to prevent a rapid decline in the primary air coal concentration. The flame stability indicator remains within the safe range after a brief disturbance, and the furnace temperature and negative pressure fluctuations are controlled.

[0072] The effect of this implementation is that the coal can still be supplied continuously after the mill stops, reducing the probability of fire extinguishing and gaining time for the main coal supply to recover.

[0073] (3) Specific implementation scenario C: Uninterrupted switchback after main powder supply is restored

[0074] The coal mill is reset and put back into operation, and the main coal supply begins to recover; the controller enters the cut-back preparation: first, the main coal supply is increased at a slope, while the coal supply to the small coal bin is reduced at the same or slightly slower slope to make the total coal supply smooth and avoid the flame from fluctuating in intensity; when the cut-back is completed, the small coal bin branch is closed and the coal replenishment is reset.

[0075] The implementation results in less disturbance to the furnace during the coal supply handover process and more stable unit parameters.

Claims

1. A deep peak-shaving and stable combustion control system for coal-fired power units based on a small pulverized coal silo, characterized in that, This includes the burner, main coal supply path, small coal hopper coal supply path, switching and isolation components, measurement unit, and controller; The main powder supply path includes a coal mill, a powder feeding device, a main powder supply pipeline, and a primary air duct, and a mixing point is provided on the primary air duct; The powder supply path of the small powder hopper includes the small powder hopper, the powder outlet and metering feeding device, the small powder hopper conveying device, and the branch pipeline; the branch pipeline is connected to the mixing point set on the burner or the primary air duct. The switching and isolation components include electric valves, pneumatic valves, check valves, and quick-opening valves installed at the outlet of the small powder silo branch pipeline and before and after the mixing point; The measurement unit is used to provide feedback on the material level in the small powder silo, the operation of the powder discharge actuator in the small powder silo, the main powder supply or feed rate, the primary air volume, the operation or tripping status of the coal mill, and the combustion stability parameters; the combustion stability parameters include flame detection signal, furnace temperature, furnace negative pressure, O2 and CO parameters; The controller is used to perform state machine control of standby preparation, commissioning, emergency supply, coordinated combustion stabilization, smooth back-off, and reset based on load, coal supply status, combustion stability parameters, and interlock status.

2. The stable combustion control system according to claim 1, characterized in that, The small powder hopper conveying device is a pneumatic conveying device or an ejector device.

3. The stable combustion control system according to claim 2, characterized in that, The controller is the unit's DCS or auxiliary control system.

4. A deep peak-shaving and stable combustion control method for coal-fired power units based on a small pulverized coal silo, implemented based on the stable combustion control system described in any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Pre-charging and verification, and before the coal-fired unit enters the deep peak shaving low load condition or during low load operation, the controller triggers the standby preparation logic of the small powder silo. Step S2, Monitoring Criterion Acquisition: The controller acquires the following indicators at fixed intervals of 1s-5s: (1) Main powder supply status: coal mill operation or trip signal, main powder supply quantity, main powder supply fluctuation range, and main powder supply lower limit margin; (2) Combustion stability parameters: flame stability indicator, furnace temperature or burner outlet temperature, furnace negative pressure fluctuation, O2 and CO parameters; (3) Equivalent index of primary air pulverized coal concentration. Step S3, Commissioning: The controller will commission the powder supply path of the small powder hopper when any of the following criteria are met: (1) Combustion side stable combustion demand criteria: flame stability indicator is below the threshold, furnace temperature rises beyond the limit, furnace negative pressure fluctuation increases, CO rises, or burner outlet temperature fluctuation exceeds the limit. (2) Risk criteria for main coal supply on the pulverizing side: the main coal supply reaches the minimum stable coal supply, the main coal supply fluctuation exceeds the limit, the coal mill operation stability margin is insufficient, and the unit load is lower than the set threshold. (3) Tripping criterion: A tripping signal of the coal mill is detected; Step S4, Emergency Mill Trip: When a mill trip signal is detected, the controller executes the emergency mill trip supply strategy. Step S5, Coordinated stable combustion: During the coal supply from the small coal hopper, the controller performs coordinated control of primary air and coal supply; Step S6, Smooth Back-off and Reset: When the main powder supply path is restored and the back-off conditions are met, the controller performs a smooth back-off and reset.

5. The stable combustion control method according to claim 4, characterized in that, Step S1 includes: S1.1, Pre-filling powder ensures that the powder level in the small powder silo reaches the set target; S1.2, Availability verification, availability includes that the material level in the small powder silo is not lower than the lower limit, the powder discharge valve is in an operable state, the powder feeding actuator provides normal feedback, the differential pressure or blockage diagnosis of the conveying pipeline is normal, and the interlock meets the commissioning conditions. S1.3, Self-check and setting: Set the small powder silo control status to standby, and record the available inventory and maximum continuous powder supply capacity.

6. The stable combustion control method according to claim 5, characterized in that, In step S2, the formula for calculating the equivalent index of primary air pulverized coal concentration is as follows: ， Where C eq It is a single-pass powder concentration, Q 主 Main powder supply, Q 小粉仓 V is the amount of powder supplied to the small powder silo. PA This is the primary air volume.

7. The stable combustion control method according to claim 6, characterized in that, In step S3, the powder supply path operation of the small powder silo includes: (1) Open the small powder silo branch valve to the pre-open position; (2) Start the powder feeding and metering actuators; (3) The powder supply of the small powder bin is increased from 0 to the target powder supply according to the slope limit; (4) Record the commissioning time and enter the "low load auxiliary" state.

8. The stable combustion control method according to claim 7, characterized in that, In step S4, the emergency power supply strategy for mill skipping includes: (1) Rapid switching: The coal supply in the small coal bin is rapidly increased from the current value to the emergency target coal supply, and the coal supply on the burner side is guaranteed to be no less than the minimum stable combustion coal supply within the set response time; (2) Powder shortage judgment and closed-loop correction: If the flame stability indicator continues to decline or the CO rises abnormally, the powder supply in the small powder bin will be further increased or stronger stabilization measures will be triggered. The stronger stabilization measures include limiting the rise of primary air and temporarily increasing the amount of stabilizing fuel oil.

9. The stable combustion control method according to claim 8, characterized in that, In step S5, the coordinated control of primary air and powder supply includes: (1) Under the premise of ensuring that the primary air volume meets the lower safety limit of the burner, priority should be given to increasing the coal supply to achieve the desired C. eq It will either rise or remain within the target range; (2) If C eq If the primary air volume is below the safety lower limit but still above the minimum lower limit, reduce the primary air volume or limit the increase in primary air volume; if the primary air volume has already reached the lower limit, increase the C only by increasing the powder supply of the small powder hopper. eq ; (3) Using the flame stability indicator as the outer loop feedback, when the flame stability indicator returns to the safe range and remains stable for a set time, the powder supply of the small powder bin is controlled to drop back to the economic target value.

10. The stable combustion control method according to claim 9, characterized in that, In step S6, the conditions for reversal are: the coal mill resumes operation, the main coal supply is restored to the target margin, and the combustion stability parameters are continuously and stably maintained for a set time of 30 s-300 s. The smooth back-cut reset includes: (1) Smooth handover: The main powder supply increases at the set slope, and the small powder silo supply decreases at the set slope; (2) Exit and reset: When the powder supply of the small powder silo drops to the exit threshold and stabilizes at the set time, close the branch valve of the small powder silo and stop the powder feeding actuator; restore the small powder silo to standby inventory and return to the status of "hot standby or standby".

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