Flue gas compensation type pulverized coal wide-load stable combustion system based on staged combustion and intelligent regulation and control and control method

Abstract

The invention discloses a flue gas compensation type pulverized coal wide-load stable combustion system based on staged combustion and intelligent regulation and control and a control method, and belongs to the technical field of coal-fired power generation. The system is composed of a combustor, an intelligent control module and a flue gas backflow module, the combustor adopts a double-ring fuel channel design, an inner ring injects high-concentration pulverized coal and is provided with an adjustable swirler, and pulverized coal-flue gas mixed airflow is introduced into an outer ring; the intelligent control module predicts a load through an LSTM neural network, and realizes accurate matching of air and coal in combination with PID adjustment; and the flue gas backflow module adopts an oxygen concentration adjustable technology to maintain the combustion intensity. Under the working condition of 30%-40% low load, the system achieves the stable combustion effect that the flame center temperature is stabilized at 920 + / -20 DEG C by means of optimizing the proportion of inner ring pulverized coal to 75%-85%, increasing the primary air temperature to 145-170 DEG C, compressing the proportion of secondary air to 20%-30%, strengthening a swirling flow field to 45 degrees and the like in cooperation with flue gas backflow with the oxygen concentration of 23%-25%, and has the advantages of efficient combustion and low emission.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal-fired power generation, and specifically relates to a flue gas compensation type pulverized coal wide load (30% to 100% rated load) stable combustion system based on staged combustion and intelligent regulation and a control method thereof. Background Art

[0002] With the deepening of power market reforms, modern power grids are placing higher technical standards on the peak-shaving capabilities of generator sets. Generator sets must not only ensure the reliability of their basic power generation functions but also possess the ability to dynamically adjust and quickly respond to grid load fluctuations. This poses a severe challenge to the wide load range of the units.

[0003] Traditional frequency regulation control strategies have significant technical flaws when addressing wide load regulation. These flaws are particularly pronounced under low-load conditions: decreased combustion stability leads to frequent flameouts (requiring oil / plasma-assisted ignition), variations in coal quality cause fluctuations in combustion efficiency, and sluggish dynamic response makes it difficult to meet the grid's rapid frequency regulation requirements. These issues not only reduce unit thermal efficiency and increase pollutant emissions, but also severely restrict the deep peak-shaving capabilities of thermal power units, ultimately impacting the economic efficiency and flexibility of grid operations.

[0004] While technologies like micro-oil ignition and plasma ignition can improve combustion stability under low-load conditions to a certain extent, their high operating costs and limited load adaptability make it difficult to meet the economic and environmental requirements of modern power systems. More importantly, traditional combustion systems designed with a fixed air-to-coal ratio are prone to deteriorating combustion conditions when the load changes rapidly, exacerbating operational instability and causing excessive carbon content in fly ash, directly conflicting with current dual-carbon goals.

[0005] Flue gas recirculation technology provides a new path to solving some of these problems. Recycling flue gas to the burner for reuse can dilute the oxygen concentration in the combustion zone and prolong the residence time of pulverized coal, which helps improve flame retention characteristics. At the same time, the reducing atmosphere formed by the recirculated flue gas can effectively suppress NOx generation, and its dynamic adjustment characteristics can also balance fluctuations in the air-coal ratio. However, existing technologies, such as the coal-fired power generation unit disclosed in Chinese patent CN119022295A, have achieved the recycling of high-temperature flue gas energy generated by the boiler through the design of a recirculation unit. However, due to the lack of deep treatment of the flue gas, systematic optimization of the burner structure and combustion strategy, and the lack of an intelligent control module, it is impossible to solve the problem of high carbon content in fly ash, and it is difficult to overcome the hysteresis defects of the traditional feedback mechanism. Simple recirculation may even lead to a decrease in combustion efficiency. This highlights the need to develop a new system that integrates flue gas treatment, combustion optimization, and intelligent control.

[0006] Therefore, the development of a new generation of wide-load stable combustion systems is imperative. The ideal solution must transcend existing technological frameworks and integrate innovative technologies such as advanced flue gas treatment, burner structure optimization, and intelligent control to create a comprehensive solution that is both economical, adaptable, and environmentally friendly, providing reliable technical support for deep peak shaving of coal-fired units. Summary of the Invention

[0007] To address the challenges of poor combustion stability, slow dynamic response, and high pollutant emissions in traditional pulverized coal combustion systems under low-load conditions, an innovative flue gas compensation pulverized coal wide-load stable combustion system and control method based on staged combustion and intelligent regulation have been proposed. This system utilizes a dual-ring concentration gradient burner structure to achieve staged fuel supply, incorporates an intelligent predictive control algorithm to enhance the system's dynamic response, and innovatively develops flue gas oxygen back-injection technology to optimize the combustion environment. This technical solution effectively addresses the industry's challenge of balancing combustion stability and environmental performance during wide-load operation of coal-fired units.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent control, comprising: a burner module, including a multi-stage adaptive burner and a swirl control component, the multi-stage adaptive burner comprising a burner body, the front end of which is connected to the furnace combustion space and has an integrated air temperature adjustment unit; a concentric double-ring fuel channel, including an inner ring fuel channel and an outer ring fuel channel, for staged delivery of fuel media in different states;

[0009] The intelligent control module includes: a combustion prediction submodule for predicting combustion load changes; a dynamic air-coal matching submodule for adjusting the air volume and pulverized coal supply ratio according to real-time combustion conditions; and a central control unit, which is connected to the burner module and flue gas reflow module to achieve combustion parameter optimization and closed-loop control of operating conditions.

[0010] The flue gas reflow module includes: a flue gas recovery unit, which is used to connect the boiler tail flue and the outer ring fuel channel to extract and return part of the flue gas to the burner; an oxygen concentration adjustment unit, which is used to adjust the oxygen concentration in the reflowing flue gas; and a closed-loop temperature control unit, which dynamically adjusts the flue gas reflow volume based on the temperature feedback signal of the burner outlet area to maintain flame stability.

[0011] Furthermore, the inner ring fuel channel is configured to inject a high-concentration pulverized coal airflow with a pulverized coal concentration ≥30 kg / kg of air, and a primary air cyclone with an adjustable blade angle is integrated at its end; the outer ring fuel channel is arranged around the inner ring fuel channel, and is used to inject a pulverized coal-recirculated flue gas mixed airflow, and is provided with a mixed flue gas pressure stabilization chamber, which is closed-loop connected to the boiler tail flue through a flue gas recirculation interface; a primary air channel is provided on the inner ring fuel channel, and a primary air volume regulating valve group is provided at the channel entrance; a secondary air channel is provided on the outer ring fuel channel, and a secondary air volume regulating valve group is provided at the channel entrance.

[0012] Furthermore, the combustion prediction submodule includes: a load prediction unit, which has a built-in load prediction model based on an LSTM neural network, whose input variables include real-time grid dispatch instructions and historical load data, and outputs a thermal load forecast value for the next 5-10 minutes; a combustion parameter pre-adjustment unit, which generates a primary air pressure correction value ΔP and a pulverized coal concentration correction coefficient Kc based on the load forecast value; the dynamic air-coal matching submodule includes: a temperature field monitoring unit, which is used to obtain the standard deviation σ of the furnace temperature distribution through optical temperature measuring devices in several areas of the furnace;

[0013] The air volume control unit includes a primary air PID regulation system and a secondary air PID regulation system. The primary air PID regulation system synchronously adjusts the primary air flow rate and the cyclone blade angle according to the burner inner ring wind pressure data; the secondary air PID regulation system dynamically optimizes the secondary air ratio parameter α by adjusting the secondary air channel opening;

[0014] Coal quality online analysis unit, used to detect the moisture content Wc and volatile matter content Vc of coal powder;

[0015] The central control unit controls the opening of the primary air regulating valve group through the PID algorithm based on the ΔP, Kc signals and σ, Wc, Vc data, calculates the secondary air volume proportion α and dynamically corrects the air-coal ratio γ.

[0016] Furthermore, the dynamic air-coal matching submodule is also provided with a secondary compensation mechanism: when the furnace temperature still fluctuates continuously by more than ±40°C after the main adjustment response, the pulverized coal fineness dynamic adjustment unit is automatically linked to achieve combustion rate compensation by adjusting the pulverized coal particle size distribution.

[0017] Furthermore, the flue gas recovery unit includes:

[0018] The flue gas extraction pipeline has its inlet end connected to the outlet side of the boiler tail flue dust collector, and its outlet end connected to the mixed flue gas pressure stabilization chamber of the outer ring fuel channel;

[0019] High-efficiency electrostatic precipitator, installed in the middle section of the flue gas extraction pipeline, is used for secondary dust removal of the extracted flue gas. The extracted flue gas temperature is 200-300℃ and the flow rate accounts for 10%-30% of the total flue gas volume;

[0020] The oxygen concentration regulating unit comprises an oxygen delivery branch pipe and a static mixer, which is used to mix oxygen into the reflux flue gas so that the mixed oxygen concentration reaches 23%-25%;

[0021] The closed-loop temperature control unit comprises:

[0022] Thermocouple groups are spaced 500-800 mm downstream of the burner outlet along the burner axis to monitor flame temperature distribution in real time.

[0023] Interlocking PID controller: When the thermocouple detects that the flame center temperature is lower than 900℃, it triggers the maximum flow mode of the flue gas recovery unit and controls the flue gas extraction volume to increase to 80%-100% of the rated flow rate;

[0024] The dynamic balance module adjusts the opening of the oxygen delivery branch valve through the PID algorithm based on real-time flue gas temperature and oxygen concentration data to maintain a dynamic balance between the flue gas calorific value and the combustion temperature.

[0025] Furthermore, the swirler blade angle adjustment range is 15°-45°.

[0026] This application also discloses a stable combustion control method that is compatible with the above-mentioned flue gas compensation type pulverized coal wide load stable combustion system. It includes the following steps:

[0027] S1. Low load stable combustion stage control:

[0028] a) Activate the high-concentration combustion mode of the burner, increase the mass proportion of pulverized coal in the inner ring fuel channel to 75%-85%, and maintain the primary air temperature at 145-170°C through the air temperature adjustment unit;

[0029] b) Adjust the opening of the secondary air volume regulating valves of the inner and outer ring fuel channels so that the secondary air volume accounts for 20%-30% of the total air supply;

[0030] c) Increase the extraction ratio of recirculated flue gas to 20%-30%, and use the oxygen concentration control component to make the oxygen concentration of the mixed flue gas reach 23%-25%;

[0031] d) Drive the primary air cyclone blade angle to 45°, forming a strong turbulent field with a swirl number greater than 1.2, and maintain the flame center temperature at 920±20℃;

[0032] S2. Medium and high load transition stage control:

[0033] a) Receive the migration instructions output by the load forecasting model, linearly increase the secondary air volume to 40% within 5 minutes, reduce the primary air temperature to 120°C, reduce the flue gas return volume to 15%, and no longer add oxygen to the return flue gas;

[0034] b) The swirl control component drives the primary air cyclone blades to adjust the angle to 15°;

[0035] c) By real-time monitoring of the furnace temperature distribution standard deviation σ, the air-to-coal ratio γ is dynamically corrected to constrain the temperature fluctuation range to less than ±5°C;

[0036] d) Synchronously linked pulverized coal fineness adjustment unit to reversely compensate for pulverized coal particle size distribution according to changes in flame height.

[0037] Furthermore, the low-load stable combustion stage corresponds to a rated load range of 30%-40%, and the medium-to-high load transition stage corresponds to a rated load range of 40%-100%.

[0038] The beneficial effects of the present invention are:

[0039] 1. The flue gas compensation-type pulverized coal wide-load stable combustion system based on staged combustion and intelligent control disclosed in this application includes three core modules: burner, intelligent control, and flue gas recirculation. Through the synergistic effect of the dual-ring concentration gradient burner structure optimization, intelligent control prediction algorithm, and flue gas oxygen back-injection compensation technology, it effectively improves the operating stability and reliability of coal-fired units under a wide range of load conditions, and solves the technical bottlenecks of traditional combustion systems such as easy flameout under low-load conditions, delayed dynamic response, and poor pollutant emission control.

[0040] 2. The multi-fuel channel burner disclosed in this application utilizes a differentiated supply strategy for the inner and outer ring fuel channels, coupled with precisely controlled primary air temperature and secondary air volume ratios. By optimizing swirl intensity and flue gas recirculation compensation mechanisms, a highly stable flame core temperature field structure is constructed. This design significantly improves combustion stability under low-load conditions, effectively suppresses combustion oscillation, and reduces the risk of flameout. Furthermore, the system integrates flue gas recirculation technology and dynamic oxygen concentration adjustment to further enhance the controllability of the combustion process, thereby ensuring efficient, continuous, and stable combustion across a wide load range.

[0041] 3. The combustion stabilization system disclosed in this application uses an intelligent control module to achieve dynamic optimization of the combustion process. Its core lies in the coordinated control of two major sub-modules: combustion prediction and dynamic matching of air and coal. By analyzing fuel characteristics and combustion requirements in real time, it significantly improves the pulverized coal combustion efficiency and the overall thermal efficiency of the boiler. The system innovatively integrates flue gas recirculation technology to create a low-oxygen reduction environment while reducing the excess air coefficient, thereby effectively suppressing the formation of nitrogen oxides and achieving source reduction of pollutant emissions. Combined with the precise control function of the closed-loop temperature control unit, the system further optimizes combustion uniformity and significantly reduces the formation of unburned products, ensuring combustion stability while comprehensively improving environmental performance.

[0042] 4. This application innovatively integrates an online coal quality analysis unit with a combustion prediction submodule to construct an intelligent regulation system with autonomous adaptability. The system monitors changes in fuel characteristics in real time and automatically optimizes combustion parameters, achieving automated management from fuel identification to combustion regulation. This intelligent dynamic response mechanism enables the unit to demonstrate excellent stability when responding to dynamic load changes such as grid peak regulation, effectively overcoming the regulation lag problem existing in traditional control methods. More importantly, the system continuously accumulates operating experience through deep learning algorithms, continuously improving its adaptability to various complex operating conditions, providing reliable guarantees for the flexible and efficient operation of thermal power generating units.

[0043] 5. The flue gas reflow module disclosed in this application realizes the comprehensive optimization of the combustion system through the coordinated control of multiple units. The flue gas recovery unit extracts and purifies the flue gas at the tail of the boiler, the oxygen concentration adjustment unit accurately adjusts the oxygen content of the mixed gas, and the closed-loop temperature control unit dynamically adjusts the operating parameters according to the real-time flame temperature. The technical solution can significantly improve the combustion stability, effectively inhibit the generation of harmful gases, and reduce the risk of equipment coking, thereby achieving a dual improvement in clean combustion and system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of a multi-stage adaptive burner, where 1-burner body, 2-furnace combustion space, 3-inner ring fuel channel, 4-outer ring fuel channel, 5-swirler, 6-mixed flue gas pressure stabilization chamber, 7-primary air channel, 8-secondary air channel, 9-feed pipe;

[0045] Figure 2 This is a system flow chart of a flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent control;

[0046] Figure 3 This is a dual-axis time correlation diagram of fly ash carbon content and NOx emission concentration provided by the application example;

[0047] Figure 4 This is a graph showing steam temperature fluctuations over time, provided in the application example. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0049] Example 1

[0050] This embodiment discloses a flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent regulation, which includes a burner module, an intelligent control module and a flue gas reflow module.

[0051] The burner module includes a multi-stage adaptive burner and a swirl control component. The multi-stage adaptive burner consists of a burner body 1 and a concentric double-ring fuel channel. The front end of the burner body 1 is connected to the furnace combustion space 2. The air temperature adjustment unit is integrated in the burner module to control the primary air temperature.

[0052] A concentric double-ring fuel channel is coaxially arranged inside the burner body 1, including an inner ring fuel channel 3 and an outer ring fuel channel 4; the inner ring fuel channel 3 is used to inject a high-concentration coal powder airflow with a coal powder concentration of ≥30 kg / kg air, and a primary air swirler 5 with adjustable blade angle is provided at its end. The blade angle adjustment range of the swirler 5 is limited to 15°-45°, and a servo drive mechanism is configured to achieve enhanced control of the swirl number to >1.2 under low-load conditions.

[0053] The outer ring fuel channel 4 is arranged around the inner ring fuel channel 3 and sprays a mixed flow of coal powder and recycled flue gas with a coal powder concentration of ≤15 kg / kg air; the outer ring fuel channel 4 is provided with a mixed flue gas pressure stabilizing chamber 6, which forms a closed loop connection with the flue at the tail end of the boiler, and its outlet sprays a mixed flow of coal powder and recycled flue gas. A primary air channel 7 is provided on the inner ring fuel channel 3, and a primary air volume regulating valve group is provided at the channel entrance to provide precise combustion air distribution for the high-concentration coal powder airflow; a secondary air channel 8 is provided on the outer ring fuel channel 4, and a secondary air volume regulating valve group is provided at the channel entrance to regulate the dilution airflow supply of the mixed flue gas and coal powder. After the coal powder enters from the feed pipe 9 (the coal powder entry path is as shown in FIG. Figure 1 The outer ring airflow enhances the completeness of combustion, while the recycled flue gas is injected through the pressure stabilization chamber and realizes autonomous stable combustion with the high-concentration pulverized coal system.

[0054] The intelligent control module consists of a combustion prediction submodule, a dynamic air-coal matching submodule and a central control unit.

[0055] The combustion prediction submodule integrates a load prediction unit and a combustion parameter pre-adjustment unit; the load prediction unit has a built-in load prediction model based on the LSTM (long short-term memory) neural network. The model input variables include grid dispatch instructions and historical load data. The training data set of the LSTM neural network model contains more than 2,000 sets of boiler operating condition data, and the output is the thermal load forecast value for the next 5-10 minutes; the combustion parameter pre-adjustment unit generates a primary air pressure correction value ΔP and a pulverized coal concentration correction coefficient Kc based on the load forecast value.

[0056] The dynamic air-coal matching submodule includes a temperature field monitoring unit, an air volume control unit, and an online coal quality analysis unit. The temperature field control unit consists of a group of fiber optic temperature sensors arranged at the four corners of the furnace and an infrared thermal imager installed in the fire observation hole. The standard deviation σ of the furnace temperature distribution is obtained through the fiber optic temperature sensor group. The air volume control unit achieves dynamic control through two sets of PID adjustment systems: the primary air regulating valve group adjusts the primary air delivery flow rate based on the real-time air pressure data of the burner inner ring (measured by the air pressure sensor installed in the inner ring fuel channel). While controlling the blade angle change of the primary air cyclone, the secondary air regulating valve group adjusts the opening of the secondary air channel according to the combustion conditions, realizing dynamic optimization of the secondary air ratio parameter α, ensuring that the fuel and air mixing efficiency is always in the optimal range. The online coal quality analysis unit uses laser induced breakdown spectroscopy (LIBS) to detect the moisture content Wc and volatile matter content Vc of the coal powder at the coal feeder outlet in real time, and feeds back to the central control unit to correct the air-coal ratio γ.

[0057] The dynamic air-coal matching submodule also features an additional secondary compensation mechanism. If furnace temperature fluctuations persist by more than ±40°C after the primary adjustments (coal feed / air volume) have been made, the dynamic pulverized coal fineness adjustment unit is automatically activated, initiating a pulverizer parameter optimization program. This adjusts the pulverized coal particle size distribution to achieve precise combustion rate compensation, ultimately completing a closed-loop combustion rate control loop from temperature monitoring to air-coal ratio correction and finally to pulverized coal fineness compensation. Generally, coarse pulverized coal prolongs the combustion cycle and raises the center flame temperature, while fine pulverized coal accelerates the combustion reaction and reduces flame height. Adjusting pulverized coal fineness requires simultaneous adjustments to the primary air pressure and secondary air ratio.

[0058] The data signals of each submodule are collected and processed and then fed back to the central control unit: based on the ΔP and Kc signals of the combustion prediction submodule, the opening of the primary air regulating valve group is controlled by the PID algorithm, and the secondary air volume ratio α is calculated according to the standard deviation σ of the furnace temperature distribution collected by the temperature field monitoring unit, and the air-coal ratio γ is dynamically corrected based on the output data Wc and Vc of the coal quality analysis unit.

[0059] The flue gas reflow module includes a flue gas recovery unit, an oxygen concentration adjustment unit and a closed-loop temperature control unit. It corrects the flue gas mixing ratio by monitoring the flame temperature and ultimately determines the compensated oxygen concentration.

[0060] The flue gas recovery unit consists of a flue gas extraction pipeline and a flue gas purification device. The inlet of the flue gas extraction pipeline is connected to the outlet of the dust collector in the boiler's tail flue, and the outlet is connected to the mixed flue gas pressure stabilization chamber (flue gas inlet) in the burner's outer ring fuel channel. A high-efficiency electrostatic precipitator is installed in the middle of the pipeline to reduce the dust content of the returned flue gas. The extracted flue gas temperature is 200-300°C, and the mass flow rate accounts for 10%-30% of the boiler's total flue gas volume. An electric flue gas recirculation valve is installed at the inlet of the mixed flue gas pressure stabilization chamber. The servo motor drives the valve plate opening to adjust the recirculation flow rate (the flue gas recirculation flow rate is measured by a flue gas flow meter).

[0061] The oxygen concentration adjustment unit includes an oxygen delivery branch pipe and a static mixer. The oxygen delivery branch pipe is connected to the oxygen production system. The static mixer is located downstream of the electrostatic precipitator to mix oxygen into the return flue gas and control the oxygen concentration of the flue gas after mixing to reach 23%-25%, which can inhibit the formation of CO.

[0062] The closed-loop temperature control unit consists of a temperature sensing network and an actuator. The temperature sensing network includes a thermocouple group arranged in a ring array in the area 500-800mm downstream of the burner outlet. It monitors the temperature distribution in the center of the flame in real time and suppresses local temperature drops. The actuator includes a PID controller interlocked with the electric flue gas return valve. It is programmed to increase the flue gas extraction volume to 80%-100% of the set maximum flow rate when any thermocouple detection value is less than 900℃, and switch to proportional regulation mode to maintain thermal balance after the temperature returns to ≥900℃.

[0063] Flue gas recirculation flow, oxygen concentration data and flame center temperature data are all collected to the central control unit for further comprehensive regulation.

[0064] During the low-load operation phase of the boiler (30%-40% of rated load), the combustion system implements a low-load stable combustion strategy:

[0065] The burner module starts the high-concentration combustion mode, and the mass proportion of coal powder in the inner ring fuel channel is increased to the range of 75%-85%, and the primary air temperature is stabilized in the range of 145-170℃ through its integrated air temperature control unit; the opening of the secondary air volume regulating valve is adjusted to compress the proportion of secondary air volume in the total air supply to 20%-30%; the flue gas reflow module is simultaneously enhanced to increase the extraction ratio of recycled flue gas to 20%-30%, and at the same time, the oxygen concentration control component mixes oxygen into the recirculated flue gas to make the oxygen concentration reach the threshold of 25%; the swirl control component drives the primary air swirler blade angle to 45°, forming a strong swirl field to prolong the residence time of coal powder, so that the flame center temperature is stabilized in the range of 920±20℃.

[0066] When the load switches to the medium-to-high load (40%-100%) transition stage, the intelligent control module executes a dynamic transition program: after the central control submodule receives the operating condition migration instruction output by the load prediction model, it adjusts the system parameters in stages through the servo actuator - gradually increasing the secondary air volume to 40% of the total air volume within a 5-minute time window, simultaneously reducing the primary air temperature to 120°C, and linearly reducing the flue gas return volume to 15% of the set value; as the load increases, the swirl control component drives the primary air swirler blade angle to 15°, weakening the swirl intensity and increasing the combustion intensity; the oxygen concentration control component no longer mixes oxygen into the return flue gas, returning to normal air-assisted combustion conditions; during the above adjustment process, the combustion prediction submodule corrects the air-coal ratio parameters in real time to ensure that the furnace temperature fluctuation amplitude is less than ±5°C.

[0067] Conventional boilers face the following major challenges under low-load operating conditions: 1. They are prone to flameout, requiring oil / plasma assistance; 2. Coal quality fluctuations can cause combustion efficiency fluctuations; and 3. Load response is slow, failing to keep pace with grid speed regulation. This application addresses the technical challenges of conventional combustion systems in low-load combustion stability, dynamic response, and pollutant control through a comprehensive integration of an innovative burner structure (a dual-ring concentration gradient burner), an intelligent control algorithm (LSTM prediction), and a flue gas compensation strategy, achieving a systematic breakthrough. Specifically, regarding combustion stability, a gradient-staged combustion design combining flue gas mixing and pressure stabilization in the outer ring with a high-concentration pulverized coal injection in the inner ring, combined with the oxygen concentration suppression effect of flue gas recirculation, significantly broadens the flame stability margin under low-load conditions. To address fuel fluctuations, online pulverized coal composition monitoring and a dynamic air-to-coal ratio self-correction algorithm enable real-time closed-loop optimization of combustion parameters as coal quality changes. To address load response lag, an LSTM neural network is employed to proactively predict boiler operating trends. By pre-adjusting the burner's swirl intensity and secondary air ratio, dynamic response time is reduced to less than 30% of that of conventional systems. The entire system, through the three-dimensional coordination of structure, algorithm and gas path, simultaneously overcomes the coupling problems of stable combustion, efficiency and response rate without the need for external combustion assistance.

[0068] Application Examples

[0069] Under the low-load condition of 180 MW on a 600 MW supercritical once-through boiler, the flue gas compensation pulverized coal wide load stable combustion system based on staged combustion and intelligent control demonstrated significant control effects. The specific implementation process and operational results are as follows:

[0070] 1. Implementation of combustion control

[0071] In the coal powder distribution control link, the proportion of coal powder transportation in the inner ring fuel channel was increased from 50% under normal operating conditions to 80%, and the outer ring fuel channel was simultaneously reduced to 20%, significantly improving the ignition stability by enhancing the inner ring coal powder concentration effect.

[0072] The air distribution system implements a complex control strategy: the primary air temperature is heated to 160°C (a 33% increase over the conventional value of 120°C) by a heater. This increased primary air temperature reduces the moisture content of the pulverized coal, preventing pipe blockage and enhancing its fluidity. This compensates for the combustion delay caused by increased pulverized coal concentration at low loads. This temperature also accelerates the release of volatile matter from the pulverized coal, improving ignition stability at low loads. This, combined with the 80% pulverized coal ratio in the inner ring, effectively prevents pulverized coal deposition and incomplete combustion due to insufficient temperature, accelerating the pulverized coal preheating process. The secondary air volume is compressed to 25% of the total air volume, and the swirl vane angle is adjusted to 45°. This compression of the secondary air volume limits the oxygen concentration in the combustion zone and suppresses NOx formation. The low secondary air volume narrows the flame spread, concentrating the combustion heat, reducing the cooling effect on the flame center, and avoiding excessive temperature fluctuations. Furthermore, this system, combined with the flue gas recirculation (25%), creates alternating oxygen-deficient and oxygen-rich zones. This, combined with the adjusted swirl vane angle, enhances flue gas backmixing and helps reduce the carbon content of fly ash.

[0073] In summary, the primary air temperature (160°C) and secondary air volume (25% of the total air volume) respectively assume the core functions of coal powder transportation / ignition optimization and combustion oxygen content / flame morphology control under low-load conditions. Through systematic coordination with parameters such as the inner ring coal powder ratio and swirl intensity, the dual improvements of low-load stable combustion and environmental protection performance are achieved.

[0074] The flue gas recirculation module simultaneously extracts 25% of the tail flue gas and mixes it with pure oxygen, stabilizing the oxygen concentration of the mixed medium at 24%. This ensures both staged combustion and combustion intensity. The entire system achieves both combustion stability and environmental performance under low-load conditions through the coordinated integration of primary air temperature control, secondary air volume adjustment, swirl intensity optimization, and flue gas oxygen recirculation.

[0075] The temperature monitoring system tracks the thermal distribution of the furnace in real time through the temperature sensor network. Combined with dynamic coal feeding adjustment, the flame center temperature measured by the temperature field control unit is stably controlled in the range of 900-940℃. When the temperature fluctuation exceeds ±40℃, the coal powder fineness adjustment mechanism is automatically triggered.

[0076] 2. Dynamic load switching

[0077] During the load transition stage from 40% to 100%, the dynamic adjustment program of the air-coal ratio is started: the secondary air volume is increased in stages to 40% of the total air volume within 5 minutes, and the flue gas reflow ratio is simultaneously reduced to 15% and the primary air temperature is adjusted to 120°C. The angle of the primary air cyclone blade is adjusted to 15° to weaken the cyclone intensity, increase the combustion intensity, and no longer mix oxygen into the reflowing flue gas.

[0078] NOx emissions at low loads are less than 100 mg / Nm³ (conventional technology >150 mg / Nm³); combustion efficiency is always >98.5%.

[0079] 3. Comprehensive operational results

[0080] After 72 hours of continuous operation verification, the system's key performance indicators have been significantly optimized:

[0081] In terms of combustion stability, the flame shape remained stable without flashover / flameout, and the carbon content of fly ash decreased from 4.2% to 2.6% (see Figure 3 );

[0082] Environmental performance is improved, with NOx emission concentration reduced from 380 mg / Nm³ to 260 mg / Nm³, a 42% reduction compared to traditional technologies (see Figure 3 );

[0083] Energy efficiency index is improved, and the main steam temperature fluctuation range is less than ±5℃ ( Figure 4 ), boiler efficiency increased by 2.1 percentage points compared with conventional low-load operation;

[0084] This example verifies the superior performance of the wide-load stable combustion system under low-load conditions, and achieves the coordinated optimization of clean combustion and efficient operation.

[0085] The above shows and describes the basic principles, main features, and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any person skilled in the art without departing from the technical solution of the present invention are intended to be within the scope of the present invention.

Claims

1. A flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent control, characterized in that: include: The burner module includes a multi-stage adaptive burner and a swirl control component. The multi-stage adaptive burner includes: The burner body has a front end connected to the furnace combustion space and an integrated air temperature regulation unit; Concentric double-annular fuel channels, including an inner annular fuel channel and an outer annular fuel channel, are used to transport fuel media in different states in stages; Intelligent control module, including: Combustion prediction submodule, used to predict combustion load changes; Dynamic air-coal matching submodule, used to adjust the air volume and pulverized coal supply ratio according to real-time combustion conditions; The central control unit is connected to the burner module and the flue gas reflow module to optimize the combustion parameters; Flue gas reflow module, including: Flue gas recovery unit, used to extract and return part of the flue gas to the burner; An oxygen concentration regulating unit, used for regulating the oxygen concentration in the reflowing flue gas; The closed-loop temperature control unit dynamically adjusts the flue gas return flow rate based on the temperature feedback signal of the burner outlet area.

2. The flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent regulation according to claim 1 is characterized in that: The inner annular fuel channel is configured to inject a high-concentration coal powder airflow with a coal powder concentration of ≥30 kg / kg air, and a primary air cyclone with adjustable blade angle is integrated at the end thereof; The outer ring fuel channel is arranged around the inner ring fuel channel and is used to inject the pulverized coal-recirculated flue gas mixed flow. A mixed flue gas pressure stabilization chamber is provided on the outer ring fuel channel and is closed-loop connected to the boiler tail flue through a flue gas recirculation interface. A primary air channel is provided on the inner ring fuel channel, and a primary air volume regulating valve group is provided at the channel entrance; A secondary air channel is provided on the outer ring fuel channel, and a secondary air volume regulating valve group is provided at the channel entrance.

3. The flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent control according to claim 1 is characterized in that: The combustion prediction submodule includes: The load forecasting unit has a built-in load forecasting model based on an LSTM neural network. Its input variables include real-time grid dispatch instructions and historical load data, and it outputs the thermal load forecast value for the next 5-10 minutes. The combustion parameter pre-adjustment unit generates the primary air pressure correction value ΔP and the pulverized coal concentration correction coefficient Kc according to the load forecast value; The dynamic air-coal matching submodule includes: The temperature field monitoring unit is used to obtain the standard deviation σ of the furnace temperature distribution through optical temperature measuring devices in several areas of the furnace; Air volume control unit, including: The primary air PID regulation system adjusts the primary air flow and cyclone blade angle synchronously according to the burner inner ring wind pressure data, and The secondary air PID control system dynamically optimizes the secondary air ratio parameter α by adjusting the secondary air channel opening; Coal quality online analysis unit, used to detect the moisture content Wc and volatile matter content Vc of coal powder; The central control unit controls the opening of the primary air regulating valve group through the PID algorithm based on the ΔP, Kc signals and σ, Wc, Vc data, calculates the secondary air volume proportion α and dynamically corrects the air-coal ratio γ.

4. The flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent regulation according to claim 1 is characterized in that: The dynamic air-coal matching submodule is also equipped with a secondary compensation mechanism: when the furnace temperature still fluctuates continuously by more than ±40°C after the main adjustment response, the pulverized coal fineness dynamic adjustment unit is automatically linked to achieve combustion rate compensation by adjusting the pulverized coal particle size distribution.

5. The flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent regulation according to claim 1 is characterized in that: The flue gas recovery unit comprises: The flue gas extraction pipeline has its inlet end connected to the outlet side of the boiler tail flue dust collector, and its outlet end connected to the mixed flue gas pressure stabilization chamber of the outer ring fuel channel; High-efficiency electrostatic precipitator, installed in the middle section of the flue gas extraction pipeline, is used for secondary dust removal of the extracted flue gas. The extracted flue gas temperature is 200-300℃ and the flow rate accounts for 10%-30% of the total flue gas volume; The oxygen concentration regulating unit comprises an oxygen delivery branch pipe and a static mixer, which is used to mix oxygen into the reflux flue gas to make the mixed oxygen concentration reach 23%-25%; The closed-loop temperature control unit comprises: Thermocouple groups are spaced 500-800 mm downstream of the burner outlet along the burner axis to monitor flame temperature distribution in real time. Interlocking PID controller: When the thermocouple detects that the flame center temperature is lower than 900℃, it triggers the maximum flow mode of the flue gas recovery unit and controls the flue gas extraction volume to increase to 80%-100% of the rated flow rate; The dynamic balance module adjusts the opening of the oxygen delivery branch valve through the PID algorithm based on real-time flue gas temperature and oxygen concentration data to maintain a dynamic balance between the flue gas calorific value and the combustion temperature.

6. The flue gas compensation type pulverized coal wide load stable combustion system based on staged combustion and intelligent regulation according to claim 1 is characterized in that: The cyclone blade angle adjustment range is 15°-45°.

7. A method for controlling wide-load stable combustion of pulverized coal, characterized in that: The method is based on the flue gas compensation type pulverized coal wide load stable combustion system according to any one of claims 1 to 6, and includes the following steps: S1. Low-load stable combustion stage control: a) Activate the high-concentration combustion mode of the burner, increase the mass proportion of pulverized coal in the inner ring fuel channel to 75%-85%, and maintain the primary air temperature at 145-170°C through the air temperature adjustment unit; b) Adjust the opening of the secondary air volume regulating valves of the inner and outer ring fuel channels so that the secondary air volume accounts for 20%-30% of the total air supply; c) Increase the extraction ratio of recirculated flue gas to 20%-30%, and use the oxygen concentration control component to make the mixed flue gas oxygen concentration reach 23%-25%; d) Drive the primary air cyclone blade angle to 45°, forming a strong turbulent field with a swirl number greater than 1.2, and maintain the flame center temperature at 920±20℃; S2. Medium to high load transition control: a) Receive the migration instructions output by the load forecasting model, linearly increase the secondary air volume to 40% within 5 minutes, reduce the primary air temperature to 120°C, reduce the flue gas return volume to 15%, and no longer add oxygen to the return flue gas; b) The swirl control component drives the primary air swirler blades to adjust the angle to 15°; c) By real-time monitoring of the furnace temperature distribution standard deviation σ, the air-to-coal ratio γ is dynamically corrected to constrain the temperature fluctuation range to less than ±5°C; d) Synchronously linked pulverized coal fineness adjustment unit to reversely compensate for pulverized coal particle size distribution according to changes in flame height.

8. A method for controlling wide-load stable combustion of pulverized coal according to claim 7, characterized in that: The low-load stable combustion stage corresponds to a rated load range of 30%-40%, and the medium-to-high load transition stage corresponds to a rated load range of 40%-100%.

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