A fuel multi-stage combustion device and method along the vertical direction of the furnace

Abstract

The application relates to a fuel multi-stage grading combustion device and combustion method along the vertical direction of a furnace, and belongs to the technical field of tangentially fired boiler combustion technology. In order to solve the problems of poor deep peak regulation capability of a four-corner (or eight-corner) tangentially fired boiler, high NOx emission caused by reduced denitration efficiency during low-load operation, poor burnout during high load, and water cooling wall slagging, a two-stage concentration device is adopted to form a concentrated coal powder airflow, a first-stage dilute coal powder airflow and a second-stage dilute coal powder airflow along the vertical direction of the furnace. The central high-concentration coal powder airflow is rapidly ignited and combusted in a stable combustion chamber, then the concentrated coal powder which has been ignited and combusted is mixed with the first-stage dilute coal powder and ignites the first-stage dilute coal powder, the flame formed by the swirling burner combustion ignites the second-stage dilute coal powder flame of the straight-flow burner, the staged combustion of the coal powder is realized, the combustion energy is gradually amplified, the stable combustion of the coal power unit at 15% of the rated load is realized only by relying on the coal powder combustion, the NOx emission is reduced, the burnout effect is improved, and the water cooling wall slagging is prevented, and the like. The application is mainly used for improving the stable combustion effect of the boiler during operation.

Description

Technical Field

[0001] This invention relates to the field of tangential boiler combustion technology, specifically to a combustion device and method for multiple stages of fuel combustion along the vertical direction of the furnace. Background Technology

[0002] In recent years, due to the implementation of the national dual-carbon policy, the government has increased its support and promotion of new energy power generation. The proportion of major new energy power generation forms, including solar, wind, hydro, and biomass power generation, has been increasing year by year, while the utilization hours of thermal power plants have been decreasing, indicating a continuous change in the energy structure. However, new energy power generation faces many challenges in the power industry. These challenges mainly stem from its randomness and instability. Because the impact of new energy power generation on the power system is more complex and unpredictable, large thermal power units need to possess deep flexibility in peak shaving to maintain grid stability and promote the clean and low-carbon transformation of the power industry. The most critical issue in the flexibility retrofitting of units to improve peak shaving capacity is achieving stable boiler operation under low loads of 20%-30% or even lower.

[0003] Coal-fired boiler power generation is currently the mainstay of my country's energy structure. The combustion method of coal-fired boilers primarily employs direct-flow burners arranged at the four or eight corners of the boiler furnace. Pulverized coal gas flow and secondary air are injected into the furnace through the direct-flow burner jets, converging in a tangential circular pattern. The pulverized coal gas flow towards the fire is ignited by the direct impact of the high-temperature flames in the upstream adjacent corners. The four (or eight) corner jets support each other, forming a rotating combustion flame. The four-corner (or eight) tangential pulverized coal combustion boiler is the most widely used and mature boiler type in my country's power plants, accounting for approximately 70% or more of the total installed capacity. However, domestic coal-fired power units can only achieve 30%-40% of the rated load for stable combustion without oil injection. Relying solely on pulverized coal combustion is insufficient to achieve a 20%-30% stable combustion effect at rated load, and the four-corner (or eight) tangential pulverized coal boiler cannot meet the requirements for deep peak shaving.

[0004] Currently, to achieve 20%-30% stable combustion load in boilers without oil injection, plasma, micro-oil, or medium-frequency electric heating technologies are needed to assist combustion stabilization and maintain long-term operation at 20%-30% of the rated load. Micro-oil combustion stabilization technology uses a small amount of oil (oil gun output 0.4t / h-0.6t / h) to ignite pulverized coal, enhancing ignition and stable combustion through its own combustion heat release. It has the advantage of strong coal adaptability, suitable for boilers from lignite to anthracite. However, long-term operation has a negative impact on electrostatic precipitator electrodes and desulfurization slurry. Furthermore, using oil guns for stable combustion can consume tens of thousands of tons of oil annually, resulting in poor economic efficiency and extremely high costs. Plasma combustion stabilization technology mainly uses a high-power plasma gun to generate a high-temperature electric arc, enhancing pulverized coal ignition and stable combustion. It is economical and environmentally friendly, but suffers from a short cathode lifespan and poor coal adaptability, and is often used in boilers burning bituminous coal with high volatile matter content. Medium-frequency electric heating technology uses medium-frequency induction heating to achieve good combustion stability under low and variable loads. However, the addition of an extra pulverizing system increases system complexity and investment costs; at the same time, medium-frequency induction is required to heat flammable bituminous coal, and long-term operation can easily lead to slagging in the flame extension tube.

[0005] The paper "A Method and Apparatus for Co-combustion of a DC Burner and a Swirl Burner" developed a co-combustion device using a DC burner and a swirl burner. A self-sustaining combustion burner is installed between the DC primary air and DC secondary air, allowing the original DC burner and the self-sustaining combustion burner to co-combust, achieving stable operation of a tangential (or octagonal) boiler relying solely on pulverized coal combustion at 20%-30% of its rated load, while improving burnout efficiency at high loads. However, practical application shows that after applying this device, the tangential (or octagonal) boiler cannot operate stably at 15%-20% of its rated load. Furthermore, the co-combustion device of the DC burner and swirl burner exhibits problems such as increased NOx emissions, low burnout rate, and slight slagging on the water-cooled walls at low loads.

[0006] Therefore, in order to completely solve the problems of poor deep peak-shaving capacity, excessive NOx emissions and slagging on water-cooled walls of tangential (or octagonal) boilers, and to further improve the ability of tangential (or octagonal) boilers to operate stably under 15%-20% rated load relying solely on pulverized coal combustion, this invention proposes a combustion method and apparatus for multiple stages of fuel combustion along the vertical direction of the furnace. Summary of the Invention

[0007] The present invention aims to solve the problems of poor deep peak-shaving capacity of four-corner (or octagonal) tangential boilers, reduced denitrification efficiency leading to high NOx emissions under low load operation, poor burnout under high load, and slagging of water-cooled walls, and provides a combustion device and combustion method for fuel multi-stage combustion along the vertical direction of the furnace.

[0008] A combustion device for multi-stage fuel combustion along the vertical direction of the furnace includes a tangentially circular pulverized coal combustion boiler, a secondary air box, and four direct-current pulverized coal burners. The four direct-current pulverized coal burners are respectively arranged at the four corners of the tangentially circular pulverized coal combustion boiler. Each direct-current pulverized coal burner corresponds to at least one coal mill. The direct-current primary air nozzle of each direct-current pulverized coal burner is connected to the coal outlet of the coal mill via a coal supply pipeline. The direct-current secondary air nozzle of each direct-current pulverized coal burner is connected to the air outlet of the secondary air box via an air supply pipeline. Each direct-current pulverized coal burner includes at least one self-sustaining combustion burner, and each self-sustaining combustion burner is located in the same position within its corresponding direct-current pulverized coal burner. Between the DC primary air nozzle and the DC secondary air nozzle of the layer, the self-stable combustion burner is connected to the coal supply pipeline of the adjacent DC primary air nozzle and the air supply pipeline of the adjacent DC secondary air nozzle through the air-coal system. The combustion device also includes at least one set of concentration structure, and each set of concentration structure is correspondingly set to one self-stable combustion burner. The concentration structure includes a No. 1 concentration unit and a No. 2 concentration unit. The No. 1 concentration unit is integrated in the corresponding coal supply pipeline. The concentrated coal outlet end of the No. 1 concentration unit is connected to the corresponding self-stable combustion burner. The light coal outlet end of the No. 1 concentration unit is connected to the corresponding DC primary air nozzle. The No. 2 concentration unit is integrated in the corresponding self-stable combustion burner.

[0009] Furthermore, the coal supply pipeline includes a DC primary air channel, a primary air duct, a No. 1 regulating valve, a No. 2 regulating valve, a No. 3 regulating valve, and a No. 1 thickening unit. One end of the DC primary air channel is connected to the corresponding DC primary air nozzle, one end of the primary air duct is connected to the coal outlet of the corresponding coal mill, and the other end of the DC primary air channel is connected to the other end of the primary air duct. A No. 1 regulating valve is installed at the connection between the DC primary air channel and the primary air duct. The coal inlet of the No. 1 thickening unit is connected to the primary air duct, and a No. 2 regulating valve is connected in series at the connection between the coal inlet of the No. 1 thickening unit and the primary air duct. The light coal outlet of the No. 1 thickening unit is connected to the DC primary air channel, and a No. 3 regulating valve is connected in series on the light coal powder pipeline.

[0010] Furthermore, the No. 1 thickening unit is a louvered coal powder thickener. The louvered coal powder thickener includes a diversion baffle, a louvered structure, and a thickener shell. The coal inlet end of the thickener shell is connected to the primary air duct. A diversion baffle is installed on the coal outlet end of the thickener shell. The coal outlet end of the thickener shell is divided into a light coal powder channel and a concentrated coal powder channel through the diversion baffle. The louvered structure is installed inside the thickener shell. The louvered structure is composed of multiple thickening grids. The multiple thickening grids are arranged equidistantly along the length extension direction of the thickener shell, and each thickening grid is rotatably connected to the inner wall of the thickener shell.

[0011] Furthermore, the air supply pipeline includes a DC secondary air channel, a secondary air duct, and a No. 4 regulating valve. One end of the DC secondary air channel is connected to the corresponding DC secondary air nozzle, one end of the secondary air duct is connected to the air outlet of the secondary air box, and the other end of the DC secondary air channel is connected to the other end of the secondary air duct. A No. 4 regulating valve is installed at the connection between the DC secondary air channel and the secondary air duct.

[0012] Furthermore, the self-contained combustion stabilizer burner includes a combustion stabilizer chamber, a swirl-type internal secondary air channel, a direct-current primary air channel, and a second enrichment unit. The swirl-type internal secondary air channel is coaxially sleeved outside the direct-current primary air channel of the self-contained combustion stabilizer burner. One end of both the direct-current primary air channel and the swirl-type internal secondary air channel are connected to the combustion stabilizer chamber. The other end of the direct-current primary air channel is connected to the coal supply pipeline via a coal-air system, and the other end of the swirl-type internal secondary air channel is connected to the air supply pipeline via a coal-air system. An axial blade assembly is provided between the direct-flow primary air duct and the swirl-type internal secondary air duct of the self-sustaining combustion burner. The axial blade assembly is located close to the combustion stabilization chamber. The axial blade assembly includes multiple axial blades, which are equidistantly arranged circumferentially between the direct-flow primary air duct and the swirl-type internal secondary air duct of the self-sustaining combustion burner. One end of each axial blade is connected to the outer wall of the direct-flow primary air duct of the self-sustaining combustion burner, and the other end of each axial blade is connected to the inner wall of the swirl-type internal secondary air duct. The No. 2 enrichment unit is installed in the direct-flow primary air duct of the self-sustaining combustion burner.

[0013] Furthermore, the No. 2 enrichment unit includes multiple enrichment rings, which are arranged equidistantly along the airflow direction in the DC primary air channel of the self-stable combustion burner. The ring diameters of the multiple enrichment rings decrease sequentially, and all enrichment rings are conical rings. The small diameter end of each enrichment ring faces the outlet end of the DC primary air channel of the self-stable combustion burner.

[0014] Furthermore, the air-coal system includes a direct coal supply pipeline and a swirl air supply pipeline. The coal supply pipeline is connected to the direct primary air channel of the self-stable combustion burner through the direct coal supply pipeline, and the air supply pipeline is connected to the secondary air channel inside the swirl through the swirl air supply pipeline.

[0015] Furthermore, the DC coal supply pipeline includes a DC connection duct for the self-stable combustion burner, a No. 5 regulating valve, a concentrated pulverized coal channel, and a No. 6 regulating valve. The primary air duct is connected to the DC primary air channel of the self-stable combustion burner through the DC connection duct, and a No. 5 regulating valve is connected in series on the DC connection duct. The concentrated coal outlet end of the louvered pulverized coal thickener is connected to the DC primary air channel of the self-stable combustion burner through the concentrated pulverized coal channel, and a No. 6 regulating valve is connected in series on the concentrated pulverized coal channel.

[0016] The swirl air supply pipeline includes the swirl connecting air duct of the self-stable burner and the No. 7 regulating valve. The secondary air duct is connected to the secondary air channel inside the swirl through the swirl connecting air duct of the self-stable burner. The No. 7 regulating valve is connected in series at the connection between the secondary air channel inside the swirl and the connecting air duct of the self-stable burner.

[0017] A combustion method for a combustion device with multiple fuel stages along the vertical direction of the furnace when the boiler is operating at a load higher than 50% of its rated load; by changing the regulating valve, the pulverized coal airflow, after primary concentration, forms a concentrated pulverized coal airflow - a secondary dilute pulverized coal airflow - a primary dilute pulverized coal airflow along the vertical direction of the furnace. The specific operation is as follows: The second regulating valve is closed, and the opening of the first regulating valve is changed to 80%-100%, controlling the primary air velocity entering the direct-flow primary air channel to 26-28 m / s, thus increasing the concentration of pulverized coal in the primary air entering the direct-flow primary air channel. The concentration of pulverized coal is 0.51-0.60 kg / kg air. By adjusting the opening of valve No. 5 to 80%-100%, the primary air velocity entering the self-regulating burner is controlled to 22-26 m / s. After passing through multiple concentration rings in the direct current primary air channel of the self-regulating burner, a high pulverized coal concentration area is formed in the central area, with a pulverized coal concentration of 1.27-1.50 kg / kg air. A low pulverized coal concentration annular area is formed near the wall, with a pulverized coal concentration of 0.31-0.37 kg / kg air.

[0018] A combustion method for a combustion device with multi-stage fuel processing along the vertical direction of the furnace, used when the boiler is operating at less than 50% of its rated load; by changing the regulating valves, the pulverized coal gas flow is concentrated in two stages, forming a concentrated pulverized coal gas flow – a primary dilute pulverized coal gas flow – a secondary dilute pulverized coal gas flow along the vertical direction of the furnace. The specific operation is as follows: Regulating valves No. 1 and No. 5 are closed, and regulating valve No. 2 is opened. After the pulverized coal gas flow passes through the louvered pulverized coal concentrator, the dilute pulverized coal gas flow is controlled by adjusting the opening of regulating valve No. 3 to 50%-80%, controlling the primary air velocity entering the direct-flow primary air channel to 16-26 m / s, and the pulverized coal concentration of the primary air entering the direct-flow primary air channel to 0.12-0.20. The concentration of pulverized coal in the primary airflow is 0.48-0.80 kg pulverized coal / kg air. The primary airflow is controlled to 14-22 m / s by adjusting the opening of valve No. 6 to 40%-80%. The concentration of pulverized coal in the primary airflow entering the DC primary air channel of the self-stable combustion burner is 0.48-0.80 kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through multiple concentration rings in the DC primary air channel of the self-stable combustion burner, forming a high pulverized coal concentration area in the central area, with a pulverized coal concentration of 1.20-2.0 kg pulverized coal / kg air, and a low pulverized coal concentration annular area near the wall, with a pulverized coal concentration of 0.30-0.50 kg pulverized coal / kg air.

[0019] The beneficial effects of this application compared to the prior art are:

[0020] 1. The present invention provides a combustion device and method for multiple stages of fuel combustion along the vertical direction of the furnace. Through a two-stage concentration device, a concentrated pulverized coal airflow, a first-stage dilute pulverized coal airflow, and a second-stage dilute pulverized coal airflow are formed along the vertical direction of the furnace under low load. This achieves staged combustion of pulverized coal, with combustion energy amplified step by step. It can achieve stable combustion of coal-fired power units under 15%-20% rated load conditions by relying solely on pulverized coal combustion.

[0021] The invention, based on the synergistic combustion of a direct-flow burner and a swirl burner, utilizes the ejector effect of the direct-flow primary and secondary air from the direct-flow burner, in conjunction with the combustion stabilization chamber and secondary air within the swirl burner. This creates a central recirculation zone at the center of the swirl burner, serving as a stable ignition heat source to heat the pulverized coal. Simultaneously, the flame generated by the swirl burner ignites the primary air-pulverized coal flame in the direct-flow burner. This achieves stable combustion of coal-fired power units at 20%-30% of rated load, relying solely on pulverized coal combustion without the aid of external flame-assisted combustion technologies such as micro-oil or plasma. However, when the boiler operates at even lower loads (15%-20%), the amount of coal consumed decreases with the load reduction. Yet, to prevent pulverized coal accumulation in the conveying pipes, the primary air volume cannot be reduced too much. Thus, relative to the reduced coal consumption, the primary air volume remains relatively high, resulting in a pulverized coal concentration in the primary air that is even lower than the optimal pulverized coal concentration at low loads. Within a certain range of pulverized coal concentration, a higher pulverized coal concentration significantly reduces the ignition heat of the pulverized coal airflow, lowers the ignition temperature, and shortens the ignition time, which is beneficial for stable combustion under low load. However, increasing the pulverized coal concentration in the primary air has always been limited by the pulverized coal transportation method. Theoretically, a very small primary air ratio is needed to achieve a high pulverized coal concentration, but in practice, the primary air ratio is increased to avoid pulverized coal blockage in the primary air duct. Specifically, under 20% rated load conditions, the pulverized coal concentration in the primary air of both direct-flow and self-stable combustion burners is maintained at 0.3-0.4 kg pulverized coal / kg air.

[0022] This invention utilizes a two-stage concentration device applied to a co-combustion device combining a direct-flow burner and a swirl burner to achieve stable combustion of coal-fired power units at 15%-20% of rated load, relying solely on pulverized coal combustion. The air-coal airflow, after passing through the louvered concentration device, forms a concentrated and diluted pulverized coal airflow. The concentrated pulverized coal airflow then passes through a concentration ring at the outlet of the self-contained stable combustion burner, forming an inner concentrated and outer diluted pulverized coal airflow, ensuring the central pulverized coal airflow reaches the optimal concentration value. Under the action of the inner secondary air, the rotating jet enters the stable combustion chamber. Heated by the high temperature of the inner wall of the stable combustion chamber and the double-layer heating effect of its own recirculation zone, ignition begins from the central concentrated pulverized coal airflow, followed by the outer diluted pulverized coal airflow. After ignition, the inner concentrated and outer diluted pulverized coal airflow spirals along the inner wall of the stable combustion chamber, forming a stable high-temperature flare before entering the furnace and igniting the diluted pulverized coal airflow that has passed through the louvered concentration device and entered the direct-flow primary air nozzle. A series of airflows are formed vertically along the furnace: a concentrated pulverized coal airflow, a primary dilute pulverized coal airflow, and a secondary dilute pulverized coal airflow. The concentrated pulverized coal airflow has a pulverized coal concentration ranging from 1.20 to 1.60 kg pulverized coal / kg air, which is three times higher than the concentration in the unconcentrated airflow. The primary dilute pulverized coal airflow has a pulverized coal concentration ranging from 0.30 to 0.40 kg pulverized coal / kg air, and the secondary dilute pulverized coal airflow has a pulverized coal concentration ranging from 0.12 to 0.16 kg pulverized coal / kg air. This achieves staged combustion of pulverized coal, with the combustion energy amplified step by step, enabling stable combustion of coal-fired power units at 15%-20% of rated load using only pulverized coal combustion.

[0023] 2. The present invention provides a combustion device and method for multiple stages of fuel in the vertical direction of the furnace. Through a two-stage concentration device, a concentrated coal powder airflow - a secondary dilute coal powder airflow - a primary dilute coal powder airflow are formed in the vertical direction of the furnace under high load, which is conducive to the complete combustion of coal powder and improves combustion efficiency.

[0024] From the perspective of reaction mechanism, at low pulverized coal concentrations, the particle heating rate is low and the volatile matter release time is long, which is insufficient to cause continuous ignition of the entire pulverized coal gas flow. However, the oxygen content is relatively high, making it easy to reach the particle surface. Ignition is more likely to occur on the particle surface, resulting in multiphase ignition and an increased ignition temperature. As the pulverized coal concentration increases, the heating rate accelerates, the volatile matter release time is short, and the volatile matter concentration in the gas phase is high, leading to homogeneous ignition and a decreased ignition temperature.

[0025] This invention relates to a three-layer pulverized coal airflow structure formed vertically along the furnace during boiler high-load operation (above 50% of rated load). After primary concentration, the pulverized coal airflow forms a three-layer structure: a concentrated pulverized coal airflow, a secondary dilute pulverized coal airflow, and a primary dilute pulverized coal airflow. The concentrated pulverized coal airflow has a pulverized coal concentration range of 1.27-1.50 kg pulverized coal / kg air, the secondary dilute pulverized coal airflow has a pulverized coal concentration range of 0.31-0.37 kg pulverized coal / kg air, and the primary dilute pulverized coal airflow has a pulverized coal concentration range of 0.51-0.60 kg pulverized coal / kg air. During the combustion of the centrally concentrated pulverized coal, a higher pulverized coal concentration significantly reduces the ignition heat of the airflow, lowers the ignition temperature, and shortens the ignition time, thus extending the residence time of the pulverized coal and resulting in more complete combustion. Combined with the fact that the combustion stabilization chamber has a larger heat load than the furnace cross-section, the heat released after combustion causes the temperature within the combustion stabilization chamber to rise rapidly and remain at a high temperature, all of which contribute to improving the combustion efficiency. Simultaneously, the central area of ​​the self-regulating burner is used as the initial combustion point. This area ignites rapidly due to the pre-introduction of high-concentration pulverized coal. Under the high-concentration pulverized coal and high-temperature environment, a large amount of oxygen is consumed. Then, the flame of the central concentrated pulverized coal gas flow rapidly expands outward, effectively igniting the surrounding secondary dilute pulverized coal gas flow. The increased oxygen content in this area helps replenish the air required for complete pulverized coal combustion. The primary dilute pulverized coal gas flow, timely injected from the overhead direct-flow primary air nozzles, serves as the final combustion supplement. This not only further provides adequate air to promote complete pulverized coal combustion but also effectively utilizes its own high-temperature flame to provide a high-temperature environment for the pulverized coal gas flow, ensuring complete combustion.

[0026] 3. The combustion device and method for multiple stages of fuel along the vertical direction of the furnace provided in this application are beneficial to reducing NOx generation.

[0027] As the concentration of pulverized coal increases, the ignition mode of the pulverized coal gas flow gradually transitions from multiphase ignition to homogeneous ignition. This change in ignition mode has a strong and significant impact on NOx formation. NOx mainly forms in the initial stage of ignition, and the amount of NOx generated decreases monotonically with increasing pulverized coal concentration (i.e., decreasing O2 concentration). During dense-phase pulverized coal ignition, a large amount of volatile matter is released and burned. Because the CO formation rate is greater than the decomposition rate during homogeneous combustion, the CO content around the pulverized coal increases. The presence of reducing gas CO will undergo a reduction decomposition reaction with the generated NOx, significantly reducing NOx emissions. High-concentration pulverized coal combustion not only inhibits NOx formation but also, due to the presence of a large amount of reducing CO gas, directly reduces and decomposes the NOx around the coal particles, thereby greatly reducing NOx emission levels.

[0028] This invention utilizes a two-stage enrichment device to create a fuel staging process along the vertical direction of the furnace, consisting of a concentrated pulverized coal gas flow, a primary dilute pulverized coal gas flow, and a secondary dilute pulverized coal gas flow. Within the combustion stabilization chamber, high-concentration pulverized coal is injected from the center of a self-contained combustion stabilization burner into a high-temperature central reflux zone with a low-oxygen, strongly reducing atmosphere. The pulverized coal burns for an extended period in this fuel-rich, low-oxygen atmosphere, thus prolonging the combustion time and helping to suppress the formation of fuel-type NOx. Simultaneously, the fuel staging process along the vertical direction of the furnace promotes a two-stage combustion mode with significantly different combustion stoichiometric ratios, further reducing NOx emissions.

[0029] 4. The combustion device and method for multiple staged combustion of fuel along the vertical direction of the furnace provided in this application can effectively prevent slagging in the combustion chamber and water-cooled walls.

[0030] Due to the high temperature and limited space within the combustion chamber of a self-contained combustion burner, and the aggregation of pulverized coal particles towards the cylinder wall under centrifugal force, ash and slag accumulation are highly likely to occur on the cylinder wall. In severe cases, this can even lead to safety accidents and increase the workload of ash cleaning and slag removal for operators. Simultaneously, the airflow in a tangentially circular boiler exhibits a bias, potentially causing some airflow to directly scour the water-cooled walls. This scouring effect accelerates the slag formation process on the water-cooled walls.

[0031] This invention utilizes a two-stage enrichment device to create a fuel classification system along the vertical direction of the furnace, consisting of a concentrated pulverized coal airflow, a primary dilute pulverized coal airflow, and a secondary dilute pulverized coal airflow. High-concentration pulverized coal particles are concentrated and injected into the center of the burner within the combustion stabilization chamber. The high-concentration pulverized coal particles have high momentum, making them less prone to outward diffusion. The combustion reaction is primarily concentrated in the central region, preventing pulverized coal from being thrown onto the combustion stabilization chamber walls by secondary air, thus effectively avoiding slagging within the combustion stabilization chamber. Simultaneously, the reduced diffusion angle of the pulverized coal flame at the outlet of the self-contained combustion stabilization burner, coupled with a lower pulverized coal particle concentration in the furnace sidewall area, ensures a relatively strong oxidizing atmosphere near the water-cooled walls in the burner region. This increases the melting point of the ash, which is beneficial in preventing slagging and high-temperature corrosion of the water-cooled walls. Attached Figure Description

[0032] Figure 1 This is a front view schematic diagram of the arrangement of the self-stable combustion burner in the combustion device described in this application;

[0033] Figure 2 This is a top view schematic diagram of the arrangement of the self-stable combustion burner in the combustion device described in this application;

[0034] Figure 3 This is a diagram of the powder distribution system of the self-stable combustion burner in the combustion device described in this application;

[0035] Figure 4This is a schematic diagram of the louvered condensation device in the self-stable combustion burner of the combustion device described in this application;

[0036] Figure 5 This is a side view of the self-stable combustion burner in the combustion device described in this application;

[0037] Figure 6 This is a front view schematic diagram of the self-stable combustion burner in the combustion device described in this application;

[0038] Figure 7 A schematic diagram of the morphology of the combustion chamber and the recirculation zone in the furnace of the self-stable combustion burner when the combustion device described in this application is in operation (fuel classification diagram of concentrated pulverized coal airflow - primary light pulverized coal airflow - secondary light pulverized coal airflow);

[0039] Figure 8 This is a schematic diagram of the morphology of the combustion chamber and the recirculation zone inside the furnace of the self-stable combustion burner when the combustion device described in this application is in operation (fuel classification diagram of concentrated pulverized coal airflow - secondary light pulverized coal airflow - primary light pulverized coal airflow). Detailed Implementation

[0040] Specific implementation method one: Combining Figures 1 to 8 This embodiment describes a combustion device that provides multiple fuel stages along the vertical direction of the furnace. The combustion device includes a tangentially circular pulverized coal combustion boiler 11, a secondary air box 24, and four sets of direct-flow pulverized coal burners 10. The four direct-flow pulverized coal burners 10 are respectively arranged at the four corners of the tangentially circular pulverized coal combustion boiler 11. Each direct-flow pulverized coal burner 10 corresponds to at least one coal mill 14. The direct-flow primary air nozzle 1 in the direct-flow pulverized coal burner 10 is connected to the coal outlet end of the coal mill 14 through a coal supply pipeline. The direct-flow secondary air nozzle 3 in the direct-flow pulverized coal burner 10 is connected to the air outlet end of the secondary air box 24 through an air supply pipeline. Each direct-flow pulverized coal burner 10 is equipped with at least one self-stable combustion burner 2, and each self-stable combustion burner 2 is arranged in... Between the DC primary air nozzle 1 and the DC secondary air nozzle 3 located on the same layer in the DC pulverized coal burner 10, the self-sustaining combustion burner 2 is connected to the coal supply pipeline of the adjacent DC primary air nozzle 1 and the air supply pipeline of the adjacent DC secondary air nozzle 3 through the air-coal system. The combustion device is characterized by: the combustion device also includes at least one set of concentration structures, and each set of concentration structures is correspondingly set to one self-sustaining combustion burner 2. The concentration structure includes a first concentration unit and a second concentration unit. The first concentration unit is integrated in the corresponding coal supply pipeline. The concentrated coal outlet end of the first concentration unit is connected to the corresponding self-sustaining combustion burner 2. The light coal outlet end of the first concentration unit is connected to the corresponding DC primary air nozzle 1. The second concentration unit is integrated in the corresponding self-sustaining combustion burner 2.

[0041] The coal supply pipeline includes a DC primary air channel 5, a primary air duct 15, a first regulating valve 16, a second regulating valve 18, a third regulating valve 19, and a first thickening unit. One end of the DC primary air channel 5 is connected to the corresponding DC primary air nozzle 1. One end of the primary air duct 15 is connected to the coal outlet end of the corresponding coal mill 14. The other end of the DC primary air channel 5 is connected to the other end of the primary air duct 15. A first regulating valve 16 is installed at the connection between the DC primary air channel 5 and the primary air duct 15. The coal inlet end of the first thickening unit is connected to the primary air duct 15. A second regulating valve 18 is connected in series at the connection between the coal inlet end of the first thickening unit and the primary air duct 15. The light coal outlet end of the first thickening unit is connected to the DC primary air channel 5. A third regulating valve 19 is connected in series on the light coal powder pipeline 27.

[0042] The first concentration unit is a louvered coal powder concentrator 21. The louvered coal powder concentrator 21 includes a diversion baffle 26, a louvered structure 27, and a concentrator shell 28. The coal inlet end of the concentrator shell 28 is connected to the primary air duct 15. The diversion baffle 26 is installed on the coal outlet end of the concentrator shell 28. The coal outlet end of the concentrator shell 28 is divided into a light coal powder channel 20 and a heavy coal powder channel 22 through the diversion baffle 26. The louvered structure 27 is installed inside the concentrator shell 28. The louvered structure 27 is composed of multiple concentration grids 29. The multiple concentration grids 29 are arranged equidistantly along the length extension direction of the concentrator shell 28, and each concentration grid 29 is rotatably connected to the inner wall of the concentrator shell 28.

[0043] The air supply pipeline includes a DC secondary air channel 7, a secondary air duct 25, and a No. 4 regulating valve 32. One end of the DC secondary air channel 7 is connected to the corresponding DC secondary air nozzle 3. One end of the secondary air duct 25 is connected to the air outlet of the secondary air box 24. The other end of the DC secondary air channel 7 is connected to the other end of the secondary air duct 25. A No. 4 regulating valve 32 is installed at the connection between the DC secondary air channel 7 and the secondary air duct 25.

[0044] The self-contained combustion stabilizer 2 includes a combustion stabilization chamber 4, a swirl-flow internal secondary air channel 6, a self-contained combustion stabilizer direct primary air channel 8, and a second concentrator unit. The swirl-flow internal secondary air channel 6 is coaxially sleeved outside the self-contained combustion stabilizer direct primary air channel 8, and one end of the self-contained combustion stabilizer direct primary air channel 8 and one end of the swirl-flow internal secondary air channel 6 are both connected to the combustion stabilization chamber 4. The other end of the self-contained combustion stabilizer direct primary air channel 8 is connected to the coal supply pipeline through an air-coal system, and the other end of the swirl-flow internal secondary air channel 6 is connected to the air supply pipeline through an air-coal system. An axial blade assembly 9 is provided between the DC primary air duct 8 of the self-stable combustion burner and the swirl inner secondary air duct 6. The axial blade assembly 9 is located close to the combustion stabilization chamber 4. The axial blade assembly 9 includes multiple axial blades. The multiple axial blades are equidistantly arranged circumferentially between the DC primary air duct 8 of the self-stable combustion burner and the swirl inner secondary air duct 6. One end of each axial blade is connected to the outer wall of the DC primary air duct 8 of the self-stable combustion burner, and the other end of each axial blade is connected to the inner wall of the swirl inner secondary air duct 6. The No. 2 concentration unit is installed in the DC primary air duct 8 of the self-stable combustion burner.

[0045] The second concentration unit includes multiple concentration rings 30. The multiple concentration rings 30 are arranged at equal intervals along the air flow direction in the DC primary air channel 8 of the self-stable combustion burner. The ring diameter of the multiple concentration rings 30 decreases sequentially. All multiple concentration rings 30 are conical rings, and the small diameter end of each concentration ring 30 faces the outlet end of the DC primary air channel 8 of the self-stable combustion burner.

[0046] The air-coal system includes a DC coal supply pipeline and a swirl air supply pipeline. The coal supply pipeline is connected to the DC primary air channel 8 of the self-stable combustion burner through the DC coal supply pipeline, and the air supply pipeline is connected to the secondary air channel 6 inside the swirl through the swirl air supply pipeline.

[0047] The DC coal supply pipeline includes a DC connection duct for the self-stable combustion burner, a No. 5 regulating valve 17, a concentrated pulverized coal channel 22, and a No. 6 regulating valve 23. The primary air duct 15 is connected to the DC primary air channel 8 of the self-stable combustion burner through the DC connection duct, and the No. 5 regulating valve 17 is connected in series on the DC connection duct. The concentrated coal outlet end of the louvered pulverized coal concentrator 21 is connected to the DC primary air channel 8 of the self-stable combustion burner through the concentrated pulverized coal channel 22, and the No. 6 regulating valve 23 is connected in series on the concentrated pulverized coal channel 22.

[0048] The swirl air supply pipeline includes a self-stable burner swirl connection air duct and a No. 7 regulating valve 31. The secondary air duct 25 is connected to the secondary air channel 6 inside the swirl through the self-stable burner swirl connection air duct. The No. 7 regulating valve 31 is connected in series at the connection point between the secondary air channel 6 inside the swirl and the self-stable burner connection air duct.

[0049] In this embodiment, the DC pulverized coal burners 10 in the four-corner tangential pulverized coal combustion boiler 11 are arranged at the four corners of the furnace, and the outlet of the DC pulverized coal burner 10 is composed of a set of rectangular nozzles. The primary air pulverized coal airflow and the secondary air required for combustion are injected into the furnace in the form of DC jets through different nozzles. The DC primary air nozzle 1 and the DC secondary air nozzle 3 are arranged alternately. The flame in the upstream adjacent corner is ignited at the root of the downstream DC pulverized coal burner 2 to form an actual flame zone 12, and an imaginary tangential circle 13 is formed in the center of the four-corner tangential pulverized coal combustion boiler.

[0050] This application includes two concentration units. First, multiple concentration rings 30 are arranged sequentially from large to small along the length of the DC primary air channel 8 of the self-stable combustion burner. The small end of each concentration ring 30 faces the outlet end of the DC primary air channel 8 of the self-stable combustion burner. Typically, 2-4 stages of pulverized coal concentration rings are used, and the concentration angle of the concentration rings is 25°-35°. Second, a louvered pulverized coal concentrator 21 is installed after the No. 2 regulating valve 18 on the primary air duct 15. The louvered pulverized coal concentrator 21 itself is just a cuboid with a cross-section equivalent to that of the primary air channel. A louvered window 27 composed of multiple concentration grids 29 is placed between the flow diversion baffle 26 of the airflow inlet and the airflow outlet. The number of concentration grids 29 is generally 3-5. The tail of the concentrator shell 28 is a concentrated pulverized coal channel 22 and a light pulverized coal channel 20.

[0051] Four self-sustaining combustion burners 2 are arranged between the DC primary air nozzle 1 and the DC secondary air nozzle 3 of the DC pulverized coal burner 10. From the inside out, each self-sustaining combustion burner consists of a DC primary air channel 8, a swirling internal secondary air channel 6, and a combustion stabilization chamber 4. The DC primary air channel 8 and the swirling internal secondary air channel 6 are coaxially arranged and positioned at the front end of the combustion stabilization chamber 4, flush with its inner wall. The outlet end of the combustion stabilization chamber 4 is flush with the outlet ends of the DC primary air nozzle 1 and the DC secondary air nozzle 3. An axial blade assembly 9 is installed within the swirling internal secondary air channel 6, comprising 16 axially curved blades at 60°.

[0052] The coal powder supply in the self-stable combustion burner 2 is divided into two paths: one is that the coal mill 14 is connected to the self-stable combustion burner 2 through the primary air duct 15, the No. 5 regulating valve 17 and the DC primary air channel 8 of the self-stable combustion burner; the other is that the coal mill 14 is connected to the self-stable combustion burner 2 through the No. 2 regulating valve 18, the louvered coal powder concentrator 21, the concentrated coal powder channel 22, the No. 6 regulating valve 23 and the DC primary air channel 8 of the self-stable combustion burner. The swirl internal secondary air channel 6 is connected to the secondary air box 24 through the secondary air duct 25 and the No. 7 regulating valve 31.

[0053] The pulverized coal supply in the DC pulverized coal burner is divided into two paths: First, the pulverizer 14 is connected to the DC primary air nozzle 1 in the DC pulverized coal burner via primary air duct 15, regulating valve 16, and DC primary air channel 5. Second, the pulverizer 14 is connected to the DC primary air nozzle 1 in the DC pulverized coal burner via primary air duct 15, regulating valve 23 (No. 6), louvered pulverized coal concentrator 21, light pulverized coal channel 20, regulating valve 19 (No. 3), and DC primary air channel 5. The DC secondary air nozzle 3 in the DC pulverized coal burner is connected to the secondary air box 24 via secondary air duct 25, regulating valve 32 (No. 4), and DC secondary air channel 7.

[0054] The combustion device for multiple stages of fuel along the vertical direction of the furnace provided in this application operates as follows:

[0055] After the pulverized coal airflow enters the primary air duct 15 from the coal mill, it follows one of three paths depending on the load:

[0056] Path 1 involves the pulverized coal gas flow operating under high load conditions (above 50% of rated load). Instead of passing through the louvered pulverized coal concentrator 21, the pulverized coal undergoes primary concentration via the concentrator ring 30. After passing through the primary air duct 15, a portion of the gas flow directly enters the direct-flow primary air channel 5, entering the furnace in a direct-flow manner. The other portion enters the direct-flow primary air channel 8 of the self-sustaining burner. After passing through the concentrator ring 30, the pulverized coal gas flow is divided into two parts, forming a concentrated inner and diluted outer pulverized coal gas flow at the outlet of the direct-flow primary air channel of the self-sustaining burner, which then enters the furnace in a direct-flow manner. From the center of the self-sustaining burner, along the vertical direction outwards to the nozzle of the direct-flow burner, the pulverized coal concentration exhibits a fuel classification of concentrated pulverized coal gas flow – secondary diluted pulverized coal gas flow – primary diluted pulverized coal gas flow.

[0057] Path 2 involves secondary concentration of pulverized coal during low-load operation (below 50% of rated load) via a louvered pulverized coal concentrator 21 and a concentration ring 30. The pulverized coal flow from the mill passes through the louvered pulverized coal concentrator 21 in the primary air duct. Due to the airflow bend, some pulverized coal particles flowing with this airflow deviate from the airflow direction under centrifugal force. After passing through multiple concentration grids 29 for pulverized coal concentration and separation, a concentrated pulverized coal channel 22 and a diluted pulverized coal channel 20 are formed. The concentrated pulverized coal flow enters the concentrated pulverized coal channel 22, then passes through the self-sustaining burner's DC primary air duct 8 and enters the concentration ring 30. A low-pulverized coal concentration annular region is formed near the wall of the self-sustaining burner's DC primary air duct, while a high-pulverized coal concentration region is formed in the center of the self-sustaining burner's DC primary air duct. Therefore, a pulverized coal concentration distribution with a concentrated inner layer and a diluted outer layer is formed at the outlet of the self-sustaining burner's DC primary air duct. The pulverized coal airflow, with a richer concentration inside and a lighter concentration outside, is subjected to the action of secondary air in the swirling combustion chamber 4 and a stable reflux zone formed at the center of the combustion chamber 4, before entering the furnace in the form of a reflux zone. The lighter pulverized coal airflow, after entering the lighter pulverized coal channel 20, enters the direct-flow primary air nozzle 1 through the direct-flow primary air channel 5 and is injected into the furnace in a direct-flow manner. From the center of the self-sustaining combustion burner, along the vertical direction outwards to the direct-flow burner nozzle, the pulverized coal concentration gradually decreases, forming a fuel classification system of rich pulverized coal airflow – primary light pulverized coal airflow – secondary light pulverized coal airflow.

[0058] Path 3 is for when the self-stable combustion burner 2 is under maintenance or malfunctions. After passing through the primary air duct 15, the pulverized coal airflow does not pass through any concentration device and enters the DC primary air nozzle 1 through the DC primary air channel 5, and is injected into the furnace in a DC form. The DC secondary air enters the DC secondary air nozzle 3 through the DC secondary air channel 7 and is injected into the furnace in a DC form.

[0059] The No. 1 regulating valve 16, located on the DC primary air channel 5, and the No. 3 regulating valve 19, located on the light pulverized coal channel 20, jointly regulate the DC primary air velocity. The No. 6 regulating valve 23, located on the concentrated pulverized coal channel 22, and the No. 5 regulating valve 17, located on the DC primary air channel 8 of the self-sustaining combustion burner, jointly regulate the DC primary air velocity of the self-sustaining combustion burner. Through the louvered pulverized coal concentrator 21, most of the pulverized coal is concentrated in the concentrated pulverized coal channel 22. By adjusting the DC primary air velocity and the concentration effect of the louvered pulverized coal concentrator 21, the pulverized coal concentration in the DC primary air channel is changed. Through the concentration ring 30, most of the pulverized coal is concentrated in the center of the self-sustaining combustion burner. By adjusting the DC primary air velocity of the self-sustaining combustion burner and the concentration effect of the concentration ring 30, the pulverized coal concentration in the self-sustaining combustion burner is changed. In this configuration, without any concentration device, the pulverized coal airflow has a pulverized coal concentration of 0.30-0.60 kg pulverized coal / kg air in the DC primary air channel 5, with an airflow velocity of 16-28 m / s. After passing through the primary concentration device 30 in the DC primary air channel 8 of the self-contained combustion burner, the pulverized coal concentration in the central concentrated pulverized coal airflow ranges from 1.27-1.50 kg pulverized coal / kg air; the pulverized coal concentration near the wall ranges from 0.31-0.37 kg pulverized coal / kg air, with an airflow velocity of 14-26 m / s. After passing through the louvered pulverized coal concentrator 21 in the primary air duct 15 and the two-stage concentration device 30 in the DC primary air channel 8 of the self-contained combustion burner, the pulverized coal concentration in the concentrated pulverized coal channel 22 is 0.48-0.8 kg pulverized coal / kg air. The coal powder concentration in the light coal powder channel 20 is 0.12-0.20 kg coal powder / kg air, the coal powder concentration in the central concentrated coal powder airflow ranges from 1.20-2.0 kg coal powder / kg air, and the coal powder concentration in the near-wall light coal powder airflow ranges from 0.30-0.50 kg coal powder / kg air.

[0060] Specific Implementation Method Two: Combining Figures 1 to 8This embodiment describes a combustion method for a combustion device with multiple fuel stages along the vertical direction of the furnace when the boiler is operating at a load higher than 50% of its rated capacity. By changing the regulating valves, the pulverized coal gas flow, after primary concentration, forms a concentrated pulverized coal gas flow – a secondary dilute pulverized coal gas flow – a primary dilute pulverized coal gas flow along the vertical direction of the furnace. Specifically, the operation is as follows: The second regulating valve 18 is closed; the opening of the first regulating valve 16 is changed to 80%-100%; and the primary air velocity entering the direct-flow primary air channel 5 is controlled to 26-28 m / s. The primary air pulverized coal concentration in channel 5 is 0.51-0.60 kg pulverized coal / kg air. By changing the opening of regulating valve 17 to 80%-100%, the primary air velocity entering the self-regulating burner 2 is controlled to 22-26 m / s. After passing through multiple concentration rings 30 in the direct primary air channel 8 of the self-regulating burner, a high pulverized coal concentration area is formed in the central area, with a pulverized coal concentration of 1.27-1.50 kg pulverized coal / kg air. A low pulverized coal concentration annular area is formed near the wall, with a pulverized coal concentration of 0.31-0.37 kg pulverized coal / kg air.

[0061] In this embodiment, when the boiler is under high load, a primary concentration device is used to form a high-concentration pulverized coal airflow in the central area of ​​the self-contained combustion burner outlet, surrounded by a secondary-concentration, low-concentration pulverized coal annular area. The direct-flow primary air nozzles above supply the primary-concentration, low-concentration pulverized coal airflow. Addressing the significant increase in flue gas temperature within the furnace under high load conditions, the central area of ​​the self-contained combustion burner is used as the initial combustion point. This area is rapidly ignited due to the pre-introduction of high-concentration pulverized coal, and then the flame of the central concentrated pulverized coal airflow rapidly expands outward, effectively igniting the surrounding secondary-concentration, low-concentration pulverized coal airflow. The timely injection of the primary-concentration, low-concentration pulverized coal airflow from the direct-flow primary air nozzles above serves as a final combustion supplement, further promoting complete pulverized coal combustion and effectively utilizing the high-temperature environment within the furnace to ensure complete combustion of the pulverized coal airflow.

[0062] Specific implementation method three: Combining Figures 1 to 8This embodiment describes a combustion method for a combustion device with multiple fuel stages along the vertical direction of the furnace when the boiler is operating at less than 50% of its rated load. By changing the regulating valves, the pulverized coal airflow is concentrated in two stages, forming a concentrated pulverized coal airflow - a first-stage dilute pulverized coal airflow - a second-stage dilute pulverized coal airflow along the vertical direction of the furnace. The specific operation is as follows: Regulating valves 16 and 17 are closed, and regulating valve 18 is opened. After the pulverized coal airflow passes through the louvered pulverized coal concentrator 21, the dilute pulverized coal airflow is controlled by changing the opening of regulating valve 19 to 50%-80%, controlling the primary air velocity entering the direct-flow primary air channel 5 to 16-26 m / s, and the primary air pulverized coal concentration in the direct-flow primary air channel 5 is increased. The concentration of pulverized coal in the primary air is adjusted to 0.12-0.20 kg pulverized coal / kg air. The opening of regulating valve 23 is changed to 40%-80%, and the primary air velocity entering the DC primary air channel 8 of the self-sustaining burner is controlled to 14-22 m / s. The concentration of pulverized coal in the primary air entering the DC primary air channel 8 of the self-sustaining burner is 0.48-0.80 kg pulverized coal / kg air. The pulverized coal airflow then passes through multiple concentration rings 30 in the DC primary air channel of the self-sustaining burner, forming a high pulverized coal concentration area in the central area, with a pulverized coal concentration of 1.20-2.0 kg pulverized coal / kg air, and a low pulverized coal concentration annular area near the wall, with a pulverized coal concentration of 0.30-0.50 kg pulverized coal / kg air.

[0063] In this embodiment, when the boiler is under low load, a two-stage concentration device is used to form a high coal powder concentration airflow in the central area of ​​the self-stable combustion burner outlet, with a first-stage light coal powder concentration annular area around it. The direct current primary air nozzle arranged above provides a second-stage light coal powder airflow. Under low load, the high-concentration coal powder airflow in the center quickly ignites and burns in the stable combustion chamber. Then, the already ignited concentrated coal powder mixes with the first-stage light coal powder and ignites the first-stage light coal powder. At the same time, the flame formed by the swirl burner ignites the second-stage light coal powder flame of the direct current burner, realizing the staged combustion of coal powder. The combustion energy is amplified step by step, enabling the coal-fired power unit to achieve stable combustion at 15%-20% of the rated load by relying solely on coal powder combustion.

[0064] The synergistic combustion method provided in this embodiment is for use when the boiler is operating at less than 50% of its rated load. Specific conditions and adjustment ranges are further refined into the following situations:

[0065] Scenario 1: When the boiler is operating at 40%-50% of its rated load, the combustion method of the combustion device with multiple fuel stages along the vertical direction of the furnace is as follows: Close regulating valve 16 and regulating valve 17, open regulating valve 18. After the pulverized coal airflow passes through the louvered pulverized coal concentrator 21, the light pulverized coal airflow is controlled by changing the opening of regulating valve 19 to 70%-80%, controlling the primary air velocity entering the direct current primary air channel 5 to 22-26 m / s, and the primary air pulverized coal concentration entering the direct current primary air channel 5 to 0.18-0.20 kg pulverized coal / kg air. The concentrated pulverized coal airflow is controlled by changing regulating valve 19 to 70%-80%. Valve 23 is opened to 60%-80%, controlling the primary air velocity entering the DC primary air channel 8 of the self-stable combustion burner to 20-22 m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-stable combustion burner to 0.73-0.80 kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through multiple concentration rings 30 in the DC primary air channel of the self-stable combustion burner, forming a high pulverized coal concentration area in the central area, with a pulverized coal concentration of 1.84-2.0 kg pulverized coal / kg air, and forming a low pulverized coal concentration annular area near the wall, with a pulverized coal concentration of 0.46-0.50 kg pulverized coal / kg air.

[0066] Scenario 2: When the boiler is operating at 30%-40% of its rated load, the combustion method of the combustion device with multiple fuel stages along the vertical direction of the furnace is as follows: Close regulating valve 16 and regulating valve 17, open regulating valve 18. After the pulverized coal airflow passes through the louvered pulverized coal concentrator 21, the light pulverized coal airflow is controlled by changing the opening of regulating valve 19 to 60%-70%, controlling the primary air velocity entering the direct current primary air channel 5 to 18-22 m / s, and the primary air pulverized coal concentration entering the direct current primary air channel 5 to 0.16-0.18 kg pulverized coal / kg air. The concentrated pulverized coal airflow is controlled by changing regulating valve 19 to 60%-70%. Valve 23 is opened to 50%-60%, controlling the primary air velocity entering the DC primary air channel 8 of the self-stable combustion burner to 17-20 m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-stable combustion burner to 0.65-0.72 kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through multiple concentration rings 30 in the DC primary air channel of the self-stable combustion burner, forming a high pulverized coal concentration area in the central area, with a pulverized coal concentration of 1.64-1.80 kg pulverized coal / kg air, and forming a low pulverized coal concentration annular area near the wall, with a pulverized coal concentration of 0.41-0.45 kg pulverized coal / kg air.

[0067] Scenario 3: When the boiler is operating at 15%-30% of its rated load, the combustion method of the combustion device with multiple fuel stages along the vertical direction of the furnace is as follows: Close regulating valve 16 and regulating valve 17, open regulating valve 18. After the pulverized coal airflow passes through the louvered pulverized coal concentrator 21, the light pulverized coal airflow is controlled by changing the opening of regulating valve 19 to 50%-60%, controlling the primary air velocity entering the direct current primary air channel 5 to 16-18 m / s, and the pulverized coal concentration of the primary air entering the direct current primary air channel 5 to 0.12-0.16 kg pulverized coal / kg air. The concentrated pulverized coal airflow is controlled by changing regulating valve 19 to 50%-60%. Valve 23 is opened to 40%-50%, controlling the primary air velocity entering the DC primary air channel 8 of the self-stable combustion burner to 14-17 m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-stable combustion burner to 0.48-0.64 kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through multiple concentration rings 30 in the DC primary air channel of the self-stable combustion burner, forming a high pulverized coal concentration area in the central area, with a pulverized coal concentration of 1.2-1.6 kg pulverized coal / kg air, and forming a low pulverized coal concentration annular area near the wall, with a pulverized coal concentration of 0.30-0.40 kg pulverized coal / kg air.

[0068] Referring to Specific Implementation Methods Two and Three, when the self-regulating burner 2 is under maintenance or malfunctions, the pulverized coal airflow is prevented from passing through any concentration device by changing the regulating valves. The specific operation is as follows: the self-regulating burner 2 system is cut off by closing regulating valve 17 (No. 5) and regulating valve 18 (No. 2), and opening regulating valve 16 (No. 1), while ensuring that the direct-flow burner supplies pulverized coal for combustion, thus avoiding boiler shutdown. The pulverized coal concentration range for the airflow without any concentration device is 0.30-0.60 kg pulverized coal / kg air.

[0069] The present invention has been disclosed above with preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention. However, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention. Specific implementation examples:

[0071] This technology has been applied to a 600MW subcritical pressure drum boiler, which employs a tangential combustion method. Using the apparatus and method described in this invention, a louvered pulverized coal thickener was installed on the primary air duct of the B layer (second layer) of the direct-fired burner, and a three-stage pulverized coal thickening ring was installed in the direct-fired primary air duct of the self-sustaining burner. After the modification, the carbon content of the boiler's fly ash decreased from 6% to 4%, and the boiler efficiency increased from 92.9% to 94.5%. NOx emissions have been significantly reduced compared to before the upgrade. When burning the current type of coal, NOx emissions have reached below 300 mg / Nm3. Under the same coal quality conditions, by adopting a two-stage enrichment device, a concentrated pulverized coal airflow, a primary dilute pulverized coal airflow, and a secondary dilute pulverized coal airflow are formed along the vertical direction of the furnace. The high-concentration pulverized coal airflow in the center quickly ignites and burns in the stable combustion chamber. Then, the already ignited concentrated pulverized coal mixes with the primary dilute pulverized coal and ignites the primary dilute pulverized coal. At the same time, the flame formed by the swirl burner ignites the secondary dilute pulverized coal flame of the direct-flow burner, realizing staged combustion of pulverized coal. The combustion energy is amplified step by step, achieving a minimum stable combustion load of 15% for the boiler without oil injection. Meanwhile, no slagging phenomenon was observed on the water-cooled walls in the burner area.

[0072] Under the requirement of "fully utilizing the emergency peak-shaving capacity of existing coal-fired power units," the load for deep load regulation by thermal power units will be further reduced, and the duration of deep load regulation will increase significantly. To encourage thermal power units to reduce their load to below 30% of rated load, various regions have adopted tiered pricing policies, setting higher upper limits for bids for load rates below 30%. Taking Heilongjiang Province as an example, when the load rate reaches below 25%, a bid price of 0.7-1 yuan / kWh can be submitted. Using the present invention, "A method and apparatus for coordinated combustion of a direct-flow burner and a swirl burner," stable combustion at 15% rated load can be achieved. Overall, the increased revenue from deep load regulation after burner modification is estimated at 80-85 million yuan compared to before modification.

Claims

1. A combustion device for multi-stage fuel combustion along the vertical direction of the furnace, the combustion device comprising a tangentially circular pulverized coal combustion boiler (11), a secondary air box (24), and four direct-current pulverized coal burners (10), the four direct-current pulverized coal burners (10) being respectively arranged at the four corners of the tangentially circular pulverized coal combustion boiler (11), each direct-current pulverized coal burner (10) corresponding to at least one coal mill (14), the direct-current primary air nozzle (1) in the direct-current pulverized coal burner (10) being connected to the coal outlet end of the coal mill (14) through a coal supply pipeline, the direct-current pulverized coal burner (10)... The DC secondary air nozzle (3) is connected to the air outlet of the secondary air box (24) through an air supply pipeline. Each DC pulverized coal burner (10) has at least one self-sustaining combustion burner (2), and each self-sustaining combustion burner (2) is arranged between the DC primary air nozzle (1) and the DC secondary air nozzle (3) located on the same layer in the corresponding DC pulverized coal burner (10). The self-sustaining combustion burner (2) is connected to the coal supply pipeline of the adjacent DC primary air nozzle (1) and the air supply pipeline of the adjacent DC secondary air nozzle (3) through the air-coal system. The feature is that: The combustion device also includes at least one set of concentration structures, and each set of concentration structures is correspondingly set with a self-stable combustion burner (2). The concentration structure includes a No. 1 concentration unit and a No. 2 concentration unit. The No. 1 concentration unit is integrated in the corresponding coal supply pipeline. The concentrated coal outlet end of the No. 1 concentration unit is connected to the corresponding self-stable combustion burner (2). The light coal outlet end of the No. 1 concentration unit is connected to the corresponding DC primary air nozzle (1). The No. 2 concentration unit is integrated in the corresponding self-stable combustion burner (2).

2. The combustion device for multiple stages of fuel along the vertical direction of the furnace according to claim 1, characterized in that: The coal supply pipeline includes a DC primary air channel (5), a primary air pipe (15), a first regulating valve (16), a second regulating valve (18), a third regulating valve (19), and a first thickening unit. One end of the DC primary air channel (5) is connected to the corresponding DC primary air nozzle (1). One end of the primary air pipe (15) is connected to the coal outlet of the corresponding coal mill (14). The other end of the DC primary air channel (5) is connected to the other end of the primary air pipe (15). A first regulating valve (16) is installed at the connection between the DC primary air channel (5) and the primary air pipe (15). The coal inlet of the first thickening unit is connected to the primary air pipe (15). A second regulating valve (18) is connected in series at the connection between the coal inlet of the first thickening unit and the primary air pipe (15). The light coal outlet of the first thickening unit is connected to the DC primary air channel (5). A third regulating valve (19) is connected in series on the light coal powder pipeline (27).

3. The combustion device for multiple stages of fuel along the vertical direction of the furnace according to claim 2, characterized in that: The first thickening unit is a louvered coal powder thickener (21). The louvered coal powder thickener (21) includes a diversion baffle (26), a louvered structure (27), and a thickener shell (28). The coal inlet end of the thickener shell (28) is connected to the primary air duct (15). A diversion baffle (26) is installed on the coal outlet end of the thickener shell (28). The coal outlet end of the thickener shell (28) is divided into a light coal powder channel (20) and a concentrated coal powder channel (22) through the diversion baffle (26). The louvered structure (27) is installed inside the thickener shell (28). The louvered structure (27) is composed of multiple thickening grids (29). The multiple thickening grids (29) are arranged equidistantly along the length extension direction of the thickener shell (28), and each thickening grid (29) is rotatably connected to the inner wall of the thickener shell (28).

4. The combustion device for multiple stages of fuel along the vertical direction of the furnace according to claim 3, characterized in that: The air supply pipeline includes a DC secondary air channel (7), a secondary air duct (25), and a No. 4 regulating valve (32). One end of the DC secondary air channel (7) is connected to the corresponding DC secondary air nozzle (3), one end of the secondary air duct (25) is connected to the air outlet of the secondary air box (24), and the other end of the DC secondary air channel (7) is connected to the other end of the secondary air duct (25). A No. 4 regulating valve (32) is installed at the connection between the DC secondary air channel (7) and the secondary air duct (25).

5. A combustion device for multiple stages of fuel along the vertical direction of the furnace as described in claim 4, characterized in that: The self-contained stable combustion burner (2) includes a stable combustion chamber (4), a swirling internal secondary air channel (6), a self-contained stable combustion burner direct primary air channel (8), and a second concentration unit. The swirling internal secondary air channel (6) is coaxially sleeved outside the self-contained stable combustion burner direct primary air channel (8), and one end of the self-contained stable combustion burner direct primary air channel (8) and one end of the swirling internal secondary air channel (6) are both connected to the stable combustion chamber (4). The other end of the self-contained stable combustion burner direct primary air channel (8) is connected to the coal supply pipeline through the air-coal system, and the other end of the swirling internal secondary air channel (6) is connected to the air supply pipeline through the air-coal system. An axial blade assembly (9) is provided between the direct primary air channel (8) of the self-stable combustion burner and the swirl inner secondary air channel (6), and the axial blade assembly (9) is located close to the combustion stabilization chamber (4). The axial blade assembly (9) includes multiple axial blades, which are equidistantly arranged circumferentially between the direct primary air channel (8) of the self-stable combustion burner and the swirl inner secondary air channel (6). One end of each axial blade is connected to the outer wall of the direct primary air channel (8) of the self-stable combustion burner, and the other end of each axial blade is connected to the inner wall of the swirl inner secondary air channel (6). The second concentration unit is installed in the direct primary air channel (8) of the self-stable combustion burner.

6. A combustion device for multiple stages of fuel along the vertical direction of the furnace according to claim 5, characterized in that: The second concentration unit includes multiple concentration rings (30). The multiple concentration rings (30) are arranged at equal intervals along the air flow direction in the DC primary air channel (8) of the self-stable combustion burner. The ring diameter of the multiple concentration rings (30) decreases sequentially. All multiple concentration rings (30) are conical rings, and the small diameter end of each concentration ring (30) faces the outlet end of the DC primary air channel (8) of the self-stable combustion burner.

7. A combustion device for multiple stages of fuel along the vertical direction of the furnace as described in claim 6, characterized in that: The air-coal system includes a DC coal supply pipeline and a swirl air supply pipeline. The coal supply pipeline is connected to the DC primary air channel (8) of the self-stable combustion burner through the DC coal supply pipeline, and the air supply pipeline is connected to the secondary air channel (6) inside the swirl through the swirl air supply pipeline.

8. A combustion device for multiple stages of fuel along the vertical direction of the furnace according to claim 7, characterized in that: The DC coal supply pipeline includes a DC connection duct for the self-stable combustion burner, a No. 5 regulating valve (17), a concentrated coal powder channel (22), and a No. 6 regulating valve (23). The primary air duct (15) is connected to the DC primary air channel (8) of the self-stable combustion burner through the DC connection duct for the self-stable combustion burner. The No. 5 regulating valve (17) is connected in series on the DC connection duct for the self-stable combustion burner. The concentrated coal outlet end of the louvered coal powder concentrator (21) is connected to the DC primary air channel (8) of the self-stable combustion burner through the concentrated coal powder channel (22). The No. 6 regulating valve (23) is connected in series on the concentrated coal powder channel (22). The swirl air supply pipeline includes the self-stable burner swirl connection air duct and the No. 7 regulating valve (31). The secondary air duct (25) is connected to the secondary air channel (6) inside the swirl through the self-stable burner swirl connection air duct. The No. 7 regulating valve (31) is connected in series at the connection between the secondary air channel (6) inside the swirl and the self-stable burner connection air duct.

9. A combustion method for a boiler operating at a load exceeding 50% of its rated load, achieved using a combustion device according to any one of claims 1 to 8 that involves multiple stages of fuel combustion along the vertical direction of the furnace. By changing the regulating valve, the pulverized coal airflow, after primary concentration, forms a concentrated pulverized coal airflow - secondary dilute pulverized coal airflow - primary dilute pulverized coal airflow along the vertical direction of the furnace. The specific operation is as follows: close the second regulating valve (18), change the opening of the first regulating valve (16) to 80%-100%, control the primary air velocity entering the direct primary air channel (5) to 26-28 m / s, and the pulverized coal concentration of the primary air entering the direct primary air channel (5) is 0.51-0.60 kg pulverized coal / kg air. By changing the opening of regulating valve No. 5 (17) to 80%-100%, the primary air velocity entering the self-stable combustion burner (2) is controlled to 22-26 m / s. After passing through multiple concentration rings (30) in the direct primary air channel (8) of the self-stable combustion burner, a high coal powder concentration area is formed in the central area, with the coal powder concentration reaching 1.27-1.50 kg coal powder / kg air. A low coal powder concentration ring area is formed near the wall, with the coal powder concentration reaching 0.31-0.37 kg coal powder / kg air.

10. A combustion method for a boiler operating at less than 50% rated load, achieved by a combustion device that performs multiple stages of fuel along the vertical direction of the furnace as described in any one of claims 1 to 8, characterized in that: By changing the regulating valves, the pulverized coal airflow is concentrated in two stages, forming a concentrated pulverized coal airflow - a primary dilute pulverized coal airflow - a secondary dilute pulverized coal airflow along the vertical direction of the furnace. The specific operation is as follows: Close the No. 1 regulating valve (16) and the No. 5 regulating valve (17), open the No. 2 regulating valve (18), and after the pulverized coal airflow passes through the louvered pulverized coal concentrator (21), the dilute pulverized coal airflow changes the opening of the No. 3 regulating valve (19) to 50%-80%, controls the primary air velocity entering the DC primary air channel (5) to 16-26 m / s, and the primary air pulverized coal concentration entering the DC primary air channel (5) to 0.12-0.20 kg pulverized coal / kg air. The concentrated pulverized coal airflow passes through... Change the opening of regulating valve No. 6 (23) to 40%-80%, control the primary air velocity entering the DC primary air channel (8) of the self-stable combustion burner to 14-22 m / s, and the primary air pulverized coal concentration entering the DC primary air channel (8) of the self-stable combustion burner to 0.48-0.80 kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through multiple concentration rings (30) in the DC primary air channel of the self-stable combustion burner, forming a high pulverized coal concentration area in the central area, with a pulverized coal concentration of 1.20-2.0 kg pulverized coal / kg air, and forming a low pulverized coal concentration ring area near the wall, with a pulverized coal concentration of 0.30-0.50 kg pulverized coal / kg air.

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