Combustion device and combustion method for multi-time classification of fuel in vertical direction of hearth

Abstract

The invention discloses a combustion device and a combustion method for multiple stages of fuel in the vertical direction of a hearth, belongs to the technical field of combustion of tangential boilers, and aims to solve the problems that a quadrangular (or octagonal) tangential boiler is poor in deep peak regulation capacity, high in NOx emission due to low-load operation denitration efficiency, poor in burnout during high load, slag-bonding on a water cooling wall and the like. The two-stage concentration device is adopted, thick pulverized coal airflow, first-stage thin pulverized coal airflow and second-stage thin pulverized coal airflow are formed in the vertical direction of the hearth, the central high-concentration pulverized coal airflow is quickly ignited and combusted in the stable combustion cavity, then the ignited and combusted thick pulverized coal is mixed with the first-stage thin pulverized coal, the first-stage thin pulverized coal is ignited, and the high-concentration pulverized coal and the second-stage thin pulverized coal are mixed. And meanwhile, flames formed by combustion of the turbulent burner ignite second-stage light pulverized coal flames of the direct-current burner, staged combustion of pulverized coal is achieved, combustion energy is amplified step by step, and the effects that a coal power unit only depends on pulverized coal combustion to achieve stable combustion under 15% rated load, NOx emission is reduced, the burnout effect is improved, and slag bonding of a water cooling wall is prevented are achieved. The device is mainly used for improving the stable combustion effect of the boiler during working.

Description

Technical Field

[0001] The invention relates to the technical field of tangential boiler combustion, and in particular to a combustion device and a combustion method for multi-stage fuel along a vertical direction of a furnace. Background Art

[0002] In recent years, due to the implementation of the national dual-carbon policy, the government has increased its support and promotion of renewable energy power generation. The proportion of some major forms of renewable energy power generation, including solar power generation, wind power generation, hydropower generation, and biomass power generation, has increased year by year, the number of hours of thermal power utilization has decreased year by year, and the energy structure system is constantly changing. However, renewable energy power generation faces many challenges in the power industry. These challenges mainly stem from its randomness and instability. Since the impact of renewable energy power generation on the power system is more complex and difficult to predict, in order to maintain the stability of the power grid and promote the clean and low-carbon transformation of the power industry, large thermal power units need to have deep flexibility peak-shaving capabilities. In the flexibility transformation to improve the peak-shaving capacity of the unit, the most critical issue is to achieve stable operation of the boiler at a low load of 20%-30% or even lower.

[0003] Coal-fired boiler power generation is the main body of my country's current energy structure. The combustion method of coal-fired boilers mainly adopts the arrangement of direct current burners on the four corners or eight corners of the boiler furnace. The coal powder airflow and the secondary air are sprayed into the furnace through the direct current burner jets and merged in the form of a tangent circle. The coal powder airflow is directly hit by the high-temperature flame of the upstream adjacent corner on the side facing the fire and is ignited. The four-corner (or eight-corner) tangential pulverized coal combustion boiler is the most widely used and mature furnace type in my country's power plants, accounting for more than 70% of the total installed capacity. However, the stable combustion load of domestic coal-fired power units without oil injection can only reach 30%-40%. It is difficult to achieve a stable combustion effect of 20%-30% of the rated load by relying solely on coal powder combustion, and the four-corner (or eight-corner) tangential pulverized coal boiler cannot meet the requirements of deep peak regulation.

[0004] At present, in order to make the boiler reach a stable combustion load of 20%-30% without adding oil, it is necessary to assist the stable combustion through plasma, micro-oil or medium-frequency electric heating technology to maintain the long-term operation of the boiler at 20%-30% rated load. Micro-oil stable combustion technology uses a small amount of oil (oil gun output 0.4t / h-0.6t / h) to ignite coal powder, and strengthens the ignition and stable combustion of coal powder through its own combustion heat release. It has the advantage of strong adaptability to coal types and is applicable from lignite boilers to anthracite boilers. The disadvantage is that long-term operation has a certain negative impact on the electrostatic precipitator electrode and desulfurization slurry. On the other hand, the annual oil consumption of using oil guns for stable combustion can reach more than 10,000 tons, which is poor in economy and extremely costly. Plasma stable combustion technology mainly uses high-power plasma guns to generate high-temperature arcs to strengthen the ignition and stable combustion of coal powder. It has the characteristics of economy and environmental protection, but it has the disadvantages of short cathode working life and poor coal quality adaptability. It is often used in bituminous coal boilers with high volatile matter. Medium-frequency electric heating technology uses medium-frequency induction heating to obtain better low-load and variable-load combustion stability. However, the system becomes complicated and the investment cost increases due to the addition of an additional pulverizing system. At the same time, medium-frequency induction is required to heat the flammable bituminous coal, and slagging is likely to occur in the flame extension tube during long-term operation.

[0005] "A method and device for coordinated combustion of a DC burner and a swirl burner" has developed a device for coordinated combustion of a DC burner and a swirl burner. A self-help stabilizing combustion burner is set between the DC primary air and the DC secondary air. The original DC burner and the self-help stabilizing combustion burner are used for coordinated combustion, which enables the four-corner (or octagonal) cut-circle boiler to operate stably at 20%-30% of the rated load by relying solely on coal powder combustion, while improving the burnout effect at high loads. However, actual applications have shown that after applying the device, it was found that the four-corner (or octagonal) cut-circle boiler could not operate stably at 15%-20% of the rated load. In addition, the DC burner and swirl burner coordinated combustion device has problems such as increased NOx emissions, low burnout rate, and slight slagging of the water-cooled wall at low loads.

[0006] Therefore, in order to completely solve the problems of poor deep peak regulation capability of four-corner (or eight-corner) cut-circle boilers, excessive NOx emissions and slagging of water-cooled walls, and to further improve the ability of four-corner (or eight-corner) cut-circle boilers to operate stably at 15%-20% of the rated load relying solely on coal powder combustion, the present invention proposes a combustion method and device for multiple fuel stages along the vertical direction of the furnace. Summary of the invention

[0007] The present invention aims to solve the problems of poor deep peak regulation capability of four-corner (or eight-corner) tangential boilers, high NOx emission caused by reduced denitration efficiency during low-load operation, poor burnout during high-load operation, and slagging of water-cooled walls, and further provides a combustion device and a combustion method with multiple fuel stages in the vertical direction of the furnace;

[0008] A combustion device with multiple fuel stages in the vertical direction of a furnace, the combustion device comprising a four-corner tangential 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 four-corner tangential pulverized coal combustion boiler, each direct current pulverized coal burner corresponds to at least one coal mill, the direct current primary air nozzle in the direct current pulverized coal burner is connected to the coal outlet end of the coal mill through a coal supply pipeline, the direct current secondary air nozzle in the direct current pulverized coal burner is connected to the air outlet end of the secondary air box through an air supply pipeline, each direct current pulverized coal burner is arranged with at least one self-help stabilizing combustion burner, and each self-help stabilizing combustion burner is arranged in the corresponding direct current pulverized coal burner and is located at the same Between the DC primary air nozzle and the DC secondary air nozzle of the layer, the self-service stabilizing combustion burner is connected with 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-powder system, the combustion device also includes at least one group of concentrating structures, and each group of concentrating structures is correspondingly arranged with a self-service stabilizing combustion burner, the concentrating structure includes a No. 1 concentrating unit and a No. 2 concentrating unit, the No. 1 concentrating unit is integrated in the corresponding coal supply pipeline, the concentrated coal outlet end of the No. 1 concentrating unit is connected with the corresponding self-service stabilizing combustion burner, the light coal outlet end of the No. 1 concentrating unit is connected with the corresponding DC primary air nozzle, and the No. 2 concentrating unit is integrated in the corresponding self-service stabilizing combustion burner;

[0009] Further, 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 concentrating 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, the other end of the DC primary air channel is connected to the other end of the primary air duct, and a No. 1 regulating valve is installed at the connection between the DC primary air channel and the primary air duct, the coal inlet end of the No. 1 concentrating 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 end of the No. 1 concentrating unit and the primary air duct, the light coal outlet end of the No. 1 concentrating unit is connected to the DC primary air channel, and a No. 3 regulating valve is connected in series on the light coal pulverized coal pipeline;

[0010] Further, the No. 1 concentrating unit is a louvered coal powder concentrator, which includes a diverter baffle, a louver structure and a concentrator shell, the coal inlet end of the concentrator shell is connected to the primary air duct, the coal outlet end of the concentrator shell is installed with a diverter baffle, the coal outlet end of the concentrator shell is divided into a light coal powder channel and a thick coal powder channel by the diverter baffle, the louver structure is installed in the concentrator shell, the louver structure is composed of a plurality of concentrating grids, the plurality of concentrating grids are arranged in sequence and equidistantly along the length extension direction of the concentrator shell, and each concentrating grid is rotatably connected to the inner wall of the concentrator shell;

[0011] Further, 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 end of the secondary air box, the other end of the DC secondary air channel is connected to the other end of the secondary air duct, and 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-service stabilizing combustion burner comprises a stabilizing combustion chamber, a secondary air channel in a swirl, a DC primary air channel of the self-service stabilizing combustion burner and a No. 2 concentration unit, the secondary air channel in the swirl is coaxially sleeved on the outside of the DC primary air channel of the self-service stabilizing combustion burner, and one end of the DC primary air channel of the self-service stabilizing combustion burner and one end of the secondary air channel in the swirl are both connected to the stabilizing combustion chamber, the other end of the DC primary air channel of the self-service stabilizing combustion burner is connected to the coal supply pipeline through an air-powder system, and the other end of the secondary air channel in the swirl is connected to the air supply pipeline through an air-powder system. An axial blade group is provided between the DC primary air channel of the self-service stabilizing combustion burner and the secondary air channel in the swirl, and the axial blade group is arranged close to the stabilizing combustion chamber. The axial blade group includes a plurality of axial blades, and the plurality of axial blades are equidistantly arranged along the circumferential direction between the DC primary air channel of the self-service stabilizing combustion burner and the secondary air channel in the swirl, and one end of each axial blade is connected to the outer wall of the DC primary air channel of the self-service stabilizing combustion burner, and the other end of each axial blade is connected to the inner wall of the secondary air channel in the swirl. The second concentration unit is installed in the DC primary air channel of the self-service stabilizing combustion burner:

[0013] Furthermore, the No. 2 concentrating unit includes a plurality of concentrating rings, which are arranged equidistantly in sequence along the flow direction of the air in the DC primary air channel of the self-service stabilizing combustion burner, and the ring diameters of the plurality of concentrating rings decrease in sequence, and the plurality of concentrating rings are all conical rings, and the small-diameter end of each concentrating ring faces the outlet end of the DC primary air channel of the self-service stabilizing combustion burner;

[0014] Furthermore, the air-powder system includes a DC coal supply pipeline and a swirl air supply pipeline, the coal supply pipeline is connected with the DC primary air channel of the self-help stable combustion burner through the DC coal supply pipeline, and the air supply pipeline is connected with the secondary air channel in the swirl through the swirl air supply pipeline;

[0015] Furthermore, the DC coal supply pipeline includes a DC connecting air duct of the self-service stable combustion burner, a No. 5 regulating valve, a concentrated coal powder channel and a No. 6 regulating valve, the primary air duct is connected to the DC primary air channel of the self-service stable combustion burner through the DC connecting air duct of the self-service stable combustion burner, and the No. 5 regulating valve is connected in series to the DC connecting air duct of the self-service stable combustion burner, the concentrated coal outlet end of the louvered coal powder concentrator is connected to the DC primary air channel of the self-service stable combustion burner through the concentrated coal powder channel, and the No. 6 regulating valve is connected in series to the concentrated coal powder channel;

[0016] The swirl air supply pipeline includes a swirl connecting air duct of the self-service stabilizing combustion burner and a No. 7 regulating valve. The secondary air duct is connected with the secondary air channel in the swirl through the swirl connecting air duct of the self-service stabilizing combustion burner. The connecting point of the secondary air channel in the swirl and the self-service stabilizing combustion burner connecting air duct is connected in series with the No. 7 regulating valve.

[0017] A combustion method for a combustion device with multiple fuel stages in the vertical direction of a furnace when the boiler is operated at a load condition higher than 50% of the rated load; by changing the regulating valve, the pulverized coal airflow is concentrated in the first stage, and then forms a concentrated pulverized coal airflow-a second stage of light pulverized coal airflow-a first stage of light pulverized coal airflow in 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%, and the primary air speed entering the DC primary air channel is controlled to 26-28m / s, and the primary air pulverized coal concentration entering the DC primary air channel is increased. The concentration is 0.51-0.60kg coal powder / kg air. By changing the opening of the No. 5 regulating valve to 80%-100%, the primary wind speed entering the self-service stabilizing combustion burner is controlled to 22-26m / s. After passing through multiple concentration rings in the DC primary air channel of the self-service stabilizing combustion burner, a high coal powder concentration area is formed in the central area, and the coal powder concentration reaches 1.27-1.50kg coal powder / kg air. A low coal powder concentration annular area is formed near the wall, and the coal powder concentration reaches 0.31-0.37kg coal powder / kg air.

[0018] A combustion method for a combustion device with multiple fuel stages in the vertical direction of a furnace when the boiler is operated at a load condition lower than 50% of the rated load; by changing the regulating valve, the pulverized coal airflow is concentrated in two stages to form a concentrated pulverized coal airflow-a first-stage light pulverized coal airflow-a second-stage light pulverized coal airflow in the vertical direction of the furnace, and the specific operation is as follows: the No. 1 regulating valve and the No. 5 regulating valve are closed, and the No. 2 regulating valve is opened. After the pulverized coal airflow passes through a louvered pulverized coal concentrator, the light pulverized coal airflow is adjusted to 50%-80% by changing the opening of the No. 3 regulating valve to control the primary wind speed entering the DC primary air channel to 16-26m / s, and the primary air pulverized coal concentration entering the DC primary air channel to 0.12-0.20. kg pulverized coal / kg air, the concentrated pulverized coal airflow is controlled by changing the opening of the No. 6 regulating valve to 40%-80%, and the primary wind speed entering the DC primary air channel of the self-service stabilizing combustion burner is controlled to 14-22m / s, and the primary air pulverized coal concentration entering the DC primary air channel of the self-service stabilizing combustion burner is set to 0.48-0.80kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through multiple concentration rings in the DC primary air channel of the self-service stabilizing combustion burner to form a high pulverized coal concentration area in the central area, and the pulverized coal concentration reaches 1.20-2.0kg pulverized coal / kg air, and a low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.30-0.50kg pulverized coal / kg air.

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

[0020] 1. The present invention provides a combustion device and a combustion method with multiple fuel stages in the vertical direction of the furnace. Through a two-stage concentration device, a concentrated coal powder airflow-a first-stage light coal powder airflow-a second-stage light coal powder airflow are formed in the vertical direction of the furnace under low load, thereby realizing staged combustion of coal powder, amplifying the combustion energy step by step, and realizing a stable combustion effect of the coal-fired power unit under the rated load condition of 15%-20% by relying solely on coal powder combustion.

[0021] The invention is based on the coordinated combustion of the DC burner and the swirl burner, that is, relying on the induced effect of the DC primary air and DC secondary air of the DC burner, the coordinated swirl burner stable combustion chamber and the secondary air in the swirl, so that a central reflow zone is formed in the center of the swirl burner as a stable ignition heat source to heat the pulverized coal. At the same time, the flame formed by the combustion of the swirl burner ignites the primary air pulverized flame of the DC burner, without the help of external flame combustion-supporting technologies such as micro-oil or plasma, so as to achieve the stable combustion effect of the coal-fired power unit at a rated load of 20%-30% by relying solely on the combustion of pulverized coal. However, when the boiler is running at a lower load of 15%-20%, the amount of coal burned will decrease as the load decreases. However, in order to ensure that there is no accumulation of powder in the powder conveying pipeline, the primary air volume cannot be reduced too much. In this way, relative to the reduced amount of coal burned, the primary air volume remains relatively high, resulting in the pulverized coal concentration in the primary air being lower than the optimal pulverized coal concentration value at low load. Within a certain range of pulverized coal concentration, the greater the pulverized coal concentration, the less ignition heat of the pulverized coal airflow, the lower the ignition temperature, and the shorter the ignition time, which is conducive to low-load stable combustion. However, increasing the pulverized coal concentration in the primary air has always been limited by the means of pulverized coal transportation. In order to achieve a high pulverized coal concentration, the required primary air rate is theoretically very small, but in order to avoid clogging of the primary air duct by pulverized coal, the primary air rate is actually increased. Among them, the pulverized coal concentration of the DC primary air and the primary air of the self-service stable combustion burner is maintained at 0.3-0.4kg pulverized coal / kg air under 20% rated load conditions.

[0022] The present invention adopts a two-stage concentration device to be applied to the coordinated combustion device of the direct current burner and the swirl burner, so as to achieve the stable combustion effect of the coal-fired power unit under the rated load of 15%-20% by relying only on the combustion of coal powder. After the air-powder airflow passes through the louver concentration device, a concentrated and thin coal powder airflow is formed, wherein the concentrated coal powder airflow is then passed through the concentration ring at the outlet of the self-stable combustion burner to form an inner concentrated and outer thin coal powder airflow, so that the concentration of the central coal powder airflow reaches the optimal coal powder concentration value. And under the action of the internal secondary wind, the rotating jet enters the stable combustion chamber, and is subjected to the high temperature of the inner wall of the stable combustion chamber and the double-layer heating effect of its own reflow zone, and starts to ignite from the central concentrated coal powder airflow, and then ignites the outer thin coal powder airflow. After ignition, the inner concentrated and outer thin coal powder airflow moves forward in a spiral shape along the inner wall of the stable combustion chamber, and after forming a stable high-temperature torch, it enters the furnace and ignites the thin coal powder airflow that enters the direct current primary air nozzle after passing through the louver concentration device. A concentrated coal powder airflow, a first-level light coal powder airflow, and a second-level light coal powder airflow are formed along the vertical direction of the furnace. The coal powder concentration of the concentrated coal powder airflow ranges from 1.20 to 1.60 kg coal powder / kg air, which is three times higher than that of the unconcentrated coal powder. The coal powder concentration of the first-level light coal powder airflow ranges from 0.30 to 0.40 kg coal powder / kg air, and the coal powder concentration of the second-level light coal powder airflow ranges from 0.12 to 0.16 kg coal powder / kg air. The grading combustion of coal powder is realized, and the combustion energy is amplified step by step, so that the coal-fired power unit can achieve a stable combustion effect under the condition of 15% to 20% rated load by relying only on coal powder combustion.

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

[0024] From the perspective of reaction mechanism, at low pulverized coal concentration, the particle heating rate is low and the volatile release time is long, which is not enough to cause continuous ignition of the entire pulverized coal gas flow. However, the amount of oxygen is relatively large and it is very easy to reach the particle surface. Ignition is easy to occur on the particle surface, causing multiphase ignition and increasing ignition temperature. When the pulverized coal concentration increases, the heating rate is accelerated, the volatile release time is short, and the volatile concentration in the gas phase is high, causing homogeneous ignition and reducing the ignition temperature.

[0025] The present invention is that when the boiler is running at high load (more than 50% of the rated load), after the coal powder airflow is concentrated in the first level, a three-layer coal powder airflow structure of "concentrated coal powder airflow-secondary light coal powder airflow-primary light coal powder airflow" is formed along the vertical direction of the furnace. The coal powder concentration range of the concentrated coal powder airflow is 1.27-1.50kg coal powder / kg air, the coal powder concentration range of the secondary light coal powder airflow is 0.31-0.37kg coal powder / kg air, and the coal powder concentration range of the primary light coal powder airflow is 0.51-0.60kg coal powder / kg air. During the combustion of the central high-concentration coal powder, when the coal powder concentration is greater, the ignition heat of the coal powder airflow is significantly reduced, the ignition temperature is also reduced, the ignition time is shortened, the residence time of the coal powder is extended, the coal powder burns more fully, and the stable combustion cavity has a larger heat load than the furnace cross section. The heat released after combustion makes the temperature in the stable combustion cavity rise rapidly and maintain it at a high temperature, which helps to improve its own burnout rate. At the same time, the central area of ​​the self-help stable combustion burner is used as the initial combustion point. This area is quickly ignited due to the pre-introduction of high-concentration coal powder. A large amount of oxygen content is consumed in the high-concentration coal powder and high-temperature environment. Then the flame of the central concentrated coal powder airflow quickly expands outward, effectively igniting the secondary light coal powder airflow surrounding it. The increased oxygen content in this area is conducive to replenishing the air required for the coal powder to burn out. The primary light coal powder airflow ejected in time by the DC primary air nozzle arranged above, as the last combustion supplement, not only further provides an appropriate amount of air as a supplement, promoting the complete combustion of coal powder, but also effectively utilizes its own high-temperature flame to provide a high-temperature environment for the coal powder airflow, ensuring the full combustion of the coal powder airflow.

[0026] 3. The present application provides a combustion device and a combustion method for multiple fuel staged in the vertical direction of the furnace, which is beneficial to reducing the amount of NOx generated.

[0027] As the concentration of pulverized coal increases, the ignition mode of the pulverized coal airflow will gradually transition from multiphase ignition to homogeneous ignition. The change in ignition mode will have a strong and significant impact on the generation of NOx. NOx is mainly formed in the early stage of ignition. As the concentration of pulverized coal increases, that is, the concentration of O2 decreases, the amount of NOx generated decreases monotonically. When dense pulverized coal ignites, a large amount of volatile matter has been released and burned. Since the generation rate of CO is greater than the decomposition rate during homogeneous combustion, the CO content around the pulverized coal is getting higher and higher. The presence of reducing gas CO will undergo a reduction and decomposition reaction with the generated NOx, greatly reducing NOx. The combustion of high-concentration pulverized coal not only inhibits the generation of NOx, but also the presence of a large amount of reducing CO gas causes the NOx around the coal particles to be directly reduced and decomposed, thereby greatly reducing the emission level of NOx.

[0028] The present invention forms a fuel grading of concentrated coal powder airflow-first-stage light coal powder airflow-second-stage light coal powder airflow along the vertical direction of the furnace through a two-stage concentrating device. In the stable combustion chamber, high-concentration coal powder is sprayed from the center of the self-help stable combustion burner into the high-temperature central reflow zone of the low-oxygen and strong reducing atmosphere. The coal powder burns in the fuel-rich and low-oxygen atmosphere for a long time, which can extend the combustion time of the coal powder in the reducing atmosphere and is beneficial to suppressing the formation of fuel-type NOx. At the same time, a fuel grading of concentrated coal powder airflow-first-stage light coal powder airflow-second-stage light coal powder airflow is formed along the vertical direction of the furnace, which promotes the formation of a two-stage combustion mode far away from the combustion chemical equivalence ratio, which is beneficial to reducing NOx emissions.

[0029] 4. The present application provides a combustion device and a combustion method with multiple fuel stages in the vertical direction of the furnace, which can effectively prevent slagging in the stable combustion chamber and the water-cooled wall.

[0030] The combustion chamber of the self-service combustion stabilizing burner has high temperature and small space, and the coal powder particles gather towards the cylinder wall under the action of centrifugal force, which makes it very easy for ash and slagging to occur in the cylinder wall. In serious cases, it may even cause safety accidents, increasing the workload of operators to clean and remove ash and slag. At the same time, there is a deviation in the airflow in the four-corner tangential boiler, which may cause part of the airflow to directly flush the water-cooled wall. This flushing effect will accelerate the slagging process on the water-cooled wall.

[0031] The present invention forms a fuel classification of concentrated coal powder airflow-first-level light coal powder airflow-second-level light coal powder airflow along the vertical direction of the furnace through a two-stage concentration device. High-concentration coal powder particles are concentrated in the center of the burner and sprayed in the stable combustion chamber. The high-concentration coal powder particles have a large momentum and are not easy to diffuse outward. The coal powder combustion reaction is mainly concentrated in the central area, preventing the coal powder from being thrown onto the stable combustion chamber wall by the secondary air, thereby effectively avoiding the occurrence of slagging in the stable combustion chamber. At the same time, the diffusion angle of the coal powder flame at the outlet of the self-service stable combustion burner is reduced, and the concentration of coal powder particles in the furnace side wall area is relatively low, which ensures that a relatively strong oxidizing atmosphere is formed near the water-cooled wall in the burner area, increases the melting point of the ash, and is conducive to preventing slagging and high-temperature corrosion of the water-cooled wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the arrangement of the self-help combustion stabilizing burner in the combustion device described in this application;

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

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

[0035] Figure 4A schematic diagram of a shutter concentration device in a self-service combustion stabilizing burner in the combustion device described in the present application;

[0036] Figure 5 It is a side view schematic diagram of the self-combustion stabilizing burner in the combustion device described in this application;

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

[0038] Figure 7 This is a schematic diagram of the morphology of the self-help stabilizing combustion burner stabilizing combustion chamber and the reflow zone in the furnace when the combustion device described in this application is working (fuel classification diagram of concentrated coal powder airflow-first-level light coal powder airflow-second-level light coal powder airflow);

[0039] Figure 8 This is a schematic diagram of the morphology of the self-service stabilizing combustion burner stabilizing chamber and the recirculation zone in the furnace when the combustion device described in this application is working (fuel grading diagram of concentrated coal powder airflow-secondary light coal powder airflow-primary light coal powder airflow). DETAILED DESCRIPTION

[0040] Specific implementation method 1: Combination Figures 1 to 8 The present embodiment is described. In the present embodiment, a combustion device with multiple fuel gradings along the vertical direction of the furnace is provided. The combustion device includes a four-corner cut pulverized coal combustion boiler 11, a secondary air box 24 and four groups of direct current pulverized coal burners 10. The four direct current pulverized coal burners 10 are respectively arranged at the four corners of the four-corner cut pulverized coal combustion boiler 11. Each direct current pulverized coal burner 10 corresponds to at least one coal mill 14. The direct current primary air nozzle 1 in the direct current pulverized coal burner 10 is connected to the coal outlet end of the coal mill 14 through a coal supply pipeline. The direct current secondary air nozzle 3 in the direct current pulverized coal burner 10 is connected to the air outlet end of the secondary air box 24 through an air supply pipeline. At least one self-help stabilizing combustion burner 2 is arranged in each direct current pulverized coal burner 10, and each self-help stabilizing combustion burner 2 is arranged at 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-help stabilizing combustion burner 2 is connected with the coal supply pipeline adjacent to the DC primary air nozzle 1 and the air supply pipeline adjacent to the DC secondary air nozzle 3 through the air-powder system, and is characterized in that: the combustion device also includes at least one group of concentrating structures, and each group of concentrating structures is corresponding to a self-help stabilizing combustion burner 2, the concentrating structure includes a No. 1 concentrating unit and a No. 2 concentrating unit, the No. 1 concentrating unit is integrated in the corresponding coal supply pipeline, the concentrated coal outlet end of the No. 1 concentrating unit is connected with the corresponding self-help stabilizing combustion burner 2, the light coal outlet end of the No. 1 concentrating unit is connected with the corresponding DC primary air nozzle 1, and the No. 2 concentrating unit is integrated in the corresponding self-help stabilizing combustion burner 2;

[0041] The coal supply pipeline includes a DC primary air channel 5, a primary air duct 15, a No. 1 regulating valve 16, a No. 2 regulating valve 18, a No. 3 regulating valve 19 and a No. 1 concentrating 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, and the No. 1 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 No. 1 concentrating unit is connected to the primary air duct 15, and the No. 2 regulating valve 18 is connected in series at the connection between the coal inlet end of the No. 1 concentrating unit and the primary air duct 15, the light coal outlet end of the No. 1 concentrating unit is connected to the DC primary air channel 5, and the No. 3 regulating valve 19 is connected in series on the light coal powder pipeline 27;

[0042] The first concentrating unit is a louvered coal powder concentrator 21, which includes a diverter baffle 26, a louver structure 27 and a concentrator shell 28. The coal inlet end of the concentrator shell 28 is connected to the primary air duct 15, and a diverter 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 thick coal powder channel 22 by the diverter baffle 26. The louver structure 27 is installed in the concentrator shell 28. The louver structure 27 is composed of a plurality of concentrating grids 29. The plurality of concentrating grids 29 are arranged in sequence and equidistantly along the length extension direction of the concentrator shell 28, and each concentrating 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 channel 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 channel 25 is connected to the air outlet end 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 channel 25. A No. 4 regulating valve 32 is installed at the connection between the DC secondary air channel 7 and the secondary air channel 25.

[0044] The self-service stabilizing combustion burner 2 comprises a stabilizing combustion chamber 4, a secondary air channel 6 in a swirl, a DC primary air channel 8 of the self-service stabilizing combustion burner and a second concentration unit. The secondary air channel 6 in a swirl is coaxially sleeved on the outside of the DC primary air channel 8 of the self-service stabilizing combustion burner, and one end of the DC primary air channel 8 of the self-service stabilizing combustion burner and one end of the secondary air channel 6 in a swirl are both connected to the stabilizing combustion chamber 4, the other end of the DC primary air channel 8 of the self-service stabilizing combustion burner is connected to the coal supply pipeline through an air-powder system, the other end of the secondary air channel 6 in a swirl is connected to the air supply pipeline through an air-powder system, and the self-service stabilizing combustion burner is connected to the coal supply pipeline through an air-powder system. An axial blade group 9 is provided between the DC primary air channel 8 of the self-service combustion stabilizing burner and the secondary air channel 6 in the swirl, and the axial blade group 9 is arranged close to the combustion stabilizing chamber 4. The axial blade group 9 includes a plurality of axial blades, and the plurality of axial blades are equidistantly arranged along the circumferential direction between the DC primary air channel 8 of the self-service combustion stabilizing burner and the secondary air channel 6 in the swirl, and one end of each axial blade is connected to the outer wall of the DC primary air channel 8 of the self-service combustion stabilizing burner, and the other end of each axial blade is connected to the inner wall of the secondary air channel 6 in the swirl, and the No. 2 concentration unit is installed in the DC primary air channel 8 of the self-service combustion stabilizing burner;

[0045] The second concentrating unit includes a plurality of concentrating rings 30, which are arranged equidistantly in sequence along the flow direction of the air in the DC primary air channel 8 of the self-service stabilizing combustion burner, and the ring diameters of the plurality of concentrating rings 30 decrease in sequence, and the plurality of concentrating rings 30 are all conical rings, and the small-diameter end of each concentrating ring 30 faces the outlet end of the DC primary air channel 8 of the self-service stabilizing combustion burner;

[0046] The air-powder 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-help stable combustion burner through the DC coal supply pipeline, and the air supply pipeline is connected to the secondary air channel 6 in the swirl through the swirl air supply pipeline.

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

[0048] The swirl air supply pipeline includes a self-service stabilizing combustion burner swirl connecting air duct and a No. 7 regulating valve 31. The secondary air duct 25 is connected to the secondary air channel 6 in the swirl through the self-service stabilizing combustion burner swirl connecting air duct. The No. 7 regulating valve 31 is connected in series at the connecting point between the secondary air channel 6 in the swirl and the self-service stabilizing combustion burner connecting 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 outlets of the DC pulverized coal burners 10 are composed of a group of rectangular nozzles. The primary air pulverized coal airflow and the secondary air required for combustion are sprayed into the furnace in the form of DC jets from different nozzles. The DC primary air nozzles 1 and the DC secondary air nozzles 3 are arranged alternately. The upstream adjacent corner flame 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] The present application includes two concentrating units, one of which is to set a plurality of concentrating rings 30 in order from large to small along the length direction in the DC primary air channel 8 of the self-service stable combustion burner, and the small end of each concentrating ring 30 faces the outlet end of the DC primary air channel 8 of the self-service stable combustion burner. Usually, 2-4 levels of coal powder concentrating rings are used, and the concentrating angle of the concentrating ring is 25°-35°. The second is to install a louvered coal powder concentrator 21 behind the No. 2 regulating valve 18 on the primary air duct 15. The louvered coal powder concentrator 21 itself is just a rectangular parallelepiped with a cross section equivalent to the cross section of the primary air channel. The louvered coal powder concentrator 21 composed of a plurality of concentrating grids 29 is placed between the diverter baffle 26 at the airflow inlet and the airflow outlet. The number of concentrating grids 29 is generally 3-5, and the tail of the concentrator housing 28 is a thick coal powder channel 22 and a thin coal powder channel 20;

[0051] Four self-help combustion stabilizing burners 2 are arranged between the DC primary air nozzle 1 of the DC pulverized coal burner 10 and the DC secondary air nozzle 3 of the DC pulverized coal burner 10. The self-help combustion stabilizing burner includes, from the inside to the outside, the self-help combustion stabilizing burner DC primary air channel 8, the swirl internal secondary air channel 6 and the combustion stabilizing chamber 4. The self-help combustion stabilizing burner DC primary air channel 8 and the swirl internal secondary air channel 6 are coaxially arranged and arranged at the front end of the combustion stabilizing chamber 4, flush with the inner wall of the combustion stabilizing chamber 4. The outlet end of the combustion stabilizing 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 group 9 is installed in the swirl internal secondary air channel 6. The axial blade group 9 includes 16 60° axially curved blades;

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

[0053] The coal powder supply in the DC coal powder burner is divided into two paths: one is that the coal mill 14 is connected to the DC primary air nozzle 1 in the DC coal powder burner through the primary air duct 15, the regulating door 16 and the DC primary air channel 5. The second is that the coal mill 14 is connected to the DC primary air nozzle 1 in the DC coal powder burner through the primary air duct 15, the No. 6 regulating valve 23, the shutter coal powder concentrator 21, the light coal powder channel 20, the No. 3 regulating valve 19 and the DC primary air channel 5. The DC secondary air nozzle 3 in the DC coal powder burner is connected to the secondary air box 24 through the secondary air duct 25, the No. 4 regulating valve 32 and the DC secondary air channel 7.

[0054] The present application provides a combustion device with multiple fuel stages in the vertical direction of the furnace, and its working process is as follows:

[0055] After the pulverized coal airflow enters the primary air duct 15 from the coal mill, it is divided into the following three paths according to different load conditions:

[0056] Path 1 is when the pulverized coal airflow is operating under high load conditions (higher than 50% rated load), it does not pass through the louvered pulverized coal concentrator 21, and the pulverized coal is concentrated by the concentration ring 30. After the pulverized coal airflow passes through the primary air duct 15, a part of it directly enters the DC primary air channel 5 and enters the furnace in a DC form. The other part enters the DC primary air channel 8 of the self-service stabilizing combustion burner. The pulverized coal airflow is divided into two parts after passing through the concentration ring 30, and a pulverized coal airflow with a concentrated inside and a thin outside is formed at the outlet of the DC primary air channel of the self-service stabilizing combustion burner, and enters the furnace in a DC form. The center of the self-service stabilizing combustion burner extends outward along the vertical direction of the furnace to the DC burner nozzle, and the pulverized coal concentration presents a fuel grading of concentrated pulverized coal airflow-secondary thin pulverized coal airflow-primary thin pulverized coal airflow;

[0057] Path 2 is when the pulverized coal airflow is running under low load conditions (less than 50% of the rated load), and the pulverized coal is secondary concentrated through the louvered pulverized coal concentrator 21 and the concentrating ring 30. The pulverized coal airflow coming out of the coal mill passes through the louvered pulverized coal concentrator 21 in the primary air duct. Due to the bending of the airflow, some pulverized coal particles flowing with this part of the airflow deviate from the flow direction of the airflow under the action of centrifugal force. After passing through multiple concentrating grids 29 for pulverized coal concentration and pulverized coal separation, a concentrated pulverized coal channel 22 and a light pulverized coal channel 20 are separated. The concentrated pulverized coal airflow enters the concentrated pulverized coal channel 22, and then enters the concentrating ring 30 through the self-help combustion stabilizing burner DC primary air channel 8. A low pulverized coal concentration annular area is formed near the wall of the self-help combustion stabilizing burner DC primary air channel, and a high pulverized coal concentration area is formed in the central area of ​​the self-help combustion stabilizing burner DC primary air channel. Therefore, a pulverized coal concentration distribution with a concentrated inside and a light outside is formed at the outlet of the self-help combustion stabilizing burner DC primary air channel. Under the action of the secondary air in the swirl and the stable combustion chamber 4, the coal powder airflow with a concentrated inside and a light outside forms a stable recirculation zone in the center of the stable combustion chamber 4, and enters the furnace in the form of a recirculation zone. After the light coal powder airflow enters the light coal powder channel 20, it enters the DC primary air nozzle 1 through the DC primary air channel 5 and is injected into the furnace in a DC form. From the center of the self-service stable combustion burner along the vertical direction of the furnace to the DC burner nozzle, the coal powder concentration gradually decreases, forming a fuel grading of concentrated coal powder airflow-first-level light coal powder airflow-second-level light coal powder airflow;

[0058] Path 3 is when the self-service stable combustion burner 2 is under maintenance or fails, the coal powder airflow passes through the primary air duct 15, does not pass through any concentration device, enters the DC primary air nozzle 1 through the DC primary air channel 5, and is injected into the furnace in the form of DC. 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 the form of DC;

[0059] The No. 1 regulating valve 16 arranged on the DC primary air channel 5 and the No. 3 regulating valve 19 arranged on the light coal powder channel 20 jointly regulate the DC primary air speed; the No. 6 regulating valve 23 arranged on the concentrated coal powder channel 22 and the No. 5 regulating valve 17 arranged on the DC primary air channel 8 of the self-service stable combustion burner jointly regulate the DC primary air speed of the self-service stable combustion burner; through the louvered coal powder concentrator 21, most of the coal powder is concentrated in the concentrated coal powder channel 22, and the coal powder concentration in the DC primary air channel is changed by adjusting the DC primary air speed and the concentrating effect of the louvered coal powder concentrator 21. Through the concentrating ring 30, most of the coal powder is concentrated in the center of the self-service stable combustion burner, and the coal powder concentration of the self-service stable combustion burner is changed by adjusting the DC primary air speed of the self-service stable combustion burner and the concentrating effect of the concentrating ring 30. Among them, when the pulverized coal airflow does not pass through any concentrating device, the pulverized coal concentration of the DC primary air in the DC primary air channel 5 is in the range of 0.30-0.60 kg pulverized coal / kg air, and the airflow velocity is 16-28 m / s. After the pulverized coal airflow passes through the first-stage concentrating device of the concentrating ring 30 in the DC primary air channel 8 of the self-help stable combustion burner, the pulverized coal concentration of the central concentrated pulverized coal airflow is in the range of 1.27-1.50 kg pulverized coal / kg air; the pulverized coal concentration of the light pulverized coal airflow near the wall is in the range of 0.31-0.37 kg pulverized coal / kg air. The airflow velocity is 14-26 m / s. After the pulverized coal airflow passes through the two-stage concentrating device of the louvered pulverized coal concentrator 21 in the primary air duct 15 and the concentrating ring 30 in the DC primary air channel 8 of the self-help stable combustion burner, the pulverized coal concentration in the concentrated pulverized coal channel 22 is 0.48-0.8 kg pulverized coal / kg air. The pulverized coal concentration in the light pulverized coal channel 20 is 0.12-0.20 kg pulverized coal / kg air, the pulverized coal concentration in the center concentrated pulverized coal airflow is 1.20-2.0 kg pulverized coal / kg air; the pulverized coal concentration in the light pulverized coal airflow near the wall is 0.30-0.50 kg pulverized coal / kg air.

[0060] Specific implementation method 2: Combination Figures 1 to 8The present embodiment is described. The present embodiment provides a combustion method for a combustion device with multiple fuel stages in the vertical direction of the furnace when the boiler is operating at a load higher than 50% of the rated load. By changing the regulating valve, the pulverized coal airflow is concentrated in the first stage and then forms a concentrated pulverized coal airflow-a second stage light pulverized coal airflow-a first stage light pulverized coal airflow in the vertical direction of the furnace. The specific operation is as follows: the No. 2 regulating valve 18 is turned off, and the opening of the No. 1 regulating valve 16 is changed to 80%-100%, and the primary wind speed entering the DC primary air channel 5 is controlled to 26-28m / s, and the primary wind speed entering the DC primary air channel 5 is controlled to 26-28m / s. The primary air pulverized coal concentration of channel 5 is 0.51-0.60kg pulverized coal / kg air. The primary air speed entering the self-service stabilizing combustion burner 2 is controlled to 22-26m / s by changing the opening of the No. 5 regulating valve 17 to 80%-100%. A high pulverized coal concentration area is formed in the central area through multiple concentration rings 30 in the DC primary air channel 8 of the self-service stabilizing combustion burner, and the pulverized coal concentration reaches 1.27-1.50kg pulverized coal / kg air. A low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.31-0.37kg pulverized coal / kg air.

[0061] In this embodiment, when the boiler is in a high-load condition, a first-level concentration device is used to form a high-coal powder concentration airflow in the central area of ​​the self-service stable combustion burner outlet, and the periphery is a secondary light coal powder concentration annular area. The DC primary air nozzle arranged above is a primary light coal powder airflow. In view of the fact that the flue gas temperature in the furnace increases significantly under high-load conditions, the central area of ​​the self-service stable combustion burner is used as the initial combustion point. This area is quickly ignited due to the pre-introduction of high-concentration coal powder, and then the flame of the central concentrated coal powder airflow quickly expands outward, effectively igniting the secondary light coal powder airflow surrounding it. The first-level light coal powder airflow ejected in time by the DC primary air nozzle arranged above, as the last combustion supplement, not only further promotes the complete combustion of coal powder, but also effectively utilizes the high-temperature environment in the furnace to ensure the full combustion of the coal powder airflow.

[0062] Specific implementation method three: Combination Figures 1 to 8The present embodiment is described. In the present embodiment, there is provided a combustion method for a combustion device with multiple fuel stages in the vertical direction of the furnace when the boiler is operated at a load condition lower than 50% of the rated load; by changing the regulating valve, the pulverized coal airflow is concentrated in two stages and then forms a concentrated pulverized coal airflow-a first-stage light pulverized coal airflow-a second-stage light pulverized coal airflow in the vertical direction of the furnace. The specific operation is as follows: the No. 1 regulating valve 16 and the No. 5 regulating valve 17 are closed, and the No. 2 regulating valve 18 is opened. After the pulverized coal airflow passes through the louvered pulverized coal concentrator 21, the light pulverized coal airflow is adjusted by changing the opening of the No. 3 regulating valve 19 to 50%-80%, and the primary wind speed entering the DC primary air channel 5 is controlled to 16-26m / s, and the primary air pulverized coal concentration entering the DC primary air channel 5 is reduced. The concentrated pulverized coal airflow is controlled to 0.12-0.20kg pulverized coal / kg air by changing the opening of the No. 6 regulating valve 23 to 40%-80%, and the primary wind speed entering the DC primary air channel 8 of the self-service stabilizing combustion burner is controlled to 14-22m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-service stabilizing combustion burner is changed to 0.48-0.80kg 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-service stabilizing combustion burner to form a high pulverized coal concentration area in the central area, and the pulverized coal concentration reaches 1.20-2.0kg pulverized coal / kg air, and a low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.30-0.50kg pulverized coal / kg air.

[0063] In this embodiment, when the boiler is in a low-load condition, a two-stage concentration device is used to form a high-coal powder concentration airflow in the central area of ​​the self-service stable combustion burner outlet, and the periphery is a first-level light coal powder concentration annular area, and the DC primary air nozzle arranged above is a second-level light coal powder airflow. When the load is low, the central high-concentration coal powder airflow quickly ignites and burns in the stable combustion chamber, and then the ignited and burning concentrated coal powder is mixed with the first-level light coal powder and ignites the first-level light coal powder. At the same time, the flame formed by the combustion of the swirl burner ignites the second-level light coal powder flame of the DC burner, realizing the staged combustion of coal powder, and the combustion energy is amplified step by step, so that the coal-fired power unit relies only on coal powder combustion to achieve stable combustion at a rated load of 15%-20%;

[0064] The coordinated combustion method provided in this embodiment is used when the boiler is operated at a load condition lower than 50% of the rated load. The specific conditions and adjustment range are further divided into the following conditions:

[0065] Case 1: When the boiler is operating at 40%-50% of the rated load, the combustion method of the combustion device with multiple fuel stages in the vertical direction of the furnace is as follows: the No. 1 regulating valve 16 and the No. 5 regulating valve 17 are closed, and the No. 2 regulating valve 18 is opened. 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 the No. 3 regulating valve 19 to 70%-80%, and the primary air speed entering the DC primary air channel 5 is controlled to 22-26m / s, and the primary air pulverized coal concentration entering the DC primary air channel 5 is controlled to 0.18-0.20kg pulverized coal / kg air. The concentrated pulverized coal airflow is controlled by changing the No. 6 regulating valve. The valve 23 is opened to 60%-80%, and the primary air velocity entering the DC primary air channel 8 of the self-service stabilizing combustion burner is controlled to 20-22m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-service stabilizing combustion burner is 0.73-0.80kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through a plurality of concentrating rings 30 in the DC primary air channel of the self-service stabilizing combustion burner, forming a high pulverized coal concentration area in the central area, and the pulverized coal concentration reaches 1.84-2.0kg pulverized coal / kg air, and a low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.46-0.50kg pulverized coal / kg air;

[0066] Case 2: When the boiler is operating at 30%-40% of the rated load, the combustion method of the combustion device with multiple fuel stages in the vertical direction of the furnace is as follows: the No. 1 regulating valve 16 and the No. 5 regulating valve 17 are closed, and the No. 2 regulating valve 18 is opened. 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 the No. 3 regulating valve 19 to 60%-70%, and the primary air speed entering the DC primary air channel 5 is controlled to 18-22m / s, and the primary air pulverized coal concentration entering the DC primary air channel 5 is controlled to 0.16-0.18kg pulverized coal / kg air. The concentrated pulverized coal airflow is controlled by changing the No. 6 regulating valve. The valve 23 is opened to 50%-60%, and the primary air velocity entering the DC primary air channel 8 of the self-service stable combustion burner is controlled to 17-20m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-service stable combustion burner is 0.65-0.72kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through a plurality of concentrating rings 30 in the DC primary air channel of the self-service stable combustion burner, forming a high pulverized coal concentration area in the central area, and the pulverized coal concentration reaches 1.64-1.80kg pulverized coal / kg air, and a low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.41-0.45kg pulverized coal / kg air;

[0067] Case 3: The combustion method of the combustion device with multiple fuel stages in the vertical direction of the furnace when the boiler is operating at 15%-30% of the rated load is as follows: the No. 1 regulating valve 16 and the No. 5 regulating valve 17 are closed, and the No. 2 regulating valve 18 is opened. 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 the No. 3 regulating valve 19 to 50%-60%, and the primary air speed entering the DC primary air channel 5 is controlled to 16-18m / s, and the primary air pulverized coal concentration entering the DC primary air channel 5 is controlled to 0.12-0.16kg pulverized coal / kg air. The concentrated pulverized coal airflow is controlled by changing the No. 6 regulating valve. The valve 23 is opened to 40%-50%, and the primary air velocity entering the DC primary air channel 8 of the self-service stabilizing combustion burner is controlled to 14-17m / s, and the primary air pulverized coal concentration entering the DC primary air channel 8 of the self-service stabilizing combustion burner is 0.48-0.64kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through a plurality of concentrating rings 30 in the DC primary air channel of the self-service stabilizing combustion burner, forming a high pulverized coal concentration area in the central area, and the pulverized coal concentration reaches 1..2-1.6kg pulverized coal / kg air, and a low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.30-0.40kg pulverized coal / kg air;

[0068] In combination with the description of the second and third embodiments, when the self-service stabilizing combustion burner 2 is under maintenance or fails, the regulating valve is changed so that the coal powder airflow does not pass through any concentration device. The specific operation is as follows: the self-service stabilizing combustion burner 2 system can be cut off by closing the No. 5 regulating valve 17 and the No. 2 regulating valve 18 and opening the No. 1 regulating valve 16, while ensuring that the DC burner provides coal powder combustion to avoid shutdown. The coal powder concentration range of the coal powder airflow that does not pass through any concentration device is 0.30-0.60kg coal powder / kg air.

[0069] The present invention has been disclosed as above with preferred implementation cases, but it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent implementation cases with equivalent changes by using the above-disclosed structures and technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above implementation cases based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention. Specific embodiment:

[0071] This technology has been applied to a 600MW subcritical pressure drum boiler, which adopts a four-corner tangential combustion method. Using the device and method of the present invention, a louvered coal powder concentrator is installed on the primary air duct of the B layer (second layer) of the direct current burner, and a three-stage coal powder concentration ring is installed in the direct current primary air channel of the self-sustaining combustion burner. After the transformation, the carbon content of the fly ash of the boiler was reduced from 6% before the transformation to 4%, and the boiler efficiency was increased from 92.9% before the transformation to 94.5%. NOx emissions are significantly reduced compared to before the transformation. When burning the current coal type, the NOx emission value is below 300mg / Nm3. When burning the same coal quality, a two-stage concentration device is used to form a concentrated coal powder airflow-a first-level light coal powder airflow-a second-level light coal powder airflow along the vertical direction of the furnace. The central high-concentration coal powder airflow quickly ignites and burns in the stable combustion chamber, and then the ignited concentrated coal powder is mixed with the first-level light coal powder and ignites the first-level light coal powder. At the same time, the flame formed by the swirl burner ignites the second-level light coal powder flame of the DC burner, realizing the graded combustion of coal powder, and the combustion energy is amplified step by step, achieving the lowest stable combustion load of the boiler without oil injection of 15%. At the same time, there is no slagging phenomenon on the water-cooled wall in the burner area.

[0072] Under the requirement of "giving full play to the emergency peak-shaving capacity of existing coal-fired power units", the deep adjustment load of thermal power units will be further reduced, and the time of deep adjustment will be greatly increased. In order to encourage thermal power units to reduce the deep adjustment load to below 30% of the rated load, various regions have adopted a step-by-step quotation incentive policy, and set a higher quotation ceiling for the load rate of units below 30%. Taking the incentive policy of Heilongjiang Province as an example, when the load rate reaches below 25%, the price can be declared at 0.7-1 yuan / kwh. The use of the "a method and device for coordinated combustion of a direct current burner and a swirl burner" of the present invention can achieve stable combustion at 15% of the rated load. It can be comprehensively obtained that the deep adjustment of the burner after the transformation can generate 80-85 million yuan more income than before the transformation.

Claims

1. A combustion device with multiple fuel stages in the vertical direction of a furnace, the combustion device comprising a four-corner tangential 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 arranged at four corners of the four-corner tangential pulverized coal combustion boiler (11) respectively, 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 end of the secondary air box (24) through an air supply pipeline, each DC pulverized coal burner (10) is provided with at least one self-help combustion stabilizing burner (2), and each self-help combustion stabilizing 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), and the self-help combustion stabilizing 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-powder system, and is characterized in that: The combustion device also includes at least one group of concentrating structures, and each group of concentrating structures is arranged in correspondence with a self-help combustion stabilizing burner (2). The concentrating structures include a No. 1 concentrating unit and a No. 2 concentrating unit. The No. 1 concentrating unit is integrated in the corresponding coal supply pipeline. The concentrated coal outlet end of the No. 1 concentrating unit is connected to the corresponding self-help combustion stabilizing burner (2). The light coal outlet end of the No. 1 concentrating unit is connected to the corresponding direct current primary air nozzle (1). The No. 2 concentrating unit is integrated in the corresponding self-help combustion stabilizing burner (2).

2. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 1, characterized in that: The coal supply pipeline comprises a DC primary air channel (5), a primary air duct (15), a No. 1 regulating valve (16), a No. 2 regulating valve (18), a No. 3 regulating valve (19) and a No. 1 concentrating unit. One end of the DC primary air channel (5) is connected to a corresponding DC primary air nozzle (1), one end of the primary air duct (15) is connected to a coal outlet end of a 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), and a No. 1 regulating valve (16) is installed at the connection point between the DC primary air channel (5) and the primary air duct (15). The coal inlet end of the No. 1 concentrating unit is connected to the primary air duct (15), and a No. 2 regulating valve (18) is connected in series at the connection point between the coal inlet end of the No. 1 concentrating unit and the primary air duct (15). The light coal outlet end of the No. 1 concentrating unit is connected to the DC primary air channel (5), and a No. 3 regulating valve (19) is connected in series on the light coal pulverized pipeline (27).

3. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 2, characterized in that: The first concentrating unit is a louvered coal powder concentrator (21). The louvered coal powder concentrator (21) comprises a diverter baffle (26), a louver 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 diverter 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 thick coal powder channel (22) by the diverter baffle (26). The louver structure (27) is installed in the concentrator shell (28). The louver structure (27) is composed of a plurality of concentrating grids (29). The plurality of concentrating grids (29) are arranged in sequence and equidistantly along the length extension direction of the concentrator shell (28), and each concentrating grid (29) is rotatably connected to the inner wall of the concentrator shell (28).

4. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 3, characterized in that: The air supply pipeline comprises a DC secondary air channel (7), a secondary air channel (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 channel (25) is connected to the air outlet end 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 channel (25); and the No. 4 regulating valve (32) is installed at the connection between the DC secondary air channel (7) and the secondary air channel (25).

5. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 4, characterized in that: The self-help combustion stabilizing burner (2) comprises a combustion stabilizing chamber (4), a secondary air channel (6) in a swirl, a DC primary air channel (8) of the self-help combustion stabilizing burner and a second concentration unit. The secondary air channel (6) in the swirl is coaxially sleeved on the outside of the DC primary air channel (8) of the self-help combustion stabilizing burner, and one end of the DC primary air channel (8) of the self-help combustion stabilizing burner and one end of the secondary air channel (6) in the swirl are both connected to the combustion stabilizing chamber (4), the other end of the DC primary air channel (8) of the self-help combustion stabilizing burner is connected to a coal supply pipeline through an air powder system, the other end of the secondary air channel (6) in the swirl is connected to an air supply pipeline through an air powder system, and the self-help combustion stabilizing burner is connected to a coal supply pipeline through an air powder system. An axial blade group (9) is provided between the DC primary air channel (8) of the self-service combustion stabilizing burner and the secondary air channel (6) in the swirl, and the axial blade group (9) is arranged close to the combustion stabilizing chamber (4). The axial blade group (9) includes a plurality of axial blades, and the plurality of axial blades are equidistantly arranged along the circumferential direction between the DC primary air channel (8) of the self-service combustion stabilizing burner and the secondary air channel (6) in the swirl, and one end of each axial blade is connected to the outer wall of the DC primary air channel (8) of the self-service combustion stabilizing burner, and the other end of each axial blade is connected to the inner wall of the secondary air channel (6) in the swirl, and the second concentration unit is installed in the DC primary air channel (8) of the self-service combustion stabilizing burner.

6. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 5, characterized in that: The second concentrating unit comprises a plurality of concentrating rings (30), the plurality of concentrating rings (30) being arranged equidistantly in sequence along the flow direction of the air in the direct current primary air channel (8) of the self-service stabilizing combustion burner, and the ring diameters of the plurality of concentrating rings (30) decreasing in sequence, the plurality of concentrating rings (30) are all conical rings, and the small-diameter end of each concentrating ring (30) faces the outlet end of the direct current primary air channel (8) of the self-service stabilizing combustion burner.

7. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 6, characterized in that: The air-powder system comprises a DC coal supply pipeline and a swirl air supply pipeline. The coal supply pipeline is connected to a DC primary air channel (8) of a self-help stable combustion burner via the DC coal supply pipeline, and the air supply pipeline is connected to a secondary air channel (6) in the swirl via the swirl air supply pipeline.

8. A combustion device with multiple fuel stages in the vertical direction of the furnace according to claim 7, characterized in that: The DC coal supply pipeline comprises a DC connection air duct of a self-help combustion stabilizing 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-help combustion stabilizing burner through the DC connection air duct of the self-help combustion stabilizing burner, and the No. 5 regulating valve (17) is connected in series to the DC connection air duct of the self-help combustion stabilizing 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-help combustion stabilizing burner through the concentrated coal powder channel (22), and the No. 6 regulating valve (23) is connected in series to the concentrated coal powder channel (22); The swirl air supply pipeline comprises a swirl connecting air duct of a self-service stabilizing combustion burner and a No. 7 regulating valve (31); the secondary air duct (25) is connected to the secondary air channel (6) in the swirl through the swirl connecting air duct of the self-service stabilizing combustion burner; the No. 7 regulating valve (31) is connected in series at the connection point between the secondary air channel (6) in the swirl and the connecting air duct of the self-service stabilizing combustion burner.

9. A combustion method when the boiler is operating at a load higher than 50% of the rated load, using a combustion device with multiple fuel stages in the vertical direction of the furnace as claimed in any one of claims 1 to 8, characterized in that: By changing the regulating valve, the pulverized coal airflow is concentrated in the first stage and then forms a concentrated pulverized coal airflow, a second stage light pulverized coal airflow and a first stage light pulverized coal airflow along the vertical direction of the furnace. The specific operation is as follows: the second regulating valve (18) is closed, and the opening of the first regulating valve (16) is changed to 80%-100%, so that the primary air speed entering the DC primary air channel (5) is controlled to 26-28m / s, and the pulverized coal concentration of the primary air entering the DC primary air channel (5) is 0.51-0.60kg pulverized coal / kg air. By changing the opening of the No. 5 regulating valve (17) to 80%-100%, the primary air speed entering the self-service stabilizing combustion burner (2) is controlled to 22-26m / s. Through multiple concentration rings (30) in the direct current primary air channel (8) of the self-service stabilizing combustion burner, a high coal powder concentration area is formed in the central area, and the coal powder concentration reaches 1.27-1.50kg coal powder / kg air. A low coal powder concentration annular area is formed near the wall, and the coal powder concentration reaches 0.31-0.37kg coal powder / kg air.

10. A combustion method when the boiler is operating at a load lower than 50% of the rated load, using a combustion device with multiple fuel stages in the vertical direction of the furnace as claimed in any one of claims 1 to 8, characterized in that: By changing the regulating valve, the pulverized coal airflow is concentrated in two stages and then forms a concentrated pulverized coal airflow, a first-stage light pulverized coal airflow, and a second-stage light pulverized coal airflow along the vertical direction of the furnace. The specific operation is as follows: the No. 1 regulating valve (16) and the No. 5 regulating valve (17) are closed, and the No. 2 regulating valve (18) is opened. 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 the No. 3 regulating valve (19) to 50%-80%, and the primary air speed entering the DC primary air channel (5) is controlled to 16-26 m / s, and the primary air pulverized coal concentration entering the DC primary air channel (5) is controlled to 0.12-0.20 kg pulverized coal / kg air. The concentrated pulverized coal airflow passes through the louvered pulverized coal concentrator (21). The opening of the No. 6 regulating valve (23) is changed to 40%-80%, and the primary air speed entering the DC primary air channel (8) of the self-service stabilizing combustion burner is controlled to 14-22m / s, and the primary air pulverized coal concentration entering the DC primary air channel (8) of the self-service stabilizing combustion burner is set to 0.48-0.80kg pulverized coal / kg air. The concentrated pulverized coal airflow then passes through a plurality of concentration rings (30) in the DC primary air channel of the self-service stabilizing combustion burner, forming a high pulverized coal concentration area in the central area, and the pulverized coal concentration reaches 1.20-2.0kg pulverized coal / kg air, and a low pulverized coal concentration annular area is formed near the wall, and the pulverized coal concentration reaches 0.30-0.50kg pulverized coal / kg air.

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