Collaborative combustion device and collaborative combustion method for direct-flow combustor and turbulent-flow combustor

Abstract

The invention relates to the technical field of tangential boiler combustion, in particular to a direct-current burner and turbulent burner collaborative combustion device and method, and aims to solve the problems that a coal power unit only depends on pulverized coal combustion, the stable combustion effect is poor under the rated load of 20%-30%, the denitration efficiency is reduced during low-load operation, and combustion is unstable due to the fact that the coal quality deviates from a design value. According to the self-service combustion-stabilizing combustor, by means of the injection effect of direct-current primary air and direct-current secondary air of the direct-current combustor, a combustion-stabilizing cavity of the self-service combustion-stabilizing combustor and secondary air in rotational flow are cooperated, so that a center backflow area is formed in the center of the rotational flow combustor and serves as a stable ignition heat source to heat high-concentration pulverized coal, and meanwhile flame formed by combustion of the self-service combustion-stabilizing combustor can be used as a heat source for heating high-concentration pulverized coal. And primary air powder flame of the direct-current pulverized coal burner is ignited, external flame combustion-supporting technologies such as tiny oil or plasma are not used, and the stable combustion effect of a coal power unit only depending on pulverized coal combustion under the rated load of 20%-30% is 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 coordinated combustion device and a coordinated combustion method of a direct current burner and a swirl burner. Background Art

[0002] The proportion of some major forms of new energy power generation, including solar power generation, wind power generation, hydropower generation, and biomass power generation, has increased year by year, while the number of hours of thermal power utilization has decreased year by year, and the energy structure system is constantly changing. However, new energy power generation faces many challenges in the power industry, which mainly stem from its randomness and instability. Since the impact of new 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 20%-30% of the rated load.

[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] In addition, in thermal power plants, SCR (Selective Catalytic Reduction) denitrification generally uses medium and high temperature catalysts, and the designed operating temperature range is 320-420°C. When the power plant operating load is less than 50%, the flue gas temperature is usually lower than 320°C. When operating at low load, the performance of the SCR catalyst cannot be fully utilized, and the denitrification efficiency will drop significantly. At this time, the unit has a greater risk of exceeding the NOx standard. At the same time, my country's coal quality is changeable, and the quality of coal used in power station boilers is poor, which seriously deviates from the optimal coal parameters designed for boilers, which directly affects the combustion stability of power station boilers. Summary of the invention

[0006] In order to solve the problems that the coal-fired power unit only relies on pulverized coal combustion, the stable combustion effect is poor at 20%-30% of the rated load, the denitrification efficiency is reduced at low load operation, and the coal quality deviates from the design value, resulting in unstable combustion, and so on, the present invention provides a direct current burner and a swirl burner coordinated combustion device and a coordinated combustion method;

[0007] A coordinated combustion device of a DC burner and a swirl burner, the coordinated combustion device comprising a four-corner tangential pulverized coal combustion boiler, a secondary air box and four DC pulverized coal burners, the four DC pulverized coal burners are respectively arranged at the four corners of the four-corner tangential pulverized coal combustion boiler, each DC pulverized coal burner corresponds to at least one coal mill, the DC primary air nozzle in the DC pulverized coal burner is connected to the coal outlet end of the coal mill through a coal supply pipeline, the DC secondary air nozzle in the DC pulverized coal burner is connected to the air outlet end of the secondary air box through an air supply pipeline, at least one self-help stabilizing combustion burner is arranged in each DC pulverized coal burner, and each self-help stabilizing combustion burner is arranged between the DC primary air nozzle and the DC secondary air nozzle located on the same layer in the corresponding DC pulverized coal burner, and the self-help stabilizing 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 an air-powder system;

[0008] Furthermore, the DC pulverized coal burner is divided into three layers from bottom to top, the first layer includes a layer of DC secondary air nozzles and a layer of DC primary air nozzles, and the layer of DC primary air nozzles is located above the layer of DC secondary air nozzles, the second layer includes a second layer of DC secondary air nozzles and a second layer of DC primary air nozzles, and the second layer of DC primary air nozzles is located above the second layer of DC secondary air nozzles, the third layer includes three layers of No. 1 DC secondary air nozzles, three layers of DC primary air nozzles and three layers of No. 2 DC secondary air nozzles, and the three layers of No. 1 DC secondary air nozzles, three layers of DC primary air nozzles and three layers of No. 2 DC secondary air nozzles are arranged in sequence from bottom to top;

[0009] Further, the coal supply pipeline includes a DC primary air channel, a primary air duct and a No. 1 regulating valve, 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 end 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 the No. 1 regulating valve is installed at the connection between the DC primary air channel and the primary air duct;

[0010] Furthermore, the coal supply pipeline also includes a No. 2 regulating valve, a No. 3 regulating valve, a No. 1 pulverized coal pipeline and a pulverized coal separation device. The coal inlet end of the pulverized coal separation device is connected to the primary air duct, and the No. 2 regulating valve is connected in series to the primary air duct. The No. 1 coal outlet end of the pulverized coal separation device is connected to the DC primary air channel through the No. 1 pulverized coal pipeline, and the No. 3 regulating valve is connected in series to the No. 1 pulverized coal pipeline.

[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 corresponding 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-help combustion stabilizing burner comprises a combustion stabilizing chamber, a secondary air channel in a swirl and a DC primary air channel of the self-help combustion stabilizing burner, the secondary air channel in the swirl is coaxially sleeved on the outside of the DC primary air channel of the self-help combustion stabilizing burner, and one end of the DC primary air channel of the self-help combustion stabilizing burner and one end of the secondary air channel in the swirl are both connected to the combustion stabilizing chamber, the other end of the DC primary air channel of the self-help combustion stabilizing burner is connected to a coal supply pipeline through an air-powder system, and the other end of the secondary air channel in the swirl is connected to an air supply pipeline through an air-powder system, and an axial blade group is provided between the DC primary air channel of the self-help combustion stabilizing burner and the secondary air channel in the swirl, and the axial blade group is arranged close to the combustion stabilizing chamber, the axial blade group comprises 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-help combustion stabilizing burner and the secondary air channel in the swirl, and one end of each axial blade is connected to an outer wall of the DC primary air channel of the self-help combustion stabilizing burner, and the other end of each axial blade is connected to an inner wall of the secondary air channel in the swirl;

[0013] 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;

[0014] 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 No. 2 pulverized coal 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 No. 2 coal outlet end of the pulverized coal separation device is connected to the DC primary air channel of the self-service stable combustion burner through the No. 2 pulverized coal channel, and the No. 6 regulating valve is connected in series to the No. 2 pulverized coal channel;

[0015] 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.

[0016] A co - combustion method of a direct - current burner and a swirl burner when the boiler operates at a load above 50% of the rated load; Shut off the second regulating valve, by changing the opening of the first regulating valve to 80% - 100%, control the primary air velocity entering the direct - current primary air passage to 26 - 28 m / s, by changing the opening of the fifth regulating valve to 80% - 100%, control the primary air velocity entering the self - stabilizing combustion burner to 22 - 26 m / s, shut off the seventh regulating valve, so that there is no swirling secondary air inside the self - stabilizing combustion burner, and the secondary air can enter through the fourth regulating valve with an opening of 70% - 80%, control the secondary air velocity entering the direct - current secondary air passage to 45 - 47 m / s. After the above operations, its stable combustion cavity has a relatively large heat load compared with the furnace cross - section. The heat released after combustion makes the temperature in the stable combustion cavity rise rapidly and maintain at a high temperature state. At the same time, the unburned pulverized coal air flow rises with the flue gas to the direct - current primary air nozzle, mixes with the primary air ejected from the direct - current primary air nozzle again, and continues to burn. Compared with only arranging direct - current burners at the four corners of the original furnace, the burnout area is increased, which is beneficial to the burnout of pulverized coal, thus realizing the co - combustion of the direct - current pulverized - coal burner and the self - stabilizing combustion burner when the load is above 50% of the rated load.

[0017] A co - combustion method of a direct - current burner and a swirl burner when the boiler operates at a load below 50% of the rated load; Shut off the first regulating valve and the fifth regulating valve, open the second regulating valve, the primary air - powder can enter the pulverized - coal separation device through the second regulating valve, the pulverized - coal air flow enters the first powder passage, by changing the opening of the third regulating valve to 50% - 80%, control the primary air velocity entering the direct - current primary air passage to 16 - 26 m / s, the pulverized - coal air flow enters the second pulverized - coal passage, by changing the opening of the sixth regulating valve to 40% - 80%, control the primary air velocity entering the direct - current primary air passage of the self - stabilizing combustion burner to 14 - 22 m / s, by adjusting the opening of the seventh regulating valve to 40% - 70%, control the secondary air velocity entering the swirl inner secondary air passage to 35 - 50 m / s, by changing the opening of the fourth regulating valve to 30% - 60%, control the secondary air velocity entering the direct - current secondary air passage to 30 - 45 m / s. After the above operations, by controlling the primary air and the swirl inner secondary air velocities of the self - stabilizing combustion burner, a wide and long central recirculation zone is formed in the stable combustion cavity. By controlling the direct - current primary and secondary air velocities arranged up and down, while restricting the expansion of the swirling air flow, the air flow in the stable combustion cavity is entrained, slowing down the attenuation of the air flow, so that the length of the central recirculation zone continues to increase. Here, De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length, the diameter of the recirculation zone is 0.8De < D1 < 2De, the length is 2.5De < L1 < 4De, and the maximum flue - gas recirculation volume is 3 - 8 times the primary air volume, thus realizing the co - combustion of the direct - current pulverized - coal burner and the self - stabilizing combustion burner when operating at a load below 50% of the rated load.

[0018] The beneficial effects of this application compared to the prior art are as follows:

[0019] 1. The present invention provides a DC burner and swirl burner cooperative combustion device and a cooperative combustion method, which rely on the induced effect of the DC primary air and DC secondary air of the DC burner, cooperate with the 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 high-concentration coal powder. At the same time, the flame formed by the combustion of the swirl burner ignites the primary air powder 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 relying only on the combustion of coal powder at 20%-30% of the rated load.

[0020] In the prior art, direct current burners are arranged at the four corners or eight corners of the boiler furnace. The pulverized coal airflow and the secondary air are sprayed into the furnace through the direct current burner jets and merge in a tangential circle (such as Figure 1 As shown in the figure, 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, and the four-corner (or octagonal) jets support each other. Therefore, the high-temperature flames ejected and ignited from each corner are the main heat source for igniting the downstream coal powder airflow. During tangential combustion, the ignition of the coal powder airflow is the sequential ignition of each corner.

[0021] As the boiler load decreases, the amount of pulverized coal is gradually reduced and the coal mill is shut down. The amount of pulverized coal fed into the furnace is greatly reduced. At 20%-30% of the rated load, the amount of pulverized coal fed into the furnace is about 25%-40% of the full load. When running at low load, as the amount of coal fed decreases, the heat released by the combustion of pulverized coal decreases, while the furnace volume remains unchanged, and the heating surface in the furnace remains unchanged, resulting in a decrease in the temperature of the furnace burner area. At 20%-30% of the rated load, the temperature of the furnace burner area is only about 900°C (at full load, the temperature of the furnace burner area is about 1300°C). As the main heat source for igniting the downstream pulverized coal airflow, the upstream flame temperature drops significantly, and the convective heat transfer decreases, which is lower than the heat required for the ignition of the pulverized coal airflow. Therefore, it is difficult for a four-corner (or eight-corner) cut-circle pulverized coal boiler to achieve a stable combustion effect of 20%-30% of the rated load by relying solely on pulverized coal combustion.

[0022] The present invention delivers high-concentration coal powder airflow directly into the stable combustion chamber from the center in the form of direct current. Under the action of the secondary air in the swirl, the coal powder airflow expands toward the wall of the stable combustion chamber, and the pressure in the center of the burner is reduced. The coal powder airflow velocity after leaving the stable combustion chamber is 8-9m / s, the direct current primary air velocity ranges from 16 to 28m / s, and the direct current secondary air velocity ranges from 30 to 47m / s. With high velocity and large momentum, a wide and long central recirculation zone is formed in the center of the burner under the further introduction of high-speed direct current primary and secondary air (such as Figure 7As shown). The maximum values ​​of D and L can reach 1.5-2De and 3.5-4De respectively. De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, and L is the maximum length. The maximum flue gas recirculation volume is 7-8 times the primary air volume. The central recirculation zone sucks a large amount of high-temperature flue gas, and a turbulent mixing zone of coal powder airflow and hot recirculation flue gas is formed in the area between the outer side of the recirculation zone and the mainstream. Intense mass, momentum and energy exchange occurs in the mixing zone, and the coal powder airflow is continuously heated and heated, and reaches the ignition temperature and begins to ignite. The flame propagates from the inside to the outside, and transfers the heat to the recirculated flue gas, bringing it upstream, and then transfers the heat to the new coal powder airflow. At the same time, the recirculated high-temperature flue gas has a low speed, which effectively prolongs the residence time of coal powder in the high-temperature zone, allowing the coal powder to burn fully and release a large amount of heat, so that the flue gas temperature in the central recirculation zone can reach above 1300℃. The high-concentration coal powder airflow is concentrated in the high-temperature central recirculation zone, and a high-temperature and high-concentration area is formed in the central recirculation zone. The self-help stable combustion burner relies on the high temperature and high concentration reflow zone as a stable heat source, so that the coal powder airflow entering the stable combustion chamber can be ignited in time and burn stably. A high temperature flame is ejected from the stable combustion chamber of the self-help stable combustion burner.

[0023] The high-temperature flame ejected by the self-stable combustion burner ignites the primary air and powder airflow of the DC pulverized coal burner above. Compared with the original furnace with only DC burners arranged at the four corners or eight corners, the pulverized coal ejected by the DC burner that burns in coordination with the swirl burner ignites in time and can burn violently, which increases the temperature of the pulverized coal flame. This is conducive to the mutual ignition of the tangential DC burners, strengthens the combustion of the pulverized coal airflow during tangential combustion, makes the flame more stable, and enhances the combustion stability of the tangential DC burner at 20%-30% rated load.

[0024] 2. The coordinated combustion device and coordinated combustion method of a direct current burner and a swirl burner provided by the present invention can ensure that the flue gas temperature at the denitrification inlet is within a reasonable range under a rated load of 20%-30%.

[0025] As the boiler load decreases, the amount of pulverized coal begins to be gradually reduced and the coal mill is shut down. The amount of pulverized coal fed into the furnace is greatly reduced. At 20%-30% of the rated load, the amount of pulverized coal fed into the furnace is about 25%-40% of the full load. The amount of pulverized coal fed into the furnace is reduced, the heat released by the combustion of pulverized coal is reduced, and the furnace temperature is reduced, making the pulverized coal flame unstable. At 20%-30% of the rated load, the coal mill is shut down, and the corresponding DC primary air and DC secondary air are shut down. In order to protect the shut-down DC primary and secondary air nozzles from overheating and burning, the opening of the DC secondary air nozzle damper is maintained between 5%-10%, which plays a role in cooling the nozzle. This part of cooling secondary air accounts for approximately 20%-40% of the total secondary air. When operating at low load (such as Figure 2As shown in the figure, if the upper DC primary air and DC secondary air (secondary air nozzle No. 2 on the third layer, primary air nozzle No. 3 on the third layer, and secondary air nozzle No. 1 on the third layer) are put into operation, the low-temperature DC secondary air on the lower layer, which acts as a cooling nozzle, will be mixed with the upper DC primary air pulverized coal airflow, making the pulverized coal flame more unstable. If the lower DC primary air and DC secondary air (primary air nozzle No. 1 on the first layer and secondary air nozzle No. 1 on the first layer) are put into operation, the low-temperature DC secondary air on the upper layer, which acts as a cooling nozzle, will move upward, which will have the least impact on the DC primary air pulverized coal airflow on the lower layer. Therefore, in order to maximize the stability of the flame, the lower DC primary air and DC secondary air are generally put into operation. Compared with full-load operation, low-load operation of the lower DC primary air and DC secondary air will cause the center of the flame to move downward, the flue gas temperature at the furnace outlet will decrease, and the flue gas temperature at the SCR denitration inlet is generally as low as about 260℃-280℃, which makes it difficult to achieve the optimal flue gas temperature of the catalyst of the denitration device of a coal-fired power plant.

[0026] The present invention relies on the induced effect of the DC primary air and DC secondary air of the DC burner, and cooperates with the combustion chamber of the self-service combustion stabilizing burner and the secondary air in the swirl to form a central reflow zone in the center of the self-service combustion stabilizing burner, which serves as a stable ignition heat source to heat the high-concentration coal powder. At the same time, the high-temperature flame ejected by the swirl burner ignites the primary air powder flame of the DC burner, strengthens the combustion of the coal powder airflow during tangential combustion, makes the flame more stable, and enhances the combustion stability of coal powder at 20%-30% rated load, so that the upper DC primary air and DC secondary air or the lower DC primary air and DC secondary air can be flexibly put into operation at low load. At 20%-30% rated load, (such as Figures 8 to 10 As shown in the figure, four self-help stabilizing burners are arranged at the four corners between the first layer primary air nozzle and the second layer secondary air nozzle of the DC burner, and the flue gas temperature at the SCR denitrification inlet can be increased by 10%-15%. Four self-help stabilizing burners are arranged at the four corners between the third layer primary air nozzle and the third layer No. 1 secondary air nozzle of the DC burner, and the flue gas temperature at the SCR denitrification inlet can be increased by 15%-20%. According to the actual flue gas temperature at the SCR denitrification inlet, self-help stabilizing burners can be arranged between the primary air and secondary air nozzles of DC burners at different layers, which not only ensures the stability of the flame under low load, but also improves the position of the center of the furnace flame, and the flue gas temperature at the furnace outlet is increased, ensuring that the flue gas temperature at the SCR denitrification inlet is within a reasonable range under 20%-30% rated load, thereby preventing NOx emissions from exceeding the standard.

[0027] 3. The coordinated combustion device and coordinated combustion method of a direct current burner and a swirl burner provided in the present application can effectively improve the burnout rate of coal powder.

[0028] In the prior art, direct current burners are arranged at 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 merge in the form of a tangential circle (such as Figure 1 As shown in the figure, this tangential combustion method can make the airflows ejected from adjacent burners ignite each other, but the ignition distance of the coal powder airflow is relatively long. At the same time, the primary air-powder airflow is a straight-line jet, with a small airflow diffusion angle, large axial kinetic energy, and a long range, while the high-temperature flue gas can only be mixed around the airflow, causing the coal powder at the periphery of the airflow to ignite first, and then gradually expand to the center of the airflow, delaying the ignition, which is not conducive to the complete combustion of the coal powder.

[0029] The present invention arranges four self-help stable combustion burners at the four corners between the DC primary air nozzle and the DC secondary air nozzle of the DC pulverized coal burner. Under low load, the DC primary air and DC secondary air of the DC burner are used to ignite the pulverized coal in the self-help stable combustion burner cavity and the secondary air in the swirl, so that a high-temperature central reflow zone is formed in the center of the self-help stable combustion burner, which serves as a stable ignition heat source to heat the high-concentration pulverized coal, forming a high-temperature and high-concentration area in the central reflow zone, extending the residence time of the pulverized coal in the high-temperature zone, which is conducive to the swirl burner pulverized coal burning out. At the same time, the high-temperature flame ejected by the swirl burner located below ignites the primary air pulverized flame of the DC burner above. Compared with only arranging DC burners at the four corners or eight corners of the original furnace, the ignition distance of the pulverized coal airflow from the DC burner is shortened, the ignition is timely, and the combustion time of the pulverized coal in the furnace is increased, which is conducive to the pulverized coal burning out.

[0030] At high load, the original furnace has only DC burners arranged on the four corners or octagon, and the coal powder airflow is 28-30m / s. At high load, the present invention divides the primary air powder airflow into two, one enters the stable combustion chamber through the DC primary air channel of the self-service stable combustion burner, and the outlet area of ​​the stable combustion chamber is 1.2-1.5 times the area of ​​the DC primary air nozzle. The coal powder airflow leaves the stable combustion chamber at a speed of 8-9m / s and enters the furnace. On the one hand, the coal powder airflow has a low speed and a long residence time in the furnace, which is conducive to the combustion of coal powder. On the other hand, its stable combustion chamber has a larger heat load than the furnace cross section. The heat released after combustion causes the temperature in the stable combustion chamber to rise rapidly and maintain at a high temperature. At the same time, the unburned coal powder airflow rises to the DC primary air nozzle with the flue gas, and mixes with the primary air ejected from the DC primary air nozzle again, and continues to burn. Compared with the original furnace with only DC burners arranged on the four corners or octagon, the burnout area is increased, which is conducive to the combustion of coal powder. A stream of pulverized coal enters the DC primary air nozzle through the DC primary air channel, and enters the furnace at a speed of 26-28m / s. Compared with only DC burners arranged at the four or eight corners of the original furnace, the pulverized coal airflow velocity of the DC burner that burns in coordination with the swirl burner is reduced, and the combustion time in the furnace is sufficient, which is beneficial to the burnout of the pulverized coal and improves the combustion efficiency.

[0031] 4. The coordinated combustion device and coordinated combustion method of a direct current burner and a swirl burner provided in the present application have a larger adjustment range for the primary wind speed and better adjustment characteristics than the prior art.

[0032] In the prior art, direct current burners are arranged at the four corners or eight corners of the boiler furnace, and each coal mill corresponds to one layer of burners. The outlet of the coal mill is connected to four primary air ducts, and the air velocity of these ducts is mainly determined by the ventilation volume at the inlet of the coal mill. When the coal quantity of the coal mill remains unchanged, the air velocity can be finely adjusted within a certain range (±2 m / s). However, the range of change in air velocity for this fine adjustment is limited. When affected by coal quality fluctuations, the stable combustion performance of the direct current burners deteriorates, and the primary air velocity needs to be adjusted accordingly. If the primary air velocity is significantly reduced to improve the stable combustion characteristics, the coal grinding quantity of a single burner will decrease, resulting in a decrease in the temperature in the burner area and further reducing the stable combustion ability of the burners.

[0033] In the present invention, while keeping the air volume of the coal mill unchanged, by adjusting the valve openings of the primary air ducts of the direct current burners and the swirl burners, the air velocities of the primary air ducts of the direct current burners and the swirl burners can be precisely controlled. The adjustment range is large and the adjustment characteristics are good, enabling the boiler to maintain the best combustion state under coal quality fluctuations. When the coal quality deteriorates and the stable combustion performance of the direct current burners is poor, by changing the openings of the two regulating valves in the direct current primary air passage and the opening of the regulating valve in the No. 1 pulverized coal passage, the direct current primary air velocity is jointly adjusted, and the direct current primary air velocity range is 16 - 28 m / s. Through the above adjustment method, the direct current primary air velocity can be significantly reduced, the residence time of the pulverized coal air flow in the burner area is increased, which is beneficial to the ignition and stable combustion of the pulverized coal. While reducing the direct current primary air velocity, by changing the opening of the regulating valve in the No. 2 pulverized coal passage and the opening of the regulating valve in the direct current primary air passage of the self-stabilizing combustion burner, the direct current primary air velocity of the self-stabilizing combustion burner is jointly adjusted, and the direct current primary air velocity range of the self-stabilizing combustion burner is 14 - 26 m / s. By changing the opening of the regulating valve in the swirl inner secondary air passage, the swirl inner secondary air velocity is adjusted, and the swirl secondary air velocity range is 35 - 50 m / s. By adopting a high swirl inner secondary air velocity and a low primary air velocity, the range of the central recirculation zone is increased (the diameter of the recirculation zone is 1.2De < D2 < 2De, and the length is 3De < L2 < 4De). A large amount of high-temperature flue gas entrained by the recirculation can promptly ignite the pulverized coal. At the same time, the high-temperature flame ejected by the self-stabilizing combustion burner ignites the primary air and pulverized coal flow of the upper direct current pulverized coal burner, achieving stable combustion at low loads.

[0034] When the coal quality improves, the pulverized coal airflow at the outlet of the DC burner will ignite in advance, causing the flame to be too close to the nozzle, which is easy to cause problems such as burn damage and slagging of the burner nozzle. By changing the opening of the two regulating doors on the DC primary air channel and the opening of the regulating door on the No. 1 pulverized coal channel, the DC primary air speed is adjusted together, and the DC primary air speed range is 16 to 28 m / s. Through the above adjustment method, the DC primary air speed can be greatly increased, so that the pulverized coal airflow can be dispersed into the furnace faster after leaving the DC burner, thereby slowing down the ignition speed and moving the ignition point back appropriately. While increasing the DC primary air speed, by changing the opening of the regulating door on the No. 2 pulverized coal channel and the opening of the regulating door on the DC primary air channel of the self-service stable combustion burner, the DC primary air speed of the self-service stable combustion burner is adjusted together, and the DC primary air speed of the self-service stable combustion burner is in the range of 14 to 26 m / s. The DC primary wind speed of the self-service stable combustion burner is reduced, and the secondary wind speed in the swirl is adjusted by changing the opening of the regulating door on the secondary wind channel in the swirl. The swirl secondary wind speed range is 35-50m / s. Through the precise control of the DC primary wind speed and the secondary wind speed in the swirl of the self-service stable combustion burner, the recirculation zone is pushed away from the nozzle, and the high-temperature recirculation zone is prevented from being too close to the burner nozzle and burning while ensuring stable combustion.

[0035] 5. The present application provides a coordinated combustion device and a coordinated combustion method of a direct current burner and a swirl burner, wherein the self-sustaining combustion burner and the direct current burner can be switched for operation, thereby reducing accidents such as fire extinguishing due to burner shutdown.

[0036] Power plants often experience boiler shutdown accidents due to single burner failures, which in serious cases threaten the safe and stable operation of the boiler. The present invention realizes independent control of the self-service stable combustion burner and the direct current burner by controlling the regulating gate. When one of the burners needs to be repaired or fails, its air supply and fuel supply can be quickly cut off, while the other burner continues to work. When the self-service stable combustion burner is under repair or fails, the self-service stable combustion burner system can be cut off by closing the No. 5 regulating valve and the No. 2 regulating valve and opening the No. 1 regulating valve, while ensuring that the first layer of primary air provides coal powder combustion to avoid shutdown. When the first layer of primary air burner is under repair or fails, the first layer of primary air system can be cut off by closing the No. 1 regulating valve and the No. 5 regulating valve and opening the No. 2 regulating valve, while ensuring that the self-service stable combustion burner provides coal powder combustion to avoid shutdown. This instant switching capability avoids the shutdown of the entire furnace due to a single burner failure, greatly improves the availability and stability of the boiler, and can flexibly respond to different working conditions and fault conditions, thereby significantly improving the stable operation capability and overall safety of the boiler.

[0037] 6. The coordinated combustion device and coordinated combustion method of a direct current burner and a swirl burner provided in the present application are conducive to enhancing the coal type adaptability of the boiler and improving the capacity adaptability of the boiler.

[0038] Power plant boilers are usually optimized for specific coal types during design to ensure that their combustion efficiency and heat output meet the expected standards. When burning poor quality coal, volatile content is the main heat source for coal powder ignition. Coal with low volatile content is difficult to ignite and requires higher ignition temperature and longer ignition time, which increases the difficulty and instability of combustion. In addition, boilers of different capacities have significant differences in structure, operating parameters, and fuel requirements, which further limits the adaptability of power plant boilers in different capacity applications.

[0039] The present invention relies on the induced effect of the DC primary air and DC secondary air of the DC burner, and cooperates with the self-help stable combustion burner stable combustion chamber and the secondary air in the swirl to form a central reflow zone in the center of the self-help stable combustion burner as a stable ignition heat source to heat the high-concentration coal powder. At the same time, the high-temperature flame ejected by the swirl burner ignites the surrounding DC burner primary air powder flame, strengthens the combustion of the coal powder airflow during tangential combustion, and makes the flame more stable. According to the actual boiler capacity requirements and the requirements of the coal quality, multiple layers of self-help stable combustion burners can be installed to ensure that even if poor coal quality is burned, the temperature of the furnace burner area is still maintained at about 1300°C. Without the help of external flame combustion-supporting technologies such as micro-oil or plasma, the coal-fired power unit can achieve a stable combustion effect at 20%-30% of the rated load by relying solely on coal powder combustion. When burning bituminous coal with Vdaf>20% or in boilers with a capacity of less than 300MW, a layer of self-help stable combustion burner can be installed. When burning lean coal with Vdaf of 10%-20% or in boilers with a capacity of 300-600MW, two layers of self-help stabilizing burners can be installed. When burning anthracite with Vdaf < 10% or in boilers with a capacity of more than 600MW, three layers of self-help stabilizing burners can be installed (such as Figures 11 to 13 shown). BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the four-corner tangential circle ignition principle of the cooperative combustion device described in this application;

[0041] Figure 2 This is a schematic diagram of the arrangement of a direct current burner in the cooperative combustion device described in this application;

[0042] Figure 3 This is a BB view of a DC burner in the cooperative combustion device described in this application;

[0043] Figure 4 This is a diagram of the air-powder system of the self-help combustion stabilization burner in the cooperative combustion device described in this application;

[0044] Figure 5 A schematic diagram of a self-help combustion stabilizing burner in the cooperative combustion device described in this application;

[0045] Figure 6 This is a CC-direction schematic diagram of the self-help combustion stabilizing burner in the cooperative combustion device described in this application;

[0046] Figure 7 This is a schematic diagram of the morphology of the combustion chamber of the self-help combustion stabilizing burner and the reflow zone in the furnace when the cooperative combustion device described in this application is working;

[0047] Figure 8 This is a schematic diagram of the position of the self-help stabilizing burner arranged on the first layer of the direct current burner in the cooperative combustion device described in this application;

[0048] Fig. 9 This is a schematic diagram of the position of the self-help stabilizing burner in the cooperative combustion device described in this application arranged on the second layer of the direct current burner;

[0049] Fig.10 This is a schematic diagram of the position of the self-help stabilizing burner in the cooperative combustion device described in this application arranged on the third layer of the direct current burner;

[0050] Fig.11 This is a schematic diagram of the positions of two self-help stabilizing burners arranged on the first and second layers of the direct current burner in the cooperative combustion device described in this application;

[0051] Fig.12 This is a schematic diagram of the positions of two self-help combustion stabilizing burners arranged on the second and third layers of the direct current burner in the cooperative combustion device described in this application;

[0052] Fig.13 This is a schematic diagram of the positions of the three self-help stabilizing burners in the cooperative combustion device described in this application, which are arranged on the first, second and third layers of the direct current burners. DETAILED DESCRIPTION

[0053] Specific implementation method 1: Combination Figures 1 to 13The present embodiment is described. In the present embodiment, a DC burner and a swirl burner cooperative combustion device is provided. The cooperative combustion device comprises a four-corner tangential pulverized coal combustion boiler 11, a secondary wind box 31 and four DC pulverized coal burners 10. The four DC pulverized coal burners 10 are respectively arranged at the four corners of the four-corner tangential pulverized coal combustion boiler 11. Each DC pulverized coal burner 10 corresponds to at least one coal mill 21. The DC primary air nozzle 1 in the DC pulverized coal burner 10 is connected to the coal outlet end of the coal mill 21 through a coal supply pipeline. The DC The DC secondary air nozzle 3 in the pulverized coal burner 10 is connected to the air outlet end of the secondary air box 31 through an air supply pipeline, and is characterized in that: at least one self-help stabilizing combustion burner 2 is arranged in each DC pulverized coal burner 10, and each self-help stabilizing 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, and the self-help stabilizing 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-powder system;

[0054] The DC pulverized coal burner 10 is divided into three layers from bottom to top, the first layer includes a layer of DC secondary air nozzles 20 and a layer of DC primary air nozzles 19, and the layer of DC primary air nozzles 19 is located above the layer of DC secondary air nozzles 20, the second layer includes a second layer of DC secondary air nozzles 18 and a second layer of DC primary air nozzles 17, and the second layer of DC primary air nozzles 17 are located above the second layer of DC secondary air nozzles 18, the third layer includes a third layer of No. 1 DC secondary air nozzles 16, a third layer of DC primary air nozzles 15 and a third layer of No. 2 DC secondary air nozzles 14, and the third layer of No. 1 DC secondary air nozzles 16, the third layer of DC primary air nozzles 15 and the third layer of No. 2 DC secondary air nozzles 14 are arranged in sequence from bottom to top;

[0055] The coal supply pipeline includes a DC primary air channel 5, a primary air duct 22 and a No. 1 regulating valve 23. 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 22 is connected to the coal outlet end of the corresponding coal mill 21, and the other end of the DC primary air channel 5 is connected to the other end of the primary air duct 22. A No. 1 regulating valve 23 is installed at the connection between the DC primary air channel 5 and the primary air duct 22.

[0056] The coal supply pipeline also includes a No. 2 regulating valve 25, a No. 3 regulating valve 26, a No. 1 pulverized coal pipeline 27 and a pulverized coal separation device 28. The coal inlet end of the pulverized coal separation device 28 is connected to the primary air duct 22, and the No. 2 regulating valve 25 is connected in series to the primary air duct 22. The No. 1 coal outlet end of the pulverized coal separation device 28 is connected to the DC primary air channel 5 through the No. 1 pulverized coal pipeline 27, and the No. 3 regulating valve 26 is connected in series to the No. 1 pulverized coal pipeline 27.

[0057] The air supply pipeline includes a DC secondary air channel 7, a secondary air channel 32 and a No. 4 regulating valve 34. 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 32 is connected to the air outlet end of the corresponding secondary air box 31, and the other end of the DC secondary air channel 7 is connected to the other end of the secondary air channel 32. A No. 4 regulating valve 34 is installed at the connection between the DC secondary air channel 7 and the secondary air channel 32.

[0058] The self-help combustion stabilizing burner 2 comprises a combustion stabilizing chamber 4, a secondary air channel 6 in a swirl flow, and a DC primary air channel 8 of the self-help combustion stabilizing burner. The secondary air channel 6 in a swirl flow 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 a swirl flow are both connected to the combustion stabilizing chamber 4, and the other end of the DC primary air channel 8 of the self-help combustion stabilizing burner is connected to the coal supply pipeline through an air-powder system, and the other end of the secondary air channel 6 in a swirl flow is connected to the air supply pipeline through an air-powder system. The pipeline is connected, an axial blade group 9 is provided between the self-service stabilizing combustion burner DC primary air channel 8 and the swirl internal secondary air channel 6, and the axial blade group 9 is arranged close to the stabilizing combustion chamber 4, and 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 self-service stabilizing combustion burner DC primary air channel 8 and the swirl internal secondary air channel 6, and one end of each axial blade is connected to the outer wall of the self-service stabilizing combustion burner DC primary air channel 8, and the other end of each axial blade is connected to the inner wall of the swirl internal secondary air channel 6;

[0059] 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.

[0060] The DC coal supply pipeline includes a DC connection air duct of the self-service stable combustion burner, a No. 5 regulating valve 24, a No. 2 coal powder channel 29 and a No. 6 regulating valve 30. The primary air duct 22 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 24 is connected in series to the DC connection air duct of the self-service stable combustion burner. The No. 2 coal outlet end of the coal powder separation device 28 is connected with the DC primary air channel 8 of the self-service stable combustion burner through the No. 2 coal powder channel 29, and the No. 6 regulating valve 30 is connected in series to the No. 2 coal powder channel 29;

[0061] The swirl air supply pipeline includes a self-service stabilizing combustion burner swirl connecting air duct and a No. 7 regulating valve 33. The secondary air duct 32 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 33 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.

[0062] A DC burner and swirl burner cooperative combustion device is provided in this embodiment, wherein the outlet of the DC pulverized coal burner 10 is composed of a DC primary air nozzle 1 and a DC secondary air nozzle 3, and the DC primary air nozzle 1 and the DC secondary air nozzle 3 are both rectangular nozzles, the DC primary air nozzle 1 and the DC secondary air nozzle 3 are arranged alternately, the upstream adjacent angle flame is ignited at the root of the downstream DC pulverized coal burner 10, forming an actual flame zone 12, the DC primary air enters the DC primary air nozzle 1 from the DC primary air channel 5, and is injected into the furnace in a DC form, and forms an imaginary tangent circle 13 at the center of the furnace, and another path passes through the self-help stable combustion burner DC primary air channel 8, supplies coal powder to the self-help stable combustion burner 2, and enters the stable combustion chamber 4 in a DC form. The DC secondary air enters the DC secondary air nozzle 3 from the DC secondary air channel 7, and is injected into the furnace in a DC form. The secondary air in the swirl enters the stable combustion chamber 4 in a rotating form after passing through the axial blade group 9 in the secondary air channel 6 in the swirl. Under the action of the secondary air in the swirl and the stable combustion chamber 4, the primary air powder forms a stable reflow zone in the center of the stable combustion chamber and enters the furnace in the form of a reflow zone;

[0063] The DC pulverized coal burner 10 provided in this embodiment has three layers, wherein the arrangement principle of the coal mill 21 and the secondary air box 32 is that each layer of DC primary air nozzles and DC secondary air nozzles in the DC pulverized coal burner 10 corresponds to a coal mill 21 and a secondary air box 32, and the self-help stabilizing combustion burner 2 can be flexibly arranged according to the actual flue gas temperature at the inlet of the SCR denitration, that is, the self-help stabilizing combustion burner 2 is arranged between the primary air and secondary air nozzles of the DC burners in different layers. When the rated load is 20%-30%, in order to effectively increase the flue gas temperature at the inlet of the SCR denitration, four self-help stabilizing combustion burners 2 are arranged at the four corners between a layer of DC primary air nozzles 19 and a layer of DC secondary air nozzles 20 of the lowest layer of the DC burner (one is arranged in each DC pulverized coal burner 10), and the flue gas temperature at the inlet of the SCR denitration can be increased by 5%-10%. Arrange four self-help stable combustion burners 2 at the four corners between the second-layer DC primary air nozzle 17 and the second-layer DC secondary air nozzle 18, and the SCR denitrification inlet flue gas temperature can be increased by 10%-15%. Arrange four self-help stable combustion burners 2 at the four corners between the third-layer DC primary air nozzle 15 and the third-layer No. 1 DC secondary air nozzle 16, and the SCR denitrification inlet flue gas temperature can be increased by 10%-15%. For details of the above arrangement, please refer to the attached Figure 8 To Attachment Fig.10 ;

[0064] In actual work, multiple layers of self-help stabilizing burners 2 can be installed according to the actual boiler capacity requirements and coal quality requirements, so that the coal-fired power unit can achieve stable combustion at 20%-30% of the rated load by relying solely on coal powder combustion without the help of external flame combustion-supporting technologies such as micro-oil or plasma. When burning bituminous coal with Vdaf>20% or in boilers with a capacity of less than 300MW, one layer of self-help stabilizing burner 2 can be installed. When burning lean coal with Vdaf of 10%-20% or in boilers with a capacity of 300-600MW, two layers of self-help stabilizing burners 2 can be installed. When burning anthracite with Vdaf<10% or in boilers with a capacity of more than 600MW, three layers of self-help stabilizing burners 2 can be installed. For details of the above arrangements, please refer to the attached Fig.11 To Attachment Fig.13 .

[0065] Specific implementation method 2: Combination Figures 1 to 13 The present embodiment is described. In the present embodiment, a method for coordinated combustion of a DC burner and a swirl burner is provided when the boiler is operating at a load higher than 50% of the rated load. The No. 2 regulating valve 25 is shut off, and the primary wind speed entering the DC primary air channel 5 is controlled to 26-28 m / s by changing the opening of the No. 1 regulating valve 23 to 80%-100%. The primary wind speed entering the self-service stabilizing combustion burner 2 is controlled to 22-26 m / s by changing the opening of the No. 5 regulating valve 24 to 80%-100%. The No. 7 regulating valve 33 is shut off so that there is no rotating secondary air inside the self-service stabilizing combustion burner 2. The secondary air can be opened by the No. 4 regulating valve 34 to 70%-80%, and the secondary wind speed entering the DC secondary air channel 7 is controlled to 45-47 m / s. Through the above operation, the oxygen required for complete combustion of the fuel is supplemented, thereby realizing coordinated combustion of the DC pulverized coal burner 10 and the self-service stabilizing combustion burner 2 at a load higher than 50% of the rated load.

[0066] The synergistic combustion method provided in this embodiment is used when the boiler is operating at a load condition higher than 50% of the rated load. Introducing the self-help stabilizing burner 2 to work under high load can effectively improve the burnout rate of coal powder under high load. When the boiler is working at high load, the present invention divides the primary air and powder airflow into two parts. One part enters the stabilizing chamber 4 through the DC primary air channel 8 of the self-help stabilizing burner. The outlet area of ​​the stabilizing chamber 4 is 1.2-1.5 times the area of ​​the DC primary air nozzle 1. The coal powder airflow leaves the stabilizing chamber at a speed of 8-9m / s and enters the furnace. On the one hand, the coal powder airflow has a low velocity and stays in the furnace for a long time, which is conducive to the burnout of the coal powder. On the other hand, its stable combustion chamber has a larger heat load than the furnace cross section. The heat released after combustion causes the temperature in the stable combustion chamber to rise rapidly and maintain at a high temperature. At the same time, the unburned pulverized coal flow rises to the DC primary air nozzle with the flue gas, and mixes with the primary air ejected from the DC primary air nozzle again, and continues to burn. Compared with only DC burners arranged at the four corners or octagon of the original furnace, the burnout area is increased, which is conducive to the burnout of pulverized coal. A stream of pulverized coal enters the DC primary air nozzle through the DC primary air channel, and enters the furnace at 26-28m / s. Compared with only DC burners arranged at the four corners or octagon of the original furnace, the pulverized coal flow velocity of the DC burner that cooperates with the swirl burner is reduced, and the combustion time in the furnace is sufficient, which is conducive to the burnout of pulverized coal and improves combustion efficiency.

[0067] Specific implementation method three: Combination Figures 1 to 13For this embodiment, a co - combustion method of a direct - flow burner and a swirl burner when the boiler operates under a condition of less than 50% of the rated load is provided. Shut off the first regulating valve 23 and the fifth regulating valve 24, and open the second regulating valve 25. The primary air - pulverized coal can enter the pulverized - coal separation device 28 through the second regulating valve 25. The pulverized - coal air flow enters the first pulverized - coal passage 27. By changing the opening degree of the third regulating valve 26 to 50% - 80%, control the primary air velocity entering the direct - flow primary - air passage 5 to 16 - 26 m / s. The pulverized - coal air flow enters the second pulverized - coal passage 29. By changing the opening degree of the sixth regulating valve 30 to 40% - 80%, control the primary air velocity entering the direct - flow primary - air passage 8 of the self - stabilizing combustion burner to 14 - 22 m / s. By adjusting the opening degree of the seventh regulating valve 33 to 40% - 70%, control the secondary air velocity entering the swirl inner - secondary - air passage 6 to 35 - 50 m / s. By changing the opening degree of the fourth regulating valve 34 to 30% - 60%, control the secondary air velocity entering the direct - flow secondary - air passage 7 to 30 - 45 m / s. Through the above operations, by controlling the primary air of the self - stabilizing combustion burner and the swirl inner - secondary air velocity, a wide and long central recirculation zone is formed in the stable - combustion cavity 4. By controlling the direct - flow primary and secondary air velocities arranged vertically and horizontally, while restricting the expansion of the rotating air flow, the air flow in the stable - combustion cavity is entrained, slowing down the attenuation of the air flow, so that the length of the central recirculation zone continues to increase. Here, De refers to the inner - secondary - air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length. The diameter of the recirculation zone is 0.8De < D1 < 2De, the length is 2.5De < L1 < 4De, and the maximum flue - gas recirculation volume is 3 - 8 times the primary - air volume, thereby realizing the co - combustion of the direct - flow pulverized - coal burner 10 and the self - stabilizing combustion burner 2 when operating under a condition of less than 50% of the rated load.

[0068] The co - combustion method provided in this embodiment is for use when the boiler operates under a condition of less than 50% of the rated load. The specific situation and adjustment range are further refined into the following several cases:

[0069] Case 1: Co - combustion method of direct - flow burners and swirl burners when the boiler operates under the rated load condition of 40% - 50%. Shut off the first regulating valve 23 and the fifth regulating valve 24, and open the second regulating valve 25. The primary air - powder can enter the pulverized - coal separation device 28 through the second regulating valve 25. The pulverized - coal air flow enters the first pulverized - coal passage 27. By changing the opening degree of the third regulating valve 26 to 70% - 80%, control the primary air velocity entering the direct - flow primary air passage 5 to 22 - 26 m / s. The pulverized - coal air flow enters the second pulverized - coal passage 29. By changing the opening degree of the sixth regulating valve 30 to 60% - 80%, control the primary air velocity entering the direct - flow primary air passage 8 of the self - stabilizing combustion burner to 20 - 22 m / s. By adjusting the opening degree of the seventh regulating valve 33 to 60% - 70%, control the secondary air velocity entering the swirl inner secondary air passage 6 to 45 - 50 m / s. By adjusting the opening degree of the fourth regulating valve 34 to 50% - 60%, control the secondary air velocity entering the direct - flow secondary air passage 7 to 40 - 45 m / s. Through the above operations, by controlling the primary air of the self - stabilizing combustion burner and the swirl inner secondary air velocity, a wide and long central recirculation zone is formed in the stable - combustion cavity 4. By controlling the direct - flow primary and secondary air velocities arranged up and down, while restricting the expansion of the rotating air flow, entrain the air flow in the stable - combustion cavity, slow down the attenuation of the air flow, and make the length of the central recirculation zone continue to increase. Here, De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length. The diameter of the recirculation zone is 0.8De < D1 < 1.2De, the length is 2.5De < L1 < 3De, and the maximum flue - gas recirculation volume is 3 - 4 times the primary air volume, so as to realize the co - combustion of the direct - flow pulverized - coal burner 10 and the self - stabilizing combustion burner 2 when operating under the rated load condition of 40% - 50%.

[0070] Case 2: The collaborative combustion method of the direct current burner and the swirl burner when the boiler is operating under the rated load condition of 30%-40%. Shut off the first regulating valve 23 and the fifth regulating valve 24, and open the second regulating valve 25. The primary air powder can enter the pulverized coal separation device 28 through the second regulating valve 25. The pulverized coal air flow enters the first pulverized coal passage 27. By changing the opening degree of the third regulating valve 26 to 60%-70%, control the primary air speed entering the direct current primary air passage 5 to 18-22 m / s. The pulverized coal air flow enters the second pulverized coal passage 29. By changing the opening degree of the sixth regulating valve 30 to 50%-60%, control the primary air speed entering the direct current primary air passage 8 of the self-stabilizing combustion burner to 17-20 m / s. By adjusting the opening degree of the seventh regulating valve 33 to 50%-60%, control the secondary air speed entering the swirl inner secondary air passage 6 to 40-45 m / s. By adjusting the opening degree of the fourth regulating valve 34 to 40%-50%, control the secondary air speed entering the direct current secondary air passage 7 to 35-40 m / s. After the above operations, by controlling the primary air speed of the self-stabilizing combustion burner and the swirl inner secondary air speed, a wide and long central recirculation zone is formed in the stable combustion chamber 4. By controlling the direct current primary and secondary air speeds arranged up and down, while restricting the expansion of the rotating air flow, entrain the air flow in the stable combustion chamber, slow down the air flow attenuation, and make the length of the central recirculation zone continue to increase. Here, De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, L is the maximum length. The diameter of the recirculation zone is 1.2De < D1 < 1.5De, the length is 3De < L1 < 3.5De, and the maximum flue gas recirculation volume is 5-6 times the primary air volume, so as to realize the collaborative combustion of the direct current pulverized coal burner 10 and the self-stabilizing combustion burner 2 when operating under the rated load condition of 30%-40%;

[0071] Case 3: The collaborative combustion method of the direct current burner and the swirl burner when the boiler is operating at 20%-30% of the rated load. Shut off the first regulating valve 23 and the fifth regulating valve 24, and open the second regulating valve 25. The primary air powder can enter the pulverized coal separation device 28 through the second regulating valve 25. The pulverized coal air flow enters the first pulverized coal passage 27. By changing the opening degree of the third regulating valve 26 to 50%-60%, control the primary air velocity entering the direct current primary air passage 5 to 16-18 m / s. The pulverized coal air flow enters the second pulverized coal passage 29. By changing the opening degree of the sixth regulating valve 30 to 40%-50%, control the primary air velocity entering the direct current primary air passage 8 of the self-stabilizing combustion burner to 14-17 m / s. By adjusting the opening degree of the seventh regulating valve 33 to 40%-50%, control the secondary air velocity entering the swirl inner secondary air passage 6 to 35-40 m / s. By adjusting the opening degree of the fourth regulating valve 34 to 30%-40%, control the secondary air velocity entering the direct current secondary air passage 7 to 30-35 m / s. After the above operations, by controlling the primary air and the swirl inner secondary air velocities of the self-stabilizing combustion burner, a wide and long central recirculation zone is formed in the stable combustion cavity 4. By controlling the direct current primary and secondary air velocities arranged up and down, while restricting the expansion of the rotating air flow, entrain the air flow in the stable combustion cavity, slow down the air flow attenuation, and make the length of the central recirculation zone continue to increase. Where De refers to the inner secondary air diameter, D is the maximum diameter of the recirculation zone, and L is the maximum length. The diameter of the recirculation zone is 1.5De < D1 < 2De, the length is 3.5De < L1 < 4De, and the maximum flue gas recirculation volume is 7-8 times the primary air volume, so as to realize the collaborative combustion of the direct current pulverized coal burner 10 and the self-stabilizing combustion burner 2 when operating at 30%-40% of the rated load;

[0072] Combined with the second and third specific embodiments, when the self-stabilizing combustion burner 2 is under maintenance or fails, the system of the self-stabilizing combustion burner 2 can be cut off by shutting off the fifth regulating valve 24 and the second regulating valve 25 and opening the first regulating valve 23. At the same time, ensure that the first-layer direct current primary air nozzle 19 provides pulverized coal combustion to avoid boiler shutdown. When the direct current burner is under maintenance or fails, the direct current burner can be cut off by shutting off the first regulating valve 23 and the second regulating valve 25 and opening the fifth regulating valve 24. At the same time, ensure that the self-stabilizing combustion burner 2 provides pulverized coal combustion to avoid boiler shutdown. Thus, the separate combustion of the direct current pulverized coal burner 10 and the self-stabilizing combustion burner 2 is realized, improving the stable operation of the boiler.

[0073] 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:

[0075] This technology has been applied to a 600MW subcritical pressure drum boiler, which adopts a four-corner tangential combustion method. It burns a mixture of anthracite, lean coal and bituminous coal (the coal quality characteristics are similar to lean coal), adopts a steel ball mill direct-blowing pulverizing system, and the burner is equipped with 6 layers of coal powder direct current burners. The boiler is equipped with 6 steel ball mills. When the boiler is under MCR load, 6 layers are put into operation without spare. There is a layer of direct current primary air nozzles arranged between the adjacent 2 layers of direct current secondary air nozzles. The top and bottom layers are each equipped with a layer of direct current secondary air nozzles. The top layer of direct current secondary air nozzles plays the role of coal powder burning out, and the bottom layer of direct current secondary air nozzles plays the role of supporting bottom wind. Before the burner modification, the lowest stable combustion load of the boiler without oil injection is 40%. When the rated load is 30%-40%, the three-layer pulverizing system and the micro-oil system are put into operation, and the inlet smoke temperature of the SCR system is 280-350℃. When the rated load is below 30%, the second and third layers of pulverizing systems and micro-oil systems are put into operation, and the inlet smoke temperature of the SCR system is 260-280℃. When the coal quality fluctuates, the primary wind speed can be fine-tuned within a certain range (±2m / s) under the condition that the coal quantity of the pulverizer remains unchanged. This fine-tuning has a limited range of change in wind speed. There are 3-4 fire-fighting accidents in the boiler within a year, which seriously affects the safe operation of the unit and the loss cost is about more than 3 million yuan.

[0076] By using the device and method involved in the present invention, four self-help stabilizing burners are arranged at the four corners between the DC primary air nozzle and the DC secondary air nozzle of the second-layer DC pulverized coal burner. Powder is taken from the branch pipe of the second-layer pulverizing system, and air is taken from the secondary wind box. At high load (rated load above 50%), the carbon content of fly ash is reduced from 10% before the transformation to 6% through the coordinated combustion of the DC burner and the swirl burner, and the boiler efficiency is increased from 90.8% before the transformation to 92.9%. Under the condition of burning the same coal quality, the flame formed by the combustion of the self-help stabilizing 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 that the unit can achieve a stable combustion effect at 20%-30% of the rated load by relying solely on coal powder combustion, saving about 2 million yuan in combustion-supporting oil costs. At the same time, the inlet smoke temperature of the SCR system is increased to about 300°C. When the coal quality fluctuated greatly from anthracite (Vdaf=8%) to bituminous coal (Vdaf=38%), no accidents such as boiler fire extinguishing occurred, reducing the losses caused by fire extinguishing by a total of 3 million yuan.

[0077] Under the requirement of "giving full play to the emergency peak-shaving capacity of existing coal-fired power units", the deep regulation load of thermal power units will be further reduced, and the deep regulation time will be greatly increased. In order to encourage thermal power units to reduce the deep regulation 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 20% of the rated load. It can be comprehensively obtained that the deep regulation of the burner after the transformation can generate an additional profit of 70-80 million yuan compared with the deep regulation before the transformation.

Claims

1. A DC burner and swirl burner coordinated combustion device, the coordinated combustion device comprising a four-corner tangential pulverized coal combustion boiler (11), a secondary wind box (31) and four DC pulverized coal burners (10), the four DC pulverized coal burners (10) are respectively arranged at the four corners of the four-corner tangential pulverized coal combustion boiler (11), each DC pulverized coal burner (10) corresponds to at least one coal mill (21), the DC primary air nozzle (1) in the DC pulverized coal burner (10) is connected to the coal outlet end of the coal mill (21) through a coal supply pipeline, and the DC secondary air nozzle (3) in the DC pulverized coal burner (10) is connected to the air outlet end of the secondary wind box (31) through an air supply pipeline, characterized in that: At least one self-help combustion stabilizing burner (2) is arranged in each DC pulverized coal burner (10), and each self-help combustion stabilizing burner (2) is arranged between a DC primary air nozzle (1) and a 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 a coal supply pipeline of an adjacent DC primary air nozzle (1) and an air supply pipeline of an adjacent DC secondary air nozzle (3) through an air-powder system.

2. A direct current burner and swirl burner cooperative combustion device according to claim 1, characterized in that: The DC pulverized coal burner (10) is divided into three layers from bottom to top, the first layer includes a layer of DC secondary air nozzles (20) and a layer of DC primary air nozzles (19), and the layer of DC primary air nozzles (19) is located above the layer of DC secondary air nozzles (20), the second layer includes a second layer of DC secondary air nozzles (18) and a second layer of DC primary air nozzles (17), and the second layer of DC primary air nozzles (17) are located above the second layer of DC secondary air nozzles (18), and the third layer includes a third layer of No. 1 DC secondary air nozzles (16), a third layer of DC primary air nozzles (15) and a third layer of No. 2 DC secondary air nozzles (14), and the third layer of No. 1 DC secondary air nozzles (16), the third layer of DC primary air nozzles (15) and the third layer of No. 2 DC secondary air nozzles (14) are arranged in sequence from bottom to top.

3. A direct current burner and swirl burner coordinated combustion device according to claim 2, characterized in that: The coal supply pipeline comprises a DC primary air channel (5), a primary air duct (22) and a first regulating valve (23); 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 (22) is connected to a coal outlet end of a corresponding coal mill (21); the other end of the DC primary air channel (5) is connected to the other end of the primary air duct (22); and the first regulating valve (23) is installed at the connection point between the DC primary air channel (5) and the primary air duct (22).

4. The coordinated combustion device of a direct current burner and a swirl burner according to claim 3, characterized in that: The coal supply pipeline further comprises a No. 2 regulating valve (25), a No. 3 regulating valve (26), a No. 1 pulverized coal pipeline (27) and a pulverized coal separation device (28); the coal inlet end of the pulverized coal separation device (28) is connected to the primary air duct (22), and the No. 2 regulating valve (25) is connected in series to the primary air duct (22); the No. 1 coal outlet end of the pulverized coal separation device (28) is connected to the DC primary air channel (5) through the No. 1 pulverized coal pipeline (27), and the No. 3 regulating valve (26) is connected in series to the No. 1 pulverized coal pipeline (27).

5. The coordinated combustion device of a direct current burner and a swirl burner according to claim 4, characterized in that: The air supply pipeline comprises a DC secondary air channel (7), a secondary air channel (32) and a No. 4 regulating valve (34); 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 (32) is connected to the air outlet end of the corresponding secondary air box (31); the other end of the DC secondary air channel (7) is connected to the other end of the secondary air channel (32); and the No. 4 regulating valve (34) is installed at the connection between the DC secondary air channel (7) and the secondary air channel (32).

6. The coordinated combustion device of a direct current burner and a swirl burner according to claim 5, characterized in that: The self-help combustion stabilizing burner (2) comprises a combustion stabilizing chamber (4), a secondary air channel (6) in a swirl flow, and a DC primary air channel (8) of the self-help combustion stabilizing burner. The secondary air channel (6) in a swirl flow is coaxially sleeved outside 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 a swirl flow are both connected to the combustion stabilizing chamber (4), and 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, and the other end of the secondary air channel (6) in a swirl flow is connected to a coal supply pipeline through an air powder system. The air duct is connected, 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 arranged equidistantly 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.

7. The coordinated combustion device of a direct current burner and a swirl burner 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. The coordinated combustion device of a direct current burner and a swirl burner according to claim 7, characterized in that: The DC coal supply pipeline comprises a DC connecting air duct of a self-help combustion stabilizing burner, a No. 5 regulating valve (24), a No. 2 coal powder channel (29) and a No. 6 regulating valve (30); the primary air duct (22) is connected to the DC primary air channel (8) of the self-help combustion stabilizing burner through the DC connecting air duct of the self-help combustion stabilizing burner, and the No. 5 regulating valve (24) is connected in series to the DC connecting air duct of the self-help combustion stabilizing burner; the No. 2 coal outlet of the coal powder separation device (28) is connected to the DC primary air channel (8) of the self-help combustion stabilizing burner through the No. 2 coal powder channel (29), and the No. 6 regulating valve (30) is connected in series to the No. 2 coal powder channel (29); The swirl air supply pipeline comprises a swirl connecting air duct of a self-service stabilizing combustion burner and a No. 7 regulating valve (33); the secondary air duct (32) 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 (33) 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 coordinated combustion method using a direct current burner and a swirl burner coordinated combustion device as claimed in any one of claims 1 to 8 when the boiler is operating at a load higher than 50% of the rated load, characterized in that: Shut off the second regulating valve (25). By changing the opening degree of the first regulating valve (23) to 80%-100%, control the primary air velocity entering the DC primary air passage (5) to 26-28 m / s. By changing the opening degree of the fifth regulating valve (24) to 80%-100%, control the primary air velocity entering the self-stabilizing combustion burner (2) to 22-26 m / s. Shut off the seventh regulating valve (33) so that there is no swirling secondary air inside the self-stabilizing combustion burner (2). The secondary air can pass through the fourth regulating valve (34) with an opening degree of 70%-80% to control the secondary air velocity entering the DC secondary air passage (7) to 45-47 m / s. After the above operations, its stable combustion chamber (4) has a relatively large heat load compared to the furnace cross-section. The heat released after combustion causes the temperature inside the stable combustion chamber (4) to rise rapidly and remain in a high-temperature state. At the same time, the unburned pulverized coal air flow rises with the flue gas to the DC primary air nozzle (1) and mixes with the primary air ejected from the DC primary air nozzle (1) again to continue combustion. Compared with only arranging DC burners at the four corners of the original furnace, the burnout area is increased, which is beneficial to the burnout of pulverized coal, thus realizing the coordinated combustion of the DC pulverized coal burner (10) and the self-stabilizing combustion burner (2) when the load is higher than 50% of the rated load.

10. A coordinated combustion method using the coordinated combustion device of a direct current burner and a swirl burner according to any one of claims 1 to 8 when the boiler is operating at a load condition lower than 50% of the rated load, characterized in that: Shut off the first regulating valve (23) and the fifth regulating valve (24), and open the second regulating valve (25). The primary air and pulverized coal can enter the pulverized coal separation device (28) through the second regulating valve (25). The pulverized coal air flow enters the first pulverized coal passage (27). By changing the opening degree of the third regulating valve (26) to 50%-80%, control the primary air velocity entering the DC primary air passage (5) to 16-26 m / s. The pulverized coal air flow enters the second pulverized coal passage (29). By changing the opening degree of the sixth regulating valve (30) to 40%-80%, control the primary air velocity entering the DC primary air passage (8) of the self-stabilizing combustion burner to 14-22 m / s. By adjusting the opening degree of the seventh regulating valve (33) to 40%-70%, control the secondary air velocity entering the swirling inner secondary air passage (6) to 35-50 m / s. By changing the opening degree of the fourth regulating valve (34) to 30%-60%, control the secondary air velocity entering the DC secondary air passage (7) to 30-45 m / s. After the above operations, by controlling the primary air and the swirling inner secondary air velocities of the self-stabilizing combustion burner, a wide and long central recirculation zone is formed inside the stable combustion chamber (4). By controlling the DC primary and secondary air velocities arranged up and down, while restricting the expansion of the swirling air flow, the air flow inside the stable combustion chamber is entrained, slowing down the attenuation of the air flow, so that the length of the central recirculation zone continues to increase. Here, De refers to the diameter of the inner secondary air, D is the maximum diameter of the recirculation zone, and L is the maximum length. The diameter of the recirculation zone is 0.8De < D1 < 2De, the length is 2.5De < L1 < 4De, and the maximum flue gas recirculation volume is 3-8 times the primary air volume, thus realizing the coordinated combustion of the DC pulverized coal burner (10) and the self-stabilizing combustion burner (2) when operating under the condition of a load lower than 50% of the rated load.

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