W flame boiler and combustion method thereof
By using cyclone preburner and deep air grading combustion technology in W flame boilers, the problems of stable combustion and high NOx emissions when burning anthracite and low volatile coal are solved, and the effects of stable combustion and low NOx emissions are achieved.
Patent Information
- Application Number
- CN202311107995.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-30
- Publication Date
- 2025-02-28
AI Technical Summary
When existing W flame boilers burn anthracite and low-volatilization coal, it is difficult to achieve steady combustion and complete combustion. At the same time, NOx emissions are high, making it difficult to effectively reduce them.
A cyclone preburner with cyclone blades is used to pass the thick coal powder separated from the coal powder separator into the cyclone preburner, a cyclone flame is formed using the cyclone blades, and a secondary wind is introduced through the nozzle to form a strong cyclone flow to absorb high-temperature flue gas, heat the coal powder air flow, and achieve stable combustion. At the same time, the design of deep air staging combustion and grading combustion air ducts is reduced.
The stable and complete combustion of coal powder has been achieved, and the NOx emission concentration at the boiler outlet is controlled within 400mg/Nm3, solving the problem of high NOx emissions in the prior art.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of coal-fired boilers, and in particular to a W-flame boiler and a combustion method thereof, and in particular to a W-flame boiler with an enhanced combustion and deep air staged pre-combustion chamber and a combustion method thereof. Background Art
[0002] The W-flame boiler is a type of furnace designed for burning hard-to-burn coals such as anthracite and low-volatile lean coal. This type of furnace is divided into two furnaces, the upper and lower furnaces. The cyclone preburners are arranged on the front and rear wall furnace arches. The cyclone preburners spray the pulverized coal downward, and the pulverized coal airflow forms a W-shaped flame structure in the lower furnace, which prolongs the residence time of the primary air pulverized coal in the furnace and improves the pulverized coal burnout rate. At the same time, by laying a certain amount of fire-prevention belt in the lower furnace, increasing the furnace temperature, increasing the primary air pulverized coal concentration, and entraining the high-temperature flue gas in the furnace, the ignition and stable combustion capabilities of the pulverized coal airflow are improved. Due to the restrictions of low volatile matter (Vdaf<10%), high ignition temperature and long burnout time of the coal used (anthracite, low volatile lean coal), in order to ensure stable combustion and burnout of the boiler, the combustion temperature of the lower furnace of the W-flame boiler is relatively high. Generally, the flame temperature of the lower furnace can reach 1500-1800℃, which leads to more thermal NOx. In addition, due to the low volatile matter content of anthracite or inferior coal and the high ignition temperature of coal, it is difficult to further reduce the excess coefficient of the main combustion zone under the condition of ensuring stable combustion of the boiler. This is also the main reason why the W-flame boiler has high NOx emissions (the NOx concentration at the furnace outlet can reach 1000-2000). It is difficult to achieve deep air staged combustion, and the nitrogen reduction effect of air staged combustion is limited (after adopting air staged, low nitrogen combustion and other technologies, the NOx is generally controlled at 600-900mg / Nm 3 ), it is very difficult to further reduce the boiler NOx outlet concentration. Summary of the invention
[0003] The purpose of the present invention is to address the defect that the prior art cannot achieve stable and complete combustion of difficult-to-burn coals such as anthracite and low-volatile lean coal while reducing the NOx concentration at the boiler outlet when burning difficult-to-burn coals such as anthracite and low-volatile lean coal through a W-flame boiler, thereby proposing a W-flame boiler and a combustion method thereof. The boiler is provided with a cyclone preburner with swirl blades inside on the front and rear arches, and the concentrated coal powder separated from the coal powder separator is introduced into the cyclone preburner. The concentrated coal powder is formed into a swirl flame by the action of the swirl blades, and then the secondary air is tangentially introduced into the cyclone preburner through the nozzles arranged on the side walls of the cyclone preburner, so that the rotation direction of the secondary air is consistent with the swirl direction of the swirl flame formed by the concentrated coal powder, thereby forming a strong swirl, and then the high-temperature flue gas in the lower furnace is sucked in to heat the dense phase coal powder airflow. Since the space of the cyclone preburner is very small compared with the space of the lower furnace, the cold radiation of the lower furnace to the coal powder airflow flame can be greatly reduced. Moreover, since the entrainment in the cyclone preburner has a high temperature (1200-1400℃), it can ensure that the coal powder airflow can achieve stable combustion at a low local excess air coefficient (0.6-0.75), and at the same time, the NOx emission concentration at the boiler outlet can be controlled at 400mg / Nm 3 Within.
[0004] The first aspect of the present invention provides a W-flame boiler, which includes a furnace body, a coal powder separator, a cyclone preburner with swirl blades inside, a light-phase coal powder exhaust gas nozzle and a graded burnout air duct, wherein the furnace body includes an upper furnace, a lower furnace and furnace arches on both sides of the front and rear walls; the coal powder separator is provided with a primary air coal powder air flow inlet, and the light-phase coal powder exhaust gas nozzle is connected to the coal powder separator; the cyclone preburners are symmetrically arranged on the furnace arches on both sides of the front and rear walls, and the cyclone preburners and the coal powder separators are symmetrically arranged on the furnace arches on both sides of the front and rear walls. The dense-phase coal powder nozzle is connected; the cyclone preburner is provided with a secondary air inlet, and the secondary air enters the cyclone preburner tangentially through the secondary air inlet, and the swirl direction of the secondary air is consistent with the swirl direction of the dense-phase coal powder entering the cyclone preburner; the graded burnout air duct and the light-phase coal powder exhaust air nozzle are arranged on the side wall of the upper furnace from top to bottom in sequence, and extend into the upper furnace; a plurality of secondary air ducts are arranged on the side wall of the lower furnace, and the nozzles of the secondary air ducts extend into the lower furnace.
[0005] Preferably, a swirl blade is provided at the front end of the dense-phase pulverized coal nozzle.
[0006] Preferably, the secondary air ducts are arranged opposite to each other on the front and rear side walls of the lower furnace.
[0007] Preferably, the nozzle of the secondary air duct can swing up and down. More preferably, the angle of the up and down swing is ±15°.
[0008] Preferably, 2-5 secondary air ducts are arranged in sequence from top to bottom on one side of the lower furnace.
[0009] Preferably, the light phase pulverized coal exhaust gas nozzles are arranged opposite to each other on the front and rear side walls of the upper furnace.
[0010] Preferably, the light phase coal powder exhaust gas nozzle can swing up and down. More preferably, the angle of the up and down swing is ±15°.
[0011] Preferably, the staged overburnt air ducts are arranged opposite to each other on the front and rear side walls of the upper furnace.
[0012] Preferably, the graded burnout air duct is provided with multiple layers of nozzles on the walls on both sides of the upper furnace.
[0013] Preferably, the angle between the center line of the cyclone preburner and the wall surface of the furnace arch is 80-90°.
[0014] A second aspect of the present invention provides a combustion method for a W-flame boiler, which is implemented in the above-mentioned boiler and comprises:
[0015] The primary air pulverized coal airflow is input into the pulverized coal separator through the primary air pulverized coal airflow inlet for separation, and the separated dense phase pulverized coal enters the cyclone preburner through the dense phase pulverized coal nozzle, and at the same time, the secondary air I is tangentially transported to the cyclone preburner through the secondary air inlet, so that the swirl direction of the secondary air I is consistent with the swirl direction of the dense phase pulverized coal entering the cyclone preburner, so that the dense phase pulverized coal is swirl-flowed downward and burned;
[0016] The secondary air II is transported to the lower furnace through the secondary air duct, so that the unburned coal powder in the cyclone preburner is burned under a reducing atmosphere;
[0017] The light-phase pulverized coal exhaust air separated by the pulverized coal separator is transported to the upper furnace through the light-phase pulverized coal exhaust air nozzle, and graded burnout air is simultaneously transported to the upper furnace through the graded burnout air duct to burn out the light-phase pulverized coal.
[0018] Preferably, the excess air coefficient in the cyclone preburner is 0.45-0.65.
[0019] Preferably, the excess air coefficient in the lower furnace is ≤0.8.
[0020] Preferably, the flow rate of the dense-phase coal powder is 15-25 m / s, and the flow rate of the light-phase coal powder exhaust air is 20-50 m / s.
[0021] Preferably, the flow rate of the secondary air I is 50-80m / s.
[0022] Preferably, the flow rate of the secondary air II is 20-50 m / s.
[0023] Preferably, the flow rate of the graded overburnt air is 40-60 m / s.
[0024] Preferably, the air volume in the cyclone preburner accounts for 10-15% of the total air volume in the furnace body.
[0025] Preferably, the total air volume of the secondary air I and the secondary air II accounts for 45-60% of the total air volume in the furnace body.
[0026] Preferably, the volume of the graded burnout air accounts for 25-35% of the total air volume in the furnace body.
[0027] Preferably, the total air volume of the secondary air I, secondary air II, graded overburnt air and light-phase coal powder exhaust air is 100%, and the total air volume of the graded overburnt air and light-phase coal powder exhaust air is 25-45%.
[0028] The W-flame boiler and combustion method thereof described in the present invention have at least the following beneficial effects:.
[0029] (1) In the present invention, a cyclone preburner having swirl blades inside is arranged on the front and rear arches, and the concentrated coal powder separated from the coal powder separator is introduced into the cyclone preburner, and the concentrated coal powder is formed into a swirl flame by the action of the swirl blades. Then, secondary air is tangentially introduced into the cyclone preburner through the nozzles arranged on the side walls of the cyclone preburner, so that the rotation direction of the secondary air is consistent with the swirl direction of the swirl flame formed by the concentrated coal powder, thereby forming a strong swirl, and then entraining the high-temperature flue gas in the lower furnace for heating. The dense phase pulverized coal airflow can significantly reduce the cold radiation of the lower furnace to the pulverized coal airflow flame because the space of the cyclone preburner is very small compared to the space of the lower furnace. In addition, the cyclone preburner has a high temperature (1200-1400℃), which can ensure that the pulverized coal airflow can achieve stable combustion at a low local excess air coefficient (0.45-0.65), providing good conditions for deep air staged combustion and reducing NOx emissions, so that the NOx emission concentration at the boiler outlet can be controlled at 400mg / Nm 3 within;
[0030] (2) In the present invention, the injection position of the light coal powder separated from the coal powder separator into the furnace body is set at a distance below the graded burnout air, and the light phase coal powder exhaust air is injected at the upper edge of the W flame. On the one hand, the oxygen required for the combustion of the lower furnace can be further supplemented (the excess air coefficient of the lower furnace is controlled to be 0.8 or less); on the other hand, the high temperature flame ensures the rapid combustion and burnout of the coal powder in the exhaust air;
[0031] (3) In the present invention, under preferred circumstances, the light phase pulverized coal exhaust air, secondary air II and graded burnout air are respectively delivered into the furnace in a counter-attacking manner, so that the pulverized coal airflow burns under a certain reducing atmosphere in the furnace, thereby suppressing the generation of NOx. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 The figure is a schematic diagram of the structure of a W-flame boiler according to an embodiment of the present invention.
[0033] Reference numerals
[0034] 1. Primary air pulverized coal air flow inlet; 2. Pulverized coal separator; 21. Dense phase pulverized coal nozzle; 3. Cyclone preburner; 4. Secondary air inlet; 5. Secondary air duct; 6. Graded burnout air duct; 7. Light phase pulverized coal exhaust gas nozzle; 8. Upper furnace; 9. Lower furnace; 10. Furnace arch. DETAILED DESCRIPTION
[0035] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.
[0036] The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.
[0037] In the present invention, the dense phase pulverized coal airflow (containing a large amount of pulverized coal) is ignited by the high-temperature flue gas introduced by the strong swirl effect in the cyclone preburner 3 with a smaller spatial range having a pre-combustion effect. Since the amount of cold radiation from the furnace to the pulverized coal airflow in the cyclone preburner 3 is greatly reduced, and the water-cooled wall in the cyclone preburner 3 has limited heat absorption, the pulverized coal airflow can form a stable flame at a relatively low excess air coefficient in the cyclone preburner 3, thereby providing good conditions for deep air staged combustion and reducing NOx emissions.
[0038] The first aspect of the present invention provides a W-flame boiler, such as Figure 1As shown, the boiler includes a furnace body, a pulverized coal separator 2, a cyclone preburner 3 with swirl blades inside, a light-phase pulverized coal exhaust gas nozzle 7 and a graded burnout air duct 6. The furnace body includes an upper furnace 8, a lower furnace 9 and furnace arches 10 on both sides of the front and rear walls; the pulverized coal separator 2 is provided with a primary air pulverized coal air flow inlet 1, and the light-phase pulverized coal exhaust gas nozzle 7 is connected to the pulverized coal separator 2; the cyclone preburners 3 are symmetrically arranged on the furnace arches 10 on both sides of the front and rear walls, and the cyclone preburners 3 are symmetrically connected to the dense-phase pulverized coal nozzles of the pulverized coal separator 2. 21 is connected; the cyclone preburner 3 is provided with a secondary air inlet 4, and the secondary air enters the cyclone preburner 3 tangentially through the secondary air inlet 4, and the swirl direction of the secondary air is consistent with the swirl direction of the dense-phase coal powder entering the cyclone preburner 3; the graded burnout air duct 6 and the light-phase coal powder exhaust air nozzle 7 are arranged on the side wall of the upper furnace 8 from top to bottom in sequence, and extend into the upper furnace 8; a plurality of secondary air ducts 5 are arranged on the side wall of the lower furnace 9, and the nozzles of the secondary air ducts 5 extend into the lower furnace 9.
[0039] In the boiler described in the present invention, the furnace body can be a conventional choice in the art.
[0040] In the boiler described in the present invention, the pulverized coal separator 2 can be a conventional choice in the art. Specifically, the main body of the pulverized coal separator 2 is respectively provided with a primary air pulverized coal airflow inlet 1, a dense phase pulverized coal nozzle 21, and a light phase pulverized coal exhaust air nozzle 7 connected to the pulverized coal separator 2 through a connecting pipe, wherein the dense phase pulverized coal nozzle 21 is connected to the cyclone preburner 3.
[0041] In the boiler described in the present invention, a swirl blade is provided at the front end of the dense phase coal powder nozzle 21 coming out of the coal powder separator 2 (the dense phase coal powder nozzle 21 is the coal powder inlet of the cyclone preburner 3). During actual operation, the dense phase primary air coal powder airflow after swirl by the swirl blade enters the main body of the cyclone preburner 3, providing a stable and strong swirl effect for the subsequent dense phase coal powder to perform swirl combustion in the cyclone preburner 3.
[0042] In the boiler described in the present invention, the cyclone preburner 3 is a cylindrical structure with swirl blades inside, and the volume of the cyclone preburner 3 is relatively small relative to the boiler body. The coal powder airflow entering the cyclone preburner 3 and the high-speed secondary air entering the cylinder of the cyclone preburner 3 through a tangential direction produce a strong swirl effect, so that the dense-phase coal powder forms a cyclone combustion in the precombustion cylinder of the cyclone preburner 3. Specifically, a secondary air inlet 4 is provided on the body of the cyclone preburner 3. In actual operation, the secondary air I enters the precombustion cylinder of the cyclone preburner 3 tangentially through the secondary air inlet 4, and the secondary air I is consistent with the swirl direction of the dense-phase coal powder airflow entering the cyclone preburner 3, further strengthening the entrainment and stable combustion of the high-temperature flue gas in the cyclone preburner 3.
[0043] In the boiler described in the present invention, a secondary air duct 5 is provided on the side wall of the lower furnace 9, through which oxygen is timely added to the dense phase pulverized coal airflow flame (lack of oxygen) generated by the cyclone preburner 3 to maintain stable flame combustion.
[0044] In the boiler described in the present invention, 2-5 secondary air ducts 5 are arranged in sequence from top to bottom on one side wall of the lower furnace 9, specifically, for example, 2, 3, 4 or 5. In a preferred case, the secondary air ducts 5 are arranged in a counter-arrangement on the front and rear side walls of the lower furnace 9. In this article, the counter-arrangement refers to a symmetrical arrangement. In a more preferred case, the nozzle of the secondary air duct 5 can swing up and down, and the flame fullness in the lower furnace 9 and the smoke temperature at the furnace outlet can be controlled by adjusting the nozzle swing angle of the secondary air duct 5 according to the actual coal quality entering the furnace. Specifically, the angle of the nozzle of the secondary air duct 5 swinging up and down is ±15°, for example, it can swing upward by 5°, 10° or 15°, or it can swing downward by 5°, 10° or 15°.
[0045] In the boiler of the present invention, the graded burnout air duct 6 is arranged on the front and rear side walls of the upper furnace 8 in a counter-positioned manner, and the residual burnout air is timely supplied to the upper furnace 8 through the graded burnout air duct 6 to ensure that the pulverized coal is burnt out. In a preferred embodiment, the graded burnout air duct 6 is provided with multiple layers of nozzles on the side walls of the upper furnace 8, and the graded burnout air is sent into the upper furnace 8 through multiple nozzles, so that the coal sample entering the furnace is burned in the furnace body within the overall excess air coefficient range of 1.05-1.15, and the pulverized coal is burnt out.
[0046] In the boiler described in the present invention, the light-phase coal powder exhaust air nozzle 7 is arranged on the front and rear side walls of the upper furnace 8 in opposite directions, and is at a certain distance below the graded burnout air duct 6 arranged on both sides of the front and rear walls of the upper furnace 8. This can ensure that the exhaust air is in a reducing atmosphere. On the one hand, it further supplements the oxygen required for the combustion of coal powder in the lower furnace 9 (the excess air coefficient of the lower furnace is controlled at 0.8 or below); on the other hand, the high-temperature flame ensures the rapid combustion and burnout of coal powder in the exhaust air. Preferably, the light-phase coal powder exhaust air nozzle 7 can swing up and down. In a more preferred case, the angle of the light-phase coal powder exhaust air nozzle 7 swinging up and down is ±15°, for example, it can swing upward by 5°, 10° or 15°, or it can swing downward by 5°, 10° or 15°.
[0047] In the boiler described in the present invention, the angle between the center line of the cyclone preburner 3 and the wall of the furnace arch 10 is 80-90° (the angle can be adjusted according to the burnout characteristics of the coal, thereby adjusting the residence time of the coal powder airflow in the furnace). Specifically, it can be 80°, 85° or 90°, for example.
[0048] The second aspect of the present invention proposes a combustion method for a W-flame boiler, which is implemented in the boiler described above, and comprises: firstly, the primary air pulverized coal airflow is input into the pulverized coal separator 2 through the primary air pulverized coal airflow inlet 1 for separation, and the separated dense phase pulverized coal enters the cyclone preburner 3 through the dense phase pulverized coal nozzle 21, and at the same time, the secondary air I is tangentially transported to the cyclone preburner 3 through the secondary air inlet 4, so that the swirl direction of the secondary air I is consistent with the swirl direction of the dense phase pulverized coal entering the cyclone preburner 3, so that the dense phase pulverized coal is swirl-flowed downward and burned; the secondary air II is transported to the lower furnace 9 through the secondary air duct 5, so that the pulverized coal that has not been burned out in the cyclone preburner 3 is burned under a reducing atmosphere; the separated light phase pulverized coal is transported to the upper furnace 8 through the light phase pulverized coal exhaust air nozzle 7, and at the same time, graded burnout air is transported to the upper furnace 8 through the graded burnout air duct 6 to burn the light phase pulverized coal.
[0049] In the method of the present invention, the primary air pulverized coal airflow is produced by the coal mill during the operation of the unit boiler. During the actual operation of the boiler, the primary air pulverized coal airflow is first input into the pulverized coal separator 2 through the primary air pulverized coal airflow inlet 1 for separation, and dense phase pulverized coal and light phase pulverized coal are separated, and the dense phase pulverized coal and the light phase pulverized coal are discharged through the dense phase pulverized coal nozzle 21 and the light phase pulverized coal exhaust air nozzle 7 provided on the main body of the pulverized coal separator 2, respectively. In a preferred case, the flow rate of the dense phase pulverized coal sprayed from the dense phase pulverized coal nozzle 21 can be 15-25m / s, specifically, for example, 15m / s, 20m / s or 25m / s, and the flow rate of the light phase pulverized coal exhaust air sprayed from the light phase pulverized coal exhaust air nozzle 7 can be 20-50m / s, specifically, for example, 20m / s, 30m / s, 40m / s or 50m / s.
[0050] In the method of the present invention, since the swirl direction of the secondary air I is consistent with the swirl direction of the dense phase coal powder entering the cyclone preburner 3, the dense phase coal powder is swirl-burned downward, and the high-temperature flue gas of the lower furnace 9 is sucked to form a stable heat source near the primary air nozzle of the cyclone preburner 3 for heating the dense phase coal powder airflow, and since the space of the cyclone preburner 3 is very small compared to the space of the lower furnace 9, the cold radiation of the lower furnace 9 to the coal powder airflow flame can be greatly reduced, and since the cyclone preburner 3 has a higher temperature (1200-1400°C), it can ensure that the coal powder airflow can achieve stable combustion at a lower local excess air coefficient (0.6-0.75). In a preferred case, the excess air coefficient of the coal powder airflow in the cyclone preburner 3 is 0.45-0.65, and the excess air coefficient in the lower furnace 9 is ≤0.8.
[0051] In the method of the present invention, in order to increase the swirl intensity of the pulverized coal airflow in the cyclone preburner 3, and to increase the residence time of the pulverized coal airflow in the cyclone preburner 3 and to strengthen the combustion, the flow rate of the secondary air I entering the cyclone preburner 3 is controlled to be 50-80 m / s, specifically, for example, 50 m / s, 60 m / s, 70 m / s or 80 m / s. In a preferred case, the flow rate of the secondary air II entering the lower furnace 9 should be controlled to be 20-50 m / s, specifically, for example, 20 m / s, 30 m / s, 40 m / s or 50 m / s. In a more preferred case, the flow rate of the graded burnout air entering the upper furnace 8 should be controlled to be 40-60 m / s, for example, 40 m / s, 50 m / s or 60 m / s.
[0052] In the method of the present invention, in order to improve the nitrogen reduction effect in the furnace, the initial combustion oxygen amount is reduced under the condition of ensuring stable combustion, and the air volume in the cyclone preburner 3 accounts for 10-15% of the total air volume in the furnace body. Specifically, it can be 10%, 12% or 15%, for example.
[0053] In the method of the present invention, the total air volume of the secondary air I and the secondary air II accounts for 45-60% of the total air volume in the furnace body, specifically, for example, it can be 45%, 50%, 55% or 60%.
[0054] In the method of the present invention, the volume of the staged burnout air accounts for 25-35% of the total air volume in the furnace body, specifically, for example, it may be 25%, 30% or 35%.
[0055] In the method of the present invention, the total air volume of the secondary air I, secondary air II, graded overburnt air and light-phase coal powder exhaust air is 100%, and the total air volume of the graded overburnt air and light-phase coal powder exhaust air is 25-45%, specifically, for example, it can be 25%, 30%, 35%, 40% or 45%.
[0056] In the actual operation process of the present invention, the primary air pulverized coal airflow produced by the pulverizer during the normal operation of the unit boiler is first input into the pulverized coal separator 2 through the primary air pulverized coal airflow inlet 1 for separation, and dense phase pulverized coal and light phase pulverized coal are separated. The separated dense phase pulverized coal enters the cyclone preburner 3 through the dense phase pulverized coal nozzle 21, and at the same time, the secondary air I is tangentially transported to the cyclone preburner 3 through the secondary air inlet 4, so that the swirl direction of the secondary air I is consistent with the swirl direction of the dense phase pulverized coal entering the cyclone preburner 3, so that the dense phase pulverized coal is swirl-flowed downward and burns, and sucks in the high temperature in the lower furnace 9. The flue gas forms a stable heat source near the dense phase coal powder nozzle 21 for heating the dense phase coal powder airflow, and the unburned dense coal powder continues to be transported downward to the lower furnace 9, and the secondary air II is input into the lower furnace 9 through the secondary air duct 5, so as to organize the coal powder airflow to burn in a certain reducing atmosphere in the lower furnace 9, thereby suppressing the formation of NOx; the separated light phase coal powder is transported to the upper furnace 8 through the light phase coal powder exhaust air nozzle 7, and at the same time, the graded burnout air is transported to the upper furnace 8 through the graded burnout air duct 6 arranged above the light phase coal powder exhaust air nozzle 7 to ensure the burnout of the coal powder.
[0057] The following examples further illustrate the W-flame boiler and the combustion method of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.
[0058] The experimental methods in the following examples, unless otherwise specified, are conventional methods in the art.
[0059] The embodiments and comparative examples were all implemented in the following W-flame boiler: Figure 1 As shown, the boiler includes a furnace body, a pulverized coal separator 2, a cyclone preburner 3 with swirl blades inside, a secondary air duct 5 and a graded burnout air duct 6, and the furnace body includes an upper furnace 8, a lower furnace 9 and furnace arches 10 on both sides of the front and rear walls; the main body of the pulverized coal separator 2 is respectively provided with a primary air pulverized coal airflow inlet 1, a dense phase pulverized coal nozzle 21 with swirl blades at the front end and a light phase pulverized coal exhaust air nozzle 7; a group of cyclone preburners 3 are symmetrically arranged on the furnace arches 10 on both sides of the front and rear walls, the center line of the cyclone preburner 3 and the wall of the furnace arch 10 are at an angle of 90°, and the cyclone preburner 3 is connected with the dense phase pulverized coal nozzle 21 of the pulverized coal separator 2; the cyclone preburner 3 is provided with a secondary air inlet 4, and the secondary air enters the cyclone tangentially through the secondary air inlet 4 The cyclone preburner 3 has a swirl direction of the secondary air that is consistent with the swirl direction of the dense-phase coal powder entering the cyclone preburner 3; the graded burnout air duct 6 and the light-phase coal powder exhaust air nozzle 7 of the coal powder separator 2 are arranged on the side wall of the upper furnace 8 from top to bottom in sequence, and the light-phase coal powder exhaust air nozzle 7 is arranged on the front and rear side walls of the upper furnace 8 in opposite directions, and the light-phase coal powder exhaust air nozzle 7 can swing up and down by 5°; the graded burnout air duct 6 is arranged on the front and rear side walls of the upper furnace 8 in opposite directions, and the graded burnout air duct 6 is provided with 3 layers of nozzles; 2 secondary air ducts 5 are arranged on the side wall of the lower furnace 9 in sequence from top to bottom, and the secondary air duct 5 is arranged on the front and rear side walls of the lower furnace 9 in opposite directions, and the nozzle of the secondary air duct 5 can swing up and down by 10°.
[0060] Example 1
[0061] In this embodiment, the primary air pulverized coal airflow produced by the pulverizer during the normal operation of the unit boiler is firstly input into the pulverized coal separator 2 through the primary air pulverized coal airflow inlet 1 for separation, and dense phase pulverized coal and light phase pulverized coal are separated. The separated dense phase pulverized coal enters the cyclone preburner 3 through the dense phase pulverized coal nozzle 21 at a flow rate of 15 m / s. At the same time, the secondary air I with a flow rate of 60 m / s is tangentially transported to the cyclone preburner 3 through the secondary air inlet 4, so that the swirl direction of the secondary air I is consistent with the swirl direction of the dense phase pulverized coal entering the cyclone preburner 3, so that the dense phase pulverized coal forms a cyclone combustion in the precombustion chamber of the cyclone preburner 3, and the high-temperature flue gas in the lower furnace 9 is sucked in near the dense phase pulverized coal nozzle 21 to form a stable heat source for heating the dense phase pulverized coal airflow. The excess air coefficient of the pulverized coal airflow in the cyclone preburner 3 is 0. 55; the unburned concentrated pulverized coal continues to be transported downward to the lower furnace 9, and the secondary air II with a flow rate of 50m / s is input into the lower furnace 9 through the secondary air duct 5, so as to organize the pulverized coal airflow to burn in a certain reducing atmosphere in the lower furnace 9, so as to suppress the formation of NOx, and the excess air coefficient in the lower furnace 9 is 0.75; the separated light-phase pulverized coal is transported to the upper furnace 8 through the light-phase pulverized coal exhaust air nozzle 7 with a flow rate of 50m / s, and at the same time, the graded burnout air with a flow rate of 50m / s is transported to the upper furnace 8 through the graded burnout air duct 6 arranged above the light-phase pulverized coal exhaust air nozzle 7, wherein the total air volume of the secondary air I, secondary air II, graded burnout air and light-phase pulverized coal exhaust air is 100%, and the air volume of the light-phase pulverized coal exhaust air and graded burnout air is 30% of the total air volume, so as to ensure the burnout of the pulverized coal. According to the test, the NOx emission concentration at the boiler outlet can be controlled at 400mg / Nm 3 Within.
[0062] Example 2
[0063] The implementation is carried out in the manner of Example 1, except that the light phase coal powder exhaust air nozzle 7 can swing up and down by 15°, the nozzle of the secondary air duct 5 can swing up and down by 5°, and the angle between the center line of the cyclone preburner 3 and the wall surface of the furnace arch 10 is 80°. It is known from the test that the NOx emission concentration at the boiler outlet can be controlled at 400mg / Nm 3 Within.
[0064] Example 3
[0065] The method of Example 1 is used, except that the flow rate of the dense coal pulverized gas nozzle 21 is 25 m / s, the flow rate of the secondary air I is 80 m / s, the flow rate of the secondary air II is 20 m / s, the flow rate of the light coal pulverized gas exhaust air nozzle 7 is 20 m / s, and the flow rate of the graded burnout air is 40 m / s. It is found that the NOx emission concentration at the boiler outlet can be controlled at 400 mg / Nm 3 Within.
[0066] According to the results of Examples 1-3, the W-flame boiler of the present invention can be used to treat hard-to-burn coals such as anthracite and low-volatile lean coal, which can achieve stable combustion and complete combustion of pulverized coal, and can inhibit the generation of NOx, so that the NOx emission concentration at the boiler outlet can be controlled at 400 mg / Nm 3 Within.
[0067] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.
Claims
1. A W-flame boiler, characterized in that: The boiler comprises a furnace body, a pulverized coal separator (2), a cyclone preburner (3) having swirl blades therein, a light phase pulverized coal exhaust air nozzle (7) and a staged burnout air duct (6); the furnace body comprises an upper furnace (8), a lower furnace (9) and furnace arches (10) on both sides of the front and rear walls; The pulverized coal separator (2) is provided with a primary pulverized coal air flow inlet (1), and the light phase pulverized coal exhaust air nozzle (7) is connected to the pulverized coal separator (2); The cyclone preburners (3) are symmetrically arranged on the furnace arches (10) on both sides of the front and rear walls, and the cyclone preburners (3) are connected to the dense phase coal powder nozzle (21) of the coal powder separator (2); The cyclone preburner (3) is provided with a secondary air inlet (4), and the secondary air enters the cyclone preburner (3) tangentially through the secondary air inlet (4), and the swirl direction of the secondary air is consistent with the swirl direction of the dense phase coal powder entering the cyclone preburner (3); The staged burnout air duct (6) and the light-phase pulverized coal exhaust air nozzle (7) are sequentially arranged on the side wall of the upper furnace (8) from top to bottom, and extend into the upper furnace (8); A plurality of secondary air ducts (5) are arranged on the side wall of the lower furnace (9), and the nozzles of the secondary air ducts (5) extend into the lower furnace (9).
2. The W-flame boiler according to claim 1, characterized in that: The front end of the dense-phase pulverized coal nozzle (21) is provided with a swirl blade.
3. The W-flame boiler according to claim 1 or 2, characterized in that: The secondary air duct (5) is arranged on the front and rear side walls of the lower furnace (9) in a counter-positioned manner; Preferably, the nozzle of the secondary air duct (5) can swing up and down; Preferably, the up and down swing angle is ±15°.
4. The W-flame boiler according to claim 3, characterized in that: 2 to 5 secondary air ducts (5) are arranged in sequence from top to bottom on one side of the lower furnace (9).
5. The W-flame boiler according to claim 1 or 4, characterized in that: The light-phase pulverized coal exhaust gas nozzles (7) are arranged on the front and rear side walls of the upper furnace (8) in a counter-positioned manner; Preferably, the light phase coal powder exhaust gas nozzle (7) can swing up and down; Preferably, the up and down swing angle is ±15°.
6. The W-flame boiler according to claim 5, characterized in that: The staged burnout air ducts (6) are arranged on the front and rear side walls of the upper furnace (8) in a counter-positioned manner; Preferably, the staged burnout air duct (6) is provided with multiple layers of nozzles on the walls on both sides of the upper furnace (8).
7. The W-flame boiler according to claim 1 or 6, characterized in that: The included angle between the center line of the cyclone preburner (3) and the wall surface of the furnace arch (10) is 80-90°.
8. A combustion method for a W-flame boiler, the method being implemented in the boiler according to any one of claims 1 to 7, characterized in that: The method includes: The primary air pulverized coal airflow is input into the pulverized coal separator (2) through the primary air pulverized coal airflow inlet (1) for separation, and the separated dense phase pulverized coal enters the cyclone preburner (3) through the dense phase pulverized coal nozzle (21). At the same time, the secondary air I is tangentially transported to the cyclone preburner (3) through the secondary air inlet (4), so that the swirl direction of the secondary air I is consistent with the swirl direction of the dense phase pulverized coal entering the cyclone preburner (3), so that the dense phase pulverized coal is swirl-flowed downward and burned; The secondary air II is transported to the lower furnace (9) through the secondary air duct (5), so that the unburned coal powder in the cyclone preburner (3) is burned in a reducing atmosphere; The light-phase coal powder exhaust air separated by the coal powder separator (2) is transported to the upper furnace (8) through the light-phase coal powder exhaust air nozzle (7), and at the same time, graded burnout air is transported to the upper furnace (8) through the graded burnout air duct (6) to burn out the light-phase coal powder.
9. The method according to claim 8, characterized in that The excess air coefficient in the cyclone preburner (3) is 0.45-0.65; Preferably, the excess air coefficient in the lower furnace (9) is ≤0.
8.
10. The method according to claim 8 or 9, characterized in that: The flow rate of the dense phase coal powder is 15-25m / s, and the flow rate of the light phase coal powder exhaust air is 20-50m / s; Preferably, the flow rate of the secondary air I is 50-80 m / s; Preferably, the flow rate of the secondary air II is 20-50 m / s; Preferably, the flow rate of the graded overburnt air is 40-60 m / s.
11. The method according to claim 8 or 9, characterized in that: The air volume in the cyclone preburner (3) accounts for 10-15% of the total air volume in the furnace body; Preferably, the total air volume of the secondary air I and the secondary air II accounts for 45-60% of the total air volume in the furnace body; Preferably, the volume of the graded burnout air accounts for 25-35% of the total volume of air in the furnace body; Preferably, the total air volume of the secondary air I, secondary air II, graded overburnt air and light-phase coal powder exhaust air is 100%, and the total air volume of the graded overburnt air and light-phase coal powder exhaust air is 25-45%.