Targeted air distribution system and corner tangential boiler comprising same

Abstract

The utility model relates to the field of boilers, in particular to a targeted air distribution system and a corner tangential boiler comprising the targeted air distribution system, and the targeted air distribution system of the corner tangential boiler comprises a secondary air annular air duct, a wall type secondary air isobaric air bellow and a wall type secondary air branch pipe, the secondary air annular air duct is horizontally arranged in the middle of the furnace body, four wall type secondary air isobaric air bellows are vertically arranged on the periphery of a furnace wall and communicated with the secondary air annular air duct, a plurality of wall type secondary air branch pipes are arranged on each wall type secondary air isobaric air bellows from top to bottom, and the wall type secondary air branch pipes are communicated with the wall type secondary air isobaric air bellows. A wall type secondary air nozzle is arranged at the tail end of the wall type secondary air branch pipe, and the included angle between the wall type secondary air nozzle and the furnace wall is 30-85 degrees. The targeted air distribution system can effectively prevent the problems of serious oxygen deficit of a hearth, high-temperature corrosion of a combustor area and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of tangentially-cornered boilers, and in particular to a targeted air distribution system applied to tangentially-cornered boilers and a tangentially-cornered boiler comprising the targeted air distribution system. Background Art

[0002] At present, the low-nitrogen combustion technology of coal-fired boilers usually adopts air staged combustion technology. By changing the boiler air distribution method, a part of the air is separated to the top of the burner as burnout air, forming a main burner area, a reduction area and a burnout area in the height direction of the furnace, inhibiting the generation of NOx during the combustion of pulverized coal and effectively reducing the NOx emission concentration at the furnace outlet.

[0003] Some existing coal-fired boilers have the following problems when operating at full load: (1) The oxygen content in the furnace is low, the differential pressure between the furnace and the secondary air is large, and air supply is difficult, resulting in long-term oxygen-deficient combustion in the boiler; (2) The boiler has poor adaptability to the sulfur content of coal. When the sulfur content is ≥1.0%, coking and coking frequently occur, causing the slag remover to stop working and the slag to be discharged; (3) Large-scale high-temperature corrosion is prone to occur between the main burner and the burnout air zone, and the wall thickness of the water-cooled wall tube is thinned to varying degrees.

[0004] In order to solve the above problems, it is necessary to deliver an appropriate amount of combustion-supporting air at a reasonable location to improve the effective utilization efficiency of the combustion-supporting air entering the furnace. To this end, a boiler targeted air distribution system is needed to achieve precise air distribution in different areas of the furnace and full coverage of the entire furnace. Utility Model Content

[0005] In order to achieve accurate air distribution in different areas of the furnace and full space coverage of the entire furnace, the utility model proposes a targeted air distribution system for a four-corner tangential boiler, which can effectively prevent problems such as severe oxygen deficiency in the furnace and high-temperature corrosion in the burner area.

[0006] In order to achieve the above-mentioned purpose, the utility model proposes a targeted air distribution system for a four-corner cut-circle boiler, comprising a secondary air annular duct, a wall-type secondary air isobaric wind box and a wall-type secondary air branch pipe, wherein the secondary air annular duct is horizontally arranged in the middle of the furnace body, and four wall-type secondary air isobaric wind boxes are vertically arranged around the furnace wall, respectively, the wall-type secondary air isobaric wind boxes are connected to the secondary air annular duct, and on each wall-type secondary air isobaric wind box, a plurality of wall-type secondary air branch pipes are respectively arranged from top to bottom, and a wall-type secondary air nozzle is arranged at the end of the wall-type secondary air branch pipe, and the angle between the wall-type secondary air nozzle and the furnace wall is 50-85° (for example, 55°, 60°, 65°, 70°, 75°, 80°, etc.).

[0007] Furthermore, the wall-type secondary air isobaric wind boxes are symmetrically distributed on the upper and lower sides of the secondary air annular air duct.

[0008] Furthermore, the wall-type secondary air nozzle is a convergent nozzle.

[0009] Furthermore, the number of layers of the wall-type secondary air nozzles is 4-5 layers.

[0010] Furthermore, the wall-type secondary air nozzles of each layer are evenly distributed in the horizontal direction at a distance of 1 / 4 of the side length from the corner.

[0011] Furthermore, an adjusting damper is provided at the inlet of the wall-type secondary air branch pipe.

[0012] Furthermore, the opening of the regulating damper is 20-100%, for example, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc.

[0013] Furthermore, the wall-type secondary air nozzles are evenly distributed between the B-layer burners and the separated overburnt air in the vertical direction.

[0014] Furthermore, the diameter of the tangential circle formed by the secondary air ejected from the wall-type secondary air nozzle is the same as the diameter of the tangential circle of the nearest burner.

[0015] Furthermore, the tangential circle formed by the secondary air ejected from the wall-type secondary air nozzle has the same direction as the tangential circle of the nearest burner, which is counterclockwise or clockwise.

[0016] Furthermore, the boiler targeted air distribution system also includes an angular secondary air isobaric wind box and an angular secondary air branch pipe. The angular secondary air isobaric wind box is arranged at the four corners of the furnace wall and is connected to the secondary air annular air duct. On each angular secondary air isobaric wind box, a plurality of angular secondary air branch pipes are respectively arranged from top to bottom, and an angular secondary air nozzle is arranged at the end of the angular secondary air branch pipe.

[0017] On the other hand, the utility model also provides a four-corner tangential boiler including the targeted air distribution system.

[0018] In general, compared with the prior art, the targeted air distribution system of the utility model has the following technical advantages:

[0019] The utility model adds a wall-type secondary air system to the four walls of the local area with severe high-temperature corrosion. The multi-layer wall-type secondary air is evenly distributed between the B-layer burner and the separated burnout air in the vertical direction. The wall-type secondary air nozzle is not perpendicular to the furnace wall, but forms an angle of 55-85° with the furnace wall. The formed tangential circle has the same diameter and direction as the tangential circle of the nearest burner, thereby effectively preventing problems such as severe lack of oxygen in the furnace and high-temperature corrosion in the burner area. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following drawings are only intended to illustrate and explain the present invention, and do not limit the scope of the present invention.

[0021] Figure 1 It is a three-dimensional schematic diagram of the targeted air distribution system according to an embodiment of the utility model;

[0022] Figure 2 It is a schematic diagram of the vertical distribution of the wall-type secondary air duct of the targeted air distribution system according to the embodiment of the utility model;

[0023] Figure 3 It is a schematic diagram of the plan layout of the wall-type secondary air nozzles of the targeted air distribution system according to the embodiment of the utility model;

[0024] Figure 4 It is a structural schematic diagram of a wall-type secondary air nozzle of a targeted air distribution system according to an embodiment of the utility model;

[0025] Figure 5 It is a furnace wall water-cooled wall pipe of the targeted air distribution system described in the embodiment of the utility model;

[0026] Figure 6 It is the regulating damper of the targeted air distribution system described in the embodiment of the utility model;

[0027] Description of reference numerals:

[0028] 1-annular air duct, 2-wall-type secondary air isobaric bellows, 3-wall-type secondary air branch pipe, 4-wall-type secondary air nozzle, 5-water-cooled wall pipe, 6-adjusting damper, 7-angle-type secondary air isobaric bellows, 8-angle-type secondary air branch pipe. DETAILED DESCRIPTION

[0029] The utility model is further described below in conjunction with the embodiments. The description of the following embodiments is only used to help understand the utility model. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

[0030] In the specification of the present utility model, when "an embodiment" is mentioned, it means that the specific features, structures or parameters, steps, etc. described in the embodiment are at least included in one embodiment according to the present utility model. Therefore, in the specification of the present utility model, if terms such as "according to an embodiment of the present utility model" or "in one embodiment" are used, they are not used to specifically refer to the same embodiment, and if terms such as "in another embodiment", "according to different embodiments of the present utility model", or "according to another embodiment of the present utility model" are used, they are not used to specifically refer to that the mentioned features can only be included in specific different embodiments. It should be understood by those skilled in the art that the specific features, structures or parameters, steps, etc. disclosed in one or more embodiments of the present utility model specification can be combined in any suitable manner.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the embodiment of the utility model, the boiler type is a subcritical, single reheat, natural circulation, coal-fired drum boiler, which adopts four-corner tangential combustion, swing burner temperature adjustment, solid slag removal, and balanced ventilation. The boiler is designed with the maximum continuous evaporation capacity (B-MCR) working condition, and the maximum continuous evaporation capacity is 1165t / h. The boiler is a single furnace "∏" type layout, tight-fitting closure, high-strength bolt connection, all-steel frame suspension structure, and the expansion zero point is set on the center line of the furnace depth and width, which is achieved by the guide devices installed in front of the furnace, behind the furnace, and on both sides.

[0033] The boiler adopts a single steam drum, and the feed water from the economizer is divided into three paths along the feed water distribution pipe and directly injected into the bottom of the steam drum, reducing the temperature difference between the inner and outer walls and the upper and lower walls of the steam drum.

[0034] The furnace is composed of membrane water-cooled walls and is divided into 28 water circulation loops. In order to improve the steam-water circulation conditions, internal threaded pipes are used in the middle and upper parts of the furnace.

[0035] The superheater system consists of a ceiling, a bypass superheater, a rear smoke shaft cover, a low-temperature superheater, a partition screen superheater, a rear screen superheater and a high-temperature superheater. Level I and II desuperheaters are provided at the partition screen and the high-temperature superheater inlet respectively.

[0036] The reheater system consists of a wall-type reheater, a screen-type reheater and a high-temperature reheater. Emergency water spray desuperheaters are installed on the pipes on both sides of the wall-type reheater inlet, and a micro-spray water desuperheater is installed between the screen-type reheater and the high-temperature reheater. In order to reduce fuel consumption during cold start, a bottom heating device is also provided.

[0037] The superheated steam temperature is mainly regulated by the I and II level water spray desuperheaters, with the I level used for rough adjustment and the II level used for fine adjustment. The I level desuperheating water should be used first in the adjustment. The reheated steam temperature is mainly regulated by the swing burner, and the wall re-inlet accident desuperheater is used as an accident condition. The micro-spray desuperheater between the screen reheater and the high-temperature reheater is used as a backup means of steam temperature regulation. During operation, the burner swing angle should be used first for adjustment to reduce the amount of reheater desuperheating water used to improve boiler efficiency.

[0038] The boiler adopts a four-corner burner arrangement, tangential combustion, forming two imaginary tangential circles of Ф713 and Ф928 in the center of the furnace. The burnout air burner nozzle swings ±30°, and there are 15 nozzles in total, including 10 secondary air and 5 primary air. The burner is divided into two groups, the upper and lower groups, and the nozzle arrangement from top to bottom is 2-2-1-2-2-1-2, 2-1-2-2-1-2-1-2, CC, EF and F layers secondary air reverse tangential 11 0 . The primary air is surrounded by perimeter winds, and the perimeter wind on the back side is more than twice that on the fire side. The pulverizing system is a positive pressure direct blowing type, equipped with five medium-speed pulverizers, burning the designed coal quality, 4 in operation and 1 in standby. The outlet of each pulverizer is connected to a layer of burners by four pulverized coal pipes (from bottom to top, they are A, B, C, D, and E). Three layers of mechanical atomization oil guns are arranged on the AA, BB, and DE layers, using a two-stage ignition method. A total of 12 oil guns are arranged in the entire furnace, with a single output of 1.2t / h and a total output of 14.4t / h for the oil system. The primary air burner on the A layer is equipped with a low-oil ignition device, which can effectively reduce the oil used for startup and low-load stable combustion. In order to increase the primary air temperature at the inlet of the pulverizer during cold startup of the boiler, a start-up oil gun is installed in the hot primary air duct at the outlet of the A air preheater. When the boiler burns the designed coal, the minimum stable combustion load without oil injection is not more than 35% B-MCR.

[0039] The air and smoke system consists of two three-compartment rotary air preheaters, two axial-flow induced and supplied air fans with adjustable moving blades, and two centrifugal primary fans with adjustable inlet guide vanes. In order to prevent low-temperature corrosion at the cold end of the air preheater, primary and secondary air heaters are also installed.

[0040] During operation, the wall-type secondary air nozzle is located in the high-temperature corrosion area of ​​the water-cooled wall, vertically located from the C-layer burner to the lower part of the SOFA air (separated overfire air), and horizontally located 1 / 4 of the distance from the corner area downstream of the burner. More combustion-supporting air is required when high-sulfur coal is mixed. After the boiler is transformed with low-nitrogen combustion technology, the oxygen-deficient combustion phenomenon in the main combustion area is aggravated, causing serious coking. In addition, the reducing gas content in this position is high, and unburned carbon particles flush the water-cooled wall, causing high-temperature corrosion. In order to solve the problems of severe oxygen deficiency in the furnace and high-temperature corrosion in the burner area, the utility model adds a wall-type secondary air system to the four walls of the area with severe high-temperature corrosion.

[0041] The utility model of the targeted air distribution system for boilers is used in conjunction with the annular wind box outside the furnace and the combustion-supporting air nozzle inside the furnace to achieve accurate air distribution in different areas of the furnace and full coverage of the entire furnace space. This air distribution system not only forms the main burner area, reduction area and burnout area in the furnace height direction like the traditional air staged combustion technology, but also further divides the entire furnace space into multiple functional areas, namely the high-temperature low-oxygen reduction area, the low-temperature high-oxygen high-efficiency area, and the high-temperature high-oxygen burnout area; the entire combustion process in the furnace is divided into multiple functional reaction vortices, thereby forming the integration of three major functions of efficient energy saving (Efficient), emission control (Emission control), and anti-slagging corrosion (Erosion resistance) in the furnace space and combustion chemical reaction process.

[0042] like Figure 1-6 As shown, the boiler targeted air distribution system of the utility model includes a secondary air annular duct 1, a wall-type secondary air isobaric wind box 2 and a wall-type secondary air branch pipe 3. The secondary air annular duct 1 is horizontally arranged in a ring shape in the middle of the furnace body, and four wall-type secondary air isobaric wind boxes 2 are arranged around the furnace wall. The wall-type secondary air isobaric wind boxes 2 are connected to the secondary air annular duct 1, and are perpendicular to the secondary air annular duct 1, and are symmetrically distributed on the upper and lower sides of the secondary air annular duct 1. On each wall-type secondary air isobaric wind box 2, a plurality of wall-type secondary air branch pipes 3 are arranged from top to bottom. A wall-type secondary air nozzle 4 is arranged at the end of the wall-type secondary air branch pipe 3, a water-cooled wall pipe 5 is arranged on the inner side of the furnace wall, and an adjusting damper 6 is arranged at the entrance of the wall-type secondary air branch pipe 3.

[0043] like Figure 4 As shown, the wall-type secondary air nozzle 4 is a tapered nozzle, which can increase the wall-type secondary air velocity to a higher level, so that it has sufficient momentum to carry away the carbon particles thrown by inertia, so that the carbon particles return to the main combustion area to re-ignite, and prevent the carbon particles from accumulating on the water-cooled wall to cause coking and high-temperature corrosion. At the same time, the high wind speed has a protective effect on the nozzle, keeping the flame away from the nozzle to avoid burning.

[0044] The boiler targeted air distribution system also includes an angular secondary air isobaric wind box 7 and an angular secondary air branch pipe 8. The angular secondary air isobaric wind box 7 is arranged at the four corners of the furnace wall and is connected to the secondary air annular air duct 1. The angular secondary air isobaric wind box 7 is located below the secondary air annular air duct 1 and is perpendicular to the secondary air annular air duct 1. On each angular secondary air isobaric wind box 7, a plurality of angular secondary air branch pipes 8 are arranged from top to bottom, and an angular secondary air nozzle is arranged at the end of the angular secondary air branch pipe 8.

[0045] like Figure 3 As shown, by adjusting the angle α between the center line of the wall-type secondary air nozzle 4 and the furnace wall, the jet direction of the wall-type combustion-supporting air can be changed to match the tangential combustion under different furnace types and different coal types, forming a reasonable low-temperature, high-oxygen and high-efficiency zone, and the range of α can be 50-85°.

[0046] The resistance distribution and air volume distribution between the angle-type secondary air isobaric bellows and between the wall-type secondary air isobaric bellows are consistent, with an error of less than 10%.

[0047] like Figure 1 and 2 As shown, according to an embodiment of the utility model, there are 5 layers of wall-type secondary air nozzles 4, which are evenly distributed in the height direction between the B-layer burner and the separated burnout air SOFA, with an interval of about 2m between each layer, and the wall-type secondary air nozzles 4 on the same layer are evenly distributed in the horizontal direction at 1 / 4 of the side length (the side length is the length of the furnace wall) from the corner, and the angle α1 between the wall-type secondary air nozzles 4 and the furnace wall is 80°. The secondary air ejected from the wall-type secondary air nozzles 4 forms an imaginary tangential circle in the furnace, and the imaginary tangential circle is consistent with the direction of the burner tangential circle (for example, both are counterclockwise or both are clockwise), and the diameter of the imaginary tangential circle is consistent with the nearest burner tangential circle, and the imaginary tangential circles of the 5 layers of secondary air increase successively from top to bottom.

[0048] During operation, the combustion-supporting air enters the wall-type secondary air isobaric wind box 2 and the wall-type secondary air branch pipe 3 from the secondary air annular air duct 1. An adjusting damper 6 is provided upstream of the wall-type secondary air nozzle 4. The air volume is adjusted by adjusting the damper 6. The opening of the adjusting damper 6 is adjusted to 0%, 20%, 40% and 60% respectively, and the changes in boiler parameters at each opening are recorded.

[0049] Table 1 Wall-type secondary air opening adjustment test record

[0050]

[0051] Table 2 Comparison of main parameters of boilers before and after adopting the targeted air distribution system of the utility model

[0052]

[0053]

[0054] It can be seen that after adopting the targeted air distribution system of the utility model, the oxygen content of the boiler operation is greatly improved, from 0.5% to more than 1.0%, the CO concentration in the boiler flue gas is greatly reduced, and the carbon content of the boiler fly ash and slag is reduced; the adaptability of the boiler coal type is significantly enhanced, and it can stably burn high-sulfur coal with SO2 of 2800-3000mg / Nm3 for a long time. The boiler shows no signs of coking, which can save a lot of coal procurement costs for the enterprise.

[0055] In addition, the NOX concentration in the boiler flue gas was reduced, and the ammonia consumption was reduced by 0.231t / day, which can save 76.23 tons of ammonia consumption per year. The differential pressure between the secondary wind box and the furnace was reduced from 1.2KPa to 0.8KPa, which increased the adjustment margin of the secondary air system. The cooling water volume was significantly reduced, and the cooling water volume of the reheater was reduced by about 10t / h.

[0056] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A targeted air distribution system for a tangential boiler, characterized in that: It includes a secondary air annular duct, a wall-type secondary air isobaric wind box and a wall-type secondary air branch pipe, wherein the secondary air annular duct is horizontally arranged in the middle of the furnace body, and 4 wall-type secondary air isobaric wind boxes are vertically arranged around the furnace wall respectively, the wall-type secondary air isobaric wind boxes are connected with the secondary air annular duct, and on each wall-type secondary air isobaric wind box, a plurality of wall-type secondary air branch pipes are respectively arranged from top to bottom, and a wall-type secondary air nozzle is arranged at the end of the wall-type secondary air branch pipe, and the angle between the wall-type secondary air nozzle and the furnace wall is 30-85°.

2. The targeted air distribution system according to claim 1, characterized in that: The wall-type secondary air nozzle is a convergent nozzle.

3. The targeted air distribution system according to claim 1, characterized in that: The number of layers of the wall-type secondary air nozzles is 4-5 layers.

4. The targeted air distribution system according to claim 1, characterized in that: The wall-type secondary air nozzles on each floor are evenly distributed in the horizontal direction at 1 / 4 of the side length from the corner.

5. The targeted air distribution system according to claim 1, characterized in that: The inlet of the wall-type secondary air branch pipe is provided with an adjusting damper.

6. The targeted air distribution system according to claim 5, characterized in that: The opening degree of the regulating air door is 20-100%.

7. The targeted air distribution system according to claim 1, characterized in that: The wall-type secondary air nozzles are evenly distributed between the B-layer burners and the separated overburnt air in the vertical direction.

8. The targeted air distribution system according to claim 1, characterized in that: The tangential circle formed by the secondary air ejected from the wall-type secondary air nozzle has the same diameter and direction as the tangential circle of the nearest burner.

9. The targeted air distribution system according to claim 1, characterized in that: The boiler targeted air distribution system also includes an angular secondary air isobaric wind box and an angular secondary air branch pipe. The angular secondary air isobaric wind box is arranged at the four corners of the furnace wall and is connected to the secondary air annular air duct. On each angular secondary air isobaric wind box, a plurality of angular secondary air branch pipes are respectively arranged from top to bottom, and an angular secondary air nozzle is arranged at the end of the angular secondary air branch pipe.

10. A square tangential boiler, characterized in that: It comprises the targeted air distribution system as described in any one of claims 1 to 9.

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