Water-cooled tubular flame low-NOx combustion structure suitable for tubular steam generator

Abstract

The embodiment of the invention provides a water-cooled tubular flame low-NOx combustion structure suitable for a tubular steam generator, and relates to the technical field of combustion equipment, the water-cooled tubular flame low-NOx combustion structure comprises a furnace body and a heat exchange unit arranged in the furnace body; each heat exchange unit comprises a plurality of heat exchange pipes which are uniformly arranged in an annular array, and heat exchange longitudinal fins are connected between the adjacent heat exchange pipes; a combustion chamber is formed between the outer side wall of the heat exchange unit and the inner side wall of the furnace body, and a smoke channel communicating with the combustion chamber is formed in the inner side of the heat exchange unit. An igniter, an air inlet and a gas inlet are arranged on the side wall of the furnace body; the air inlet and the gas inlet are communicated with the combustion chamber along the tangential direction of the inner side wall of the furnace body, so that tubular flame surrounding the heat exchange unit is formed in the combustion chamber, and the high-temperature area of the tubular flame is close to the heat exchange unit as much as possible by adjusting the diameter and the length of the tubular flame; the low-temperature heat exchange tube containing heat exchange media such as water inside directly cools the high-temperature area of the tubular flame, and the effect of greatly reducing NOx emission is achieved.

Description

Technical Field

[0001] This invention relates to the field of combustion equipment technology, and more specifically to a water-cooled tubular flame low-NOx combustion structure suitable for a cross-flow steam generator. Background Technology

[0002] Conventional once-through steam generators typically place the burner at the center of a circular once-through tank and surround the heat exchanger pipes around the burner. This results in the combustion flame being far from the heat exchanger pipes, so NOx emissions can only be reduced by adding EGR pipes or through complex structural designs. Furthermore, with this structure, the normal water volume of the steam generator is likely to exceed 30L, which is very unfavorable for the design and development of steam generators. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a water-cooled tubular flame low-NOx combustion structure suitable for cross-flow steam generators. A tubular flame is formed around the heat exchange unit. The diameter of the tubular flame can be controlled by adjusting the air and gas flow rates, so that the high-temperature region of the tubular flame is as close as possible to the annularly distributed heat exchange unit, thereby reducing the flame temperature and achieving the effect of reducing NOx emissions. Furthermore, since the burner is located around the cross-flow tank, no other units need to be installed inside the cross-flow tank, which allows for a significant reduction in the diameter and internal volume of the upper and lower headers. This structure is very suitable for the design and development of steam generator tanks with a normal water volume of less than 30L.

[0004] The water-cooled tubular flame low-NOx combustion structure for a once-through steam generator provided in this embodiment of the invention includes: A cylindrical furnace body, with an upper header and a lower header respectively provided at the upper and lower ends of the furnace body; A ring-shaped heat exchange unit is disposed inside the furnace body, and the height of the two is consistent. The heat exchange unit includes multiple heat exchange tubes, and the upper and lower ends of the heat exchange tubes are respectively connected to the upper header and the lower header. The multiple heat exchange tubes are evenly arranged in a ring array, and heat exchange longitudinal fins are connected between adjacent heat exchange tubes. The outer wall of the heat exchange unit is spaced apart from the inner wall of the furnace body to define a combustion chamber located between the two. A flue gas passage is formed on the inner side of the heat exchange unit. The lower end of the heat exchange longitudinal fins is provided with a through hole for connecting the combustion chamber and the flue gas passage. The top of the furnace body is provided with a flue gas outlet that communicates with the flue gas passage. The side wall of the furnace body is provided with an igniter connected to the combustion chamber and several sets of air inlets and gas inlets; the air inlets and the gas inlets are connected to the combustion chamber along the tangential direction of the inner side wall of the furnace body to form a tubular flame surrounding the heat exchange unit in the combustion chamber.

[0005] Optionally, the air inlet and the gas inlet respectively spray combustion air and combustion gas along the tangential direction of the inner sidewall of the furnace body, and the combustion air and combustion gas are mixed in the combustion chamber, so that a tubular unburned premixed gas layer is formed between the tubular flame and the inner sidewall of the furnace body.

[0006] Optionally, multiple sets of air inlets and / or gas inlets are provided at intervals along the height direction of the furnace body.

[0007] Optionally, the air inlet is connected to a fan or a wind box, and the wind box is provided with a baffle for adjusting the airflow.

[0008] Optionally, heat exchange fins are provided on both the inner and outer sides of the heat exchange tube.

[0009] Optionally, a flame monitoring device is provided on the side wall of the furnace body.

[0010] Optionally, refractory mortar is provided between the combustion chamber and the upper header, and between the combustion chamber and the lower header.

[0011] Optionally, the furnace body is provided with an external insulation layer on its outer side.

[0012] The embodiments of the present invention have the following beneficial effects: 1. The structure is compact, and the heat exchange tubes are evenly arranged in a ring array inside the furnace body, which makes the heating of each part uniform, the thermal stress average, and the fatigue damage problem is not easy to occur. 2. Tubular flames are easy to control, safe and reliable. The diameter and length of the tubular flame can be controlled by adjusting the flow rate of the gas and air. 3. A tubular flame is formed around the heat exchange unit. By adjusting the diameter and length of the tubular flame, the high-temperature area of ​​the tubular flame can be made as close as possible to the annularly distributed heat exchange unit. This allows the low-temperature heat exchange tube containing water or other heat exchange media inside to directly cool the high-temperature area of ​​the tubular flame (water-cooled combustion method), thus significantly reducing NOx emissions. 4. A tubular unburned premixed gas layer is formed between the tubular flame and the inner wall of the furnace body. This tubular unburned premixed gas layer can isolate the tubular flame from the furnace body, thereby preventing the inner lining plate of the furnace from being heated at high temperature and greatly extending the service life of the furnace body. 5. Multiple sets of air inlets and / or gas inlets are spaced apart along the height of the furnace body, which can form multi-stage and rich-lean combustion, further reducing NOx emissions; 6. Heat exchange fins are provided on both the inner and outer sides of the heat exchange tube, which can greatly improve the heat exchange performance of the heat exchange tube. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the external structure of an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of an embodiment of the present invention; Figure 3 This is a top sectional view of an embodiment of the present invention; Figure 4 This is a schematic diagram of the combustion state in an embodiment of the present invention. Figure 1 (face); Figure 5 This is a schematic diagram of the combustion state in an embodiment of the present invention. Figure 2 (View from above); The numbers in the diagram represent: 1. Furnace body; 2. Heat exchange tubes; 3. Heat exchange longitudinal fins; 4. Upper header; 5. Lower header; 6. Combustion chamber; 7. Flue gas passage; 8. Flue gas outlet; 9. Igniter; 10. Air inlet; 11. Gas inlet; 12. Tubular flame; 13. Tubular unburned premixed gas layer; 14. Flame monitoring device; 15. Refractory mortar; 16. External insulation layer. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0016] Please see Figures 1-3As shown, an embodiment of the present invention provides a water-cooled tubular flame low-NOx combustion structure suitable for a cross-flow steam generator, including a cylindrical furnace body 1 and an annular heat exchange unit disposed within the furnace body 1 and aligned with the height of the furnace body 1. The heat exchange unit includes multiple heat exchange tubes 2, which are evenly arranged in an annular array (single or multiple rows), and adjacent heat exchange tubes 2 are connected by heat exchange longitudinal fins 3. An upper header 4 and a lower header 5 are respectively provided at the upper and lower ends of the furnace body 1, and the upper and lower ends of each heat exchange tube 2 are connected to the upper header 4 and the lower header 5, respectively. The height of the upper header 4 can be maximized, and a steam-water separation baffle is installed within the upper header 4 to improve steam dryness.

[0017] The outer wall of the heat exchange unit is spaced apart from the inner wall of the furnace body 1 to define the combustion chamber 6 located between the two. Meanwhile, a flue gas passage 7 is formed on the inner side of the heat exchange unit. The lower end of the heat exchange longitudinal fins 3 is provided with a through hole for connecting the combustion chamber 6 and the flue gas passage 7. The top of the furnace body 1 is provided with a flue gas outlet 8 that communicates with the flue gas passage 7.

[0018] After the water and other heat exchange medium in the lower header 5 enter the heat exchange tube 2, they exchange heat with the high-temperature flue gas in the combustion chamber 6 through the outer wall of the heat exchange tube 2. The heat exchange medium that has been evaporated at high temperature rises into the upper header 4 for discharge to the user or for condensation and recycling. Meanwhile, if... Figure 4 As shown, the high-temperature flue gas, after heat exchange with the outer wall of the heat exchange tube 2, can flow through the through-hole at the lower end of the heat exchange longitudinal fin 3 to the flue gas channel 7 inside the heat exchange unit. After undergoing heat exchange again with the inner wall of the heat exchange tube 2 in the flue gas channel 7, it flows through the flue gas outlet 8 at the top of the furnace body 1 to the next heat exchange device (economizer, condenser, etc.). Furthermore, heat exchange transverse fins (not shown in the figure) can be installed on both the inner and outer sides of the heat exchange tube 2 to improve the heat exchange performance of the heat exchange tube 2.

[0019] An igniter 9, which connects to the combustion chamber 6, is provided on the side wall of the furnace body 1. Figures 1-3 Not shown, see Figure 4 The combustion chamber 6 includes several air inlets 10 and gas inlets 11. Ignition 9 is located downstream of air inlets 10 and gas inlets 11, and ignition gas can be directly branched from the main gas pipeline. The combustion air and combustion gas injected from air inlets 10 and gas inlets 11 will first mix in the combustion chamber 6 before being ignited by ignition 9.

[0020] Air inlet 10 and gas inlet 11 are tangentially connected to combustion chamber 6 along the inner wall of furnace body 1, allowing combustion air and combustion gas to be injected tangentially into combustion chamber 6 along the inner wall of furnace body 1. This results in a tubular flame 12 surrounding the heat exchange unit within combustion chamber 6 after ignition. Figure 4 , Figure 5As shown. The volumetric combustion rate (Q) of the tubular flame 12 is known. burning It can be obtained through formula Q. burning =πD f L f S u Therefore, the flame diameter D of the tubular flame 12 is calculated. f and flame length L f By changing the combustion rate S u To adjust accordingly. Simultaneously, the combustion speed S u It is also related to the excess air coefficient (equivalent ratio), flame length L f It is also related to the injection angle of the combustion air and combustion gas. Therefore, the required flame diameter and flame length under different load conditions can be obtained by changing the size, number, and injection angle of the air inlet 10 and the gas inlet 11. By adjusting the diameter and length of the tubular flame 12 so that the high-temperature region of the tubular flame 12 is as close as possible to the annularly distributed heat exchange unit, the low-temperature heat exchange tube 2 containing heat exchange medium such as water can directly cool the high-temperature region of the tubular flame 12 (water-cooled combustion method), thereby achieving a significant reduction in NOx emissions.

[0021] Meanwhile, by adjusting the injection speed of the combustion air and combustion gas, a tubular unburned premixed gas layer 13 can be formed between the tubular flame 12 and the inner wall of the furnace body 1. This tubular unburned premixed gas layer 13 isolates the tubular flame 12 from the furnace body 1, preventing the inner cladding plate of the furnace body 1 from being heated at high temperatures and significantly extending the life of the furnace body 1.

[0022] Furthermore, such as Figure 4 As shown, multiple sets of air inlets 10 and / or gas inlets 11 can be spaced along the height direction of the furnace body 1. By using different air-gas input ratios, multi-stage and rich-lean combustion can be formed along the height direction of the combustion chamber 6, thereby further reducing NOx emissions.

[0023] The air inlet 10 and the gas inlet 11 can be designed as rectangular or multi-row perforated shapes, and their size ratio and quantity can be adjusted according to the designed air-gas ratio. For example, in this embodiment of the invention, multiple sets of rectangular air inlets 10 and gas inlets 11 are evenly arranged along the circumference of the furnace body 1. The air inlet 10 can be directly connected to a blower or connected to a wind box, and the airflow can be controlled by the baffle inside the wind box.

[0024] Furthermore, such as Figure 4As shown, a flame monitoring device 14 can also be installed on the side wall of the furnace body 1 to observe the flame combustion in the combustion chamber 6. For reference, in this embodiment of the invention, flame monitoring devices 14 are respectively installed below the igniter 9 and on the other side of the furnace body 1 away from the igniter 9. The flame monitoring device 14 located below the igniter 9 can observe both the ignition flame and the tubular flame 12, while the flame monitoring device 14 located on the side away from the igniter 9 can only observe the tubular flame 12.

[0025] Furthermore, to extend the service life of the equipment, refractory mortar 15 can be installed between the combustion chamber 6 and the upper header 4, and between the combustion chamber 6 and the lower header 5; an external insulation layer 16 can be installed on the outside of the furnace body 1.

[0026] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of the present invention. Those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator, characterized in that, include: A cylindrical furnace body, with an upper header and a lower header respectively provided at the upper and lower ends of the furnace body; A ring-shaped heat exchange unit is disposed inside the furnace body, and the height of the two is consistent. The heat exchange unit includes multiple heat exchange tubes, and the upper and lower ends of the heat exchange tubes are respectively connected to the upper header and the lower header. The multiple heat exchange tubes are evenly arranged in a ring array, and heat exchange longitudinal fins are connected between adjacent heat exchange tubes. The outer wall of the heat exchange unit is spaced apart from the inner wall of the furnace body to define a combustion chamber located between the two. A flue gas passage is formed on the inner side of the heat exchange unit. The lower end of the heat exchange longitudinal fins is provided with a through hole for connecting the combustion chamber and the flue gas passage. The top of the furnace body is provided with a flue gas outlet that communicates with the flue gas passage. The side wall of the furnace body is provided with an igniter connected to the combustion chamber and several sets of air inlets and gas inlets; the air inlets and the gas inlets are connected to the combustion chamber along the tangential direction of the inner side wall of the furnace body to form a tubular flame surrounding the heat exchange unit in the combustion chamber.

2. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: The air inlet and the gas inlet respectively spray combustion air and combustion gas along the tangential direction of the inner sidewall of the furnace body. The combustion air and combustion gas are mixed in the combustion chamber, so that a tubular unburned premixed gas layer is formed between the tubular flame and the inner sidewall of the furnace body.

3. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: Multiple sets of air inlets and / or gas inlets are provided at intervals along the height direction of the furnace body.

4. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: The air inlet is connected to a fan or a wind box, and the wind box is equipped with a baffle for adjusting the airflow.

5. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: The heat exchange tube is provided with heat exchange fins on both its inner and outer sides.

6. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: A flame monitoring device is installed on the side wall of the furnace body.

7. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: Refractory mortar is provided between the combustion chamber and the upper header, and between the combustion chamber and the lower header.

8. The water-cooled tubular flame low-NOx combustion structure suitable for a once-through steam generator according to claim 1, characterized in that: The furnace body is provided with an external insulation layer on the outside.

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