Low-load stable combustion device of pulverized coal fired boiler

Abstract

The invention discloses a low-load stable combustion device of a pulverized coal fired boiler, which relates to the field of combustors and comprises nozzles arranged at four corners of the pulverized coal fired boiler, the air inlet ends of the nozzles are connected with pulverized coal pipe elbows, and the air outlet ends of the nozzles are communicated with the interior of the pulverized coal fired boiler. And primary air carrying pulverized coal in the pulverized coal pipe elbow enters from the air inlet end of the nozzle and is discharged into the pulverized coal boiler from the air outlet end of the nozzle. According to the low-load stable combustion device for the pulverized coal fired boiler, primary air is shunted through cooperation of the concentration cover and the light phase groove, pulverized coal entering the gathering pipe can be concentrated under the cooperation effect of the air groove and the gathering cover, the content of the pulverized coal in airflow exhausted from the gathering pipe is higher, the flow speed is higher, and meanwhile under the cooperation of the electric heating strip, the combustion efficiency is improved. According to the pulverized coal boiler, the ignition point of pulverized coal entering the pulverized coal boiler from the gathering pipe is effectively reduced, the ignition point is advanced, the pulverized coal can be better ignited, low-concentration pulverized coal flowing around can be ignited, and therefore better stable combustion can be conducted on the pulverized coal boiler.

Description

Technical Field

[0001] The invention relates to burner technology, and in particular to a low-load stable combustion device for a pulverized coal boiler. Background Art

[0002] For coal-fired boiler systems, the stability of pulverized coal combustion during low-load operation and rapid load changes is the main factor restricting the flexibility of thermal power units. At present, the implementation of the combustion system design scheme based on flexibility transformation can reduce the unit output to a certain extent under certain conditions. However, at lower loads (such as less than 30% of the rated load), the change in coal combustion characteristics will cause delayed pulverized coal ignition and unstable combustion.

[0003] Typical direct current pulverized coal combustion devices include two types: dense-lean separation combustion and uniform surface combustion. Among them, dense-lean separation is further divided into horizontal dense-lean separation and vertical dense-lean separation combustion. Both dense-lean separations rely on efficient concentration devices to achieve, and it is necessary to reasonably control the concentration ratio of the primary air-powder mixture at the outlet of the combustion device to meet the requirements of stable combustion and nitrogen reduction. However, traditional direct current pulverized coal dense-lean separation devices, such as shutters, have weak pulverized coal concentration capacity at the outlet of the combustion device, poor dense-lean separation effect, and are limited by the space of the project site. The pulverized coal pipeline of the combustion device has various turning forms, which affects the uniform distribution of the air-powder airflow entering the shutter concentration device, and will further reduce the concentration effect. In this way, under the ultra-low load condition of the boiler (the number of coal mills in operation is the least), the stable combustion capacity of a single pulverized coal combustion device is insufficient, resulting in unstable combustion in the furnace, which in turn undermines the safe and stable operation of the unit.

[0004] With the increasingly urgent demand for low-nitrogen and deep peak-shaving of pulverized coal boilers in the industry, the existing structure of pulverized coal combustion devices and their monitoring equipment are difficult to achieve flexible deep peak-shaving. Therefore, it is urgent to optimize the design of the burner to solve the problem of insufficient ultra-low load stable combustion capacity of pulverized coal combustion devices. Summary of the invention

[0005] The object of the present invention is to provide a low-load stable combustion device for a pulverized coal boiler to solve the above-mentioned deficiencies in the prior art.

[0006] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions: a low-load stable combustion device for a pulverized coal boiler, used for a pulverized coal boiler, comprising nozzles arranged at the four corners of the pulverized coal boiler, the air inlet end of the nozzle is connected to a pulverized coal pipe elbow, the air outlet end of the nozzle is connected to the inside of the pulverized coal boiler, the primary air entrained with pulverized coal in the pulverized coal pipe elbow enters from the air inlet end of the nozzle and is discharged from its air outlet end into the inside of the pulverized coal boiler, a converging pipe is arranged on one side of the nozzle near the air outlet end, a plurality of partitions are fixedly connected in an annular shape and equidistantly between the outer side surface of the converging pipe and the inner wall of the nozzle, and a plurality of groups of diffusion grooves are formed between two adjacent partitions and the inner wall of the nozzle;

[0007] A converging hood is fixedly connected to the converging pipe on the side close to the air inlet end, and the converging hood is in the shape of a truncated cone, and the diameter of the end of the converging hood close to the air inlet end is greater than the diameter of the end close to the air outlet end. A concentrating hood is fixedly connected to the converging hood on the side close to the air inlet end, and the shape of the concentrating hood is in the shape of a truncated cone, and the diameter of the end of the concentrating hood close to the air inlet end is greater than the diameter of the end close to the air outlet end. A plurality of air grooves are provided on the surface of the concentrating hood, and the aperture value of the air grooves is smaller than the particle size value of the coal powder. A light phase cavity is formed between the converging hood and the inner wall of the nozzle.

[0008] Furthermore, the diameter of the converging tube is 2 / 5 of the inner diameter of the nozzle, the inner diameter of the converging tube is 1 / 3 of the inner diameter of the end of the converging hood close to the air inlet end, and the inner diameter of the end of the concentrating hood close to the air inlet end is 3 / 4 of the inner diameter of the nozzle.

[0009] Furthermore, all diffusion slots are connected to the light phase cavity.

[0010] Furthermore, a spirally arranged electric heating strip is embedded in the inner wall of the converging tube.

[0011] Furthermore, an annular sleeve is fixedly connected to the outside of the nozzle, an annular groove is provided inside the annular sleeve near the nozzle air outlet end, a plurality of transfer grooves are equidistantly provided inside the annular sleeve in a circular shape, an installation cavity is provided inside the annular sleeve near the nozzle air inlet end, an air guide pipe is fixedly installed inside the installation cavity, a control valve is installed on the outside of the air guide pipe, a first connecting groove is provided between the annular groove and the transfer groove, two connecting boxes are symmetrically fixedly connected to the side of the annular sleeve near the nozzle air outlet end, negative suction grooves are provided on the sides of the two connecting boxes away from each other, and a second connecting groove is provided between the connecting box and the annular groove.

[0012] Furthermore, the number of the air guide pipes is consistent with the transfer tank, and two ends of the air guide pipes are respectively connected to the transfer tank and the inside of the nozzle.

[0013] Furthermore, a deflector is fixedly installed on one side of the inner wall of the nozzle close to the air inlet end, and the deflector includes a connecting section, an outward expansion section and a deflector section, and the connecting section, the outward expansion section and the deflector section are arranged in sequence along the flow direction of the primary air.

[0014] Furthermore, the positions of the connecting section and the outward expansion section correspond to the positions of the connecting points between the air guide pipe and the inside of the nozzle.

[0015] Furthermore, the shape of the outward expansion section is a truncated cone, and the diameter of the end portion of the outward expansion section close to the air inlet end is smaller than the diameter of the end portion close to the air outlet end.

[0016] Furthermore, the inner diameter of the guide section is greater than the outer diameter of the concentration hood on the side close to the air inlet end.

[0017] Compared with the prior art, the low-load stable combustion device for a pulverized coal boiler provided by the present invention has the following features:

[0018] Beneficial effects:

[0019] 1. The low-load stable combustion device for the pulverized coal boiler diverts the primary air through the cooperation of the concentration hood and the light phase slot, and with the cooperation of the gas slot and the converging hood, the pulverized coal entering the converging pipe can be concentrated, so that the pulverized coal content in the airflow discharged from the converging pipe is higher and the flow rate is faster. At the same time, with the cooperation of the electric heating strip, the ignition point of the pulverized coal entering the pulverized coal boiler at the converging pipe is effectively reduced, and the ignition point is advanced, so that the low-concentration pulverized coal flowing around can be better ignited, thereby achieving better stable combustion of the pulverized coal boiler.

[0020] 2. The low-load stable combustion device of the pulverized coal boiler, through the mutual cooperation between the guide cover and the control valve, can negatively suck part of the high-temperature gas in the pulverized coal boiler when the pulverized coal boiler is in a high-temperature operation state, so that it enters the nozzle to preheat the primary air. When the pulverized coal boiler is in a low-load operation state, part of the high-temperature gas in the pulverized coal boiler is no longer negatively sucked, so that the stable combustion effect of the pulverized coal boiler is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0022] Figure 1 A schematic diagram of the overall layout structure of the nozzle and pulverized coal boiler provided in an embodiment of the present invention;

[0023] Figure 2A schematic diagram of the primary air flow state inside the nozzle provided by an embodiment of the present invention;

[0024] Figure 3 The embodiment of the present invention provides Figure 2 The enlarged structural diagram at A in the middle;

[0025] Figure 4 A schematic diagram of the three-dimensional structure of a nozzle and an annular sleeve provided in an embodiment of the present invention;

[0026] Figure 5 A schematic diagram of the internal structure of the nozzle and the annular sleeve provided in an embodiment of the present invention.

[0027] Description of reference numerals:

[0028] 1. Pulverized coal boiler; 2. Nozzle; 3. Pulverized coal pipe elbow; 4. Converging pipe; 41. Partition; 42. Diffusion groove; 5. Converging cover; 51. Concentrating cover; 52. Gas groove; 53. Light phase cavity; 54. Electric heating strip; 6. Annular sleeve; 61. Annular groove; 62. Transfer groove; 63. Installation cavity; 64. Air guide pipe; 65. Control valve; 66. First connecting groove; 67. Connecting box; 68. Negative suction groove; 69. Second connecting groove; 7. Flow guide cover; 71. Connecting section; 72. Outward expansion section; 73. Flow guide section. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Embodiment 1:

[0031] See also Figure 1-Figure 5 A low-load stable combustion device for a pulverized coal boiler is used for a pulverized coal boiler 1, comprising nozzles 2 arranged at four corners of the pulverized coal boiler 1, the air inlet end of the nozzle 2 is connected to a pulverized coal pipe elbow 3, the air outlet end of the nozzle 2 is connected to the inside of the pulverized coal boiler 1, the primary air entrained with pulverized coal in the pulverized coal pipe elbow 3 enters from the air inlet end of the nozzle 2 and is discharged from its air outlet end into the inside of the pulverized coal boiler 1, a converging pipe 4 is arranged on one side of the nozzle 2 near the air outlet end, a plurality of partitions 41 are fixedly connected to the outer side of the converging pipe 4 and the inner wall of the nozzle 2 in a circular shape with equal distances, and a plurality of groups of diffusion grooves 42 are formed between two adjacent partitions 41 and the inner wall of the nozzle 2;

[0032] A converging hood 5 is fixedly connected to the converging pipe 4 on the side close to the air inlet end. The converging hood 5 is in the shape of a truncated cone, and the diameter of the end of the converging hood 5 close to the air inlet end is greater than the diameter of the end close to the air outlet end. A concentrating hood 51 is fixedly connected to the converging hood 5 on the side close to the air inlet end. The concentrating hood 51 is in the shape of a truncated cone, and the diameter of the end of the concentrating hood 51 close to the air inlet end is greater than the diameter of the end close to the air outlet end. A plurality of air grooves 52 are provided on the surface of the concentrating hood 51. The aperture value of the air grooves 52 is smaller than the particle size value of the coal powder. A light phase cavity 53 is formed between the converging hood 5 and the inner wall of the nozzle 2.

[0033] In this embodiment, the diameter value of the converging tube 4 is 2 / 5 of the inner diameter value of the nozzle 2, the inner diameter value of the converging tube 4 is 1 / 3 of the inner diameter value of the end of the converging cover 5 close to the air inlet end, and the inner diameter value of the end of the concentration cover 51 close to the air inlet end is 3 / 4 of the inner diameter value of the nozzle 2.

[0034] It should be noted that the dimensional relationship between the above-mentioned converging pipe 4 and the nozzle 2, the dimensional relationship between the converging pipe 4 and the converging hood 5, and the dimensional relationship between the concentration hood 51 and the nozzle 2 are not fixed, and can be set during the production process according to the actual power of the pulverized coal boiler 1 and other conditions.

[0035] Through the above-mentioned arrangement, after the primary air enters the nozzle 2, in the initial stage, most of the airflow will enter the concentration hood 51, and the airflow entering the concentration hood 51 will significantly increase its flow rate after passing through the converging hood 5 and entering the converging tube 4, while the small amount of airflow entering the dilute phase cavity 53 will flow out from the multiple groups of diffusion grooves 42, and its flow rate will be reduced.

[0036] In this embodiment, all diffusion slots 42 are connected to the light phase cavity 53 .

[0037] In this embodiment, a spirally arranged electric heating strip 54 is embedded in the inner wall of the converging tube 4 .

[0038] like Figure 2 As shown, the primary air a containing coal powder that enters from the elbow 3 of the coal powder tank pipe will be split into a large airflow b and a small airflow c after entering the nozzle 2, wherein the large airflow a enters the converging cover 5 under the guiding effect of the concentrating cover 51, flows along the inside of the converging cover 5 to the converging pipe 4, and finally sprays out from the end of the converging pipe 4 to the coal powder boiler 1. During the flow of the large airflow b along the inside of the converging cover 5, its accommodating space gradually shrinks, so that its flow rate is accelerated, and finally it is discharged from the end of the converging pipe 4 to the inside of the coal powder boiler 1 at a higher flow rate, while the small airflow c will enter the light phase cavity 53 during the flow, and during the flow, its accommodating space gradually increases, so that its flow rate is lower, and finally it enters the coal powder boiler 1 from the ends of the plurality of diffusion slots 42 at a relatively slow flow rate;

[0039] During the flow of the large airflow b, the amount of pulverized coal it carries is greater than the amount of pulverized coal carried by the small airflow c. When entering the concentration hood 51, part of the airflow passes through the gas grooves 52 on the concentration hood 51 and flows into the light phase cavity 53, while the pulverized coal it carries cannot pass through the gas grooves 52 on the concentration hood 51. Therefore, under the entrainment of the large airflow b, it can continue to flow in the direction of the convergence hood 5, and gradually concentrate as the accommodating space gradually shrinks, so that the concentration when it is discharged from the end of the convergence pipe 4 to the inside of the pulverized coal boiler 1 is higher. In addition, when the large airflow b passes through the convergence pipe 4, it is preheated by the electric heating strip 54, so that the temperature when it enters the pulverized coal boiler 1 is higher, thereby effectively reducing its ignition heat, and can also make the ignition point of the large airflow b advanced, so as to provide a better stable combustion effect.

[0040] During the flow of the small airflow c, the amount of coal powder it carries is less than that carried by the large airflow b. When entering the light phase cavity 53, part of the large airflow b passes through the gas groove 52 and converges with the small airflow c in the light phase cavity 53, so that the coal powder concentration in the light phase cavity 53 is relatively low.

[0041] When the large airflow b is discharged from the end of the converging tube 4 at a higher flow rate, it is easier to ignite due to its lower ignition heat, and due to its higher flow rate, its overall air pressure is lower. Therefore, the low-speed small airflows c discharged from its surroundings will converge to the large airflow b. Due to the high temperature generated after the large airflow b is ignited, the small airflow c can be ignited well.

[0042] Embodiment 2:

[0043] See also Figure 2 , Figure 4-Figure 5 This embodiment provides a technical solution based on the above embodiment: an annular sleeve 6 is fixedly connected to the outside of the nozzle 2, an annular groove 61 is provided inside the annular sleeve 6 near the air outlet end of the nozzle 2, a plurality of transfer grooves 62 are equidistantly provided inside the annular sleeve 6 in a circular shape, a mounting cavity 63 is provided inside the annular sleeve 6 near the air inlet end of the nozzle 2, an air guide pipe 64 is fixedly installed inside the mounting cavity 63, a control valve 65 is installed outside the air guide pipe 64, a first connecting groove 66 is provided between the annular groove 61 and the transfer groove 62, two connecting boxes 67 are symmetrically fixedly connected to the side of the annular sleeve 6 near the air outlet end of the nozzle 2, negative suction grooves 68 are provided on the sides of the two connecting boxes 67 away from each other, and a second connecting groove 69 is provided between the connecting box 67 and the annular groove 61.

[0044] It should be noted that the negative suction groove 68 is arranged on the side away from each other of the two connecting boxes 67, so that the negative suction groove 68 faces the inner wall of the pulverized coal boiler 1, so as not to suck in the low-concentration pulverized coal flowing out of the diffusion groove 42, so that it will not interfere with the stable combustion operation of the pulverized coal boiler 1.

[0045] In this embodiment, the number of the air guide tubes 64 is the same as the transfer tank 62 , and two ends of the air guide tubes 64 are respectively connected to the transfer tank 62 and the inside of the nozzle 2 .

[0046] In this embodiment, a deflector 7 is fixedly installed on the inner wall of the nozzle 2 near the air inlet end. The deflector 7 includes a connecting section 71, an outward expansion section 72 and a deflector section 73. The connecting section 71, the outward expansion section 72 and the deflector section 73 are arranged in sequence along the flow direction of the primary air.

[0047] It should be added that the positions of the connecting section 71 and the expanding section 72 correspond to the positions of the connecting points between the air guide pipe 64 and the inside of the nozzle 2, so that the connecting section 71 and the expanding section 72 can block the connecting points between the air guide pipe 64 and the inside of the nozzle 2, thereby ensuring that the primary air flows normally to the air outlet end of the nozzle 2.

[0048] In addition, since the initial velocity of the primary air when entering the nozzle 2 is relatively high, when the control valve 65 is open, that is, when the air guide pipe 64 is connected to the inner cavity of the nozzle 2, under the shielding of the connecting section 71 and the outer expansion section 72, a relatively low pressure area is formed at m, and a relatively high pressure area is formed at n. Figure 2 As shown, the gas in the air duct 64 can pass through n and flow toward m. After the gas inside the air duct 64 is discharged, its interior is at a lower pressure than the interior of the pulverized coal boiler 1. Therefore, part of the high-temperature gas in the pulverized coal boiler 1 can pass through the negative suction groove 68, the annular groove 61 and the transfer groove 62 in turn to enter the air duct 64, and continue to supply high-temperature airflow to the interior of the nozzle 2.

[0049] In this embodiment, the shape of the outward expansion section 72 is a truncated cone, and the diameter value of the end of the outward expansion section 72 close to the air inlet end is smaller than the diameter value of the end close to the air outlet end, and the inner diameter value of the guide section 73 is larger than the outer diameter value of the concentration hood 51 close to the air inlet end, so that the primary air discharged from the outward expansion section 72 can diffuse normally to the outside and flow into the light phase cavity 53.

[0050] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A low-load stable combustion device for a pulverized coal boiler, used for a pulverized coal boiler (1), comprising nozzles (2) arranged at four corners of the pulverized coal boiler (1), the air inlet end of the nozzle (2) being connected to a pulverized coal pipe elbow (3), the air outlet end of the nozzle (2) being connected to the inside of the pulverized coal boiler (1), the primary air entrained with pulverized coal in the pulverized coal pipe elbow (3) entering from the air inlet end of the nozzle (2) and being discharged from the air outlet end thereof into the inside of the pulverized coal boiler (1), characterized in that: A converging tube (4) is arranged on one side of the nozzle (2) near the air outlet end, a plurality of partitions (41) are fixedly connected in an annular shape at equal intervals between the outer side surface of the converging tube (4) and the inner wall of the nozzle (2), and a plurality of groups of diffusion grooves (42) are formed between two adjacent partitions (41) and the inner wall of the nozzle (2); A converging hood (5) is fixedly connected to the converging pipe (4) on the side close to the air inlet end. The converging hood (5) is in the shape of a truncated cone, and the diameter of the end of the converging hood (5) on the side close to the air inlet end is greater than the diameter of the end of the end close to the air outlet end. A concentrating hood (51) is fixedly connected to the side close to the air inlet end. The concentrating hood (51) is in the shape of a truncated cone, and the diameter of the end of the concentrating hood (51) on the side close to the air inlet end is greater than the diameter of the end of the end close to the air outlet end. A plurality of air grooves (52) are provided on the surface of the concentrating hood (51). The aperture value of the air grooves (52) is smaller than the particle size value of the coal powder. A light phase cavity (53) is formed between the converging hood (5) and the inner wall of the nozzle (2).

2. A low-load stable combustion device for a pulverized coal boiler according to claim 1, characterized in that: The diameter of the converging tube (4) is 2 / 5 of the inner diameter of the nozzle (2), the inner diameter of the converging tube (4) is 1 / 3 of the inner diameter of the end of the converging hood (5) close to the air inlet end, and the inner diameter of the end of the concentrating hood (51) close to the air inlet end is 3 / 4 of the inner diameter of the nozzle (2).

3. A low-load stable combustion device for a pulverized coal boiler according to claim 2, characterized in that: All diffusion grooves (42) are connected to the light phase cavity (53).

4. A low-load stable combustion device for a pulverized coal boiler according to claim 3, characterized in that: The inner wall of the converging tube (4) is embedded with a spirally arranged electric heating strip (54).

5. A low-load stable combustion device for a pulverized coal boiler according to claim 4, characterized in that: The outside of the nozzle (2) is fixedly connected to an annular sleeve (6), an annular groove (61) is provided inside the annular sleeve (6) on a side close to the air outlet end of the nozzle (2), a plurality of transfer grooves (62) are provided inside the annular sleeve (6) at equal intervals in a circular ring shape, a mounting cavity (63) is provided inside the annular sleeve (6) on a side close to the air inlet end of the nozzle (2), an air guide pipe (64) is fixedly installed inside the mounting cavity (63), a control valve (65) is installed outside the air guide pipe (64), a first connecting groove (66) is provided between the annular groove (61) and the transfer groove (62), two connecting boxes (67) are symmetrically fixedly connected to the side of the annular sleeve (6) close to the air outlet end of the nozzle (2), negative suction grooves (68) are provided on the sides of the two connecting boxes (67) that are away from each other, and a second connecting groove (69) is provided between the connecting box (67) and the annular groove (61).

6. A low-load stable combustion device for a pulverized coal boiler according to claim 5, characterized in that: The number of the air guide pipes (64) is consistent with the transfer tank (62), and the two ends of the air guide pipes (64) are respectively connected to the transfer tank (62) and the inside of the nozzle (2).

7. A low-load stable combustion device for a pulverized coal boiler according to claim 6, characterized in that: A flow guide cover (7) is fixedly mounted on one side of the inner wall of the nozzle (2) close to the air inlet end, the flow guide cover (7) comprising a connecting section (71), an outward expansion section (72) and a flow guide section (73), the connecting section (71), the outward expansion section (72) and the flow guide section (73) being arranged in sequence along the flow direction of the primary air.

8. A low-load stable combustion device for a pulverized coal boiler according to claim 7, characterized in that: The positions of the connecting section (71) and the expanding section (72) correspond to the positions of the connecting points inside the air guide tube (64) and the nozzle (2).

9. A low-load stable combustion device for a pulverized coal boiler according to claim 8, characterized in that: The outward expansion section (72) is in the shape of a truncated cone, and the diameter of the end portion of the outward expansion section (72) close to the air inlet end is smaller than the diameter of the end portion close to the air outlet end.

10. A low-load stable combustion device for a pulverized coal boiler according to claim 9, characterized in that: The inner diameter of the flow guide section (73) is greater than the outer diameter of the concentration cover (51) on the side close to the air inlet end.

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