A low NOx self-preheating high-speed burner and its control method

Abstract

The present invention relates to a low NOx self-preheating high-speed burner and a control method thereof, and belongs to the field of burners. The burner changes the structural form of the ignition combustion chamber, and forms an outer air channel, an inner air channel, a secondary air channel and a primary air nozzle correspondingly, and the main gas ejection position is located in the front half of the contraction section of the ignition combustion chamber. The structure realizes the independent setting of the ignition gas circuit and the main gas circuit, wherein the ignition gas circuit is only used for ignition at medium and low temperatures, so that the burner has the function of adjusting the flow ratio of "ignition gas" and "main gas". The input ratio of the ignition gas is small, so the adiabatic combustion intensity in the ignition combustion chamber can be greatly reduced, thereby realizing the control of NOx; the output position of the main gas with a large proportion is in the front half of the contraction section of the ignition combustion chamber, which can effectively ensure that the gas is stably ignited at medium and low temperatures, and can also ensure that the gas does not burn in the ignition combustion chamber at high temperatures.

Description

Technical Field

[0001] The invention belongs to the field of burners, and in particular relates to a low NOx self-preheating high-speed burner and a control method thereof. Background Art

[0002] Self-preheating high-speed burners are widely used in metallurgical heat treatment furnaces. In order to produce high-speed flames, this type of burner usually produces a high-intensity combustion reaction in a small space to rapidly heat up and expand the gas volume, thereby achieving high-speed flame ejection. However, high-intensity combustion reactions in a small space usually have relatively high NOx emissions. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a low NOx self-preheating high-speed burner and a control method thereof, which can significantly reduce high-intensity combustion in a small space under medium and low temperature conditions, thereby achieving effective control of NOx emissions while ensuring the high-speed flame temperature; and completely avoid combustion in a small space under high temperature conditions, thereby achieving ultra-low NOx emissions.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A low NOx self-preheating high-speed burner, comprising a main gas channel, an ignition gas channel, an air channel and a smoke exhaust channel arranged in sequence from the inside to the outside; an ignition gas nozzle is arranged at the outlet end of the ignition gas channel, the main gas channel is inserted in the ignition gas channel and the gas outlet end of the main gas channel extends a distance outside the ignition gas nozzle, a preheater is arranged axially between the air channel and the smoke exhaust channel to separate the air channel and the smoke exhaust channel, and a guide plate closing in the direction of gas ejection is arranged on the tail end side of the preheater; an automatic igniter, an ignition air distribution plate and a partition are arranged in the air channel, wherein the ignition air distribution plate is arranged at the ignition gas channel, and the ignition gas distribution plate is arranged at the ignition gas channel. In front of the gas nozzle; the partition surrounds the ignition air distribution plate and the outside of the ignition gas nozzle to separate the ignition combustion chamber at the outlet end of the air channel; the partition has a tapered section that gradually closes in the direction of gas ejection, and the gas outlet end surface of the main gas channel extends to the tapered section of the partition; the inner wall surface of the partition is spaced from the outer peripheral surface of the ignition air distribution plate to form a secondary air channel for circulating air, and the outer wall surface of the partition is spaced from the inner wall surface of the preheater and the guide plate thereon to form an outer air channel for circulating air.

[0006] Furthermore, the tapered section of the partition is a truncated cone structure, and the angle α between the generatrix and the axis is 30° to 90°; the length of the tapered section of the partition is L, and the length of the gas outlet end face of the main gas channel extending into the tapered section is D, and the two satisfy: 0≤D≤0.5L.

[0007] Furthermore, the gap between the outer peripheral surface of the ignition gas nozzle and the inner wall surface of the partition is recorded as the inner air channel. On the same cross section, the ratio of the effective area of ​​the inner air channel to the effective area of ​​the outer air channel is 1:2 to 1:1.

[0008] Furthermore, at least three ignition gas nozzles are evenly distributed around the circumference of the ignition gas nozzle, and the angle β between the axis of each ignition gas nozzle and the axis of the ignition gas channel is 45° to 90°.

[0009] Furthermore, the ignition air distribution plate is arranged on the outer circumference of the ignition gas passage or on the outer circumference of the ignition gas nozzle; and at least three ignition air nozzles are evenly arranged on the ignition air distribution plate around the circumference.

[0010] Furthermore, the ratio of the effective area of ​​the ignition air nozzles on the ignition air distribution plate to the cross-sectional area of ​​the secondary air passage is 1:2 to 2:1.

[0011] Furthermore, an ignition gas automatic valve is provided at the inlet end of the ignition gas channel, and a main gas automatic valve is provided at the inlet end of the main gas channel. The inlet ends of the ignition gas automatic valve and the main gas automatic valve are connected in parallel to the gas pipeline.

[0012] Furthermore, a flame detector is also provided in the air passage.

[0013] A control method applicable to the above-mentioned low NOx self-preheating high-speed burner comprises the following steps:

[0014] (a) starting the automatic igniter and supplying air into the air passage, then opening the automatic ignition gas valve to introduce ignition gas and igniting the ignition gas so that the ignition gas burns in the ignition combustion chamber;

[0015] (b) After the flame in the ignition combustion chamber becomes a stable flame, the main gas automatic valve is opened to allow the main gas to enter. Under the action of the stable flame, the main gas undergoes combustion reactions at the outlet of the ignition combustion chamber and in the main combustion space outside the guide plate in turn;

[0016] Staged combustion mode: When the temperature of the main combustion space outside the guide plate is lower than the set temperature, the ignition gas automatic valve and the main gas automatic valve are both in the open state;

[0017] Flameless combustion mode: When the temperature of the main combustion space outside the guide plate is not lower than the set temperature, the ignition gas automatic valve is closed and the main gas automatic valve is kept open;

[0018] The set temperature is determined by the type of gas and the combustion heating mode, and ranges from 750℃ to 880℃.

[0019] Furthermore, in step (b), the ratio of the amount of gas introduced into the ignition gas channel to the amount of gas introduced into the main gas channel is 1:9 to 1:1; and the ejection speed of the main gas in the main gas channel is not less than 50 m / s.

[0020] Furthermore, the ratio of the air temperature passing through the preheater to the flue gas temperature in the main combustion space is controlled to be no less than 0.75.

[0021] Further, in step (b), the types of fuel gas are classified according to the H2 content contained therein;

[0022] When the H2 content in the gas is not less than 10%: when the heating mode is direct heating, the set temperature is 750°C; when the heating mode is radiant tube indirect heating, the set temperature is 800°C;

[0023] When the H2 content in the fuel gas is less than 10%: when the heating mode is direct heating, the set temperature is 800°C; when the heating mode is radiant tube indirect heating, the set temperature is 880°C.

[0024] The beneficial effects of the present invention are:

[0025] The structure realizes the independent setting of the ignition gas circuit and the main gas circuit. The ignition gas circuit is only used for ignition at medium and low temperatures. The input proportion of this part of gas is small, and there is no need to grade this part of gas. This not only simplifies the control structure, but also enables the burner to have the function of adjusting the flow ratio of "ignition gas" and "main gas".

[0026] The ignition gas circuit can be used as an ignition source. Relying on the ignition effect of the ignition source, the burner is in the low NOx mode of gas staged combustion under medium and low temperature conditions. At this time, the combustion volume in the ignition combustion chamber is small, which greatly reduces the high-intensity combustion in a small space. Under the premise of ensuring the high-speed flame temperature, effective control of NOx emissions is achieved. If the ignition gas is turned off under high temperature conditions, combustion in a small space is completely avoided, the main source of NOx generation disappears, and ultra-low NOx emissions are achieved.

[0027] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0029] Figure 1This is a schematic diagram of the structure of a low NOx self-preheating high-speed burner;

[0030] Figure 2 for Figure 1 A top view of a cross section;

[0031] Figure 3 for Figure 1 A partial enlarged view of

[0032] Figure 4 for Figure 3 Schematic diagram of gas flow;

[0033] Figure 5 for Figure 3 MM section view.

[0034] Reference numerals:

[0035] Main gas channel 1, ignition gas channel 2, air channel 3, smoke exhaust channel 4, ignition gas nozzle 5, preheater 6, guide plate 7, automatic igniter 8, ignition air distribution plate 9, partition 10, ignition combustion chamber 11, main combustion space 12, flame detector 13, gas pipeline 14;

[0036] Narrowing section 1001, cylindrical section 1002, cylindrical section 1003, main gas automatic valve 101, ignition gas automatic valve 201, ignition gas nozzle 501, ignition air nozzle 901;

[0037] Outer air channel H1, inner air channel H2, secondary air channel H3, primary air nozzle K1. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0040] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] See also Figure 1 to Figure 5 , which is a low NOx self-preheating high-speed burner, comprising a main gas channel 1, an ignition gas channel 2, an air channel 3 and a smoke exhaust channel 4 arranged in sequence from the inside to the outside; wherein an ignition gas nozzle 5 is arranged at the outlet end of the ignition gas channel 2, the main gas channel 1 is inserted in the ignition gas channel 2 and the gas outlet end of the main gas channel 1 extends a distance outside the ignition gas nozzle 2. A preheater 6 is arranged axially between the air channel 3 and the smoke exhaust channel 4 to separate the air channel 3 from the smoke exhaust channel 4, and a guide plate 7 closing in the direction of gas ejection is arranged on the tail end side of the preheater 6. An automatic igniter 8, an ignition air distribution plate 9 and a partition 10 are arranged in the air channel 3, wherein the ignition air distribution plate 9 is arranged in front of the ignition gas nozzle 5; the partition 10 surrounds the ignition air distribution plate 9 and the outside of the ignition gas nozzle 5 to separate and form an ignition combustion chamber 11 at the outlet end of the air channel 3. The partition 10 has a constricted section 1001 which gradually closes in the direction of gas ejection, and the gas outlet end face of the main gas channel 1 extends to the constricted section 1001 of the partition. The inner wall surface of the partition 10 is spaced apart from the outer peripheral surface of the ignition air distribution plate to form a secondary air channel H3 for circulating air, and the outer wall surface of the partition 10 is spaced apart from the inner wall surface of the preheater and the guide plate thereon to form an outer air channel H1 for circulating air.

[0042] The partition plate 10 in this embodiment has a tapered section 1001 and two cylindrical sections 1002 and 1003, wherein the tapered section 1001 is a truncated cone that gradually narrows toward the direction of gas ejection, and the two cylindrical sections are arranged at both ends of the tapered section. The cylindrical section 1002 is connected to the upper bottom surface of the tapered section 1001, and the cylindrical section 1003 is connected to the lower bottom surface of the tapered section 1001.

[0043] Specifically, the ignition gas channel 2 is located outside the main gas channel 1, and its inlet end (gas input end) is provided with an ignition gas automatic valve 201 to control the input amount of ignition gas, and its end (gas outlet end) is provided with an ignition gas nozzle 5. The main gas channel 1 passes through and out of the ignition gas nozzle 5 at the end of the ignition gas channel 2, and the amount of passing out is based on the constricted section 1001 extending into the partition 10. The front end (gas input end) of the main gas channel 1 is provided with a main gas automatic valve 101 to control the input amount of the main gas. On the outside of the ignition gas nozzle 5 is an ignition combustion chamber 11 separated by a partition 10, and the ignition combustion chamber 11 is connected to the air channel 3 at its front end. The outside of the ignition combustion chamber 11 is provided with a preheater 6 and a guide plate 7, and the outlet of the ignition combustion chamber 11 and the outside of the guide plate 7 are the main combustion space 12.

[0044] Here, the air channel 3 and the smoke exhaust channel 4 are separated by the preheater 6, so that the flue gas waste heat recovery and efficient air preheating can be achieved. The guide plate 7 arranged at the end of the preheater 6 corresponds to the outer side of the ignition combustion chamber 11 (located at the end of the air channel 3). The channel formed between the outer periphery of the partition 10 surrounding the ignition combustion chamber 11 and the inner wall surface of the guide plate is recorded as the outer air channel H1, and the channel between the outer peripheral surface of the ignition gas nozzle 5 and the inner wall of the partition 10 is recorded as the inner air channel H2; the inner wall surface of the partition 10 and the outer peripheral surface of the ignition air distribution plate are spaced to form a secondary air channel H3 for circulating air, and the ignition air nozzle 901 on the ignition air distribution plate 9 is recorded as the primary air nozzle K1. The outer air channel H1 is connected to the main combustion space 12 behind the ignition combustion chamber 11.

[0045] In the burner, the outer air channel H1 and the ignition combustion chamber 11 are both connected to the main combustion space 12. The air channel is divided into the outer air channel H1, the inner air channel H2, the secondary air channel H3 and the primary air nozzle K1 by the partition 10 and the ignition air distribution plate 9. Under the control of the ignition gas automatic valve 201, the ignition gas enters the ignition combustion chamber 11. Part of the preheated air directly enters the main combustion space 12 from the outer air channel H1, and part of the air enters the ignition combustion chamber 11 from the inner air channel H2 (i.e., passing through the secondary air channel H3 and the primary air nozzle K1 respectively), and starts to participate in the combustion reaction in the ignition combustion chamber.

[0046] In this embodiment, the ignition air distribution plate 9 is arranged on the periphery of the ignition gas nozzle 5, and the ignition air distribution plate 9 has a plurality of evenly arranged ignition air nozzles 901, which are the primary air nozzles K1. The air flowing through the primary air nozzles K1 directly reacts with the ignition gas sprayed from the rear ignition gas nozzle 5 to form a stable ignition source, while the air flowing through the secondary air channel H3 partially reacts with the main gas in the combustion chamber under the action of the automatic igniter 8 until the main gas is ensured to react smoothly with the outside air in the main combustion space 12 after being sprayed out of the ignition combustion chamber to prevent deignition. As a structural variation, the ignition air distribution plate 9 can also be arranged on the outer peripheral surface of the ignition gas channel 2.

[0047] It should be noted that the presence of the cylindrical section 1002 in the ignition combustion chamber 11 of the burner makes the constricted section 1001 and the main combustion space 12 separated by a certain distance, and the gas outlet end of the main gas channel 1 is located at the constricted section 1001 (i.e., the constricted section 1001 on the partition 10), so that the ejection position of the main gas is adjusted so that the ejection position of the main gas is located in the middle of the ignition combustion chamber 11 rather than at the outlet or outside the outlet of the ignition combustion chamber 11. When the temperature of the main combustion space 12 is high, the ignition source is turned off, and under the action of the constricted section (inner diameter gradually decreases) of the ignition combustion chamber 11, combustion cannot be achieved in the ignition combustion chamber 11, and the gas is flamelessly burned outside the ignition combustion chamber 11. When the temperature of the main combustion space 12 is low, staged combustion can be achieved through the independently set ignition gas circuit and the main gas circuit.

[0048] As a further optimization of the above scheme, in order to control the combustion intensity of the main gas in the ignition combustion chamber 11, the angle α between the generatrix on the tapered section of the truncated cone structure and the axis is 30° to 90°; the length of the tapered section of the baffle is L, and the length of the gas outlet end face of the main gas channel extending into the tapered section is D, and the two satisfy: 0≤D≤0.5L; the main gas ejection position is controlled and located in the front half of the tapered section of the ignition combustion chamber 11. On the same cross section, the ratio of the effective area H2 of the inner air channel to the effective area of ​​the outer air channel H1 is 1:2 to 1:1. At the same time, the ratio of the effective area of ​​the ignition air nozzle on the ignition air distribution plate to the cross-sectional area of ​​the secondary air channel is 1:2 to 2:1.

[0049] In order to ensure the stable combustion of the ignition gas in the ignition combustion chamber 11, at least three ignition gas nozzles 501 are evenly distributed around the circumference on the ignition gas nozzle 5, and the angle β between the axis of each ignition gas nozzle 501 and the axis of the ignition gas channel 2 is 45° to 90°. Correspondingly, at least three ignition air nozzles 901 are evenly distributed around the circumference on the ignition air distribution plate 9. Here, the ignition gas diverges into the ignition combustion chamber 11 at an angle of 2β, and the axis direction of the ignition air nozzle 901 as the primary air nozzle K1 is parallel to the axis of the ignition gas channel 2 (also the burner axis) or has a tangential angle within 45°. The direction of the ejection of this part of the air does not have a divergence angle, and can be better mixed with the ignition gas for combustion.

[0050] In this embodiment, the inlet end of the ignition gas automatic valve 201 and the main gas automatic valve 101 are connected in parallel to the gas pipeline 14. In this way, the independent setting of the ignition gas circuit and the main gas circuit is realized from the structural point of view, wherein the ignition gas circuit is only used for ignition at medium and low temperatures, the input proportion of this part of the gas is small, and there is no need to classify this part of the gas in particular, which not only simplifies the control structure, but also enables the burner to have the function of adjusting the flow ratio of "ignition gas" and "main gas", and the small proportion of ignition gas can greatly reduce the adiabatic combustion intensity in the ignition combustion chamber 11, thereby realizing the control of NOx, and the large proportion of the main gas output position is in the front half of the constriction section of the ignition combustion chamber 11, which can effectively ensure that the gas is stably ignited at medium and low temperatures, and can ensure that the gas does not burn in the ignition combustion chamber 11 at high temperatures.

[0051] In this embodiment, a flame detector 13 is further provided in the air passage 3 , and the flame detector 13 is used to detect the combustion condition in the ignition combustion chamber 11 so as to control the opening or closing of the ignition gas automatic valve 201 and the main gas automatic valve 101 .

[0052] A control method applicable to the above-mentioned low NOx self-preheating high-speed burner comprises the following steps:

[0053] (a) Start the automatic igniter 8 and supply air into the air passage 3, then open the ignition gas automatic valve 201 to pass the ignition gas, ignite, so that the ignition gas and the air in the inner air passage H2 burn in the ignition combustion chamber 11; during this combustion process, the gas temperature in the ignition combustion chamber 11 rises sharply and the volume expands, thereby forming a high-speed airflow that is ejected from the outlet (of the ignition combustion chamber 11), and at the same time, the flame in the ignition combustion chamber 11 becomes a stable ignition source.

[0054] (b) After the flame in the ignition combustion chamber 11 becomes a stable ignition source (detected by the flame detector 13), the main gas automatic valve 101 is opened to allow the main gas to flow in. Under the action of the stable flame, the main gas reacts with the air in the ignition combustion chamber 11 (including the air flowing through the secondary air channel H3 and the air supplied from the outer air channel H1) in turn at the outlet of the ignition combustion chamber and in the main combustion space 12 outside the guide plate to cause a combustion reaction. The combustion reaction mainly occurs in the main combustion space 12.

[0055] When the temperature of the main combustion space outside the guide plate is lower than the set temperature, the ignition gas automatic valve 201 and the main gas automatic valve 101 are always in the open state. A small amount of ignition gas burns in the ignition combustion chamber 11, and a large amount of main gas burns in the main combustion space 12. The outer air flow and the inner gas flow in the main combustion space are parallel high-speed jets, which drive the smoke to be sucked back and the combustion intensity is low; because the ignition gas automatic valve 201 is open, the ignition gas has an ignition effect when it burns, and a small amount of combustion in the ignition combustion chamber 11 can cause the gas volume to expand and then realize a high-speed flame. Under the ignition effect of the ignition source, the burner has an obvious flame, and the amount of combustion in the ignition combustion chamber 11 is small, which is close to a uniform heat combustion state. At this time, the burner is in a low NOx mode of gas staged combustion.

[0056] When the temperature of the main combustion space 12 outside the guide plate 7 is greater than or equal to the set temperature, the air reaches a relatively high preheating temperature, and the combustion reaction in the main combustion space 12 no longer needs to be driven by the ignition source. The ignition gas automatic valve 201 is closed. Under the restriction of the constriction section of the ignition combustion chamber 11, the main gas and the inner air do not have the combustion conditions in the ignition combustion chamber. At this time, the flame in the ignition combustion chamber 11 (i.e., the ignition gas combustion flame) disappears; the main gas automatic valve is kept open, and the combustion reaction is all carried out in the main combustion space 12. After being preheated to a relatively high temperature, the volume of the air increases significantly, reaching a relatively large operating flow rate. The burner relies on a relatively high air ejection velocity and a relatively high gas ejection velocity to achieve a high-speed airflow, which is ejected into the main combustion space 12 in parallel; the burner enters a flameless, low-NOx combustion mode with a high air preheating temperature, a high ejection velocity, and strong smoke entrainment and reflux. In the absence of direct ignition by open flame, the combustion intensity in the main combustion space is further weakened, and the NOx production in the main combustion space is reduced; the ignition combustion chamber is no longer close to adiabatic combustion, the main source of NOx production disappears, and the system NOx emissions are significantly reduced.

[0057] The set value of the main combustion space temperature located outside the guide plate is determined by the type of gas and the combustion heating mode, and the temperature range is usually between 750°C and 880°C. Specifically, the type of gas is divided according to the H2 content contained in the gas. When the H2 content in the gas is not less than 10%, the gas at this time may be producer gas, coke oven gas, or a mixed gas of high and coke ovens, etc. For such gas, if direct heating is adopted, the set temperature is 750°C, and if radiant tube indirect heating is adopted, the set temperature is 800°C. When the H2 content in the gas is less than 10%, the gas at this time may be natural gas or liquefied petroleum gas, etc. For such gas, if direct heating is adopted, the set temperature is 800°C, and if radiant tube indirect heating is adopted, the set temperature is 880°C.

[0058] In order to control the combustion intensity of the main gas in the ignition combustion chamber 11, in step (b), the ratio of the gas amount entering the ignition gas channel 2 to the gas amount entering the main gas channel 1 is 1:9 to 1:1; the ejection speed of the main gas in the main gas channel is not less than 50m / s.

[0059] In order to increase the air preheating temperature, increase the air volume expansion, increase the air working flow rate, and strengthen the flue gas heat recovery, the ratio of the air temperature passing through the preheater 6 to the flue gas temperature in the main combustion space is not less than 0.75.

[0060] The burner is suitable for direct heating and can also be used for indirect heating of I-type, P-type or double P-type radiant tubes.

[0061] The burner can significantly reduce NOx emissions while ensuring heating quality. Taking the application effect of the burner in the double P radiant tube heating system as an example, the specific indicators are as follows:

[0062]

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A low NOx self-preheating high-speed burner, comprising a main gas channel, an ignition gas channel, an air channel and a smoke exhaust channel arranged in sequence from the inside to the outside; wherein an ignition gas nozzle is arranged at the outlet end of the ignition gas channel, the main gas channel is inserted in the ignition gas channel and the gas outlet end of the main gas channel extends a distance outside the ignition gas nozzle, a preheater is arranged axially between the air channel and the smoke exhaust channel to separate the air channel and the smoke exhaust channel, and a guide plate closing in the direction of gas ejection is arranged at the tail end side of the preheater; an automatic igniter, an ignition air distribution plate and a partition are arranged in the air channel, wherein the ignition air distribution plate is arranged in front of the ignition gas nozzle; characterized in that: The partition surrounds the ignition air distribution plate and the outside of the ignition gas nozzle to separate the ignition combustion chamber at the outlet end of the air channel; the partition has a constricted section that gradually closes in the direction of gas ejection, and the gas outlet end face of the main gas channel extends to the constricted section of the partition; the length of the constricted section of the partition is L, and the length of the gas outlet end face of the main gas channel extending into the constricted section is D, and the two satisfy: 0≤D≤0.5L; the inner wall surface of the partition is spaced from the outer peripheral surface of the ignition air distribution plate to form a secondary air channel for circulating air, and the outer wall surface of the partition is spaced from the inner wall surface of the preheater and the guide plate thereon to form an outer air channel for circulating air; The outlet of the ignition combustion chamber and the outer side of the guide plate are used as the main combustion space; when the temperature of the main combustion space is high, the ignition source is turned off, and under the action of the contraction section of the ignition combustion chamber, combustion cannot be achieved in the ignition combustion chamber, and the gas burns flamelessly outside the ignition combustion chamber; and when the temperature of the main combustion space is low, staged combustion is achieved through the independently set ignition gas circuit and the main gas circuit.

2. The low NOx self-preheating high-speed burner according to claim 1 is characterized in that: The constricted section of the partition is a truncated cone structure, and the angle α between the generatrix and the axis is 30° to 90°.

3. The low NOx self-preheating high-speed burner according to claim 1 or 2, characterized in that: The gap between the outer peripheral surface of the ignition gas nozzle and the inner wall surface of the partition is recorded as the inner air channel. On the same cross section, the ratio of the effective area of ​​the inner air channel to the effective area of ​​the outer air channel is 1:2 to 1:

1.

4. The low NOx self-preheating high-speed burner according to claim 3 is characterized in that: At least three ignition gas nozzles are evenly distributed around the circumference of the ignition gas nozzle, and the angle β between the axis of each ignition gas nozzle and the axis of the ignition gas channel is 45° to 90°.

5. The low NOx self-preheating high-speed burner according to claim 4 is characterized in that: The ignition air distribution plate is arranged on the outer peripheral surface of the ignition gas passage or on the outer periphery of the ignition gas nozzle; at least three ignition air nozzles are evenly arranged on the ignition air distribution plate around the circumference.

6. The low NOx self-preheating high-speed burner according to claim 5 is characterized in that: The ratio of the effective area of ​​the ignition air nozzle on the ignition air distribution plate to the cross-sectional area of ​​the secondary air passage is 1:2 to 2:

1.

7. The low NOx self-preheating high-speed burner according to claim 1 is characterized in that: An ignition gas automatic valve is arranged at the inlet end of the ignition gas channel, and a main gas automatic valve is arranged at the inlet end of the main gas channel. The inlet ends of the ignition gas automatic valve and the main gas automatic valve are connected in parallel to the gas pipeline.

8. The low NOx self-preheating high-speed burner according to claim 1 is characterized in that: A flame detector is also provided in the air passage.

9. A control method for a low NOx self-preheating high-speed burner as claimed in any one of claims 4 to 8, characterized in that The following steps are involved: (a) starting the automatic igniter and supplying air into the air passage, then opening the automatic ignition gas valve to introduce ignition gas and igniting the ignition gas so that the ignition gas burns in the ignition combustion chamber; (b) After the flame in the ignition combustion chamber becomes a stable flame, the main gas automatic valve is opened to allow the main gas to enter. Under the action of the stable flame, the main gas undergoes combustion reactions at the outlet of the ignition combustion chamber and in the main combustion space outside the guide plate in turn; Staged combustion mode: When the temperature of the main combustion space outside the guide plate is lower than the set temperature, the ignition gas automatic valve and the main gas automatic valve are both in the open state; Flameless combustion mode: When the temperature of the main combustion space outside the guide plate is not lower than the set temperature, the ignition gas automatic valve is closed and the main gas automatic valve is kept open; The set temperature is determined by the type of gas and the combustion heating mode, and ranges from 750℃ to 880℃.

10. The control method of the low NOx self-preheating high-speed burner according to claim 9, characterized in that: In step (b), the ratio of the amount of gas introduced into the ignition gas channel to the amount of gas introduced into the main gas channel is 1:9 to 1:1; and the ejection speed of the main gas in the main gas channel is not less than 50 m / s.

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