Heater for radiant tube of annealing furnace

Abstract

The invention relates to an annealing furnace radiant tube heater which comprises a radiant tube and a burner disc installed at one end of the radiant tube, the burner disc is provided with a gas nozzle located in the center and a plurality of circles of combustion-supporting gas nozzles arranged around the gas nozzle, and the inclination angles between every two adjacent circles of combustion-supporting gas nozzles are opposite. The inclination angles of the combustion-supporting gas nozzles of every two adjacent circles are set to be opposite, so that the injection directions of the combustion-supporting gas intersect, and therefore rotating airflow is formed, the contact area of the combustion-supporting gas and fuel gas is enlarged, the fuel gas is fully combusted, generation of nitric oxide and sulfide is reduced, pollution to ambient air is reduced, and the service life of the combustion-supporting gas is prolonged. And up-to-standard discharge is realized.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a radiant tube heater for an annealing furnace. Background Technology

[0002] Radiant tube heaters are heating devices for chemical heat treatment fuel furnaces, made of heat-resistant steel or low-carbon steel. Common structures include U-shaped, W-shaped, straight-rod squirrel-cage, and small spiral coil-wound ceramic tubes. This equipment generates radiant heat through combustion gas or electric heating elements inside the tube, with a surface temperature range of 150~1250℃ (ceramic material) and a thermal efficiency of no less than 90%. Gas-fired radiant tubes use a combination of burner and ejector; combustion products can be exchanged through a jacket or recycled. An induced draft fan controls flue gas emissions, and temperature fluctuations can be controlled within ±5℃.

[0003] There are two main ways to arrange the gas nozzles and combustion-supporting gas nozzles in existing gas-fired radiant tube heaters: Method 1: Traditional burners use a linear injection method during combustion. The high air-fuel ratio and concentrated combustion result in excessively concentrated temperatures, which can easily cause localized burn-through of the radiant tube, reducing its service life. The mixing of combustion-supporting gas and fuel gas is uneven and insufficient, which can easily lead to the formation of large amounts of sulfides and nitrides that are released into the atmosphere, causing pollution from the combustion-supporting gas.

[0004] Method 2: Arrange combustion-supporting gas nozzles with a certain angle around the gas nozzle, thereby forming a rotating jet flame on the inner wall of the radiant tube. After this rotating flame is formed, the flame length is extended accordingly. In this way, the radiant tube is heated more evenly, and the cross-mixing of air and gas can partially reduce the formation of sulfides and nitrogen oxides. However, the disadvantage is that when the flame comes into contact with the surface of the radiant tube, it will form local high temperatures, causing the temperature to be too high. Summary of the Invention

[0005] The purpose of this invention is to provide a radiant tube heater for an annealing furnace to solve the above-mentioned problems. To this end, the technical solution adopted by this invention is as follows: An annealing furnace radiant tube heater includes a radiant tube and a burner plate installed at one end of the radiant tube. The burner plate is provided with a gas nozzle located at the center and multiple rings of combustion-supporting gas nozzles arranged around the gas nozzle, wherein the inclination angles between adjacent rings of combustion-supporting gas nozzles are opposite.

[0006] In one embodiment, the tilt angle of the innermost combustion-supporting gas nozzle is 15°~25°, preferably 17.2°.

[0007] In one embodiment, the orifice diameter of the combustion-supporting gas nozzle is 2-5 mm, preferably 3.5 mm.

[0008] In one embodiment, the number of revolutions of the combustion-supporting gas nozzle is 6 to 20, preferably 15.

[0009] In one embodiment, the spacing between two adjacent combustion-supporting gas nozzles is 6-10 mm, preferably 8 mm.

[0010] In one embodiment, the radiant tube is a U-shaped or W-shaped radiant tube.

[0011] This application sets the tilt angles of the combustion-supporting gas nozzles of two adjacent rings to opposite angles, so that the injection directions of the combustion-supporting gas intersect, thereby forming a rotating airflow. This increases the contact area between the combustion-supporting gas and the gas, allowing the gas to burn more completely, thereby reducing the generation of nitrogen oxides and sulfides, reducing air pollution, and achieving emission standards. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a radiant tube heater according to an embodiment of the present invention; Figure 2 yes Figure 1 A schematic plan view of the burner plate of the radiant tube heater shown; Figure 3 yes Figure 1 The diagram shows a cross-sectional view of the burner plate of the radiant tube heater. Detailed Implementation

[0013] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to provide a clearer understanding of the purpose, features, and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative of the essential spirit of the technical solution of the present invention.

[0014] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0015] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0016] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0017] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0018] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0019] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0020] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] like Figures 1-3 As shown, an annealing furnace radiant tube heater includes a radiant tube 1, a burner plate 2 installed at one end of the radiant tube 1, and a heat exchanger 3 installed at the other end of the radiant tube 1. The structures of the radiant tube 1 and the heat exchanger 3 are well-known and will not be described in detail here. The burner plate 2 is provided with a gas nozzle 4 located at the center and multiple rings of combustion-supporting gas nozzles 5 arranged around the gas nozzle 4. The gas nozzle 4 is connected to a gas pipe 200, and the combustion-supporting gas nozzles 5 are connected to the heat exchanger 3. The combustion-supporting gas (air or oxygen, etc.) enters the heat exchanger 3 through the inlet pipe 100, exchanges heat, and is then guided through a pipe to the combustion-supporting gas nozzles 5, which are injected into the radiant tube 1 to mix and burn with the gas. The inclination angle θ between two adjacent rings of combustion-supporting gas nozzles 5 is opposite, such as... Figure 3As shown. Specifically, assuming the tilt angle θ of the innermost (first) combustion gas nozzle 5 is +15° (i.e., tilted 15° towards the pipe wall), then the tilt angle θ of the second ring of combustion gas nozzles 5 is -15° (i.e., tilted 15° towards the center of the radiant tube), the tilt angle θ of the third combustion gas nozzle 5 is +15°, and so on. Because the tilt angles of adjacent rings of combustion gas nozzles are opposite, the injection directions of the combustion gas intersect, thus forming a rotating airflow. This increases the contact area between the combustion gas and the combustion gas, allowing for more complete combustion and reducing nitrogen oxides (NOx). x This reduces the generation of sulfur compounds and sulfides, thereby lowering air pollution levels and achieving emission standards.

[0022] like Figure 3 As shown, in Zone I (pre-combustion zone), a large amount of combustion gas (e.g., natural gas or coal gas) is concentrated in Zone I, resulting in insufficient oxygen in the combustion-supporting gas and thus incomplete combustion (i.e., oxygen-deficient combustion). As the gas and combustion gas move forward, the combustion gas and air enter Zone II, along with the incompletely combusted combustion gas from Zone I, forming a secondary mixed combustion in Zone II. In Zone II (fully combusted zone), there is more air and less combustion gas, allowing the combustion gas and the flue gas from Zone I to burn completely. Due to the cross-injection of combustion-supporting gas and the mixing of combustion gas to form combustion states in Zones I and II, combustion is more complete, naturally increasing the flame length and resulting in a more uniform temperature on the radiant tube wall, reducing the generation of nitrogen oxides and sulfides. Experiments show that the nitrogen oxide and sulfide content in the exhaust gas produced by the annealing furnace radiant tube heater of this application is reduced by more than 20% compared to the existing Method 1 and by more than 10% compared to the existing Method 2, with the nitrogen oxide and sulfide content in the exhaust gas being less than 40 mg / m³. 3 and 30mg / m 3 It is lower than the emission standards for waste gas from the steel industry.

[0023] The tilt angle θ of the innermost combustion-supporting gas nozzle is designed according to the specific specifications of the radiant tube 1, and is usually between +15° and 25°. Experiments show that for a radiant tube 1 with a diameter of 219mm, the combustion effect is best when the tilt angle θ of the innermost combustion-supporting gas nozzle is 17.2°.

[0024] The orifice diameter of the combustion-supporting gas nozzle 5 is typically 2-5 mm to ensure a certain injection velocity and volume of the combustion-supporting gas, forming a rotating airflow, increasing the contact area between the combustion-supporting gas and the combustion gas, and making combustion more complete. The spacing between two adjacent rings of combustion-supporting gas nozzles 5 is 6-10 mm. The number of rings of combustion-supporting gas nozzles is related to the specifications of the radiant tube 1 and the orifice diameter and spacing of the combustion-supporting gas nozzles 5, and is typically 6-20 rings. It should be noted that the number of combustion-supporting gas nozzles 5 in the attached drawings is only illustrative. In a specific embodiment, for a radiant tube 1 with a diameter of 219 mm, the orifice diameter of the combustion-supporting gas nozzle 5 is 3.5 mm, the spacing between two adjacent rings of combustion-supporting gas nozzles 5 is 8 mm, and the number of combustion-supporting gas nozzles is 15 rings.

[0025] In the illustrated embodiment, radiator 1 is a W-shaped radiator. It should be understood that radiator 1 can also be a U-shaped radiator or other configurations.

[0026] The preferred embodiments of the present invention have been described in detail above. However, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A radiant tube heater for an annealing furnace, comprising a radiant tube and a burner plate installed at one end of the radiant tube, characterized in that, The burner disc is provided with a gas nozzle located at the center and multiple rings of combustion-supporting gas nozzles arranged around the gas nozzle, wherein the inclination angles between adjacent rings of combustion-supporting gas nozzles are opposite.

2. The annealing furnace radiant tube heater according to claim 1, characterized in that, The tilt angle of the innermost combustion-supporting gas nozzle is 15°~25°.

3. The annealing furnace radiant tube heater according to claim 2, characterized in that, The tilt angle of the innermost combustion-supporting gas nozzle is 17.2°.

4. The annealing furnace radiant tube heater according to claim 1, characterized in that, The orifice diameter of the combustion-supporting gas nozzle is 2~5mm.

5. The annealing furnace radiant tube heater according to claim 4, characterized in that, The orifice diameter of the combustion-supporting gas nozzle is 3.5 mm.

6. The annealing furnace radiant tube heater according to claim 1, characterized in that, The number of revolutions of the combustion-supporting gas nozzle is 6 to 20.

7. The annealing furnace radiant tube heater according to claim 6, characterized in that, The combustion-supporting gas nozzle has 15 revolutions.

8. The annealing furnace radiant tube heater according to claim 1, characterized in that, The spacing between two adjacent combustion-supporting gas nozzles is 6~10mm.

9. The annealing furnace radiant tube heater according to claim 8, characterized in that, The spacing between two adjacent combustion-supporting gas nozzles is 8 mm.

10. The annealing furnace radiant tube heater according to claim 1, characterized in that, The radiant tube is a U-shaped or W-shaped radiant tube.

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