A low NO x Flameless combustion devices and combustion methods for emissions

Abstract

This invention discloses a low NO x A flameless combustion device and its combustion method are disclosed. The flameless combustion device includes a burner body, a burner brick made of high-temperature refractory material, a pre-combustion chamber on the burner brick, fuel pipes, a primary air passage, and a secondary air passage. At least one fuel nozzle is located at the bottom of the pre-combustion chamber; a primary air annular slit is located at the bottom of the pre-combustion chamber; and secondary air nozzles are located on the burner brick, consisting of several first and second secondary nozzles, with the diameter of the first and second secondary nozzles being smaller than that of the second and second secondary nozzles. This flameless combustion device and its combustion method can achieve both low-temperature and high-temperature combustion modes, meeting the needs of practical industrial applications. In the low-temperature combustion stage, it improves the stability of low-temperature start-up combustion and ensures safety; in the high-temperature stage, it achieves efficient and low-pollution flameless combustion, reducing energy consumption and pollution, improving product quality, and extending kiln life.

Description

Technical Field

[0001] This invention belongs to the field of industrial burners, and relates to a low-NOx burner for high-temperature furnaces and kilns used in steel, chemical, boiler, glass, and non-ferrous metal smelting industries. x Flameless combustion devices and their combustion methods for emissions. Background Technology

[0002] Industries such as steel, boilers, petrochemicals, glass, and non-ferrous metal smelting have numerous high-temperature kilns that burn various gaseous fuels, liquid fuels such as oil, and solid fuels to provide the heat and high-temperature environment required for production processes. High-temperature combustion is a violent chemical reaction process; flame-fired kilns not only produce various waste gases such as CO2, but also NO. x Pollutants such as SO2 and CO2 are prevalent, and CO2 is also a major cause of climate change. Conserving energy and reducing the concentration and total emissions of various pollutants are fundamental social and legal requirements, as well as the obligations of all production enterprises.

[0003] NO x It can cause serious human health problems and is one of the main air pollutants from industrial kilns. During high-temperature combustion, NO... x The generation of NO has its own mechanism, based on NO x The study of the formation mechanism during combustion has led to the research and development of numerous low-NOx products both domestically and internationally. x Burners, combustion devices, and combustion methods, such as the published patent CN104990078A, disclose a burner and combustion method that can quickly achieve flameless combustion. This burner is equipped with a central gas nozzle, a loop gas nozzle, two symmetrical air nozzles, and a loop air nozzle. A flame-stabilizing blunt body with an annular protrusion at the front end is connected to the front end of the central gas nozzle and the loop gas nozzle, enabling rapid switching between flaming and flameless combustion. While this patent achieves flameless combustion in principle, its simple structure does not consider the various fuels used in actual industrial applications, nor the actual heating process requirements of industrial kilns, making it difficult to meet practical needs.

[0004] The published patent CN104266190A discloses an oxygen-enriched flameless gas burner and its control method. It incorporates a pure oxygen nozzle into a conventional burner, utilizing a high-speed oxygen jet to entrain the combustion flue gas, controlling the oxygen-to-flue gas mixing ratio, reducing the oxygen concentration, and then combining it with the combustion gas to achieve flameless combustion. This improves temperature uniformity and reduces NO₂ levels. x And for the purpose of energy saving. However, the published patent requires high-speed, high-pressure pure oxygen, but cannot completely eliminate air, and the equipment and the entire combustion pipeline system are complex; it is difficult to apply to oxygen-deficient factories, and the cost is high.

[0005] The published patent CN104633658A discloses a low-NOx burner. The burner body is equipped with a fuel nozzle that introduces fuel into the combustion zone and a primary air nozzle, a secondary air nozzle, and a tertiary air nozzle that introduce air into the combustion zone. This three-stage combustion structure, connected sequentially, supplies the necessary air for combustion in three stages. This ensures stable combustion while avoiding localized high-intensity combustion, significantly reducing NOx emissions. x However, this published patent cannot achieve flameless combustion, NO x The reduction in concentration is limited and can hardly meet current and future environmental protection requirements.

[0006] Publicly available patent CN102230623A discloses a flat combustion device, including a nozzle arrangement unit, an air intake unit and a flame control unit respectively connected to both sides of the nozzle arrangement unit. The nozzle arrangement unit is equipped with a fuel nozzle, a primary air nozzle, a secondary air nozzle, and a flame stabilization zone. It employs a flat fuel nozzle and a specially arranged multi-stage air nozzle to achieve staged combustion and a flat flame shape, improving the uniformity of heating temperature. However, this published patent also uses a traditional combustion method with a distinct flame, which may result in NO... x The defect is that it is too high. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a low-NOx content for high-temperature furnaces and kilns used in steel, chemical, boiler, glass, and non-ferrous metal smelting industries, addressing the deficiencies in the existing technology. x Flameless combustion devices and their combustion methods for emissions.

[0008] This invention provides a low NO x The flameless combustion device, through specially designed and arranged air nozzles and staged air supply, allows air and fuel to be mixed separately with the exhaust gases before combustion. This creates a flameless combustion state where the combustion reaction produces a uniform temperature throughout the furnace or combustion space without any significantly high-temperature areas. This greatly improves the temperature uniformity of the entire heating zone and minimizes NO emissions. x The emissions are different from those of conventional burners that have a distinct flame pattern.

[0009] The low NO of the present invention xThe flameless combustion device for emissions is designed based on considerations of flame temperature and kiln safety during actual industrial applications, including ambient temperature ignition, low-temperature start-up or operation of the kiln. It achieves ambient temperature ignition and stable operation at low temperatures by setting a primary air annular gap to stabilize the combustion flame. Furthermore, by installing an air regulating valve at the inlet of the air main to adjust and control the ratio and / or switch between primary and secondary air, the device can freely switch between high and low temperature operating modes, ensuring the reliability of low-temperature operation. It can also switch to high-temperature mode under high-temperature conditions in the kiln, achieving clean and efficient combustion of fuel with ultra-low pollution.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention is to provide a low NO... x The flameless combustion device for emissions includes a burner brick and an expanded pre-combustion chamber disposed on the burner brick, wherein:

[0011] At least one fuel nozzle is provided at the bottom of the pre-combustion chamber;

[0012] The bottom of the pre-combustion chamber is provided with a primary air annular gap, which is arranged in a ring around the outer periphery of the fuel nozzle.

[0013] The burner brick is provided with a secondary air injection hole, which is composed of a plurality of first secondary injection holes arranged on the upper and lower sides of the fuel injection port and a plurality of second secondary injection holes arranged on the left and right sides, and the diameter of the first secondary injection hole is smaller than the diameter of the second secondary injection hole.

[0014] Furthermore, the fuel nozzle is located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber;

[0015] The primary air annular gap is located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber outside the fuel nozzle; and

[0016] The secondary air nozzles are located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber.

[0017] Furthermore, the first and second nozzles are parallel to the geometric center line of the pre-combustion chamber, or have an inward deviation angle β relative to the geometric center line, wherein the deviation angle β is 0-60°. Preferably, the deviation angle β is 0-55°; more preferably, the deviation angle β is 5-40°.

[0018] Furthermore, the second and secondary nozzles are parallel to the geometric center line of the pre-combustion chamber, or have an expansion angle γ relative to the geometric center line, wherein the expansion angle γ is 0-60°. Preferably, the deflection angle γ is 5-55°; more preferably, the deflection angle γ is 10-50°.

[0019] Furthermore, the fuel nozzle is circular or elliptical, and the fuel flow rate is 8-200 m / s; preferably, the fuel flow rate is 15-140 m / s; more preferably, the fuel flow rate is 20-130 m / s.

[0020] Furthermore, a swirl vane is provided within the primary air annular gap, and the air injected by the vane accounts for 0-100% of the oxygen required for complete combustion of the fuel; the air velocity at the primary air annular gap is 0.1-1.5 times the fuel velocity; preferably, the air velocity at the primary air annular gap is 0.2-1.3 times the fuel velocity; more preferably, the air velocity at the primary air annular gap is 0.5-1.2 times the fuel velocity.

[0021] Furthermore, the primary air injected at the primary air circumferential seam and / or the secondary air injected at the secondary air nozzle can be dynamically adjusted between 0% and 100% of their respective proportions.

[0022] More preferably, the primary air supplied through the primary air annular seam can be completely closed or opened, or the secondary air supplied through the secondary air nozzle can be completely closed or opened, or the primary air and secondary air can be quantitatively distributed in a certain proportion to achieve dynamic adjustment.

[0023] More preferably, both the primary air annular gap and the secondary air nozzle are connected to the air inlet manifold through an air transmission channel, and the air inlet manifold is equipped with an air regulating valve for adjusting the supply ratio of the primary air and the secondary air.

[0024] Furthermore, the ratio of the distance between the first and second spray holes and the geometric center line of the pre-combustion chamber to their diameter is greater than 5.

[0025] Furthermore, the air velocity of the secondary air nozzle is 10-300 m / s, and it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-18%.

[0026] More preferably, the air velocity of the secondary air nozzle is 15-200 m / s, which is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-9%.

[0027] More preferably, the air velocity of the secondary air nozzle is 20-150 m / s, which is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 3-8%.

[0028] More preferably, the air velocity of the secondary air nozzle is 30-120 m / s, which is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 4-7%.

[0029] Furthermore, an oxidizer nozzle is provided at the geometric center of the bottom of the pre-combustion chamber, and the oxidizer nozzle is located inside the fuel nozzle.

[0030] Furthermore, the oxidant sprayed from the oxidant nozzle is ordinary air, oxygen-enriched air with an oxygen concentration greater than 21%, or pure oxygen with an oxygen concentration greater than 90%; the fuel sprayed from the fuel nozzle is natural gas, coal gas, liquefied petroleum gas, fuel oil, coal, or petroleum coke.

[0031] A second aspect of the present invention is to provide a low NO content in the combustion device. x The flameless combustion method for emissions includes the following steps:

[0032] (1) Normal temperature start-up stage: When the furnace burner brick temperature is normal or the process temperature is below 850℃, the fuel ignition point is reached. Primary air is supplied to the primary air ring gap through the air regulating valve, and fuel is supplied to the fuel injection hole for ignition.

[0033] (2) Low-temperature combustion stage: After ignition and combustion at room temperature, the temperature of the furnace burner bricks rises. The air supply to the primary air annular gap is increased through the air regulating valve, or air is supplied to the secondary air nozzle through the air regulating valve at the same time as the primary air annular gap, so that all the oxygen required for combustion is supplied by the primary air or by both primary and secondary air, so as to carry out stable low-temperature combustion.

[0034] (3) High-temperature combustion stage: When the temperature of the furnace burner brick or the process temperature is higher than the ignition point of the fuel itself, the secondary air supplied by the secondary air nozzle is increased through the air regulating valve, or all the oxygen required for combustion is supplied by the secondary air, which mixes with the combustion products to form a mixture with an oxygen concentration of 2-18%, and then mixes with the fuel to carry out flameless combustion without obvious flame.

[0035] Furthermore, in the aforementioned low NO x In the flameless combustion method for emissions, the fuel flow rate is 10-150 m / s; the primary air flow rate is 0.1-1.5 times the fuel flow rate; and the secondary air flow rate is 10-300 m / s.

[0036] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0037] (1) The low NO xThe flameless combustion device employs a staged, high-speed, multi-point supply of combustion air. In particular, the structural design of small-diameter primary and secondary nozzles combined with large-diameter secondary nozzles significantly enhances the pre-mixing of air with the exhaust gases (or combustion products) and effectively improves the spread and morphology of the combustion reaction. This achieves flameless combustion suitable for industrial applications, completely eliminates the high-temperature zone of the flame, improves the temperature uniformity of the entire heating space, and significantly reduces NO₂ levels. x The emission levels meet the requirements of current and future environmental emission regulations;

[0038] (2) The amount of air injected at the primary and / or secondary air nozzles is controlled by an air regulating valve to dynamically adjust the distribution ratio of primary and secondary air during actual use, so that the low NO x The flameless combustion device for emissions control features dynamically adjusted low-temperature and high-temperature modes. In the low-temperature stage, it achieves stable combustion and safe heating to prevent explosions; in the high-temperature stage, it achieves flameless combustion, ensuring temperature uniformity along the length and width, thereby reducing NOx emissions. x Emissions;

[0039] (3) The low NO x The flameless combustion device can meet the needs of actual industrial applications. Through the low-temperature combustion mode, it improves the stability of low-temperature start-up combustion and ensures safety. At high-temperature stages, it achieves efficient and low-pollution flameless combustion, reducing energy consumption and pollution, improving product quality, and extending the life of the kiln. Attached Figure Description

[0040] Figure 1 This invention provides a low NO content x A top view of the flameless combustion device for emissions.

[0041] Figure 2 for Figure 1 Low NO shown x A schematic cross-sectional view of the AA section of the flameless combustion device for emissions.

[0042] Figure 3 for Figure 1 Low NO shown x A cross-sectional view of the BB section of the emission flameless combustion device.

[0043] The attached figures are labeled as follows: 1-burner brick, 2-pre-combustion chamber, 3-fuel nozzle, 4-primary air annular seam, 5-first and second secondary nozzles, 6-second and third secondary nozzles, 7-oxidant nozzle, 8-main air pipe, 9-air regulating valve, 10-air transmission channel, 11-swirl vane, 12-primary air channel, 13-secondary air channel, 14-baffle plate, 15-main fuel pipe, 16-branch fuel pipe, 17-oxidant pipe. Detailed Implementation

[0044] This invention provides a low NO x Flameless combustion devices and methods thereof, particularly a method for achieving flameless combustion to reduce NO content. x or ultra-low NO x The main technical solution of the combustion device and combustion method for emissions is to design mutually cooperating fuel injection holes 3, primary air annular gaps 4 and secondary air injection holes on the burner bricks of the furnace. During operation, primary air is injected into the fuel injection hole 3 in a ring around the fuel injection hole through the primary air annular gap 4, and secondary air is injected into the fuel injection hole through the secondary air injection hole arranged outside the primary air annular gap 4. The secondary air injection hole is located further away from the fuel injection hole 3. The secondary air injection hole includes at least two types of first secondary injection holes 5 and second secondary injection holes 6 with different diameters.

[0045] In the low NO x In flameless combustion devices, based on the principle of jet entrainment, the specific nozzle design and flow rate selection of the secondary air nozzles ensure that a large amount of combustion products or exhaust gases are entrained before the secondary air mixes with the fuel, forming a mixture with an oxygen concentration between 2% and 18%. This mixture is then mixed and burned with the fuel, resulting in the absence of a distinct flame shape. The combustion reaction occurs throughout the entire furnace space or heating zone. This combustion method differs from traditional combustion with a distinct flame shape and is commonly known as "flameless combustion." The combustion reaction in flameless combustion occurs throughout the entire furnace area, resulting in a uniform temperature distribution in the heating zone, which greatly improves the temperature uniformity of heating. Furthermore, because the peak flame temperature is eliminated, the highest flame temperature is significantly lower than that of traditional "flaming combustion." Theoretical analysis and numerous experiments and practical applications have proven that this flameless combustion method significantly reduces NO₂ levels. x Emissions.

[0046] Furthermore, because the secondary air nozzle employs a multi-nozzle structure design with two different orifice diameters or various types of different orifice sizes, such as a small-diameter primary and secondary nozzle 5 and a large-diameter secondary nozzle 6, it helps control the flame length, resulting in a wider combustion reaction area and better temperature uniformity. It particularly helps the combustion reaction spread across the horizontal width of the burner brick, improving the heating temperature uniformity in both the length and horizontal width directions. Simultaneously, to increase the operating range and load adjustment ratio of the combustion device, an oxidizer nozzle 7 can be installed at the centerline of the pre-combustion chamber 2, supplying air, oxygen-enriched air, or pure oxygen through the oxidizer nozzle 7.

[0047] The present invention will now be described in detail and specifically through specific embodiments to enable a better understanding of the invention. However, the following embodiments do not limit the scope of the invention. Example 1

[0048] Please see Figure 1-3 As shown, this embodiment provides a low NO x The flameless combustion device includes a burner body, a burner brick 1 made of high-temperature refractory material, an expanding pre-combustion chamber 2 on the burner brick 1, and fuel pipes, a primary air passage 12, a secondary air passage 13, etc. The burner brick 1 is the furnace lining of high-temperature furnaces in industries such as steelmaking, chemical manufacturing, boilers, glassmaking, and non-ferrous metal smelting, and is composed of refractory material. The pre-combustion chamber 2 has an expansion angle α, which is 30-60°. Preferably, the deflection angle α is 0-55°; more preferably, the deflection angle α is 10-55°; and even more preferably, the deflection angle α is 25-50°.

[0049] In this embodiment, please refer to Figure 1 As shown, a fuel branch pipe 16 is provided on the burner brick 1. The distal end of the fuel branch pipe 16 is connected to the main fuel pipe 15. The proximal end of the fuel branch pipe 16 is provided with at least one fuel nozzle 3 at the bottom of the combustion chamber 2, and the fuel nozzle 3 is located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber 2. A primary air annular slit 4 is provided at the bottom of the pre-combustion chamber 2. The primary air annular slit 4 is arranged in a ring around the outer periphery of the fuel nozzle 3, and the primary air annular slit 4 is located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber 2.

[0050] In this embodiment, please refer to Figure 1 As shown, on the burner brick 1 made of refractory brick, a secondary air nozzle is provided at a position further away from the fuel injection hole 3 from the outer side of the primary air annular seam 4. The secondary air nozzles are divided into at least two types with different orifice diameters, and are all located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber 2. As a preferred embodiment, as... Figure 1 As shown, the secondary air nozzle is composed of a plurality of first secondary nozzles 5 arranged on the upper and lower sides of the fuel nozzle 3 and a plurality of second secondary nozzles 6 arranged on the left and right sides, and the diameter of the first secondary nozzles 5 is smaller than the diameter of the second secondary nozzles 6.

[0051] This embodiment has low NO x The main technical solution of the flameless combustion device for emissions reduction is as follows: Fuel injection holes 3, primary air annular gaps 4, and secondary air injection holes are designed to cooperate on the burner brick 1. These holes enable staged, high-speed, and multi-point supply of combustion air. In particular, the structural design of the small-diameter primary and secondary injection holes 5 combined with the large-diameter secondary injection holes 6 significantly enhances the mixing of air and combustion exhaust gases, effectively improves the spread and morphology of the combustion reaction, achieves flameless combustion that meets industrial application requirements, and greatly reduces NOx emissions. xThe emission levels meet the requirements of current and future environmental emission regulations. Example 2

[0052] Please see Figure 1-3 As shown, unlike Embodiment 1 above, this embodiment uses low NO x In the flameless combustion device for emissions, the secondary air nozzles consist of a plurality of first secondary nozzles 5 and a plurality of second secondary nozzles 6, wherein the diameter of the first secondary nozzles 5 is smaller than the diameter of the second secondary nozzles 6. The smaller diameter first secondary nozzles 5 are arranged on the upper and lower sides of the fuel nozzle 3, and the larger diameter second secondary nozzles 6 are arranged on the left and right sides of the fuel nozzle 3.

[0053] In this embodiment, please refer to Figure 2 As shown, the first and secondary nozzles 5 are parallel to the geometric center line of the pre-combustion chamber 2, or have an inward deviation angle β relative to the geometric center line. The deviation angle β is 0-60°, preferably 0-55°; more preferably, the deviation angle β is 5-40°. That is, the small-diameter first and secondary nozzles 5 can be arranged horizontally, or set at a certain angle β to be deflected towards the geometric center line of the pre-combustion chamber 2. This high-speed, fine airflow ejected from the first and secondary nozzles 5 enhances the mixing of secondary air and combustion exhaust gas, and ensures the combustion reaction in the vicinity of the combustion device, as well as the flame stability in the low-temperature stage.

[0054] In this embodiment, please refer to Figure 3 As shown, the second secondary nozzle 6 is parallel to the geometric center line of the pre-combustion chamber 2, or has an expansion angle γ relative to the geometric center line. The deviation angle γ is 0-60°, preferably 5-55°; more preferably, the deviation angle γ is 10-50°. That is, the large-diameter second secondary nozzles 5 arranged on the left and right sides of the fuel nozzle 3 can be parallel to the geometric center line of the pre-combustion chamber 2, or have a certain expansion angle γ that deviates from the geometric center line of the pre-combustion chamber 2, so that the airflow through the large-diameter second secondary nozzle 6 deviates from the fuel flow, guiding the distribution and expansion of the combustion reaction in the horizontal width direction. Example 3

[0055] Based on Embodiments 1 and 2 above, this embodiment provides a more specific low NO xA flameless combustion device for emissions. The fuel nozzle 3 is circular or elliptical to form a specific flame shape and to facilitate maximum pre-mixing with the combustion exhaust gas; and the fuel nozzle velocity is between 8-200 m / s; preferably, the fuel velocity is 15-140 m / s; more preferably, the fuel velocity is 20-130 m / s; even more preferably, the fuel velocity is 50-120 m / s; and even more preferably, the fuel velocity is 75-105 m / s.

[0056] In this embodiment, primary air is injected from the primary air annular slit 4 around the fuel nozzle 3. To maximize the mixing of the primary air injected from the primary air annular slit 4 with the fuel injected from the fuel spray hole 3 and ensure flame stability, a swirl vane 11 can be provided inside the primary air annular slit 4. The swirl vane 11 allows the primary air jet ejected from the primary air annular slit 4 to rotate around the geometric center of the fuel nozzle 3. The rotating jet promotes the mixing of primary air and fuel and ensures stable combustion. On the other hand, it entrains a large amount of high-temperature combustion products and ensures stable ignition.

[0057] In this embodiment, the air injected from the primary air annular gap 4 accounts for 0-100% of the oxygen required for complete combustion of the fuel; the air velocity at the primary air annular gap 4 is 0.1-1.5 times the fuel velocity. Preferably, the air velocity at the primary air annular gap is 0.2-1.3 times the fuel velocity; more preferably, the air velocity at the primary air annular gap is 0.3-1.2 times the fuel velocity; even more preferably, the air velocity at the primary air annular gap is 0.6-1.0 times the fuel velocity. Example 4

[0058] Unlike the embodiments described above, please refer to... Figure 1-2 As shown, the low NO sprayed in this embodiment x The flameless combustion device also includes an air regulating valve 9 for dynamically adjusting the supply air to the primary air annular gap 4 and the secondary air nozzle. This air regulating valve 9 is installed on the air inlet manifold 8, which is connected to the secondary air annular gap 4 and the secondary air nozzle via an air transmission channel 10, supplying air to both the secondary air annular gap 4 and the secondary air nozzle. The air transmission channel 10 is divided into two parts, a secondary air chamber 12 and a primary air chamber 13, by a partition 14. The secondary air chamber 12 is connected to the secondary air nozzle, and the primary air chamber 13 is connected to the primary air annular gap 4, supplying air to both the primary air annular gap 4 and the secondary air nozzle.

[0059] In this embodiment, the low NO xDuring operation, the ratio of primary air at the primary air annular gap 4 and / or secondary air at the secondary air nozzle can be dynamically adjusted via the air regulating valve 9. Both primary and secondary air ratios can be dynamically adjusted between 0% and 100%. Specifically, in the low-temperature stage when the furnace is just about to start up, all the air required for fuel combustion is injected through the primary air annular gap 4, at which point all secondary air nozzles are closed. In the high-temperature stage of stable combustion, all the air required for fuel combustion is injected through the secondary air nozzles. Because the secondary air nozzles are far from the fuel nozzles 3, the high-speed, fine air jets ejected from the secondary air nozzles entrain a large amount of exhaust gas, forming flameless combustion. Example 5

[0060] Unlike the embodiments described above, please refer to... Figure 1 As shown, the low NO sprayed in this embodiment x In the flameless combustion device, the secondary air nozzles include two types of nozzles, namely, a first secondary nozzle 5 and a second secondary nozzle 6, with different inner diameters. The ratio of the distance of the first secondary nozzle 5 from the geometric center of the fuel nozzle 3 to the diameter of the first secondary nozzle 5 is greater than 5. The second secondary nozzles 6 expand to the left and right sides on the burner brick 1, forming a fan-shaped spread, with an expansion angle between 0 and 60°. Several first secondary nozzles 5 and several second secondary nozzles 6 are arranged in a circular or elliptical position around the fuel nozzle, and the first secondary nozzles 5 are arranged on a circular or elliptical trajectory at the geometric center of the fuel nozzle 3.

[0061] In this embodiment, the airflow velocity of the secondary air nozzle is 10-300 m / s, and it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-18%; preferably, it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-15%; more preferably, it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-10%; even more preferably, it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 4-8%. Preferably, the airflow velocity of the secondary air nozzle is 15-200 m / s, and it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-9%. More preferably, the airflow velocity of the secondary air nozzle is 20-150 m / s, and it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 3-8%. More preferably, the airflow velocity of the secondary air nozzle is 30-120 m / s, and it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 4-7%. Based on the principle of jet entrainment, the design and flow rate selection of the secondary air nozzle ensure that a large amount of combustion products, or combustion exhaust gas, are entrained before the secondary air is mixed with the fuel, forming a mixture with an oxygen concentration between 2% and 18%, which is then mixed with the fuel to achieve flameless combustion.

[0062] This embodiment uses two secondary air nozzles 5 and 6 with different orifice diameters and a specific arrangement design, which helps to control the length of the flame and form a flat flame with a horizontal width much larger than its vertical height, thereby improving the heating temperature uniformity in both the length and horizontal width directions. Example 6

[0063] Based on the above embodiments, please refer to Figure 1 and Figure 2 As shown, in order to improve low NO x The operating range and load regulation ratio of the flameless combustion device for low NO emissions x The flameless combustion device is also equipped with an oxidizer nozzle 7, which is connected to an oxidizer pipe 17 located on the centerline of the pre-combustion chamber 2. The oxidizer nozzle 7 is located at the geometric center of the bottom of the pre-combustion chamber 2, and is situated inside the fuel nozzle 3. The oxidizer ejected from the oxidizer nozzle 7 is ordinary air, oxygen-enriched air with an oxygen concentration greater than 21%, or pure oxygen with an oxygen concentration greater than 90%. The fuel ejected from the fuel nozzle 3 is natural gas, coal gas, liquefied petroleum gas, fuel oil, coal, or petroleum coke.

[0064] In this embodiment, fuel, central oxidant, and primary air, injected sequentially from fuel nozzle 3, oxidant nozzle 7, and primary air annular slit 4, are injected into the furnace or heating zone inside the pre-combustion chamber 2 composed of refractory material. The high-temperature combustion exhaust gas—flue gas—is entrained, and the oxygen concentration in the air and central oxidant, as well as the fuel concentration in the fuel, are diluted before being mixed and combusted in the pre-combustion chamber 2. Example 7

[0065] The low NO sprayed in the above embodiments x Based on the flameless combustion device for emissions, this embodiment provides a low NO emission... x The flameless combustion method for emissions can be used in high-temperature furnaces and kilns in industries such as steel, chemicals, boilers, glass, and non-ferrous metal smelting. Specifically, the flameless combustion method includes the following steps:

[0066] (1) Normal temperature start-up stage: When the furnace burner brick temperature is normal or the process temperature is below 850℃, the fuel ignition point is reached. Primary air is supplied to the primary air ring gap through the air regulating valve and fuel is supplied to the fuel injection hole for ignition.

[0067] (2) Low-temperature combustion stage: After ignition and combustion at room temperature, the temperature of the furnace burner bricks rises. The air supply to the primary air annular gap is increased through the air regulating valve, or air is supplied to the secondary air nozzle through the air regulating valve at the same time as the primary air annular gap, so that all the oxygen required for combustion is supplied by the primary air or by both primary and secondary air, so as to carry out stable low-temperature combustion.

[0068] (3) High-temperature combustion stage: When the temperature of the furnace burner brick or the process temperature is higher than the ignition point of the fuel itself, the secondary air supplied by the secondary air nozzle is increased through the air regulating valve, or all the oxygen required for combustion is supplied by the secondary air, which mixes with the combustion products to form a mixture with an oxygen concentration of 2-18%, and then mixes with the fuel to carry out flameless combustion without obvious flame.

[0069] In this embodiment, the fuel flow rate is 8-200 m / s; the primary air flow rate is 0.1-1.5 times the fuel flow rate; and the secondary air flow rate is 10-300 m / s.

[0070] In this embodiment, in step 1, the primary air supplied from the primary air annular gap 4 can ensure reliable ignition and flame temperature, facilitating use during normal temperature start-up or low-temperature stages; the secondary air supplied from the secondary air nozzle is used to achieve flameless combustion and ensure low NO levels during normal high-temperature stages. xUniform emission and heating temperatures are crucial. To accommodate both ambient temperature ignition and low-temperature operation, an air regulating valve 9 is installed in the air inlet manifold 8 to regulate the ratio of primary and secondary air. By controlling the rotation angle of the regulating baffle, the air regulating valve 9 can completely close or open the primary air supply, or completely close or open the secondary air supply, or dynamically adjust the primary and secondary air to a specific ratio.

[0071] Specifically, the air regulating valve 9 allows for arbitrary control of the primary and / or secondary air levels between 0% and 100% of the required combustion air during actual use of the combustion device. Because the nozzles of the primary air annular gap 4 are closer to the fuel nozzles 3, combustion is promoted. In actual use, combustion is often unstable at furnace temperatures of ambient or below 850°C. To ensure stable combustion and reliable ignition, and to prevent flameout and related safety hazards, more or all of the required air is injected through the primary air annular gap 4 at low temperatures to maintain combustion temperature and prevent flameout. When the furnace or process temperature exceeds the fuel's ignition point, combustion has reached a certain temperature, eliminating the risk of flameout. At this point, more or all of the air is injected through the secondary air nozzles. Due to the special design and flow rate of the multiple secondary air nozzles, the air is pre-mixed with the combustion exhaust gas inside the furnace to form an oxygen concentration of 2-18%, which is then mixed with the fuel for combustion, resulting in flameless combustion without a visible flame. This achieves uniform temperature and significantly reduces NO. x The purpose is to achieve both low-temperature and high-temperature combustion modes in the combustion device.

[0072] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A low NO x The flameless combustion device for emissions is characterized in that, It includes a burner brick and a pre-combustion chamber disposed on the burner brick in an expanded shape, wherein: At least one fuel nozzle is provided at the bottom of the pre-combustion chamber; The bottom of the pre-combustion chamber is provided with a primary air annular gap, which is arranged in a ring around the outer periphery of the fuel nozzle. The burner brick is provided with a secondary air injection hole, which is composed of a plurality of first secondary injection holes arranged on the upper and lower sides of the fuel injection port and a plurality of second secondary injection holes arranged on the left and right sides of the fuel injection port, and the diameter of the first secondary injection hole is smaller than the diameter of the second secondary injection hole. The ratio of the distance between the first and second secondary spray holes and the geometric center line of the pre-combustion chamber to their diameter is greater than 5; the second and second secondary spray holes expand to the left and right sides on the burner bricks respectively, forming a fan-shaped spread; A plurality of first and second secondary injection holes and a plurality of second and second secondary injection holes are arranged in a circular position around the fuel injection port; The first and second nozzles have an inward bias angle β relative to the geometric center line of the pre-combustion chamber toward the combustion zone, and the bias angle β is 5°-40°. The second and secondary nozzles have an expansion angle γ relative to the geometric center line of the pre-combustion chamber and outward toward the combustion zone, and the expansion angle γ is 10°-50°.

2. The low NO content according to claim 1 x The flameless combustion device for emissions is characterized in that, The fuel nozzle is located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber; The primary air annular gap is located on a circular or elliptical trajectory at the geometric center of the pre-combustion chamber outside the fuel nozzle; and The secondary air nozzle is located on a circular trajectory at the geometric center of the pre-combustion chamber.

3. The low NO content according to claim 1 x The flameless combustion device for emissions is characterized in that, The fuel nozzle is circular or elliptical, and the fuel flow rate is 8-200 m / s.

4. The low NO content according to claim 1 x The flameless combustion device for emissions is characterized in that, A swirl vane is provided inside the primary air annular gap; the air velocity at the primary air annular gap is 0.1-1.5 times the fuel velocity.

5. The low NO content according to claim 1 x The flameless combustion device for emissions is characterized in that, Both the primary air circumferential seam and the secondary air nozzle are connected to the air inlet manifold through an air transmission channel. The air inlet manifold is equipped with an air regulating valve for adjusting the supply ratio of primary and secondary air.

6. The low NO content according to claim 1 x The flameless combustion device for emissions is characterized in that, The air velocity of the secondary air nozzle is 10-300 m / s, and it is pre-mixed with the exhaust gas produced by combustion to form a mixture with an oxygen concentration of 2-18%.

7. The low NO content according to claim 1 x The flameless combustion device for emissions is characterized in that, An oxidizer nozzle is provided at the geometric center of the bottom of the pre-combustion chamber, and the oxidizer nozzle is located inside the fuel nozzle.

8. A low NO x The flameless combustion method for reducing emissions, applied to the low NOx emission method described in claim 5. x The flameless combustion device for emissions is characterized in that, Includes the following steps: (1) Normal temperature start-up stage: When the temperature of the burner bricks in the furnace is normal, primary air is supplied to the primary air ring gap through the air regulating valve and fuel is supplied to the fuel nozzle for ignition. (2) Low-temperature combustion stage: After ignition and combustion at room temperature, the temperature of the furnace burner bricks rises. At the same time as air is supplied into the primary air annular gap, air is supplied into the secondary air nozzle through the air regulating valve, so that the oxygen required for combustion is supplied by both primary and secondary air, and stable low-temperature combustion is carried out. (3) High-temperature combustion stage: When the temperature of the furnace burner bricks is higher than the ignition point of the fuel itself, all the oxygen required for combustion is supplied by secondary air, which mixes with the combustion products to form a mixture with an oxygen concentration of 2-18%, and then mixes with the fuel to carry out flameless combustion without obvious flame.

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