Low-nitrogen combustion flue gas heating furnace system

Abstract

The utility model provides a low-nitrogen combustion flue gas heating furnace system which comprises a heating furnace and a main burner arranged on the heating furnace, and the main burner is provided with a secondary air interface, a primary air interface, a fuel gas interface and a combustion nozzle. Fuel gas input from the fuel gas connector and combustion-supporting gas input from the primary air connector are mixed and then enter the heating furnace through the combustion nozzle. A secondary air flue is arranged on the furnace wall of the heating furnace, a plurality of secondary air nozzles are evenly distributed on the heating furnace with the main burner as the center, and combustion-supporting gas input from the secondary air connector passes through the secondary air flue and then enters the heating furnace through the secondary air nozzles. Original combustion-supporting gas input at a time is divided into primary air and secondary air, so that the primary air is not enough to completely burn out the fuel gas, and the residual unburned fuel gas is mixed with the secondary air again in the heating furnace to be burnt again, so that the effects of dispersing a combustion area and reducing the highest combustion temperature of a hearth are achieved; the generation of thermal nitrogen oxides is effectively inhibited.

Description

Technical Field

[0001] This utility model relates to the field of flue gas heating furnace technology, and specifically to a low-NOx combustion flue gas heating furnace system. Background Technology

[0002] Nitrogen oxides (NOx) are one of the main air pollutants emitted by steel enterprises and are a key monitoring target in the air pollutant emission standards for the steel industry. NOx is classified into fuel-type, rapid-type, and thermal-type based on its formation pathway. Fuel-type NOx is formed by the thermal decomposition and further oxidation of nitrogen-containing compounds in fuels during combustion, commonly found in solid fuels such as coal. Rapid-type NOx is formed during mixed combustion, where nitrogen in the air reacts with hydrocarbon ions in the fuel; the amount formed is relatively small, usually less than 5% of the total. Thermal NOx is typically formed at high temperatures (≥1200℃) during combustion, through the oxidation of nitrogen in the air; when the temperature exceeds 1300℃, the formation rate of NOx increases exponentially with increasing temperature.

[0003] Flue gas heaters are commonly used thermal equipment in steel enterprises, employing various types of fuel gas as the combustion medium to generate high-temperature flue gas for processes such as drying, preheating, and roasting. Existing flue gas heater systems consist of the heater body and its associated piping and instrumentation. The main burner on the heater is a dual-channel burner, with one air channel and one fuel gas channel. The fuel gas and air are distributed and mixed by the burner before being fed into the furnace for combustion.

[0004] The combustion temperatures of various types of fuel gas commonly used in steel enterprises are relatively high. When neither air nor fuel gas is preheated, and an excess air coefficient of 1.1 is selected, the converter gas (approximately 1450 kcal / Nm³)... 3 The theoretical combustion temperature of coke oven gas is approximately 1600℃, and the combustion temperature of coke oven gas is approximately 4000 kcal / Nm³. 3 ) and natural gas (approximately 8400 kcal / Nm³) 3 The theoretical combustion temperature of the gas is approximately 1900℃, and it exceeds 1250℃ even with a furnace temperature coefficient of 0.8. Due to the high combustion temperature of the gas in the heating furnace, a large amount of thermal nitrogen oxides are generated, making it difficult for the nitrogen oxide concentration in the flue gas to meet emission standards. Therefore, it is necessary to carry out emission reduction modifications and upgrades to the original process system and equipment.

[0005] In summary, there is an urgent need for a low-NOx combustion flue gas heating furnace system to solve the problems existing in the current technology. Utility Model Content

[0006] The purpose of this invention is to provide a low-NOx combustion flue gas heating furnace system, which aims to solve the problem that existing heating furnaces generate a large amount of thermal nitrogen oxides due to high combustion temperatures, making it difficult for the NOx concentration in the flue gas to meet emission standards. The specific technical solution is as follows:

[0007] A low-NOx combustion flue gas heating furnace system includes a heating furnace and a main burner mounted on the heating furnace. The main burner is equipped with a secondary air inlet, a primary air inlet, a gas inlet, and a combustion nozzle. Gas input from the gas inlet mixes with combustion-supporting gas input from the primary air inlet and then enters the interior of the heating furnace through the combustion nozzle. The furnace wall of the heating furnace is provided with a secondary air duct, and multiple secondary air nozzles are evenly distributed on the heating furnace around the main burner. Combustion-supporting gas input from the secondary air inlet passes through the secondary air duct and then enters the interior of the heating furnace through the secondary air nozzles.

[0008] Preferably, the air volume input from the primary air interface accounts for 25%-35% of the total input air volume, and the air volume input from the secondary air interface accounts for 65%-75% of the total input air volume; wherein, the total input air volume is the sum of the air volume input from the primary air interface and the air volume input from the secondary air interface.

[0009] Preferably, the main burner is provided with multiple combustion nozzles, which are evenly distributed around the axis of the main burner.

[0010] Preferably, the main burner is provided with a mounting flange, and the main burner is mounted on the heating furnace through the mounting flange.

[0011] Preferably, multiple secondary air nozzles are evenly distributed around the main burner on the end wall where the main burner is installed and / or on the ring wall of the heating furnace.

[0012] Preferably, it also includes a gas delivery pipeline and a combustion-supporting gas delivery main pipeline, wherein the output end of the combustion-supporting gas delivery main pipeline is provided with a first branch and a second branch in parallel, wherein the first branch is connected to the primary air interface, the second branch is connected to the secondary air interface, and the gas delivery pipeline is connected to the gas interface.

[0013] Preferably, the heating furnace is equipped with a pressure detector, a flame detector, and a temperature detector; a gas leak detector is installed at the main burner.

[0014] Preferably, regulating valves are provided on the gas transmission pipeline, the first branch, and the second branch;

[0015] The gas delivery pipeline is equipped with a pressure detector and a flow detector; the main gas delivery pipeline is equipped with a pressure detector, and the first branch and the second branch are both equipped with flow detectors.

[0016] The gas delivery pipeline is equipped with a quick-cut valve, which is linked to the flame detector, the pressure detector on the gas delivery pipeline, and the pressure detector on the main gas delivery pipeline.

[0017] Preferably, the gas delivery pipeline, the first branch, and the second branch are all equipped with butterfly valves at the end near the main burner.

[0018] Preferably, the system also includes a fan and a silencer, wherein the outlet of the fan is connected to the input end of the main combustion gas delivery pipeline, the inlet of the fan is connected in series with the silencer, and a damper is provided between the fan and the silencer.

[0019] The application of the technical solution of this utility model has the following beneficial effects:

[0020] The flue gas heating furnace system of this utility model is equipped with a secondary air delivery channel in the main burner and the heating furnace. The original one-time input combustion gas is divided into primary air and secondary air. By controlling the ratio of primary air to secondary air, the primary air is insufficient to completely burn the gas. The remaining unburned gas is mixed with the secondary air in the heating furnace to achieve re-combustion. This achieves the effect of dispersing the combustion zone, reducing the maximum combustion temperature in the furnace, effectively inhibiting the generation of thermal nitrogen oxides, and protecting the refractory lining of the heating furnace.

[0021] The secondary air nozzle is located on the end wall where the main burner is installed in the heating furnace and / or on the ring wall of the heating furnace, which can recover part of the heat from the end wall and ring wall of the heating furnace and improve the thermal efficiency of the flue gas heating furnace system.

[0022] This utility model achieves the supply of natural gas, primary combustion gas, and secondary combustion gas by setting up a natural gas delivery pipeline, a main combustion gas delivery pipeline, a first branch pipeline, and a second branch pipeline. The supply flow rate in the pipeline can be easily adjusted by regulating valves on each pipeline, increasing the adjustability of the system and ensuring that the flue gas heating furnace system is in a highly efficient combustion condition. Pressure detectors and flow detectors facilitate real-time monitoring of the pressure and flow rate of each pipeline, ensuring the safe and efficient operation of the system.

[0023] The flue gas heating furnace system of this utility model is equipped with a gas leak detector, which can detect whether a gas leak has occurred and prevent gas leaks from causing safety accidents.

[0024] The flue gas heating furnace system of this utility model links the quick-cut valve with the flame detector, the pressure detector on the gas supply pipeline, and the pressure detector on the main combustion gas supply pipeline. When the furnace is extinguished, or the pressure in the gas supply pipeline or the main combustion gas supply pipeline is too low, the gas supply is cut off by the quick-cut valve to prevent unburned gas from being continuously supplied to the furnace and causing a safety accident. At the same time, cutting off the gas supply when the pressure in the main combustion gas supply pipeline is too low can prevent gas from entering the main combustion gas supply pipeline and causing backfire and explosion.

[0025] In addition to the objectives, features, and advantages described above, this utility model has other objectives, features, and advantages. The present utility model will now be described in further detail with reference to the figures. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0027] Figure 1 This is a flowchart of the flue gas heating furnace system of this utility model;

[0028] Figure 2 yes Figure 1 Schematic diagram of the structure of the intermediate heating furnace and the main burner;

[0029] Figure 3 yes Figure 2 Sectional view at point AA;

[0030] Figure 4 yes Figure 1 Front view of the main burner;

[0031] Among them, 1. Main burner, 1.1 Mounting flange, 1.2 Secondary air interface, 1.3 Primary air interface, 1.4 Gas interface, 1.5 Combustion nozzle, 2. Heating furnace, 2.1 Secondary air duct, 2.2 Secondary air nozzle, 3. Gas transmission pipeline, 4. Main combustion gas transmission pipeline, 4.1 First branch, 4.2 Second branch, 5. Pressure detector, 6. Flow detector, 7. Regulating valve, 8. Quick-cut valve, 9. Gas leak detector, 10. Flame detector, 11. Fan, 12. Silencer, 13. Butterfly valve, 14. Temperature detector, 15. Damper. Detailed Implementation

[0032] To facilitate understanding of this invention, a more comprehensive description is provided below, along with preferred embodiments. However, this invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0034] Example:

[0035] See Figures 1-4 This embodiment provides a low-NOx combustion flue gas heating furnace system, including a heating furnace 2 and a main burner 1 disposed on the heating furnace 2. The main burner 1 is provided with a secondary air inlet 1.2, a primary air inlet 1.3, a gas inlet 1.4, and a combustion nozzle 1.5. The gas input from the gas inlet 1.4 is mixed with the combustion-supporting gas input from the primary air inlet 1.3 and then enters the interior of the heating furnace 2 through the combustion nozzle 1.5. The furnace wall of the heating furnace 2 is provided with a secondary air duct 2.1, and multiple secondary air nozzles 2.2 are evenly distributed on the heating furnace 2 with the main burner 1 as the center. The combustion-supporting gas input from the secondary air inlet 1.2 passes through the secondary air duct 2.1 and then enters the interior of the heating furnace 2 through the secondary air nozzles 2.2.

[0036] In the flue gas heating furnace system of this embodiment, the combustion-supporting gas input through the primary air interface 1.3 and the gas input through the gas interface 1.4 are fully mixed in the main burner 1 (for the structure to achieve full mixing of the two gases, please refer to the prior art), and then injected into the interior of the heating furnace through the combustion nozzle 1.5 for combustion. The combustion-supporting gas input through the secondary air interface 1.2 enters the secondary air duct 2.1 and is then injected into the interior of the heating furnace through the secondary air nozzle 2.2, thereby assisting in the combustion of unburned gas in the heating furnace. By setting up primary and secondary air, the combustion zone in the heating furnace can be dispersed, the maximum combustion temperature of the furnace can be reduced, the generation of thermal nitrogen oxides can be suppressed, and the refractory lining of the heating furnace can be protected.

[0037] Furthermore, in this embodiment, the air volume input from the primary air interface 1.3 accounts for 25%-35% of the total input air volume, and the air volume input from the secondary air interface 1.2 accounts for 65%-75% of the total input air volume; wherein, the total input air volume is the sum of the air volume input from the primary air interface 1.3 and the air volume input from the secondary air interface 1.2. By controlling the proportion of primary and secondary air, the primary air is insufficient to completely burn the gas, and the remaining unburned gas diffuses in the heating furnace and mixes with the secondary air again to achieve re-combustion, thereby achieving the effect of dispersing the combustion zone and reducing the maximum combustion temperature in the furnace.

[0038] See Figures 2-3 The main burner 1 is provided with multiple combustion nozzles 1.5, which are evenly distributed around the axis of the main burner 1. Each combustion nozzle 1.5 is evenly distributed circumferentially around the axis of the main burner 1, thereby achieving uniform injection of the mixed gas and primary combustion-supporting gas into the interior of the heating furnace and avoiding concentration of the combustion area. Furthermore, in this embodiment, one combustion nozzle 1.5 is arranged on the axis of the main burner 1, and the remaining combustion nozzles 1.5 are arranged in multiple rings on the main burner, wherein the center of the ring coincides with the axis of the main burner.

[0039] See Figure 4 The main burner 1 is provided with a mounting flange 1.1. The main burner 1 is mounted on the heating furnace 2 through the mounting flange 1.1, and the main burner is detachably assembled on the heating furnace through the mounting flange 1.1.

[0040] like Figures 2-3 As shown, in this embodiment, multiple secondary air nozzles 2.2 are evenly distributed around the main burner 1 on the end wall and / or the annular wall of the heating furnace 2 where the main burner 1 is installed. This allows for the uniform injection of secondary combustion-supporting gas around the main burner, thereby expanding the combustion zone in the heating furnace and recovering some of the heat from the end wall and annular wall of the heating furnace, thus improving thermal efficiency. In this embodiment, the annular wall refers to the side wall circumferentially along the axis of the heating furnace.

[0041] See Figure 1 The flue gas heating furnace system further includes a gas supply pipeline 3 and a combustion-supporting gas supply pipeline 4. The output end of the combustion-supporting gas supply pipeline 4 is connected in parallel with a first branch 4.1 and a second branch 4.2. The first branch 4.1 is connected to the primary air interface 1.3, the second branch 4.2 is connected to the secondary air interface 1.2, and the gas supply pipeline 3 is connected to the gas interface 1.4, thereby realizing the supply of gas, primary combustion-supporting gas and secondary combustion-supporting gas.

[0042] Furthermore, regulating valves 7 are provided on the gas transmission pipeline 3, the first branch 4.1, and the second branch 4.2. The flow rate of each pipeline can be adjusted by the regulating valves to adjust the supply of gas, primary combustion-supporting gas, and secondary combustion-supporting gas according to demand. Pressure detectors 5 and flow detectors 6 are provided on the gas transmission pipeline 3, pressure detectors 5 are provided on the main combustion-supporting gas transmission pipeline 4, and flow detectors 6 are provided on the first branch 4.1 and the second branch 4.2. The flow rate and pressure of each pipeline can be detected by pressure detectors 5 and flow detectors 6, so as to facilitate real-time understanding of the flow rate and pressure of each pipeline.

[0043] Preferably, the heating furnace 2 is equipped with a pressure detector 5, a flame detector 10, and a temperature detector 14, so as to detect the pressure, temperature, and flame inside the heating furnace, and facilitate understanding of the combustion situation in the heating furnace.

[0044] Furthermore, the gas supply pipeline 3 is equipped with a quick-cut valve 8, which is linked with the flame detector 10, the pressure detector 5 on the gas supply pipeline 3, and the pressure detector 5 on the main combustion gas supply pipeline 4 for control. When the furnace is extinguished, the pressure in the gas supply pipeline 3 is too low, or the pressure in the main combustion gas supply pipeline 4 is too low, the gas supply is cut off by the quick-cut valve 8 to prevent unburned gas from being continuously supplied to the furnace, which could cause a safety accident. At the same time, cutting off the gas supply when the pressure in the main combustion gas supply pipeline 4 is too low can prevent gas from entering the main combustion gas supply pipeline 4 and causing a backfire explosion.

[0045] Preferably, a gas leak detector 9 is provided at the main burner 1. The gas leak detector 9 can detect whether a gas leak has occurred, so as to prevent the gas leak from causing a safety accident. In this embodiment, the gas leak detector is preferably a carbon monoxide sensor.

[0046] Furthermore, the gas transmission pipeline 3, the first branch 4.1 and the second branch 4.2 are each equipped with a butterfly valve 13 at the end near the main burner 1. The butterfly valve 13 is used to control the opening and closing of the pipeline, which facilitates the maintenance of the equipment.

[0047] Furthermore, the flue gas heating furnace system also includes a fan 11 and a silencer 12. The air outlet of the fan 11 is connected to the input end of the main pipeline 4 for supplying combustion gas, and the air inlet of the fan is connected in series with the silencer. A damper 15 is provided between the fan and the silencer. In this embodiment, a butterfly valve 13 is also provided at the air outlet of the fan 11 (in some embodiments, the butterfly valve 13 may not be provided at the air outlet of the fan; those skilled in the art can flexibly adjust the pipeline design). The silencer 12 can reduce the noise generated when the system is working.

[0048] Specifically, in this embodiment, the gas transmission pipeline 3 includes a pressure detector 5, a flow detector 6, a regulating valve 7, a quick-cut valve 8, and a butterfly valve 13 arranged sequentially along the gas transmission direction; the combustion-supporting gas transmission main pipeline 4 includes a silencer 12, a damper 15, a fan 11, a butterfly valve 13, and a pressure detector 5 arranged sequentially along the combustion-supporting gas transmission direction; the first branch 4.1 includes a flow detector 6, a regulating valve 7, and a butterfly valve 13 arranged sequentially along the primary combustion-supporting gas transmission direction; the second branch 4.2 includes a flow detector 6, a regulating valve 7, and a butterfly valve 13 arranged sequentially along the secondary combustion-supporting gas transmission direction.

[0049] Preferably, the combustion-supporting gas in this embodiment is air.

[0050] The effect of applying the technical solution of this embodiment is:

[0051] In this embodiment, the flue gas heating furnace system incorporates a secondary air delivery channel in the main burner and the heating furnace. This divides the originally input combustion gas into primary and secondary air. By controlling the ratio of primary and secondary air, the primary air is insufficient to completely burn the gas. The remaining unburned gas is then mixed with the secondary air in the heating furnace for re-combustion. This disperses the combustion zone, reduces the maximum combustion temperature in the furnace, effectively suppresses the formation of thermal nitrogen oxides, and protects the refractory lining of the heating furnace.

[0052] The secondary air nozzle is located on the end wall of the heating furnace 2 where the main burner 1 is installed and / or on the ring wall of the heating furnace 2, which can recover part of the heat from the end wall and the ring wall of the heating furnace and improve the thermal efficiency of the flue gas heating furnace system.

[0053] This embodiment achieves the supply of natural gas, primary combustion gas, and secondary combustion gas by setting up a natural gas delivery pipeline 3, a combustion-supporting gas delivery main pipeline 4, a first branch pipeline 4.1, and a second branch pipeline 4.2. The supply flow rate in the pipeline can be easily adjusted by the regulating valves on each pipeline, increasing the adjustability of the system and ensuring that the flue gas heating furnace system is in a highly efficient combustion condition. Pressure detectors and flow detectors facilitate real-time monitoring of the pressure and flow rate of each pipeline, ensuring the safe and efficient operation of the system.

[0054] The flue gas heating furnace system in this embodiment is equipped with a gas leak detector. The gas leak detector 9 can detect whether a gas leak has occurred, thus preventing gas leaks from causing safety accidents.

[0055] In this embodiment, the flue gas heating furnace system links the quick-cut valve with the flame detector, the pressure detector on the gas supply pipeline, and the pressure detector on the main combustion gas supply pipeline. When the furnace is extinguished, or the pressure in the gas supply pipeline or the main combustion gas supply pipeline is too low, the gas supply is cut off by the quick-cut valve to prevent unburned gas from being continuously supplied to the furnace, which could cause a safety accident. At the same time, cutting off the gas supply when the pressure in the main combustion gas supply pipeline is too low can prevent gas from entering the main combustion gas supply pipeline and causing a backfire explosion.

[0056] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A low NOx combustion flue gas heater system, characterized by, The application relates to a heating furnace (2) and a main burner (1) arranged on the heating furnace (2), wherein the main burner (1) is provided with a secondary air interface (1.2), a primary air interface (1.3), a gas interface (1.4) and a combustion nozzle (1.5); the gas input from the gas interface (1.4) is mixed with the combustion-supporting gas input from the primary air interface (1.3) and then enters the inside of the heating furnace (2) through the combustion nozzle (1.5); the heating furnace (2) is provided with a secondary air channel (2.1) on the furnace wall; the heating furnace (2) is uniformly provided with a plurality of secondary air nozzles (2.2) around the main burner (1); the combustion-supporting gas input from the secondary air interface (1.2) enters the inside of the heating furnace (2) through the secondary air nozzles (2.2) after passing through the secondary air channel (2.1).

2. The low NOx combustion flue gas heater system of claim 1, wherein, The air volume input from the primary air interface (1.3) accounts for 25%-35% of the total air volume, and the air volume input from the secondary air interface (1.2) accounts for 65%-75% of the total air volume; wherein the total air volume is the sum of the air volume input from the primary air interface (1.3) and the air volume input from the secondary air interface (1.2).

3. The low NOx combustion flue gas heater system of claim 1, wherein, The main burner (1) is provided with a plurality of combustion nozzles (1.5), and the plurality of combustion nozzles (1.5) are uniformly arranged around the axis of the main burner (1).

4. The low NOx combustion flue gas heater system of claim 1, wherein, The main burner (1) is provided with a mounting flange (1.1), and the main burner (1) is mounted on the heating furnace (2) through the mounting flange (1.1).

5. The low NOx combustion flue gas heater system of claim 1, wherein, A plurality of secondary air nozzles (2.2) are uniformly arranged around the main burner (1) on the end wall of the heating furnace (2) where the main burner (1) is mounted and / or the ring wall of the heating furnace (2).

6. The low NOx combustion flue gas heater system of any of claims 1-5, wherein, The application further comprises a gas delivery pipeline (3) and a combustion-supporting gas delivery main pipeline (4); the output end of the combustion-supporting gas delivery main pipeline (4) is provided with a first branch (4.1) and a second branch (4.2) in parallel, wherein the first branch (4.1) is connected with the primary air interface (1.3), the second branch (4.2) is connected with the secondary air interface (1.2), and the gas delivery pipeline (3) is connected with the gas interface (1.4).

7. The low NOx combustion flue gas heater system of claim 6, wherein, The heating furnace (2) is provided with a pressure detector (5), a flame detector (10) and a temperature detector (14); the main burner (1) is provided with a gas leakage detector (9).

8. The low NOx combustion flue gas heater system of claim 7, wherein, The gas delivery pipeline (3), the first branch (4.1) and the second branch (4.2) are all provided with adjusting valves (7); The gas delivery pipeline (3) is provided with a pressure detector (5) and a flow detector (6); the combustion-supporting gas delivery main pipeline (4) is provided with a pressure detector (5), and the first branch (4.1) and the second branch (4.2) are both provided with flow detectors (6); The gas delivery pipeline (3) is provided with a quick cut valve (8), and the quick cut valve (8) is linked and controlled by the flame detector (10), the pressure detector (5) on the gas delivery pipeline (3) and the pressure detector (5) on the combustion-supporting gas delivery main pipeline (4).

9. The low NOx combustion flue gas heater system of claim 8, wherein, The gas delivery pipeline (3), the first branch (4.1) and the second branch (4.2) are each provided with a butterfly valve (13) at one end close to the main burner (1).

10. The low NOx combustion flue gas heater system of claim 6, wherein, The fan (11) and the silencer (12) are further included, the air outlet of the fan (11) is connected with the input end of the combustion-supporting gas delivery main pipeline (4), the air inlet of the fan (11) is connected with the silencer in series, and the fan and the silencer are provided with an air door (15) therebetween.

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