A flue gas recirculation swirl burner for coal gas

Abstract

The present invention discloses a flue gas recirculation swirl burner for coal gas, comprising a central air duct, a coke oven gas channel, an inner secondary air channel, a gas channel and an outer secondary air channel which are coaxially arranged in stages from the inside to the outside; the burner also comprises a flue gas interlayer which is coaxially arranged between the inner secondary air channel and the gas channel; a coal gas swirl blade is also annularly arranged at a position near the outlet end of the gas channel; an outer secondary air swirl blade is also annularly arranged at a position near the outlet end of the outer secondary air channel; the coal gas swirl blades and the outer secondary air swirl blades are uniformly distributed along the radial direction of the corresponding pipeline. The present invention arranges a flue gas interlayer between the coal gas channel and the inner secondary channel, and introduces recirculated flue gas into the flue gas interlayer to delay the mixing of the fuel in the air and the gas channel, so that the present invention can burn coal gases of different calorific values ​​alone or in mixture, and has a wide range of fuel applications, and can also reduce nitrogen oxides for high calorific value coal gases.

Description

Technical Field

[0001] The invention belongs to the field of boiler combustion, and in particular relates to a flue gas recirculation swirl burner for coal gas. Background Art

[0002] Steel companies usually produce a variety of by-products during the iron-making process. Coal gas contains a large amount of CO, H 2 , CH 4 The gas has low impurity content and other combustible components. Using this part of the gas for power generation can not only effectively reduce energy waste, but also reduce pollutant emissions. The gas composition and calorific value produced are different. Common high calorific value gas includes COREX gas and coke oven gas, and common low calorific value gas includes blast furnace gas. The pollutants produced during gas combustion are mainly NO x and SO 2 , where NO x The amount of gas generated is closely related to the structure of the burner.

[0003] As my country's control over nitrogen oxide emissions becomes more stringent, low-nitrogen swirl burners are increasingly used in large power station boilers. x Mainly thermal NO x , the flue gas recirculation technology commonly used in low nitrogen combustion technology is for thermal NO x The principle of this technology is to extract a part of low-temperature flue gas and send it into the furnace, through the flue gas absorbing heat and reacting with O 2 The dilution effect can reduce the combustion speed and furnace temperature. The existing gas burners are mostly suitable for low calorific value fuel gas such as blast furnace gas, while the calorific value of COREX gas is 2.5 times that of blast furnace gas. When such high calorific value gas is burned or the boiler load increases, the original gas burners often have problems such as reduced burner efficiency and excessive nitrogen oxide concentration at the outlet. Therefore, it is very important to combine swirl combustion and flue gas recirculation combustion technology to research and develop a flue gas recirculation swirl burner with a wide range of applications for coal gas.

[0004] The flue gas recirculation swirl burner in the prior art is mostly suitable for boilers burning low calorific value gases. Its main purpose is to solve the instability problem in the combustion process of low calorific value gas. It is not suitable for low-nitrogen swirl combustion of high calorific value gas. It cannot solve the phenomena of decreased combustion efficiency and increased nitrogen oxide content that occur during the combustion of high calorific value gases such as COREX gas. Summary of the invention

[0005] In view of the fact that gas burners in the prior art are mostly suitable for burning low calorific value gases, and cannot effectively solve the problems of decreased combustion efficiency and increased nitrogen oxide content during the combustion of high calorific value gases, the present invention proposes a gas burner with a wide range of fuel applications and a good effect of reducing nitrogen oxides for high calorific value gases.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A flue gas recirculation swirl burner for coal gas, comprising a central air duct, a coke oven gas channel, an inner secondary air channel, a fuel gas channel and an outer secondary air channel which are coaxially arranged in stages from the inside to the outside;

[0008] The burner also includes a coaxially arranged smoke interlayer disposed between the inner secondary air channel and the gas channel;

[0009] Gas cyclone blades are also arranged in an annular manner in the gas passage near the outlet end;

[0010] The outer secondary air swirl blades are also arranged in an annular manner at a position near the outlet end of the outer secondary air channel;

[0011] The coal gas cyclone blades and the outer secondary air cyclone blades are uniformly distributed along the radial direction of the corresponding pipeline.

[0012] Furthermore, the thickness of the annular airflow channel of the smoke interlayer is 10 to 20 mm.

[0013] Furthermore, the inlets of the flue gas interlayer and the central air duct are both connected to Roots blowers, and the recirculated flue gas is introduced through the Roots blowers.

[0014] Furthermore, there are 24 outer secondary air swirl blades in total, and the blade inclination angle is 30°.

[0015] Furthermore, there are 12 coal gas cyclone blades in total, and the blade inclination angle is 45°.

[0016] Furthermore, the coal gas cyclone blades and the outer secondary air cyclone blades have the same blade inclination direction.

[0017] Furthermore, the outlet end of the coke oven gas channel is flush with the outlet end of the central air duct; the outlet ends of the inner secondary air channel, the smoke interlayer, the fuel gas channel, and the outer secondary air channel are flush.

[0018] The beneficial effects of the present invention are as follows:

[0019] (1) In the prior art, burners using flue gas recirculation technology mostly introduce air through the central channel, and there is no flue gas interlayer structure between the air inlet and the fuel inlet, which may cause excessive nitrogen oxide generation when burning high calorific value gas. The present invention provides a flue gas interlayer between the coal gas channel and the inner secondary channel, and introduces recirculated flue gas into the flue gas interlayer to delay the mixing of the air and fuel in the gas channel, so that the present invention can burn coal gases of different calorific values ​​alone or in combination, and when burning high calorific value gas, it can reduce the nitrogen oxide content generated during the combustion process while ensuring stable combustion.

[0020] (2) The burner of the present invention has a double swirl structure. Both the gas channel and the external secondary air channel are provided with swirl blades with blade inclination angles of different angles, which further strengthens the mixing between air and gas fuel and enhances combustion stability, thereby playing a role in stabilizing combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A cross-sectional view of the structure of a flue gas recirculation swirl burner for coal gas;

[0022] Figure 2 A side view of a flue gas recirculation swirl burner for coal gas;

[0023] Figure 3 It is a three-dimensional schematic diagram of the swirl blade;

[0024] Figure 4 is a cross-sectional view of the gas cyclone blade 5-2;

[0025] Figure 5 It is a cross-sectional view of the outer secondary air swirl blade 6-2.

[0026] Figure 6 This is a cloud diagram of nitrogen oxide concentration in the cross section of a commonly used burner in a gas boiler.

[0027] Figure 7 A cloud diagram of nitrogen oxide concentration in a burner cross section when the flue gas interlayer is subtracted from the burner of the present invention;

[0028] Figure 8 The figure is a nitrogen oxide concentration cloud diagram of the burner cross section using the present invention.

[0029] In the figure, 1-central air duct; 1-1 central air inlet; 2-coke oven gas channel; 2-1 coke oven gas inlet; 3-inner secondary air channel, 3-1 inner secondary air inlet; 4-smoke interlayer; 4-1 recycled smoke inlet; 5-gas channel; 5-1 gas inlet; 5-2 gas cyclone blades; 6-external secondary air channel; 6-1 external secondary air inlet; 6-2 external secondary air cyclone blades. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] like Figure 1 and 2 As shown in FIG. 1 , the flue gas recirculation swirl burner for coal gas of the present invention comprises a central air tube 1, a coke oven gas channel 2, an inner secondary air channel 3, a flue gas interlayer 4, a gas channel 5 and an outer secondary air channel 6 which are coaxially arranged in stages from the inside to the outside, and also comprises coal gas swirl blades 5-2 annularly arranged in the gas channel 5, and outer secondary air swirl blades 6-2 annularly arranged in the outer secondary air channel 6, and each swirl blade is arranged along the radial direction of the corresponding air pipe, as shown in FIG. Figures 3 to 5 shown.

[0032] Among them, the inner secondary air channel 3 and the outer secondary air channel 6 are both used for introducing air; the central air duct 1 and the smoke interlayer 4 are used for introducing recycled smoke.

[0033] The central air duct 1 is used to introduce recirculated flue gas. The inlet air duct is a curved pipe channel, and the other end of the curved pipe is connected to a Roots blower. The flue gas is drawn from the tail channel to the central air duct 1 and sprayed into the furnace to dilute the oxygen concentration in the central area of ​​the burner, effectively reducing the temperature of the main combustion zone, thereby reducing the emission of nitrogen oxides.

[0034] A coke oven gas inlet 2-1 is provided on the side wall of the coke oven gas channel 2. The coke oven gas inlet 2-1 is used to introduce coke oven gas. The coke oven gas plays a role in ignition and stable combustion during low-load operation. When the load is less than 40%, it is usually necessary to ignite the coke oven gas first, and blast furnace gas or COREX gas can be added after it is stabilized; the outlet end of the coke oven gas channel 2 is flush with the central air duct 1.

[0035] An inner secondary air inlet 3-1 is provided on the side wall of the inner secondary air channel 3, and the inner secondary air inlet 3-1 is used to introduce hot air to meet the needs of fuel combustion.

[0036] A recirculating flue gas inlet 4-1 is provided on the side wall of the flue gas interlayer 4, and the other end of the inlet is connected to a Roots blower, which draws the flue gas from the tail channel to the flue gas interlayer 4 and sprays it into the furnace. The thickness of the annular airflow channel of the flue gas interlayer 4 is 10-20 mm, thereby ensuring the stability of combustion.

[0037] The inlet 5-1 of the gas channel 5 is arranged at the end of the channel, and is used to introduce coal gas; the coal gas swirl blade 5-2 is located in the gas channel near the outlet end.

[0038] An external secondary air inlet 6-1 is provided on the side wall of the external secondary air channel 6, and the external secondary air inlet 6-1 is used to introduce hot air to ensure complete combustion of the fuel. At the same time, the external secondary air swirl blade 6-2 is located in the external secondary air channel near the outlet end.

[0039] The outlet ends of the inner secondary air channel 3, the smoke interlayer 4, the fuel gas channel 5, and the outer secondary air channel 6 are flush.

[0040] During the operation of the burner, the entrances of the central air duct 1 and the smoke interlayer 4 are connected to the Roots blower, and the smoke is drawn from the tail flue to the central air duct 1 and the smoke interlayer 4 through the Roots blower, and sprayed into the furnace. The smoke from the central air duct 1 can dilute the oxygen concentration in the central area of ​​the burner and reduce the temperature of the main combustion area. Due to the existence of the smoke interlayer 4, the smoke entering the smoke interlayer 4 will play a certain role in spacing the hot air entering the internal secondary air channel 3 and the coal gas entering the fuel gas channel 5, delaying the mixing of air and fuel, and reducing the temperature of this combustion area, thereby playing a role in reducing the emission of nitrogen oxides. The ratio of the two entering the smoke can be adjusted according to the actual combustion situation.

[0041] The hot air entering the flue gas recirculation swirl burner for coal gas is divided into two streams, inner secondary air and outer secondary air, which are respectively passed into the furnace from the inner secondary air channel 3 and the outer secondary air channel 6, with an excess air coefficient of 1.05-1.1 to meet the needs of fuel combustion. An outer secondary air swirl blade 6-2 is arranged near the outlet end of the outer secondary air channel 6, which has a certain blade inclination angle, and forms an annular outer swirl wind area in the outer secondary air channel 6, which strengthens the mixing of air and gas fuel, enhances the combustion stability, and plays a role in stabilizing combustion. Preferably, the outer secondary air swirl blade 6-2 is arranged in 24 evenly distributed pieces, and the blade inclination angle is set to 30°.

[0042] The gas fuel is introduced into the gas channel 5; the gas swirl blades 5-2 are located near the outlet end of the gas channel and have a certain blade inclination angle, forming a ring-shaped inner swirl wind area in the gas channel 5, which strengthens the mixing of air and gas fuel, enhances the combustion stability, and plays a role in stabilizing combustion. Preferably, the gas swirl blades 5-2 are arranged in a manner of 12 pieces evenly distributed, and the blade inclination angle is set to 45°.

[0043] When the flue gas recirculation swirl burner of the present invention is used to reduce the amount of nitrogen oxides generated during gas combustion, when the combustion of low calorific value gas or the low load operation of the boiler causes unstable combustion, the coke oven gas is first introduced into the coke oven gas channel 2 for ignition, and blast furnace gas or COREX gas can be added after the combustion is stable. Coke oven gas has more combustible components and belongs to high calorific value gas, which has a certain combustion stabilizing effect. The hot secondary air is divided into two streams, the inner secondary air and the outer secondary air, and sent into the furnace in stages. The two streams enter the furnace through the inner secondary air channel 3 and the outer secondary air channel 6 respectively. Due to the formation of different combustion areas, the temperature of the local area can be avoided from being too high, so that the generation of some nitrogen oxides is suppressed by air classification technology. Finally, the flue gas at the tail of the furnace is sucked into the central wind channel 1 of the burner by a fan, and the oxygen concentration in the central area of ​​the burner is diluted by the low-temperature and low-oxygen flue gas, and the temperature of the main combustion area is reduced, thereby reducing the emission of nitrogen oxides.

[0044] In order to prove the effect of the flue gas recirculation swirl burner for coal gas of the present invention on reducing the nitrogen oxide content at the furnace outlet, a numerical simulation calculation is carried out on the model of the flue gas recirculation swirl burner for coal gas of the present invention. The calculation results show that when burning COREX coal gas, the present invention can achieve the following performance indicators:

[0045] (1) When using the original burner of the gas boiler, the nitrogen oxide content at the furnace outlet is about 214.85 mg / m 3 After adopting this technical solution, the nitrogen oxide content at the furnace outlet can be reduced to 70.76 mg / m 3 The nitrogen oxide concentration cloud diagram at the burner cross section is as follows: Figure 6 , Figure 8 shown.

[0046] (2) The effect of the presence or absence of a flue gas sandwich structure on reducing the nitrogen oxide content was studied. The results showed that the installation of a flue gas sandwich structure can reduce the nitrogen oxide content at the furnace outlet by about 10 mg / m 3 The nitrogen oxide content at the furnace outlet is 80mg / m 3 After the flue gas interlayer 4 structure is set between the inner secondary air channel 3 and the gas channel 4, the nitrogen oxide content at the furnace outlet is 70.76 mg / m 3 The nitrogen oxide concentration cloud diagram at the burner cross section is as follows: Figure 7 , Figure 8 It can be seen that the provision of the flue gas interlayer 4 in the present invention plays an important role in reducing the overall nitrogen oxide concentration inside the furnace.

[0047] Those skilled in the art can understand that the above are only preferred examples of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above examples, those skilled in the art can still modify the technical solutions recorded in the above examples or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. A flue gas recirculation swirl burner for coal gas, It is characterized in that It comprises a central air duct (1), a coke oven gas channel (2), an inner secondary air channel (3), a fuel gas channel (5) and an outer secondary air channel (6) which are coaxially arranged in stages from the inside to the outside; The burner further comprises a coaxially arranged flue gas interlayer (4) provided between the inner secondary air channel (3) and the gas channel (5); Gas cyclone blades (5-2) are also arranged in an annular manner inside the gas channel (5) near the outlet end; External secondary air swirl blades (6-2) are also arranged in an annular manner in a position near the outlet end of the external secondary air channel (6); The coal gas cyclone blades (5-2) and the outer secondary air cyclone blades (6-2) are evenly distributed along the radial direction of the corresponding pipeline; The inlets of the flue gas interlayer (4) and the central air duct (1) are both connected to a Roots blower, through which the recirculated flue gas is introduced; The outer secondary air swirl blades (6-2) have a total of 24 blades, and the blade inclination angle is 30°; The coal gas cyclone blades (5-2) have a total of 12 blades, and the blade inclination angle is 45°; The coal gas cyclone blades (5-2) and the outer secondary air cyclone blades (6-2) have the same blade inclination direction.

2. The flue gas recirculation swirl burner for coal gas according to claim 1, It is characterized in that The thickness of the annular airflow channel of the smoke interlayer (4) is 10-20 mm.

3. The flue gas recirculation swirl burner for coal gas according to claim 1, It is characterized in that The outlet end of the coke oven gas channel (2) is flush with the outlet end of the central air duct (1); the outlet ends of the inner secondary air channel (3), the smoke interlayer (4), the fuel gas channel (5), and the outer secondary air channel (6) are flush.

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