Natural gas non-premixed hydrogen-doped ultra-low no x coaxial burner

Abstract

The application discloses a natural gas non-premixed hydrogen-mixed ultra-low NOx coaxial burner, which comprises a burner outer throat, a premixing cavity, a natural gas cylinder, a natural gas pipeline, an air pipeline, a central hydrogen pipe and a cyclone device. Hydrogen is transported through the central hydrogen pipe, and a non-premixed mode is adopted. Since hydrogen does not need to be premixed with air and natural gas, the hydrogen-mixed proportion is greatly improved, and the hydrogen production proportion can be close to 100%. Natural gas and air are leanly premixed in the premixing cavity, the central hydrogen pipe provides a pilot flame, and the distance between the cyclone device and the central hydrogen pipe is set to have the effect of stabilizing the flame and suppressing the risk of backfire. No flue gas external circulation is used, and the NOx emission can be stabilized at ≤30 mg / Nm 3 under different loads.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of industrial gas burner combustion, in particular to a natural gas non-premixed hydrogen-doped ultra-low NOx coaxial burner. BACKGROUND

[0002] Natural gas is increasingly replacing coal-based energy, and the carbon emission intensity of natural gas used for heating or power generation is only 57% of that of coal. It is predicted that the proportion of natural gas in primary energy consumption in China will increase to 15% by 2030. However, natural gas still has its own carbon emissions, and China has a high degree of dependence on foreign countries. Therefore, with the decreasing cost of hydrogen produced by wind and solar energy in China, the use of hydrogen and other zero-carbon fuels to gradually replace natural gas is a major demand for further development.

[0003] There are mainly two ways to use natural gas hydrogen-doped combustion, one is pipeline hydrogen-doping, which has developed rapidly in recent years, but is limited by safety problems such as hydrogen embrittlement of pipeline materials and leakage, and the hydrogen-doping ratio is less than 20%, and the actual application is less than 10%. With the increasing demand for large-scale, non-premixed hydrogen-doping, China currently urgently needs to make breakthroughs in non-premixed hydrogen-doping combustion technology. SUMMARY

[0004] The application provides a natural gas non-premixed hydrogen-doped ultra-low NOx coaxial burner, which can solve the problem of low hydrogen-doping ratio of pipeline hydrogen-doping.

[0005] In the application, a natural gas non-premixed hydrogen-doped ultra-low NOx coaxial burner is provided, which comprises an outer throat of a burner and comprises: a premixing cavity fixedly connected at one end to the outer throat of the burner; a natural gas cylinder fixedly arranged on the outer wall of the premixing cavity; a plurality of natural gas inlet holes are arranged on the outer wall of the premixing cavity and located at the natural gas cylinder; a natural gas pipeline, one end of which is fixedly connected to the natural gas cylinder and communicates with the inside of the natural gas cylinder; an air pipeline, one end of which is fixedly connected to the premixing cavity and communicates with the inside of the premixing cavity; a central hydrogen pipe, which is located inside the premixing cavity, the distance between one end of the central hydrogen pipe and the outer throat of the burner is 10 mm, and the other end of the central hydrogen pipe extends out of the premixing cavity from the upstream end of the premixing cavity; a swirler, which comprises a plurality of blades, the plurality of blades are arranged obliquely in a circumferential array on the outer wall of the central hydrogen pipe, and the central hydrogen pipe is fixedly connected to the inner wall of the premixing cavity through the plurality of blades.

[0006] In one embodiment, the natural gas cylinder is fixedly arranged upstream of the premixing cavity, and the distance between the natural gas cylinder and the outer throat of the burner is greater than or equal to 385 mm; the air pipeline is also fixedly arranged upstream of the premixing cavity.

[0007] In one embodiment, the air pipe is located behind the natural gas pipe in the front-rear direction.

[0008] In one embodiment, the distance between the swirler and the outer throat of the combustor is 20 mm.

[0009] In one embodiment, the vanes are 12, and the 12 vanes are equidistantly arranged on the outer wall of the central hydrogen pipe, and the inclination angle of each vane is 45°.

[0010] In one embodiment, the natural gas inlet holes are 4, and the 4 natural gas inlet holes are arranged equidistantly on the premixing pipe in a circular array.

[0011] In summary, in the present application, the natural gas non-premixed hydrogen-doped ultra-low NOx coaxial combustor has the following beneficial effects compared to the prior art:

[0012] The hydrogen is transported by the central hydrogen pipe, and a non-premixed mode is adopted. Since the hydrogen does not need to be premixed with air and natural gas, the hydrogen-doped ratio is greatly improved, and the hydrogen production ratio can be as high as nearly 100%;

[0013] The natural gas and air are leanly premixed in the premixing chamber, the central hydrogen pipe provides a pilot flame, and the distance between the swirler and the central hydrogen pipe has the effect of stabilizing the flame and suppressing the risk of backfire;

[0014] No flue gas external circulation is used, and the NOx emission can be stabilized at ≤30 mg / Nm 3 under different loads. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to better clarify the technical solutions in the embodiments or background art of the present application, the drawings required to be used in the embodiments or background art of the present application will be described below.

[0016] Figure 1 It is a whole structure view of the natural gas non-premixed hydrogen-doped ultra-low NOx coaxial combustor.

[0017] Figure 2 It is a front view of the natural gas non-premixed hydrogen-doped ultra-low NOx coaxial combustor.

[0018] Figure 3 It is Figure 2 a sectional view along A-A.

[0019] Figure 4 It is Figure 3 an enlarged view of the B area.

[0020] Figure 5 It isFigure 4 Enlarged view of region C;

[0021] Figure 6 For Figure 4 Enlarged view of region D;

[0022] Figure 7 For isometric view;

[0023] Figure 8 For fuel component cloud Figure 1 ;

[0024] Figure 9 For fuel component cloud Figure 2 ;

[0025] Figure 10 For temperature cloud;

[0026] Figure 11 For flow field.

[0027] In the figure, 1, burner outer throat; 2, premixing chamber; 3, natural gas inlet hole; 4, natural gas cylinder; 5, air duct; 6, swirler; 7, blade; 8, central hydrogen pipe; 9, natural gas duct. Embodiment

[0028] The specific embodiments of the present application will be further described in conjunction with the accompanying drawings. The following examples are intended to describe the present application and are not intended to limit the scope of the present application. The described embodiments are part of the embodiments of the present disclosure, but not all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present disclosure.

[0029] Unless otherwise defined, technical or scientific terms used in the present disclosure should be understood as having the ordinary meaning commonly used by those skilled in the art to which the present disclosure belongs. The terms "comprise" or "include" and similar words used in the present disclosure mean that the elements or objects before the word encompass the elements or objects listed after the word and their equivalents, and do not exclude other elements or objects. "Front", "back", "left", "right" and the like are only used to represent relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] The natural gas non-premixed hydrogen mixing ultra-low NOx coaxial burner comprises a burner outer throat 1, a premixing chamber 2, a natural gas cylinder 4, a natural gas duct 9, an air duct 5, a central hydrogen pipe 8 and a swirler 6.

[0031] Please refer to Figure 1 , the burner outer throat 1 is prior art, which will not be described in detail here.

[0032] Referring to Figure 1 In the present application, the upstream of the premixing pipe is defined as the front, and the downstream is defined as the back.

[0033] Referring to Figure 1 The fluid outlet end of the premixing cavity 2 is fixedly connected to the outer throat 1 of the burner, the premixing cavity 2 is a hollow pipe, the other end of the premixing cavity 2 is sealed, and the premixing cavity 2 is in communication with the inside of the outer throat 1 of the burner. The premixing cavity 2 is used to realize the premixing of natural gas and air.

[0034] Referring to Figure 2 , Figure 3 , Figure 4 , Figure 5 The natural gas cylinder 4 is fixedly arranged on the outer wall of the premixing cavity 2, and the natural gas cylinder 4 is a hollow cylinder. The premixing cavity 2 is provided with a plurality of natural gas inlet holes 3, which are through holes located at the natural gas cylinder 4. Natural gas enters the premixing cavity 2 from the natural gas cylinder 4 through the natural gas inlet holes 3. In one embodiment, the natural gas inlet holes 3 are four, the positions of the four natural gas inlet holes 3 in the front-back direction are consistent, and the four natural gas inlet holes 3 are arranged on the premixing pipe in a circumferential array with equal intervals. In this way, natural gas can enter the premixing cavity 2 from the natural gas cylinder 4 more uniformly, which is conducive to the premixing of natural gas and air. In one embodiment, the diameter of the natural gas inlet hole 3 is 4mm, which is a conventional setting.

[0035] Referring to Figure 5 One end of the natural gas pipeline 9 is fixedly connected to the natural gas cylinder 4 and is in communication with the inside of the natural gas cylinder 4, and is used to transport natural gas fluid into the natural gas cylinder 4.

[0036] Referring to Figure 5 One end of the air pipeline 5 is fixedly connected to the premixing cavity 2 and is in communication with the inside of the premixing cavity 2, and is used to transport air into the premixing cavity 2.

[0037] Referring to Figure 5In one embodiment, the natural gas cylinder 4 is fixed upstream of the pre-mixing chamber 2, i.e. on the side of the pre-mixing chamber 2 further away from the combustor outer throat 1, and the distance between the natural gas cylinder 4 and the combustor outer throat 1 is ≥ 385 mm; the air pipe 5 is also fixed upstream of the pre-mixing chamber 2. In this way, sufficient pre-mixing length is provided for air and natural gas to mix more uniformly. Preferably, the distance between the natural gas cylinder 4 and the combustor outer throat 1 is equal to 385 mm. In this way, sufficient pre-mixing of air and natural gas can be achieved without using excessive materials, which would result in material waste and increase the size of the mechanism.

[0038] Please refer to Figure 5 In one embodiment, preferably, in the front-rear direction, the air pipe 5 is located rearward of the natural gas pipe 9. In this way, a large amount of natural gas can be prevented from accumulating at the rear end of the pre-mixing chamber 2, resulting in waste.

[0039] Please refer to Figure 5 , Figure 6 The central hydrogen pipe 8 is located inside the pre-mixing chamber 2, and the central hydrogen pipe 8 is a hollow pipe-shaped structure for conveying hydrogen gas. Hydrogen gas is conveyed through the central hydrogen pipe 8 in a non-premixed manner, which greatly increases the hydrogen mixing ratio, allowing the hydrogen production ratio to be as high as nearly 100% without pre-mixing with air and natural gas. The distance between one end of the central hydrogen pipe 8 and the combustor outer throat 1 is 10 mm, and the other end of the central hydrogen pipe 8 extends out of the pre-mixing chamber 2 from the upstream end of the pre-mixing chamber 2.

[0040] Please refer to Figure 6 The swirler 6 includes a plurality of blades 7, and the plurality of blades 7 are obliquely arranged in a circumferential array on the outer wall of the central hydrogen pipe 8, and the central hydrogen pipe 8 is fixedly connected to the inner wall of the pre-mixing chamber 2 through the plurality of blades 7. In one embodiment, in the front-rear direction, the distance between the swirler 6 and the combustor outer throat 1 is 20 mm, and the distance between the swirler 6 and the front end of the central hydrogen pipe 8 is 10 mm. In this way, the flame is stabilized and the risk of backfire is suppressed. In one embodiment, the swirler 6 includes 12 blades 7, and the 12 blades 7 are equidistantly arranged on the outer wall of the central hydrogen pipe 8, and the oblique angle of each blade 7 is 45°, and the thickness of the blade 7 is 8 mm.

[0041] Please refer to Figure 7, after the simulation data, in the steady-state numerical calculation of this natural gas non-premixed hydrogen mixed ultra-low NOx coaxial burner hot state, as shown in the simulation isometric view, the calculation domain contains the swirler structure, and the model is simplified, the premixed section at the upstream end of the burner is removed, the methane and air inlets are set in the circular ring area, it is assumed to be fully mixed, unstructured polyhedral grid is adopted, the grid number is about 58,000, the combustion chamber is a cylindrical cavity with a diameter of 250 mm and a length of 690 mm.

[0042] The designed power of the burner is 50 kW, and the calculation conditions are 60% hydrogen mixed ratio and 0.75 equivalence ratio. The simulation inlet boundary conditions are all mass flow rate, the center hydrogen pipe fuel inlet is set to 0.0002621 kg / s of 100% hydrogen, the circular ring inlet is set to 0.0223399 kg / s of 20.28% oxygen, 76.28% nitrogen and 3.44% methane mixed gas, the outlet is set to a 100 mm diameter coaxial circular plane pressure outlet; the turbulence model is k-ε Realizable model, the combustion model is edc model, and the radiation model is DO model, and the wall surface is set to 500 K temperature.

[0043] Referring to Figures 8-10 The simulation results are as follows: From the fuel component cloud map, it can be seen that the methane and air mixed gas stream burns at the nozzle, and no extraction combustion occurs, and the combustion width and length are larger than the hydrogen combustion range. From the temperature cloud map, it can be seen that the flame occurs lifting phenomenon, the root is wide, and the flame shape is similar to "bowl-shaped" structure, which is beneficial to avoid the occurrence of backfire phenomenon. The flow field diagram shows a standard strong swirl flow field diagram, the strong swirl nozzle generates a central large recirculation zone through strong swirl to make the flame stable on the central bluff body, and forms a small outer recirculation zone on the wall. The formation of the recirculation zone can make the reaction flow obtain the required heat in the shear layer to occur reaction, which greatly improves the stability of the combustion reaction.

[0044] Finally, the weighted average parameters of the outlet surface are counted to monitor the flue gas after combustion. The temperature of the outlet surface is 1203k, the oxygen molar fraction is 4.6%, the carbon monoxide is 0.114 ppm, and the nitrogen monoxide is 7.4 ppm, i.e. 9.3 mg / m3 O23.5%, which meets the high proportion of hydrogen mixed pollutant emission requirements.

Claims

1. Natural gas non-premixed hydrogen blended ultra-low NOx co-axial burner comprising a burner outer throat (1), characterized in that, It includes: Premixing cavity (2), one end of the premixing cavity (2) is fixedly connected to the combustor outer throat (1); Natural gas cylinder (4), the natural gas cylinder (4) is fixedly arranged on the outer wall of the premixing cavity (2); The outer wall of the premixing cavity (2) is provided with a plurality of natural gas inlet holes (3) located at the natural gas cylinder (4); Natural gas pipeline (9), one end of the natural gas pipeline (9) is fixedly connected to the natural gas cylinder (4) and is communicated with the inside of the natural gas cylinder (4); Air pipeline (5), one end of the air pipeline (5) is fixedly connected to the premixing cavity (2) and is communicated with the inside of the premixing cavity (2); Center hydrogen pipe (8), the center hydrogen pipe (8) is located in the premixing cavity (2), one end of the center hydrogen pipe (8) is 10mm away from the combustor outer throat (1), and the other end of the center hydrogen pipe (8) extends out of the premixing cavity (2) from the upstream end of the premixing cavity (2); Swirl (6), the swirl (6) includes a plurality of blades (7), a plurality of the blades (7) are arranged on the outer wall of the center hydrogen pipe (8) in a circumferential array, and the center hydrogen pipe (8) is fixedly connected to the inner wall of the premixing cavity (2) through a plurality of the blades (7).

2. The natural gas non-premixed hydrogen blended ultra-low NOx co-axial burner of claim 1, wherein, The natural gas cylinder (4) is fixedly arranged upstream of the premixing cavity (2), and the distance between the natural gas cylinder (4) and the combustor outer throat (1) is greater than or equal to 385mm; The air pipeline (5) is also fixedly arranged upstream of the premixing cavity (2).

3. The natural gas non-premixed hydrogen blended ultra-low NOx co-axial burner of claim 1, wherein, In the front-rear direction, the air pipeline (5) is located behind the natural gas pipeline (9).

4. The natural gas non-premixed hydrogen blended ultra-low NOx co-axial burner of claim 1, wherein, The distance between the swirl (6) and the combustor outer throat (1) is 20mm.

5. The natural gas non-premixed hydrogen blended ultra-low NOx co-axial burner of claim 1, wherein, The blades (7) are 12, and the 12 blades (7) are equidistantly arranged on the outer wall of the center hydrogen pipe (8), and the inclination angle of each blade (7) is 45°.

6. The natural gas non-premixed hydrogen blended ultra-low NOx co-axial burner of claim 1, wherein, The natural gas inlet holes (3) are four, the positions of the four natural gas inlet holes (3) in the front-rear direction are consistent, and the four natural gas inlet holes (3) are equidistantly arranged on the premixing pipe in a circumferential array.

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