An ammonia burner with a function of spatially hierarchical ammonia injection

Abstract

The present invention discloses an ammonia burner with a spatial hierarchical ammonia injection function, which includes a burner housing with a double-layer housing structure, comprising an inner burner housing and an outer burner housing fixed as an integral structure. There is a gap between the inner burner housing and the outer burner housing, and this gap is a reduction ammonia channel for injecting ammonia gas and reducing the products after ammonia combustion. The outer burner housing is provided with a reduction ammonia inlet communicating with the reduction ammonia channel, and the front end of the inner burner housing is provided with a reduction ammonia outlet communicating with the reduction ammonia channel; inside the inner burner housing, there is a fuel ammonia pipe with an air inlet located outside the burner housing and an air outlet located inside the inner burner housing for injecting ammonia for combustion. The inner burner housing is connected with an air pipe for injecting air into it; the reduction ammonia outlet is located in front of the air outlet of the fuel ammonia pipe. The ammonia burner designed by the present invention has a simple structure and low maintenance cost.

Description

Technical Field

[0001] The present invention relates to the technical field of burners, and specifically refers to an ammonia burner with a function of spatially staged ammonia injection. Background Art

[0002] At present, in the face of the urgent need for carbon dioxide emission reduction, ammonia fuel, as a new zero-carbon alternative fuel, has been favored in many fields such as power, industry, and transportation. Ammonia fuel can be produced carbon-free using the energy provided by renewable energy, and has a relatively high hydrogen density, which can be directly burned and utilized in power devices. At the same time, the condensation pressure and boiling point of ammonia fuel are very close to those of propane, and the equipment for transporting propane can also be used to transport ammonia. Therefore, the transition from traditional fossil fuels to ammonia fuel incurs a lower cost and has more obvious economic advantages compared to other zero-carbon fuels. However, the low calorific value of ammonia is about 40% of that of general hydrocarbon fuels, and the laminar burning speed is only about 20% of that of general hydrocarbon fuels. At the same time, as a high-nitrogen fuel, ammonia has a potential tendency to generate and emit high levels of nitrogen oxides. It can be seen that the stable ignition and combustion of ammonia and low nitrogen oxide emissions are problems that need to be urgently solved for the large-scale and energy-based utilization of ammonia fuel. Therefore, it is highly necessary to design a low-nitrogen oxide ammonia burner that can stably ignite and burn.

[0003] A Chinese patent document (CN115264496A) discloses an ammonia burner and a control method for the ammonia burner, which can achieve zero-carbon and low-nitrogen combustion in industrial kilns. However, when burning pure ammonia in this patent document, a certain amount of ammonia needs to be decomposed into hydrogen and nitrogen through an ammonia decomposer, and a catalyst is required. Among them, the decomposed hydrogen has a combustion-supporting function, and the nitrogen element in ammonia is decomposed and converted into nitrogen, resulting in a reduction in the generation of nitrogen oxides. However, the presence of the ammonia decomposer makes the burner structure complex, costly, and limited in application scope.

[0004] A Chinese patent document (CN113294801A) discloses a combustion device and a control method thereof that can achieve efficient and clean combustion of pure ammonia, which can achieve efficient and stable combustion of pure ammonia, and at the same time has a compact structure and can achieve low-level emissions of nitrogen oxides in a single combustion chamber. However, in this patent document, ammonia gas needs to pass through an additional ammonia pyrolysis electric heater to decompose part of the ammonia into hydrogen and nitrogen, and an ammonia pyrolysis catalyst is used inside the heater, resulting in high costs and difficult maintenance.

[0005] Chinese patent document (CN113864775A) discloses an ammonia-doped multiphase fuel staged swirl burner, which can regulate the fuel and air ratios in each combustion zone to achieve multi-stage stable combustion and multi-stage lean-rich combustion to inhibit the formation of nitrogen oxides in a multi-effect coupling manner. However, there are many pipes installed in the combustion zone of this burner for transporting fuel and air, the internal structure of the combustion chamber is complex, and the low-level emission of nitrogen oxides depends on very precise staged air volume control.

[0006] Chinese patent document (CN112963833A) discloses an ammonia low-nitrogen multi-stage swirl burner. By using a staged burner, it promotes the mixing of gas and air and the combustion of gas, making the heat load of the combustion chamber more uniform, thereby achieving low-nitrogen emissions during ammonia combustion. However, the internal structure of this burner is complex, and low nitrogen oxide emissions require precise fuel-air ratio control.

[0007] Chinese patent document (CN107477573A) discloses a combustion device for injecting ammonia into the center of a burner for a pulverized coal boiler, which can reduce the content of nitrogen oxides in the flue gas in an existing horizontal industrial pulverized coal boiler furnace. However, in this patent document, only ammonia is used as a reducing agent for nitrogen oxides and cannot directly burn ammonia as a fuel.

[0008] Through the above analysis, for the existing technologies for reducing nitrogen oxide emissions during ammonia combustion, on the one hand, through an ammonia catalytic or cracking device, ammonia is converted into hydrogen and nitrogen and then burned or used for combustion support. This makes the control of nitrogen oxide formation and the combustion stability effect seriously dependent on the catalytic device or catalyst, and the cost is relatively high. On the other hand, low-level nitrogen oxide emissions are achieved through precise staged air volume control and fuel-air ratio control. This makes the internal pipeline structure of the burner relatively complex, the production cost high, and the maintenance difficult. Summary of the Invention

[0009] The object of the present invention is to solve the deficiencies in the above background technology and provide an ammonia burner that achieves efficient and stable combustion through staged ammonia injection.

[0010] To achieve this purpose, the ammonia burner designed by the present invention with a spatial hierarchical ammonia injection function includes a burner housing. The burner housing is a double-layer housing structure, which includes an inner burner housing and an outer burner housing fixed as an integral structure. There is a gap between the inner burner housing and the outer burner housing, and this gap is a reduction ammonia channel for injecting ammonia and reducing the products after ammonia combustion. The outer burner housing is provided with a reduction ammonia inlet communicating with the reduction ammonia channel, and the front end of the inner burner housing is provided with a reduction ammonia outlet communicating with the reduction ammonia channel; a fuel ammonia pipe for injecting ammonia for combustion is arranged in the inner burner housing, with an air inlet located outside the burner housing and an air outlet located inside the inner burner housing. The inner burner housing is connected with an air pipe for injecting air into it; the reduction ammonia outlet is located in front of the air outlet of the fuel ammonia pipe.

[0011] Furthermore, a guide vane is arranged in the inner burner housing to provide air for the gas at the air outlet of the fuel ammonia pipe and wrap the gas at the air outlet of the fuel ammonia pipe to move towards the outside of the front end of the burner housing.

[0012] Furthermore, the inner burner housing includes an inner cylindrical housing section and an inner flared housing section coaxially and fixedly connected to the front end of the inner cylindrical housing section and integrated with the inner cylindrical housing section; the outer burner housing includes an outer cylindrical housing section and an outer flared housing section coaxially and fixedly connected to the front end of the outer cylindrical housing section and integrated with the outer cylindrical housing section; the gap between the inner cylindrical housing section and the outer cylindrical housing section and the gap between the inner flared housing section and the outer flared housing section constitute the reduction ammonia channel.

[0013] Furthermore, the reduction ammonia inlet is arranged on the outer cylindrical housing section, and the reduction ammonia outlet is opened on the inner flared housing section.

[0014] Furthermore, the reduction ammonia outlet is a plurality of reduction ammonia outlet holes arranged at intervals along the circumferential direction of the inner flared housing section on the inner flared housing section.

[0015] Furthermore, the inner flared housing section is provided with multiple groups of reduction ammonia outlet holes at intervals along its circumferential direction, and each group of reduction ammonia outlet holes includes a plurality of the reduction ammonia outlet holes arranged at intervals along the expansion direction of the inner flared housing section.

[0016] Further, the guide vane is of an annular structure, and its middle part is coaxially fixed on the fuel ammonia pipeline. The outer surface of the guide vane is fixed on the inner surface of the inner burner housing. The guide vane is located behind the air outlet of the fuel ammonia pipeline.

[0017] Further, a plurality of straight-through air holes for supplying air to the gas at the air outlet of the fuel ammonia pipeline are spaced apart along the circumferential direction on the inner side of the guide vane.

[0018] Further, a plurality of swirl air grooves extending from the outer surface of the guide vane to the inner side of the guide vane along the circumferential direction are spaced apart on the outer side of the guide vane, and are used for wrapping the gas at the air outlet of the fuel ammonia pipeline and moving it to the outside of the front end of the burner housing.

[0019] Furthermore, the ratio of the ventilation area of the straight-through air holes to the ventilation area of the swirl air grooves is 1:5 to 1:6.

[0020] The beneficial effects of the present invention are as follows: Through the burner housing with a double-layer shell structure, in the form of staged ammonia injection, when ammonia in the fuel ammonia pipeline burns, the generation limit of nitrogen oxides does not need to be considered. The ammonia in the reduction ammonia channel is used to reduce the ammonia combustion products, so that as much nitrogen oxides generated after ammonia combustion as possible are reduced by ammonia. While achieving better ignition and combustion stability, low-level emissions of nitrogen oxides are also realized. At the same time, the double-layer burner housing forms a special energy-gathering and flame-stabilizing cavity, which has a better heat preservation effect, increases the temperature inside the ammonia burner, realizes the energy-gathering feedback for enhanced combustion of heat energy and preheating of secondary reduction ammonia, and promotes the efficient and stable combustion of ammonia. The ammonia burner designed by the present invention has a simple structure and low maintenance cost, and there is no need to arrange complex pipelines inside the burner. The guide vanes in the ammonia burner are provided with inner and outer layers of air outlets. The inner air outlet provides direct current air to prevent ammonia from flowing back, and the outer air outlet provides swirling air to wrap the ammonia gas flow and flow forward, providing most of the air required for ammonia combustion, promoting ammonia combustion and flame stabilization, and realizing controllable fuel-air zoning. The outlet end of the fuel ammonia pipeline has a certain chamfer, which avoids the occurrence of a local high-temperature area in front of the outlet end, causing damage to the burner or the generation of high nitrogen oxides. The ammonia burner designed by the present invention can be applied to boilers such as coal-fired and biomass in thermal power plants, reducing the carbon dioxide emissions of power plants from the source, promoting the rapid and large-scale carbon emission reduction in the power industry, and there is no need to carry out a large number of renovations on the original boiler furnace structure. It extends the service life of existing generator sets and solves the problem that generator sets are forced to be retired in advance due to carbon dioxide emission restrictions. The ammonia burner designed by the present invention can be applied to thermal power boilers such as coal-fired, oil-fired, and gas-fired, or industrial furnaces such as cement, glass, and ceramics, filling the technical gap of a compact ammonia burner with both low nitrogen oxide emissions and strong combustion functions. Description of the Drawings

[0021] Figure 1 is a three-dimensional view of the ammonia burner with a spatial staged ammonia injection function in the present invention;

[0022] Figure 2 is an axial sectional view of the ammonia burner with a spatial staged ammonia injection function in the present invention;

[0023] Figure 3 is a three-dimensional view of the internal structure of the ammonia burner with a spatial staged ammonia injection function in the present invention;

[0024] Figure 4 is a three-dimensional view of the air pipeline in the present invention;

[0025] Figure 5 is a three-dimensional view of the connection structure between the fuel ammonia pipeline and the guide vane in the present invention;

[0026] Figure 6Isometric view of the flow guiding vane in the present invention;

[0027] Figure 7 Front view of the flow guiding vane in the present invention;

[0028] Figure 8 Front view of the fuel ammonia pipeline in the present invention;

[0029] Figure 9 Schematic diagram of the combustion state of the ammonia burner with the function of spatially graded ammonia injection in the present invention;

[0030] Wherein, 1 - burner housing (1.1 - inner burner housing, 1.2 - outer burner housing), 2 - reduction ammonia channel, 3 - reduction ammonia inlet, 4 - reduction ammonia outlet, 5 - fuel ammonia pipeline, 6 - air pipeline, 7 - flow guiding vane, 8 - inner cylindrical housing section, 9 - inner flared housing section, 10 - outer cylindrical housing section, 11 - outer flared housing section, 12 - direct current air holes, 13 - swirl air grooves, 14 - high nitrogen oxide generation area, 15 - fuel ammonia outlet. Detailed implementation manners

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] As Figure 1 The ammonia burner with the function of spatially graded ammonia injection shown in FIGS. 1 - 8 includes a burner housing 1. The burner housing 1 is a double - layer housing structure, which includes an inner burner housing 1.1 and an outer burner housing 1.2 fixed as an integral structure. There is a gap between the inner burner housing 1.1 and the outer burner housing 1.2. This gap is the reduction ammonia channel 2 for injecting ammonia gas and the products after the combustion of reduction ammonia. The outer burner housing 1.2 is provided with a reduction ammonia inlet 3 communicating with the reduction ammonia channel 2. The front end of the inner burner housing 1.1 is provided with a reduction ammonia outlet 4 communicating with the reduction ammonia channel 2. Inside the inner burner housing 1.1, there is a fuel ammonia pipeline 5 with an air inlet outside the burner housing 1 and an air outlet inside the inner burner housing 1.1 for injecting ammonia for combustion. The front end of the fuel ammonia pipeline 5 is a closed structure, and a plurality of oblique cutting holes with an oblique cutting angle of 30° are spaced along the circumferential direction at the front end of the fuel ammonia pipeline 5, and the oblique cutting direction is towards the front of the fuel ammonia pipeline 5. The inner burner housing 1.1 is connected with an air pipeline 6 for injecting air into its interior. The reduction ammonia outlet 4 is located in front of the air outlet of the fuel ammonia pipeline 5.

[0033] As Figure 1As shown in FIG. 2, the inner burner housing 1.1 includes an inner cylindrical housing section 8 and an inner flared housing section 9 that is coaxially and fixedly connected to the front end of the inner cylindrical housing section 8 and is an integral structure with the inner cylindrical housing section 8; the outer burner housing 1.2 includes an outer cylindrical housing section 10 and an outer flared housing section 11 that is coaxially and fixedly connected to the front end of the outer cylindrical housing section 10 and is an integral structure with the outer cylindrical housing section 10; the gap between the inner cylindrical housing section 8 and the outer cylindrical housing section 10 and the gap between the inner flared housing section 9 and the outer flared housing section 11 form a reduced ammonia channel 2. The inner flared housing section 9 and the outer flared housing section 11 form an energy-concentrating and flame-stabilizing chamber structure with a 45° expansion angle. A reduced ammonia inlet 3 is provided on the outer cylindrical housing section 10, and a reduced ammonia outlet 4 is opened on the inner flared housing section 9. The reduced ammonia outlet 4 is a plurality of reduced ammonia outlet holes that are circumferentially spaced and opened on the inner flared housing section 9. Specifically, the inner flared housing section 9 is circumferentially spaced with multiple groups of reduced ammonia outlet holes, and each group of reduced ammonia outlet holes includes a plurality of reduced ammonia outlet holes that are spaced along the expansion direction of the inner flared housing section 9.

[0034] As Figure 2 shown in FIGS. 3 and Figure 5 As shown in FIGS. 7, a flow guiding vane 7 is provided inside the inner burner housing 1.1 for supplying air to the gas at the outlet of the fuel ammonia pipeline 5 and wrapping the gas at the outlet of the fuel ammonia pipeline 5 to move outward to the front end of the burner housing 1. The flow guiding vane 7 is of an annular structure, the middle of which is coaxially fixed to the fuel ammonia pipeline 5, the outer surface of the flow guiding vane 7 is fixed to the inner surface of the inner burner housing 1.1, and the flow guiding vane 7 is located behind the outlet of the fuel ammonia pipeline 5. A plurality of direct current air holes 12 for supplying air to the gas at the outlet of the fuel ammonia pipeline 5 are circumferentially spaced on the inner side of the flow guiding vane 7. A plurality of swirl air grooves 13 that extend from the outer surface of the flow guiding vane 7 to the inner side of the flow guiding vane 7 and are used for wrapping the gas at the outlet of the fuel ammonia pipeline 5 to move outward to the front end of the burner housing 1 are circumferentially spaced on the outer side of the flow guiding vane 7. The groove surface of the swirl air groove 13 is a swirl inclined surface that forms a 15° angle with the horizontal direction. The ratio of the ventilation area of the direct current air holes 12 to the ventilation area of the swirl air grooves 13 is 1:6.

[0035] As Figure 9As shown in the figure, the inner flared shell section 9 and the outer flared shell section 11 form an energy-gathering and stable combustion chamber structure with a 45° expansion angle. The inside is lined with heat-insulating materials with high reflectivity, enabling the heat of the combustion flame to be gathered and fed back through thermal radiation to heat the jet flame and promote combustion. At the same time, part of the flame heat is also conducted to heat and preheat the ammonia gas in the reduction ammonia channel 2, strengthening the combustion reaction. The usage method of the ammonia burner designed in the present invention is as follows: The ammonia gas injected through the fuel ammonia pipeline 5 is controlled to have an equivalence ratio of about 1.2, so that the ammonia gas burns under the fuel-air ratio conditions most favorable for ignition and combustion. After the ammonia gas burns stably, reduction ammonia fuel is injected through the reduction ammonia inlet 3 and the reduction ammonia channel 2. Through the denitrification reaction 4NO + 4NH3 + O2 → 4N2 + 6H2O, the nitrogen oxides generated by the combustion of the ammonia gas in the fuel ammonia pipeline 5 are converted into nitrogen and water, achieving low nitrogen oxide emissions of the ammonia burner. At the same time, the reduction ammonia fuel plays a role in cooling the wall surface and providing safety protection.

[0036] In summary, through the burner housing 1 with a double-layer shell structure, the present invention allows the ammonia gas introduced into the fuel ammonia pipeline 5 to burn without considering the generation limit of nitrogen oxides in the form of staged ammonia injection. The ammonia gas in the reduction ammonia channel 2 is used to reduce the ammonia combustion products, enabling as much of the nitrogen oxides generated after ammonia combustion as possible to be reduced by ammonia. While achieving better ignition and combustion stability, it also realizes low-level emissions of nitrogen oxides. At the same time, the double-layer shell structure of the burner housing 1 forms a special energy-gathering and stable combustion cavity, which has a better heat preservation effect, increases the temperature inside the ammonia burner, realizes the energy-gathering feedback of heat energy to strengthen combustion and the preheating of secondary reduction ammonia, and promotes the efficient and stable combustion of ammonia. The ammonia burner designed in the present invention has a simple structure and low maintenance cost, and there is no need to arrange complex pipelines inside the burner. The guide vanes 7 inside the ammonia burner are provided with inner and outer layers of air outlets. The inner air outlet provides direct current air to prevent the ammonia gas from flowing back, and the outer air outlet provides swirling air to wrap the ammonia gas flow and flow forward, providing most of the air required for ammonia combustion, promoting ammonia combustion and stable combustion, and realizing controllable fuel-air zoning. The outlet end of the fuel ammonia pipeline 5 has a certain chamfer, avoiding the occurrence of a local high-temperature area in front of the outlet end, which may cause damage to the burner or the generation of high nitrogen oxides. The ammonia burner designed in the present invention can be applied to coal-fired, biomass, etc. boilers in thermal power plants, reducing the carbon dioxide emissions of power plants from the source, promoting the rapid and large-scale carbon emission reduction in the power industry, and there is no need to carry out a large number of renovations on the original boiler furnace structure. It extends the service life of existing generator sets and solves the problem that generator sets are forced to be retired prematurely due to carbon dioxide emission restrictions. The ammonia burner designed in the present invention can be applied to thermal power boilers such as coal-fired, oil-fired, and gas-fired, or industrial kilns such as cement, glass, and ceramics, filling the technical gap of a compact ammonia burner with both low nitrogen oxide emissions and strong combustion functions.

[0037] As described above, it is only the preferred embodiment of the present invention, and does not impose any formal restrictions on the structure of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An ammonia burner with a spatially hierarchical ammonia injection function, comprising a burner housing (1), characterized in that: The burner housing (1) has a double-layer housing structure, which includes an inner burner housing (1.1) and an outer burner housing (1.2) fixed as an integral structure. There is a gap between the inner burner housing (1.1) and the outer burner housing (1.2), and this gap is a reducing ammonia channel (2) for injecting ammonia and reducing the products after the combustion of ammonia. The outer burner housing (1.2) is provided with a reducing ammonia inlet (3) communicating with the reducing ammonia channel (2), and the front end of the inner burner housing (1.1) is provided with a reducing ammonia outlet (4) communicating with the reducing ammonia channel (2). Inside the inner burner housing (1.1), there is a fuel ammonia pipeline (5) with an air inlet outside the burner housing (1) and an air outlet inside the inner burner housing (1.1) for injecting ammonia for combustion. The inner burner housing (1.1) is connected with an air pipeline (6) for injecting air into it. The reducing ammonia outlet (4) is located in front of the air outlet of the fuel ammonia pipeline (5).

2. The ammonia burner with the function of spatially graded ammonia injection according to claim 1, characterized in that: Inside the inner burner housing (1.1), there are guide vanes (7) for providing air to the gas at the air outlet of the fuel ammonia pipeline (5) and wrapping the gas at the air outlet of the fuel ammonia pipeline (5) to move towards the outside of the front end of the burner housing (1).

3. The ammonia burner with a spatially graded ammonia injection function according to claim 1, characterized in that: The inner burner housing (1.1) includes an inner cylindrical housing section (8) and an inner flared housing section (9) coaxially and fixedly connected to the front end of the inner cylindrical housing section (8) and being an integral structure with the inner cylindrical housing section (8); the outer burner housing (1.2) includes an outer cylindrical housing section (10) and an outer flared housing section (11) coaxially and fixedly connected to the front end of the outer cylindrical housing section (10) and being an integral structure with the outer cylindrical housing section (10); the gap between the inner cylindrical housing section (8) and the outer cylindrical housing section (10) and the gap between the inner flared housing section (9) and the outer flared housing section (11) form the reducing ammonia channel (2).

4. The ammonia burner with the function of spatially graded ammonia injection according to claim 3, characterized in that: The reducing ammonia inlet (3) is provided on the outer cylindrical housing section (10), and the reducing ammonia outlet (4) is opened on the inner flared housing section (9).

5. The ammonia burner with the function of spatially graded ammonia injection according to claim 4, characterized in that: The reducing ammonia outlet (4) is a plurality of reducing ammonia outlet holes spaced along the circumferential direction of the inner flared housing section (9) and opened on the inner flared housing section (9).

6. The ammonia burner with a spatially hierarchical ammonia injection function according to claim 5, characterized in that: The inner flared housing section (9) is provided with multiple groups of reducing ammonia outlet holes spaced along its circumferential direction. Each group of reducing ammonia outlet holes includes a plurality of the reducing ammonia outlet holes spaced along the expansion direction of the inner flared housing section (9).

7. The ammonia burner with the function of spatially hierarchical ammonia injection according to claim 2, characterized in that: The guide vanes (7) are of an annular structure, with its middle coaxially fixed on the fuel ammonia pipeline (5), the outer surface of the guide vanes (7) fixed on the inner surface of the inner burner housing (1.1), and the guide vanes (7) are located behind the air outlet of the fuel ammonia pipeline (5).

8. The ammonia burner with a spatially graded ammonia injection function according to claim 7, characterized in that: A plurality of straight-through air holes (12) for supplying air to the gas at the outlet of the fuel ammonia pipeline (5) are arranged at intervals along the circumferential direction on the inner side of the guide vane (7).

9. The ammonia burner with a spatially graded ammonia injection function as described in claim 8, characterized in that: A plurality of swirl air grooves (13) extending from the outer surface of the guide vane (7) to the inner side of the guide vane (7) are arranged at intervals along the circumferential direction on the outer side of the guide vane (7) and are used for wrapping the gas at the outlet of the fuel ammonia pipeline (5) and moving it to the outside of the front end of the burner housing (1).

10. The ammonia burner with a spatially hierarchical ammonia injection function according to claim 9, characterized in that: The ratio of the ventilation area of the straight-through air holes (12) to the ventilation area of the swirl air grooves (13) is 1:5 to 1:6.

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