Ammonia burner

Abstract

The present invention discloses an ammonia burner, which includes an ammonia heating and ionization device, a second pipe sleeved outside the ammonia heating and ionization device, and a third pipe sleeved outside the second pipe. A primary air duct is formed between the second pipe and the third pipe, and an annular fuel pipe sleeved outside the second pipe is arranged in the primary air duct; the ammonia heating and ionization device is used for heating and ionizing ammonia or ammonia mixed gas, and the air input into the primary air duct and the ammonia output from the fuel nozzle arranged on the annular fuel pipe form a premixed gas in the primary air duct. The present invention realizes the ignition and low-load stable combustion of the ammonia burner through a plasma igniter; the use of the plasma igniter to ionize ammonia effectively avoids the oxidation of the cathode and anode materials of the plasma igniter; the rotating wind formed by multiple circumferential inclined channels at the air outlet of the plasma igniter drives the ionized plasma to generate axial rotation, and under the action of free radicals and high temperature in the plasma, a violent combustion chemical reaction is triggered.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion, and in particular to an ammonia burner. Background Art

[0002] At present, more than 80% of the primary energy utilization in energy consumption is achieved through combustion. The combustion process is the main source of carbon emissions. Therefore, the key to achieving zero CO2 emissions is to increase the utilization of renewable, zero-carbon or low-carbon fuels in primary energy. Hydrogen energy is the preferred zero-emission fuel, but the energy per unit volume of hydrogen is extremely low, and it is difficult to store and transport. In addition, hydrogen also has difficult-to-solve safety problems. To solve the economic and safety problems of H2, people actively seek hydrogen-carrying and hydrogen-substituting media.

[0003] Ammonia (NH3) is a zero-carbon fuel for carrying and substituting hydrogen. The products after complete combustion of NH3 are N2 and H2O. It has the characteristics of high volumetric energy density, and can be liquefied at only 0.7 - 0.8 MPa at room temperature, which is convenient for storage and transportation. Compared with conventional fuels, ammonia has relatively low laminar burning velocity and calorific value, high ignition temperature, and narrow combustion limit range. If not controlled well, it is extremely easy to produce a large amount of nitrogen oxide emissions. Therefore, there are certain difficulties in the use process. Currently, in the use process, ammonia is usually mixed with other fuels for combustion (such as hydrogen, methane, pulverized coal, etc.). Existing ammonia burners use an internal combustion chamber and a porous regenerator to increase the fuel and air temperature to achieve stable ignition and combustion, but existing ammonia burners do not consider how to control the problem of a large amount of nitrogen oxides generated by ammonia combustion; secondly, there is a relatively high pressure drop in the air and combustion channels, which increases the power consumption of the fan; and when the temperature of the regenerator has not decreased, if the burner is ignited again, it is easy to produce flashback, causing damage to the burner.

[0004] Therefore, at present, how to achieve ignition and stable combustion during the ammonia combustion process and control the nitrogen oxide emissions and ammonia escape indexes within the standard range is a problem that a new type of ammonia burner needs to solve. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing ammonia burners do not consider the problems of re-ignition flashover and unstable combustion during the ammonia combustion process, and existing ammonia burners do not have measures to control the nitrogen oxide emissions and ammonia escape indexes within the standard range.

[0006] To solve the above technical problems, the present invention provides an ammonia burner, including an ammonia heating and ionization device, a second pipeline sleeved outside the ammonia heating and ionization device, and a third pipeline sleeved outside the second pipeline. A primary air duct is formed between the second pipeline and the third pipeline, and an annular fuel pipe sleeved outside the second pipeline is arranged in the primary air duct.

[0007] Among them, the ammonia heating and ionization device is used to heat and ionize ammonia or ammonia mixture gas. The primary air duct inlet is used to input air. The annular fuel pipe is used to output ammonia to form a premixed gas in the primary air duct, and the equivalence ratio range of the premixed gas is 1.1 - 1.5. The ammonia heating and ionization device can effectively avoid the oxidation of the anode and cathode materials of the ammonia heating and ionization device, greatly extending the service life of the ammonia heating and ionization device; and when the ammonia heating and ionization device stops operating, the ammonia or ammonia mixture gas in the central air duct of the ammonia heating and ionization device forms a diffusion combustion, playing the role of a pilot flame; setting the ammonia in the premixed gas in the primary air duct to be in a fuel-rich state can effectively reduce the emission of nitrogen oxides during the combustion process.

[0008] Preferably, a central air distribution channel is formed between the second pipe and the outer wall pipe of the ammonia heating and ionization device. The end of the second pipe is connected to the end of the outer wall pipe of the ammonia heating and ionization device, so that a plurality of circumferential inclined orifices surrounding the air outlet of the ammonia heating and ionization device can be arranged at the end of the second pipe. The air output from the plurality of circumferential inclined orifices forms a swirling air at the air outlet of the ammonia heating and ionization device; the arrangement of the plurality of circumferential inclined orifices can drive the ionized plasma to generate axial rotation by the swirling air formed at the air outlet of the plasma igniter, and under the action of free radicals and high temperature in the plasma, a violent combustion chemical reaction occurs.

[0009] Preferably, a plurality of fuel nozzles are arranged on the annular fuel pipe, and the plurality of fuel nozzles are used to output ammonia. Arranging a plurality of fuel nozzles on the annular fuel pipe can make the fuel and air fully and evenly mixed, and outputting the fuel in the form of nozzles can effectively avoid the flashback phenomenon during the combustion process.

[0010] Preferably, the included angle between the air outlet direction of the fuel nozzle and the transmission direction of the premixed gas in the primary air duct is less than 90 degrees.

[0011] Preferably, a plurality of fuel inlet pipes are further arranged in the primary air duct, and all the fuel inlet pipes are communicated with the annular fuel pipe; the arrangement of the plurality of fuel inlet pipes can ensure the uniform distribution of the ammonia flow rate ejected from the fuel nozzles on the annular fuel pipe.

[0012] Preferably, a rotating vane is further arranged in the primary air duct.

[0013] Preferably, the ammonia burner further includes a fourth pipe sleeved outside the third pipe, a secondary air duct is formed between the third pipe and the fourth pipe, the end of the third pipe extends outwards beyond the end of the second pipe, and the end of the fourth pipe extends outwards beyond the end of the third pipe.

[0014] Preferably, rotating vanes are provided in the secondary air duct. The secondary air duct is mainly used to supplement air during the combustion process and control the exhaust gas temperature of the burner by controlling the air flow rate.

[0015] Preferably, the ammonia heating and ionization device is a plasma igniter. Using a plasma igniter can achieve ignition of the burner and stable combustion at low loads.

[0016] Preferably, the plasma igniter includes a cathode rod and an anode pipe sleeved outside the cathode rod. A central air duct is formed between the cathode rod and the anode pipe. A tapered portion is provided in the anode pipe so that an arc is formed between the tapered portion of the anode pipe and the end of the cathode rod when the plasma igniter ignites. The anode pipe is the outer wall pipe of the plasma igniter.

[0017] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0018] Applying the ammonia burner provided by the embodiment of the present invention, ignition of the ammonia burner and stable combustion at low loads are achieved through a plasma igniter; and by using the plasma igniter to ionize ammonia or ammonia mixture, oxidation of the cathode and anode materials of the plasma igniter can be effectively avoided, greatly extending the service life of the plasma igniter; the rotating wind formed by multiple circumferential inclined orifices at the air outlet of the plasma igniter drives the ionized plasma to generate axial rotation, and under the action of free radicals and high temperature in the plasma, a violent combustion chemical reaction is triggered; setting the ammonia in the premixed gas in the primary air duct to a rich combustion state can reduce the emission of nitrogen oxides during the combustion process; rotating vanes are provided in both the primary air duct and the secondary air duct, which can effectively control the swirl number to ensure staged and stable combustion of ammonia; and the gas flow rate in each fuel or air channel can also be controlled to cool the wall of the combustion zone to ensure that the burner is not burned out.

[0019] Other features and advantages of the present invention will be described in the following specification, and will become partially obvious from the specification, or be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the specification, claims, and drawings. Description of the Drawings

[0020] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0021] Figure 1 A schematic cross-sectional structure diagram of the ammonia burner according to Embodiment 1 of the present invention is shown;

[0022] Figure 2The cross-sectional structure diagram of the circumferential inclined channel in the first embodiment of the present invention is shown;

[0023] Figure 3 The structure diagram of the annular fuel pipe in the first embodiment of the present invention is shown;

[0024] Among them, 1 is the cathode rod, 2 is the anode pipe, 3 is the central air duct, 4 is the central air distribution channel, 5 is the fuel inlet pipe, 6 is the fuel nozzle, 7 is the primary air duct, 8 is the secondary air duct, 9 is the rotating blade, 10 is the circumferential inclined channel, 11 is the second pipe, 12 is the third pipe, 13 is the fourth pipe, and 14 is the annular fuel pipe. Detailed implementation manners

[0025] The following will detail the implementation manners of the present invention in conjunction with the drawings and embodiments, so as to fully understand how the present invention uses technical means to solve technical problems and the implementation process of achieving technical effects and implement accordingly. It should be noted that as long as there is no conflict, the various embodiments in the present invention and the various features in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0026] Embodiment 1

[0027] To solve the technical problems existing in the prior art, an ammonia burner is provided in an embodiment of the present invention.

[0028] Figure 1 The cross-sectional structure diagram of the ammonia burner in the first embodiment of the present invention is shown; Refer to Figure 1 As shown, the ammonia burner in the embodiment of the present invention includes an ammonia heating and ionization device, a second pipe 11, a third pipe 12, and a fourth pipe 13. Among them, the ammonia heating and ionization device is preferably a plasma igniter. Further, a central air distribution channel 4 is formed between the outer wall pipe of the plasma igniter and the second pipe 11, a primary air duct 7 is formed between the second pipe 11 and the third pipe 12, and a secondary air duct 8 is formed between the third pipe 12 and the fourth pipe 13.

[0029] Furthermore, the plasma igniter specifically includes a cathode rod 1, an anode duct 2, and a central air duct. The anode duct 2 is sleeved outside the cathode rod 1, and a central air duct is formed between the cathode rod 1 and the anode duct 2. A tapered portion is provided near the end of the cathode rod 1 inside the anode duct 2. The diameter of the tapered portion inside the anode duct 2 is smaller than the diameter of the non-tapered portion inside the anode duct 2, so as to shorten the distance between the end of the cathode rod 1 and the anode duct 2, such that an arc can be formed between the tapered portion of the anode duct 2 and the end of the cathode rod 1 when the plasma igniter ignites, thereby realizing the ionization of the gas in the central air duct. The outlet at the end of the anode duct 2 is the air outlet of the plasma igniter. At the same time, in order to facilitate the output of the ionized gas and provide more reaction space for the combustion chemical reaction, the outlet at the end of the anode duct 2 is set to be gradually expanding. Preferably, the anode duct 2 is cylindrical. It should be noted that the anode duct 2 is the outer wall duct of the plasma igniter.

[0030] The second duct 11 is sleeved outside the plasma igniter, and a central air distribution channel 4 is formed between the outer wall duct of the plasma igniter and the second duct 11. The end of the second duct 11 is connected to the end of the outer wall duct of the plasma igniter, so that the end of the second duct 11 surrounds the air outlet of the plasma igniter. Figure 2 The sectional structure diagram of the circumferential inclined orifice in the first embodiment of the present invention is shown; refer to Figure 2 As shown, a plurality of circumferential inclined orifices 10 are further provided at the end of the second duct 11, and the plurality of circumferential inclined orifices 10 surround the air outlet of the plasma igniter. The circumferential inclined orifices 10 do not blow air in the axial direction of the air outlet of the plasma igniter, but need to be set to blow air in a direction at a certain angle with the axial direction of the air outlet of the plasma igniter, so that the air output by all the circumferential inclined orifices 10 forms a swirling air at the air outlet of the plasma igniter. The swirling air formed by the plurality of circumferential inclined orifices 10 at the air outlet of the plasma igniter drives the ionized plasma to rotate axially, and under the action of free radicals and high temperature in the plasma, a violent combustion chemical reaction occurs.

[0031] In this embodiment, the central air duct 3 is mainly used to pass ammonia or ammonia mixed gas (the ammonia mixed gas is a mixed gas of ammonia and oxygen or a mixed gas of ammonia and air, but ammonia is the main component in both mixed gases), and the central air distribution channel 4 is mainly used to pass air. In the embodiment of the present invention, the gas ionized by the plasma igniter is ammonia instead of air, thereby avoiding the oxidation of the materials of the cathode and anode, and greatly prolonging the service life of the cathode and anode.

[0032] The third duct 12 is sleeved outside the second duct 11, and a primary air duct 7 is formed between the second duct 11 and the third duct 12. An annular fuel pipe 14 is further provided in the primary air duct 7, and the annular fuel pipe 14 is sleeved outside the second duct. Figure 3 The structural diagram of the annular fuel pipe in the first embodiment of the present invention is shown; refer to Figure 3As shown, a plurality of fuel nozzles 6 are provided on the annular fuel pipe 14 for outputting fuel gas in the primary air duct 7. Further, a plurality of fuel inlet pipes 5 are also provided in the primary air duct 7, and all the fuel inlet pipes 5 are communicated with the annular fuel pipe 14 to transmit fuel to the annular fuel pipe 14. In the primary air duct 7, the air inlet of the primary air duct 7 is mainly used for inputting air, while the plurality of fuel nozzles 6 of the annular fuel pipe 14 are mainly used for outputting ammonia gas, which is mixed in the primary air duct 7 to form a premixed gas. In order to avoid the generation of nitrogen oxides during the combustion process, the premixed gas needs to be set in a fuel-rich state. Specifically, the equivalence ratio of the premixed gas can be set in the range of 1.1 - 1.5. Preferably, the equivalence ratio of the premixed gas is set in the range of 1.1 - 1.3.

[0033] It should be noted that in order to enable the fuel to burn sufficiently during combustion, the end of the third pipe 12 is set to extend outward beyond the end of the second pipe 11. In order to enable the ammonia fuel and the air in the primary air duct 7 to be fully and evenly mixed, we need to set the included angle between the air outlet direction of the fuel nozzle 6 and the transmission direction of the premixed gas in the primary air duct 7 to be less than 90 degrees. And in order to further enable the premixed gas in the primary air duct 7 to be fully mixed and stably combusted, a rotating vane 9 is also provided in the primary air duct 7, and the rotating vane 9 is provided with a relatively high swirl number.

[0034] The fourth pipe 13 is sleeved outside the third pipe 12, and a secondary air duct 8 is formed between the third pipe 12 and the fourth pipe 13. A rotating vane 9 is also provided in the secondary air duct 8, and the rotating vane 9 at this place is also provided with a relatively high swirl number. And in order to enable the excess fuel in the primary air duct 7 to be further fully and completely combusted, the end of the fourth pipe 13 is set to extend outward beyond the end of the third pipe 12.

[0035] The working process of the ammonia burner in the embodiment of the present invention is as follows:

[0036] When the ammonia burner in this embodiment is ignited, the plasma generator is started, and an electric field is generated between the anode and the cathode; when ammonia or ammonia mixture enters the central air duct 3 and passes between the cathode and the anode, under the action of the electric field, the ammonia or ammonia mixture molecules are ionized to form high-energy plasma. At this time, the air from the central air distribution channel forms a rotating wind at the air outlet of the igniter, driving the plasma to generate circumferential rotation, and under the action of free radicals and high temperature in the plasma, a violent combustion chemical reaction occurs. Among them, the plasma has a relatively high temperature and is mainly composed of electrons and charged particles.

[0037] The ammonia in the annular fuel pipe 14 in the primary air duct 7 is fully mixed with the flowing air through multiple fuel nozzles to form a premixed gas, which passes through the rotating blades 9 in the primary air duct 7 to generate a swirling premixed rich gas that gathers inward, meets the high-temperature gas that has already started to burn inside and is ignited, and then continues to burn. The rich combustion of ammonia is conducive to avoiding the generation of nitrogen oxides. In addition, during the combustion process, the flow rate of the gas in the primary air duct 7 can achieve airflow cooling on the combustion zone wall to ensure that the burner is not burned.

[0038] The air in the secondary air duct 8 passes through the rotating blades to generate swirling air, which meets the excess ammonia from the rich combustion inside, providing excess air for combustion, so that the ammonia is completely burned. In addition, during the combustion process, the exhaust temperature of the burner is controlled by controlling the air flow in the secondary air duct 8 to meet the performance requirements of the burner.

[0039] When the burner is operating at normal rated conditions, the plasma igniter is disabled, and the central air duct 3 is only a fuel channel for ammonia or ammonia mixed gas, which accounts for a relatively low proportion of the entire fuel. The central air distribution channel 4 provides corresponding air to maintain the diffusion combustion state, and serves as a duty flame to stabilize combustion. The premixed gas in the primary air duct 7 maintains combustion in a swirl state, and is entrained by the continuously refluxed high-temperature flue gas, thereby ensuring continuous combustion. The air in the secondary air duct 8 serves to supplement air, ensure the complete combustion of ammonia, and control the exhaust temperature of the burner. At the same time, the swirl combustion also serves to reflux high-temperature flue gas to maintain the temperature required for combustion.

[0040] The ammonia burner provided by the embodiment of the present invention realizes ignition and low-load stable combustion of the ammonia burner through a plasma igniter; and the plasma igniter is used to ionize ammonia or ammonia mixture, which can effectively avoid the oxidation of the cathode and anode materials of the plasma igniter, and greatly extend the service life of the plasma igniter; the rotating wind formed by multiple circumferential inclined channels at the air outlet of the plasma igniter drives the ionized plasma to produce axial rotation, and under the action of free radicals and high temperature in the plasma, a violent combustion chemical reaction is triggered; the ammonia in the premixed gas in the primary air duct is set to a rich combustion state, which can reduce the emission of nitrogen oxides during the combustion process; rotating blades are provided in both the primary air duct and the secondary air duct, which can effectively control the swirl number to ensure the graded and stable combustion of ammonia; and the gas flow rate in each fuel or air channel can also be used to cool the burner wall to ensure that the burner is not burned.

[0041] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. An ammonia burner, characterized in that, It includes a plasma igniter, a second pipe sleeved outside the plasma igniter, and a third pipe sleeved outside the second pipe. A primary air duct is formed between the second pipe and the third pipe, and an annular fuel pipe sleeved outside the second pipe is arranged in the primary air duct; A central air distribution channel is formed between the second pipe and the outer wall pipe of the plasma igniter; Among them, the plasma igniter is used to achieve ignition and stable combustion at low load of the ammonia burner; The air inlet of the primary air duct is used to input air, and the annular fuel pipe is used to output ammonia to form a premixed gas in the primary air duct. The equivalence ratio range of the premixed gas is 1.1 - 1.5; The ammonia mixture gas is a mixed gas of ammonia and oxygen or a mixed gas of ammonia and air.

2. The ammonia burner according to claim 1, wherein, The end of the second pipe is connected to the end of the outer wall pipe of the plasma igniter, so that a plurality of circumferential inclined orifices surrounding the air outlet of the plasma igniter can be arranged at the end of the second pipe, and the air output from the plurality of circumferential inclined orifices forms a swirling air flow at the air outlet of the plasma igniter.

3. The ammonia burner according to claim 1, characterized in that, A plurality of fuel nozzles are arranged on the annular fuel pipe, and the plurality of fuel nozzles are used to output ammonia.

4. The ammonia burner according to claim 3, wherein, The included angle between the air outlet direction of the fuel nozzle and the transmission direction of the premixed gas in the primary air duct is less than 90 degrees.

5. The ammonia burner according to claim 3, characterized in that, A plurality of fuel inlet pipes are also arranged in the primary air duct, and all the fuel inlet pipes are communicated with the annular fuel pipe.

6. The ammonia burner according to claim 1, characterized in that, Rotating blades are also arranged in the primary air duct.

7. The ammonia burner according to claim 1, characterized in that, The ammonia burner further includes a fourth pipe sleeved outside the third pipe. A secondary air duct is formed between the third pipe and the fourth pipe. The end of the third pipe extends outward beyond the end of the second pipe, and the end of the fourth pipe extends outward beyond the end of the third pipe.

8. The ammonia burner according to claim 7, characterized in that, Rotating blades are arranged in the secondary air duct.

9. The ammonia burner according to claim 1, characterized in that, The plasma igniter includes a cathode rod and an anode pipe sleeved outside the cathode rod. A central air duct is formed between the cathode rod and the anode pipe. A tapered portion is arranged in the anode pipe, so that an arc is formed between the tapered portion of the anode pipe and the end of the cathode rod when the plasma igniter ignites. The anode pipe is the outer wall pipe of the plasma igniter.

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