DEVICE FOR COMBUSTING AMMONIA

Abstract

 The invention relates to the field of chemical engineering, and more particularly to a device for combusting ammonia, which can be used in heating devices for producing heat and in devices for decomposing ammonia into a nitrogen-hydrogen mixture. The device for combusting ammonia comprises a cylindrical combustion chamber, a device for supplying air-ammonia mixture, including at least one main channel for its supply, at the outlet of which is installed tangential swirler, spark plug installed in the combustion chamber, a channel for supplying auxiliary fuel with increased flammability. A cylindrical body is introduced, inside of which a cylindrical combustion chamber is located coaxially with the formation between them, the entrance of the main channel and the tangential swirler, an additional annular channel for supplying and heating the air-ammonia mixture, wherein the cylindrical side surfaces of the body and the combustion chamber have at least one through hole for installation of the spark plug, a flame sensor, a device for secondary air supply and a flame stabilizer are introduced, wherein the combustion chamber is a cooling chamber, at the outlet of which a catalytic unit is installed. The achieved technical result is the increase of ecological parameters of the burner, reliability of its operation and safety.

Description

TECHNICAL FIELD

[0001] The invention relates to the field of chemical engineering, and more particularly to a device for combusting ammonia, which can be used in heating devices for producing heat and in devices for decomposing ammonia into a nitrogen-hydrogen mixture.

BACKGROUND ART

[0002] For many years, fossil hydrocarbons, primarily oil and natural gas, have been used as the primary fuel for various combustion devices in the power and heating engineering. However, fossil fuel resources are not infinite, and the combustion products produced by burning raw hydrocarbons contain carbon dioxide in quantities that threaten the environment, primarily as a factor in global warming. Therefore, there is a need to find an alternative fuel to hydrocarbons that is made from renewable sources and does not emit carbon dioxide when used.

[0003] Until recently, hydrogen was considered to be such a fuel with high combustion quality, which produces only water vapor. However, at large-scale application of hydrogen instead of raw hydrocarbons, questions arise about the economic feasibility of such replacement, associated primarily with low energy density of hydrogen. Taking into account the above, it is considered that instead of raw hydrocarbons it is more expedient to use hydrogen not in pure form, but in chemically bound form - in the form of liquid ammonia, which can be stored in liquid form at low pressures and room temperature or at atmospheric pressure and temperature of minus 33°C.

[0004] However, ammonia is a highly flammable fuel and, unlike pure hydrogen, requires the use of technical solutions aimed at ensuring its qualitative combustion.

[0005] This is due to the low flame temperature of ammonia (1955°K, for gasoline 2336°K), low combustion rate, high ignition temperature of ammonia-air mixtures.

[0006] One of the most common solutions for ammonia combustion is the use of vortex burners, which provide high-quality preparation of ammonia-air mixtures due to intensive mixing of these components. Examples of such technical solutions are applications for inventions: JP2018155412 dated 10.04.2018 "Fuel combustion device and method for implementing it", JP2020186843 dated 13.05.2019 "Combustion device"; JP2016130619 dated 15.01.2015 "Device for combusting fuels with low combustion properties".

[0007] However, the analysis of the above technical solutions has shown that they provide high-quality combustion with a minimum amount of nitrogen oxides and residual ammonia vapor in the exhaust gases, in addition to nitrogen and water vapors. Research in this direction, given the importance of the problem, is being conducted everywhere by leading international firms.

[0008] The "Ammonia combustion device" is known, Japanese application 20180022676 dated 13.02.2018, published as application No. JP2019138565 dated 22.08 2019. The combustion device contains a combustion cylinder, a fuel injector for supplying mixed gas in the form of a swirling air stream, an igniter 14 located at a place where the mixed gas remains in the combustion cylinder. The first fuel is ammonia and the second fuel is combustible. The combustion device additionally contains a mixer that performs a mixing function.

[0009] The above device is the closest in technical essence to the claimed device and is therefore selected as a prototype. The disadvantage of the known device is a narrow range of operation and shot operational life due to overheating of the side walls of the burner.

SUMMARY OF INVENTION

[0010] The solved technical problem is the creation of a device for combusting ammonia with a large range of regulation and a long operational life.

[0011] The achieved technical result is the increase of ecological parameters of the burner, reliability of its operation and safety.

[0012] To achieve technical result, the device for combusting ammonia, comprising a cylindrical combustion chamber, a device for supplying air-ammonia mixture, including at least one main channel for its supply, at the outlet of which is installed tangential swirler, spark plug installed in the combustion chamber, a channel for supplying auxiliary fuel with increased flammability, the new is that a cylindrical body is additionally introduced, inside of which a cylindrical combustion chamber is located coaxially with the formation between them, the entrance of the main channel and the tangential swirler, an additional annular channel for supplying and heating the air-ammonia mixture, wherein the cylindrical side surfaces of the body and the combustion chamber have at least one through hole for installation of the spark plug, a flame sensor, a device for secondary air supply and a flame stabilizer are introduced, wherein the combustion chamber is a cooling chamber, at the outlet of which a catalytic unit is installed.

[0013] The flame sensor is made in the form of a thermocouple and is located along the axis of the device in the secondary air supply channel, located in the annular gap between the flame sensors and the auxiliary fuel gas supply channel. An axial swirler is installed at the outlet of the secondary air channel. The auxiliary fuel supply channel is made in the form of an annular gap between the outer casing and the inner shell of the secondary air supply channel, with axial nozzles at its outlet. The additional fuel may be H₂, CH₄, C₃H₈, wherein the catalytic unit contains a fire barrier plate combined with a mesh catalyst and contains (Pt, Pd) as the active ingredient. The heat exchanger is designed as a tube in a tube, in the annular gap of which passes an ammonia-air mixture containing intensifiers to improve heat exchange. The spark plug is cooled by an ammonia-air mixture. Secondary air is supplied to the device in the volume of no more than 50% of the primary air volume, and additional fuel is supplied in the volume of 5-15% of the primary fuel (ammonia) volume.

BRIEF DESCRIPTION OF DRAWINGS

[0014] 

Fig.1 shows the design of the claimed device, longitudinal section;

Fig. 2 shows a cross section along the plane A-A.

DESCRIPTION OF EMBODIMENTS

[0015] A device for combusting ammonia (Fig. 1) comprises a cooled combustion chamber 1 of cylindrical shape with a burner device 3 located in it with tangential input of working reagents - ammonia with primary air, one or more spark plugs 2 located on the cylindrical surface, flame sensors 4 located along the axis of the burner device 3, channels for supplying secondary air 6 and secondary fuel 5, a flame stabilizer 7, a mesh unit 8 with catalysts. An axial swirler 12 is installed at the outlet of the secondary air channel 6, and axial nozzles 13 are installed at the outlet of the secondary fuel channel 5. The gas mixture of ammonia and primary air is supplied through the connection 11 into the annular type intertube space formed by inner 14 and outer 15 cylinders. Secondary air is supplied in the connection 10 to the intertube space formed by cylinders 17 and 18, and secondary fuel is supplied in the connection 9 to the intertube space formed by cylinders 16 and 17.

[0016] The device operates as follows.

[0017] At startup, the ammonia-air mixture is supplied through the connection 11 into the intertube space 18 and exits into the combustion chamber 1, at the same time the plugs 2 are energized. When necessary or required, secondary fuel is supplied to the combustion chamber 1 through the connection 9, which enters the combustion chamber 1 through the axial nozzles 13. The flame sensor 4 mounted in the axis of the device detects the presence of ignition in the device. By regulating the supply of ammonia-air mixture, secondary fuel and air, ignition and regulation of the operation modes of the ammonia combustion device are provided.

[0018] Gas ammonia-air mixture before entering the tangential swirler passes through the gas-cooled jacket, where it is additionally mixed and heated, which contributes to the increase of ammonia combustion rate and completeness of combustion and leads to the reduction of NOx and NH₃ emissions. At the same time, the inner cylinder and the spark plug body are cooled, which ensures longer operational life. On the inner cylinder of the device there is a stabilizing device in the form of a washer, which creates a zone of recirculation of combustion products and contributes to an increase in the time of combustion of fuel and, as a consequence, to an increase in the completeness of combustion. Unlike devices for combustion of raw hydrocarbons, where spark plugs are located mainly near the supply of the fuel-air mixture on the end surface, in the claimed device at least one spark plug is located on the side surface, which ensures more stable ignition and the ability to install the spark plug or multiple spark plugs at different heights. In the absence of ammonia-air mixtures of soot in the combustion products, this solution allows for long-lasting plug operation. The large area of the inner cylinder allows, if necessary, to install several plugs, both on the cylinder circumference and height, which also contributes to the reliability of ignition of ammonia-air mixtures.

[0019] Ensuring qualitative and complete combustion of ammonia-air mixtures requires, in addition to complete and uniform mixing of ammonia with air and its ignition, also a long combustion process. To meet this requirement, a stabilizing membrane in the form of a washer is installed inside the cylinder, which ensures that the combustion products are swirled and increases the residence time of the combustion products in the combustion chamber. The products of complete combustion of ammonia-air mixtures are N₂ and H₂O, while those of incomplete combustion are NOx and NH₃ residues. NOx and NH₃ in the combustion products must be minimized in order to completely eliminate the combustion products. To fulfill this requirement, it is proposed to install at the outlet of combustion products a mesh unit containing both screens of heat-resistant material in the form of stainless steel or nichrome and an afterburning catalyst placed on the screen. The invention proposed by the inventors is a technical solution aimed at solving the problem of qualitative combustion of ammonia. The invention provides stable, reliable environmentally friendly combustion of ammonia, increasing the operating life of the device and safety.

Claims

1. A device for combusting ammonia, comprising: a cylindrical combustion chamber, a device for supplying air-ammonia mixture, including at least one main channel for its supply, at the outlet of which is installed tangential swirler, spark plug installed in the combustion chamber, a channel for supplying auxiliary fuel with increased flammability, characterized in that a cylindrical body is additionally introduced, inside of which a cylindrical combustion chamber is located coaxially with the formation between them, the entrance of the main channel and the tangential swirler, an additional annular channel for supplying and heating the air-ammonia mixture, wherein the cylindrical side surfaces of the body and the combustion chamber have at least one through hole for installation of the spark plug, a flame sensor, a device for secondary air supply and a flame stabilizer are introduced, wherein the combustion chamber is a cooling chamber, at the outlet of which a catalytic unit is installed.

2. The device according to claim 1, characterized in that the flame sensor is made in the form of a thermocouple.

3. The device according to claim 1, characterized in that the flame sensor is installed along the axis of the device in the secondary air supply channel.

4. The device according to claim 1, characterized in that the secondary air channel is formed in the annular gap between the flame sensors and the auxiliary fuel gas supply channel.

5. The device according to claim 1, characterized in that the axial swirler is installed at the outlet of the secondary air channel.

6. The device according to claim 1, characterized in that the secondary fuel supply channel is made in the form of an annular gap between the outer casing and the inner shell of the secondary air supply channel.

7. The device according to claim 1, characterized in that the outlet of the additional fuel channel has axial nozzles.

8. The device according to claim 1, characterized in that the additional fuel may be H₂, CH₄, C₃H₈.

9. The device according to claim 1, characterized in that the catalytic unit contains a fire barrier plate combined with a mesh catalyst.

10. The device according to claim 9, characterized in that the catalytic unit contains (Pt, Pd) as the active substance.

11. The device according to claim 1, characterized in that the heat exchanger is made as a pipe in a pipe, in the annular gap of which passes ammonia-air mixture containing intensifiers to improve heat exchange.

12. The device according to claim 1, characterized in that the spark plug is cooled by an ammonia-air mixture.

13. The device according to claim 1, characterized in that the secondary air is supplied to the device in a volume of no more than 50% of the primary air volume.

14. The device according to claim 1, characterized in that the additional fuel is supplied in the volume of 5-15% of the ammonia volume.

Drawing