CN119403757A

CN119403757A - Method for cracking ammonia and cracking device for cracking ammonia

Info

Publication number: CN119403757A
Application number: CN202280097349.4A
Authority: CN
Inventors: A·I·乔桑; O·I·林德洛夫; L·格洛纳斯
Original assignee: Wartsila Natural Gas Solutions Norway Ltd
Current assignee: Wartsila Natural Gas Solutions Norway Ltd
Priority date: 2022-07-04
Filing date: 2022-07-04
Publication date: 2025-02-07
Also published as: WO2024008270A1; KR20250028235A

Abstract

The present invention relates to a method for cracking ammonia, comprising: - feeding a first portion of ammonia into a burner (14) arranged in a cracking container (12); - feeding an oxygen-containing gas into the burner (14); - burning the first portion of ammonia to form a combustion zone (101) in the cracking container (12) to generate heat; - feeding a second portion of ammonia into a cracking zone (102) outside the combustion zone (101) of the cracking container (12); and - using the heat generated by the combustion of the first portion of ammonia to crack the second portion of ammonia, and generating a product gas including hydrogen and nitrogen from the second portion of ammonia. The present invention also relates to a cracking device (10) for cracking ammonia.

Description

Method for cracking ammonia gas and cracking device for cracking ammonia gas

Technical Field

The invention relates to a method for cracking ammonia gas and a cracking device for cracking ammonia gas.

Background

Ammonia, despite its toxicity, is still considered a promising candidate for carbon-free fuels and/or hydrogen carriers. Excess energy from one location may be used to produce NH ₃, which may be transported to a location where energy is needed. The energy in NH ₃ can be utilized by direct combustion or cracking to H ₂. At high temperature, and in the presence of a suitable catalyst, ammonia is cleaved into its constituent elements. The cracking of ammonia is a slightly endothermic process requiring 23kJ/mol (5.5 kcal/mol) of ammonia and generates hydrogen and nitrogen.

As an example of using NH ₃ as a hydrogen carrier and hydrogen contained in NH ₃, reference is made to US 6936363. This document discloses a process for generating a mixture of hydrogen and nitrogen from gaseous ammonia and utilizing the mixture in an alkaline fuel cell. Ammonia gas is fed into the ammonia cracker. The exhaust gas from the fuel cell is sent to the heating unit of the ammonia cracker. The heating unit is a lean gas combustion chamber or a catalytic burner.

Traditional plants for decomposing molecular compounds require high temperatures due to the endothermic nature of the process. This source of energy typically uses electricity for small scale, NH ₃ or combustion of fossil fuels for large scale, and heat is transferred to the incoming NH ₃. This heat transfer is carried out at high temperatures, imposing stringent requirements on the heat exchanger.

The object of the present invention is to provide a method and a cracking device for cracking ammonia gas, wherein the improvement is in its simple construction and efficient operation.

Disclosure of Invention

The object of the invention is substantially met as disclosed in the independent claims and in the other claims describing further details of the different embodiments of the invention.

According to the invention, a method for cracking ammonia gas comprises

-Feeding a first portion of ammonia gas into a burner arranged to a cracking vessel;

-feeding an oxygen-containing gas into a burner;

-combusting a first portion of the ammonia gas to form a combustion zone in the cracking vessel, generating heat;

feeding a second portion of the ammonia gas into a cracking zone of a cracking vessel outside the combustion zone, and

-Cracking the second portion of ammonia gas using heat generated by combustion of the first portion of ammonia gas and generating a product gas comprising hydrogen and nitrogen from the second portion of ammonia gas.

According to one aspect of the invention, a first portion of the ammonia gas consumes the fed oxygen in the combustion zone, and a non-oxidizing zone is formed in the combustion zone in the pyrolysis vessel.

According to one aspect of the invention, the second portion of ammonia is cracked in the presence of an ammonia cracking catalyst.

According to one aspect of the invention, a first portion of the ammonia consumes the fed oxygen in the combustion zone, a non-oxidizing zone is formed in the combustion zone in the cracking vessel, and a second portion of the ammonia is cracked in the presence of an ammonia cracking catalyst.

According to one aspect of the invention, the second portion of ammonia is cracked using a non-catalytic reaction.

According to one aspect of the invention, a first portion of the ammonia gas consumes the fed oxygen in the combustion zone and forms a non-oxidation zone in the combustion zone in the cracking vessel and a second portion of the ammonia gas is cracked using a non-catalytic reaction.

According to one aspect of the invention, a first portion of the ammonia and oxygen-containing gas is fed into the burner as a gas mixture.

According to one aspect of the invention, the ammonia gas is preheated by heat transfer from the product gas to the gas mixture prior to being fed to the burner.

According to one aspect of the invention, the ammonia gas is vaporized by heat transfer from the product gas to the gas mixture prior to being fed to the burner.

According to an aspect of the invention, the vessel has a cylindrical inner reaction space with a diameter and a length, the length being larger than the diameter, wherein a first portion of the ammonia and oxygen comprising gas is fed into a first end of the reaction space of the vessel in the longitudinal direction of said vessel and the product gas is taken from a second end of the reaction space of the cracking vessel.

According to one aspect of the invention, the second portion of ammonia is heated to a predetermined temperature by heat provided by combustion of the first portion of ammonia, and the heated second portion of ammonia is sent to the cracking catalyst under non-oxidizing conditions.

According to one aspect of the invention, the combustion zone is formed on the central axis of the cracking vessel and at least a portion of the ammonia gas of the second portion is fed from the first end of the space in the vessel around the combustion zone.

According to one aspect of the invention, at least a portion of the ammonia gas of the second portion is fed into the container adjacent its side wall between the first and second ends of the space in the container.

According to one aspect of the invention, at least a portion of the second portion of ammonia is fed into the cracking zone near the vessel wall.

According to an aspect of the invention, the oxygen comprising gas is a mixture of NH ₃ and oxygen comprising gas.

According to an aspect of the invention, the oxygen comprising gas is air.

According to one aspect of the invention, the oxygen-containing gas is pure O ₂.

According to one aspect of the invention, for example, the ammonia cracking catalyst is a nickel-based catalyst, a ruthenium-based catalyst, a lithium amide or a sodium amide-based catalyst.

According to one aspect of the invention, the combustion zone temperature is maintained at about 800 ℃ to 1800 ℃.

According to one aspect of the invention, the temperature in the cracking zone is maintained at 350 ℃ to 800 ℃ by combustion of the first portion of ammonia in the combustion zone of the vessel.

According to one aspect of the invention, the amount of oxygen present in the combustion zone is controlled such that all of the oxygen reacts with the ammonia.

According to one aspect of the invention, the oxygen-containing gas is a mixture of NH ₃ and air, and the air-fuel ratio in the combustion zone is rich.

According to one aspect of the invention, the product gas is fed from the reaction space to an oxidant section, wherein the product gas is oxidized by feeding an oxygen-containing gas into the product gas stream.

A cracking apparatus for cracking ammonia gas according to the present invention includes:

A cracking vessel and a burner arranged to the cracking vessel, the burner comprising a first inlet for feeding ammonia gas into the burner and a second inlet for feeding an oxygen-containing gas into the burner, and

A product gas outlet in the pyrolysis vessel, characterized in that

The pyrolysis vessel is a cylindrical vessel, wherein the burner is arranged at a first end of the vessel, arranged on a central axis of the vessel, and the outlet is arranged at a second end of the space of the vessel,

The cracking vessel further comprises a third inlet for feeding ammonia gas into the cracking vessel, arranged near the side wall and/or near the first end of the space in the vessel.

According to one aspect of the invention, the interior of the pyrolysis vessel comprises an open space comprising a combustion zone adjacent the burner at a first end of the vessel and a pyrolysis zone surrounding the burner and a second end of the space in the vessel.

According to an aspect of the invention, the vessel is provided with an ammonia cracking catalytic converter in the cracking zone at the second end of the space in the vessel.

According to one aspect of the invention, the catalytic converter includes at least one of a bulk catalyst bed, a catalyst support coated with a catalyst material, or a catalyst coating on the interior surface of the vessel.

According to an aspect of the invention, the third inlet comprises a number of inlets into the internal reaction space of the vessel, said number of inlets being arranged around the burner on the end wall at the first end of the space in the vessel.

According to an aspect of the invention, the third inlet comprises a number of inlets arranged near the side wall of the container at a distance from the end wall at the first end of the space in the container.

According to an aspect of the invention, the vessel comprises an oxidant section arranged downstream of the cracking zone, and the oxidant section is provided with at least one inlet for an oxygen containing gas.

The present invention provides several benefits. Since the basic concept is to mix both the NH ₃ to be cracked and the combustion gas in a single vessel, heat is directly mixed to the NH ₃ to be cracked. The NH ₃ to be cracked is heated by internal combustion inside the vessel. Because heat is transferred by mixing, convective heat transfer, and radiation, efficient heat transfer between the combustion gases and the NH ₃ is achieved.

The exemplary embodiments of the invention presented in this patent application should not be interpreted as imposing limitations on the applicability of the appended claims. The verb "comprise" is used in this patent application as an open limitation that does not exclude the existence of unrecited features. The features recited in the dependent claims are freely combinable with each other unless explicitly stated otherwise. The novel features believed characteristic of the invention are set forth with particularity in the appended claims.

Drawings

The invention will hereinafter be described with reference to the exemplary, schematic drawing figures in which

Figure 1 shows a pyrolysis apparatus according to an embodiment of the invention,

Figure 2 shows a pyrolysis apparatus according to another embodiment of the invention,

Figure 3 shows a pyrolysis apparatus according to another embodiment of the invention,

Figure 4 shows a pyrolysis apparatus according to another embodiment of the invention,

Fig. 5 shows a pyrolysis apparatus according to another embodiment of the invention.

Detailed Description

Fig. 1 schematically depicts a cracking apparatus 10 for cracking ammonia gas according to an embodiment of the invention. The apparatus includes a cleavage vessel 12. The pyrolysis container 12 is advantageously a rotationally symmetrical (e.g., cylindrical) container having a longitudinal central axis 16. When the vessel is cylindrical, the length of the internal reaction space 100 of the vessel is greater than the diameter of the vessel. At the first end 12.1 of the reaction space 100 of the vessel 12a burner 14 is arranged for fuel combustion. In a second end 12.2 of the reaction space 100 of the vessel 12, opposite the burner 14, the cracking vessel 12 is provided with an outlet 18 for product gas. Even though this is shown in the figures, the outlet 18 is not necessarily arranged on the central axis 16.

However, the burner 14 is arranged on the central axis 16 of the container such that its flame is coaxial with the central axis 16 inside the container 12. The burner 14 comprises a first inlet 20 connected to an ammonia source 22 for feeding ammonia as fuel into the burner 14, and a second inlet 24 connected to an oxygen-containing gas source 26 for feeding oxygen-containing gas into the burner 14. The first inlet 20 and the second inlet 24 are used to introduce gases required to generate heat for cracking ammonia in the vessel 12.

The cracking vessel 12 further comprises a number of third inlets 28 for feeding ammonia gas into the cracking vessel 12, arranged on the side walls 30 and/or on the end walls 32 at the first end 12.1 of the space 100 in the vessel. The third inlet 28 is for introducing ammonia gas into the cracking vessel 12 for cracking the ammonia gas by means of heat generated by combustion of the gas by the burner 14.

The reaction space 100 inside the cracking vessel 12 is an open space 100, wherein a combustion zone 101 adjacent to the burner 14 is formed when the burner 14 is operated, the cracking zone 102 being in a part of the space 100 at the second end 12.2 of the space 100 of the vessel 12. The combustion zone 101 may be considered a flame zone where fuel oxidation occurs in the presence of oxygen. The space of the vessel is larger in diameter at its first end 12.1 than the effective diameter of the flame (i.e. combustion zone 101), so that the annular portion around the combustion zone 101 is part of the cracking zone 102. Since the vessel is intended to operate at a rather high temperature, its walls are preferably provided with an insulation and/or cooling system (like a fluid jacket).

Advantageously, the vessel 12 comprises a number of third inlets 28 which are uniformly arranged around the burner 14 on the end wall 32 at the first end of the space 100 of the vessel. These inlets 28 at the end wall 32 are arranged to feed ammonia gas into an annular cracking zone 102 around the burner. Advantageously, there are several third inlets 28 arranged at the side walls 30 of the container at a distance from the end wall 32 at the first end 12.1 of the space 100 of the container 12. The third inlet 28 is positioned such that the ammonia gas introduced via the third inlet 28 is heated by combustion in the burner in the space 100. The cracking zone 102 outside of the combustion zone 101 is effectively a non-oxidizing zone. A control valve 34 may be arranged in connection with each of the inlet and inlet channels adapted to balance the flow of gas.

In the embodiment shown in fig. 1, the space 100 is empty. When space 100 is empty, the cracking reaction is non-catalytic thermal cracking, and thus cracking zone 102 in the embodiment of fig. 1 may be referred to as non-catalytic cracking zone 102. Alternatively, the inner wall adjacent to the space 100 may be provided with a catalyst coating on its surface, wherein the catalyst will promote the cracking reaction in the vessel 12.

The method of cracking ammonia gas is practiced in the cracking vessel according to fig. 1 in the following manner. Ammonia is fed from the ammonia source 22 to the burner 14 and in addition an oxygen-containing gas is fed to the burner 14. A first portion of the ammonia is combusted in the combustor 14, wherein heat is generated into the vessel 12 and a combustion zone 101 is formed in the cracking vessel 12. A first portion of the ammonia gas is fed through a first inlet 20 and an oxygen-containing gas is fed into the burner 14 through a second inlet 24. The oxygen-containing gas fed through the first inlet 20 may be air or other oxygen-containing gas or even pure O ₂.

The combustion of ammonia generally follows the following reaction:

4NH₃+3O₂->2N₂+6H₂O

The combustion of ammonia is an exothermic reaction that generates heat and consumes oxygen in the vessel. Thus, combustion of the first portion of ammonia gas forms a substantially oxygen-free region (i.e., non-oxidized region 102) outside of the combustion zone in the vessel.

A second portion of the ammonia is fed via the third inlet 28 into the cracking zone 102 of the cracking vessel 12 outside the combustion zone 101, wherein the second portion of the ammonia is thermally cracked using heat generated by combustion of the first portion of the ammonia. As shown in fig. 5, the second portion of ammonia may be derived from a different ammonia source than the first portion of ammonia. The same applies technically to the embodiments shown in fig. 1 to 4.

The cleavage of ammonia gas generally follows the following reaction:

2NH₃->3H₂+N₂

The resulting product gas produced from the second portion of ammonia thus comprises hydrogen and nitrogen. In this embodiment, the space in the vessel is empty and the cleavage is a non-catalytic reaction.

The gas resulting from the cracking and combustion of the ammonia gas is directed from the vessel 12 via outlet 18 for the desired use of the product gas.

More precisely, a first portion of the ammonia and oxygen comprising gas is fed into a first end 12.1 of the space 100 of the vessel in the longitudinal direction of said vessel and product gas is taken away from a second end of the space of the cracking vessel 12.

The second portion of the ammonia is heated to a predetermined temperature at which the ammonia cracks in the absence of any catalyst. Heat is provided by combustion of the first portion of ammonia gas and the heated second portion of ammonia gas is cracked in the empty cracking zone 102 under non-oxidizing conditions. Because heat is transferred by mixing, convective heat transfer and radiation, efficient heat transfer between the combustion gases and ammonia in the cracking zone is provided.

By combustion of the first portion of ammonia, the combustion zone temperature is maintained at 800 ℃ to 1800 ℃ and the cracking zone temperature is maintained at 350 ℃ to 800 ℃. In some practical cases, the temperature may also be higher, but spontaneous cleavage will occur as the NH ₃ temperature approaches 800 ℃. The cracking reaction itself cools the gas as an endothermic reaction. A catalyst is required to support cracking in the lower portion of the temperature range.

Since the burner is arranged on the central axis 16, the combustion zone 101 is also formed on the central axis 16 of the cracking vessel 12, and advantageously at least a part of the ammonia gas of the second portion is fed from the first end wall 32 of the vessel 12 around the combustion zone 101, meaning also around the burner 14. At least a portion of the second portion of ammonia is fed longitudinally between the combustion zone and the cracking zone 102 through the side wall 30 of the vessel. In this way, the thermal effects of the space of the vessel and the combustion zone are effectively used for the cracking reaction.

Advantageously, the amount of oxygen present in the combustion zone is controlled such that all of the oxygen in the combustion zone reacts with ammonia to provide a non-oxidative cracking zone 102 in the vessel 12. Advantageously, the oxygen-containing gas is air and the air-fuel ratio in the combustion zone is rich (rich). In this way, it is ensured that all the oxygen present in the combustion zone 101 is consumed. This also means that a portion of the ammonia fed to the first portion of the burner may remain as ammonia. Even though the burner may produce ammonia slip, the remaining ammonia will be cracked into hydrogen and nitrogen in the cracking zone 102.

Fig. 2 discloses a cracking device 10 for cracking ammonia gas according to another embodiment of the invention. In practice, this is similar to that shown in FIG. 1, except that the first and second inlets are combined into a common gas inlet 24' such that the oxygen-containing gas fed to the combustor 14 is a mixture of NH ₃ and oxygen-containing gas. In other words, in the embodiment according to fig. 2, both the oxygen-containing gas source 26 and the ammonia gas source 22 are connected to the common gas inlet 24'. This makes it easier to control the operation of the burner and to preheat both gases as a mixture in a more direct manner.

Fig. 3 discloses a cracking apparatus 10 for cracking ammonia gas according to another embodiment of the present invention. In practice, this is similar to that shown in FIG. 1, except that the first and second inlets are combined as one common gas inlet 24' as shown in FIG. 2, and the cracking zone 102 includes an ammonia catalytic converter 103 in this zone.

The common second outlet 24' results in the oxygen comprising gas fed to the burner 14 being a mixture of NH ₃ and oxygen comprising gas. In other words, in the embodiment according to fig. 2, both the oxygen-containing gas source 26 and the ammonia gas source 22 are connected to the common gas inlet 24'. This makes it easier to control the operation of the burner and to preheat both gases as a mixture in a more direct manner.

The catalytic converter 103 is arranged from the third inlet 28 arranged on the side wall 30 of the vessel 12 to the second end of the space in the vessel (on the outlet side of the vessel 12). Thus, the second portion of ammonia is cracked in the presence of an ammonia cracking catalyst.

Here, the catalytic converter 103 is shown as a support grid with a catalyst material disposed on its surface. The catalytic converter may also be arranged in a different way, for example alternatively comprising a bed of bulk material with a catalyst on its surface, as shown in fig. 4. As examples of the use of the present invention, suitable catalyst materials are presently considered to be nickel-based, ruthenium-based, lithium amide or sodium amide catalysts. Each catalyst is effective at temperatures from 350 ℃ to 800 ℃. However, conversion efficiency and life expectancy differ.

The second portion of ammonia is heated to a predetermined temperature at which ammonia cracking occurs in the absence of any catalyst. Heat is provided by combustion of the first portion of ammonia gas and the heated second portion of ammonia gas is fed to the cracking catalyst under non-oxidizing conditions.

Fig. 4 schematically depicts a cracking apparatus 10 for cracking ammonia gas according to another embodiment of the invention. The device comprises a pyrolysis container 12, which is advantageously a rotationally symmetrical container (e.g. cylindrical), having a longitudinal central axis 16. When the vessel is cylindrical, the length of the internal reaction space 100 of the vessel is greater than the diameter of the vessel.

Advantageously, the container 12 is in an upright position such that the central axis 12 is disposed substantially in a vertical position. In this way, the flame and heat distribution in the container is advantageously symmetrically formed about the central axis 16. A burner 14 is arranged at the lower end 12.1 of the vessel 12 to facilitate combustion of the fuel. The cracking vessel 12 is provided with an outlet 18 for product gas in the upper end 12.2 of the vessel 12 opposite the burner 14.

The burner 14 is arranged on the central axis 16 of the container such that its flame is directed upwards inside the container 12 coaxially with the central axis 16. The burner 14 comprises a combined second inlet 24 'connected to the ambient air 26, the ammonia source 22 and the pressurized oxygen source 26' for feeding a mixture of oxygen enriched air and ammonia into the burner 14. The oxygen source is not an essential feature of the invention and when it is absent the gas mixture fed into the burner consists essentially of air and ammonia. The second inlet 24' is combined for introducing the gas required to generate heat for cracking ammonia in the vessel 12.

The cracking vessel 12 further comprises a number of third inlets 28 for feeding ammonia gas into the cracking vessel 12, arranged on or near the side walls 30 and/or end walls 32 at the first end 12.1 of the space 100 in the vessel. The third inlet 28 is for introducing ammonia gas into the cracking vessel 12 for cracking the ammonia gas by means of heat generated by combustion of the gas by the burner 14.

The interior of the pyrolysis vessel 12 comprises an open space 100 in which a combustion zone 101 adjacent to the burner 14 is formed when the burner 14 is operated, the pyrolysis zone 102 being in a portion of the space 100 at the second end 12.2 of the space in the vessel 12. The diameter of the space 100 in the vessel at its first end 12.1 is greater than the effective diameter of the flame (i.e. the combustion zone 101), so that the annular portion around the combustion zone 101 is part of the cracking zone 102.

Advantageously, the vessel 12 comprises a third inlet 28 arranged uniformly around the burner 14 on the end wall 32 at the first end of the space 100 of the vessel. Like other embodiments of the invention, these inlets 28 at the end wall 32 are arranged to feed ammonia gas into an annular cracking zone 102 formed around the burner. Advantageously, there are several third inlets 28 arranged on the side walls 30 of the container at a distance from the end wall 32 at the first end 12.1 of the space 100 in the container 12. The third inlet 28 is positioned such that the ammonia gas introduced via the third inlet 28 is heated by combustion in the burner and is in a non-oxidized zone in the space 100. The third inlet at the side wall is connected to a feed channel 27, the feed channel 27 being arranged in direct heat transfer communication with the annular cracking zone 102, the annular cracking zone 102 preheating ammonia gas due to heat transfer from the gas and/or flame in the space 100. A feed channel 27 extending inside the vessel is an optional feature. The feed channel 27 may also extend outside the vessel 12 if no preheating is required in terms of process design, as depicted in fig. 1-3. For example, the feed passage may actually be achieved by providing an annular groove passage inside the vessel 12 between the vessel wall and a sleeve or shroud 29 inside the vessel 12, as indicated by the dashed line. The cracking zone 102 outside of the combustion zone 101 is effectively a non-oxidizing zone. A control valve 34 may be disposed in connection with each of the inlet and inlet passages, adapted to balance the gas flow.

In the embodiment shown in fig. 1 and 2, the space 100 is empty in the combustion zone 101 and in the upper part of the vessel 12, whereas in the embodiment shown in fig. 3a catalytic converter 103 is provided in the upper part of the space 100. In fig. 4, an embodiment is shown in which the upper part of the space 100 is provided with a catalytic converter 103. In practice, both options (with or without catalyst) may be used according to the desired design, but catalysts are preferred because the cleavage of ammonia thus takes place at lower temperatures, which results in reduced heat loss and consumption of ammonia as fuel, thereby reducing the H ₂ yield from available ammonia. The cracking reaction in the embodiment shown in fig. 4 is catalytic thermal cracking, and thus the cracking zone 102 in the embodiment of fig. 1 may be referred to as catalytic cracking zone 102.

In the device 10a gas mixture feed line 25 is provided, which feed line 25 is connected to the burner 14, more precisely to a combined second inlet 24' at a second end of the feed line 25. A first end of feed line 25 is connected to ammonia gas source 22. The ammonia source in this example is configured to store ammonia in a liquid phase. The feed line 25 is provided with a pump 23 for raising the pressure of the ammonia gas to a suitable pressure.

The cracking unit according to fig. 4 further comprises a heat recovery device 36 (e.g. a heat exchanger) connected to the feed line 25 and the outlet line 38 for evaporating the ammonia gas by means of the heat contained in the product gas. The vessel outlet 18 is connected to the heat recovery device 36 by an outlet line 38 such that the product gas is arranged to be cooled in the heat recovery device 36 and the ammonia gas is arranged to be evaporated in the heat recovery device 36. Thus, the heat recovery device 36 acts as an aftercooler for the process gas and as an evaporator for the ammonia gas. In this way, the ammonia is vaporized and preheated by heat transfer from the product gas to the gas mixture before being fed to the burner. Downstream of the heat recovery device 36 there is a branch feed line 21 connected to the feed line 25, such that the vaporized ammonia gas is arranged to flow through the branch feed line 21 to the third inlet 28 of the vessel 12. The term downstream refers to the direction of flow from ammonia source 22 to vessel 12.

The apparatus further comprises an air feed line 40 configured to feed air from the ammonia gas into the gas mixture feed line 25. The air feed line is provided with a compressor 42 for appropriately pressurizing the air, alternatively the air feed line 40 may be connected to a source of pressurized air. An air feed line is connected to the gas mixture feed line 25 at a location downstream of the heat recovery device 36 and downstream of the branch feed line 21 delivering ammonia gas to the third inlet 28 of the vessel 12. Alternatively, the air feed line 40 is connected to the oxygen source 26 'and pure oxygen may be fed from the oxygen source 26' to the air so that the oxygen-containing gas fed to the burner 14 is a mixture of ammonia, air and pure oxygen.

The process for cracking ammonia gas is carried out in the cracking vessel according to fig. 4 in the following manner. Ammonia is fed from the ammonia source 22 into the gas mixture feed line 25 by suction from pump 23. The pump 23 raises the pressure of the ammonia gas to a desired level and sends the ammonia gas (liquid phase) to the heat recovery device 36. The ammonia is vaporized in the heat recovery device 36 by heat transfer from the product gas. A portion of the vaporized ammonia gas is fed via branch feed line 21 to third inlet 28 of vessel 12.

Air (optionally enriched in oxygen) is fed into the gaseous ammonia stream after the heat recovery device 36. A mixture of ammonia and air (optionally oxygen enriched air) is fed to the burner 14 via a gas mixture feed line 25. In this way, a first portion of the ammonia is combusted in the combustor 14, wherein heat is generated into the vessel 12 and a combustion zone 101 is formed in the cracking vessel 12.

The ammonia combustion and ammonia cracking in the cracking vessel 12 and other operating features of the cracking vessel 12 are described in connection with the description of FIG. 1, which also applies to the embodiment of FIG. 4.

Fig. 5 discloses a cracking apparatus 10 for cracking ammonia gas according to another embodiment of the present invention. The present invention relates to such practical applications in which the product gas is not intended to be produced for use, but is merely a gas that is converted into a less environmentally damaging component. In practice, the pyrolysis apparatus 10 differs from that shown in FIG. 1 as follows. The first and second inlets are combined into one common gas inlet 24' such that the oxygen-containing gas fed to the burner 14 is a mixture of NH ₃ and oxygen-containing gas. In other words, both the oxygen-containing gas source 26 and the ammonia gas source 22 are connected to a common gas inlet 24' of the burner 14. In addition, the cracking vessel 12 is provided with an oxidant section 104 following the cracking zone 120 in the direction of flow of the gas in use. In addition, at least a portion of the walls of the container 12 are cooled. The embodiment of fig. 5 is also distinguished in that the gas mixture feed line 25 is connected to a first ammonia gas source 22 (corresponding to the ammonia gas source in the embodiment of fig. 1 to 4) such that a first portion of the ammonia gas is fed into the burner 14. The second portion of ammonia gas is derived from a second ammonia gas source 22', which may be different from the ammonia gas source that feeds the first portion of ammonia gas to the burner 14. Thus, in this embodiment, the combustion gas used in the burner 14 may have a different composition than the ammonia-containing gas cracked in the cracking zone 102 of the vessel. For example, the second ammonia source 22' may be an ammonia fuel line that is connected to a gas consumer (e.g., an internal combustion engine) during inerting of the fuel line with nitrogen.

The vessel 12 includes a fluid jacket 44 arranged for cooling the vessel by circulating a cooling fluid (e.g., water) therein. To this end, the fluid jacket 44 is provided with a fluid inlet 46 and a fluid outlet 48. In the pyrolysis vessel 12, the pyrolysis zone 102 is provided with an outlet 18' that creates a constriction in the cross-sectional area of the pyrolysis zone 102. As shown, the constriction is preferably conical on both sides of the constriction, thereby smoothly separating the cracking zone and the oxidant section 104. The oxidant section 104 is provided with one or more oxidant inlets 50 connected to the oxygen-containing gas source 26 via the flow channels 52. The flow channel opens into an annular groove 54 arranged radially outside the sleeve 29. An annular groove 54 is formed between the inner wall of the container 12 and a second sleeve 56. The second sleeve 56 extends from the end wall 32 to the outlet 18' such that the slot 54 has a substantially constant radial width. The slots extending axially further from the end wall 32 than the sleeve 29 and the second sleeve 56 are arranged in direct heat transfer communication with the cracking zone 102 to preheat the gas due to heat transfer from the gas and/or flame in the space 100. The flow channels 52 are preferably arranged so as not to be in direct heat transfer connection with the fluid jacket 44 or the cooling wall of the vessel 12. The oxygen-containing gas source 26 is connected to the flow channel 52. As shown, the oxygen-containing gas source 26 connected to the flow passage 52 may be different from the oxygen-containing gas source connected to the combustor 14 in order to improve the controllability of the combustor 14. The oxidant inlet 50 opens into the oxidant section 104 in a space adjacent the cracking zone outlet 18'.

As described in other embodiments, the burner 14 burns ammonia gas and provides heat for cracking, and the ammonia gas is cracked in the cracking zone 102. The product gas from cracking zone 102 is fed into oxidant section 104, which auto-ignites in the presence of oxygen because the gas temperature is higher than its natural temperature.

The ammonia gas 22 and combustion air 26 are premixed and swirled in the burner inlet 14, ignited, and produce a rich (i.e., excess) fuel flame 101. The flame will provide heat for ammonia cracking 102. Exhaust gas (preferably a mixture of ammonia and nitrogen) from the process of inerting the fuel line with nitrogen (second ammonia source 22'), which will vary in composition, is injected into the annular space between the sidewall 30 and the inner shroud 29 and heated as it flows to the cracking zone 102. Where the heat from combustion will decompose the ammonia into nitrogen and hydrogen. Because of the rich combustion, there is no air available for combusting the hydrogen. The offgas consisting of N ₂、NO、NO₂ and H ₂ will leave the stage 102 of the cracking zone through outlet 18', where air is supplied through inlet 50, mixed with hydrogen and ignited by the hot surface. The outlet region is made of a high temperature resistant material, not cooled by the cooling fluid, and the mixture will burn in the oxidant section 104. The downstream exhaust gas will consist of N ₂、H₂ O and trace amounts of NO and NO ₂ (in the range of 10-15 ppm).

While the invention has been described herein by way of example in connection with what is presently considered to be the most preferred embodiments, it will be obvious to those skilled in the art that as the technology advances, the basic concepts of the invention can be implemented in many ways. The invention and its embodiments are thus not limited to the examples and samples described above, but they may vary within the content of the patent claims and their legal equivalents. When combining techniques are feasible, the details mentioned in connection with any of the embodiments above may be used in connection with another embodiment.

Parts list

Cracking plant 10

Cracking vessel 12

First end of space in vessel 12.1 second end of space in vessel 12.2 burner 14

Central axis 16 outlet 18 of pyrolysis container

First inlet 20

Branch feed line 21

Ammonia gas source 22

Pump 23

Second inlet 24

Public gas inlet 24'

Gas mixture feed line 25 oxygen-containing gas source 26

Pressurized oxygen source 26'

Feed channel 27

Third inlet 28

Sleeve 29

Side wall 30

End wall 32

Valve 34

Heat recovery device 36

Outlet line 38

Air feed line 40

Compressor 42

Fluid jacket 44

Fluid inlet 46

Fluid outlet 48

Oxidant inlet 50

Oxidant flow passage 52

Interior space 100 of container

Combustion zone 101

Cracking zone 102

Ammonia cracking catalytic converter 103

Oxidant section 104

Claims

1. A method of cracking ammonia gas, the method comprising the steps of:

-feeding a first portion of ammonia gas into a burner (14) arranged to a cracking vessel (12);

-feeding an oxygen-containing gas into the burner (14);

-combusting said first portion of ammonia gas with said burner (14), forming a combustion zone (101) in said cracking vessel (12), and generating heat;

-feeding a second portion of ammonia gas into a cracking zone (102) of said cracking vessel (12) outside said combustion zone (101), and

-Cracking the second portion of ammonia gas using heat generated by combustion of the first portion of ammonia gas, and generating a product gas comprising hydrogen and nitrogen from the second portion of ammonia gas.

2. A method of cracking ammonia according to claim 1, wherein in the combustion zone (101) the first portion of ammonia consumes the fed oxygen, thereby forming a non-oxidized zone outside the combustion zone (101) in the cracking vessel (12).

3. A method of cracking ammonia according to claim 1 or 2, characterized in that the second portion of ammonia is cracked in the presence of an ammonia cracking catalyst (103).

4. A method of cracking ammonia according to claim 1 or 2, wherein the second portion of ammonia is cracked using a non-catalytic reaction.

5. A method of cracking ammonia according to claim 1, characterized in that the first portion of ammonia and the oxygen-containing gas are fed into the burner (14) as a gas mixture.

6. A method according to claim 1, characterized in that ammonia is preheated by heat transfer from the product gas to the gas mixture before being fed to the burner (14).

7. A method of cracking ammonia according to any one of the preceding claims, wherein the vessel (12) has a cylindrical inner reaction space (100) with a diameter and a length, the length being larger than the diameter, characterized in that the first part of ammonia and the oxygen-containing gas is fed into a first end (12.1) of the reaction space (100) of the vessel (12) in the longitudinal direction of the vessel, and the product gas is taken from a second end (12.2) of the reaction space (100) of the cracking vessel (12).

8. A method of cracking ammonia gas according to claim 3 or 7 wherein the second portion of ammonia gas is heated to a predetermined temperature by heat provided by combustion of the first portion of ammonia gas and the heated second portion of ammonia gas is sent to the cracking catalyst under non-oxidizing conditions.

9. A method of cracking ammonia according to any one of the preceding claims, characterized in that the combustion zone (101) is formed on a central axis (16) of the cracking vessel (12) and at least a part of the ammonia of the second portion is fed from the first end (12.1) of the space (100) in the vessel (12) around the combustion zone (101).

10. A method of cracking ammonia according to any one of the preceding claims wherein at least a portion of the ammonia of the second portion is fed into the container (12) between a first end (12.1) and a second end (12.2) of the space (100) in the container (12) near a side wall of the container.

11. The method according to any of the preceding claims, wherein the oxygen comprising gas is a mixture of NH ₃ and oxygen comprising gas.

12. The method according to any of the preceding claims 1 to 9, wherein the oxygen comprising gas is air.

13. The method according to any of the preceding claims 1 to 9, characterized in that the oxygen comprising gas is pure O ₂.

14. The method of claim 3, wherein the ammonia cracking catalyst is selected from the group consisting of nickel-based catalysts, ruthenium-based catalysts, lithium amide and sodium amide-based catalysts.

15. The method according to any of the preceding claims, wherein the combustion zone (101) temperature is maintained at 800 ℃ to 1800 ℃.

16. A method according to any of the preceding claims, characterized in that the temperature in the cracking zone (102) is maintained at 350 ℃ to 800 ℃ by combustion of the first portion of ammonia in the combustion zone (101) of the vessel (12).

17. A method according to any of the preceding claims, characterized in that the amount of oxygen present in the combustion zone (101) is controlled such that all the oxygen reacts with the ammonia.

18. The method according to claim 12, characterized in that the air-fuel ratio in the combustion zone (101) is rich.

19. A method according to any one of the preceding claims, characterized in that the product gas is fed from the reaction space (100) into an oxidant section (104), in which oxidant section (104) the product gas is oxidized by feeding an oxygen-containing gas into the flow of the product gas.

20. A cracking device (10) for cracking ammonia gas, the device comprising:

A cracking vessel (12) and a burner (14) arranged to an open space (100) inside the cracking vessel (12), the burner (14) comprising a first inlet (20) for feeding ammonia gas into the burner (14) and a second inlet (24) for feeding an oxygen containing gas into the burner (14), and

An outlet (18) for product gas in the cracking vessel (12), characterized in that

The cracking vessel (12) is a cylindrical vessel (12), wherein the burner (14) is arranged at a first end (12.1) of the space (100) in the vessel (12), on a central axis (16) of the vessel (12), and the outlet (18) is arranged at a second end (12.2) of the space (100) in the vessel (12),

The cracking vessel (12) further comprises a third inlet (28) for feeding ammonia gas into the cracking vessel (12), which third inlet is arranged in the vessel (12) near a side wall of the space (100) and/or the first end (12.1).

21. The pyrolysis apparatus (10) of claim 19, wherein the open space (100) comprises a combustion zone (101) adjacent the burner (14) at the first end (12.1) of the space (100) in the vessel (12), and a pyrolysis zone (102) surrounding the burner (14) at the second end (12.2) of the space (100) in the vessel (12).

22. The cracking vessel (12) according to claim 19 or 20, characterized in that the vessel (12) is provided with an ammonia cracking catalytic converter (103) in the cracking zone (102) at the second end (12.2) of the space (100) in the vessel (12).

23. The pyrolysis vessel (12) of claim 20, wherein the catalytic converter (103) comprises at least one of a bulk catalyst bed, a catalyst support coated with a catalyst material, or a catalyst coating on an inner surface of the vessel (12).

24. The cracking apparatus according to claim 19, wherein the third inlet (28) comprises several inlets into the space (100) inside the vessel (12), which are arranged around the burner (14) on an end wall at the first end (12.1) of the space (100) in the vessel (12).

25. The cracking apparatus according to claim 18 or 23, characterized in that the third inlet (28) comprises several inlets arranged near a side wall of the vessel (12) at a distance from the end wall at the first end (12.1) of the space (100) in the vessel (12).

26. The cracking apparatus according to claim 23, wherein the first inlet (20) and the second inlet (24) are formed as a single common gas inlet (24').

27. The lysis apparatus according to claims 23 and 24.

28. A cracking apparatus according to any one of claims 20 to 27, characterized in that the vessel comprises an oxidant section (104) arranged downstream of the cracking zone (102), and that the oxidant section (104) is provided with at least one inlet (50) for an oxygen containing gas.