Combustion device and gas turbine with ammonia cracker and method for operating a combustion device and gas turbine

Abstract

The invention relates to a combustion device (01) of a gas turbine (05) with a burner (02) and a combustion chamber (03), which (01) further comprises an ammonia cracker (11). This (11) is provided with a reaction channel (12) and a heating device, wherein a transmission section (13) of the combustion chamber (03) simultaneously forms part of the heating device.

Description

TECHNICAL FIELD

[0001] The invention relates to a combustion device, in particular a gas turbine with an ammonia cracker. The gas turbine typically comprises a compressor, a combustion device comprising a burner and a combustion chamber, and an expansion turbine. The ammonia cracker is used to split the ammonia into a mixture of hydrogen and nitrogen, which can be combusted in the combustion chamber. BACKGROUND

[0002] Typically, most gas turbines use natural gas as fuel. However, to reduce carbon dioxide emissions, a proportion of hydrogen is increasingly being used as gas turbine fuel. However, the supply and storage of hydrogen is expensive and raises safety concerns. Therefore, ammonia is a preferred medium for storing and transporting hydrogen from a production site to a power plant.

[0003] The direct combustion of ammonia as a fuel in a gas turbine is not permitted due to the release of excessive amounts of nitrogen oxides (NOx). Furthermore, the direct combustion of ammonia is difficult due to its ignition inertia. Therefore, at least some of the ammonia must be split into hydrogen and nitrogen before combustion in the gas turbine combustion chamber.

[0004] A high temperature is required to break down the ammonia. A wide variety of technologies are used to achieve the required heat within an ammonia cracker.

[0005] In general, it is preferred to operate the power plant, including ammonia cracking and gas turbine operation, as efficiently as possible, with as little energy wasted as possible. Furthermore, it is preferred that ammonia cracking does not require external heat or energy sources.

[0006] Exemplary solutions enabling the combustion of ammonia are presented in EP 3314166 B1, EP 3377745 B1, and EP 3417205 B1. In all cases, a portion of the ammonia is fed to an ammonia cracker, with the resulting hydrogen and nitrogen subsequently being fed to the gas turbine combustion chamber. Advantageously, the heat from the gas turbine exhaust gas is used to heat the ammonia cracker.

[0007] However, the existing solutions require significant installation effort. Another disadvantage is that the waste heat from the gas turbine cannot be used in the usual way, for example, for a steam generator. SUMMARY OF THE INVENTION

[0008] The object of the present invention is to develop an alternative solution for arranging an ammonia cracker in a combustion plant that enables high efficiency and low installation costs. Furthermore, the use of external heat or an external energy source should be avoided as far as possible.

[0009] The object is achieved by a combustion device according to the invention with an ammonia cracker according to claim 1. A gas turbine according to the invention with a corresponding combustion device is specified in claim 11. Methods according to the invention for operating a combustion device and a gas turbine with an ammonia cracker are defined in claims 9 and 13. Advantageous embodiments are the subject of the dependent claims.

[0010] A combustion device of this type is expediently used in a gas turbine. Irrespective of this, the embodiment can also be used for other devices in which ammonia combustion is intended. At a minimum, the combustion device comprises at least one burner and a combustion chamber. The burner is supplied with combustion air and fuel as intended during use of the combustion device. Both are fed through the burner into the combustion chamber and can be combusted accordingly in the combustion chamber.

[0011] Furthermore, it can be provided that several burners are arranged on the combustion chamber. In this case, the implementation according to the invention can relate to one or more of the existing burners. In this case, the solution according to the invention is preferably integrated into all existing burners.

[0012] The generic combustion device further comprises an ammonia cracker for splitting ammonia into hydrogen and nitrogen. For this purpose, the ammonia cracker has a reaction channel and a heating device. Gaseous ammonia is supplied to the reaction channel on the inlet side, whereby the reaction channel is connected to an ammonia source on the inlet side. During operation of the combustion device, the heating device heats the ammonia in the reaction channel, causing it to split into hydrogen and nitrogen. Accordingly, a mixture of hydrogen and nitrogen, along with a residual amount of ammonia, leaves the reaction channel on the outlet side during operation of the combustion device. For the combustion of the hydrogen, the reaction channel is connected to the combustion chamber on the outlet side.

[0013] According to the invention, efficiency is increased and installation costs are reduced by arranging the ammonia cracker adjacent to the combustion chamber, with a transfer section of the combustion chamber simultaneously forming part of the heating device. This means that the combustion chamber wall, heated by the combustion process, is used in sections to supply at least a portion of the necessary heat energy to the reaction channel.

[0014] In this process, ammonia from an ammonia source is passed through the reaction channel, where, due to the high temperatures, it is at least partially split into hydrogen and nitrogen. This mixture is then fed into the combustion chamber as fuel. The high temperatures generated during combustion heat up the combustion chamber.

[0015] According to the invention, heat is extracted from the combustion chamber via a transfer section to heat the reaction channel and transferred from there to the reaction channel. Thus, the ammonia flowing through the reaction channel is heated using the thermal energy from the combustion in the combustion chamber.

[0016] The arrangement preferably heats the ammonia during the combustion process to a temperature above 600 °C. A temperature above 700 °C is particularly advantageous.

[0017] This advantageous use of the heat generated during combustion in the combustion chamber to split the ammonia avoids complex piping, for example when an ammonia cracker is arranged on a flue gas line, and the split ammonia is fed to the combustion chamber as a mixture of hydrogen and nitrogen via a short route.

[0018] The splitting of the ammonia immediately before the combustion chamber eliminates the need for measures otherwise required during hydrogen combustion to prevent damage caused by hydrogen, such as hydrogen embrittlement. The piping up to the burner can essentially be designed without special requirements—i.e., it is suitable for ammonia. Piping for hydrogen generally requires a change in the material to prevent damage over its lifetime.

[0019] It is particularly advantageous if the ammonia cracker is integrated into the burner. In this respect, the burner and the ammonia cracker form a single unit adjacent to the combustion chamber. The burner surface adjacent to the combustion chamber, i.e., the combustion chamber, forms the transfer section for conducting heat from the combustion chamber to the reaction channel.

[0020] To facilitate advantageous heat transfer from the transfer section to the reaction channel, the ammonia cracker advantageously has a heat-conducting body. The reaction channel runs through the heat-conducting body.

[0021] In order to enable advantageous heat transfer from the heat conducting body into the reaction channel, the reaction channel is preferably provided with an enlarged surface in the heat conducting body.

[0022] For this purpose, in one embodiment it can be provided that the heat conducting body has a plurality of ribs projecting into the reaction channel.

[0023] The reaction channel can, for example, be a single annular reaction channel. Alternatively, it is also possible to form the reaction channel by a plurality of reaction holes traversing the heat-conducting body. These holes can be distributed around the circumference, arranged in a grid, or arranged in another configuration.

[0024] Regardless of the specific design of the reaction channel, it is particularly advantageous if the surface area of ​​the heat-conducting body adjacent to the reaction channel—for example, formed by a plurality of reaction bores or other structures—corresponds to at least five times the surface area of ​​a substitute cylinder (cylinder surface). This means that an enlarged heat transfer surface is provided in the reaction channel. The substitute cylinder is defined, on the one hand, by the mean path length of the reaction channel in the heat-conducting body from an inlet to an outlet, which is located directly adjacent to the combustion chamber at the transfer section or at a short distance therefrom. On the other hand, the substitute cylinder is determined by a circular area corresponding to the cross-sectional area of ​​the reaction channel.

[0025] In this respect, it is also possible to construct the reaction channel as a porous structure or for the heat conducting body to surround the reaction channel and also be arranged in the reaction channel in the form of a grid.

[0026] An additive manufacturing process is advantageously used for production, which enables complex geometries to achieve a large surface area.

[0027] Furthermore, it may be advantageous to provide the surface of the reaction channel with a catalytic coating.

[0028] Furthermore, the heat-conducting body must be made of a material that offers both high temperature resistance and favorable thermal conductivity. Silicon-infiltrated silicon carbide (SiSiC) is particularly preferred for this purpose. This material possesses the required properties, including high temperature resistance and high thermal conductivity.

[0029] It is obvious that combustion air must be able to be supplied to the combustion chamber. For this purpose, the burner advantageously has an air duct that runs from an air inlet through the burner to the combustion chamber. The shape of the air duct is initially irrelevant. It can be a single, for example, central or annular air duct, or multiple air ducts.

[0030] The reaction channel can also end at the air duct near the combustion chamber, allowing the fuel to be introduced into the air duct. This allows the fuel to mix with the combustion air, allowing the mixture to subsequently flow into the combustion chamber.

[0031] Particularly preferably, the air duct is arranged at a thermal distance from the heat conducting body, so that there is no direct transfer of heat energy from the heat conducting body into the air duct.

[0032] For this purpose, a wall of the air duct can be spaced apart from the heat-conducting body, with a gap, for example, between the wall of the air duct and the heat-conducting body. In the simplest case, the heat-conducting body is provided with a coating on the air duct side that has particularly low thermal conductivity.

[0033] To enable heating of the ammonia in the ammonia cracker to the temperature required for cracking the ammonia, it is advantageous if the ammonia supplied to the ammonia cracker is already at an elevated temperature. A fuel heat exchanger is advantageously used for this purpose. The fuel heat exchanger has a fuel passage, the outlet of which is connected to the inlet of the reaction channel. When using the combustion device, one inlet of the fuel passage is obviously connected to an ammonia source.

[0034] In order to enable effective heating of the ammonia in the reaction channel to the required temperature for the cracking process, the arrangement is preferably designed such that the ammonia is preheated to a temperature of above 300 °C, preferably above 400 °C, as it passes through the fuel passage of the fuel heat exchanger.

[0035] It is also advantageous if the fuel heat exchanger has an air passage that is connected to the burner's air duct on the outlet side. In this case, the combustion air first flows through the fuel heat exchanger's air passage and then through the burner's air duct. The air passage should obviously be connected to a combustion air supply on the inlet side.

[0036] The combustion air is usually supplied to the combustion unit at elevated pressure. If the combustion air is at an elevated temperature, the heat from the combustion air can be used to preheat the ammonia.

[0037] Although the size of the burner increases, it is still advantageous to arrange the fuel heat exchanger on the burner or to integrate it into the burner.

[0038] The combustion device is particularly preferably used in a gas turbine. The gas turbine also has a compressor and an expansion turbine.

[0039] Preferably, the compressor is connected to the air duct on the outlet side. Accordingly, when the gas turbine is used, the compressor supplies the necessary combustion air for burning the fuel in the combustion chamber.

[0040] If a fuel heat exchanger is present, it is particularly preferred to connect the compressor outlet to an inlet of the fuel heat exchanger's air passage. Thus, the combustion air, at elevated pressure and temperature, coming from the compressor initially flows, at least in part, through the fuel heat exchanger and then through the burner to enable combustion in the combustion chamber.

[0041] It should be noted that not all of the air mass flow from the compressor necessarily needs to be routed through the fuel heat exchanger and the burner. It may also be possible to bypass a portion of the combustion air past the fuel heat exchanger. It is also common practice for a portion to be routed to the expansion turbine for cooling purposes.

[0042] When the gas turbine is in operation, the flue gases produced during combustion are directed from the combustion device to the expansion turbine, thus driving a rotor of the gas turbine. LIST OF CHARACTERS Fig. 1 schematically outlines an example of a combustion device 01 according to the invention. Fig. 2 schematically outlines an example of a gas turbine 05 according to the invention with corresponding combustion device 01. FIGURE DESCRIPTION

[0043] The Fig. Figure 1 illustrates an exemplary embodiment of a combustion device 01 according to the invention, comprising a combustion chamber 03 and a burner 02. However, a combustion device could also have multiple burners arranged on the combustion chamber 03. The supplied fuel is burned with combustion air in the combustion chamber 03. The combustion air is supplied to the combustion chamber 03 via an air duct 15 through the burner 02.

[0044] Furthermore, the fuel flows through the burner 02 from an inlet side to the combustion chamber 03.

[0045] The combustion device 01 is intended to enable the combustion of ammonia. For this purpose, the combustion device 01 has an ammonia cracker 11. In this exemplary embodiment, the ammonia cracker 11 is integrated into the burner 02. A transfer section 13 of the burner 02 borders the combustion chamber 03, with the transfer section 13 being heated accordingly during the combustion process. It is relevant here that the transfer section 13 enables heat transfer into the ammonia cracker 11.

[0046] In this embodiment, the transfer section 13 forms the end of a heat-conducting body 14, which extends along the burner 02. A reaction channel 12 passes through the heat-conducting body 14, enabling heat conduction from the transfer section 13 through the heat-conducting body 14 into the reaction channel 12.

[0047] A fuel heat exchanger 21 is arranged upstream of the burner 02 in the direction of flow. This 21 has a fuel passage 22 and an air passage 25. The air passage 25 is connected on the outlet side to the inlet of the air duct 15 in the burner 02. Combustion air at an elevated temperature and pressure is supplied to the air passage 25 on the inlet side as intended.

[0048] The fuel passage 22 is connected on the output side to an inlet of the reaction channel 12 of the ammonia cracker 11. During operation of the combustion device 01, the ammonia is preheated in the fuel heat exchanger 21, thus facilitating the effective heating of the ammonia to the temperature required for cracking in the ammonia cracker 11.

[0049] The inlet of the fuel passage 22 is connected to an ammonia evaporator 24, which is intended to evaporate liquid ammonia coming from an ammonia source 04, so that gaseous ammonia can be supplied to the fuel heat exchanger 21.

[0050] In the Fig. 2 shows an example of a possible integration of the combustion device 01 from Fig. 1 for a gas turbine 05. The gas turbine 05 comprises the compressor 06, the combustion device 01 and an expansion turbine 07.

[0051] The combustion air compressed and preheated by the compressor 06 is fed to the fuel heat exchanger 21 and, after passing through, is directed to the burner 02 of the combustion device 01.

[0052] Coming from an ammonia source 04, liquid ammonia is passed through an ammonia evaporator 24 and then in gaseous form through the fuel heat exchanger 21. The ammonia preheated in the fuel heat exchanger 21 is then passed on to the ammonia cracker 11 integrated in the burner 02.

[0053] The combustion air and the fuel are fed from the burner 02 into the combustion chamber 03 and, after combustion, are passed through the expansion turbine 07 as flue gases. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3314166 B1

[0006] EP 3377745 B1

[0006] EP 3417205 B1

[0006]

Claims

[1] Combustion device (01), in particular of a gas turbine (05), comprising at least one burner (02) and a combustion chamber (03), wherein combustion air and fuel can be supplied to the burner (02) as intended and burned in the combustion chamber (03), further comprising an ammonia cracker (11) with a reaction channel (12) and a heating device, wherein the reaction channel (12) is connected on the output side to the combustion chamber (03) and can be connected on the input side to an ammonia source (04); characterized by that the heating device comprises a transfer section (13) which partially delimits the combustion chamber (03) and enables heat transfer from the combustion chamber (03) to the reaction channel (12). [2] Combustion device (01) according to claim 1, wherein the ammonia cracker (11) is integrated in the burner (02). [3] Combustion device (01) according to claim 1 or 2, wherein the heating device comprises a heat conducting body (14) through which the reaction channel (12) passes. [4] Combustion device (01) according to claim 3, wherein the heat conducting body (14) has a plurality of ribs projecting into the reaction channel (12); and / or wherein the reaction channel (12) comprises a plurality of reaction bores traversing the heat conducting body; and / or wherein the surface of the heat conducting body (14) facing the reaction channel (12) corresponds to at least 5 times a theoretical cylinder surface, wherein in particular the cylinder surface is determined by the length of the heat conducting body and a circular area corresponding to the cross-sectional area of ​​the reaction channel (12). [5] Combustion device (01) according to one of claims 1 to 4, wherein at least one air duct (15) traverses the burner (02) from an air inlet to the combustion chamber (03). [6] Combustion device (01) according to claim 5, wherein the air duct (15) is thermally spaced from the heat conducting body (14). [7] Combustion device (01) according to one of claims 1 to 6, further comprising a fuel heat exchanger (21) with a fuel passage (22), which (22) can be connected on the output side to the reaction channel (12) and, as intended, on the input side to an ammonia source (04). [8] Combustion device (01) according to claim 7, wherein the fuel heat exchanger (21) comprises an air passage (25) which (25) can be connected on the output side to the air duct (15) and, as intended, on the input side to a combustion air supply. [9] Method for operating a combustion device (01) according to one of the preceding claims, wherein ammonia coming from an ammonia source (04) is passed through the reaction channel (12) and is split therein at least partially into hydrogen and nitrogen and conveyed as fuel into the combustion chamber (03); wherein thermal energy generated by the combustion is transferred proportionally via the transfer section (13), in particular further via the heat conducting body (14), to the ammonia flowing through the reaction channel (12). [10] Method according to claim 9, wherein ammonia coming from an ammonia source (04) is passed through the fuel passage (22) and is preheated to a temperature above 300°C, in particular above 400°C; and / or wherein ammonia coming from an ammonia source (04), in particular from the fuel heat exchanger (21), is passed through the reaction channel (12) and is heated to a temperature above 600°C, in particular above 700°C. [11] Gas turbine (05) comprising a compressor (06) and a combustion device (01) according to one of the preceding claims and an expansion turbine (07). [12] Gas turbine (05) according to claim 11, wherein the compressor (06) is connected on the output side to the air duct (15); or wherein the compressor (06) is connected on the output side to the air passage (25). [13] A method for operating a gas turbine according to any one of the preceding claims, wherein - combustion air is compressed and heated in the compressor (06), - the heated combustion air is passed through the air duct (15), - the fuel is burned in the combustion chamber (03) with the combustion air, - the flue gases produced from the combustion chamber (03) are passed through the expansion turbine (07). [14] Method according to claim 13, wherein the heated combustion air coming from the compressor (06) is at least partially first guided through the air passage (25).

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