Gas turbine plant having ammonia cracker, power plant having such plant, and method for operating gas turbine plant

Abstract

The invention relates to a gas turbine arrangement (01) comprising a gas turbine and an ammonia cracker (11). The gas turbine comprises a gas compressor (02), a combustion chamber (03) and an expansion turbine (04). The ammonia cracker (11) comprises a heater (15) and an air passage from an air inlet to an air outlet and a reaction passage from an ammonia inlet to a fuel outlet. In order to increase the efficiency of the gas turbine plant, a hot air line connects the compressor outlet to the air inlet and a cold air line connects the air outlet to the combustion chamber (03), with a fuel line connecting the fuel outlet to the combustion chamber (03).

Description

TECHNICAL FIELD

[0001] The present invention relates to a gas turbine plant comprising an ammonia cracker. A gas turbine generally comprises a compressor, a combustion section and an expansion turbine. The ammonia cracker is used to crack ammonia into a mixture of hydrogen and nitrogen, wherein the hydrogen can be combusted in the combustion section of the gas turbine. BACKGROUND

[0002] Generally, most gas turbines are fueled with natural gas. In order to reduce the amount of carbon dioxide, it is preferred to use hydrogen as a fuel for the gas turbine. The supply and storage of hydrogen is expensive and can raise safety concerns. Therefore, ammonia is the preferred medium to store hydrogen and to transport hydrogen from the production site to the power plant.

[0003] Direct combustion of ammonia as a fuel in a gas turbine is not possible because of the release of an unpermitted amount of nitrogen oxides (NOx). Furthermore, direct combustion of ammonia is difficult due to the ignition inertness of ammonia. Therefore, at least part of the ammonia needs to be cracked into hydrogen and nitrogen before it is combusted in the combustion chamber of the gas turbine.

[0004] Cracking of ammonia requires high temperatures. Here, various different techniques are used to achieve the required heat within the ammonia cracker.

[0005] Generally, it is preferred to operate a power plant comprising ammonia cracking and gas turbine operation as efficient as possible with a minimum of energy waste. Secondly, the cracking of ammonia preferably does not require an external heat source or energy source.

[0006] Exemplary solutions to enable combustion of ammonia are presented in EP 3314166 B1, EP 3377745 B1 and EP 3417205 B1. In all solutions, part of the ammonia is supplied to an ammonia cracker, producing hydrogen and nitrogen, and the produced hydrogen and nitrogen are further supplied to the combustion chamber of the gas turbine. Advantageously, the heat from the exhaust gas of the gas turbine can be used to heat the ammonia cracker.

[0007] If the exhaust gas of the gas turbine is intentionally used in a steam generator to produce steam for another steam turbine, only a reduced temperature can be obtained within the steam generator, because a considerable amount of heat has already been used for the ammonia cracker. SUMMARY

[0008] It is the task of the present invention to develop an alternative solution for the ammonia cracker installed in a gas turbine plant, without a corresponding reduction of the exhaust gas temperature (thus enabling the use of the exhaust gas in a steam generator). Furthermore, the use of external heat or external energy sources is to be avoided as much as possible.

[0009] This task is solved by the gas turbine plant according to the invention of claim 1. The method of operating the gas turbine plant with ammonia cracker is defined in claim 6. Advantageous embodiments are subject to the claims.

[0010] The gas turbine plant comprises a compressor, a combustion chamber and an expansion turbine, wherein during operation of the gas turbine combustion air is compressed in the compressor and at least part of the combustion air is supplied from the outlet of the compressor to the combustion chamber, while during operation of the gas turbine exhaust gas is supplied from the combustion chamber to the expansion turbine.

[0011] An ammonia cracker with a heater and a cracker air channel and a cracker reaction channel is required to achieve combustion of ammonia. The plant further comprises a fuel heat exchanger comprising an exchanger fuel passage and an exchanger ammonia passage, the inlet of which must be connected to an ammonia source, wherein the outlet of the exchanger ammonia passage is connected to the inlet of the cracker reaction channel.

[0012] If a hot air duct connects the outlet of the compressor with the inlet of the cracker air channel and a cold air duct connects the outlet of the cracker air channel with the combustion chamber, efficiency can be increased. Furthermore, a first fuel duct connects the outlet of the cracker reaction channel with the inlet of the exchanger fuel passage and a second fuel duct connects the outlet of the exchanger fuel passage with the combustion chamber (03). DETAILED DESCRIPTION

[0013] A generic gas turbine plant comprises a gas turbine and an ammonia cracker. The gas turbine comprises a compressor, at least one combustion chamber and an expansion turbine.

[0014] The compressor comprises a compressor inlet, several compressor stages and a compressor outlet. During operation of the gas turbine combustion air (typically filtered ambient air) flows into the compressor inlet, is compressed and supplied from the compressor outlet. Thus, due to the compression process, the compressed combustion air at the compressor outlet is at an elevated temperature.

[0015] For the solution of the invention different types of combustion plants can be employed. A can-annular combustion chamber can be used, wherein a plurality of burners is distributed around the central axis of the gas turbine. Alternatively, a silo combustion system can be used or a plurality of pot combustion chambers (typically each comprising one burner and one combustion chamber) distributed around the central axis of the gas turbine can be used. In any case, the compressed combustion air is at least partially supplied (directly or indirectly) from the compressor outlet to the at least one combustion chamber. Furthermore, during operation of the gas turbine, fuel needs to be supplied to at least one burner of the at least one combustion chamber.

[0016] The expansion turbine is arranged downstream of the at least one combustion chamber and is driven by the hot exhaust gas stream during operation of the gas turbine. After expansion of the hot exhaust gas in the expansion turbine, the exhaust gas leaves the expansion turbine at the output of the gas turbine at a reduced temperature.

[0017] A general ammonia cracker is required to crack the ammonia into hydrogen and nitrogen. Therefore, the ammonia cracker has a cracker reaction channel through the ammonia cracker from an inlet to an outlet.

[0018] It is to be expected that the ammonia supplied from the ammonia source has a lower temperature compared to the required temperature within the ammonia cracker. On the other hand, the fuel gas containing hydrogen and nitrogen leaving the ammonia cracker has a higher temperature due to the heating within the ammonia cracker required for the cracking process. Here, it is advantageous to reuse the heat in the fuel gas for heating the ammonia supplied to the ammonia cracker.

[0019] The gas turbine arrangement of the present invention comprises a fuel heat exchanger. The fuel heat exchanger shall comprise an exchanger ammonia passage and an exchanger fuel passage. The inlet of the exchanger ammonia passage needs to be connected to the ammonia source during use of the gas turbine arrangement. The outlet of the exchanger ammonia passage of the fuel heat exchanger needs to be connected to the inlet of the cracker reaction channel of the ammonia cracker.

[0020] In order to be able to transfer heat, a first fuel conduit is required to connect the outlet of the cracker reaction channel with the inlet of the exchanger fuel passage of the fuel heat exchanger. Obviously, in embodiments of the present invention, the fuel stream (first ammonia and second fuel gas containing hydrogen and nitrogen) passes twice through the fuel heat exchanger.

[0021] Furthermore, a second fuel conduit is required to connect the outlet of the fuel passage of the fuel heat exchanger with the at least one combustion chamber. If several combustors are given, it is obvious that the second fuel conduit is branched to all installed combustors.

[0022] In order to realize the cracking process, the ammonia cracker needs to be operated at a required temperature. In order to achieve a more optimal efficiency and to avoid the use of heat in the exhaust gas leaving the gas turbine, it is creatively required to use at least part of the compressed air in the ammonia cracker to introduce heat for the cracking process. During operation of the gas turbine arrangement, the temperature of the compressed air at the outlet of the compressor is typically lower than the exhaust gas temperature downstream of the combustion chamber. Nevertheless, the temperature is still much higher than the usual ambient temperature.

[0023] In order to be able to utilize the heat of the compressed air, the ammonia cracker further comprises a cracker air passage to flow the compressed combustion air from an inlet to an outlet of the cracker air passage through the ammonia cracker.

[0024] The gas turbine arrangement comprises a hot air duct connecting the compressor outlet of the compressor with the inlet of the cracking air channel of the ammonia cracker. Further, a cold air duct is comprised, which connects the outlet of the cracking air channel with at least one combustion chamber for the flow of combustion air for the combustion of fuel in the combustion chamber. During operation of the gas turbine arrangement, the "cold air duct" is still warmer than ambient air, but at a lower temperature than the "hot air duct".

[0025] The general ammonia cracker comprises a heater for heating the ammonia to the required temperature to enable the cracking of the ammonia into hydrogen and nitrogen.

[0026] By using the heat of the compressed air and the additional heating of the heater, the efficiency of the gas turbine arrangement can be increased, so that the hot exhaust gases leaving the gas turbine can still be used for the operation of the steam generator.

[0027] Instead of using an external energy source for the heater of the ammonia cracker, it is advantageous to use the cracked hydrogen as fuel for the heater. The combustion of the cracked hydrogen in the heater in the ammonia cracker can further increase the efficiency of the gas turbine arrangement.

[0028] Obviously, for the initial start-up procedure, hydrogen for the additional heat in the ammonia cracker needs to be supplied externally. But in principle, during normal operation of the gas turbine arrangement, the hydrogen required for operating the heater should advantageously be tapped from the hydrogen and nitrogen stream leaving the ammonia cracker at the fuel outlet.

[0029] In principle, a separate combustion system can be installed in the ammonia cracker for the combustion of the hydrogen. However, it is advantageous to directly combust the hydrogen in the air channel within the ammonia cracker, which reduces the installation effort and increases the efficiency.

[0030] In order to provide part of the cracked ammonia for the heater of the ammonia cracker, the heater can be connected with a first fuel duct between the outlet of the cracking reactor channel and the inlet of the exchanger ammonia channel. Alternatively, the heater can be connected with a second fuel duct between the outlet of the exchanger ammonia channel and the combustion chamber.

[0031] The ammonia can be provided in gaseous form by an ammonia source.

[0032] If the ammonia is provided in liquid form by an ammonia source, it is preferred to additionally use an ammonia evaporator. The ammonia evaporator comprises a fluid channel and a gasification channel, wherein the gasification channel of the ammonia evaporator is exclusively connected with the fuel source at the input side and with the inlet of the exchanger ammonia channel at the output side of the ammonia evaporator.

[0033] In this case, a heated medium needs to be supplied to the fluid channel of the ammonia evaporator.

[0034] In a preferred embodiment, the gas turbine plant comprises a steam generator arranged downstream of the expansion turbine. Within the steam generator, a plurality of heat exchangers is required to transfer the heat of the exhaust gas to generate steam.

[0035] In combination with the preferred ammonia evaporator, the heat of the exhaust gas is advantageously utilized in addition to the steam generated for ammonia preheating. Two different solutions are presented here.

[0036] In a first embodiment, the fluid channel of the ammonia evaporator is connected to the output side and to the input side of at least one heat exchanger installed within the steam generator.

[0037] In a second embodiment, part of the steam generator also constitutes the ammonia evaporator, wherein the gasification channel is installed as a heat exchanger within the steam generator and the channel for the exhaust gas is the fluid channel of the ammonia evaporator.

[0038] In both cases, the heat exchanger connected to the ammonia evaporator or the ammonia evaporator as part of the steam generator should be arranged at the downstream end of the steam generator so that the heat from the exhaust gas can be used primarily to generate steam. BRIEF DESCRIPTION OF DRAWINGS

[0039] An exemplary embodiment of the inventive gas turbine plant 01 is schematically shown in the figure.

[0040] The gas turbine plant 01 comprises a gas turbine which comprises a compressor 02, a combustion chamber 03 and an expansion turbine 04. A steam generator 05 is arranged downstream of the expansion turbine 04.

[0041] Within the steam generator 05, a plurality of heat exchangers (not shown) is installed, wherein at least one heat exchanger is connected to a steam turbine 06.

[0042] The compressed combustion air is generally supplied by the compressor 02 to the combustion chamber 03, wherein the exhaust gas generated by the combustion chamber 03 is supplied to the expansion turbine 04 to drive the gas turbine rotor.

[0043] Here, at least a part of the compressed combustion air is required to be split off and supplied to the ammonia cracker 11. The cracker air channel enables the compressed air to flow through the ammonia cracker 11. The inlet of the cracker air channel is thus connected to the outlet of the compressor. The outlet of the cracker air channel is connected to the combustion chamber 03. Thereby, the compressed combustion air, after flowing through the ammonia cracker 11, at least partially flows into the combustion chamber 03.

[0044] Within the ammonia cracker 11 a cracker reaction channel and a heater 15 are arranged. Gaseous ammonia is supplied to the inlet of the cracker reaction channel. A mixture of hydrogen and nitrogen is discharged from the outlet of the cracker reaction channel. The heat in the cracker reaction channel is able to crack the ammonia, the heat is partly provided by compressed air and partly by the heater 15.

[0045] The inlet of the cracker reaction channel and the outlet of the cracker reaction channel are both connected with the fuel heat exchanger 12. Therefore, the fuel heat exchanger 12 comprises an exchanger ammonia passage and an exchanger fuel passage.

[0046] Ammonia is supplied to the inlet of the exchanger ammonia passage. By passing the fuel heat exchanger 12 through the exchanger ammonia passage, the ammonia is heated with the heat in the mixture of hydrogen and nitrogen that passes through the exchanger fuel passage. This is beneficial for an efficient re-use of heat, which is required in the ammonia cracker 11.

[0047] The outlet of the exchanger fuel passage of the fuel heat exchanger 12 is connected to the combustion chamber 03, so that the fuel (mixture of hydrogen and nitrogen) can be used for the combustion process within the gas turbine.

[0048] A part of the produced hydrogen is tapped off and supplied to the heater 15 within the ammonia cracker 11 to reach the required temperature for the cracking process. In this embodiment, the heater 15 is attached to the second fuel pipe between the outlet of the exchanger fuel passage and the combustion chamber 03. But alternatively, the heater can be connected to the first fuel pipe between the outlet of the cracker reaction channel of the ammonia cracker 11 and the inlet of the exchanger ammonia passage of the heat exchanger 12.

[0049] In order to be able to use liquid ammonia as ammonia source 14, an ammonia evaporator 13 is installed between the ammonia source 14 and the fuel heat exchanger 12. In the ammonia evaporator 13, the ammonia is changed from liquid to gaseous by heat transfer.

[0050] Therefore, the ammonia evaporator 13 is connected with a heat exchanger that is installed within the steam generator 05.

Claims

1. A gas turbine unit (01), comprising: - A gas turbine, comprising a compressor (02), a combustion chamber (03), and an expansion turbine (04), wherein, during operation of the gas turbine, combustion air is compressed in the compressor (02), and at least a portion of the combustion air is supplied from the outlet of the compressor (02) to the combustion chamber (03), and during operation of the gas turbine, exhaust gas is supplied from the combustion chamber (03) to the expansion turbine (04); and - An ammonia cracker (11), including a heater (15), a cracker air passage, and a cracker reaction passage; and - Fuel heat exchanger (12), including exchanger fuel passage and exchanger ammonia passage; In the case of the gas turbine unit (01), the inlet of the ammonia passage of the exchanger is configured to be connected to the ammonia source (14), and the outlet of the ammonia passage of the exchanger is connected to the inlet of the reaction channel of the pyrolysis unit. The first fuel pipeline connects the outlet of the pyrolysis chamber passage to the inlet of the exchanger fuel passage, and the second fuel pipeline connects the outlet of the exchanger fuel passage to the combustion chamber (03). The hot air duct connects the compressor outlet to the inlet of the pyrolyzer air passage, and the cold air duct connects the pyrolyzer air passage outlet to the combustion chamber (03).

2. The gas turbine unit (01) according to claim 1, in, A heater pipe branches off from the second fuel pipe and leads to the heater (15).

3. The gas turbine unit (01) according to claim 2, in, The heater (15) enables hydrogen to burn in the air passage.

4. The gas turbine unit (01) according to any one of claims 1-3, Further includes: - An ammonia evaporator (13) includes an evaporator fluid passage and an evaporator ammonia passage, wherein the inlet of the evaporator ammonia passage is configured to be connected to an ammonia source (14), and the outlet of the evaporator ammonia passage is connected to the inlet of an exchanger ammonia passage.

5. The gas turbine unit (01) according to claim 4, Further includes: - Steam generator (05), which is arranged downstream of expansion turbine (04) and includes multiple heat exchangers; The ammonia evaporator (13) is connected to at least one of the heat exchangers, or Among them, the ammonia evaporator (13) is arranged as a heat exchanger inside the steam generator (05).

6. A method of operating a gas turbine unit (01) comprising the gas turbine unit (01) according to any one of the preceding claims, - in, At least a portion of the compressed air is supplied to the ammonia cracker (11). - Wherein, additional heat is introduced into the ammonia cracker (11) through the heater (15); - Wherein, ammonia is supplied from the ammonia source (14) to the fuel heat exchanger (12), guided through the ammonia passage of the exchanger, and guided from the fuel heat exchanger (12) to the ammonia cracker (11). - In this process, ammonia is heated in the cracker reaction channel, thereby being cracked into fuel gas containing hydrogen and nitrogen. - Wherein, the cracked fuel gas is supplied from the ammonia cracker (11) to the fuel heat exchanger (12) and guided through the fuel passage of the exchanger to transfer heat to the ammonia in the ammonia passage of the exchanger; - Wherein, fuel gas is supplied from fuel heat exchanger (12) to combustion chamber (03).

7. The method according to claim 6, in, A portion of the fuel gas is drawn from the second fuel pipeline and supplied to the heater (15), and a portion of the fuel gas is burned in the ammonia cracker (11).

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