Power generation method in a gas turbine

Abstract

A method for providing thermal energy to an ammonia decomposition reactor. The present invention includes the steps of recovering oxygen-containing offgas from a gas turbine fueled by hydrogen and supplying at least a portion of the offgas to a fuel combustion zone to generate thermal energy for the ammonia decomposition reactor. The present invention is used in chemical manufacturing facilities such as ammonia production facilities.

Description

Technical Field

[0001] The present invention relates to a method for decomposing (cracking) ammonia. More specifically, the present invention relates to a method for providing heat to an ammonia decomposition reactor. The present invention further relates to a method for retrofitting an ammonia plant using the method of the present invention.

Background Art

[0002] There is a growing interest in using carbon-free fuels to power gas turbine systems in order to generate carbon-free electrical energy. Among such carbon-free fuels, ammonia has attracted attention for carbon-free power generation in ammonia production facilities where ammonia is abundantly supplied. However, the development of gas turbine systems using ammonia as fuel is in its initial stage. Many commercially available gas turbines are not supplied as being suitable for use with ammonia fuel.

[0003] A potential solution for directly using ammonia as a fuel is to decompose ammonia to form a mixture of hydrogen and nitrogen so that the gas turbine can be driven by the combustion of hydrogen.

[0004] The decomposition of ammonia into hydrogen and nitrogen has been used for many years in ammonia plants to provide hydrogen and activate catalysts. The reaction can be shown as follows.

[0005]

Equation

[0006] The ammonia decomposition reaction is endothermic and can be usefully achieved by passing ammonia over a suitable catalyst in an externally heated catalyst-containing reaction tube disposed in a furnace. For example, such furnaces for steam reforming of natural gas or naphtha feedstocks are known.

[0007] It is known to burn a hydrogen stream in a gas turbine. U.S. Patent Application Publication Nos. 2022 / 162999 and 2022 / 162989 disclose methods including a gas turbine driven by the combustion of a stream containing hydrogen and a compressed air stream. The stream containing hydrogen is generated in an ammonia decomposition device to which an ammonia stream is supplied. The gas turbine is used to generate electrical energy and mechanical energy. The heat generated by the combustion of the stream containing hydrogen is supplied directly to the decomposition device or used to preheat the ammonia stream upstream of the decomposition device through a heat exchanger.

[0008] There remains a need to improve the efficiency of gas turbines driven by the combustion of carbon-free fuels, particularly ammonia-derived fuels. SUMMARY OF THE INVENTION

[0009] An object of the present invention is to improve the energy efficiency of a gas turbine system driven by the combustion of a carbon-free fuel obtained from the catalytic decomposition of ammonia.

[0010] Accordingly, in a first aspect of the present invention, there is provided a method for generating electricity using a gas turbine fueled by a carbon-free fuel obtained from the catalytic decomposition of ammonia, comprising: supplying an ammonia stream to an ammonia decomposition reactor; decomposing ammonia in the ammonia stream in the ammonia decomposition reactor to produce a hydrogen-containing stream; combining the hydrogen-containing stream with an oxygen-containing feed and burning the hydrogen-containing stream together with the oxygen-containing feed to produce a burned gas stream; using the burned gas stream to drive a gas turbine to produce an oxygen-containing off-gas stream; supplying at least a portion of the oxygen-containing off-gas stream to a fuel combustion zone; burning a fuel stream and the oxygen-containing off-gas stream in the fuel combustion zone to generate thermal energy for the ammonia decomposition reactor.

[0011] Surprisingly, it has been found that the off-gas stream from the gas turbine contains sufficient oxygen to be used for combustion of the fuel stream in the fuel combustion zone. Further, since the oxygen-containing off-gas exits the gas turbine at a high temperature, little or no preheating is required before combustion with the fuel stream. It has surprisingly been found that an unexpected energy saving can be achieved by supplying the thermal energy generated from the combustion of the fuel stream and the oxygen-containing off-gas to an ammonia decomposition reactor.

[0012] A further advantage of the method of the present invention is that the cost of capital equipment can also be reduced. For example, since at least a portion of the oxygen-containing off-gas is used for combustion of the fuel stream, less energy needs to be recovered from the remaining oxygen-containing off-gas that is not used for combustion of the fuel stream. That is, smaller and less expensive equipment (e.g., heat recovery equipment such as a heat recovery steam generator) can be specified.

[0013] The gas turbine described in the present invention is sometimes referred to as an integrated gas turbine since the generated oxygen-containing off-gas stream is recovered and supplied to the fuel combustion zone. In contrast, references to non-integrated gas turbines also include methods in which the oxygen-containing off-gas stream generated from the gas turbine is not used for combustion.

[0014] The method of the present invention is particularly suitable for implementation in or near an ammonia production facility or storage facility, where the supply of ammonia serves as an input to an ammonia decomposition reactor, hydrogen gas can be produced in a hydrogen-containing stream, and is provided as a fuel stream to be combusted with the oxygen-containing off-gas stream, and can provide heat to the ammonia decomposition reactor. However, the method of the present invention is not limited to implementation in an ammonia production facility and can be used in any suitable environment where a supply of ammonia is possible.

[0015] In another aspect of the present invention, there is provided a method of retrofitting an ammonia production facility by implementing the method of the first aspect of the present invention in the ammonia production facility.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Best Mode for Carrying Out the Invention

[0017] From this, the preferred and / or optional features of the present invention are described. Any aspect of the present invention can be combined with any other aspect of the present invention unless otherwise required by the context. Any preferred and / or optional features of any aspect can be combined with any aspect of the present invention, either singly or in combination, unless otherwise required by the context.

[0018] The method of the present invention includes a step of supplying an ammonia stream to an ammonia decomposition reactor.

[0019] The ammonia stream can be obtained from any source. In a preferred method of the present invention, the ammonia stream is produced by a catalytic combination of hydrogen and nitrogen. For example, the ammonia stream can be produced from a Haber-Bosch ammonia synthesis process. In a preferred method of the present invention, the ammonia stream can be produced in an ammonia production facility located upstream of the ammonia decomposition reactor. Alternatively, the ammonia stream can be provided from an ammonia gas storage facility or an ammonia gas pipeline.

[0020] In a preferred method of the present invention, the ammonia stream can be preheated before being fed to the ammonia decomposition reactor. Thus, the method of the present invention can include a step of preheating the ammonia stream. The ammonia stream can be preheated to a temperature above 350°C, above 400°C, above 450°C, above 500°C, or above 550°C. The ammonia stream can be preheated to a temperature below 1000°C, below 950°C, below 850°C, below 750°C, or below 700°C. The ammonia stream can be preheated to a temperature in the range of 350°C to 1000°C, 400°C to 950°C, 450°C to 850°C, or 500°C to 750°C, for example 550°C to 700°C.

[0021] Suitable ammonia decomposition reactors are known and can include a box furnace that provides a radiant section including one or more burners to which a fuel stream and an oxygen supply gas, such as air, are supplied. The radiant section includes one or more catalyst-containing tubes through which the ammonia stream passes. Combustion of the fuel stream in the one or more burners generates radiant heat for heating one or more reaction tubes containing the ammonia decomposition catalyst. There can be dozens or hundreds of tubes in the radiant section. Optionally, downstream of the radiant section, the combustion gas can be used to preheat one or more feed streams in a convection section. Reactors comprising a radiant section containing reaction tubes and convection for preheating the feed are known in steam methane reforming and can be applied to the present invention.

[0022] For example, an alternative ammonia decomposition reactor can be used if the combustion of the fuel in the fuel combustion zone is split into a reactor comprising catalyst-containing tubes. Such a reactor is a small reformer available from Johnson Matthey Davy Technologies Limited.

[0023] The catalyst may be any ammonia decomposition catalyst. A nickel catalyst and a ruthenium catalyst may be used. A preferred catalyst is a nickel catalyst. The catalyst can contain 3 to 30% by weight of nickel, preferably 8 to 20% by weight of nickel, expressed as NiO, on a suitable refractory support such as alumina or metal aluminate. The catalyst may be in the form of a unit molded into pellets, which may contain one or more through-holes, or may be provided as a washcoat on a structured metal or ceramic catalyst. A particularly preferred catalyst is KATALCO® 27-2 available from Johnson Matthey PLC, which contains 12% nickel expressed as NiO on cylindrical pellets formed from a high surface area alumina support.

[0024] The method of the present invention includes a step of decomposing ammonia in an ammonia stream in an ammonia decomposition reactor to produce a hydrogen-containing stream.

[0025] The temperature of the ammonia stream at the inlet of the ammonia decomposition reactor can be in the range of 350°C to 1000°C, 400°C to 950°C, 450°C to 850°C, or 500°C to 750°C, for example 550°C to 700°C. The temperature of the hydrogen-containing stream exiting the ammonia decomposition reactor affects the equilibrium position of the decomposition reaction and can be in the range of 500 to 950°C. When a nickel catalyst is used in the ammonia decomposition reactor, the temperature of the hydrogen-containing stream exiting the ammonia decomposition reactor can preferably be above about 700°C.

[0026] The inlet pressure to the ammonia decomposition reactor is set by the flow sheet design and can be in the range of 1 to 100 bar absolute pressure, preferably 10 to 90 bar absolute pressure, for example 31 to 51 bar absolute pressure.

[0027] An ammonia decomposition reaction produces a hydrogen-containing stream, which may also contain nitrogen and may contain residual ammonia.

[0028] The hydrogen-containing stream may contain 40 mol% or more of hydrogen, 50 mol% or more of hydrogen, or 60 mol% or more of hydrogen. The hydrogen-containing stream may contain 75 mol% or less of hydrogen, 70 mol% or less of hydrogen, or 65 mol% or less of hydrogen. For example, the hydrogen-containing stream may contain 40 mol% to 75 mol% of hydrogen, 50 mol% to 70 mol% of hydrogen, or 60 mol% to 65 mol% of hydrogen.

[0029] The hydrogen-containing stream may optionally be fed to a purification unit such as a pressure swing absorption unit to separate hydrogen from other components and increase the hydrogen content. Accordingly, the method of the present invention may include a step of feeding the hydrogen-containing stream to a purification unit and increasing the hydrogen content of the hydrogen-containing stream to produce a hydrogen-enriched stream and tail gas.

[0030] The hydrogen-enriched stream may contain 50 mol% or more of hydrogen, 60 mol% or more of hydrogen, or 75 mol% or more of hydrogen. The hydrogen-enriched stream may contain 100 mol% or less of hydrogen, 90 mol% or less of hydrogen, or 80 mol% or less of hydrogen. For example, the hydrogen-enriched stream may contain 50 mol% to 100 mol% of hydrogen, 60 mol% to 90 mol% of hydrogen, or 70 mol% to 80 mol% of hydrogen, for example, about 75 mol% of hydrogen.

[0031] The tail gas may contain nitrogen and a small amount of ammonia and hydrogen. For example, the tail gas may contain nitrogen, 1 mol% to 10 mol% of ammonia (e.g., about 5 mol% or less of ammonia), and 2 mol% to 40 mol% of hydrogen (e.g., 15 mol% to 25 mol% of hydrogen).

[0032] As used herein, the term "hydrogen-containing stream" may be used to refer to either a hydrogen-containing stream or a hydrogen-enriched stream.

[0033] The hydrogen-containing stream may be fed to a steam generation unit and / or a heat recovery zone before being burned with an oxygen-containing feed. As will be understood by those skilled in the art, the steam generation unit and / or the heat recovery zone may be used to recover low or medium levels of heat.

[0034] Before burning the hydrogen-containing stream together with the oxygen-containing feed, it is desirable to separate residual ammonia from the hydrogen-containing stream. Removal of ammonia can be achieved, for example, by washing with water using a conventional washing device.

[0035] The method of the present invention includes the steps of combining a hydrogen-containing stream with an oxygen-containing feed and burning the hydrogen-containing stream together with the oxygen-containing feed to produce a burned gas stream.

[0036] The oxygen-containing feed can be air, oxygen, or oxygen-enriched air. In a preferred method of the present invention, the oxygen-containing feed is a compressed oxygen-containing feed, such as compressed air, compressed oxygen, or compressed oxygen-enriched air.

[0037] The method of the present invention includes the step of driving a gas turbine using the burned gas stream to produce an oxygen-containing off-gas stream. Thus, the oxygen-containing off-gas stream is the exhaust gas from the gas turbine.

[0038] The method of the present invention can use any type of gas turbine. The combustion of the hydrogen-containing stream and the oxygen-containing feed to produce the burned gas stream can be carried out in a hydrogen combustion zone. The hydrogen combustion zone may be incorporated within the gas turbine or may be external to the gas turbine. Typically, the hydrogen combustion zone can be incorporated within the gas turbine.

[0039] Typically, in the method of the present invention, the gas turbine and the ammonia decomposition reactor are separate devices.

[0040] The oxygen-containing off-gas stream can have a temperature of 500°C to 800°C, 500°C to 750°C, or 600°C to 700°C, for example, about 650°C.

[0041] The oxygen-containing offgas stream can contain oxygen in an amount greater than 5 mol%, greater than 8 mol%, greater than 11 mol%, or greater than 13 mol%. The oxygen-containing offgas stream can contain oxygen in an amount less than 25 mol%, less than 22 mol%, less than 20 mol%, or less than 18 mol%. For example, the oxygen-containing offgas stream can contain oxygen in an amount of 5 mol% to 25 mol%, 8 mol% to 22 mol%, 11 mol% to 20 mol%, or 13 mol% to 18 mol%, for example, about 15 or about 16 mol%.

[0042] In a preferred method of the present invention, a gas turbine can be used to generate power, such as electrical power and / or mechanical power. The gas turbine can generate power directly or indirectly. For example, the gas turbine can be connected to any suitable generator for the generation of electrical power, and / or the gas turbine can be connected to a compressor for the generation of mechanical power.

[0043] The method of the present invention includes the step of supplying at least a portion of the oxygen-containing offgas to a fuel combustion zone. The fuel combustion zone may be within the ammonia decomposition reactor or may be fluidly connected to the ammonia decomposition reactor such that combustion provides heat for the ammonia decomposition reaction.

[0044] The fuel combustion zone may be within the ammonia decomposition reactor or may be within a separate vessel for combustion. Heat is generated by the combustion of the fuel, and this heat is used to assist the endothermic ammonia decomposition reaction.

[0045] The fuel combustion zone can preferably be the radiant section within the box furnace of the ammonia decomposition reactor. Thus, the fuel combustion zone can provide thermal energy (e.g., radiant heat) to the ammonia decomposition reactor. Alternatively, if the fuel combustion zone is within a vessel separate from the ammonia decomposition furnace, the ammonia decomposition furnace can be of a heat exchange design such as a gas-heated reformer or a small reformer, in which case the catalyst-containing tubes are heated by convection from the high-temperature combustion gas passing around the outer surface of the tubes.

[0046] As can be easily understood, the fuel combustion zone functions to provide the necessary thermal energy to catalytically decompose ammonia in the ammonia stream to produce a hydrogen-containing stream.

[0047] The oxygen-containing offgas stream can be supplied to the fuel combustion zone at a temperature of 500°C to 800°C, 500°C to 750°C, or 600°C to 700°C, for example, about 650°C.

[0048] One skilled in the art can calculate the portion of the oxygen-containing offgas stream that needs to be supplied to the fuel combustion zone. Typically, the portion of the oxygen-containing offgas stream supplied to the fuel combustion zone can be more than 5%, more than 7%, more than 8%, or more than 9% of all the offgas streams exiting the gas turbine. Typically, the portion of the oxygen-containing offgas stream supplied to the fuel combustion zone can be less than 75%, less than 50%, less than 30%, or less than 20% of all the offgas streams exiting the gas turbine. For example, the portion of the oxygen-containing offgas stream supplied to the fuel combustion zone can be 5% to 75%, 7% to 50%, 8% to 30%, or 9% to 20% of all the offgas streams exiting the gas turbine. For example, the portion of the oxygen-containing offgas stream supplied to the fuel combustion zone may preferably be 10% to 15% or 11% to 13% of all the offgas streams exiting the gas turbine.

[0049] The method of the present invention includes the step of burning a fuel stream together with an oxygen-containing offgas stream in a fuel combustion zone to generate thermal energy for the ammonia decomposition reactor.

[0050] The fuel stream used to provide heat for the ammonia decomposition reaction can be a carbon-free fuel stream. As used herein, the term "carbon-free fuel stream" is understood to include combustible compounds that do not contain carbon, such as ammonia and hydrogen. In a preferred method of the present invention, the fuel stream contains ammonia. The amount of ammonia in the fuel stream is not particularly limited. For example, the fuel stream can contain ammonia in an amount of 1 mol% to 100 mol% of all the fuel streams, such as 5 mol% to 75 mol%, 10 mol% to 50 mol%, or 15 mol% to 30 mol% of all the fuel streams. Preferably, the fuel stream contains ammonia in an amount greater than 10 mol%, greater than 12 mol%, or greater than 15 mol%. The fuel stream preferably contains ammonia in an amount less than 45 mol%, less than 35 mol%, or less than 35 mol% of all the fuel streams. For example, the fuel stream preferably contains ammonia in an amount of 10 mol% to 45 mol%, 12 mol% to 35 mol%, or 15 mol% to 25 mol% of all the fuel streams.

[0051] When the fuel stream contains ammonia, the ammonia-containing fuel stream can be supplied from the same source or a different source as the ammonia stream supplied to the ammonia decomposition reactor. When the fuel stream contains ammonia, the ammonia-containing fuel stream is preferably supplied from the same source as the ammonia stream supplied to the ammonia decomposition reactor.

[0052] The fuel stream may include one or more additional fuel sources. The additional fuel source is not necessarily a carbon-free fuel source, but the additional fuel source is preferably a carbon-free fuel source. The additional fuel source may include one or more of hydrogen, natural gas, methane, refinery offgas, biogas, tail gas from a hydrogen purification unit, or a portion of a hydrogen-containing stream from an ammonia decomposition reactor. As described above, the preferred method of the present invention includes a purification unit used to produce a hydrogen-enriched stream and a tail gas. In a particularly preferred method of the present invention, the additional fuel source includes the tail gas from the purification unit used to produce the hydrogen-enriched stream. Thus, in a particularly preferred method of the present invention, the method includes supplying a hydrogen-containing stream to a purification unit to increase the hydrogen content of the hydrogen-containing stream to produce a hydrogen-enriched stream and a tail gas, supplying the tail gas to a fuel combustion zone, and combusting the fuel stream and the tail gas together with an oxygen-containing offgas.

[0053] An advantage of the present invention is that the tail gas from the purification unit used to produce the hydrogen-enriched feed, and the fuel stream, can be combusted together with the oxygen-containing offgas. By using the tail gas in this manner, it has unexpectedly been found that the overall efficiency of the method of the present invention is improved by maximizing the amount of combustible fuel recovered from the process and reducing the loss of combustible and / or toxic chemicals (such as ammonia) to the atmosphere.

[0054] The additional fuel source can be present in the fuel stream in any suitable amount as long as the fuel stream maintains a combustible state together with the oxygen-containing offgas stream.

[0055] In a preferred method of the present invention, the fuel stream is preheated before being combusted in the fuel combustion zone. The fuel stream can be preheated to any temperature below the auto-ignition temperature of the fuel stream. For example, the fuel stream can be preheated to a temperature above 100°C, above 150°C, or above 200°C. The fuel stream can be preheated to a temperature below the auto-ignition temperature of the fuel stream, for example, below 400°C, below 350°C, or below 300°C. For example, the fuel stream can be preheated to a temperature from 100°C to the auto-ignition temperature of the fuel stream, for example, from 100°C to 400°C. In a preferred method of the present invention, the fuel stream is an ammonia-containing fuel stream and is provided from a preheated ammonia stream.

[0056] The ratio of the fuel stream to the oxygen-containing off-gas stream before combustion in the fuel combustion zone can be suitably selected to enable efficient combustion of the fuel stream. The ratio of the fuel stream to the oxygen-containing off-gas stream before combustion in the fuel combustion zone can vary depending on the amount of oxygen present in the oxygen-containing off-gas stream. For example, when the fuel stream is pure ammonia and the oxygen-containing off-gas contains 13.2 mol% oxygen, the ratio of the fuel stream to the oxygen-containing off-gas stream before combustion in the fuel combustion zone can be selected to be in the range of 1:6 to 1:7, for example, 1:6.5.

[0057] The thermal energy generated by combustion using an oxygen-containing off-gas stream in the fuel combustion zone provides up to 100%, for example, up to 95%, up to 90%, up to 85%, or up to 80% of the thermal energy required for the ammonia decomposition reactor to decompose ammonia in the ammonia stream. The thermal energy generated by combustion using an oxygen-containing off-gas stream in the fuel combustion zone preferably provides more than 50%, for example, more than 60%, more than 70%, or more than 75% of the thermal energy required for the ammonia decomposition reactor to decompose ammonia in the ammonia stream. For example, the thermal energy generated by combustion using an oxygen-containing off-gas stream in the fuel combustion zone preferably provides more than 50% and up to 100% of the thermal energy required for the ammonia decomposition reactor.

[0058] Optionally, the method of the present invention may include the step of sending a portion of the oxygen-containing off-gas to a heat recovery zone such as a heat recovery steam generator. If desired, unburned ammonia or nitrogen oxides in the oxygen-containing off-gas may be washed out or reacted out of the oxygen-containing gas before the oxygen-containing gas is sent to the fuel combustion zone.

[0059] Combustion in the fuel combustion zone generates flue gas, which can be recovered from the ammonia decomposition reactor. The flue gas may be cooled in one or more cooling stages and subjected to one or more purification stages before being discharged to the atmosphere. The one or more cooling stages may include a preheating stage for one or more reactants for the ammonia decomposition reactor and / or a stage for generating steam. The one or more purification stages may include a selective catalytic reduction step in which nitrogen oxides react with ammonia to form nitrogen and water vapor, i.e., an SCR step. Any flue gas selective catalytic reduction technology can be used.

[0060] In a particular embodiment of the method of the present invention, the method The step of supplying an ammonia stream to an ammonia decomposition reactor, The step of decomposing ammonia in the ammonia stream within the ammonia decomposition reactor to produce a hydrogen-containing stream, Optionally, the step of supplying the hydrogen-containing stream to a purification unit such as a pressure swing absorption unit to increase the hydrogen content and produce a hydrogen-enriched stream and a tail gas, Optionally, the step of supplying the hydrogen-enriched stream to a steam generation unit and / or a heat recovery zone, The step of combining the hydrogen-enriched stream with an oxygen-containing feed and combusting the hydrogen-enriched stream with the oxygen-containing feed to produce a combusted gas stream, The step of using the combusted gas stream to drive a gas turbine to produce an oxygen-containing offgas stream, The step of supplying at least a portion of the oxygen-containing offgas stream to a fuel combustion zone, Optionally, the step of supplying an additional fuel source to the fuel combustion zone, The step of combusting a fuel stream and an optional additional fuel source with the oxygen-containing offgas stream within the fuel combustion zone to generate thermal energy for the ammonia decomposition reactor, and includes.

[0061] In certain embodiments of the method of the present invention, the method comprises The step of supplying an ammonia stream to an ammonia decomposition reactor, The step of decomposing ammonia in the ammonia stream within the ammonia decomposition reactor to produce a hydrogen-containing stream, The step of supplying the hydrogen-containing stream to a purification unit such as a pressure swing absorption unit to increase the hydrogen content and produce a hydrogen-enriched stream and a tail gas, Optionally, the step of supplying the hydrogen-enriched stream to a steam generation unit and / or a heat recovery zone, The step of combining the hydrogen-enriched stream with an oxygen-containing feed and combusting the hydrogen-enriched stream with the oxygen-containing feed to produce a combusted gas stream, The step of using the combusted gas stream to drive a gas turbine to produce an oxygen-containing offgas stream, The step of supplying at least a portion of the oxygen-containing offgas stream to a fuel combustion zone, Optionally, supplying an additional fuel source to the fuel combustion zone; Supplying tail gas to the fuel combustion zone; Combusting the fuel stream and the tail gas, and optionally the additional fuel source, with an oxygen-containing off-gas stream within the fuel combustion zone to generate thermal energy for the ammonia decomposition reactor.

[0062] FIG. 1 shows a block flow diagram of a method according to the present invention that does not include an integrated gas turbine. The block flow diagram of FIG. 1 shows the flow in which ammonia (1) is supplied to an ammonia preheating and vaporization zone (2) outside the ammonia decomposition reactor, and the ammonia is vaporized. The preheated and vaporized ammonia is supplied to an ammonia superheating zone (3) and a decomposition unit combustion zone (13). In the block flow diagram of FIG. 1, the ammonia decomposition reactor (4), the ammonia superheating zone (3), and the decomposition unit combustion zone (13) are all part of the same single piece of equipment. The ammonia from the ammonia superheating zone (3) is supplied to the ammonia decomposition reactor (4), and a hydrogen-containing stream is generated. The hydrogen-containing stream is supplied to a steam generator (5) and a heat recovery zone (6). The hydrogen-containing stream from the heat recovery zone (6) is supplied to a gas turbine (7) and burned in the presence of an oxygen-containing feed, which is air (17) compressed by a compressor (8). The steam from the steam generator (5) and the off-gas from the gas turbine (7) are used to generate electricity (10). The heat from the off-gas from the gas turbine (5) is recovered by a heat recovery steam generator (9). In the fuel combustion zone (13), the ammonia fuel is combined with the preheated air from the air preheating zone (12). The ammonia fuel and the preheated air are burned within the fuel combustion zone (13) to generate thermal energy for the ammonia decomposition reactor (4). The exhaust gas from the ammonia decomposition reactor (4) is recovered in the heat recovery zone (14), and the exhaust gas is sent to a chimney (15) and discharged as flue gas (16). The heat from the heat recovery zone (14) is used in the ammonia preheating and vaporization zone (2) and the air preheating zone (12) (not shown for clarity). One or more process streams can be heated by exchanging with the exhaust gas in the heat recovery zone (14).

[0063] Figure 2 shows a block flow diagram of a method according to the invention with an integrated gas turbine. The block flow diagram of Figure 2 shows the flow in which ammonia (21) is supplied to an ammonia preheating and vaporization zone (22) outside the ammonia decomposition reactor, and the ammonia is vaporized. The preheated and vaporized ammonia is supplied to an ammonia superheating zone (23) and a fuel combustion zone (213). In the block flow diagram of Figure 2, the ammonia decomposition reactor (24), the ammonia superheating zone (23), and the fuel combustion zone (213) are all part of the same single piece of equipment. The ammonia from the ammonia superheating zone (23) is supplied to the ammonia decomposition reactor (24) to produce a hydrogen-containing stream. The hydrogen-containing stream is supplied to a steam generator (25) and a heat recovery zone (26). The hydrogen-containing stream from the heat recovery zone (26) is supplied to a gas turbine (27) and burned in the presence of an oxygen-containing feed, which is air (217) compressed by a compressor (28). Steam from the steam generator (25) and a portion of the off-gas from the gas turbine (27) are used to generate power (210). A portion of the heat from the off-gas from the gas turbine (25) is recovered by a heat recovery steam generator (29). In the fuel combustion zone (213), the ammonia fuel is combined with a portion of the oxygen-containing off-gas from the gas turbine (27). The ammonia fuel and the oxygen-containing off-gas are burned in the fuel combustion zone (213) to generate thermal energy for the ammonia decomposition reactor (24). The exhaust gas from the ammonia decomposition reactor (24) is recovered in a heat recovery zone (214), and the exhaust gas is sent to a chimney (215) and discharged as flue gas (216). The heat from the heat recovery zone (214) is used in the ammonia preheating and vaporization zone (22) (not shown for clarity).

Example

[0064] To demonstrate the efficiency savings by the method of the present invention, a simulation was performed comparing a flowsheet with a non-integrated gas turbine (not according to the present invention) according to Figure 1 and a flowsheet with an integrated gas turbine (according to the present invention) according to Figure 2.

[0065] For both flow sheets, the following assumptions were made: ● The same ammonia decomposition reactor and gas turbine were used for both flow sheets. ● The energy requirement of the ammonia decomposition reactor was satisfied by the combustion of ammonia, and the total amount of ammonia available to the entire system was set at 1200 metric tons per day (MTPD). ● The inlet ammonia temperature to the decomposer was 600 °C. ● The inlet ammonia temperature to the combustion side of the decomposer was 90 °C. ● The ambient air temperature was 10 °C. ● The fuel requirement was set to achieve 0.58% ammonia slip for both flow sheets. ● The flue gas from the HRSG was set to 280 °C, and the HPS was raised within the HRSG.

[0066]

Table 1

[0067] *** Based on the following equation:

[0068]

Equation

[0069] The above simulation demonstrates that the system equipped with the integrated gas turbine according to the present invention has higher energy efficiency and generates more power for the output per unit of ammonia supplied to the system compared to the non-integrated gas turbine.

Claims

1. A method for generating electricity using a gas turbine fueled with carbon-free fuel obtained from catalytic decomposition of ammonia, comprising: supplying an ammonia stream to an ammonia decomposition reactor; decomposing the ammonia in the ammonia stream in the ammonia decomposition reactor to produce a hydrogen-containing stream; combining the hydrogen-containing stream with an oxygen-containing feedstock and burning the hydrogen-containing stream together with the oxygen-containing feedstock to produce a burned gas stream; driving a gas turbine using the burned gas stream to produce an oxygen-containing off-gas stream; supplying at least a portion of the oxygen-containing off-gas stream to a fuel combustion zone; burning a fuel stream and the oxygen-containing off-gas stream in the fuel combustion zone to generate thermal energy for the ammonia decomposition reactor.

2. The method according to claim 1, further comprising preheating the ammonia stream to a temperature of 350°C to 1000°C.

3. The method according to claim 1 or 2, wherein the temperature of the ammonia stream at the inlet of the ammonia decomposition reactor is in the range of 350°C to 1000°C, 400°C to 950°C, 450°C to 850°C, or 500°C to 750°C.

4. The method according to any one of claims 1 to 3, wherein the hydrogen-containing stream contains 40 mol% to 75 mol% hydrogen.

5. The method according to any one of claims 1 to 4, further comprising supplying the hydrogen-containing stream to a purification unit to increase the hydrogen content of the hydrogen-containing stream to produce a hydrogen-enriched stream and tail gas.

6. The method according to claim 5, wherein the hydrogen-enriched stream contains 50 mol% to 100 mol% hydrogen.

7. The method according to any one of claims 1 to 6, wherein the oxygen-containing feedstock is a compressed oxygen-containing feedstock.

8. The method according to any one of claims 1 to 7, wherein the oxygen-containing feedstock is air, oxygen, or oxygen-enriched air.

9. The method according to any one of claims 1 to 8, wherein the oxygen-containing off-gas stream may contain oxygen in an amount of 5 mol% to more than 25 mol%.

10. The method according to any one of claims 1 to 9, wherein the oxygen-containing off-gas stream is supplied to the fuel combustion zone at a temperature of 500°C to 800°C, 500°C to 750°C, or 600°C to 700°C.

11. The method according to any one of claims 1 to 10, wherein the portion of the oxygen-containing offgas stream supplied to the fuel combustion zone is 5% to 75%, 7% to 50%, 8% to 30%, or 9% to 20% of all the offgas streams exiting the gas turbine.

12. The method according to any one of claims 1 to 11, wherein the fuel stream contains ammonia.

13. The method according to any one of claims 1 to 12, wherein the fuel stream contains ammonia in an amount of 1 mol% to 100 mol% of all the fuel streams, preferably 5 mol% to 75 mol%, 10 mol% to 50 mol%, or 15 mol% to 30% of all the fuel streams.

14. The method according to any one of claims 5 to 13, comprising the step of supplying the tail gas to the fuel combustion zone and the step of combusting the fuel stream and the tail gas together with the oxygen-containing offgas.

15. The method according to any one of claims 1 to 14, wherein the fuel stream contains hydrogen, natural gas, methane, refinery offgas, biogas, the tail gas from the hydrogen purification unit, and a portion of the hydrogen-containing stream from the ammonia decomposition reactor, and one or more additional fuel sources.

16. The method according to any one of claims 12 to 15, wherein the fuel stream contains ammonia, and the ammonia-containing fuel stream is supplied from the same source as the ammonia stream supplied to the ammonia decomposition reactor.

17. The method according to any one of claims 1 to 16, wherein the thermal energy generated by combustion using the oxygen-containing offgas stream in the combustion zone provides more than 50% and at most 100% of the thermal energy required for the ammonia decomposition reactor.

18. A method for retrofitting an ammonia production facility, the method comprising the step of implementing the method according to any one of claims 1 to 17 in the ammonia production facility.

Images