Ammonia decomposition system

Abstract

An ammonia decomposition system includes: a first decomposition part for thermally decomposing ammonia into nitrogen and hydrogen; a steam supply part for generating steam and supplying the steam to the first decomposition part as a heat source; a recovery line for recovering steam after passage through the first decomposition part; a turbine driven by the steam recovered by the recovery line; and a power generation part for generating electric power by being driven by the turbine.

Description

Ammonia Decomposition System

[0001] This disclosure relates to an ammonia decomposition system. This application claims priority to Japanese Patent Application No. 2024-099484, filed on June 20, 2024, the contents of which are incorporated herein by reference.

[0002] The ammonia decomposition system converts ammonia into hydrogen and nitrogen gas. Ammonia is a low-cost chemical raw material. It has the advantages of high energy density, easy compression and liquefaction, convenient storage and transportation, and no CO2 emissions when burned. Therefore, the idea of ​​using ammonia as a hydrogen transport carrier has attracted widespread attention. Furthermore, ammonia's high mass density and volumetric hydrogen storage density make it a promising hydrogen transport carrier. Furthermore, the nitrogen gas produced by ammonia catalytic decomposition is an excellent protective gas and has wide applications in the semiconductor and metallurgical industries.

[0003] A catalytic reaction using heat is widely used to decompose ammonia. Because the decomposition requires relatively high calorie heat, it has been common to use steam generated in a boiler as a heat medium (see, for example, Patent Document 1 below).

[0004] JP 2023-90810 A

[0005] However, when considering the energy efficiency of the plant or the entire system, it is necessary to find a way to more effectively utilize the thermal energy provided for the decomposition of ammonia.

[0006] The present disclosure provides an ammonia decomposition system that can more effectively utilize thermal energy.

[0007] The ammonia decomposition system according to the present disclosure includes a first decomposition section that thermally decomposes ammonia into nitrogen and hydrogen, a steam supply section that generates steam and supplies the steam to the first decomposition section as a heat source, a recovery line that recovers the steam after passing through the first decomposition section, a turbine that is driven by the steam recovered by the recovery line, and a power generation section that is driven by the turbine to generate electricity.

[0008] According to the present disclosure, it is possible to provide an ammonia decomposition system that can more effectively utilize thermal energy.

[0009] Fig. 1 is a system diagram showing the configuration of an ammonia decomposition system according to a first embodiment of the present disclosure. Fig. 2 is a system diagram showing the configuration of an ammonia decomposition system according to a second embodiment of the present disclosure. Fig. 3 is a functional block diagram showing the configuration of a control unit according to a second embodiment of the present disclosure. Fig. 4 is a flowchart showing the processing flow of a control unit according to a second embodiment of the present disclosure. Fig. 5 is an enlarged view of a main part showing a modified example of an ammonia decomposition system according to the second embodiment of the present disclosure. Fig. 6 is a hardware configuration diagram of a computer according to an embodiment of the present disclosure.

[0010] First Embodiment (Configuration of Ammonia Decomposition System 1) Hereinafter, an ammonia decomposition system 1 according to a first embodiment of the present disclosure will be described with reference to Fig. 1. The ammonia decomposition system 1 generates hydrogen and nitrogen by thermally decomposing ammonia gas, which serves as a raw material. The generated hydrogen and nitrogen are stored externally and used for various purposes.

[0011] As shown in FIG. 1 , the ammonia decomposition system 1 includes a first decomposition section 10, an ammonia supply line 11, a product gas recovery line 12, a steam supply section 20, a turbine 30, a power generation section 40, a reflux line 31, a condenser 32, and a feedwater pump 33.

[0012] (First decomposition unit 10) The first decomposition unit 10 decomposes gaseous ammonia to produce nitrogen gas and hydrogen gas. The first decomposition unit 10 contains a metal that acts as a predetermined catalyst. Ammonia, which is the raw material, is supplied to the first decomposition unit 10 through an ammonia supply line 11. The nitrogen and hydrogen produced in the first decomposition unit 10 are extracted to the outside through a product gas recovery line 12. Outside, these produced gases are stored in a tank or the like (not shown), liquefied, or directly used for various purposes. Depending on the use of hydrogen, a hydrogen purification device may be installed to process it to a predetermined purity.

[0013] (Steam supply section 20) The steam supply section 20 supplies high-temperature steam as a heat source to the first decomposition section 10. The steam supply section 20 has a steam supply section main body 21, a steam supply line 22, and a steam recovery line 23 (recovery line). The steam supply section main body 21 generates steam by superheating water. As the steam supply section main body 21, for example, a boiler or a heat recovery steam generator (HRSG) installed in the plant is suitably used. The steam supply line 22 guides the steam generated in the steam supply section main body 21 to the first decomposition section 10.

[0014] In the first decomposition section 10, the thermal energy of the steam is used to decompose the ammonia. The temperature drop of the steam caused by the decomposition of ammonia is, for example, about 50°C. Therefore, for example, when steam at 500°C is supplied to the first decomposition section 10, the temperature of the steam after passing through the first decomposition section 10 remains at about 450°C. This steam is recovered by the steam recovery line 23.

[0015] (Turbine 30 / Power Generation Unit 40) The turbine 30 is connected downstream of the steam recovery line 23. The turbine 30 is rotationally driven by steam at approximately 450°C supplied through the steam recovery line 23. The power generation unit 40 is connected to a shaft end of the turbine 30. As the turbine 30 rotates, its rotational energy is extracted from the shaft end and drives a generator serving as the power generation unit 40. Electric power is thereby generated. This electric power is used to drive the auxiliary equipment 50 (such as a compressor and a pump, not shown) of the first cracking section 10.

[0016] (Condenser 32 / Feedwater Pump 33) A reflux line 31 is connected to the exhaust port of the turbine 30. The reflux line 31 recovers steam after it has done work in the turbine 30. The downstream end of the reflux line 31 is connected to the steam supply unit main body 21 described above. A condenser 32 and a feedwater pump 33 are provided on the reflux line 31. The condenser 32 exchanges heat between the steam flowing on the reflux line 31 and a medium supplied from the outside, thereby cooling the steam and turning it back into water, thereby maximizing the work of the turbine 30. This water is pumped by the feedwater pump 33 along the reflux line 31 and sent to the steam supply unit main body 21. In the steam supply unit main body 21, the water is heated again to generate steam. The above cycle occurs continuously, thereby progressing the ammonia decomposition process.

[0017] (Effects) Heat-based catalytic reactions are widely used to decompose ammonia. Because decomposition requires relatively high-calorie heat, it has been common practice to use steam generated in a boiler as a heat medium. However, when considering the energy efficiency of a plant or the entire system, it is necessary to find ways to more effectively utilize the thermal energy provided for the decomposition of ammonia. As an example of how to achieve this objective, the ammonia decomposition system 1 according to this embodiment employs the above-described configurations.

[0018] According to the above-described configuration, the steam used for decomposing ammonia in the first decomposition section 10 is recovered by the steam recovery line 23. This recovered steam drives the turbine 30, which in turn drives the power generation section 40. The electric power generated by the power generation section 40 is used to drive the auxiliaries 50 associated with the first decomposition section 10, such as a compressor and a pump. This reduces the amount of electric power supplied from external sources, thereby improving the energy efficiency of the entire system.

[0019] According to the above configuration, the steam after driving the turbine 30 is returned to the steam supply unit 20 through the reflux line 31. As a result, the thermal energy remaining after being used for the two purposes of decomposing ammonia and driving the turbine 30 can be utilized again in the steam supply unit 20. In other words, because water in a relatively high temperature state is used as the steam generation source, it is possible to reduce energy consumption of the entire system and further improve efficiency compared to a configuration in which low-temperature water is supplied from the outside to generate new steam.

[0020] The first embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the gist of the present disclosure.

[0021] For example, in the first embodiment, an example has been described in which only one first decomposition section 10 is provided. However, the number of first decomposition sections 10 is not limited to one, and two or more first decomposition sections 10 may be provided in parallel depending on the scale and specifications of the system. This configuration can further increase the amount of ammonia treated.

[0022] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 2 to Fig. 4. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0023] As shown in FIG. 2 , the ammonia decomposition system 2 according to this embodiment further includes a second decomposition section 110, an electric heating section 60, a second ammonia supply line 111, an on-off valve 112, a second product gas recovery line 113, a monitoring section 70, and a control section 80, in addition to the configuration described in the first embodiment.

[0024] (Second decomposition section 110) The second decomposition section 110 is arranged in parallel with the first decomposition section 10. Ammonia is supplied to the second decomposition section 110 through a second ammonia supply line 111. The second ammonia supply line 111 branches off from the above-mentioned ammonia supply line 11, and an on-off valve 112 is provided midway along the second ammonia supply line 111. The on-off valve 112 is a solenoid valve or a flow rate control valve that switches the flow state of ammonia on the second ammonia supply line 111. The on-off state of the on-off valve 112 is controlled by a control unit 80, which will be described later.

[0025] The product gas (hydrogen and nitrogen) generated in the second decomposition section 110 is extracted to the outside through a second product gas recovery line 113. The second product gas recovery line 113 merges with the product gas recovery line 12 described above.

[0026] (Electric heating unit 60) The second decomposition unit 110 is provided with an electric heating unit 60. The electric heating unit 60 is, for example, an electric heater, and the heat from the electric heating unit 60 causes ammonia to be decomposed into hydrogen and nitrogen in the second decomposition unit 110. A portion of the electric power generated by the power generation unit 40 described above is used to operate the electric heating unit 60. That is, the power generation unit 40 generates electric power for operating the various auxiliary devices 50 and the electric heating unit 60.

[0027] (Monitoring unit 70 and control unit 80) The power generation unit 40 is provided with a monitoring unit 70 for monitoring its operating state. The monitoring unit 70 acquires physical quantities such as the rotation speed of the generator serving as the power generation unit 40 and the amount of power generated, and transmits these as electrical signals to the control unit 80. Specifically, a potentiometer, a voltmeter, or the like is preferably used as the monitoring unit 70.

[0028] The control unit 80 controls the opening and closing of the on-off valve 112 based on the physical quantity acquired by the monitoring unit 70. Specifically, as shown in Fig. 3, the control unit 80 has a drive state receiving unit 81, a determination unit 82, a valve drive unit 83, and a storage unit 84 as functional blocks.

[0029] The operating state receiving unit 81 receives, as an electrical signal, the physical quantity (described above) related to the operating state of the power generating unit 40 acquired by the monitoring unit 70. The determining unit 82 compares this physical quantity with a predetermined threshold value.

[0030] The threshold value referred to here is, for example, the rotation speed or voltage of the power generation unit 40. More specifically, a physical quantity that reflects the minimum amount of power generation required to operate the electric heating unit 60 provided next to the second decomposition unit 110 is set as the threshold value. More specifically, a physical quantity that allows the electric heating unit 60 to obtain enough electric power to generate the heat required to advance the ammonia decomposition reaction in the second decomposition unit 110 is set as the threshold value.

[0031] When the determination unit 82 determines that the physical quantity exceeds the threshold value, the valve driving unit 83 adjusts the opening degree of the on-off valve 112 to increase in order to operate the second decomposition unit 110. The memory unit 84 stores these physical quantities and threshold values.

[0032] Next, the processing flow of the control unit 80 will be described with reference to FIG. 4 . As shown in the figure, first, the drive status receiving unit 81 acquires the above-mentioned physical quantity from the monitoring unit 70 (step S1). Next, the determination unit 82 compares the physical quantity with a threshold value (step S2). Specifically, it is determined whether the physical quantity is greater than the threshold value. If the determination in step S2 is No, the process returns to step S1 again. If the determination in step S2 is Yes, in the subsequent step S3, the valve drive unit 83 adjusts the opening of the on-off valve 112 in a direction to increase. As a result, ammonia is supplied to the second decomposition unit 110, and ammonia processing in the first decomposition unit 10 and the second decomposition unit 110 is started.

[0033] (Effects) According to the above configuration, in addition to the first decomposition section 10 that decomposes ammonia using heat from steam, the second decomposition section 110 that decomposes ammonia using electrical heating (a heater, etc.) is further provided. In this second decomposition section 110, a portion of the electric power generated in the power generation section 40 is used to generate heat. Therefore, the electric power generated in the power generation section 40 can be used more effectively, and the provision of the second decomposition section 110 makes it possible to significantly increase the amount of ammonia processed per unit time.

[0034] According to the above configuration, when the ammonia decomposition system 2 is started, the control unit 80 controls the on-off valve 112 based on the power generation status of the power generation unit 40. That is, when the amount of power generated by the power generation unit 40 is below a threshold, the on-off valve 112 is closed, and ammonia is not supplied to the second decomposition unit 110. On the other hand, when it is determined that the amount of power generated exceeds the threshold, the on-off valve 112 is opened, and the supply of ammonia to the second decomposition unit 110 is started and adjusted. In this way, it is possible to autonomously switch between use and non-use of the second decomposition unit 110 and adjust the amount of ammonia decomposition depending on the operating status of the entire system. This makes it possible to reduce the operating costs of the system.

[0035] The second embodiment of the present disclosure has been described above. Note that various changes and modifications can be made to the above configuration without departing from the spirit and scope of the present disclosure.

[0036] For example, in the second embodiment, the second decomposition section 110 is arranged in parallel with the first decomposition section 10. However, as shown in FIG. 5 as a modified example, the second decomposition section 110 may be arranged in series downstream of the first decomposition section 10. With this configuration, when decomposing ammonia, a catalytic reaction occurs at a relatively low temperature in the upstream first decomposition section 10 due to the heat of steam. Next, a catalytic reaction occurs at a relatively high temperature in the second decomposition section 110 due to the heat of the electric heating section 60. In this way, the ammonia decomposition process is performed continuously in two different temperature ranges, significantly reducing the possibility of unreacted (uncracked) ammonia being generated. Therefore, the ammonia used as a raw material can be utilized to the maximum extent possible without waste. As a result, the efficiency of the entire system can be further improved.

[0037] Furthermore, the power required to drive the electric heating unit 60 does not necessarily have to come from the power generation unit 40. That is, it is possible to employ a configuration in which the electric heating unit 60 receives power from an external power source until it operates, and when the amount of power generated by the power generation unit 40 reaches the threshold value, the power supply system is switched to power from the power generation unit 40.

[0038] In addition, although gaseous ammonia is introduced as the raw material in each of the above-described embodiments, it is also possible to use liquid ammonia as the raw material by providing a vaporizer upstream of the first decomposition section 10 and the second decomposition section 110. Even in this case, the same effects as those described above can be obtained.

[0039] Furthermore, in each of the above-described embodiments, the electricity generated by driving the generator serving as the power generation unit 40 is used for the auxiliary equipment 50 and the electric heating unit 60, but it is not limited to these and can also be used for other purposes.

[0040] It is also possible to provide a plurality of pairs of the first decomposition section 10 and the second decomposition section 110 connected in series as described above in parallel, thereby making it possible to flexibly increase or decrease the amount of ammonia treated depending on the scale and specifications of the system.

[0041] Note that the control unit 80 in the embodiment of the present disclosure may change the order of processing as long as appropriate processing is performed.

[0042] The storage unit 84 and other storage devices in the embodiments of the present disclosure may be provided anywhere within a range where appropriate information can be transmitted and received. Furthermore, multiple storage units 84 and other storage devices may exist within a range where appropriate information can be transmitted and received, and data may be stored in a distributed manner.

[0043] The above-described processing steps performed by the control unit 80 are stored in the form of a program on a recording medium that can be read by the computer 200, and the above processing is performed by reading and executing this program by the computer 200. A specific example of the computer 200 is shown below.

[0044] 6, the computer 200 includes a CPU 201, a main memory 202, a storage 203, and an interface 204. For example, the control unit 80 described above is implemented in the computer 200. The operations of the above-described processing units are stored in the storage 203 in the form of a program. The CPU 201 reads the program from the storage 203, loads it into the main memory 202, and executes the above-described processing in accordance with the program. The CPU 201 also allocates a storage area in the main memory 202 corresponding to the above-described storage unit 84 in accordance with the program.

[0045] Examples of storage 203 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 203 may be an internal medium directly connected to the bus of computer 200, or an external medium connected to computer 200 via interface 204 or a communication line. Furthermore, when this program is distributed to computer 200 via a communication line, computer 200 that receives the program may deploy the program in main memory 202 and execute the above-described processing. Storage 203 is a non-transitory tangible storage medium.

[0046] The program may also implement some of the functions described above. Furthermore, the program may be a file that can implement the functions described above in combination with a program already recorded on computer 200, that is, a so-called differential file (differential program).

[0047] In addition to or instead of the above configuration, a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device), an ASIC (Application Specific Integrated Circuit), a GPU (Graphics Processing Unit), or a processing device similar thereto may be provided. Examples of PLDs include programmable array logic (PAL), generic array logic (GAL), complex programmable logic device (CPLD), and field programmable gate array (FPGA). In this case, some or all of the functions realized by a processor may be realized by the integrated circuit.

[0048] <Additional Notes> The ammonia decomposition system 1 described in each embodiment can be understood, for example, as follows.

[0049] (1) The ammonia decomposition system 1 according to the first aspect includes a first decomposition section 10 that thermally decomposes ammonia into nitrogen and hydrogen, a steam supply section 20 that generates steam and supplies the steam to the first decomposition section 10 as a heat source, a recovery line (steam recovery line 23) that recovers the steam after passing through the first decomposition section 10, a turbine 30 that is driven by the steam recovered by the recovery line, and a power generation section 40 that is driven by the turbine 30 to generate electricity.

[0050] According to the above configuration, the energy efficiency of the entire system can be improved.

[0051] (2) The ammonia decomposition system 1 according to a second aspect is the ammonia decomposition system 1 according to (1), further including a reflux line 31 that recovers the steam after driving the turbine 30 and returns the steam to the steam supply unit 20.

[0052] According to the above configuration, it is possible to reduce the energy consumption of the entire system and further improve the efficiency.

[0053] (3) The ammonia decomposition system 1 according to a third aspect is the ammonia decomposition system 1 according to (1) or (2), in which the power generation unit 40 supplies part or all of the generated electricity to drive the auxiliary equipment 50 of the first decomposition unit 10.

[0054] According to the above configuration, the energy efficiency of the entire plant can be improved by effectively utilizing electric power.

[0055] (4) The ammonia decomposition system 1 according to a fourth aspect is the ammonia decomposition system 1 according to any one of the aspects (1) to (3), further comprising a second decomposition section 110 provided next to the first decomposition section 10 and decomposing ammonia into nitrogen and hydrogen by electrothermal heating, and the power generation section 40 supplies a portion of the generated electricity to the second decomposition section 110.

[0056] According to the above configuration, the electricity generated in the power generation section 40 can be utilized more effectively, and by providing the second decomposition section 110, it is possible to significantly increase the amount of ammonia processed per unit time.

[0057] (5) The ammonia decomposition system 1 according to a fifth aspect is the ammonia decomposition system 1 of (4), further comprising: a supply line for supplying the ammonia to the second decomposition section 110; an on-off valve 112 provided on the supply line; a monitoring section 70 for monitoring the operating state of the power generation section 40; and a control section 80 for controlling the on-off state of the on-off valve 112, wherein when it is determined that the power generation section 40 is generating the electric power for operating the second decomposition section 110, the control section 80 opens the on-off valve 112 and supplies the electric power to the second decomposition section 110.

[0058] According to the above configuration, the operating costs of the system can be reduced.

[0059] (6) The ammonia decomposition system 1 according to a sixth aspect is the ammonia decomposition system 1 according to (5), in which the first decomposition section 10 is provided upstream of the second decomposition section 110 in the flow direction of the ammonia.

[0060] According to the above-described configuration, ammonia as a raw material can be utilized to the maximum extent possible without any waste.

[0061] According to the present disclosure, it is possible to provide an ammonia decomposition system that can more effectively utilize thermal energy.

[0062] DESCRIPTION OF SYMBOLS 1, 2... Ammonia decomposition system 10... First decomposition section 11... Ammonia supply line 12... Produced gas recovery line 20... Steam supply section 21... Steam supply section main body 22... Steam supply line 23... Steam recovery line 30... Turbine 31... Reflux line 32... Condenser 33... Feedwater pump 40... Power generation section 50... Auxiliary equipment 60... Electric heating section 70... Monitoring section 80... Control section 81... Driving state reception section 82... Determination section 83... Valve driving section 84... Memory section 110... Second decomposition section 111... Second ammonia supply line 112... On-off valve 113... Second produced gas recovery line 200... Computer 201... CPU 202... Main memory 203... Storage 204... Interface

Claims

1. An ammonia decomposition system comprising: a first decomposition section that thermally decomposes ammonia into nitrogen and hydrogen; a steam supply section that generates steam and supplies the steam to the first decomposition section as a heat source; a recovery line that recovers the steam after passing through the first decomposition section; a turbine that is driven by the steam recovered by the recovery line; and a power generation section that is driven by the turbine to generate electricity.

2. The ammonia decomposition system according to claim 1, further comprising a reflux line for recovering the steam after driving the turbine and returning it to the steam supply section.

3. The ammonia decomposition system according to claim 1, wherein the power generation unit supplies part or all of the generated electricity to drive auxiliary equipment of the first decomposition unit.

4. The ammonia decomposition system according to any one of claims 1 to 3, further comprising a second decomposition unit arranged adjacent to the first decomposition unit and decomposing ammonia into nitrogen and hydrogen by electrothermal heating, wherein the power generation unit supplies a portion of the generated electricity to the second decomposition unit.

5. The ammonia decomposition system according to claim 4, further comprising: a supply line that supplies the ammonia to the second decomposition section; an on-off valve provided on the supply line; a monitoring section that monitors the operating state of the power generation section; and a control section that controls the on-off state of the on-off valve, wherein when it is determined that the power generation section is generating the electricity for operating the second decomposition section, the control section opens the on-off valve and supplies the electricity to the second decomposition section.

6. An ammonia decomposition system according to claim 5, wherein the first decomposition section is provided upstream of the second decomposition section in the direction of ammonia flow.

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