Dehydrogenation system and hydrogen storage / transport system

Abstract

Provided are a dehydrogenation system and a hydrogen storage / transport system capable of suitably removing heavy components as impurities.　The present invention provides a dehydrogenation system for a hydrogenated aromatic compound, the dehydrogenation system comprising a dehydrogenation reaction unit, a first separation unit, and a second separation unit. The dehydrogenation reaction unit is configured to generate a mixed product containing hydrogen, an aromatic compound, and heavy components from a hydrogenated aromatic compound through a dehydrogenation reaction. The first separation unit is configured to separate the heavy components and a portion of the aromatic compound from the mixed product of the dehydrogenation reaction unit as a liquid phase product through gas-liquid separation. The second separation unit is configured to separate a gas phase product of the first separation unit into hydrogen and an aromatic compound through gas-liquid separation.

Description

Dehydrogenation system and hydrogen storage and transportation system

[0001] The present invention relates to a dehydrogenation system for desorbing hydrogen from a hydrogenated aromatic compound, and a hydrogen storage and transportation system including the same.

[0002] The hydrogen storage and transportation system as a hydrogen supply chain has a hydrogenation system and a dehydrogenation system. The hydrogenation system is installed at the hydrogen production site and is configured to convert the produced hydrogen into hydrogenated aromatic compounds. On the other hand, the dehydrogenation system is installed at the hydrogen usage site and is configured to produce hydrogen and aromatic compounds by desorbing hydrogen from the hydrogenated aromatic compounds transported from the hydrogen production site. The aromatic compounds produced in the dehydrogenation system can be transported back to the hydrogenation system at the hydrogen production site and reused.

[0003] In the hydrogenation reaction or dehydrogenation reaction of a hydrogen storage and transportation system, impurities that can poison the hydrogenation catalyst or dehydrogenation catalyst (for example, polymerization products of dimers, trimers, or higher of six-membered ring compounds (heavy components)) may be generated. It is not desirable for such impurities to circulate in the hydrogen storage and transportation system, so it is preferable to remove the generated heavy components appropriately.

[0004] Patent Document 1 discloses a technology for removing heavy components as impurities by distilling the product of a hydrogenation reaction, taking advantage of the fact that the hydrogenation reaction is a highly exothermic reaction and a large amount of reaction heat can be recovered.

[0005] Japanese Patent Application Laid-Open No. 2007-269522

[0006] It is said that the removal of heavy components as impurities in a hydrogen storage and transportation system is easier on the exothermic hydrogenation system side than on the endothermic dehydrogenation system side, but it is preferable to be able to remove heavy components appropriately on the dehydrogenation system side as well.

[0007] The present invention has been made in view of the above circumstances, and provides a dehydrogenation system and a hydrogen storage and transportation system that can suitably remove heavy components as impurities.

[0008] According to the present invention, the following inventions are provided: [1] A dehydrogenation system for desorbing hydrogen from hydrogenated aromatic compounds, comprising a dehydrogenation reaction unit, a first separation unit, and a second separation unit, wherein the dehydrogenation reaction unit is configured to produce a mixed product containing hydrogen, aromatic compounds, and heavy components from the hydrogenated aromatic compounds by a dehydrogenation reaction, the first separation unit is configured to separate a portion of the aromatic compounds and the heavy components as a liquid-phase product from the mixed product of the dehydrogenation reaction unit by gas-liquid separation, and the second separation unit is configured to separate the gas-phase product of the first separation unit into hydrogen and the aromatic compounds by gas-liquid separation. [2] The dehydrogenation system according to [1], further comprising a distillation unit configured to separate the liquid-phase product of the first separation unit into the aromatic compounds and the heavy components by distillation, wherein the aromatic compounds separated by distillation and the aromatic compounds separated in the second separation unit are mixed, and the heavy components contained in the aromatic compounds after mixing are 100 ppm by weight or less. [3] The dehydrogenation system according to [2], further comprising a heating unit, the heating unit being configured to comprise a reaction heat supply unit that heats a heat medium that supplies heat to the dehydrogenation reaction unit, and a steam generating unit that generates steam to be supplied to the distillation unit. [4] The dehydrogenation system according to any one of [1] to [3], wherein the temperature of the mixed product separated into gas and liquid in the first separation unit is maintained within a range of 80°C to 150°C. [5] The dehydrogenation system according to any one of [1] to [4], wherein the weight of the liquid phase product separated in the first separation unit is 5 to 20% of the total weight of the mixed product. [6] The dehydrogenation system according to any one of [1] to [5], wherein the heavy fraction comprises one or more bicyclic or polycyclic compounds selected from biphenyl, bicyclohexyl, 4,4-dimethylbicyclohexyl, and 3,3-dimethylbicyclohexyl.[7] A dehydrogenation system for hydrogenated aromatic compounds, comprising a dehydrogenation reaction unit, a first separation unit, and a distillation unit, wherein the dehydrogenation reaction unit is configured to produce a mixed product containing hydrogen, aromatic compounds, and heavy components from the hydrogenated aromatic compounds by a dehydrogenation reaction, the first separation unit is configured to separate a portion of the aromatic compounds and the heavy components as a liquid-phase product from the mixed product of the dehydrogenation reaction unit by gas-liquid separation, and the distillation unit is configured to distill and separate the liquid-phase product of the first separation unit into aromatic compounds and the heavy components. [8] A hydrogen storage and transportation system, comprising the dehydrogenation system according to any one of [1] to [7] and a hydrogenation system, wherein the hydrogenation system is configured to produce hydrogenated aromatic compounds from the aromatic compounds and hydrogen separated by the dehydrogenation system.

[0009] In the dehydrogenation system and hydrogen storage and transportation system of the present invention, a mixed product from the dehydrogenation reaction section containing hydrogen, aromatic compounds, and heavy components is first separated in the first separation section as a liquid-phase product containing a small amount of aromatic compounds, which contains a large amount of heavy components. Therefore, the heavy components can be efficiently separated from the hydrogen and aromatic compounds. As a result, even in a dehydrogenation system that cannot utilize reaction heat like a hydrogenation system, it is possible to effectively remove heavy components as impurities.

[0010] 1 is a diagram showing a schematic configuration of a hydrogen storage and transportation system 1 according to an embodiment of the present invention. 2 is a diagram showing an example of a schematic configuration of a dehydrogenation system 1A. 3 is a diagram showing the relationship between the condensation rate (wt%) in a first separation section 3A and the dimer removal rate and the duty reduction rate (%).

[0011] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0012] <Hydrogen Storage and Transportation System 1> As shown in Figure 1, the hydrogen storage and transportation system 1 includes a dehydrogenation system 1A and a hydrogenation system 1B. The dehydrogenation system 1A is installed in a hydrogen-using area and is configured to produce hydrogen and an aromatic compound (toluene in this embodiment) by desorbing hydrogen from a hydrogenated aromatic compound (methylcyclohexane in this embodiment). The dehydrogenation system 1A includes a dehydrogenation reaction section 2, a separation section 3 (first separation section 3A, second separation section 3B, distillation section 3C), a methylcyclohexane tank 4A, and a toluene tank 5A. The configuration of each section of the dehydrogenation system 1A will be described later.

[0013] The hydrogenation system 1B is installed in a hydrogen production site and is configured to convert hydrogen produced by an adjacent facility into hydrogenated aromatic compounds and store the converted hydrogen. The hydrogenation system 1B includes a hydrogenation reaction unit 6, a separation unit 7, a methylcyclohexane tank 4B, and a toluene tank 5B. The hydrogenation reaction unit 6 is configured to perform a toluene hydrogenation reaction using hydrogen produced by a hydrogen production device such as an electrolyzer. Examples of hydrogenation catalysts used in the hydrogenation reaction unit 6 include those in which at least one active metal selected from nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru) is supported on a support selected from alumina, silica-alumina, and silica. However, the catalyst is not limited to these, and any known catalyst used to hydrogenate aromatic compounds such as toluene can be used. Toluene is supplied to the hydrogenation reaction unit 6 from the toluene tank 5B. This toluene may be, for example, toluene separated by the dehydrogenation system 1A and supplied from the dehydrogenation system 1A.

[0014] The separation unit 7 is configured to separate the product of the hydrogenation reaction unit 6 into gas and liquid. The methylcyclohexane separated as a liquid in the separation unit 7 is sent from the separation unit 7 to a methylcyclohexane tank 4B and stored therein. Of the residues separated as a gas in the separation unit 7 (unreacted residual hydrogen, gases such as by-products), hydrogen is circulated, for example, to the upstream side of the hydrogenation reaction unit 6.

[0015] The methylcyclohexane stored in the methylcyclohexane tank 4B has the function of storing hydrogen as a liquid at room temperature and pressure. The methylcyclohexane stored in the methylcyclohexane tank 4B can be transported to the methylcyclohexane tank 4A on the dehydrogenation system 1A side by a ship such as a chemical tanker, a vehicle such as a chemical tanker, or via piping such as a pipeline. Note that the toluene stored in the toluene tank 5A on the dehydrogenation system 1A side can also be transported to the toluene tank 5B on the hydrogenation system 1B side by similar means.

[0016] <Dehydrogenation System 1A> Next, the dehydrogenation system 1A will be described using Figure 2. In Figure 2, the process fluid is shown flowing from top to bottom, but the actual fluid flow may be either downward or upward as long as the flow of the process fluid follows the order of the arrows. The dehydrogenation reaction section 2 is configured to produce a mixed product containing hydrogen, toluene, and heavy components from methylcyclohexane through a dehydrogenation reaction. Examples of heavy components include, but are not limited to, one or more bicyclic or polycyclic compounds selected from biphenyl, bicyclohexyl, 4,4-dimethylbicyclohexyl, and 3,3-dimethylbicyclohexyl.

[0017] <Dehydrogenation Reaction Section 2> The dehydrogenation reaction section 2 includes an evaporator 21, a superheater 22, and a dehydrogenation reactor 23. The evaporator 21 is configured to vaporize methylcyclohexane supplied from the methylcyclohexane tank 4A via a raw material supply line L1 by a pump or the like. The superheater 22 is configured to further superheat the methylcyclohexane vaporized in the evaporator 21 to increase the temperature.

[0018] The dehydrogenation reactor 23 is configured to produce hydrogen from the vaporized and superheated methylcyclohexane. The dehydrogenation reactor 23 may be configured, for example, as a shell-and-tube fixed-bed multi-tube heat exchange reactor. The dehydrogenation reactor 23 has a cylindrical shell and a plurality of tubes extending within the shell. The internal space of each tube is isolated from the internal space of the shell. The inside of each tube is filled with a dehydrogenation catalyst that promotes the dehydrogenation reaction.

[0019] The dehydrogenation catalyst used in the dehydrogenation reactor 23 may be a catalyst in which at least one active metal selected from nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru) is supported on a carrier selected from alumina, silica alumina, and silica. However, the type of catalyst is not limited to these, and known catalysts used in dehydrogenation reactions of organic hydrides such as methylcyclohexane can be used.

[0020] <First Separation Section 3A> The separation section 3 includes a first separation section 3A, a second separation section 3B, and a distillation section 3C. The reaction product is sent to the first separation section 3A from the dehydrogenation reaction section 2 via the reaction product supply line L2. The first separation section 3A is configured to separate a portion of the toluene and heavy components as a liquid-phase product from the mixed product of the dehydrogenation reaction section 2 by gas-liquid separation. The first separation section 3A includes a first cooler 31A, a first separator 32A, and a flow control valve 33. The first cooler 31A is configured to cool the mixed product circulating through the reaction product supply line L2. The first cooler 31A may be configured, for example, as a water-cooled or air-cooled cooler. However, this is not limited thereto, and known temperature control devices, heat transfer devices, heat dissipation devices, etc. may be appropriately used as long as they can substantially cool the mixed product as required. For example, a heat exchange system that recovers and uses cold energy available near the dehydrogenation system 1A may also be used.

[0021] The first cooler 31A is configured to maintain the temperature of the mixed product separated into gas and liquid in the first separator 32A within a range of 80°C to 150°C. Specific examples of the temperature of the mixed product include 80, 90, 100, 110, 120, 130, 140, and 150°C, and may be within a range between any two of the values ​​exemplified here. Setting the temperature of the mixed product to approximately 80 to 110°C is more preferable because the weight of the liquid-phase product separated in the first separator 32A can be adjusted to 5 to 20% of the total weight of the mixed product.

[0022] FIG. 3 shows the relationship between the condensation rate (wt%), dimer removal rate (also referred to as heavy component removal rate) (%), and duty reduction rate (%) in the first separation section 3A (pressure: 185 kPaG). Here, the duty reduction rate (%) refers to the energy reduction rate in the distillation section 3C compared to the energy required to send almost all of the toluene and heavy components to the distillation section 3C by water-cooling or air-cooling the temperature of the mixed product to approximately 40°C to 50°C. In the figure, the duty reduction rate (%) is shown by line X1, and the dimer removal rate (%) is shown by line X2. The condensation rate (wt%) in the first separation section 3A is calculated as the weight ratio of the liquid phase product separated in the first separator 32A to the total weight of the mixed product. When the condensation rate (wt%) in the first separation section 3A is in the range of 5 to 20%, both the dimer removal rate (%) and the duty reduction rate (%) show good values.

[0023] In this embodiment, the temperature of the mixed product is adjusted by suitably utilizing the flow rate adjustment valve 33 and the bypass line L3. The flow rate adjustment valve 33 is configured to adjust the flow rate of the mixed product flowing from the reaction product supply line L2 into the bypass line L3. The bypass line L3 is configured to send the mixed product to the first separator 32A without passing through the first cooler 31A. When the flow rate of the mixed product flowing into the bypass line L3 is zero, the temperature of the mixed product is cooled to 80°C or lower. However, by appropriately adjusting the flow rate of the mixed product flowing into the bypass line L3 based on the detection value of a thermometer (not shown) provided in the first separation section 3A, the temperature of the mixed product can be maintained within the range of 80°C to 150°C.

[0024] <Second Separation Unit 3B> The second separation unit 3B is configured to separate the gas phase product of the first separator 32A into hydrogen and toluene by gas-liquid separation. The second separation unit 3B is connected to the first separator 32A via a gas phase line L4 and includes a second cooler 31B and a second separator 32B. The second cooler 31B is configured to cool the gas phase product of the first separator 32A to approximately 40°C to 50°C. The second cooler 31B may have a configuration similar to that of the first cooler 31A. The second separator 32B is configured to separate a product gas containing hydrogen from the toluene liquefied in the second cooler 31B. A known adsorption device (not shown) capable of removing vapor components of toluene and unreacted methylcyclohexane contained in the product gas may be disposed downstream of the second separator 32B. The toluene separated in the second separator 32B is sent to a toluene tank 5A for storage. Thereafter, the toluene may be transported to the toluene tank 5B on the hydrogenation system 1B side, or may be used for other purposes, such as blending with gasoline.

[0025] <Distillation Unit 3C> The distillation unit 3C is configured to distill and separate the liquid-phase product of the first separator 32A into toluene and heavy components. The distillation unit 3C is connected to the first separator 32A via a liquid-phase line L5 and includes a third cooling unit 31C and a distillation column 34. The distillation column 34 distills and separates the liquid-phase product of the first separator 32A, supplied via the liquid-phase line L5, into toluene and heavy components. The distillation column 34 may be configured as, for example, a tray column or a packed column. The toluene distilled and separated by the distillation column 34 merges with the toluene downstream of the second separator 32B via a merger line L6. The toluene flowing through the merger line L6 is cooled (condensed) in the third cooling unit 31C and then mixed with the toluene downstream of the second separator 32B. In this embodiment, the heavy components contained in the toluene after mixing are suppressed to 100 ppm by weight or less.

[0026] <Heating Section 8> The dehydrogenation system 1A includes a heating section 8. The heating section 8 includes a heating furnace 8A and a steam generation section 8B. The heating furnace 8A corresponds to the reaction heat supply section of the present invention and is configured to heat a heat transfer medium (thermal oil in this embodiment) that supplies heat to the dehydrogenation reaction section 2. The heating furnace 8A can be configured to obtain the desired amount of heat by burning natural gas, for example. However, other known configurations, such as a configuration using an electric heating wire, can be used as long as the desired amount of heat can be obtained stably. The heating furnace 8A heats the thermal oil within the furnace to approximately 400°C. The thermal oil heated in the heating furnace 8A is transported to the dehydrogenation reactor 23 via the thermal oil transport line L7, where it heats the methylcyclohexane and dehydrogenation catalyst in the tubes of the dehydrogenation reactor 23. The thermal oil can also be used as a heat source for the evaporator 21 and the superheater 22 (not shown).

[0027] The heat transfer medium is preferably a thermal oil, but other heat transfer mediums such as high-pressure steam or gas at about 400°C can also be used. A mixture of diphenyl oxide and biphenyl can be suitably used as the heat transfer oil. However, other types of heat transfer oils may also be used as long as they have good chemical stability under the temperature conditions used as the heat source for the dehydrogenation reaction.

[0028] The steam generating section 8B is configured to generate steam to be supplied to the distillation section 3C. The steam generating section 8B is configured to heat water flowing through the steam supply line L8 by heat exchange with the thermal oil in the thermal oil transport line L7. The water on the steam supply line L8 downstream of the steam generating section 8B becomes high-temperature steam, and this steam is used as a heat source for the reboiler of the distillation section 3C. Note that the configuration of the steam generating section 8B is not limited to this, and for example, it may be configured to generate steam by heat exchange with high-temperature exhaust gas from the heating furnace 8A (not shown).

[0029] <Energy Reduction Effect> As described above, in the dehydrogenation system 1A, by distilling the liquid separated by the first separation section 3A (i.e., a product in which the amount of toluene is reduced by about 80% and heavy components (high-boiling point components) are concentrated), the amount of steam used in the distillation column 34 can be reduced, for example, compared to distilling a liquid containing almost all of the toluene. This reduces the energy required for distillation. That is, when the heavy components are separated by distillation without the first separation section 3A, the throughput in the distillation section 3C is greater than when the first separation section 3A is provided. Therefore, by adopting the configuration of this embodiment, the energy required for distilling and separating the heavy components can be reduced. Furthermore, by mixing the toluene recovered in the distillation column 34 with the toluene downstream of the second separator 32B via the confluence line L6, it is also possible to reduce the loss of toluene that would otherwise be removed together with impurities such as heavy components.

[0030] In this way, the energy required to remove impurities such as heavy components is significantly reduced, making it possible to effectively remove heavy components even in the endothermic dehydrogenation system 1A. In particular, since heavy components are believed to be more likely to be generated in the dehydrogenation system 1A than in the hydrogenation system 1B, being able to immediately remove heavy components generated in the dehydrogenation system 1A contributes to the overall optimization of the hydrogen supply chain.

[0031] The distillation column 34 may have a built-in heater, but in this embodiment, steam generated in the steam generating section 8B is supplied to the distillation column 34 via the steam supply line L8. Therefore, heat from the heating furnace 8A is stably supplied to the distillation column 34. As a result, there is no need to provide a separate heat source for the distillation column 34. However, the configuration for supplying heat from the heating furnace 8A to the distillation column 34 is not limited to this. For example, the heat of the heat transfer oil may be directly utilized in the reboiler of the distillation column 34 by extending the heat transfer oil transport line L7 to the vicinity of the distillation column 34.

[0032] <Other Embodiments> In the above-described embodiment, the separation unit 3 of the dehydrogenation system 1A includes the first separation unit 3A, the second separation unit 3B, and the distillation unit 3C, but when the focus is on the purpose of efficiently removing heavy components in the dehydrogenation system 1A, it can be said that it is sufficient to include the first separation unit 3A and the distillation unit 3C. By adopting a configuration in which a small amount of aromatic compounds containing a large amount of heavy components are separated as a liquid-phase product, and then the aromatic compounds and heavy components are separated by distillation, it is possible to reduce the energy required for distillation separation.

[0033] Alternatively, instead of adjusting the flow rate of the mixed product flowing into the bypass line L3, the temperature of the dehydrogenation reaction mixed product separated into gas and liquid in the first separator 32A may be controlled by controlling the cooling capacity of the first cooler 31A based on the detected value of a thermometer provided in the first separation section 3A. It is advisable to select an appropriate method for stably adjusting the temperature of the mixed product separated into gas and liquid in the first separation section 3A within the desired temperature range. The condensation rate in the first cooler 31A can be controlled not only by temperature but also by appropriately adjusting the pressure.

[0034] The organic hydride that is the reactant of the dehydrogenation reaction in dehydrogenation system 1A is not limited to methylcyclohexane, but may be a monocyclic hydrogenated aromatic compound such as cyclohexane, a bicyclic hydrogenated aromatic compound such as tetralin, decalin, or methyldecalin, or a tricyclic hydrogenated aromatic compound such as tetradecahydroanthracene, either singly or as a mixture of two or more. Taking into consideration the convenience of storage and transportation, it is advisable to select an organic hydride that can be handled as a stable liquid at room temperature and normal pressure.

[0035] The aromatic compounds generated together with hydrogen in the dehydrogenation reaction of the dehydrogenation system 1A are not limited to toluene, and depending on the type of organic hydride, for example, monocyclic aromatic compounds such as benzene and xylene, bicyclic aromatic compounds such as naphthalene, tetralin and methylnaphthalene, and tricyclic aromatic compounds such as anthracene can be used alone or as a mixture of two or more types.

[0036] The dehydrogenation reactor 23 is not limited to a fixed-bed multi-tubular heat exchange reactor, and an adiabatic reactor may also be used. The adiabatic reactor may have a known configuration in which a catalyst is packed in a catalytic reaction vessel lined with a heat insulating material. Regarding the reactor arrangement, the reactor may be configured as a single reactor, or may be configured as an array of multiple reactor stages.

[0037] In general, heavy components (impurities) that can poison the hydrogenation catalyst or dehydrogenation catalyst in the hydrogen storage and transport system 1 include, when the aromatic compound is a monocyclic aromatic compound such as toluene or benzene, polymerization products of dimers, trimers, or higher of six-membered ring compounds and polymerization products of dimers, trimers, or higher of five-membered ring compounds. Furthermore, when the aromatic compound is a bicyclic aromatic compound such as naphthalene, in addition to the polymerization products described above, polymerization products of dimers, trimers, or higher of bicyclic aromatic compounds are also considered. The heavy components are not limited to those described above. As examples of heavy components, the boiling point of bicyclic compounds of bicyclohexyls is 235°C for bicyclohexyls without alkyl groups, and 240°C or higher for bicyclohexyls with alkyl groups. Furthermore, the boiling points of polymerized bicyclopentanes of five-membered rings and bicyclic compounds formed by polymerizing five-membered and six-membered rings, which are thought to be undetectable due to their small amounts, are both 190°C or higher. In any case, the heavy components have a higher boiling point than toluene, and therefore can be said to have the property of being easily and suitably removed by the first separation section 3A and the distillation section 3C.

[0038] Furthermore, even if waste occurs, such as toluene being removed along with the heavy components, the loss is smaller than if methylcyclohexane were wasted. This is because wasting methylcyclohexane would also result in wasting the produced hydrogen. Therefore, performing the heavy component removal operation on the dehydrogenation system 1A side is advantageous, assuming that some raw material loss will occur.

[0039] 1: Hydrogen storage and transportation system, 1A: Dehydrogenation system, 1B: Hydrogenation system, 2: Dehydrogenation reaction section, 3: Separation section, 3A: First separation section, 3B: Second separation section, 3C: Distillation section, 4A: Methylcyclohexane tank, 4B: Methylcyclohexane tank, 5A: Toluene tank, 5B: Toluene tank, 6: Hydrogenation reaction section, 7: Separation section, 8: Heating section, 8A: Heating furnace, 8B: Steam generation section, 21: Evaporator, 22: superheater, 23: dehydrogenation reactor, 31A: first cooler, 31B: second cooler, 31C: third cooling section, 32A: first separator, 32B: second separator, 33: flow rate control valve, 34: distillation column, L1: raw material supply line, L2: reaction product supply line, L3: bypass line, L4: vapor phase line, L5: liquid phase line, L6: joining line, L7: heat transfer oil transport line, L8: steam supply line

Claims

1. A dehydrogenation system for desorbing hydrogen from hydrogenated aromatic compounds, comprising a dehydrogenation reaction unit, a first separation unit, and a second separation unit, wherein the dehydrogenation reaction unit is configured to produce a mixed product containing hydrogen, aromatic compounds, and heavy components from the hydrogenated aromatic compounds by a dehydrogenation reaction, the first separation unit is configured to separate a portion of the aromatic compounds and the heavy components as liquid-phase products from the mixed product of the dehydrogenation reaction unit by gas-liquid separation, and the second separation unit is configured to separate the gas-phase product of the first separation unit into hydrogen and the aromatic compounds by gas-liquid separation.

2. A dehydrogenation system according to claim 1, further comprising a distillation section configured to separate the liquid phase product of the first separation section into the aromatic compounds and the heavy components by distillation, wherein the aromatic compounds separated by distillation are mixed with the aromatic compounds separated in the second separation section, and the heavy components contained in the aromatic compounds after mixing are 100 ppm by weight or less.

3. A dehydrogenation system according to claim 2, further comprising a heating section, the heating section being configured to comprise a reaction heat supply section that heats a heat medium that supplies heat to the dehydrogenation reaction section, and a steam generation section that generates steam to be supplied to the distillation section.

4. A dehydrogenation system according to any one of claims 1 to 3, wherein the temperature of the mixed product separated into gas and liquid in the first separation section is maintained within a range of 80°C to 150°C.

5. A dehydrogenation system according to any one of claims 1 to 3, wherein the weight of the liquid phase product separated in the first separation section is 5 to 20% of the total weight of the mixed product.

6. A dehydrogenation system according to any one of claims 1 to 3, wherein the heavy fraction contains one or more bicyclic or polycyclic compounds selected from biphenyl, bicyclohexyl, 4,4-dimethylbicyclohexyl, and 3,3-dimethylbicyclohexyl.

7. A dehydrogenation system for hydrogenated aromatic compounds, comprising a dehydrogenation reaction section, a first separation section, and a distillation section, wherein the dehydrogenation reaction section is configured to produce a mixed product containing hydrogen, aromatic compounds, and heavy components from the hydrogenated aromatic compounds by a dehydrogenation reaction, the first separation section is configured to separate a portion of the aromatic compounds and the heavy components as liquid-phase products from the mixed product of the dehydrogenation reaction section by gas-liquid separation, and the distillation section is configured to separate the liquid-phase product of the first separation section by distillation into the aromatic compounds and the heavy components.

8. A hydrogen storage and transportation system comprising: the dehydrogenation system according to any one of claims 1 to 3; and a hydrogenation system, wherein the hydrogenation system is configured to produce a hydrogenated aromatic compound from the aromatic compound and hydrogen separated by the dehydrogenation system.

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