JP2016013937A - Method for producing hydrogen donor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a hydrogen donor which enables efficient production of a hydrogen donor by using hydrogen obtained from methane hydrate as a raw material, and can reduce carbon dioxide emissions.SOLUTION: The method for producing a hydrogen donor comprises: a methane recovery step of recovering methane from methane hydrate by using carbon dioxide; a modification step of obtaining a synthesis gas containing hydrogen and carbon monoxide by reacting methane recovered in the methane recovery step with a gas containing oxygen; a shift reaction step of obtaining a gas containing hydrogen and carbon dioxide by reacting carbon monoxide contained in the synthesis gas obtained in the modification step with water; a carbon dioxide separation step of separating carbon dioxide from the gas containing hydrogen and carbon dioxide obtained in the shift reaction step; a hydrogenation step of obtaining a hydrogen donor by reacting the gas from which carbon dioxide has been separated in the carbon dioxide separation step and which contains hydrogen, with a hydrogen storage body; and a carbon dioxide circulation step of circulating carbon dioxide separated in the carbon dioxide separation step into the methane recovery step to serve as carbon dioxide used in the methane recovery step.

Description

  The present invention relates to a method for manufacturing a hydrogen supply body, in which a hydrogen supply body is manufactured by hydrogenating a hydrogen storage body using hydrogen obtained from methane hydrate as a raw material.

  In order to store and transport the hydrogen necessary for fuel cells, etc., the so-called Organic Chemical Hydride Method is known in which aromatic compounds such as toluene are hydrogenated to hydrogenated aromatic compounds such as methylcyclohexane. It has been. By reacting hydrogen with an aromatic compound to convert it to a hydrogenated aromatic compound, hydrogen in the gaseous state can be fixed as a hydrogenated aromatic compound in the liquid state at room temperature and pressure, and the hydrogen can be stored and transported in the liquid state can do.

  In such an organic chemical hydride method, carbon monoxide contained in the resultant synthesis gas is obtained by obtaining a synthesis gas containing carbon monoxide and hydrogen by a reforming reaction of natural gas containing methane as hydrogen in the hydrogenation reaction. There is a technique of converting hydrogen to carbon dioxide by a shift reaction in which water is reacted with water and using the obtained hydrogen (see Patent Document 1).

JP 2011-207641 A JP-A-6-71161

"Substitution rate of methane and CO2 in methane hydrate", Journal of the Japan Institute of Energy, Vol. 79, No. 10 (2000), 1011-1018 “Replacement rate of methane in methane hydrate with CO 2”, “High Pressure Science and Technology”, Vol. 12, no. 1 (2002), pp. 56-61

  However, natural gas is finite and it is desirable to produce hydrogen from methane sources other than methane contained in natural gas.

  Here, the technique which can obtain methane from methane hydrate is disclosed (refer patent document 2, nonpatent literature 1, and nonpatent literature 2). Specifically, in these documents, as a countermeasure to the global warming problem, methane hydrate is used to dispose of carbon dioxide generated by the use of fossil fuels and carbon dioxide contained in combustion exhaust gas discharged from power plants. By injecting carbon dioxide into the rate to replace methane and carbon dioxide, carbon dioxide is fixed as carbon dioxide hydrate and methane is produced.

  Methane hydrate is present in a large amount on the seabed and the like near Japan, and it would be very beneficial if this methane hydrate could be used.

  Therefore, combining the above technologies, that is, producing hydrogenated aromatic compounds by the reforming reaction, shift reaction and organic chemical hydride method using methane generated when disposing carbon dioxide using methane hydrate as the methane source It is possible.

  However, in order to produce methane from methane hydrate, it is necessary to supply carbon dioxide. However, in general, the bottom of the seabed, etc. Since it exists at a position far from the methane hydrate layer existing in the area, transport and storage over a long distance is required, resulting in a problem of poor efficiency. On the other hand, since carbon dioxide generated by the shift reaction causes global warming, it is desirable to suppress carbon dioxide emissions.

  In view of these problems, the present invention provides a method for producing a hydrogen supplier that can efficiently produce a hydrogen supplier using hydrogen obtained from methane hydrate as a raw material, and that can suppress carbon dioxide emissions. The purpose is to do.

  As a result of diligent research, the inventors of the present invention have made a shift when producing a hydrogen supplier through a sequence of methane recovery from methane hydrate, methane reforming reaction, shift reaction, and hydrogen storage hydrogenation reaction. The inventors have found that the above object can be achieved by separating carbon dioxide from the gas obtained by the reaction and recovering methane from methane hydrate using the separated carbon dioxide, thereby completing the present invention.

  Such a method for producing a hydrogen supplier of the present invention includes a methane recovery step of recovering methane from methane hydrate using carbon dioxide, and reacting the methane recovered in the methane recovery step with a gas containing oxygen to generate hydrogen. And a reforming step for obtaining a synthesis gas containing carbon monoxide, and a shift reaction step for obtaining a gas containing hydrogen and carbon dioxide by reacting carbon monoxide contained in the synthesis gas obtained in the reforming step with water. A carbon dioxide separation step for separating carbon dioxide from the gas containing hydrogen and carbon dioxide obtained in the shift reaction step; and a gas containing hydrogen separated from the carbon dioxide in the carbon dioxide separation step and reacted with a hydrogen storage body. A hydrogenation step for obtaining a hydrogen supplier, and carbon dioxide separated in the carbon dioxide separation step is circulated in the methane recovery step and used in the methane recovery step. It characterized by having a carbon dioxide circulating step of the carbon.

  It is preferable to have a heat circulation step in which the reaction heat generated in the hydrogenation step is circulated to the methane recovery step and used in the methane recovery step.

  Moreover, in the said methane collection | recovery process, it is preferable to decompose | disassemble methane hydrate, collect | recover methane, and produce | generate a carbon dioxide hydrate.

  The reforming step may be performed by a direct contact partial oxidation method.

  The reforming step, the shift reaction step, the carbon dioxide separation step, and the hydrogenation step are preferably performed offshore.

  According to the present invention, a methane hydrate recovery, a methane reforming reaction, a shift reaction, and a hydrogen storage hydrogenation reaction are sequentially performed to produce a hydrogen supplier, which is obtained by a shift reaction. By separating carbon dioxide from gas and using this separated carbon dioxide to recover methane from methane hydrate, it is possible to obtain methane without supplying carbon dioxide from outside the system. Therefore, it is not necessary to transport and store carbon dioxide over a long distance, and the hydrogen supplier can be manufactured efficiently. In addition, since carbon dioxide generated by the shift reaction is used to recover methane from methane hydrate and converted to carbon dioxide hydrate, the amount of carbon dioxide emitted can be suppressed. This carbon dioxide circulation is very well balanced in terms of stoichiometry, and a sufficient amount of carbon dioxide can be circulated and used. Furthermore, by using the reaction heat generated in the hydrogenation reaction as the reaction heat in the recovery of methane from methane hydrate, the production of methane from methane hydrate can be promoted.

It is a schematic diagram which shows an example of the hydrogen supply body manufacturing equipment which can apply the manufacturing method of the hydrogen supply body of this invention. It is typical sectional drawing which shows an example of the methane collection | recovery means which performs a methane collection | recovery process. It is a schematic diagram which shows the other example of the hydrogen supply body manufacturing equipment which can apply the manufacturing method of the hydrogen supply body of this invention.

  The method for producing a hydrogen supplier of the present invention includes a methane recovery step of recovering methane from methane hydrate using carbon dioxide, and reacting the methane recovered in the methane recovery step with a gas containing oxygen to generate hydrogen and A reforming step for obtaining a synthesis gas containing carbon oxide, a shift reaction step for reacting carbon monoxide contained in the synthesis gas obtained in the reforming step with water to obtain a gas containing hydrogen and carbon dioxide, and a shift A carbon dioxide separation step for separating carbon dioxide from a gas containing hydrogen and carbon dioxide obtained in the reaction step, and a hydrogen supplier by reacting the gas containing hydrogen separated from the carbon dioxide in the carbon dioxide separation step with a hydrogen storage body. And a carbon dioxide circulation system that circulates the carbon dioxide separated in the carbon dioxide separation step to the methane recovery step to form carbon dioxide used in the methane recovery step With the door.

  Specifically, first, methane is recovered from methane hydrate using carbon dioxide (methane recovery step).

  Methane hydrate is a hydrate of methane, and is a solid crystal having a structure in which methane molecules are trapped in a cage-like lattice formed of water molecules. Also, methane hydrate is often present in layers at low temperatures and high pressures, for example, in the ground at about 100 to 1000 m below the seabed.

  Carbon dioxide hydrate is a compound in which methane is converted to carbon dioxide in the above methane hydrate, and is a hydrate of carbon dioxide. Carbon dioxide molecules are trapped in a cage-like lattice formed of water molecules. It is a solid crystal having the structure. Carbon dioxide hydrate can then exist at a lower pressure than methane hydrate. That is, carbon dioxide hydrate is more stable than methane hydrate.

As described above, since carbon dioxide hydrate is more stable than methane hydrate and exists at a lower pressure than methane hydrate, for example, a condition in which methane hydrate can exist in the presence of methane hydrate. By adding carbon dioxide at a lower pressure and allowing carbon dioxide hydrate to exist, methane hydrate is decomposed to produce methane and carbon dioxide hydrate is produced. That is, as shown by the following formula (1), methane contained in methane hydrate is replaced with carbon dioxide. Specifically, for example, by injecting carbon dioxide into methane hydrate such as the methane hydrate layer contained in the ground and reducing the pressure until methane hydrate can no longer exist, methane hydrate decomposes and methane is produced In addition, carbon dioxide is taken in instead of methane to produce carbon dioxide hydrate. In formula (1), CH ₄ · nH ₂ O is methane hydrate, CO ₂ · nH ₂ O is carbon dioxide hydrate, and n represents a hydration number and is usually 6 to 7.
CH ₄ · nH ₂ O + CO ₂ → CO ₂ · nH ₂ O + CH ₄ (1)

  Here, as shown in the formula (1), 1 mole of methane is generated by using 1 mole of carbon dioxide stoichiometrically. Accordingly, a large amount of carbon dioxide is required to obtain a sufficient amount of methane to produce a hydrogen supplier. As a carbon dioxide source used in this reaction, carbon dioxide generated by using fossil fuel or carbon dioxide contained in combustion exhaust gas discharged from a power plant or the like can be used. ) And the power plant are located far from the methane hydrate layer that exists in the ground. Therefore, it is necessary to transport and store carbon dioxide from fossil fuel consumption areas and power plants. However, in the method for producing a hydrogen supplier of the present invention, carbon dioxide generated in the subsequent shift reaction step is used as carbon dioxide used in this methane recovery step. A storage body can be manufactured. Theoretically, carbon dioxide generated in the shift reaction step can be prevented from being discharged, and the amount of carbon dioxide generated in the shift reaction can be suppressed.

  A specific method for recovering methane from methane hydrate using carbon dioxide is not particularly limited, and examples thereof include methods described in Patent Document 2, Non-Patent Document 1, and Non-Patent Document 2. When the methane hydrate layer contains a substance other than methane hydrate, lower hydrocarbons (hydrocarbons having about 2 to 4 carbon atoms) other than methane may be obtained in the methane recovery step.

  Next, the methane recovered in the methane recovery step is reacted with a gas containing oxygen to obtain a synthesis gas containing hydrogen and carbon monoxide (reforming step).

For example, air can be used as the gas containing oxygen. Although it may be used as a gas containing oxygen obtained by an oxygen production apparatus such as a cryogenic separation that produces oxygen from air, the use of an oxygen production apparatus such as a cryogenic separation will increase the equipment and cost. Therefore, it is preferable to use air that can reduce the equipment and reduce the cost. Here, main components other than oxygen contained in the air are an inert gas such as nitrogen and carbon dioxide, and the latter stage of the reforming process is a shift reaction process, a carbon dioxide separation process, and a hydrogenation process. An inert gas such as nitrogen does not hinder the subsequent reaction. Further, carbon dioxide is not preferable because a reverse reaction of the shift reaction (CO ₂ + H ₂ → CO + H ₂ O) is caused by the hydrogenation reaction catalyst in the hydrogenation step. However, since it is separated in the carbon dioxide separation step performed between the shift reaction step and the hydrogenation step, it is difficult to inhibit the hydrogenation step. Therefore, in the present invention, air can be used as the gas containing oxygen to be reacted in the reforming step.

A reforming reaction performed in the reforming step to produce a synthesis gas containing hydrogen and carbon monoxide by reacting methane and oxygen, that is, a partial oxidation reaction of methane is represented by the following formula (2). In addition, reaction shown by this Formula (2) is a reaction (following Formula (2-1)) which produces | generates a carbon dioxide and water (steam) from methane and oxygen, and the produced | generated carbon dioxide and water (steam) are respectively It is a reaction in which reactions (reactions (2-2-1) and (2-2-2) below) that react with methane occur almost simultaneously.
CH ₄ + 1 / 2O ₂ → CO + 2H ₂ (2)
CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O (2-1)
CH ₄ + H ₂ O → CO + 3H ₂ (2-2-1)
CH ₄ + CO ₂ → 2CO + 2H ₂ (2-2-2)

  As described above, the reforming step is not particularly limited as long as a synthesis gas containing carbon monoxide and hydrogen can be obtained by reacting methane and oxygen. For example, the direct contact partial oxidation method (D-CPOX) : Direct-Catalytic Partial Oxidation) and Auto Thermal Reforming (ATR). In the autothermal reforming method, a part of methane is burner-burned by adding oxygen or air, and the generated high-temperature combustion gas is reformed through a catalyst layer, that is, carbon dioxide and water by combustion of methane. These are further reacted with methane in the catalyst layer to produce hydrogen and carbon monoxide. The direct contact partial oxidation method is, for example, a method described in JP-A-2005-199263, in which methane is partially oxidized with oxygen (formula (2)) and reformed in the presence of a catalyst. It is.

  An apparatus for performing partial oxidation of methane, such as an apparatus for performing D-CPOX or an apparatus for performing ATR, particularly an apparatus for performing D-CPOX, is relatively compact, and thus can reduce the installation area. Therefore, for example, it is suitable for manufacturing offshore where a small installation area is required. In addition, as described above, in the partial oxidation reaction of methane, part of the methane is burned with oxygen, and the generated carbon dioxide and water are used to reform the methane, so that combustion heat can be used and energy efficiency is high. .

In the reforming step, the catalyst and reaction conditions are specified as described in, for example, JP-A-2005-199263, specifically, alkaline earth metal oxidation containing magnesium (Mg) as a catalyst. By using a catalyst supporting a Group VIII metal on a solid support and performing direct catalytic partial oxidation of methane under the reaction conditions of oxygen and methane contact time of 5 × 10 ⁻⁴ to 2 × 10 ⁻² [sec], the formula Only the reaction of the above formula (2) that suppresses the reaction of (2-1) and suppresses complete oxidation in the middle can be caused.

  As the reforming step, the reforming reaction of methane by oxidation such as a direct contact partial oxidation method or an autothermal reforming method has been described above. However, reforming by steam or reforming by carbon dioxide (carbon dioxide gas) may be used. In the reforming of methane with steam, steam is added to methane to cause the reaction of formula (2-2-1). In reforming with carbon dioxide, carbon dioxide is added to methane to cause the reaction of formula (2-2-2). However, since the reaction is an endothermic reaction in the reforming with steam or the reforming with carbon dioxide, it is necessary to supply heat necessary for the reforming reaction from the outside, and the manufacturing apparatus becomes large.

Next, carbon monoxide contained in the synthesis gas obtained in the reforming step is reacted with water to obtain a gas containing hydrogen and carbon dioxide (shift reaction step). The shift reaction step is a step of performing a shift reaction in which carbon monoxide contained in the synthesis gas is reacted with water (water vapor) to convert it into hydrogen and carbon dioxide, and the reaction of the following formula (3) occurs.
CO + H ₂ O → H ₂ + CO ₂ (3)

  The shift reaction step can be performed by a CO converter or the like, for example, by the production method described in Patent Document 1.

Next, carbon dioxide is separated from the gas containing hydrogen and carbon dioxide obtained in the shift reaction step (carbon dioxide separation step). The method for separating carbon dioxide is not particularly limited. For example, a normal carbon dioxide separation method such as a chemical absorption method, a physical absorption method, or a membrane separation can be applied. The chemical absorption method is a method of absorbing carbon dioxide using an alkaline solution such as an amine that can selectively dissolve carbon dioxide as an absorbing solution. The absorption reaction of carbon dioxide by the aqueous amine solution is, for example, the following formula (4). In the following formula (4), R represents a hydrocarbon group. The physical absorption method is a method of absorbing carbon dioxide using methanol, polyethylene glycol or the like as an absorption liquid. In these methods, a large amount of heat energy is required for the recovery of carbon dioxide from the absorbing solution. The membrane separation method is a method of separating carbon dioxide with a separation membrane such as an organic polymer membrane such as a polyimide membrane, a polyvinyl alcohol membrane, or a cellulose acetate membrane, or an inorganic membrane such as a zeolite membrane, a carbon membrane, or a ceramic porous membrane. . Membrane separation is basically a low energy method that utilizes only pressure. Carbon dioxide does not have to be completely separated, but the remaining carbon dioxide is an inhibiting factor for the subsequent hydrogenation reaction. Therefore, it is preferable to separate carbon dioxide as much as possible. For example, the concentration of carbon dioxide contained in the gas containing hydrogen obtained by separating carbon dioxide in the carbon dioxide separation step is preferably 1.0 vol% or less.
R—NH ₂ + CO ₂ + H ₂ O → R—NH ₃ ⁺ + HCO ₃ ⁻ (4)

  Next, carbon dioxide is separated in the carbon dioxide separation step, and a gas containing hydrogen is reacted with the hydrogen storage body to obtain a hydrogen supply body (hydrogenation step).

  In the hydrogenation process, a gas obtained by separating carbon dioxide from a gas containing hydrogen and carbon dioxide in the carbon dioxide separation process, that is, a gas containing hydrogen is reacted with the hydrogen storage body to hydrogenate the hydrogen storage body. To obtain a hydrogen supplier. Hydrogen to be reacted in the hydrogenation process is hydrogen generated in the reforming process or hydrogen generated in the shift reaction process. Hydrogenation is performed using a hydrogenation catalyst (hydrogenation catalyst) as described in, for example, JP-A-2007-269522. In this way, hydrogen is reacted with a hydrogen storage body and converted into a hydrogen supply body, thereby fixing hydrogen in a gaseous state as a hydrogen supply body in a liquid state at normal temperature and normal pressure, and hydrogen in a liquid state at normal temperature and normal pressure. It will be possible to store and transport.

  The hydrogen supplier thus obtained is more suitable for storage and transportation when it is in a liquid state at normal temperature and pressure than when it is in the form of hydrogen as a gas. The hydrogen can be used by carrying out a reaction to desorb hydrogen from the hydrogen supplier at the hydrogen consuming place. The reaction for desorbing hydrogen from the hydrogen supplier can be performed by adding a dehydrogenation catalyst or the like as described in, for example, JP-A-2007-269522. Examples of the use of hydrogen include a fuel cell.

Examples of the hydrogen store include monocyclic aromatic compounds such as toluene and benzene, and aromatic compounds having two or more rings such as naphthalene. The hydrogenation reaction when toluene is used as the hydrogen storage body is shown in the following formula (5). When toluene is used as the hydrogen reservoir, a catalyst used for the production of cyclohexane by hydrogenation of normal benzene can be used, and a catalyst in which Ni is supported on an inorganic oxide such as diatomaceous earth, silica, silica alumina, etc. Can do. Examples of the hydrogen supplier obtained by reacting hydrogen with these hydrogen storage bodies include hydrogenated aromatic compounds such as methylcyclohexane and cyclohexane. In addition to aromatic compounds, organic compounds other than aromatic compounds, and hydrogen storage bodies such as alloys, borides, metal amide metal hydrides, and metal storage alloys may be used.
_{CH 3 -C 6 H 5 + 3H} 2 → CH 3 -C 6 H 11 (5)

  On the other hand, the carbon dioxide separated in the carbon dioxide separation step is circulated in the methane recovery step to be used as carbon dioxide used in the methane recovery step (carbon dioxide circulation step). In addition, when carbon dioxide was separated by the chemical absorption method or the physical absorption method in the carbon dioxide separation step, the carbon dioxide absorbed in the absorption liquid was taken out from the absorption liquid before or during the carbon dioxide circulation step and taken out. Carbon dioxide may be used in the methane recovery step.

  Note that methane hydrate is often present in layers below the seabed, so the reforming process, shift reaction process, carbon dioxide separation process, and hydrogenation process are performed on the methane hydrate layer, that is, offshore. Or on the ground surface. For example, a reforming process, a shift reaction process, a carbon dioxide separation process, and a hydrogenation process are performed in a movable floating plant (floating plant) installed on a ship floating on the ocean, that is, an offshore plant.

  Thus, in the method for producing a hydrogen supplier of the present invention, since carbon dioxide generated in the shift reaction step is circulated into carbon dioxide used in the methane recovery step, long-distance transportation of carbon dioxide is unnecessary, and efficiency A hydrogen storage body can be manufactured well. At the same time, the emission of carbon dioxide generated by the shift reaction can be suppressed.

  In the method for producing a hydrogen supplier of the present invention, 1 mol of methane is generated from 1 mol of carbon dioxide in the methane recovery step (formula (1)), and 1 mol of 1 mol of methane is generated in the reforming step. Carbon oxide is produced (formula (2)), and 1 mol of carbon dioxide is produced from 1 mol of carbon monoxide in the shift reaction step (formula (3)). When 1 mol of carbon dioxide generated in this shift reaction step is circulated to the methane recovery step and used in the methane recovery step, 1 mol of methane is generated again. In other words, the method for producing a hydrogen supplier of the present invention is one that circulates and uses an amount of carbon dioxide that is very stoichiometrically balanced and that is not excessive or insufficient.

  Moreover, it is preferable to use the heat of reaction generated in the hydrogenation step in the methane recovery step. That is, it is preferable to have a heat circulation step in which reaction heat generated in the hydrogenation step is circulated to the methane recovery step and used in the methane recovery step. Carbon dioxide hydrate is more thermodynamically stable than methane hydrate. The reaction in which methane hydrate decomposes to produce methane is an endothermic reaction, and the reaction in which carbon dioxide hydrate is generated from carbon dioxide is an exothermic reaction. And the heat of formation of carbon dioxide hydrate is larger than the reaction heat required for the decomposition of methane hydrate, which is an endothermic reaction. Therefore, in an environment where methane hydrate exists, if carbon dioxide is injected into methane hydrate and decompression is performed as necessary, methane hydrate is decomposed to produce methane and carbon dioxide hydrate is produced. However, these methane hydrate decomposition and carbon dioxide hydrate formation reactions (that is, reactions that replace methane and carbon dioxide in methane hydrate) are very slow occurring only at the interface of methane hydrate and carbon dioxide. It is a reaction. Accordingly, in order to replace a sufficient amount of methane and carbon dioxide in methane hydrate, a great amount of energy (time and heat of reaction) is required, which can be a major obstacle to practical use from the viewpoint of cost and the like.

  On the other hand, since the hydrogenation reaction is an exothermic reaction, reaction heat is generated in the hydrogenation process. Therefore, by using the reaction heat generated in the hydrogenation process as the reaction heat necessary for the decomposition of methane hydrate, the speed of the decomposition reaction of methane hydrate can be increased and the replacement of methane with carbon dioxide proceeds. Carbon dioxide hydrate can also be generated quickly. Therefore, practical application is easy.

  A hydrogen supply production facility to which the method for producing a hydrogen supply of the present invention can be applied will be described with reference to FIG. FIG. 1 is a schematic diagram showing an example of a hydrogen supplier manufacturing facility to which the method for manufacturing a hydrogen supplier of the present invention can be applied.

  As shown in FIG. 1, the hydrogen supplier manufacturing facility 10 includes a methane recovery unit 11 that recovers methane from methane hydrate while being supplied with carbon dioxide, and a methane recovery unit 11 that is supplied with gas containing oxygen. Oxidation reforming means 12 for reacting the discharged methane with oxygen to obtain a synthesis gas containing hydrogen and carbon monoxide, and steam contained in the synthesis gas discharged from the oxidation reforming means 12 Shift reaction means 13 for reacting carbon oxide with water to obtain a gas containing hydrogen and carbon dioxide, and carbon dioxide separation means 14 for separating carbon dioxide from the gas containing hydrogen and carbon dioxide discharged from the shift reaction means 13. The hydrogen storage body is supplied, and the carbon dioxide is separated by the carbon dioxide separation means 14 and the gas containing hydrogen is reacted with the hydrogen storage body to obtain a hydrogen supply body. Having a hydrogenation unit 15, the carbon dioxide circulating means 16 for circulating the carbon dioxide discharged from the carbon dioxide separation unit 14 to the methane recovery unit 11.

  An example of the methane recovery unit 11 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view showing an example of methane recovery means for performing the methane recovery step. As shown in FIG. 2, the methane recovery means 11 includes, for example, a carbon dioxide injection pipe 21 that penetrates from the sea surface to a methane hydrate layer existing deep in the sea bottom and injects carbon dioxide into the methane hydrate layer, and a carbon dioxide injection pipe 21. And a methane discharge pipe 22 that carries methane generated by decomposition of methane hydrate to the sea surface. Of course, the methane recovery means 11 may not be a double-structured pipe, and a pipe for supplying carbon dioxide and a pipe for recovering methane may be provided separately.

  Examples of the oxidation reforming means 12 include a D-CPOX apparatus that performs a direct contact partial oxidation method and an ATR apparatus that performs an autothermal reforming method. As a D-CPOX apparatus for performing the direct contact partial oxidation method, for example, Japanese Patent Application Laid-Open No. 2006-62925 and the like, a reaction tower (reactor) is filled with a catalyst, and methane and oxygen are reacted in the filled catalyst layer. Apparatus.

  Examples of the shift reaction means 13 include an apparatus capable of performing a shift reaction for generating hydrogen and carbon dioxide from normal carbon monoxide and water vapor, such as a CO converter.

  As the carbon dioxide separation means 14, a chemical absorption device using an absorption solution such as an alkaline solution, a physical absorption device using an absorption solution such as methanol or polyethylene glycol, a membrane separation device that separates carbon dioxide through a membrane, or A device that combines these is mentioned.

  The hydrogenation means 15 is an apparatus for producing a hydrogen supply body by reacting hydrogen supplied from the carbon dioxide separation means 14 with a hydrogen storage body. The hydrogenation means 15 may have a hydrogenation catalyst addition means for adding a hydrogenation reaction catalyst, if necessary.

  The carbon dioxide circulation means 16 is composed of, for example, a pipe that supplies the carbon dioxide separated by the carbon dioxide separation means 14 to the methane recovery means 11, and this pipe is connected to the carbon dioxide injection pipe 21 of the methane recovery means 11. .

  In addition, each means is connected with piping etc. in which conveyance means, such as a pump, were provided as needed, and it has the structure which can transfer the raw material and product in each means between each means.

  Since methane hydrate is often present in layers in the ground below the seabed, the hydrogen supplier production facility 10 is preferably an offshore plant.

  In such a hydrogen supplier manufacturing facility 10, first, carbon dioxide is injected into a methane hydrate layer from a carbon dioxide injection pipe 21 constituting the methane recovery means 11. Thereby, methane in the methane hydrate is replaced with carbon dioxide, so that methane is generated and carbon dioxide hydrate is generated. The produced methane is transported to the sea level via the methane discharge pipe 22. Methane carried on the sea surface is supplied to the oxidation reforming means 12 and reacts with oxygen contained in the air supplied to the oxidation reforming means 12 to generate synthesis gas containing carbon monoxide and hydrogen. . Subsequently, the synthesis gas containing carbon monoxide and hydrogen produced by the oxidation reforming means 12 is supplied to the shift reaction means 13 and reacts with the water supplied to the shift reaction means 13 to contain hydrogen and carbon dioxide. Generate gas. The gas containing hydrogen and carbon dioxide discharged from the shift reaction means is supplied to the carbon dioxide separation means 14, and the carbon dioxide is separated and removed by the carbon dioxide separation means 14.

  The gas from which carbon dioxide has been separated and removed by the carbon dioxide separation means 14, that is, the gas containing hydrogen is supplied to the hydrogenation means 15, and in the presence of a hydrogenation catalyst added as necessary, the hydrogenation means. It reacts with a hydrogen storage body such as toluene supplied to 15 to produce a hydrogen storage body such as methylcyclohexane. Since the hydrogen storage body thus produced is usually in a liquid state at normal temperature and pressure, it is very easy to transport and store as compared with hydrogen in a gaseous state.

  On the other hand, the carbon dioxide separated by the carbon dioxide separation means 14 is supplied to the carbon dioxide injection pipe 21 constituting the methane recovery means 11 through the carbon dioxide circulation means 16. Carbon dioxide supplied to the carbon dioxide injection pipe 21 via the carbon dioxide circulation means 16 is injected into the methane hydrate layer, and replaces methane in the methane hydrate layer to generate methane and carbon dioxide hydrate. To do.

  Further, the hydrogen supply production apparatus to which the method for producing a hydrogen supply of the present invention can be applied may have a reaction heat circulation means for circulating reaction heat generated in the hydrogenation means 15 to the methane recovery means 11. FIG. 3 is a configuration in which the heat of reaction obtained by the hydrogenation means 15 is further circulated to the methane recovery means 11 in addition to the configuration of FIG. 1. The same configurations as those in FIG. Description is omitted.

  As shown in FIG. 3, the hydrogen supplier manufacturing apparatus 20 includes a cooling unit 17 that cools the hydrogenating unit 15 with cooling water, for example, as a reaction heat circulation unit. In the cooling means 17, the cooling water heated by cooling the hydrogenation means 15 is circulated again to the hydrogenation means 15 via a heat exchanger 18 provided in the middle of the carbon dioxide circulation means 16. This is a configuration. The reaction heat generated in the hydrogenation means 15 is supplied to the carbon dioxide injection pipe 21 constituting the methane recovery means 11 through the cooling water, the heat exchanger 18 and the carbon dioxide circulated in the carbon dioxide circulation means 16. Is done.

  Since the reaction for generating methane from the methane hydrate generated by the methane recovery means 11 is an endothermic reaction, the reaction heat obtained by the hydrogenation means 15 is supplied to the methane recovery means 11 to generate methane from the methane hydrate. Reaction can be promoted.

DESCRIPTION OF SYMBOLS 10, 20 Hydrogen supply body manufacturing equipment 11 Methane collection | recovery means 12 Methane oxidation reforming means 13 Shift reaction means 14 Carbon dioxide separation means 15 Hydrogenation means 16 Carbon dioxide circulation means 17 Cooling means 18 Heat exchanger

Claims (5)

A methane recovery process for recovering methane from methane hydrate using carbon dioxide,
A reforming step of reacting the methane recovered in the methane recovery step with a gas containing oxygen to obtain a synthesis gas containing hydrogen and carbon monoxide;
A shift reaction step of reacting carbon monoxide contained in the synthesis gas obtained in the reforming step with water to obtain a gas containing hydrogen and carbon dioxide;
A carbon dioxide separation step for separating carbon dioxide from a gas containing hydrogen and carbon dioxide obtained in the shift reaction step;
A hydrogenation step in which carbon dioxide is separated in the carbon dioxide separation step and a gas containing hydrogen is reacted with a hydrogen storage body to obtain a hydrogen supply body;
And a carbon dioxide circulation step for circulating the carbon dioxide separated in the carbon dioxide separation step into the methane recovery step to obtain carbon dioxide used in the methane recovery step.   The method for producing a hydrogen supplier according to claim 1, further comprising a heat circulation step of circulating the reaction heat generated in the hydrogenation step to the methane recovery step and using the heat in the methane recovery step.   The method for producing a hydrogen supplier according to claim 1 or 2, wherein in the methane recovery step, methane hydrate is decomposed to recover methane and to generate carbon dioxide hydrate.   The said reforming process is performed by the direct contact partial oxidation method, The manufacturing method of the hydrogen supply body as described in any one of Claims 1-3 characterized by the above-mentioned.   The method for producing a hydrogen supplier according to any one of claims 1 to 4, wherein the reforming step, the shift reaction step, the carbon dioxide separation step, and the hydrogenation step are performed offshore.

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