Hydrogen storage fuel and manufacturing method of the same

Abstract

To provide a hydrogen storage fuel improved in handling safety and in a form suitable for storage and transportation.SOLUTION: A hydrogen storage fuel is composed mainly of ammonia (NH3) which is made solid under normal temperature and normal pressure, with ammonia hydrate (NH3 (H2O)) and ammonia borane (NH3BH3) incorporated as unavoidable impurities. The ammonia (NH3(cr)) constituting the hydrogen storage fuel is produced as a crystalline solid by freezing a mixed aqueous solution prepared by dissolving ammonia (NH3) in water and adding boric acid (B3O2) to form a frozen solidified body and subjecting this frozen solidified body to freeze-drying thereby incorporating ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3) as unavoidable impurities.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrogen storage fuel that uses ammonia, which is a hydrogen-containing compound, and a method for producing the hydrogen storage fuel. [Background technology]

[0002] Traditionally, hydrogen has attracted attention as an energy source that reduces environmental damage. Ammonia (NH3), a hydrogen-containing compound that has a high content density per volume and mass and does not emit carbon dioxide (CO2) when burned, has attracted attention as a fuel for internal combustion engines and power generation systems.

[0003] Ammonia, a hydrogen-containing compound, is produced in large quantities at industrial levels by the Haber-Bosch process, which produces ammonia by directly reacting hydrogen with nitrogen using iron as a catalyst at 400-600°C and 200-1000 atm.

[0004] The Haber-Bosch process has problems such as the large amount of electrical energy required, and therefore alternative methods for synthesizing ammonia to the Haber-Bosch process have been proposed (Patent Document 1).

[0005] Patent Document 2 discloses an ammonia engine system that uses ammonia as fuel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 115582 Brochure [Patent Document 2] International Publication No. 2010 / 058807 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] Ammonia is a gas at room temperature and pressure. Ammonia, being a gas, can easily be inhaled into the body, irritating the mucous membranes of the respiratory organs and potentially inducing respiratory arrest due to shock. In addition, ammonia being inhaled into the body can increase the ammonia concentration in the blood of the body, potentially causing impaired consciousness.

[0008] As described above, gaseous ammonia is a substance that is extremely harmful to living organisms, and is difficult to store, manage, and transport, making it difficult to use it as a widely applicable energy carrier.

[0009] In addition, since ammonia liquefies at 20°C and 8.46 atm, it can be stored as a liquid by filling pressurized cylinders with it. However, liquid ammonia can cause blindness if it comes into contact with the eyes of a living body. Furthermore, liquid ammonia must be stored in a pressurized cylinder under pressure, which makes storage and transportation difficult.

[0010] Ammonia can be converted into a stable solid form by cooling it to −78° C. or lower under normal pressure.

[0011] However, in order to maintain a stable solid state of ammonia under normal pressure, it needs to be kept cooled to -78°C or below, which makes storage and transportation difficult, making it difficult to use ammonia as fuel for ammonia engine systems installed in automobiles and other vehicles used as a means of transportation.

[0012] Therefore, an object of the present invention is to provide a new hydrogen storage fuel that can solve the problems associated with ammonia, which is a hazardous substance to living organisms, difficult to store, and difficult to transport.

[0013] A further technical object of the present invention is to provide a hydrogen storage fuel that can be used safely and is in a form suitable for storage and transportation.

[0014] Other technical objects of the present invention will become more apparent from the following description with reference to the drawings. [Means for solving the problem]

[0015] The present invention was completed as a result of intensive research conducted by the present inventors in order to solve the above-mentioned technical problems. The inventors discovered that ammonia (NH3) becomes solid at room temperature and pressure by mixing ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3) as inevitable impurities into ammonia (NH3).

[0016] Therefore, the present invention is a solid hydrogen storage fuel, which is mainly composed of ammonia (NH3) that is solidified at room temperature and pressure and contains ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3) as unavoidable impurities.

[0017] This hydrogen storage fuel is produced through the following process.

[0018] First, a mixed aqueous solution is prepared by mixing boric acid (B3O2) with an aqueous solution in which ammonia (NH3) has been dissolved. Next, the mixed aqueous solution is frozen to prepare a frozen solid. The frozen solid is then freeze-dried to remove the water vapor (H2O(g)) remaining as a gas in the frozen solid and the boron compounds (BH(g), B2H6(g), B2O3(g)) contained as a gas, and obtain a solidified body in which the ammonia (NH3(cr)) in the frozen solid is concentrated. The concentrated and solidified ammonia (NH3(cr)) is solidified with ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3) mixed in as unavoidable impurities, and is used as a solid hydrogen storage fuel.

[0019] In the method of the present invention, the ammonia (NH3) in the frozen solidified body is solidified in a state where ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3) are mixed in as unavoidable impurities, and becomes a solid hydrogen storage fuel.

[0020] Then, the mixed aqueous solution obtained by mixing boric acid (B3O2) with an aqueous solution in which ammonia (NH3) is dissolved is cooled with liquid nitrogen and frozen into a solid.

[0021] Furthermore, the frozen solid is cooled with liquid nitrogen, decompressed, and freeze-dried to produce solid ammonia (NH3) containing unavoidable impurities such as ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3), and this solid is used as hydrogen storage fuel. Effect of the Invention

[0022] Since the hydrogen storage fuel according to the present invention is composed of solid ammonia, it can be safely stored and can also be easily transported.

[0023] The solidified hydrogen storage fuel can be used as a hydrogen energy carrier that can be widely and generally used, and can be provided as fuel for ammonia engine systems, ammonia power generation systems, and other ammonia-fueled equipment. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing a production apparatus used for producing hydrogen storage fuel according to the present invention. [Diagram 2] 1 is a photograph showing the appearance of solid ammonia produced by the method of the present invention. [Diagram 3] FIG. 1 is an X-ray diffraction diagram of solid ammonia produced by the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a hydrogen storage fuel and a method for producing the same according to the present invention will be described with reference to the drawings.

[0026] The present invention is a hydrogen storage fuel that uses ammonia (NH3) as a hydrogen storage medium. This hydrogen storage fuel is mainly composed of ammonia (NH3) that is mixed with ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3) as inevitable impurities and is solidified at room temperature and normal pressure. The ammonia that is mixed with ammonia hydrate and ammonia borane as inevitable impurities and freeze-dried is solidified at room temperature and normal pressure and maintains its solid state.

[0027] The ammonia that is solidified at room temperature and pressure and that constitutes the hydrogen storage material according to the present invention is produced using a production apparatus shown in FIG.

[0028] This manufacturing equipment comprises a reaction vessel 1 into which a mixed aqueous solution of ammonia, which is the raw material for solid ammonia, is poured, a vacuum exhaust tank 2 in which the reaction vessel 1 is housed and evacuated, and a first liquid nitrogen cooling tank 3 filled with liquid nitrogen. The vacuum exhaust tank 2 is installed in the first liquid nitrogen cooling tank 3, and is cooled together with the reaction vessel 1 by the liquid nitrogen filled in the first liquid nitrogen cooling tank 3.

[0029] The vacuum exhaust tank 2 housing the reaction vessel 1 is connected to the outside of the liquid nitrogen cooling tank 3 via an exhaust valve 4. The exhaust valve 4 is attached to hermetically seal the first liquid nitrogen cooling tank 3. The exhaust valve 4 opens and closes the vacuum exhaust tank 2 by operating an opening and closing valve provided inside.

[0030] A vacuum pump 5 is connected to the vacuum exhaust tank 2. A gas trap mechanism 6 is provided between the vacuum pump 5 and the vacuum exhaust tank 2. This gas trap mechanism 6 is installed in a second liquid nitrogen cooling tank 7, and is cooled by the liquid nitrogen filled in the second liquid nitrogen cooling tank 7.

[0031] The vacuum evacuation tank 2 and the gas trapping mechanism 6 are connected via a connecting pipe 8. One end of this connecting pipe 8 is connected to the vacuum evacuation tank 2 via the exhaust valve 4, and the other end passes through the second liquid nitrogen cooling tank 7 and is inserted into the gas trapping mechanism 6, thereby connecting the vacuum evacuation tank 2 and the gas trapping mechanism 6.

[0032] The vacuum pump 5 is connected to the gas trap mechanism 6 via a vacuum pump connecting pipe 9. One end of the vacuum pump connecting pipe 9 is connected to the vacuum pump 5, and the other end passes through the second liquid nitrogen cooling tank 7 and is inserted into the gas trap mechanism 6, thereby connecting the vacuum pump 5 and the exhaust gas trap mechanism 6.

[0033] Therefore, the inside of the vacuum exhaust tank 2 is suctioned and depressurized by the vacuum pump 5 via the gas trap mechanism 6. Then, the gas sucked from the vacuum exhaust tank 2 by driving the vacuum pump 5 is discharged to the outside of the vacuum exhaust tank 2 via the exhaust valve 4, introduced into the gas trap mechanism 6 via the connecting pipe 8, and cooled by the liquid nitrogen filled in the second liquid nitrogen cooling tank 7.

[0034] A process for producing solid ammonia using the production apparatus having the above-mentioned configuration will be described.

[0035] First, to produce solid ammonia, ammonia water and boric acid (B2O3) powder are prepared, and a mixed aqueous solution is made by mixing the boric acid powder into the ammonia water.

[0036] It is desirable to mix this mixed aqueous solution in an amount of 532 g of boric acid powder per 1 L of ammonia water containing 29 wt % ammonia by weight.

[0037] In addition, as long as the mixed aqueous solution is one that can be concentrated to solid ammonia using the production process for solid ammonia described below, it is possible to use ammonia water containing ammonia at an appropriate ratio, and further to appropriately select the mixing ratio of boric acid powder to this ammonia water.

[0038] Next, the mixed aqueous solution obtained by mixing ammonia water with boric acid powder is poured into the reaction vessel 1 housed in the vacuum exhaust tank 2 of the above-mentioned manufacturing apparatus. Next, the vacuum exhaust tank 2 is filled with liquid nitrogen, and the mixed aqueous solution in the reaction vessel 1 is cooled via the vacuum exhaust tank 2 and the reaction vessel 1. At this time, the mixed aqueous solution in the reaction vessel 1 is cooled to at least -78°C or lower, at which ammonia solidifies, and is frozen and solidified.

[0039] With the mixed aqueous solution in the reaction vessel 1 frozen and solidified, the exhaust valve 4 is opened and the vacuum pump 5 is driven to evacuate and reduce the pressure inside the vacuum exhaust tank 2. This evacuation is performed for 2-10 hours with the mixed aqueous solution frozen and solidified in the reaction vessel 1. When the vacuum exhaust tank 2 is evacuated and reduced in pressure for a predetermined time, freeze-drying is performed to discharge moisture (H2O(g)) remaining as a water vapor component in the frozen solidified material frozen and solidified in the reaction vessel 1, and boron compounds BH(g), B2H6(cr) and B2O3(g) remaining as gas components, to the outside of the frozen solidified material.

[0040] When the frozen solid is subjected to the freeze-drying process, water and boric acid compounds are discharged from the frozen solid, and the ammonia components are concentrated, inevitably producing solid ammonia (NH3(cr)) mixed with ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3).

[0041] The ammonia that is solidified by the inclusion of the unavoidable components ammonia hydrate and ammonia borane is stable at room temperature and normal pressure, i.e., the ammonia generated here maintains a solid state at room temperature and normal pressure.

[0042] This is believed to be due to the fact that ammonia hydrate and ammonia borane are mixed into the solid ammonia component as unavoidable components, as will be shown in the Examples described later.

[0043] The moisture and boron compounds discharged from the frozen solidified bodies frozen and solidified in the reaction vessel 1 to the outside are sucked by the vacuum pump 5 and exhausted to the outside of the vacuum exhaust tank 2 via the exhaust valve 4. The moisture as a water vapor component and the boron compounds as a gas component exhausted to the outside of the vacuum exhaust tank 2 are introduced into the gas trap mechanism 6 via a connecting pipe 8. The moisture and boric acid compounds introduced into the gas trap tank 6 are cooled and frozen by the liquid nitrogen filled in the second liquid nitrogen cooling tank 7, and are recovered as frozen boric acid water.

[0044] That is, the water vapor component and the boron compound gas component are condensed and frozen into a solid by cooling the gas trap mechanism 6 with liquid nitrogen. The water and boron compound discharged from the frozen solidified body can be easily taken out of the device by being solidified.

[0045] The solid ammonia produced here is configured as a hydrogen storage fuel in which hydrogen is stored, and is used as fuel for ammonia engine systems, ammonia power generation systems, and other ammonia-fueled equipment. EXAMPLES

[0046] An example of solid ammonia constituting the hydrogen storage fuel according to the present invention will be described below.

[0047] In the embodiment shown here, a mixed aqueous solution is prepared by mixing 160 mg of boric acid powder with 0.3 mL of ammonia water containing 29 wt % ammonia by weight ratio.

[0048] Next, the mixed aqueous solution is poured into a reaction vessel 1 housed in an evacuation tank 2 of a manufacturing apparatus having a configuration as shown in Fig. 1. Next, liquid nitrogen is filled into the evacuation tank 2, and the mixed aqueous solution in the reaction vessel 1 is cooled via the evacuation tank 2 and the reaction vessel 1. At this time, the mixed aqueous solution in the reaction vessel 1 is cooled to at least -78°C or lower at which ammonia solidifies, and is frozen and solidified.

[0049] With the mixed aqueous solution in the reaction vessel 1 frozen and solidified, the exhaust valve 4 is opened and the vacuum pump 5 is driven to evacuate and reduce the pressure inside the vacuum exhaust tank 2. This evacuation is performed for 8 hours with the mixed aqueous solution frozen and solidified in the reaction vessel 1. When the vacuum exhaust tank 2 is evacuated and reduced pressure for a predetermined time, the moisture (H2O(g)) remaining as a water vapor component in the frozen solidified material frozen and solidified in the reaction vessel 1 and the boron compounds BH(g), B2H6(cr) and B2O3(g) remaining as gas components are freeze-dried and discharged to the outside of the frozen solidified material.

[0050] Then, by subjecting the frozen solid to a freeze-drying process, moisture and boric acid compounds are expelled from the frozen solid, and the ammonia components in the frozen solid are concentrated, inevitably producing solid ammonia (NH3(cr)) mixed with ammonia hydrate (NH3(H2O)) and ammonia borane (NH3BH3).

[0051] The moisture and boron compounds discharged from the frozen solidified bodies frozen and solidified in the reaction vessel 1 to the outside are sucked by the vacuum pump 5 and exhausted to the outside of the vacuum exhaust tank 2 via the exhaust valve 4. The moisture as a water vapor component and the boron compounds as a gas component exhausted to the outside of the vacuum exhaust tank 2 are introduced into the gas trap tank 6 via the connecting pipe 8. The moisture and boric acid compounds introduced into the gas trap tank 6 are cooled and frozen by the liquid nitrogen filled in the second liquid nitrogen cooling tank 7, and are recovered as frozen boric acid water.

[0052] The ammonia produced here was confirmed to be a solid that precipitated as white crystals under normal temperature and pressure conditions, as shown in the photograph of its appearance in Figure 2. This ammonia was in powder form.

[0053] The solid ammonia obtained as white crystals was observed using an X-ray diffraction apparatus. The results are shown in Figure 3. As shown in Figure 3, the white crystals produced in this example showed a sharp solid ammonia peak. In addition to the peak of solid ammonia (NH3(cr)), the crystals also showed peaks of ammonia hydrate (NH3H2O(cr)) and ammonia borane (NH3BH3(cr)), which are unavoidable contaminants.

[0054] In this way, the solid ammonia obtained as a white crystalline substance is deemed to stably maintain a solid state at room temperature and pressure due to the inclusion of unavoidable components of ammonia hydrate and ammonia borane. [Industrial Applicability]

[0055] The hydrogen storage fuel in which the solid ammonia according to the present invention is used as a hydrogen storage medium, and the hydrogen sculpture fuel in which the solid ammonia produced by the method of the present invention is used as a hydrogen storage medium, can be used as fuel for ammonia engine systems, ammonia power generation systems, and other ammonia fuel devices. [Explanation of symbols]

[0056] 1 Reaction vessel 2 Vacuum Exhaust Chamber 3 First liquid nitrogen cooling tank 4 Exhaust valve 5. Vacuum Pump 6 Gas trap mechanism 7 Second liquid nitrogen cooling tank

Claims

1. A solid hydrogen storage fuel, comprising: As an inevitable impurity, ammonia hydrate (NH ３ (H ２ O) and ammonia borane (NH ３ BH ３ ) is mixed in and solidified at room temperature and pressure. ３ ) A hydrogen storage fuel.

2. Ammonia (NH ３ ) was dissolved in an aqueous solution of boric acid (B ３ O ２ ) to prepare a mixed aqueous solution, Next, the mixed aqueous solution is frozen to prepare a frozen solid, Thereafter, the frozen solid is freeze-dried to remove water vapor (H ２ O(g)) and boron compounds contained as gas (BH, B ２ H ６ , B ２ O ３ ) in the frozen solidified body is discharged, and ammonia (NH ３ ) was concentrated to a solid A method for producing hydrogen storage fuel.

3. The ammonia (NH ３ ) contains ammonia hydrate (NH ３ (H ２ O) and ammonia borane (NH ３ BH ３ ) was mixed in and solidified.

3. The method for producing hydrogen storage fuel according to claim 2.

4. 4. The method for producing a hydrogen storage fuel according to claim 2, wherein the mixed aqueous solution is cooled with liquid nitrogen to be frozen and solidified.

5. 5. The method for producing a hydrogen storage fuel according to claim 2, wherein the frozen solid is subjected to a decompression treatment and freeze-dried while being cooled by liquid nitrogen.

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