Magnesium hydride manufacturing method and manufacturing apparatus

Abstract

To provide a method for producing magnesium hydride which has reduced running costs associated with the use of inert gas (noble gas) such as argon gas.SOLUTION: There is provided a method for producing magnesium hydride which comprises: a pulverization step of pulverizing magnesium by adding a fatty acid; and a hydrogenation step of hydrogenating the pulverized magnesium by heating the magnesium to a temperature of 140°C or more and less than the decomposition temperature of magnesium hydride in a reaction vessel to which hydrogen gas is supplied so as to keep the pressure 5 atmospheres or less, wherein a storage treatment of storing the pulverized magnesium in the reaction vessel is performed under an atmosphere of nitrogen gas and the pulverized magnesium is not allowed to contact with oxygen until the hydrogenation step has been completed.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for producing magnesium hydride. [Background technology]

[0002] In recent years, hydrogen has been attracting attention as an energy source, and magnesium hydride is one method for storing this hydrogen.

[0003] Patent Document 1 discloses a method for producing a magnesium-based hydride from a raw material powder, which is mainly composed of magnesium, by holding the raw material powder in a hydrogen gas atmosphere sealed in a sealed container, maintaining the pressure of the hydrogen gas atmosphere in the sealed container at a predetermined pressure, raising the temperature of the hydrogen gas atmosphere in the sealed container from room temperature, and maintaining the temperature of the hydrogen gas atmosphere in the sealed container at a temperature higher than the temperature corresponding to the predetermined pressure on the equilibrium curve for the reaction in which elemental magnesium and hydrogen molecules combine to produce magnesium hydride, and the reverse reaction, and at a temperature within 100°C of the temperature corresponding to the predetermined pressure on the equilibrium curve, for a predetermined first period, thereby removing the coating on the raw material powder surface, and then maintaining the temperature of the hydrogen gas atmosphere in the sealed container at a temperature lower than the temperature corresponding to the predetermined pressure on the equilibrium curve and within 100°C of the temperature corresponding to the predetermined pressure on the equilibrium curve, without returning it to room temperature, for a predetermined second period, thereby producing a magnesium-based hydride from the raw material powder.

[0004] In other words, the first feature of Patent Document 1 is that the temperature is maintained for a predetermined first period at a temperature higher than the temperature corresponding to a predetermined pressure on the equilibrium curve for the reaction in which elemental magnesium and hydrogen molecules combine to produce magnesium hydride and the reverse reaction, and the temperature difference from the temperature corresponding to the predetermined pressure on the equilibrium curve is within 100°C.

[0005] According to Patent Document 1, this first feature promotes the thermal decomposition of magnesium hydroxide (Mg(OH)2) formed on the surface of magnesium (Mg), and the reduction of magnesium oxide (MgO) formed by the thermal decomposition with hydrogen molecules also progresses, thereby removing the coating on the surface of magnesium (Mg), making it possible for the magnesium (Mg) to react quickly with hydrogen (H2).

[0006] Furthermore, Patent Document 1 has a second feature in that the temperature of the hydrogen gas atmosphere is maintained for a predetermined second period at a temperature lower than the temperature corresponding to the predetermined pressure on the equilibrium curve and within 100°C of the temperature corresponding to the predetermined pressure on the equilibrium curve, without being returned to room temperature.

[0007] Due to this second feature, Patent Document 1 claims that it is possible to obtain high-purity magnesium hydride (MgH2) with less input energy than conventional techniques that require activation treatment in which hydrogen is repeatedly absorbed and released by repeated heating and cooling. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-44832 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, in Patent Document 1, the examples show that the hydrogen gas pressure during hydrogenation treatment is 10 atmospheres (approximately 1 MPa) or more.

[0010] Patent Document 1 also explains that in order to produce magnesium hydride within a realistic time range, the pressure should be at least 6 atmospheres or more.

[0011] However, the specifications required for an apparatus that performs processing under a high-pressure hydrogen gas atmosphere (for example, pressure resistance) are strict.

[0012] Therefore, we are currently developing a technology that can perform hydrogenation treatment even when the hydrogen gas pressure is kept low by improving the reactivity of magnesium. However, as the reactivity increases, it has become necessary to handle magnesium under an atmosphere of an inert gas (rare gas) such as argon gas.

[0013] However, when handling large amounts of magnesium, the amount of inert gas (rare gas) such as argon gas used also increases significantly, resulting in higher running costs.

[0014] The present invention has been made in consideration of the above circumstances, and aims to provide a magnesium hydride manufacturing method and manufacturing apparatus that reduce the running costs associated with the use of an inert gas (rare gas) such as argon gas. [Means for solving the problem]

[0015] In order to achieve the above object, the present invention is realized by the following configuration. (1) The method for producing magnesium hydride of the present invention comprises a crushing step of crushing magnesium by adding fatty acid, and a hydrogenation step of heating the crushed magnesium to a temperature of 140°C or higher, below the decomposition temperature of magnesium hydride, in a reaction vessel to which hydrogen gas is supplied so as to maintain a pressure of 5 atmospheres or less, and hydrogenating the magnesium. The process of storing the crushed magnesium in the reaction vessel is carried out in a nitrogen gas atmosphere, and the crushed magnesium is not exposed to oxygen until the completion of the hydrogenation step.

[0016] (2) In the above configuration (1), the pulverization step is carried out in a nitrogen gas atmosphere.

[0017] (3) In the configuration of (1) or (2) above, the nitrogen gas is supplied from a nitrogen generator that generates nitrogen gas with a purity of 99.9% or higher from the atmosphere.

[0018] (4) In any one of the above (1) to (3), the amount of the fatty acid added in the grinding step is 3% by mass or more of the total mass of the magnesium and the fatty acid.

[0019] (5) The magnesium hydride manufacturing apparatus of the present invention comprises, in order, a crusher that discharges crushed magnesium from an outlet, a hydrogenation furnace having a reaction vessel that stores the crushed magnesium and performs a hydrogenation reaction, a booth that stores the crusher and the reaction vessel that is installed at the outlet so that the crushed magnesium can be stored and that prevents outside air from entering, and a nitrogen gas supply system that supplies nitrogen gas to the booth.

[0020] (6) In the configuration of (5) above, the nitrogen gas supply system is a nitrogen generator that generates nitrogen gas with a purity of 99.9% or higher from the atmosphere. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a magnesium hydride production method and production apparatus that reduce the running costs associated with the use of an inert gas (rare gas) such as argon gas. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view of a pulverizer used in a pulverization step of a first embodiment according to the present invention. FIG. [Figure 2] 1 is a perspective view showing a state in which a hood of a crusher according to a first embodiment of the present invention is open. [Figure 3] 1 is a perspective view of a grinding container according to a first embodiment of the present invention. FIG. [Figure 4] FIG. 1 is an exploded perspective view of a grinding container according to a first embodiment of the present invention. [Figure 5] 1 is a side view showing a hydrogenation furnace according to a first embodiment of the present invention. [Figure 6] 1 is a flowchart showing the procedure of a hydrogenation step according to a first embodiment of the present invention. [Figure 7]1 is a graph showing the decomposition and production boundary line of magnesium hydride obtained by thermodynamic calculation. [Figure 8] FIG. 4 is a schematic diagram illustrating the configuration of an apparatus used in a pulverization step of a second embodiment according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the accompanying drawings. It should be noted that the same elements are denoted by the same reference numerals throughout the description of the embodiments.

[0024] (First embodiment) The method for producing magnesium hydride according to the first embodiment of the present invention comprises a grinding step in which pre-grinding magnesium (hereinafter sometimes simply referred to as magnesium) is ground by adding a fatty acid, and a hydrogenation step in which the ground magnesium is heated to a temperature of 140°C or higher, but lower than the decomposition temperature of magnesium hydride, in a reaction vessel to which hydrogen gas is supplied so as to maintain a pressure of 5 atmospheres or lower, thereby hydrogenating the magnesium.

[0025] Therefore, the apparatus used is a pulverizer 1 (see Figure 1) for carrying out the pulverization process and a hydrogenation furnace 8 (see Figure 5) for carrying out the hydrogenation process. Therefore, we will first explain the pulverizer 1 and the hydrogenation furnace 8 (including the work procedures in the hydrogenation furnace 8), and then explain specific examples.

[0026] (Crusher) FIG. 1 is a perspective view of a grinder 1 used in a grinding process of a first embodiment according to the present invention, FIG. 2 is a perspective view showing a state in which a hood 3 of the grinder 1 of the first embodiment according to the present invention is open, FIG. 3 is a perspective view of a grinding container 4 of the first embodiment according to the present invention, and FIG. 4 is an exploded perspective view of the grinding container 4 of the first embodiment according to the present invention. The pulverizer 1 used in the first embodiment described below is a planetary ball mill manufactured by Fritsch GmbH.

[0027] As shown in Figures 1 and 2, the crusher 1 used in the first embodiment comprises a crusher main body 2 that controls the rotation of a crushing container 4 (see Figure 2) that is removably fixed, and a hood 3 that is connected to the crusher main body 2 with a hinge structure that allows it to be opened and closed, and that can cover and conceal the crushing container 4.

[0028] As shown in FIG. 1, the crusher main body 2 includes a condition input section 21 for inputting conditions for controlling the rotation of the crushing container 4, and an emergency stop button 22.

[0029] As shown in Figures 3 and 4, the grinding container 4 comprises a bottomed grinding container body 41 with an upper opening that forms a storage section for storing the object to be ground (not shown) and spherical grinding media (not shown) that promotes grinding, and a lid section 42 that closes the upper opening of the grinding container body 41.

[0030] As shown in FIG. 4, the grinding container body 41 has a groove 411 in which an O-ring 5 is placed at the edge on the upper opening side, and a screw threading hole 412 formed radially outward from the groove 411 and into which a screw is threaded. A total of four screw holes 412 are provided at 90° intervals in the circumferential direction.

[0031] On the other hand, the cover 42 has a through hole 421 on its outer surface (see FIG. 3) that is provided with a counterbore for accommodating the head of a screw. In addition, since this through hole 421 is a through hole 421 for passing the threaded portion of the screw into the grinding container body 41 when screwing the lid portion 42 to the grinding container body 41, the position at which the through hole 421 is provided (such as the distance from the center) corresponds to the screw threading hole 412 of the grinding container body S41, and like the screw threading hole 412, a total of four through holes 421 are provided at 90° intervals in the circumferential direction.

[0032] Then, the material to be crushed (not shown) and spherical crushing media (not shown) that promote crushing are placed in the crushing container body 41, and a screw (not shown) is threaded into the screw threading hole 412 of the crushing container body 41 through the through hole 421 from the lid portion 42 side so that the lid portion 42 presses the O-ring 5 toward the crushing container body 41, and the material to be crushed (not shown) and the spherical crushing media (not shown) that promote crushing are placed inside the crushing container 4 in a completely sealed state.

[0033] After the object to be crushed (not shown) and spherical crushing media (not shown) that promotes crushing are placed inside the crushing container 4 in this manner, the crushing container 4 is fixed to the crusher main body 2 as shown in FIG. 2, the hood 3 of the crusher main body 2 is closed as shown in FIG. 1, the condition input unit 21 is operated to input the conditions for controlling the rotation of the crushing container 4, and the crushing start button is pressed to start crushing.

[0034] Specifically, when the grinding start button is pressed, the grinding container 4 itself begins to rotate, and within the sealed grinding container 4, the rotational force vigorously mixes the grinding media to promote grinding, specifically, hard balls (for example, 5 mmφ high-hardness balls (hard balls such as SUS440C, chrome steel, etc.)) and the magnesium to be ground, and the grinding proceeds.

[0035] As described above, the grinding container 4 is configured to be completely sealed, so that outside air does not get mixed in during grinding.

[0036] Therefore, if the object to be ground (not shown) and spherical grinding media (not shown) that promotes grinding are placed in the grinding container body 41, and the lid portion 42 is fixed to the grinding container body 41 with screws (not shown) in a glove box with an argon gas atmosphere, the grinding container 4 will be filled with an argon gas atmosphere, and grinding can be carried out in an argon gas atmosphere.

[0037] Furthermore, if the work of placing the material to be crushed (not shown) and spherical crushing media (not shown) that promotes crushing into the crushing vessel body 41 and fixing the lid portion 42 to the crushing vessel body 41 with screws (not shown) is performed in a glove box with a nitrogen gas atmosphere, the inside of the crushing vessel 4 will be filled with a nitrogen gas atmosphere, and crushing can be carried out in a nitrogen gas atmosphere.

[0038] Then, when the crushing process is completed, the crushing container 4 is again removed from the crusher main body 2, and the crushing container 4 is moved into the glove box. The crushed material is then transferred to an airtight bottle in the glove box that can prevent outside air from entering, and the crushed material is then recovered.

[0039] If this recovery operation is carried out in a glove box with an argon gas atmosphere, the crushed material will be stored in an airtight bottle filled with argon gas, and if it is carried out in a glove box with a nitrogen gas atmosphere, the crushed material will be stored in an airtight bottle filled with nitrogen gas.

[0040] Furthermore, as will be described later, when magnesium, which is the object to be crushed, is placed in the crushing container 4, a crushing process can be performed in which fatty acid is added to crush the magnesium, thereby producing crushed magnesium with good hydrogenation efficiency and high reactivity.

[0041] The reason for the high reactivity is that fatty acids have carboxyl groups, which react with the oxygen in metal oxides (for example, the oxygen in the oxide film formed on the surface of magnesium) to form metal soaps with significantly lower melting points, boiling points, hardness, etc. than metal oxides. It is presumed that this reaction somehow contributes to the formation of highly reactive crushed magnesium with good hydrogenation efficiency. It is believed that fatty acids also react with metals themselves to form metal soaps.

[0042] For example, the fatty acid to be added may suitably be butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, icosanoic acid, henicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, octacosanoic acid, triacontanoic acid, or the like.

[0043] However, if the alkyl chain is short, the hydrophobicity will be weaker and the fatty acid will be more likely to absorb moisture, so it must be handled carefully to prevent it from absorbing moisture. Conversely, if the alkyl chain is long, the melting point will be higher, and the rise in temperature during the grinding process will not cause the fatty acid to melt, making it difficult to add to magnesium.

[0044] For this reason, it is considered that fatty acids with a total carbon number of approximately 7 to 30, such as heptanoic acid (carbon number 7), octanoic acid (carbon number 8), nonanoic acid (carbon number 9), decanoic acid (carbon number 10), dodecanoic acid (carbon number 12), tetradecanoic acid (carbon number 14), pentadecanoic acid (carbon number 15), hexadecanoic acid (carbon number 16), heptadecanoic acid (carbon number 17), octadecanoic acid (carbon number 18), icosanoic acid (carbon number 20), henicosanoic acid (carbon number 21), docosanoic acid (carbon number 22), tetracosanoic acid (carbon number 24), hexacosanoic acid (carbon number 26), octacosanoic acid (carbon number 28), and triacontanoic acid (carbon number 30), are more suitable.

[0045] (hydrogenation furnace) FIG. 5 is a side view showing the hydrogenation furnace 8 of the first embodiment according to the present invention. For ease of understanding, FIG. 5 illustrates the heating furnace 81 in a cross section. Also, for ease of understanding, FIG. 5 only shows the mounting position of clamp 824 with a dotted line, and the clamp actually used is a commercially available clamp that clamps NW standard flanges.

[0046] As shown in Figure 5, the hydrogenation furnace 8 comprises a reaction vessel 82 in which the reaction to hydrogenate the crushed magnesium takes place, a heating furnace 81 that can detachably receive the reaction vessel 82 and heat the temperature inside the reaction vessel 82 to a temperature suitable for hydrogenation, and a pressure adjustment tank 83 that is controlled to maintain the pressure of hydrogen gas at a predetermined pressure and is connected to the reaction vessel 82 via a flexible gas piping FGP so that the hydrogen gas can be supplied.

[0047] The reaction vessel 82 has a flange portion 8211 that is supported by the heating furnace 81 on its outer periphery at a midpoint in the vertical direction, and is equipped with a reaction vessel main body 821 that is open at the top so that it can contain crushed magnesium, a lid portion 822 for closing the top opening, an O-ring 823 that is placed on the edge of the opening side of the reaction vessel main body 821 and is sandwiched between the reaction vessel main body 821 and the lid portion 822 to ensure airtightness, and a clamp 824 that secures the O-ring 823 by pressing it with the reaction vessel main body 821 and the lid portion 822.

[0048] The cover 822 also has an intake / exhaust port 8221 to which a detachable needle valve N1 is attached to a flexible gas pipe FGP, and which can be opened and closed by operating the needle valve N1.

[0049] The heating furnace 81 comprises an insulated housing 811 having an opening for receiving the reaction vessel body 821, a heater section 812 provided inside the insulated housing 811, and a temperature regulator (not shown) that controls the heater section 812 to maintain a set temperature, and the opening for receiving the reaction vessel body 821 is set to have an inner diameter slightly smaller than the outer diameter of the flange section 8211 so as to be able to support the flange section 8211 of the reaction vessel body 821.

[0050] However, the opening for receiving the reaction vessel main body 821 is set to have an inner diameter larger than the outer diameter of the body of the reaction vessel main body 821 so that the reaction vessel main body 821 can be received.

[0051] The temperature regulator includes a temperature measurement unit (e.g., a thermocouple) that measures the temperature of the heater unit 812, and a power control unit that controls the power supplied to the heater unit 812 based on the results of the temperature measurement to maintain the set temperature.

[0052] The pressure adjustment tank 83 is a stainless steel tank with an airtight structure that traps gas, and is equipped with: an attachment port PT1 for attaching a digital pressure gauge DP to measure the pressure inside the tank; a hydrogen gas receiving port PT2 to which an on-off valve OCB2 is attached and for receiving hydrogen gas; an argon gas receiving port PT3 to which an on-off valve OCB3 is attached and for receiving argon gas; a gas supply port PT4 to which a needle valve N2 is attached and to which a flexible gas piping FGP is connected for sending gas inside the tank to the reaction vessel 82; and an exhaust port PT5 to which an on-off valve OCB5 is attached and for connecting to a vacuum pump P2 used to replace the gas inside the tank.

[0053] The hydrogen gas is supplied to the pressure adjustment tank 83 in such a manner that the hydrogen gas is reduced in pressure to 0.2 to 0.3 MPa, which is the operating pressure of the mass flow controller, by the pressure reducing valve of the high-pressure hydrogen gas cylinder B2, and then supplied via the hydrogen gas mass flow controller MFC-H, which is connected to the hydrogen gas receiving port PT2 via piping.

[0054] In addition, argon gas is supplied to the pressure adjustment tank 83 in such a manner that the argon gas is reduced in pressure to 0.2 to 0.3 MPa, which is the operating pressure of the mass flow controller, by the pressure reducing valve of the high-pressure argon gas cylinder B3, and then supplied via the argon gas mass flow controller MFC-A, which is connected to the argon gas receiving port PT3 via piping.

[0055] The hydrogenation furnace 8 is equipped with a control device for controlling the supply of gas, and specifically, a sequencer PLC, which is a controller capable of constructing a control program for the control device, is used. In FIG. 5, the dashed lines connecting the sequencer PLC with the digital pressure gauge DP, the hydrogen gas mass flow controller MFC-H, and the argon gas mass flow controller MFC-A indicate that they are connected by signal lines that transmit input and output signals.

[0056] The control program for the sequencer PLC has two modes: a direct input mode in which the mass flow controller to be operated and the flow rate are specified on the LCD screen of the sequencer PLC, and the specified mass flow controller (hydrogen gas mass flow controller MFC-H, argon gas mass flow controller MFC-A) is operated to supply that flow rate; and a pressure control mode in which the mass flow controller to be operated and the upper and lower pressure limits are specified on the LCD screen of the sequencer, and when the output value of the digital pressure gauge DP falls below the lower pressure limit, the specified mass flow controller is operated to supply gas at the preset flow rate.

[0057] In the pressure control mode, when the output value of the digital pressure gauge DP reaches the upper pressure limit due to the supply of gas, the operation of the mass flow controller is stopped and the supply of gas is stopped.

[0058] In addition, in the above description, the hydrogenation furnace 8 is configured to be supplied with argon gas, but there is no problem if the argon gas is replaced with nitrogen gas. In this case, the high-pressure argon gas cylinder B3 should be replaced with a high-pressure nitrogen gas cylinder or a nitrogen generator that generates nitrogen gas with a purity of 99.9% or higher from the atmosphere, and the argon gas mass flow controller MFC-A should be replaced with a nitrogen gas mass flow controller.

[0059] (Hydrogenation furnace work procedure) Next, the procedure for the operation using the hydrogenation furnace 8 (procedure for the hydrogenation step) will be described. FIG. 6 is a flowchart showing the procedure of the hydrogenation step according to the first embodiment of the present invention. In the following explanation, we will explain a configuration in which argon gas is supplied to the hydrogenation furnace 8, but as explained above, there is no problem if argon gas is replaced with nitrogen gas, so in that case, the descriptions regarding argon gas should be understood as referring to nitrogen gas.

[0060] Prior to explaining the procedure of the hydrogenation process, it is assumed that argon gas at atmospheric pressure is filled from the pressure adjustment tank 83 to the reaction vessel 82, and that the opening and closing valves OCB2, OCB3, and OCB5 attached to the hydrogen gas receiving port PT2, the argon gas receiving port PT3, and the exhaust port PT5 are in a closed state. Also, the needle valves N1 and N2 attached to the intake / exhaust port 8221 of the cover part 822 and the gas supply port PT4 are also in a closed state.

[0061] (Step 1) First, the reaction vessel 82 is removed from the hydrogenation furnace 8 (S1). Specifically, the needle valve N1 attached to the intake / exhaust port 8221 of the lid portion 822 is disconnected from the flexible gas pipe FGP, and the reaction vessel 82 is removed from the hydrogenation furnace 8.

[0062] By disconnecting the flexible gas piping FGP, outside air (atmosphere) will enter the flexible gas piping FGP, but since the needle valve N1 attached to the intake / exhaust port 8221 of the lid 822 of the reaction vessel 82 is closed, no outside air will enter the reaction vessel 82. Similarly, the needle valve N2 is also closed, so that outside air does not enter the pressure adjustment tank 83.

[0063] (Step 2) Next, the removed reaction vessel 82 is placed in the glove box, and the material to be crushed (specifically, crushed magnesium) crushed in the crushing step is placed in the reaction vessel 82 (S2).

[0064] Specifically, the clamp 824 of the reaction vessel 82 is removed in the glove box, the lid 822 is removed from the reaction vessel body 821, and the crushed magnesium is placed into the reaction vessel body 821 through the opening on the top side of the reaction vessel body 821. Next, the lid 822 is placed to close the upper opening of the reaction vessel body 821, and a clamp 824 is attached to create a sealed state in which the outside air (atmospheric air) does not enter the reaction vessel 82.

[0065] Furthermore, when placing the crushed magnesium in the reaction vessel 82 in this glove box, if the glove box is filled with an argon gas atmosphere, the reaction vessel 82 containing the crushed magnesium will be filled with argon gas.

[0066] Similarly, when placing crushed magnesium in reaction vessel 82 in this glove box, if the glove box is filled with a nitrogen gas atmosphere, reaction vessel 82 containing the crushed magnesium will be filled with nitrogen gas.

[0067] (Step 3) Next, the reaction vessel 82 containing the crushed magnesium is attached to the heating furnace 8 again (S3). Specifically, as shown in Figure 5, the reaction vessel 82, which is filled with atmospheric gas, is installed in a glove box so that the flange portion 8211 of the reaction vessel body 821 is supported by the insulated housing 811, and a needle valve N1 attached to the intake / exhaust port 8221 of the lid portion 822 is connected to a flexible gas pipe FGP.

[0068] (Step 4) Next, the outside air (atmosphere) mixed in the flexible gas piping FGP, the argon gas in the pressure adjustment tank 83, and the gas in the reaction vessel 82 are exhausted, and a vacuum is drawn to create a state in which hydrogen gas can be filled (S4).

[0069] First, the vacuum pump P2 is driven, and the on-off valve OCB5 attached to the exhaust port PT5 is opened to start exhausting the argon gas from the pressure adjustment tank 83.

[0070] Next, the needle valve N2 attached to the gas supply port PT4 is opened to exhaust the outside air (atmosphere) mixed in the flexible gas pipe FGP.

[0071] Then, wait in this state for a while until the outside air (atmospheric air) mixed in the flexible gas piping FGP is completely discharged.

[0072] After sufficient evacuation has been performed in this manner (for example, after evacuation has been performed to about several Pa), the needle valve N1 attached to the intake / exhaust port 8221 of the lid part 822 is slowly turned to the open state.

[0073] The needle valve N1 attached to the intake / exhaust port 8221 is slowly turned to the open position in order to slowly exhaust the gas inside the reaction vessel 82 so that the crushed magnesium inside the reaction vessel 82 is not sucked in.

[0074] (Step 5) Once the inside of the reaction vessel 82 is in a vacuum state, hydrogenation treatment is carried out by heating the pulverized magnesium to a temperature at which hydrogenation proceeds in a hydrogen gas atmosphere (S5).

[0075] First, before actually supplying hydrogen gas to perform hydrogenation treatment, the heater part 812 of the heating furnace 81 is turned on while continuing to evacuate, and heating of the pulverized magnesium is started. The set temperature of the heater section 812 may be a temperature at which the pulverized magnesium is heated to a temperature suitable for hydrogenation.

[0076] Specifically, when the pressure of the hydrogen gas is about 90 kPa (approximately 0.9 atmospheres), the heating temperature for hydrogenation should be set to 140°C or higher, because the hydrogenation reaction slows down rapidly if the temperature drops below 140°C.Since the hydrogenation efficiency is relatively good in the range of about 220°C ± 40°C, in the first embodiment, the set temperature of the heater section 812 is set to a temperature that heats the crushed magnesium to 220°C.

[0077] In this way, by starting heating under vacuum conditions, excess fatty acids added during the crushing process and adhering to the surface of the crushed magnesium can be removed, preventing a decrease in hydrogenation efficiency due to the influence of the fatty acids.

[0078] However, if the amount of fatty acid added is not large, the heat treatment of heating the pulverized magnesium while evacuating the mixture may be omitted. That is, the supply of hydrogen gas may be started first, and then heating may be started.

[0079] Next, the on-off valve OCB5 attached to the exhaust port PT5 is closed to stop the operation of the vacuum pump P2, and then the on-off valve OCB2 attached to the hydrogen gas receiving port PT2 is opened to start the pressure control mode of the sequencer PLC.

[0080] In the first embodiment, the pressure of the hydrogen gas is controlled to approximately 90 kPa (approximately 0.9 atmospheres), so the upper and lower limits of the controlled pressure are set to a lower limit of 89 kPa and an upper limit of 91 kPa, respectively. When the output value of the digital pressure gauge DP reaches 91 kPa, the operation of the hydrogen gas mass flow controller MFC-H stops, and the supply of hydrogen gas stops.

[0081] As the hydrogenation proceeds, hydrogen gas is taken into the crushed magnesium, causing the pressure in the pressure adjustment tank 83 to drop, and the output value of the digital pressure gauge DP becomes 89 kPa.

[0082] This causes the hydrogen gas mass flow controller MFC-H to operate again, and hydrogen gas is supplied until the output value of the digital pressure gauge DP reaches 91 kPa.

[0083] In this way, while maintaining the pressure of the hydrogen gas atmosphere at approximately 90 kPa, the crushed magnesium is heated to approximately 220°C and hydrogenated for a predetermined time, after which the heater part 812 of the heating furnace 81 is turned off, the pressure control mode of the sequencer PLC is ended, and the hydrogenation process is completed.

[0084] (Step 6) After the hydrogenation process is completed, the hydrogenated material (magnesium hydride) is removed. However, since the pressure adjustment tank 83 and the reaction vessel 82 are filled with hydrogen gas, the gas is first replaced with argon gas (S6).

[0085] Specifically, after closing the on-off valve OCB2 attached to the hydrogen gas receiving port PT2, the vacuum pump P2 is driven and the on-off valve OCB5 attached to the exhaust port PT5 is opened.

[0086] After sufficient evacuation, the on-off valve OCB5 attached to the exhaust port PT5 is closed, the vacuum pump P2 is stopped, and the on-off valve OCB3 attached to the argon gas receiving port PT3 is opened to supply argon gas until atmospheric pressure is reached.

[0087] When the pressure adjustment tank 83 and the reaction vessel 82 have been filled with argon gas until the pressure reaches atmospheric pressure, the supply of argon gas is stopped and the opening / closing valve OCB3 attached to the argon gas receiving port PT3 is closed.

[0088] At this time, the needle valve N1 attached to the intake / exhaust port 8221 of the lid 822 of the reaction vessel 82 and the needle valve N2 attached to the gas supply port PT4 of the pressure adjustment tank 83 are closed, thereby completing the gas replacement operation.

[0089] (Step 7) After the gas exchange is completed, the magnesium hydride, which is the hydrogenated material, is finally removed (S7). Since magnesium hydride is relatively stable in the atmosphere unless exposed to moisture, it is not necessary to carry out the process in the glove box used when placing the crushed magnesium in the reaction vessel 82.

[0090] However, if the work is performed inside a glove box, the magnesium hydride can be extracted in an environment with extremely low humidity, so the magnesium hydride can be recovered in an airtight bottle or the like in a glove box filled with a nitrogen gas or argon gas atmosphere.

[0091] In this way, once the hydrogenated material, magnesium hydride, has been removed from the reaction vessel 82, the hydrogenation process is completed.

[0092] Here, the hydrogen gas atmosphere and heating conditions for the hydrogenation treatment will be briefly explained. FIG. 7 is a graph showing the decomposition and production boundary line of magnesium hydride determined by thermodynamic calculation. The temperature on this decomposition boundary line may be called the decomposition boundary temperature. The graph shown in Figure 7 shows the pressure of the hydrogen gas atmosphere (unit: Pa) on the vertical axis and the temperature (unit: °C) on the horizontal axis, and was created by determining the lowest temperature at which magnesium hydride begins to decompose at each pressure and graphing it.

[0093] In other words, on the right side (high temperature side) of the magnesium hydride decomposition boundary line BL, magnesium hydride decomposes into magnesium and hydrogen gas, while on the left side (low temperature side), no decomposition of magnesium hydride occurs, and if magnesium and hydrogen gas are present, the generation reaction to form magnesium hydride proceeds.

[0094] In the first embodiment, the pressure of the hydrogen gas atmosphere is set to about 90 kPa, which is slightly lower than 100,000 Pa, and the temperature on the decomposition boundary line BL of magnesium hydride is about 280°C.

[0095] However, since the actual heating temperature is about 220°C, it is sufficient to set the temperature to about 60°C lower than the temperature on the decomposition boundary line BL of magnesium hydride.

[0096] For this reason, for example, if the treatment is performed in a hydrogen gas atmosphere of 5 atm (5 atmospheres), as shown by the dotted line on the graph, the temperature on the decomposition boundary line BL of magnesium hydride is approximately 350°C, so the actual heating temperature can be considered to be 300°C or less.

[0097] On the other hand, as shown in prior art documents, if treatment is carried out at a temperature about 50°C higher than the temperature on the decomposition boundary line BL of magnesium hydride, in the case of treatment in a hydrogen gas atmosphere of 5 atm (5 atmospheres), heating will be required to a temperature of 400°C or higher, in which case radiant heat will become dominant.

[0098] Generally, the reaction vessel 82 is made of a metal material such as stainless steel, but using stainless steel or the like reflects radiation, which reduces the heat transfer efficiency and increases energy loss.

[0099] However, by carrying out a milling step in which fatty acids are added and magnesium is milled, it is possible to produce magnesium hydride of sufficiently high purity, even without the need for treatment at a temperature about 50°C higher than the temperature on the decomposition boundary line BL of magnesium hydride, as shown in prior art documents.

[0100] Therefore, if the pressure of the hydrogen gas atmosphere during the hydrogenation process is kept below 5 atm (5 atmospheres), hydrogenation can be carried out at low temperatures, from about 400°C where radiant heat is dominant to above 100°C, making it possible to achieve energy-efficient hydrogenation.

[0101] Furthermore, since processing is possible at relatively low pressures of 5 atm (5 atmospheres) or less, there is no need to increase the thickness of the reaction vessel 82 in order to ensure pressure resistance, which allows for good heat conduction and makes it possible to heat the crushed magnesium efficiently, which is also considered to be energy efficient.

[0102] On the other hand, thermodynamic calculations show that magnesium hydride can exist stably even at low temperatures, but thermodynamic calculations do not take into account the reaction rate factor, and when the heating temperature of the magnesium falls below 140°C, the decrease in pressure seen in the hydrogenation process due to the absorption of hydrogen gas into the magnesium slows down significantly.

[0103] For this reason, it is preferable to heat magnesium to a temperature of 140° C. or higher in the hydrogenation treatment in the hydrogenation step.

[0104] Specifically, the dashed line in the graph of Figure 7 is 500 Pa. In this case, the temperature on the decomposition boundary line BL of magnesium hydride is approximately 150°C. Therefore, if the pressure of the hydrogen gas atmosphere is set to 500 Pa or higher, magnesium hydride will not decompose at a temperature of 140°C.

[0105] Therefore, it is preferable to carry out the hydrogenation treatment in the hydrogenation step by heating the crushed magnesium to a temperature of 140°C or higher, below the decomposition temperature of magnesium hydride, under a hydrogen gas pressure of 500 Pa or higher and 5 atmospheres or lower.This allows treatment to be carried out at a temperature range that is 100°C or higher lower than 400°C, at which the influence of radiant heat becomes strong, and also allows for good heat conduction and energy-efficient treatment, as there is no need to increase the thickness of the reaction vessel 82.

[0106] For example, if the hydrogen gas pressure in the hydrogenation process is less than 0.2 MPa, even regular inspections are not required by law, and in order to promote hydrogenation, a high pressure, for example, 30 kPa (approximately 0.3 atmospheres) or more is preferable, so it is more preferable to perform the hydrogenation treatment in the hydrogenation process by heating the crushed magnesium under a hydrogen gas pressure of 30 kPa or more and less than 0.2 MPa.

[0107] Next, Example 1 and Comparative Example 1 will be described. In both the grinding steps of Example 1 and Comparative Example 1, the grinding conditions were as follows: 5 mm diameter hard balls made of high-hardness stainless steel (SUS440C) were placed in the grinding container 4 so that they occupied one-third of the internal volume; and 70 g of magnesium with an average particle size of 180 μm was placed in the grinding container 4 so that they occupied one-third of the internal volume.

[0108] Furthermore, when magnesium was placed in the crushing vessel 4, octadecanoic acid was added as the fatty acid, so that the crushing step was carried out in which the magnesium was crushed with the fatty acid added.

[0109] Specifically, in both Example 1 and Comparative Example 1, magnesium (70 g) and octadecanoic acid (3.684 g) were placed in the grinding container 4, and 5% by mass (wt%) of octadecanoic acid (fatty acid) was added based on the total combined mass (73.684 g) of magnesium and octadecanoic acid, and 5% by mass (wt%) of octadecanoic acid was added based on the total mass, to perform the grinding process for grinding the magnesium.

[0110] In both Example 1 and Comparative Example 1, the operation of the crusher 1 was such that it was operated at a rotation speed of 330 rpm for one hour and then stopped for one hour, and this operation was repeated 24 times, so that the time during which the crushing container 4 was rotating for crushing was 24 hours.

[0111] The reason for stopping the machine for one hour after one hour of operation is to prevent the temperature of the grinding container 4 from rising during grinding, and the manufacturer recommends that the temperature not exceed 100°C.

[0112] In Example 1, the operation of placing magnesium, fatty acids, and hard balls into the grinding container 4 was carried out in a glove box with a nitrogen gas atmosphere, so that the atmosphere inside the grinding container 4 was nitrogen gas and the grinding process was carried out under a nitrogen gas atmosphere.

[0113] To create a nitrogen gas atmosphere inside the glove box, nitrogen gas generated by a nitrogen generator (manufactured by Hitachi Industrial Equipment Systems Co., Ltd.) that generates nitrogen gas with a purity of 99.9% from the atmosphere was supplied to the gas receiving port of the glove box, and the oxygen concentration display on the oxygen concentration meter installed inside the glove box was set to 0%, and in this state, magnesium, fatty acids, and hard balls were placed into the grinding container 4.

[0114] In Example 1, the operation of recovering the crushed magnesium in an airtight bottle after crushing was also carried out in a glove box filled with a nitrogen gas atmosphere using nitrogen gas from a nitrogen generator.

[0115] On the other hand, in Comparative Example 1, the work of placing magnesium, fatty acid, and hard balls into the grinding container 4 was carried out in a glove box with an argon gas atmosphere, so that the atmosphere inside the grinding container 4 was argon gas and the grinding process was carried out under an argon gas atmosphere.

[0116] To create an argon gas atmosphere inside the glove box, argon gas was supplied from a high-purity argon cylinder to the gas receiving port of the glove box, and the oxygen concentration display on the oxygen concentration meter installed inside the glove box was set to 0%, and in this state, magnesium, fatty acid, and hard balls were placed into the grinding container 4.

[0117] In Comparative Example 1, the operation of recovering the crushed magnesium in an airtight bottle after crushing was also carried out in a glove box filled with an argon gas atmosphere using argon gas from a high-purity argon cylinder.

[0118] Next, the pulverized magnesium of Example 1 and Comparative Example 1 was subjected to the hydrogenation step according to the procedure described above.

[0119] However, in Example 1, the operation of transferring the crushed magnesium from the airtight bottle to the reaction vessel 82 of the hydrogenation furnace 8, that is, the process of storing the crushed magnesium in the airtight bottle in the reaction vessel 82 of the hydrogenation furnace 8, was carried out in a glove box filled with a nitrogen gas atmosphere, and the storage process was carried out under a nitrogen gas atmosphere.

[0120] On the other hand, in Comparative Example 1, the operation of transferring the crushed magnesium from the airtight bottle to the reaction vessel 82 of the hydrogenation furnace 8, that is, the process of storing the crushed magnesium in the airtight bottle in the reaction vessel 82 of the hydrogenation furnace 8, was carried out in a glove box with an argon gas atmosphere, and the storing process was carried out under an argon gas atmosphere.

[0121] The specific conditions for the hydrogenation treatment were the same for both Example 1 and Comparative Example 1. Specifically, the temperature was set to heat the crushed magnesium to 220°C, which is suitable for hydrogenating the magnesium, and the heater unit 812 was turned on while the vacuum was still drawn.The vacuum state was maintained until the set temperature was reached, and once the set temperature was reached, hydrogen gas was supplied and heating (hydrogenation treatment) was carried out for 4 hours while maintaining the pressure of the hydrogen gas atmosphere at approximately 90 kPa (approximately 0.9 atmospheres).After the heater unit 812 was turned off, the system was cooled to room temperature and the hydrogenated magnesium was removed.

[0122] As can be seen from the above explanation, in Example 1, the crushed magnesium was only exposed to nitrogen gas and hydrogen gas from the crushing process to the end of the hydrogenation process, while in Comparative Example 1, the crushed magnesium was only exposed to argon gas and hydrogen gas from the crushing process to the end of the hydrogenation process.

[0123] Therefore, in both Example 1 and Comparative Example 1, the magnesium was handled so as not to come into contact with the atmosphere from the crushing process until the end of the hydrogenation process, and the crushed magnesium was prevented from coming into contact with oxygen until the end of the hydrogenation process, so that the reactivity of the magnesium increased by the crushing process would not deteriorate due to the influence of the atmosphere.

[0124] Next, the crushed magnesium after hydrogenation in Example 1 and Comparative Example 1 was subjected to an X-ray diffraction apparatus (XRD apparatus) to determine the hydrogenation rate, i.e., the content of magnesium hydride in the crushed magnesium after hydrogenation. The average hydrogenation rate in Example 1 was 22.8% by mass (wt%), and the average hydrogenation rate in Comparative Example 1 was 7.6% by mass (wt%).

[0125] The average hydrogenation rate refers to the average hydrogenation rate, which includes variations in particle size without sieving, since crushed magnesium contains variations in particle size and hydrogenation efficiency is thought to depend on particle size, and therefore the smaller the particle size, the more hydrogenation is thought to proceed.

[0126] Since the hydrogenation reaction is thought to proceed from the surface towards the centre of the crushed magnesium, the results of Example 1 suggest that, when looking at the entire crushed magnesium, hydrogenation has progressed from the surface to a depth where a hydrogenation rate of 22.8 mass % (wt %) can be achieved.

[0127] Therefore, if the magnesium is atomized to particles with a diameter approximately twice the depth to which it has progressed, specifically, if the particle size (average particle size) of the magnesium is reduced to approximately 1 / 13 of that of the crushed magnesium in Example 1, it is expected that magnesium hydride close to 100% by mass (wt%) can be obtained under the same hydrogenation conditions as in Example 1.

[0128] For example, in a planetary ball mill, the larger the diameter of the hard balls used to promote grinding, the faster the grinding speed, but the larger the limit particle size that can be achieved by grinding. Conversely, the smaller the diameter of the hard balls, the slower the grinding speed, but the smaller the limit particle size that can be achieved by grinding. From this, it is believed that a higher hydrogenation rate can be obtained by performing additional crushing using hard balls with a small diameter.

[0129] It is generally said that the presence of a nitride film or oxide film on the surface of magnesium makes hydrogenation less likely to occur, but the above results show that the hydrogenation efficiency does not deteriorate even when the grinding process for grinding magnesium is carried out in an atmosphere of nitrogen gas generated by a nitrogen generator, and contrary to expectations, better results were obtained than when the grinding process was carried out in argon gas.

[0130] Furthermore, in Example 1, the process of storing the crushed magnesium in the reaction vessel 82 of the hydrogenation furnace 8 was also carried out under a nitrogen gas atmosphere, and the hydrogenation efficiency was not deteriorated even if such an operation was carried out under a nitrogen gas atmosphere.

[0131] Next, Example 2 will be described, in which the amount of fatty acid added in the grinding step was increased. In Example 2, octadecanoic acid was used as the fatty acid, and the magnesium used was the same as in Example 1.

[0132] In Example 2, magnesium (70 g) and octadecanoic acid (6.923 g) were placed in the grinding container 4, and 9% by mass (wt%) of octadecanoic acid was added to the total mass (76.923 g) of magnesium and octadecanoic acid to grind the magnesium.

[0133] Example 2 is the same as Example 1 except for the amount of fatty acid added.

[0134] That is, Example 2 is the same as Example 1 except for the amount of fatty acid added from the crushing step to the hydrogenation step.

[0135] The crushed magnesium after hydrogenation in Example 2 was then subjected to an X-ray diffraction device (XRD device) to determine the hydrogenation rate, i.e., the content of magnesium hydride in the crushed magnesium after hydrogenation. The average hydrogenation rate was found to be 54.2% by mass (wt%), and by increasing the amount of fatty acid added, an even higher hydrogenation rate than in Example 1 was achieved.

[0136] In this way, increasing the amount of fatty acid added during the crushing process significantly improves the reactivity of the crushed magnesium, but it is thought that adding too much will increase the time required to remove the organic compound film by vacuum heating during the hydrogenation process.

[0137] Furthermore, fatty acids liquefy at the temperature during grinding, but if added in excess, the liquefied fatty acids may act as a lubricant that reduces frictional resistance during grinding, resulting in a decrease in the grinding speed.

[0138] Therefore, the amount of fatty acid added should be kept to 15% by mass or less, and more preferably 14% by mass or less, of the total mass of magnesium and fatty acid combined.

[0139] On the other hand, fatty acids also have the effect of preventing the crushed magnesium particles from agglomerating together during the crushing process, so it is advisable to add fatty acids in an amount of at least 3 mass% or more of the total mass of magnesium and fatty acids combined during the crushing process.

[0140] Furthermore, looking at Examples 1 and 2, it can be seen that the hydrogenation rate improves when the amount of fatty acid added in the grinding step is increased, so it is preferable to add 4 mass% or more of fatty acid based on the total mass of magnesium and fatty acid in the grinding step, and more preferably the amount added increases in the following order: 5 mass% or more, 6 mass% or more, 7 mass% or more, 8 mass% or more, 9 mass% or more, and 10 mass% or more.

[0141] (Second embodiment) Next, a second embodiment will be described mainly with reference to FIG. 8, which is a schematic diagram for explaining the configuration of an apparatus used in the pulverization step.

[0142] In the second embodiment, the magnesium hydride manufacturing apparatus is similar to the first embodiment in that it includes a crusher S1 (see Figure 8), a hydrogenation furnace 8 (see Figure 5), and a nitrogen gas supply system 10 (see Figure 8) that supplies nitrogen gas used to prevent the crushed magnesium from coming into contact with oxygen in the atmosphere, and the main difference from the first embodiment is the configuration of the apparatus used in the crushing process.

[0143] Therefore, in the following explanation, the configuration of the device used in the pulverization step will be mainly described, and explanations of the same points as in the first embodiment will be omitted.

[0144] As shown in Figure 8, the configuration of the equipment used in the crushing process in the magnesium hydride manufacturing apparatus of the second embodiment includes a crusher S1, a booth 9 that houses the crusher S1 and the reaction vessel 82 of the hydrogenation furnace 8 used in the hydrogenation process, a nitrogen gas supply system 10 that supplies nitrogen gas to the booth 9, and a transport mechanism CON that transports the reaction vessel 82 of the hydrogenation furnace 8. In addition, since FIG. 8 only shows the reaction vessel 82 schematically, please refer to FIG. 5 for details.

[0145] (Crusher) The pulverizer 1 of the first embodiment is a planetary ball mill device, and uses a sealed pulverizing container 4, so the pulverizing process is batch processing, which is not suitable for building an efficient production line.

[0146] Therefore, a bead mill device capable of continuous processing is used as the pulverizer S1 in the second embodiment. For example, bead mills manufactured by Ashizawa Finetech Co., Ltd., Nippon Coke & Engineering Co., Ltd., etc. can be suitably used.

[0147] In a bead mill device, when grinding the material to be ground, spherical grinding media K (hard balls) that promote grinding are used, and the grinding process is progressed by vigorously stirring the material to be ground and the grinding media K. However, unlike a bead mill device, this stirring is not achieved by rotating the grinding container 4, but by using a stirring screw feeder called an agitator as the stirring mechanism S32, which forcibly stirs the material to be ground and the grinding media K to progress the grinding process.

[0148] As in the first embodiment, the hard balls for accelerating the pulverization may be, for example, 5 mmφ hard balls (hard balls made of SUS440C, chrome steel, or the like).

[0149] As shown in Figure 8, the crusher S1 comprises a stand S2, a crushing section S3 arranged on the stand S2 and having an outlet S31 through which crushed material to be crushed (specifically, crushed magnesium) is successively discharged, a motor S4 for rotating an agitation mechanism S32 in the crushing section S3, a screen S33 provided between the agitation mechanism S32 and the outlet S31 and allowing only the finely divided material to be crushed (specifically, crushed magnesium) to pass through to the outlet S31 side, and a crushing material storage section S5 (specifically, a magnesium storage section for storing magnesium) arranged on the stand S2 and located on the opposite side of the crushing section S3 from the outlet S31 in the left-right (horizontal) direction and having a feeder (not shown) that successively supplies the material to be crushed (specifically, magnesium).

[0150] (Nitrogen gas supply system) The nitrogen gas supply system 10 may be a high-pressure nitrogen gas cylinder, which is cheaper than a high-pressure argon gas cylinder, and therefore has lower running costs than argon gas.

[0151] However, when using large amounts of nitrogen gas, using a nitrogen generator that produces 99.9% pure nitrogen gas from the atmosphere can be significantly more cost-effective than using high-pressure nitrogen gas cylinders. For this reason, in the second embodiment as well, a nitrogen generator (manufactured by Hitachi Industrial Equipment Systems Co., Ltd.) that generates nitrogen gas with a purity of 99.9% from the atmosphere is used in the nitrogen gas supply system 10. The dotted arrows in FIG. 8 indicate the flow of nitrogen gas generated by the nitrogen generator.

[0152] (booth) As shown in Figure 8, the booth 9 comprises a booth main body 91 capable of accommodating the crusher S1 and the reaction vessel 82, a pass box 92 used for transporting the reaction vessel 82 into and out of the booth main body 91, and a pass box 93 used for transporting a container C containing a material to be crushed (specifically, magnesium) to be newly supplied to the crushing material storage section S5 into and out of the booth main body 91.

[0153] The pass box 92 is provided near the discharge port S31 of the crushing section S3, and the pass box 93 is provided near the crushing object storage section S5.

[0154] The booth main body 91, pass box 92, and pass box 93 each have an inlet port IN for receiving nitrogen gas supplied from the nitrogen gas supply system 10, and an exhaust port OUT for exhausting the internal gas to the outside.

[0155] Nitrogen gas is constantly supplied to the receiving port IN, and the internal gas is constantly exhausted from the exhaust port OUT, so that gas replacement is constantly performed to make the internal atmosphere a nitrogen gas atmosphere.

[0156] Pass box 92 and pass box 93 each have an inner door ID on the booth main body 91 side that is opened and closed during loading and unloading, and an outer door OD on the outside, and the inner door ID and outer door OD can be opened and closed by operating an operating switch (not shown) installed outside booth 9.

[0157] The transport mechanism CON is a mechanism for transporting the reaction vessel 82 placed in the pass box 92 so as to place the reaction vessel 82 at the discharge outlet S31 so as to be able to accommodate the crushed magnesium discharged from the discharge outlet S31 of the crusher S1, and in this embodiment, it is equipped with a booth main body 91, a rotating roller R provided in the pass box 92, and a pallet P provided on the rotating roller R to receive the reaction vessel 82.

[0158] The rotating roller R is connected to a motor (not shown), and its rotation is controlled by operating an operation switch (not shown) that controls the drive of the motor installed outside the booth 9. For example, when the operation switch for installing the reaction vessel 82 at the discharge outlet is pressed, the motor rotates in the forward direction.

[0159] As a result, the pallet P, which is placed on the rotating rollers R and on which the reaction vessels 82 are placed, moves toward the discharge port S31.

[0160] Then, when the pallet P reaches the predetermined position, a proximity switch (not shown) for detecting the pallet P is activated, the motor stops rotating, and the reaction vessel 82 placed on the pallet P is placed at the discharge outlet S31 so that it can contain the crushed magnesium.

[0161] Although not shown in FIG. 8, the booth main body 91 also includes a lid operating mechanism for automatically removing and attaching the lid 822 (see FIG. 5) of the reaction vessel 82.

[0162] In order to realize a lid operating mechanism with a simple configuration, the reaction vessel 82 of the second embodiment does not fix the reaction vessel body 821 and the lid 822 with an NW clamp, but rather adopts a structure in which they are fixed with screws, similar to the grinding vessel 4 of the grinder 1 of the first embodiment described above, and the lid operating mechanism is composed of a robot arm for attaching and detaching the screws and moving the lid 822.

[0163] On the other hand, when the operating switch for storing the reaction container 82 in the pass box 92 is pressed, the motor operates in the reverse direction, and when the pallet P carrying the reaction container 82, which is mounted on a rotating roller R, reaches a position within the pass box 92, a proximity switch (not shown) for detecting the pallet P operates, the motor stops rotating, and the pallet P carrying the reaction container 82 is stored within the pass box 92.

[0164] Furthermore, a robot arm is provided within the booth main body 91 to transport the container C containing the material to be crushed from the pass box 93 to the crushed material storage section S5, place the material into the crushed material storage section S5, and then return the empty container C back into the pass box 93.

[0165] Here, when the outer doors OD of pass boxes 92 and 93 are opened from the outside and the reaction container 82 and the container C containing the material to be crushed are placed into pass boxes 92 and 93, outside air (atmospheric air) will naturally be drawn into pass boxes 92 and 93.

[0166] However, as explained earlier, gas replacement is constantly performed in pass boxes 92 and 93 to make the internal atmosphere a nitrogen gas atmosphere, so if you close the outer doors OD of pass boxes 92 and 93 and wait a while, the inside of pass boxes 92 and 93 will be replaced with a nitrogen gas atmosphere.

[0167] Although not shown in Figure 8, the exhaust ports OUT of pass boxes 92 and 93 are connected to an oxygen concentration meter, and when the oxygen concentration displayed on the oxygen concentration meter reaches 0%, it can be determined that the atmosphere has been replaced with nitrogen gas.If the inner doors ID of pass boxes 92 and 93 are opened after this state is reached, it is possible to reliably prevent outside air (atmospheric air) from entering the booth main body 91.

[0168] In other words, pass box 92 and pass box 93 are intended to prevent outside air (atmospheric air) from entering the booth main body 91 when reaction container 82 is being transported into or out of the booth main body 91, and when container C containing new material to be crushed to be supplied to the crushing material storage section S5 is being transported into or out of the booth main body 91.

[0169] Since the inside of the booth main body 91 is always in a nitrogen gas atmosphere, the process of storing the crushed magnesium discharged from the outlet S31 of the crusher S1 into the reaction vessel 82 is carried out in a nitrogen gas atmosphere.

[0170] In the second embodiment, the crusher S1 is installed inside the booth main body 91, so the crushing process itself is carried out in a nitrogen gas atmosphere.

[0171] As described above, in the present invention, in order to increase the reactivity of magnesium so that hydrogenation can be performed even when the hydrogen gas pressure is kept low, a crushing process is performed in which fatty acids are added to crush the magnesium, and as the reactivity increases, magnesium is handled in a nitrogen gas atmosphere rather than in an inert gas (rare gas) atmosphere such as argon gas, thereby significantly reducing running costs compared to when an inert gas (rare gas) such as argon gas is used.

[0172] Although specific embodiments have been described above, the present invention is not limited to the specific embodiments, and appropriate modifications and improvements are also included within the technical scope of the present invention, which will be clear to those skilled in the art from the description of the claims. [Explanation of symbols]

[0173] 1. Crusher 2 Crusher body 21 Condition input section 22 Emergency stop button 3. Food 4 Grinding container 41 Grinding container body 411 Groove 412 Screw hole 42 Lid 421 Through Hole 5 O-rings 8 Hydrogenation Furnace 81 Heating furnace 811 Insulated housing 812 Heater section 82 Reaction vessel 821 Reaction vessel body 8211 Flange part 822 Lid 8221 Intake and exhaust port 823 O-ring 824 Clamp 83 Pressure Regulating Tank Booth 9 91 Booth main body 92, 93 Pass Box 10 Nitrogen gas supply system B1 High-pressure gas cylinder B2 Hydrogen gas cylinder B3 Argon gas cylinder BL decomposition production boundary line DP Digital Pressure Gauge FGP gas piping ID inner door IN receiving port K Grinding Media OD outer door OUT Exhaust port MFC-A Argon Gas Mass Flow Controller MFC-H Mass Flow Controller for Hydrogen Gas N, N1, N2 needle valves OCB2, OCB3, OCB5 shut-off valve P Palette P1, P2 vacuum pumps PLC sequencer PT1 mounting port PT2 Receiving port PT3 Receiving Port PT4 gas supply port PT5 exhaust port R rotating roller S1 Crusher S2 Mount S3 Crushing Unit S31 outlet S32 Stirring mechanism S33 Screen S4 motor S5 Crushed material storage section

Claims

1. A method for producing magnesium hydride, comprising: a grinding step of grinding magnesium by adding fatty acid; a hydrogenation step of heating the pulverized magnesium to a temperature of 140°C or higher and lower than the decomposition temperature of magnesium hydride in a reaction vessel to which hydrogen gas is supplied so as to maintain a pressure of 5 atmospheres or lower, The process of placing the pulverized magnesium in a reaction vessel is carried out under a nitrogen gas atmosphere, A method for producing magnesium hydride, wherein the crushed magnesium is not exposed to oxygen until the end of the hydrogenation step.

2. The method for producing magnesium hydride according to claim 1, wherein the grinding step is carried out under a nitrogen gas atmosphere.

3. 3. The method for producing magnesium hydride according to claim 1, wherein the nitrogen gas is supplied from a nitrogen generator that generates nitrogen gas with a purity of 99.9% or higher from the atmosphere.

4. 4. The method for producing magnesium hydride according to claim 1, wherein the amount of the fatty acid added in the pulverization step is 3 mass% or more of the total mass of the magnesium and the fatty acid.

5. An apparatus for producing magnesium hydride, comprising: a crusher that sequentially discharges crushed magnesium from an outlet; a hydrogenation furnace having a reaction vessel for accommodating pulverized magnesium, into which hydrogen gas is supplied so as to maintain a pressure of 5 atmospheres or less, and for heating the pulverized magnesium to a temperature of 140°C or more but lower than the decomposition temperature of magnesium hydride to carry out a hydrogenation reaction; a booth that accommodates the crusher and the reaction vessel that is installed at the outlet so as to be able to accommodate crushed magnesium and that prevents outside air from entering; a nitrogen gas supply system for supplying nitrogen gas to the booth; Magnesium hydride manufacturing equipment.

6. 6. The magnesium hydride manufacturing apparatus according to claim 5, wherein the nitrogen gas supply system is a nitrogen generator that generates nitrogen gas with a purity of 99.9% or higher from the atmosphere.

7. The number of carbon atoms of the fatty acid is 7 or more and 30 or less. The method for producing magnesium hydride according to any one of claims 1 to 4.

8. In the crushing step, the oxide film of the magnesium is scraped off to expose the magnesium surface. The method for producing magnesium hydride according to any one of claims 1 to 4.

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