Method for producing anhydrous metal chlorides

Abstract

To provide a method for producing an anhydrous metal chloride that minimizes the emission of carbon dioxide gas into the atmosphere.SOLUTION: A method for producing an anhydrous metal chloride includes a chlorination step for heating metal oxide in a mixed gas of carbon monoxide gas and chlorine gas at a temperature of 300°C or higher and 1200°C or lower, to produce anhydrous metal chloride; and a gas reduction step for reducing the emission of carbon dioxide gas in the chlorination step, to produce carbon monoxide gas. The carbon monoxide gas produced in the gas reduction step is used in the chlorination step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing anhydrous metal chlorides. [Background technology]

[0002] For example, when magnesium is produced by molten salt electrolysis, magnesium chloride is used as the material. If the magnesium chloride contains moisture, it can cause deterioration of the electrodes used in the molten salt electrolysis.

[0003] For this reason, anhydrous magnesium chloride is used in molten salt electrolysis, and Patent Document 1 discloses a method for producing anhydrous magnesium chloride, in which solid magnesium carbonate is reacted with chlorine gas at a temperature of 1200°C or less in the presence of carbon monoxide gas, and anhydrous magnesium chloride is extracted in a molten state to produce anhydrous magnesium chloride.

[0004] However, the method of Patent Document 1 has a problem in that carbon dioxide gas, a greenhouse gas, is generated as a by-product, and a disposal method such as atmospheric release is required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 55-20296 [Patent Document 2] International Publication No. 2018 / 221698 [Patent Document 3] Japanese Patent Publication No. 2022-42280 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing anhydrous metal chlorides in which the release of carbon dioxide gas into the atmosphere is suppressed. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention is realized by the following configuration. (1) The method for producing anhydrous metal chloride of the present invention comprises a chlorination step in which a metal oxide is heated to 300°C or higher and 1200°C or lower in a mixed gas of carbon monoxide gas and chlorine gas to produce anhydrous metal chloride, and a gas reduction step in which carbon dioxide gas discharged in the chlorination step is reduced to produce carbon monoxide gas, and the carbon monoxide gas produced in the gas reduction step is used in the chlorination step.

[0008] (2) In the above configuration (1), a dehydration step is provided in which a metal hydroxide is dehydrated to produce a metal oxide, and the metal oxide produced in the dehydration step is used in the chlorination step.

[0009] (3) In the above configuration (2), the dehydration step is carried out in the reactor in which the chlorination step is carried out, as a pretreatment before the mixed gas for the chlorination step is supplied.

[0010] (4) In the configuration of (1) above, the gas reduction step is a step of reducing carbon dioxide gas using hydrogen gas as a reducing agent to produce carbon monoxide gas, or a step of electrolyzing carbon dioxide gas to produce carbon monoxide gas.

[0011] (5) In any one of the above (1) to (4), the metal oxide is magnesium oxide, and the anhydrous metal chloride is anhydrous magnesium chloride.

[0012] (6) The method for producing anhydrous metal chloride of the present invention comprises an electrolysis step of electrolyzing seawater, bittern water, or a mixture of seawater and bittern water to produce a metal hydroxide and chlorine gas; a dehydration step of dehydrating the metal hydroxide to produce a metal oxide; a chlorination step of heating the metal oxide to 300°C or higher and 1200°C or lower in a mixed gas of carbon monoxide gas and chlorine gas to produce anhydrous metal chloride; and a gas reduction step of reducing carbon dioxide gas discharged in the chlorination step to produce carbon monoxide gas, wherein the metal hydroxide produced in the electrolysis step is used in the dehydration step, the chlorine gas produced in the electrolysis step is used in the chlorination step, the carbon monoxide gas produced in the gas reduction step is used in the chlorination step, the metal hydroxide is magnesium hydroxide, the metal oxide is magnesium oxide, and the anhydrous metal chloride is anhydrous magnesium chloride.

[0013] (7) The method for producing anhydrous metal chloride of the present invention comprises an electrolysis step of electrolyzing seawater, bittern water, or a mixture of seawater and bittern water to produce metal hydroxide, chlorine gas, and hydrogen gas; a gas production step of reacting chlorine gas with hydrogen gas to produce hydrogen chloride gas; a dehydration step of dehydrating the metal hydroxide to produce a metal oxide; and a chlorination step of heating the metal oxide in hydrogen chloride gas to 300°C or higher and 1200°C or lower to produce anhydrous metal chloride, wherein the chlorine gas and hydrogen gas produced in the electrolysis step are used in the gas production step, the metal hydroxide produced in the electrolysis step is used in the dehydration step, the metal hydroxide is magnesium hydroxide, the metal oxide is magnesium oxide, and the anhydrous metal chloride is anhydrous magnesium chloride. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a method for producing anhydrous metal chlorides in which release of carbon dioxide gas into the atmosphere is suppressed. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an apparatus for carrying out a chlorination step of a first embodiment according to the present invention. [Figure 2] FIG. 2 is a diagram illustrating the configuration of an apparatus for carrying out a chlorination step according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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.

[0017] (First embodiment) The method for producing anhydrous metal chloride according to the first embodiment of the present invention comprises a chlorination step in which anhydrous metal chloride is produced from a metal oxide using a mixed gas of carbon monoxide gas and chlorine gas, and a gas reduction step in which carbon dioxide gas (CO) emitted in the chlorination step is reduced to produce carbon monoxide gas (CO). Specific examples of the method will be described below using an example in which the metal oxide is magnesium oxide (MgO) and the anhydrous metal chloride is anhydrous magnesium chloride (MgCl).

[0018] (Chlorination process) FIG. 1 is a diagram illustrating the configuration of an apparatus for carrying out the chlorination step of this embodiment. As shown in FIG. 1, the apparatus for carrying out the chlorination step has a reactor, and the reactor is equipped with a reaction section 1 (e.g., a reaction vessel) and a heating section H (e.g., a heater) for heating the reaction section 1.

[0019] The reaction unit 1 comprises a cylindrical main body 11 , an upper lid 12 that closes the upper opening of the main body 11 , and a lower lid 13 that closes the lower opening of the main body 11 .

[0020] For example, when magnesium oxide is to be placed in the reaction unit 1, the top lid 12 is opened, the magnesium oxide is placed in, and the top lid 12 is closed.

[0021] Conversely, when the anhydrous magnesium chloride produced after the treatment is to be taken out, the lower lid 13 is opened, the anhydrous magnesium chloride is taken out, and the lower lid 13 is closed.

[0022] The main body 11 of the reaction section 1 is connected to a gas supply pipe IN for supplying gas to the lower side and a gas exhaust pipe OUT for discharging gas to the upper side.

[0023] The gas supply pipe IN is connected to a line for mixed gas (process gas) supplied from a gas mixer M that mixes carbon monoxide gas and chlorine gas, and a line for general gas (inert gases such as nitrogen gas and argon gas), and the line supplied to the gas supply pipe IN can be switched by controlling the valve B1. For example, the general gas is used when replacing the gas in the reaction chamber 1 before the upper cover 12 and the lower cover 13 are opened.

[0024] The gas exhaust pipe OUT branches into two lines, one of which is connected to a vacuum pump (not shown) and the other to a gas processing facility (not shown) for recovering the gas. The exhaust gas from the vacuum pump (not shown) is sent to a detoxification device (for example, a scrubber, etc.) that detoxifies chlorine gas and the like, although this is not shown.

[0025] The gas treatment facility mainly comprises a chlorine gas recovery section (chlorine gas recovery device) that recovers chlorine gas from the exhaust gas, and a carbon dioxide gas recovery section (carbon dioxide gas recovery device) that recovers carbon dioxide gas from the exhaust gas.

[0026] In addition, in the gas exhaust pipe OUT, it is possible to select whether to send the exhaust to one line side (vacuum pump side) or the other line side (gas processing equipment side) by controlling the valve B2.

[0027] Then, magnesium oxide is poured into the reaction section 1, the top lid 12 is closed, and the reaction section 1 is sealed. First, without supplying gas from the gas supply pipe IN, the gas exhaust pipe OUT is connected to the vacuum pump side, and the heating section H is driven while drawing a vacuum inside the reaction section 1, and the reaction section 1 is heated to a temperature of 400°C or higher.

[0028] In this way, as a pretreatment before supplying the mixed gas (treatment gas) of carbon monoxide gas and chlorine gas in the chlorination process, the magnesium oxide is vacuum heated to remove adsorbed water adsorbed on the surface of the magnesium oxide.

[0029] The temperature of the subsequent chlorination treatment is to be below the melting point of anhydrous magnesium chloride (714°C) if anhydrous magnesium chloride is to be produced in a solid state, and it is preferable to treat it at a temperature in the range of, for example, about 500°C to 700°C.

[0030] The temperature for the chlorination treatment should be 300°C or higher, but considering the reaction rate, it is better to set the temperature in the range of about 500°C to 700°C.

[0031] Therefore, if the temperature during vacuum heating of this magnesium oxide is set to a range of 500 to 700°C, chlorination will begin simply by starting the supply of the treatment gas, so it is best to set the temperature during vacuum heating in the range of 500 to 700°C.

[0032] After vacuum heating for a predetermined time, valve B2 on the vacuum side line is closed to seal the reaction section 1, and then the supply of treatment gas (a mixture of carbon monoxide gas and chlorine gas) begins from the gas supply pipe IN.

[0033] After that, when the pressure inside the reaction section 1 reaches atmospheric pressure, the valve B2 is controlled so that exhaust gas can be supplied from the gas exhaust pipe OUT to the gas treatment equipment side, and the exhaust gas flows to the other line side (gas treatment equipment side).

[0034] That is, a flow of the processing gas is generated within the reaction section 1 from the gas supply pipe IN toward the gas exhaust pipe OUT. This type of treatment while the gas is still flowing is sometimes called windsock treatment.

[0035] In this way, when magnesium oxide (metal oxide) is heated in a mixed gas of carbon monoxide gas and chlorine gas, the reaction of the following formula (1) occurs, and anhydrous magnesium chloride (anhydrous metal oxide) is produced. MgO+CO+Cl2→ MgCl2+CO2 (1)

[0036] Then, carbon monoxide gas, chlorine gas that did not contribute to the reaction, and carbon dioxide gas produced by the reaction are discharged from the gas exhaust pipe OUT, and this exhaust gas is sent to the gas treatment facility (not shown) described above.

[0037] In the gas treatment facility (not shown), chlorine gas is recovered in a chlorine gas recovery section, and the recovered chlorine gas is reused as chlorine gas to be sent to the gas mixer M.

[0038] Furthermore, carbon dioxide gas is recovered in the carbon dioxide gas recovery section, and the recovered carbon dioxide gas is sent to a gas reduction step, which will be explained later.

[0039] Furthermore, the remaining carbon monoxide gas is also used again as carbon monoxide gas to be sent to the gas mixer M.

[0040] Then, when the production of anhydrous magnesium chloride is complete, the supply of treatment gas to reaction section 1 is stopped, and valve B2 is controlled to stop exhaust to the gas treatment equipment (not shown), reaction section 1 is sealed, heating of heating section H is stopped, and after waiting for the temperature inside reaction section 1 to drop to at least 600°C or less, valve B2 is controlled to connect the gas exhaust pipe OUT to the line on the vacuum pump side, and reaction section 1 is evacuated.

[0041] The reason why the vacuum is drawn after waiting for the temperature inside the reaction section 1 to drop to 600°C or below is that anhydrous magnesium chloride can be vaporized at a temperature of about 650°C under vacuum, and therefore the generated anhydrous magnesium chloride is prevented from being discharged outside the reaction section 1 by vacuum drawing.

[0042] Then, after the reaction section 1 has been evacuated, the valve B2 is controlled again to seal the reaction section 1, and then a general gas (e.g., nitrogen gas) is supplied to the reaction section 1 from the gas supply pipe IN. Once atmospheric pressure is reached, the lower cover 13 is opened and the anhydrous magnesium chloride is removed, completing the chlorination process.

[0043] (Gas reduction process) Next, a gas reduction step will be described in which the carbon dioxide gas discharged in the chlorination step (that is, the carbon dioxide gas recovered in the carbon dioxide gas recovery section described above) is reduced to produce carbon monoxide gas.

[0044] In recent years, various methods for reducing carbon dioxide gas to carbon monoxide gas have rapidly emerged and become common, so here we will briefly explain those that are suitable for carrying out the present invention.

[0045] For example, as disclosed in Patent Document 2, a gas reduction step according to the reaction formula (2) below (so-called reverse shift reaction), that is, a gas reduction step is preferably a step in which carbon dioxide gas is reduced using hydrogen gas as a reducing agent to produce carbon monoxide gas. CO2+H2→ CO+H2O (2)

[0046] As can be seen from equation (1) shown above, in the chlorination step, the same amount of carbon dioxide gas is generated as the carbon monoxide gas that contributed to the reaction. Therefore, by setting the gas reduction step to also generate approximately the same amount of carbon monoxide gas as the generated carbon dioxide gas, a gas circulation loop with just the right amount of excess and deficiency between the chlorination step and the gas reduction step can be realized.

[0047] Therefore, all of the carbon dioxide gas generated in the chlorination step can be converted into carbon monoxide gas in the gas reduction step and reused in the chlorination step, eliminating the need for a disposal method such as releasing carbon dioxide gas into the atmosphere.

[0048] Another suitable method is to electrolyze carbon dioxide gas to generate carbon monoxide gas, as disclosed in Patent Document 3.

[0049] In this way, when oxygen is directly extracted from carbon dioxide gas by electrolysis, the amount of carbon dioxide gas input and the amount of carbon monoxide gas produced are almost the same, so a gas circulation loop with just the right amount of excess or deficiency can be realized between the chlorination process and the gas reduction process.

[0050] On the other hand, as shown in Patent Document 1, when magnesium carbonate ore is chlorinated with carbon monoxide gas and chlorine gas, the amount of carbon dioxide gas produced is twice the amount of carbon monoxide gas used, as shown in the following formula (3). MgCO3+CO+Cl2→ MgCl2+2CO2·········(3)

[0051] For this reason, even if carbon dioxide gas were converted into carbon monoxide gas and reused, only half of the produced carbon dioxide gas could be used, and the remaining half would have to be disposed of by means of atmospheric release or other methods.

[0052] Therefore, when magnesium oxide, which is a metal oxide, is treated with a mixed gas of carbon monoxide gas and chlorine gas as in this embodiment, the amount of carbon monoxide gas used in the chlorination step and the amount of carbon monoxide gas generated in the gas reduction step are approximately the same, making it possible to create a gas circulation loop with just the right amount of carbon monoxide gas and carbon dioxide gas, and eliminating the need for a disposal method such as releasing carbon dioxide gas into the atmosphere.

[0053] Furthermore, in the present embodiment, when magnesium oxide is converted into anhydrous magnesium chloride, only carbon monoxide gas is used as a reducing agent containing a carbon component. This has the advantage that impurities resulting from the carbon-based solid reducing agent (e.g., carbon powder, impurities contained in coke) are prevented from being mixed into the produced anhydrous magnesium chloride, as occurs when a carbon-based solid reducing agent such as coke is used.

[0054] (Second embodiment) In the first embodiment, the case where the treatment temperature in the chlorination step is lower than the melting point of anhydrous magnesium chloride is described, but in the second embodiment, the case where the treatment temperature in the chlorination step is higher than the melting point of anhydrous magnesium chloride is described.

[0055] FIG. 2 is a diagram illustrating the configuration of an apparatus for carrying out the chlorination step of the second embodiment. The device configuration shown in FIG. 2 is similar in many respects to the device configuration including the reactor described in the first embodiment, and therefore, a description of the same points as in the first embodiment may be omitted.

[0056] As shown in Figure 2, the reactor differs from the first embodiment in that the lower cover 13 (see Figure 1) is omitted and the main body 11 has a bottom, and that the main body 11 is located slightly above the middle in the vertical direction and is connected to a recovery section 2 that recovers anhydrous magnesium chloride via a pipe having a valve B3.

[0057] The recovery section 2 for recovering anhydrous magnesium chloride comprises a cylindrical main body 21 having a ceiling and an opening on the lower side, and a lower lid 22 for closing the opening on the lower side.

[0058] As described above, the main body 21 of the recovery section 2 is connected to the main body 11 of the reactor via a pipe having a valve B3, and is also connected to a vacuum pump (not shown) via a pipe having a valve B4. Although not shown, a gas pipe that is controlled to open and close by a valve is connected to the recovery unit 2 so that general gas can also be supplied.

[0059] The chlorination treatment procedure is carried out with the valve B3 closed to isolate the reaction section 1 from the recovery section 2, and is substantially the same as in the first embodiment except for the treatment temperature.

[0060] Specifically, after magnesium oxide is placed in the reaction section 1, it is vacuum heated to remove the adsorbed water on the surface of the magnesium oxide, and then a mixed gas of carbon monoxide gas and chlorine gas (treatment gas) is supplied to the reaction section 1 to produce anhydrous magnesium chloride.

[0061] The amount of magnesium oxide introduced is set so that it does not reach the position of the pipe connected to the recovery unit 2 and having the valve B3.

[0062] In this case, for example, the temperature from vacuum heating until completion of the reaction for producing anhydrous magnesium chloride may be set to a temperature above the melting point of anhydrous magnesium chloride and below 1200°C (for example, around 1000°C).

[0063] In this case, the reaction formula itself is the same as that shown in Equation 1, but since the treatment temperature is kept above the melting point of anhydrous magnesium chloride, when anhydrous magnesium chloride is produced, it becomes liquid, but does not boil because its boiling point is 1412°C. The melting point of magnesium oxide is 2852°C, so it remains solid.

[0064] Therefore, since the boiling point of anhydrous magnesium chloride is not exceeded, even if the treatment gas is supplied using a streamer as in the first embodiment, the anhydrous magnesium chloride will hardly turn into steam and disappear, so it is sufficient to use a streamer.

[0065] In this way, the treatment gas is supplied so as to bubble through the anhydrous magnesium chloride liquid, increasing the probability of contact with the unreacted magnesium oxide contained therein, allowing the reaction to proceed efficiently.

[0066] After the chlorination treatment is carried out for a predetermined time, the supply of the treatment gas is stopped, the heating by the heating unit H is stopped, the reaction unit 1 is left sealed, and it is waited until the temperature inside the reaction unit 1 drops to a temperature of 600°C or less.

[0067] While waiting for the temperature to drop, the recovery unit 2 is evacuated by the vacuum pump with the valve B4 open, until the internal pressure reaches, for example, 10 Pa or less. After the evacuation is completed, the valve B4 is closed to put the recovery unit 2 into a vacuum-sealed state.

[0068] On the other hand, when the temperature inside the reaction section 1 drops below 600°C, the reaction section 1 is also evacuated, for example, until the pressure reaches 10 Pa or less, and the reaction section 1 is again sealed (vacuum sealed).

[0069] Thereafter, valve B3 is opened to connect reaction section 1 and recovery section 2, and heating section H is driven to raise the temperature in reaction section 1 to a temperature at which anhydrous magnesium chloride vaporizes. Since the anhydrous magnesium chloride is in a vacuum state, when it is heated to a temperature exceeding 650°C, for example, to about 700°C, the anhydrous magnesium chloride will vaporize.

[0070] The vaporized anhydrous magnesium chloride then flows into recovery section 2, where it returns to a solid state within recovery section 2, which is at a temperature lower than the vaporization temperature, and is no longer in a gaseous state. As a result, the pressure in recovery section 2 drops, and gaseous anhydrous magnesium chloride flows in succession from reaction section 1, and the anhydrous magnesium chloride is recovered in recovery section 2.

[0071] Although not shown, the pipe having the valve B3 is equipped with a heating mechanism for keeping the temperature (heating) so that the anhydrous magnesium chloride does not solidify inside.

[0072] Then, when the recovery of anhydrous magnesium chloride is completed, valve B3 is closed, the operation of heating section H is stopped, and ordinary gas (e.g., nitrogen gas) is supplied into recovery section 2 to bring the pressure inside recovery section 2 to atmospheric pressure, and lower cover section 22 is opened and anhydrous magnesium chloride is removed from recovery section 2, completing the chlorination process.

[0073] In this embodiment, carbon dioxide gas is also generated during the chlorination treatment, but the generated carbon dioxide gas is recovered and converted back into carbon monoxide gas in the gas reduction step, and the carbon monoxide gas is used again in the chlorination step, which is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0074] On the other hand, when the produced anhydrous magnesium chloride is recovered as vapor, as in the second embodiment, even if there is magnesium oxide that has not reacted, magnesium oxide, which has a high boiling point, does not vaporize, so there is an advantage that anhydrous magnesium chloride can be recovered with almost no magnesium oxide contamination.

[0075] (Third embodiment) Although Japan is said to be poor in natural resources, magnesium resources are abundant in seawater. For example, when bittern water concentrated using the ion exchange membrane permeation method is treated with alkali, magnesium hydroxide (Mg(OH)2), a metal hydroxide, is obtained. When magnesium hydroxide is heated to several hundred degrees Celsius, a dehydration reaction occurs, turning it into magnesium oxide, a metal oxide.

[0076] The alkali treatment is a process in which, for example, calcium oxide (CaO), sodium hydroxide (NaOH), or the like is added to the bittern water to convert the magnesium chloride in the bittern water into magnesium hydroxide, which has low solubility, and precipitates, which is then filtered and collected.

[0077] Therefore, by using magnesium oxide produced in this way, it is possible to secure a stable supply of raw materials that are not affected by world situations, etc.

[0078] For this reason, it is desirable that the magnesium oxide (metal oxide) used in the chlorination process of the previously described embodiment be one produced by a dehydration process in which magnesium hydroxide (metal hydroxide) is heated to dehydrate it, and as a third embodiment, a case in which this dehydration process is included will be briefly described.

[0079] That is, the method for producing anhydrous metal chloride includes a dehydration step in which a metal hydroxide is dehydrated to produce a metal oxide, and the metal oxide produced in the dehydration step is used in the chlorination step.

[0080] As explained above, magnesium oxide is not a material that forms hydrates, but it does have adsorbed water.

[0081] For this reason, as explained in the first embodiment, vacuum heating is performed as a pretreatment for the chlorination step before supplying the mixed gas (treatment gas) of carbon monoxide gas and chlorine gas. However, when a metal oxide is produced from a metal hydroxide and the metal oxide is used in the chlorination step, a dehydration step can be performed in this pretreatment.

[0082] In other words, if the dehydration process is carried out in the reactor (for example, in the reaction section 1) where the chlorination process is carried out as a pretreatment before supplying the mixed gas (treated gas) for the chlorination process, an efficient production method will be achieved in which the dehydration process and the chlorination process are connected. The reactor may have a dehydration processing section that is provided so that the material after dehydration can be supplied to the reaction section 1 .

[0083] Therefore, the vacuum heating step for removing adsorbed water from magnesium oxide in the first embodiment simply becomes a dehydration step, and the subsequent flow of the chlorination step and the flow of the gas reduction step may be the same as those described in the first and second embodiments.

[0084] (Fourth embodiment) In the third embodiment, a method was described in which magnesium hydroxide is obtained by alkaline treatment of bittern water, and then magnesium oxide is obtained by dehydrating the magnesium hydroxide. In the fourth embodiment, another method for obtaining magnesium hydroxide from seawater or bittern water will be described.

[0085] If seawater or bittern water is placed in an electrolysis furnace equipped with an anode and a cathode connected to a power source, and electricity is passed through it to carry out the electrolysis process, chlorine gas is generated from the anode and hydrogen gas is generated from the cathode. This reaction generates hydrogen ions (H + ), and chloride ions (Cl - ) decreases. In addition, a similar reaction occurs with a mixture of seawater and bittern water, so a mixture of seawater and bittern water may also be used.

[0086] As hydrogen ions decrease, hydroxide ions (OH - ) increases, the aqueous solution becomes alkaline, but the decrease in chloride ions causes the magnesium ions (Mg 2+ ) also increases, so they react to produce magnesium hydroxide. In other words, the hydroxyl group reacts to compensate for the loss of chlorine in magnesium chloride, producing magnesium hydroxide.

[0087] However, magnesium hydroxide has low solubility in water, so it precipitates in seawater or bittern water, and the magnesium hydroxide can be easily recovered by filtration.

[0088] In this case, as described above, chlorine gas is also generated from the anode, and if this chlorine gas is recovered by a chlorine gas recovery device, there is an advantage that the recovered chlorine gas can be used as chlorine gas in the chlorination step.

[0089] Therefore, the method for producing anhydrous metal chloride comprises an electrolysis step of electrolyzing seawater, bittern water, or a mixture of seawater and bittern water to produce magnesium hydroxide (metal hydroxide) and chlorine gas, the magnesium hydroxide produced in the electrolysis step is used in the dehydration step described in the third embodiment, and the chlorine gas produced in the electrolysis step is recovered by a chlorine gas recovery device, and the recovered chlorine gas is used in the chlorination step.

[0090] (Other forms) As explained in the fourth embodiment, in the electrolysis process in which seawater, bittern water, or a mixture of seawater and bittern water is electrolyzed, hydrogen gas (H) is also produced in addition to magnesium hydroxide and chlorine gas (Cl), and hydrogen chloride gas (HCl) can be produced by reacting the chlorine gas with the hydrogen gas (see formula 4). Cl2+H2→ 2HCl (4)

[0091] If the temperature is between 300°C and 1200°C as shown in the chlorination step, hydrogen chloride gas reacts quickly with magnesium oxide to produce magnesium chloride (see formula 5). MgO+2HCl → MgCl2+H2O (5)

[0092] Therefore, if hydrogen gas is recovered in a hydrogen gas recovery device in addition to the chlorine gas generated in the electrolysis step, and a sludge generation step is provided in which the chlorine gas and hydrogen gas are reacted to generate hydrogen chloride gas, magnesium chloride can be generated even if hydrogen chloride gas is used instead of the embodiment in which a mixed gas of carbon monoxide gas and chlorine gas is used in the chlorination step described above.

[0093] As shown in formula (5), water (HO) is generated as a reaction by-product. However, as explained above, if the chlorination step is performed using a gas blow-off process, that is, if hydrogen chloride gas is used, the generated water will continue to be exhausted from the reaction section 1, and anhydrous magnesium chloride can be obtained by continuing the process until the water runs out.

[0094] Furthermore, since hydrogen chloride gas does not contain any carbon components, no carbon dioxide is generated by this process.

[0095] For this reason, even if a method for producing anhydrous metal chloride includes an electrolysis step in which seawater, bittern water, or a mixture of seawater and bittern water is electrolyzed to produce magnesium hydroxide (metal hydroxide), chlorine gas, and hydrogen gas, a gas production step in which chlorine gas and hydrogen gas are reacted to produce hydrogen chloride gas, a dehydration step in which magnesium hydroxide (metal hydroxide) is dehydrated to produce magnesium oxide (metal oxide), and a chlorination step in which magnesium oxide (metal oxide) is heated to 300°C or higher and 1200°C or lower in hydrogen chloride gas to produce anhydrous magnesium chloride (anhydrous metal chloride), it is still possible to achieve a method for producing anhydrous magnesium chloride (anhydrous metal chloride) that does not require the release of carbon dioxide into the atmosphere.

[0096] In the above specific embodiments, the metal oxide is magnesium oxide and the anhydrous metal chloride is anhydrous magnesium chloride, but the present invention is not limited to the specific embodiments. For example, the metal oxide may be titanium oxide (TiO) and the anhydrous metal chloride may be titanium tetrachloride (TiCl4).

[0097] In the embodiment, carbon monoxide gas and chlorine gas are mixed in the gas mixer M and supplied to the reaction section 1 in a uniformly dispersed state.

[0098] In this way, the mixed gas that has been homogeneously dispersed and mixed by the gas mixer M does not separate due to differences in the specific gravity of the gases. For example, the air mainly contains oxygen gas and nitrogen gas, but because the air is a homogeneously dispersed mixture of these gases, separation of the gases due to specific gravity does not occur. As a result, just as people do not suffocate, the Gas Mixer M mixes the gases without causing separation. The gas mixer itself is a device that is generally used when producing a mixed gas cylinder to prevent gas separation from occurring within the cylinder.

[0099] Therefore, if carbon monoxide gas and chlorine gas are sent to the gas mixer M in a one-to-one ratio and the resulting homogeneously dispersed mixed gas is supplied to the reaction section 1, the mixed gas will come into contact with the magnesium oxide uniformly in a reaction equivalence ratio (one-to-one ratio), thereby improving the reaction efficiency.

[0100] However, since the chlorination treatment itself can be performed by joining carbon monoxide gas and chlorine gas and supplying them to the reaction section 1 without passing them through the gas mixer M, it is not essential to make a mixed gas using the gas mixer M.

[0101] Furthermore, in the first embodiment, the anhydrous magnesium chloride was handled so as not to evaporate until it was extracted, but the treatment temperature until the anhydrous magnesium chloride was produced may be set to a temperature below the melting point of the anhydrous magnesium chloride, and after the anhydrous magnesium chloride was produced, the anhydrous magnesium chloride may be recovered in the chlorination step as vapor recovery (sent in a gaseous state from the reaction section 1 to the recovery section 2, solidified in the recovery section 2, and recovered) as in the second embodiment.

[0102] In this way, as explained above, even if unreacted magnesium oxide is present, anhydrous magnesium chloride can be obtained with reduced contamination by the magnesium oxide.

[0103] In this way, appropriate modifications and improvements to the specific embodiments are also included within the technical scope of the present invention, and this will be clear to those skilled in the art from the description of the claims. [Explanation of symbols]

[0104] 1. Reaction section 11 Main body 12 Top cover 13 Lower lid part 2. Recovery Section 21 Main body 22 Lower lid part B1, B2, B3, B4 valves H heating section M Gas Mixer IN gas supply pipe OUT Gas exhaust pipe

Claims

1. 1. A method for producing anhydrous metal chlorides, comprising: a chlorination step in which a metal oxide is heated in a mixture of carbon monoxide gas and chlorine gas to produce an anhydrous metal chloride; a gas reduction step of reducing the carbon dioxide gas discharged in the chlorination step to produce carbon monoxide gas, The carbon monoxide gas produced in the gas reduction step is used in the chlorination step, the metal oxide is magnesium oxide, the anhydrous metal chloride is anhydrous magnesium chloride; Method for producing anhydrous metal chlorides.

2. a dehydration step of dehydrating the metal hydroxide to produce a metal oxide, 2. The method for producing an anhydrous metal chloride according to claim 1, wherein the metal oxide produced in the dehydration step is used in the chlorination step.

3. 3. The method for producing an anhydrous metal chloride according to claim 2, wherein the dehydration step is carried out in a reactor in which the chlorination step is carried out as a pretreatment before the mixed gas in the chlorination step is supplied.

4. 2. The method for producing an anhydrous metal chloride according to claim 1, wherein the gas reduction step is a step of reducing carbon dioxide gas using hydrogen gas as a reducing agent to produce carbon monoxide gas, or a step of electrolyzing carbon dioxide gas to produce carbon monoxide gas.

5. 2. The method for producing an anhydrous metal chloride according to claim 1, wherein the metal oxide is heated at a temperature of 300° C. or higher and 1200° C. or lower in the chlorination step.

6. a chlorine gas recovery step of recovering chlorine gas from the exhaust gas discharged in the chlorination step; a carbon dioxide gas recovery step of recovering carbon dioxide gas from the exhaust gas, The recovered chlorine gas is contained in the chlorine gas in the mixed gas, The recovered oxygen dioxide gas is used in the gas reduction step. The method for producing anhydrous metal chloride according to claim 1.

7. 1. A method for producing anhydrous metal chlorides, comprising: an electrolysis step of electrolyzing seawater, bittern water, or a mixture of seawater and bittern water to produce metal hydroxides and chlorine gas; a dehydration step of dehydrating the metal hydroxide to produce a metal oxide; a chlorination step in which a metal oxide is heated to 300°C or higher and 1200°C or lower in a mixed gas of carbon monoxide gas and chlorine gas to produce an anhydrous metal chloride; a gas reduction step of reducing the carbon dioxide gas discharged in the chlorination step to produce carbon monoxide gas, The metal hydroxide produced in the electrolysis step is used in the dehydration step, The chlorine gas produced in the electrolysis step is used in the chlorination step, The carbon monoxide gas produced in the gas reduction step is used in the chlorination step, the metal hydroxide is magnesium hydroxide; the metal oxide is magnesium oxide, The method for producing an anhydrous metal chloride, wherein the anhydrous metal chloride is anhydrous magnesium chloride.

8. 1. A method for producing anhydrous metal chlorides, comprising: an electrolysis step of electrolyzing seawater, bittern water, or a mixture of seawater and bittern water to generate metal hydroxides, chlorine gas, and hydrogen gas; a gas generating step of reacting chlorine gas with hydrogen gas to generate hydrogen chloride gas; a dehydration step of dehydrating the metal hydroxide to produce a metal oxide; a chlorination step of heating a metal oxide in hydrogen chloride gas at 300°C or higher and 1200°C or lower to produce an anhydrous metal chloride; The chlorine gas and hydrogen gas generated in the electrolysis step are used in the gas generation step, The metal hydroxide produced in the electrolysis step is used in the dehydration step, the metal hydroxide is magnesium hydroxide; the metal oxide is magnesium oxide, The method for producing an anhydrous metal chloride, wherein the anhydrous metal chloride is anhydrous magnesium chloride.

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