WO2023243337A1

WO2023243337A1 - Method for smelting metal with use of hydrogen obtained in molten salt

Info

Publication number: WO2023243337A1
Application number: PCT/JP2023/019245
Authority: WO
Inventors: 律夫吉岡; 靖彦伊藤; 誠二寺田; 亨中西
Original assignee: 株式会社トリウムテックソリューション
Priority date: 2022-06-17
Filing date: 2023-05-24
Publication date: 2023-12-21

Abstract

The present invention provides: a technology for producing a metal by means of the reduction of a metal compound, while suppressing a carbon dioxide gas to be discharged into the environment as much as possible, the technology being capable of further reducing the production cost; and a technology for producing a larger amount of hydrogen, the technology being able to be applied to the production of a metal by means of the reduction of a metal compound.　The present invention provides a method for producing a metal, wherein a metal is produced by reducing a metal compound by means of hydrogen that is obtained by electrolyzing water in a molten salt. The present invention also provides a method for producing hydrogen, wherein hydrogen is obtained by electrolyzing water in a molten salt.

Description

Method for smelting metals using hydrogen obtained in molten salt

The present invention relates to a metal manufacturing method, a hydrogen manufacturing method, a metal manufacturing method using hydrogen obtained by the hydrogen manufacturing method, and the like.

In recent years, in the fields of electricity supply and heat source supply, carbon neutrality and carbon dioxide reduction have been required from the perspective of global warming and SDGs (Sustainable Development Goals). Research and development of mechanisms and devices that use natural energy, etc., rather than fossil fuels such as coal, oil, and natural gas, is progressing. However, even in the use of these natural energies, stable supply and cost are difficult. There is a need for reduction.

Currently, metals are smelted by reducing minerals (mainly metal oxides, metal sulfides, metal chlorides, etc.) using carbothermal reduction or metal thermal reduction methods, and in some cases, metals are smelted by reducing minerals (mainly metal oxides, metal sulfides, metal chlorides, etc.). It is further refined to further increase its purity. However, the biggest drawback in manufacturing such metals is the generation of large amounts of carbon dioxide gas, which is a greenhouse gas, and we also face a shortage of resources for reducing agents, which are raw materials.

For example, in Patent Document 1, the purpose is to reduce metal oxides to obtain metals at near room temperature without emitting global warming gases such as carbon dioxide. A method of reducing the activated metal oxide powder by placing it in a container, applying physical energy to the metal oxide powder to activate it, and introducing a reducing gas into the container, bringing the reducing gas into contact with the activated metal oxide powder. is proposed.
For example, in Patent Document 2, when obtaining molten metal by melting and reducing chromium ore, iron ore, etc. in a smelting-reduction furnace, the exhaust gas discharged from the smelting-reduction furnace is removed without using a carbon dioxide separation device. A melt reduction method has been proposed in which the exhaust gas after wet dust removal can be effectively used as reducing gas or fuel gas by simply removing dust with a wet dust removal device.
Further, Patent Document 5 discloses a method for producing hydrogen gas by high-temperature molten salt electrolysis in a humid atmosphere, in which hydrogen gas is produced by molten salt electrolysis in a humid molten salt electrolysis environment. The temperature of the salt is 150-1000°C, and the water vapor content of the molten salt protective atmosphere is 0.1-100 Vol. %, and the molten salt electrolyte is a mixture of one or more alkali metal and/or alkaline earth metal halides. is disclosed.

Japanese Patent Application Publication No. 2001-64733 Japanese Patent Application Publication No. 2011-006744 Special Publication No. 2021-517209 Japanese Patent Application Publication No. 2016-042090 Japanese Patent Application Publication No. 2001-133572

As mentioned above, there are currently technologies that can efficiently produce metals by reducing metal compounds without emitting as much carbon dioxide gas into the environment as possible, and technologies that can be used to efficiently reduce such metal compounds. There is a need for technology to produce hydrogen in large quantities. Moreover, industrially, manufacturing costs are also important.

Therefore, the present invention provides a technology for producing a metal by reducing a metal compound, which can further reduce manufacturing costs without emitting carbon dioxide gas into the environment as much as possible, and a technology that can also be used for metal production by reducing such a metal compound. The main objective of each project is to develop technologies that can produce large quantities of hydrogen.

As a result of extensive studies, the present inventors have discovered that hydrogen can be obtained by electrolyzing water in molten salt, and that metals can be produced by reducing metal compounds using the hydrogen thus obtained. The present invention has been completed. Therefore, the present invention is as follows.
Note that it is generally a liquid obtained by melting a salt made by neutralizing an acid and an alkali at a high temperature. However, in this specification, metal hydroxide is a type of molten salt. In addition, in this specification, unless otherwise specified, "generation of hydrogen" means "generation of hydrogen atoms", "generation of hydrogen" means "generation of hydrogen gas", and "generation of hydrogen" means "generation of hydrogen gas". "Manufacturing" may include the meanings of "producing" and "generating".

The present invention provides a metal manufacturing method in which a metal is manufactured by reducing a metal compound with hydrogen obtained by electrolyzing water in a molten salt.
The present invention provides a method for producing hydrogen, in which hydrogen is obtained by electrolyzing water in a molten salt.

The metal compound may be in the form of particles.
The electrolysis may be based on electrical energy and/or thermal energy supplied from a molten salt nuclear reactor.
The metal compound includes one or more metal elements selected from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, and molybdenum, and the group consisting of oxygen atoms, sulfur atoms, and chlorine atoms. It may be a metal compound containing one or more selected nonmetallic elements.
The molten salt is (a) at least one of an alkali metal halide or an alkaline earth metal halide, or (b) at least one of an alkali metal hydroxide or an alkaline earth metal hydroxide. or (c) alkali metal chloride, alkaline earth metal chloride, alkali metal hydroxide, alkaline earth metal hydroxide, alkali metal fluoride, alkaline earth metal fluoride, alkali metal nitrate, alkali metal It may contain one or more selected from sulfates, alkali metal carbonates, alkali metal acetates, and alkali metal phosphates.

The present invention is a technology for producing metals by reducing metal compounds, which can further reduce production costs without emitting carbon dioxide gas into the environment as much as possible, and can also be used for metal production by reducing such metal compounds. It is possible to provide a technology for producing hydrogen more easily and easily. Note that the effects of the present invention are not necessarily limited to the effects described herein, and may be any of the effects described herein.

It is an example which shows the relationship between reduction rate (%) and temperature (degreeC) when iron oxide is reduced to iron with hydrogen in this embodiment. In this embodiment, the relationship between the electrolysis voltage (V) and energy (MJ/Kg-H ₂ O) used for water electrolysis and the temperature (energy) (° C.) of the molten salt is shown. In this embodiment, it is a schematic diagram (this 1st embodiment) which manufactures metal by reducing a metal compound with hydrogen obtained using electrolysis in a molten salt. It is a schematic diagram (this 2nd embodiment) which shows the metal compound reduction apparatus which uses the hydrogen obtained in the molten salt in this embodiment, and the recovery of the hydrogen generated when metal manufacturing is carried out. 1 is a diagram showing an example of a schematic diagram of a metal manufacturing system including one metal manufacturing apparatus and one molten salt nuclear reactor that reduce a metal compound using a molten salt nuclear reactor. It is a figure showing the current steel manufacturing cost, the manufacturing cost in the present invention case 1 (in the case of only a power generation furnace) and the present invention case 2 (in the case of a combined thermoelectric furnace). FIG. 2 is a diagram showing a schematic diagram of the final configuration of the RIMS base (an example of a system for the molten salt iron manufacturing method) in this embodiment. It is a figure which shows that efficiency can be improved when a molten salt nuclear reactor is used as a power generation-only reactor when used as a combined heat and power reactor. It is a figure showing the current hydrogen price, the hydrogen cost in present invention case 1 (in the case of only a power generation furnace) and present invention case 2 (in the case of a combined thermoelectric furnace). It is a schematic diagram showing a hydrogen production device and a metal compound reduction device in this embodiment (this 3rd embodiment). FIG. 3 is a diagram showing changes over time in current values and both electrode potentials in this example (Test Example 1). Left vertical axis: potential/V vs. MoQRE, horizontal axis: time/s, right vertical axis: current/A. It is a figure showing the X-ray diffraction (measurement conditions: X-ray: Cu/40kV/40mA, scan speed: 2 degrees/min) of the iron oxide sample before electrolysis in this example (test example 1). Sample: Fe ₂ O ₃ , left vertical axis: intensity (Counts), horizontal axis: 2θ (deg). It is a figure which shows the X-ray diffraction (measurement conditions, X-ray: Cu/40kV/40mA, scan speed: 2 degrees/min) after electrolysis in this Example. Sample: Li ₂ Fe ₃ O ₅ , left vertical axis: intensity (Counts), horizontal axis: 2θ (deg). FIG. 2 is a diagram showing a secondary electron image of iron oxide particles before an experiment in this example (Test Example 1). FIG. 2 is a diagram showing a secondary electron image of iron oxide particles after an experiment in this example (Test Example 1). This is a diagram showing changes over time in the current value, both electrode potentials, and the potential difference between the electrodes in this example (Test Example 1). The upper diagram shows the changes over time in the current value and the potential difference between the electrodes (right vertical axis: current/A , horizontal axis: time/s), the figure below shows the temporal change in both electrode potential and the potential difference between the electrodes (right vertical axis: potential/V vs MoQRE, horizontal axis: time/s, right vertical axis: potential difference between the electrodes/V ). FIG. 3 is a diagram showing X-ray diffraction after electrolysis (measurement conditions: X-ray: Cu/40 kV/40 mA, scan speed: 2°/min) in this example. Sample: Li ₂ Fe ₃ O ₄ , left vertical axis: intensity (Counts), horizontal axis: 2θ (deg). FIG. 2 is a diagram showing a secondary electron image of iron oxide particles after an electrolytic experiment in this example (Test Example 1). FIG. 2 is a schematic diagram of an electrolytic cell for electrolytic reduction of molten salt of iron oxide by supplying water vapor in this example (Test Example 3). FIG. 3 is a diagram showing a secondary electron image after electrically reducing iron oxide particles (5 g) by supplying water vapor in this example (Test Example 3). Shows X-ray diffraction (measurement conditions: X-ray: Cu/40kV/15mA, scan speed: 2°/min) after electrically reducing iron oxide particles (5 g) by supplying water vapor in Example (Test Example 3) It is a diagram. Sample: Fe ₂ O ₃ , left vertical axis: intensity (Counts), horizontal axis: 2θ (deg). It is a figure which shows the X-ray diffraction (measurement conditions: X-ray: Cu/40kV/15mA, scan speed: 2 degrees/min) after reduction with hydrogen gas in this test example 4. Sample: Fe ₂ O ₃ , left vertical axis: intensity (Counts), horizontal axis: 2θ (deg).

Hereinafter, a preferred embodiment for implementing the present technology will be described. Note that the embodiment described below shows an example of a typical embodiment of the present technology, and therefore the scope of the present technology should not be interpreted narrowly. Note that the explanation will be given in the following order.

1. Overview of this technology 1-1. 1-2. Overview of metal production by reduction of metal compounds and hydrogen production by electrolysis in this technology. 1-3. Overview of hydrogen production using this technology. Regarding the feasibility of creating a hydrogen society 1-4. 2. Overview of the iron manufacturing method using hydrogen in this technology. Metal manufacturing method according to the present embodiment 2-1. Hydrogen production process 2-1-1. Electrolysis mechanism 2-1-2. Electrolytic bath 2-2. Metal compound reduction step 3. Hydrogen production method using molten salt according to this embodiment 4. Metal production equipment, hydrogen production equipment, electrolysis equipment, etc. and systems thereof according to the present embodiment 4-1. 4-1-1. Metal manufacturing equipment, etc. according to the present embodiment. <First embodiment>
4-1-2. <Second embodiment>
4-1-3. <Third Embodiment>
4-2. Molten salt reactor 5. Another aspect of this embodiment

1. Overview of this technology

The present inventors have completed the present invention by deriving new ideas and new technical ideas from their own unique viewpoints, as described below. In addition, although the following explanation uses iron as a metal applicable to the present invention for convenience, the present invention is not limited to iron and can be applied to a wide range of metals.

The present invention relates to a metal manufacturing method or smelting method, etc., in which hydrogen is obtained in a molten salt, a metal compound such as iron oxide, which is a raw material, is reduced by the hydrogen, and a metal such as iron, which is not a raw material metal compound, is obtained. It is something. Furthermore, by obtaining the electricity and high-temperature heat necessary to obtain hydrogen from a molten salt nuclear reactor, it is also possible to provide a smelting method (iron manufacturing method in the case of iron) that does not emit carbon dioxide. . The metal obtained by the metal production method of the present invention is preferably a metal that has been further reduced compared to the metal compound before reduction, and for example, it may be a partially reduced metal compound. , metals that have been reduced from the metal compound before reduction to the same degree or more than conventional smelting techniques are more suitable.

1-1. Overview of metal production by reduction of metal compounds and hydrogen production by electrolysis using this technology

All iron ore existing on the earth is iron oxide (mostly Fe ₂ O ₃ ), and iron making is a reduction technology that extracts oxygen from iron oxide to obtain iron (Fe). However, the iron element in iron oxide is strongly bound to oxygen, and it requires a large amount of energy to separate the oxygen, so a method of reducing it to iron using high-temperature carbon has been adopted. This method has not changed at all in the 3,000 years of human history of iron manufacturing. In other words, the carbon used has simply changed from charcoal to coal. The chemical formula for the reduction method using carbon is as follows.

3C+3O ₂ →3CO ₂ (carbon combustion)
3C + 3CO ₂ → 6CO (CO generation)
2Fe ₂ O ₃ +6CO→4Fe+6CO ₂ (reduction of iron oxide)

In addition, in these processes, 0.5 tons of coal is required to produce 1 ton of iron, and 2 tons of carbon dioxide (CO ₂ ) are emitted during this process. Currently, from the perspective of global environmental issues, there is a need for a steel manufacturing method that does not emit _CO2 , but no practical technology currently exists.

By the way, in the chemical field, it is well known that hydrogen is a strong reducing agent, and it is possible to reduce iron oxide to iron with hydrogen (for example, Non-Patent Document 1). The chemical formula for the reduction method using hydrogen is as follows. Further, FIG. 1 shows the relationship between reduction rate and temperature in an example of a principle experiment in which iron oxide is reduced in a hydrogen atmosphere. From this, the present inventors believe that 100% of iron oxide can be reduced to iron by reacting hydrogen with iron oxide in a fluid (gas, liquid) at a high temperature of 550° C. or higher.

Fe ₂ O ₃ +3H ₂ →2Fe+3H ₂ O

However, since hydrogen is a gas, its energy is extremely dilute compared to solids such as coal, and when compared with the same volume, it has only 1/3000 of the energy of coal. Therefore, the present inventors thought that in order to obtain the same amount of heat using conventional techniques, it would be necessary to blow in a large amount of gas. Furthermore, it is generally known that hydrogen is easily ignited and that it is difficult to safely handle large amounts of hydrogen. These are considered to be one of the reasons why steelmaking using hydrogen (hydrogen steelmaking) has not been realized.
Furthermore, even if hydrogen steelmaking were possible, with current technology, hydrogen is mainly generated from fossil fuels such as methane, and the actual situation is that _CO2 and CO are emitted during hydrogen production. Hydrogen steelmaking, which uses the hydrogen generated by hydrogen, will overall emit carbon dioxide and carbon monoxide. The process is shown below using a chemical formula.

CH ₄ +2O ₂ →CO ₂ +2H ₂ O (high temperature steam generation)
CH ₄ +H ₂ O → CO + 3H ₂ (hydrogen generation)

As mentioned above, the present inventors believe that since hydrogen is optimal for reducing iron ore, it would be most efficient if (a) hydrogen could be produced at a low cost and (b) iron oxide could be reduced with the hydrogen. Ta. The inventors also considered it important to (c) avoid using fossil fuels as much as possible. One of the features of the present invention is that the present inventors used molten salt as a medium that can simultaneously achieve the above (a) and (b). Note that (c) will be described later.

It is said that there are several thousand types of molten salt, and for example, lithium chloride (LiCl) molten salt having a melting point of 613° C. may be used. If this salt is heated to about 650°C, water is blown into it, and this water is further electrolyzed, hydrogen (H ₂ ) is produced at the cathode and oxygen (O ₂ ) will appear.
Strictly speaking, in the water electrolysis described above, the following reaction proceeds at the cathode.
H ⁺ +e ^- →H
H ₂ O+e ^- →H+OH ^-
OH ^- +e ^- →H+O ^--
That is, hydrogen atoms (H) are generated from hydrogen ions and the like. Thereafter, two hydrogen atoms combine to generate hydrogen molecules (H ₂ ), that is, hydrogen gas.

The present inventors have noticed that when iron oxide particles are introduced into molten salt near the cathode, they are reduced by the above-mentioned generated hydrogen atoms, and the iron oxide particles become iron particles (Fe).
_Fe2O3 + _6H →2Fe+ _3H2O
Further, the iron oxide particles are also reduced by the above-mentioned generated hydrogen molecules to become iron particles.
Fe ₂ O ₃ +3H ₂ →2Fe+3H ₂ O

In the above, an example using LiCl molten salt was first described. However, chloride has a high melting point, and even LiCl has a melting point of 613°C. Therefore, other suitable molten salts include alkali metal hydroxides and/or alkaline earth metal hydroxides (for example, LiOH, NaOH, KOH, RbOH, CsOH, MG(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ , Ba(OH) _{2 ,} etc.), and at least one of these or a combination thereof is suitable. In particular, NaOH has a melting point of 318°C and a boiling point of 1388°C, and KOH has a melting point of 360°C and a boiling point of 1320°C, so the melting point is lower than that of chlorides such as LiCl, and the present invention can be carried out better even with a low temperature heat source. This allows for a large degree of freedom in selecting heat sources. In addition, these two types of hydroxides, NaOH and KOH, have a high deliquescent property and can take in a large amount of water vapor, so they have the advantage of a higher reaction rate than chlorides.

Note that, as described later, NaOH is a type of solvent and is not consumed. Also, in the case of lithium chloride, it is not consumed.

The chemical formula for water electrolysis in sodium hydroxide (caustic soda: NaOH) is as follows. Note that the NaOH molten salt is composed of Na ⁺ ions and OH ^- ions, Na has a strong tendency to ionize, and Na remains unchanged. That is, NaOH is a type of solvent and is not consumed.

4H ₂ O+4e ^- →2H ₂ +4OH ^- (Hydrogen is generated from the cathode)
4OH ^- →O ₂ +2H ₂ O+4e ^- (Oxygen is generated on the anode side)

From these two chemical formulas, it follows that water was transformed into hydrogen and oxygen. The chemical formula is as follows.
2H ₂ O → 2H ₂ +O ₂

Furthermore, when iron oxide particles are introduced into a molten salt of an alkali metal hydroxide (for example, NaOH), they are reduced by hydrogen, and the chemical reaction formula in which the iron oxide becomes iron particles (Fe) is based on the above-mentioned LiCl as the molten salt. The situation is the same as in the case below.
Fe ₂ O ₃ +3H ₂ →2Fe+3H ₂ O

Furthermore, one of the features of the present invention relates to the above-mentioned (a), that is, an inexpensive method for producing hydrogen. Generally, water electrolysis requires a large amount of electrical energy. In contrast, the present invention can obtain hydrogen with less energy using both electrical energy and thermal energy.
Although solid electrolytes were considered, they currently require a temperature of about 1000° C., and various problems associated with this have prevented them from being put into practical use. The high-temperature steam electrolysis of the present invention can be carried out at a practical temperature of about 300° C. to 700° C., and hydrogen can be obtained with less energy.

By the way, thermal power generation is a technology for obtaining electrical energy and thermal energy at the same time, but thermal power generation uses fossil fuels, so the possibility of reducing carbon dioxide emissions is out of the question. Furthermore, the reality is that solar cells and wind power, which are considered promising sources of renewable energy, can only generate electricity. In contrast, the present inventors discovered that a molten salt nuclear reactor, which can supply both electrical energy and high heat, can be used as an energy source, reduce carbon dioxide emissions, and be done at a lower cost. This is another feature of the invention ((c) above).
Generally, a method in which water is electrolyzed using a combination of electrical energy (electrolytic method) and thermal energy (thermochemical method) is called a "hybrid thermochemical method." Using a combination of electrolysis and thermochemical methods, the required energy is only about 3kWh per ^cubic meter of hydrogen, which is cheaper than the conventional water electrolysis method (about 5kWh).

As shown in the lower curve of FIG. 2, water electrolysis is possible even at room temperature, but requires high voltage (energy). However, it turns out that if the temperature during electrolysis is raised, the voltage can be lowered.
The upper curve in FIG. 2 shows the total enthalpy (ΔH) of the input electrical energy (ΔG) and thermal energy (TΔS). This curve shows that the higher the temperature, the less total energy required. In the present invention, it is desirable to set the temperature of the molten salt and its container to 650°C, which is currently possible. However, if the durability of the container against high temperatures is proven or improved in the future, it will be possible to carry out smelting at even higher temperatures and with even less energy (that is, at a lower cost).

The present inventors have already studied and developed various techniques for injecting water into molten salt and electrolyzing this water. For example, there is a technology that utilizes this technology for ammonia synthesis, and this technology is a technology that generates hydrogen atoms by electrolysis (see Fig. 7 of Non-Patent Document 3).

As a result of further intensive studies, the present inventors have discovered the present invention, in which hydrogen is produced in molten salt by electrolysis, and the produced hydrogen is utilized for reducing iron oxide. This mechanism has been confirmed in principle experiments described later in [Example]. Furthermore, the present inventors heated lithium chloride (LiCl) molten salt to about 650° C. by using the metal compound reduction device using hydrogen in this embodiment shown in FIG. If this water is electrolyzed, hydrogen will come out at the cathode and oxygen will come out at the anode.Furthermore, if iron oxide particles are present in the molten salt near the cathode, the iron oxide particles will be reduced by hydrogen, and the iron oxide will be reduced. It has been found that it becomes a reduced product, and as the reduction progresses further, it becomes iron particles (Fe).

As can be seen from Fig. 3, the iron manufacturing method and the iron manufacturing equipment of the present invention are extremely simple equipment for iron manufacturing, and the temperature required for iron manufacturing is lower than the approximately 2000°C that is used in current iron manufacturing. It is. The molten salt used in the iron manufacturing method and the iron manufacturing equipment of the present invention has a very low vapor pressure and hardly evaporates, so it has the advantage that it can be operated at normal pressure. The raw materials required for the iron manufacturing method and the iron manufacturing equipment of the present invention are only iron ore and water, and the molten salt is advantageous in that it can be used continuously because it is not consumed. Moreover, with the iron manufacturing method and the iron manufacturing apparatus of the present invention, as is clear from the chemical formula, no CO ₂ is generated.

Note that the iron manufacturing method and iron manufacturing apparatus of the present invention shown in FIG. 3 are designed to blow the water (preferably water vapor at a temperature exceeding 100° C.) initially introduced into the molten salt. However, as described above, in the iron manufacturing method and the iron manufacturing apparatus of the present invention, although hydrogen is produced by electrolysis of the initially introduced water, it is returned to water by reduction of iron oxide. Therefore, in the iron manufacturing method and the iron manufacturing equipment of the present invention, the reactions of hydrogen generation and iron oxide reduction should proceed with the water initially contained in the molten salt without directly blowing water into the molten salt. In order to replenish enough water into the molten salt and make the reaction proceed better, it is more reliable to blow water into the molten salt.

Furthermore, not all of the 100% of the produced hydrogen can be used for the reduction of iron oxide, and some surplus hydrogen tends to escape from the upper part of the molten salt in the form of gas. Therefore, since there is a possibility of ignition when hydrogen is mixed with oxygen, the present inventors developed a second embodiment of the present invention that has a configuration that allows hydrogen and oxygen to be discharged separately, as shown in FIG. Discovered iron manufacturing methods and iron manufacturing equipment.
According to the iron manufacturing method and iron manufacturing apparatus according to the second embodiment of the present invention, this surplus hydrogen is again blown into the molten salt system, and this hydrogen can also be used for reducing iron oxide. Alternatively, since hydrogen can reduce iron oxide even if it is not in the molten salt, the inventors can transfer this excess generated hydrogen to another container (e.g., free of molten salt), as shown in FIG. A manufacturing method and iron manufacturing apparatus thereof according to a third embodiment of the present invention can also be considered, which has a configuration that can be introduced and used for reducing iron oxide.

To summarize the above-mentioned process, the main characteristic elements of the present invention discovered by the present inventors are the following three items. Although embodiments and examples regarding iron smelting have been described in this specification, the following three items also apply to metals (other than iron, which are produced as metal compounds such as oxides and sulfides). For example, it can also be applied to the smelting of copper, zinc, etc.).
(1) Electrolyze water in molten salt.
(2) Metal oxides such as iron oxide are reduced by hydrogen obtained by electrolysis.
(3) In water electrolysis, the necessary electric power and high-temperature heat are obtained using a molten salt nuclear reactor (commonly known as FUJI).

The above molten salt iron manufacturing method will be referred to as RIMS (Reduction of Iron-oxide by Molten Salt), and the economic efficiency of RIMS will be evaluated below. The energy for producing iron (Fe) by RIMS is equivalent to the energy for producing hydrogen, which is approximately 2,500 kWh per ton of iron. Therefore, if the power generation cost by the molten salt furnace FUJI is 5 yen/kWh, it is 12,500 yen. Since RIMS is a simple system, the equipment cost (capital cost) is expected to be considerably lower than that of a molten metal furnace.

On the other hand, as mentioned above, 0.5 tons of coal is required to produce 1 ton of iron, and 2 tons of CO ₂ ) are emitted during this process. The coal cost at the end of 2021 is over 20,000 yen per ton, and the current coal cost per ton of iron is 10,000 yen, which is almost the same as the cost from RIMS. Furthermore, if we assume that the carbon tax per ton of CO ₂ emitted is 10,000 yen, the target cost for smelting (excluding iron ore raw material costs) is approximately 30,000 yen, and the manufacturing cost of RIMS (14,000 yen). ) is well below this value.

Furthermore, if heat is supplied from a molten salt furnace as shown in FIG. 5, it should be even cheaper than the above. That is, the heat generation efficiency of the molten salt furnace is approximately 44%, which means that half of the calorific value is wasted. Therefore, if part of the high-temperature heat used for power generation in the molten salt furnace could be used as is, efficiency would be further improved and costs would be reduced. The above-described technology for combined heat and power reactors can also be applied to other nuclear reactors, such as high-temperature gas reactors that can discharge high temperature.
The outlet temperature of the molten salt furnace is about 700°C, and since the molten salts are liquids, heat exchange is easy. The molten salt used in the molten salt furnace is a fluoride, and the molten salt used in this RIMS is a chloride or a hydroxide, but the physical properties as a liquid are not significantly different. Both are chemically inert and stable substances.

The results of the above economic evaluation are shown in Figure 6. As mentioned above, the smelting costs excluding capital costs and iron ore raw material costs are compared. Case 1 of the present invention is a trial calculation for the original molten salt furnace FUJI exclusively for power generation, and Case 2 of the present invention is an evaluation for a combined heat and power furnace.

The standard power generation capacity of the molten salt furnace FUJI is 200,000 kWe (200 MWe), and 2,500 kWh is consumed to produce hydrogen for one ton of iron, resulting in a production rate of 80 tons per hour. Therefore, 700,000 tons of iron can be produced annually. On the other hand, Japan has about 30 molten metal furnaces (blast furnaces) and produces about 90 million tons annually. That is, on average, one unit produces 3 million tons per year. From the above, as shown in Figure 7, it is desirable to have about 5 FUJI units per blast furnace (as there is a periodic inspection once every two years, the annual average operating rate is assumed to be about 90%). Based on this assumption, if Japan as a whole were to produce 700,000 tons of steel per year, 150 FUJI units would be required, and 20 times that number, 3,000 units, would be needed worldwide.

In addition, we will consider whether this power supply can be covered by renewable energy such as solar power generation or wind power generation. As discussed in the section on hydrogen production below, it is unrealistic to use renewable energy to power even one FUJI molten salt reactor, much less the power needed to power 150 FUJI molten salt reactors in Japan. It is impossible to obtain. Therefore, the present invention is highly economical and feasible.

In addition to iron, metals such as copper, zinc, nickel, tin, lead, cobalt, and molybdenum, which are produced as oxides and sulfides, are currently reduced using carbon, and the RIMS described above is applied. This allows smelting without emitting _CO2 .
Furthermore, the molten salt electrolysis method for hydrogen production has the potential to produce other metals such as aluminum, titanium, potassium, calcium, sodium, and magnesium more advantageously than by simple electrolysis; for example, using a nuclear reactor. It may also be applicable to chloride reprocessing (dry reprocessing) of spent fuel.

As described above, the present invention fundamentally changes the 3,000-year history of steel manufacturing. Furthermore, it can also be applied to the field of smelting and refining, in which metal compounds such as other metal oxides are reduced to produce metals other than metal compounds from metal compounds such as oxides. Furthermore, the present invention greatly contributes to the prevention of global warming by not emitting CO ₂ .

A molten salt nuclear reactor (hereinafter referred to as a molten salt reactor, commonly known as FUJI) is a nuclear reactor that uses liquid fuel containing uranium, thorium, etc., and has been proposed as a power reactor (for example, Non-Patent Document 4). A molten salt reactor has a moderator in its core, and when liquid fuel flows through the moderator, a nuclear fission reaction occurs, generating thermal energy, which is used for power generation. Molten salt reactors have been attracting attention in recent years as an inexpensive power generation system because the fuel is liquid, so there is no fuel damage, no hydrogen explosions, and other safety features.Furthermore, the structure is simple. There is. The power generation cost of 5 yen/kWh using the molten salt furnace FUJI is shown in Non-Patent Document 5.

1-2. Overview of hydrogen production using this technology

Generally, a method in which water is electrolyzed using a combination of electrical energy (electrolytic method) and thermal energy (thermochemical method) is called a "hybrid thermochemical method." By using the above-mentioned electrolytic method and thermochemical method in combination, the energy required for iron manufacturing is only about ³ kWh per cubic meter of hydrogen. As mentioned above, if the power generation cost using the molten salt furnace FUJI is 5 yen/kWh, the cost ^per cubic meter of hydrogen will be 15 yen, which can significantly reduce the manufacturing cost, which is currently around 100 yen.

Furthermore, regarding the molten salt iron manufacturing RIMS that adopts the configuration as shown in FIG. It is as follows. That is, the present inventors assume, from FIG. 2 described above, that the thermal energy and electrical energy required for water electrolysis (hydrogen production) at 650° C. are approximately half. Assuming that the electric output of the original FUJI molten salt furnace exclusively for power generation was 200,000 kWe and the thermal efficiency was 50%, we now set the power generation amount to 100,000 kWe as shown in Figure 2, and the thermal energy for the remaining 100,000 kWe (approximately 200,000 kWe). kWt), approximately 1.5 times more energy can be supplied. This calculation process is shown in FIG.
Therefore, the present inventors were able to show that if a combined heat and power furnace is used, the hydrogen production cost will be reduced to 1/1.5, and hydrogen can be produced at a cost of about 10 yen per 1 m ³ of hydrogen. The present inventors show the comparison results with the current hydrogen cost in FIG. 9, and were able to demonstrate that the present invention can achieve a significant cost reduction.

1-3. Regarding the feasibility of creating a hydrogen society As mentioned above, 3 kWh is required to produce 1 m ³ of hydrogen using the hybrid thermochemical method. The production volume is 67,000 m ³ /hour (=200,000 kWe/3 kWh). Therefore, the annual production amount is 530 million m ³ /year (=67000x24x365x0.9) if the operating rate is 90%. The present inventors were able to show that if a combined heat and power system is used, the amount will be 1.5 times this, 100,000 m ³ /hour, and 800 million m ³ /year.

On the other hand, the present inventors also examined the feasibility of solar cells, which are well known as eco-energy, in a hydrogen society. The present inventors assume that the average operation rate is about 20% for so-called mega solar (rated 1000 kW). Since 5 kWh is required to produce 1 m ³ of hydrogen using the conventional electrolysis method, the amount of hydrogen produced per hour is 40 m ³ /hour (=200 kWe/5 kWh). Therefore, the annual production amount is 350,000 m ³ /year (=40x24x365). In order to produce the same amount of hydrogen as one FUJI combined heat and power generation system, 2,500 mega solar units would be required. The site area of one mega solar power plant is said to be approximately 20,000 square ^meters , which is equivalent to one baseball field, and the total area of 2,500 mega solar power plants is equivalent to 2,500 baseball fields.
The present inventors also examined the feasibility of wind power generation, which is well known as eco-energy, in a hydrogen society. For this type of wind power generation, if we target mega-class (1,000 kWe) wind turbines, the average operating rate is about 20%, so 2,500 mega-scale wind turbines are required. Assuming that one mega wind turbine is built every 500 meters, 2,500 mega wind turbines would cover an area of 1,250 km.
Therefore, although the future of Japan's hydrogen society is uncertain, it is estimated that Japan alone will require tens of billions of ^cubic meters of hydrogen per year, and solar power generation and wind power generation will not exceed Japan's annual hydrogen needs. , it turns out that it is very difficult to cover.

1-4. Overview of the steel manufacturing method using hydrogen in the present technology The hydrogen production technology described above involves electrolysis of water in molten salt. By the way, as shown in FIG. 1, it is possible to reduce iron oxide even in a gaseous hydrogen atmosphere. What can be done even in this gaseous hydrogen atmosphere is to introduce the hydrogen generated by the hydrogen production method of the present invention into a separate container, reduce the metal compound with the hydrogen, and obtain the metal, which is included in the metal production method. be.

That is, in the present invention, hydrogen and oxygen can be obtained by introducing water vapor into a high-temperature molten salt and performing electrolysis using a hybrid thermochemical method. If the obtained hydrogen is discharged, recovered, or supplied from the electrolytic section and introduced into a container different from the electrolytic section (preferably the hydrogen production section) in which iron oxide particles are arranged, iron oxide can be reduced by hydrogen. The inventors have found that it is possible to obtain iron (more reduced iron or iron compounds) that is not in its initial oxide form. As mentioned above, the energy required for reducing iron oxide is equal to the energy for producing hydrogen, so the economic efficiency (manufacturing cost) of the present invention is equivalent to and superior to the above-mentioned iron manufacturing technology. An example of a technique in the present invention in which generated hydrogen is introduced into a separate container and a metal compound is reduced by the hydrogen to obtain a metal is shown in FIG. 10, but the technique is not particularly limited to this configuration.

2. Metal Manufacturing Method According to the Present Embodiment In the explanation of the example of the metal manufacturing method according to the present embodiment, the electrical Descriptions of each structure and each method, such as the decomposition mechanism, hydrogen production method or process, metal compound (preferably metal oxide) reduction method or process, molten salt, metal production method, control, etc., will be omitted as appropriate. , the explanations “1.” to “5.” etc. also apply to this embodiment and can be adopted as appropriate.

This embodiment describes a metal manufacturing method for manufacturing or obtaining a metal by reducing a metal compound in a molten salt with hydrogen obtained by electrolyzing water in the molten salt, and a method for manufacturing a metal used for smelting. A manufacturing method or a smelting method can be provided. The metal manufacturing method of this embodiment can be understood with reference to FIGS. 3, 4, 10, 6, and 7.

Further, the present embodiment provides a method for producing a metal, including a hydrogen production process of producing hydrogen by electrolysis in a molten salt, and/or a metal compound reduction process of reducing a metal compound with the hydrogen. You can also do that. Further, the hydrogen production process may employ a water electrolysis process, and hydrogen may be generated or generated at the cathode by electrolysis of the water. The water electrolysis step preferably includes a hydrogen production step of producing or generating hydrogen at the cathode and an oxygen production step of producing oxygen at the anode. Moreover, by going through the metal compound reduction step in this embodiment, it is possible to obtain a metal compound or metal that is further reduced compared to the metal compound before reduction.

The hydrogen production step and the metal compound reduction step in this embodiment can be performed separately or at the same time, and it is also possible to perform the metal compound reduction step using the obtained hydrogen after the hydrogen production step. In addition, the hydrogen generated in the hydrogen production process is recovered or stored, and the recovered or stored hydrogen is further widely used or reused in the metal compound reduction process or the metal production process (for example, in the metal compound reduction process or the metal production process). It is also possible to reuse it by returning it to the compound reduction process, etc.).

In this embodiment, "hydrogen obtained by electrolyzing the water" is, for example, hydrogen obtained from the electrolytic section or the hydrogen production section, more preferably "hydrogen obtained by electrolyzing the water" It may also be hydrogen discharged, recovered, or transferred from a hydrogen production section that is configured (for example, see FIGS. 4 and 10). In addition, if the generated hydrogen is mixed with oxygen generated at the anode, oxygen removal and/or hydrogen adsorption materials or equipment may be used to reduce the oxygen concentration or substantially eliminate oxygen. Hydrogen may be obtained and hydrogen with reduced oxygen concentration may be used.

In addition, the hydrogen production process and the metal compound reduction process in this embodiment are performed in the same reaction vessel from the viewpoint of reducing the metal compound with the obtained hydrogen, reducing carbon dioxide emissions, manufacturing cost reduction, and manufacturing efficiency. A diaphragm electrolytic method may be adopted if desired from the viewpoint of the above, and if necessary. Further, the hydrogen production process and the metal compound reduction process can be performed in separate reaction vessels or reaction devices, and in such a case, the hydrogen generated in the hydrogen production process is transferred to a gas recovery mechanism or a gas supply mechanism. It is preferable that the metal compound be supplied to a metal compound reduction step carried out in a separate reaction vessel or the like using a flow path such as piping or the like.

2-1. Hydrogen Production Process In the hydrogen production process in this embodiment, it is preferable to electrolyze water in a molten salt to obtain hydrogen.
The hydrogen production process used in this embodiment is not particularly limited, but it is possible to adopt an electrolysis process configured to use molten salt as an electrolytic bath, and to produce hydrogen using the electrolysis process. can be manufactured.
The electrolysis mechanism or hydrogen production mechanism preferably includes a water supply mechanism to the molten salt, cathode and anode electrodes, and a reaction vessel (electrolytic section) containing the molten salt as an electrolytic bath. Further, the vertical cross-sectional view of the reaction vessel may be U-shaped as shown in FIG. 3, but it is convenient to have an H-shape as shown in FIGS. 4 and 10. This is because hydrogen can be easily separated from the oxygen production region, hydrogen can be brought into contact with metal compounds in the region where the amount of oxygen atoms is reduced and the amount of hydrogen is increased, and/or each gas can be mixed. This is suitable because it is easy to generate and recover without any waste.

2-1-1. Electrolysis Mechanism In this embodiment, the electrolysis unit (or tank) that performs electrolysis preferably includes a molten salt and cathode and anode electrodes (see, for example, FIGS. 3, 4, and 10), and further includes: It is more preferable to have a hydrogen production section (also referred to as a cathode chamber) equipped with a cathode and an oxygen production section (also referred to as an anode chamber) equipped with an anode. It is further advantageous to provide a connection configured to allow movement of the electrolytic bath (see, for example, FIGS. 4, 10).
Preferably, the hydrogen production section includes a liquid region in which a molten salt and a cathode exist, and a gas region in which hydrogen generated from the liquid region exists. Further, it is preferable that the oxygen production section includes a liquid region in which molten salt and an anode exist, and a gas region in which oxygen generated from the liquid region exists. However, the structure may be such that there is no gas region in the hydrogen production section and/or the oxygen production section.
Further, it is preferable that the connection section is connected so that the gas existing in the gas regions of the hydrogen production section and the oxygen production section cannot move between each other. It is more preferable that the structure is such that only the molten salt exists and can move between the two parts, and even more preferably, the liquid level of the molten salt that exists in both the hydrogen production section and the oxygen production section is It is also preferable to arrange the connection section below the surface.

The electrolysis mechanism is configured so that hydrogen and oxygen can be obtained from water contained in the molten salt by passing a direct current through the cathode and anode.
The electrolytic current value in this embodiment is not particularly limited, but for example, when a metal chloride (also referred to as metal chloride) (such as LiCl) is used as a molten salt, the cathode side reaches the metal (Li) deposition potential, and the anode side On the other hand, the current value is set to be as large as possible within the range up to the potential at which chloride gas (for example, Cl, etc.) is generated, and electrolysis can be carried out while checking changes in the cathode and anode potentials over time. Further, the current density is preferably 1 A/m ² or more, and 100 A/m ² or less, for example.

In this embodiment, the cathode and anode, which are electrodes, are not particularly limited, and any known cathode or anode used for electrolysis in molten salt can be employed. It is preferable that the electrode is arranged so that there is a gap between the inner wall and the electrode so that the electrode does not come into direct contact with the inner wall of the reaction vessel.

The material of the base of the electrode is not limited as long as it has conductivity sufficient to allow current to flow at the temperature at which electrolysis occurs in molten salt, and the size of the base is also not limited. It can be selected as appropriate depending on the purpose of use of the bath and substrate.

Examples of the material of the electrode include nickel, iron, molybdenum, tungsten, graphite, flash carbon, ferrite, and electron conductive ceramic, and one or more selected from these can be used. For example, nickel or the like can be used as the cathode, and graphite or the like can be used as the anode.

In this embodiment, it is preferable to further use a temperature control mechanism (for example, a heating furnace, etc.) that can control the reaction temperature in the reaction vessel, and it is more preferable that the reaction vessel is a closed type reaction vessel. be.

An advantage of using molten salt in electrolysis is that it can be carried out at high temperatures and under normal pressure. "Normal pressure" in this specification refers to the pressure when no special operation to change the atmospheric pressure, such as pressurization or depressurization, is applied, and is usually about 1±0.05 atm (101,325 pa).
The temperature during electrolysis (preferably temperature under normal pressure) is not particularly limited, but its preferred lower limit is preferably 20°C or higher, more preferably 30°C or higher; The upper limit is preferably 1000°C or less, more preferably 900°C or less, and the preferred numerical range is preferably 20 to 1000°C. In addition, when reducing a metal compound in the molten salt existing in the electrolysis section or the hydrogen production section, the temperature for the reduction reaction of the metal compound described below can be appropriately adopted.

The water supply mechanism is preferably provided with a water supply mechanism configured to be able to supply a fluid (preferably gas) containing water to the electrolytic bath. The water supply mechanism may be configured to supply a gas containing water to the gas region in the reaction vessel, but it is not possible to supply a gas containing water to the liquid surface or in the liquid of the molten salt that is the electrolytic bath. Such a configuration is suitable. The water supply mechanism can, for example, supply water-containing gas to the gas region to create a humid atmosphere, or blow water-containing gas into the liquid region to supply water into molten salt, which is an electrolytic bath.
The water used for the "water-containing fluid" is preferably water vapor, and the water vapor may be heated water vapor or water vapor produced by a spraying device, etc., but in this embodiment, heated The amount of water reacting with the molten salt can be adjusted by adjusting the heating.

The gas used for the "fluid containing water" is not particularly limited, but an inert gas is suitable, and examples of the inert gas include helium gas, neon gas, argon gas, krypton gas, xenon gas, radon gas, etc. Examples include rare gases and nitrogen gas, and one or more selected from these can be used. Among these, rare gases are preferred, and helium gas and/or argon gas are more preferred.

The amount of water added to the molten salt is not particularly limited, but can be calculated, for example, from the following reaction formula, and the minimum necessary amount of water used for reduction of the metal compound can be determined. However, in the case of metals other than iron, the water content can be determined from the reaction formula of the metal. Using the following reaction formula as an example, the amount of water to be added can be set in consideration of the fact that 3/2 H ₂ O is required for Fe to be reduced.
3/2H ₂ O→3/2H ₂ +3/4O ₂
1/2Fe ₂ O ₃ + 3/2H ₂ →Fe+3/2H ₂ O

The temperature of the "water-containing fluid" (preferably water vapor) may be about the melting point temperature of the molten salt, but is not particularly limited, and the lower limit thereof is preferably 20°C or higher, or more. Preferably it is 50°C or higher, more preferably 95 to 100°C or higher, and its preferred upper limit is preferably 150°C or lower, more preferably 120°C or lower, and in the case of NaOH, the preferred numerical range The temperature is 100 to 150°C.

Furthermore, it is preferable that this embodiment further includes a gas recovery mechanism, whereby hydrogen and oxygen generated in the electrolytic section can be recovered in a mixed state or in separate states. In the case of an electrolytic section (electrolytic cell) that is not divided into a hydrogen production section (cathode chamber) and an oxygen production section (anode chamber) as shown in Figure 3, oxygen and hydrogen are mixed in this gas region. It is preferable to discharge or recover these gases together using a gas recovery mechanism. Furthermore, when the hydrogen production section and the oxygen production section are separated, it is preferable to provide a gas recovery mechanism in each section to recover the respective gases. More preferably, the hydrogen production section is provided with a hydrogen recovery mechanism that is provided with piping in the gas region, and the oxygen production section is provided with an oxygen recovery mechanism that is provided with piping in the gas region. Since the gases generated separately can be recovered, each hydrogen and oxygen can be recovered with higher purity and reused. Furthermore, a configuration may be adopted in which the recovered gas or the gas generated in another gas generator is returned to or supplied to the molten salt, for example, the recovered gas or the gas generated in another gas generator can be returned to or supplied to the molten salt. It is possible to adopt a configuration in which a hydrogen supply line is provided to blow the supplied hydrogen into the molten salt.

2-1-2. Electrolytic Bath In this embodiment, it is preferable to use the molten salt as an electrolytic solution in the electrolytic section (electrolytic reaction vessel), and the molten salt can be used as the electrolytic bath.

In addition, the molten salts include, but are not particularly limited to, chemical forms of halides (chlorides, bromides, fluorides, etc.), hydroxides, carbonates, sulfates, phosphates, acetates, nitrates, and silicate salts. It is preferable to use one or more selected from acid salts. As the metal used to form the salt, for example, one or two selected from alkali metals (e.g., sodium, potassium, lithium, etc.), alkaline earth metals (e.g., magnesium, calcium, etc.), aluminum, tin, etc. The above can be used. Furthermore, examples of the halogen include fluorine, chlorine, bromine, and iodine, and one or more selected from these can be used.

Among the molten salts, metal halides (e.g., metal chlorides, metal fluorides), metal hydroxides, metal nitrates, metal sulfates, metal carbonates, metal acetates, metal phosphates, metal silicates A molten salt containing one or more selected from the following is preferable from the viewpoints of high water absorption, improvement in power efficiency for hydrogen production, improvement in reaction efficiency for metal compound reduction, etc., and furthermore, a molten salt containing one or more selected from metal halides and A molten salt containing/or a metal hydroxide is preferable, and it is more preferable to use a metal halide.

Among the metal hydroxides, alkali metal hydroxides and/or alkaline earth metal hydroxides have high water absorption properties, improved power efficiency for hydrogen production, improved reaction efficiency for metal compound reduction, etc. suitable. One or more selected from alkali metal hydroxides and alkaline earth metal hydroxides can be used. Furthermore, alkali metal hydroxides are more suitable from the viewpoints of melting point, cost, etc.
Examples of the alkali metal hydroxide include, but are not particularly limited to, alkali metal hydroxides such as LiOH, NaOH, KOH, RbOH, and CsOH. Among these, NaOH and/or KOH are more suitable from the viewpoint of melting point, cost, etc. Further, the alkaline earth metal hydroxide is not particularly limited, and examples thereof include Mg(OH) ₂ , Ca(OH) ₂ , Sr(OH) ₂ , and Ba(OH) ₂ . One or more selected from these hydroxides can be used.

Among the metal halogen compounds, alkali metal halides and/or alkaline earth metal halides are preferred from the viewpoints of high water absorption, improvement in power efficiency for hydrogen production, improvement in reaction efficiency for reduction of metal compounds, etc. . One or more selected from alkali metal halides and alkaline earth metal halides can be used.

The alkali metal halides include, but are not particularly limited to, alkali metal fluorides such as LiF, NaF, KF, RbF, and CsF; alkali metal chlorides such as LiCl, NaCl, KCl, RbCl, and CsCl; LiBr, NaBr, Examples include alkali metal bromides such as KBr, RbBr, and CsBr; alkali metal iodides such as LiI, NaI, KI, RbI, and CsI. One or more selected from these halides can be used.

The alkaline earth metal halides are not particularly limited, but include, for example, alkaline earth metal fluorides such as MgF ₂ , CaF ₂ , SrF ₂ , BaF ₂ ; alkaline earths such as MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl ₂ , etc. Metal chlorides; alkaline earth metal bromides such as MgBr ₂ , CaBr ₂ , SrBr ₂ and BaBr ₂ ; alkaline earth iodides such as MgI ₂ , CaI ₂ , SrI ₂ and BaI ₂ ; and the like. One or more selected from these halides can be used.

Among the molten salts, alkali metal halogen chlorides are more preferred, and alkali metal chlorides (more preferably lithium chloride) are even more preferred.
Moreover, among the above-mentioned molten salts, those having a melting point of 300° C. or lower are easy to handle. However, from the viewpoint of hydrogen production efficiency, a molten salt with a high melting point is preferable. That is, among the above-mentioned molten salts, those that can dissolve hydrogen and can be heated to about 1000° C. are preferable.

The above molten salt compounds can be used alone or in combination of two or more. The combination of these compounds, the number of compounds to be combined, the mixing ratio, etc. are not limited, and can be appropriately selected depending on the type of metal used for electrolysis, etc.

In the electrolytic bath used in this embodiment, impurities, solubilizing agents, electrolytic auxiliary agents, and the like may be appropriately blended or used as other components mentioned above. Examples of the other components include oxides, hydroxides, and carbonates of alkali metals or alkaline earth metals such as Li ₂ O, LiOH, and Li ₂ CO ₃ . One type or two or more types selected from these can be used.

Further, the temperature of the molten salt (preferably temperature under normal pressure) is not particularly limited, but from the viewpoint of hydrogen production efficiency and energy efficiency, a suitable lower limit is preferably 500°C or higher, more preferably 600°C or higher. ℃ or higher, more preferably 650℃ or higher, and a suitable upper limit is not particularly limited, but from the viewpoint of reducing energy loss and reducing deterioration of the base material, preferably 1000℃ or lower, more preferably 900℃ or lower, More preferably, it is 800°C or less, and the preferred numerical range is more preferably 600°C to 900°C.

2-2. Metal compound reduction step In the metal compound reduction step in this embodiment, it is preferable to reduce the metal compound with hydrogen (more preferably hydrogen produced by electrolyzing water in a molten salt). In this way, a metal obtained by reducing a metal compound can be obtained. One of the advantages of water electrolysis in molten salt is that hydrogen is produced or generated in molten salt, and by bringing the hydrogen present in the molten salt into contact with the metal compound, a reduction reaction of the metal compound can be achieved. can be further promoted.

The metal compound to be reduced may be present in the molten salt in the electrolysis section or the hydrogen production section, and/or in the fluid (e.g., gas such as hydrogen gas, liquid such as molten salt) in the metal compound reduction section. It is preferable to make it exist. When the fluid is a liquid, the structure of the electrolysis mechanism described above can be adopted as appropriate. For example, hydrogen in the molten salt comes into contact with the metal compound near the cathode in the molten salt, Metal compounds can be strongly reduced with good power efficiency and reaction efficiency. Further, when the fluid is a gas, the metal compound can be reduced with hydrogen gas under heating.
The reduction temperature of the metal compound (preferably the temperature under normal pressure) is not particularly limited, and the above-mentioned temperature of the molten salt or known techniques can be adopted as appropriate, and from the viewpoint of reaction efficiency and energy efficiency, it is suitable The lower limit value is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 650°C or higher, and even more preferably 700°C or higher, and the preferred upper limit value is not particularly limited, but energy loss reduction And from the viewpoint of reducing deterioration of the base material, the temperature is preferably 1000°C or less, more preferably 900°C or less, even more preferably 800°C or less, and the preferred numerical range is more preferably 600°C to 900°C. .

As the heating energy in the metal compound reduction process, it is more preferable to use thermal energy than to use electrical energy from the viewpoint of cost reduction, and it is preferable to use thermal energy obtained by heat exchange from the heat source of the molten salt furnace. is more suitable.

Furthermore, the hydrogen generated by the hydrogen production process or method described above is introduced into a container (part) different from the container (part) in which the hydrogen was generated, and the metal compound is reduced with the hydrogen. It is also possible that the separate container (part) is a metal compound reduction part. Thereby, it is possible to obtain a metal obtained by reducing a metal compound, and it is also possible to effectively utilize hydrogen generated in the atmosphere.

Examples of the metal compound used in this embodiment include, but are not limited to, ores, metal oxides, metal sulfides, and metal chlorides, and one or more selected from these may be used. can.
The "metal" of the metal compound used in this embodiment is not particularly limited, but it is preferable to include a metal element, and it may also include a metal element and a non-metal element.
The metal element is not particularly limited, but for example, one selected from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, molybdenum, aluminum, titanium, potassium, calcium, sodium, and magnesium. Or two or more types can be mentioned.
The nonmetallic element is not particularly limited, but may include one or more selected from the group consisting of oxygen atoms, sulfur atoms, chlorine atoms, and the like.
The metal compound is, for example, one or more metals selected from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, molybdenum, aluminum, titanium, potassium, calcium, sodium, and magnesium. Preferably, it is a metal compound containing an element and one or more nonmetallic elements selected from the group consisting of oxygen atoms, sulfur atoms, and chlorine atoms.
Further, the metal compound is, for example, one or more selected from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, molybdenum, aluminum, titanium, potassium, calcium, sodium, and magnesium. Suitable are metal oxides, metal sulfides, or metal chlorides containing metals.
A more preferable metal element is one selected from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, molybdenum, etc., and more preferably one selected from the group consisting of iron, copper, nickel, cobalt, molybdenum, etc. A species or two or more species may be mentioned.

It is preferable that the metal compound is in the form of particles. The size of the particles is not particularly limited to the particle diameter at 50% of the integrated value in the particle size distribution determined by laser diffraction scattering method (average particle diameter D50), but the upper limit of the preferred "average particle diameter D50" The value is preferably 10 mm or less, more preferably 5 mm or less, still more preferably 3 mm or less, more preferably 1 mm or less, and still more preferably 100 μm, 50 μm or less, or 10 μm or less from the viewpoint of reaction efficiency, and its suitable The lower limit of the "average particle diameter D50" is preferably 0.01 μm or more, more preferably 0.1 μm or more, even more preferably 0.5 μm or more, and the preferred numerical range is, for example, 0.01 μm to It may be 5 mm.

In this specification, D10 is the particle diameter at which the volume-based cumulative value in the particle size distribution of metal compound particles is 10%, D50 is the particle diameter at which 50%, as measured by laser diffraction scattering method, The diameter is set to D90. Note that the average particle size can be determined, for example, from a volumetric integrated value measured by a laser diffraction scattering particle size distribution analyzer.
The size of the metal compound is preferably a particle diameter (average particle diameter D50) at 50% of the integrated value in the particle size distribution determined by a laser diffraction scattering method.
For example, a laser diffraction scattering particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.) can be used.

In the process or apparatus for reducing metal compounds, it is preferable to use a support part for holding or supporting the metal compound and its reduced product used in this embodiment, and the support part is resistant to heat, combustion, etc. A material having impact resistance is suitable. The shape of the support part is not particularly limited, and examples thereof include a container (for example, cup shape, dish shape, box shape, etc.), and one or more of these can be used (for example, as shown in the figure). cup-shaped in Figure 3, plate-shaped in Figure 4, etc.). It is preferable that a cathode is further connected to the support part of the container, etc., and one or more support parts (for example, rod-shaped) may be further provided to move, hold, support, etc. the container.

When reducing a metal compound in a molten salt, a support rod may be used to easily take it in and out of the molten salt, and/or a container may be provided with a mesh or porous structure to facilitate the removal of the liquid. A part of the support part that supports the metal compound used in the molten salt may be connected to the cathode. For example, a plurality of metal compounds arranged in the support part are arranged near the cathode, and the cathode and its Metal compounds can be efficiently reduced using hydrogen obtained from nearby water by electrolysis.

The materials of the support part, reaction vessel, etc. for supporting the metal compound are not particularly limited. When the support part is used on the cathode side or near the cathode, it preferably has electrical insulation (also referred to as non-conductivity) and thermal shock resistance. Examples of the electrically insulating material include ceramics such as alumina, and one or more selected from these can be used.

3. Hydrogen production method using molten salt according to the present embodiment In the description of an example of the hydrogen production method using a molten salt according to the present embodiment, the above-mentioned "1." and "2." and the later-described "4." and "5. '' and content that overlaps with the electrolysis mechanism, hydrogen production method or process, metal compound (preferably metal oxide) reduction method or process, molten salt, metal production method, control, etc. configurations and methods Although explanations such as "1." to "5." are omitted as appropriate, the explanations "1." to "5." etc. also apply to this embodiment and can be adopted as appropriate.

This embodiment can provide a hydrogen production method in which hydrogen is produced by electrolyzing water in a molten salt. The produced hydrogen is preferably used to reduce metal compounds in the molten salt, but may also be recovered and used as hydrogen fuel.
In addition, in hydrogen production in this embodiment, by adopting the configuration related to "2. Metal manufacturing method according to this embodiment" above, the hydrogen production process and the metal compound reduction process can be performed at the same time or in the same manner. It may be configured such that the reaction is carried out within a reaction vessel (for example, see FIGS. 3 and 4).

It is preferable to use the hydrogen produced above as a reducing agent from the viewpoint of power efficiency and reaction efficiency. Furthermore, the hydrogen recovery mechanism may further include a flow path (for example, piping) and a valve (on-off valve, flow rate control valve) for releasing hydrogen gas outside the reaction vessel, which is outside the hydrogen production system. Thereby, hydrogen gas released into the atmosphere from the molten salt after generation can be suppressed, recovered, sucked, or released outside the hydrogen production system. One end of the channel for discharging hydrogen gas out of the system projects inside the reaction vessel and is provided in the upper part of the reaction vessel (preferably in the gas region and upper part). It is preferable because the mass of the hydrogen gas is light, and it is more preferable that the flow path is further provided with a fluid pump and/or a flow rate control valve for transferring (collecting, suctioning, discharging, etc.) the hydrogen gas in the flow path. It is. Further, a hydrogen adsorption mechanism including a hydrogen adsorbent capable of adsorbing and releasing hydrogen gas in the flow path and/or a hydrogen supply mechanism (preferably It is preferable to include a hydrogen circulation mechanism, a hydrogen reuse mechanism, etc.). A known hydrogen adsorbent can be used as the hydrogen adsorbent, and examples thereof include metal alloys, ceramics, porous materials (zeolite, etc.), but are not limited to these.

4. Metal manufacturing device, hydrogen manufacturing device, electrolyzer, etc., and their systems according to the present embodiment In the description of the metal manufacturing device, hydrogen manufacturing device, electrolyzer, etc., and these systems according to the present embodiment, the above-mentioned Electrolysis mechanism, hydrogen production method or process, metal compound reduction method or process, molten salt, metal production method, control, etc. that overlap with "1." to "3." and "5." described later, content, etc. Although descriptions of each configuration and each method will be omitted as appropriate, the descriptions of "1." to "5." etc. apply to this embodiment and can be adopted as appropriate.

This embodiment describes a metal manufacturing device configured to reduce a metal compound, and one or more nuclear reactors configured to supply electrical energy and/or thermal energy to the metal manufacturing device, etc. (preferably a molten salt nuclear reactor), it is possible to provide a system for metal production, hydrogen production, etc. (see, for example, FIGS. 5 and 7).

This embodiment is a metal manufacturing apparatus configured to produce hydrogen by electrolysis of water and/or configured to reduce a hydrogen metal compound using hydrogen obtained by electrolysis of water. and one or more nuclear reactors (preferably molten salt reactors) configured to supply electrical energy and/or thermal energy to the metal manufacturing equipment, etc. can be provided. The metal production equipment, etc. may perform the hydrogen production process and/or metal compound reduction process as explained in "2-1." and "2-2." above in the same or separate reaction vessels. good. The hydrogen production process and the metal compound reduction process may be carried out in the same reaction vessel or department, for example, in an apparatus configured to also carry out the metal compound reduction process within the hydrogen production unit, or in a metal compound reduction unit. The device may also be configured so that it can also perform the hydrogen production process.

This embodiment includes an electrolysis unit including a cathode and an anode capable of electrolyzing water in molten salt;
a sealable reaction vessel containing a molten salt as an electrolytic bath;
a water supply configured to supply water to the molten salt;
An electrolyzer, a metal manufacturing device, a manufacturing device for reducing a metal compound to obtain a metal, etc. can be provided (see, for example, FIGS. 3, 4, 10, 5, and 7). Preferably, the manufacturing apparatus and the like further include a temperature control section configured to control the reaction temperature.

The reaction vessel is preferably equipped with a cathode and an anode, and includes a hydrogen production region where hydrogen is produced or generated near the cathode by electrolysis of water in molten salt, and an oxygen production region where oxygen is produced or generated near the anode. These regions may be of a non-separable type (for example, a U-shaped reaction vessel in the vertical section in FIG. 3) or a separated type (for example, a A letter-shaped reaction vessel) may also be used.
More preferably, the reaction vessel further includes a hydrogen production section (a section is also referred to as a region) that includes a cathode, an oxygen production section that includes an anode, and a connection section that connects the liquid regions of these sections. Preferably, each of the hydrogen production section and the oxygen production section is comprised of a gas region and a liquid region, respectively.

In this embodiment, in the hydrogen production region or the hydrogen production section, it is preferable that particles of a plurality of metal compounds are arranged near the cathode from the viewpoint of reduction of the metal compound, and the hydrogen production region or the hydrogen production section is It can also be used as a reduction section. Thereby, the metal compound is present in a region where hydrogen produced by water electrolysis in the molten salt is present at a high concentration, so that the metal compound can be reduced with good power efficiency and reaction efficiency. It is preferable that the metal compound reduction section includes a temperature control section outside the metal compound reduction section that can control the temperature of the reduction reaction.

Further, in this embodiment, it is preferable that the hydrogen generated from the hydrogen production section be introduced into a container or section separate from the hydrogen production section or the electrolysis section. This separate container or section can also be used as a metal compound reduction section in which particles of a plurality of metal compounds can be placed. In addition, another container or section may be used as a hydrogen recovery section or a hydrogen storage section, and the recovered or stored hydrogen is transferred to a metal compound reduction section, a hydrogen production section, and a hydrogen supply section equipped with piping or a flow path. or an electrolysis section. More specifically, it is more preferable that the tip of the piping of the hydrogen supply section is disposed in a liquid region so that hydrogen can be blown into the molten salt of the hydrogen production section. Each of these parts may be appropriately equipped with piping or flow paths, fluid transfer or circulation pumps, fluid flow rate control valves, etc. so that hydrogen can be transferred, circulated, or refluxed.

This embodiment includes various devices such as the metal manufacturing device, the electrolysis device, the hydrogen production device, and the hydrogen production device, and a melting device configured to supply electrical energy and/or thermal energy to the device. It is preferable to include a salt nuclear reactor (see FIGS. 5 and 7).

This embodiment is an electrolysis reaction device or a metal manufacturing device, which further includes a molten salt nuclear reactor 100 configured to supply electrical energy and/or thermal energy to various devices 1 such as the metal manufacturing device. A manufacturing apparatus 1000 for obtaining a metal by reducing a compound, an electrolysis reaction system 10000, or a manufacturing system 1000 for obtaining a metal by reducing a metal compound is more suitable (for example, see FIG. 5). Note that the heat exchange mechanism provided in the manufacturing apparatus 1000, the manufacturing system 1000, etc. is preferably equipped with a circulation flow path, a heat exchanger, etc., as appropriate.

The electrical energy supply mechanism 130 includes a primary heat exchange mechanism 106 provided in the molten salt nuclear reactor 101 and a generator 131 such as a steam turbine that uses a heat source from the primary heat exchange mechanism 106. It is more preferable to include a power generation device 132 that generates electricity and obtains electrical energy, and a power transmission mechanism 133 (including electric wires, a transformer device, etc.) that transmits electrical energy from the power generation device 132 to a metal manufacturing device or the like. Thereby, electrical energy can be supplied to metal manufacturing equipment, hydrogen manufacturing equipment, and the like.

The thermal energy supply mechanism 120 includes a primary heat exchange mechanism 106 provided in the molten salt nuclear reactor, and a secondary heat exchanger that converts the heat source from the primary heat exchange mechanism 106 into a heat source for the metal manufacturing equipment, etc. It is more preferable to include a secondary heat exchange mechanism 120 that transfers a heat source (such as water vapor) via 121 . A tertiary heat exchange mechanism including a tertiary heat exchanger or the like may be further provided in the metal manufacturing apparatus 1 or the like. In addition, using thermal energy supplied from a molten salt nuclear reactor using a secondary heat exchange mechanism or a tertiary heat exchange mechanism, water can be converted into steam (e.g. heated steam at 650°C or higher, room temperature (20 to 30°C ) and can be used as water for electrolysis. Thereby, the heat source received from the tertiary heat exchanger can be used in the metal manufacturing apparatus 1. Thereby, thermal energy can be supplied to metal manufacturing equipment, hydrogen manufacturing equipment, and the like.

4-1. Metal manufacturing equipment, etc. according to this embodiment

This embodiment is a metal manufacturing apparatus that includes an electrolysis section that includes an anode and a cathode that are configured to electrolyze water in molten salt, and a metal compound reduction section that is configured to reduce a metal compound. It is preferable to provide Another aspect of this embodiment can also provide a hydrogen production device that includes an electrolysis section that includes an anode and a cathode that are configured to electrolyze water in a molten salt.
Furthermore, this embodiment preferably includes a temperature control section that controls the molten salt temperature of the electrolytic section and/or the reduction temperature of the metal compound reduction section.
Further, in the present embodiment, it is preferable that the electrolytic section and/or the metal compound reducing section include a container for electrolysis and/or a container for reducing the metal compound that can be sealed.
Furthermore, this embodiment preferably further includes a water supply section configured to supply a fluid containing water into the molten salt, and the water supply section includes piping or a fluid flow path, More preferably, the tip of the piping or fluid flow path is located within the molten salt. Furthermore, the water supply section of this embodiment may be configured to be able to mix heated steam using a heat source supplied from a molten salt nuclear reactor or the like with gas from the gas supply section.

Furthermore, this embodiment is configured to connect a hydrogen production section including a cathode and an oxygen production section including an anode, so that the molten salt that is an electrolytic bath can move between the two sections. It is preferable to include a connecting portion. The hydrogen production section and the oxygen production section may be configured such that they each consist of only a liquid region in which molten salt exists and have substantially no gas region, or they may have a structure in which they each include a gas region in which generated gas exists. , and a liquid region in which molten salt is present.
This embodiment is configured such that a metal compound (for example, a metal oxide, etc.) placed near the cathode can be reduced in the hydrogen production section using hydrogen obtained at the cathode in a molten salt. is suitable.
In this embodiment, it is preferable to recover hydrogen existing in the gas region of the hydrogen production section.
In this embodiment, it is further preferable that the hydrogen generated in the hydrogen production section is introduced into a metal compound reduction section separate from the electrolysis section, and it is more preferable to reduce the metal compound using the introduced hydrogen. This is preferred, and it is even more preferred to reduce the metal compound at a temperature of 650° C. or higher in a hydrogen atmosphere.

Furthermore, it is preferable to further include a hydrogen recovery device configured to recover hydrogen generated in the electrolytic section as a gas, and configured to supply the recovered hydrogen into the molten salt. It is preferable to further include a hydrogen supply device.

Below, the first to third embodiments will be described as examples of the metal manufacturing apparatus using hydrogen obtained by electrolysis of water in molten salt in this embodiment. It is not limited to this. The first embodiment, the second embodiment, and the third embodiment are constructed by appropriately combining or adding the configurations and parts adopted in the first to third embodiments. Good too.

Further, the metal manufacturing device in this embodiment can also be used as a hydrogen manufacturing device that manufactures hydrogen by electrolysis of water in molten salt, and even if it is equipped with metal compound particles and the metal compound reduction process is performed at the same time. Alternatively, the hydrogen production process may be mainly performed without providing metal compound particles. Further, the metal production apparatus in this embodiment has a configuration in which a hydrogen production apparatus for producing hydrogen by electrolysis of water in molten salt is incorporated, and a metal compound reduction process is performed in a separate apparatus from the hydrogen production apparatus. It may be.

4-1-1. <First embodiment>
The first embodiment includes an electrolysis region that includes a cathode 2 and an anode 3 and uses a molten salt as an electrolytic bath 4, and a metal compound reduction region that reduces a metal compound 5 disposed near the cathode in the molten salt. A metal manufacturing apparatus 1a can be provided, which includes a reaction vessel 6 including a reaction vessel 6, and a heating furnace 7 that controls the temperature of the reaction vessel (see FIG. 3). The heating furnace 7 is preferably equipped with a heating mechanism such as a heating coil, a cooling mechanism such as a cooling fan, a control section for controlling the reaction temperature, and the like. As shown in FIG. 3, the reaction vessel is U-shaped in vertical section, and the gas region of the hydrogen production region including the cathode and the gas region of the oxygen production region including the anode are in a non-separated state.

The reaction in the first embodiment is preferably carried out in a closed system. For example, a member in contact with the upper part of the reaction vessel 6 may be used as a closed system, or a closed intermediate vessel 9 may be used. A reaction container 6 may also be provided. Further, it is more preferable to provide an intermediate container 8 between the reaction container 6 or the closed container 7 and the heating furnace 7 from the viewpoint of further improving the sealing performance. Note that it is desirable that there be a gap between the closed container 7, the intermediate container 9, and the heating furnace 8 to the extent that these do not come into contact with each other.

The first embodiment preferably includes a water supply section 20 configured to blow water into the molten salt of the electrolytic bath 4. The water supply section 20 includes a gas supply section 21 equipped with a gas cylinder or the like for supplying a gas (preferably an inert gas) for blowing a gas containing water into the molten salt, and a gas supply section 21 that includes a gas cylinder or the like for supplying a gas (preferably an inert gas) for blowing a gas containing water into the molten salt. It is preferable to include a mixing section 22 for containing the water in the molten salt, and a flow path 23 for blowing the water-containing gas from the mixing section 22 into the molten salt. The gas from the gas supply section is preferably transferred to the mixing section 22 through a pipe 24, and if water is present in the mixing section, the pipe 24 is preferably inserted so as to blow into the water. It is. Further, it is preferable that the pipe 23 be connected to the gas region of the mixing section 22 without contacting the water region, and configured to be able to transfer the gas containing water present in the gas region. Further, the water supply section 20 may be appropriately equipped with a compressor, a flow rate control valve, and the like. Further, in the first embodiment, a bubbling type mixing section 22 is shown, but a configuration that can mix heated steam from a molten salt nuclear reactor or the like and gas from a gas supply section may be used.
The first embodiment preferably further includes a support section 15 that supports the metal compound 5 and is configured to be able to reduce the metal compound 5 without contacting the inner wall of the reaction vessel 6. The metal compound 5 may be connected to the cathode 2, and it is preferable that the metal compound 5 is disposed near the cathode 2.

As a result, in the first embodiment, the metal compound (preferably in particulate form) is reduced by the obtained hydrogen in the presence of the molten salt, and the metal compound is reduced to a further reduced level, or a reduced metal compound is obtained. The metal can be obtained, and the molten salt may be heated to control the temperature. Furthermore, it is preferable to include a gas recovery mechanism 30 for discharging or recovering gas (hydrogen gas, oxygen gas) generated by water electrolysis. The gas recovery mechanism 30 arranges the tip of a pipe in the gas region so as to collect the gas present in the gas region, and the pipe 31 connected to the gas recovery device 30 transfers the gas into the gas recovery device 30. One or more of the following may be provided: a flow rate control valve 32 for adjusting the flow rate of the gas to be collected; and a gas storage section 33 for further separating the recovered gas, removing impurities, storing the gas, etc.

In the description of the example of the first embodiment, explanations of each configuration, each method, etc. that overlap with the contents of the second embodiment and the third embodiment, which will be described later, will be omitted as appropriate, but these explanations will be omitted. , which also applies to the first embodiment and can be adopted as appropriate.

4-1-2. <Second embodiment>
The second embodiment includes a cathode chamber 10 that includes a cathode 2 and produces hydrogen through electrolysis of water in molten salt, an anode chamber 11 that includes an anode 3 that produces oxygen, and a liquid region in these chambers. a reaction vessel 6a comprising an electrolytic region using a molten salt as an electrolytic bath 4; and a metal compound reduction region that reduces a metal compound disposed near the cathode in the molten salt; A metal manufacturing apparatus 1b including a heating furnace 8 that controls the temperature of the reaction vessel can be provided (see FIG. 4). It is preferable that the second embodiment further includes a support section 15 configured to support the metal compound 5 and perform reduction without contacting the inner wall of the reaction vessel 6a. Moreover, it is suitable that the reaction container 6a is in a closed state. Note that it is desirable that there be a gap between each of the reaction container 6a, intermediate container 8, and heating furnace 8 to the extent that these do not come into contact with each other.

The reaction vessel 6a is configured such that a hydrogen production region 10 including a cathode and an oxygen production region 11 including an anode are separated. At this time, it is preferable to employ three parts: the hydrogen production section 10, the oxygen production section 11, and the connection section 12.The production sections 10 and 11 are provided with liquid regions 14a and 14b, respectively, and the connection section 12 is It is preferable that the molten salt 4 is configured to be able to move between the manufacturing section 10 (liquid region 14a) and the manufacturing section 11 (liquid region 14b).
Further, the reaction vessel 6a may be provided with gas regions 13a, 13b and liquid regions 14a, 14b in the respective manufacturing sections 10, 11, respectively. It is preferable that the structure is such that hydrogen and oxygen in the gas regions 13a and 13b cannot move. By adopting such a configuration, hydrogen is obtained by water electrolysis in the liquid region 14a of the hydrogen production section 10, and this hydrogen comes into contact with the metal compound present in the liquid region 14a, so that power efficiency and reaction efficiency can be improved. It can often promote the reduction of the metal compound.
Further, it is preferable that the inner wall of the upper part of the connection part is configured not to exceed the liquid level of each of the liquid regions 14a and 14b of the hydrogen production part and the oxygen production part, but to be below the liquid level. . By adopting such a separation configuration, hydrogen and oxygen generated in the respective gas regions 13a and 13b can be easily and efficiently removed using the gas recovery mechanisms 30a and 30b without mixing them. Each is configured to be easily and efficiently collected. The gas recovery mechanism 30a is a hydrogen gas recovery mechanism, and the gas recovery mechanism 30b is an oxygen gas recovery mechanism, and the configuration of the recovery mechanism can appropriately adopt the gas recovery mechanism of the first embodiment. . Further, the water supply mechanism 20 can appropriately employ the water supply mechanism of the first embodiment. Moreover, the support part 15 can appropriately adopt the support part of the first embodiment.

As a result, in the second embodiment, the obtained hydrogen is brought into contact with the metal compound (preferably particulate) more efficiently in the presence of the molten salt, and is reduced, so that the metal compound is further reduced. Metal compounds or reduced metals can be obtained.
Further, the cathode chamber 10 may be composed of a liquid region 14a of molten salt and a gas region 13a containing hydrogen gas. It is preferable to include a mechanism 30a. The recovered hydrogen may be used by being supplied to another reaction system using piping or a flow path, or it may be refluxed or supplied to the cathode chamber 10 where the hydrogen was produced for the reduction of metal compounds. Hydrogen may be reused.

4-1-3. <Third Embodiment>
The third embodiment includes a cathode chamber 10 for producing hydrogen, an anode chamber 11 for producing oxygen, and a connection part 12 for connecting the liquid regions 14a and 14b of these chambers by electrolysis in molten salt. A hydrogen production section 50a includes a reaction vessel 6a having an electrolysis region using molten salt as an electrolytic bath, and a heating furnace 8 for controlling the temperature of the reaction vessel, and hydrogen generated by the hydrogen production section is introduced. , and a metal compound reducing section 50b that reduces the metal compound in the hydrogen atmosphere (see FIG. 10).

The hydrogen production section 50a in the third embodiment includes a reaction vessel 6a that can perform the hydrogen production process without disposing the metal compound 5, and the reaction vessel 6a is described in the second embodiment above. It is possible to employ a reaction vessel 6a having a similar structure.
The gas recovery mechanism 30a in the third embodiment is preferably provided with a flow path for introducing hydrogen generated in the hydrogen production section 50a into a metal compound reduction section 50b, which is another container or device. A configuration in which the hydrogen generated in the section 50a can be transferred to the metal compound reducing section 50b is preferable, and the gas recovery mechanism 50 of the first embodiment described above can be adopted as appropriate.

The metal compound reduction unit 50b in the third embodiment can reduce the metal compound by controlling heating in a hydrogen atmosphere, and may employ a known metal compound reduction apparatus or method. Alternatively, the metal compound reducing section may be configured to adopt the metal compound reducing step used in this embodiment and reduce the metal compound with hydrogen in a molten salt.
Further, the water supply mechanism 20 can appropriately employ the water supply mechanism of the first embodiment.

As a result, the hydrogen generated by electrolysis of water is introduced into another part, and the hydrogen is efficiently brought into contact with the metal compound and reduced to obtain a more reduced metal compound or a metal. Since the reduced product of the metal compound is not in the molten salt but in the atmosphere, there is no need to remove the molten salt or to cool down the molten salt, and subsequent recovery is easy.

4-2. Molten Salt Nuclear Reactor The molten salt nuclear reactor used in this embodiment will be described with reference to FIG. 5, but is not particularly limited thereto. The molten salt nuclear reactor 100 is preferably a nuclear reactor configured to use molten salt as a fuel and can serve as a power source and/or a heat source, and is a general or known molten salt reactor. (For example, see Patent Document 4 and Patent Document 5). For example, the molten salt reactor 100 includes a reactor core 102 that uses molten salt as fuel to cause a nuclear reaction to generate heat, and a reactor core 102 in which a primary fluid (for example, primary coolant) 105 containing fuel circulates in a reactor vessel 101. It is provided with at least a fluid circulation mechanism 106, a control rod 103 for controlling the nuclear fission reaction in the reactor, and a control rod drive mechanism 104 for controlling the drive for moving the control rod in and out of the reactor core. Furthermore, the control rods are typically used to start or stop a nuclear fission reaction, and may also be used to control the nuclear fission reaction and control the in-reactor power.

Furthermore, the molten salt reactor 100 may be equipped with a fuel circulation pump for controlling the circulation of the primary fluid, and the primary fluid circulation mechanism in the reactor core is equipped with the fuel circulation pump, and the pump head is equipped with the fuel circulation pump. The flow rate, speed, etc. of the fluid in the primary fluid circulation may be controlled by operation control.
Furthermore, in the core of the molten salt reactor 100, one or more block members are arranged that generate heat through a nuclear reaction when the molten salt fuel passes through, and the core is constituted by the one or more block members. is suitable, and the block member is preferably a graphite block.

The thermometer (not shown) used in this embodiment may be either a contact type or a non-contact type, and the thermometer may be placed, for example, inside molten salt, its flow path, or inside a power source or heat source. In addition, various temperatures can be monitored or measured. Examples of contact type thermometers include thermistors, thermocouples, resistance temperature detectors, etc., and examples of non-contact type thermometers include radiation thermometers, color thermometers, etc., and one or two types of these can be used. You can select from the above.

In this embodiment, the "molten salt fuel fluid" of the molten salt nuclear reactor is referred to as the "primary fluid", the "fluid for receiving heat from the molten salt fuel fluid through heat exchange" as the "secondary fluid", and the "the fluid ( A fluid that is heated using a secondary fluid as a heating source medium is also called a tertiary fluid. In addition, in this embodiment, a system using a primary fluid as a heat source (preferably a fluid circulation mechanism in which molten salt fuel fluid circulates) is used as a primary system, and a secondary fluid that exchanges heat with the primary fluid of the primary system is used as a heat source. A system to be used (preferably a fluid circulation mechanism in which a secondary fluid circulates) is a secondary system, a system that uses a tertiary fluid that exchanges heat with a secondary fluid of the secondary system, or a system that uses a tertiary fluid as a tertiary heat source. A system (preferably a tertiary fluid circulation mechanism or a tertiary heat source) is also referred to as a tertiary system. However, the n-th numbers such as primary, secondary, and tertiary are added for convenience of explanation, and by adding n-th, this embodiment is not limited in a narrow sense, but is particularly limited. isn't it.

The molten salt nuclear reactor 100 can use the molten salt fuel fluid in the molten salt nuclear reactor as a primary fluid, and can give heat to a fluid (secondary fluid) for receiving heat from the primary fluid by heat exchange. Then, the secondary fluid circulates through the circulation channel, and during the circulation, a mechanism or device serving as a power supply source and/or heat supply source generates electrical energy and/or Thermal energy can be supplied to other mechanisms, devices, systems, etc. In this way, the heat receiving fluid of the secondary or tertiary fluid can be used as a heating source medium.
In the case of a power source, a power generation mechanism or device (e.g., a steam turbine, It is suitable for use in power generation mechanisms (e.g., power generation mechanisms equipped with a generator connected to a generator, a condenser that cools steam and returns it to water, etc.).
In the case of a heat source, it is usually preferable to use it in a mechanism or device that uses a tertiary fluid that has received heat from a secondary fluid through a secondary heat exchange mechanism as a heat source. The heated steam can be used as water for electrolysis.

Further, the molten salt reactor used in this embodiment is not particularly limited in terms of output scale, size, etc., but by controlling the output of the molten salt reactor of this embodiment, even if the output is small, There is an advantage that a stable amount of heat can be given to the secondary fluid from the molten salt nuclear reactor which is the heat source. The molten salt nuclear reactor is preferably a small molten salt nuclear reactor of 200,000 kW or less, 10,000 to 50,000 kW, or 10,000 to 30,000 kW. Note that 1 watt is the power that produces energy equal to 1 joule per second. Further, the temperature inside the molten salt nuclear reactor during operation or at which the secondary fluid can be supplied in this embodiment is not particularly limited, but for example, in FIG. °C, more preferably 500 to 900 °C, still more preferably 500 to 700 °C. Further, the reactor and cooling system may be at normal pressure.

Moreover, the molten salt of the fuel used in the molten salt nuclear reactor is not particularly limited, but is stable, for example, by melting at 500°C and not decomposing the molten salt when the anode and cathode are immersed and a current is applied. It is preferable that the potential window, which is the range of potential that can be electrolyzed, is wide. Specifically, the molten salt used in the electrolysis mechanism described above may be appropriately employed, and the molten salt of the fuel used in this embodiment is not particularly limited, but may be selected from protonium, uranium, thorium, etc. Examples include molten salts containing one or more of the following, and thorium molten salts are preferred.
Further, as the secondary fluid used in this embodiment, it is preferable to use one or more fluids selected from fluids that can be used as coolants for nuclear reactors, such as metal fluids, the above-mentioned molten salts, and the like. The metal may be selected from, for example, potassium metal (melting point 64°C), sodium metal (melting point 98°C), lithium (melting point 181°C), sodium-potassium alloy (for example, 56% sodium-44% potassium (melting point 19°C)), etc. Among these, sodium molten salt or sodium metal is preferred as the secondary fluid, and sodium metal is more preferred.

5. Another Aspect of the Present Embodiment In the description of the example of another aspect of the present embodiment, the electrolysis mechanism, hydrogen production process, metal compound, etc., which overlap with the above-mentioned "1." to "4." and the content described later, will be described. Although explanations of each structure and each method such as the reduction process, molten salt, and metal manufacturing method will be omitted as appropriate, the explanations of "1." to "4." and the contents to be described later will be explained in this embodiment. This also applies and can be adopted as appropriate. The control unit used in this embodiment is configured to execute the method in this embodiment, and instead of the control unit, an operator (human) may appropriately execute the method in this embodiment.

An apparatus or system that utilizes the metal production method, hydrogen production process, metal compound reduction process, method of smelting metal using hydrogen obtained in molten salt, etc. according to the present embodiment includes at least the above-mentioned methods. It is preferable that an apparatus such as an electrolysis reaction apparatus or a metal manufacturing apparatus equipped with a control unit is provided, or that the method according to the present embodiment is incorporated as a program or the like. A system such as an electrolysis reaction system or a metal production system of the present embodiment has a control unit or a control device for electrolysis reaction or metal production, etc. equipped with the control unit, and other units or other devices. , a communication unit capable of transmitting and receiving wirelessly and/or by wire may be further provided.

Note that the method according to the present embodiment may be applied to a device or control unit including a CPU in a management device (for example, a computer, PLC, server, cloud service, etc.) for the production of metal obtained by electrolysis reaction or reduction of a metal compound. It is also possible to realize this by Further, the method according to the present embodiment is stored as a program in a hardware resource including a recording medium (non-volatile memory (USB memory, SSD, etc.), HDD, CD, DVD, Blu-ray disc, etc.), and is realized by the control unit. It is also possible. With the control unit, it is also possible to provide an apparatus including the control unit or the system, such as a management system for electrolysis reactions or metal production. Further, the device may include an input unit such as a keyboard, a communication unit such as a network, a display unit such as a display, and the like.

A management device or a management system for electrolysis reactions, metal manufacturing, etc. can include an input unit such as a keyboard, a communication unit such as a network, an output unit such as a display, a storage unit such as an HDD, and the like. The device or system preferably includes an input section, an output section, and a storage section, and further preferably includes a communication section and/or a measurement section.
The input unit can receive user operations by an operator who performs the method of this embodiment. The input unit can include, for example, a mouse and/or a keyboard. Further, the display surface of the display device may be configured as an input unit that accepts touch operations.
The output unit can output various situations such as electrolysis reactions or metal manufacturing, and information related thereto (for example, tables, diagrams, explanatory text, etc.). Examples of the output unit include, but are not limited to, a display device that displays an image, a speaker that outputs sound, a printing device that prints on a print medium such as paper, and the like.
The storage unit can store data input by an operator, data set for monitoring or executing various conditions of electrolysis reactions, or metal production, and information related thereto. . The storage unit may include, for example, a recording medium.
Furthermore, the system according to this embodiment can be executed by using programs and hardware. An embodiment (not shown) of a computer 1 according to an embodiment of the present invention includes, but is not limited to, at least a CPU as components of the computer 1, and further includes a RAM, a storage section, an output section, and an input section. It is preferable to include one or two selected from the following: a RAM, a storage section, an output section, and an input section; , a measuring section, a ROM, and the like. Preferably, the respective components are connected by, for example, a bus serving as a data transmission path.

The present technology can also adopt the following configuration.
・[1] A metal manufacturing method, a smelting method, or a chemical method in which a metal compound is reduced using hydrogen obtained by electrolyzing water in a molten salt to produce or obtain a metal. Electrolysis method. It is preferable to produce or obtain a metal by reducing a metal compound in the molten salt with hydrogen in the molten salt generated by water electrolysis.
・[2] Includes a hydrogen production process in which hydrogen is obtained by electrolyzing water in a molten salt, and a metal compound reduction process in which a metal compound is reduced with the hydrogen to produce a metal or a metal is obtained. , metal manufacturing method, smelting method, or chemical electrolysis method.

- [3] The method according to [1] or [2] above, wherein the metal compound is in the form of particles. Regarding the size of the particles, the smaller the particle size (average particle size D50) at 50% of the integrated value in the particle size distribution determined by laser diffraction scattering method, the better, and is preferably 10 mm or less.
・[4] Any one of [1] to [3] above, in which the hydrogen is introduced from a reaction container for hydrogen production into another container (reaction container for metal compound reduction), and the hydrogen is used. The method described in. The other container is preferably a container different from the container for electrolyzing water (more preferably the hydrogen production section and the oxygen production section). More preferably, the metal compound is reduced to obtain the metal in the separate container.

- [5] The method according to any one of [1] to [4], wherein the electrolysis is performed using electrical energy and/or thermal energy supplied from a molten salt nuclear reactor. As for the molten salt reactor, a small molten salt reactor is suitable from the viewpoint of zero carbon dioxide gas emission and cost reduction, and furthermore, by using multiple small molten salt reactors in conjunction, it can be stably operated. This is suitable from the viewpoint of stably supplying electrical energy and thermal energy.
・[6] The molten salt is (a) a metal halide (preferably a metal chloride, a metal fluoride), a metal hydroxide, a metal nitrate, a metal carbonate, a metal sulfate, a metal acetate, a metal phosphorus. One or more selected from acid salts, metal silicates, etc., (b) at least one of alkali metal chlorides or alkaline earth metal chlorides, or (c) alkali metal hydroxides. or (d) selected from alkali metal chlorides, alkaline earth metal chlorides, alkali metal hydroxides, alkaline earth metal hydroxides, etc. (e) a mixture of (b) and (c). Further, the molten salt preferably contains a metal hydroxide, more preferably an alkali metal hydroxide or an alkaline earth metal hydroxide (LiOH, NaOH, KOH, RbOH, CsOH, Mg(OH) ) ₂ , Ca(OH) ₂ , Sr(OH) ₂ , and Ba(OH) ₂ ), or both thereof.

- [7] The method according to any one of [1] to [6], wherein the metal compound is a metal compound containing a metal element and a non-metal element. More preferred metal elements are one or more selected from the group consisting of Groups 4A and 5A, and more preferred nonmetallic elements are hydrogen, nitrogen atom, chlorine atom, carbon atom, and boron atom. , sulfur atoms, and oxygen atoms. More preferably, the metal is from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, molybdenum, aluminum, titanium, potassium, calcium, sodium, and magnesium, more preferably iron, copper, zinc. , nickel, tin, lead, cobalt, and molybdenum. Further, more preferably, the nonmetallic element is one or more selected from the group consisting of oxygen atoms, sulfur atoms, and chlorine atoms.

・[8] The water in the molten salt is water that is present in the molten salt due to the hygroscopic action of a gas containing water in a humid atmosphere from the surface of the molten salt, and/or water that is present in the molten salt by a gas containing water being absorbed into the molten salt. The method according to any one of [1] to [7] above, wherein the water is made to exist in the molten salt by a mechanical mechanism such as blowing, stirring, or mixing. More preferably, the water is water obtained by blowing a moisture-containing inert gas (for example, rare gas, etc.) into a molten salt.
- [9] The method according to any one of [1] to [8] above, wherein the method for producing the metal is used as smelting.

・[10] A hydrogen production method in which hydrogen is obtained by electrolyzing water in molten salt.
・[11] The molten salt includes (a) a metal halide (preferably a metal chloride, a metal fluoride), a metal hydroxide, a metal nitrate, a metal carbonate, a metal sulfate, a metal acetate, and a metal One or more selected from phosphates, etc., (b) at least one of an alkali metal chloride or an alkaline earth metal chloride, or (c) an alkali metal hydroxide or an alkaline earth metal chloride. at least one of metal hydroxides, or (d) alkali metal chloride, alkaline earth metal chloride, alkali metal hydroxide, and alkaline earth metal hydroxide, alkali metal fluoride, alkaline earth One or more selected from metal fluorides, alkali metal nitrates, alkali metal sulfates, alkali metal carbonates, alkali metal acetates, and alkali metal phosphates, (e) (b) and (c) The method according to [10] above, which comprises a mixture of.

・[12] A hydrogen production region including a cathode and an oxygen production region including an anode,
The method according to [10] or [11] above, wherein hydrogen is obtained in the hydrogen production region by electrolyzing water in molten salt in the hydrogen production region.
・[13] Further comprising a region or a container (for hydrogen storage, metal compound reduction, etc.) separate from the hydrogen production region and the oxygen production region,
The method according to any one of [10] to [12], wherein the hydrogen produced or generated in the hydrogen production region is transferred or introduced into the other region or another container.

- [14] The hydrogen production region and the oxygen production region are each separate regions, and the liquid regions of these regions are connected to each other via a flow path through which molten salt can move. 13].

・[15] The method of [1] to [9] above, in which a metal compound is reduced with hydrogen obtained by the hydrogen production method according to any one of [10] to [14] above, to produce a metal. Any one of the methods described.
・[16] The hydrogen produced by the hydrogen production method according to any one of [10] to [15] above is introduced into a separate container, and the metal compound is reduced with the hydrogen to obtain the metal, [ The method described in any one of [1] to [9].

・[17] A hydrogen production region including a cathode and an oxygen production region including an anode,
Any of the above [1] to [10], wherein a metal is produced by reducing a metal compound using hydrogen obtained in the hydrogen production region by electrolyzing water in molten salt in the hydrogen production region. The method described in one of the following.

・[18] A hydrogen production region equipped with a cathode and an oxygen production region equipped with an anode, and a region or another container (for hydrogen storage, metal compound reduction, etc.) separate from these regions,
Hydrogen generated in the hydrogen production region by electrolyzing water in molten salt in the hydrogen production region is introduced into the another region or another container,
The method according to any one of [1] to [10] above, wherein a metal is produced by reducing a metal compound using hydrogen introduced into the separate region or separate container.

・[19]
an electrolysis mechanism comprising an anode and a cathode that can be electrolyzed with water in molten salt;
a water supply mechanism for supplying water to the molten salt;
a sealable molten salt container containing molten salt;
A metal manufacturing device, an electrolysis reaction device, or a manufacturing device for reducing a metal compound to obtain a metal. Preferably, the device further includes a molten salt temperature adjustment mechanism that adjusts the temperature of the molten salt.
・[20]
The device according to [19] above, wherein the container includes a hydrogen production region, an oxygen production region, and a flow path region connecting the liquid region (molten salt) of these regions. It is preferable that the hydrogen production region is provided with a cathode and the oxygen production region is provided with an anode, and each region is composed of a liquid region where molten salt exists and a gas region where generated gas exists. It is more preferable that
- [21] The apparatus according to [19] above, comprising a heat region or another container for introducing the hydrogen obtained from the hydrogen production region. It is preferable to utilize or store the hydrogen introduced into the other region or another container, and more preferably to use the introduced hydrogen for reduction.
・[22]
A metal manufacturing device or a hydrogen manufacturing device, comprising a control unit that implements the method according to any one of [1] to [18] or controls the implementation of the method.
・[23]
Furthermore, an electrolytic reaction device or A manufacturing device or an electrolysis reaction system for reducing a metal compound to obtain a metal, or a manufacturing system for reducing a metal compound to obtain a metal.

Hereinafter, the present invention will be explained in more detail based on Examples and the like. It should be noted that the examples described below are merely representative examples of the present invention, and the scope of the present invention should not be construed narrowly thereby.

The present inventors conducted experiments to determine whether it is actually possible to produce hydrogen through electrolysis in molten salt and to reduce iron oxide particles to iron using the hydrogen.

[Test Example 1]
<1-1. Experimental method>
The present inventors conducted a preliminary experiment to confirm the electrolytic conditions based on the experience in experiments shown in Non-Patent Document 2 and Non-Patent Document 3. Next, based on the preliminary experimental results, we conducted an experiment to confirm the production of hydrogen by electrolysis in molten salt under conditions of a constant water vapor flow rate, and the reduction of iron oxide particles to iron by the hydrogen.

<1-1.1 Materials and electrolytic cell>
The electrolyte, iron oxide sample, and electrolytic cell constituent materials used in the experiment are shown below.
(1) Electrolyte; anhydrous LiCl (Wako special grade), 320g
(2) Iron oxide sample; Fe ₂ O ₃ particles (purity 99.5%), average particle size (D50) particles 2 to 5 mm, 15 g
(3) Constituent materials of the electrolyzer and electrolytic cell used in this example Table 1 shows the constituent materials of the electrolytic cell, their properties, and dimensions.
A schematic diagram of the electrolyzer used in this example can be seen in FIG. 1, and the main components, from the outside, are an Inconel container, an alumina protective container, a graphite crucible, an alumina crucible, and an iron oxide The particles were placed in an alumina crucible. In the electrolyzer used in Example 1, as shown in Fig. 1, a pipe for supplying inert gas (Ar gas) containing water is extended below the liquid level of the molten salt and blown into the molten salt. Rather than having such a configuration, the supply pipe is a pipe that is shortened to about half so as not to come into contact with the liquid surface of the molten salt, and is configured to supply an inert gas containing water to the gas region inside the container. . The electrolyzer used in this example was further equipped with an electrochemical measuring device. As the lead wires for the cathode and anode, Cu wire was used in the preliminary experiment, and Ni wire was used in the reduction confirmation experiment.

<1-1.2 Experimental conditions>
In the electrolyzer of the present example, electrolysis was performed for 1.5 hours or more at an electrolysis temperature of 670° C. and an electrolysis current of 10 A or less. First, in a preliminary experiment, using an inert gas supply mechanism, Ar gas was passed through a container containing water at a rate of 100 mL/min to 600 mL/min to supply water vapor (an inert gas containing moisture) into an Inconel container. did.
The amount of water vapor supplied was also adjusted by heating a container containing water to 30°C to 50°C in a water bath.
The electrolytic current value was set so that the cathode side was within the Li deposition potential and the anode side was within the range of the chlorine gas generation potential. Next, referring to the preliminary experiment results, in an experiment to confirm whether reduction using hydrogen produced by electrolysis is actually possible, the Ar gas supply rate was set at 600 mL/min, and the water bath temperature was set at room temperature (25°C). ), a constant amount of water vapor is supplied, and the electrolytic current value is set as large as possible within the range of Li deposition potential on the cathode side and chlorine gas generation potential on the anode side. Electrolysis was performed while checking the change over time.

<1-1.3 Evaluation method>
After collecting and washing the sample after electrolysis, iron oxide was analyzed using an X-ray diffraction device (RINT-Ultima III, manufactured by Rigaku Corporation) and an energy dispersive X-ray spectrometer (JSM-6010PLUS/LA, manufactured by JEOL Ltd.). The reduction state of the particles was evaluated and confirmed.

<1-2. Experiment results>
<1-2.1 Preliminary experiment>
Approximately 3.6 hours after the start of the experiment, the Ar gas flow rate was fixed at 600 mL/min and the water bath temperature was fixed at 30°C. Figure 11 shows the changes in current value and potential of both electrodes over time (total current flow; 17,147 coulombs).
FIG. 12 shows the X-ray diffraction pattern of the iron oxide particles before the experiment, and FIG. 13 shows the X-ray diffraction pattern of the iron oxide particles taken out from the molten salt after the experiment, washed and dried to remove the salt. Further, FIG. 14 shows a secondary electron image of the iron oxide particles before the experiment, and FIG. 15 shows a secondary electron image of the iron oxide particles after the salt was washed and dried after the experiment.

<1-2.2 Reduction confirmation experiment>
Figure 16 shows the changes over time in the current value, both electrode potential, and interelectrode potential difference when electrolysis was carried out with the Ar gas flow rate fixed at 600 mL/min and the water bath temperature fixed at 25°C. Hydrogen concentration was measured using a gas detection tube (total current flow: 27,187 coulombs).

After the experiment, the iron oxide particles were taken out from the molten salt, the salt was washed and dried, and the X-ray diffraction and secondary electron images are shown in FIG. 17 and FIG. 18, respectively.

<1-3. Consideration＞
<1-3.1 Preliminary experiment>
Hydrogen is produced by water electrolysis in molten salt, and the hydrogen reduces iron oxide Fe ₂ O ₃ to iron.
Fe ₂ O ₃ (s) + 3H ₂ (g) → 2Fe (s) + 3[H ₂ O] _LiCl

In addition, since 1 mole of Fe ₂ O ₃ (molecular weight 159.7 g/mol) generates 2 moles of Fe in a 6-electron reaction, all 15 g of Fe ₂ O ₃ (0.0939 mol) is reduced to Fe. In order to do this, it is necessary to supply an amount of electricity of 0.0939 (mol) x 96,485 (coulombs/mol) x 6 = 54,377 (coulombs).
The total energization amount in the preliminary experiment was 17,147 coulombs, which was about 32% of the theoretical energization amount, and although the iron oxide Fe ₂ O ₃ particles were reduced to Li ₂ Fe ₃ O ₅ , they were not reduced to Fe. This became clear from the X-ray diffraction pattern shown in FIG.

Regarding the reason why Li ₂ Fe ₃ O ₅ is generated, the present inventors believe that, considering that it is difficult for H ⁺ to exist in LiCl of the molten salt, Li ₂ Fe ₃ O ₅ is generated by the following reaction. I assume that it was generated by.
3Fe ₂ O ₃ +4Li ⁺ +H ₂ O+e ^- →2Li ₂ Fe ₃ O ₅ +H ₂
In any case, in the preliminary experiment, the secondary electron images of the iron oxide particles before and after the experiment in FIGS. 14 and 15 show that the large particles before the experiment were Li ₂ Fe ₃ with a particle shape of around 10 μm after the experiment. It was confirmed that it was reduced to _O5 .

<1-3.2 Reduction confirmation experiment>
Comparing the secondary electron images in Figures 9 and 12, the particle size in the reduction confirmation experiment is smaller than in the preliminary experiment, and the energization amount in the reduction confirmation experiment is 27 coulombs compared to 17,147 coulombs in the preliminary experiment. , 187 coulombs, indicating that reduction is progressing. This is clear from the fact that Fe ₃ O ₄ is produced in the X-ray diffraction results shown in FIG.

Therefore, the present inventors thought that the starting material Fe ₂ O ₃ would eventually be reduced to Fe at the cathode as shown in the following formula.
6H ₂ O+6e ^- →3H ₂ +6OH ^-
Fe ₂ O ₃ +3H ₂ →2Fe+3H ₂ O
Total reaction formula Fe ₂ O ₃ +3H ₂ O+6e ^- →2Fe+6OH ^-

In addition, the inventors found that the hydrogen concentration in the hydrogen gas detection tube measured before the end of the experiment exceeded the measurement upper limit of 1.5% because hydrogen gas generated from excessively supplied water was detected. In the reduction reaction at the cathode, hydrogen atoms directly attack Fe ₂ O ₃ in the solid phase and reduce it to Fe.

<1-4. Summary＞
The present inventors discovered that when water is supplied into a molten salt (LiCl) and iron oxide (Fe ₂ O ₃ ) immersed in this LiCl is used as a cathode for electrolysis, the hydrogen produced in the molten salt converts the iron oxide. The possibility of reduction to iron (Fe) was confirmed.

Taking this into consideration, the present inventors derived the above-mentioned "1. Overview of the present technology" and completed the present invention. That is, the present invention provides a technology for producing a metal by reducing a metal compound, which can further reduce manufacturing costs without emitting carbon dioxide gas into the environment as much as possible, and a technology that can also be used for metal production by reducing such a metal compound. The main objective is to provide a technology that can produce hydrogen more easily. In order to achieve the object, the present invention provides a method for producing a metal, in which a metal is produced by reducing a metal compound with hydrogen obtained by electrolyzing water in a molten salt; It is possible to provide a hydrogen production method in which hydrogen is obtained by electrolyzing.

[Test Example 2]
The present inventors melted water vapor according to [Test Example 1] except that the molten salt used in [Test Example 1] was replaced with "molten sodium hydroxide" and iron oxide was not added to the molten salt. Steam electrolysis can be performed using an electrolyte that is blown into sodium hydroxide and electrolyzes water in molten sodium hydroxide to produce hydrogen and oxygen. As the electrolyzer at this time, an electrolyzer including one electrolytic cell as shown in FIG. 3, and an electrolyzer having a hydrogen production section and an oxygen production section as shown in FIG. 4 can be used.

When using an electrolyzer as shown in FIG. 3, the melting point of sodium hydroxide is 328°C, so the temperature of the electrolyte could be maintained at 330-450°C. At water partial pressure (P _H2O : 0-1.0 atm) and temperature (336°C, 385°C, 412°C, 440°C), the injected water is highly soluble in molten sodium hydroxide, and at 336°C P At about 0.8 atm _H2O , the water solubility (W/O) was about 2.8. The solubility of water decreases in the order of 336°C, 385°C, 412°C, and 440°C, and the solubility of water at 336°C is about 2.5 times that of water at 385°C. Ta.

When using the electrolyzer device shown in Fig. 4, when water vapor ^is blown into molten sodium hydroxide, the hydrogen production section side High purity hydrogen could be obtained. Furthermore, the generated hydrogen gas could be recovered using a recovery mechanism.

In this way, hydrogen can be obtained by electrolyzing molten sodium hydroxide while blowing water vapor into it. Also, based on Test Example 1, metals can be produced by reducing metal reduction products using hydrogen obtained by electrolyzing water in molten sodium hydroxide.

[Test Example 3]
<Experiment to confirm reduction to iron>
The materials, experimental conditions, and evaluation method for supplying water into molten salt and confirming that iron oxide is reduced to iron by electrolytic reduction are shown below.

<3-1. Material>
The electrolyte, iron oxide sample, and electrolytic cell constituent materials used in the experiment are shown below. Note that materials and electrolytic cells were selected and used in accordance with [Test Example 1] above.
(1) Electrolyte: Anhydrous LiCl (Wako special grade), amount used: 500g
(2) Iron oxide sample; Fe ₂ O ₃ powder (purity 99.9%), average particle size (D50) particle size 1 μm, amount used: 5 g
(3) Electrolytic cell constituent materials Electrolyzer and electrolytic cell constituent materials The constituent materials of the electrolytic cell, their materials and dimensions are shown in Table 2, and a schematic diagram of the electrolytic cell is shown in FIG. The electrolytic cell device configuration employs almost the same configuration as the above <1-1.1 Materials and electrolytic cell>. As shown in FIG. 20, the cathode lead wire was used by threading the tip of a Fe round rod with a diameter of 3 mm and joining it to the Fe disk. Further, as shown in FIG. 20, the lead wire of the anode was a Ni wire with a diameter of 1 mm passed through a hole made in the upper part of the graphite crucible and joined. The supply pipe of the electrolytic cell device shown in Fig. 20 is similar to the electrolytic cell device of [Test Example 1] described above, and is a pipe that is shortened to about half so as not to come into contact with the liquid surface of the molten salt. The structure is such that an inert gas containing water is supplied.

<3-2. Experimental conditions>
Constant current electrolysis was performed at an electrolysis temperature of 670° C. when the amount of iron oxide charged was 5 g. The current value was set to be as large as possible within the range of the Li deposition potential on the cathode side and the chlorine gas generation potential on the anode side, and electrolysis was performed while checking changes in the cathode and anode potentials over time. Note that water was supplied into the molten salt by passing Ar gas at 600 mL/min through a container containing water at room temperature.

<3-3. Evaluation method＞
After collecting and washing the sample after electrolysis, it was evaluated and confirmed using an energy dispersive X-ray spectrometer (JSM-6010 PLUS/LA, manufactured by JEOL Ltd.) and an X-ray diffraction device (MiniFlex, manufactured by Rigaku Corporation).

<3-4. Experiment results>
Ar gas (600 mL/min) was blown into a container containing water at room temperature at 25° C., and water vapor entrained in the Ar gas was supplied into the molten salt at 670° C. to electrolytically reduce iron oxide (amount charged: 5 g).
In order to supply an amount of electricity that can theoretically be completely reduced to Fe, an electrolytic reduction experiment was conducted with the amount of iron oxide charged as 5 g. Current value and potential of both electrodes over time when electrolyzed by blowing 600 mL/min of Ar gas into a container containing water at 25°C at room temperature and supplying water vapor accompanied by Ar gas into molten salt at 670°C changes were obtained (not shown). In addition, the total amount of current to be reduced to Fe was 18,131 coulombs, which exceeds the theoretically required amount of 18,126 coulombs.
After electrolysis, the weight of the particulate Fe recovered after being taken out from the molten salt, washed and dried was 1.9419 g, and the weight of the sponge Fe was 1.7886 g, for a total of 3.7305 g. The amount of weight decrease was 1.2695 g, and the calculated weight of oxygen in 5 g of iron oxide powder was 1.503 g, resulting in a decrease in oxygen of about 84.5%.
A secondary electron beam image after electrolytically reducing 5 g of iron oxide powder is shown in FIG. 20, and an X-ray diffraction pattern is shown in FIG.
In the secondary electron beam image of the sample after electrolytic reduction shown in FIG. 20, many particles of 10 μm or more were observed. Moreover, in the X-ray pattern of FIG. 21, only the diffraction peaks of the 100, 200, and 211 planes of Fe were seen, and the diffraction peak of Li ₂ Fe ₃ O ₄ before electrolytic reduction had disappeared.
It was found that iron oxide was reduced to Fe as a result of applying a coulomb of electricity that exceeded the theoretically required amount of electricity.

[Test Example 4]
<Reduction experiment using only hydrogen gas>
In Test Example 4, electrolysis was not performed, and a reduction experiment was performed while supplying hydrogen gas, in order to confirm whether iron oxide could be reduced to iron by simply supplying hydrogen gas into the molten salt. I did it. A reduction experiment was conducted for 3.5 hours while supplying 10 mL/min of hydrogen gas and 590 mL/min of Ar gas to 5 g of Fe ₂ O ₃ powder in molten salt (670° C.). After the reduction experiment, the raw material sample was taken out from the molten salt, the salt was washed and dried, and the weight of the Fe ₂ O ₃ powder was 4.8256 g, which was a weight decrease of 0.1746 g. Assuming that all the weight loss was due to oxygen, 1.503 g of oxygen was contained in 5 g of Fe ₂ O ₃ powder, resulting in approximately 11.6% of oxygen being consumed. The X-ray diffraction pattern after reduction with hydrogen gas is shown in FIG. From this, it was found that the rate of the reduction reaction of iron oxide is quite slow when hydrogen gas alone is used.

[Considerations from Test Examples 3 and 4]
(1) Reduction experiment using only hydrogen gas Even if the amount of hydrogen gas theoretically required to reduce iron oxide to iron is supplied and the iron oxide in the molten salt is reacted, iron oxide will not be converted to iron. Reduction occurred only about 11.6%. The reason for this is thought to be that the concentration of hydrogen gas supplied into the molten salt was low, and the frequency of contact (collision) between iron oxide and hydrogen gas molecules did not reach a point where a complete reduction reaction occurred.
(2) Experiment to confirm reduction to iron Using iron oxide powder instead of iron oxide particles as a raw material, supplying H ₂ O to molten salt (LiCl), theoretically using iron oxide powder immersed in LiCl as a cathode. It was confirmed that iron oxide can be reduced to iron when electrolyzed until the amount of electricity required is reached.

In addition, the following explanation is given in [0028] above.
In water electrolysis, the following reactions proceed at the cathode.
H ⁺ +e ^- →H
H ₂ O+e ^- →H+OH ^-
OH ^- +e ^- →H+O ^--
That is, hydrogen atoms (H) are generated from hydrogen ions and the like. The explanation is that the two hydrogen atoms then combine to generate hydrogen molecules (H ₂ ), that is, hydrogen gas.

It should be noted here that the hydrogen atoms (H) generated above are known to have high activity and are called "hydrogen radicals" because they easily cause chemical reactions. If these hydrogen radicals react with each other to form hydrogen molecules and stabilize, the original high activity is lost. From this, it can be easily concluded that hydrogen radicals have higher activity than hydrogen molecules (hydrogen gas) (Non-Patent Document 6). Further, this is explained as being mentioned in Tafel's paper from 1905 (Non-Patent Document 7).
From the above phenomenon, it is expected that if iron oxide is placed near hydrogen radicals before they become hydrogen molecules, a chemical reaction will occur with the iron oxide, and the iron oxide will be reduced. To achieve this, the inventors used molten salt to chemically react hydrogen radicals generated by electrolytic reduction of H ₂ O with iron oxide, thereby achieving a highly efficient reaction.
This has been proven by the inventors' experimental results. In other words, results have been obtained in which the reduction efficiency of iron oxide by hydrogen radicals in the molten salt is higher than the reduction efficiency of iron oxide by hydrogen molecules.
Although hydrogen radicals cannot be directly observed, we believe that we have comprehensively proven the effect of hydrogen radicals in molten salt from the above theory and experimental results.

Note that in this specification, the upper and lower limits of numerical values can be arbitrarily combined as desired. In addition, in this specification, for example, "doing" such as "monitoring" may be used as a process, step, or means, and "step" may be replaced with "doing", process, or means. It may be used as a means, or a "process" may be used as a "doing", a step, or a means, and a "means" may be a "doing", a process, or a step. Furthermore, in this specification, a "system" may be a mechanism, a device, a means, or a section; a "mechanism" may be a system, a device, a means, or a section; a "device" may be a mechanism, a device, a means, or a section; It may be a system, a mechanism, a means, or a section; "means" may be a mechanism, a system, a device, or a section; a "section" may be a mechanism, a means, a device, or a system; Alternatively, it may be a mechanism, means, or device for preparing for these.

1 Metal manufacturing equipment, 2 Cathode, 3 Anode, 4 Molten salt, 5 Metal compound, 6 Reaction container, 7 Closed container, 8 Heating furnace, 9 Intermediate container, 10 Cathode chamber, 11 Anode chamber, 12 Connection part, 13a, 13b Gas region, 14a, 14b liquid region, 15 support section 20 water supply mechanism, 21 gas supply section, 22 mixing section, 23 piping (flow path), 24 piping (flow path), 30 gas recovery mechanism, 30a hydrogen recovery mechanism, 30b oxygen recovery mechanism, 31 piping (flow path), 32 flow control valve, 33 gas storage section, 50a hydrogen production section, 50b metal compound reduction section, 100 molten salt reactor, 101 reactor vessel, 102 core, 103 control rod, 104 Control rod drive control device, 120 Thermal energy supply mechanism, 121 Heat exchanger, 130 Electric energy supply mechanism, 131 Power generation mechanism, 132 Power generation device, 133 Electric wire

Claims

A metal production method in which metals are produced by reducing metal compounds with hydrogen obtained by electrolyzing water in molten salt.
A hydrogen production method that obtains hydrogen by electrolyzing water in molten salt.
The metal manufacturing method according to claim 1, wherein the metal compound is in a particulate form.
The metal manufacturing method according to claim 1, wherein the electrolysis is performed using electrical energy and/or thermal energy supplied from a molten salt nuclear reactor.
The hydrogen production method according to claim 2, wherein the electrolysis is performed using electrical energy and/or thermal energy supplied from a molten salt nuclear reactor.
The metal compound is
One or more metal elements selected from the group consisting of iron, copper, zinc, nickel, tin, lead, cobalt, and molybdenum;
and one or more nonmetallic elements selected from the group consisting of oxygen atoms, sulfur atoms, and chlorine atoms.
The metal manufacturing method according to claim 1 or 3, wherein the metal compound is a metal compound.
The metal manufacturing method according to claim 1, wherein the molten salt contains at least one of an alkali metal halide and an alkaline earth metal halide.
The metal manufacturing method according to claim 1, wherein the molten salt contains at least one of an alkali metal hydroxide or an alkaline earth metal hydroxide.
The molten salts include alkali metal chlorides, alkaline earth metal chlorides, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal fluorides, alkaline earth metal fluorides, alkali metal nitrates, and alkali metal sulfates. The method for producing hydrogen according to claim 2, which contains one or more selected from salts, alkali metal carbonates, alkali metal acetates, and alkali metal phosphates.