WO2025159186A1 - Thermal power generation method - Google Patents

Abstract

Provided is a thermal power generation method in which emission of carbon dioxide during power generation is suppressed by using techniques gained in coal-fired power generation. The present disclosure relates to a resource circulation-type thermal power generation method comprising: a power generation step for generating power by combusting fuel in a combustion chamber of a boiler device; and a resource regeneration step for generating a raw material for fuel from combustion ash generated in said combustion. The fuel is magnesium or calcium, or magnesium hydride or calcium hydride having a layer hydrogenated on at least the surface thereof. The combustion ash contains magnesium oxide, magnesium hydroxide, or a mixture thereof, or calcium oxide, calcium hydroxide, or a mixture thereof. The resource regeneration step serves to generate, from the combustion ash, magnesium or calcium, or magnesium hydride or calcium hydride having a layer hydrogenated on at least the surface.

Description

Thermal power generation method

This disclosure relates to a thermal power generation method.

2. Description of the Related Art Coal-fired power generation systems equipped with power generation boilers are generally known (see, for example, Non-Patent Document 1).
Although Japan possesses some of the world's leading coal-fired power generation technologies, opportunities for utilizing this technology are being lost due to the problem of carbon dioxide emissions when coal is burned.

One technology that could solve these problems is CCS, which involves separating and capturing carbon dioxide from the exhaust gases of thermal power plants and storing the captured carbon dioxide.

For example, Non-Patent Document 2 introduces the CCS efforts being undertaken in Tomakomai City, Hokkaido, and specifically explains that carbon dioxide is separated and captured from the exhaust gases of thermal power plants, and that the captured carbon dioxide is then injected and stored deep underground beneath the seabed, approximately 3 to 4 km from the coast.
It is believed that carbon dioxide injected deep underground in this way will be stored stably for a long period of time, and will dissolve into salt water over a long period of time and become minerals in the gaps between rocks.

However, there are many constraints to achieving this type of storage, such as the layer having gaps large enough to store carbon dioxide, and being covered by a layer of rock that does not allow carbon dioxide to pass through.

“Promoting Regional Environmental Conservation: The Structure of Coal-Fired Power Plants and Various Environmental Conservation Measures,” [online], Okinawa Electric Power Company, Inc., [searched June 30, 2022], Internet <URL: https://www.okiden.co.jp/environment/report2017/sec6/sec63.html> “CCS: Capture and bury CO2: After Demonstration Tests, Realization is Near (Part 1),” [online], November 27, 2020, Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry, [Retrieved June 16, 2022], Internet <URL: https://www.enecho.meti.go.jp/about/special/johoteikyo/ccs_tomakomai.html>

This disclosure has been made in light of these circumstances, and aims to provide a thermal power generation method that utilizes technology cultivated in coal-fired power generation to reduce carbon dioxide emissions during power generation.

In order to achieve the above object, the present disclosure is grasped by the following configuration.
(1) A resource-circulating thermal power generation method according to an embodiment of the present disclosure includes a power generation process of burning fuel in a combustion chamber of a boiler apparatus to generate electricity, and a resource recycling process of producing raw materials for fuel from combustion ash generated by the combustion, wherein the fuel is magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface, and the combustion ash contains magnesium oxide, magnesium hydroxide, or a mixture thereof, or calcium oxide, calcium hydroxide, or a mixture thereof, and the resource recycling process produces magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface, from the combustion ash.

(2) In the configuration of (1) above, the resource recycling process may include an atomization process for atomizing the generated magnesium or calcium.

(3) In the configuration of (2) above, the combustion may be carried out using a powder combustion burner.

(4) In the configuration of (2) above, the atomization process may include a coarse grinding process for coarsely grinding the produced magnesium or calcium, and a fine grinding process for further grinding the magnesium or calcium ground in the coarse grinding process.

(5) In the configuration of (4) above, the fine grinding step may be carried out by adding powder of an inorganic compound as a grinding aid.

(6) In the configuration of (5) above, the inorganic compound may be magnesium oxide or calcium oxide.

(7) In the configurations (2) to (6) above, the resource recycling process may further include a hydrogenation process in which the surface of the magnesium or calcium atomized in the atomization process is hydrogenated to produce magnesium hydride or calcium hydride having a hydrogenation rate of 30% by mass or less.

(8) In the configuration of (7) above, after the atomization process, the atomized magnesium or calcium may be handled so as not to come into contact with oxygen until the hydrogenation process is completed.

(9) In the configurations (1) to (8) above, moisture may be supplied into the combustion chamber as a combustion promoter.

(10) In the configurations (1) to (9) above, the fuel may be magnesium or the magnesium hydride, and the resource recycling process may include a chlorination process that uses the combustion ash to produce magnesium chloride, and a molten salt electrolysis process that performs molten salt electrolysis using the magnesium chloride produced in the chlorination process to produce magnesium.

This disclosure makes it possible to provide a thermal power generation method that utilizes technology developed in coal-fired power generation and reduces carbon dioxide emissions during power generation.

1 is a diagram for explaining the configuration of a power generation system for performing a power generation process according to an embodiment of the present invention. FIG. 1 is a diagram illustrating an apparatus for performing a hydrogen chloride gas method according to an embodiment of the present invention. FIG. 1 is a diagram illustrating the configuration of an apparatus for carrying out a hydrogenation step according to an embodiment of the present invention.

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

(Embodiment)
FIG. 1 is a diagram illustrating the schematic configuration of a power generation system (hereinafter sometimes referred to as a "power plant," and in this specification, "power plant" can be replaced with "power generation system") according to this embodiment. The power generation system includes a generator 1 and a boiler unit 2 (hereinafter sometimes referred to as a "power generation boiler 2," and in this specification, "power generation boiler" can be replaced with "boiler unit") having a combustion chamber B1. In the power generation system of this embodiment, the generator 1 generates electricity using steam generated by the boiler unit 2. The resource recycling thermal power generation method of this embodiment includes a power generation process of burning fuel in the combustion chamber B1 of the boiler unit 2 to generate electricity, and a resource recycling process of generating raw materials for fuel from combustion ash generated by the combustion.
Therefore, the following description will be given in the order of the power generation process and the resource recycling process.

(Power generation process)
The power generation process is a process carried out at a power plant, but the technology used there utilizes technology that has been developed for coal-fired power generation, so explanations of points that are similar to conventional technology may be omitted.

In the embodiment shown in Figure 1, the power plant comprises a generator 1, a power generation boiler 2 that drives the generator 1, a fuel storage tank 3 that stores fuel to be supplied to the power generation boiler 2, an auxiliary fuel storage tank 4 that stores auxiliary fuel to be supplied to the power generation boiler 2, a denitration device 5 that neutralizes nitrogen oxides (NOx) contained in the exhaust gas from the power generation boiler 2, a dust collector 6 that collects combustion ash contained in the exhaust gas that has passed through the denitration device 5, and a combustion ash storage tank 7 that stores the combustion ash.

The power generation boiler 2 may include a combustion chamber B1, a steam turbine B2 whose rotating shaft is connected to the generator 1 and is driven by steam produced in the combustion chamber B1, and piping B3 for supplying the steam to the steam turbine B2 and for supplying water returned to a liquid state in the condenser FU back to the combustion chamber B1.

In addition, a water supply pump P is installed midway along the pipe B3 connecting the condenser FU and the combustion chamber B1, and is designed to send water to the combustion chamber B1 side.

Combustion chamber B1 is equipped with a burner 31 that burns fuel supplied from fuel storage 3. The burner 31 may be, for example, a powder combustion burner 31 that burns powder fuel. Below, we will explain an embodiment in which the burner 31 is a powder combustion burner, but it is not intended that the fuel be limited to powder.

The combustion chamber B1 may further include an auxiliary combustion burner 41 that burns liquid fuel (e.g., heavy oil, light oil, etc.) supplied from the auxiliary fuel storage tank 4.

The burner 31 or powder combustion burner 31 may be similar to the pulverized coal burners used in coal-fired power plants, and the supply system (not shown) that supplies powdered fuel to the powder combustion burner 31 may also be similar to that used in coal-fired power plants.

The auxiliary combustion burner 41 is a burner that provides auxiliary heating power until the temperature in the combustion chamber B1 rises and the combustion in the powder combustion burner 31 stabilizes, and this may also be similar to that used in coal-fired power plants.

The auxiliary combustion burner 41 may be shut down after the combustion in the powder combustion burner 31 has stabilized. Furthermore, since thermal power plants often operate without being shut down, the amount of carbon dioxide generated by the auxiliary combustion burner 41, which is mainly used at the start of operation, is extremely small.

Fuel storage 3 stores a fuel that does not emit carbon dioxide when burned, preferably a powder fuel such as magnesium or calcium, or magnesium hydride or calcium hydride with at least a hydrogenated layer on its surface. In this embodiment, the fuel is preferably adjusted to an appropriate particle size.

However, since magnesium or calcium, or magnesium hydride or calcium hydride that has at least a hydrogenated layer on its surface, are not perfectly spherical, the particle size referred to here can be considered to be the size that allows the particles to pass through a sieve with a specified mesh opening.

In the powder combustion burner 31, fuel mixed with air is burned, but since the fuel is magnesium or calcium, or a substance consisting of magnesium or calcium and hydrogen, no carbon dioxide is produced during the combustion.
The combustion ash may contain hydroxides due to a reaction between water generated by the combustion of the hydride and some of the oxides.

The magnesium hydride and calcium hydride used in the fuel may be adjusted to a particle size of, for example, 150 μm or less. Furthermore, the magnesium hydride and calcium hydride are not 100% pure, and it is preferable that they are low-purity hydrides with a hydrogenation rate of 30 mass% or less, with at least the surface side hydrogenated.

In other words, it is preferable that the magnesium or calcium is not hydrogenated to the core, but that the surface is covered with a layer of magnesium hydride or calcium hydride.

In the case of such low-purity hydrides, when air is used as the combustion supporting gas, two reactions must be considered: the combustion reaction of the magnesium hydride or calcium hydride portion, and the combustion reaction of the magnesium or calcium portion.

However, the combustion reaction between the magnesium hydride portion or calcium hydride portion and oxygen is as shown in the following formulas (1) and (1'), and the combustion reaction between the magnesium portion or calcium portion and oxygen is as shown in the following formulas (2) and (2'). Therefore, even if a low-purity hydride is used as the fuel, no carbon dioxide is generated during combustion.
MgH ₂ + O ₂ → MgO + H ₂ O (1)
2Mg + O ₂ → 2MgO・・・・・・・・・・・・・・・(2)
CaH ₂ + O ₂ → CaO + H ₂ O・・・・・・・・・・・・(1')
2Ca + O ₂ → 2CaO・・・・・・・・・・・・・・・(2')

On the other hand, when the hydride mixed with air is burned in the powder combustion burner 31, nitrogen and a small amount of carbon dioxide are present together with oxygen.
In particular, magnesium and calcium may also react with nitrogen at high temperatures and in an oxygen-deficient atmosphere to produce magnesium nitride and calcium nitride, as shown in the following formulas (3) and (3'). Furthermore, the reactions of magnesium and calcium, as well as magnesium hydride and calcium hydride, with carbon dioxide are as shown in the following formulas (11) to (14).
3Mg + N ₂ → Mg ₃ N ₂・・・・・・・・・・・・・・・・・・(3)
3Ca + N ₂ → Ca ₃ N ₂・・・・・・・・・・・・・・・・(3')
2Mg + CO ₂ → 2MgO + C・・・・・・・・・・・・・・・(11)
2MgH ₂ + CO ₂ → 2MgO + 2H ₂ + C (12)
2Ca + CO ₂ → 2CaO + C・・・・・・・・・・・・・・・(13)
2CaH ₂ + CO ₂ → 2CaO + 2H ₂ + C (14)

For this reason, when fuel burns incompletely, nitrides may form and become mixed into the combustion ash. Furthermore, because high temperatures and oxygen-deficient conditions are favorable for nitride formation, the nitride formation reaction is thought to occur within or near the combustion flame.

The nitride quickly decomposes upon reaction with moisture, and changes into magnesium hydroxide or calcium hydroxide and ammonia, as shown in the following formulas (4) and (4').
Mg ₃ N ₂ + 6H ₂ O → 3Mg(OH) ₂ + 2NH ₃ ... (4)
Ca ₃ N ₂ + 6H ₂ O → 3Ca(OH) ₂ + 2NH ₃ ... (4')

Therefore, if nitrides are produced, there is a possibility that ammonia gas may be generated from the combustion ash after it is collected.

For this reason, it is preferable to increase the humidity within combustion chamber B1 so that even if nitrides are formed, they can be decomposed quickly. In this way, even if nitrides are formed, they will be decomposed immediately, and the ammonia produced by this decomposition can also contribute to combustion as combustion gas. Therefore, moisture may be supplied into combustion chamber B1 as a combustion promoter. This will ultimately suppress the incomplete combustion that forms nitrides.

In addition, methods for increasing the humidity inside the combustion chamber B1 include providing an air intake port that sends highly humid air (for example, air with a humidity of 50% or more, preferably 70% or more, and more preferably 80% or more) into the combustion chamber B1, or sending air with increased humidity in advance to the powder combustion burner 31, where the humid air is mixed with fuel to form a burner flame.

Furthermore, considering that moist air has a higher thermal conductivity than dry air, this configuration tends to increase the heat exchange efficiency in the pipe B3 that runs through the combustion chamber B1.

When air is used as a combustion supporting gas, nitrogen gas is contained therein, and therefore nitrogen oxides (NOx) may be generated during combustion. Therefore, in the embodiment shown in Figure 1, the power generation system is provided with a denitration device 5 in the exhaust pipe 8 that sends the exhaust gas from the combustion chamber B1 to a dust collector 6 in order to neutralize the nitrogen oxides (NOx) in the exhaust gas.
In addition, in order to suppress the generation of nitrogen oxides (NOx), air with an increased oxygen concentration may be used as the combustion supporting gas, or oxygen itself may be used as the combustion supporting gas, instead of or in addition to providing the denitration device 5. If the oxygen concentration of the combustion supporting gas can be increased and the generation of nitrogen oxides (NOx) can be suppressed to a level that satisfies environmental standards, the denitration device 5 may be omitted.

The denitration device 5 may be similar to the denitration devices commonly used in coal-fired power plants, and may, for example, be configured to add ammonia to the exhaust gas and pass it through a catalyst layer, thereby breaking down nitrogen oxides (NOx) into harmless nitrogen and water.

Furthermore, the exhaust gas that has passed through the denitrification device 5 may contain combustion ash generated during combustion, some of which has extremely small particle size. Therefore, in the embodiment shown in Figure 1, the exhaust pipe 8 is connected to the dust collector 6, and after the combustion ash is collected by the dust collector 6, the exhaust gas is released into the atmosphere.

This dust collector 6 may be similar to that used in coal-fired power plants; specifically, an electrostatic precipitator may be used. As shown in Figure 1, an exhaust device 81 is provided downstream of the dust collector 6, allowing the exhaust gas from the combustion chamber B1 to be released into the atmosphere via the denitration device 5 and dust collector 6.

On the other hand, in coal-fired power generation, coal is used as fuel, so the sulfur components contained in the coal end up in the exhaust gas. For this reason, in coal-fired power generation, a desulfurization unit is also installed before the exhaust gas is released into the atmosphere. In contrast, in this embodiment, the fuel does not contain sulfur components, so there is an advantage in that a desulfurization unit is not required.

Furthermore, in coal-fired power plants, carbon dioxide is contained in the exhaust gas, so when the exhaust gas is released into the atmosphere, it must be released through a tall chimney. However, in this embodiment, the generation of carbon dioxide during power generation is suppressed, so such a tall chimney is not necessary.

The combustion ash that accumulates at the bottom of the combustion chamber B1 and the combustion ash collected by the dust collector 6 are collected in the combustion ash storage shed 7, and for resource circulation purposes, they undergo the resource recycling process described below, where they are recycled into fuel that can be used again in the power generation process.

In addition, in coal-fired power plants, coal residue accumulates at the bottom of the combustion chamber and is also contained in the exhaust gas, so a dust collector is used, and the mechanism for collecting the combustion ash generated in this embodiment can be a similar mechanism.

However, in this embodiment, since the amount of combustion ash generated is greater than when coal is burned, it is preferable to improve the capacity of the recovery mechanism compared to recovery mechanisms used in coal-fired power generation.

As can be seen from the above explanation, if magnesium or calcium, or at least magnesium hydride or calcium hydride with a hydrogenated layer on the surface, is used as fuel, it is possible to carry out a power generation process that is extremely compatible with the coal-fired power generation technology that has been developed up to now and that reduces carbon dioxide emissions.

Furthermore, the combustion ash produced when fuel is burned is magnesium oxide or calcium oxide. Because magnesium oxide and calcium oxide have high melting points (for example, the melting point of magnesium oxide is approximately 2850°C), they are prevented from melting even in high-temperature locations such as the inside of combustion chamber B1.

On the other hand, because coal contains silicon, some of its combustion ash melts at 1000-1300°C, which can cause molten deposits to form in various places, such as inside the combustion chamber and chimney.

Therefore, this embodiment has the advantage of being able to suppress the occurrence of molten deposits and reducing the effort required for cleaning, etc.

(Resource recycling process)
The power generation method of this embodiment includes a resource recycling step of producing raw material for fuel from combustion ash generated in combustion. The resource recycling step of this embodiment is a step of producing magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface, from the combustion ash. Hereinafter, a resource recovery step will be described in which magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface, is produced again using combustion ash (including magnesium oxide, magnesium hydroxide, calcium oxide, and/or calcium hydroxide) generated in the power generation step as a starting material.

In addition, hydroxides undergo a dehydration reaction when heated to become oxides, so the starting material for the resource recovery process can be considered to be oxides. For example, magnesium hydroxide contained in combustion ash undergoes a dehydration reaction when heated to become magnesium oxide, as shown in the following formula (5).
Mg(OH) ₂ → MgO + H ₂ O・・・・・・・・・・・・・・・(5)

Furthermore, when the combustion ash contains calcium hydroxide (Ca(OH) ₂ ), a dehydration reaction occurs by heating, as shown in the following reaction formula (5'), to produce calcium oxide (CaO).
Ca(OH) ₂ → CaO + H ₂ O・・・・・・・・・・・・・(5')

The resource recycling process preferably produces fuel (magnesium or calcium) from oxides (magnesium oxide or calcium oxide) contained in the combustion ash of the fuel. The resource recycling process may produce fuel by directly reducing the oxides using a known method, or may produce an intermediate from the oxide and then reduce the intermediate to produce fuel. Such intermediates include chlorides.

Therefore, the resource recycling process may include a chlorination process in which chlorides are produced using oxides contained in the fuel combustion ash as material, and a molten salt electrolysis process in which fuel is produced using the chlorides produced in the chlorination process as material. Alternatively, the resource recycling process may include a direct reduction process in which fuel is produced by directly reducing oxides contained in the fuel combustion ash.

When the fuel is magnesium or magnesium hydride, a chlorination process is first carried out to produce magnesium chloride from the starting material, magnesium oxide, and then the magnesium chloride produced in the chlorination process is used to carry out molten salt electrolysis to produce magnesium.

When the fuel is calcium or calcium hydride, the resource recycling process may include a chlorination process in which calcium chloride is produced using calcium oxide in the combustion ash as a material, and a molten salt electrolysis process in which calcium is produced using the calcium chloride produced in the chlorination process as a material, or it may include a direct reduction process in which calcium oxide in the combustion ash is directly reduced to produce calcium.

The magnesium or calcium obtained in this manner may be further pulverized in an atomization process, and then subjected to a hydrogenation process to produce a hydride having a hydrogenated layer at least on the surface.

(Chlorination process)
The chlorination process is a process for producing chlorides using oxides contained in the combustion ash of the fuel as a material. Hereinafter, an example will be described in which magnesium chloride is produced using magnesium oxide, which is the combustion ash as a material. The magnesium chloride can be used in the subsequent molten salt electrolysis process.

Methods for the chlorination step include, for example, a method using hydrogen chloride water (hydrochloric acid) (hereinafter referred to as the "hydrogen chloride water method"), a method using hydrogen chloride gas (hereinafter referred to as the "hydrogen chloride gas method"), a method using chlorine gas (hereinafter referred to as the "chlorine gas method"), and a method using ammonium chloride (hereinafter referred to as the "ammonium chloride method"). Among these, the chlorine gas method is preferred in this embodiment. By using the chlorine gas method, the chlorination step and the molten salt electrolysis step can be easily carried out continuously. This is particularly preferred because the chlorine gas produced in the molten salt electrolysis step described below can be used directly to carry out the chlorination step.

(hydrogen chloride gas method)
The hydrogen chloride gas method is a method for producing magnesium chloride by causing a reaction of magnesium oxide with hydrogen chloride gas at a temperature of about 300 to 600°C according to the following formula (6). The method will be described with reference to FIG. 2, which is a diagram illustrating an apparatus for carrying out the hydrogen chloride gas method.
It should be noted that FIG. 2 shows only the main parts.
MgO + 2HCl → MgCl ₂ + H ₂ O (6)

As shown in Figure 2, the apparatus for performing the hydrogen chloride gas method includes a reaction vessel section 9 in which magnesium oxide and hydrogen chloride gas are reacted, and a heater H that heats the reaction vessel section 9.

The reaction vessel section 9 comprises a cylindrical body section 91 that opens at the top and bottom, an upper lid 92 that closes the upper opening of the body section 91, and a lower lid 93 that closes the lower opening of the body section 91.

A gas supply port IN is provided on the lower side of the body 91, and a gas exhaust port OUT is provided on the upper side of the body 91.

When magnesium oxide is added to the reaction vessel section 9, the upper lid 92 is opened, and when magnesium chloride is removed after the reaction, the lower lid 93 is opened.

Specific processing may involve first placing magnesium oxide in the reaction vessel section 9, heating it with heater H until the temperature inside the reaction vessel section 9 reaches around 400°C, supplying dry gas (e.g., dry air or dry nitrogen) through the gas supply port IN, and discharging the gas that has passed through the magnesium oxide through the gas exhaust port OUT. Note that processing that involves both gas supply and exhaust is sometimes referred to as streamer processing.

This allows moisture adhering to the magnesium oxide to be removed. After the magnesium oxide drying process has been carried out as described above, the gas supplied from the gas supply port IN can be changed to hydrogen chloride gas, and a chlorination process can be carried out in which the magnesium oxide and hydrogen chloride gas react to produce magnesium chloride.

As can be seen from equation (6) shown above, water is also produced during the reaction, but by carrying out this chlorination process using the streamer method, the magnesium chloride does not become a hydrate, and anhydrous magnesium chloride can be produced.

In addition, hydrogen chloride gas that did not contribute to the reaction is also exhausted from the gas exhaust port OUT, but this hydrogen chloride gas may be dehydrated and then supplied again from the gas supply port IN.

Then, as mentioned above, the anhydrous magnesium chloride produced is removed from the reaction vessel 9 by opening the bottom lid 93 and used as a material in the next step, the molten salt electrolysis step. Before opening the bottom lid 93, the gas being supplied may be switched to, for example, dry nitrogen, to replace the hydrogen chloride gas in the reaction vessel 9.

A method in which an alkali metal or alkaline earth metal chloride is added to the reaction vessel section 9 along with magnesium oxide may also be used. Examples of alkali metal or alkaline earth metal chloride include sodium chloride, potassium chloride, and calcium chloride.

In this way, by adding an alkali metal or alkaline earth metal chloride, the alkali metal or alkaline earth metal chloride can be melted at a temperature lower than the melting point of magnesium oxide, and the magnesium oxide can be chlorinated in the molten salt. Therefore, it is preferable that the alkali metal or alkaline earth metal chloride has a lower melting point than magnesium oxide.

In this method, the reaction vessel section 9 contains a molten salt of an alkali metal or alkaline earth metal chloride and magnesium oxide, and hydrogen chloride gas is supplied from the gas supply port IN. This method may also include a step of drying the magnesium oxide before introducing it into the reaction vessel section 9. The drying step may be, for example, a step of blowing the magnesium oxide with a dry gas (e.g., dry air or dry nitrogen) before supplying it to the reaction vessel section 9.

The magnesium chloride produced by the reaction dissolves because it is a substance with high solubility in molten salts of alkali metal or alkaline earth metal chlorides. On the other hand, magnesium oxide exists as a solid in the molten salt until it reacts according to the above reaction formula (6). Therefore, by monitoring the amount of solids in reaction vessel section 9, the progress of the chlorination process can be estimated. For example, the chlorination process can be determined to be complete when the rate at which the amount of solids in reaction vessel section 9 decreases falls below a certain level.

Even in this method, by performing the chlorination treatment using a streamer process, magnesium chloride does not become a hydrate, and anhydrous magnesium chloride can be produced. In this case, the hydrogen chloride gas that did not contribute to the reaction and is exhausted from the gas exhaust port OUT can be dehydrated and supplied again from the gas supply port IN.

When the chlorination reaction has progressed to completion, a molten salt of alkali metal or alkaline earth metal chlorides, including magnesium chloride, is obtained as a liquid phase. This liquid phase can be used in the next step, the molten salt electrolysis step. Before discharging the liquid phase, the gas being supplied can be switched to, for example, dry nitrogen, to replace the hydrogen chloride gas in the reaction vessel section 9.

(Chlorine gas method)
The chlorine gas method is a method in which, for example, magnesium oxide, optionally together with an alkali metal or alkaline earth metal chloride, is charged into a chlorination furnace and the magnesium oxide is brought into contact with chlorine gas to produce magnesium chloride. The chlorine gas method can be carried out in the same manner as the hydrogen chloride gas method, except for the following points, and the configuration of the apparatus used may be the same as that explained in FIG. 2.

In the chlorine gas method, magnesium oxide and chlorine gas react with each other to produce magnesium chloride as shown in the following reaction formula (16). The reaction temperature may be 300 to 800° C. Examples of chlorides of alkali metals or alkaline earth metals include sodium chloride, potassium chloride, and calcium chloride.
2MgO + 2Cl ₂ → 2MgCl ₂ + O ₂ (16)

In the chlorine gas method, chlorine gas is supplied from the gas supply port IN. When magnesium oxide is chlorinated using the chlorine gas method, oxygen is generated as shown in the above formula (16). Therefore, by monitoring the oxygen concentration in the reaction vessel section 9, the reaction progress of the chlorination process can be estimated. For example, when the oxygen concentration in the reaction vessel section 9 reaches or exceeds a pre-calculated value, it can be determined that the chlorination process has been completed.

Even in the chlorine gas method, by performing the chlorination process using a streamer process, magnesium chloride does not become a hydrate, and anhydrous magnesium chloride can be produced. In this case, the chlorine gas that did not contribute to the reaction and is exhausted from the gas exhaust port OUT can optionally be subjected to an oxygen removal process and then supplied again from the gas supply port IN.

In order to improve the reaction efficiency, the chlorination step using the chlorine gas method may be carried out first, followed by the chlorination step using the hydrogen chloride gas method. In this case, after supplying chlorine gas, the oxygen concentration and the amount of solids in the molten salt may be monitored to confirm that chlorination has progressed to a certain extent, and then the supply gas may be switched from chlorine gas to hydrogen chloride gas, and chlorination using hydrogen chloride gas may be carried out.

(Ammonium chloride method)
The ammonium chloride method is a method of reacting magnesium oxide with ammonium chloride, and there are two possible procedures for this method. In either case, the apparatus configuration may be the same as that described with reference to Figure 2, and therefore the following description will also refer to Figure 2.

The first procedure is a method in which magnesium oxide and ammonium chloride are reacted at a temperature of about 300 to 600°C to produce magnesium chloride. The reaction that occurs at this time is as shown in formula (7) below.
MgO + 2NH ₄ Cl → MgCl ₂ + H ₂ O + 2NH ₃ ... (7)

For example, a mixture of magnesium oxide and ammonium chloride, in which the molar ratio of ammonium chloride to the amount of magnesium oxide is at least twice as much, is added to the reaction vessel section 9.

As shown in formula (7), from a chemical standpoint, the molar ratio of magnesium oxide to ammonium chloride should be 1:2, but in actual processing, taking into account that there will be ammonium chloride that does not contribute to the reaction, it is best to keep the molar ratio of magnesium oxide to ammonium chloride around 1:3 to 1:5.

Then, while blowing in dry nitrogen, heating is performed with heater H until the temperature inside reaction vessel section 9 reaches around 400°C. Due to this heating, ammonium chloride, which is solid at room temperature, begins to sublimate at around 300°C and decomposes into ammonia gas and hydrogen chloride gas. The hydrogen chloride gas produced by this decomposition reacts with magnesium oxide, and magnesium chloride is produced. After the heating process has been performed for a predetermined time, heater H is turned off, the vessel is cooled, and the produced magnesium chloride is then recovered.

The reason for blowing dry nitrogen is that, as can be seen from equation (7), moisture is generated simultaneously with the production of magnesium chloride, and this moisture is quickly discharged outside the reaction vessel 9, preventing the magnesium chloride from becoming a hydrate and producing anhydrous magnesium chloride. It is also possible to provide an ammonium chloride supply port in the reaction vessel 9 to supply additional ammonium chloride, so that ammonium chloride can be added midway through the process.

The second step involves reacting magnesium oxide and ammonium chloride in a molar ratio of 1:3 to produce ammonium carbohydrate, and then removing the water and ammonium chloride to obtain anhydrous magnesium chloride.

Specifically, a mixture of magnesium oxide and ammonium chloride in a molar ratio of 1:3 is poured into the reaction vessel 9. Dry nitrogen is then blown in for a while, replacing the atmosphere inside the reaction vessel 9 with dry nitrogen.

Once the reaction vessel 9 is filled with a dry nitrogen atmosphere, the gas supply port IN and gas exhaust port OUT are closed to seal the reaction vessel 9, and heating with heater H begins so that the temperature inside the reaction vessel 9 reaches around 400°C.

This causes the reaction shown in formula (8) below to produce an ammonium carbohydrate.
MgO+ _3NH4Cl → _MgCl2・_NH4Cl・_H2O + _2NH3 ...(8)

As can be seen from equation (8), in this reaction, the solid magnesium oxide reacts with ammonium chloride, producing ammonia gas, which causes the internal pressure to increase.

For this reason, it is advisable to use a pressure-resistant vessel for the reaction vessel section 9 that can withstand this pressure increase. However, if the pressure exceeds atmospheric pressure slightly, the gas exhaust port OUT can open to prevent the pressure increase, so it is not necessary to use a pressure-resistant vessel.

Then, after the heating process has been carried out for a predetermined time, the set temperature of the heater H is changed so that the temperature inside the reaction vessel portion 9 is kept slightly lower than the sublimation temperature of ammonium chloride (approximately 5 to 20°C lower than the sublimation temperature).

Once the temperature inside the reaction vessel section 9 has dropped to the set temperature, ammonia gas is supplied through the gas supply port IN and exhausted through the gas exhaust port OUT, causing the ammonia gas to flow freely, and heating is carried out for the specified period of time.

In this way, when a hydrate of ammonium carbohydrate is heat-treated in an ammonia gas atmosphere, the water content of the hydrate inhibits the hydrolysis reaction of the ammonium carbohydrate from proceeding, and the dehydration reaction shown in the following formula (9) proceeds.
_{MgCl2.NH4Cl.H2O → MgCl2.NH4Cl} + _{H2O ...} (9 ₎

Furthermore, because ammonia gas is blown away, the water generated by dehydration is quickly discharged outside the reaction vessel section 9, preventing the formation of hydrates again.

Then, once the dehydration process is complete, the set temperature of heater H is changed so that the temperature inside reaction vessel section 9 is maintained at a temperature higher than the sublimation temperature of ammonium chloride (for example, around 400°C).

Furthermore, once the dehydration process is complete, there is no need to create an ammonia gas atmosphere inside the reaction vessel section 9, so the state is changed to one where dry nitrogen is blown in when the set temperature of the heater H is changed.

Then, as shown in the following formula (10), the ammonium carbohydrate decomposes into magnesium chloride, ammonia gas, and hydrogen chloride gas, and the ammonium chloride portion is removed from the ammonium carbohydrate (hereinafter, also referred to as "ammonium dechlorination treatment"), thereby producing anhydrous magnesium chloride.
_MgCl2・_NH4Cl → _MgCl2 + _NH3 +HCl・・・・・・・・・(10)

The ammonia gas and hydrogen chloride gas are exhausted to the outside of the reaction vessel section 9 along with the dry nitrogen blown in. Once the ammonium chloride removal process is complete, the heater H is turned off, the system is cooled, and the anhydrous magnesium chloride produced is recovered.

(hydrogen chloride water method)
The hydrogen chloride water method involves dropping combustion ash and hydrogen chloride (HCl) water into a chlorination tank to chlorinate magnesium oxide. Magnesium oxide reacts in hydrogen chloride water to form magnesium chloride (MgCl ₂ ) according to the following reaction formula (15):
MgO + 2HCl → MgCl ₂ + H ₂ O (15)

Magnesium chloride, produced by the reaction, is a substance with high solubility in water, so it will dissolve if the hydrogen chloride solution contains a sufficient amount of water. On the other hand, magnesium oxide exists as a solid in the hydrogen chloride solution until it reacts according to reaction equation (15) above. Therefore, by monitoring the amount of solids in the chlorination tank, it is possible to estimate the progress of the chlorination process. For example, the chlorination process can be determined to be complete when the rate at which the amount of solids in the chlorination tank decreases falls below a certain level.

In the above method, it is preferable to proceed with the chlorination reaction while heating the chlorination tank. The temperature of the chlorination tank may be, for example, room temperature to 400°C, or 80 to 300°C. It is also preferable to proceed with the chlorination reaction while stirring the hydrogen chloride water. If the temperature of the chlorination tank exceeds the boiling point of the hydrogen chloride water at atmospheric pressure, the chlorination step may be carried out under pressure-resistant conditions (sealed conditions).

(Pretreatment process)
Prior to the chlorination step by any of the above methods, a step of pretreating the combustion ash may be carried out. The pretreatment step and the chlorination step may be repeated as a set. The number of repetitions is not particularly limited, but may be, for example, 2 to 10 times. In this case, any of the above methods may be used for the chlorination step.

Pretreatment processes include crushing the magnesium oxide in the combustion ash and heating the magnesium oxide in the combustion ash.

The process of pulverizing the magnesium oxide in the combustion ash involves pulverizing the combustion ash using a pulverizer such as a ball mill, bead mill, hammer mill, pin mill, roller mill, or jet mill, or a combination of these pulverizers. For example, pulverization using a ball mill may be carried out at 50 to 1000 rpm, preferably 100 to 600 rpm, for example, for 1 minute to 30 hours, preferably 10 minutes to 20 hours, and more preferably 1 to 10 hours. Pulverization using a bead mill may be carried out at 50 to 5000 rpm, preferably 100 to 1000 rpm, for example, for 15 seconds to 10 hours, preferably 1 minute to 3 hours.

The process of heating the magnesium oxide in the combustion ash involves heating the combustion ash in a heating furnace. By heating the magnesium oxide, impurities coated on the magnesium oxide particles can be removed. Heating conditions may be, for example, 100 to 1000°C, preferably 200 to 900°C, or preferably 400 to 600°C, for example, 5 minutes to 40 hours, preferably 10 minutes to 30 hours, and more preferably 1 to 20 hours.

The pretreatment process may be a combination of a process of pulverizing the magnesium oxide in the combustion ash and a process of heating the magnesium oxide in the combustion ash; for example, it may be a process of pulverizing the magnesium oxide in the combustion ash and then further heating the magnesium oxide in the combustion ash.

(Molten salt electrolysis process)
The molten salt electrolysis process is a process for producing fuel using the chloride produced in the chlorination process as a material. Hereinafter, an example will be described in which magnesium is produced by electrolysis using anhydrous magnesium chloride produced in the chlorination process as a material. The molten salt electrolysis process may be, for example, a method used to produce magnesium.

So, to put it simply, in the molten salt electrolysis process, for example, magnesium chloride is heated to a temperature of around 700°C in a molten salt electrolysis tank (e.g., a brick furnace) to melt the magnesium chloride.

At least one pair of electrodes is installed inside the molten salt electrolysis cell. When a power source is connected between the electrodes and a voltage of 2.5 V or more is applied, chlorine gas is generated at the anode and magnesium is produced at the cathode.

The chlorine gas generated in the molten salt electrolysis process may be used in the chlorination process using the chlorine gas method. Furthermore, since hydrogen chloride gas is produced by reacting hydrogen gas with chlorine gas, hydrogen chloride gas may be produced using the chlorine gas generated in the molten salt electrolysis process as a material and used in the chlorination process using the hydrogen chloride gas method, hydrogen chloride water method, or ammonium chloride method.

(Direct reduction process)
The direct reduction step is a step of directly reducing oxides contained in the combustion ash of a fuel to produce fuel. When the combustion ash contains calcium oxide, calcium may be produced by directly reducing the oxides contained in the combustion ash without going through the chlorination step.

The direct reduction process can be carried out by referring to the molten salt electrolysis process, except that the starting material is an oxide.

Unlike the molten salt electrolysis process, which uses inorganic chlorides as a material, the direct reduction process can generate oxygen at the anode. Therefore, the anode material in the direct reduction process can be changed from that in the molten salt electrolysis process. Examples of such anodes include solid oxide electrodes made of oxides such as zirconia, and carbon electrodes. Solid oxide electrodes are stable against oxygen, so oxygen is generated at the anode. On the other hand, when a carbon electrode is used, carbon dioxide can be generated at the anode.

(Playback system)
The resource recycling process has been described above, but the resource recycling process may be performed by a recycling system that integrates a reaction vessel section (hereinafter referred to as a chlorination furnace) for performing the chlorination process and a molten salt electrolysis cell for performing the molten salt electrolysis process. By using such a recycling system, for example, chlorine generated at the anode in the molten salt electrolysis process can be utilized in the chlorination process. Since chlorine gas is highly corrosive, it is preferable to be able to utilize the chlorine generated in the molten salt electrolysis process in the chlorination process, since this shortens the storage time of the chlorine gas. Since the chlorine generated in the molten salt electrolysis process can be utilized directly in the chlorination process, a recycling system for performing the chlorination process using a chlorine gas method will be described below.

In the regeneration system, the chlorination furnace and molten salt electrolysis furnace are preferably connected by at least a supply path that supplies the inorganic chlorides produced in the chlorination process from the chlorination furnace to the molten salt electrolysis furnace, and a supply path that supplies the chlorine gas produced in the molten salt electrolysis process from the molten salt electrolysis cell to the chlorination furnace. From the perspective of shortening the storage time of chlorine gas, the chlorine gas storage chamber may be omitted from the chlorine gas supply path.

The chlorination furnace may be a batch-type reactor or a flow-type reactor. When using a batch-type reactor, the inorganic chloride is transferred from the chlorination furnace to the molten salt electrolytic cell after detecting that the chlorination reaction in the chlorination furnace has been completed. When using a flow-type reactor, the inorganic chloride is transferred continuously from the chlorination furnace to the molten salt electrolytic cell.

The following explains an example in which magnesium oxide and chlorine gas are added in a chlorination furnace to produce magnesium chloride, and then chlorine and magnesium are produced from the magnesium chloride in a molten salt electrolytic cell.

In the chlorination furnace, magnesium oxide and chlorine gas are added to a molten salt of an alkali metal or alkaline earth metal chloride (e.g., sodium chloride, potassium chloride, calcium chloride, etc.). Because the solubility of magnesium oxide in the molten salt is low and the solubility of magnesium chloride is high, magnesium oxide exists as a solid and magnesium chloride exists in the liquid phase. Furthermore, oxygen is generated during the chlorination reaction of magnesium oxide. Therefore, if the chlorination furnace is a batch type, the solid components in the liquid phase can be monitored, and the contents of the chlorination furnace can be transported to the molten salt electrolytic cell when the decrease in the solid components falls below a certain level. Alternatively, the oxygen concentration in the chlorination furnace can be measured, and the contents of the chlorination furnace can be transported to the molten salt electrolytic cell when the oxygen concentration exceeds a pre-calculated value.

Therefore, the chlorination furnace may be equipped with a measuring device that measures the concentration of solid components in the liquid phase and/or a measuring device that measures the oxygen concentration in the gas phase. Measuring devices that measure the concentration of solid components in the liquid phase include absorbance measuring devices that measure the absorbance or light transmittance of the suspension. Measuring devices that measure the oxygen concentration in the gas phase include well-known oxygen meters.

Furthermore, if the chlorination furnace is a flow type, it is preferable to install a filter at the exhaust port of the chlorination furnace to trap solid magnesium oxide so that unreacted magnesium oxide is not discharged from the chlorination furnace.

In addition, impurities may be removed from the liquid phase of the contents of the chlorination furnace before being transported to the molten salt electrolytic cell. Furthermore, if a filter to trap magnesium oxide is installed at the outlet of the chlorination furnace, the pore size of the filter may be large enough to allow particulate impurities to pass through. Particulate impurities may be recovered separately using a filter with an even smaller pore size.

The chlorides produced in the chlorination process are transferred in liquid form from the chlorination furnace to the molten salt electrolytic cell via a supply path. Here, along the supply path, the inorganic chlorides may be supplied to the molten salt electrolytic cell together with a molten salt of an alkali metal or alkaline earth metal chloride without being separated. For example, when a molten salt of sodium chloride is used as the molten salt of an alkali metal or alkaline earth metal, a molten salt of sodium chloride with magnesium chloride dissolved therein may be supplied to the molten salt electrolytic cell.

In this way, the inorganic chloride supplied from the chlorination furnace may differ from the operating temperature of the molten salt electrolytic cell. Therefore, the temperature of the liquid phase supplied to the molten salt electrolytic cell and the temperature of the molten salt electrolytic cell may be measured, and the temperature of the liquid phase supplied to the molten salt electrolytic cell may be adjusted according to these temperatures. Therefore, the molten salt electrolytic cell may be equipped with a thermometer that measures the temperature of the molten salt, and the supply path from the chlorination furnace to the molten salt electrolytic cell may be equipped with a thermometer that measures the temperature of the supply (liquid phase), as well as a cooler and/or heater that controls the temperature of the supply.

As an example of temperature control, if the molten salt electrolytic cell is at a temperature higher than the desired reaction temperature, the temperature of the molten salt electrolytic cell can be lowered by supplying a liquid phase from the chlorination furnace that is lower than the temperature of the molten salt in the molten salt electrolytic cell; if the molten salt electrolytic cell is within the desired reaction temperature, the temperature change caused by supplying the liquid phase can be suppressed by adjusting the temperature of the liquid phase supplied from the chlorination furnace to the desired reaction temperature.

In a molten salt electrolytic cell, inorganic chlorides are electrolyzed in molten salt to produce chlorine and magnesium. The chlorine produced at the anode is recovered and supplied to the chlorination furnace for reuse in the chlorination process. Magnesium may also liquefy in the molten salt and remain on the surface of the molten salt. In such cases, the liquefied magnesium can be recovered and cooled to obtain solid magnesium.

(Atomization process)
The resource recycling process may further include an atomization process for powdering the fuel (magnesium or calcium) produced in the molten salt electrolysis process or the direct reduction process. The atomization process may be performed using a general pulverizer or a fine powder production device called a gas atomizer.

If the atomization process is carried out using a pulverizer, it is advisable to divide the pulverization process into two stages to improve pulverization efficiency. Specifically, the atomization process may include a coarse pulverization process in which the fuel is coarsely pulverized to a primary particle size (e.g., a particle size of approximately 180 to 800 μm) using a device with a high pulverization speed, and a fine pulverization process in which the fuel pulverized in the coarse pulverization process is further pulverized.

Note that the particle size referred to here does not mean an exact sphere, but rather the coarse grinding process can be thought of as meaning the size that will pass through a sieve with a mesh opening of approximately 0.8 mm.

If the fuel is an inorganic solid fuel with low hardness, such as magnesium, it is preferable to add a grinding aid to the coarsely ground inorganic solid fuel in the fine grinding process. This prevents the fuel particles from sticking together during the grinding process.

For example, stearic acid and the like can be used as grinding aids, but it is preferable to use an inorganic compound powder. Specifically, when magnesium or magnesium hydride is used as the fuel, it is preferable to use magnesium oxide, an inorganic compound powder, as the grinding aid, and when calcium or calcium hydride is used as the fuel, it is preferable to use calcium oxide, an inorganic compound powder, as the grinding aid. This makes it possible to reuse part of the combustion ash as a grinding aid.

(Hydrogenation step)
As described above, the inorganic solid fuel in this embodiment may be magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface. Therefore, the resource recycling step may include a hydrogenation step of hydrogenating the magnesium or calcium atomized in the atomization step. Hereinafter, a step of producing magnesium hydride from magnesium will be described as an example.

If the inorganic solid fuel is a metal such as magnesium that is highly reactive with air, contact with oxygen after the atomization process can result in the formation of an oxide film on the surface, potentially reducing reaction efficiency. If the resource recycling process includes a hydrogenation process, the formation of such an oxide film can be suppressed. Therefore, if the resource recycling process includes a hydrogenation process, it is preferable to handle the magnesium or calcium atomized in the atomization process so that it does not come into contact with oxygen until the hydrogenation process is complete.

Specifically, a method for performing the hydrogenation process without exposing the material to outside air will be described with reference to Figure 3, which illustrates the configuration of the equipment used to perform the hydrogenation process.

As shown in Figure 3, the apparatus for carrying out the hydrogenation process includes a heating vessel HB that contains atomized magnesium and reacts it with hydrogen, a heater H1 that heats the heating vessel HB, and a pipe 10 that is detachably connected to the inlet HB1 of the heating vessel HB.

The heating vessel HB is provided with a valve HB4 at a conduit section HB3 extending from an inlet HB1 to a heating section HB2, and when the valve HB4 is closed, the vessel becomes airtight.
On the other hand, the pipe 10 is connected to a hydrogen gas supply system, an argon gas supply system, and a vacuum pump, although not shown.

The heating vessel HB also serves as a recovery vessel for recovering the pulverized magnesium in the fine pulverization step.
Therefore, the fine grinding process is carried out in an argon gas atmosphere, and before removing the heating container HB from the grinding device that performs the fine grinding process, the valve HB4 is closed and the heating container HB is removed, and the magnesium recovered in the heating container HB is connected to the device shown in Figure 3 in an argon-filled state.

Then, before opening valve HB4, a vacuum is drawn to exhaust the air from pipe 10 and above valve HB4, and then valve HB4 is opened to exhaust the argon gas from heating section HB2.

Then, heater H1 is driven to heat the interior of heating section HB2 to a temperature suitable for hydrogenation (specifically, 180°C to 220°C), and hydrogen gas is supplied to heating vessel HB to perform the hydrogenation process.

Magnesium is highly flammable when it is broken down into a fine powder. On the other hand, magnesium hydride is less flammable because it has been hydrogenated.

Furthermore, magnesium hydride with a hydrogenation rate of about 20% by mass has roughly the same calorific value as coal, so low-purity magnesium hydride can be used as a fuel to replace coal. Therefore, the hydrogenation carried out here only needs to achieve a hydrogenation rate that allows for safe handling in terms of transportation, storage, etc.

The hydrogenation of magnesium is not proportional to time, but rather the hydrogenation rate slows significantly as the purity increases. Therefore, as mentioned above, if low-purity magnesium hydride is used, with a hydrogenation rate of 30 mass% or less, at least on the surface side, the time required for the hydrogenation process can be significantly reduced, greatly increasing productivity.

After the short-time hydrogenation treatment, the heater H1 is turned off, and after cooling, the hydrogen gas in the heating vessel HB is replaced with argon gas, and low-purity magnesium hydride is taken out.
The low-purity magnesium hydride thus produced, in which at least the surface side has been hydrogenated to a hydrogenation rate of 30 mass % or less, is reused as fuel in the power generation process.

As described above, the thermal power generation method of this embodiment does not produce carbon dioxide during power generation, and is a resource-recycling thermal power generation method in which fuel resources are recycled.
Furthermore, since the resource recycling process described above is comprised entirely of facilities that run on electricity, fuel can be recycled and produced using only surplus electricity that cannot be connected to a grid.

Therefore, if the resource recycling process is carried out using surplus electricity, it functions as a receptacle for surplus electricity from renewable energy sources, while the thermal power generation method described above is a power generation method with inertia that can balance supply and demand in accordance with electricity demand and supply.

In other words, by carrying out the resource recycling process using electricity without inertia, such as renewable energy, the method can be a thermal power generation method that can convert that electricity without inertia into electricity with inertia.

In the above, a power generation boiler using the powder combustion burner 31 has been described.
However, there are also coal-fired power plants called stoker boilers, which do not use pulverized coal burners, but instead have a combustion chamber that is simply configured like a combustion furnace, with coal simply being fed into the boiler to keep it burning constantly.The fuel described above may also be used in such a configuration.

Furthermore, in this case, the pulverization process required to sustain combustion as a burner flame is not necessary, and fuel only needs to be supplied to maintain the heat, so relatively large fuel particles are sufficient.

Furthermore, even in the case of magnesium, ignition potential is reduced if the particle size is kept to around 500 μm and fine grinding is avoided, so a thermal power generation method using magnesium as fuel may be adopted, with only the magnesium being appropriately coarsely ground to a size of 500 μm or larger, and the hydrogenation process being omitted.

As such, even in thermal power generation methods that use magnesium as fuel, carbon dioxide is naturally not produced, and the combustion ash becomes magnesium oxide, so it is possible to carry out a resource recycling process. In other words, the resource recycling process can be limited to coarse pulverization, and the fine pulverization and hydrogenation processes described above can be omitted.

Even if the fuel is not hydrogenated as described above and is instead magnesium itself, magnesium nitride will be produced if combustion occurs in an oxygen-deficient state. Therefore, as explained above, it is preferable to increase the humidity in the combustion chamber so that even if magnesium nitride is produced, it can be decomposed quickly.

Furthermore, a mixture of magnesium and magnesium hydride (i.e., a mixture of magnesium and magnesium hydride) can also be used as fuel, and although production efficiency will be significantly reduced, using magnesium hydride with a high hydrogenation rate will not pose any problems as a thermal power generation method.

As such, the present invention is not limited to specific embodiments, and appropriate modifications and improvements are also included within the technical scope of the present invention, which will be clear to those skilled in the art from the claims.

1... Generator, 2... Boiler unit (power generation boiler), B1... Combustion chamber, B2... Steam turbine, B3... Piping, 3... Fuel storage tank, 31... Powder combustion burner, 4... Auxiliary fuel storage tank, 41... Auxiliary combustion burner, 5... Denitrification unit, 6... Dust collector, 7... Combustion ash storage tank, 8... Exhaust pipe, 81... Exhaust system, FU... Condenser, P... Feedwater pump, 9... Reaction vessel section, 91... Body section, 92... Top cover, 93... Bottom cover, IN... Inlet, OUT... Exhaust port, H... Heater, 10... Piping, HB... Heating vessel, HB1... Inlet, HB2... Heating section, HB3... Pipe section, HB4... Valve, H1... Heater

Claims (10)

A resource recycling type thermal power generation method,
a power generation step of burning fuel in a combustion chamber of the boiler device to generate power;
a resource recycling process for generating raw materials for fuel from combustion ash generated by the combustion,
the fuel is magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface,
the combustion ash comprises magnesium oxide, magnesium hydroxide, or a mixture thereof, or calcium oxide, calcium hydroxide, or a mixture thereof;
The method, wherein the resource recovery step produces magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on the surface thereof, from the combustion ash. The resource recycling step includes a micronization step of micronizing the produced magnesium or calcium.
The method of claim 1. The combustion is carried out using a powder combustion burner.
The method of claim 2. The atomization step comprises:
a coarse pulverization step of coarsely pulverizing the produced magnesium or calcium;
A fine pulverization step of further pulverizing the magnesium or calcium pulverized in the coarse pulverization step.
The method of claim 2. The fine pulverization step is carried out by adding a powder of an inorganic compound as a pulverization aid.
The method of claim 4. The inorganic compound is magnesium oxide or calcium oxide.
The method of claim 5. The resource recycling step further includes a hydrogenation step of hydrogenating the surface of the magnesium or calcium atomized in the atomization step to produce magnesium hydride or calcium hydride with a hydrogenation rate of 30 mass% or less.
The method of claim 2. After the atomization step, the atomized magnesium or calcium is handled so as not to come into contact with oxygen until the hydrogenation step is completed.
The method of claim 7. Moisture is supplied into the combustion chamber as a combustion promoter.
The method according to any one of claims 1 to 8. the fuel is magnesium or magnesium hydride;
The resource recycling step
a chlorination step of producing magnesium chloride using the combustion ash;
a molten salt electrolysis step of performing molten salt electrolysis using the magnesium chloride produced in the chlorination step to produce magnesium,
The method according to any one of claims 1 to 8.