Thermal power generation method and operating method for boiler device

Abstract

To provide a thermal power generation method that suppresses emissions of carbon oxide that is discharged from a thermal electric power plant and affects global warming during power generation, such as carbon dioxide.SOLUTION: In a thermal power generation method, fuel containing carbon and inorganic solid fuel that does not contain carbon are mixed and burned in a combustion chamber 21 of a power generation boiler 2. The inorganic solid fuel includes one or more types of fuel selected from magnesium, calcium, lithium, aluminum and hydride obtained through hydrogenation of at least part of magnesium, calcium, lithium and aluminum.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal power generation method and a boiler system operation method. [Background technology]

[0002] Currently, the main source of power generation in Japan is thermal power generation (see Non-Patent Document 1).

[0003] However, in order to achieve carbon neutrality by 2050, it is urgent to reduce carbon dioxide emissions from thermal power plants. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] “Promoting Regional Environmental Conservation: The Structure of Coal-Fired Power Plants and Various Environmental Conservation Measures,” [online], Okinawa Electric Power Co., Inc., [Retrieved June 30, 2022], Internet<URL:https: / / www.okiden.co.jp / environment / report2017 / sec6 / sec63.html> Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a thermal power generation method that suppresses emissions of carbon dioxide, which has an impact on global warming and is emitted from thermal power plants during power generation. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention is realized by the following configuration. (1) One embodiment of the present invention is a thermal power generation method in which a fuel containing carbon and an inorganic solid fuel not containing carbon are mixed and burned in a combustion chamber of a boiler apparatus, wherein the inorganic solid fuel contains one or more materials selected from magnesium, calcium, lithium, aluminum, and hydrides in which at least a portion of magnesium, calcium, lithium, and aluminum has been hydrogenated.

[0007] (2) In the above configuration (1), the inorganic solid fuel is made of one or more materials selected from magnesium, calcium, a hydride of magnesium in which at least a portion is hydrogenated, and a hydride of calcium in which at least a portion is hydrogenated.

[0008] (3) In the configuration of (1) above, the carbon-containing fuel is a solid fuel mainly composed of carbon.

[0009] (4) In the configuration of (3) above, the solid fuel is in powder form, the solid fuel is burned using a powder combustion burner provided in the combustion chamber, and the inorganic solid fuel is supplied into the flame formed by the powder combustion burner.

[0010] (5) In the configuration of (1) above, the carbon-containing fuel is a hydrocarbon-based fuel that is liquid or gaseous at room temperature and pressure.

[0011] (6) In the configuration of (5) above, the hydrocarbon fuel is burned using a combustion burner provided in the combustion chamber, and the inorganic solid fuel is supplied into the flame of the combustion burner.

[0012] (7) One embodiment of the present invention is a method for operating a boiler apparatus, in which a fuel containing carbon and an inorganic solid fuel containing no carbon are mixed and burned in a combustion chamber of the boiler apparatus. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a thermal power generation method that suppresses the emission of carbon dioxide, which has an impact on global warming and is emitted from a thermal power plant during power generation. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a configuration of a power generation system for explaining a thermal power generation method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the same elements are designated by the same reference numerals throughout the description of the embodiments.

[0016] (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") of 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 21. In the power generation system of this embodiment, the generator 1 generates electricity using steam generated by the boiler unit 2.

[0017] In the embodiment shown in FIG. 1, the power plant includes a generator 1, a power generation boiler 2 that drives the generator 1, a fuel storage 3 that stores fuel containing carbon to be supplied to the power generation boiler 2, a fuel storage 4 that stores inorganic solid fuel that does not contain carbon to be supplied to the power generation boiler 2, and an auxiliary fuel storage 5 that stores auxiliary fuel to be supplied to the power generation boiler 2.

[0018] Furthermore, the power plant for carrying out the thermal power generation method of this embodiment is equipped with a denitration device 6 that neutralizes nitrogen oxides (NOx) contained in the exhaust gas, a dust collector 7 that recovers combustion ash contained in the exhaust gas that has passed through the denitration device 6, and a desulfurization device 8 that removes sulfur dioxide (SO2) contained in the exhaust gas that has passed through the dust collector 7.

[0019] The power generation boiler 2 may include a combustion chamber 21, a steam turbine 22 whose rotating shaft is connected to the generator 1 and driven by steam produced in the combustion chamber 21, and piping 23 for supplying the steam to the steam turbine 22 and for supplying water returned to a liquid state in the condenser FU back to the combustion chamber 21.

[0020] A water supply pump P is provided in the middle of the pipe 23 connecting the condenser FU and the combustion chamber 21, and is configured to send water to the combustion chamber 21 side.

[0021] Furthermore, the power plant for carrying out the thermal power generation method of this embodiment is equipped with a combustion ash storage 9 for storing the combustion ash accumulated in the combustion chamber 21 and the combustion ash collected by the dust collector 7.

[0022] The overall configuration of the power plant shown in Figure 1 is similar to that of a power plant that uses pulverized coal burners to burn coal in a combustion chamber, so the following will mainly describe the differences, and may omit a description of the similarities with steam power plants that generate electricity using general pulverized coal burners.

[0023] In addition, in the description of this embodiment, the case where the fuel containing carbon is coal, which is a solid fuel mainly composed of carbon, will be described.

[0024] The combustion chamber 21 is provided with a burner 31 that burns fuel supplied from the fuel storage 3. The burner 31 may be, for example, a powder combustion burner 31 that burns coal powder. The following describes an embodiment in which the burner 31 is a powder combustion burner, but it is not intended that the fuel be limited to powder.

[0025] The combustion chamber 21 may further include an auxiliary combustion burner 51 that burns liquid fuel (for example, heavy oil, light oil, etc.) supplied from the auxiliary fuel storage 5.

[0026] The powder combustion burner 31 may be similar to the pulverized coal burner used in coal-fired power generation, and as in a typical coal-fired power plant, a coal pulverizer C may be installed just before the coal is sent to the powder combustion burner 31.

[0027] The coal may then be pulverized in a coal pulverizer C to produce pulverized coal with an appropriate particle size, and the pulverized coal may be supplied to the powder combustion burner 31.

[0028] The supply mechanism for supplying the pulverized coal to the powder combustion burner 31 may be the same as that used in coal-fired power generation, for example, a pressure feeding system.

[0029] In addition, the inorganic solid fuel stored in the fuel storage tank 4 is in powder form similar to pulverized coal, as will be explained later, and is supplied so as to merge with the line that supplies pulverized coal from the fuel storage tank 4 to the powder combustion burner 31. Therefore, in the combustion chamber 21, the fuel containing carbon and the inorganic solid fuel not containing carbon are mixed and burned.

[0030] The auxiliary combustion burner 51 is a burner for generating auxiliary heat until the temperature in the combustion chamber 21 rises and the combustion in the powder combustion burner 31 stabilizes, and this may also be similar to that used in coal-fired power generation.

[0031] The auxiliary combustion burner 41 may be stopped after the combustion in the powder combustion burner 31 has stabilized. 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.

[0032] The inorganic solid fuel stored in the fuel storage 4 is, for example, 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 having at least a hydrogenated layer on its surface. In this embodiment, the fuel is preferably adjusted to an appropriate particle size.

[0033] Magnesium or calcium, or magnesium hydride or calcium hydride having at least a hydrogenated layer on its surface, is not perfectly spherical, and therefore the particle size referred to here can be considered to be a size that allows the particles to pass through a sieve with a specified mesh opening.

[0034] The inorganic solid fuel does not have to be limited to magnesium hydride, but may be composed of one or more materials selected from magnesium (Mg), calcium (Ca), lithium (Li), aluminum (Al), and hydrides in which at least a portion of magnesium, calcium, lithium, and aluminum has been hydrogenated, and these materials can be burned well as inorganic solid fuel. However, from the viewpoint of good combustion characteristics, it is preferable to use magnesium, calcium, magnesium hydride, calcium hydride, or a mixture thereof as the inorganic solid fuel.

[0035] Furthermore, magnesium, calcium, lithium, and aluminum are highly flammable when they are reduced to fine powders, so if the particle size is to be, for example, 150 μm or less, it is advisable to provide at least a hydrogenated layer on the surface to reduce flammability.

[0036] Since pulverized coal and magnesium hydride or calcium hydride are supplied to the powder combustion burner 31, the magnesium hydride or calcium hydride is supplied into the stable combustion flame of the pulverized coal, thereby promoting stable combustion of the magnesium hydride or calcium hydride.

[0037] In this embodiment, the carbon-containing fuel is coal, but the powder combustion burner 31 may be replaced with a combustion burner that burns a liquid fuel, and the carbon-containing fuel may be a fuel that is liquid at room temperature and normal pressure, for example, a petroleum-based fuel such as heavy oil or light oil (a hydrocarbon-based fuel that is liquid at room temperature and normal pressure).

[0038] In addition, instead of the powder combustion burner 31 being a combustion burner that burns gas, a carbon-containing fuel such as liquefied natural gas (a hydrocarbon fuel that is gaseous at room temperature and pressure) may be used, which is gaseous at room temperature and pressure.

[0039] In this way, when the type of burner is changed and the carbon-containing fuel is changed to a liquid fuel or gas (vapor), a separate powder sprayer that sprays powder toward the flame formed by the burner can be provided, and the inorganic solid fuel can be sprayed toward the flame using the powder sprayer.

[0040] Incidentally, when magnesium hydride and magnesium, and calcium hydride and calcium are in an oxygen-deficient state during combustion, they may react with nitrogen in the air to produce magnesium nitride (Mg3N2) and calcium nitride (Ca3N2).

[0041] Therefore, if any of the magnesium hydride and magnesium, and calcium hydride and calcium is incompletely burned, it may be converted into nitrides and mixed into the combustion ash.

[0042] The nitride then reacts with moisture and changes into magnesium hydroxide (Mg(OH)2) or calcium hydroxide (Ca(OH)2) and ammonia (NH3), as shown in the following formulas (1) and (1'). Mg3N2+ 6H2O → 3Mg(OH)2+ 2NH3... (1) Ca3N2+ 6H2O → 3Ca(OH)2+ 2NH3... (1')

[0043] Therefore, if nitrides are mixed in the combustion ash, there is a possibility that ammonia will be generated from the combustion ash after the combustion ash is collected.

[0044] Therefore, it is preferable to increase the humidity inside the combustion chamber 21 so that even if nitrides are generated, they can be decomposed quickly. In this way, even if nitrides are produced, they are quickly decomposed, and the ammonia generated by the decomposition can also contribute to combustion as combustion gas.

[0045] As a method for increasing the humidity inside the combustion chamber 21, for example, an intake port may be provided to send highly humid air (for example, air with a humidity of 50% or more, more preferably 70% or more, or even 80% or more) into the combustion chamber 21, or air with increased humidity may be sent to the powder combustion burner 31 in advance to increase the humidity in the flame, and the method is not particularly limited.

[0046] Furthermore, according to this embodiment, considering that moist air has a higher thermal conductivity than dry air, the heat exchange efficiency in the pipe 23 passing through the combustion chamber 21 tends to be increased.

[0047] On the other hand, there is a possibility that the exhaust gas discharged from the combustion chamber 21 contains nitrogen oxides (NOx). Therefore, in the embodiment shown in Fig. 1, the power generation system is provided with a denitration device 6 in the exhaust pipe 10 that sends the exhaust gas from the combustion chamber 21 to a dust collector 7 in order to render the nitrogen oxides (NOx) in the exhaust gas harmless.

[0048] The denitration device 6 may be similar to the denitration devices generally used in coal-fired power plants, and may have a configuration in which, for example, ammonia is added to the exhaust gas and the exhaust gas is passed through a catalyst layer to decompose nitrogen oxides (NOx) into harmless nitrogen and water.

[0049] In addition to or instead of providing the denitration device 6, air with an increased oxygen concentration may be used as a combustion supporting gas, or oxygen itself may be used as the combustion supporting gas, in order to suppress the generation of nitrogen oxides (NOx). If the oxygen concentration of the combustion supporting gas can be increased and the amount of nitrogen oxides (NOx) generated can be suppressed to a level that satisfies environmental standards, the denitration device 6 may be omitted.

[0050] The exhaust gas that has passed through the denitration device 6 may contain combustion ash that is generated during combustion and has an extremely small particle size. For this reason, in the embodiment shown in Fig. 1, the exhaust pipe 10 is connected to a dust collector 7, and after the combustion ash is collected by the dust collector 7, the exhaust gas is released into the atmosphere.

[0051] In addition, since the exhaust gas may contain sulfur dioxide, a desulfurization device 8 is provided immediately after an exhaust fan 11 provided on an exhaust pipe 10 downstream of the dust collector 7 to remove the sulfur dioxide.

[0052] In this way, the exhaust gas from which nitrogen oxides (NOx), fine combustion ash particles, and sulfur dioxide have been removed is released into the atmosphere through a chimney.

[0053] For example, if the magnesium hydride has a low purity of about 20 mass % when a hydrogenation film is provided on the surface, the calorific value per weight when burned will be approximately equal to that of coal.

[0054] Therefore, if the amount of coal used is reduced to half of the normal amount and magnesium hydride or calcium hydride with a purity of 20 mass% is added instead, the amount of heat generated during combustion will be about the same as before the amount of coal was reduced, even though the amount of coal used is halved.

[0055] In the case of magnesium hydride or calcium hydride with a purity of 20% by mass, two combustion reactions occur: a combustion reaction of the magnesium hydride or calcium hydride portion (see formulas (2) and (2') below) and a combustion reaction of the magnesium or calcium portion (see formulas (3) and (3') below). However, neither combustion reaction produces carbon dioxide. MgH2+ O2→ MgO + H2O·······(2) 2Mg + O2→ 2MgO (3) CaH2+ O2→ CaO + H2O·······(2') 2Ca + O2→ 2CaO············(3')

[0056] Therefore, the same calorific value can be obtained as before the reduction in coal use, and the amount of electricity generated can be maintained at the same level as before the reduction in coal use.However, by adding inorganic solid fuel, which does not emit carbon dioxide when burned, the amount of coal used itself is halved, and carbon dioxide emissions can be halved relative to the amount of electricity generated.

[0057] Furthermore, the magnesium or calcium portion also burns in carbon dioxide as shown in the following formulas (4) and (4'), decomposing the carbon dioxide into solid carbon. Therefore, the combustion ash contains carbon that is produced as a result of the decomposition of carbon dioxide but is not re-burned, which results in a reduction in carbon dioxide emissions that is greater than that achieved by reducing the amount of coal used. 2Mg + CO2→ 2MgO + C (4) 2Ca + CO2→ 2CaO + C·······(4')

[0058] Furthermore, magnesium hydride and magnesium, as well as magnesium oxide (MgO) or calcium oxide (CaO), which are combustion products of calcium hydride and calcium, are solid and are therefore recovered in the combustion ash storage 9. If the magnesium or calcium is extracted from this magnesium oxide or calcium oxide and hydrogenated, it can be recycled again as inorganic solid fuel.

[0059] The main components of the combustion products of magnesium hydride and magnesium, and calcium hydride and calcium are magnesium oxide and calcium oxide, but they may contain small amounts of magnesium hydroxide and calcium hydroxide, which does not pose a problem, as will be explained later.

[0060] In other words, a resource recycling thermal power generation method in which magnesium or calcium resources are recycled can be realized. Therefore, the following will briefly explain a method for extracting inorganic solid fuels such as magnesium and calcium from oxides and recycling the resources (resource recycling process).

[0061] In this embodiment, an example of a resource recycling process is shown that includes a chlorination process for producing anhydrous magnesium chloride and a molten salt electrolysis process for producing magnesium using the anhydrous magnesium chloride, but the resource recycling process is not limited to this.

[0062] (Chlorination process) The chlorination step includes an extraction step of extracting the magnesium component as magnesium chloride hydrate, and an anhydrous chloride production step of removing impurities and water from the extracted magnesium chloride hydrate. When the inorganic solid fuel is calcium or its hydride, the extraction process includes an extraction step of extracting the calcium component as calcium chloride hydrate, and an anhydrous chloride production step of removing impurities and water from the extracted calcium chloride hydrate. The same applies to aluminum, lithium, and their hydrides.

[0063] (extraction process) In addition to the magnesium oxide described above, coal combustion ash is also collected in the combustion ash storage facility 9. The main components of coal ash vary slightly depending on the place of origin, but are generally SiO2 (40-75%), Al2O3 (15-35%), and Fe2O3 (2-10%), in descending order. It also contains carbon powder produced by the decomposition of carbon dioxide as mentioned above.

[0064] Therefore, carbon powder and SiO2 are removed from the combustion ash collected in the combustion ash storage 9. Specifically, when combustion ash is placed in hydrochloric acid water, MgO, Al2O3, and Fe2O3 react with the hydrochloric acid to become chlorides and dissolve in the solution, but carbon powder and SiO2 do not react with the hydrochloric acid and do not dissolve in the solution, so by filtering this solution, the carbon powder and SiO2 can be removed.

[0065] MgO reacts quickly with hydrochloric acid to become magnesium chloride, which dissolves in the solution, but Al2O3 reacts slowly with hydrochloric acid, so by the time all the MgO has turned into magnesium chloride (MgCl2), most of the Al2O3 may not yet have dissolved. In addition, magnesium hydroxide (Mg(OH)2), like MgO, reacts quickly with hydrochloric acid to form chloride, so there is no problem if it is contained in combustion ash.

[0066] It is sufficient that the Mg component dissolves in the solution, and after a sufficient time has passed for MgO and Mg(OH)2 to turn into MgCl2, filtration is carried out to remove the solid components that have not dissolved in the solution.

[0067] It goes without saying that the temperature of the solution may be raised slightly or the solution may be stirred to facilitate the conversion of MgO and Mg(OH)2 to MgCl2.

[0068] Next, the water in the filtrate from which solids such as carbon powder and SiO2 have been removed is evaporated to recover hydrates of MgCl2, AlCl3, FeCl3, and FeCl2.

[0069] As described above, the extraction process includes a filtration process in which the combustion ash is placed in hydrochloric acid and filtered, and a hydrate recovery process in which the filtrate is dried and the hydrates of the chlorides in the filtrate are recovered.

[0070] (Pretreatment process) Prior to the extraction step, a pretreatment step of the combustion ash may be carried out. The pretreatment step and the extraction step may be repeated as a set. The number of repetitions is not particularly limited, but may be, for example, 2 to 10 times.

[0071] The pretreatment step includes a step of pulverizing the combustion ash and a step of heating the combustion ash.

[0072] The step of pulverizing the combustion ash is a step of 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.

[0073] The step of heating the combustion ash is a step of heating the combustion ash in a heating furnace. By heating the combustion ash, impurities coated on the magnesium oxide particles can be removed. The heating conditions may be, for example, 100 to 1000°C, preferably 200 to 900°C, more preferably 400 to 600°C, for example, 5 minutes to 40 hours, preferably 10 minutes to 30 hours, more preferably 1 to 20 hours.

[0074] The pretreatment step may be a combination of a step of pulverizing the combustion ash and a step of heating the combustion ash, for example, a step of pulverizing the combustion ash and then further heating the combustion ash.

[0075] (Anhydrous chloride production step) The material obtained in the extraction process (chloride hydrate) contains a lot of water and other components besides magnesium chloride, so it needs to be dehydrated and treated to remove impurities and produce high-purity anhydrous magnesium chloride.

[0076] The water in hydrates is contained as water of crystallization, and therefore heating is required to remove this water of crystallization. However, simply heating the recovered hydrates to remove the water will cause a hydrolysis reaction, converting them into oxides.

[0077] Therefore, in order to suppress the reaction that turns into this oxide, hydrogen chloride gas is blown over the material, and the temperature is kept at about 400 to 550°C, and a dehydration treatment is carried out.

[0078] The term "swept-away state" means that gas is supplied into a sealed heating vessel for the reaction, and the gas is exhausted in accordance with the gas supply, creating a gas flow within the heating vessel, and the gas in the heating vessel is constantly being replaced. Therefore, the moisture generated by dehydration is exhausted outside the heating vessel together with the exhaust of the gas.

[0079] Since the sublimation point of anhydrous AlCl3 is around 180°C and the boiling point of anhydrous FeCl3 is around 350°C, as the anhydrification progresses, the AlCl3 is discharged out of the heating vessel together with the hydrogen chloride that is blowing away.

[0080] In this embodiment, the inorganic solid fuel is described as being low-purity magnesium hydride, but if the inorganic solid fuel is aluminum (Al) or its hydride, the material obtained in the extraction process will be aluminum chloride hydrate.

[0081] Therefore, in this case, the hydrate is heated at a temperature below 180°C, which is the sublimation temperature of anhydrous aluminum chloride, while hydrogen chloride is blown away, and the dehydration is promoted. After that, the heating temperature is set to about 300°C, and anhydrous AlCl3 is discharged outside the heating vessel together with the exhaust gas, and it can be recovered.

[0082] Since the boiling point of anhydrous FeCl3 is around 350°C, heating to around 300°C can prevent anhydrous FeCl3 from being included in the exhaust gas.

[0083] Returning to the case where the inorganic solid fuel of this embodiment is low-purity magnesium hydride, after removing AlCl3 and FeCl3 in this manner, the flowing gas is changed from hydrogen chloride to chlorine.

[0084] This causes FeCl2 to react with chlorine to form FeCl3, but because the heating vessel is maintained at a temperature above the boiling point of FeCl3, this is expelled from the heating vessel along with the chlorine that is blowing away, and as a result, only anhydrous MgCl2 remains in the heating vessel.

[0085] If the inorganic solid fuel is lithium (Li) or its hydride, the boiling point is around 1380°C, so the same procedure as for obtaining anhydrous MgCl2 can be used.

[0086] In this way, by carrying out the anhydrous chloride production process in which process gases are first hydrogen chloride and then chlorine, and then heated while the process gas is blown away, it is possible to obtain anhydrous magnesium chloride (MgCl) with increased purity.

[0087] In the case of aluminum, since aluminum oxide is used in the molten salt electrolysis, the highly pure anhydrous aluminum chloride recovered as described above is again put into pure water, and this time, aluminum oxide is obtained by heating and dehydrating it without using a gas that inhibits hydrolysis, such as hydrogen chloride. Therefore, when the inorganic solid fuel is aluminum, a re-oxidation step of obtaining aluminum oxide from anhydrous aluminum chloride can be carried out before the molten salt electrolysis step.

[0088] (molten salt electrolysis process) The molten salt electrolysis step is a step in which the anhydrous magnesium chloride obtained in the anhydrous chloride production step is supplied to a molten salt electrolysis furnace and subjected to electrolysis to obtain magnesium.

[0089] Specifically, the temperature of the molten salt electrolysis furnace is set to around 700°C, anhydrous magnesium chloride is molten, and the molten magnesium chloride is electrolyzed to produce magnesium.

[0090] In this embodiment, when magnesium hydride is used as the inorganic solid fuel, a hydrogenation step may be carried out to hydrogenate the magnesium obtained in the molten salt electrolysis step.

[0091] Specifically, magnesium hydride as the inorganic solid fuel of this embodiment can be obtained by heat treating magnesium pulverized to an appropriate particle size (for example, 150 μm or less) in a hydrogen atmosphere and hydrogenating it. Note that when the inorganic solid fuel is magnesium, the hydrogenation step is not necessary.

[0092] The only energy required for the resource recycling process described above is electricity, so no carbon dioxide is emitted during the resource recycling process.

[0093] It is expected that the proportion of electricity generated using renewable energy will increase in the future, but the amount of electricity generated by renewable energy generally depends on the natural environment, and there is a problem that excess electricity cannot be connected to the power grid.

[0094] Furthermore, in the case of wind power generation, as equipment is being replaced with fewer wind turbines that can generate electricity more efficiently, the problem of remaining wind turbines is coming to the forefront. This means that, despite being capable of generating electricity, some old wind turbines cannot be connected to the grid due to the capacity of the transmission lines. Therefore, by using such power that cannot be connected to the grid, it is possible to receive surplus power.

[0095] (Playback System) The resource recycling process has been described above, but the resource recycling process may also be carried out by a recycling system that integrates a reaction vessel section (hereinafter referred to as a chlorination vessel) for carrying out the extraction process with a molten salt electrolysis vessel for carrying out the molten salt electrolysis process. By using such a recycling system, for example, hydrogen chloride can be produced from chlorine generated at the anode in the molten salt electrolysis process and used in the extraction process. Since chlorine gas is highly corrosive, it is preferable to produce hydrogen chloride water gas using chlorine generated in the molten salt electrolysis process and use this hydrogen chloride water gas in the extraction process, as this shortens the storage time of chlorine gas.

[0096] In the regeneration system, the chlorination tank and the molten salt electrolytic furnace are preferably connected by at least a supply path for supplying the inorganic chloride produced in the chlorination step from the chlorination tank to the molten salt electrolytic furnace, and a supply path for supplying the chlorine gas produced in the molten salt electrolytic step from the molten salt electrolytic tank to the chlorination tank. Each supply path may be provided with a device for performing further processing as described below. From the viewpoint of shortening the storage time of chlorine gas, the chlorine gas storage chamber may be omitted from the chlorine gas supply path.

[0097] The chlorination tank may be used for the reaction in a batch system or a flow system. In the case of the reaction in a batch system, after the completion of the chlorination reaction in the chlorination tank is detected, the inorganic chloride is transferred in liquid form from the chlorination tank to the molten salt electrolytic tank. In the case of the reaction in a flow system, the inorganic chloride is continuously transferred in liquid form from the chlorination tank to the molten salt electrolytic tank.

[0098] Hereinafter, an example will be described in which combustion ash and hydrogen chloride water (hydrochloric acid) are added to a chlorination tank to produce magnesium chloride, and chlorine and magnesium are produced from the magnesium chloride in a molten salt electrolytic tank.

[0099] In the chlorination tank, combustion ash containing magnesium oxide is added to hydrogen chloride water. As described above, when combustion ash is added to hydrochloric acid, the magnesium oxide dissolves as magnesium chloride, while other impurities do not dissolve or dissolve slowly. In hydrogen chloride water, magnesium oxide exists as a solid, and magnesium chloride exists in the liquid. Therefore, if the chlorination tank is a batch type, the solid components in the liquid can be monitored, and when the decrease in the solid components falls below a certain level, the contents of the chlorination tank can be transported to a molten salt electrolytic tank.

[0100] Therefore, the chlorination tank may be provided with a measuring device for measuring the concentration of solid components in the liquid phase. Examples of the measuring device for measuring the concentration of solid components in the liquid phase include an absorbance measuring device for measuring the absorbance or light transmittance of the suspension.

[0101] Furthermore, when the chlorination tank is of a flow type, it is preferable to provide a filter at the outlet of the chlorination tank to trap solid magnesium oxide so that unreacted magnesium oxide is not discharged from the chlorination tank.

[0102] The contents of the chlorination tank may have impurities removed from the liquid phase before being transported to the molten salt electrolytic tank. When a filter for trapping magnesium oxide is provided at the outlet of the chlorination tank, the pore size of the filter may be set to a size that allows particulate impurities to pass through. The particulate impurities may be separately recovered using a filter with an even smaller pore size.

[0103] The chlorides produced in the chlorination step are transferred from the chlorination tank to the molten salt electrolytic tank via a supply path. An anhydrous chloride production step for separating inorganic chlorides from the hydrogen chloride solution may be carried out along the supply path. Therefore, the regeneration system of this embodiment may include an anhydrous chloride production device (e.g., a heating furnace) for separating inorganic chlorides from the hydrogen chloride solution between the chlorination tank and the molten salt electrolytic tank.

[0104] The inorganic chlorides supplied from the chlorination tank in this manner (including inorganic chlorides supplied from the chlorination tank via a heating furnace) may differ from the operating temperature of the molten salt electrolytic tank. Therefore, the temperature of the liquid phase supplied to the molten salt electrolytic tank and the temperature of the molten salt electrolytic tank may be measured, and the temperature of the liquid phase supplied to the molten salt electrolytic tank may be adjusted depending on these temperatures. Therefore, the molten salt electrolytic tank may be equipped with a thermometer that measures the temperature of the molten salt, and the supply path from the chlorination tank to the molten salt electrolytic tank may be equipped with a thermometer that measures the temperature of the supply (liquid phase), and a cooler and / or heater that controls the temperature of the supply.

[0105] As an example of temperature control, when the temperature of the molten salt electrolytic cell is higher than the desired reaction temperature, the temperature of the molten salt electrolytic cell may be lowered by supplying a liquid phase from a chlorination cell that has a temperature lower than that of the molten salt in the molten salt electrolytic cell; when the temperature of the molten salt electrolytic cell is within the desired reaction temperature, the temperature change caused by supplying the liquid phase may be suppressed by adjusting the temperature of the liquid phase supplied from the chlorination cell to the desired reaction temperature.

[0106] In the molten salt electrolysis tank, inorganic chlorides are electrolyzed in the molten salt to produce chlorine and magnesium. Chlorine produced from the anode is recovered and supplied to a chlorination tank for reuse in the chlorination step. Here, hydrogen chloride may be produced by reacting chlorine gas with hydrogen gas before supplying the recovered chlorine to the chlorination tank. Hydrogen chloride may be produced in the gas phase in the chlorination tank, but it is preferable to produce it in a hydrogen chloride production device provided upstream of the chlorination tank. Furthermore, magnesium may liquefy in the molten salt and remain on the surface of the molten salt. In such cases, solid magnesium can be obtained by recovering the liquefied magnesium and cooling it.

[0107] Although the thermal power generation method according to the present invention has been described above using specific embodiments, the present invention is not limited to these specific embodiments.

[0108] The above has been explained using the example of a power generation boiler equipped with a burner for combustion in the combustion chamber 21, but there are also power generation boilers, such as stoker-type boilers, which do not use a burner for combustion but simply send fuel into the combustion chamber, and the present invention is also effective in the case of such a type of power generation boiler.

[0109] Even in a configuration that does not use such a combustion burner, it is advisable to increase the humidity in the combustion chamber, for example, by supplying air with a humidity of 50% or more into the combustion chamber in order to suppress the formation of magnesium nitride.

[0110] Furthermore, in the case of a power generation boiler that does not use such a combustion burner, the coal is burned as lump coal, so there is no need for the inorganic solid fuel to be pulverized.

[0111] As mentioned earlier, magnesium, calcium, lithium, and aluminum are highly flammable when they are reduced to fine powders, but their flammability generally decreases once the particle size is 400 μm or larger.

[0112] Therefore, in the case of a power generation boiler that does not use a combustion burner, the powder need not be pulverized, but may be sized to 400 μm or more, so that it can be combusted without any problems together with fuels containing carbon such as coal.

[0113] Furthermore, in the above embodiment, magnesium hydride, which is an inorganic solid fuel, and pulverized coal are mixed and supplied to the powder combustion burner 31, and the inorganic solid fuel is supplied into the flame formed by the powder combustion burner.

[0114] However, the method of supplying the inorganic solid fuel into the flame formed by the powder combustion burner does not have to be limited to this, and it may also be a method of spraying the inorganic solid fuel using a powder sprayer that is installed so as to be able to spray powder toward the flame formed by the powder combustion burner.

[0115] 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 description of the claims. [Explanation of symbols]

[0116] 1...generator, 2...power generation boiler, 21...combustion chamber, 22...steam turbine, 23...piping, 3...fuel storage tank, 31...powder combustion burner, 4...fuel storage tank, 5...auxiliary fuel storage tank, 51...auxiliary combustion burner, 6...denitrification device, 7...dust collector, 8...desulfurization device, 9...combustion ash storage tank, 10...exhaust pipe, 11...exhaust fan, C...coal pulverizer, FU...condenser, P...water supply pump

Claims

1. A thermal power generation method in which a fuel containing carbon and an inorganic solid fuel not containing carbon are mixed and burned in a combustion chamber of a boiler device, A method in which the inorganic solid fuel contains one or more materials selected from magnesium, calcium, lithium, and aluminum, and hydrides of magnesium, calcium, lithium, or aluminum in which at least a portion of the elements has been hydrogenated.

2. 2. The method according to claim 1, wherein the inorganic solid fuel comprises one or more materials selected from magnesium, calcium, a hydride of magnesium in which at least a portion of the material is hydrogenated, and a hydride of calcium in which at least a portion of the material is hydrogenated.

3. The method of claim 1 , wherein the carbon-containing fuel is a carbon-based solid fuel.

4. The solid fuel is in a powder form, The solid fuel is burned using a powder combustion burner provided in the combustion chamber, The method according to claim 3 , wherein the inorganic solid fuel is fed into a flame formed by the powder combustion burner.

5. The method of claim 1 , wherein the carbon-containing fuel is a hydrocarbon-based fuel that is liquid or gaseous at room temperature and pressure.

6. The hydrocarbon fuel is combusted using a combustion burner provided in the combustion chamber, The method of claim 5 , wherein the inorganic solid fuel is fed into the flame of the combustion burner.

7. A fuel containing carbon and an inorganic solid fuel not containing carbon are mixed and burned in a combustion chamber of the boiler device. How to operate a boiler system.

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