Thermal power generation method and method for operating boiler device

Abstract

Provided is a thermal power generation method that suppresses the emission of oxidized carbon that affects global warming such as carbon dioxide emitted from a thermal power plant during generation of power. The present disclosure pertains to a thermal power generation method for mixing and combusting an inorganic solid fuel not containing carbon and a fuel containing carbon in a combustion chamber (21) of a power generation boiler (2). The inorganic solid fuel contains at least one material selected from magnesium, calcium, lithium, aluminum, and hydrides obtained by at least partially hydrogenating magnesium, calcium, lithium, and aluminum.

Description

Thermal power generation method and boiler device operation method

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

[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.

[0004] “Promoting Regional Environmental Conservation: The Structure of Coal-Fired Power Plants and Various Environmental Conservation Measures,” [online], Okinawa Electric Power Company, Inc., [Retrieved June 30, 2022], Internet <URL: https: / / www.okiden.co.jp / environment / report2017 / sec6 / sec63.html>

[0005] The present disclosure 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.

[0006] To achieve the above object, the present disclosure is grasped by the following configurations: (1) One embodiment of the present disclosure is a thermal power generation method in which a fuel containing carbon and an inorganic solid fuel containing no carbon are mixed and burned in a combustion chamber of a boiler apparatus, the inorganic solid fuel containing one or more materials selected from magnesium, calcium, lithium, aluminum, and hydrides in which at least a portion of magnesium, calcium, lithium, and aluminum is hydrogenated.

[0007] (2) In the configuration of (1) above, 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 disclosure 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.

[0013] According to the present disclosure, it is possible 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.

[0014] 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.

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description of the present invention will be given with reference to the accompanying drawings. 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") according to this embodiment. The power generation system includes a power 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 power 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] The power plant for carrying out the thermal power generation method of this embodiment includes a denitration device 6 that detoxifies nitrogen oxides (NOx) contained in 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 sulfur dioxide (SO ) collector that recovers combustion ash contained in the exhaust gas that has passed through the dust collector 7. ２ and a desulfurization device 8 for removing sulfur dioxide.

[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 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 facility 9 for storing combustion ash accumulated in the combustion chamber 21 and combustion ash recovered by the dust collector 7.

[0022] The configuration of the power plant shown in Figure 1 is similar overall to 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 to 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 a 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 of 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] As will be explained later, the inorganic solid fuel stored in the fuel storage 4 is in a powder form similar to pulverized coal, and is supplied so as to merge with a line that supplies pulverized coal from the fuel storage 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 combusted together.

[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 need to be limited to magnesium hydride, but may be 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 are hydrogenated, and these materials can be burned well as inorganic solid fuel. However, from the viewpoint of good combustibility, 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 flammable when they are reduced to fine powders, so when the particle size is, for example, 150 μm or less, it is advisable to provide at least a hydrogenated layer on the surface to suppress 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] Furthermore, 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 for spraying 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] By the way, when magnesium hydride and magnesium, and calcium hydride and calcium are in an oxygen-deficient state during combustion, they react with nitrogen in the air to form magnesium nitride (Mg ３ N ２ ) and calcium nitride (Ca ３ N ２ ) can be generated.

[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 reacts with moisture to form magnesium hydroxide (Mg(OH) ２ ) or calcium hydroxide (Ca(OH) ２ ) and ammonia (NH ３ ) changes to Mg ３ N ２ + 6H ２ O → 3Mg(OH) ２ + 2NH ３ ... (1) Ca ３ N ２ + 6H ２O → 3Ca(OH) ２ + 2NH ３ ... (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 in the combustion chamber 21 so that even if nitrides are generated, they can be decomposed quickly. In this way, even if nitrides are generated, they will be decomposed immediately, 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; the method is not particularly limited.

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

[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 neutralize the nitrogen oxides (NOx) in the exhaust gas.

[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, 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 6. 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 6 may be omitted.

[0050] The exhaust gas that has passed through the denitration device 6 may contain combustion ash that has an extremely small particle size, which is generated during combustion. Therefore, 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] Here, for example, if a hydrogenation film is provided on the surface and the magnesium hydride has a low purity of about 20 mass % overall, the calorific value per weight when burned will be approximately equal to the calorific value 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 approximately the same as that before the amount of coal was reduced, even though the amount of coal used is reduced by half.

[0055] In the case of magnesium hydride or calcium hydride with a purity of 20% by mass, the combustion reactions that occur are the combustion reaction of the magnesium hydride or calcium hydride portion (see the following formulas (2) and (2')) and the combustion reaction of the magnesium or calcium portion (see the following formulas (3) and (3')), but neither combustion reaction produces carbon dioxide. ２ + O ２ → MgO + H２ O・・・・・・(2) 2Mg + O ２ → 2MgO・・・・・・・・・・・・(3) CaH ２ + O ２ → CaO + H ２ O・・・・・・(2') 2Ca + O ２ → 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 moiety 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 generated as a result of the decomposition of carbon dioxide that has not been re-burned, resulting in a carbon dioxide emission reduction effect that exceeds that achieved by reducing the amount of coal used: 2Mg + CO ２ → 2MgO + C・・・・・・(4) 2Ca + CO ２ → 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 the 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 type thermal power generation method in which magnesium or calcium resources are recycled can be realized. Therefore, hereinafter, a method for extracting inorganic solid fuels such as magnesium and calcium from oxides and recycling the resources (resource recycling process) will be briefly described.

[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 Step) The chlorination step comprises an extraction step of extracting the magnesium component as a magnesium chloride hydrate, and an anhydrous chloride generation step of removing impurities and water from the extracted magnesium chloride hydrate. When the inorganic solid fuel is calcium or its hydride, the extraction step comprises an extraction step of extracting the calcium component as a calcium chloride hydrate, and an anhydrous chloride generation step of removing impurities and water from the extracted calcium chloride hydrate, and the same applies to aluminum, lithium, and their hydrides.

[0063] (Extraction Process) In the combustion ash storage 9, not only the magnesium oxide described above but also coal combustion ash is collected. The main components of coal ash vary slightly depending on the place of production, but are generally, in descending order of abundance, SiO ２ (40-75%), Al ２ O ３ (15-35%), Fe ２ O ３ (2 to 10%). It also contains the carbon powder produced by the decomposition of carbon dioxide mentioned above.

[0064] Therefore, carbon powder and SiO are extracted from the combustion ash collected in the combustion ash storage 9. ２ Specifically, when combustion ash is placed in hydrochloric acid water, MgO, Al are removed. ２ O ３ , Fe ２ O ３reacts with hydrochloric acid to form chlorides, which dissolve in the solution, but ２ does not react with hydrochloric acid and is insoluble in the solution, so if you filter this solution, you can get rid of carbon powder and SiO ２ can be removed.

[0065] MgO reacts quickly with hydrochloric acid to become magnesium chloride, which dissolves in the solution. ２ O ３ Since the reaction rate with hydrochloric acid is slow, all of the MgO is converted to magnesium chloride (MgCl ２ ) at the time of Al ２ O ３ Most of the magnesium hydroxide (Mg(OH) ２ ) reacts quickly with hydrochloric acid to form chlorides, similar to MgO, so there is no problem even if it is contained in combustion ash.

[0066] Since it is sufficient for the Mg component to dissolve in the solution, MgO and Mg(OH) ２ However, MgCl ２ After a sufficient time has passed to allow the solution to become soluble, filtration may be carried out to remove any solid components that are not dissolved in the solution.

[0067] Also, MgO, Mg(OH) ２ However, MgCl ２ It goes without saying that the solution temperature may be raised slightly or the solution may be stirred to facilitate this.

[0068] Next, carbon powder and SiO ２ The water content of the filtrate was evaporated after removing the solids such as MgCl ２ , AlCl ３ , FeCl ３ , FeCl ２ of hydrate is recovered.

[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 step) Prior to the extraction step, a step of pretreating 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 under conditions of, for example, 50 to 1000 rpm, preferably 100 to 600 rpm, for example, 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 under conditions of, for example, 50 to 5000 rpm, preferably 100 to 1000 rpm, for example, 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 (chloride hydrate) obtained in the extraction step contains a large amount of water and components other than magnesium chloride. Therefore, a process for removing water (dehydration) and impurities to produce highly pure anhydrous magnesium chloride is required.

[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. to carry out the dehydration treatment.

[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] and anhydrous AlCl ３ has a sublimation point of around 180°C, and anhydrous FeCl ３ Since the boiling point of is about 350°C, as the dehydration progresses, it is discharged out of the heating vessel together with the hydrogen chloride 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, if 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 proceeds, the heating temperature can be set to about 300°C, and then anhydrous AlCl ３ is discharged to the outside of the heating vessel together with the exhaust gas, and can be collected.

[0082] In addition, anhydrous FeCl ３ The boiling point of is around 350 °C, so if you heat it to about 300 °C, anhydrous FeCl ３ can be prevented from being contained in the exhaust gas.

[0083] Let's return to the case where the inorganic solid fuel of this embodiment is low-purity magnesium hydride.３ , and FeCl ３ After removing the gas, the blowing gas is changed from hydrogen chloride to chlorine.

[0084] Then, FeCl ２ reacts with chlorine to form FeCl ３ However, the heating vessel is FeCl ３ Since the temperature is kept above the boiling point of MgCl, it is discharged out of the heating vessel together with the chlorine that is blowing away, resulting in the formation of anhydrous MgCl ２ Only the remaining liquid remains in the heating vessel.

[0085] In addition, when the inorganic solid fuel is lithium (Li) or its hydride, the boiling point is around 1380°C, so anhydrous MgCl ２ The same procedure can be used to obtain

[0086] In this way, by using hydrogen chloride and chlorine as process gases in this order and carrying out the anhydrous chloride production step in which the process gases are heated in a blown-off state, it is possible to produce anhydrous magnesium chloride (MgCl ２ ) can be obtained.

[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 Step) 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 from renewable energy sources is generally dependent 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 leftover wind turbines that cannot be connected to the grid despite being capable of generating electricity due to the capacity of the transmission lines is also coming to the forefront. Therefore, by using the electricity that cannot be connected to the grid, it is possible to receive surplus electricity.

[0095] (Regeneration System) The resource recycling process has been described above, but the resource recycling process may be carried out using a regeneration system that integrates a reaction vessel section (hereinafter referred to as a chlorination vessel) for carrying out the extraction process and a molten salt electrolysis vessel for carrying out the molten salt electrolysis process. By using such a regeneration 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] The following describes an example 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 temperatures of the liquid phase supplied to the molten salt electrolytic tank and 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 have a structure in which fuel is sent 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, in order to suppress the formation of magnesium nitride, it is advisable to increase the humidity within the combustion chamber, for example, by supplying air with a humidity of 50% or more into the combustion chamber.

[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 above, magnesium, calcium, lithium, and aluminum are highly flammable when they are reduced to fine powders, but their flammability generally decreases when the particle size is 400 μm or greater.

[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.

[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 containing no carbon are co-fired in a combustion chamber of a boiler device, wherein the inorganic solid fuel contains one or more materials selected from magnesium, calcium, lithium, and aluminum, and hydrides in which at least a part of magnesium, calcium, lithium, or aluminum is hydrogenated.

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

3. The method according to claim 1, wherein the fuel containing carbon is a solid fuel mainly composed of carbon.

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

5. The method according to claim 1, wherein the fuel containing carbon is a liquid or gaseous hydrocarbon fuel at normal temperature and normal pressure.

6. 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. The method according to claim 5.

7. An operation method of a boiler device in which a fuel containing carbon and an inorganic solid fuel containing no carbon are co-fired in a combustion chamber of the boiler device.

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