Power generation methods and facilities

Abstract

To provide an electric power generation method and an electric power generation facility which suppress emission of carbon dioxide in electric power generation.SOLUTION: An inorganic solid fuel, and carbon monoxide or carbon dioxide as an auxiliary combustion gas are combusted within a combustion chamber 21 of an electric power generation boiler 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a power generation method and a power generation facility. [Background technology]

[0002] BACKGROUND ART Coal-fired power generation systems equipped with power generation boilers are generally known (see, for example, Non-Patent Document 1).

[0003] However, even though 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 being emitted when coal is burned.

[0004] One technology that could solve these problems is carbon dioxide capture and storage (CCS), which involves separating and capturing carbon dioxide from the exhaust gases of thermal power plants and storing the captured carbon dioxide.

[0005] For example, Non-Patent Document 2 introduces CCS efforts in Tomakomai City, Hokkaido, specifically explaining that carbon dioxide is separated and captured from exhaust gases from thermal power plants, and then the captured carbon dioxide is injected and stored deep underground beneath the seabed about 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 in salt water over a long period of time and become minerals in the gaps between rocks.

[0006] However, there are many constraints to achieving this type of storage, such as the need for a geological layer with gaps that allow carbon dioxide to be stored, and for the layer to be covered with a layer that does not allow carbon dioxide to pass through. [Prior art documents] [Non-patent literature]

[0007] [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> [Non-patent document 2] “CCS: CO2 Capture and Burial, Demonstration Tests Now Close to Realization (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> Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above circumstances, and has an object to provide a power generation method and power generation facility that suppresses the generation of carbon dioxide during power generation. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention is realized by the following configuration. (1) In the power generation method of the present invention, inorganic solid fuel and carbon dioxide gas as a combustion supporting gas are combusted in the combustion chamber of a power generation boiler.

[0010] (2) In the above configuration (1), the inorganic solid fuel is at least one of lithium, magnesium, boron, and aluminum.

[0011] (3) In the configuration of (1) above, the inorganic solid fuel is at least one of lithium, magnesium, and aluminum, and the oxides that are combustion products of the inorganic solid fuel are reduced and repeatedly used as the inorganic solid fuel.

[0012] (4) In the above configuration (1), the inorganic solid fuel is at least one of lithium, magnesium, boron, and aluminum, which is at least partially hydrogenated.

[0013] (5) In the configuration of (1) above, the inorganic solid fuel is at least one of lithium, magnesium, and aluminum, which are at least partially hydrogenated, and the oxides that are combustion products of the inorganic solid fuel are reduced and hydrogenated, and are repeatedly used as the inorganic solid fuel.

[0014] (6) In the configuration of (1) above, the combustion supporting gas is at least one of carbon monoxide and carbon dioxide.

[0015] (7) In the above configuration (1), the combustion supporting gas consists of carbon dioxide gas alone.

[0016] (8) In the power generation equipment of the present invention, inorganic solid fuel and carbon dioxide gas as a combustion supporting gas are combusted in the combustion chamber of a power generation boiler, and the amount of the combustion supporting gas supplied to the combustion chamber is adjusted to maintain the pressure in the combustion chamber at a predetermined pressure. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a power generation method and power generation facility that suppress the generation of carbon dioxide during power generation. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a system diagram for explaining a schematic configuration of an integrated coal gasification combined cycle power generation facility according to an embodiment. [Figure 2] 1 is a system diagram for explaining a schematic configuration of a coal gasification fuel cell combined cycle power generation facility according to an embodiment. [Figure 3] 1 is a diagram for explaining a schematic configuration of a power plant for carrying out a power generation process according to an embodiment of the present invention. FIG. [Figure 4]FIG. 1 is a diagram illustrating a schematic configuration of an apparatus for carrying out a hydrogenation step according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the accompanying drawings.

[0020] As an example, the power generation facility according to the present invention may be installed alongside an integrated coal gasification combined cycle (IGCC) plant or an integrated coal gasification fuel cell combined cycle (IGFC) plant. Therefore, first, an integrated coal gasification combined cycle power generation plant and an integrated coal gasification fuel cell combined cycle power generation plant to which the power generation facility according to the present invention may be installed will be described. An integrated coal gasification combined cycle power generation plant and an integrated coal gasification fuel cell combined cycle power generation plant are also referred to as "coal gasification power generation plant."

[0021] (Integrated coal gasification combined cycle (IGCC)) FIG. 1 is a system diagram for explaining the schematic configuration of an integrated coal gasification combined cycle power generation facility 100 according to an embodiment.

[0022] The integrated coal gasification combined cycle power generation facility 100 is a power generation facility that generates electricity by burning coal gasification gas produced in a coal gasification facility 101 in a combustor 103 to drive a gas turbine 104, and also generates electricity by driving a steam turbine 107 with steam generated by recovering exhaust heat from the gas turbine 104. The integrated coal gasification combined cycle power generation facility 100 is a well-known mechanism, so a detailed description will be omitted, but the general configuration (particularly the configuration related to the present invention) is as follows.

[0023] The coal gasification facility 101 includes a coal gasifier, receives supplies of coal and an oxidant, and produces coal gasification gas by gasifying the coal through a reaction of the oxidant. The oxidant supplied to the coal gasifier of the coal gasification facility 101 is an oxygen (O2)-containing gas, the main components of which may be oxygen, oxygen and nitrogen (N2), or air. The coal gasification gas contains carbon monoxide (CO) and hydrogen (H2) as main components.

[0024] The coal gasification facility 101 includes a dust remover and a heat exchanger, and performs dust removal processing on the coal gasification gas produced in the coal gasifier and adjusts the coal gasification gas to a predetermined temperature. The coal gasification gas produced by the coal gasification facility 101 is sent to the gas purification facility 102.

[0025] Coal gasification gas contains impurities, sulfur, etc. in addition to combustible components such as carbon monoxide (CO) and hydrogen (H2). The gas purification facility 102 purifies the coal gasification gas supplied from the coal gasification facility 101 by removing the impurities, sulfur, etc.

[0026] The gas purification equipment 102 includes, for example, a dust filter that removes solid impurities from the coal gasification gas, a halide removal device that has a halide absorbent that chemically reacts with halides contained in the coal gasification gas, and a desulfurization device that has a metal oxide desulfurization agent that chemically reacts with sulfur compounds contained in the coal gasification gas. The coal gasification gas (referred to as "fuel gas") purified by the gas purification equipment 102 is sent to the combustor 103.

[0027] The combustor 103 combusts fuel gas (CO, H2) supplied from the gas purification facility 102, and supplies high-temperature, high-pressure gas (referred to as "combustion gas") to the gas turbine 104. Oxygen (O2) is supplied to the combustor 103 as an oxidant. The high-temperature, high-pressure combustion gas discharged from the combustor 103 is sent to the gas turbine 104. The combustion gas contains carbon dioxide (CO2) and moisture (H2O).

[0028] The gas turbine 104 rotates the turbine by expanding high-temperature, high-pressure combustion gas supplied from the combustor 103 , thereby driving the generator 105 .

[0029] The heat recovery steam generator 106 recovers heat from the exhaust gas discharged from the gas turbine 104 to generate steam. The exhaust gas from which heat has been recovered in the heat recovery steam generator 106 is sent to a compressor 110.

[0030] The steam turbine 107 uses steam generated in the heat recovery boiler 106 to rotate the turbine and drive the generator 108 .

[0031] The recovery device 109 separates moisture (H2O) from at least a portion of the flue gas (CO2, H2O) discharged from the heat recovery boiler 106, and recovers carbon dioxide (CO2). The recovery device 109 separates (in other words, removes) moisture from the flue gas, for example, by drying the flue gas. The flue gas (CO2) from which moisture has been separated / removed is called "dry gas."

[0032] The compressor 110 receives the exhaust gas discharged from the heat recovery boiler 106, compresses the exhaust gas, and supplies it to the combustor 103. At this time, excess carbon dioxide from the exhaust gas discharged from the heat recovery boiler 106 is recovered by the recovery device 109.

[0033] (Integrated coal gasification fuel cell combined cycle power plant (IGFC)) FIG. 2 is a system diagram for explaining the schematic configuration of a coal gasification fuel cell combined cycle power generation facility 120 according to an embodiment.

[0034] The coal gasification fuel cell integrated power generation plant 120 is a power generation plant that uses coal gasification gas produced in the coal gasification plant 101 as the anode (fuel) supplied to the anode (fuel electrode; not shown) of a fuel cell 124, and supplies an oxidant to the cathode (air electrode, oxygen electrode; not shown) of the fuel cell 124 to generate electricity through an electrochemical reaction. At the same time, it generates electricity by driving a gas turbine 104 with exhaust gas discharged from the fuel cell 124, and also generates electricity by driving a steam turbine 107 with steam generated by recovering exhaust heat from the gas turbine 104. The coal gasification fuel cell integrated power generation plant 120 is a well-known mechanism, so a detailed description will be omitted, but its general configuration (particularly the configuration relevant to the present invention) is as follows. Furthermore, in the coal gasification fuel cell integrated power generation plant 120, components equivalent to those of the above-mentioned coal gasification integrated power generation plant 100 will be designated by the same reference numerals, and their description will be omitted as appropriate.

[0035] The shift reaction equipment 121 generates hydrogen and carbon dioxide by reacting carbon monoxide and water (specifically, for example, steam) contained in the fuel gas obtained after the coal gasification gas produced in the coal gasification equipment 101 is purified by the gas purification equipment 102. Specifically, the shift reaction equipment 121 generates hydrogen (H) and carbon dioxide (CO) by reacting carbon monoxide (CO) with water (H2O) using the water-gas shift reaction (see reaction formula 1 below). CO + H2O → H2+ CO2(1)

[0036] The gas (CO 2 , H 2 ; referred to as “shift gas”) produced by the shift reaction facility 121 after the water-gas shift reaction is sent to a separation facility 122.

[0037] The separation equipment 122 separates hydrogen (H) from the components of the shift gas (CO, H) supplied from the shift reaction equipment 121 and supplies the hydrogen to the fuel cell 124. The gas obtained after hydrogen is separated from the shift gas is carbon dioxide (CO) gas.

[0038] The compressor 123 compresses the air and supplies it to the fuel cell 124 .

[0039] The fuel cell 124 receives a supply of hydrogen from the separation equipment 122 and a supply of compressed air from the compressor 123. Hydrogen as fuel is sent to the anode of the fuel cell 124, and compressed air as an oxidant is sent to the cathode of the fuel cell 124, where electricity is generated by an electrochemical reaction.

[0040] The anode gas and cathode gas after the reaction in the fuel cell 124 are combusted in a fuel cell post-stage combustor 125 to become high-temperature, high-pressure gas (ie, combustion gas), which is then supplied to the gas turbine 104 .

[0041] The gas turbine 104 rotates the turbine by expanding high-temperature, high-pressure combustion gas supplied from the fuel cell post-stage combustor 125 , thereby driving the generator 105 .

[0042] (Resource recycling power generation facilities) The power generation method of an embodiment of the present invention includes a power generation process in which fuel is combusted in the combustion chamber 21 of the power generation boiler 2 to generate power, and a resource recycling process in which raw materials for fuel are produced (in other words, recycled) from the combustion ash generated by the combustion.

[0043] (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 (specifically, burning inorganic solid fuel powder instead of pulverized coal), so explanations of the similarities with conventional technology may be omitted.

[0044] FIG. 3 is a diagram illustrating a schematic configuration of a power plant 10 for carrying out a power generation process according to an embodiment of the present invention.

[0045] In the power generation method according to the embodiment of the present invention, inorganic solid fuel and carbon monoxide and carbon dioxide as combustion supporting gases are combusted in the combustion chamber 21 of the power generation boiler 2.

[0046] As shown in Figure 3, the power plant 10 includes 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 denitrification device 5 that neutralizes (in other words, removes) nitrogen oxides (NOx) contained in the exhaust gas discharged from the power generation boiler 2, a dust collector 6 that recovers combustion ash contained in the exhaust gas that has passed through the denitrification device 5, and a combustion ash storage tank 7 that stores the combustion ash.

[0047] The power generation boiler 2 comprises a combustion chamber 21, a steam turbine 22 whose rotating shaft is connected to the generator 1 and is 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 that has been returned to a liquid state in the condenser 9 back to the combustion chamber 21.

[0048] A water supply pump 24 is provided in the middle of the pipe 23 connecting the condenser 9 and the combustion chamber 21, and sends the water that has been returned to a liquid state in the condenser 9 to the combustion chamber 21 side.

[0049] The combustion chamber 21 is equipped with a powder combustion burner 31 that burns powdered fuel supplied from the fuel storage tank 3, and an auxiliary combustion burner 41 that burns liquid fuel (e.g., heavy oil, light oil, etc.) supplied from the auxiliary fuel storage tank 4.

[0050] In the present invention, the combustion of the powder fuel in the combustion chamber 21 is preferably carried out in an oxygen-free environment (in other words, in an atmosphere). Even if the atmosphere in the combustion chamber 21 contains oxygen, the oxygen concentration is preferably adjusted to a concentration low enough to allow the production of carbon (C) as a combustion product. In other words, the oxygen concentration is preferably adjusted to a low enough level that the reaction between magnesium and oxygen is not dominant (in other words, not preferred) compared to the reaction between magnesium and the combustion-supporting gas (e.g., carbon monoxide, carbon dioxide) in the present invention.

[0051] The powder combustion burner 31 may be similar to the pulverized coal burner used in coal-fired power generation, for example, and the supply system for supplying powdered fuel and combustion supporting gas to the powder combustion burner 31 may also be similar to that used in coal-fired power generation.

[0052] The auxiliary combustion burner 41 is a burner for providing auxiliary heating power 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.

[0053] After the combustion of the powder combustion burner 31 has stabilized, there is no need for auxiliary heating power from the auxiliary combustion burner 41. Furthermore, since a thermal power plant will basically operate without being shut down, the amount of carbon dioxide generated by the auxiliary heating power, which is used only at the start of operation, is almost negligible.

[0054] Magnesium (Mg) is stored as a powder fuel that does not emit carbon dioxide when burned, which is the inorganic solid fuel of the present invention, in the fuel storage 3. The magnesium stored in the fuel storage 3 may be magnesium hydride (MgH2) having a hydrogenated layer at least on its surface, or a mixture of magnesium and magnesium hydride.

[0055] Magnesium (including magnesium hydride; the same applies below) as an inorganic solid fuel is preferably adjusted to a particle size of 150 μm or less. However, since magnesium is not perfectly spherical, a particle size of 150 μm or less here means a particle size that can pass through a sieve with a mesh opening of about 0.16 mm, for example.

[0056] Here, the pulverized coal used in pulverized coal burners used in coal-fired power generation is generally 150 μm or less, and by making the particle size of the magnesium 150 μm or less, there is an advantage that a burner with a similar structure to the pulverized coal burner can be used as the powder combustion burner 31.

[0057] In the powder combustion burner 31, magnesium mixed with a combustion-supporting gas is burned.

[0058] The combustion supporting gas supplied to the powder combustion burner 31 may be carbon monoxide or carbon dioxide generated in the system of the above-mentioned integrated coal gasification combined cycle power generation plant 100, or may be carbon monoxide or carbon dioxide generated in the system of the above-mentioned integrated coal gasification fuel cell combined cycle power generation plant 120.

[0059] A) The combustion reaction (including the generation of heat; the same applies below) between magnesium (Mg) and carbon monoxide (CO) in the coal gasification gas (CO, H2) discharged from the coal gasification equipment 101 of the integrated coal gasification combined cycle power plant 100 or the integrated coal gasification fuel cell combined cycle power plant 120 or the fuel gas (CO, H2) discharged from the gas purification equipment 102 is shown in the following reaction formula 2. Also, the combustion reaction between magnesium hydride (MgH2) and carbon monoxide is shown in the following reaction formula 3. Note that magnesium oxide (MgO) and carbon (C) produced by the combustion reaction are solids (specifically, powders). Mg + CO → MgO + C (2) MgH2+ CO → MgO + H2+ C (3)

[0060] A) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) in the combustion gas (CO2, HO) discharged from the combustor 103 of the integrated coal gasification combined cycle power plant 100 is shown in the following reaction formula 4. The combustion reaction between magnesium hydride (MgH2) and carbon dioxide is shown in the following reaction formula 5. In addition, the combustion reaction between magnesium and moisture (HO) is shown in the following reaction formula 6. The combustion reaction between magnesium hydride (MgH2) and moisture is shown in the following reaction formula 7. 2Mg + CO2 → 2MgO + C (4) 2MgH2+ CO2→ 2MgO + 2H2+ C (5) Mg + H2O → MgO + H2(6) MgH2+ H2O → MgO + 2H2(7)

[0061] C) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) gas (i.e., dry gas) discharged from the recovery device 109 of the integrated coal gasification combined cycle power generation facility 100 is as shown in the following reaction formula 8. Also, the combustion reaction between magnesium hydride (MgH2) and carbon dioxide is as shown in the following reaction formula 9. 2Mg + CO2 → 2MgO + C (8) 2MgH2+ CO2→ 2MgO + 2H2+ C (9)

[0062] d) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) in the shift gas (CO2, H2) discharged from the shift reaction equipment 121 of the coal gasification fuel cell combined cycle power generation equipment 120 is as shown in the following reaction formula 10. Also, the combustion reaction between magnesium hydride (MgH2) and carbon dioxide is as shown in the following reaction formula 11. 2Mg + CO2 → 2MgO + C (10) 2MgH2+ CO2→ 2MgO + 2H2+ C (11)

[0063] E) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) remaining after hydrogen (H2) is separated from the shift gas (CO2, H2) in the separation process in the separation equipment 122 of the coal gasification fuel cell combined cycle power generation facility 120 is shown in the following reaction formula 12. The combustion reaction between magnesium hydride (MgH2) and carbon dioxide is shown in the following reaction formula 13. 2Mg + CO2 → 2MgO + C (12) 2MgH2+ CO2→ 2MgO + 2H2+ C (13)

[0064] As described above, only magnesium oxide (MgO) and carbon (C) are produced in the combustion reaction in the powder combustion burner 31, and no carbon dioxide (CO2) is produced during combustion for power generation. However, if the combustion supporting gas supplied to the powder combustion burner 31 contains moisture, for example, the water may react with part of the magnesium oxide, resulting in magnesium hydroxide (Mg(OH)2) being contained in the combustion ash.

[0065] Here, the combustion reaction between magnesium and the combustion supporting gas is a pressure-reducing reaction in which a solid is produced by a reaction between a solid and a gas, and since the pressure inside the combustion chamber 21 may decrease when the inorganic solid fuel and the combustion supporting gas are completely combusted inside the combustion chamber 21, the amount of the combustion supporting gas supplied to the combustion chamber 21 may be adjusted to maintain the pressure inside the combustion chamber 21 at a predetermined pressure (for example, about 1 atmosphere, or about the range of pressures allowed for the pressure inside the combustion chamber 21). In this case, for example, a pressure adjustment system may be provided separately from the supply system and combustion system associated with the powder combustion burner 31, in which gas discharged outside the combustion chamber 21 without contributing to the reaction inside the combustion chamber 21 is collected and then reintroduced into the combustion chamber 21.

[0066] In order to deal with cases in which nitrogen oxides (NOx) are generated during combustion in the combustion chamber 21, a denitration device 5 is provided midway through the exhaust pipe 8 that sends the exhaust gas discharged from the combustion chamber 21 to a dust collector 6 in order to render the nitrogen oxides in the exhaust gas discharged from the combustion chamber 21 harmless (in other words, to remove them).

[0067] The denitration device 5 may be similar to a denitration device used in coal-fired power plants, which has the function of decomposing nitrogen oxides into harmless nitrogen and water by adding ammonia (NH3) to the exhaust gas and passing it through a catalyst layer.

[0068] The exhaust gas after passing through the denitration device 5 does not contain any harmful gases, but does contain combustion ash (specifically, powdered magnesium oxide, magnesium hydroxide, and carbon) generated during combustion that has extremely small particle size. For this reason, 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.

[0069] The dust collector 6 may be the same as a dust collector used in coal-fired power plants, and specifically may be, for example, an electrostatic precipitator.

[0070] In the example shown in FIG. 3, an exhaust device 81 is provided downstream of the dust collector 6, and this allows the exhaust gas from the combustion chamber 21 to pass through the denitration device 5 and the dust collector 6 and be released into the atmosphere.

[0071] On the other hand, in coal-fired power plants, coal is used as fuel, and sulfur components contained in the coal are contained in the exhaust gas. For this reason, in coal-fired power plants, a desulfurization device is further installed before the exhaust gas is released into the atmosphere. In contrast, the present invention has the advantage that a desulfurization device is not required because magnesium does not contain sulfur components.

[0072] In addition, in coal-fired power plants, because the exhaust gas contains carbon dioxide, it is necessary to release the exhaust gas into the atmosphere from a tall chimney. In contrast, the present invention does not require such a tall chimney.

[0073] The combustion ash deposited at the bottom of the combustion chamber 21 and the combustion ash collected by the dust collector 6 are collected in the combustion ash storage 7 and are repeatedly regenerated into magnesium through the resource regeneration process described below for resource circulation. The regenerated magnesium is used as inorganic solid fuel supplied to the powder combustion burner 31.

[0074] In coal-fired power generation, 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 recovering magnesium combustion ash may be the same as the mechanism used in coal-fired power generation.

[0075] As can be seen from the above explanation, if magnesium with a particle size of 150 μm or less is used as fuel, it is highly compatible with the coal-fired power generation technology that has been developed so far, in which pulverized coal is burned in a pulverized coal burner to generate electricity, and a power generation process with reduced carbon dioxide emissions can be carried out.

[0076] (Resource recycling process) Next, a resource recovery process will be described in which magnesium is regenerated using as a starting material an oxide of magnesium (specifically, magnesium oxide) contained in combustion ash, which is a combustion product generated in the power generation process.

[0077] Regarding the magnesium hydroxide (Mg(OH)2) contained in the combustion ash, when heated, a dehydration reaction occurs and it becomes magnesium oxide (MgO) as shown in the following reaction formula 14, so it can be considered that the starting material for the resource recovery process is magnesium oxide. Mg(OH) → MgO + HO (14)

[0078] The procedure for producing magnesium from magnesium oxide, which is the starting material, can be divided into a chlorination process, in which magnesium chloride is produced using magnesium oxide, which is combustion ash, as a material, and a molten salt electrolysis process, in which magnesium is produced using the magnesium chloride produced in the chlorination process as a material.

[0079] (Chlorination process) The chlorination process is a process in which magnesium chloride is produced from magnesium oxide, which is combustion ash, as a raw material and is used in the subsequent molten salt electrolysis process.

[0080] In the chlorination process, powdered magnesium oxide (MgO) and carbon (C), which are combustion ash, are first added to hydrogen chloride (HCl) water. The magnesium oxide undergoes the reaction shown in Equation 15 below in the hydrogen chloride water to become magnesium chloride (MgCl2). The magnesium chloride produced by the reaction is a substance that is highly soluble in water, so it will dissolve if the hydrogen chloride water has a sufficient amount of water. MgO + 2HCl → MgCl2+ H2O (15)

[0081] On the other hand, carbon does not react or dissolve, so it remains in powder form in the hydrogen chloride water. Therefore, by filtering the hydrogen chloride water in which magnesium chloride is dissolved, the carbon in the combustion ash can be recovered.

[0082] The carbon recovered by the above method is highly pure and useful as an industrial material, and is particularly useful in fields where highly pure carbon materials are required.

[0083] After filtering the carbon, anhydrous magnesium chloride is recovered from the hydrogen chloride solution. For example, anhydrous magnesium chloride can be recovered from hydrogen chloride solution by heating the hydrogen chloride solution while blowing hydrogen chloride gas into it. This method is well known, so a detailed description will be omitted.

[0084] As a method for recovering anhydrous magnesium chloride from hydrogen chloride water, alternatively, hydrogen chloride water (wherein magnesium chloride is dissolved in the form of a hexahydrate) may be heated in a nitrogen atmosphere to desorb water and obtain anhydrous magnesium chloride, or hydrogen chloride may be desorbed to obtain magnesium oxide, which may then be further processed.

[0085] In the above case, magnesium oxide may be converted into magnesium chloride by causing the reaction of magnesium oxide with hydrogen chloride gas at a temperature of about 300 to 600°C according to the following reaction formula 16. MgO + 2HCl → MgCl2+ H2O (16)

[0086] In the above case, magnesium oxide may be converted into magnesium chloride by reacting magnesium oxide with ammonium chloride (NH4Cl) at a temperature of about 300 to 600°C according to the reaction represented by the following reaction formula 17. MgO + 2NH4Cl → MgCl2+ H2O + 2NH3(17)

[0087] In the above case, for magnesium oxide, alternatively, a molar ratio of magnesium oxide to ammonium chloride is 1:3 and the reaction of the following reaction formula 18 is caused at a temperature of about 400°C to produce an ammonium carnallite hydrate, and then the ammonium carnallite hydrate is heated in a state where ammonia gas is blown over it to a temperature slightly lower than the sublimation temperature of ammonium chloride (for example, a temperature about 5 to 20°C lower than the sublimation temperature) to cause a dehydration reaction of the following reaction formula 19 to remove moisture, and further heated in a state where dry nitrogen is blown over it to a temperature higher than the sublimation temperature of ammonium chloride (for example, around 400°C) to cause the reaction of the following reaction formula 20 to remove the ammonium chloride moiety to produce anhydrous magnesium chloride. MgO+3NH4Cl→MgCl2·NH4Cl·H2O+2NH3(18) MgCl2·NH4Cl·H2O→MgCl2·NH4Cl+H2O (19) MgCl2·NH4Cl→MgCl2+NH3+HCl (20)

[0088] (molten salt electrolysis process) The molten salt electrolysis process is a process for producing magnesium by electrolysis using anhydrous magnesium chloride produced in the chlorination process as a raw material, and is one method used for producing magnesium.

[0089] The outline of the molten salt electrolysis process is, for example, to heat magnesium chloride to a temperature of around 700°C in a brick furnace to melt the magnesium chloride.

[0090] At least one pair of electrodes is installed inside the brick furnace, and when a power supply is connected between these electrodes and a voltage of 2.5V or more is applied, chlorine (Cl2) gas is generated at the anode and magnesium is produced at the cathode.

[0091] Hydrogen chloride gas is produced by reacting hydrogen gas with chlorine gas, so hydrogen chloride gas may be produced using chlorine gas generated in the molten salt electrolysis process as a material and used in the chlorination process.

[0092] (Atomization process) The atomization process is a process for converting the magnesium produced in the molten salt electrolysis process into powdered magnesium, and may be carried out using a general grinding machine or a fine powder manufacturing device called a gas atomizer.

[0093] When a pulverizing device is used to carry out the pulverization step, it is preferable to carry out the pulverization step in two stages in consideration of pulverization efficiency.

[0094] Specifically, the atomization process is preferably carried out in two stages: a coarse crushing process in which the magnesium is coarsely crushed to a particle size of about 180 to 800 μm using a device with a high crushing speed, although not to the point of atomization; and a fine crushing process in which the magnesium crushed in the coarse crushing process is crushed to a particle size of 150 μm or less.

[0095] The particle size in the atomization step does not mean an exact sphere, but the particle size in the coarse pulverization step is a particle size that can pass through a sieve with a mesh opening of about 0.8 mm, for example.

[0096] Here, when magnesium is coarsely crushed, the fact that magnesium is a soft metal does not cause any problems, but when it is finely crushed, the magnesium particles may stick together during the crushing process, making it difficult to form a fine powder. For this reason, it is preferable to add a crushing aid to the coarsely crushed magnesium in the fine crushing step.

[0097] As the grinding aid, for example, stearic acid or the like can be used, but it is preferable to use an inorganic compound powder. Specifically, for example, by using magnesium oxide, which is an inorganic compound powder, as the grinding aid, it becomes possible to use a part of the combustion ash as the grinding aid, since it has the same composition as the combustion ash.

[0098] (Hydrogenation process) As described above, magnesium hydride having at least a hydrogenated layer on its surface may be used as the inorganic solid fuel in the present invention. Therefore, the magnesium atomized in the atomization step may be hydrogenated (this treatment is referred to as the "hydrogenation step").

[0099] If the magnesium comes into contact with oxygen after atomization, an oxide film will form on the surface, significantly reducing the reaction efficiency. For this reason, the magnesium pulverized in the fine pulverization process must be handled in such a way that it does not come into contact with oxygen until the hydrogenation process is completed.

[0100] A method for performing the hydrogenation step without exposing the material to the outside air will be described with reference to FIG. 4, which is a diagram illustrating the configuration of an apparatus for performing the hydrogenation step.

[0101] As shown in Figure 4, the apparatus 300 for carrying out the hydrogenation process includes a heating container 310 that contains atomized magnesium and reacts it with hydrogen, a heater 320 that heats the heating container 310, and a pipe 315 that is detachably connected to the inlet 311 of the heating container 310.

[0102] Heating vessel 310 is provided with a valve 314 at a conduit section 313 extending from inlet 311 to heating section 312, and when valve 314 is closed, the vessel becomes airtight.

[0103] Although not shown, the pipe 315 is connected to a hydrogen gas supply system, an argon gas supply system, and a vacuum pump.

[0104] The heating vessel 310 also serves as a recovery vessel for recovering the magnesium pulverized in the fine pulverization step.

[0105] As described above, the fine pulverization process is carried out under an argon gas atmosphere, and before the heating container 310 is removed from the pulverization device performing the fine pulverization process, the valve 314 is closed and the heating container 310 is removed, and the magnesium recovered in the heating container 310 is connected to the device 300 shown in Figure 4 in an argon-filled state.

[0106] Then, before the valve 314 is opened, a vacuum is drawn, and after the air in the pipe 315 and upstream of the valve 314 is exhausted, the valve 314 is opened and the argon gas in the heating section 312 is exhausted.

[0107] Thereafter, the heater 320 is driven to heat the temperature inside the heating section 312 to a temperature suitable for hydrogenation (specifically, 180°C to 220°C), and hydrogen gas is supplied to the heating vessel 310 to perform the hydrogenation process (see reaction formula 21 below). Mg + H2 → MgH2(21)

[0108] Here, magnesium hydride with a hydrogenation rate of about 20% by mass has roughly the same calorific value per weight as coal, so low-purity magnesium hydride can be used as a fuel to replace coal (in other words, to replace coal). Furthermore, magnesium becomes more flammable when it is reduced to a fine powder, and is generally treated as a hazardous material under the Fire Service Act. On the other hand, magnesium hydride has low flammability due to its hydrogenation, and even in its fine powder form, it does not fall under the category of a hazardous material under the Fire Service Act. Therefore, it is sufficient for magnesium hydrogenation to achieve a hydrogenation rate that does not make it a hazardous material in terms of transportation, storage, etc.

[0109] The hydrogenation of magnesium does not proceed in proportion to the treatment time, but rather the rate of progress slows significantly as the purity increases. Therefore, if low-purity magnesium hydride is used, in which at least the surface side is hydrogenated to a hydrogenation rate of 30 mass% or less (for example, about 20 mass%), the time required for the hydrogenation process can be significantly reduced, making it possible to significantly increase productivity.

[0110] After the hydrogenation treatment, the heater 320 is turned off, and after cooling, the hydrogen gas in the heating vessel 310 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 (for example, about 20 mass %), is used again as fuel in the power generation process.

[0111] In the present invention, magnesium hydride, which has a high hydrogenation rate, may be used as the inorganic solid fuel, or a mixture of magnesium and magnesium hydride may be used.

[0112] (Action and effect) According to the power generation method and power plant 10 of the embodiment, inorganic solid fuel (specifically, magnesium, magnesium hydride) and carbon monoxide and carbon dioxide as combustion supporting gases are combusted in the combustion chamber 21 of the power generation boiler 2, so no carbon dioxide is generated during power generation, and it is possible to realize resource-circulating thermal power generation in which magnesium resources are recycled. Furthermore, according to the power generation method and power plant 10 of the embodiment, by generating power using carbon dioxide as a combustion supporting gas, it is possible to significantly reduce the environmental load of various facilities and activities that emit carbon dioxide.

[0113] According to the power generation method and power plant 10 of the embodiment, and because the resource recycling process is composed only of equipment that runs on electricity, it is possible to regenerate and produce fuel 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, etc., while the power generation method and power plant 10 of the embodiment can be said to be power generation with inertia that can balance supply and demand in accordance with the supply and demand of electricity. In other words, by carrying out the resource recycling process using electricity without inertia, such as electricity from renewable energy, it can be said to be a power generation method that can convert that electricity without inertia into electricity with inertia.

[0114] The above describes an embodiment of the present invention, but the specific configuration of the present invention is not limited to the above embodiment, and the present invention also includes forms in which modifications and changes are made to the above embodiment within the scope of the gist of the present invention.

[0115] For example, in the above embodiment, the power plant 10 is installed alongside a coal gasification power generation facility (specifically, the integrated coal gasification combined cycle power generation facility 100 and the integrated coal gasification fuel cell combined cycle power generation facility 120), but the power generation facility according to the present invention is not limited to being installed alongside a coal gasification power generation facility. The power generation facility according to the present invention may also be installed alongside a carbon monoxide storage facility or a carbon dioxide capture and storage (CCS) facility, for example.

[0116] Furthermore, while the above embodiment has been described using a power boiler that uses a powder combustion burner 31, there are also coal-fired power plants known as stoker boilers, which do not use pulverized coal burners but instead simply feed coal into the combustion chamber for continuous combustion. The fuel described above may also be used in such configurations. In this case, atomization, which is necessary for sustaining combustion in a burner flame, is not required, and fuel only needs to be supplied to maintain thermal power, so a relatively large fuel size is sufficient. Furthermore, since magnesium is not considered a hazardous material under the Fire Service Act if its particle size is approximately 500 μm, a power generation method using magnesium as fuel may be used in which only the magnesium is appropriately coarsely crushed to a size of 500 μm or greater and no hydrogenation process is performed. In other words, when supplying magnesium with a particle size of approximately 500 μm to a stoker boiler to carry out the power generation method of the present invention, the resource recycling process may be performed up to coarse crushing, without the fine crushing and hydrogenation processes.

[0117] Furthermore, in the above embodiment, magnesium is supplied as the inorganic solid fuel to the powder combustion burner 31, but in the present invention, the inorganic solid fuel supplied to the powder combustion burner 31 is not limited to magnesium, and may be lithium (Li), boron (B), or aluminum (Al). A plurality of substances may also be supplied to the powder combustion burner 31 as the inorganic solid fuel. Similar to magnesium in the above embodiment, lithium is converted into a chloride in a chlorination process, and then electrolyzed and reduced in a molten salt electric field process. Aluminum is not converted into a chloride in a chlorination process, but is electrolyzed and reduced in a molten salt electric field process.

[0118] Furthermore, in the above-described embodiment, the combustion supporting gas supplied to the powder combustion burner 31 is coal gasification gas (including gas obtained by subjecting coal gasification gas produced in the coal gasification plant 101 to predetermined processing, and containing carbon monoxide and carbon dioxide as components) produced in the system of the coal gasification power generation plant (specifically, the integrated coal gasification combined cycle power generation plant 100 and the integrated coal gasification fuel cell combined cycle power generation plant 120). However, in the present invention, the combustion supporting gas supplied to the powder combustion burner 31 is not limited to coal gasification gas produced in the system of the coal gasification power generation plant, and may be carbon monoxide or carbon dioxide produced in another system or stored or preserved independently.

[0119] Furthermore, in the above embodiment, carbon monoxide or carbon dioxide is supplied as the combustion supporting gas to the powder combustion burner 31, but in the present invention, the combustion supporting gas to be supplied to the powder combustion burner 31 is not limited to carbon monoxide or carbon dioxide, but may be any oxide of carbon (in other words, carbon oxide gas) including carbon nitroxide (where N is an integer of 3 or more) and carbon suboxide (e.g., tricarbon dioxide (CO), pentacarbon dioxide (CO)), and more specifically, any substance capable of undergoing an oxidation reaction (particularly, a combustion reaction) with an inorganic solid fuel. Taking this into consideration, in the present invention, the inorganic solid fuel to be supplied to the powder combustion burner 31 may be at least one substance (including a mixture of multiple substances) capable of undergoing an oxidation reaction (particularly, a combustion reaction) with a substance selected as the combustion supporting gas, and the combustion supporting gas to be supplied to the powder combustion burner 31 may be at least one substance (including a mixture of multiple substances) capable of undergoing an oxidation reaction (particularly, a combustion reaction) with a substance selected as the inorganic solid fuel.

[0120] Furthermore, in the above embodiment, the oxide of magnesium (specifically, magnesium oxide), which is a combustion product of combustion in the combustion chamber 21, is reduced by electrolysis, but the method of reduction in the present invention is not limited to electrolysis, and reduction may be performed by other methods. [Explanation of symbols]

[0121] 10. Power Plant 1. Generator 2. Power generation boilers 21 Combustion chamber 22 Steam turbine 23 Piping 24 Water supply pump 3 Fuel storage 31 Powder combustion burner 4 Auxiliary Fuel Storage 41 Auxiliary combustion burner 5 Denitration equipment 6 Dust collector 7. Ash storage facility 8 exhaust pipe 81 Ventilation device 9 Condenser 100 Coal gasification combined cycle power generation facility 101 Coal gasification facility 102 Gas purification equipment 103 Combustor 104 Gas Turbine 105 Generator 106 Waste heat recovery boiler 107 Steam Turbine 108 Generator 109 Recovery Device 110 Compressor 120 Coal gasification fuel cell combined cycle power generation facility 121 Shift reaction facility 122 Separation equipment 123 Compressor 124 Fuel Cell 125 Fuel cell post-combustor 300 Apparatus for carrying out the hydrogenation process 310 Heating container 311 Entrance 312 Heating section 313 Vessel Department 314 Valve 315 Piping 320 Heater

Claims

1. In a combustion chamber of a power generation boiler, inorganic solid fuel and carbon dioxide gas as a combustion supporting gas are combusted, the inorganic solid fuel is at least one of at least partially hydrogenated lithium, magnesium, boron, and aluminum; combustion ash produced by the combustion is a mixture of oxides and carbon, which are combustion products of the inorganic solid fuel; The mixture is poured into hydrogen chloride water to convert the oxide into a chloride and dissolve it in the water, and only the powdery carbon is recovered by filtration. a hydrogenation rate of the at least partially hydrogenated lithium, magnesium, boron, and aluminum is 30 mass% or less based on the total amount of the at least partially hydrogenated lithium, magnesium, boron, and aluminum; Power generation method.

2. The oxides, which are combustion products of the inorganic solid fuel, are subjected to reduction treatment and hydrogenation treatment, and are repeatedly used as the inorganic solid fuel. The power generation method according to claim 1 .

3. The combustion-supporting gas is at least one of carbon monoxide and carbon dioxide. The power generation method according to claim 1 .

4. The combustion supporting gas consists of only carbon dioxide gas. The power generation method according to claim 1 .

5. The amount of the combustion supporting gas supplied to the combustion chamber is adjusted to maintain the pressure in the combustion chamber at a predetermined pressure. The power generation method according to claim 1 .

6. In a combustion chamber of a power generation boiler, inorganic solid fuel and carbon dioxide gas as a combustion supporting gas are combusted, The amount of the combustion supporting gas supplied to the combustion chamber is adjusted to maintain the pressure in the combustion chamber at a predetermined pressure, the inorganic solid fuel is at least one of at least partially hydrogenated lithium, magnesium, boron, and aluminum; combustion ash produced by the combustion is a mixture of oxides and carbon, which are combustion products of the inorganic solid fuel; The mixture is poured into hydrogen chloride water to convert the oxide into a chloride and dissolve it in the water, and only the powdery carbon is recovered by filtration. a hydrogenation rate of the at least partially hydrogenated lithium, magnesium, boron, and aluminum is 30 mass% or less based on the total amount of the at least partially hydrogenated lithium, magnesium, boron, and aluminum; Power generation equipment.

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