Power generation method, operating method for boiler device, boiler device and power generation system

Abstract

To provide a power generation method and a power generation facility that suppress generation of carbon dioxide during power generation.SOLUTION: A power generation method includes burning inorganic solid fuel and carbon monoxide and carbon dioxide that function as combustion-supporting gas in a combustion chamber 21 of a boiler device 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a power generation method, a boiler device operating method, a boiler device, and a power generation system. [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) The power generation method of the present invention includes burning an inorganic solid fuel and carbon dioxide gas as a combustion supporting gas in a combustion chamber of a boiler device.

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

[0011] (3) In the above configuration (2), oxides, which 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, calcium, boron, and aluminum, which is at least partially hydrogenated.

[0013] (5) In the above configuration (4), 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.

[0014] (6) In the above configurations (1) to (5), the combustion supporting gas contains at least one of carbon monoxide and carbon dioxide.

[0015] (7) In the above configurations (1) to (6), the combustion supporting gas consists of carbon dioxide gas alone.

[0016] (8) In the above configurations (1) to (6), the combustion supporting gas contains carbon oxide gas and oxygen gas.

[0017] (9) A method for operating a boiler apparatus according to the present invention includes burning an inorganic solid fuel and a carbon dioxide gas as a combustion supporting gas in a combustion chamber of the boiler apparatus.

[0018] (10) The boiler apparatus of the present invention is provided with a combustion chamber for burning inorganic solid fuel and carbon dioxide gas as a combustion supporting gas, 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.

[0019] (11) A power generation system of the present invention includes the boiler device according to (10) above, and a power generation device that generates power using steam generated by the boiler device. [Effects of the Invention]

[0020] 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]

[0021] [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

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described with reference to the accompanying drawings.

[0023] As an example, the power generation facility according to this embodiment may be installed alongside an integrated coal gasification combined cycle (IGCC) facility or alongside an integrated coal gasification fuel cell combined cycle (IGFC) facility. Therefore, first, an integrated coal gasification combined cycle power generation facility and an integrated coal gasification fuel cell combined cycle power generation facility to which the power generation facility according to this embodiment may be installed will be described. An integrated coal gasification combined cycle power generation facility and an integrated coal gasification fuel cell combined cycle power generation facility are also referred to as "coal gasification power generation facility."

[0024] (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.

[0025] 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 detailed description will be omitted, but the general configuration (particularly the configuration related to this embodiment) is as follows.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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).

[0031] 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 .

[0032] 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.

[0033] The steam turbine 107 uses steam generated in the heat recovery boiler 106 to rotate the turbine and drive the generator 108 .

[0034] 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."

[0035] 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.

[0036] (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.

[0037] The coal gasification fuel cell integrated power generation system 120 is a power generation system that uses coal gasification gas produced in the coal gasification system 101 as an 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 drives a gas turbine 104 with exhaust gas discharged from the fuel cell 124 to generate electricity, and recovers exhaust heat from the gas turbine 104 to generate steam to drive a steam turbine 107 to generate electricity. The coal gasification fuel cell integrated power generation system 120 is a well-known system, so a detailed description will be omitted, but its general configuration (particularly the configuration related to this embodiment) is as follows. Furthermore, in the coal gasification fuel cell integrated power generation system 120, components equivalent to those of the above-mentioned coal gasification integrated power generation system 100 will be designated by the same reference numerals, and their description will be omitted as appropriate.

[0038] 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)

[0039] 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.

[0040] 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.

[0041] The compressor 123 compresses the air and supplies it to the fuel cell 124 .

[0042] 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.

[0043] 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 .

[0044] 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 .

[0045] (Power generation system / power generation method) FIG. 3 is a diagram illustrating the schematic configuration of a power generation system 10 (hereinafter sometimes referred to as a "power plant 10," and in this specification, "power plant" can be replaced with "power generation system") of this embodiment. The power generation system 10 includes a generator 1 and a boiler unit 2 (hereinafter sometimes referred to as a "power generation boiler 2," and in this specification, "power generation boiler" can be replaced with "boiler unit") that includes a combustion chamber 21. In the power generation system 10, the generator 1 generates electricity using steam generated by the boiler unit 2.

[0046] The power generation method of this embodiment includes a power generation step of generating power by burning fuel in the combustion chamber 21 of the boiler device 2. The power generation method of this embodiment may further include a resource recycling step of generating (in other words, recycling) raw materials for fuel from combustion ash generated by burning the fuel in the combustion chamber 21 in the power generation step.

[0047] (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.

[0048] The power generation method of this embodiment includes burning inorganic solid fuel and carbon monoxide and carbon dioxide as combustion supporting gases in the combustion chamber 21 of the boiler device 2. In the power generation method of this embodiment, steam is generated by this combustion, and the steam is used to rotate the turbine of a generator to generate electricity.

[0049] In the embodiment shown in Figure 3, the power generation system 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 denitration 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 denitration device 5, and a combustion ash storage tank 7 that stores the combustion ash.

[0050] (Boiler equipment) The boiler apparatus 2 of this embodiment includes a combustion chamber 21. In the embodiment shown in Fig. 3, the boiler apparatus 2 includes the combustion chamber 21, a steam turbine 22 whose rotating shaft is connected to the generator 1 and which 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 returned to a liquid state in the condenser 9 back to the combustion chamber 21.

[0051] 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.

[0052] The combustion chamber 21 is equipped with a burner 31 that burns inorganic solid fuel supplied from the fuel storage 3. The burner 31 may be, for example, a powder combustion burner that burns powder fuel. The following describes an embodiment in which the burner 31 is a powder combustion burner, but it is not intended that the inorganic solid fuel be limited to powder.

[0053] The combustion chamber 21 may further include an auxiliary combustion burner 41 that burns liquid fuel (for example, heavy oil, light oil, etc.) supplied from the auxiliary fuel storage 4.

[0054] The combustion of the inorganic solid fuel in the combustion chamber 21 is carried out in the presence of carbon oxide gas as a combustion supporting gas. In this embodiment, the combustion may be carried out in an oxygen-free environment (in other words, an atmosphere) or in an oxygen-containing atmosphere. When oxygen is contained in the atmosphere in the combustion chamber 21, the oxygen concentration may be adjusted so that carbon (C) can be produced as a combustion product. In other words, the oxygen concentration may be adjusted to a low level such that the reaction between the inorganic solid fuel and the combustion supporting gas in this embodiment is prioritized over the reaction between the inorganic solid fuel and oxygen. Examples of the combustion supporting gas in this embodiment include carbon monoxide and carbon dioxide.

[0055] The powder combustion burner 31 may be the same as a pulverized coal burner used in coal-fired power generation, for example. The powder combustion burner 31 burns the inorganic solid fuel when supplied with an inorganic solid fuel and a combustion supporting gas. The supply system for supplying the powdered inorganic solid fuel and the combustion supporting gas to the powder combustion burner 31 may also be the same as that used in coal-fired power generation.

[0056] 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 the same as that used in coal-fired power generation.

[0057] 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.

[0058] The inorganic solid fuel of this embodiment is stored in the fuel storage 3. The inorganic solid fuel of this embodiment is a fuel that does not emit carbon dioxide when burned, and specifically is at least one selected from the group consisting of lithium, magnesium, calcium, boron, and aluminum, and at least partially hydrogenated lithium, magnesium, calcium, boron, and aluminum. The inorganic solid fuel of this embodiment may be stored in the fuel storage 3 in a powder state and supplied to the combustion chamber 21.

[0059] The inorganic solid fuel is preferably at least one selected from the group consisting of magnesium (Mg), calcium (Ca), and at least partially hydrogenated magnesium (Mg) and calcium (Ca). The inorganic solid fuel may be used alone or in combination of two or more.

[0060] The at least partially hydrogenated lithium, magnesium, calcium, boron, and aluminum may have a surface hydrogenated layer, may consist of a non-hydrogenated core and a hydrogenated surface layer, or may consist of only the hydrogenated portion.

[0061] The following description will be given taking as an example a case where the inorganic solid fuel is magnesium (including magnesium hydride; the same applies below). The magnesium used as the inorganic solid fuel is preferably adjusted to an appropriate particle size. However, since magnesium is not perfectly spherical, the particle size referred to here is, for example, a particle size that allows it to pass through a sieve with a specified mesh opening.

[0062] In the powder combustion burner 31, magnesium mixed with a combustion-supporting gas is burned.

[0063] The combustion supporting gas supplied to the powder combustion burner 31 contains at least carbon oxide gas, and may be a gas consisting of carbon oxide gas, or a gas containing carbon oxide gas and oxygen gas, or a gas consisting of carbon oxide gas and oxygen gas. Examples of carbon oxide gas include carbon monoxide and carbon dioxide. The carbon oxide gas may include carbon monoxide and carbon dioxide generated in the system of the above-mentioned integrated coal gasification combined cycle power plant 100, or may include carbon monoxide and carbon dioxide generated in the system of the above-mentioned integrated coal gasification fuel cell combined cycle power plant 120.

[0064] 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 gas purification equipment 102 is shown in reaction formula (2) below. Also, the combustion reaction between magnesium hydride (MgH2) and carbon monoxide is shown in reaction formula (3) below. Note that magnesium oxide (MgO) and carbon (C) produced by the combustion reaction are solids (specifically, for example, powders). Mg + CO → MgO + C (2) MgH2+ CO→ MgO + H2+ C (3)

[0065] 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)

[0066] 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)

[0067] 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)

[0068] 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). Also, 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)

[0069] 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.

[0070] Although the above description has been given taking the case where the inorganic solid fuel is magnesium as an example, it goes without saying that the inorganic solid fuel is not limited to magnesium. For example, when the inorganic solid fuel contains calcium (including calcium hydride; the same applies below), the reactions between calcium and carbon monoxide, carbon dioxide, or moisture, and the reactions between calcium hydride and carbon monoxide, carbon dioxide, or moisture are shown in the following reaction formulas (22) to (27), respectively.

[0071] Ca + CO → CaO + C (22) 2Ca +CO2 → 2CaO + C (23) Ca + H2O → CaO + H2(24) CaH2+ CO → CaO + H2+ C (25) 2CaH2+ CO2→ 2CaO+ 2H2+ C (26) CaH2+ H2O → CaO+ 2H2(27)

[0072] Here, the combustion reaction between an inorganic solid fuel such as magnesium or calcium and a combustion supporting gas is a pressure-reducing reaction in which a solid is produced by a reaction between a solid and a gas. When the inorganic solid fuel and the combustion supporting gas are completely combusted in the combustion chamber 21, the pressure in the combustion chamber 21 may decrease. Therefore, the amount of the combustion supporting gas supplied to the combustion chamber 21 may be adjusted to maintain the pressure in the combustion chamber 21 at a predetermined pressure (for example, about 1 atmosphere, or about within an allowable pressure range for the pressure in the combustion chamber 21). In this case, the boiler apparatus 2 may be equipped with a pressure regulation system for maintaining the pressure in the combustion chamber 21 at the predetermined pressure. The pressure regulation system may include, for example, an inlet port for introducing an inert gas or a combustion supporting gas that does not contribute to the reaction in the combustion chamber 21 into the combustion chamber 21, and an outlet port for discharging the introduced inert gas and unreacted combustion supporting gas to the outside of the combustion chamber 21. The pressure regulation system may further include a treatment unit for collecting and treating the discharged gas, and the treated gas may be reintroduced into the combustion chamber 21 from the inlet port. The pressure regulation system may be provided separately from the supply system and combustion system associated with the powder combustion burner 31.

[0073] Furthermore, combustion ash of the inorganic solid fuel accumulates at the bottom of the combustion chamber 21. The boiler apparatus 2 may be equipped with a dust collector for collecting the combustion ash, and the collected combustion ash may be accumulated in the combustion ash storage 7. By recovering the combustion ash in this manner, it is recycled as reusable inorganic solid fuel through a resource recycling process described below. The recycled inorganic solid fuel can be used again as combustion fuel for the boiler apparatus 2.

[0074] (Other configurations) 3, exhaust gas discharged from the combustion chamber 21 is sent to a dust collector 6 through an exhaust pipe 8. In case nitrogen oxides (NOx) are generated during combustion in the combustion chamber 21, a denitration device 5 may be provided in the exhaust pipe 8 to render the nitrogen oxides in the exhaust gas discharged from the combustion chamber 21 harmless (in other words, to remove them).

[0075] 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.

[0076] The exhaust gas discharged from the combustion chamber 21 may contain combustion ash (specifically, powdered magnesium oxide, magnesium hydroxide, and carbon) generated during combustion, which has an extremely small particle size, even after passing through the denitration device 5. For this reason, after the combustion ash is collected by the dust collector 6, the exhaust gas is released into the atmosphere.

[0077] 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. The combustion ash collected by the dust collector 6 may be stored in a combustion ash storage 7.

[0078] In the embodiment shown in FIG. 3, an exhaust device 81 is provided downstream of the dust collector 6, so that the exhaust gas from the combustion chamber 21 passes through the denitration device 5 and the dust collector 6 and is released into the atmosphere.

[0079] On the other hand, in coal-fired power generation, coal is used as fuel, and therefore sulfur components contained in the coal are contained in the exhaust gas. For this reason, in coal-fired power generation, a desulfurization device is further installed before the exhaust gas is released into the atmosphere. In contrast, in this embodiment, magnesium does not contain sulfur components, so there is an advantage that a desulfurization device is not required.

[0080] In addition, in coal-fired power plants, because the exhaust gas contains carbon dioxide, the exhaust gas must be released into the atmosphere through a tall chimney. In contrast, in this embodiment, such a tall chimney is not necessary.

[0081] In coal-fired power generation, too, a dust collector is used because coal residue accumulates at the bottom of the combustion chamber and is also contained in the exhaust gas, and the mechanism for recovering the combustion ash of inorganic solid fuel may be similar to the mechanism used in coal-fired power generation.

[0082] (Resource recycling process) The power generation method of this embodiment may include a resource recycling step of recycling inorganic solid fuel from the combustion ash of the inorganic solid fuel that is generated in the combustion chamber 21 in the power generation step and collected in the combustion ash storage 7. For example, when the inorganic solid fuel is magnesium, the resource recycling step is a resource recovery step of producing magnesium again using as a starting material an oxide of magnesium (specifically, magnesium oxide) contained in the combustion ash that is a combustion product generated in the power generation step.

[0083] The hydroxides contained in the combustion ash undergo a dehydration reaction when heated, turning them into oxides, so the starting material for the resource recovery process can be considered to be oxides. For example, when magnesium hydroxide (Mg(OH)2) is heated, a dehydration reaction occurs, turning it into magnesium oxide (MgO), as shown in reaction formula (14) below. Mg(OH)2 → MgO + HO (14)

[0084] Furthermore, when the combustion ash contains calcium hydroxide (Ca(OH)2), heating causes a dehydration reaction to occur, producing calcium oxide (CaO), as shown in reaction formula (28) below. Ca(OH)2 → CaO + H2O (28)

[0085] The resource recycling step preferably involves producing an inorganic solid fuel (preferably a metal) from an inorganic oxide (preferably a metal oxide) contained in the combustion ash of the inorganic solid fuel. The resource recycling step may involve directly reducing the inorganic oxide by a known method to produce the inorganic solid fuel, or may involve producing an intermediate from the inorganic oxide and reducing the intermediate to produce the inorganic solid fuel. Such intermediates include chlorides.

[0086] Therefore, the resource recycling process may include a chlorination process for producing inorganic chlorides using inorganic oxides contained in the combustion ash of the inorganic solid fuel as a material, and a molten salt electrolysis process for producing inorganic solid fuel using the inorganic chlorides produced in the chlorination process as a material. Alternatively, the resource recycling process may include a direct reduction process for producing inorganic solid fuel by directly reducing inorganic oxides contained in the combustion ash of the inorganic solid fuel.

[0087] For example, taking the procedure of producing magnesium from magnesium oxide as a starting material as an example, the resource regeneration process may include a chlorination process in which magnesium chloride is produced using magnesium oxide in the 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.

[0088] Furthermore, taking the procedure of producing calcium from calcium oxide as a starting material as an example, the resource recycling process may include a chlorination process in which calcium chloride is produced using calcium oxide in the combustion ash as a material, and a molten salt electrolysis process in which calcium is produced using the calcium chloride produced in the chlorination process as a material, or may include a direct reduction process in which calcium oxide in the combustion ash is directly reduced to produce calcium.

[0089] (Chlorination process) The chlorination process is a process for producing inorganic chlorides using inorganic oxides contained in the combustion ash of inorganic solid fuel as a material. Hereinafter, an example will be described in which magnesium chloride is produced using magnesium oxide, which is the combustion ash as a material. The magnesium chloride can be used in the subsequent molten salt electrolysis process.

[0090] Examples of methods for the chlorination step include a method using hydrogen chloride water (hydrochloric acid) (hereinafter referred to as the "hydrogen chloride water method"), a method using hydrogen chloride gas (hereinafter referred to as the "hydrogen chloride gas method"), a method using chlorine gas (hereinafter referred to as the "chlorine gas method"), and a method using ammonium chloride (hereinafter referred to as the "ammonium chloride method"). In this embodiment, the hydrogen chloride water method is preferred. In this embodiment, the combustion ash contains not only magnesium oxide (MgO) but also carbon (C) generated by the reduction of carbon oxide gas. By using the hydrogen chloride water method, it is likely that magnesium oxide can be efficiently chlorinated while removing carbon from the combustion ash. In the chlorination step, in addition to the hydrogen chloride water method, the hydrogen chloride gas method, the chlorine gas method, and / or the ammonium chloride method may be combined.

[0091] (hydrogen chloride water method) The chlorination process using the hydrogen chloride water method may be, for example, a process in which combustion ash and hydrogen chloride (HCl) water are dropped into a chlorination tank to chlorinate inorganic oxides. The combustion ash contains not only magnesium oxide (MgO) but also carbon (C) produced by the reduction of carbon oxide gas. Therefore, in this case, in the chlorination process, powdered magnesium oxide (MgO) and carbon (C) that are combustion ash are first added to hydrogen chloride (HCl) water in the chlorination tank. The magnesium oxide undergoes a reaction in the hydrogen chloride water according to the following reaction formula (15) to become magnesium chloride (MgCl2). MgO + 2HCl → MgCl2 + H2O (15)

[0092] Magnesium chloride, produced by the reaction, has high solubility in water and will dissolve if the hydrogen chloride solution contains sufficient water. On the other hand, carbon does not react and does not dissolve in the hydrogen chloride solution, so it remains in powder form in the hydrogen chloride solution. Therefore, carbon from the combustion ash can be recovered by filtering the hydrogen chloride solution containing dissolved magnesium chloride. Furthermore, magnesium oxide exists as a solid in the hydrogen chloride solution until it reacts according to the above reaction formula (15). Therefore, the progress of the chlorination process can be estimated by monitoring the amount of solids in the chlorination tank. For example, the chlorination process can be determined to be complete when the rate at which the amount of solids in the chlorination tank decreases reaches a certain level.

[0093] In the above step, it is preferable to proceed with the chlorination reaction while heating the chlorination tank. The temperature of the chlorination tank may be, for example, room temperature to 400°C, or 80 to 300°C. It is also preferable to proceed with the chlorination reaction while stirring the hydrogen chloride water. When the temperature of the chlorination tank exceeds the boiling point of the hydrogen chloride water at atmospheric pressure, the chlorination step may be carried out under pressure-resistant conditions (sealed conditions).

[0094] Prior to the chlorination step using the hydrogen chloride water method, it is preferable to carry out a step of pretreating inorganic oxides in the combustion ash. Since inorganic oxide particles in the combustion ash may be coated with carbon, carrying out such a pretreatment step tends to increase the efficiency of the chlorination reaction in the chlorination step. Furthermore, from the viewpoint of further increasing the efficiency of the chlorination reaction, the pretreatment step and the chlorination step may be repeated as a set. The number of repetitions is not particularly limited, but may be, for example, 2 to 10 times. Furthermore, in this case, the chlorination step may not only be a chlorination step using the hydrogen chloride water method, but also a chlorination step using the hydrogen chloride gas method, the chlorine gas method, or the ammonium chloride method. When multiple chlorination steps are carried out, it is preferable to first carry out a chlorination step using the hydrogen chloride water method, and then carry out a chlorination step using any of the hydrogen chloride water method, the hydrogen chloride gas method, the chlorine gas method, and the ammonium chloride method. A pretreatment step may be carried out before each chlorination step.

[0095] Examples of the pretreatment step include a step of pulverizing inorganic oxides in the combustion ash and a step of heating inorganic oxides in the combustion ash.

[0096] The step of pulverizing the inorganic oxides in 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. By pulverizing the inorganic oxides, the carbon coating layer can be removed from the inorganic oxide particles, and the chlorination step can be enhanced.

[0097] For example, pulverization using a ball mill may be carried out at 50 to 1000 rpm, preferably 100 to 600 rpm, for example, for 1 minute to 30 hours, preferably 10 minutes to 20 hours, and more preferably 1 to 10 hours. Pulverization using a bead mill may be carried out at 50 to 5000 rpm, preferably 100 to 1000 rpm, for example, for 15 seconds to 10 hours, preferably 1 minute to 3 hours.

[0098] The step of heating the inorganic oxides in the combustion ash is a step of heating the combustion ash in a heating furnace. By heating the inorganic oxides, the carbon covering the inorganic oxide particles can be converted into carbon dioxide gas and 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.

[0099] The pretreatment step may be a combination of a step of pulverizing the inorganic oxides in the combustion ash and a step of heating the inorganic oxides in the combustion ash, for example, a step of pulverizing the inorganic oxides in the combustion ash and then further heating the inorganic oxides in the combustion ash.

[0100] The effects on the conversion rate of magnesium oxide in combustion ash to magnesium chloride of the presence or absence of a pretreatment step or the conditions thereof, and the conditions of the chlorination step in the hydrogen chloride water method, are shown in Tables 1 and 2. Furthermore, the effects on the conversion rate of the presence or absence of a pretreatment step or the conditions thereof, and of a further chlorination step after the chlorination step in the hydrogen chloride water method, are shown in Table 3. Furthermore, the results of the increase in conversion rate due to the repetition of the pretreatment step and the chlorination step are shown in Table 4.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3]

[0104] [Table 4]

[0105] The carbon recovered by the chlorination process using the hydrogen chloride solution method is highly pure and useful as an industrial material, and is particularly useful in fields where highly pure carbon materials are required.

[0106] In the chlorination process using the hydrogen chloride water method, anhydrous magnesium chloride is recovered from the hydrogen chloride water after filtering the carbon. As a method for recovering anhydrous magnesium chloride from hydrogen chloride water, for example, a method of heating hydrogen chloride water while blowing hydrogen chloride gas into it can be mentioned. This method is a well-known procedure, so a detailed explanation will be omitted.

[0107] As a method for recovering anhydrous magnesium chloride from hydrogen chloride water, the hydrogen chloride water may be heated in a nitrogen atmosphere to desorb water and obtain an anhydrous magnesium chloride, or the hydrogen chloride may be desorbed to obtain magnesium oxide, which may then be further processed.

[0108] (Chlorine gas method) The chlorination step using the chlorine gas method may be, for example, a step of charging combustion ash, optionally together with an alkali metal or alkaline earth metal chloride, into a chlorination furnace and bringing the inorganic oxides in the combustion ash into contact with chlorine gas to chlorinate the inorganic oxides. In this case, for magnesium oxide, the magnesium oxide and chlorine gas react with each other as shown in the following reaction formula (16) to produce magnesium chloride. The reaction temperature may be 300 to 800°C. Examples of alkali metal or alkaline earth metal chlorides include sodium chloride, potassium chloride, and calcium chloride. 2MgO + 2Cl2 → 2MgCl2 + O2(16)

[0109] In order to increase the reaction efficiency, the chlorination step by the chlorine gas method may be followed by the chlorination step by the hydrogen chloride gas method described below.

[0110] (Hydrogen chloride gas method) The chlorination step using the hydrogen chloride gas method may be, for example, a step of charging combustion ash, optionally together with an alkali metal or alkaline earth metal chloride, into a chlorination furnace and bringing inorganic oxides in the combustion ash into contact with hydrogen chloride gas to chlorinate the inorganic oxides. In this case, for magnesium oxide, the magnesium oxide and hydrogen chloride gas react with each other as shown in the following reaction formula (29) to produce magnesium chloride. The reaction temperature may be 300 to 800°C. Examples of alkali metal or alkaline earth metal chlorides include sodium chloride, potassium chloride, and calcium chloride. MgO + 2HCl → MgCl2 + H2O (29)

[0111] (Ammonium chloride method) The chlorination step using the ammonium chloride method may be, for example, a step of chlorinating inorganic oxides by dropping combustion ash and ammonium chloride (NH4Cl) into a chlorination tower and heating them. In the above case, for magnesium oxide, the magnesium oxide and ammonium chloride (NH4Cl) react with each other as shown in the following reaction formula (17) to produce magnesium chloride. The reaction temperature may be 300 to 600°C. MgO +2NH4Cl → MgCl2+ H2O + 2NH3(17)

[0112] The chlorination step using the ammonium chloride method may be, for example, a step in which inorganic oxides in the combustion ash and ammonium chloride (NH4Cl) are reacted at an appropriate equivalent ratio to produce 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 and 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 remove the ammonium chloride moiety and obtain anhydrous chloride. In the above case, for magnesium oxide, the molar ratio of magnesium oxide to ammonium chloride is 1:3 and the reaction shown in the following reaction formula (18) is caused at a temperature of about 400°C to produce ammonium carnallite hydrate. Then, the ammonium carnallite hydrate is heated in a stream of ammonia gas to a temperature slightly lower than the sublimation temperature of ammonium chloride to cause the dehydration reaction shown in the following reaction formula (19) to remove moisture. Then, in a stream of dry nitrogen, the ammonium chloride portion is heated to a temperature higher than the sublimation temperature of ammonium chloride to cause the reaction shown in the following reaction formula (20) to remove the ammonium chloride portion and produce anhydrous magnesium chloride. MgO+3NH4Cl→MgCl2·NH4Cl·H2O+2NH3(18) MgCl2·NH4Cl·H2O→MgCl2·NH4Cl+H2O (19) MgCl2·NH4Cl→MgCl2+NH3+HCl (20)

[0113] (molten salt electrolysis process) The molten salt electrolysis process is a process for producing an inorganic solid fuel using the inorganic chloride produced in the chlorination process as a material. Hereinafter, an example will be described in which magnesium is produced by electrolysis using the anhydrous magnesium chloride produced in the chlorination process as a material. The molten salt electrolysis process may be, for example, a method used for producing magnesium.

[0114] In the molten salt electrolysis step, for example, magnesium chloride is heated to a temperature of about 700° C. in a molten salt electrolysis bath (for example, a brick furnace) to melt the magnesium chloride.

[0115] At least one pair of electrodes is installed in the molten salt electrolysis cell, and when a power supply is connected between these electrodes and a voltage of 2.5 V or more is applied, chlorine (Cl2) gas is generated at the anode and magnesium is produced at the cathode.

[0116] The chlorine gas generated in the molten salt electrolysis step may be used in a chlorination step using a chlorine gas method. Also, since hydrogen chloride gas is produced by reacting hydrogen gas with chlorine gas, hydrogen chloride gas may be produced using the chlorine gas generated in the molten salt electrolysis step as a material and used in a chlorination step using a hydrogen chloride gas method, a hydrogen chloride water method, or an ammonium chloride method.

[0117] (Direct reduction process) The direct reduction step is a step of directly reducing inorganic oxides contained in the combustion ash of an inorganic solid fuel to produce inorganic solid fuel. When the combustion ash contains calcium oxide or aluminum oxide, elemental metals may be produced by directly reducing the inorganic oxides contained in the combustion ash without going through the chlorination step.

[0118] The direct reduction step can be carried out with reference to the molten salt electrolysis step, except that the starting material is an inorganic oxide.

[0119] Unlike the molten salt electrolysis process using inorganic chlorides, the direct reduction process can generate oxygen at the anode. Therefore, the anode material in the direct reduction process can be changed from that in the molten salt electrolysis process. Examples of such anodes include solid oxide electrodes made of oxides such as zirconia and carbon electrodes. Solid oxide electrodes are stable against oxygen, so oxygen is generated at the anode. On the other hand, when a carbon electrode is used, carbon dioxide can be generated at the anode. The generated carbon dioxide can be recovered and used as a combustion supporting gas in the power generation process.

[0120] (Playback System) Although the resource recycling step has been described above, the resource recycling step may be carried out by a recycling system in which a chlorination furnace or chlorination tank for carrying out the chlorination step and a molten salt electrolysis tank for carrying out the molten salt electrolysis step are integrated. By using such a recycling system, for example, chlorine generated at the anode in the molten salt electrolysis step can be utilized in the chlorination step. Since chlorine gas is highly corrosive, it is preferable that the chlorine generated in the molten salt electrolysis step can be utilized in the chlorination step, since this shortens the storage time of chlorine gas.

[0121] First, a system in which a chlorination tank and a molten salt electrolytic tank are integrated will be described below. In the regeneration system, the chlorination tank and the molten salt electrolytic tank are preferably connected by at least a supply path for supplying inorganic chlorides produced in the chlorination step from the chlorination tank to the molten salt electrolytic tank, and a supply path for supplying chlorine gas produced in the molten salt electrolysis 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.

[0122] 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.

[0123] Hereinafter, an example will be described in which combustion ash containing magnesium oxide and carbon and hydrogen chloride water are added in a chlorination tank to produce magnesium chloride, and chlorine and magnesium are produced from the magnesium chloride in a molten salt electrolytic tank.

[0124] In the chlorination tank, magnesium oxide is added to hydrogen chloride water. Since magnesium chloride has a high solubility 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 the molten salt electrolytic tank.

[0125] 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.

[0126] 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.

[0127] As described above, the content of the chlorination vessel may contain carbon, and therefore carbon may be removed from the liquid before being transported to the molten salt electrolytic vessel. When a filter for trapping magnesium oxide is provided at the outlet of the chlorination vessel, the pore size of the filter is preferably set to a size that allows fine particle carbon to pass through.

[0128] The inorganic chlorides produced in the chlorination step are transferred from the chlorination tank to the molten salt electrolytic tank via a supply path. The inorganic chlorides may be separated from the hydrogen chloride solution along the supply path. For example, when combustion ash containing magnesium oxide is used as a raw material, the hydrogen chloride solution containing dissolved magnesium chloride may be heated to separate the magnesium chloride. Therefore, the regeneration system of this embodiment may include a heating furnace between the chlorination tank and the molten salt electrolytic tank for separating the inorganic chlorides from the hydrogen chloride solution.

[0129] The inorganic chlorides supplied from the chlorination tank (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 inorganic chlorides supplied to the molten salt electrolytic tank and the temperature of the molten salt electrolytic tank may be measured, and the temperature of the inorganic chlorides 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 inorganic chlorides, and a cooler and / or heater that control the temperature of the inorganic chlorides.

[0130] 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 can be lowered by supplying inorganic chlorides having a temperature lower than that of the molten salt in the molten salt electrolytic cell from a chlorination cell; when the molten salt electrolytic cell is within the desired reaction temperature, the temperature change caused by supplying inorganic chlorides can be suppressed by adjusting the temperature of the inorganic chlorides supplied from the chlorination cell to the desired reaction temperature.

[0131] In the molten salt electrolysis tank, chlorine and inorganic solid fuel are produced by electrolyzing inorganic chlorides in the molten salt. Chlorine produced from the anode is recovered and supplied to a chlorination tank for reuse in the chlorination process. Here, hydrogen chloride may be produced by reacting chlorine gas with hydrogen gas before supplying 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, when the inorganic solid fuel is magnesium, the 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.

[0132] Next, a system integrating a chlorination furnace and a molten salt electrolytic cell will be described below, with reference to differences from the above-described system. In such a regeneration system, the chlorination furnace and the molten salt electrolytic cell are preferably connected by at least a supply path for supplying the inorganic chloride produced in the chlorination step from the chlorination furnace to the molten salt electrolytic cell, and a supply path for supplying the chlorine gas produced in the molten salt electrolysis step from the molten salt electrolytic cell to the chlorination furnace.

[0133] Hereinafter, an example will be described in which magnesium oxide and chlorine gas are added in a chlorination furnace to produce magnesium chloride, and chlorine and magnesium are produced from the magnesium chloride in a molten salt electrolytic cell. It is also possible to produce magnesium chloride by adding magnesium oxide and hydrogen chloride gas in a chlorination furnace, but it is preferable to use chlorine gas for chlorination, since chlorine gas produced in the molten salt electrolytic cell can be used directly in the chlorination furnace. However, this does not intend to exclude the chlorination step using the hydrogen chloride gas method, and for example, after the chlorination step using the chlorine gas method is performed, hydrogen chloride gas may be supplied to the chlorination furnace as a final step.

[0134] In the chlorination furnace, magnesium oxide and chlorine gas are introduced into a molten salt of an alkali metal or alkaline earth metal chloride (e.g., sodium chloride, potassium chloride, calcium chloride, etc.). Since the solubility of magnesium oxide in the molten salt is low and the solubility of magnesium chloride is high, magnesium oxide exists as a solid, while magnesium chloride exists in the liquid. Therefore, when the chlorination furnace is a batch-type furnace, the solid components in the liquid may be monitored, and the contents of the chlorination furnace may be transported to a molten salt electrolytic cell when the decrease in the solid components reaches a certain level or less. Furthermore, oxygen is generated during the chlorination of magnesium oxide using the chlorine gas method. Therefore, the oxygen concentration in the chlorination furnace may be measured, and the contents of the chlorination furnace may be transported to a molten salt electrolytic cell when the oxygen concentration reaches or exceeds a predetermined value. Therefore, the chlorination furnace may be equipped with a measuring device for measuring the concentration of solid components in the liquid phase and / or a measuring device for measuring the oxygen concentration in the gas phase. A known oxygen meter may be used as a measuring device for measuring the oxygen concentration in the gas phase.

[0135] The inorganic chloride produced in the chlorination step is transferred from the chlorination furnace to the molten salt electrolytic cell via a supply path. The inorganic chloride may be supplied to the molten salt electrolytic cell together with a molten salt of an alkali metal or alkaline earth metal chloride without being separated from the inorganic chloride along the supply path. For example, when a molten salt of sodium chloride is used as the molten salt of an alkali metal or alkaline earth metal, a molten salt of sodium chloride having magnesium chloride dissolved therein may be supplied to the molten salt electrolytic cell.

[0136] In addition, the regeneration system including the chlorination furnace may be equipped with a filter for trapping solid magnesium oxide at the outlet of the chlorination furnace, a thermometer for measuring the temperature of the supply path from the chlorination furnace to the molten salt electrolytic tank, and a cooler and / or heater for controlling the temperature, as in the regeneration system including the chlorination tank.

[0137] (Atomization process) The resource recycling step may further include an atomization step of converting the inorganic solid fuel produced in the molten salt electrolysis step or the direct reduction step into powdered inorganic solid fuel. In the atomization step, a general pulverizer may be used, or a fine powder manufacturing device called a gas atomizer may be used.

[0138] 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.

[0139] Specifically, the atomization process may include a coarse pulverization process in which the inorganic solid fuel is coarsely pulverized to a primary particle size (for example, a particle size of about 180 to 800 μm) using a device with a high pulverization speed, and a fine pulverization process in which the inorganic solid fuel pulverized in the coarse pulverization process is further pulverized.

[0140] 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.

[0141] Here, when the inorganic solid fuel is an inorganic solid fuel with low hardness such as magnesium, it is preferable to add a grinding aid to the coarsely ground inorganic solid fuel in the fine grinding step, which can prevent the inorganic solid fuel from sticking together during the grinding process.

[0142] As the grinding aid, for example, stearic acid or the like can be used, but it is preferable to use an inorganic compound powder. When the inorganic solid fuel is magnesium, specifically, for example, magnesium oxide, which is an inorganic compound powder, can be used. In this case, part of the combustion ash can be used as the grinding aid.

[0143] (Hydrogenation process) As described above, the inorganic solid fuel in this embodiment may be at least partially hydrogenated lithium, magnesium, calcium, boron, or aluminum. Therefore, the resource recycling process may include a hydrogenation process for hydrogenating the inorganic solid fuel atomized in the atomization process. Hereinafter, a process for producing magnesium hydride from magnesium will be described as an example.

[0144] In addition, when the inorganic solid fuel is a metal such as magnesium that is highly reactive with air, if the inorganic solid fuel comes into contact with oxygen after the atomization step, an oxide film may form on the surface, which may reduce the reaction efficiency. Therefore, if the resource recycling step includes a hydrogenation step, the formation of such an oxide film can be suppressed. Therefore, if the resource recycling step includes a hydrogenation step, it is preferable that the inorganic solid fuel atomized in the atomization step be handled so as not to come into contact with oxygen until the hydrogenation step is completed.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] Although not shown, the pipe 315 is connected to a hydrogen gas supply system, an argon gas supply system, and a vacuum pump.

[0149] The heating vessel 310 also serves as a recovery vessel for recovering the magnesium pulverized in the fine pulverization step.

[0150] 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.

[0151] 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.

[0152] 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)

[0153] 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 is easily combustible when it is reduced to a fine powder. On the other hand, magnesium hydride is less flammable because it has been hydrogenated. Therefore, it is sufficient for magnesium hydrogenation to achieve a hydrogenation rate that allows it to be handled safely in terms of transportation, storage, etc.

[0154] 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.

[0155] 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.

[0156] In this embodiment, 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.

[0157] (Action and effect) According to the power generation method and power plant 10 of the embodiment, an inorganic solid fuel (specifically, at least one selected from the group consisting of lithium, magnesium, calcium, boron, and aluminum, and at least partially hydrogenated lithium, magnesium, calcium, boron, and aluminum) and a carbon oxide gas (e.g., carbon monoxide or carbon dioxide) serving as a combustion supporting gas are combusted in the combustion chamber 21 of the power generation boiler 2, thereby suppressing the carbon dioxide generated during power generation and realizing resource-circulating thermal power generation in which the inorganic solid fuel (e.g., magnesium resource) is circulated. Furthermore, according to the power generation method and power plant 10 of the embodiment, the ability to generate power using carbon dioxide as a combustion supporting gas makes it possible to significantly reduce the environmental impact of various facilities and activities that emit carbon dioxide.

[0158] According to the power generation method and power plant 10 of the embodiment, the resource recycling process can be composed only of electrically powered equipment, making it 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.

[0159] 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.

[0160] 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 this embodiment is not limited to being installed alongside a coal gasification power generation facility. The power generation facility according to this embodiment may also be installed alongside a carbon monoxide storage facility or a carbon dioxide capture and storage (CCS) facility, for example.

[0161] Furthermore, while the above embodiment has been described using a power boiler using a powder combustion burner 31 as an example, 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 of a power boiler like a combustion furnace to maintain continuous combustion. The fuel described above may also be used in such configurations. In this case, atomization, which is necessary for sustaining combustion as 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 particles have reduced flammability with particle sizes of approximately 500 μm, a power generation method using magnesium as fuel may be possible in which only the magnesium particles are appropriately coarsely crushed to a size of 500 μm or greater and no hydrogenation process is performed. In other words, when supplying magnesium particles with particle sizes of approximately 500 μm to a stoker boiler to carry out the power generation method according to this embodiment, the resource recycling process may be performed up to coarse crushing, without the fine crushing and hydrogenation processes.

[0162] Furthermore, in the above embodiment, the case where magnesium is supplied as the inorganic solid fuel to the powder combustion burner 31 has been mainly described, but in this embodiment, the inorganic solid fuel supplied to the powder combustion burner 31 is not limited to magnesium, and may be calcium (Ca), lithium (Li), boron (B), or aluminum (Al). Furthermore, a plurality of substances may be supplied to the powder combustion burner 31 as the inorganic solid fuel. Like 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.

[0163] Furthermore, in the above 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 embodiment, 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.

[0164] Furthermore, in the above embodiment, carbon monoxide or carbon dioxide is supplied as the combustion supporting gas to the powder combustion burner 31. However, in the present embodiment, 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 the inorganic solid fuel. Taking this into consideration, the inorganic solid fuel to be supplied to the powder combustion burner 31 in the present embodiment may be at least one substance (including a mixture of multiple substances) capable of undergoing an oxidation reaction (particularly, a combustion reaction) with the substance selected as the combustion supporting gas, and the combustion supporting gas to be supplied to the powder combustion burner 31 in the present embodiment may be at least one substance (including a mixture of multiple substances) capable of undergoing an oxidation reaction (particularly, a combustion reaction) with the substance selected as the inorganic solid fuel.

[0165] 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 this embodiment is not limited to electrolysis, and reduction may be performed by other methods. [Explanation of symbols]

[0166] 10...Power generation system (power plant), 1...Generator, 2...Boiler equipment (power generation boiler), 21...Combustion chamber, 22...Steam turbine, 23...Pipe, 24...Feedwater pump, 3...Fuel storage, 31...Powder combustion burner, 4...Auxiliary fuel storage, 41...Auxiliary combustion burner, 5...Denitrification equipment, 6...Dust collector, 7...Combustion ash storage, 8...Exhaust pipe, 81...Exhaust air device, 9...Condenser, 100...Coal gasification combined cycle power generation equipment, 101...Coal gasification equipment, 102...Gas purification equipment, 103...Combustor, 104...Gasta bin, 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 equipment, 121...shift reaction equipment, 122...separation equipment, 123...compressor, 124...fuel cell, 125...fuel cell post-stage combustor, 300...apparatus for carrying out hydrogenation process, 310...heating vessel, 311...inlet, 312...heating section, 313...piping section, 314...valve, 315...piping, 320...heater.

Claims

1. The method includes burning an inorganic solid fuel and a carbon dioxide gas as a combustion supporting gas in a combustion chamber of a boiler device. Power generation method.

2. The inorganic solid fuel is at least one of lithium, magnesium, calcium, boron, and aluminum. The power generation method according to claim 1 .

3. The oxides that are combustion products of the inorganic solid fuel are subjected to a reduction treatment and are repeatedly used as the inorganic solid fuel. The power generation method according to claim 2 .

4. The inorganic solid fuel is at least one of at least partially hydrogenated lithium, magnesium, calcium, boron, and aluminum. The power generation method according to claim 1 .

5. The oxides that 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 4.

6. The combustion supporting gas contains at least one of carbon monoxide and carbon dioxide. The power generation method according to any one of claims 1 to 5.

7. The combustion supporting gas consists of only carbon dioxide gas. The power generation method according to any one of claims 1 to 5.

8. The combustion-supporting gas includes carbon oxide gas and oxygen gas. The power generation method according to any one of claims 1 to 5.

9. In the combustion chamber of the boiler device, inorganic solid fuel and carbon dioxide gas as a combustion supporting gas are burned. How to operate a boiler system.

10. A combustion chamber is provided for burning an inorganic solid fuel and a carbon dioxide gas as a combustion supporting gas, 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. Boiler equipment.

11. The boiler apparatus according to claim 10; a generator that generates electricity using steam generated by the boiler device; A power generation system comprising:

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