Power generation methods and power generation equipment

Abstract

To provide a power generation method and power generation equipment that leverage the technology developed in coal thermal power generation to reduce carbon dioxide emissions.SOLUTION: In a combustion chamber 21 of a power generation boiler 2, an inorganic solid fuel and a coal gasification gas as an assistive combustion gas are burnt.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a power generation method and power generation equipment.

Background Art

[0002] A coal-fired power generation system including a power generation boiler is generally known (see, for example, Non-Patent Document 1).

[0003] However, in Japan, despite having some of the world's leading coal-fired power generation technologies, the use of these technologies is being lost due to the problem of coal emitting carbon dioxide during combustion.

[0004] As one solution to such problems, efforts are being made on so-called CCS (Carbon Dioxide Capture and Storage), which separates and recovers carbon dioxide from the exhaust gas of a thermal power plant and stores the recovered carbon dioxide.

[0005] For example, Non-Patent Document 2 introduces efforts in Tomakomai City, Hokkaido regarding CCS. Specifically, it explains that carbon dioxide is separated and recovered from the exhaust gas of a thermal power plant and injected deep underground beneath the seabed about 3 to 4 km from the coast for storage. The carbon dioxide injected deep underground is considered to be stably stored over a long period of time and to dissolve in salt water and become minerals in the gaps of rocks over a long period of time.

[0006] However, there is a problem that there are many restrictions for such storage, such as the formation having gaps capable of storing carbon dioxide and being covered by a formation that does not allow carbon dioxide to pass through above it.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

[0008] This invention has been made in view of these circumstances, and aims to provide a power generation method and power generation equipment that reduces carbon dioxide emissions by utilizing the technology cultivated in coal-fired power generation. [Means for solving the problem]

[0009] To achieve the above objective, the present invention is understood by the following configuration. (1) The power generation method of the present invention involves burning an inorganic solid fuel and coal gasification gas as a combustion-supporting gas in the combustion chamber of a power generation boiler.

[0010] (2) In the configuration of (1) above, 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 oxide which is a combustion product of the inorganic solid fuel is subjected to reduction treatment and used repeatedly as the inorganic solid fuel.

[0012] (4) In the configuration of (1) above, 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 is at least partially hydrogenated, and the oxide which is a combustion product of the inorganic solid fuel is subjected to reduction treatment and hydrogenation treatment and used repeatedly as the inorganic solid fuel.

[0014] (6) In the configuration of (1) above, the combustion-supporting gas is coal gasified gas produced in the coal gasification equipment of the coal gasification power generation facility.

[0015] (7) In the configuration of (1) above, the combustion-supporting gas is a fuel gas obtained by refining coal gasified gas produced in the coal gasification equipment of the coal gasification power generation facility in a gas purification facility.

[0016] (8) In the configuration of (1) above, the combustion-supporting gas is the exhaust gas discharged when the coal gasification gas produced in the coal gasification equipment of the coal gasification power generation equipment is purified in the gas purification equipment to become fuel gas, and the fuel gas is burned in the combustor.

[0017] (9) In the configuration of (1) above, the combustion-supporting gas is the dry gas obtained after the coal gasification gas produced in the coal gasification equipment of the coal gasification power generation equipment is purified in the gas purification equipment to become fuel gas, and the water is separated from the exhaust gas discharged when the fuel gas is burned in the combustor.

[0018] (10) In the configuration of (1) above, the combustion-supporting gas is a shift gas obtained by purifying coal gasified gas produced in the coal gasification equipment of the coal gasification power generation equipment in the gas purification equipment to make it a fuel gas, and then performing a water-gas shift reaction on the fuel gas.

[0019] (11) In the configuration of (1) above, the combustion-supporting gas is carbon dioxide gas after hydrogen is separated from shift gas obtained by purifying coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility with a gas purification facility and subjecting the fuel gas to a water gas shift reaction.

[0020] (12) In the power generation facility of the present invention, in the combustion chamber of a power generation boiler, an inorganic solid fuel and coal gasification gas as a combustion-supporting gas are burned, and in order to maintain the pressure in the combustion chamber at a predetermined pressure, the amount of the combustion-supporting gas supplied to the combustion chamber is adjusted.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide a power generation method and a power generation facility that utilize the technology cultivated in coal-fired power generation and suppress carbon dioxide emissions.

Brief Description of the Drawings

[0022] [Figure 1] It is a system diagram for explaining the schematic configuration of a coal gasification combined power generation facility in an embodiment. [Figure 2] It is a system diagram for explaining the schematic configuration of a coal gasification fuel cell combined power generation facility in an embodiment. [Figure 3] It is a diagram for explaining the schematic configuration of a power plant for performing a power generation process according to an embodiment of the present invention. [Figure 4] It is a diagram for explaining the schematic configuration of an apparatus for implementing a hydrogenation process according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0023] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the accompanying drawings.

[0024] The power generation equipment according to the present invention can, for example, be installed alongside an integrated gasification combined cycle (IGCC) or an integrated gasification fuel cell combined cycle (IGFC). Therefore, first, we will describe the integrated gasification combined cycle and integrated gasification fuel cell combined cycle equipment in which the power generation equipment according to the present invention can be installed alongside. Integrated gasification combined cycle equipment and integrated gasification fuel cell combined cycle equipment are also referred to as "coal gasification power generation equipment."

[0025] (Integrated Gasification Combined Cycle (IGCC)) Figure 1 is a schematic diagram illustrating the general configuration of the coal gasification combined cycle power generation facility 100 in an embodiment.

[0026] The coal gasification combined cycle power generation facility 100 is a power generation facility that generates electricity by burning coal gasified gas produced in the coal gasification facility 101 in the combustor 103 to drive a gas turbine 104, and also generates electricity by driving a steam turbine 107 with steam generated by recovering the exhaust heat from the gas turbine 104. The coal gasification combined cycle power generation facility 100 is a well-known mechanism, so a detailed explanation will be omitted, but the general configuration (especially the configuration related to the present invention) is as follows.

[0027] The coal gasification facility 101 includes a coal gasifier and receives coal and an oxidizer as supplies. It produces coal gasified gas by gasifying the coal through a reaction with the oxidizer. The oxidizer supplied to the coal gasifier of the coal gasification facility 101 is an oxygen (O2)-containing gas, and its main component may be oxygen, oxygen and nitrogen (N2), or air. The coal gasified gas contains carbon monoxide (CO) and hydrogen (H2) as its main components.

[0028] The coal gasification equipment 101 includes a dust remover and a heat exchanger, and performs dust removal on the coal gasified gas produced in the coal gasifier, and adjusts the coal gasified gas to a predetermined temperature. The coal gasified gas produced by the coal gasification equipment 101 is sent to the gas purification equipment 102.

[0029] Coal gasification gas contains combustible components such as carbon monoxide (CO) and hydrogen (H2), as well as impurities and sulfur. The gas purification facility 102 purifies the coal gasification gas supplied from the coal gasification facility 101 by removing impurities and sulfur.

[0030] The gas purification equipment 102 includes, for example, a dust filter for removing solid impurities from the coal gasification gas, a halogen removal device equipped with a halogen absorbent that chemically reacts with halogens contained in the coal gasification gas, and a desulfurization device equipped with a metal oxide-based desulfurizing 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.

[0031] The combustor 103 burns fuel gas (CO, H2) supplied from the gas purification equipment 102 to produce high-temperature, high-pressure gas (referred to as "combustion gas") which is then supplied to the gas turbine 104. Oxygen (O2) is supplied to the combustor 103 as an oxidizer. 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 water (H2O).

[0032] The gas turbine 104 rotates the turbine by expanding the high-temperature, high-pressure combustion gas supplied from the combustor 103, thereby driving the generator 105.

[0033] The waste heat recovery boiler 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 by the waste heat recovery boiler 106 is sent to the compressor 110.

[0034] The steam turbine 107 uses the steam generated in the heat recovery boiler 106 to rotate the turbine and drive the generator 108.

[0035] The recovery device 109 recovers carbon dioxide (CO2) by separating the water (H2O) from the exhaust gas (CO2, H2O) discharged from the waste heat recovery boiler 106, for at least a portion of the exhaust gas. The recovery device 109 separates (in other words, removes) the water from the exhaust gas by, for example, drying the exhaust gas. The exhaust gas (CO2) after the water has been separated / removed is called "dry gas".

[0036] The compressor 110 receives exhaust gas discharged from the heat recovery boiler 106, compresses this 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.

[0037] (Integrated Gasification Fuel Cell Combined Cycle (IGFC)) Figure 2 is a schematic diagram illustrating the general configuration of the coal gasification fuel cell combined cycle power generation equipment 120 in an embodiment.

[0038] The coal gasification fuel cell combined cycle power generation equipment 120 uses coal gasification gas produced by the coal gasification equipment 101 as the anode (fuel) supplied to the anode electrode (fuel electrode; not shown) of the fuel cell 124, and supplies an oxidizer to the cathode electrode (air electrode, oxygen electrode; not shown) of the fuel cell 124 to generate electricity through an electrochemical reaction. At the same time, it uses the exhaust gas discharged from the fuel cell 124 to drive a gas turbine 104 to obtain electricity, and also uses the steam generated by recovering the exhaust heat from the gas turbine 104 to drive a steam turbine 107 to obtain electricity. The coal gasification fuel cell combined cycle power generation equipment 120 is a well-known mechanism, so a detailed explanation will be omitted, but the general configuration (especially the configuration related to the present invention) is as follows. Furthermore, for the coal gasification fuel cell combined cycle power generation equipment 120, the same reference numerals are used for components equivalent to those of the coal gasification combined cycle power generation equipment 100 described above, and their explanations will be omitted as appropriate.

[0039] The shift reaction unit 121 reacts carbon monoxide contained in the fuel gas, which is produced after the coal gasification gas manufactured in the coal gasification unit 101 has been purified by the gas purification unit 102, with water (specifically, for example, water vapor) to produce hydrogen and carbon dioxide. Specifically, the shift reaction unit 121 uses a water-gas shift reaction (see reaction equation 1 below) to react carbon monoxide (CO) with water (H2O) to produce hydrogen (H2) and carbon dioxide (CO2). CO + H2O → H2 + CO2(1)

[0040] The gas produced by the water-gas shift reaction in the shift reaction equipment 121 (CO2, H2; referred to as "shift gas") is sent to the separation equipment 122.

[0041] The separation unit 122 separates hydrogen (H2) from the shift gas (CO2, H2) supplied from the shift reaction unit 121 and supplies it to the fuel cell 124. The gas remaining after hydrogen has been separated from the shift gas is carbon dioxide (CO2) gas.

[0042] The compressor 123 compresses air and supplies it to the fuel cell 124.

[0043] The fuel cell 124 receives hydrogen from the separation equipment 122 and compressed air from the compressor 123. Hydrogen, as fuel, is sent to the anode electrode of the fuel cell 124, and compressed air, as an oxidizer, is sent to the cathode electrode of the fuel cell 124, where electricity is generated by an electrochemical reaction.

[0044] The anode gas and cathode gas produced after the reaction in the fuel cell 124 are combusted in the fuel cell downstream combustor 125 to produce high-temperature, high-pressure gas (i.e., combustion gas) which is then supplied to the gas turbine 104.

[0045] The gas turbine 104 rotates the turbine by expanding the high-temperature, high-pressure combustion gas supplied from the fuel cell downstream combustor 125, thereby driving the generator 105.

[0046] (Resource-recycling power generation facility) The power generation method according to an embodiment of the present invention comprises a power generation step of generating electricity by burning fuel in the combustion chamber 21 of a power generation boiler 2, and a resource recycling step of generating (in other words, recycling) raw materials for fuel from combustion ash generated during combustion.

[0047] (Power generation process) The power generation process is carried out at the power plant, but the technology used there is based on technologies developed for coal-fired power generation (specifically, burning powdered inorganic solid fuel instead of pulverized coal). Therefore, explanations of aspects that are the same as conventional technologies may be omitted.

[0048] Figure 3 is a diagram illustrating the schematic configuration of a power plant 10 for performing a power generation process according to an embodiment of the present invention.

[0049] The power generation method according to the embodiment of the present invention involves burning an inorganic solid fuel and coal gasification gas as a combustion-supporting gas in the combustion chamber 21 of a power generation boiler 2, and in particular, the combustion-supporting gas is coal gasification gas produced in the coal gasification equipment 101 of a coal gasification power generation facility.

[0050] As shown in Figure 3, the power plant 10 comprises a generator 1, a power boiler 2 that drives the generator 1, a fuel storage facility 3 for storing fuel supplied to the power boiler 2, an auxiliary fuel storage facility 4 for storing auxiliary fuel supplied to the power boiler 2, a denitrification device 5 that neutralizes (in other words, removes) nitrogen oxides (NOx) contained in the exhaust gas discharged from the power 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 facility 7 for storing the combustion ash.

[0051] The power generation boiler 2 comprises a combustion chamber 21, a steam turbine 22 whose rotating shaft is connected to the generator 1 and which is driven by the steam produced in the combustion chamber 21, and piping 23 that supplies the steam to the steam turbine 22 and also supplies the water, which has been returned to a liquid state in the condenser 9, back to the combustion chamber 21.

[0052] Furthermore, the water supply pump 24 is installed in the middle of the piping 23 connecting the condenser 9 and the combustion chamber 21, and is configured to send the water that has been returned to a liquid state in the condenser 9 to the combustion chamber 21.

[0053] The combustion chamber 21 includes a powder combustion burner 31 for burning powdered fuel supplied from the fuel storage 3, and an auxiliary combustion burner 41 for burning liquid fuel (e.g., heavy oil, light oil, etc.) supplied from the auxiliary fuel storage 4.

[0054] In this invention, the combustion of powdered fuel in the combustion chamber 21 is preferably carried out in an oxygen-free environment (in other words, in an oxygen-free atmosphere). Even if oxygen is present in the atmosphere of the combustion chamber 21, it is preferable that the oxygen concentration be adjusted to a level low enough to allow for the formation of carbon (C) as a combustion product. That is, it is preferable that the oxygen concentration be adjusted to a level low enough that the reaction between magnesium and oxygen does not become dominant (in other words, is not preferred) over the reaction between magnesium and the combustion-supporting gas (e.g., carbon monoxide, carbon dioxide) in this invention.

[0055] The powder combustion burner 31 can be, for example, the same as the pulverized coal burner used in coal-fired power plants, and the supply system for supplying powdered fuel and combustion-supporting gases to the powder combustion burner 31 can also be the same as that used in coal-fired power plants.

[0056] The auxiliary combustion burner 41 is a burner that provides auxiliary heat until the temperature inside the combustion chamber 21 rises and the combustion of the powder combustion burner 31 stabilizes, and it can be the same as the one used in coal-fired power plants.

[0057] Furthermore, once the combustion of the powder combustion burner 31 stabilizes, auxiliary heating from the auxiliary combustion burner 41 is no longer necessary. And since the thermal power plant will basically operate without being shut down, the amount of carbon dioxide generated by the auxiliary heating used only at the start of operation is negligible.

[0058] In the fuel storage facility 3, magnesium (Mg) is stored as an inorganic solid fuel in the present invention, which is a powdered fuel that does not emit carbon dioxide when burned. The magnesium stored in the fuel storage facility 3 may be magnesium hydride (MgH2) having at least a hydrogenated layer on its surface, or it may be a mixture of magnesium and magnesium hydride.

[0059] Magnesium as an inorganic solid fuel (including magnesium hydride; the same applies hereinafter) is preferably adjusted to a particle size of 150 μm or less. However, since magnesium is not perfectly spherical, the particle size of 150 μm or less referred to here is, for example, a particle size that can pass through a sieve with a mesh opening of about 0.16 mm.

[0060] Here, the pulverized coal used in pulverized coal burners used in coal-fired power plants is generally 150 μm or smaller, and by reducing the magnesium particle size to 150 μm or smaller, it is possible to use a burner with a similar structure to a pulverized coal burner as a powder combustion burner 31, which is an advantage.

[0061] In the powder combustion burner 31, magnesium mixed with a combustion-supporting gas burns.

[0062] As the combustion-supporting gas supplied to the powder combustion burner 31, carbon monoxide or carbon dioxide produced in the system of the above-mentioned coal gasification combined cycle power generation facility 100 may be supplied, or carbon monoxide or carbon dioxide produced in the system of the above-mentioned coal gasification fuel cell combined cycle power generation facility 120 may be supplied.

[0063] a) The combustion reaction (including heat generation; the same applies hereinafter) between magnesium (Mg) and carbon monoxide (CO) from the coal gasification gas (CO, H2) emitted from the coal gasification equipment 101 of the coal gasification combined cycle power plant 100 and the coal gasification fuel cell combined cycle power plant 120, and from the fuel gas (CO, H2) emitted from the gas purification equipment 102, is as shown in reaction equation 2 below. The combustion reaction between magnesium hydride (MgH2) and carbon monoxide is as shown in reaction equation 3 below. Note that the 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)

[0064] (i) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) from the combustion gas (CO2, H2O) emitted from the combustor 103 of the coal gasification combined cycle power plant 100 is as shown in reaction equation 4 below. Furthermore, the combustion reaction between magnesium hydride (MgH2) and carbon dioxide is as shown in reaction equation 5 below. In addition, the combustion reaction between magnesium and water (H2O) is as shown in reaction equation 6 below. Furthermore, the combustion reaction between magnesium hydride (MgH2) and water is as shown in reaction equation 7 below. 2Mg + CO2 → 2MgO + C (4) 2MgH2+ CO2→ 2MgO + 2H2+ C (5) Mg + H2O → MgO + H2(6) MgH2 + H2O → MgO + 2H2(7)

[0065] (c) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) gas (i.e., dry gas) emitted from the recovery device 109 of the coal gasification combined cycle power plant 100 is as shown in reaction equation 8 below. The combustion reaction between magnesium hydride (MgH2) and carbon dioxide is as shown in reaction equation 9 below. 2Mg + CO2 → 2MgO + C (8) 2MgH2+ CO2→ 2MgO + 2H2+ C (9)

[0066] E) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) from the shift gas (CO2, H2) emitted from the shift reaction equipment 121 of the coal gasification fuel cell combined cycle power generation facility 120 is as shown in reaction equation 10 below. Furthermore, the combustion reaction between magnesium hydride (MgH2) and carbon dioxide is as shown in reaction equation 11 below. 2Mg + CO2 → 2MgO + C (10) 2MgH2+ CO2→ 2MgO + 2H2+ C (11)

[0067] (o) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) after hydrogen (H2) has been separated from the shift gas (CO2, H2) in the separation process at the separation equipment 122 of the coal gasification fuel cell combined cycle power generation facility 120 is as shown in reaction equation 12 below. Furthermore, the combustion reaction between magnesium hydride (MgH2) and carbon dioxide is as shown in reaction equation 13 below. 2Mg + CO2 → 2MgO + C (12) 2MgH2+ CO2→ 2MgO + 2H2+ C (13)

[0068] As described above, the combustion reaction in the powder combustion burner 31 produces magnesium oxide (MgO) and carbon (C), and no carbon dioxide (CO2) is produced during combustion for power generation. However, if, for example, the combustion-supporting gas supplied to the powder combustion burner 31 contains moisture, some of the water will react with the magnesium oxide, and magnesium hydroxide (Mg(OH)2) may be present in the combustion ash.

[0069] Here, the combustion reaction between magnesium and the combustion-supporting gas is a pressure-reducing reaction in which a solid is produced by the reaction of 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 inside the combustion chamber 21 may decrease. Therefore, in order to maintain the pressure inside the combustion chamber 21 at a predetermined pressure (for example, around 1 atmosphere, or within the range of acceptable pressure inside the combustion chamber 21), the amount of combustion-supporting gas supplied to the combustion chamber 21 may be adjusted. In this case, for example, a pressure adjustment system may be provided separately from the supply system and combustion system related to the powder combustion burner 31, in which gas that is discharged outside the combustion chamber 21 without contributing to the reaction inside the combustion chamber 21 is treated as dust and then reintroduced into the combustion chamber 21.

[0070] To address the generation of nitrogen oxides (NOx) during combustion in the combustion chamber 21, a denitrification device 5 is installed in the exhaust pipe 8 that sends the exhaust gas discharged from the combustion chamber 21 to the dust collector 6, in order to neutralize (in other words, remove) the nitrogen oxides in the exhaust gas discharged from the combustion chamber 21.

[0071] The denitrification unit 5 can be similar to those used in coal-fired power plants, having 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.

[0072] Although the exhaust gas after passing through the denitrification device 5 does not contain harmful gases, it does contain extremely small particles of combustion ash (specifically, powdered magnesium oxide, magnesium hydroxide, and carbon) generated during combustion. For this reason, the exhaust pipe 8 is connected to a dust collector 6, and the exhaust gas is released into the atmosphere after the combustion ash is collected in the dust collector 6.

[0073] The dust collector 6 can be the same type of dust collector used in coal-fired power plants; specifically, it can be an electrostatic precipitator, for example.

[0074] In the example shown in Figure 3, an exhaust fan 81 is provided downstream of the dust collector 6, thereby releasing the exhaust gas from the combustion chamber 21 into the atmosphere via the denitrification device 5 and the dust collector 6.

[0075] On the other hand, in coal-fired power generation, since coal is used as fuel, sulfur components contained in coal are included in the exhaust gas. For this reason, coal-fired power generation is further equipped with a desulfurization device before releasing the exhaust gas into the atmosphere. In contrast, the present invention has the advantage that a desulfurization device is unnecessary because magnesium does not contain sulfur components.

[0076] In addition, coal-fired power plants produce exhaust gas containing carbon dioxide, which requires the exhaust gas to be released into the atmosphere through a tall chimney. In contrast, the present invention eliminates the need for such a tall chimney.

[0077] The combustion ash that accumulates 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 unit 7 and, for resource recycling purposes, are repeatedly recycled into magnesium through the resource recycling process described below. The recycled magnesium is used as an inorganic solid fuel supplied to the powder combustion burner 31.

[0078] Furthermore, in coal-fired power plants, dust collectors are used because unburned coal accumulates at the bottom of the combustion chamber and is also contained in the exhaust gas. Therefore, the mechanism for recovering magnesium combustion ash can be the same as the one used in coal-fired power plants.

[0079] As can be seen from the above explanation, by using magnesium with a particle size of 150 μm or less as fuel, it is possible to implement a power generation process that reduces carbon dioxide emissions, which is extremely compatible with the coal-fired power generation technology that has been cultivated so far, which involves burning pulverized coal in pulverized coal burners to generate electricity.

[0080] (Resource recycling process) Next, we will describe a resource recovery process that uses magnesium oxide (specifically, magnesium oxide) contained in the combustion ash, a combustion product generated in the power generation process, as a starting material to produce magnesium again.

[0081] Furthermore, since the magnesium hydroxide (Mg(OH)2) contained in the combustion ash undergoes a dehydration reaction upon heating, as shown in reaction equation 14 below, to become magnesium oxide (MgO), it is reasonable to consider magnesium oxide as the starting material for the resource recovery process. Mg(OH)2 → MgO + H2O (14)

[0082] The procedure for producing magnesium from magnesium oxide, the starting material, is divided into two steps: a chlorination step in which magnesium chloride is produced using magnesium oxide (combustion ash) as the material, and a molten salt electrolysis step in which magnesium is produced using the magnesium chloride generated in the chlorination step as the material.

[0083] (Chlorination process) The chlorination process uses magnesium oxide, which is combustion ash, as a material to produce magnesium chloride, which is used in the subsequent molten salt electrolysis process.

[0084] In the chlorination process, first, powdered magnesium oxide (MgO) and carbon (C), which are combustion ash, are added to hydrogen chloride (HCl) water. The magnesium oxide undergoes the reaction shown in reaction equation 15 below in the hydrogen chloride water to become magnesium chloride (MgCl2). Since the magnesium chloride produced by this reaction is a substance with high solubility in water, it will dissolve if there is a sufficient amount of water in the hydrogen chloride water. MgO + 2HCl → MgCl2+ H2O (15)

[0085] On the other hand, carbon does not react and does not dissolve, so it remains in the hydrogen chloride water as a powder. Therefore, the carbon in the combustion ash can be recovered by filtering the hydrogen chloride water in which magnesium chloride is dissolved.

[0086] The carbon recovered by the above method is of high purity and is useful as an industrial material, and is especially useful in fields where high-purity carbon materials are required.

[0087] Anhydrous magnesium chloride is recovered from the hydrogen chloride solution after carbon filtration. One method for recovering anhydrous magnesium chloride from hydrogen chloride solution is to heat the solution while blowing hydrogen chloride gas through it. This method is a well-known procedure, so a detailed explanation will be omitted.

[0088] As a method for recovering anhydrous magnesium chloride from hydrogen chloride solution, one may heat hydrogen chloride solution (in which case magnesium chloride is dissolved in hexahydrate form) in a nitrogen atmosphere to remove water and obtain anhydrous magnesium chloride, or remove hydrogen chloride to obtain magnesium oxide and then further process the magnesium oxide.

[0089] In the above case, magnesium oxide may be converted to magnesium chloride by carrying out the reaction shown in reaction equation 16 below with magnesium oxide and hydrogen chloride gas at a temperature of approximately 300 to 600°C. MgO + 2HCl → MgCl2+ H2O (16)

[0090] In the above case, magnesium oxide may be converted to magnesium chloride by reacting magnesium oxide with ammonium chloride (NH4Cl) at a temperature of approximately 300-600°C according to the reaction shown in reaction equation 17 below. MgO + 2NH4Cl → MgCl2+ H2O + 2NH3(17)

[0091] In the above case, for magnesium oxide, the reaction shown in reaction equation 18 below may be carried out with magnesium oxide and ammonium chloride in a molar ratio of 1:3 at a temperature of about 400°C to produce ammonium carnalit hydrate. Then, the ammonium carnalit hydrate may be heated under a flow of ammonia gas 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 carry out the dehydration reaction shown in reaction equation 19 below to remove water. Furthermore, the ammonium chloride portion may be removed by heating under a flow of dry nitrogen to a temperature higher than the sublimation temperature of ammonium chloride (for example, around 400°C) to carry out the reaction shown in reaction equation 20 below to obtain anhydrous magnesium chloride. MgO+3NH4Cl→MgCl2·NH4Cl·H2O+2NH3(18) MgCl2·NH4Cl·H2O→MgCl2·NH4Cl+H2O (19) MgCl2·NH4Cl→MgCl2+NH3+HCl (20)

[0092] (Molten salt electrolysis process) The molten salt electrolysis process is a method used in magnesium production, in which anhydrous magnesium chloride produced in the chlorination process is used as the raw material to produce magnesium through electrolysis.

[0093] The general outline of the molten salt electrolysis process is as follows: for example, magnesium chloride is heated to a temperature of around 700°C in a brick furnace and melted.

[0094] At least one pair of electrodes are provided inside the brick furnace. When a power supply is connected between these electrodes and a voltage of 2.5V or higher is applied, chlorine (Cl2) gas is generated at the anode and magnesium is produced at the cathode.

[0095] Since hydrogen chloride gas is produced by reacting hydrogen gas and chlorine gas, hydrogen chloride gas may be generated using chlorine gas produced in the molten salt electrolysis process as a material and then used in the chlorination process.

[0096] (Atomization process) The atomization process is a process of converting the magnesium produced in the molten salt electrolysis process into a powder, and may be carried out using a general-purpose pulverizer, or it may be carried out using a fine powder production device called a gas atomizer.

[0097] When a pulverization process is carried out using a pulverizing device, it is preferable to divide the pulverization process into two stages to consider pulverization efficiency.

[0098] Specifically, the pulverization process is preferably carried out in two stages: a coarse pulverization stage in which the magnesium is coarsely pulverized to a particle size of about 180 to 800 μm using a device with a high pulverization speed, although it does not reach the level of pulverization; and a fine pulverization stage in which the magnesium pulverized in the coarse pulverization stage is pulverized to a particle size of 150 μm or less.

[0099] In the pulverization process, particle size does not necessarily mean a perfectly spherical shape. In the coarse grinding process, for example, the particle size is such that it can pass through a sieve with a mesh opening of approximately 0.8 mm.

[0100] When grinding magnesium coarsely, the fact that magnesium is a soft metal does not cause any problems. However, when grinding it finely, a problem can arise where the magnesium particles stick together during the grinding process, making it difficult to obtain a fine powder. For this reason, it is preferable to add a grinding aid to the coarsely ground magnesium in the fine grinding process.

[0101] For example, stearic acid can be used as a grinding aid, but it is preferable to use an inorganic compound powder. Specifically, for example, by using magnesium oxide, which is an inorganic compound powder, as a grinding aid, it becomes possible to reuse a portion of the combustion ash as a grinding aid because it has the same composition as the combustion ash.

[0102] (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 that has been atomized in the atomization process may be hydrogenated (this process is referred to as the "hydrogenation process").

[0103] Here, if magnesium comes into contact with oxygen after micronization, an oxide film forms on its surface, significantly reducing the reaction efficiency. Therefore, the magnesium pulverized in the micronization process is handled in a way that prevents it from coming into contact with oxygen until the hydrogenation process is completed.

[0104] Referring to Figure 4, which illustrates the equipment configuration for carrying out the hydrogenation process, we will now explain a method for performing the hydrogenation process without exposure to the outside air.

[0105] As shown in Figure 4, the apparatus 300 for carrying out the hydrogenation process includes a heating vessel 310 that contains atomized magnesium and reacts it with hydrogen, a heater 320 that heats the heating vessel 310, and piping 315 that is detachably connected to the inlet 311 of the heating vessel 310.

[0106] The heating container 310 is equipped with a valve 314 in the conduit section 313 leading from the inlet 311 to the heating section 312, and when the valve 314 is closed, it becomes a sealed structure.

[0107] Although not shown in the diagram, piping 315 is connected to the hydrogen gas supply system, the argon gas supply system, and the vacuum pump.

[0108] The heating container 310 also serves as a recovery container for recovering the magnesium that has been pulverized in the fine grinding process.

[0109] As described above, the fine grinding process is carried out in an argon gas atmosphere, and the valve 314 is closed and the heating container 310 is removed from the grinding apparatus performing the fine grinding process. The magnesium recovered in the heating container 310 is then connected to the apparatus 300 shown in Figure 4 in an argon-filled state.

[0110] Then, before valve 314 is opened, a vacuum is performed, and after the air in the piping 315 and upstream of valve 314 is exhausted, valve 314 is opened, and the argon gas in the heating section 312 is exhausted.

[0111] Subsequently, 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 container 310 to perform the hydrogenation treatment (see reaction equation 21 below). Mg + H2 → MgH2(21)

[0112] Here, magnesium hydride with a hydrogenation rate of about 20% by mass has roughly the same calorific value per unit weight as coal, so low-purity magnesium hydride is sufficient as a fuel to replace coal (in other words, as a substitute for coal). Also, when magnesium is in the form of a fine powder, it becomes more flammable and is generally treated as a hazardous material under the Fire Service Act. On the other hand, magnesium hydride has reduced flammability due to hydrogenation, and even in fine powder form, it does not fall under the category of a hazardous material under the Fire Service Act. Therefore, the hydrogenation of magnesium only needs to be achieved at a hydrogenation rate that does not classify it as a hazardous material in terms of transportation and storage.

[0113] Furthermore, the hydrogenation of magnesium does not proceed in proportion to the processing time; rather, the rate of hydrogenation slows down significantly as the purity increases. Therefore, if low-purity magnesium hydride with a hydrogenation rate of 30% by mass or less (for example, around 20% by mass), where at least the surface is hydrogenated, is used, the time required for the hydrogenation process can be significantly reduced, and productivity can be greatly increased.

[0114] After the hydrogenation treatment, the heater 320 is stopped, and after cooling, the hydrogen gas in the heating container 310 is replaced with argon gas, and low-purity magnesium hydride is extracted. The low-purity magnesium hydride produced in this way, with a hydrogenation rate of 30% by mass or less (for example, about 20% by mass) and at least the surface side being hydrogenated, is again used as fuel in the power generation process.

[0115] Furthermore, in the present invention, magnesium hydride with a high hydrogenation rate may be used as the inorganic solid fuel, or a mixture of magnesium and magnesium hydride may be used.

[0116] (Effects and Benefits) According to the power generation method and power plant 10 of this embodiment, inorganic solid fuel (specifically, magnesium and magnesium hydride) and coal gasification gas as a combustion-supporting gas are burned in the combustion chamber 21 of the power generation boiler 2. As a result, carbon dioxide is not generated during power generation, and it is possible to realize a resource-recycling type of thermal power generation in which magnesium resources are recycled. Furthermore, according to the power generation method and power plant 10 of this embodiment, by using carbon dioxide emitted from coal gasification power generation equipment (specifically, coal gasification combined cycle power generation equipment and coal gasification fuel cell combined cycle power generation equipment) as a combustion-supporting gas for power generation, it is possible to significantly reduce the environmental burden of coal-fired power generation.

[0117] According to the power generation method and power plant 10 of this embodiment, it is also possible to use mechanisms similar to those used in coal-fired power generation, thus enabling the use of technologies cultivated in coal-fired power generation to reduce carbon dioxide emissions.

[0118] According to the power generation method and power plant 10 of the embodiment, the resource recycling process is composed solely of equipment powered by electricity, making it possible to regenerate fuel using only surplus electricity that cannot be connected to the 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. On the other hand, the power generation method and power plant 10 of the embodiment can be said to be a power generation method with inertia that can balance supply and demand in accordance with the demand and supply of electricity. In other words, by carrying out the resource recycling process using electricity without inertia, such as renewable energy sources, it can also be said that this is a power generation method that can convert that electricity without inertia into electricity with inertia.

[0119] Although embodiments of the present invention have been described above, the specific configurations of the present invention are not limited to the embodiments described above. The present invention also includes forms in which modifications and changes are made to the above embodiments without departing from the spirit of the invention.

[0120] For example, in the above embodiment, the power plant 10 was described as being installed alongside a coal gasification power generation facility (specifically, a coal gasification combined cycle power generation facility 100, a coal gasification fuel cell combined cycle power generation facility 120). However, 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, for example, be installed alongside a coal gasification gas storage facility.

[0121] Furthermore, although the above embodiment described an example of a power generation boiler using a powder combustion burner 31, there are also coal-fired power plants called stoker boilers, which do not use pulverized coal burners and have a combustion chamber that is simply a combustion furnace, with coal being supplied to keep combustion going at all times. The fuel described above may be used in such a configuration. In this case, atomization, which was necessary to sustain combustion as a burner flame, is not required, and it is only necessary to supply fuel to maintain the heat output, so relatively large-sized fuel is acceptable. Moreover, even magnesium does not fall under the category of hazardous materials under the Fire Service Act if its particle size is around 500 μm, so a power generation method using magnesium as fuel may be used, where only appropriate coarse grinding is performed to keep the magnesium size at 500 μm or more, and the hydrogenation process is not carried out. In other words, when supplying magnesium with a particle size of around 500 μm to a stoker boiler and implementing the power generation method according to the present invention, the resource recycling process may be limited to coarse grinding, and the fine grinding process and hydrogenation process may be omitted.

[0122] Furthermore, in the above embodiment, magnesium is supplied as the inorganic solid fuel to the powder combustion burner 31. However, in the present invention, the inorganic solid fuel supplied to the powder combustion burner 31 is not limited to magnesium, but may be lithium (Li), boron (B), or aluminum (Al). In addition, multiple substances may be supplied to the powder combustion burner 31 as the inorganic solid fuel. In this embodiment, lithium is converted to chloride by a chlorination process, similar to magnesium in the above embodiment, and then reduced by electrolysis in a molten salt field process. Aluminum is not converted to chloride by a chlorination process, but is reduced by electrolysis in a molten salt field process.

[0123] Furthermore, in the above embodiment, the combustion-supporting gas supplied to the powder combustion burner 31 is coal gasification gas generated in the system of a coal gasification power generation facility (specifically, a coal gasification combined cycle power generation facility 100, a coal gasification fuel cell combined cycle power generation facility 120) (including gas that has been subjected to a predetermined treatment from the coal gasification gas produced in the coal gasification facility 101, and which contains carbon monoxide and carbon dioxide as components). However, in the present invention, the combustion-supporting gas supplied to the powder combustion burner 31 is not limited to coal gasification gas generated in the system of a coal gasification power generation facility, but may be coal gasification gas generated in other systems or stored independently.

[0124] Furthermore, in the above embodiment, magnesium oxide (specifically, magnesium oxide), which is a combustion product from combustion in the combustion chamber 21, is reduced by electrolysis. However, the method of reduction in the present invention is not limited to electrolysis, and the reduction may be carried out by other methods. [Explanation of symbols]

[0125] 10 Power Plants 1 Generator 2. Power generation boiler 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. Combustion Ash Storage Facility 8 Exhaust pipes 81 Ventilation device 9. Condenser 100 Coal gasification combined cycle power generation facility 101 Coal gasification equipment 102 Gas purification equipment 103 Combustor 104 Gas Turbine 105 Generator 106 Waste heat recovery boiler 107 Steam Turbine 108 Generators 109 Recovery device 110 Compressor 120 Coal gasification fuel cell combined cycle power generation facility 121 Shift Reaction Equipment 122 Separation equipment 123 Compressor 124 Fuel Cell 125 Fuel cell downstream combustor 300 Equipment 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 the combustion chamber of a power generation boiler, an inorganic solid fuel and a combustion-supporting gas are burned. The combustion-supporting gas includes at least one of the following: coal gasification gas, fuel gas obtained by purifying coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility in a gas purification facility, shift gas obtained by a water-gas shift reaction of the fuel gas, and carbon dioxide gas after hydrogen has been separated from the shift gas. The oxides, which are combustion products of the inorganic solid fuel, are subjected to reduction treatment and repeatedly used as the inorganic solid fuel. The reduction treatment of the oxide includes reacting the oxide with hydrogen chloride gas to obtain a chloride, and electrolyzing the chloride. The inorganic solid fuel is at least one of lithium, magnesium, and boron, which is at least partially hydrogenated. The hydrogenation rate of the lithium, magnesium, and boron that have been partially hydrogenated is 30% by mass or less of the total amount of the lithium, magnesium, and boron that have been partially hydrogenated. Method of generating electricity.

2. The inorganic solid fuel is at least one of lithium and magnesium, which are at least partially hydrogenated. The oxides, which are combustion products of the inorganic solid fuel, are subjected to reduction and hydrogenation treatments, and are repeatedly used as the inorganic solid fuel. The power generation method according to claim 1.

3. The aforementioned combustion-supporting gas is coal gasified gas produced in the coal gasification equipment of a coal gasification power generation facility. The power generation method according to claim 1.

4. The aforementioned combustion-supporting gas is a fuel gas obtained by refining coal gasified gas produced in the coal gasification equipment of a coal gasification power generation facility in a gas purification facility. The power generation method according to claim 1.

5. The aforementioned combustion-supporting gas is the exhaust gas produced when coal gasification gas, manufactured in the coal gasification equipment of a coal gasification power generation facility, is purified in a gas purification facility to become fuel gas, and then the fuel gas is burned in a combustor and discharged. The power generation method according to claim 1.

6. The aforementioned combustion-supporting gas is the dry gas obtained after removing moisture from the exhaust gas discharged when coal gasification gas produced in the coal gasification equipment of a coal gasification power generation facility is purified in a gas purification facility to become fuel gas, and the fuel gas is burned in a combustor. The power generation method according to claim 1.

7. The aforementioned combustion-supporting gas is a shift gas obtained by purifying coal gasified gas produced in the coal gasification equipment of a coal gasification power generation facility in a gas purification facility to obtain fuel gas, and then subjecting the fuel gas to a water-gas shift reaction. The power generation method according to claim 1.

8. The aforementioned combustion-supporting gas is carbon dioxide gas obtained by purifying coal gasified gas produced in the coal gasification equipment of a coal gasification power generation facility into fuel gas in a gas purification facility, and then separating hydrogen from the shift gas obtained by a water-gas shift reaction of the fuel gas. The power generation method according to claim 1.

9. In order to maintain the pressure inside the combustion chamber at a predetermined pressure, the amount of the combustion-supporting gas supplied to the combustion chamber is adjusted. The power generation method according to claim 1.

10. In the combustion chamber of a power generation boiler, an inorganic solid fuel and a combustion-supporting gas are burned. In order to maintain the pressure inside the combustion chamber at a predetermined pressure, the amount of the combustion-supporting gas supplied to the combustion chamber is adjusted. The combustion-supporting gas includes at least one of the following: coal gasification gas, fuel gas obtained by purifying coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility in a gas purification facility, shift gas obtained by a water-gas shift reaction of the fuel gas, and carbon dioxide gas after hydrogen has been separated from the shift gas. The oxides, which are combustion products of the inorganic solid fuel, are subjected to reduction treatment and repeatedly used as the inorganic solid fuel. The reduction treatment of the oxide includes reacting the oxide with hydrogen chloride gas to obtain a chloride, and electrolyzing the chloride. The inorganic solid fuel is at least one of lithium, magnesium, and boron, which is at least partially hydrogenated. The hydrogenation rate of the aforementioned lithium, magnesium, and boron, which are at least partially hydrogenated, is 30% by mass or less of the total amount of the aforementioned lithium, magnesium, and boron, which are at least partially hydrogenated. Power generation equipment.

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