WO2025159189A1 - Power generation method, method for operating boiler device, boiler device, and power generation system - Google Patents

Abstract

Provided are a power generation method and a power generation facility, in which emission of carbon dioxide is suppressed by using technology accumulated through coal-fired power generation. This power generation method involves combusting inorganic solid fuel and coal gasification gas as a combustion supporting gas in a combustion chamber (21) of a boiler device (2).

Description

Power generation method, boiler device operation method, boiler device, and power generation system

This disclosure relates to a power generation method, a boiler device operating method, a boiler device, and a power generation system.

Coal-fired power generation systems equipped with power generation boilers are commonly known (see, for example, Non-Patent Document 1).

However, despite Japan possessing some of the world's leading coal-fired power generation technology, opportunities for utilizing this technology are being lost due to the issue of carbon dioxide emissions when coal is burned.

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.

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 injected and stored deep underground beneath the seabed, approximately 3-4 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.

However, there are many constraints to achieving this type of storage, such as the need for a geological layer with gaps large enough to store carbon dioxide, and for it to be covered by a layer that does not allow carbon dioxide to pass through.

“Promoting Regional Environmental Conservation: The Structure of Coal-Fired Power Plants and Various Environmental Conservation Measures,” [online], Okinawa Electric Power Company, Inc., [searched June 30, 2022], Internet <URL: https://www.okiden.co.jp/environment/report2017/sec6/sec63.html> “CCS: Capture and bury CO2: After Demonstration Tests, Realization is Near (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>

This disclosure has been made in light of these circumstances, and aims to provide a power generation method and power generation equipment that utilizes technology cultivated in coal-fired power generation and reduces carbon dioxide emissions.

In order to achieve the above object, the present disclosure is grasped by the following configuration.
(1) The power generation method disclosed herein includes burning an inorganic solid fuel and a coal gasification gas as a combustion supporting gas in a combustion chamber of a boiler apparatus.

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

(3) In the configuration of (2) above, the oxides that are combustion products of the inorganic solid fuel are reduced and repeatedly used as the inorganic solid fuel.

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

(5) In the configuration of (4) above, the oxides that are combustion products of the inorganic solid fuel are reduced and hydrogenated, and are repeatedly used as the inorganic solid fuel.

(6) In the configurations (1) to (5) above, the combustion supporting gas includes coal gasification gas produced in the coal gasification facility of the coal gasification power generation facility.

(7) In the configurations (1) to (5) above, the combustion supporting gas includes 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.

(8) In the configurations (1) to (5) above, the combustion supporting gas includes exhaust gas discharged from a coal gasification power generation facility, which is produced in a coal gasification facility, refined in a gas refinery facility to produce fuel gas, and then combusted in a combustor.

(9) In the configurations (1) to (5) above, the combustion supporting gas includes dry 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 to produce fuel gas, and then combusting the fuel gas in a combustor to discharge exhaust gas from which moisture has been separated.

(10) In the configurations (1) to (5) above, the combustion supporting gas includes a shift gas obtained by subjecting coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility to a water-gas shift reaction after the coal gasification gas is purified in a gas purification facility to produce a fuel gas.

(11) In the configurations (1) to (5) above, the combustion supporting gas comprises carbon dioxide gas obtained by subjecting coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility to a water-gas shift reaction to a water-gas shift gas obtained by purifying the coal gasification gas in a gas purification facility to produce a fuel gas, and separating hydrogen from the resulting shift gas.

(12) The method of operating a boiler apparatus disclosed herein involves combusting inorganic solid fuel and coal gasification gas as a combustion supporting gas in a combustion chamber of the boiler apparatus.

(13) The power generation equipment disclosed herein includes a combustion chamber for combusting inorganic solid fuel and coal gasification gas as a combustion supporting gas within the combustion chamber of a boiler device, and the amount of the combustion supporting gas supplied to the combustion chamber is adjusted to maintain the pressure within the combustion chamber at a predetermined pressure.

(14) The power generation system of the present disclosure includes the boiler apparatus described in (13) above and a power generation apparatus that generates power using steam generated by the boiler apparatus.

This disclosure makes it possible to provide a power generation method and power generation equipment that reduces carbon dioxide emissions by utilizing technology developed in coal-fired power generation.

1 is a system diagram for explaining a schematic configuration of an integrated coal gasification combined cycle power generation facility according to an embodiment. 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. 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. 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.

The following describes an embodiment of the present invention (hereinafter referred to as the present embodiment) with reference to the accompanying drawings.

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

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

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 by recovering exhaust heat from the gas turbine 104 to generate steam to drive a steam turbine 107. The integrated coal gasification combined cycle power generation facility 100 is a well-known system, so a detailed explanation will be omitted, but the general configuration (particularly the configuration relevant to this embodiment) is as follows:

The coal gasification facility 101 includes a coal gasifier, receives supply 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.

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 gasification furnace 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.

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 impurities, sulfur, etc.

The gas purification equipment 102 includes, for example, a dust filter that removes solid impurities from the coal gasification gas, a halide removal device equipped with a halide absorbent that chemically reacts with the halides contained in the coal gasification gas, and a desulfurization device equipped with a metal oxide desulfurization agent that chemically reacts with the 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.

The combustor 103 burns fuel gas (CO, _H2 ) supplied from the gas purification facility 102 to produce high-temperature, high-pressure gas (referred to as "combustion gas"), which is supplied 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 ).

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.

The heat recovery boiler 106 recovers heat from the exhaust gas discharged from the gas turbine 104 to generate steam. The exhaust gas whose heat has been recovered by the heat recovery boiler 106 is sent to the compressor 110.

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

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, thereby recovering 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."

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.

(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 the embodiment.

The coal gasification fuel cell integrated power generation system 120 uses coal gasification gas produced in the coal gasification system 101 as the anode (fuel) supplied to the anode (fuel electrode; not shown) of the 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, the system generates electricity by driving a gas turbine 104 with exhaust gas discharged from the fuel cell 124, and also generates electricity by driving a steam turbine 107 with steam generated by recovering exhaust heat from the gas turbine 104. The coal gasification fuel cell integrated power generation system 120 is a well-known system, so a detailed description will be omitted, but its general configuration (particularly the configuration relevant 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 where appropriate.

The shift reaction equipment 121 produces 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 refined by the gas refinement equipment 102. Specifically, the shift reaction equipment 121 produces hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) by reacting carbon monoxide (CO) and water (H ₂ O) using the water-gas shift reaction (see reaction formula 1 below).
CO + H ₂ O → H ₂ + CO ₂ (1)

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

The separation equipment 122 separates hydrogen (H 2 ) from the components of the shift gas (CO ₂ , H ₂ ) supplied from the shift reaction equipment 121 and supplies the hydrogen (H ₂ ) to the fuel cell 124. The gas remaining after hydrogen has been separated from the shift gas is carbon dioxide (CO ₂ ) gas.

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

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, generating electricity through an electrochemical reaction.

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

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

(Power generation system/power generation method)
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") according to this embodiment. The power generation system 10 includes a power generator 1 and a boiler unit 2 (hereinafter sometimes referred to as a "power generation boiler 2," and in this specification, "power generation boiler" can be replaced with "boiler unit") that includes a combustion chamber 21. In the power generation system 10, the power generator 1 generates electricity using steam generated by the boiler unit 2.

The power generation method of this embodiment includes a power generation process in which fuel is combusted in the combustion chamber 21 of the boiler apparatus 2 to generate power. The power generation method of this embodiment may further include a resource recycling process in which raw materials for fuel are produced (in other words, recycled) from combustion ash generated by burning fuel in the combustion chamber 21 in the power generation process.

(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.

The power generation method of this embodiment involves burning inorganic solid fuel and coal gasification gas as a combustion supporting gas in the combustion chamber 21 of the boiler device 2, and in particular, the combustion supporting gas is coal gasification gas produced in the coal gasification facility 101 of the coal gasification power generation facility. The power generation method of this embodiment generates steam through this combustion, and then uses this steam to rotate the turbine of a generator to generate electricity.

In the embodiment shown in FIG. 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 detoxifies (in other words, removes) nitrogen oxides (NOx) contained in the exhaust gas discharged from the power generation boiler 2, a dust collector 6 that collects 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.

(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.

In addition, a water supply pump 24 is installed midway along 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.

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 31 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.

The combustion chamber 21 may further be equipped with an auxiliary combustion burner 41 that burns liquid fuel (e.g., heavy oil, light oil, etc.) supplied from the auxiliary fuel storage tank 4.

The combustion of the inorganic solid fuel in the combustion chamber 21 is carried out in the presence of coal gasification 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. If the atmosphere in the combustion chamber 21 contains oxygen, 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 low enough 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 combustion supporting gases in this embodiment include carbon monoxide and carbon dioxide.

The powder combustion burner 31 may be similar to the pulverized coal burner used in coal-fired power generation, for example. The powder combustion burner 31 burns the inorganic solid fuel when supplied with inorganic solid fuel and combustion supporting gas. The supply system that supplies the powdered inorganic solid fuel and combustion supporting gas to the powder combustion burner 31 may also be similar to that used in coal-fired power generation.

The auxiliary combustion burner 41 is a burner that provides auxiliary heating power until the temperature inside the combustion chamber 21 rises and the combustion in the powder combustion burner 31 stabilizes, and can be similar to that used in coal-fired power plants.

Furthermore, once combustion in the powder combustion burner 31 has stabilized, auxiliary heating power from the auxiliary combustion burner 41 is no longer necessary. Furthermore, since thermal power plants generally operate without being shut down, the amount of carbon dioxide generated by the auxiliary heating power, which is only used at the start of operation, is virtually negligible.

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 is specifically at least one selected from the group consisting of lithium, magnesium, calcium, boron, 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.

The inorganic solid fuel is preferably at least one selected from the group consisting of magnesium (Mg) and 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 types.

At least partially hydrogenated lithium, magnesium, calcium, boron, and aluminum may have a hydrogenated surface layer, may consist of an unhydrogenated core and a hydrogenated surface layer, or may consist of only the hydrogenated portion.

The following explanation will be given using an example where the inorganic solid fuel is magnesium (including magnesium hydride; the same applies below). It is preferable that the magnesium used as the inorganic solid fuel be 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 will pass through a sieve with a specified mesh opening.

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

The combustion supporting gas supplied to the powder combustion burner 31 contains at least coal gasification gas, and may be a gas consisting of coal gasification gas, or a gas containing coal gasification gas and oxygen gas, or a gas consisting of coal gasification gas and oxygen gas. In this embodiment, the coal gasification gas may include fuel gas obtained by refining coal gasification gas in a gas purification system; dry gas obtained after moisture is separated from the exhaust gas discharged by purifying coal gasification gas in a gas purification system to produce fuel gas and combusting the fuel gas in a combustor; shifted gas obtained by purifying coal gasification gas in a gas purification system to produce fuel gas and subjecting the fuel gas to a water-gas shift reaction; and carbon dioxide gas obtained after hydrogen is separated from shifted gas obtained by purifying coal gasification gas in a gas purification system to produce fuel gas and subjecting the fuel gas to a water-gas shift reaction. The coal gasification gas may include carbon monoxide and carbon dioxide generated in the system of the above-mentioned integrated coal gasification combined cycle power plant 100, and may also include carbon monoxide and carbon dioxide generated in the system of the above-mentioned integrated coal gasification combined cycle power plant 120.

A) The combustion reaction (including the generation of heat; the same applies below) between magnesium (Mg) and carbon monoxide (CO) in the coal gasification gas (CO, _H2 ) discharged from the coal gasification equipment 101 of the integrated coal gasification combined cycle power plant 100 or the integrated coal gasification fuel cell combined cycle power plant 120 or the fuel gas (CO, _H2 ) discharged from the gas purification equipment 102 is shown in 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)
MgH ₂ + CO→ MgO + H ₂ + C (3)

a) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) in the combustion gas ( _CO2 , _H2O ) discharged from the combustor 103 of the integrated coal gasification combined cycle power generation facility ₁₀₀ is as shown in the following reaction formula (4). The combustion reaction between magnesium hydride ( _MgH2 ) and carbon dioxide is as shown in the following reaction formula (5). In addition, the combustion reaction between magnesium and moisture ( _H2O ) is as shown in the following reaction formula (6). The combustion reaction between magnesium hydride ( _MgH2 ) and moisture is as shown in the following reaction formula 7.
2Mg +CO ₂ → 2MgO+ C (4)
2MgH ₂ + CO ₂ → 2MgO+ 2H ₂ + C (5)
Mg + H ₂ O → MgO + H ₂ (6)
MgH ₂ + H ₂ O → MgO+ 2H ₂ (7)

C) The combustion reaction between magnesium (Mg) and carbon dioxide (CO ₂ ) 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 (MgH ₂ ) and carbon dioxide is as shown in the following reaction formula (9).
2Mg +CO ₂ → 2MgO+ C (8)
2MgH ₂ + CO ₂ → 2MgO+ 2H ₂ + C (9)

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 +CO ₂ → 2MgO+ C (10)
2MgH ₂ + CO ₂ → 2MgO+ 2H ₂ + C (11)

E) The combustion reaction between magnesium (Mg) and carbon dioxide (CO2) remaining after hydrogen (H2) has been 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 +CO ₂ → 2MgO+ C (12)
2MgH ₂ + CO ₂ → 2MgO+ 2H ₂ + C (13)

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.

The above explanation has been given using an example where the inorganic solid fuel is magnesium, but 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.

Ca + CO → CaO + C (22)
2Ca + CO ₂ → 2CaO+ C (23)
Ca + H ₂ O → CaO + H ₂ (24)
CaH ₂ + CO→ CaO + H ₂ + C (25)
2CaH ₂ + CO ₂ → 2CaO+ 2H ₂ + C (26)
CaH ₂ + H ₂ O → CaO+ 2H ₂ (27)

Here, the combustion reaction between inorganic solid fuels such as magnesium and 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, and 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 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, approximately 1 atmosphere, or approximately within the range of pressures acceptable for the pressure in the combustion chamber 21). In this case, the boiler apparatus 2 may be equipped with a pressure adjustment system for maintaining the pressure in the combustion chamber 21 at a predetermined pressure. The pressure adjustment system may include, for example, an inlet for introducing an inert gas or combustion supporting gas that does not contribute to the reaction in the combustion chamber 21 into the combustion chamber 21, and an outlet for discharging the introduced inert gas and unreacted combustion supporting gas outside the combustion chamber 21. The pressure adjustment system may further include a treatment unit for collecting and treating the discharged gas, and the treated gas may be re-introduced into the combustion chamber 21 from the inlet. The pressure regulation system may be provided separately from the supply system and combustion system associated with the powder combustion burner 31.

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

(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).

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 (NH ₃ ) to the exhaust gas and passing it through a catalyst layer.

Even after passing through the denitration device 5, the exhaust gas discharged from the combustion chamber 21 may contain extremely small particles of combustion ash (specifically, powdered magnesium oxide, magnesium hydroxide, and carbon) generated during combustion. For this reason, the combustion ash is collected by the dust collector 6 before the exhaust gas is released into the atmosphere.

The dust collector 6 may be similar to the 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 the combustion ash storage 7.

In the embodiment shown in Figure 3, an exhaust device 81 is provided downstream of the dust collector 6, allowing exhaust gas from the combustion chamber 21 to be released into the atmosphere via the denitration device 5 and dust collector 6.

On the other hand, in coal-fired power generation, coal is used as fuel, and the sulfur components contained in the coal are contained in the exhaust gas. For this reason, in coal-fired power generation, a desulfurization unit is also 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 in that a desulfurization unit is not required.

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

In addition, in coal-fired power plants, dust collectors are used because coal residue accumulates at the bottom of the combustion chamber and is also contained in the exhaust gas, and the mechanism for collecting the combustion ash of inorganic solid fuels can be similar to the mechanism used in coal-fired power plants.

(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 produced 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.

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 and it turns into magnesium oxide (MgO), as shown in the following reaction formula (14).
Mg(OH) ₂ → MgO+ H ₂ O (14)

Furthermore, when the combustion ash contains calcium hydroxide (Ca(OH) ₂ ), a dehydration reaction occurs by heating, as shown in the following reaction formula (28), to produce calcium oxide (CaO).
Ca(OH) ₂ → CaO+ H ₂ O (28)

The resource recycling process preferably produces 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 process may produce the inorganic solid fuel by directly reducing the inorganic oxide using a known method, or may produce an intermediate from the inorganic oxide and then reduce the intermediate to produce the inorganic solid fuel. Such intermediates include chlorides.

Therefore, the resource recycling process may include a chlorination process in which inorganic chlorides are produced using inorganic oxides contained in the combustion ash of the inorganic solid fuel as a material, and a molten salt electrolysis process in which inorganic solid fuel is produced using the inorganic chlorides produced in the chlorination process as a material. Alternatively, the resource recycling process may include a direct reduction process in which inorganic oxides contained in the combustion ash of the inorganic solid fuel are directly reduced to produce inorganic solid fuel.

For example, taking the procedure of producing magnesium from magnesium oxide as a starting material, the resource recycling 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.

Furthermore, taking the procedure for 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 it may include a direct reduction process in which calcium oxide in the combustion ash is directly reduced to produce calcium.

(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.

Methods for the chlorination process include, for example, 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 possible to efficiently chlorinate magnesium oxide while removing carbon from the combustion ash. In addition to the hydrogen chloride water method, the chlorination process may combine the hydrogen chloride gas method, chlorine gas method, and/or ammonium chloride method.

(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 → MgCl ₂ + H ₂ O (15)

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

In the above process, 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. One example of a stirring method is ultrasonic stirring.

The chlorination process using the hydrogen chloride water method may include a step of pretreating the inorganic oxides in the combustion ash prior to the above reaction. Because inorganic oxide particles in the combustion ash may be coated with carbon, performing such a pretreatment step tends to increase the efficiency of the above chlorination reaction. Furthermore, to further increase the efficiency of the chlorination reaction, the pretreatment step and the above chlorination step of chlorinating the inorganic oxides may be repeated as a set. The number of repetitions is not particularly limited, but may be, for example, 2 to 10 times. In this case, the chlorination process may not only be a chlorination process using the hydrogen chloride water method, but also a chlorination process using the hydrogen chloride gas method, the chlorine gas method, or the ammonium chloride method. When multiple chlorination processes are performed, it is preferable to first perform a chlorination process using the hydrogen chloride water method, and then perform a chlorination process 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 performed before each chlorination process.

Pretreatment processes include grinding inorganic oxides in the combustion ash and heating the inorganic oxides in the combustion ash.

The process of pulverizing the inorganic oxides in the combustion ash is a process in which the combustion ash is pulverized 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, enhancing the chlorination process.

For example, when using a ball mill, grinding 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. When using a bead mill, grinding 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.

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 oxide, the carbon coating the inorganic oxide particles can be converted into carbon dioxide gas and removed. Heating conditions may be, for example, 100 to 1000°C, preferably 200 to 900°C, and preferably 400 to 600°C, for example, 5 minutes to 40 hours, preferably 10 minutes to 30 hours, and more preferably 1 to 20 hours.

The pretreatment process may be a combination of a process of pulverizing the inorganic oxides in the combustion ash and a process of heating the inorganic oxides in the combustion ash; for example, it may be a process of pulverizing the inorganic oxides in the combustion ash and then further heating the inorganic oxides in the combustion ash.

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

In the chlorination process using the hydrogen chloride water method, anhydrous magnesium chloride is recovered from the hydrogen chloride water after filtering the carbon. One method for recovering anhydrous magnesium chloride from hydrogen chloride water is to heat the hydrogen chloride water while blowing hydrogen chloride gas through it. This method is well known, so a detailed explanation will be omitted.

Methods for recovering anhydrous magnesium chloride from hydrogen chloride water include heating the hydrogen chloride water in a nitrogen atmosphere to desorb water and obtain anhydrous magnesium chloride, or desorbing hydrogen chloride to obtain magnesium oxide, which can then be further processed.

(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 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 +2Cl ₂ → 2MgCl ₂ + O ₂ (16)

To increase the reaction efficiency, the chlorination step using the hydrogen chloride gas method, which will be described below, may be carried out after the chlorination step using the chlorine gas method.

(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 → MgCl ₂ + H ₂ O (29)

(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 (NH ₄ Cl) into a chlorination tower and heating them. In the above case, for magnesium oxide, the reaction between magnesium oxide and ammonium chloride (NH ₄ Cl) occurs as shown in the following reaction formula (17) to produce magnesium chloride. The reaction temperature may be 300 to 600°C.
MgO + 2NH ₄ Cl → MgCl ₂ + H ₂ O + 2NH ₃ (17)

The chlorination process using the ammonium chloride method may be, for example, a process in which inorganic oxides in the combustion ash and ammonium chloride (NH ₄ Cl) are reacted in an appropriate equivalent ratio to produce ammonium carbohydrate, and then the ammonium carbohydrate is heated in a stream 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 cause a dehydration reaction and remove moisture, and then further heated in a stream of dry nitrogen to a temperature higher than the sublimation temperature of ammonium chloride (for example, around 400°C) to remove the ammonium chloride portion 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 of the following reaction formula (18) is caused at a temperature of about 400°C 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 to cause the dehydration reaction of the following reaction formula (19) to remove moisture, and further heated in a state where dry nitrogen is blown over it to a temperature higher than the sublimation temperature of ammonium chloride to cause the reaction of the following reaction formula (20) to remove the ammonium chloride moiety and produce anhydrous magnesium chloride.
MgO+ _3NH4Cl → _MgCl2・_NH4Cl・_H2O + _2NH3 (18)
_MgCl2・_NH4Cl・_H2O → _MgCl2・_NH4Cl + _H2O (19)
MgCl ₂ .NH ₄ Cl → MgCl ₂ +NH ₃ +HCl (20)

(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, one method used for producing magnesium.

In the molten salt electrolysis process, for example, magnesium chloride is heated to a temperature of around 700°C in a molten salt electrolysis tank (e.g., a brick furnace) to melt the magnesium chloride.

At least one pair of electrodes is provided in the molten salt electrolytic cell, and when a power supply is connected between these electrodes and a voltage of 2.5 V or more is applied, chlorine (Cl ₂ ) gas is generated at the anode and magnesium is produced at the cathode.

The chlorine gas generated in the molten salt electrolysis process may be used in a chlorination process using a chlorine gas method. Furthermore, 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 process as a material and used in a chlorination process using the hydrogen chloride gas method, hydrogen chloride water method, or ammonium chloride method.

(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.

The direct reduction process can be carried out by referring to the molten salt electrolysis process, except that the starting material is an inorganic oxide.

Unlike the molten salt electrolysis process, which uses inorganic chlorides as a material, 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.

(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.

First, a system integrating a chlorination tank and a molten salt electrolytic tank 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 that supplies the inorganic chlorides produced in the chlorination process from the chlorination tank to the molten salt electrolytic tank, and a supply path that supplies the chlorine gas produced in the molten salt electrolytic process 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 perspective of shortening the storage time of chlorine gas, the chlorine gas storage chamber may be omitted from the chlorine gas supply path.

The chlorination tank may be operated in a batch or flow mode. When operating in a batch mode, the inorganic chloride is transferred from the chlorination tank to the molten salt electrolytic tank after detecting that the chlorination reaction in the chlorination tank has been completed. When operating in a flow mode, the inorganic chloride is transferred continuously from the chlorination tank to the molten salt electrolytic tank.

The following explains an example in which hydrogen chloride water is added to combustion ash containing magnesium oxide and carbon in a chlorination tank to produce magnesium chloride, and then chlorine and magnesium are produced from the magnesium chloride in a molten salt electrolysis tank.

In the chlorination tank, magnesium oxide is added to hydrogen chloride water. Because 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 electrolysis tank.

Therefore, the chlorination tank may be equipped with a measuring device that measures the concentration of solid components in the liquid phase. An example of a measuring device that measures the concentration of solid components in the liquid phase is an absorption meter that measures the absorbance or light transmittance of the suspension.

Furthermore, if the chlorination tank is a flow type, it is preferable to install 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.

As mentioned above, the contents of the chlorination tank may contain carbon, so carbon may be removed from the liquid before transport to the molten salt electrolytic tank. Furthermore, if a filter to trap magnesium oxide is installed at the outlet of the chlorination tank, it is preferable that the filter pore size be large enough to allow fine carbon particles to pass through.

The inorganic chlorides produced in the chlorination process are transferred from the chlorination tank to the molten salt electrolysis 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 be equipped with a heating furnace between the chlorination tank and the molten salt electrolysis tank to separate the inorganic chlorides from the hydrogen chloride solution.

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 temperature 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 according to 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, as well as a cooler and/or heater that controls the temperature of the inorganic chlorides.

As an example of temperature control, if the molten salt electrolytic cell is hotter than the desired reaction temperature, the temperature of the molten salt electrolytic cell can be lowered by supplying inorganic chlorides from a chlorination cell that are colder than the molten salt in the molten salt electrolytic cell; if the molten salt electrolytic cell is within the desired reaction temperature, the temperature of the inorganic chlorides supplied from the chlorination cell can be adjusted to the desired reaction temperature, thereby suppressing temperature changes caused by supplying inorganic chlorides.

In the molten salt electrolysis tank, inorganic chlorides are electrolyzed in the molten salt to produce chlorine and inorganic solid fuel. The chlorine produced from the anode is recovered and supplied to the chlorination tank for reuse in the chlorination process. Here, hydrogen chloride may be produced by reacting chlorine gas with hydrogen gas before supplying it to the chlorination tank. Hydrogen chloride may be produced in the gas phase in the chlorination tank, but it is preferable to produce it in a hydrogen chloride production device installed 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, the liquefied magnesium can be recovered and cooled to obtain solid magnesium.

Next, we will explain the differences between a system integrating a chlorination furnace and a molten salt electrolytic cell and the above-mentioned system. In such a regeneration system, the chlorination furnace and the molten salt electrolytic cell are preferably connected by at least a supply path that supplies the inorganic chlorides produced in the chlorination process from the chlorination furnace to the molten salt electrolytic cell, and a supply path that supplies the chlorine gas produced in the molten salt electrolytic process from the molten salt electrolytic cell to the chlorination furnace.

The following describes an example in which magnesium oxide and chlorine gas are added in a chlorination furnace to produce magnesium chloride, and then 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 chlorination using chlorine gas is preferable, as the chlorine gas produced in the molten salt electrolytic cell can be used directly in the chlorination furnace. However, this does not mean to exclude the chlorination process using the hydrogen chloride gas method; for example, after the chlorination process using the chlorine gas method is carried out, hydrogen chloride gas may be supplied to the chlorination furnace as the final process.

In the chlorination furnace, magnesium oxide and chlorine gas are added to a molten salt of an alkali metal or alkaline earth metal chloride (e.g., sodium chloride, potassium chloride, calcium chloride, etc.). Because magnesium oxide has a low solubility in the molten salt and magnesium chloride has a high solubility, magnesium oxide exists as a solid and magnesium chloride exists in the liquid. Therefore, if the chlorination furnace is a batch-type furnace, the solid components in the liquid can be monitored, and the contents of the chlorination furnace can be transported to a molten salt electrolytic cell when the decrease in the solid components reaches a certain level. Furthermore, oxygen is generated during the chlorination reaction of magnesium oxide using the chlorine gas method. Therefore, the oxygen concentration in the chlorination furnace can be measured, and the contents of the chlorination furnace can be transported to a molten salt electrolytic cell when the oxygen concentration exceeds a pre-calculated value. Therefore, the chlorination furnace can be equipped with a measuring device to measure the concentration of solid components in the liquid phase and/or a measuring device to measure the oxygen concentration in the gas phase. A known oxygen meter can be used as a measuring device to measure the oxygen concentration in the gas phase.

The inorganic chlorides produced in the chlorination process are transferred in liquid form from the chlorination furnace to the molten salt electrolytic cell via a supply path. Here, along the supply path, the inorganic chlorides 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. 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 with magnesium chloride dissolved therein may be supplied to the molten salt electrolytic cell.

In addition, like regeneration systems including a chlorination furnace, regeneration systems including a chlorination tank may be equipped with a filter that traps solid magnesium oxide at the outlet of the chlorination furnace; a thermometer that measures the temperature in the supply path from the chlorination furnace to the molten salt electrolytic tank; and a cooler and/or heater that controls the temperature.

(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.

If a grinding device is used to carry out the micronization process, it is preferable to carry out the grinding process in two stages, taking grinding efficiency into consideration.

Specifically, the atomization process may include a coarse pulverization process in which the inorganic solid fuel is coarsely pulverized to a primary particle size (e.g., a particle size of approximately 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.

The particle size in the micronization process does not mean an exact sphere, but the particle size in the coarse grinding process is a particle size that will pass through a sieve with a mesh opening of approximately 0.8 mm, for example.

Here, if 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 process. This makes it possible to prevent the inorganic solid fuel from sticking together during the grinding process.

As a grinding aid, for example, stearic acid can be used, but it is preferable to use an inorganic compound powder. When the inorganic solid fuel is magnesium, 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 a grinding aid.

(Hydrogenation step)
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.

Furthermore, if the inorganic solid fuel is a metal such as magnesium that is highly reactive with air, when the inorganic solid fuel comes into contact with oxygen after the atomization process, an oxide film may form on the surface, reducing the reaction efficiency. For this reason, if the resource recycling process includes a hydrogenation process, the formation of such an oxide film can be suppressed. Therefore, if the resource recycling process includes a hydrogenation process, it is preferable to handle the inorganic solid fuel atomized in the atomization process so that it does not come into contact with oxygen until the hydrogenation process is completed.

With reference to Figure 4, which illustrates the configuration of the equipment used to carry out the hydrogenation process, we will explain a method for carrying out the hydrogenation process without exposing the material to outside air.

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

The heating vessel 310 has a valve 314 in the conduit section 313 that runs from the inlet 311 to the heating section 312, and when the valve 314 is closed, the vessel becomes airtight.

Although not shown, piping 315 is connected to a hydrogen gas supply system, an argon gas supply system, and a vacuum pump.

The heating container 310 also serves as a recovery container for recovering the magnesium pulverized during the fine grinding process.

As described above, the fine grinding process is carried out in an argon gas atmosphere, and before the heating container 310 is removed from the grinding device performing the fine grinding process, valve 314 is closed and the heating container 310 is removed. This allows the magnesium recovered in the heating container 310 to be connected to the device 300 shown in Figure 4 while still sealed in argon.

Then, before valve 314 is opened, a vacuum is drawn, and the air upstream of pipe 315 and valve 314 is exhausted. After that, valve 314 is opened, and the argon gas inside heating section 312 is exhausted.

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 container 310 to perform the hydrogenation process (see reaction equation 21 below).
Mg + H ₂ → MgH ₂ (21)

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, as a substitute for coal). Furthermore, magnesium is highly combustible when reduced to fine powder. On the other hand, magnesium hydride becomes less flammable once 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.

It should be noted that the hydrogenation of magnesium does not progress in proportion to the processing time, but rather the rate of progress slows significantly as the purity increases. For this reason, if low-purity magnesium hydride is used, where at least the surface side is hydrogenated to a hydrogenation rate of 30 mass% or less (for example, around 20 mass%), the time required for the hydrogenation process can be significantly reduced, making it possible to significantly increase productivity.

After the hydrogenation process, 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 extracted. The low-purity magnesium hydride thus produced, with at least the surface side hydrogenated and having a hydrogenation rate of 30% by mass or less (for example, around 20% by mass), is reused as fuel in the power generation process.

In addition, 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.

(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, carbon dioxide emitted from a coal gasification power generation facility (specifically, an integrated coal gasification combined cycle power generation facility or an integrated coal gasification fuel cell combined cycle power generation facility) can be used as a combustion supporting gas to generate power, thereby significantly reducing the environmental impact of coal-fired power generation.

The power generation method and power plant 10 according to the embodiment can utilize mechanisms similar to those used in coal-fired power generation, making it possible to utilize technology developed in coal-fired power generation and reduce carbon dioxide emissions.

According to the power generation method and power plant 10 of the embodiment, and because the resource recycling process can be composed only of electrically powered equipment, it is possible to regenerate and produce fuel using only surplus electricity that cannot be connected to a grid. Therefore, if the resource recycling process is carried out using surplus electricity, it functions as a receptacle for surplus electricity from renewable energy sources, etc., and on the other hand, 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 also be said to be a power generation method that can convert that electricity without inertia into electricity with inertia.

Although the embodiments of the present invention have been described above, the specific configuration of the present invention is not limited to the above embodiments, and the present invention also includes modifications and alterations to the above embodiments that do not deviate from the gist of the present invention.

For example, in the above embodiment, an example was given of the power plant 10 being installed alongside a coal gasification power generation facility (specifically, an integrated coal gasification combined cycle power generation facility 100, an 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 coal gasification gas storage facility, for example.

In addition, while the above embodiment has been described using an example of a power boiler that uses a powder combustion burner 31, there are also coal-fired power plants known as stoker boilers, which do not use pulverized coal burners and instead have a combustion chamber configured like a simple combustion furnace, with coal simply fed into the boiler to ensure continuous combustion. The fuel described above can also be used in these configurations. In this case, atomization, which was previously necessary to sustain 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 with a particle size of approximately 500 μm are less flammable, a power generation method using magnesium as fuel can also be used in which only the magnesium is appropriately coarsely crushed to a size of 500 μm or larger and no hydrogenation process is performed. In other words, when magnesium with a particle size of approximately 500 μm is supplied to a stoker boiler and the power generation method of this embodiment is carried out, the resource recycling process can be carried out up to coarse crushing, without the fine crushing and hydrogenation processes being performed.

Furthermore, in the above embodiment, the inorganic solid fuel supplied to the powder combustion burner 31 is mainly described as magnesium, 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. Note that, 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.

In addition, 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 this 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 coal gasification gas produced in another system or stored or preserved independently.

Furthermore, in the above embodiment, the magnesium oxide (specifically, magnesium oxide), which is a combustion product produced by 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.

10...power generation system (power plant), 1...generator, 2...boiler equipment (power generation boiler), 21...combustion chamber, 22...steam turbine, 23...piping, 24...feedwater pump, 3...fuel storage tank, 31...powder combustion burner, 4...auxiliary fuel storage tank, 41...auxiliary combustion burner, 5...denitrification device, 6...dust collector, 7...combustion ash storage tank, 8...exhaust pipe, 81...exhaust device, 9...condenser, 100...coal gasification combined cycle power generation equipment, 101...coal gasification equipment, 102...gas purification equipment, 103...combustor, 104...gas tower steam turbine, 105...generator, 106...exhaust heat recovery boiler, 107...steam turbine, 108...generator, 109...recovery device, 110...compressor, 120...coal gasification fuel cell combined cycle power generation system, 121...shift reaction system, 122...separation system, 123...compressor, 124...fuel cell, 125...fuel cell post-stage combustor, 300...device for carrying out hydrogenation step, 310...heating vessel, 311...inlet, 312...heating section, 313...duct section, 314...valve, 315...piping, 320...heater.

Claims (14)

The method includes burning an inorganic solid fuel and a coal gasification gas as a combustion supporting gas in a combustion chamber of a boiler device.
Power generation method. The inorganic solid fuel is at least one of lithium, magnesium, calcium, boron, and aluminum.
The power generation method according to claim 1 . 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 . 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 . 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. The combustion supporting gas includes coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility.
The power generation method according to any one of claims 1 to 5. The combustion supporting gas includes a fuel gas obtained by purifying a coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility in a gas purification facility.
The power generation method according to any one of claims 1 to 5. the combustion supporting gas includes exhaust gas discharged from a coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility by purifying the coal gasification gas in a gas purification facility to produce a fuel gas, and combusting the fuel gas in a combustor;
The power generation method according to any one of claims 1 to 5. the combustion supporting gas is obtained by purifying coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility in a gas purification facility to produce a fuel gas, and combusting the fuel gas in a combustor to discharge an exhaust gas from which moisture has been separated, and the dried gas is
The power generation method according to any one of claims 1 to 5. the combustion supporting gas includes a shift gas obtained by purifying a coal gasification gas produced in a coal gasification facility of a coal gasification power generation facility into a fuel gas in a gas purification facility, and subjecting the fuel gas to a water-gas shift reaction;
The power generation method according to any one of claims 1 to 5. the combustion supporting gas comprises carbon dioxide 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 to produce a fuel gas, and subjecting the fuel gas to a water-gas shift reaction to obtain a shift gas from which hydrogen has been separated.
The power generation method according to any one of claims 1 to 5. In a combustion chamber of the boiler device, inorganic solid fuel and coal gasification gas as a combustion supporting gas are combusted.
How to operate a boiler system. a combustion chamber for burning inorganic solid fuel and coal gasification 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. The boiler apparatus according to claim 13;
a generator that generates electricity using steam generated by the boiler device;
A power generation system comprising: