Thermal power generation method and boiler device operation method

Abstract

Provided is a thermal power generation method with which a discharge amount of greenhouse gas such as carbon dioxide discharged from a power plant during power generation is suppressed. The present disclosure is a thermal power generation method using biomass fuel (F1) combustion heat and inorganic fuel (F2) combustion heat, wherein the inorganic fuel (F2) is a fuel that does not generate carbon oxide gas during combustion.

Description

Thermal power generation method and boiler device operation method

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

[0002] In response to the problem of global warming, it has become urgent to reduce emissions of greenhouse gases such as carbon dioxide emitted by thermal power plants.

[0003] Japanese Patent Application Laid-Open No. 2022-102636

[0004] The present disclosure has been made in consideration of the above circumstances, and aims to provide a thermal power generation method and a boiler device operating method that reduce emissions of greenhouse gases such as carbon dioxide emitted from a power plant during power generation.

[0005] In order to achieve the above object, the present disclosure is grasped by the following configurations: (1) A thermal power generation method of one embodiment according to the present disclosure is a thermal power generation method that utilizes combustion heat of biomass fuel and combustion heat of inorganic fuel, wherein the inorganic fuel is a fuel that does not generate carbon oxide gas when burned.

[0006] (2) In the configuration of (1) above, a mixed fuel obtained by mixing the biomass fuel and the inorganic fuel is burned.

[0007] (3) In the configuration of (1) above, the inorganic fuel is a fuel that can be burned using carbon oxide gas as a combustion supporting gas, the biomass fuel and the inorganic fuel are not mixed but are burned separately, and the inorganic fuel is burned in the presence of a combustion supporting gas containing carbon oxide gas that is generated when the biomass fuel is burned.

[0008] (4) In the configurations (1) to (3) above, the inorganic fuel is magnesium, calcium, at least partially hydrogenated magnesium hydride, at least partially hydrogenated calcium hydride, or a mixture thereof.

[0009] (5) A method of operating a boiler apparatus according to one embodiment of the present disclosure includes burning biomass fuel and inorganic fuel in a combustion chamber of the boiler apparatus, wherein the inorganic fuel is a fuel that does not generate carbon dioxide gas when burned.

[0010] (6) In the configuration of (5) above, a mixed fuel obtained by mixing the biomass fuel and the inorganic fuel is burned in the combustion chamber.

[0011] (7) In the configuration of (5) above, the combustion chamber has a first combustion chamber and a second combustion chamber connected to the first combustion chamber, the biomass fuel is burned in the first combustion chamber, the inorganic fuel is burned in the second combustion chamber, and the carbon dioxide gas generated in the first combustion chamber is supplied to the second combustion chamber.

[0012] According to the present disclosure, it is possible to provide a thermal power generation method that reduces emissions of greenhouse gases such as carbon dioxide emitted from a power plant during power generation.

[0013] 1 is a diagram for explaining a power generation system that implements a thermal power generation method according to a first embodiment of the present invention; FIG. 2 is a diagram for explaining a power generation system that implements a thermal power generation method according to a second embodiment of the present invention;

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description of embodiments of the present invention will be given with reference to the accompanying drawings. Note that the same elements are designated by the same reference numerals throughout the description of the embodiments.

[0015] (First embodiment) A thermal power generation method according to a first embodiment of the present invention is implemented in a thermal power plant, but many of the components are similar to those of current thermal power plants, and therefore, a description of the similarities may be omitted.

[0016] FIG. 1 is a diagram illustrating the schematic configuration of a power generation system (hereinafter sometimes referred to as a "power plant", and in this specification, "power plant" can be replaced with "power generation system") according to this embodiment. The power generation system includes a generator 1 and a boiler unit 2 (hereinafter sometimes referred to as a "power generation boiler 2", and in this specification, "power generation boiler" can be replaced with "boiler unit") having a combustion chamber 21. In the power generation system according to this embodiment, the generator 1 generates electricity using steam generated by the boiler unit 2. FIG. 1 shows a steam power generation system using a so-called stoker boiler as an example of a power generation system.

[0017] In the embodiment shown in FIG. 1 , the power plant includes a generator 1 , a power generation boiler 2 that drives the generator 1 , and a hopper 3 that supplies fuel F to the power generation boiler 2 .

[0018] The power generation boiler 2 comprises a combustion chamber 21, a superheater 22 that generates steam using the heat of combustion of fuel F, and a steam turbine 23 that is driven by the steam generated in the superheater 22 and whose rotating shaft is connected to the generator 1.

[0019] As indicated by the solid arrows, the steam that drives the steam turbine 23 is returned to liquid water in the condenser FU, and is supplied again to the superheater 22 by the feedwater pump P, where it becomes steam and is supplied to the steam turbine 23.

[0020] The combustion chamber 21 includes a main combustion chamber 21A and a flue 21B that forms a flow path for high-temperature exhaust gas generated in the main combustion chamber 21A.

[0021] The flue 21B is formed so as to make a 180-degree turn, and combustion ash and other materials contained in the exhaust gas are efficiently collected in the combustion ash collection section (not shown) via the chute 4, as indicated by the thick black arrow.

[0022] A superheater 22 is disposed in the flue 21B on the downstream side in terms of the flow of exhaust gas (see dotted arrow).

[0023] The exhaust gas after passing through the superheater 22 is exhausted through an exhaust pipe PU, and after undergoing necessary treatment, is released into the atmosphere from a chimney.

[0024] For example, when nitrogen oxides (NOx) are generated, the necessary treatment is to detoxify the nitrogen oxides (NOx) in a denitration device.

[0025] However, in recent years, it has become possible to prevent the generation of nitrogen oxides (NOx) exceeding environmental emission standards by controlling the combustion temperature and increasing the concentration of oxygen in the air as a combustion-supporting gas, so in such cases denitration equipment is not required.

[0026] After passing through the denitrification equipment, the exhaust gas is cooled, and then a dust collector collects fine combustion ash and other particles contained in the exhaust gas. The gas is then sent to a chimney via an exhaust fan and released into the atmosphere.

[0027] In this embodiment, the fuel F is a mixed fuel obtained by mixing a biomass fuel F1 and an inorganic fuel F2, and is supplied to the main combustion chamber 21A by a hopper 3.

[0028] For example, solid fuels such as wood chips, wood pellets, palm kernel shells, etc. can be suitably used as the biomass fuel F1.

[0029] Furthermore, for example, the inorganic fuel F2 may be one or more materials selected from magnesium, calcium, aluminum, lithium, and magnesium hydride, calcium hydride, aluminum hydride, and lithium hydride, which are at least partially hydrogenated.

[0030] However, from the viewpoint of combustibility, etc., the inorganic fuel F2 is preferably magnesium, calcium, at least partially hydrogenated magnesium hydride, at least partially hydrogenated calcium hydride, or a mixture thereof (for example, a mixture of magnesium and magnesium hydride).

[0031] The mixed fuel supplied to the main combustion chamber 21A by the hopper 3 passes through the drying stoker 5, the combustion stoker 6, and the post-combustion stoker 7, which are provided in the main combustion chamber 21A, in that order, and the combustion ash after combustion is then collected via the chute 4 in a combustion ash collection section (not shown).

[0032] Primary combustion air is supplied into the main combustion chamber 21A from below the drying stoker 5, combustion stoker 6, and post-combustion stoker 7, and the biomass fuel F1 is dried and heated to near the ignition point on the drying stoker 5. The biomass fuel F1 is then ignited on the combustion stoker 6 and combusts on the combustion stoker 6 and post-combustion stoker 7.

[0033] Furthermore, a portion of the ignited biomass fuel F1 decomposes, generating combustible gas, which moves to the top of the main combustion chamber 21A. However, since secondary combustion air is supplied from the ceiling of the main combustion chamber 21A into the main combustion chamber 21A, the combustible gas is mixed with the secondary combustion air and is completely burned.

[0034] On the other hand, the mixed fuel also contains inorganic fuel F2, which is burned together with biomass fuel F1. However, magnesium (Mg), calcium (Ca), aluminum (Al), lithium (Li), and at least partially hydrogenated magnesium hydride (MgH2), calcium hydride (CaH2), aluminum hydride (AlH3), and lithium hydride (LiH) do not contain carbon components, and therefore, as shown in the following formula, no carbon oxide gases such as carbon dioxide or carbon monoxide are generated during combustion.

[0035] 2Mg + O2 → 2MgO 2Ca + O2 → 2CaO 4Al + 3O2 → 2Al2O3 4Li + O2 → 2Li2O MgH2 + O2 → MgO + H2O CaH2 + O2 → CaO + H2O 2AlH3 + 3O2 → Al2O3 + 3H2O 2LiH + O2 → Li2O + H2O

[0036] However, since inorganic fuel F2 releases high-temperature heat when burned, it is possible to maintain the same amount of power generation as before reducing the amount of biomass fuel F1 used, even if the amount of biomass fuel F1 used is at least the amount of heat released.

[0037] Furthermore, since the biomass fuel F1 is a fuel derived from plants that grow by absorbing greenhouse gases such as carbon dioxide from the atmosphere, the circulation cycle of greenhouse gases in nature is achieved.

[0038] Therefore, thermal power generation using biomass fuel F1 is positioned as a power generation method that has achieved carbon neutrality.

[0039] Furthermore, as in this embodiment, the thermal power generation method, which adds inorganic fuel F2 that does not generate greenhouse gases such as carbon dioxide when burned, and can reduce the amount of biomass fuel F1 used while maintaining the amount of power generated, further reduces the generation of greenhouse gases such as carbon dioxide, resulting in carbon-negative power generation.

[0040] Incidentally, when inorganic fuel F2 is burned in an oxygen-deficient state, it can react with nitrogen in the combustion air to form nitrides. However, in the presence of moisture, the nitrides are hydrolyzed even more rapidly to produce ammonia and hydroxides.

[0041] Therefore, it is preferable to increase the humidity of the primary combustion air supplied from below the post-combustion stoker 7 toward the inside of the main combustion chamber 21A.

[0042] For example, if the humidity is increased to 50%, preferably 70%, and more preferably 80%, even if the inorganic fuel F2 undergoes incomplete combustion and produces nitrides, a hydrolysis reaction will immediately occur, generating ammonia, a flammable gas, which will contribute to combustion.

[0043] In this way, it is preferable to carry out combustion of the inorganic fuel F2 in a state where moisture that contributes to the combustion accelerator is supplied.

[0044] As shown in FIG. 1, a flue 21B near the main combustion chamber 21A may also be supplied with tertiary combustion air to form a re-combustion section N (see the shaded area) for promoting combustion.

[0045] This ensures that carbon monoxide that was not completely combusted, hydrogen generated by decomposition of hydrides, ammonia generated by decomposition of nitrides, etc. are combusted, thereby ensuring efficient use of thermal energy and suppression of the release of harmful gases (carbon monoxide, ammonia, etc.).

[0046] In the above, air (air with an increased oxygen concentration) is presented as the combustion supporting gas for combustion, but it goes without saying that oxygen itself can be used as the primary combustion air, secondary combustion air, and tertiary combustion air. Furthermore, air and carbon dioxide gas may be used in combination as the combustion supporting gas.

[0047] Second Embodiment Next, a thermal power generation method according to a second embodiment of the present invention will be described. Fig. 2 is a diagram for explaining a power plant in which the thermal power generation method according to this embodiment is implemented, and will be described as a steam power generation system using a stoker boiler, as in the first embodiment. Note that a description of the same configuration as in the first embodiment may be omitted.

[0048] In the first embodiment, the fuel F burned in the power generation boiler 2 was a mixed fuel of biomass fuel F1 and inorganic fuel F2, but in the second embodiment, the biomass fuel F1 and inorganic fuel F2 are not mixed and are burned separately.

[0049] Therefore, as shown in FIG. 2, in addition to the combustion chamber (first combustion chamber) 21 described in the first embodiment, a combustion chamber (second combustion chamber) 24 for burning inorganic fuel F2 is added.

[0050] As can be seen from the fact that the opening of the exhaust pipe PU is visible above the superheater 22, the components such as the steam turbine 23 and the generator 1 depicted on the right side of FIG. 1 are located toward the back of the paper in FIG. 2 .

[0051] Therefore, although not visible in Figure 2, the power generation boiler 2 of this embodiment also includes a steam turbine 23 that is driven by steam generated in the superheater 22 and has a rotating shaft connected to the generator 1.

[0052] The combustion chamber 24 for burning the inorganic fuel F2 has a configuration similar to that of the combustion chamber 21 of the first embodiment described with reference to Figure 1, and the combustion chamber 24 includes a main combustion chamber 24A and a flue 24B that forms a flow path for the high-temperature exhaust gas generated in the main combustion chamber 24A.

[0053] As shown in FIG. 2, the flue 24B is formed so as to merge with the flue 21B where the superheater 22 is provided.

[0054] Then, inorganic fuel F2 is supplied to the main combustion chamber 24A by the hopper 31, and after passing through the heating stoker 51, combustion stoker 61, and post-combustion stoker 71 provided in the main combustion chamber 24A in that order, the combustion ash after combustion is collected via the chute 41 to the inorganic fuel F2 combustion ash collection section (not shown), as indicated by the thick white arrow.

[0055] Incidentally, with regard to the biomass fuel F1, the combustion ash generated after combustion is collected via a chute 4 in a combustion ash collection section (not shown) for the biomass fuel F1.

[0056] Here, the inorganic fuel F2 described above, i.e., magnesium, calcium, aluminum, lithium, and at least partially hydrogenated magnesium hydride, calcium hydride, aluminum hydride, and lithium hydride, are all fuels that can be burned using carbon oxide gases such as carbon dioxide and carbon monoxide as combustion-supporting gases.

[0057] Therefore, carbon dioxide gas (mainly carbon dioxide) contained in the exhaust gas coming out of the exhaust pipe PU is recovered, and the carbon dioxide gas is supplied from below the heating stoker 51, the combustion stoker 61, and the post-combustion stoker 71 toward the inside of the main combustion chamber 24A.

[0058] Specifically, a separation and recovery device that separates and recovers carbon dioxide is provided further downstream of the dust collection device described in the first embodiment, and the carbon dioxide recovered by the separation and recovery device is supplied from below the heating stoker 51, combustion stoker 61, and post-combustion stoker 71 toward the inside of the main combustion chamber 24A.

[0059] Unlike biomass fuels such as wood chips, inorganic fuel F2 does not need to be dried, so the stoker close to the hopper 31 serves as a heating stoker 51 that heats the inorganic fuel F2 to a temperature close to the ignition point.

[0060] The inorganic fuel F2 is heated to near the ignition point on the heating stoker 51, ignites on the combustion stoker 61, and burns in the presence of a combustion supporting gas containing carbon oxide gas on the combustion stoker 61 and the post-combustion stoker 71. The combustion supporting gas contains at least carbon oxide gas, and may be a gas consisting of carbon oxide gas, a gas containing carbon oxide gas and oxygen gas, or a gas consisting of carbon oxide gas and oxygen gas.

[0061] Incidentally, in the case of inorganic fuel F2 such as magnesium, calcium, aluminum, and lithium, combustion using carbon dioxide as a combustion supporting gas results in a reduced pressure reaction because only solid components are produced after combustion, as shown in the following formula: During combustion, carbon dioxide is decomposed (reduced) to solid carbon (C), thereby suppressing the release of carbon dioxide.

[0062] 2Mg + CO2 → 2MgO + C 2Ca + CO2 → 2CaO + C 4Al + 3CO2 → 2Al2O3 + 3C 4Li + CO2 → 2Li2O + C

[0063] Therefore, the carbon dioxide recovered by the separation and recovery device may be temporarily collected in a gas tank, and an excess amount of carbon dioxide may be supplied from the gas tank in excess of the amount required for the reaction so as to maintain an internal pressure sufficient to prevent the exhaust gas from flowing back into the main combustion chamber 24A.

[0064] On the other hand, when inorganic fuel F2 is a hydride of magnesium, calcium, aluminum, and lithium and is burned using carbon dioxide as a combustion supporting gas, hydrogen is generated after combustion, as shown in the following formula: Note that carbon dioxide is decomposed (reduced) during combustion to become solid carbon (C), so no carbon dioxide is released.

[0065] 2MgH2 + CO2 → 2MgO + 2H2 + C 2CaH2 + CO2 → 2CaO + 2H2 + C 4AlH3 + 3CO2 → 2Al2O3 + 6H2 + 3C 4LiH + CO2 → 2Li2O + 2H2 + C

[0066] The generated hydrogen then moves to the upper part of the main combustion chamber 24A, so in this case, as explained in the first embodiment, combustion air is supplied from the ceiling part of the main combustion chamber 24A toward the inside of the main combustion chamber 24A, and the hydrogen gas is mixed with the combustion air to be completely combusted.

[0067] In this way, when combustion air is supplied from the ceiling portion of the main combustion chamber 24A toward the inside of the main combustion chamber 24A, when the air reaches the inorganic fuel F2 being burned, combustion also occurs due to reaction with oxygen, and the amount of carbon dioxide decomposed is reduced.

[0068] Therefore, even if the combustion reaction of the hydride does not become a reduced pressure reaction, it is preferable to supply carbon dioxide into the main combustion chamber 24A from below the heating stoker 51, the combustion stoker 61, and the post-combustion stoker 71 so that the combustion air supplied from the ceiling portion of the main combustion chamber 24A toward the inside of the main combustion chamber 24A does not reach the inside directly, or even if it does reach the inside, the concentration is sufficiently low.

[0069] Furthermore, when sending combustion air, there is a risk of nitrides being formed, so as explained in the first embodiment, it is preferable that the carbon dioxide supplied from below the post-combustion stoker 71 toward the main combustion chamber 24A contains moisture.

[0070] In this manner, in the present embodiment, the inorganic fuel F2 is burned using the carbon oxide gas generated when the biomass fuel F1 is burned as a combustion supporting gas, and as a result of this combustion, the carbon oxide gas is decomposed (reduced) into solid carbon, resulting in further carbon-negative power generation.

[0071] As shown in FIG. 1, similar to that described in the first embodiment, a re-burning section N (see FIG. 1) that supplies tertiary combustion air and promotes combustion may be provided in the flue 21B near the main combustion chamber 21A and the flue 24B near the main combustion chamber 24A in the second embodiment.

[0072] The combustion ash recovered in the combustion ash recovery section (not shown) of the inorganic fuel F2 is composed of highly pure carbon powder and oxides of magnesium, calcium, aluminum, and lithium (which may contain some hydroxides).

[0073] Therefore, if the carbon powder is recovered, it is an ideal raw material for carbon materials, and magnesium, calcium, aluminum, and lithium can be regenerated from the oxides as starting materials.

[0074] In other words, it is possible to realize a resource-recycling thermal power generation method in which resources such as magnesium, calcium, aluminum, and lithium are recycled.

[0075] The method is briefly explained below. First, the collected combustion ash is placed in hydrochloric acid water. The oxides of magnesium, calcium, aluminum, and lithium all react with the hydrochloric acid to become chlorides, which dissolve in the solution (chlorination process).

[0076] In addition, hydroxides of magnesium, calcium, aluminum, and lithium also become chlorides and dissolve in the solution, so as mentioned above, it is not a problem if some hydroxides are contained.

[0077] However, since aluminum oxide takes time to dissolve, it is a good idea to stir the solution or raise the temperature of the solution.

[0078] On the other hand, carbon powder does not react with hydrochloric acid and therefore does not dissolve in the solution, so by filtering the solution, only the carbon powder can be recovered.

[0079] Prior to the chlorination step, a step of pretreating the combustion ash (pretreatment step) may be carried out. The pretreatment step and the chlorination step may be repeated as a set. The number of repetitions is not particularly limited, but may be, for example, 2 to 10 times.

[0080] The pretreatment step includes a step of pulverizing the combustion ash and a step of heating the combustion ash.

[0081] The step of pulverizing the combustion ash is a step of pulverizing the combustion ash using a pulverizer such as a ball mill, bead mill, hammer mill, pin mill, roller mill, or jet mill, or a combination of these pulverizers. For example, pulverization using a ball mill may be carried out under conditions of, for example, 50 to 1000 rpm, preferably 100 to 600 rpm, for example, 1 minute to 30 hours, preferably 10 minutes to 20 hours, and more preferably 1 to 10 hours. Pulverization using a bead mill may be carried out under conditions of, for example, 50 to 5000 rpm, preferably 100 to 1000 rpm, for example, 15 seconds to 10 hours, preferably 1 minute to 3 hours.

[0082] The step of heating the combustion ash is a step of heating the combustion ash in a heating furnace. By heating an inorganic oxide such as magnesium oxide, impurities (e.g., carbon generated by combustion with carbon dioxide gas) coated on the inorganic oxide particles can be removed. The 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.

[0083] The pretreatment step may be a combination of a step of pulverizing the combustion ash and a step of heating the combustion ash, for example, a step of pulverizing the combustion ash and then further heating the combustion ash.

[0084] Next, the regeneration methods will be described in the order of magnesium, calcium, aluminum, and lithium. If the inorganic fuel F2 is magnesium, at least partially hydrogenated magnesium hydride, or a mixture thereof, the magnesium chloride dissolved in the solution after the hydrochloric acid treatment described above will be magnesium chloride.

[0085] In this case, if the water in the solution is evaporated at a low temperature at which magnesium chloride does not turn into magnesium oxide through a hydrolysis reaction, magnesium chloride hydrate will precipitate as crystals.

[0086] A dehydration treatment is carried out to prevent the hydrolysis reaction of the water of crystallization contained in the magnesium chloride hydrate crystals. There are other methods, but for example, if the mixture is heated to about 400 to 550°C while passing hydrogen chloride gas through it, the hydrolysis reaction is suppressed and only the dehydration reaction proceeds, resulting in anhydrous magnesium chloride.

[0087] Then, by performing molten salt electrolysis using the anhydrous magnesium chloride as a raw material, magnesium can be produced (molten salt electrolysis process).

[0088] If the inorganic fuel F2 is calcium, at least a part of which is hydrogenated calcium hydride, or a mixture thereof, calcium chloride will be dissolved in the solution in the above-mentioned hydrochloric acid treatment.

[0089] In this case, the procedure for regenerating calcium may be the same as that described above for magnesium, or calcium may be produced by directly subjecting calcium oxide to molten salt electrolysis.

[0090] If the inorganic fuel F2 is aluminum, at least partially hydrogenated aluminum hydride, or a mixture thereof, the aluminum chloride will be dissolved in the solution in the above-mentioned hydrochloric acid treatment.

[0091] The solution is then heated to a temperature at which the aluminum chloride hydrolyzes to form aluminum oxide, thereby removing the water, and aluminum oxide powder can be obtained. Aluminum is generally produced by mixing aluminum oxide as a raw material with a material that lowers the melting point and performing molten salt electrolysis, so aluminum can be regenerated using the aluminum oxide powder obtained as a raw material.

[0092] If the inorganic fuel F2 is lithium, at least partially hydrogenated lithium hydride, or a mixture thereof, the lithium chloride will be dissolved in the solution after the hydrochloric acid treatment described above.

[0093] In this case, the procedure for regenerating lithium can be the same as that explained for magnesium above.

[0094] Furthermore, the resource recycling method described above uses only electricity as energy, so this resource recycling process does not generate greenhouse gases such as carbon dioxide.

[0095] (Regeneration System) The resource recycling process has been described above, but the resource recycling process may be carried out by a regeneration system that integrates a reaction vessel section (hereinafter referred to as a chlorination tank) for carrying out the chlorination step and a molten salt electrolysis tank for carrying out the molten salt electrolysis step. By using such a regeneration system, for example, hydrogen chloride can be produced from chlorine generated at the anode in the molten salt electrolysis step and used in the chlorination step. Since chlorine gas is highly corrosive, if hydrogen chloride water gas can be produced using chlorine generated in the molten salt electrolysis step and the hydrogen chloride water gas can be used in the chlorination step, the storage time of chlorine gas can be shortened, which is preferable.

[0096] In the regeneration system, the chlorination tank and the molten salt electrolytic furnace are preferably connected by at least a supply path for supplying the inorganic chloride produced in the chlorination step from the chlorination tank to the molten salt electrolytic furnace, and a supply path for supplying the chlorine gas produced in the molten salt electrolytic step from the molten salt electrolytic tank to the chlorination tank. Each supply path may be provided with a device for performing further processing as described below. From the viewpoint of shortening the storage time of chlorine gas, the chlorine gas storage chamber may be omitted from the chlorine gas supply path.

[0097] The chlorination tank may be used for the reaction in a batch system or a flow system. In the case of the reaction in a batch system, after the completion of the chlorination reaction in the chlorination tank is detected, the inorganic chloride is transferred in liquid form from the chlorination tank to the molten salt electrolytic tank. In the case of the reaction in a flow system, the inorganic chloride is continuously transferred in liquid form from the chlorination tank to the molten salt electrolytic tank.

[0098] The following describes an example in which combustion ash and hydrogen chloride water (hydrochloric acid) are added to a chlorination tank to produce magnesium chloride, and chlorine and magnesium are produced from the magnesium chloride in a molten salt electrolytic tank.

[0099] In the chlorination tank, combustion ash containing magnesium oxide is added to hydrogen chloride water. As described above, when combustion ash is added to hydrochloric acid, the magnesium oxide dissolves as magnesium chloride, while other impurities do not dissolve or dissolve slowly. In hydrogen chloride water, magnesium oxide exists as a solid, and magnesium chloride exists in the liquid. Therefore, if the chlorination tank is a batch type, the solid components in the liquid can be monitored, and when the decrease in the solid components falls below a certain level, the contents of the chlorination tank can be transported to a molten salt electrolytic tank.

[0100] Therefore, the chlorination tank may be provided with a measuring device for measuring the concentration of solid components in the liquid phase, such as an absorbance measuring device for measuring the absorbance or light transmittance of the suspension.

[0101] Furthermore, when the chlorination tank is of a flow type, it is preferable to provide a filter at the outlet of the chlorination tank to trap solid magnesium oxide so that unreacted magnesium oxide is not discharged from the chlorination tank.

[0102] The contents of the chlorination tank may have impurities removed from the liquid phase before being transported to the molten salt electrolytic tank. When a filter for trapping magnesium oxide is provided at the outlet of the chlorination tank, the pore size of the filter may be set to a size that allows particulate impurities to pass through. The particulate impurities may be separately recovered using a filter with an even smaller pore size.

[0103] The chlorides produced in the chlorination step are transferred from the chlorination tank to the molten salt electrolytic tank via a supply path. An anhydrous chloride production step for separating inorganic chlorides from the hydrogen chloride solution may be carried out along the supply path. Therefore, the regeneration system of this embodiment may include an anhydrous chloride production device (e.g., a heating furnace) for separating inorganic chlorides from the hydrogen chloride solution between the chlorination tank and the molten salt electrolytic tank.

[0104] The inorganic chlorides supplied from the chlorination tank in this manner (including inorganic chlorides supplied from the chlorination tank via a heating furnace) may differ from the operating temperature of the molten salt electrolytic tank. Therefore, the temperatures of the liquid phase supplied to the molten salt electrolytic tank and the molten salt electrolytic tank may be measured, and the temperature of the liquid phase supplied to the molten salt electrolytic tank may be adjusted depending on these temperatures. Therefore, the molten salt electrolytic tank may be equipped with a thermometer that measures the temperature of the molten salt, and the supply path from the chlorination tank to the molten salt electrolytic tank may be equipped with a thermometer that measures the temperature of the supply (liquid phase), and a cooler and / or heater that controls the temperature of the supply.

[0105] As an example of temperature control, when the temperature of the molten salt electrolytic cell is higher than the desired reaction temperature, the temperature of the molten salt electrolytic cell may be lowered by supplying a liquid phase from a chlorination cell that has a temperature lower than that of the molten salt in the molten salt electrolytic cell; when the temperature of the molten salt electrolytic cell is within the desired reaction temperature, the temperature change caused by supplying the liquid phase may be suppressed by adjusting the temperature of the liquid phase supplied from the chlorination cell to the desired reaction temperature.

[0106] In the molten salt electrolysis tank, inorganic chlorides are electrolyzed in the molten salt to produce chlorine and magnesium. Chlorine produced from the anode is recovered and supplied to a chlorination tank for reuse in the chlorination step. Here, hydrogen chloride may be produced by reacting chlorine gas with hydrogen gas before supplying the recovered chlorine to the chlorination tank. Hydrogen chloride may be produced in the gas phase in the chlorination tank, but it is preferable to produce it in a hydrogen chloride production device provided upstream of the chlorination tank. Furthermore, magnesium may liquefy in the molten salt and remain on the surface of the molten salt. In such cases, solid magnesium can be obtained by recovering the liquefied magnesium and cooling it.

[0107] Although the thermal power generation method of the present invention has been described above through specific embodiments, the present invention is not limited to the specific embodiments.

[0108] For example, in the embodiment, a solid fuel such as wood chips is exemplified as the biomass fuel, but the biomass fuel may also be a liquid fuel such as bioethanol or biodiesel, or a gaseous fuel such as biogas.

[0109] In this case, a combustion burner for burning liquid fuel or gaseous fuel may be provided in the combustion chamber, and the biomass fuel may be burned.

[0110] However, when a mixed material of biomass fuel F1 and inorganic fuel F2 is used as fuel F as in the first embodiment, it is preferable that the biomass fuel F1 is solid, as this facilitates mixing.

[0111] In this way, appropriate modifications and improvements to the specific embodiments are also included within the technical scope of the present invention, and this will be clear to those skilled in the art from the description of the claims.

[0112] 1... Generator, 2... Power generation boiler, 21, 24... Combustion chamber, 21A, 24A... Main combustion chamber, 21B, 24B... Flue, 22... Superheater, 23... Steam turbine, 3, 31... Hopper, 4, 41... Chute, 5... Drying stoker, 51... Heating stoker, 6, 61... Combustion stoker, 7, 71... Post-combustion stoker, F... Fuel, F1... Biomass fuel, F2... Inorganic fuel, FU... Condenser, N... Re-combustion section, P... Feedwater pump, PU... Exhaust pipe

Claims

1. A thermal power generation method using the combustion heat of biomass fuel and the combustion heat of inorganic fuel, wherein the inorganic fuel is a fuel that does not generate carbon dioxide gas during combustion.

2. The method according to claim 1, wherein a mixed fuel in which the biomass fuel and the inorganic fuel are mixed is burned.

3. The inorganic fuel is a fuel that can burn with carbon dioxide gas as a combustion-supporting gas, the biomass fuel and the inorganic fuel are not mixed and are burned separately, and the inorganic fuel is burned in the presence of a combustion-supporting gas containing carbon dioxide gas generated during the combustion of the biomass fuel. The method according to claim 1.

4. The method according to any one of claims 1 to 3, wherein the inorganic fuel is magnesium, calcium, magnesium hydride in which at least a part is hydrogenated, calcium hydride in which at least a part is hydrogenated, or a mixture thereof.

5. An operation method of a boiler device, wherein a biomass fuel and an inorganic fuel are burned in a combustion chamber of the boiler device, and the inorganic fuel is a fuel that does not generate carbon dioxide gas during combustion.

6. The operation method according to claim 5, wherein a mixed fuel in which the biomass fuel and the inorganic fuel are mixed is burned in the combustion chamber.

7. The combustion chamber has a first combustion chamber and a second combustion chamber connected to the first combustion chamber. The biomass fuel is burned in the first combustion chamber, the inorganic fuel is burned in the second combustion chamber, and carbon dioxide gas generated in the first combustion chamber is supplied to the second combustion chamber. The operation method according to claim 5.

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