Thermal power generation method

Abstract

To provide a thermal electric power generation method which suppresses an emission amount of greenhouse gas, such as carbon dioxide, emitted from a thermal electric power plant.SOLUTION: A thermal electric power generation method utilizes combustion heat of a biomass fuel F1 and combustion heat of an inorganic material fuel F2. The inorganic material fuel F2 is a fuel which emits no carbon dioxide gas in combustion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-102636 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above circumstances, and aims to provide a thermal power generation method that reduces emissions of greenhouse gases such as carbon dioxide emitted from thermal power plants. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention is realized by the following configuration. (1) The thermal power generation method of the present invention is a thermal power generation method that utilizes the combustion heat of biomass fuel and the combustion heat of inorganic fuel, and the inorganic fuel is a fuel that does not generate carbon dioxide 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 using carbon oxide gas generated during combustion of the biomass fuel as a combustion supporting gas.

[0008] (4) In any one of the above (1) to (3), the inorganic fuel is magnesium, at least partially hydrogenated magnesium hydride, or a mixture thereof. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a thermal power generation method that reduces the amount of greenhouse gases such as carbon dioxide emitted from a thermal power plant. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram for explaining a thermal power plant in which a thermal power generation method according to a first embodiment of the present invention is implemented. [Figure 2] FIG. 2 is a diagram for explaining a thermal power plant in which a thermal power generation method according to a second embodiment of the present invention is implemented. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the accompanying drawings. It should be noted that the same elements are denoted by the same reference numerals throughout the description of the embodiments.

[0012] (First embodiment) The thermal power generation method of the first embodiment according to the present invention is carried out in a thermal power plant, but since many of its components are similar to those of current thermal power plants, a description of the similarities may be omitted.

[0013] FIG. 1 is a diagram for explaining a thermal power plant in which the thermal power generation method of the present embodiment is implemented, and shows a steam power generation system using a so-called stoker boiler.

[0014] The thermal 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.

[0015] The power generation boiler 2 includes 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.

[0016] As indicated by the solid arrow, the steam that drives the steam turbine 23 is returned to liquid water in the condenser FU, and is then supplied again to the superheater 22 by the feedwater pump P, where it becomes steam and is then supplied to the steam turbine 23.

[0017] 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.

[0018] Furthermore, flue 21B is configured 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 chute 4, as indicated by the thick black arrow.

[0019] Then, superheater 22 is arranged in flue 21B on the downstream side in terms of the flow of exhaust gas (see dotted arrow).

[0020] The exhaust gas that has passed through the superheater 22 is exhausted through an exhaust pipe PU, and after undergoing necessary treatment, is released into the atmosphere through a chimney.

[0021] For example, if nitrogen oxides (NOx) are generated, the necessary treatment is to detoxify the nitrogen oxides (NOx) in a denitration device.

[0022] However, in recent years, it has become possible to prevent the generation of nitrogen oxides (NOx) that exceed environmental emission standards by controlling the combustion temperature and increasing the concentration of oxygen in the air as a combustion-supporting gas, so in these cases denitration equipment is not necessary.

[0023] 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.

[0024] In this embodiment, a mixed fuel of biomass fuel F1 and inorganic fuel F2 is supplied as fuel F to the main combustion chamber 21A by a hopper 3.

[0025] For example, solid fuels such as wood chips, wood pellets, palm kernel shells, etc. can be suitably used as the biomass fuel F1.

[0026] Furthermore, for example, the inorganic fuel F2 may be one or more materials selected from magnesium, aluminum, lithium, and magnesium hydride, aluminum hydride, and lithium hydride, which are at least partially hydrogenated.

[0027] However, from the viewpoint of combustibility and the like, it is preferable that the inorganic fuel F2 be magnesium, magnesium hydride which is at least partially hydrogenated, or a mixture thereof (a mixture of magnesium and magnesium hydride).

[0028] 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 installed in the main combustion chamber 21A, in that order, and the combustion ash after combustion is then collected in the combustion ash collection section (not shown) via the chute 4.

[0029] 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 on the drying stoker 5 and heated to near the ignition point. Then, the biomass fuel F1 is ignited on the combustion stoker 6 and combusts on the combustion stoker 6 and the post-combustion stoker 7.

[0030] 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.

[0031] On the other hand, the mixed fuel also contains inorganic fuel F2, which is burned together with biomass fuel F1. However, magnesium (Mg), aluminum (Al), lithium (Li), and at least partially hydrogenated magnesium hydride (MgH2), aluminum hydride (AlH3), lithium hydride (LiH), etc. do not contain carbon components, and therefore do not generate carbon oxide gases such as carbon dioxide or carbon monoxide during combustion, as shown in the following formula.

[0032] 2Mg + O2→ 2MgO + heat 4Al + 3O2→ 2Al2O3+ Heat 4Li + O2→ 2Li2O + heat MgH2+ O2→ MgO + H2O + heat 2AlH3+ 3O2→ Al2O3+ 3H2O + heat 2LiH + O2 → Li2O + H2O + heat

[0033] 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.

[0034] Furthermore, since the biomass fuel F1 is derived from plants that grow by absorbing greenhouse gases such as carbon dioxide from the atmosphere, it achieves a natural cycle of greenhouse gases.

[0035] Therefore, thermal power generation using biomass fuel F1 is positioned as a power generation method that has achieved carbon neutrality.

[0036] Furthermore, in the thermal power generation method of this embodiment, 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 generation, the generation of greenhouse gases such as carbon dioxide is further suppressed, resulting in carbon-negative power generation.

[0037] When inorganic fuel F2 is burned in an oxygen-deficient state, it reacts with nitrogen in the combustion air to form nitrides, but if moisture is present, it quickly undergoes hydrolysis, generating ammonia and becoming hydroxides.

[0038] 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.

[0039] For example, if the humidity is increased to 50%, preferably 70%, and more preferably 80%, even if the inorganic fuel F2 reaches a state of incomplete combustion in which it turns into nitrides, a hydrolysis reaction will immediately occur, generating ammonia, a flammable gas, which will contribute to combustion.

[0040] 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.

[0041] As shown in FIG. 1, tertiary combustion air may also be supplied to the flue 21B near the main combustion chamber 21A to form a re-burning section N (see the shaded area) that promotes combustion.

[0042] This ensures that carbon monoxide that was not completely combusted, hydrogen generated by the decomposition of hydrides, ammonia generated by the 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.).

[0043] Furthermore, although the above describes air (air with an increased oxygen concentration) as a combustion-supporting gas for combustion, it goes without saying that there is no problem with using oxygen itself as the primary combustion air, secondary combustion air, and tertiary combustion air.

[0044] (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 thermal power plant in which the thermal power generation method of this embodiment is implemented, and will be explained as a steam power generation system using a stoker boiler as in the first embodiment. Note that the description of the same configuration as in the first embodiment may be omitted.

[0045] 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.

[0046] Therefore, as shown in FIG. 2, in addition to the combustion chamber 21 described in the first embodiment, a combustion chamber 24 for burning the inorganic fuel F2 is added.

[0047] 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 Figure 1 are located towards the back of the paper in Figure 2.

[0048] 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.

[0049] 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.

[0050] As shown in FIG. 2, the flue 24B is formed so as to merge with the flue 21B where the superheater 22 is provided.

[0051] Then, inorganic fuel F2 is supplied to the main combustion chamber 24A by the hopper 31, and passes through the heating stoker 51, combustion stoker 61, and post-combustion stoker 71 provided in the main combustion chamber 24A in that order, and the combustion ash after combustion is collected via the chute 41 in a combustion ash collection section for inorganic fuel F2 (not shown), as indicated by the thick white arrow.

[0052] Incidentally, with regard to the biomass fuel F1, the combustion ash after combustion is collected via a chute 4 in a combustion ash collection section (not shown) for the biomass fuel F1.

[0053] Here, the inorganic fuel F2 described above, i.e., magnesium, aluminum, lithium, and at least partially hydrogenated magnesium 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.

[0054] 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.

[0055] Specifically, a separation and recovery device for separating and recovering carbon dioxide is provided further downstream of the dust collector 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.

[0056] 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.

[0057] The inorganic fuel F2 is heated to near the ignition point on the heating stoker 51, ignites on the combustion stoker 61, and burns on the combustion stoker 61 and the post-combustion stoker 71 with carbon oxide gas as a combustion supporting gas.

[0058] Incidentally, in the case of inorganic fuel F2 such as magnesium, aluminum, and lithium, combustion using carbon dioxide as a combustion supporting gas results in a reduced pressure reaction since only solid components are produced after combustion, as shown in the following formula. During combustion, carbon dioxide is decomposed (reduced) to become solid carbon (C), so no carbon dioxide is released.

[0059] 2Mg + CO2→ 2MgO + C + heat 4Al + 3CO2→ 2Al2O3+ 3C + heat 4Li + CO2→ 2Li2O + C + heat

[0060] Therefore, it is advisable to temporarily collect the carbon dioxide recovered by the separation and recovery device in a gas tank, and then supply an amount of carbon dioxide from the gas tank in excess of the amount required for the reaction so that the internal pressure can be maintained to a level that prevents the exhaust gas from flowing back into the main combustion chamber 24A.

[0061] On the other hand, when the inorganic fuel F2 is a hydride of magnesium, 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. During combustion, carbon dioxide is decomposed (reduced) to become solid carbon (C), so no carbon dioxide is released.

[0062] 2MgH2+ CO2→ 2MgO + H2+ C + heat 4AlH3+ 3CO2→ 2Al2O3+ 6H2+ 3C + heat 4LiH + CO2→ 2Li2O + 2H2+ C + heat

[0063] The generated hydrogen then moves to the top 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, so that the hydrogen gas mixes with the combustion air and is completely burned.

[0064] 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.

[0065] 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 part of the main combustion chamber 24A into the main combustion chamber 24A does not reach the interior directly, or even if it does reach the interior, the concentration is sufficiently low.

[0066] 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.

[0067] 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) and becomes solid carbon, resulting in further carbon-negative power generation.

[0068] As shown in Figure 1, similar to that described in the first embodiment, a re-burning section N (see Figure 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.

[0069] Incidentally, 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, aluminum, and lithium (which may contain some hydroxides).

[0070] Therefore, if the carbon powder is recovered, it is an ideal raw material for carbon materials, and magnesium, aluminum, and lithium can be regenerated from the oxides as starting materials.

[0071] In other words, it is possible to realize a resource-recycling thermal power generation method in which resources such as magnesium, aluminum, and lithium are recycled.

[0072] The method will be briefly explained below. First, the collected combustion ash is placed in hydrochloric acid water. In this way, the oxides of magnesium, aluminum, and lithium all react with hydrochloric acid to become chlorides, which dissolve in the solution.

[0073] In addition, hydroxides of magnesium, 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.

[0074] However, since aluminum oxide takes time to dissolve, it is a good idea to stir the solution or raise the temperature of the solution.

[0075] 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.

[0076] Next, the regeneration methods will be explained for magnesium, aluminum, and lithium, in that order. If the inorganic fuel F2 is magnesium, at least partially hydrogenated magnesium hydride, or a mixture thereof, the magnesium chloride will be dissolved in the solution after the hydrochloric acid treatment described above.

[0077] 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.

[0078] A dehydration treatment is carried out to prevent hydrolysis reaction from occurring with the water of crystallization contained in the magnesium chloride hydrate crystals. There are other methods, but for example, if hydrogen chloride gas is passed through the solution and the solution is heated to about 400 to 550°C, the hydrolysis reaction is suppressed and only the dehydration reaction proceeds, resulting in anhydrous magnesium chloride.

[0079] Then, by carrying out molten salt electrolysis using this anhydrous magnesium chloride as a raw material, magnesium can be produced.

[0080] 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 after the hydrochloric acid treatment described above.

[0081] The solution is then heated to a temperature at which aluminum chloride is hydrolyzed to form aluminum oxide, thereby removing the moisture, and aluminum oxide powder can be obtained. Aluminum is generally produced by mixing aluminum oxide with a material that lowers its melting point and then performing molten salt electrolysis. Therefore, aluminum can be recycled using the resulting aluminum oxide powder as a raw material.

[0082] If the inorganic fuel F2 is lithium, at least partially hydrogenated lithium hydride, or a mixture thereof, the lithium chloride dissolved in the solution after the hydrochloric acid treatment described above will be lithium chloride.

[0083] In this case, the procedure for regenerating lithium can be the same as that explained for magnesium above.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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. [Explanation of symbols]

[0090] 1. Generator 2. Power generation boilers 21, 24 Combustion chamber 21A, 24A Main combustion chamber 21B, 24B Flue 22 Superheater 23 Steam turbine 3, 31 Hopper 4, 41 shots 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 Reburning section P Water supply pump PU exhaust pipe

Claims

1. A thermal power generation method that utilizes the combustion heat of biomass fuel and the combustion heat of inorganic fuel, The inorganic fuel is a fuel that does not generate carbon oxide gas when burned, A thermal power generation method, wherein the inorganic fuel is only magnesium or at least partially hydrogenated magnesium hydride.

2. The thermal power generation 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 be burned using carbon dioxide gas as a combustion-supporting gas, The biomass fuel and the inorganic fuel are not mixed and are burned separately, 2. The thermal power generation method according to claim 1, wherein the inorganic fuel is burned using carbon oxide gas generated during combustion of the biomass fuel as a combustion-supporting gas.

4. supplying moisture when burning the inorganic fuel; The thermal power generation method according to claim 1 .

5. Combusting the gas generated after burning the inorganic fuel. The thermal power generation method according to claim 1 .

6. The biomass fuel and the inorganic fuel are combusted in the combustion chamber of the boiler device, The inorganic fuel is a fuel that does not generate carbon oxide gas when burned, The inorganic fuel is magnesium or at least partially hydrogenated magnesium hydride alone. How to operate a boiler system.

7. A mixed fuel obtained by mixing the biomass fuel and the inorganic fuel is burned in the combustion chamber. The operating method according to claim 6.

8. The combustion chamber has a first combustion chamber and a second combustion chamber connected to the first combustion chamber, The biomass fuel is combusted in the first combustion chamber; The inorganic fuel is combusted in the second combustion chamber; supplying carbon oxide gas generated in the first combustion chamber to the second combustion chamber; The operating method according to claim 6.

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