WO2023017803A1

WO2023017803A1 - Combustion apparatus and combustion method

Info

Publication number: WO2023017803A1
Application number: PCT/JP2022/030238
Authority: WO
Inventors: 一芳伊藤
Original assignee: 住友重機械工業株式会社
Priority date: 2021-08-10
Filing date: 2022-08-08
Publication date: 2023-02-16
Also published as: JPWO2023017803A1

Abstract

A circulating fluidized bed boiler as a combustion apparatus according to the present invention is provided with: a first furnace (11A) which combusts a carbon-containing fuel that contains carbon; a second furnace (11B) which combusts a material such as calcium sulfate that produces a reactant such as calcium oxide that is reactive with carbon dioxide by means of combustion; and a cleanup device (5) which causes a reaction between carbon dioxide produced in the first furnace (11A) and the reactant produced in the second furnace (11B), thereby depositing a product such as calcium carbonate. The reactant is calcium oxide; and calcium carbonate is produced by a reaction at a reaction part. The material contains calcium sulfate. The material is cement.

Description

Combustion device, combustion method

The present invention relates to a combustion device that generates combustion.

Combustion devices that generate combustion include a fluidized bed (BFB: Bubbling Fluidized Bed) boiler and a circulating fluidized bed that burns fuel through a fluidized bed or fluidized bed formed by a fluidized material such as silica sand that flows in the combustion chamber. (CFB: Circulating Fluidized Bed) boilers are known. Patent Literature 1 discloses a CFB boiler.

JP 2012-255612 A

BFB boilers and CFB boilers can achieve high combustion efficiency by using a high-temperature fluid material that flows in the combustion chamber as a medium. It is suitable for burning fuels of unstable quality such as tires, etc., and flame-retardant fuels. However, since these fuels are mainly composed of carbon, they generate greenhouse gases such as carbon dioxide when burned, which may further exacerbate global warming.

The present invention has been made in view of these circumstances, and its purpose is to provide a combustion apparatus capable of reducing the generation of greenhouse gases.

In order to solve the above problems, a combustion apparatus according to one aspect of the present invention includes a first combustion chamber that burns a carbon-containing fuel containing carbon, and a material that generates a reactant that can react with carbon dioxide by combustion. and a reaction section for reacting the carbon dioxide produced in the first combustion chamber with the reactant produced in the second combustion chamber. According to this aspect, the carbon dioxide generated in the first combustion chamber can be consumed in the reaction section, so the generation of greenhouse gases from the combustion device can be reduced.

Another aspect of the present invention is a combustion method. The method comprises a first combustion step of combusting a carbon-containing fuel containing carbon; a second combustion step of combusting a material that upon combustion produces a reactant capable of reacting with carbon dioxide; and a reaction step of reacting the carbon dioxide with the reactants produced in the second combustion step.

It should be noted that any combination of the above constituent elements, and any conversion of the expression of the present invention between methods, devices, systems, recording media, computer programs, etc. are also effective as embodiments of the present invention.

According to the present invention, it is possible to reduce the generation of greenhouse gases in the combustion device.

1 shows the overall configuration of a combustion apparatus in which a first combustion section and a second combustion section are configured by a circulating fluidized bed boiler. 1 schematically shows a configuration example for recovering carbon dioxide as calcium carbonate in a cleaning device. 2 shows a first variant of the combustion device of FIG. 1; Fig. 2 shows a second variant of the combustion device of Fig. 1; 1 shows the overall configuration of a combustion apparatus in which the first combustion section is configured by a rotary kiln and the second combustion section is configured by a circulating fluidized bed boiler.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate. The scales and shapes of the illustrated parts are set for convenience in order to facilitate explanation, and should not be construed as limiting unless otherwise specified. The embodiments are illustrative and do not limit the scope of the invention in any way. Individual features and combinations thereof described in the embodiments are not necessarily essential to the invention.

The combustion device of the present invention is any device that generates combustion. For example, when the combustion apparatus is configured as a boiler, the combustion apparatus can be configured as a BFB boiler or a CFB boiler that burns fuel using a fluidized bed or a fluidized bed formed by a fluid material such as silica sand that flows in the combustion chamber. The combustion device can also be configured as a rotary kiln. Although the combustor of this embodiment includes two combustors, each combustor can be comprised of any combustor including BFB boilers, CFB boilers, and rotary kilns. In this embodiment, an example in which the first combustion section and the second combustion section are configured with a CFB boiler and an example in which the first combustion section is configured with a rotary kiln and the second combustion section is configured with a CFB boiler will be described. Any combination of combustion devices can constitute the first combustion section and the second combustion section.

FIG. 1 shows the overall configuration of a combustion apparatus in which the first combustion section 1A and the second combustion section 1B are composed of CFB boilers (circulating fluidized bed boilers). In the following description, the first combustion section 1A and the second combustion section 1B may be collectively referred to as the combustion section 1. Equivalent elements in the cleaning device 5, chimney 6, etc.) may be given the same reference numerals and common descriptions. Also, the first furnace 11A as the first combustion chamber and the second furnace 11B as the second combustion chamber are also collectively called the combustion chamber or the furnace 11 in some cases. The second combustion section 1B and accompanying configuration shown on the left side of FIG. 1 are simplified compared to the first combustion section 1A and accompanying configuration shown on the right side of FIG. 1, but have been simplified or omitted. This does not preclude the configuration (for example, the steam generating section 2) from being provided in the second combustion section 1B. On the other hand, as described above, the configurations of the first combustion section 1A and the second combustion section 1B and the configurations associated with the first combustion section 1A and the second combustion section 1B may be different from each other.

Each CFB boiler includes a combustion unit 1 that supplies and burns fuel in a furnace 11 in which a fluid material such as silica sand flows, a steam generation unit 2 that generates steam from water by the heat generated in the combustion unit 1, and a furnace 11 Fluid material circulation unit 3 as a circulation unit that collects the fluid material that has flowed out and returns it to the furnace 11, air supplied to the combustion unit 1, water supplied to the steam generation unit 2, and steam generation unit As a heat transfer part 4 that heats the steam generated in 2 by the high temperature exhaust of the combustion part 1, and a reaction part that separates and collects soot and dust in the exhaust from the heat transfer part 4 and recovers carbon dioxide and a chimney 6 for discharging the exhaust gas cleaned by the cleaning device 5 to the atmosphere.

The combustion section 1 has a furnace 11 as a combustion chamber. Specifically, the first combustion section 1A has a first furnace 11A as a first combustion chamber, and the second combustion section 1B has a second furnace 11B as a second combustion chamber. The furnace 11 has a vertically elongated cylindrical shape, and has a tapered bottom in order to increase the density of the solid fuel and the fluidized material to enable efficient combustion. The bottom portion of the furnace 11 may not be tapered, and the furnace 11 may be formed in a cylindrical shape with a substantially constant cross-sectional shape from the top to the bottom. The area indicated by "A" at the bottom of the furnace 11 indicates a fluidized bed (also called fluidized bed or sand bed) formed by high-density fluidized material. In the fluidized bed A, a powdery, particulate, or lumpy fluidizing material such as silica sand is fluidized by air as a fluidizing fluid supplied from the bottom of the furnace 11 . Solid fuels such as coal, biomass, and waste cement introduced into the fluidized bed A are efficiently combusted by repeatedly contacting the high-temperature fluidizing material and air so as to be agitated within the fluidized bed A.

In addition, since the fluidized material rises in the furnace 11 due to the ascending air current generated by combustion, the fluidized material also exists in the free board B, which is the space above the fluidized bed A. The density of the fluidized material in the freeboard B is lower than the density of the fluidized material in the fluidized bed A, and decreases toward the top of the furnace 11 . In the freeboard B, the fuel that has not been completely burned in the fluidized bed A is burned while coming into contact with the floating fluidized material. Silica sand was exemplified as the fluidizing material, but any material may be used as long as it functions as a medium for transferring heat to the fuel while maintaining a solid state without burning even in the high-temperature furnace 11 and flowing. Sand, stones such as limestone, and ash may also be used.

At the bottom of the furnace 11, a perforated plate (also called a dispersion plate) 121 is provided as a fluid permeable part made of a porous material that allows fluid including air to pass through. The air box 122, which is a space directly below the perforated plate 121, supplies pressurized air supplied from the first blower 71 as a blower via the first flow control valve 71A into the furnace 11 via the perforated plate 121. It constitutes a flowing fluid supply section (air supply section). The pressurized air supplied to the bottom of the furnace 11 by the wind box 122 fluidizes the fluid material to form the fluidized bed A and is used to burn the fuel in the fluidized bed A or the freeboard B.

In addition, a carbon-free fluid fuel such as ammonia or hydrogen or a carbon-free fuel is supplied from the wind box 122 through the perforated plate 121 into the furnace 11 together with pressurized air, and is burned in the fluidized bed A or the freeboard B. You may let Replacing some or all of conventional carbon-containing fuels, such as coal, biomass, sludge, and waste wood, with non-carbon-containing fuels can reduce greenhouse gas emissions in combustion equipment such as CFB boilers.

A second blower 72 provided in addition to the first blower 71 has a second flow rate of Pressurized air is supplied into the freeboard B through the control valve 72A. In FIG. 1, the perforated plate 121 is used as an example to describe the fluid permeable portion, but the fluid permeable portion may be anything as long as it can cause the fluid material to flow in the fluidized bed A. It may be formed from a number of plates with slits formed therein.

In order to circulate the fluidized material in the fluidized bed A, an external circulation mechanism 13 having a circulation path outside the furnace 11 is provided. The external circulation mechanism 13 includes an extraction tube 131 that communicates with the bottom of the furnace 11 and can extract a part of the fluidized material in the fluidized bed A, and controls the opening and closing of the extraction tube 131 to control the flow rate of the fluidized material, that is, the extraction tube. An on-off valve 132 capable of adjusting the amount of the fluidized material withdrawn by the extraction pipe 131, a fluidized material conveyor 133 such as a bucket conveyor that conveys upward the fluidized material extracted by the extraction pipe 131, and corresponding to the upper part of the fluidized bed A A fluid material silo 134 is provided on the outer periphery of the furnace 11 and receives the fluid material conveyed by the fluid material conveyer 133 , and a fluid material re-injection unit 135 reintroduces the fluid material stored in the fluid material silo 134 into the furnace 11 . Prepare.

The extraction pipe 131, the on-off valve 132, the fluid material conveyor 133, the fluid material silo 134, and the fluid material re-injection unit 135 constitute a fluid material circulation path that connects the bottom surface and the side surface of the furnace 11 outside the furnace 11. . That is, the fluid material extracted from the bottom surface of the furnace 11 by the extraction pipe 131 passes through the on-off valve 132, the fluid material conveyor 133, and the fluid material silo 134, and is discharged from the side surface of the furnace 11 by the fluid material re-injection unit 135. It is put into the fluidized bed A again.

The furnace wall, which is the side wall of the furnace 11, has a material supply unit 14 for supplying fuel and other materials into the furnace 11, and a fluid material supply unit 15 for supplying a fluid material for forming the fluidized bed A into the furnace 11. and a starting unit 16 for starting the CFB boiler. The material supply unit 14 includes a funnel-shaped hopper 141 that stores materials, a crushing unit 142 that crushes the material discharged from the bottom of the hopper 141 into granules, and supplies the material crushed by the crushing unit 142 into the furnace 11. It has a feeder 143 for feeding. Hereinafter, the material supply unit 14 will be described as supplying solid fuel or solid material, but may supply fluid fuel such as oil, ammonia, hydrogen, etc. in addition to or instead of the solid fuel.

The material supply unit 14 in the first combustion unit 1A supplies carbon-containing fuel containing carbon into the first furnace 11A. Carbon-containing fuels are not particularly limited, but examples thereof include various types of coal such as anthracite, bituminous coal, lignite, biomass, sludge, and waste wood. These carbon-containing fuels generate carbon dioxide when burned in the first furnace 11A. In order to reduce the amount of carbon dioxide generated in the first furnace 11A, the material supply unit 14 in the first combustion unit 1A adds a carbon-free fuel containing no carbon to the carbon-containing fuel and may be supplied.

The material supply unit 14 in the second combustion unit 1B supplies materials into the second furnace 11B that generate reactants capable of reacting with carbon dioxide by combustion. For example, when the material supply unit 14 in the second combustion unit 1B supplies cement or concrete containing calcium sulfate (CaSO ₄ ) as a material into the second furnace 11B, calcium oxide (CaO) is produced as a reactant by combustion of calcium sulfate. is generated in the second furnace 11B. For example, a chemical reaction represented by the formula “CaSO ₄ →CaO + SO ₃ ” occurs inside the second furnace 11B, and calcium sulfate is decomposed to produce calcium oxide and sulfur trioxide (SO ₃ ). As will be described later, calcium oxide produced in the second furnace 11B reacts with carbon dioxide produced in the first furnace 11A in the cleaning device 5 and is recovered as calcium carbonate (CaCO ₃ ) (CaO + CO ₂ → _CaCO3 ). Cement and concrete as materials to be supplied into the second furnace 11B can be inexpensively obtained from waste materials such as dismantled buildings. According to this embodiment, such waste materials can be effectively used to effectively recover carbon dioxide generated in the combustion apparatus.

　The aforementioned chemical reaction, in which calcium sulfate is decomposed to form calcium oxide, generally occurs at a temperature of about 1000°C or higher. As described above, since the combustion temperature in the first furnace 11A is about 900° C., the combustion temperature in the second furnace 11B needs to be higher than that. Alternatively, since the decomposition of calcium sulfate is a reduction reaction, the reduction can be achieved even at a temperature lower than about 1000° C. by creating a reducing environment in the second furnace 11B with a sufficiently lower oxygen concentration than in the first furnace 11A. A decomposition reaction can occur.

The material supply unit 14 in the second combustion unit 1B supplies, in addition to the material containing calcium sulfate, fuel for burning the material in the second furnace 11B into the second furnace 11B. Although the fuel is not particularly limited, for example, various types of coal such as anthracite, bituminous coal, lignite, etc., carbon-containing fuels such as biomass, sludge, and waste materials, ammonia , carbon-free fuels such as hydrogen. However, if carbon-containing fuel is used, the carbon dioxide generated by its combustion consumes calcium oxide generated by decomposition of calcium sulfate in the second furnace 11B, so carbon-free fuel is possible in the second combustion section 1B. It is preferable to use as much as possible.

The crushing section 142 in the material supply section 14 crushes the material into granules before being supplied to the furnace 11 . The size of the material suitable for transportation to the CFB boiler or hopper 141 and the size of the material suitable for combustion in the furnace 11 may differ, and the crushing section 142 crushes the material into particles having a particle size suitable for the latter. Smash. In addition, when the particle size suitable for each material is different, the pulverizing unit 142 may be provided for each material, or the particle size when pulverizing each material in order by one pulverizing unit 142 is changed for each material. may If there is no problem in supplying the material of particle size stored in the hopper 141 to the furnace 11 as it is, the pulverizing section 142 may not be provided. Here, the terms "particle", "granular", and "particle size" do not refer to specific sizes or dimensions, and any size or dimension may be used as long as the materials supplied into the furnace 11 perform their intended functions. do not have. For example, the terms "lump", "lump", and "lump diameter" used for relatively large particles, and the terms "powder", "powder", and "powder diameter" used for relatively small particles are used in the present embodiment. Included in "particle", "granular", and "particle size". A necessary amount of the granular material pulverized by the pulverizing unit 142 is fed into the furnace 11 by a feeder 143 whose rotational speed is controllable.

The fluid material supply unit 15 that supplies the fluid material for forming the fluidized bed A includes a funnel-shaped fluid material hopper 151 that stores the fluid material, and a fluid material discharged from the bottom of the fluid material hopper 151 into the furnace 11 . A fluid material feeder 152 is provided to supply to. By controlling the rotational speed of the fluid material feeder 152 , a required amount of fluid material is fed into the furnace 11 .

The starting unit 16 that starts the CFB boiler includes a starting fuel reservoir 161 , a starting fuel control valve 162 and a starting burner 163 . The starting fuel reservoir 161 stores heavy oil as carbon-containing fuel. The starting fuel control valve 162 controls the amount of heavy oil supplied from the starting fuel reservoir 161 to the starting burner 163 . Specifically, the starting fuel control valve 162 is opened when the CFB boiler is started, and supplies the heavy oil stored in the starting fuel reservoir 161 to the starting burner 163 . The starting burner 163 heats the fluidized material in the fluidized bed A with a flame generated by combustion of the heavy oil supplied from the starting fuel control valve 162 . Since the starting burner 163 is provided with a downward inclination, the surface of the fluidized bed A formed by the fluidized material is directly heated, and the temperature of the fluidized bed A and the inside of the furnace 11 is efficiently raised. Since the starting burner 163 heats the sand-like fluidized bed A from above in this way, it is also called a sand top burner.

After startup of the CFB boiler in which the fluidized bed A and the furnace 11 are sufficiently heated, specifically after the fuel or material supplied from the material supply unit 14 in the fluidized bed A can be burned (for example, sulfuric acid After the cement or concrete containing calcium is heated to about 1000° C. or higher), the starting fuel control valve 162 is closed to stop the supply of heavy oil to the starting burner 163 . In the subsequent normal operating state, the fuel supplied from the material supply section 14 is burned in the high-temperature furnace 11 . As described above, in the second furnace 11B heated to about 1000° C. or higher, calcium sulfate contained in cement or concrete is decomposed to produce calcium oxide.

The combustion section 1 of the CFB boiler has been described in detail above. Next, the configuration of the CFB boiler other than the combustion section 1 will be described. The steam generating unit 2 includes a drum 21 that stores water for generating steam, a water supply pipe 22 that supplies water to the drum 21, a water pipe 23 that guides the water in the drum 21 into the high-temperature furnace 11 to heat it, A steam pipe 24 is provided for discharging steam generated from water heated in the water pipe 23 from the drum 21 as the output of the CFB boiler. The water supply pipe 22 meanders in the heat transfer section 4 through which the high-temperature exhaust gas of the combustion section 1 passes to form an economizer that preheats the water supply, and the steam pipe 24 is a heat transfer section through which the high-temperature exhaust gas of the combustion section 1 passes. A superheater that superheats steam is configured by meandering inside 4 . Similarly, the pressurized air supplied into the furnace 11 by the first blower 71 and the second blower 72 is also preheated by the high-temperature exhaust gas inside the heat transfer section 4 .

The fluid material circulation unit 3 includes a cyclone 31 that separates and collects the granular fluid material from the exhaust discharged from the upper part of the furnace 11 and a seal pot 32 that returns the fluid material collected by the cyclone 31 into the furnace 11. Prepare. The cyclone 31 is a cyclone-type powder separator having a generally cylindrical upper portion and a generally conical lower portion, and generates an air flow spirally descending along the inner wall. The granular fluid material contained in the exhaust gas from the furnace 11 is collected by coming into contact with the inner wall of the cyclone 31 and dropping when spirally descending along the airflow.

A seal pot 32 provided below the cyclone 31 is filled with a fluid material to prevent backflow of unburned gas from the furnace 11 to the cyclone 31. The granular fluid material filled in the seal pot 32 is pushed out by the weight of the fluid material newly collected by the cyclone 31 and gradually returned into the furnace 11 .

The cleaning device 5 separates and collects soot and dust in the exhaust gas from the heat transfer unit 4, and reacts carbon dioxide produced in the first furnace 11A and calcium oxide produced in the second furnace 11B. and the product, calcium carbonate, is recovered. FIG. 2 schematically shows a configuration example for recovering carbon dioxide as calcium carbonate in the cleaning device 5. As shown in FIG. The cleaning device 5 as a reaction unit includes a container 51 containing an aqueous solution of calcium oxide. collected by settling to the bottom of the The container 51 has a first supply port 52 to which the exhaust gas containing calcium oxide from the second furnace 11B or a calcium hydroxide (Ca(OH) ₂ ) aqueous solution, which is an aqueous solution of calcium oxide in the exhaust gas, is supplied; A second supply port 53 is provided to which exhaust gas containing carbon dioxide from the first furnace 11A is supplied.

When the calcium oxide contained in the exhaust gas from the second furnace 11B dissolves in water, it becomes an aqueous solution of calcium hydroxide according to the chemical reaction formula "CaO+ _H2O →Ca(OH) ₂ ". Also, when calcium hydroxide comes into contact with carbon dioxide contained in the exhaust gas from the first furnace 11A, calcium carbonate is produced according to the chemical reaction formula "Ca(OH) ₂ +CO ₂ →CaCO ₃ +H ₂ O". Since calcium carbonate is almost insoluble in water, it precipitates in the aqueous solution and settles on the bottom of the container 51 . Thus, carbon dioxide contained in the exhaust gas from the first furnace 11A is recovered or removed in the cleaning device 5 in the form of calcium carbonate. Therefore, according to this embodiment, the amount of carbon dioxide in the exhaust discharged from the chimney 6 to the atmosphere can be reduced. In FIG. 2, the chemical reaction that produces calcium carbonate from calcium oxide and carbon dioxide takes place in an aqueous solution, that is, in the liquid phase, but a similar chemical reaction may take place in the gas phase. Specifically, the exhaust gas containing carbon dioxide from the first furnace 11A and the exhaust gas containing calcium oxide from the second furnace 11B are mixed in gaseous state, and carbonic acid is produced by the chemical reaction formula “CaO + CO ₂ →CaCO ₃ ”. Calcium may be generated or precipitated.

FIG. 3 shows a first modification of the combustion device of FIG. The second combustion section 1B shown on the left side of FIG. 3 and its associated configuration are the same as those in FIG. 1, and redundant description will be omitted. In addition, of the first combustion section 1A and associated components shown on the right side of FIG. 3, the description of the contents common to those in FIG. 1 will be omitted. A first combustion section 1A as a CFB boiler shown on the right side of FIG.

The first combustion section 1A generates electricity by oxygen-enriched combustion of fuel containing biomass, which is renewable energy. Biomass fuels, also called biofuels, are fuels in various forms such as solids, liquids, and gases that utilize the energy of living organisms such as animals and plants. Like fossil fuels such as coal and petroleum, biomass fuels generate carbon dioxide when they are burned, but in plant-derived biomass fuels, it can be viewed that the carbon dioxide that plants take in from the atmosphere is simply returned to the atmosphere. , is attracting attention as a carbon-neutral fuel with zero net carbon dioxide emissions. As will be described later in detail, in order to further reduce the amount of carbon dioxide discharged into the atmosphere, a carbon dioxide recirculation section 421 and a purification device 5 as a carbon dioxide recovery section are provided in association with the first combustion section 1A.

The carbon dioxide circulating unit 421 circulates at least part of the carbon dioxide generated by the combustion of biomass fuel or the like in the first furnace 11A to the first furnace 11A, thereby supplying from the oxygen supply unit 47 outside the first combustion unit 1A. Biomass fuel or the like is combusted in an oxygen-enriched manner together with the supplied oxygen. Oxygen-enriched combustion not only has high combustion efficiency, but also reduces the amount of nitrogen oxides, which are air pollutants, because the amount of nitrogen contained in normal air is greatly reduced. It can be increased to more than 90%. The cleaning device 5 can efficiently recover such high-concentration carbon dioxide in the form of calcium carbonate. Since the carbon dioxide recovered by the purification device 5 is not discharged into the atmosphere, the first combustion unit 1A and the combustion device as a whole emit negative emissions in which the net amount of carbon dioxide emissions is negative (the net amount of carbon dioxide recovered is positive). realizable.

The CFB boiler provided with the first combustion unit 1A supplies fuel such as biomass fuel and fossil fuel such as coal into the first furnace 11A in which the fluid material such as silica sand flows, and performs oxygen-enriched combustion. 1A, a steam generating section 2 that generates steam from water by heat generated in the first combustion section 1A, and a fluidized material circulation that collects the fluidized material that has come out of the first furnace 11A and returns it to the inside of the first furnace 11A. Exhaust gas containing oxygen supplied to the first combustion section 1A from the section 3 and an oxygen supply section 47 outside the first combustion section 1A and carbon dioxide recirculated to the first combustion section 1A, and supplied to the steam generation section 2 A heat transfer unit 4 that heats the steam generated in the water/steam generation unit 2 by the high-temperature exhaust gas from the first combustion unit 1A, separates and collects soot and dust in the exhaust gas from the heat transfer unit 4, and collects carbon dioxide. It is provided with a purifier 5 having a function of a carbon dioxide recovery section for recovering carbon, and a chimney 6 for discharging the purified exhaust after the carbon dioxide is recovered by the purifier 5 into the atmosphere.

At the bottom of the first furnace 11A, a perforated plate 121 made of a porous material that allows oxygen-enriched gas containing oxygen and carbon dioxide to permeate is provided. The wind box 122, which is a space directly below the perforated plate 121, receives oxygen-enriched gas as a flowing fluid supplied from the first blower 71 as a blower through the first flow control valve 71A through the perforated plate 121. It is supplied into the first furnace 11A. The oxygen-enriched gas is obtained by mixing exhaust gas containing carbon dioxide from the cleaning device 5 with oxygen from the oxygen supply 47 . The oxygen-enriched gas supplied to the bottom of the first furnace 11A by the wind box 122 fluidizes the fluidized material to form the fluidized bed A, and is used for oxygen-enriched combustion of the fuel in the fluidized bed A or the freeboard B. will be The oxygen supply unit 47 may be anything as long as it supplies oxygen to the first combustion unit 1A from the outside. Oxygen produced together with hydrogen is supplied to the first combustion section 1A in a water electrolysis facility that electrolyzes water with a large amount of electric power.

The second blower 72 provided in addition to the first blower 71 promotes oxygen-enriched combustion of the fuel in the freeboard B and suppresses the generation of harmful substances such as dioxin and carbon monoxide due to incomplete combustion. An oxygen-enriched gas obtained by mixing exhaust gas containing carbon dioxide from the cleaning device 5 and oxygen from the oxygen supply section 47 is supplied into the freeboard B through the second flow control valve 72A. In this way, the first blower 71 and the second blower 72 circulate at least part of the exhaust gas containing carbon dioxide generated by the combustion of biomass fuel or the like in the first furnace 11A from the cleaning device 5 to the first furnace 11A. A carbon dioxide circulation unit 421 is configured.

In addition, in order to promote oxygen-enriched combustion of the fuel supplied from the material supply unit 14 into the first furnace 11A, oxygen from the oxygen supply unit 47 is directly supplied to each part of the material supply unit 14, and The oxygen may be mixed and supplied into the first furnace 11A. In addition, in order to promote the oxygen-enriched combustion of the heavy oil as the starting fuel in the starting section 16, the oxygen from the oxygen supply section 47 is directly supplied to each part of the starting section 16, and the heavy oil and the oxygen are mixed. It may be supplied to the starting burner 163 .

The purification device 5, which also serves as a carbon dioxide recovery unit, separates and collects soot and dust in the exhaust gas from the heat transfer unit 4, and removes the high-concentration dioxide generated by the oxygen-enriched combustion in the first furnace 11A. Recover carbon. The cleaning device 5 is similar to that shown in FIG. A branch path for recirculating the carbon dioxide to the first furnace 11A via the carbon dioxide recirculation section 421 is further provided. Since the concentration of carbon dioxide in the exhaust is further increased by recirculating the exhaust to the first furnace 11A by the carbon dioxide recirculation unit 421, very high concentration carbon dioxide exceeding 90% is discharged from the second supply port 53. It is fed into container 51 .

The high-concentration carbon dioxide contained in the exhaust gas from the first furnace 11A reacts with calcium oxide or calcium hydroxide from the second furnace 11B and is recovered or removed in the cleaning device 5 in the form of calcium carbonate. Calcium carbonate separated and collected in this way can be used as an aggregate or a roadbed material when making building bricks or civil engineering blocks. Since the carbon dioxide recovered by the purifying device 5 is not discharged into the atmosphere through the chimney 6, the amount of carbon dioxide emitted from the combustion device can be reduced according to this embodiment. In particular, in this embodiment, by using a carbon-neutral biomass fuel or a carbon-free fuel such as ammonia or hydrogen that does not generate carbon dioxide when burned, the net carbon dioxide emissions in the combustion device are negative (net carbon dioxide It is possible to achieve negative emissions with a positive carbon recovery amount.

FIG. 4 shows a second modification of the combustion device of FIG. In this modification, in order to reduce the amount of carbon dioxide generated in the furnace 11, the material supply unit 14 supplies a hydrogen storage material such as a hydrogen storage alloy into the furnace 11 in addition to the carbon-containing fuel. In the fluidized bed A in the furnace 11 , powdery, particulate, or lumpy fluid materials such as silica sand and hydrogen-absorbing alloys are fluidized by air supplied from the bottom of the furnace 11 as a fluid fluid. Solid fuel such as coal, biomass, and waste cement charged into the fluidized bed A or hydrogen released from the hydrogen storage alloy charged into the fluidized bed A is heated to a high temperature so as to be stirred in the fluidized bed A. Efficient combustion is achieved by repeated contact with fluid materials and air.

Since the hydrogen storage material such as the hydrogen storage alloy that supports hydrogen as fuel also functions as a fluid material, a sufficient amount of the hydrogen storage material for realizing the function of the fluidized bed A is supplied to the furnace 11. If so, it is not necessary to supply other fluid materials such as silica sand to the furnace 11 . As described above, with the hydrogen storage material such as the hydrogen storage alloy, the fuel (hydrogen) and fluid material (hydrogen storage material before and after hydrogen release) can be supplied to the furnace 11 at once.

The material supply unit 14 supplies a hydrogen storage material such as a hydrogen storage alloy as a carbon-free fuel that does not contain carbon into the furnace 11 in addition to the carbon-containing fuel. The hydrogen storage material is a material capable of releasing stored hydrogen when heated, and is exemplified by a hydrogen storage alloy. Hydrogen Storage Alloy, Hydrogen Absorbing Alloy, Metal Hydride is an alloy that reacts with hydrogen to store or absorb hydrogen in the form of a metal hydride compound and releases hydrogen when heated. AB2 type (based on alloys of transition elements such as titanium, manganese, zirconium, nickel, etc.), AB5 type such as LaNi ₅ , ReNi ₅ (one rare earth element, niobium, alloys containing transition elements such as cobalt and aluminum), Ti-Fe (titanium-iron) type, V (vanadium) type, Mg (magnesium) type, Pd (palladium) type, Ca (calcium) type etc. are known.

Among these hydrogen storage alloys, the Ti-Fe type, which is available at a relatively low cost, needs to be placed in a high temperature environment of about 450 ° C in order to efficiently store or release hydrogen, and it is popular because of its complexity. was not progressing. On the other hand, in this embodiment, the furnace 11, which reaches a high temperature of about 900° C. during normal operation (in order to suppress the generation of harmful substances such as dioxin and carbon monoxide due to incomplete combustion, the freeboard B is also installed in the furnace 11). The hydrogen-absorbing alloy can be naturally heated by heating, and the hydrogen-absorbing alloy can be naturally heated. Thus, hydrogen storage alloys or hydrogen as carbon-free fuels can replace some of the traditional carbon-containing fuels such as coal, biomass, sludge, waste wood, etc. with clean fuels with low greenhouse gas emissions.

Note that the hydrogen storage material is not limited to hydrogen storage alloys, and any material that can release stored hydrogen when heated may be used. For example, the organic macromolecules or organic polymers capable of storing hydrogen disclosed in WO2015/005280 may also be used as the hydrogen storage material in this embodiment.

As described above, the hydrogen storage alloy supplied by the material supply unit 14 also functions as a fluidized material. The fluid material supply unit 15 for supplying other fluid material such as silica sand to the furnace 11 may not be provided.

After starting the CFB boiler in which the fluidized bed A and the inside of the furnace 11 are sufficiently heated by the starting unit 16, specifically, after the fuel or material supplied from the material supply unit 14 in the fluidized bed A becomes combustible (For example, in the case of a Ti--Fe type hydrogen storage alloy, after the temperature rises to about 450.degree. In the subsequent normal operating state, the fuel supplied from the material supply unit 14 (including hydrogen released by the hydrogen storage material) is burned in the high-temperature furnace 11 . In addition, the hydrogen storage material after releasing hydrogen as fuel flows in the furnace 11 and functions as a fluid material that mediates the combustion of the fuel. is collected by the collection unit 17 provided in the circulation route.

The recovery unit 17 that recovers the hydrogen storage material from the bottom of the furnace 11 includes a separation unit 171 that separates and recovers excess hydrogen storage material from the fluid material circulating through the external circulation mechanism 13 . The separation unit 171 can separate substances having desired properties by using differences in mechanical or dynamic properties such as mass, density, particle size, shape, etc., and physical properties such as magnetism. For example, even if the fluid material circulating in the external circulation mechanism 13 contains a fluid material other than a hydrogen-absorbing alloy such as silica sand, or ash or soot generated by combustion in the furnace 11, hydrogen Only the storage alloy can be efficiently separated and recovered. In particular, in the case of a magnetic hydrogen storage alloy such as a Ti—Fe type, the magnetic separator 1711 can efficiently separate and recover only the magnetic hydrogen storage alloy by magnetism. In addition, even when the fluid material circulating in the external circulation mechanism 13 contains hydrogen storage alloys with different particle sizes, only the hydrogen storage alloys with a desired particle size range can be efficiently separated and recovered. . The hydrogen-absorbing alloy separated and recovered after releasing hydrogen in this manner is transported to a hydrogen filling facility (not shown) and refilled with hydrogen, and then re-charged into the hopper 141 of the material supply unit 14 to be used as hydrogen fuel. reused.

According to the above configuration, the CFB boiler can be efficiently operated by introducing the hydrogen storage material that functions as a hydrogen fuel source and fluid material into the furnace 11, and the existing carbon-containing fuel can be replaced with hydrogen fuel. Emission of effect gas can be reduced.

The fluidizing material circulation unit 3 includes a cyclone 31 that separates and collects the fluidizing material containing the granular hydrogen-absorbing alloy from the exhaust gas discharged from the upper part of the furnace 11 , and the fluidizing material collected by the cyclone 31 is passed through the furnace 11 . It has a seal pot 32 that returns to the Fluid materials such as granular hydrogen-absorbing alloys contained in the exhaust gas from the furnace 11 are collected by coming into contact with the inner wall of the cyclone 31 and falling down while descending spirally along the airflow. The fluid material such as granular hydrogen-absorbing alloy filled in the seal pot 32 is gradually returned into the furnace 11 in the form of being pushed out by the weight of the fluid material newly collected by the cyclone 31 .

FIG. 5 shows the overall configuration of a combustion apparatus in which the first combustion section is configured with a rotary kiln 100 and the second combustion section 1B is configured with a CFB boiler. Since the second combustion section 1B is the same as that shown in FIG. 1, the description thereof is omitted. The rotary kiln 100 includes a rotary kiln 200 and a secondary combustion chamber 300 as first combustion chambers, a communication chute (connecting portion) 400, and an electric furnace 600 as a recovery portion. The rotary kiln 100 is a combustion apparatus that separates a metal-containing workpiece W into slag and metal by means of a rotary furnace 200 or an electric furnace 600 and recovers the metal. The objects to be processed W containing metal are, for example, substrates of electronic devices, electric wire scraps, and copper, gold and silver slag. The rotary kiln 100 can recover metals such as Cu (copper), Au (gold), Ag (silver), Pb (lead), Sn (tin), and Pd (palladium) from these workpieces W to be processed. As will be described later, when a hydrogen storage alloy (hydrogen storage material H) as a hydrogen fuel source is put into the rotary kiln 100 in addition to the workpiece W, the hydrogen storage alloy can be separated and recovered together with the metal.

A rotary furnace 200 that burns and melts the object W to be processed is formed in a cylindrical shape, and the inner wall is lined with a refractory material. The workpiece W charged into the rotary furnace 200 is burned or melted at about 1400-1500° C. by hot air from the burner 10 . Fuel oil as a carbon-containing fuel is supplied to the burner 10 together with air from the fuel supply unit. Since it can be used as fuel, the amount of fuel oil that generates greenhouse gases can be reduced.

The rotary furnace 200 during combustion treatment is rotationally driven around a cylindrical shaft, and while stirring the object W to be treated and the hydrogen storage material H inside, hydrogen released from the hydrogen storage material H stirs the object W to be treated. Burn efficiently. Since the rotating shaft of the rotary furnace 200 is inclined downward, the material to be processed W flows from the high-side inlet 2a to the low-side outlet 2b together with the hydrogen storage material H while being burned. On the side of the inlet 2a of the rotary furnace 200, there is a charging chute 7 for charging the workpiece W and the hydrogen storage material H, and a loading chute 7 for pushing the charged workpiece W and the hydrogen storage material H into the rotary furnace 200. A pusher 8 is provided.

Within the rotary furnace 200, the burned material W to be processed and the melted hydrogen storage material H (hydrogen storage alloy) are separated into slag S and metal M1 due to the difference in specific gravity. In addition, combustible substances in the object to be processed W are thermally decomposed into gas. The metal M1 (including the hydrogen storage alloy) separated from the object to be processed W and the hydrogen storage material H is in a molten or semi-molten state and accumulates on the lower layer side. be. The peripheral wall 2c forming the bottom (lower part in FIG. 5) of the cylindrical rotary furnace 200 whose axial direction is substantially horizontal is covered with the molten metal M1 (including the hydrogen storage alloy) accumulated at the bottom of the rotary furnace 200. A tapping nozzle (exhaust port) 9 is provided as a collecting portion capable of downwardly discharging the .

The tapping nozzle 9 is kept closed while the rotary furnace 200 rotates and burns or melts the workpiece W and the hydrogen storage material H. By opening the tapping nozzle 9 after the workpiece W and the hydrogen storage material H are completely burned or melted and the rotary furnace 200 stops rotating, The accumulated metal M1 can be separated and recovered from the tapping nozzle 9. - 特許庁The metal M1 and slag S that have not been separated and recovered by the tapping nozzle 9 are thrown into the electric furnace 600 from the bottom of the secondary combustion chamber 300 .

The secondary combustion chamber 300 connected to the outlet 2b at the right end of the rotary furnace 200 further burns the gas generated in the rotary furnace 200 to decompose dioxins and malodorous substances and supply them to the exhaust gas treatment equipment. In the secondary combustion chamber 300, a burner 110 for secondary combustion is provided near the outlet 2b of the rotary furnace 200, and a supply unit and a stirring blower for supplying urea, air, and SCC temperature-controlled water are provided above the burner 110. Fuel oil as a carbon-containing fuel is supplied to the burner 110 from the fuel supply unit together with air. Since the object W to be processed and the gas can be effectively burned in the second combustion, the amount of fuel oil used in the burner 110 for secondary combustion can be reduced.

A communication chute 400 extending downward from the connection between the rotary furnace 200 and the secondary combustion chamber 300 is a communication passage that connects the rotary furnace 200 and the electric furnace 600 . The wall of the communication chute 400 is provided at a position where the slag S discharged from the outlet 2b of the rotary furnace 200 does not contact. Therefore, the slag S discharged from the outlet 2b of the rotary furnace 200 drops without coming into contact with the wall of the communication chute 400 and is thrown into the electric furnace 600. As shown in FIG. On the other hand, an emergency burner 120 is provided to melt the slag S in case it adheres to the walls of the connecting chute 400 .

The electric furnace 600 is connected to the rotary furnace 200 via a communication chute 400, and heats the metal containing the hydrogen storage alloy from the melted material W and the hydrogen storage material H put into the rotary furnace 200 by electrical heat treatment. separate. Specifically, the electric furnace 600 can recover the metal containing the hydrogen-absorbing alloy remaining in the slag S separated in the rotary furnace 200 . An electric furnace 600 configured as an electric resistance heating furnace includes a tank 20 in which a molten material is retained to separate a metal M2 containing a hydrogen-absorbing alloy from the slag S, and

electrodes

21A, 21B, and 21C for electrically heating the slag S. Prepare. In the bath 20 heated by the

electrodes

21A, 21B, 21C, a layer of metal M2 containing a molten hydrogen-absorbing alloy is formed on the lower side and a layer of molten slag S is formed on the upper side.

The electric furnace 600 is provided with a coke supply device 22A, which supplies coke as a reducing agent into the tank 20 through a supply line 22B. The slag S that has undergone combustion treatment, that is, oxidation treatment, in the rotary furnace 200 contains metal oxides, but the metal oxides can be recovered by being reduced to metal M2 by the reducing action of coke. In addition to coke, coal, waste carbon, or the like may be used as the reducing agent. By maintaining the bath 20 of the electric furnace 600 as described above at about 1400-1500° C. similar to that of the rotary furnace 200 by means of the

electrodes

21A, 21B, and 21C, the slag S is retained for about 3-6 hours. Almost all metal components can be recovered as metal M2 (including hydrogen storage alloy). Specifically, the metal M2 containing the hydrogen-absorbing alloy is discharged from the metal recovery line 230 connected to the lower part of the tank 20, and the slag S not containing the metal M2 is discharged from the slag recovery line 240 connected to the upper part of the tank 20. Ejected.

According to the above configuration, by putting the hydrogen storage material H functioning as a hydrogen fuel source into the rotary kiln 200, the combustion efficiency in the rotary kiln 100 can be improved, and the existing fuel oil as a carbon-containing fuel can be replaced with hydrogen fuel. This can reduce greenhouse gas emissions.

On the other hand, since the

burners

10, 110, 120 burn fuel oil as a carbon-containing fuel, the generation of carbon dioxide in the rotary furnace 200 as the first combustion chamber and the secondary combustion chamber 300 cannot be completely eliminated. Carbon dioxide is also produced when the object W to be burned contains carbon. Therefore, as in FIG. 1, carbon dioxide produced in the rotary kiln 100 is recovered or removed as calcium carbonate by calcium oxide produced in the second furnace 11B of the second combustion section 1B. Specifically, calcium oxide produced in the second furnace 11B or an aqueous calcium hydroxide solution, which is an aqueous solution thereof, is supplied to an exhaust gas treatment facility for treating exhaust gas containing carbon dioxide from the rotary kiln 100 . In the exhaust gas treatment facility, a carbon dioxide removal device similar to that shown in FIG. 2 is used to react calcium oxide or calcium hydroxide with carbon dioxide to remove carbon dioxide in the form of calcium carbonate. The exhaust gas containing calcium oxide from the second furnace 11B may be supplied above the secondary combustion chamber 300 together with urea, air, SCC temperature-controlled water, etc., instead of supplying the exhaust gas to the exhaust gas treatment facility.

The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that the embodiments are examples, and that various modifications can be made to combinations of each component and each treatment process, and such modifications are also within the scope of the present invention.

Although a CFB boiler has been described as an example of a boiler in the embodiments, the present invention can also be applied to a BFB boiler (a bubbling fluidized bed boiler). The configuration of the BFB boiler is the same as that of the CFB boiler except that it does not include the fluid material circulation unit 3 that collects the fluid material that has flowed out of the furnace 11 and returns it to the inside of the furnace 11 .

In the embodiment, calcium sulfate was exemplified as a material that burns in the second furnace 11B, but any material that produces a reactant that can react with carbon dioxide produced in the first furnace 11A can be burned in the second furnace 11B. Similarly, the reactant that reacts with carbon dioxide is not limited to calcium oxide or calcium hydroxide in the exemplary embodiment, nor is the product produced by the reaction of the reactant and carbon dioxide limited to calcium carbonate.

In the embodiment, the first furnace 11A that produces carbon dioxide and the second furnace 11B that produces reactants are configured as separate combustion chambers. good. In this case, the first combustion chamber and the second combustion chamber are the same combustion chamber. In addition, since carbon dioxide and a reactant are generated in the same combustion chamber, a reaction section for removing carbon dioxide by reacting the two can be provided in or near the combustion chamber.

Note that the functional configuration of each device described in the embodiments can be realized by hardware resources or software resources, or by cooperation between hardware resources and software resources. Processors, ROMs, RAMs, and other LSIs can be used as hardware resources. Programs such as operating systems and applications can be used as software resources.

The present invention relates to a combustion device that generates combustion.

1A first combustion section, 1B second combustion section, 5 cleaning device, 11A first furnace, 11B second furnace, 14 material supply section, 51 container, 52 first supply port, 53 second supply port, 100 rotary kiln, 142 pulverizing section, 200 rotary furnace, 300 secondary combustion chamber.

Claims

a first combustion chamber for burning a carbon-containing fuel containing carbon;
a second combustion chamber for burning a material that upon combustion produces a reactant capable of reacting with carbon dioxide;
a reaction unit for reacting the carbon dioxide produced in the first combustion chamber and the reactant produced in the second combustion chamber;
Combustion device comprising
the reactant is calcium oxide;
Calcium carbonate is produced by the reaction in the reaction section.
Combustion device according to claim 1 .
The combustion device according to claim 2, wherein said material comprises calcium sulfate.
The combustion device according to claim 3, wherein said material is cement.
The combustion apparatus according to any one of claims 1 to 4, further comprising a pulverizing section for pulverizing the material before being supplied to the second combustion chamber.
5. The reaction unit according to any one of claims 1 to 4, wherein the reaction unit includes a container that stores an aqueous solution of the reactant, and carbon dioxide generated in the first combustion chamber is passed through the aqueous solution to precipitate a product. combustion device.
The combustion apparatus according to any one of claims 1 to 4, wherein the combustion temperature in said second combustion chamber is higher than the combustion temperature in said first combustion chamber.
The combustion device according to any one of claims 1 to 4, wherein the oxygen concentration in the second combustion chamber is lower than the oxygen concentration in the first combustion chamber.
The combustion apparatus according to any one of claims 1 to 4, wherein the combustion apparatus is at least one of a circulating fluidized bed boiler, a bubbling fluidized bed boiler, and a rotary kiln.
a first combustion step of burning a carbon-containing fuel containing carbon;
a second combustion step of burning a material that upon combustion produces a reactant capable of reacting with carbon dioxide;
a reaction step of reacting the carbon dioxide produced in the first combustion step with the reactant produced in the second combustion step;
Combustion method comprising: