Cement clinker manufacturing system and cement clinker manufacturing method

Abstract

The present invention provides a cement clinker manufacturing system capable of increasing the carbon dioxide concentration for a portion of exhaust gas to obtain a gas containing high concentration of carbon dioxide. The cement clinker manufacturing system (1) comprises: a cyclone preheater (2) for preheating cement clinker raw materials; a rotary kiln (3) for firing the preheated cement clinker raw materials to obtain cement clinker; a calcining furnace (4) for promoting decarbonization of the cement clinker raw materials; a clinker cooler (5) for cooling the cement clinker; and a kiln exhaust gas discharge path (6a-6e) for discharging exhaust gas generated in the rotary kiln (3), wherein the manufacturing system comprises: a combustion-supporting gas supply device for supplying a combustion-supporting gas having an increased oxygen concentration compared to air; a combustion-supporting gas supply path (8) for introducing the combustion-supporting gas into the calcining furnace; and a calcining furnace exhaust gas discharge path (9) (wherein it is limited to the calcining furnace exhaust gas discharge path (9) that is different from the kiln exhaust gas discharge path (6)) for discharging exhaust gas generated in the calcining furnace (4).

Description

Technical Field

[0001] This invention relates to a cement clinker manufacturing system and a cement clinker manufacturing method. Background Technology

[0002] In recent years, reducing carbon dioxide emissions has become an important issue in order to curb global warming. On the other hand, the cement industry is one of the industries with the largest carbon dioxide emissions.

[0003] Of the total amount of carbon dioxide (gaseous carbon dioxide) emitted during cement manufacturing, approximately 60% is emitted through the decarbonation of limestone used as a raw material for cement, and approximately 40% is emitted through the combustion of fuels used in the manufacturing process.

[0004] Methods for reducing carbon dioxide emissions from fuel combustion include improving energy efficiency and using biomass fuels. For example, Patent Document 1 describes a cement kiln apparatus capable of reducing the amount of carbon dioxide generated by fuel combustion, characterized by having a main burner that blows combustible gas, the main fuel, and combustible waste, the auxiliary fuel, into the cement kiln.

[0005] On the other hand, as a raw material for cement, it is difficult to reduce the amount of carbon dioxide produced by decarbonation of limestone because it is difficult to replace limestone, which produces a lot of carbon dioxide, with calcium-containing raw materials that produce less carbon dioxide.

[0006] As a method to reduce carbon dioxide emissions, there are known methods for separating, recovering, storing, isolating, or effectively utilizing the generated carbon dioxide.

[0007] As a method for separating and recovering generated carbon dioxide, for example, Patent Document 2 describes a method for separating and recovering carbon dioxide from by-product gas generated by a steel plant through chemical absorption. The method is characterized by utilizing or making use of low-grade exhaust heat below 500°C generated by the steel plant in the process of absorbing carbon dioxide from the gas using a chemical absorption liquid and then heating the chemical absorption liquid to separate carbon dioxide.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2018-52746

[0011] Patent Document 2: Japanese Patent Application Publication No. 2004-292298 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] In addition to carbon dioxide, the waste gas generated during the production of cement clinker also contains large amounts of nitrogen and oxygen. Therefore, in order to separate and recover carbon dioxide from the waste gas, chemical absorption methods based on amine compounds are required.

[0014] If the concentration of carbon dioxide in the aforementioned waste gas can be increased, the separation and recovery of carbon dioxide becomes easier. Furthermore, by reducing the amount of nitrogen and other substances in the waste gas, the volume of the generated waste gas can be relatively reduced, and the equipment used for separating and recovering carbon dioxide can be made smaller.

[0015] The object of the present invention is to provide: a cement clinker manufacturing system that can increase the carbon dioxide concentration of a portion of the waste gas during the manufacture of cement clinker to obtain a gas containing a high concentration of carbon dioxide that is easy to use for carbon dioxide immobilization and methane generation; a cement clinker manufacturing system that can effectively generate methane using the aforementioned carbon dioxide; or a cement clinker manufacturing system that can reduce the amount of waste gas emitted.

[0016] Methods for solving problems

[0017] To address the aforementioned issues, the inventors conducted in-depth research and discovered that the above objectives can be achieved using the following cement clinker manufacturing system, thus completing this invention. This manufacturing system comprises: a cyclone preheating device for preheating cement clinker raw materials; a rotary kiln for calcining the preheated cement clinker raw materials to obtain cement clinker; a calcining furnace located upstream of the rotary kiln for promoting decarbonation of the cement clinker raw materials; a clinker cooler located downstream of the rotary kiln for cooling the cement clinker; and a kiln exhaust gas discharge path for discharging exhaust gas generated in the rotary kiln after passing through the cyclone preheating device. The manufacturing system further comprises: a combustion gas supply device for supplying a combustion gas with a higher oxygen concentration than air; a combustion gas supply path for introducing the combustion gas into the calcining furnace; and a calcining furnace exhaust gas discharge path for discharging exhaust gas generated in the calcining furnace (limited to a calcining furnace exhaust gas discharge path different from the kiln exhaust gas discharge path).

[0018] That is, the present invention provides the following [1] to

[16] .

[0019] [1] A cement clinker manufacturing system, comprising: a cyclone preheating device for preheating cement clinker raw materials; a rotary kiln for calcining the cement clinker raw materials preheated by the cyclone preheating device to obtain cement clinker; a calcining furnace, disposed upstream of the rotary kiln together with the cyclone preheating device, for promoting decarbonation of the cement clinker raw materials; a clinker cooler, disposed downstream of the rotary kiln, for cooling the cement clinker; and a kiln exhaust gas discharge path for discharging the cement clinker raw materials into the kiln exhaust gas discharge path. The waste gas generated in the rotary kiln is discharged after passing through the aforementioned cyclone preheating device. The manufacturing system is characterized by comprising: a combustion gas supply device for supplying a combustion gas with a higher oxygen concentration than air; a combustion gas supply path for introducing the combustion gas from the combustion gas supply device into the calcining furnace; and a calcining furnace waste gas discharge path for discharging the carbon dioxide-containing waste gas generated in the calcining furnace (limited to a calcining furnace waste gas discharge path different from the aforementioned kiln waste gas discharge path).

[0020] [2] The cement clinker manufacturing system described in [1] above includes a chlorine bypass device for extracting and cooling a portion of the waste gas generated in the rotary kiln without passing through the cyclone preheating device, removing solid components, discharging the waste gas with the solid components removed, and classifying the solid components into coarse powder and fine powder, using the coarse powder as part of the raw material for the cement clinker, and recovering the fine powder.

[0021] [3] The cement clinker manufacturing system as described in [1] or [2] above, wherein a confluence flow path is included for merging a portion of the carbon dioxide-containing waste gas flowing in the calciner exhaust gas discharge path with the combustion-supporting gas flowing in the combustion-supporting gas supply path.

[0022] [4] The cement clinker manufacturing system as described in [1] or [2] above, comprising: a preheating raw material supply path for supplying preheated cement clinker raw materials to the calcining furnace via the cyclone preheating device; a first recovery means disposed midway in the calcining furnace exhaust gas path for recovering raw materials containing quicklime from the exhaust gas containing carbon dioxide; and a calcining furnace exhaust gas supply path connected to the calcining furnace exhaust gas path midway in the calcining furnace exhaust gas path and downstream of the first recovery means, and for supplying raw materials containing quicklime via the calcining furnace exhaust gas path. A portion of the carbon dioxide-containing waste gas flowing in the exhaust gas discharge path merges with the combustion-supporting gas flowing in the combustion-supporting gas supply path. The cyclone preheating device consists of two or more cyclone heat exchangers. The calcining furnace includes a heating means for promoting the decarbonation of the cement clinker raw materials. The combustion-supporting gas supply path is used to allow the carbon dioxide-containing waste gas flowing in the calcining furnace exhaust gas discharge path to exchange heat with the combustion-supporting gas at a position midway through the calcining furnace exhaust gas discharge path and upstream of the first recovery means.

[0023] [5] The cement clinker manufacturing system as described in [4] above includes a fuel conveying gas supply path, which branches off from at least one of the locations of the combustion-supporting gas supply path where the portion of the exhaust gas containing carbon dioxide exchanges heat with the combustion-supporting gas is closer to the combustion-supporting gas supply device and the middle of the calciner exhaust gas supply path, for supplying fuel conveying gas to the heating means of the calciner.

[0024] [6] The cement clinker manufacturing system as described in [4] or [5] above includes an air supply path for introducing air from the clinker cooler into the kiln exhaust path.

[0025] [7] The cement clinker manufacturing system as described in any one of [4] to [6] above, wherein the preheating raw material supply path is connected to one of the two or more cyclone heat exchangers constituting the cyclone preheating device, which is located at the second or moreth position from the downstream side. The manufacturing system includes: a raw material supply path containing quicklime for supplying the raw material containing quicklime recovered by the first recovery means from the first recovery means to one of the two or more cyclone heat exchangers connected to the preheating raw material supply path, or a cyclone heat exchanger located upstream of the cyclone heat exchanger; and a first decarbonating raw material supply path for supplying the cement clinker raw material that has been decarbonated by the calciner from the calciner to the... A rotary kiln; a second decarbonation feedstock supply path for supplying a portion of the decarbonated cement clinker feedstock from the first decarbonation feedstock supply path to the most downstream cyclone heat exchanger among the two or more cyclone heat exchangers; a temperature measuring device for measuring the temperature of the exhaust gas in the kiln exhaust path as it passes through the cyclone heat exchanger connected to the preheating feedstock supply path; and a decarbonation feedstock supply quantity control device for adjusting the amount of decarbonated cement clinker feedstock supplied from the second decarbonation feedstock supply path to the most downstream cyclone heat exchanger based on the temperature measured by the temperature measuring device, thereby adjusting the temperature within the cyclone heat exchanger connected to the preheating feedstock supply path.

[0026] [8] The cement clinker manufacturing system as described in [7] above includes a water supply device for supplying water or water-containing waste to the waste gas flowing in the kiln waste gas discharge path between the portion connected to the rotary kiln and the upstream portion of the cyclone heat exchanger located at the downstream side.

[0027] [9] The cement clinker manufacturing system as described in [7] or [8] above, wherein a denitrification agent supply device is included for supplying denitrification agent to the waste gas flowing in the kiln waste gas discharge path between the portion connected to the rotary kiln and the upstream portion of the cyclone heat exchanger located at the downstream side.

[0028]

[10] The cement clinker manufacturing system as described in any one of [1] to [3] above comprises: a mixing device for mixing the waste gas containing carbon dioxide with hydrogen to prepare a mixed gas of the waste gas containing carbon dioxide and hydrogen, and adjusting the temperature of the mixed gas; a hydrogen supply device for supplying the hydrogen; a hydrogen supply path for introducing the hydrogen from the hydrogen supply device to the mixing device; a methane generating device for reacting the carbon dioxide contained in the mixed gas with hydrogen using a catalyst to generate methane and water vapor; and a mixed gas supply path for introducing the mixed gas from the mixing device to the methane generating device, and a calciner waste gas discharge path for introducing the waste gas containing carbon dioxide from the calciner to the mixing device.

[0029]

[11] The cement clinker manufacturing system as described in

[10] above includes a methane supply path for supplying methane-containing gas generated by the methane generating device to the calcining furnace.

[0030]

[12] The cement clinker manufacturing system as described in

[10] or

[11] above, wherein the combustion-supporting gas supply device and the hydrogen supply device are water electrolysis devices for electrolyzing water to obtain hydrogen and oxygen.

[0031]

[13] A method for manufacturing cement clinker, which is a method for manufacturing cement clinker using any one of the cement clinker manufacturing systems described in any one of [1] to [9] above, characterized in that the above-mentioned waste gas containing carbon dioxide is recovered and the carbon dioxide in the above-mentioned waste gas containing carbon dioxide is utilized.

[0032]

[14] The cement clinker manufacturing method described in

[13] above, wherein the oxygen concentration of the combustion-supporting gas is adjusted so that the carbon dioxide concentration of the exhaust gas containing carbon dioxide is 80% or more of 100% of volume excluding water vapor.

[0033]

[15] The cement clinker manufacturing method described in

[13] or

[14] above, wherein methane is generated from hydrogen and carbon dioxide in the recovered waste gas containing carbon dioxide using a catalyst, and the generated methane is used as fuel for at least one of the rotary kiln and the calcining furnace.

[0034]

[16] The cement clinker manufacturing method as described in any one of

[13] to

[15] above, wherein the recovered waste gas containing carbon dioxide is brought into contact with calcium-containing waste, and the carbon dioxide contained in the waste gas containing carbon dioxide is absorbed by the calcium-containing waste, and the calcium-containing waste that has absorbed the carbon dioxide is used as a raw material for cement clinker.

[0035] Invention Effects

[0036] According to the cement clinker manufacturing system of the present invention, during the manufacturing of cement clinker, a portion of the waste gas can be increased to obtain a gas containing a high concentration of carbon dioxide that is easily used for carbon dioxide immobilization and methane generation.

[0037] Furthermore, the cement clinker manufacturing system according to the present invention can efficiently generate methane using the aforementioned carbon dioxide.

[0038] Furthermore, the cement clinker manufacturing system according to the present invention can reduce the amount of waste gas emissions. Attached Figure Description

[0039] Figure 1 This is a schematic diagram illustrating an example of the cement clinker manufacturing system of the present invention.

[0040] Figure 2 This is a schematic diagram illustrating an example of the cement clinker manufacturing system of the present invention.

[0041] Figure 3 This is a schematic diagram illustrating an example of the cement clinker manufacturing system of the present invention. Detailed Implementation

[0042] Figures 1-3 Each embodiment of the cement clinker manufacturing system of the present invention is illustrated schematically.

[0043] The following is for reference Figures 1-3 The cement clinker manufacturing system of the present invention will be described in detail.

[0044] Figure 1 The cement clinker manufacturing system 1 includes: a cyclone preheating device 2 for preheating cement clinker raw materials; a rotary kiln 3 for calcining the cement clinker raw materials preheated by the cyclone preheating device 2 to obtain cement clinker; a calcining furnace 4 arranged upstream of the rotary kiln 3 together with the cyclone preheating device 2 for promoting decarbonation of the cement clinker raw materials; a clinker cooler 5 arranged downstream of the rotary kiln 3 for cooling the cement clinker; and waste gas generated in the rotary kiln 3 (hereinafter sometimes referred to as...) The manufacturing system includes: a combustion gas supply device 7 for supplying combustion gas with a higher oxygen concentration than air; a combustion gas supply path 8 for introducing combustion gas from the combustion gas supply device into the calcining furnace 4; and a calcining furnace exhaust gas discharge path 9 (which is different from the kiln exhaust gas discharge path 6) for discharging the exhaust gas containing carbon dioxide generated in the calcining furnace 4.

[0045] The cyclone preheating device 2 is formed by a plurality of (two or more) cyclone heat exchangers 2a to 2d. The plurality of cyclone heat exchangers 2a to 2d are connected by a flow path for moving cement clinker raw materials and a kiln exhaust gas discharge path 6a to 6e for discharging the exhaust gas generated by the rotary kiln 3 after passing through the plurality of cyclone heat exchangers 2a to 2d. It should be noted that the kiln exhaust gas discharge path 6a to 6e can also serve as a flow path for moving cement clinker raw materials. The number of cyclone heat exchangers is not particularly limited, but is typically two or more, usually four to five. Furthermore, the plurality of cyclone heat exchangers are usually arranged in a vertical direction.

[0046] Cement clinker raw material is fed into the cyclone heat exchanger 2a located at the upstream end of the cyclone preheating device 2. Within the cyclone heat exchanger 2a, it undergoes both heat exchange and centrifugal separation with the kiln exhaust gas. After being fed from the lower part of the cyclone heat exchanger 2a into the downstream cyclone heat exchanger 2b, it again undergoes both heat exchange and centrifugal separation with the aforementioned exhaust gas, and is further fed into the downstream cyclone heat exchanger 2c. In this way, the cement clinker raw material is preheated (heated) by the aforementioned exhaust gas while sequentially moving to the downstream cyclone heat exchangers 2b-2c. The preheated cement clinker raw material is then fed (supplied) from the cyclone preheating device 2 into the calcining furnace 4 via the preheated raw material supply path 12 for supplying to the calcining furnace 4.

[0047] In the cyclone preheating device 2, by preheating the cement clinker raw materials, the amount of fuel required to promote decarbonation in the calciner 4 can be reduced.

[0048] Within the cyclone preheating device 2, the cement clinker raw materials are preheated to a preferred temperature of 400–900°C, more preferably 500–850°C, further preferably 550–800°C, and particularly preferably 600–750°C. If the temperature is 400°C or higher, the amount of fuel required to promote decarbonation in the calciner can be reduced. If the temperature is below 900°C, decarbonation of the cement clinker raw materials is not easily promoted within the cyclone preheating device 2, thus preventing an increase in the carbon dioxide concentration in the kiln exhaust gas.

[0049] It should be noted that the temperature inside the cyclone preheating device 2 is usually 50 to 100°C lower than the temperature inside the calcining furnace 4 (described later).

[0050] There are no particular limitations on the raw materials used for cement clinker; any common materials used as raw materials for cement clinker can be used. Specifically, examples include natural raw materials such as limestone, soil, clay, silica, and iron ore; and waste or byproducts such as fly ash, iron slag, municipal solid waste incineration ash, sewage sludge incineration ash, ready-mixed concrete slurry, and waste concrete powder. Additionally, calcium-containing waste materials that have absorbed carbon dioxide can be used as raw materials for cement clinker (discussed later).

[0051] Regarding cement clinker raw materials, various raw materials are crushed and mixed in appropriate proportions using a raw material mill, and then fed into the cyclone preheating device 2. From the perspective of making cement clinker manufacturing easier, the particle size of cement clinker raw materials is preferably below 100μm.

[0052] Alternatively, a portion of the cement clinker raw materials (such as contaminated soil containing a large amount of organic matter) can be directly fed into the rotary kiln 3 without being fed into the cyclone preheating device 2.

[0053] To promote the decarbonation of cement clinker raw materials, the calcining furnace 4 and the cyclone preheating device 2 are installed on the upstream side of the rotary kiln 3.

[0054] Figure 1 In this system, the calcining furnace 4 is positioned between the cyclone heat exchanger 2c (which is the second downstream unit of the cyclone preheating device 2) and the cyclone heat exchanger 2d (which is the most downstream unit). Cement clinker raw materials, preheated by the cyclone heat exchangers 2a to 2c, are fed into the calcining furnace 4 from the cyclone heat exchanger 2c. The cement clinker raw materials fed into the calcining furnace 4 are heated within the furnace, promoting decarbonation of the cement clinker raw materials.

[0055] Here, decarbonation of cement clinker raw materials refers to the process of heating the main component of limestone, namely calcium carbonate (CaCO3), contained in cement clinker raw materials to decompose it into quicklime (CaO) and carbon dioxide (CO2).

[0056] When cement clinker raw materials are heated in the calcining furnace 4 using a combustion-supporting gas with a higher oxygen concentration than air, the partial pressure of carbon dioxide increases. Therefore, the temperature required to promote decarbonation increases, necessitating a higher temperature compared to using air as the combustion-supporting gas. Thus, the preferred heating temperature for the cement clinker raw materials is 850–1,100°C, more preferably 880–1,050°C, and particularly preferably 900–1,000°C. If the temperature is 850°C or higher, decarbonation of the cement clinker raw materials can be further promoted even in an atmosphere with a high carbon dioxide partial pressure. If the temperature is 1,100°C or lower, blockage due to sintering of the raw materials can be prevented.

[0057] In the decarbonation of cement clinker raw materials, the fuel is burned using a combustion-supporting gas in the calcining furnace 4 by heating means 13, thereby directly heating the cement clinker raw materials and promoting the decarbonation.

[0058] Examples of heating means 13 include burners, etc.

[0059] There are no particular limitations on the fuels used in calcining furnaces. Examples include fossil fuels such as coal, heavy oil, and natural gas; biomass such as coconut shells; biogas produced by gasifying biomass; and methane produced by methanation using carbon dioxide as a raw material. One of these fuels can be used alone, or two or more can be used in combination.

[0060] If carbon-free fuels such as biomass are used, carbon dioxide emissions in cement clinker manufacturing can be substantially reduced further.

[0061] As the gas used to transfer solid fuels such as coal and biomass or liquid fuels such as heavy oil into the heating means 13 in the calcining furnace 4 (hereinafter also referred to as "fuel transfer gas"), carbon dioxide or a mixed gas consisting of carbon dioxide and a combustion-supporting gas (such as oxygen) is preferred. Alternatively, a gas obtained by cooling the exhaust gas containing carbon dioxide generated in the calcining furnace 4 can be used as the transfer gas.

[0062] By using these fuel-transmitting gases, it is possible to further increase the carbon dioxide concentration in the exhaust gas containing carbon dioxide discharged from the calciner exhaust gas discharge path 9, and to further reduce the volume of the exhaust gas containing carbon dioxide.

[0063] The combustion-supporting gas used in the calcining furnace 4 is a gas with a higher oxygen concentration compared to air. By using such a combustion-supporting gas, the carbon dioxide concentration of the exhaust gas containing carbon dioxide (hereinafter sometimes simply referred to as "carbon dioxide-containing exhaust gas") generated in the calcining furnace 4 can be further increased. In addition, by using the aforementioned combustion-supporting gas, the combustibility of the fuel can be further improved, so even fuels that were previously difficult to use due to their difficulty in being finely pulverized can be used.

[0064] From the perspective of further increasing the carbon dioxide concentration in the exhaust gas containing carbon dioxide, the oxygen concentration of the aforementioned combustion-supporting gas relative to 100% of the volume containing water vapor is preferably 21% by volume or more, more preferably 25% by volume or more, and particularly preferably 30% by volume or more. Furthermore, from the perspective of easily controlling combustion, the aforementioned oxygen concentration is preferably 90% by volume or less, more preferably 80% by volume or less, further preferably 70% by volume or less, further preferably 60% by volume or less, and particularly preferably 50% by volume or less.

[0065] The combustion-supporting gas used in the calcining furnace 4 is supplied from the combustion-supporting gas supply device 7 and introduced into the calcining furnace 4 through the combustion-supporting gas supply path 8.

[0066] The combustion gas supply path 8 can be configured to indirectly heat the combustion gas passing through it using air heated by heat exchange with the cement clinker in the clinker cooler 5. Alternatively, the combustion gas supply path 8 can be partially located downstream of the cement cooler (outlet side of the clinker cooler), thereby utilizing the heat of the cement clinker to heat the combustion gas.

[0067] By heating the combustion-supporting gas, the amount of fuel used in the calcining furnace 4 can be reduced.

[0068] As a combustion gas supply device 7 for supplying combustion gas to the calcining furnace 4, examples include oxygen tanks, air separation units (ASU) that separate oxygen from air, and water electrolysis devices that generate oxygen by electrolysis of water.

[0069] Methods for separating oxygen from the air include cryogenic separation, adsorption separation, and membrane separation. Among these, cryogenic separation is preferred from the perspective of obtaining a large amount of oxygen.

[0070] The combustion-supporting gas supplied from the combustion-supporting gas supply device 7 is a gas with a higher oxygen concentration compared to air. This combustion-supporting gas can be used directly in the calcining furnace 4, or its composition can be appropriately adjusted before use in the calcining furnace 4.

[0071] For example, from the perspective of preventing the oxygen concentration of the combustion-supporting gas used in the calcining furnace 4 from increasing excessively and making combustion difficult to control, further increasing the carbon dioxide concentration of the carbon dioxide-containing waste gas and reducing the amount of oxygen remaining in the carbon dioxide-containing waste gas, the combustion-supporting gas supplied from the combustion-supporting gas supply device 7 can be mixed with carbon dioxide, and the resulting mixed gas can be used as the combustion-supporting gas in the calcining furnace 4.

[0072] In addition, in order to reduce the temperature required to promote decarbonation by lowering the partial pressure of carbon dioxide, the combustion gas supplied from the combustion gas supply device 7 can be mixed with water vapor, and the resulting mixed gas can be used as the combustion gas in the calcining furnace 4.

[0073] The carbon dioxide concentration of the above-mentioned mixed gas (a gas formed by mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 7 with at least one of carbon dioxide and water vapor) is preferably 10 to 79 vol% relative to 100 vol% of the volume containing water vapor, more preferably 20 to 75 vol%, and even more preferably 30 to 70 vol%.

[0074] Furthermore, from the perspective of further reducing the volume of exhaust gas generated in the calcining furnace 4 and further increasing the carbon dioxide concentration of the exhaust gas, the combustion-supporting gas used in the calcining furnace 4 preferably does not contain gases other than oxygen, carbon dioxide, and water vapor (e.g., nitrogen). The concentration of the combustion-supporting gas other than oxygen, carbon dioxide, and water vapor is preferably 10% or less, more preferably 5% or less, and particularly preferably 2% or less, relative to 100% by volume of the volume containing water vapor.

[0075] As an example of a method for mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 7 with carbon dioxide, a method for mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 7 with exhaust gas containing carbon dioxide can be given. Since the temperature of the exhaust gas containing carbon dioxide discharged from the calcining furnace 4 is a high temperature of about 800°C, the combustion-supporting gas can be heated by using the exhaust gas.

[0076] When mixing exhaust gas containing carbon dioxide, a merging passage 11 is provided for merging a portion of the exhaust gas flowing in the exhaust gas discharge passage 9 (which is limited to exhaust gas discharge passages 9 containing carbon dioxide that are different from the kiln exhaust gas discharge passages 6a to 6e) that discharges the exhaust gas generated in the calcining furnace 4 with the combustion gas (the combustion gas supplied from the combustion gas supply device 7) flowing in the combustion gas supply passage 8, so that the combustion gas flowing in the combustion gas supply passage 8 can be mixed with the exhaust gas.

[0077] Furthermore, if the combustion gas supply path 8 is configured to indirectly heat the combustion gas passing through the combustion gas supply path 8 by means of air heated through heat exchange with the cement clinker in the clinker cooler 5, then the aforementioned merging flow path 11 is preferably configured to merge the combustion gas with a portion of the exhaust gas at the location where the combustion gas is indirectly heated by the aforementioned air.

[0078] The waste gas containing carbon dioxide is discharged from the calcining furnace waste gas discharge path 9. After the waste gas containing carbon dioxide is treated with a cyclone separator, bag filter or electrostatic precipitator to remove dust, moisture is further removed, and then carbon dioxide is separated and recovered.

[0079] It should be noted that the calciner exhaust gas discharge path 9 is different from the kiln exhaust gas discharge paths 6a-6e, which are used to discharge the exhaust gas generated in the rotary kiln 3. By completely separating the calciner exhaust gas discharge path 9 from the kiln exhaust gas discharge paths 6a-6e, it is possible to recover only the exhaust gas containing carbon dioxide with a high carbon dioxide concentration.

[0080] Because of its high carbon dioxide concentration, the exhaust gas containing carbon dioxide is easily separated and recovered. The carbon dioxide concentration in the exhaust gas relative to 100% by volume (excluding water vapor) is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more.

[0081] The aforementioned carbon dioxide concentration can be obtained by adjusting the oxygen concentration of the combustion-supporting gas. Specifically, the carbon dioxide concentration can be further increased by further increasing the oxygen concentration of the combustion-supporting gas, or by further decreasing the concentration of gases other than oxygen, carbon dioxide, and water vapor (such as nitrogen) in the combustion-supporting gas.

[0082] In addition, the temperature of the carbon dioxide-containing waste gas varies depending on the decarbonation conditions of the calcining furnace 4, but is typically between 700 and 900°C. Since the carbon dioxide-containing waste gas is high-temperature, it can be used to heat water to generate steam, which can then be used to power a steam turbine.

[0083] Carbon dioxide can be purified by removing oxygen, nitrogen, and water vapor from waste gas containing carbon dioxide. When the concentration of carbon dioxide in the waste gas is high, it can be directly compressed and cooled to liquefy it without using chemical absorbents such as amines for separation and recovery, thus purifying the carbon dioxide.

[0084] After decarbonation is promoted in the calcining furnace 4, the cement clinker raw material is fed into the cyclone heat exchanger 2d, which is located at the downstream end of the cyclone preheating device 2, while maintaining the high temperature after heating. Then it is fed into the rotary kiln 3.

[0085] It should be noted that the calcining furnace can also be installed between the cyclone preheating device and the rotary kiln, so that the cement clinker raw materials can be directly fed into the rotary kiln after decarbonation is promoted in the calcining furnace (not shown).

[0086] In rotary kiln 3, cement clinker raw materials are fired to obtain cement clinker. The firing temperature of the cement clinker raw materials can be a common temperature in cement clinker manufacturing, typically above 1,400°C.

[0087] In rotary kiln 3, the fuel used for calcining cement clinker can be the same fuel used in calciner 4. Additionally, contaminated soil containing large amounts of organic matter or waste tires, which are difficult to break down, can be directly fed into the rotary kiln 3 through its feed inlet.

[0088] In addition, the exhaust gas generated in the rotary kiln 3 is discharged from the top of the cyclone preheating device 2 after passing through the kiln exhaust gas discharge path 6a to 6e, and is then removed by dust removal using a cyclone separator, bag filter or electrostatic precipitator, etc., and discharged to the outside through the chimney.

[0089] From the perspective of further reducing carbon dioxide emissions, carbon dioxide can be separated and recovered from kiln exhaust gas.

[0090] Examples of methods for separating and recovering carbon dioxide from kiln exhaust gas include chemical absorption using monoethanolamine as a carbon dioxide absorbent, calcium looping using quicklime as a carbon dioxide absorbent, solid adsorption, and membrane separation.

[0091] Quicklime used in the calcium recycling process can be obtained by decarbonating limestone. After repeated use, the limestone can ultimately be used as a raw material for cement clinker.

[0092] In addition, a chlorine bypass device 10 can be installed to extract and cool a portion of the kiln exhaust gas without passing through the cyclone preheating device 2, remove solid components, discharge the exhaust gas after removing solid components, and classify the solid components into coarse powder and fine powder, use the coarse powder as part of the cement clinker raw material, and recover the fine powder.

[0093] It should be noted that "coarse powder" tends to have more raw material components and less chlorine in cement clinker, while "fine powder" tends to have more chlorine.

[0094] The alkali bypass device 10 is usually installed at the connection between the cyclone preheating device 2 and the rotary kiln 3. By installing the chlorine bypass device 10, a larger amount of chlorine-containing waste such as municipal solid waste incineration ash can be used as raw material for cement clinker and fuel for the rotary kiln.

[0095] The kiln exhaust gas discharged from the chlorine bypass device 10 is usually sent back to the kiln exhaust gas discharge path 6a.

[0096] The cement clinker obtained from the rotary kiln 3 is fed into the clinker cooler 5, which is located downstream of the rotary kiln 3, for cooling.

[0097] From the perspective of more effectively heating the calcining furnace 4 and the rotary kiln 3, the air used for cooling the cement clinker can be divided into the upstream side and the downstream side of the clinker cooler 5. The air on the downstream side after the cement clinker has been cooled can be used for indirect heating of the combustion gas passing through the combustion gas supply path 8.

[0098] Alternatively, the gases used for cooling on the upstream and downstream sides can be different. Specifically, air can be used as the gas for cooling the upstream side of the clinker cooler 5, while combustion-supporting gas passing through the combustion-supporting gas supply path 8 can be used as the gas for cooling the downstream side.

[0099] The gas cooled on the upstream side is used as a combustion-supporting gas for burning fuel in the rotary kiln 3 after heat exchange with the high-temperature cement clinker. It should be noted that the gas cooled on the upstream side undergoes heat exchange at the inlet side of the clinker cooler 5, and therefore becomes hotter after heat exchange compared to the gas cooled on the downstream side.

[0100] Furthermore, electrical energy can be used for heating the air and combustion gases used in fuel combustion within the rotary kiln, as well as to assist in heating the rotary kiln and calcining furnace. Examples of heating methods using electrical energy include plasma heating, resistance heating, and microwave heating. Using renewable energy sources can further reduce carbon dioxide emissions.

[0101] In the cement clinker manufacturing method using the above-mentioned cement clinker manufacturing system, the carbon dioxide-containing waste gas generated in the calcining furnace 4 can be recovered and utilized.

[0102] As an example of the utilization of carbon dioxide, methanation can be cited. It should be noted that methanation refers to the reaction of hydrogen and carbon dioxide to produce methane and water.

[0103] Specifically, one example is the use of a catalyst to produce methane from hydrogen and carbon dioxide contained in the aforementioned waste gas.

[0104] Hydrogen can be obtained through processes such as water electrolysis. Using electricity generated from renewable sources such as hydropower, wind power, geothermal energy, or solar power can further reduce carbon dioxide emissions, especially during water electrolysis. Oxygen is also produced during this process and can be used as an oxygen component in the aforementioned combustion-supporting gases.

[0105] Examples of the catalysts mentioned above include Rh / Mn-based, Rh-based, Ni-based, Pd-based, and Pt-based catalysts. Additionally, supports for these catalysts can be used. Examples of such supports include CeO2, ZrO2, Y2O3, Al2O3, MgO, TiO2, and SiO2. These can be appropriately selected for use.

[0106] From the perspective of further reducing carbon dioxide emissions, the generated methane can be used as fuel for at least one of the rotary kiln 3 and the calciner 4. Additionally, the generated methane can be used as fuel for power generation.

[0107] Another example of the application of carbon dioxide is the carbonation of calcium-containing waste.

[0108] Specifically, this method involves contacting the aforementioned waste gas with calcium-containing waste, allowing the carbon dioxide contained in the waste gas to be absorbed by the calcium-containing waste. By absorbing and immobilizing the carbon dioxide in the calcium-containing waste, the amount of carbon dioxide emitted into the atmosphere can be reduced. Examples of calcium-containing waste include waste concrete.

[0109] Calcium-containing waste that has absorbed carbon dioxide can be used as a raw material for cement clinker in the above-mentioned cement clinker manufacturing system.

[0110] In addition, calcium-containing waste that has absorbed carbon dioxide can be crushed and graded for use as roadbed materials and concrete aggregates. Furthermore, in the case of waste concrete containing calcium, only the paste component that has absorbed carbon dioxide can be separated and recovered for use as a cement raw material.

[0111] In the aforementioned methanation and carbonation of calcium-containing waste, methanation and carbonation of waste concrete can be carried out more effectively by directly applying the waste gas containing carbon dioxide at high temperature without refining it (without separating or removing carbon dioxide).

[0112] It should be noted that in the production of cement clinker using the above-mentioned cement clinker manufacturing system, the waste gas containing carbon dioxide generated in the calcining furnace 4 can be directly stored and isolated.

[0113] Figure 2The cement clinker manufacturing system 101 includes: a cyclone preheating device 102 for preheating cement clinker raw materials; a rotary kiln 103 for calcining the cement clinker raw materials preheated by the cyclone preheating device 102 to obtain cement clinker; a calcining furnace 104 arranged upstream of the rotary kiln 103 together with the cyclone preheating device 102 for promoting decarbonation of the cement clinker raw materials; a clinker cooler 105 arranged downstream of the rotary kiln 103 for cooling the cement clinker; and a kiln exhaust gas discharge path 106 for discharging the exhaust gas generated in the rotary kiln 103 after passing through the cyclone preheating device 102. The manufacturing system also includes: a combustion gas supply device (which may also be a water electrolysis device 109, described later, that also serves as a hydrogen supply device) for supplying combustion gas with a higher oxygen concentration than air; and a combustion gas supply path for discharging the combustion gas from the combustion gas supply device 102. The apparatus includes: a combustion gas supply path 107 for introducing combustion-supporting gas into the calcining furnace 104; a mixing device 108 for mixing carbon dioxide-containing waste gas with hydrogen to prepare a mixed gas containing carbon dioxide and hydrogen, and adjusting the temperature of the mixed gas; a hydrogen supply device 109 for supplying hydrogen; a hydrogen supply path 110 for introducing hydrogen from the hydrogen supply device 109 into the mixing device 108; a calcining furnace waste gas discharge path 111 for discharging carbon dioxide-containing waste gas generated in the calcining furnace 104 (limited to a calcining furnace waste gas discharge path 111 different from the kiln waste gas discharge path 106); a methane generating device 112 for reacting carbon dioxide and hydrogen contained in the mixed gas with a catalyst to generate methane and water vapor; and a mixed gas supply path 113 for introducing the mixed gas from the mixing device 108 into the methane generating device 112. In addition, the calciner exhaust gas path 111 is used to introduce carbon dioxide-containing exhaust gas from the calciner 104 into the mixing device 108.

[0114] The cyclone preheating device 102, cyclone heat exchangers 102a, 102b, 102c, 102d, rotary kiln 103, clinker cooler 105, kiln exhaust gas outlets 106, 106a, 106b, 106c, 106d, 106e, heating means 115a, and chlorine bypass device 117 are the same as those in the aforementioned cyclone preheating device 2, cyclone heat exchangers 2a, 2b, 2c, 2d, rotary kiln 3, clinker cooler 5, kiln exhaust gas outlets 6, 6a, 6b, 6c, 6d, 6e, heating means 13, and chlorine bypass device 10. Furthermore, the cement clinker raw material fed into the cyclone preheating device 102 is the same as that fed into the aforementioned cyclone preheating device 2.

[0115] Calcining furnace 104 is the same as calcining furnace 4 described above. In addition, from the perspective of reducing carbon dioxide emissions in cement clinker manufacturing and reducing fuel costs, the fuel used in calcining furnace 104 is preferably methane generated in the methane generation apparatus 112 described later by methanating carbon dioxide contained in the carbon dioxide-containing waste gas generated in calcining furnace 104 as a raw material.

[0116] The combustion-supporting gas used in calcining furnace 104 is the same as that used in calcining furnace 4.

[0117] The aforementioned combustion-supporting gas is supplied from the combustion-supporting gas supply device ( Figure 2 The gas is supplied to the water electrolysis device 109 and introduced into the calcining furnace 104 through the combustion-supporting gas supply path 107.

[0118] The combustion-supporting gas supply device is the same as the combustion-supporting gas supply device 7 described above. Alternatively, a water electrolysis device can be used as the combustion-supporting gas supply device. In this case, the combustion-supporting gas supply device can also function as the hydrogen supply device described later.

[0119] The combustion-supporting gas supply path 107 is the same as the combustion-supporting gas supply path 7 described above.

[0120] As an example of a method for mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device with carbon dioxide, a method for mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device with waste gas containing carbon dioxide can be given. The waste gas containing carbon dioxide discharged from the calcining furnace 104 has a high temperature of about 800°C, so by using the above-mentioned waste gas, the temperature of the combustion-supporting gas can be raised.

[0121] When mixing exhaust gas containing carbon dioxide, a merging passage 118 can be provided to merge a portion of the exhaust gas containing carbon dioxide flowing in the calciner exhaust gas discharge passage 111 with the combustion gas (supply from the combustion gas supply device) flowing in the combustion gas supply passage 107, thereby merging the combustion gas flowing in the combustion gas supply passage 107 with a portion of the exhaust gas containing carbon dioxide.

[0122] Furthermore, if the combustion gas supply path 107 is configured to indirectly heat the combustion gas passing through the combustion gas supply path 107 by using air heated through heat exchange with the cement clinker in the clinker cooler 105, then the aforementioned merging flow path 118 is preferably configured to merge the combustion gas with a portion of the exhaust gas at the location where the combustion gas is indirectly heated by the aforementioned air.

[0123] The carbon dioxide-containing waste gas generated in the calcining furnace 104 is introduced into the mixing device 108 after passing through the calcining furnace 104 in the calcining furnace waste gas discharge path (calcining furnace waste gas supply path) 111.

[0124] It should be noted that the calciner exhaust gas discharge path 111 is different from the kiln exhaust gas discharge paths 106a to 106e used to discharge the exhaust gas generated in the rotary kiln 103. By completely separating the calciner exhaust gas discharge path 111 from the kiln exhaust gas discharge paths 106a to 106e, it is possible to recover only the exhaust gas containing carbon dioxide with a high carbon dioxide concentration.

[0125] Because the exhaust gas containing carbon dioxide has a high concentration of carbon dioxide and low levels of nitrogen, the equipment such as the methane generating unit 112 can be reduced in size, and it is suitable as a feedstock for methane generation. In addition, because the exhaust gas containing carbon dioxide has a high temperature, the amount of heat supplied from the outside can be reduced in order to bring the temperature inside the methane generating unit 112 into a temperature range suitable for methane generation (e.g., 200°C to 800°C).

[0126] The carbon dioxide concentration of the exhaust gas containing carbon dioxide is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more, relative to 100% of the volume excluding water vapor.

[0127] The aforementioned carbon dioxide concentration can be obtained by adjusting the oxygen concentration of the combustion-supporting gas. Specifically, the carbon dioxide concentration can be further increased by further increasing the oxygen concentration of the combustion-supporting gas and further decreasing the concentration of gases other than oxygen, carbon dioxide, and water vapor (such as nitrogen) in the combustion-supporting gas.

[0128] The temperature of the carbon dioxide-containing waste gas varies depending on the decarbonation conditions of the calcining furnace 104, but it is usually between 700 and 900°C. Because the carbon dioxide-containing waste gas is high-temperature, it can be used to heat water to produce steam, which can then be used to generate electricity via a steam turbine.

[0129] The mixing device 108 is used to mix waste gas containing carbon dioxide with hydrogen to prepare a mixed gas formed by waste gas containing carbon dioxide and hydrogen, and to adjust the temperature of the mixed gas.

[0130] In the mixing device 108, by appropriately adjusting the mixing ratio of waste gas containing carbon dioxide and hydrogen, and adjusting the temperature of the mixed gas, methane generation in the methane generation device 112 (details to follow) can be achieved more effectively.

[0131] The hydrogen used in the mixing device 108 can be supplied from the hydrogen supply device ( Figure 2The hydrogen gas is introduced into the mixing device 108 through the hydrogen supply path 110 of the water electrolysis device 109 and is supplied to the mixing device 108.

[0132] As a hydrogen supply device, anything that can supply hydrogen is acceptable, such as hydrogen storage cylinders; hydrogen storage tanks; alkaline water electrolysis devices, solid polymer water electrolysis devices, steam electrolysis devices, and other water electrolysis devices.

[0133] From the perspective of constructing an effective cement clinker manufacturing system, a water electrolysis device capable of electrolyzing water to obtain hydrogen and oxygen is preferred.

[0134] Alternatively, when using a steam electrolysis device, steam generated in the methane generating unit 112 or steam generated by a heat exchange device appropriately installed in the cement clinker manufacturing system can be used as raw materials.

[0135] When the water electrolysis device 109 is used as a hydrogen supply device, oxygen is also generated along with the hydrogen, and this oxygen can be used as oxygen contained in the combustion-supporting gas. In this case, the water electrolysis device 109 also functions as a combustion-supporting gas supply device. The oxygen generated in the water electrolysis device 109 is supplied to the combustion-supporting gas supply path 107.

[0136] Alternatively, hydrogen supply devices such as hydrogen tanks can be prepared separately from the water electrolysis device, and hydrogen can be supplied separately from the hydrogen supply device to the hydrogen supply path 110.

[0137] In addition, as the electricity used for water electrolysis, if electricity from renewable energy sources such as hydropower, wind power, geothermal energy or solar energy is used, or if electricity is generated by using methane produced by the methane generation unit 112 as fuel, carbon dioxide emissions can be further reduced.

[0138] The exhaust gas containing carbon dioxide produced in the calcining furnace 104 contains a small amount of oxygen, but in the mixing device 108, when the exhaust gas containing carbon dioxide is mixed with hydrogen, the oxygen reacts with the hydrogen to form water vapor.

[0139] In the mixing apparatus 108, the mixed gas is prepared such that the volume ratio of hydrogen to carbon dioxide (hydrogen / carbon dioxide) in the mixed gas after the reaction of oxygen and hydrogen is preferably 3.8 to 4.5, more preferably 3.9 to 4.2. The mixed gas is generally prepared by increasing or decreasing the amount of hydrogen supplied from the hydrogen supply path 110.

[0140] If the ratio is 3.8 or higher, the amount of carbon dioxide (the carbon dioxide that remains in the methane generating unit 112 that has not reacted) in the methane gas is reduced, and more methane can be generated.

[0141] If the ratio is 4.5 or less, the amount of hydrogen (hydrogen that has not reacted and remains in the methane generating unit 112) in the methane-containing gas (hereinafter also referred to as "methane-containing gas") generated by the methane generating unit 112 is reduced, and when the methane-containing gas is used as fuel, it is possible to prevent difficulties in temperature control or the generation of NOx.

[0142] The temperature of the mixed gas is preferably 200–600°C, more preferably 220–500°C, even more preferably 240–400°C, and particularly preferably 250–300°C. When the mixed gas temperature is 200°C or higher, the methane generation efficiency in the methane generation apparatus 112 can be improved. The temperature of the mixed hydrogen gas is usually room temperature (20°C), making it difficult to obtain a mixed gas with a temperature higher than 600°C. Furthermore, if the temperature is below 600°C, the burden on equipment such as the mixing apparatus 108 and the mixed gas supply line 113 can be reduced.

[0143] In order to keep the temperature of the mixed gas within the above-mentioned range, the mixed gas can be heated or cooled in the mixing device 108.

[0144] The mixed gas after mixing in the mixing device 108 is supplied to the methane generating device 112 via the mixed gas supply path 113 for introducing the mixed gas from the mixing device 108 to the methane generating device 112.

[0145] When the dust concentration in the mixed gas is high, to more effectively generate methane and reduce the burden on the methane generating unit 112, a cyclone separator, bag filter, or electrostatic precipitator can be installed midway through the mixed gas supply path 113 to recover the dust. The preferred dust concentration in the mixed gas is 1 g / m³. 3 N or less, more preferably 0.5 g / m 3 the following.

[0146] In addition, a methanation inhibition component separation device can be installed midway through the mixed gas supply path 113 to separate the inhibitory components (components that inhibit the action of the catalyst and reduce the performance of the catalyst) used in the methane generation unit 112.

[0147] Examples of the aforementioned inhibitory components include sulfur oxides (SOx), nitrogen oxides (NOx), and hydrogen chloride (HCl). The methanation inhibitor separation apparatus can be used in a suitable combination of known methods or apparatus for removing the aforementioned inhibitory components such as sulfur oxides, nitrogen oxides, and hydrogen chloride.

[0148] In addition, water (water vapor) can be removed as needed in the methanation inhibition component separation device.

[0149] Furthermore, nitrogen (N2) in the exhaust gas containing carbon dioxide is a useless gas that does not participate in the formation of methane. Therefore, from the perspective of efficiently generating methane, nitrogen can be removed from the gas mixture.

[0150] The methane generating device 112 is used to react carbon dioxide and hydrogen contained in the above-mentioned mixed gas with a catalyst to generate methane and water vapor.

[0151] The catalyst described above, as well as the support that can be used to support the catalyst, are the same as those used in the methanation process described above.

[0152] The temperature of the internal space of the methane generating apparatus 112 (the space where carbon dioxide and hydrogen react to generate methane) is preferably 200 to 800°C, more preferably 250 to 700°C.

[0153] The reaction of producing methane from carbon dioxide and hydrogen using a catalyst (the so-called methanation reaction) is an exothermic reaction, but methanation will not occur unless a certain level of energy is applied. In this invention, the high-temperature carbon dioxide-containing waste gas generated in the calcining furnace 104 is used, and the temperature of the mixed gas is adjusted in the mixing device 108, so that the temperature of the internal space of the methane generating device 112 can be easily brought within the aforementioned temperature range.

[0154] In addition, heat energy can be supplied from the outside to promote the above reaction. For example, heating means can be arranged around the methane generating device 112 to indirectly heat the internal space of the methane generating device 112.

[0155] Furthermore, when the internal temperature exceeds 800°C due to the exothermic reaction, the methanation reaction may sometimes decrease drastically. In such cases, refrigerant can be introduced for cooling. The heat recovered using the refrigerant can be used for power generation, etc.

[0156] As for the methane generation device 112, there are no particular limitations as long as the internal space can be filled with a catalyst to carry out a methanation reaction, for example, a fixed-bed reactor can be cited.

[0157] The methane and water vapor generated in the methane generating device 112 can be discharged in the form of a methane-containing gas containing the methane, the water vapor, and unreacted residual carbon dioxide and hydrogen.

[0158] From the perspective of reducing carbon dioxide emissions in cement clinker production and reducing fuel costs, methane-containing gas can be supplied to the calciner 104 via methane supply path 114. The methane contained in the methane-containing gas supplied to the calciner 104 is used as fuel for the heating means 115a of the calciner 104.

[0159] The methane-containing gas supplied to the calcining furnace 104 may contain water vapor generated in the methane generating unit 112. When the methane-containing gas contains water vapor, the partial pressure of carbon dioxide in the calcining furnace 104 decreases, and decarbonation can be carried out even at low temperatures of 10 to 50°C, compared to the case where the methane-containing gas does not contain water vapor is supplied.

[0160] In addition, from the perspective of increasing the heat release of methane-containing gas, water vapor can be removed from the methane-containing gas.

[0161] Furthermore, the methane-containing gas supplied to the calcining furnace 104 may include unreacted hydrogen gas remaining in the methane generating unit 112. This hydrogen gas can be used as fuel for the heating means 115a of the calcining furnace 104.

[0162] It should be noted that when the proportion of hydrogen in methane gas is greater than 15% by mass, temperature control of the calcining furnace 104 becomes difficult and problems such as NOx generation arise. Therefore, a heating method suitable for using hydrogen as fuel is sometimes required.

[0163] Alternatively, methane-containing gas can be supplied to the heating means 115b of the rotary kiln 103 and used as fuel for the heating means 115b.

[0164] The aforementioned methane-containing gas is at a high temperature (e.g., 200–800°C). By supplying it to the calcining furnace 104 and the rotary kiln 103 while maintaining a high temperature, compared to supplying methane-containing gas at room temperature, a smaller amount of gas can be used to achieve the desired temperature inside the calcining furnace 104 and the rotary kiln 103.

[0165] In addition, the methane generated in the methane generating unit 112 can be used separately as fuel for power generation.

[0166] Figure 3The cement clinker manufacturing system 201 includes: a cyclone preheating device 202 for preheating cement clinker raw materials; a rotary kiln 203 for calcining the cement clinker raw materials preheated by the cyclone preheating device 202 to obtain cement clinker; a calcining furnace 204 arranged upstream of the rotary kiln 203 together with the cyclone preheating device 202 for promoting decarbonation of the cement clinker raw materials; a clinker cooler 205 arranged downstream of the rotary kiln 203 for cooling the cement clinker; a kiln exhaust gas discharge path 206 for discharging the exhaust gas generated in the rotary kiln 203 after passing through the cyclone preheating device 202; a combustion gas supply device 208 for supplying combustion gas with a higher oxygen concentration than air; and a combustion gas supply path 209 for introducing the combustion gas from the combustion gas supply device 208 into the calcining furnace 204. ; a calciner exhaust gas discharge path 210 for discharging carbon dioxide-containing waste gas generated in the calciner 204 (limited to a calciner exhaust gas discharge path 210 different from the kiln exhaust gas discharge path 206); a preheated raw material supply path 207 for supplying preheated cement clinker raw materials from the cyclone preheating device 202 to the calciner 204; a first recovery means 211a disposed midway in the calciner exhaust gas discharge path 210 for recovering raw materials containing quicklime from the carbon dioxide-containing waste gas; and a calciner exhaust gas supply path 219 connected to the calciner exhaust gas discharge path 210 midway in the calciner exhaust gas discharge path 210 and downstream of the first recovery means 211a, for merging a portion of the carbon dioxide-containing waste gas flowing in the calciner exhaust gas discharge path 210 with the combustion-supporting gas flowing in the combustion-supporting gas supply path 209.

[0167] Additionally, the cyclone preheating device 202 is formed by two or more cyclone heat exchangers. The calcining furnace 204 includes a heating means 221, which is used to promote decarbonation of cement clinker raw materials. The combustion gas supply path 209 is used to exchange heat between the carbon dioxide-containing waste gas flowing in the calcining furnace waste gas discharge path 210 and the combustion gas at a location midway through the calcining furnace waste gas discharge path 210 and upstream of the first recovery means 211a.

[0168] The cyclone preheating device 202 is the same as the cyclone preheating device 2 described above.

[0169] Furthermore, in the two or more cyclone heat exchangers 202a to 202d constituting the cyclone preheating device 202, the cement clinker raw material is preheated at a temperature preferably 550 to 850°C, more preferably 600 to 750°C, in the cyclone heat exchanger 202c connected to the preheating raw material supply path 207. By preheating within such a temperature range, when the kiln exhaust gas passes through the cyclone preheating device 202 (especially the cyclone heat exchanger 202c connected to the preheating raw material supply path 207), it is easier for the carbon dioxide contained in the kiln exhaust gas to be immobilized (carbonated) in the raw material containing quicklime (details described later) fed into the cyclone preheating device 202 from the raw material supply path 218 containing quicklime. This reduces the amount of carbon dioxide in the kiln exhaust gas and further increases the concentration of carbon dioxide in the exhaust gas containing carbon dioxide.

[0170] In addition, the cement clinker raw material fed into the cyclone preheating device 202 is the same as the cement clinker raw material fed into the cyclone preheating device 2.

[0171] The preheated cement clinker raw material is supplied to the calcining furnace 204 from the preheated raw material supply line 207, which is connected to any one of the two or more cyclone heat exchangers 202a to 202d constituting the cyclone preheating device 202.

[0172] Figure 3 In this system, the preheating raw material supply path 207 is connected to the cyclone heat exchanger 202c, which is located at the second or higher position from the downstream side of the cyclone preheating device 202. Cement clinker raw material, preheated by the cyclone heat exchangers 202a to 202c, is fed into the calcining furnace 204 from the cyclone heat exchanger 202c via the preheating raw material supply path 207. By connecting the preheating raw material supply path 207 to the cyclone heat exchanger 202c located at the second position from the downstream side, fully preheated cement clinker raw material can be fed into the calcining furnace 204.

[0173] For the purpose of promoting decarbonation of cement clinker raw materials by burning fuel through heating means 221, calciner 204 is arranged on the upstream side of rotary kiln 203 together with cyclone preheating device 202.

[0174] The temperature at which the cement clinker raw materials are heated in the calcining furnace 204 is preferably 850–1,100°C, more preferably 880–1,050°C, and particularly preferably 900–1,000°C. If the temperature is 850°C or higher, decarbonation of the cement clinker raw materials can be further promoted even in an atmosphere with high carbon dioxide partial pressure, and even if the decarbonated cement clinker raw materials are directly fed from the calcining furnace 204 into the rotary kiln 203 through the first decarbonated raw material supply path 212, the temperature inside the rotary kiln 203 will not drop excessively. If the temperature is 1,100°C or lower, blockage due to sintering of the raw materials can be prevented.

[0175] By using heating means 221 in the calcining furnace 204 to burn fuel with combustion-supporting gas to directly heat the cement clinker raw materials, the decarbonation of the cement clinker raw materials can be promoted.

[0176] Examples of heating means 221 include burners, etc.

[0177] The fuel and combustion-supporting gas used in calcining furnace 204 are the same as those used in calcining furnace 4.

[0178] The combustion-supporting gas used in the calcining furnace 204 is supplied from the combustion-supporting gas supply device 208 and introduced into the calcining furnace 204 through the combustion-supporting gas supply path 209.

[0179] The combustion-supporting gas supply path 209 is configured such that the carbon dioxide-containing waste gas flowing in the furnace waste gas discharge path 210 and the combustion-supporting gas are heat-exchanged in the middle of the furnace waste gas discharge path 210 and upstream of the first recovery means 211a described later.

[0180] By arranging it in this way, the combustion gas flowing in the combustion gas supply path 209 is indirectly heated and its temperature is increased, which can reduce the amount of fuel input used in the calciner 204. In addition, the temperature of the carbon dioxide-containing waste gas flowing in the calciner exhaust path 210 can be reduced, which can improve the efficiency of recovering raw materials containing quicklime (including quicklime powder) from the carbon dioxide-containing waste gas in the first recovery means 211a.

[0181] Furthermore, the combustion gas supply path 209 can be configured to indirectly heat the combustion gas passing through it using air heated by heat exchange with the cement clinker in the clinker cooler 205. Alternatively, the combustion gas supply path 209 can be partially located downstream of the cement cooler (outlet side of the clinker cooler), thereby utilizing the heat from the cement clinker to heat the combustion gas.

[0182] By heating the combustion-supporting gas, the amount of fuel used in the calcining furnace 204 can be reduced.

[0183] The combustion-supporting gas supply device 208 is the same as the combustion-supporting gas supply device 7 described above.

[0184] The combustion-supporting gas supplied from the combustion-supporting gas supply device 208 is a gas with a higher oxygen concentration compared to air.

[0185] In addition, from the perspective of preventing the oxygen concentration of the combustion-supporting gas used in the calcining furnace 204 from being too high and difficult to control combustion, further increasing the carbon dioxide concentration of the carbon dioxide-containing waste gas and reducing the amount of residual oxygen in the carbon dioxide-containing waste gas, the combustion-supporting gas supplied to the calcining furnace 204 is a gas formed by mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 208 with carbon dioxide.

[0186] The aforementioned carbon dioxide is supplied via the calciner exhaust gas supply route 219, which will be described later.

[0187] In addition, in order to reduce the temperature required to promote decarbonation by lowering the partial pressure of carbon dioxide, the combustion gas supplied from the combustion gas supply device 208 can be mixed with water vapor, and the resulting mixed gas can be used as the combustion gas in the calcining furnace 204.

[0188] The carbon dioxide concentration of the above-mentioned mixed gas (a gas formed by mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 208 with at least one of carbon dioxide and water vapor) is preferably 10 to 79 vol% relative to 100 vol% of the volume containing water vapor, more preferably 20 to 75 vol%, and even more preferably 30 to 70 vol%.

[0189] Furthermore, from the perspective of further reducing the volume of carbon dioxide-containing waste gas generated in the calcining furnace 204 and further increasing the carbon dioxide concentration of the waste gas, the combustion-supporting gas used in the calcining furnace 204 preferably does not contain gases other than oxygen, carbon dioxide, and water vapor (e.g., nitrogen). The concentration of the combustion-supporting gas other than oxygen, carbon dioxide, and water vapor is preferably 10% or less, more preferably 5% or less, and particularly preferably 2% or less, relative to 100% of the volume containing water vapor.

[0190] The carbon dioxide-containing waste gas produced in the calcining furnace 204 is discharged through the calcining furnace waste gas discharge path 210.

[0191] A first recovery means 211a is provided in the middle of the calciner exhaust gas discharge path 210 for recovering the raw material containing quicklime (including micro powder of quicklime) contained in the carbon dioxide-containing exhaust gas flowing in the calciner exhaust gas discharge path 210.

[0192] Examples of primary recycling methods 211a include cyclone separators, bag filters, and electrostatic precipitators.

[0193] For the purpose of immobilizing (carbonating) the carbon dioxide in the kiln exhaust gas in the raw material containing quicklime, the raw material containing quicklime recovered by the first recovery means 211a can be supplied from the first recovery means 211a to the cyclone preheating device 202 through the raw material supply path 218a containing quicklime.

[0194] It should be noted that, Figure 3 In the middle, the raw material supply path 218a containing quicklime is connected to the raw material supply path 218 containing quicklime.

[0195] A calciner exhaust gas supply passage 219 is provided midway through the calciner exhaust gas discharge passage 210 and downstream of the first recovery means 211a. This passage is connected to the calciner exhaust gas discharge passage 210 and is used to merge a portion of the carbon dioxide-containing exhaust gas flowing in the calciner exhaust gas discharge passage 210 with the combustion-supporting gas flowing in the combustion-supporting gas supply passage 209.

[0196] By using a portion of the carbon dioxide-containing waste gas as part of the combustion-supporting gas and recirculating it, the amount of waste gas ultimately discharged to the outside from the calciner waste gas discharge path 210 can be reduced. The recirculation rate of the carbon dioxide-containing waste gas used as part of the combustion-supporting gas flowing through the calciner waste gas discharge path 210 is preferably 50-70% by volume.

[0197] Furthermore, the carbon dioxide-containing exhaust gas that flows from the calciner exhaust gas supply path 219 and the combustion-supporting gas flowing in the combustion-supporting gas supply path 209 is the gas after the dust containing quicklime (the raw material containing quicklime) has been recovered in the first recovery means 211a. Therefore, the retention or adhesion of the aforementioned dust in the calciner 204 and its adverse effects on fuel combustion can be reduced. In the calciner exhaust gas discharge path 210, the retention or adhesion of the aforementioned dust and its adverse effects on the heat exchange between the carbon dioxide-containing exhaust gas and the combustion-supporting gas can be reduced.

[0198] In the first recovery method 211a, the waste gas containing carbon dioxide after recovering the raw material containing quicklime is further dehydrated, and then the carbon dioxide is separated and recovered.

[0199] It should be noted that the calciner exhaust gas discharge path 210 is different from the kiln exhaust gas discharge paths 206a to 206e, which are used to discharge the exhaust gas generated in the rotary kiln 203. By completely separating the calciner exhaust gas discharge path 210 from the kiln exhaust gas discharge paths 206a to 206e, it is possible to recover only the exhaust gas containing carbon dioxide with a high carbon dioxide concentration.

[0200] The carbon dioxide concentration in the exhaust gas produced in the calcining furnace 204 is high, making it easy to separate and recover carbon dioxide from the exhaust gas. The carbon dioxide concentration in the exhaust gas relative to 100% by volume (excluding water vapor) is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more.

[0201] The aforementioned carbon dioxide concentration can be obtained by adjusting the oxygen concentration of the combustion-supporting gas. Specifically, the carbon dioxide concentration can be further increased by further increasing the oxygen concentration of the combustion-supporting gas and further decreasing the concentration of gases other than oxygen, carbon dioxide, and water vapor (such as nitrogen) in the combustion-supporting gas.

[0202] The temperature of the carbon dioxide-containing exhaust gas discharged from the calcining furnace 204 is typically 950–1,100°C. Because the carbon dioxide-containing exhaust gas is high-temperature, it can be used to heat water to generate steam, which can then be used to generate electricity via a steam turbine.

[0203] Carbon dioxide can be purified by removing oxygen, nitrogen, and water vapor from waste gas containing carbon dioxide. When the concentration of carbon dioxide in the waste gas is high, it can be directly compressed and cooled to liquefy it without using chemical absorbents such as amines for separation and recovery, thus purifying the carbon dioxide.

[0204] A calciner exhaust gas temperature reduction device (not shown) can be installed midway through the calciner exhaust gas discharge path 210 and upstream of the first recovery means 211a to reduce the temperature of the carbon dioxide-containing exhaust gas flowing in the calciner exhaust gas discharge path 210. There are no particular limitations on the calciner exhaust gas temperature reduction device, as long as it can reduce the temperature of the carbon dioxide-containing exhaust gas. Examples include devices for heat exchange between air and carbon dioxide-containing exhaust gas, and devices for heat exchange between liquid and carbon dioxide-containing exhaust gas.

[0205] By reducing the temperature of the carbon dioxide-containing waste gas to, for example, 100–400°C, the micro-powder containing quicklime in the carbon dioxide-containing waste gas can be recovered more effectively in the first recovery method 211a. Furthermore, the adverse effects on various devices caused by the high temperature of the carbon dioxide-containing waste gas can be reduced.

[0206] Additionally, a fuel transfer gas supply line 220 can be provided, branching from at least one of the following locations (not shown): a portion of the combustion gas supply line 209 closer to the combustion gas supply device 208 than the portion where the carbon dioxide-containing exhaust gas exchanges heat with the combustion gas, and a midway point of the calciner exhaust gas supply line 219. This fuel transfer gas supply line 220 can be connected to the heating means 221 of the calciner 204.

[0207] The gas used for fuel transfer is the gas used to transfer solid fuels such as coal and biomass or liquid fuels such as heavy oil to the heating means 221 inside the calcining furnace 204.

[0208] The combustion-supporting gas flowing in the combustion-supporting gas supply path 209 (a lower-temperature combustion-supporting gas before heat exchange with the high-temperature carbon dioxide-containing exhaust gas discharged from the calciner 204) or the carbon dioxide-containing exhaust gas flowing in the calciner exhaust gas supply path 219 can be used directly as fuel transfer gas, or can be appropriately mixed with carbon dioxide and oxygen. Furthermore, the temperature of the fuel transfer gas can be appropriately adjusted.

[0209] By using fuel-transmitting gas, the concentration of carbon dioxide in the exhaust gas containing carbon dioxide discharged from the calciner exhaust gas discharge path 210 can be further increased, and the volume of the exhaust gas containing carbon dioxide can be further reduced.

[0210] Additionally, a fuel supply device (not shown) for supplying fuel to the fuel transfer gas flowing in the fuel transfer gas supply path 220 may be provided midway through the fuel transfer gas supply path 220.

[0211] Figure 3 In the process, cement clinker raw materials are decarbonated in the calcining furnace 204 and then supplied to the rotary kiln 203 through the first decarbonation raw material supply path 212 while maintaining the high temperature after heating.

[0212] A second recovery method 211b may be installed midway through the first decarbonation raw material supply route 212 to recover a portion of the decarbonated cement clinker raw material flowing in the first decarbonation raw material supply route 212 as a raw material containing quicklime.

[0213] Regarding the quicklime-containing raw material recovered in the second recovery method 211b, for the purpose of immobilizing (carbonating) the carbon dioxide in the kiln exhaust gas in the quicklime-containing raw material, it is supplied from the second recovery method 211b through the second quicklime-containing raw material supply path 218b and the quicklime-containing raw material flowing in the quicklime-containing raw material supply path 218a, and then supplied to the cyclone preheating device 202.

[0214] It should be noted that the second raw material supply path 218b containing quicklime is connected to the raw material supply path 218a containing quicklime (not shown). Additionally, Figure 3 In the middle, the raw material supply path 218a containing quicklime is connected to the raw material supply path 218 containing quicklime.

[0215] In addition, after decarbonation is promoted in the calcining furnace 204, the above-mentioned raw material containing quicklime can be supplied to the downstream cyclone heat exchanger (not shown) while maintaining the high temperature after heating.

[0216] The quicklime-containing raw materials (including quicklime powder or decarbonated cement clinker raw materials containing quicklime) recovered in the first recovery method 211a and the second recovery method 211b are supplied through the quicklime-containing raw material supply path 218 to one of the two or more cyclone heat exchangers 202a to 202d constituting the cyclone preheating device 202, which is connected to the preheating raw material supply path 207, or to any one of the cyclone heat exchangers 202a to 202b located upstream of the cyclone heat exchanger.

[0217] By supplying quicklime-containing raw materials to either a cyclone heat exchanger 202c connected to a preheating raw material supply path 207, or any of the cyclone heat exchangers 202a to 202b located upstream of the cyclone heat exchanger, the carbon dioxide contained in the kiln exhaust gas flowing through the kiln exhaust gas discharge path 210 is immobilized (carbonated) in the quicklime-containing raw materials when passing through the cyclone preheating device 202. This reduces the amount of carbon dioxide (carbonic acid) contained in the kiln exhaust gas discharged from the kiln exhaust gas discharge path.

[0218] The carbon dioxide fixed in the raw materials containing quicklime is fed into the calcining furnace 204 along with other cement clinker raw materials. After decarbonation in the calcining furnace, it can be recovered as waste gas containing carbon dioxide.

[0219] The second decarbonation feedstock supply path 213 is connected to the first decarbonation feedstock supply device 212 and is used to supply a portion of the decarbonated cement clinker feedstock from the first decarbonation feedstock supply path 212 to the downstream cyclone heat exchanger 202d among the two or more cyclone heat exchangers constituting the cyclone preheating device 202.

[0220] The decarbonated cement clinker raw material flowing in the first decarbonated raw material supply path 212 is at a high temperature (e.g., 950 to 1,000°C). By supplying this raw material to the cyclone heat exchanger 202d located at the downstream end, the temperature inside the cyclone preheating device 202 can be made even higher, which can more effectively preheat the cement clinker raw material and immobilize (carbonate) the carbon dioxide contained in the kiln exhaust gas.

[0221] The cement clinker raw material supplied to the cyclone heat exchanger 202d exchanges heat with the kiln exhaust gas passing through the cyclone heat exchanger 202d and is then centrifugally separated before being fed into the rotary kiln 203.

[0222] It should be noted that a portion of the second decarbonation feedstock supply path 213 can also serve as the kiln exhaust gas discharge path 206.

[0223] The decarbonation feedstock supply control device 215 adjusts the amount of decarbonated cement clinker feedstock supplied from the second decarbonation feedstock supply line 213 to the downstream cyclone heat exchanger 202d. By adjusting the amount of feedstock, the temperature inside the cyclone heat exchanger 202d and the temperature of the kiln exhaust gas passing through the cyclone heat exchanger 202d are adjusted, thereby adjusting the temperature inside the cyclone heat exchanger 202c connected to the preheating feedstock supply line 207.

[0224] The adjustment of the amount of the above-mentioned raw materials is based on the temperature of the kiln exhaust gas in the kiln exhaust gas discharge path 206 when it passes through the cyclone heat exchanger 202c connected to the preheating raw material supply path 207.

[0225] The aforementioned temperature can be the temperature near the inlet of the kiln exhaust gas discharge path 206 (the location where the kiln exhaust gas enters the cyclone heat exchanger 202c) via the cyclone heat exchanger 202c connected to the preheating raw material supply path 207, or the temperature near the outlet of the kiln exhaust gas discharge path 206 (the location where the kiln exhaust gas exits the cyclone heat exchanger 202c).

[0226] The aforementioned temperature is measured using a temperature measuring device 214. The temperature measuring device 214 may be suitably installed in a cyclone heat exchanger 202c connected to the preheating raw material supply line 207.

[0227] For the purpose of adjusting the temperature within the cyclone heat exchanger 202c connected to the preheated raw material supply path 207, a section can be provided between the portion connected to the rotary kiln 203 and the upstream portion of the cyclone heat exchanger 202d located at the downstream end for supplying water or water-containing waste to the kiln exhaust gas discharge path 206a (in... Figure 3 (Shown in dashed line) A moisture supply device (not shown) for the waste gas flowing in the kiln exhaust gas discharge path 206. The temperature of the waste gas is adjusted by supplying water or water-containing waste to the waste gas. This adjustment is based on the temperature measured by the temperature measuring device 214 and can be linked to the decarbonation feedstock supply control device 215.

[0228] Additionally, an air supply passage 217 can be provided to introduce air from the clinker cooler 205 into the kiln exhaust gas discharge passage 206a. This air is heated through heat exchange with the cement clinker within the clinker cooler 205. By adjusting the amount of air supplied from the air supply passage 217 to the kiln exhaust gas discharge passage 206a, the temperature and quantity of the kiln exhaust gas in the kiln exhaust gas discharge passage 206a can be adjusted, and incomplete combustion of waste fed into the kiln tail can be eliminated.

[0229] The amount of air can be adjusted based on the temperature measured by the temperature measuring device 214, and can also be adjusted in conjunction with the decarbonation feedstock supply control device 215.

[0230] The fuel used in rotary kiln 203 is the same as the fuel used in rotary kiln 3 and rotary kiln 103 mentioned above.

[0231] In addition, the exhaust gas generated in the rotary kiln 203 is discharged from the top of the cyclone preheating device 202 after passing through the kiln exhaust gas discharge path 206a to 206e, which is used to discharge the exhaust gas after passing through the cyclone preheating device 202. After being dusted by a cyclone separator, bag filter or electrostatic precipitator, it is discharged to the outside through the chimney.

[0232] A section for supplying denitrification agent to the kiln exhaust gas discharge path 206 can be configured between the portion connected to the rotary kiln 203 and the upstream portion of the cyclone heat exchanger 202d located at the downstream end (in... Figure 3 The device for supplying denitrifying agent (not shown) to the exhaust gas flowing in the kiln exhaust gas discharge path 206 (shown in dashed line) is a denitrifying agent supply device. By spraying the exhaust gas with a denitrifying agent such as urea, the NOx content in the exhaust gas can be reduced.

[0233] Typically, spraying a denitrifying agent onto exhaust gas at a temperature of around 900°C can reduce NOx levels. In typical cement clinker manufacturing systems, the exhaust gas temperature is around 900°C in the region from the kiln tail to the bottom cyclone separator (the downstream cyclone heat exchanger). However, this region contains a large amount of fine powder from cement clinker raw materials. Therefore, the sprayed denitrifying agent may be adsorbed by this fine powder, reducing the aforementioned effectiveness.

[0234] On the other hand, according to Figure 3 The cement clinker manufacturing system 201 can reduce the amount of fine powder from cement clinker raw materials in the exhaust gas of the aforementioned area (the part of the kiln exhaust gas discharge path 206 from the part connected to the rotary kiln 203 to the part passing through the cyclone heat exchanger 202d located at the downstream side), thus effectively reducing the amount of NOx in the exhaust gas.

[0235] Carbon dioxide can also be separated and recovered from kiln exhaust gas, unlike the reduction in carbon dioxide contained in kiln exhaust gas due to the supply of raw materials containing quicklime. Examples of methods for separating and recovering carbon dioxide from kiln exhaust gas include chemical absorption, solid adsorption, and membrane separation, which use monoethanolamine or similar carbon dioxide absorbents.

[0236] Alternatively, a chlorine bypass device 216 may be provided. The chlorine bypass device 216 is the same as the chlorine bypass device 10 described above.

[0237] The cement clinker obtained in the rotary kiln 203 is fed into a clinker cooler 205, which is located downstream of the rotary kiln, for cooling. The rotary kiln 203 is the same as the rotary kiln 3 described above.

[0238] In the cement clinker manufacturing method using the above-mentioned cement clinker manufacturing system 201, the carbon dioxide-containing waste gas generated in the calcining furnace 204 can be recovered and the carbon dioxide in the waste gas can be utilized.

[0239] As for the utilization of carbon dioxide, examples include the same utilization of carbon dioxide as in the cement clinker manufacturing system 1 described above (methanation, carbonation of calcium-containing waste, etc.).

[0240] The following reference Figure 3 An example of a method for utilizing carbon dioxide based on methanation is illustrated.

[0241] The calciner exhaust gas discharge path 210 is connected to the mixing device 228 at a downstream position (further away from the calciner 204) from the location where the first recovery means 211a is installed and the location connected to the calciner exhaust gas supply path 219. The exhaust gas containing carbon dioxide passes through the calciner exhaust gas discharge path 210 and is introduced into the mixing device 228.

[0242] The preparation of the mixing device 228, the carbon dioxide-containing waste gas introduced into the mixing device, and the mixed gas in the mixing device 228 are the same as those of the mixing device 108, the carbon dioxide-containing waste gas introduced into the mixing device 108, and the mixed gas in the mixing device 108.

[0243] The hydrogen used in mixing device 228 is supplied by a hydrogen supply device ( Figure 3 The hydrogen gas introduced into the mixing device 228 by the water electrolysis device 225 is supplied to the mixing device 228 via the hydrogen supply path 227.

[0244] The hydrogen supply device is the same as the hydrogen supply device used in the cement clinker manufacturing system 101 described above.

[0245] When using water electrolysis device 225 as a hydrogen supply device, oxygen is also generated simultaneously with hydrogen, and this oxygen can be used as oxygen contained in combustion-supporting gases.

[0246] The oxygen generated in the water electrolysis device 225 is supplied to the combustion gas supply device 208 via the oxygen supply path 226.

[0247] Figure 3 In this document, the combustion-supporting gas supply device 208 and the water electrolysis device 225 are described as different devices, but the water electrolysis device 225 can also be used as a combustion-supporting gas supply device.

[0248] In addition, hydrogen supply devices such as hydrogen tanks can be prepared separately from the water electrolysis device, and hydrogen can be supplied separately from the hydrogen supply device to the hydrogen supply line 227.

[0249] In addition, if the electricity used for water electrolysis is generated from renewable energy sources such as hydropower, wind power, geothermal energy or solar power, or from electricity generated by using methane generated in the methane generating unit 223 as fuel, carbon dioxide emissions can be further reduced.

[0250] The mixed gas mixed in the mixing device 228 is supplied to the methane generating device 223 via the mixed gas supply path 222 for introducing the mixed gas from the mixing device 228 to the methane generating device 223.

[0251] The mixed gas supply path 222 is the same as the mixed gas supply path 113 described above. In the middle of the mixed gas supply path 222, a cyclone separator, bag filter, or electrostatic precipitator, or a methanation inhibition component separation device, can be installed, just like in the mixed gas supply path 113.

[0252] The methane generating apparatus 223 is the same as the methane generating apparatus 112 described above.

[0253] The methane and water vapor generated in the methane generating device 223 are discharged in the form of a methane-containing gas containing the methane, the water vapor, and unreacted residual carbon dioxide and hydrogen.

[0254] From the perspective of reducing carbon dioxide emissions in cement clinker production and reducing fuel costs, methane-containing gas can be supplied to the calciner 204 via methane supply path 224. The methane contained in the methane-containing gas supplied to the calciner 204 is used as fuel for the heating means 221 of the calciner 204.

[0255] The methane-containing gas supplied to calcining furnace 204 is the same as the methane-containing gas supplied to calcining furnace 104.

[0256] Alternatively, methane-containing gas can be supplied to the heating means of the rotary kiln 203 and used as fuel for that heating means.

[0257] In addition, the methane generated in the methane generating unit 223 can be used separately as fuel for power generation.

[0258] In the aforementioned methanation and carbonation of calcium-containing waste, by directly using waste gas containing carbon dioxide at high temperature without refining (without separating or removing carbon dioxide), methanation and carbonation of waste concrete can be carried out more effectively.

[0259] It should be noted that in the production of cement clinker using the above-mentioned cement clinker manufacturing system, the waste gas containing carbon dioxide generated in the calcining furnace 204 can also be directly stored and isolated.

[0260] Symbol Explanation

[0261] 1,101,201 Cement Clinker Manufacturing System

[0262] 2,102,202 Cyclone Preheating Device

[0263] 2a,2b,2c,2d,102a,102b,102c,102d,202a,202b,202c,202d Cyclone heat exchanger

[0264] 3,103,203 rotary kilns

[0265] 4,104,204 calcining furnace

[0266] 5,105,205 clinker coolers

[0267] 6,6a,6b,6c,6d,6e,106,106a,106b,106c,106d,106e,206,206a,206b,206c,206d,206e Kiln exhaust gas discharge path

[0268] 7,208 Combustion-supporting gas supply device

[0269] 8,107,209 Combustion-supporting gas supply route

[0270] 9,111,210 Calcination furnace exhaust gas discharge path

[0271] 10,117,216 Chlorine Bypass Unit

[0272] 11,118 merging flow path

[0273] 12,119,207 Preheating raw material supply route

[0274] 108,228 mixing unit

[0275] 109,225 Water Electrolysis Unit (Combustion Gas Supply Unit, Hydrogen Supply Unit)

[0276] 110,227 Hydrogen Supply Route

[0277] 112,223 Methane generation unit

[0278] 113,222 Mixed Gas Supply Path

[0279] 114,224 methane supply route

[0280] 13,115a,115b,221 Heating methods

[0281] 211a First Recovery Method

[0282] 211b Second Recovery Method

[0283] 212 First Decarbonation Feed Supply Route

[0284] 213 Second Decarbonation Feed Supply Route

[0285] 214 Temperature measuring device

[0286] 215 Decarbonation Feed Supply Control Device

[0287] 217 Air Supply Route

[0288] 218,218a Raw material supply route containing quicklime

[0289] 218b Second raw material supply route containing quicklime

[0290] 219 Calcination furnace exhaust gas supply path

[0291] 220 Gas supply path for fuel transmission

[0292] 226 Oxygen Supply Route

Claims

1. A cement clinker manufacturing system, comprising: Cyclone preheating device is used to preheat cement clinker raw materials; A rotary kiln is used to fire the cement clinker raw materials that have been preheated by the cyclone preheating device to obtain cement clinker. A calcining furnace, together with the cyclone preheating device, is installed on the upstream side of the rotary kiln to promote the decarbonation of the cement clinker raw materials; A clinker cooler is provided on the downstream side of the rotary kiln for cooling the cement clinker; as well as A kiln exhaust gas discharge path is provided to allow the exhaust gas generated in the rotary kiln to be discharged after passing through the cyclone preheating device. The manufacturing system is characterized by comprising: Combustion-supporting gas supply device, used to supply combustion-supporting gas with a higher oxygen concentration than air; A combustion-supporting gas supply path is used to introduce the combustion-supporting gas from the combustion-supporting gas supply device into the calcining furnace; A calcining furnace exhaust gas discharge path is used to discharge the carbon dioxide-containing exhaust gas generated in the calcining furnace, wherein it is limited to a calcining furnace exhaust gas discharge path that is different from the kiln exhaust gas discharge path. A cyclone separator is used to separate the decarbonated cement clinker raw materials and waste gas generated in the calcining furnace into solid components and the waste gas containing carbon dioxide. as well as The solid flow path is used to allow the solid components separated by the cyclone separator to merge midway in the flow path of the kiln exhaust gas discharge path connected to the rotary kiln, and to feed the solid components into the cyclone heat exchanger located at the downstream end of the cyclone preheating device.

2. The cement clinker manufacturing system as described in claim 1, wherein, The system includes a chlorine bypass device for extracting and cooling a portion of the waste gas generated in the rotary kiln without passing through the cyclone preheating device, removing solid components, discharging the waste gas after removing the solid components, and classifying the solid components into coarse powder and fine powder, using the coarse powder as part of the cement clinker raw material, and recovering the fine powder.

3. The cement clinker manufacturing system as described in claim 1 or 2, wherein, It includes a merging flow path for merging a portion of the carbon dioxide-containing waste gas flowing in the calciner exhaust gas path with the combustion-supporting gas flowing in the combustion-supporting gas supply path.

4. The cement clinker manufacturing system as described in claim 1 or 2, wherein, Include: A preheating raw material supply path is used to supply the preheated cement clinker raw material to the calcining furnace via the cyclone preheating device; The first recovery method is installed midway through the exhaust gas path of the calcining furnace for recovering raw materials containing quicklime from the carbon dioxide-containing exhaust gas; and The calcining furnace exhaust gas supply path is connected to the calcining furnace exhaust gas discharge path midway and downstream of the first recovery means, and is used to merge a portion of the carbon dioxide-containing exhaust gas flowing in the calcining furnace exhaust gas discharge path with the combustion-supporting gas flowing in the combustion-supporting gas supply path. The cyclone preheating device consists of two or more cyclone heat exchangers. The calcining furnace includes a heating means for promoting the decarbonation of the cement clinker raw materials. The combustion-supporting gas supply path is used to allow the carbon dioxide-containing waste gas flowing in the calciner waste gas discharge path to exchange heat with the combustion-supporting gas at a position midway in the calciner waste gas discharge path and upstream of the first recovery means.

5. The cement clinker manufacturing system as described in claim 4, wherein, A heating means for supplying fuel-transfer gas to the calcining furnace, comprising a fuel-transfer gas supply path, branching off from at least one of the locations of the combustion-supporting gas supply path (where the portion of the combustion-supporting gas that allows the carbon dioxide-containing exhaust gas to exchange heat with the combustion-supporting gas is closer to the combustion-supporting gas supply device) and a location midway along the calcining furnace exhaust gas supply path.

6. The cement clinker manufacturing system as described in claim 4 or 5, wherein, It includes an air supply path for introducing air from the clinker cooler into the kiln exhaust gas discharge path.

7. The cement clinker manufacturing system according to any one of claims 4 to 6, wherein, The preheating raw material supply path is connected to the second or more cyclone heat exchangers located from the downstream side among the two or more cyclone heat exchangers constituting the cyclone preheating device. The manufacturing system includes: A raw material supply path containing quicklime is used to supply the raw material containing quicklime recovered by the first recovery means from the first recovery means to the cyclone heat exchanger connected to the preheating raw material supply path in the two or more cyclone heat exchangers, or to the cyclone heat exchanger located upstream of the cyclone heat exchanger. The first decarbonation feedstock supply path is used to supply the cement clinker feedstock, which has undergone decarbonation in the calcining furnace, from the calcining furnace to the rotary kiln; The second decarbonation feedstock supply path is used to supply a portion of the decarbonated cement clinker feedstock from the first decarbonation feedstock supply path to the most downstream cyclone heat exchanger among the two or more cyclone heat exchangers. A temperature measuring device is used to measure the temperature of the exhaust gas in the kiln exhaust gas discharge path as it passes through the cyclone heat exchanger connected to the preheated raw material supply path; and A decarbonation feedstock supply control device is used to adjust the amount of decarbonated cement clinker feedstock supplied from the second decarbonation feedstock supply path to the cyclone heat exchanger located at the downstream end based on the temperature measured by the temperature measuring device, thereby adjusting the temperature inside the cyclone heat exchanger connected to the preheating feedstock supply path.

8. The cement clinker manufacturing system as described in claim 7, wherein, It includes a moisture supply device for supplying water or water-containing waste to the waste gas flowing in the kiln waste gas discharge path from the portion connected to the rotary kiln to the upstream portion of the cyclone heat exchanger located at the downstream end.

9. The cement clinker manufacturing system as described in claim 7 or 8, wherein, It includes a denitrification agent supply device for supplying denitrification agent to the waste gas flowing in the kiln waste gas discharge path from the portion connected to the rotary kiln to the upstream portion of the cyclone heat exchanger located at the downstream end.

10. The cement clinker manufacturing system according to any one of claims 1 to 3, wherein, Include: A mixing device is used to mix the waste gas containing carbon dioxide with hydrogen to prepare a mixed gas of the waste gas containing carbon dioxide and hydrogen, and to adjust the temperature of the mixed gas. A hydrogen supply device for supplying the hydrogen; A hydrogen supply path is provided for introducing hydrogen from the hydrogen supply device to the mixing device; A methane generating device for using a catalyst to react carbon dioxide and hydrogen contained in the mixed gas to produce methane and water vapor; as well as A mixed gas supply path is provided for introducing the mixed gas from the mixing device to the methane generating device. The calcining furnace exhaust path is used to introduce the carbon dioxide-containing exhaust gas from the calcining furnace into the mixing device.

11. The cement clinker manufacturing system as described in claim 10, wherein, Includes a methane supply path for supplying methane-containing gas generated by the methane generating device to the calcining furnace.

12. The cement clinker manufacturing system as described in claim 10 or 11, wherein, The combustion-supporting gas supply device and the hydrogen supply device are water electrolysis devices used to electrolyze water to obtain hydrogen and oxygen.

13. A method for manufacturing cement clinker, comprising using the cement clinker manufacturing system according to any one of claims 1 to 9 to manufacture cement clinker, characterized in that, The waste gas containing carbon dioxide is recovered, and the carbon dioxide in the waste gas is utilized.

14. The method for manufacturing cement clinker as described in claim 13, wherein, The oxygen concentration of the combustion-supporting gas is adjusted so that the carbon dioxide concentration of the exhaust gas containing carbon dioxide is 80% or more of 100% of the volume excluding water vapor.

15. The method for manufacturing cement clinker as described in claim 13 or 14, wherein, Methane is produced by using a catalyst from hydrogen and the recovered carbon dioxide-containing waste gas, and the produced methane is used as fuel for at least one of the rotary kiln and the calcining furnace.

16. The method for manufacturing cement clinker according to any one of claims 13 to 15, wherein, The recovered carbon dioxide-containing waste gas is brought into contact with calcium-containing waste, so that the carbon dioxide contained in the carbon dioxide-containing waste gas is absorbed by the calcium-containing waste. The calcium-containing waste that has absorbed the carbon dioxide is then used as a raw material for cement clinker.

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