CEMENT CLINKER PRODUCTION SYSTEM AND CEMENT CLINKER PRODUCTION METHOD

Abstract

To provide a cement clinker manufacturing system capable of efficiently obtaining exhaust gas having a high carbon dioxide gas concentration and from which chlorine is removed.SOLUTION: A cement clinker manufacturing system 1 comprises: a cyclone preheating device 2; a rotary kiln 3; a calcination furnace 4 for promoting decarboxylation of a raw material; a clinker cooler 5; a kiln exhaust gas discharge path 6; a combustion-supporting gas supply path 9 for guiding combustion-supporting gas to the calcination furnace 4; a calcination furnace exhaust gas discharge path 10; a calcination furnace exhaust gas temperature lowering device 11 for lowering a temperature of carbon dioxide gas-containing exhaust gas flowing through the exhaust gas discharge path 10; a dust collector 12 for recovering a lime-containing raw material from the carbon dioxide gas-containing exhaust gas; and a water washing device 13 for washing the recovered lime-containing raw material; and an exhaust gas treatment agent supply device 25 for supplying at least a portion of a lime-containing residue generated by water washing into a calcination furnace exhaust gas supply path 10 between the calcination furnace exhaust gas temperature lowering device 11 and the dust collector 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cement clinker production system and a cement clinker production method. [Background technology]

[0002] In recent years, reducing carbon dioxide emissions has become an important issue in order to curb global warming. Meanwhile, the cement industry is one of the industries that emits a large amount of carbon dioxide. Of the total amount of carbon dioxide (gaseous carbon dioxide) emitted during the production of cement, approximately 60% is emitted through the decarbonation of limestone, which is used as a raw material for cement, and approximately 40% is emitted through the combustion of fuel used in production. Methods for reducing the amount of carbon dioxide gas generated by fuel combustion include methods for improving energy efficiency, methods for using biomass fuel as fuel, etc. For example, Patent Document 1 describes a cement calcination device capable of reducing the amount of carbon dioxide gas generated by fuel combustion, which is characterized by having a main burner that injects combustible gas as the main fuel and combustible waste as the auxiliary fuel into a cement kiln.

[0003] On the other hand, it is difficult to use a calcium-containing raw material that generates less carbon dioxide gas as a cement raw material to replace limestone, which generates a large amount of carbon dioxide gas. Therefore, it is difficult to reduce the amount of carbon dioxide gas generated by the decarbonation of limestone. Known methods for reducing carbon dioxide emissions include separating and capturing the generated carbon dioxide gas, and then storing, isolating, or effectively utilizing the gas. As a method for separating and recovering the generated carbon dioxide gas, for example, Patent Document 2 describes a method for separating and recovering carbon dioxide from by-product gas generated in a steelworks by a chemical absorption method, in which carbon dioxide is absorbed from the gas by a chemical absorption liquid, and then the chemical absorption liquid is heated to separate the carbon dioxide, and the carbon dioxide separation and recovery method is characterized by utilizing or making use of low-grade exhaust heat of 500°C or less generated in the steelworks in the process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-52746 A [Patent Document 2] JP 2004-292298 A Summary of the Invention [Problem to be solved by the invention]

[0005] Exhaust gas generated during the production of cement clinker contains large amounts of nitrogen, oxygen, etc. in addition to carbon dioxide gas. Therefore, in order to separate and recover carbon dioxide gas from the exhaust gas, it is necessary to use a chemical absorption method using an amine compound, etc. If the concentration of carbon dioxide gas contained in the exhaust gas can be increased, it becomes easier to separate and recover the carbon dioxide gas. In addition, by reducing the amount of nitrogen and other substances contained in the exhaust gas, the volume of the exhaust gas generated can be relatively reduced, and the equipment for separating and recovering the carbon dioxide gas can be made smaller. An object of the present invention is to provide a cement clinker production system which, when producing cement clinker, can increase the carbon dioxide concentration in a part of exhaust gas to efficiently obtain a gas containing a high concentration of carbon dioxide which is easily usable for the fixation of carbon dioxide, and can also efficiently remove chlorine from the exhaust gas. [Means for solving the problem]

[0006] As a result of intensive research by the present inventors to solve the above problems, they have discovered a cement clinker production system including a cyclone-type preheating device for preheating cement clinker raw materials, a rotary kiln for burning the cement clinker raw materials to obtain cement clinker, a calciner for promoting decarbonation of the cement clinker raw materials, a preheated raw material supply path for supplying the preheated cement clinker raw materials to the calciner, a clinker cooler for cooling the cement clinker, and a kiln exhaust gas exhaust path for discharging exhaust gas generated in the rotary kiln, the system including a combustion supporting gas supply device for supplying a combustion supporting gas having a higher oxygen concentration than air, and a combustion supporting gas supply path for guiding the combustion supporting gas to the calciner, The inventors have found that the above-mentioned object can be achieved by a cement clinker production system including a calciner exhaust gas discharge passage for discharging carbon dioxide-containing exhaust gas generated in the calciner, a calciner exhaust gas temperature reducing device for reducing the temperature of the carbon dioxide-containing exhaust gas, a dust collecting device for recovering quicklime-containing raw materials from the carbon dioxide-containing exhaust gas, a water washing device for washing the quicklime-containing raw materials supplied from the dust collecting device, a slaked lime-containing residue discharge passage for discharging the slaked lime-containing residue generated in the water washing device, an exhaust gas treating agent supplying device for supplying an exhaust gas treating agent containing the slaked lime-containing residue to the carbon dioxide-containing exhaust gas, and an exhaust gas treating agent supplying passage for supplying at least a portion of the slaked lime-containing residue to the exhaust gas treating agent supplying device, and have completed the present invention. That is, the present invention provides the following [1] to

[10] .

[0007] [1] A cyclone-type preheating device for preheating cement clinker raw materials, which is composed of two or more cyclone-type heat exchangers; a rotary kiln for burning the cement clinker raw materials preheated by the cyclone-type preheating device to obtain cement clinker; a calcination furnace for promoting decarbonation of the cement clinker raw materials, which is disposed upstream of the rotary kiln together with the cyclone-type preheating device; a preheated raw material supply passage for supplying the preheated cement clinker raw materials from the cyclone-type preheating device to the calcination furnace; a clinker cooler for cooling the cement clinker, and a kiln exhaust gas exhaust passage for discharging exhaust gas generated in the rotary kiln after passing through the cyclone-type preheating device, the system further comprising a combustion supporting gas supply device for supplying a combustion supporting gas having a higher oxygen concentration than air, a combustion supporting gas supply passage for guiding the combustion supporting gas from the combustion supporting gas supply device to the calciner, and a calciner exhaust gas exhaust passage (limited to being different from the kiln exhaust gas exhaust passage) for discharging carbon dioxide-containing exhaust gas generated in the calciner.a calciner exhaust gas temperature reducing device disposed in the calciner exhaust gas discharge path for reducing the temperature of the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge path; a dust collecting device disposed in the calciner exhaust gas discharge path and downstream of the calciner exhaust gas temperature reducing device for recovering a quicklime-containing raw material from the carbon dioxide-containing exhaust gas; a water washing device for washing the quicklime-containing raw material; a first quicklime-containing raw material supply path for supplying the quicklime-containing raw material from the dust collecting device to the water washing device; an exhaust gas treatment agent supplying device for supplying at least a portion of the slaked lime-containing residue recovered from the slaked lime-containing residue discharge path to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge path between the calciner exhaust gas temperature reducing device and the dust collecting device; and an exhaust gas treatment agent supplying path for supplying the slaked lime-containing residue recovered by the exhaust gas treatment agent supplying device to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge path between the calciner exhaust gas temperature reducing device and the dust collecting device.

[0008] [2] The cement clinker production system according to [1], further comprising a chlorine bypass device for extracting and cooling a portion of the exhaust gas generated in the rotary kiln without passing through the cyclone preheating device, removing solids therefrom, discharging the exhaust gas from which the solids have been removed, and classifying the solids into coarse powder and fine powder, using the coarse powder as a part of the cement clinker raw material, and recovering the fine powder. [3] The cement clinker production system according to [1] or [2], further comprising a confluence passage for confluence a portion of the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge passage with the combustion-supporting gas flowing through the combustion-supporting gas supply passage.

[0009] [4] The preheating raw material supply passage is connected to a cyclone heat exchanger located second or more downstream from the rearmost side among the two or more cyclone heat exchangers constituting the cyclone preheating device, and includes a quicklime-containing raw material recovery means for recovering quicklime-containing raw material from the cement clinker raw material decarbonated in the calciner, a second quicklime-containing raw material supply passage for supplying the quicklime-containing raw material recovered by the quicklime-containing raw material recovery means from the quicklime-containing raw material recovery means to a cyclone heat exchanger to which the preheating raw material supply passage is connected among the two or more cyclone heat exchangers, or to a cyclone heat exchanger located upstream of the cyclone heat exchanger, and a first decarbonated raw material supply passage for supplying the cement clinker raw material decarbonated in the calciner to the rotary kiln from the calciner, and a second decarbonation raw material supply passage for supplying a portion of the decarbonated cement clinker raw material from the first decarbonation raw material supply passage to a cyclone type heat exchanger located at the most rearmost side of the two or more cyclone type heat exchangers; a temperature measuring device for measuring a temperature of the exhaust gas in the kiln exhaust gas discharge passage when it passes through the cyclone type heat exchanger connected to the preheating raw material supply passage; and a decarbonation raw material supply amount control device for adjusting an amount of the decarbonated cement clinker raw material supplied from the second decarbonation raw material supply passage to the cyclone type heat exchanger located at the most rearmost side based on the temperature measured by the temperature measuring device, and adjusting a temperature in the cyclone type heat exchanger connected to the preheating raw material supply passage by said adjustment.

[0010] [5] The cement clinker production system according to [4], further comprising a moisture supplying device for supplying water or water-containing waste to the exhaust gas flowing through the kiln exhaust gas discharge passage between the portion of the kiln exhaust gas discharge passage connected to the rotary kiln and the upstream portion of the cyclone-type heat exchanger located at the most downstream side. [6] The cement clinker production system according to [4] or [5], further comprising a denitrification agent supplying device for supplying a denitrification agent to the exhaust gas flowing through the kiln exhaust gas exhaust passage between the portion of the kiln exhaust gas exhaust passage connected to the rotary kiln and the upstream portion of the cyclone heat exchanger located at the most downstream side.

[0011] [7] A method for producing cement clinker using the cement clinker production system according to any one of [1] to [6] above, comprising using the calciner exhaust gas temperature reducing device to adjust a temperature of the carbon dioxide-containing exhaust gas supplied to the dust collector to 100 to 400°C. [8] The method for producing cement clinker according to [7], further comprising adjusting the oxygen concentration of the combustion supporting gas so that the carbon dioxide concentration of the carbon dioxide-containing exhaust gas generated in the calciner is 80 volume % or more relative to 100 volume % excluding water vapor. [9] The method for producing cement clinker according to the above [7] or [8], wherein the carbon dioxide-containing exhaust gas generated in the calciner is recovered and the carbon dioxide contained in the carbon dioxide-containing exhaust gas is utilized.

[10] A method for producing cement clinker using the cement clinker production system according to any one of [4] to [6], comprising: heating the cement clinker raw material in the calciner so that the temperature of the cement clinker raw material is 950 to 1,100°C; and heating the cement clinker raw material in the calciner so that the temperature of the cement clinker raw material in the cyclone heat exchanger to which the preheated raw material supply passage is connected is 700 to 900°C. Decarbonation raw material supply amount control device The method for producing cement clinker further comprises adjusting an amount of the decarbonated cement clinker raw material supplied from the second decarbonated raw material supply passage to a cyclone type heat exchanger located at the most downstream side using the above-mentioned. Effect of the Invention

[0012] According to the cement clinker production system of the present invention, when producing cement clinker, it is possible to efficiently obtain gas containing a high concentration of carbon dioxide that is easily usable for the fixation of carbon dioxide, by increasing the carbon dioxide concentration in a portion of the exhaust gas, and it is also possible to efficiently remove harmful substances such as chlorine from the exhaust gas. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating a schematic diagram of an example of a cement clinker production system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the cement clinker production system of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic diagram showing an example of an embodiment of a cement clinker production system according to the present invention. The cement clinker production system 1 includes a cyclone-type preheating device 2 consisting of two or more cyclone-type heat exchangers 2a to 2d for preheating the cement clinker raw material, a rotary kiln 3 for burning the cement clinker raw material preheated by the cyclone-type preheating device 2 to obtain cement clinker, a calciner 4 disposed upstream of the rotary kiln 3 together with the cyclone-type preheating device 2 for promoting decarbonation of the cement clinker raw material, a preheated raw material supply passage 7 for supplying the preheated cement clinker raw material from the cyclone-type preheating device 2 to the calciner 4, and a rotary kiln 3 for supplying the preheated cement clinker raw material from the cyclone-type preheating device 2 to the calciner 4. The cement clinker production system includes a clinker cooler 5 for cooling cement clinker, which is disposed downstream of a rotary kiln 3, and a kiln exhaust gas discharge passage 6 for discharging exhaust gas generated in the rotary kiln 3 after passing through a cyclone type preheating device 2. The cement clinker production system includes a combustion supporting gas supply device 8 for supplying a combustion supporting gas having a higher oxygen concentration than air, a combustion supporting gas supply passage 9 for introducing the combustion supporting gas from the combustion supporting gas supply device 8 to a calciner 4, and a calciner exhaust gas discharge passage 10 for discharging carbon dioxide-containing exhaust gas generated in the calciner 4 (however, the kiln exhaust gas a calciner exhaust gas temperature reducing device 11 arranged in the calciner exhaust gas discharge path 10 for reducing the temperature of the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge path 10; a dust collector 12 arranged in the calciner exhaust gas discharge path 10 and downstream of the calciner exhaust gas temperature reducing device 11 for recovering quicklime-containing raw material from the carbon dioxide-containing exhaust gas; a water washing device 13 for washing the quicklime-containing raw material; a first quicklime-containing raw material supply path 14 for supplying the quicklime-containing raw material from the dust collector 12 to the water washing device 13; The system includes a slaked lime-containing residue discharge conduit 16 for discharging the generated slaked lime-containing residue, an exhaust gas treatment agent supplying device 25 for supplying at least a portion of the slaked lime-containing residue recovered from the slaked lime-containing residue discharge conduit 16 to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge conduit 10 between the calciner exhaust gas temperature reducing device 11 and the dust collector 12, and an exhaust gas treatment agent supplying conduit 15 for supplying the slaked lime-containing residue recovered by the exhaust gas treatment agent supplying device 25 to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge conduit 10 between the calciner exhaust gas temperature reducing device 11 and the dust collector 12.

[0015] The cyclone preheating device 2 is composed of two or more cyclone heat exchangers 2a to 2d. The multiple cyclone heat exchangers 2a to 2d are connected by a flow path for moving the cement clinker raw material and kiln exhaust gas discharge paths 6a to 6e for discharging the exhaust gas generated in the rotary kiln 3 after passing through the multiple cyclone heat exchangers 2a to 2d. The kiln exhaust gas discharge paths 6a to 6e may also serve as a flow path for moving the cement clinker raw material. The number of cyclone heat exchangers is two or more, typically four to five. The multiple cyclone heat exchangers are typically arranged vertically. The cement clinker raw materials are charged into the cyclone heat exchanger 2a disposed at the front end of the cyclone preheating device 2, where they are centrifuged while exchanging heat with the kiln exhaust gas, and then charged from the bottom of the cyclone heat exchanger 2a into the cyclone heat exchanger 2b disposed downstream, and then again centrifuged while exchanging heat with the exhaust gas, and then charged into the cyclone heat exchanger 2c disposed downstream. In this way, the cement clinker raw materials are preheated (heated) by the exhaust gas, and are transferred successively to the cyclone heat exchangers 2b to 2c disposed downstream, and then charged into the calciner 4.

[0016] By preheating the raw cement clinker in the cyclone preheater 2, the amount of fuel input used to promote decarbonation in the calciner 4 can be reduced. In the cyclone preheating device 2, the cement clinker raw material is preheated to preferably 400 to 900°C, more preferably 500 to 800°C, and particularly preferably 600 to 750°C. If the temperature is 400°C or higher, the amount of fuel used to promote decarbonation in the calciner 4 can be reduced. If the temperature is 900°C or lower, decarbonation of the cement clinker raw material is not promoted easily in the cyclone preheating device 2, so that it is possible to prevent the carbon dioxide concentration in the kiln exhaust gas from becoming high. Among the two or more cyclone heat exchangers 2a to 2d constituting the cyclone preheating device 2, the cement clinker raw material is preheated at preferably 600 to 900 ° C, more preferably 700 to 900 ° C in the cyclone heat exchanger 2c connected to the preheating raw material supply passage 7. By preheating in such a temperature range, when the kiln exhaust gas passes through the cyclone preheating device 2 (particularly the cyclone heat exchanger 2c connected to the preheating raw material supply passage 7), it becomes easier to fix (carbonate) the carbon dioxide gas contained in the kiln exhaust gas in the quicklime-containing raw material (described in detail later) fed from the second quicklime-containing raw material supply passage 22b to the cyclone preheating device 2, thereby reducing the amount of carbon dioxide gas in the kiln exhaust gas and increasing the concentration of carbon dioxide gas in the calciner exhaust gas.

[0017] The cement clinker raw material is not particularly limited, and may be any of the raw materials commonly used for cement clinker. Specific examples include natural raw materials such as limestone, soil, clay, silica stone, and iron raw materials, and waste materials or by-products such as coal ash, steel slag, municipal waste incineration ash, sewage sludge incineration ash, raw concrete sludge, and fine waste concrete powder. Calcium-containing waste materials (described later) that have absorbed carbon dioxide may also be used as the cement clinker raw material. The cement clinker raw materials are prepared by pulverizing and mixing various raw materials in an appropriate ratio using a raw material mill, and then the raw materials are fed into the cyclone-type preheating device 2. The particle size of the cement clinker raw materials is preferably 100 μm or less from the viewpoint of facilitating the production of cement clinker. In addition, a part of the cement clinker raw material (for example, contaminated soil containing a large amount of organic matter) may be directly charged into the rotary kiln 3 without being charged into the cyclone-type preheating device 2.

[0018] The preheated cement clinker raw material is supplied to the calciner 4 through a preheated raw material supply passage 7 connected to any one of the two or more cyclone heat exchangers 2a to 2d that constitute the cyclone preheating device 2. In Fig. 1, the preheated raw material supply passage 7 is connected to the cyclone heat exchanger 2c disposed second or more from the rearmost side of the cyclone preheating device 2, and the cement clinker raw material preheated by passing through the cyclone heat exchangers 2a to 2c is fed from the cyclone heat exchanger 2c through the preheated raw material supply passage 7 to the calciner 4. By connecting the preheated raw material supply passage 7 to the cyclone heat exchanger 2c located second from the rearmost side, it is possible to feed sufficiently preheated cement clinker raw material into the calciner 4.

[0019] The calciner 4 is disposed upstream of the rotary kiln 3 together with the cyclone preheater 2 for the purpose of promoting decarbonation of the cement clinker raw material by burning fuel using a heating means. Here, decarbonation of cement clinker raw materials means decarbonation of calcium carbonate (CaCO 3 ) is heated to produce quicklime (CaO) and carbon dioxide (CO 2 ) When the cement clinker raw material is heated in the calciner 4 using a combustion supporting gas having a higher oxygen concentration than air, the carbon dioxide partial pressure becomes high. Therefore, the temperature required to promote decarbonation becomes higher, and the temperature needs to be higher than when air is used as the combustion supporting gas. For this reason, the calciner 4 is heated so that the temperature of the heated cement clinker raw material is preferably 950 to 1,100°C, more preferably 975 to 1,080°C, and particularly preferably 1,000 to 1,050°C. If the temperature is 950°C or higher, the decarbonation of the cement clinker raw material can be further promoted even in an atmosphere with a high carbon dioxide partial pressure, and the temperature in the rotary kiln 3 is not excessively lowered even if the decarbonated cement clinker raw material is directly charged into the rotary kiln 3 from the calciner 4 through the first decarbonation raw material supply passage 18. If the temperature is 1,100°C or lower, clogging due to sintering of the raw material can be prevented.

[0020] Decarbonation of the cement clinker raw material is facilitated in the calciner 4 by using heating means to combust a fuel with a combustion supporting gas to directly heat the cement clinker raw material. An example of the heating means 26 is a burner. The fuel used in the calciner is not particularly limited, and examples thereof include fossil fuels such as coal, heavy oil, and natural gas; biomass such as coconut shells; biogas obtained by gasifying biomass; methane produced by methanation using carbon dioxide as a raw material; etc. These may be used alone or in combination of two or more. In particular, if carbon-free fuel such as biomass is used, the amount of carbon dioxide emissions in the production of cement clinker can be substantially reduced. In addition, from the viewpoint of effective use of waste materials and reduction of the amount of fuel used, waste plastics may be used as a substitute for the above fuel. When waste plastics are used as a substitute for fuel, hydrogen chloride gas and CaCl 2 However, the cement clinker production system of the present invention has a dust collector 12, a water washing device 13, etc., which will be described later, and therefore can remove hydrogen chloride gas and alkali chlorides, and can use waste plastics as a substitute for fuel.

[0021] The combustion supporting gas used in the calciner 4 has a higher oxygen concentration than air. By using such a combustion supporting gas, the carbon dioxide concentration of the calciner exhaust gas can be increased. In addition, by using the combustion supporting gas, the combustibility of the fuel is improved, so that even fuels that have been difficult to use in the past because they are difficult to finely grind can be used. From the viewpoint of increasing the carbon dioxide gas concentration in the calciner exhaust gas, the oxygen concentration of the combustion supporting gas is preferably 21% by volume or more, more preferably 25% by volume or more, and particularly preferably 30% by volume or more, based on 100% by volume including steam. Also, from the viewpoint of making it easier to control combustion, the oxygen concentration is preferably 90% by volume or less, more preferably 80% by volume or less, even more preferably 70% by volume or less, even more preferably 60% by volume or less, and particularly preferably 50% by volume or less.

[0022] The combustion-supporting gas used in the calciner 4 is supplied from a combustion-supporting gas supply device 8 and led to the calciner 4 through a combustion-supporting gas supply path 9 . The combustion supporting gas supply passage 9 may be disposed so that the temperature of the combustion supporting gas passing through the combustion supporting gas supply passage 9 is indirectly heated by air heated by heat exchange with the cement clinker in the clinker cooler 5. In addition, the temperature of the combustion supporting gas may be raised by the heat of the cement clinker by passing the combustion supporting gas through the combustion supporting gas supply passage 9 through a part of the downstream side of the cement cooler (the outlet side of the clinker cooler). By increasing the temperature of the combustion supporting gas, the input amount of fuel used in the calciner 4 can be reduced.

[0023] Examples of the combustion supporting gas supply device 8 include an oxygen tank, an air separation unit (ASU) that separates oxygen from air, and a water electrolysis device that generates oxygen by electrolysis of water. Methods for separating oxygen from air include cryogenic separation, adsorption separation, membrane separation, etc. Among these, cryogenic separation is preferred from the viewpoint of obtaining a large amount of oxygen.

[0024] The combustion supporting gas supplied from the combustion supporting gas supply device 8 has a higher oxygen concentration than air. The combustion supporting gas may be used in the calciner 4 as it is, but the composition thereof may be appropriately adjusted before being used in the calciner 4. For example, from the viewpoint of preventing the oxygen concentration of the combustion-supporting gas used in the calciner 4 from becoming excessively high, which would make it difficult to control combustion, increasing the carbon dioxide concentration of the calciner exhaust gas, and reducing the amount of oxygen remaining in the calciner exhaust gas, the combustion-supporting gas supplied from the combustion-supporting gas supply device 8 may be mixed with carbon dioxide gas, and the resulting mixed gas may be used as the combustion-supporting gas used in the calciner 4.

[0025] Furthermore, in order to lower the temperature required to promote decarbonation by lowering the partial pressure of carbon dioxide, the combustion-supporting gas supplied from the combustion-supporting gas supply device 8 may be mixed with water vapor, and the resulting mixed gas may be used as the combustion-supporting gas in the calciner 4. The carbon dioxide gas concentration of the above mixed gas (a mixture of the combustion-supporting gas supplied from the combustion-supporting gas supply device 7 and at least one of carbon dioxide gas and water vapor) is preferably 10 to 79 volume %, more preferably 20 to 75 volume %, and even more preferably 30 to 70 volume %, relative to 100 volume % including water vapor. From the viewpoint of reducing the volume of the exhaust gas generated in the calciner 4 and increasing the carbon dioxide concentration of the exhaust gas, it is preferable that the combustion supporting gas used in the calciner 4 does not contain gases other than oxygen, carbon dioxide, and water vapor (e.g., nitrogen). The concentration of gases other than oxygen, carbon dioxide, and water vapor in the combustion supporting gas is preferably 10% by volume or less, more preferably 5% by volume or less, and particularly preferably 2% by volume or less, relative to 100% by volume including water vapor.

[0026] An example of a method for mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 8 with carbon dioxide gas is a method for mixing the combustion-supporting gas supplied from the combustion-supporting gas supply device 8 with calciner exhaust gas. Since the temperature of the calciner exhaust gas discharged from the calciner 4 is as high as about 950 to 1,100°C, the temperature of the combustion-supporting gas can be increased by using the exhaust gas. When calciner exhaust gas is mixed, a junction flow passage 24 is provided for merging a portion of the exhaust gas flowing through the calciner exhaust gas exhaust passage 10 (which must be different from the kiln exhaust gas exhaust passages 6a to 6e) for discharging the exhaust gas generated in the calciner 4 with the combustion-supporting gas (the combustion-supporting gas supplied from the combustion-supporting gas supply device 8) flowing through the combustion-supporting gas supply passage 9, and the combustion-supporting gas flowing through the combustion-supporting gas supply passage 9 is mixed with the exhaust gas. From the viewpoint of using high-temperature carbon dioxide-containing exhaust gas, the position where the confluence flow passage 24 is connected to the calciner exhaust gas discharge passage 10 is midway through the calciner exhaust gas discharge passage 10 and is a position upstream of the calciner exhaust gas temperature reducing device 11 (a position closer to the calciner 4 than the calciner exhaust gas temperature reducing device). The upstream side of the calciner exhaust gas discharge passage 10 means a position in the calciner exhaust gas discharge passage 10 that is closer to the calciner 4, and the downstream side of the calciner exhaust gas discharge passage 10 means a position closer to the exhaust port of the calciner exhaust gas discharge passage 10 (the portion where the calciner exhaust gas is discharged to the outside). In addition, when the combustion-supporting gas supply passage 9 is arranged so that the combustion-supporting gas passing through the combustion-supporting gas supply passage 9 is indirectly heated and heated by air heated by heat exchange with the cement clinker in the clinker cooler 5, it is preferable to arrange the confluence flow passage 24 so that the combustion-supporting gas and a part of the exhaust gas are joined at a point after the combustion-supporting gas is indirectly heated by the air.

[0027] The carbon dioxide-containing exhaust gas produced in the calciner 4 is discharged through a calciner exhaust gas discharge passage 10 . A calciner exhaust gas temperature reducing device 11 for reducing the temperature of the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge path 10 is provided in the calciner exhaust gas discharge path 10 . The calciner exhaust gas temperature reducing device 11 is not particularly limited as long as it can reduce the temperature of the carbon dioxide-containing exhaust gas. For example, it may be a device for exchanging heat between air and the carbon dioxide-containing exhaust gas, or a device for exchanging heat between a liquid and the carbon dioxide-containing exhaust gas. By lowering the temperature of the carbon dioxide-containing exhaust gas to, for example, 100 to 400°C, chlorine (derived from cement clinker raw materials or waste plastics used as fuel substitutes in calciners) contained in the carbon dioxide-containing exhaust gas can be precipitated as alkali chlorides in the dust collector 12. In addition, fine powder containing quicklime in the carbon dioxide-containing exhaust gas can be more efficiently collected.

[0028] A dust collector 12 is provided in the calciner exhaust gas discharge passage 10 and downstream of the calciner exhaust gas temperature reducing device 11 for recovering lime-containing raw materials (fine powder containing lime) contained in the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas supply passage 10. The lime-containing raw materials include precipitated CaCl in addition to lime. 2 and alkali chlorides such as KCl. Examples of the dust collector 12 include a cyclone, a bag filter, and an electrostatic precipitator. The quicklime-containing raw material collected by the dust collector 12 is supplied to the water washing device 13 through a first quicklime-containing raw material supply passage 14 . In addition, for the purpose of fixing (carbonating) the carbon dioxide gas in the kiln exhaust gas in the quicklime-containing raw material, a part of the quicklime-containing raw material recovered by the dust collector 12 may pass through the second quicklime-containing raw material supply passage 22a, merge with the quicklime-containing raw material flowing through the second quicklime-containing raw material supply passage 22b, and be supplied to the cyclone-type preheater 2 via the second quicklime-containing raw material supply passage 22. The second calcareous raw material supply path 22a and the second calcareous raw material supply path 22b join together (the joining point is not shown) to form the second calcareous raw material supply path 22.

[0029] In the water washing device 13, the quicklime-containing material is washed with water to remove chlorine (CaCl 2 It is possible to remove chlorine, which exists in the form of alkali chlorides such as potassium chloride and potassium chloride. In the water washing device 13, the slaked lime-containing residue generated after the water washing is discharged to the outside through the slaked lime-containing residue discharge passage 16. The residue generated after the water washing contains slaked lime (Ca(OH) 2 ), it can also be used as a raw material for cement clinker.

[0030] At least a portion of the slaked lime-containing residue flowing through the slaked lime-containing residue discharge passage 16 is recovered by an exhaust gas treatment agent supplying device 25 disposed midway through the slaked lime-containing residue discharge passage 16 . The recovered slaked lime-containing residue is supplied to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge passage 10 between the calciner exhaust gas temperature reducing device 11 and the dust collector 12 through the exhaust gas treating agent supply passage 15. The recovered slaked lime-containing residue may also be supplied to the dust collector 12 through the exhaust gas treating agent supply passage 15. The slaked lime-containing residue to be supplied is preferably one that has been dried in advance. The slaked lime-containing residue is supplied, for example, by spraying the slaked lime-containing residue. By supplying the slaked lime-containing residue to the carbon dioxide-containing flue gas, the hydrogen chloride gas contained in the carbon dioxide-containing flue gas can be converted into an alkali chloride. The alkali chloride is recovered in the dust collector 12. Various exhaust gas treatment agents such as slaked lime may be separately supplied together with the slaked lime-containing residue.

[0031] In the dust collector 12, the carbon dioxide-containing exhaust gas from which the quicklime-containing raw material has been recovered is further dewatered, and then the carbon dioxide is separated and recovered. Since the carbon dioxide-containing exhaust gas has a high carbon dioxide concentration, it is easy to separate and recover the carbon dioxide from the carbon dioxide-containing exhaust gas. The carbon dioxide concentration of the carbon dioxide-containing exhaust gas is preferably 80% by volume or more, more preferably 85% by volume or more, and particularly preferably 90% by volume or more, based on 100% by volume excluding water vapor. The carbon dioxide concentration can be increased by adjusting the oxygen concentration of the combustion-supporting gas. Specifically, the carbon dioxide concentration can be increased by increasing the oxygen concentration of the combustion-supporting gas or decreasing the concentrations of gases other than oxygen, carbon dioxide, and water vapor (e.g., nitrogen) in the combustion-supporting gas. In addition, since the carbon dioxide-containing exhaust gas that has passed through the dust collector 12 has had chlorine removed, adverse effects due to the inclusion of chlorine can be prevented. The temperature of the carbon dioxide-containing exhaust gas discharged from the calciner 4 is usually 950 to 1,100° C. Since the carbon dioxide-containing exhaust gas has a high temperature, the exhaust gas may be used to heat water to generate steam, and the steam may be used with a steam turbine to generate power.

[0032] Carbon dioxide may be purified by removing oxygen, nitrogen, water vapor, etc. from the calciner exhaust gas. When the concentration of carbon dioxide in the calciner exhaust gas is high, the carbon dioxide can be purified by directly compressing and cooling it to liquefy it without separating and recovering the carbon dioxide using a chemical absorbent such as an amine.

[0033] The calciner exhaust gas discharge path 10 is different from the kiln exhaust gas discharge paths 6a to 6e for discharging the exhaust gas generated in the rotary kiln 3. By completely separating the calciner exhaust gas discharge path 10 from the kiln exhaust gas discharge paths 6a to 6e, it is possible to recover only the calciner exhaust gas having a high carbon dioxide concentration.

[0034] In FIG. 1, after decarbonation of the cement clinker raw material is promoted in a calciner 4, the raw material is supplied to a rotary kiln 3 through a first decarbonation raw material supply passage 18 while maintaining the high temperature after heating. A quicklime-containing raw material recovery means 17 may be provided in the first decarbonated raw material supply passage 18 to recover a portion of the decarbonated cement clinker raw material flowing through the first decarbonated raw material supply passage 18 as a quicklime-containing raw material. The quicklime-containing raw material recovered by the quicklime-containing raw material recovery means 17 is supplied from the quicklime-containing raw material recovery means 17 through the second quicklime-containing raw material supply passage 22b and the second quicklime-containing raw material supply passage 22 to a cyclone-type preheating device for the purpose of fixing (carbonating) the carbon dioxide gas in the kiln exhaust gas in the quicklime-containing raw material. In addition, after decarbonation is promoted in the calciner 4, the mixture may be supplied to a final cyclone-type heat exchanger (not shown) while maintaining the high temperature after heating.

[0035] The quicklime-containing raw material (decarbonated cement clinker raw material containing quicklime) recovered by the quicklime-containing raw material recovery means 17 is supplied through the second quicklime-containing raw material supply passage 22b to either the cyclone heat exchanger 2c to which the preheated raw material supply passage 7 is connected or one of the cyclone heat exchangers 2a to 2b located upstream of the cyclone heat exchanger, among the two or more cyclone heat exchangers 2a to 2d constituting the cyclone preheating device 2.

[0036] By supplying the quicklime-containing raw material to the cyclone heat exchanger 2c connected to the preheating raw material supply passage 7 or to any one of the cyclone heat exchangers 2a to 2b located upstream of the cyclone heat exchanger, the carbon dioxide gas contained in the kiln exhaust gas is fixed (carbonated) in the quicklime-containing raw material when the kiln exhaust gas flowing through the kiln exhaust gas discharge passage 6 passes through the cyclone preheating device 2. This makes it possible to reduce the amount of carbon dioxide gas (carbon dioxide) contained in the kiln exhaust gas discharged from the kiln exhaust gas discharge passage. The carbon dioxide fixed in the quicklime-containing raw material is fed into a calciner 4 together with other cement clinker raw materials, and is then decarbonated in the calciner, and can be recovered as calciner exhaust gas.

[0037] The second decarbonated raw material supply passage 19 is connected to the first decarbonated raw material supply passage 18, and serves to supply a portion of the decarbonated cement clinker raw material from the first decarbonated raw material supply passage 18 to the cyclone type heat exchanger 2d located on the most downstream side of the two or more cyclone type heat exchangers constituting the cyclone type preheating device 2. The decarbonated cement clinker raw material flowing through the first decarbonated raw material supply passage 18 is at a high temperature (for example, 950 to 1,000°C). By supplying the raw material to the cyclone heat exchanger 2d located at the rearmost stream side, the temperature inside the cyclone preheating device 2 can be made higher, and the preheating of the cement clinker raw material and the fixation (carbonation) of the carbon dioxide gas contained in the kiln exhaust gas can be performed more efficiently. The cement clinker raw material supplied to the cyclone heat exchanger 2d is centrifuged while exchanging heat with the kiln exhaust gas passing through the cyclone heat exchanger 2d, and then is charged into the rotary kiln 3. A part of the second decarbonated raw material supply passage 19 may also serve as the kiln exhaust gas discharge passage 6 .

[0038] The decarbonation raw material supply amount control device 21 adjusts the amount of decarbonated cement clinker raw material supplied from the second decarbonation raw material supply passage 19 to the cyclone heat exchanger 2d located at the rearmost stream side, and by adjusting the amount of the raw material, adjusts the temperature in the cyclone heat exchanger 2d and the temperature of the kiln exhaust gas passing through the cyclone heat exchanger 2d, thereby adjusting the temperature in the cyclone heat exchanger 2c connected to the preheating raw material supply passage 7. The amount of the raw material is adjusted based on the temperature of the kiln exhaust gas in the kiln exhaust gas discharge passage 6 when it passes through the cyclone-type heat exchanger 2c connected to the preheated raw material supply passage 7. The above temperature may be the temperature near the inlet of the kiln exhaust gas discharge passage 6 which passes through a cyclone-type heat exchanger 2c connected to the preheating raw material supply passage 7 (the position where the kiln exhaust gas enters the cyclone-type heat exchanger 2c), or it may be the temperature near the outlet of the kiln exhaust gas discharge passage 6 (the position where the kiln exhaust gas leaves the cyclone-type heat exchanger 2c). The above temperature is measured by a temperature measuring device 20. The temperature measuring device 20 may be appropriately disposed in the cyclone type heat exchanger 2c connected to the preheated raw material supply path 7.

[0039] For the purpose of adjusting the temperature in the cyclone-type heat exchanger 2c connected to the preheating raw material supply passage 7, a moisture supplying device (not shown) for supplying water or water-containing waste to the exhaust gas flowing through the kiln exhaust gas discharge passage 6 between the part of the kiln exhaust gas discharge passage 6 connected to the rotary kiln 3 and the part upstream of the cyclone-type heat exchanger 2d located at the most downstream side (shown surrounded by a dashed line in FIG. 1). The temperature is adjusted by supplying water or water-containing waste to the exhaust gas. The adjustment may be made based on the temperature measured by the temperature measuring device 20, and may be linked to the decarbonation raw material supply amount control device 21.

[0040] Also, an air supply passage (not shown) may be provided to guide the air in the clinker cooler 5 from the clinker cooler 5 into the kiln exhaust gas discharge passage 6a. The air is heated by heat exchange with the cement clinker in the clinker cooler 5. By adjusting the amount of the air supplied from the air supply passage to the kiln exhaust gas discharge passage 6a, the temperature and amount of the kiln exhaust gas in the kiln exhaust gas discharge passage 6 can be adjusted. The amount of the air may be adjusted based on the temperature measured by the temperature measuring device 20, and may be adjusted in conjunction with the decarbonated raw material supply amount control device 21.

[0041] Cement clinker can be obtained by burning the cement clinker raw materials in the rotary kiln 3. The burning temperature of the cement clinker raw materials may be a general temperature in the production of cement clinker, and is usually 1,400°C or higher. In the rotary kiln 3, the fuel used for burning the raw materials for cement clinker can be the same as the fuel used in the calciner 4. In addition, fuels that are difficult to crush, such as contaminated soil containing a large amount of organic components and waste tires, may be directly charged through the raw material charging port of the rotary kiln 3.

[0042] The exhaust gas generated in the rotary kiln 3 flows through kiln exhaust gas exhaust passages 6a to 6e, which are used to discharge the exhaust gas after passing through the cyclone-type preheating device 2, and is then discharged from the top of the cyclone-type preheating device 2. The exhaust gas is then cleaned using a cyclone, a bag filter, an electric dust collector, or the like, and is then discharged to the outside through a chimney. A denitration agent supplying device (not shown) for supplying a denitration agent to the exhaust gas flowing through the kiln exhaust gas discharge passage 6 may be provided between the portion of the kiln exhaust gas discharge passage 6 connected to the rotary kiln 3 and the portion upstream of the cyclone-type heat exchanger 2d located at the most downstream side (shown as surrounded by a dashed line in FIG. 1). By spraying a denitration agent such as urea into the exhaust gas, the NOx in the exhaust gas can be reduced.

[0043] Usually, the effect of reducing NOx in the exhaust gas can be obtained by spraying a denitrification agent into the exhaust gas at a temperature of about 900°C. In a typical cement clinker production system, the temperature of the exhaust gas is about 900°C in the region from the bottom of the rotary kiln to the bottom cyclone (a cyclone-type heat exchanger located at the rearmost stream side), and a large amount of fine powder derived from the cement clinker raw materials is present in this region. Therefore, there is a problem that the sprayed denitrification agent is adsorbed by the fine powder, reducing the above-mentioned effect. On the other hand, according to the cement clinker production system 1 in FIG. 1, the amount of fine powder originating from the cement clinker raw materials in the exhaust gas in the above-mentioned region (the portion of the kiln exhaust gas discharge passage 6 that runs from the portion connected to the rotary kiln 3 through the cyclone-type heat exchanger 2d located at the most downstream side) can be reduced, and therefore the amount of NOx in the exhaust gas can be efficiently reduced.

[0044] In addition to the reduction in the amount of carbon dioxide contained in the kiln exhaust gas by the supply of the quicklime-containing raw material described above, carbon dioxide may be separated and recovered from the kiln exhaust gas. Examples of the method for separating and recovering carbon dioxide from the kiln exhaust gas include a chemical absorption method using monoethanolamine or the like as a carbon dioxide absorbent, a solid adsorption method, and a membrane separation method. In addition, a portion of the kiln exhaust gas may be extracted and cooled without passing through the cyclone preheating device 2, and after the solids have been removed, the exhaust gas from which the solids have been removed may be discharged and the solids may be classified into coarse and fine powder. The coarse powder may be used as part of the cement clinker raw material, and a chlorine bypass device 23 may be provided to recover the fine powder. Incidentally, "coarse powder" tends to have a high content of cement clinker raw material components and low chlorine, while "fine powder" tends to have a high content of chlorine. The base bypass device 23 is usually disposed at the connection between the cyclone preheating device 2 and the rotary kiln 3. By disposing the chlorine bypass device 23, waste containing chlorine, such as municipal waste incineration ash, can be used in larger quantities as a cement clinker raw material or fuel for the rotary kiln. The kiln exhaust gas discharged from the chlorine bypass device 23 is usually returned to the kiln exhaust gas discharge line 6a.

[0045] The cement clinker obtained in the rotary kiln 3 is fed into a clinker cooler 5, which is disposed downstream of the rotary kiln, for cooling the cement clinker, and is cooled there. In order to perform heating in the calciner 4 and the rotary kiln 3 more efficiently, the air used to cool the cement clinker may be divided into an upstream side and a downstream side of the clinker cooler 5, and the air on the downstream side after cooling the cement clinker may be used to indirectly heat the combustion-supporting gas passing through the combustion-supporting gas supply passage 9. Also, different gases may be used for cooling the upstream side and the downstream side. Specifically, air may be used as the gas for cooling the upstream side of the clinker cooler 5, and the combustion supporting gas passing through the combustion supporting gas supply passage 9 may be used as the gas for cooling the downstream side. The gas cooling the front stream side is heat exchanged with the high-temperature cement clinker, and then used as a combustion supporting gas for burning fuel in the rotary kiln 3. Since the gas cooling the front stream side is heat exchanged at the inlet side of the clinker cooler 5, it has a higher temperature after heat exchange than the gas cooling the rear stream side.

[0046] Electric energy may also be used to heat the air and combustion supporting gas used when burning fuel in the rotary kiln, and to assist in heating the rotary kiln and the calciner. Examples of heating methods using electric energy include plasma heating, resistance heating, and microwave heating. If renewable energy is used as the electric energy, carbon dioxide emissions can be further reduced.

[0047] In the method for producing cement clinker using the above-mentioned cement clinker production system, the carbon dioxide-containing exhaust gas generated in the calciner 4 may be recovered and the carbon dioxide gas in the exhaust gas may be utilized. One example of the use of carbon dioxide gas is methanation, which is the reaction of hydrogen with carbon dioxide to produce methane and water. Specifically, there is a method of producing methane from hydrogen gas and carbon dioxide gas contained in the exhaust gas using a catalyst. Hydrogen gas can be obtained by electrolyzing water, etc. If the electric energy used for electrolyzing water is derived from renewable energy sources such as hydraulic power, wind power, geothermal power, or solar power, the amount of carbon dioxide emissions can be further reduced. At this time, oxygen is also produced, and this oxygen may be used as the oxygen contained in the combustion-supporting gas described above.

[0048] Examples of the catalyst include Rh / Mn-based, Rh-based, Ni-based, Pd-based, and Pt-based catalysts. A carrier may be used to support the catalyst. Examples of the carrier include CeO 2 , ZrO 2 , Y 2 O 3 , Al 2 O 3 , MgO, TiO 2 These may be appropriately selected and used. From the viewpoint of 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. In addition, the generated methane may be used separately as fuel for power generation.

[0049] Another example of the use of carbon dioxide gas is the carbonation of calcium-containing waste materials. Specifically, the exhaust gas is brought into contact with calcium-containing waste, and carbon dioxide contained in the exhaust gas is absorbed by the calcium-containing waste. By absorbing and immobilizing carbon dioxide in the calcium-containing waste, it is possible to reduce the amount of carbon dioxide emitted into the atmosphere. An example of calcium-containing waste is waste concrete. The calcium-containing waste that has absorbed carbon dioxide may be used as a cement clinker raw material in the above-mentioned cement clinker production system. In addition, the calcium-containing waste that has absorbed carbon dioxide may be crushed, classified, etc., and used as roadbed material, concrete aggregate, etc. Furthermore, when the calcium-containing waste is waste concrete, only the paste component in the waste concrete that has absorbed carbon dioxide may be separated and recovered and used as a cement raw material.

[0050] In the above-mentioned methanation and carbonation of calcium-containing waste, the carbon dioxide-containing exhaust gas is not purified (without separating or removing the carbon dioxide) and is directly used at a high temperature for methanation or carbonation of calcium-containing waste, thereby making it possible to more efficiently carry out methanation or carbonation of waste concrete. In addition, in the production of cement clinker using the above-mentioned cement clinker production system, the carbon dioxide-containing exhaust gas generated in the calciner 4 may be stored and isolated as it is. [Explanation of symbols]

[0051] 1 Cement clinker production system 2 Cyclone preheating device 2a, 2b, 2c, 2d Cyclone type heat exchanger 3. Rotary Kiln 4 Calciner 5 Clinker Cooler 6,6a,6b,6c,6d,6e Kiln exhaust gas exhaust duct 7 Preheating material supply line 8. Combustion-supporting gas supply device 9. Combustion-supporting gas supply line 10 Calciner exhaust gas exhaust passage 11 Calciner exhaust gas temperature reduction device 12 Dust collector 13 Water washing device 14 First quicklime-containing raw material supply line 15 Exhaust gas treatment agent supply line 16. Lime-containing residue discharge channel 17 Means for recovering raw materials containing quicklime 18 First decarbonation raw material supply line 19 Second decarbonation raw material supply route 20 Temperature measuring device 21 Decarbonation raw material supply amount control device 22, 22a, 22b Second lime-containing raw material supply line 23 Chlorine Bypass Unit 24 Merging flow path 25 Exhaust gas treatment agent supply device 26 Heating means

Claims

1. a cyclone preheating device for preheating the cement clinker raw material, the cyclone preheating device comprising two or more cyclone heat exchangers; a rotary kiln for burning the cement clinker raw material preheated by the cyclone preheating device to obtain cement clinker; a calciner disposed upstream of the rotary kiln together with the cyclone preheating device for promoting decarbonation of the cement clinker raw material; a preheated raw material supply passage for supplying the preheated cement clinker raw material from the cyclone preheating device to the calciner; a clinker cooler disposed downstream of the rotary kiln for cooling the cement clinker; A kiln exhaust gas exhaust passage for discharging the exhaust gas generated in the rotary kiln after passing through the cyclone type preheating device; A cement clinker production system comprising: a combustion supporting gas supplying device for supplying a combustion supporting gas having an oxygen concentration higher than that of air; a combustion-supporting gas supply line for introducing the combustion-supporting gas from the combustion-supporting gas supply device to the calciner; A calciner exhaust gas exhaust duct (which must be different from the kiln exhaust gas exhaust duct) for discharging carbon dioxide-containing exhaust gas generated in the calciner; a calciner exhaust gas temperature reducing device disposed in the calciner exhaust gas discharge passage for reducing the temperature of the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge passage; a dust collector disposed in the calciner exhaust gas discharge passage and downstream of the calciner exhaust gas temperature reducing device for recovering quicklime-containing raw materials from the carbon dioxide-containing exhaust gas; A washing device for washing the quicklime-containing raw material with water; a first quicklime-containing raw material supply passage for supplying the quicklime-containing raw material from the dust collector to the water washing device; a slaked lime-containing residue discharge passage for discharging the slaked lime-containing residue generated in the water washing device; an exhaust gas treatment agent supplying device for supplying at least a portion of the slaked lime-containing residue recovered from the slaked lime-containing residue discharge path to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge path between the calciner exhaust gas temperature reducing device and the dust collecting device; an exhaust gas treatment agent supply passage for supplying the slaked lime-containing residue recovered by the exhaust gas treatment agent supply device to the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge passage between the calciner exhaust gas temperature reducing device and the dust collecting device; A cement clinker production system comprising:

2. 2. The cement clinker production system according to claim 1, further comprising a chlorine bypass device for extracting and cooling a portion of the exhaust gas generated in the rotary kiln without passing through the cyclone preheating device, removing solids therefrom, discharging the exhaust gas from which the solids have been removed, and classifying the solids into coarse powder and fine powder, using the coarse powder as a part of the cement clinker raw material, and recovering the fine powder.

3. 3. The cement clinker production system according to claim 1, further comprising a confluence passage for confluence a portion of the carbon dioxide-containing exhaust gas flowing through the calciner exhaust gas discharge passage with the combustion-supporting gas flowing through the combustion-supporting gas supply passage.

4. The preheating raw material supply passage is connected to a cyclone type heat exchanger located at the second or more rearmost side among the two or more cyclone type heat exchangers constituting the cyclone type preheating device, a means for recovering a calcined raw material from the cement clinker raw material decarbonated in the calciner; a second calcined raw material supply passage for supplying the calcined raw material recovered by the calcined raw material recovery means from the calcined raw material recovery means to a cyclone type heat exchanger connected to the preheated raw material supply passage, or to a cyclone type heat exchanger located upstream of the cyclone type heat exchanger, among the two or more cyclone type heat exchangers; a first decarbonated raw material supply passage for supplying the cement clinker raw material decarbonated in the calciner to the rotary kiln from the calciner; a second decarbonation raw material supply passage for supplying a portion of the decarbonated cement clinker raw material from the first decarbonation raw material supply passage to a cyclone type heat exchanger located at the most downstream side of the two or more cyclone type heat exchangers; a temperature measuring device for measuring the temperature of the exhaust gas in the kiln exhaust gas discharge passage when the exhaust gas passes through the cyclone heat exchanger connected to the preheating raw material supply passage; a decarbonation raw material supply amount control device for adjusting the amount of the decarbonated cement clinker raw material supplied from the second decarbonation raw material supply line to the cyclone type heat exchanger located at the most downstream side based on the temperature measured by the temperature measuring device, and adjusting the temperature in the cyclone type heat exchanger connected to the preheating raw material supply line by said adjustment; The cement clinker production system according to any one of claims 1 to 3, comprising:

5. 5. The cement clinker production system according to claim 4, further comprising a moisture supplying device for supplying water or water-containing waste to the exhaust gas flowing through the kiln exhaust gas discharge passage between a portion of the kiln exhaust gas discharge passage connected to the rotary kiln and a portion upstream of the cyclone-type heat exchanger located at the most downstream side.

6. 6. The cement clinker production system according to claim 4 or 5, further comprising a denitrification agent supplying device for supplying a denitrification agent to the exhaust gas flowing through the kiln exhaust gas discharge passage between a portion of the kiln exhaust gas discharge passage connected to the rotary kiln and a portion upstream of the cyclone-type heat exchanger located at the most downstream side.

7. A method for producing cement clinker using the cement clinker production system according to any one of claims 1 to 6, A method for producing cement clinker, comprising adjusting the temperature of the carbon dioxide-containing exhaust gas supplied to the dust collector to 100 to 400°C using the calciner exhaust gas temperature reducing device.

8. 8. The method for producing cement clinker according to claim 7, wherein the oxygen concentration of the combustion supporting gas is adjusted so that the carbon dioxide concentration of the carbon dioxide-containing exhaust gas generated in the calciner is 80 volume % or more relative to 100 volume % excluding water vapor.

9. 9. A method for producing cement clinker according to claim 7 or 8, wherein the carbon dioxide-containing exhaust gas produced in the calciner is recovered and the carbon dioxide contained in the carbon dioxide-containing exhaust gas is utilized.

10. A method for producing cement clinker using the cement clinker production system according to any one of claims 4 to 6, In the calciner, the cement clinker raw material is heated to a temperature of 950 to 1,100°C, A method for producing cement clinker, comprising: adjusting an amount of the decarbonated cement clinker raw material supplied from the second decarbonation raw material supply passage to a cyclone-type heat exchanger located at the most downstream side by using the decarbonation raw material supply amount control device so that a temperature in the cyclone-type heat exchanger to which the preheating raw material supply passage is connected is 700 to 900°C.

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