Cement-firing facility and method for producing cement clinker

Abstract

To provide a cement-firing facility capable of suppressing the amount of carbon dioxide released into the atmosphere and efficiently drying a cement raw material, and to provide a method for producing a cement clinker.SOLUTION: A cement-firing facility includes: a drying and grinding apparatus for cement raw materials; a suspension preheater; a rotary kiln; a clinker cooler; a carbon dioxide recovery apparatus; and a carbonation apparatus. A method for producing a cement clinker using the facility is also provided.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a cement calcination facility and a method for producing cement clinker. [Background technology]

[0002] In recent years, interest in global warming has grown, and there is a demand for reducing the amount of carbon dioxide emitted into the atmosphere. In order to reduce the amount of carbon dioxide-containing exhaust gases emitted into the atmosphere during operation at various facilities, such as power plants, incinerators, cement plants, steel mills, and industrial facilities, the separation and capture of carbon dioxide from exhaust gases is being considered. Reducing carbon dioxide emissions from cement plants is considered a particularly important issue.

[0003] An example of the configuration of a typical cement plant is that disclosed in Patent Document 1, which is a cement manufacturing facility that includes a preheater that preheats cement raw materials by heat exchange with high-temperature gas, a cement calcination furnace that calcines the cement raw materials to produce cement clinker, a cooling device that directs part of the air that has been heated by heat exchange with the cement clinker as burner combustion air for the cement calcination furnace, an absorption tower that stores an absorbing liquid that absorbs carbon dioxide, and a regeneration tower that heats the absorbing liquid to volatilize the carbon dioxide, and an exhaust gas introduction pipe that uses exhaust gas from the preheater as a heat source via the regeneration tower before directing it to the absorption tower.

[0004] As an example of the above-mentioned suspension preheater, a heating device is known, as shown in Patent Document 2, which has a structure in which a plurality of independent hot gases flow through each of a plurality of air passages formed by a plurality of dust collectors, while a powdered material is introduced through the air passage leading to the uppermost dust collector of the plurality of dust collectors, passed through the dust collectors in sequence, and discharged from the bottom of the lowest dust collector.

[0005] Patent Document 3 also discloses a system including a cyclone-type preheating device for preheating cement clinker raw materials, a rotary kiln for burning the preheated cement clinker raw materials to obtain cement clinker, a calciner disposed upstream of the rotary kiln for promoting decarbonation of the cement clinker raw materials, a preheated raw material supply path for supplying the cement clinker raw materials from the preheating device to the calciner, a clinker cooler for cooling the cement clinker, and a kiln exhaust gas exhaust system for discharging exhaust gas generated in the rotary kiln after passing through the preheating device. a calciner exhaust gas discharge conduit for discharging carbon dioxide-containing exhaust gas generated in the calciner; a supply device for a combustion-supporting gas with an increased oxygen concentration; first recovery means for recovering quicklime-containing raw materials from the carbon dioxide-containing exhaust gas; a combustion-supporting gas supply conduit for heat exchange between the carbon dioxide-containing exhaust gas and the combustion-supporting gas, upstream of the first recovery means; and a calciner exhaust gas supply conduit for joining a part of the carbon dioxide-containing exhaust gas with the combustion-supporting gas, downstream of the first recovery means of the calciner exhaust gas supply conduit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-110485 [Patent Document 2] Japanese Patent Application Publication No. 55-22322 [Patent Document 3] Japanese Patent Publication No. 2022-148255 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide cement firing equipment and a method for producing cement clinker that can suppress the amount of carbon dioxide released into the atmosphere and efficiently dry cement raw materials. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following cement burning equipment. 1. Drying and crushing equipment for drying and crushing cement raw materials into powder raw materials; a suspension preheater for preheating and calcining the powder raw material; a rotary kiln for burning the preheated and calcined powdered raw material to form cement clinker; a cement clinker cooler for cooling the cement clinker; a carbon dioxide recovery device that recovers carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater; and a carbonation device that produces a powder containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater with a powder containing calcium oxide; The suspension preheater is a calciner for calcining the powdered raw material; two different air ducts, namely, a calciner system air duct through which the calciner combustion exhaust gas discharged from the calciner passes and a kiln system air duct through which the kiln combustion exhaust gas discharged from the rotary kiln passes; a calciner combustion exhaust gas outlet for discharging the calciner combustion exhaust gas, which has preheated and calcined the powdered raw material by passing through the calciner system air duct, from the suspension preheater; and a kiln combustion exhaust gas outlet for discharging the kiln combustion exhaust gas, which has preheated and calcined the powdered raw material by passing through the kiln system air duct, from the suspension preheater; a preheater having: moreover, a calciner combustion exhaust gas exhaust duct for supplying the calciner combustion exhaust gas discharged from the calciner combustion exhaust gas outlet to the carbon dioxide recovery device; a kiln combustion exhaust gas exhaust duct for supplying the kiln combustion exhaust gas discharged from the kiln combustion exhaust gas outlet to a drying device included in the drying and pulverizing device; a carbonation device air supply duct for supplying the kiln combustion exhaust gas passing through the kiln combustion exhaust gas discharge duct to the carbonation device; and a carbonation device exhaust duct for supplying the kiln combustion exhaust gas discharged from the carbonation device to the kiln combustion exhaust gas exhaust duct; exhaust gas duct; a fractionating device that fractionates the preheated and calcined powder raw material from the suspension preheater, and a powder supplying device 1 that supplies the powder raw material fractionated by the fractionating device to the carbonation device as a powder containing calcium oxide; and an air extraction device that extracts the kiln combustion exhaust gas before it is supplied to a cyclone dust collector at the lowest stage of a kiln system air duct of the suspension preheater; a powder raw material separation device that separates powder raw material contained in the kiln combustion exhaust gas extracted by the air extraction device; and a powder supply device 2 that supplies the powder raw material separated by the powder raw material separation device to the carbonation device as a powder containing calcium oxide; Cement baking equipment equipped with:

[0009] The present invention provides the following cement burning equipment as a preferred embodiment. 2. The method for producing cement clinker according to 1 above, wherein the separation device is provided in a powder raw material conduit that supplies the powder raw material preheated and calcined in the suspension preheater to the rotary kiln. 3. The cement burning facility according to claim 1 or 2, further comprising: a powder raw material supplying device that supplies the powder raw material discharged from the drying and crushing device to the suspension preheater; and a powder transporting device for carbonation device that combines the powder containing calcium carbonate produced in the carbonation device with the powder raw material discharged from the drying and crushing device. 4. The cement firing facility according to 3 above, further comprising a powder raw material mixture sampling device that samples a powder raw material mixture of the powder containing calcium carbonate transported by the carbonation device-produced powder transport device and the powder raw material discharged from the drying and crushing device, a chemical component measuring device that measures the chemical components of the powder raw material mixture sampled by the powder raw material mixture sampling device, and a cement raw material blending device that adjusts the blend of the cement raw materials based on the measurement results of the chemical component measuring device. 5. The cement burning facility according to any one of the above 1 to 4, wherein the carbonation device is a fluidized bed reactor.

[0010] The present invention also provides the following method for producing cement clinker. 6. A method for producing cement clinker using the cement burning equipment described in any one of 1 to 5 above, and adjusting the conditions according to any one of (i) to (iii) below. (i) Adjusting the amount of powder raw material supplied to the suspension preheater (ii) adjusting the amount of fuel supplied to said rotary kiln; (iii) Adjusting the amount of water sprayed onto the kiln combustion exhaust gas exhaust duct 7. The method for producing cement clinker according to 6 above, wherein the temperature of the kiln combustion exhaust gas discharged from the kiln combustion exhaust gas outlet is adjusted to 250°C or higher and 600°C or lower under the above conditions. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide cement firing equipment and a method for producing cement clinker that can suppress the amount of carbon dioxide released into the atmosphere and efficiently dry cement raw materials. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a preferred embodiment of the cement firing equipment of the present embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a preferred embodiment of a suspension preheater employed in the cement firing facility of the present embodiment. [Figure 3] FIG. 1 is a schematic diagram showing a preferred embodiment of a carbonation device employed in the cement burning facility of the present embodiment. [Figure 4] FIG. 1 is a schematic diagram for explaining the results of an example. [Figure 5] FIG. 10 is a schematic diagram for explaining the results of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (hereinafter, sometimes referred to as "the present embodiment") will be described. The present invention is not limited to the following embodiment, and can be implemented with any modifications within the scope that does not impair the effects of the invention. In this specification, the notation of a numerical range as "AA to BB" means "at least AA and at most BB." In addition, in this specification, the numbers associated with "at least," "at most," and "to" in describing a numerical range are numbers that can be arbitrarily combined. For example, when a certain numerical range is described as "CC to DD" and "EE to FF," the numerical ranges "CC to FF" and "EE to DD" are also included.

[0014] [Cement baking equipment] The cement firing equipment of this embodiment includes: Drying and crushing equipment for drying and crushing cement raw materials to produce powder raw materials; a suspension preheater for preheating and calcining the powder raw material; a rotary kiln for burning the preheated and calcined powdered raw material to form cement clinker; a cement clinker cooler for cooling the cement clinker; a carbon dioxide recovery device that recovers carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater; and a carbonation device that produces a powder containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater with a powder containing calcium oxide; The suspension preheater is a calciner for calcining the powdered raw material; two different air ducts, namely, a calciner system air duct through which the calciner combustion exhaust gas discharged from the calciner passes and a kiln system air duct through which the kiln combustion exhaust gas discharged from the rotary kiln passes; a calciner combustion exhaust gas outlet for discharging the calciner combustion exhaust gas, which has preheated and calcined the powdered raw material by passing through the calciner system air duct, from the suspension preheater; and a kiln combustion exhaust gas outlet for discharging the kiln combustion exhaust gas, which has preheated and calcined the powdered raw material by passing through the kiln system air duct, from the suspension preheater; a preheater having: moreover, a calciner combustion exhaust gas exhaust duct for supplying the calciner combustion exhaust gas discharged from the calciner combustion exhaust gas outlet to the carbon dioxide recovery device; a kiln combustion exhaust gas exhaust duct for supplying the kiln combustion exhaust gas discharged from the kiln combustion exhaust gas outlet to a drying device included in the drying and pulverizing device; a carbonation device air supply duct for supplying the kiln combustion exhaust gas passing through the kiln combustion exhaust gas discharge duct to the carbonation device; and a carbonation device exhaust duct for supplying the kiln combustion exhaust gas discharged from the carbonation device to the kiln combustion exhaust gas exhaust duct; exhaust gas duct; a fractionating device that fractionates the preheated and calcined powder raw material from the suspension preheater, and a powder supplying device 1 that supplies the powder raw material fractionated by the fractionating device to the carbonation device as a powder containing calcium oxide; and an air extraction device that extracts the kiln combustion exhaust gas before it is supplied to a cyclone dust collector at the lowest stage of a kiln system air duct of the suspension preheater; a powder raw material separation device that separates powder raw material contained in the kiln combustion exhaust gas extracted by the air extraction device; and a powder supply device 2 that supplies the powder raw material separated by the powder raw material separation device to the carbonation device as a powder containing calcium oxide; The idea is to have the following.

[0015] The cement calcination equipment disclosed in Patent Document 1 uses the exhaust gas discharged from a preheater, which preheats cement raw materials by heat exchange with high-temperature gas, as a heat source via a regeneration tower before being introduced into an absorption tower, thereby utilizing the thermal energy of the exhaust gas generated in the cement manufacturing facility to inexpensively remove carbon dioxide from the exhaust gas. However, since the absorption tower attempts to capture carbon dioxide from the entire amount of exhaust gas discharged from the preheater, the concentration of carbon dioxide contained in the exhaust gas to be captured is low. As a result, the carbon dioxide capture efficiency of the carbon dioxide capture equipment cannot be said to be high, and there is room for improvement in this regard. Furthermore, the system lacks a focus on efficiently drying the cement raw materials.

[0016] The suspension preheater disclosed in Patent Document 2 aims to improve its own thermal efficiency, thereby enabling the exhaust fan to be made smaller and achieving a significant reduction in thermal energy and electrical energy during heating. Although the thermal efficiency has certainly been improved and is excellent, it is assumed that the hot gas used to heat the powdered material (powdered cement raw material) in the suspension preheater will be exhausted from the exhaust fan, and there is room for further improvement in terms of reducing the amount of carbon dioxide emitted.

[0017] The cement clinker production system disclosed in Patent Document 3 does not consider the thermal utilization of the kiln exhaust gas released into the atmosphere. Furthermore, there is room for further improvement in reducing the amount of carbon dioxide contained in the kiln exhaust gas, i.e., the amount of carbon dioxide released into the atmosphere.

[0018] Generally, cement calcination facilities emit carbon dioxide of non-energy origin generated from powdered raw materials in addition to carbon dioxide of energy origin generated from fuels used in suspension preheaters and rotary kilns. The ratio of carbon dioxide of energy origin to carbon dioxide of non-energy origin is said to be 40:60. Therefore, in order to reduce the amount of carbon dioxide released into the atmosphere from cement calcination facilities, it is necessary to consider both carbon dioxide of energy origin and carbon dioxide of non-energy origin, and the present inventors decided to particularly focus on reducing carbon dioxide of non-energy origin.

[0019] First, the inventors focused on the fact that the calciner flue gas from the calciner of the suspension preheater, which is used as a heat source for the suspension preheater, has a higher carbon dioxide content than the kiln flue gas from the rotary kiln. Since the calciner flue gas has a higher carbon dioxide content than the kiln flue gas, they believed that capturing carbon dioxide from the calciner flue gas would improve the carbon dioxide capture efficiency. Furthermore, in the suspension preheater, calcium contained in the powdered raw material is converted to calcium oxide through decarbonation. Therefore, they believed that by using the carbon dioxide contained in the kiln flue gas to carbonate the calcium oxide contained in the powdered raw material, the carbon dioxide contained in the kiln flue gas could be captured and the amount of carbon dioxide released into the atmosphere could be reduced.

[0020] Based on the above studies, we have come to the conclusion that by installing a carbon dioxide capture device and a carbonation device in a cement calcination facility, and supplying calciner flue gas to the carbon dioxide capture device and kiln flue gas to the carbonation device, we can reduce the amount of carbon dioxide released into the atmosphere. Furthermore, since the kiln flue gas supplied to the carbonation device is an exothermic reaction and its temperature is maintained, we have decided to effectively utilize it for drying powdered raw materials. This has led to the completion of a cement calcination facility and a method for producing cement clinker that can reduce the amount of carbon dioxide released into the atmosphere and efficiently dry cement raw materials.

[0021] The cement calcination facility and the method for producing cement clinker of this embodiment will be described below with reference to Fig. 1. Fig. 1 is a schematic diagram showing a preferred embodiment of the cement calcination facility of this embodiment.

[0022] FIG. 1 shows that the cement burning facility includes a drying and crushing device for drying and crushing cement raw materials to produce powdered raw materials, a suspension preheater (1) for preheating and calcining the powdered raw materials, a rotary kiln for burning the powdered raw materials to produce cement clinker, and a cement clinker cooler for cooling the cement clinker.

[0023] Regarding the carbonation device, it is shown that the powdered raw material preheated and calcined in the suspension preheater (1) is supplied to the carbonation device as a powder containing calcium oxide via a separation device (12) and a powder supply device 1 (13), that the kiln combustion exhaust gas is extracted by an extraction device (8) before being supplied to the cyclone dust collector K1 at the bottom of the kiln system air duct of the suspension preheater (1), and the powdered raw material separated in the powdered raw material separation device (9) is supplied to the carbonation device as a powder containing calcium oxide via a powder supply device 2 (10), and that the kiln combustion exhaust gas passing through the kiln combustion exhaust gas duct of the suspension preheater (1) as combustion exhaust gas is supplied to the carbonation device via a kiln combustion exhaust gas outlet (4), a kiln combustion exhaust gas exhaust duct (6) and a carbonation device air intake duct (7).

[0024] FIG. 1 shows that the kiln flue gas used in the carbonation device is supplied to the kiln flue gas discharge duct (6) via the carbonation device exhaust duct (14), and the kiln flue gas is used as a heat source in the drying device of the drying and crushing device, and is finally released into the atmosphere via a dust collector and a chimney. The powder containing calcium carbonate produced in the carbonation device is passed through a powder conveying device (15) for carbonation device-produced powder and, together with the powder raw material discharged from the drying and crushing device, is supplied as a powder raw material mixture to a suspension preheater (1) by a powder raw material supplying device (16), where it is preheated and calcined. A portion of the powder raw material mixture of the powder raw material discharged from the drying and crushing device and the powder containing calcium carbonate produced in the carbonation device is sampled by a powder raw material mixture sampling device (17) and analyzed by a chemical component measuring device (18). The system also shows a cement raw material blending device that adjusts the blend of the cement raw materials (Ca raw material, Si raw material, Al raw material, and Fe raw material) based on the measurement results.

[0025] [Suspension preheater] The suspension preheater provided in the cement firing equipment of this embodiment has a calciner for calcining the powdered raw materials, two different air ducts, namely, a calciner system air duct through which calciner combustion exhaust gas discharged from the calciner passes and a kiln system air duct through which kiln combustion exhaust gas discharged from the rotary kiln passes, a calciner combustion exhaust gas outlet for discharging the calciner combustion exhaust gas, which has passed through the calciner system air duct to preheat and calcinate the powdered raw materials, from the suspension preheater, and a kiln combustion exhaust gas outlet for discharging the kiln combustion exhaust gas, which has passed through the kiln system air duct to preheat and calcinate the powdered raw materials, from the suspension preheater.

[0026] The suspension preheater is not particularly limited in its configuration as long as it has the above-mentioned calciner, two different air ducts, a calciner system air duct and a kiln system air duct, a calciner combustion exhaust gas outlet, and a kiln combustion exhaust gas outlet. A preferred embodiment of the suspension preheater will be described with reference to FIG. 2.

[0027] FIG. 2 shows that the suspension preheater has four stages of cyclone dust collectors (four stages of cyclone dust collectors C1 to C4 and K1 to K4) that collect powder raw materials, and gas flow paths (gas flow paths C0a to C4a and K0a to K4a) that sequentially connect the four stages of cyclone dust collectors, and has two air passages (a calciner system flow path and a kiln system flow path) through which different exhaust gases pass independently. Calciner combustion exhaust gas and kiln combustion exhaust gas, which are different from each other, pass independently through the calciner system air duct and the kiln system air duct. The calciner combustion exhaust gas passes through the lowest cyclone dust collector C1 to the highest cyclone dust collector C4 in order via gas flow paths (C0a to C4a), and the kiln combustion exhaust gas passes through the lowest cyclone dust collector K1 to the highest cyclone dust collector K4 in order via gas flow paths (K1a to K4a).

[0028] 2 shows that the calciner flue gas passes through the calciner system air duct of the suspension preheater (1) and is discharged from the calciner flue gas outlet (3), and the kiln flue gas passes through the kiln system air duct and is discharged from the kiln flue gas outlet (4). Also, as shown in FIG. 2, the calciner flue gas and the kiln flue gas pass through the calciner flue gas exhaust air duct (5) and the kiln flue gas exhaust air duct (6), respectively, and are supplied to their respective uses.

[0029] By providing two separate air passages through which different exhaust gases pass, the calciner flue gas and the kiln flue gas can be handled separately, allowing for more efficient capture of carbon dioxide from the calciner flue gas, which contains a high carbon dioxide content, using a carbon dioxide capture device. Furthermore, by supplying the kiln flue gas to a carbonation device, the carbon dioxide can be captured and used to carbonate the calcium oxide contained in the powdered raw materials, thereby reducing the amount of carbon dioxide released into the atmosphere.

[0030] As shown in Figure 2, the two air ducts through which different exhaust gases pass independently are preferably equipped with induced draft fans (calciner flue gas induced draft fan and kiln flue gas induced draft fan). Air volume control dampers (not shown) are also preferably provided. The provision of induced draft fans and air volume control dampers makes it possible to easily adjust the flow rate and pressure of the flue gas. In particular, the kiln flue gas duct is preferably equipped with an induced draft fan and air volume control damper to adjust the flow rate to the downstream carbonation device and drying and pulverizing device.

[0031] Regarding powder raw materials, FIG. 2 shows raw material conduits including raw material conduits (K2b-K4b) that connect the cyclone dust collector of the kiln system air duct to the gas flow path that supplies calciner combustion exhaust gas to the cyclone dust collector of the calciner system air duct at the same stage as the cyclone dust collector of the kiln system air duct, and kiln system raw material conduits (K1b) that connect the cyclone dust collector at the bottom stage of the kiln system air duct to the calciner. The calciner system air duct includes raw material conduits (C2b-C4b) that connect the cyclone dust collector in the calciner system air duct to a gas flow path that supplies kiln combustion exhaust gas to a cyclone dust collector in the kiln system air duct one level below the cyclone dust collector in the calciner system air duct, and a raw material conduit (C1b) that connects the cyclone dust collector in the lowest level of the calciner system air duct to the rotary kiln.

[0032] A powder raw material mixture of the powder raw material discharged from the drying and grinding device and the powder containing calcium carbonate produced in the carbonation device is supplied to the suspension preheater (1) by a powder raw material supply device (16), more specifically, from the powder raw material supply device (16) to the cyclone dust collector at the top of the suspension preheater 1. In Fig. 2, the powder raw material mixture that becomes the powder raw material is shown as being supplied from the powder raw material supply device (16K) of the kiln system to the cyclone dust collector K4 at the top of the kiln system air duct, and from the powder raw material supply device (16C) of the calciner system to the cyclone dust collector C4 at the top of the calciner system air duct.

[0033] The powder raw material mixture supplied from the kiln-based powder raw material supply device (16K) passes through the cyclone dust collector K4, raw material conduit K4b, gas flow path C3a, cyclone dust collector C4, raw material conduit C4b, gas flow path K2a, cyclone dust collector K3, raw material conduit K3b, gas flow path C2a, cyclone dust collector C3, raw material conduit C3b, gas flow path K1a, cyclone dust collector K2, raw material conduit K2b, gas flow path C1a, cyclone dust collector C2, raw material conduit C2b, gas flow path K0a, cyclone dust collector K1, raw material conduit K1b, calciner, gas flow path C0a, cyclone dust collector C1, and raw material conduit C1b in this order, where it is preheated and calcined, and then supplied to the rotary kiln. The powdered raw material supplied from the powdered raw material supply device (16C) of the calciner system is supplied to the cyclone dust collector C4, and together with the powdered raw material supplied from the powdered raw material supply device (16K) of the kiln system, it passes through the raw material conduit C4b and the raw material conduit C1b, where it is preheated and calcined, and then supplied to the rotary kiln.

[0034] In this way, the powdered raw material supplied to the suspension preheater 1 moves alternately from the upper to lower cyclone collectors of the calciner system air duct and the kiln system air duct, passing through all of the cyclone collectors before being supplied to the rotary kiln. Furthermore, the powdered raw material moving from the top to the bottom cyclone collector comes into contact with the combustion exhaust gas (calciner combustion exhaust gas and kiln combustion exhaust gas) moving in the opposite direction through the air duct, i.e., from the bottom cyclone collector to the top cyclone collector, thereby enabling efficient preheating and calcination.

[0035] The powdered raw material supplying device (16) provided in the cement calcination facility of this embodiment can be of the same type as the powdered raw material supplying device provided in a conventional cement calcination facility. For example, the powdered raw material supplying device (16) preferably includes a pipe for supplying the powdered raw material discharged from the drying and crushing device to the suspension preheater (1), and a mixer for mixing the powdered raw material with the powder containing calcium carbonate transported from the carbonation device by the carbonation device-produced powder transporting device (15) to prepare a powdered raw material mixture. In addition, the powder raw material supply device (16) and the powder transport device (15) produced by the carbonation device may be equipped with pipes through which the objects to be supplied or transported pass, as well as equipment such as a feeder for pressure-feeding as needed.

[0036] [Carbonation device] The cement firing facility of this embodiment includes a carbonation device that converts the combustion exhaust gas discharged from the suspension preheater 1 into a powder containing calcium carbonate by a reaction between the combustion exhaust gas and a powder containing calcium oxide. The carbonation device will be described with reference to FIG. 3.

[0037] Fig. 3 is a schematic diagram showing a preferred embodiment of a carbonation apparatus. Fig. 3 shows that the carbonation apparatus is equipped with a carbonation reaction tower in which a reaction between a kiln flue gas and a powder containing calcium oxide takes place, a dust collector that separates the kiln flue gas from the powder produced by the carbonation reaction tower and contained in the kiln flue gas discharged from the carbonation reaction tower, a carbonation induction fan that discharges the kiln flue gas from the dust collector and supplies it to a dryer, and a forced draft fan for fluidization that recycles the kiln flue gas discharged from the dust collector to the carbonation reaction tower for fluidization.

[0038] (combustion exhaust gas) The combustion exhaust gas is supplied to the carbonation device through a kiln combustion exhaust gas exhaust duct (6) for supplying the kiln combustion exhaust gas discharged from the kiln combustion exhaust gas outlet to the drying equipment of the drying and pulverizing device, and a carbonation device air supply duct (7) for supplying the kiln combustion exhaust gas passing through the kiln combustion exhaust gas exhaust duct to the carbonation device. In other words, the combustion exhaust gas used in the carbonation device is the kiln combustion exhaust gas.

[0039] The flow rate of the kiln flue gas supplied to the carbonator (the flow rate of the kiln flue gas to the carbonator air intake duct (7)) and the flow rate of the kiln flue gas supplied directly to the dryer without being supplied to the carbonator (the flow rate of the kiln flue gas to the kiln flue gas exhaust duct (6)) can be arbitrarily distributed. This allows the amount of carbon dioxide released into the atmosphere to be adjusted. Alternatively, the entire amount of the kiln flue gas may be supplied to the carbonator.

[0040] The distribution of the flow rate of the kiln flue gas can be adjusted by taking into consideration, for example, the amount of kiln flue gas discharged from the suspension preheater (1), the amount of cement raw material to be dried in the dryer of the drying and crushing device, the amount of powder containing calcium oxide, etc., and can be achieved by adjusting the air volume control damper, carbonation device induction fan, etc. For example, if the carbon dioxide content in the kiln flue gas is extremely low, the power consumption of the carbonation device induction fan can be reduced by reducing the amount of air supplied to the carbonation device.

[0041] The kiln flue gas supplied to the carbonation device is supplied from the suspension preheater (1) through the kiln flue gas outlet (4) and the kiln flue gas exhaust duct (6). Therefore, the temperature of the kiln flue gas supplied to the carbonation device is approximately the same as the temperature of the gas discharged from the suspension preheater (1). The temperature of the kiln flue gas supplied to the carbonation device is preferably 250°C or higher and 600°C or lower. A temperature of 250°C or higher allows for satisfactory drying of the cement raw materials, while a temperature of 600°C or lower facilitates an improvement of the reaction efficiency of the carbonation reaction of calcium oxide in the carbonation device to 100%.

[0042] Methods for adjusting the temperature of the kiln combustion exhaust gas supplied to the carbonation device include, for example, the following methods (i) to (iii), which can be used alone or in combination of two or more methods. (i) Adjust the amount of powdered raw material fed to the suspension preheater (1). By increasing the amount of powdered raw material fed, the temperature of the kiln flue gas can be reduced, thereby lowering the temperature of the kiln flue gas fed to the carbonation device. (ii) Adjusting the amount of fuel supplied to the rotary kiln. Increasing the amount of fuel can raise the temperature of the kiln flue gas supplied to the carbonation device. The temperature of the kiln flue gas can also be raised by, for example, adding waste materials with a calorific value, such as waste clay, waste tires, and other waste plastics, to the raw material conduit (before the calciner) such as the raw material conduit K0a. (iii) The amount of water sprayed onto the kiln flue gas exhaust duct (specifically, any point from the kiln flue gas outlet (4) to the kiln flue gas exhaust duct (6)) is adjusted. By adjusting the amount of water sprayed, it is possible to adjust the temperature of the kiln flue gas supplied to the carbonation device. Here, industrial water or tap water can be used for the water spraying, or waste materials such as liquid wastes such as waste acid and waste alkali, or high-moisture wastes such as sewage sludge can be added.

[0043] The kiln flue gas used in the carbonation device consumes carbon dioxide through the carbonation reaction of calcium oxide, resulting in a flue gas with a reduced carbon dioxide content. Furthermore, because the carbonation reaction is exothermic, the temperature of the kiln flue gas discharged from the carbonation device increases, depending on the temperature at which the kiln flue gas is supplied to the carbonation device. Although the kiln flue gas supplied to the carbonation device is subject to a temperature drop due to heat dissipation in the kiln flue gas exhaust duct, the temperature increases due to the exothermic reaction, and therefore the kiln flue gas can be used as a heat source for drying cement raw materials in the drying device of the drying and crushing device.

[0044] As will be described later, when a fluidized bed type carbonation reaction tower is used, it is preferable to recycle the kiln combustion exhaust gas discharged from the carbonation unit for use in forming the fluidized bed. The flow rate of the kiln combustion exhaust gas discharged from the carbonation unit can be determined taking into consideration the operating status of the cement firing facility, and can be controlled using an air volume adjustment damper.

[0045] (powder containing calcium oxide) The powder material containing calcium oxide supplied to the carbonation device is a powder raw material (hereinafter also referred to as "powder raw material 1") that is preheated and calcined in a suspension preheater and supplied to a rotary kiln, and a powder raw material (hereinafter also referred to as "powder raw material 2") contained in the kiln combustion exhaust gas before being supplied from the rotary kiln to the suspension preheater (1).

[0046] The powdered raw material 1 is supplied to the carbonation device via a fractionation device (12) that fractionates the powdered raw material preheated and calcined in the suspension preheater (1) and a powder supply device 1 (13) that supplies the powdered raw material fractionated by the fractionation device (12) to the carbonation device. The powdered raw material 1 contains a large amount of calcium oxide because the calcium carbonate contained in the powdered raw material supplied to the suspension preheater (1) is preheated and calcined to become calcium oxide while releasing carbon dioxide through a decarbonation reaction (CaCO3 → CaO + CO2).

[0047] In the carbonation system, calcium oxide contained in the powdered raw material 1 adsorbs and carbonates carbon dioxide contained in the kiln flue gas, thereby reducing the carbon dioxide content in the kiln flue gas. Therefore, it is preferable to use powdered raw material 1 discharged from a lower cyclone dust collector, as it has a higher calcium oxide content. In the suspension preheater (1), the powdered raw material undergoes a decarbonation reaction as it passes through lower cyclone dust collectors, increasing the calcium oxide content. The decarbonation rate of the powdered raw material just before being introduced into the calciner (2) (raw material conduit K1b in FIG. 2) is about 10%, while the powdered raw material discharged from the lowest cyclone dust collector (cyclone dust collector C1 and raw material conduit C1b in FIG. 2) has a decarbonation rate of about 90%. The calcium oxide content of the powdered raw material increases dramatically after passing through the calciner. Therefore, it is more preferable to use powdered raw material 1 discharged from the lowest cyclone dust collector. Therefore, as shown in FIG. 2, the fractionation device (12) is preferably provided in the powder raw material conduit (11, C1b) that supplies the powder raw material preheated and calcined in the suspension preheater (1) to the rotary kiln, i.e., in the powder raw material conduit (11, C1b) between the rotary kiln and the lowest cyclone dust collector C1 in the calciner system air duct.

[0048] Before being supplied from the rotary kiln to the suspension preheater (1), the powdered raw material 2 contained in the kiln combustion exhaust gas has a decarbonation rate of nearly 100% of the calcium carbonate contained in the powdered raw material (powdered raw material mixture) supplied to the suspension preheater (1), i.e., the entire amount of calcium carbonate has been converted to calcium oxide. Therefore, as described above, the carbonation reaction with carbon dioxide contained in the kiln combustion exhaust gas (CaO + CO2 → CaCO3) in the carbonation device can extremely efficiently reduce the carbon dioxide content in the kiln combustion exhaust gas.

[0049] Here, the decarbonation rate in this specification is a value that can be calculated by the following formula. Decarboxylation rate (%)=(Ca0-Ca1) / Ca0×100 Ca0: The amount of calcium carbonate (ton / h) contained in the powder raw material fed into the suspension preheater. Ca1: The amount of calcium carbonate contained in the powder raw material in the cyclone dust collector C1 (ton / h).

[0050] The powdered raw material 2 is supplied to the carbonation device via an extraction device (8) that extracts the kiln combustion exhaust gas before being supplied to the cyclone dust collector at the lowest stage of the kiln system air duct of the suspension preheater, a powdered raw material separation device (9) that separates the powdered raw material contained in the kiln combustion exhaust gas extracted by the extraction device (8), and a powdered material supply device 2 (10) that supplies the powdered raw material separated by the powdered raw material separation device (9) to the carbonation device.

[0051] As the powder material containing calcium oxide to be supplied to the carbonation device, the above-mentioned powdered raw material 1 alone, the above-mentioned powdered raw material 2 alone, or the above-mentioned powdered raw materials 1 and 2 simultaneously can be supplied. As described above, the decarbonation rate of the powdered raw material 1 supplied to the rotary kiln is lower than the decarbonation rate of the powdered raw material 2 contained in the kiln combustion exhaust gas before being supplied from the rotary kiln to the suspension preheater 1. Therefore, it is preferable to use at least the powdered raw material 2 as the powder material containing calcium oxide.

[0052] On the other hand, the amount of powdered raw material 1 used can be adjusted as desired within a range that does not affect the production of cement clinker. For example, if the amount of calcium oxide is insufficient by supplying only powdered raw material 2 and the carbon dioxide content in the kiln flue gas is not sufficiently reduced, powdered raw material 1 can be used or the amount of powdered raw material 1 used can be increased.

[0053] The location of the extraction device (8) is not particularly limited as long as it can extract the kiln combustion exhaust gas before it is supplied to the cyclone dust collector at the lowest stage in the kiln system air duct of the suspension preheater, and may be any location in the gas flow path K0a connecting the rotary kiln and the lowest cyclone dust collector K1, where the kiln combustion exhaust gas supplied from the rotary kiln first enters the suspension preheater (1). The extraction device used in the extraction device 8 may be a conventional, commonly used device, such as a suction nozzle, etc. The separation device used in the powder material separation device 9 may be a conventional, commonly used device, such as a cyclone dust collector, similar to the extraction device.

[0054] (carbonation reactor) The carbonation reaction tower can be any reaction tower that can produce a powder containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater (1) with a powder containing calcium oxide.

[0055] For example, a simple reaction tower may be used in which calcium carbonate is produced by injecting powder containing calcium oxide into an air duct through which kiln flue gas flows. Alternatively, a reaction tower that can ensure a longer contact time between the powder containing calcium oxide and the kiln flue gas and thereby increase reaction efficiency may be employed. A preferred example of a device that can increase reaction efficiency is a fluidized-bed carbonation reaction tower, as shown in Figure 3, which can ensure reaction time by agitating the powder containing calcium oxide with the kiln flue gas. This improves the reaction efficiency of the carbonation reaction and increases the calcium carbonate production rate, thereby reducing the amount of powder containing calcium oxide added. This effectively reduces the carbon dioxide content in the kiln flue gas, thereby more efficiently suppressing carbon dioxide emissions into the atmosphere.

[0056] 3, the kiln combustion exhaust gas supplied to the carbonation reaction tower is shown as being split into two by a gas distributor and supplied from two directions, but this is not limited thereto and may be supplied from, for example, one direction, or alternatively, three, four, or even five or more directions. Of these, supplying from two directions is preferred in view of the fact that a swirling flow can be generated more efficiently. In this case, it is preferable to supply the kiln combustion exhaust gas into the carbonation reaction tower so as to generate a swirling flow, which can ensure a longer contact time between the calcium oxide-containing powder and the kiln combustion exhaust gas and improve the reaction efficiency between the calcium oxide and the carbon dioxide contained in the kiln combustion exhaust gas.

[0057] When a fluidized-bed type carbonation reaction tower is used as the carbonation reaction tower, it is preferable to recycle the kiln flue gas discharged from the carbonation reaction tower and use it as the fluidizing gas to form the fluidized bed, as shown in Fig. 3. More specifically, it is preferable to use the kiln flue gas, which is discharged from the carbonation reaction tower and contains the powdered material produced by the carbonation apparatus, after separating the powdered material produced by the carbonation apparatus using a dust collector, and then extracting the kiln flue gas from the outlet of the carbonation apparatus induction fan that supplies the dryer, to form the fluidized bed.

[0058] The temperature in the carbonation reaction tower is linked to the temperature of the kiln combustion exhaust gas supplied to the carbonation device, and therefore the temperature in the carbonation reaction tower can be adjusted by adjusting the temperature of the kiln combustion exhaust gas supplied to the carbonation device, specifically by the above methods (i) to (iii). The temperature in the carbonation reaction tower is preferably 250°C or higher, with the upper limit preferably being 600°C or lower. A temperature of 250°C or higher allows for good drying of the cement raw materials, while a temperature of 600°C or lower makes it easier to achieve 100% reaction efficiency for the carbonation reaction of calcium oxide in the carbonation equipment. Considering that drying the cement raw materials with more capacity allows the drying equipment to be shut down depending on the inventory of dried raw materials, thereby reducing the power consumption of the drying equipment, and that maintenance inspections can be performed in conjunction with the shutdown of the drying equipment to prevent breakdowns, a temperature of 300°C or higher is more preferable. Furthermore, considering that inexpensive general structural rolled steel can be used for the air duct material, resulting in more economical cement burning equipment, a temperature of 400°C or lower is more preferable.

[0059] The temperature of the kiln flue gas discharged from the carbonation reaction tower cannot be generalized because it is linked to the temperature at which the kiln flue gas is supplied to the carbonation device, but because the carbonation reaction is an exothermic reaction, it will be higher than the temperature at which the kiln flue gas is supplied to the carbonation device. Therefore, by using this to form a fluidized bed, the temperature inside the carbonation reaction tower can be maintained at a high temperature, and the kiln flue gas discharged from the carbonation device can be used effectively as a heat source for drying the cement raw materials.

[0060] (dust collector) The carbonation apparatus preferably includes a dust collector that separates the kiln combustion exhaust gas from the powdery material produced by the carbonation apparatus contained in the kiln combustion exhaust gas discharged from the carbonation reaction tower. By including the dust collector, the kiln combustion exhaust gas can be easily separated from the powdery material produced by the carbonation apparatus. As the dust collector, any conventionally used dust collector may be used, and various types of dust collectors such as a bag filter, an electric dust collector, an inertial dust collector, etc. may be employed.

[0061] (forced draft fan and induced draft fan) The carbonation device is preferably equipped with a forced draft fan and an induced draft fan. For example, as shown in Figure 3, it is preferable to have a fluidization forced draft fan for supplying the kiln combustion exhaust gas used to form the fluidized bed to the carbonation reaction tower. By providing the fluidization forced draft fan, it becomes easier to maintain the formation of the fluidized bed by the kiln combustion exhaust gas in a good condition. It is also preferable to provide a carbonator induction fan for discharging the kiln combustion exhaust gas from the dust collector and supplying it to the dryer.

[0062] (Air volume control damper) The kiln flue gas duct of the carbonator can be equipped with an air volume adjustment damper as needed. For example, as shown in Figure 3, air volume adjustment dampers can be provided in the kiln flue gas exhaust duct (6), the carbonator air intake duct (7), the carbonator exhaust duct (14), the inlet duct of the carbonator induction fan, the inlet duct of the fluidization forced draft fan, and the like. By providing these air volume adjustment dampers, it is possible to adjust the flow rate of the kiln flue gas, such as the flow rate of the kiln flue gas supplied to the carbonator, the flow rate of the kiln flue gas supplied directly to the dryer without being supplied to the carbonator, and the flow rate of the kiln flue gas used to form a fluidized bed, and it is also possible to adjust the pressure of the kiln flue gas.

[0063] The damper used for adjusting the air volume is not particularly limited as long as it can adjust the flow rate of the kiln combustion exhaust gas, but it can be appropriately selected from various dampers such as louver type, butterfly type, vane control type, etc.

[0064] (carbon dioxide concentration meter) The carbonation device is preferably equipped with a carbon dioxide concentration meter, for example, in the carbonation device exhaust air duct (14). By installing a carbon dioxide concentration meter in the carbonation device exhaust air duct (14), the progress of the carbonation reaction in the carbonation reaction tower can be monitored. This makes it easier to adjust the amount of powder containing calcium oxide to be added depending on the carbon dioxide concentration of the kiln combustion exhaust gas discharged from the carbonation device. As a result, it is possible to more efficiently suppress the amount of carbon dioxide released into the atmosphere and efficiently dry the cement raw materials.

[0065] (Use of powder produced by carbonation equipment) The powder containing calcium carbonate (carbonation-unit-produced powder) produced by the carbonation reaction of the powder containing calcium oxide in the carbonation unit contains cement raw material compositions such as silicon oxide, aluminum oxide, and iron oxide in addition to calcium carbonate, and is therefore preferably used as a cement raw material. Therefore, as shown in Figures 1 and 3, the cement firing equipment of this embodiment preferably includes a carbonation-unit-produced powder conveying device (15) that merges the powder containing calcium carbonate produced in the carbonation unit with a powder raw material supplying device (16) that supplies the powder raw material discharged from the drying and crushing device to the suspension preheater.

[0066] The powder containing calcium carbonate (powder produced in the carbonation device) is combined with the powder raw material discharged from the drying and crushing device, and is then supplied to a suspension preheater (1) and then to a rotary kiln. The powder containing calcium carbonate (powder produced in the carbonation device) then undergoes a decarbonation reaction, releasing carbon dioxide into the combustion exhaust gas (calciner combustion exhaust gas and kiln combustion exhaust gas). In the cement firing equipment of this embodiment, approximately 20% of the carbon dioxide generated by the decarbonation reaction from powder containing calcium carbonate (powder produced in the carbonation unit) is released into the kiln flue gas, and the remaining approximately 80% is released into the calciner flue gas. The amount of carbon dioxide released into the atmosphere can be reduced by reducing the carbon dioxide contained in the kiln flue gas in the carbonation unit and using it to dry cement raw materials before releasing it into the atmosphere. Furthermore, by using the powder that has adsorbed carbon dioxide in the carbonation unit as a cement raw material, a portion of the carbon dioxide adsorbed in the powder can be released into the calciner flue gas. This increases the amount of carbon dioxide in the calciner flue gas, thereby improving the recovery rate of the carbon dioxide capture unit.

[0067] The powder produced in the carbonation device, which has been calcined in the calciner system air duct and released carbon dioxide, is either fired in a rotary kiln to form part of cement clinker, or separated in a separation device (12) and supplied to the carbonation device as powder containing calcium oxide via a powder supply device 1 (13), thereby being reused in the carbonation device.

[0068] Furthermore, the powder containing calcium carbonate (powder produced by a carbonation apparatus) can be effectively used as a filler (admixture) in asphalt mixtures, in addition to being used as part of the cement raw material described above.

[0069] [Carbon dioxide capture device] The cement calcination system of this embodiment includes a carbon dioxide capture device that captures carbon dioxide contained in the flue gas discharged from the suspension preheater, and a calciner flue gas exhaust duct (5) for supplying the calciner flue gas discharged from the calciner flue gas outlet to the carbon dioxide capture device. In other words, in the cement calcination system of this embodiment, the flue gas supplied to the carbon dioxide capture device must be at least calciner flue gas. As mentioned above, calciner flue gas contains more carbon dioxide than kiln flue gas. Therefore, capturing carbon dioxide from calciner flue gas improves the carbon dioxide capture efficiency. Furthermore, by using the carbon dioxide contained in the kiln flue gas recovered as powder in the carbonation system as a cement raw material, the carbon dioxide content in the calciner flue gas can be increased. Therefore, it is effective to supply the calciner flue gas to a carbon dioxide capture device and capture carbon dioxide.

[0070] The cement burning facility of this embodiment may also include a kiln combustion exhaust gas exhaust duct (not shown) for supplying the kiln combustion exhaust gas to the carbon dioxide capture device.

[0071] There are no particular limitations on the type of carbon dioxide recovery equipment, as long as it can recover carbon dioxide from combustion exhaust gas, and it can be appropriately selected from, for example, a liquid absorption system, a membrane separation system, a solid adsorption system, a compression liquefaction recovery system, etc.

[0072] The carbon dioxide captured by the carbon dioxide capture device can be effectively utilized, for example, by underground burial or methanation, thereby reducing the amount of carbon dioxide contained in combustion exhaust gases such as calciner combustion exhaust gases that are released into the atmosphere.

[0073] [Drying and grinding equipment] The cement firing facility of this embodiment includes a drying and pulverizing device that dries and pulverizes cement raw materials to produce powdered raw materials. As described above, the kiln combustion exhaust gas supplied to the carbonation device is used as a heat source for drying the cement raw materials.

[0074] Examples of drying and pulverizing devices that dry and pulverize cement raw materials to produce powder raw materials include drying and pulverizing devices that combine a drying device such as a rotary dryer with a pulverizing device such as a tube mill, and drying and pulverizing devices that can simultaneously perform drying and pulverizing, such as a vertical roller mill.

[0075] [Mixing cement raw materials] The cement firing facility of this embodiment preferably further includes a powdered raw material mixture sampling device (17) that samples the powdered raw material mixture, a chemical component measuring device (18) that measures the chemical components of the powdered raw material mixture sampled by the powdered raw material mixture sampling device, and a cement raw material blending device that adjusts the blending of the cement raw materials based on the measurement results of the chemical component measuring device.

[0076] (Powder raw material mixture sampling device, chemical component measuring device) In the cement firing equipment of this embodiment, in addition to the cement raw materials described above, a powdered raw material mixture containing the powdered material produced by the carbonation device (powdered material containing calcium carbonate) delivered from the carbonation device and the powdered raw material discharged from the drying and crushing device is preferably used as the cement raw material. In this case, it is necessary to blend the cement raw material taking into account the chemical components of the powdered material produced by the carbonation device (powdered material containing calcium carbonate) delivered from the carbonation device. By providing these devices, when the powdered material containing calcium carbonate delivered from the carbonation device is used as the cement raw material, the chemical components of the powdered raw material mixture containing the powdered raw material discharged from the drying and crushing device and the powdered material containing calcium carbonate delivered from the carbonation device can be quickly measured. Then, by feeding back the measured chemical components to the cement raw material blending device, the chemical components of the powdered raw material supplied to the suspension preheater (1) can be quickly adjusted to target values.

[0077] The sampling and measuring devices are not particularly limited in type. For example, various samplers such as slot samplers, screw samplers, and benzine samplers can be used as sampling devices. Various measuring devices such as X-ray fluorescence analyzers, ICP emission spectrometers, and atomic absorption spectrophotometers can be used as chemical component measuring devices. Furthermore, automatic control can be adopted for adjusting the cement raw materials.

[0078] (Cement raw material mixing equipment) The cement firing equipment of this embodiment preferably includes a cement raw material blending device for adjusting the powdered raw material to be supplied to the suspension preheater to have a target chemical composition based on the chemical composition of the powdered raw material to be supplied to the suspension preheater measured by the chemical composition measuring device.

[0079] In the cement raw material blending equipment, the calcium content of the cement raw materials can be adjusted by increasing or decreasing the supply amount of Ca raw materials such as limestone, the silica content can be adjusted by increasing or decreasing the supply amount of Si raw materials such as silica stone, the aluminum content can be adjusted by increasing or decreasing the supply amount of Al raw materials such as coal ash, and the iron content can be adjusted by increasing or decreasing the supply amount of Fe raw materials such as copper tangle. In this way, the chemical components of the clinker can be adjusted to the target values. More specifically, the calcium content in the cement raw materials can be adjusted by increasing or decreasing the supply amount of a Ca raw material such as limestone; the silica content can be adjusted by increasing or decreasing the supply amount of a Si raw material such as silica stone; the aluminum content can be adjusted by increasing or decreasing the supply amount of an Al raw material such as coal ash; and the iron content can be adjusted by increasing or decreasing the supply amount of an Fe raw material such as copper tangle.

[0080] The powder supplying device and conveying device, i.e., the powder supplying device 2 (10), the powder supplying device 1 (13), the powder conveying device 15 produced by the carbonation device, and the powder raw material supplying device 16, may be equipped with a device for supplying and conveying the powder, if necessary. Examples of the device for supplying and conveying include conveying devices such as a screw conveyor and an apron feeder.

[0081] (Other devices) The cement calcination equipment of this embodiment has been described above with regard to the configuration and various conditions of the suspension preheater, the configuration and various conditions of the carbonation equipment, the configuration and various conditions of the carbon dioxide capture equipment, the configuration and various conditions of the drying and pulverization equipment, etc. In addition to these devices, the cement calcination equipment of this embodiment also has a rotary kiln and a clinker cooler as main devices.

[0082] The rotary kiln is a device that burns the powdered raw materials that have been preheated and calcined in the suspension preheater (1) to produce cement clinker, and more specifically, it is a device that completely decarbonates the calcium carbonate contained in the powdered raw materials to produce calcium oxide, and then burns it at a high temperature of about 1450°C to produce cement clinker.The clinker cooler is a device that cools the clinker produced in the rotary kiln. As these rotary kilns and clinker coolers, conventionally used devices can be used without any restrictions.

[0083] [Cement clinker manufacturing method] The method for producing cement clinker of this embodiment is as follows: This is a production method using the cement burning equipment of the present embodiment and adjusting by any one of the following adjustment methods (i) to (iii). (i) Adjusting the amount of powder raw material supplied to the suspension preheater (ii) adjusting the amount of fuel supplied to said rotary kiln; (iii) Adjusting the amount of water sprayed onto the rotary kiln combustion exhaust gas duct

[0084] The cement burning equipment used in the cement clinker manufacturing method of this embodiment is the cement burning equipment of this embodiment described above.

[0085] In addition, with regard to the above-mentioned adjustment methods (i) to (iii), in the manufacturing method of this embodiment, one of the above-mentioned adjustment methods (i) to (iii) may be adopted, or a combination of two or more of the adjustment methods may be adopted. In consideration of ease of adjustment, it is preferable to adopt a combination of two or more of the above-mentioned adjustment methods (i) to (iii).

[0086] In the method for producing cement clinker of this embodiment, it is preferable to adjust the temperature of the kiln combustion exhaust gas to 250° C. or higher and 600° C. or lower using any of the above adjustment methods (i) to (iii). As explained above in connection with the cement calcination equipment of this embodiment, the temperature of the kiln flue gas discharged from the kiln flue gas outlet is adjusted to 250°C or higher and 600°C or lower. By keeping the temperature within this range, the cement raw materials can be dried well, and the reaction efficiency of the carbonation reaction of calcium oxide in the carbonation device can be easily improved to nearly 100%. Furthermore, as explained above in connection with the cement calcination equipment of this embodiment, it is also preferable to keep the temperature between 300°C and 400°C. [Example]

[0087] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0088] (Example) Cement raw materials were fed at a rate of 200 ton / h using a cement calcination facility with the flow diagram shown in Figure 1 to produce cement clinker. The temperature of the kiln flue gas at the kiln flue gas outlet was adjusted to 380°C. The entire amount of kiln flue gas (Jg in Figure 4) discharged from the kiln flue gas outlet was supplied to a carbonation device, and the entire amount of kiln flue gas discharged from the carbonation device (Kg in Figure 4) was supplied to a dryer and used to dry the cement raw materials. The amount of powdered raw material separated from the fractionator and supplied to the carbonation device (F in Figure 4) was adjusted so that the amount of carbon dioxide in the kiln flue gas discharged from the carbonation device was 10% of the amount of carbon dioxide in the kiln flue gas supplied to the carbonation device. The entire amount of powdered material containing calcium carbonate (G in Figure 4) transported from the carbonation device was used as cement raw material. The entire amount of the calciner combustion exhaust gas (Mg in Figure 4) discharged from the calciner combustion exhaust gas outlet was supplied to the carbon dioxide capture device.

[0089] When the operation of the cement calcination plant reached a steady state, the flow rates of the powdered raw material (A) at the outlet of the drying and grinding device, the powdered raw material mixture (B) of the powdered raw material (A) and the powdered material containing calcium carbonate (G) transported from the carbonation device, the powdered raw material (C) discharged from the cyclone dust collector at the bottom of the kiln system air duct of the suspension preheater, the powdered raw material (D) discharged from the cyclone dust collector at the bottom of the calciner system air duct, the powdered raw material (E) separated from the powdered raw material (D) by the fractionator and supplied to the rotary kiln, the powdered raw material (F) separated from the fractionator and supplied to the carbonation device, and the powdered material containing calcium carbonate (G) transported from the carbonation device, as well as the contents of calcium carbonate and calcium oxide contained in the powdered materials, were measured. In addition, the balance of calcium carbonate, calcium oxide, and carbon dioxide was calculated from the flow rates of combustion exhaust gases such as kiln combustion exhaust gas and calciner combustion exhaust gas ((Ig), (Jg), (Kg), (Lg), and (Mg)), the carbon dioxide concentrations contained in these combustion exhaust gases, and the flow rate and carbon content of the fuel. The results are shown in Table 1.

[0090] By using the carbonation device, it was confirmed that the amount of carbon dioxide (Lg) contained in the kiln combustion exhaust gas and released into the atmosphere was 4 ton / h, and the amount of carbon dioxide (Mg) captured in the carbon dioxide capture device was 111 ton / h.

[0091] The temperature of the kiln flue gas, which was adjusted to 380°C at the kiln flue gas outlet, dropped to 350°C at the carbonator inlet due to heat dissipation in the kiln flue gas exhaust duct. The temperature of the kiln flue gas in the carbonator exhaust duct (the temperature just before it merged with the kiln flue gas exhaust duct) was 380°C, and rose by 30°C due to the carbonation reaction (exothermic reaction) in the carbonator. When the entire amount of this kiln flue gas was used to dry cement raw materials in the drying and crushing equipment, the required amount of cement raw materials could be dried. The temperature of the kiln flue gas at the dryer outlet was 180°C.

[0092] (Comparative Example) In the example, the cement calcination equipment was operated in the same manner as in the example, except that no powdered raw material was supplied to the carbonation device. When the operation of the cement calcination equipment reached a steady state, measurements were performed in the same manner as in the example, and the balance of calcium carbonate, calcium oxide, and carbon dioxide was calculated. The measurement locations are shown in Figure 5, and the calculation results are shown in Table 1.

[0093] It was confirmed that without the use of a carbonation device, the amount of carbon dioxide released into the atmosphere along with the kiln combustion exhaust gas is 37 tons / h, and the amount of carbon dioxide captured by the carbon dioxide capture device is 78 tons / h.

[0094] [Table 1] *"Non-energy-origin CO2" refers to carbon dioxide generated from powdered raw materials, and "energy-origin CO2" refers to carbon dioxide generated from fuels used in the suspension preheater and rotary kiln.

[0095] In the above table, the abbreviations A to Mg are as follows: (A): Powder raw material at the outlet of the drying and grinding device (B): A powder mixture of the powder raw material (A) and the powder material (G) containing calcium carbonate transported from the carbonation device. (C): Powdered raw material discharged from the cyclone dust collector K1 at the bottom of the kiln system air duct of the suspension preheater (Cg): Carbon dioxide produced by decarbonation of the powdered raw material supplied to the cyclone dust collector K1 (D) Powdered raw materials discharged from the cyclone dust collector at the bottom of the calciner system air duct (Dg) Carbon dioxide produced by decarbonation of powder raw material (C) in the cyclone dust collector C1 from the calciner (E) Powder raw material that is separated from powder raw material (D) by a separation device and then supplied to the rotary kiln (F) Powder raw material taken from the fractionator and supplied to the carbonation device (G) Powder containing calcium carbonate transported from a carbonation device · (H): Powder produced by decarbonation of powder raw material (E) in a rotary kiln · (Hg): Carbon dioxide produced by decarbonation of powdered raw material (E) in the rotary kiln ·(Ig): Kiln combustion exhaust gas discharged from the rotary kiln ·(Jg): Kiln flue gas discharged from the kiln flue gas outlet ·(Kg): Kiln flue gas discharged from the carbonation unit · (Lg): Kiln combustion exhaust gas discharged from the drying device · (Mg): Calciner flue gas discharged from the calciner flue gas outlet

[0096] From the results of the Examples and Comparative Examples, it was confirmed that, while keeping the input amount of powdered raw materials and the production amount of clinker the same, the amount of carbon dioxide emitted into the atmosphere (Lg) can be reduced from 37 ton / h to 4 ton / h, the amount of carbon dioxide captured in the carbon dioxide capture equipment (Mg) can be increased from 78 ton / h to 111 ton / h, and further, the cement raw materials can be dried. As described above, it was confirmed that the cement firing equipment of this embodiment and the cement clinker production method using the same can suppress the amount of carbon dioxide emitted into the atmosphere and efficiently dry the cement raw materials.

Claims

1. Drying and crushing equipment for drying and crushing cement raw materials to produce powder raw materials; a suspension preheater for preheating and calcining the powder raw material; a rotary kiln for burning the preheated and calcined powdered raw material to form cement clinker; a cement clinker cooler for cooling the cement clinker; a carbon dioxide recovery device that recovers carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater; and a carbonation device that produces a powder containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater with a powder containing calcium oxide; The suspension preheater is a calciner for calcining the powdered raw material; two different air ducts, namely, a calciner system air duct through which the calciner combustion exhaust gas discharged from the calciner passes and a kiln system air duct through which the kiln combustion exhaust gas discharged from the rotary kiln passes; a calciner combustion exhaust gas outlet for discharging the calciner combustion exhaust gas, which has preheated and calcined the powdered raw material by passing through the calciner system air duct, from the suspension preheater; and a kiln combustion exhaust gas outlet for discharging the kiln combustion exhaust gas, which has preheated and calcined the powdered raw material by passing through the kiln system air duct, from the suspension preheater; a preheater having: moreover, a calciner combustion exhaust gas exhaust duct for supplying the calciner combustion exhaust gas discharged from the calciner combustion exhaust gas outlet to the carbon dioxide recovery device; a kiln combustion exhaust gas exhaust duct for supplying the kiln combustion exhaust gas discharged from the kiln combustion exhaust gas outlet to a drying device included in the drying and pulverizing device; a carbonation device air supply duct for supplying the kiln combustion exhaust gas passing through the kiln combustion exhaust gas discharge duct to the carbonation device; and a carbonation device exhaust duct for supplying the kiln combustion exhaust gas discharged from the carbonation device to the kiln combustion exhaust gas exhaust duct; Exhaust gas duct; a fractionating device that fractionates the preheated and calcined powder raw material from the suspension preheater, and a powder supplying device 1 that supplies the powder raw material fractionated by the fractionating device to the carbonation device as a powder containing calcium oxide; and an air extraction device that extracts the kiln combustion exhaust gas before it is supplied to the cyclone dust collector at the lowest stage of the kiln system air duct of the suspension preheater, a powder raw material separation device that separates powder raw material contained in the kiln combustion exhaust gas extracted by the air extraction device, and a powder supply device 2 that supplies the powder raw material separated by the powder raw material separation device to the carbonation device as a powder containing calcium oxide; Cement baking equipment equipped with:

2. 2. The method for producing cement clinker according to claim 1, wherein the separating device is provided in a powder raw material conduit that supplies the powder raw material preheated and calcined in the suspension preheater to the rotary kiln.

3. 2. The cement burning facility according to claim 1, further comprising: a powder raw material supplying device that supplies the powder raw material discharged from the drying and crushing device to the suspension preheater; and a carbonation device-produced powder conveying device that combines the powder containing calcium carbonate produced in the carbonation device with the powder raw material discharged from the drying and crushing device.

4. 4. The cement firing facility according to claim 3, further comprising: a powder raw material mixture sampling device that samples a powder raw material mixture of the powder containing calcium carbonate transported by the carbonation device-produced powder transport device and the powder raw material discharged from the drying and crushing device; a chemical component measuring device that measures chemical components of the powder raw material mixture sampled by the powder raw material mixture sampling device; and a cement raw material blending device that adjusts the blending of the cement raw materials based on measurement results from the chemical component measuring device.

5. 2. The cement burning facility according to claim 1, wherein the carbonation device is a fluidized bed reactor.

6. A method for producing cement clinker, using the cement burning equipment according to claim 1, and adjusting the cement clinker by any one of the following adjustment methods (i) to (iii): (i) Adjusting the amount of powder raw material supplied to the suspension preheater (ii) adjusting the amount of fuel supplied to the rotary kiln; (iii) Adjustment of the amount of water sprayed onto the rotary kiln combustion exhaust gas duct

7. The method for producing cement clinker according to claim 6, wherein the temperature of the kiln combustion exhaust gas discharged from the kiln combustion exhaust gas outlet is adjusted to 250°C or higher and 600°C or lower by the adjusting method.

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