Cement firing facility and method for producing cement clinker

Abstract

The present invention provides: a cement firing facility which is provided with an apparatus for drying and pulverizing a cement staring material, the apparatus being capable of suppressing the amount of carbon dioxide released to the atmosphere and efficiently drying the cement starting material, a suspension preheater, a rotary kiln, a clinker cooler, a carbon dioxide recovery apparatus, and a carbonation apparatus; and a method for producing cement clinker using the cement firing facility.

Description

Cement burning equipment and cement clinker manufacturing method

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

[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 including 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 a portion 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 multiple independent hot gases flow through multiple air passages formed by multiple dust collectors, while a powdered substance is introduced through an air passage leading to the uppermost dust collector of the multiple 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.

[0006] Japanese Patent Laid-Open No. 9-110485 Japanese Patent Laid-Open No. 55-22322 Japanese Patent Laid-Open No. 2022-148255

[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.

[0008] In order to solve the above problems, the present invention provides the following cement burning equipment: 1. a drying and grinding device for drying and grinding cement raw materials to produce powdered raw materials; a suspension preheater for preheating and calcining the powdered raw materials; a rotary kiln for burning the preheated and calcined powdered raw materials to produce cement clinker; a cement clinker cooler for cooling the cement clinker; a carbon dioxide recovery device for recovering carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater; and a carbonation device for producing powdered material containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater with a powdered material containing calcium oxide; the suspension preheater comprises: a calciner for calcining the powdered raw materials; 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 materials by passing through the calciner system air duct, from the suspension preheater; a kiln flue gas outlet that discharges the kiln flue gas, which has passed through the kiln system air duct to preheat and calcinate the powdered raw material, from the suspension preheater; and further comprising: a calciner flue gas exhaust duct for supplying the calciner flue gas discharged from the calciner flue gas outlet to the carbon dioxide capture device; a kiln flue gas exhaust duct for supplying the kiln flue gas discharged from the kiln flue gas outlet to a drying device included in the drying and pulverizing device; a carbonator air intake duct for supplying the kiln flue gas passing through the kiln flue gas exhaust duct to the carbonator; and a carbonator exhaust duct for supplying the kiln flue gas discharged from the carbonator to the kiln flue gas exhaust 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 a gas 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 materials contained in the kiln combustion exhaust gas extracted by the gas extraction device, and a powder supply device 2 that supplies the powder raw materials separated by the powder raw material separation device to the carbonation device as powdered materials containing calcium oxide.

[0009] The present invention provides the following cement firing equipment as preferred embodiments. 2. The method for producing cement clinker as set forth in item 1 above, wherein the fractionating device is provided in a powdered raw material conduit that supplies the powdered raw material preheated and calcined in the suspension preheater to the rotary kiln. 3. The cement firing equipment as set forth in item 1 or 2 above, further comprising: a powdered raw material supplying device that supplies the powdered raw material discharged from the drying and crushing device to the suspension preheater, and a carbonation-device-produced powder conveying device that merges the powdered material containing calcium carbonate produced in the carbonation device with the powdered raw material discharged from the drying and crushing device. 4. The cement firing equipment as set forth in item 3 above, further comprising: a powdered raw material mixture sampling device that samples a powdered raw material mixture of the powdered material containing calcium carbonate conveyed by the carbonation-device-produced powder conveying device and the powdered raw material discharged from the drying and crushing device; a chemical component measuring device 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. 5. The cement burning facility according to any one of 1 to 4 above, 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 firing equipment described in any one of 1 to 5 above, and adjusting the conditions by any one of (i) to (iii) below: (i) adjusting the amount of powdered raw materials supplied to the suspension preheater (ii) adjusting the amount of fuel supplied to the rotary kiln (iii) adjusting the amount of water sprayed onto the kiln combustion exhaust gas exhaust duct 7. The method for producing cement clinker described in 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 by the above conditions.

[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.

[0012] Fig. 1 is a schematic diagram showing a preferred embodiment of the cement calcination facility of the present embodiment; Fig. 2 is a schematic diagram showing a preferred embodiment of a suspension preheater employed in the cement calcination facility of the present embodiment; Fig. 3 is a schematic diagram showing a preferred embodiment of a carbonation device employed in the cement calcination facility of the present embodiment; Fig. 4 is a schematic diagram for explaining the results of an example; Fig. 5 is a schematic diagram for explaining the results of a comparative example.

[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. Note that the notation of a numerical range as "AA to BB" in this specification means "at least AA and at most BB." Furthermore, in this specification, the numerical values ​​associated with "at least," "at most," and "to" in describing a numerical range are values ​​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 Calcination Equipment] The cement calcination equipment of this embodiment includes: a drying and pulverizing device that dries and pulverizes cement raw materials to produce powdered raw materials; a suspension preheater that preheats and calcines the powdered raw materials; a rotary kiln that calcines the preheated and calcined powdered raw materials to produce cement clinker; a cement clinker cooler that cools the cement clinker; a carbon dioxide capture device that captures carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater; and a carbonation device that produces powdered material containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater with a powdered material containing calcium oxide; the suspension preheater includes: a calciner that calcines the powdered raw materials; and 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, from the suspension preheater, the calciner combustion exhaust gas that has preheated and calcined the powdered raw materials by passing through the calciner system air duct, and a kiln combustion exhaust gas outlet for discharging, from the suspension preheater, the kiln combustion exhaust gas that has preheated and calcined the powdered raw materials by passing through the kiln system air duct; and 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 capture 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 carbonator air intake duct for supplying the kiln combustion exhaust gas that passes through the kiln combustion exhaust gas exhaust duct to the carbonator, and a carbonator exhaust duct for supplying the kiln combustion exhaust gas discharged from the carbonator to the kiln combustion exhaust gas exhaust duct. an 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 the 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.

[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 equipment lacks the perspective of 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 emitted 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. The present inventors have therefore decided to study the reduction of carbon dioxide of non-energy origin in particular.

[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 according to 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 according to 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 powder 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 powder raw material separated in the powder 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] 1 shows that the kiln flue gas used in the carbonation device is supplied to the kiln flue gas exhaust duct (6) via the carbonation device exhaust duct (14), where it is used as a heat source in the drying device of the drying and crushing device and finally released into the atmosphere via a dust collector and a chimney. Also shown is that the powder containing calcium carbonate produced in the carbonation device is supplied to the suspension preheater (1) by the powder raw material supply device (16) as a powder raw material mixture together with the powder raw material discharged from the drying and crushing device via the carbonation device-produced powder conveying device (15), where it is preheated and calcined. 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 partially sampled by the powder raw material mixture sampling device (17) and analyzed by the chemical component measuring device (18). The cement raw material blending device adjusts the blending 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 that calcines 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 that discharges 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 that discharges 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, the two different air ducts of the calciner system and the kiln system, the calciner combustion exhaust gas outlet, and the kiln combustion exhaust gas outlet. A preferred embodiment of the suspension preheater will be described with reference to FIG.

[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 cyclone collector C1 at the bottom to the cyclone collector C4 at the top, in order, via gas flow paths (C0a to C4a). The kiln combustion exhaust gas passes through the cyclone collector K1 at the bottom to the cyclone collector K4 at the top, 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 the powder raw material, FIG. 2 shows raw material conduits including raw material conduits (K2b to 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 a kiln system raw material conduit (K1b) that connects the cyclone dust collector at the bottom stage of the kiln system air duct to the calciner. the calciner system air duct has a raw material conduit (C1b) for connecting the cyclone dust collector in the calciner system air duct to a gas flow path for supplying kiln combustion exhaust gas to a cyclone dust collector in the kiln system air duct one stage below the cyclone dust collector in the calciner system air duct; and the calciner system raw material conduit (C1b) for connecting the cyclone dust collector in the lowest stage 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 powdered material containing calcium carbonate produced in the carbonation device is supplied by a powder raw material supply device (16) to the suspension preheater (1), more specifically, from the powder raw material supply device (16) to the cyclone dust collector at the top of the suspension preheater 1. Fig. 2 shows that the powder raw material mixture to be used as the powder raw material is 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 upper to lower cyclone collectors in 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 mixing device for mixing the powdered raw material with a 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. Furthermore, the powdered raw material supplying device (16) and the carbonation device-produced powder transporting device (15) may include a pipe for passing the objects to be supplied or transported, as well as a device such as a feeder for pressure-feeding as needed.

[0036] [Carbonation Device] The cement firing facility of this embodiment includes a carbonation device that produces a powder containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater (1) with a powder containing calcium oxide. The carbonation device will be described with reference to FIG.

[0037] Fig. 3 is a schematic diagram showing a preferred embodiment of a carbonation apparatus, which includes a carbonation reaction tower in which a reaction between a kiln flue gas and a powder containing calcium oxide takes place, a dust collector for separating the kiln flue gas from the powder produced by the carbonation reaction tower, a carbonation induction fan for discharging the kiln flue gas from the dust collector and supplying 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 by passing 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 pulverization 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 (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 (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, the 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. If the temperature is 250°C or higher, the cement raw materials can be dried well, and if the temperature is 600°C or lower, the reaction efficiency of the carbonation reaction of calcium oxide in the carbonation device can be easily improved to 100%.

[0042] Methods for adjusting the temperature of the kiln flue gas supplied to the carbonation device include, for example, the following methods (i) to (iii), which can be used alone or in combination. (i) Adjusting the amount of powdered raw material supplied 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 supplied to the carbonation device. (ii) Adjusting the amount of fuel fed to the rotary kiln. By increasing the amount of fuel, the temperature of the kiln flue gas supplied to the carbonation device can be increased. Furthermore, the temperature of the kiln flue gas can also be increased by feeding waste materials with a calorific value, such as waste clay or waste plastics such as waste tires, into a raw material conduit such as the raw material conduit K0a (located before the calciner). (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] (Powdered material containing calcium oxide) The powdered material containing calcium oxide supplied to the carbonation device is a powdered raw material (hereinafter also referred to as "powdered raw material 1") that is preheated and calcined in a suspension preheater and supplied to a rotary kiln, and a powdered raw material (hereinafter also referred to as "powdered raw material 2") contained in the kiln combustion exhaust gas before being supplied from the rotary kiln to the suspension preheater (1).

[0046] The powder raw material 1 is supplied to the carbonation device via a fractionation device (12) that fractionates the powder raw material preheated and calcined in the suspension preheater (1) and a powder supply device 1 (13) that supplies the powder raw material fractionated by the fractionation device (12) to the carbonation device. The powder raw material 1 is supplied to the carbonation device via a fractionation device (12) that fractionates the powder raw material preheated and calcined in the suspension preheater (1) and supplies the powder raw material fractionated by the fractionation device (12) to the carbonation device. The powder raw material 1 is supplied to the suspension preheater (1) via a decarbonation reaction (CaCO ３ →CaO+CO ２ ) turns into calcium oxide while releasing carbon dioxide, so it contains a lot of calcium oxide.

[0047] In the carbonation device, 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. For this reason, it is preferable to use powdered raw material 1 that has a higher calcium oxide content and is discharged from a lower cyclone dust collector. In the suspension preheater (1), as the powdered raw material advances to lower cyclone dust collectors, the decarbonation reaction progresses, and the calcium oxide content increases. The decarbonation rate of the powdered raw material immediately before being charged 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 in FIG. 2 and raw material conduit C1b) has a decarbonation rate of about 90%. The calcium oxide content in the powdered raw material increases dramatically by passing through the calciner. Therefore, it is more preferable to use the powdered raw material discharged from the lowest cyclone dust collector as the powdered raw material 1. Therefore, as shown in FIG. 2, the fractionation device (12) is preferably provided in the powdered raw material conduit (11, C1b) that supplies the powdered raw material preheated and calcined in the suspension preheater (1) to the rotary kiln, i.e., in the powdered raw material conduit (11, C1b) between the lowest cyclone dust collector C1 in the calciner system air duct and the rotary kiln.

[0048] The powdered raw material 2 contained in the kiln combustion exhaust gas before being supplied from the rotary kiln to the suspension preheater (1) 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 is converted to calcium oxide. Therefore, as described above, in the carbonation device, the carbonation reaction with carbon dioxide contained in the kiln combustion exhaust gas (CaO + CO ２ →CaCO ３ ) can reduce the carbon dioxide content in the kiln combustion exhaust gas extremely efficiently.

[0049] Here, the decarboxylation rate in this specification is a value that can be calculated by the following formula: Decarboxylation rate (%) = (Ca０ -Ca １ ) / Ca ０ x 100 Ca ０ : The amount of calcium carbonate contained in the powder raw material fed into the suspension preheater (ton / h). １ : The amount of calcium carbonate contained in the powder raw material in the cyclone dust collector C1 (tons / 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 combustion exhaust 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 air extraction device (8) is not particularly limited as long as it can extract the kiln combustion exhaust gas before it is supplied to the lowest cyclone dust collector in the kiln-system air duct of the suspension preheater. It may be located anywhere 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 air extraction device used in the air extraction device (8) may be a conventional, commonly used device, such as a suction nozzle. The separation device used in the powder raw material separation device (9) may be a conventional, commonly used device, such as a cyclone dust collector, similar to the air extraction device.

[0054] (Carbonation Reaction Tower) As the carbonation reaction tower, any reaction tower can be used without particular limitation as long as it 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 FIG. 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 efficiently reduces the carbon dioxide content in the kiln flue gas, thereby more efficiently suppressing the amount of carbon dioxide released into the atmosphere.

[0056] In Figure 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. Among these, supplying from two directions is preferred, considering 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. This allows for a longer contact time between the calcium oxide-containing powder and the kiln combustion exhaust gas, improving 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 combustion exhaust 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 combustion exhaust gas, which is obtained after separating the carbonation-apparatus-produced powder product from the kiln combustion exhaust gas discharged from the carbonation reaction tower using a dust collector, 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 flue gas supplied to the carbonation device. Therefore, the temperature in the carbonation reaction tower can be adjusted by adjusting the temperature of the kiln flue gas supplied to the carbonation device, specifically by methods (i) to (iii) above. 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 satisfactory drying of the cement raw materials, while a temperature of 600°C or lower facilitates achieving 100% reaction efficiency for the calcium oxide carbonation reaction in the carbonation device. By providing more room for drying the cement raw materials, the dryer can be shut down depending on the inventory of dried raw materials, thereby reducing the dryer's power consumption. Furthermore, by performing maintenance and inspections in conjunction with the shutdown of the dryer, the dryer can be shut down to prevent breakdowns. A temperature of 300°C or higher is more preferable. Furthermore, considering the use of inexpensive general structural rolled steel for the air ducts and the resulting more economical cement firing 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 powdery material produced by the carbonation apparatus contained in the kiln combustion exhaust gas discharged from the carbonation reaction tower from the kiln combustion exhaust gas. By including the dust collector, it becomes possible to easily separate the kiln combustion exhaust gas from the powdery material produced by the carbonation apparatus. As the dust collector, a conventionally widely used dust collector may be used, and various types of dust collectors such as a bag filter, an electrostatic precipitator, 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 FIG. 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 a fluidization forced draft fan, it becomes easier to maintain the formation of the fluidized bed by the kiln combustion exhaust gas in a good state. It is also preferable to have a carbonation device induced draft fan for discharging the kiln combustion exhaust gas from the dust collector and supplying it to the dryer.

[0062] (Airflow Control Dampers) The kiln flue gas ducts of the carbonator can be equipped with airflow control dampers as needed. For example, as shown in Figure 3, airflow control 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, and the inlet duct of the fluidization forced draft fan. By providing these airflow control dampers, it is possible to adjust the flow rate of the kiln flue gas, for example, 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, it is preferable to provide a carbon dioxide concentration meter in the carbonation device exhaust air duct (14). By providing a carbon dioxide concentration meter in the carbonation device exhaust air duct (14), it is possible to grasp the degree of progress of the carbonation reaction in the carbonation reaction tower. This makes it easier to adjust, for example, 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 in Carbonator) The powder containing calcium carbonate (powder produced in the carbonator) produced by the carbonation reaction of powder containing calcium oxide in the carbonator 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. For this reason, as shown in Figures 1 and 3, the cement firing equipment of this embodiment preferably includes a carbonator-produced powder conveying device (15) that merges the powder containing calcium carbonate produced in the carbonator 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 by the carbonation device) is combined with the powdered raw material discharged from the drying and crushing device and supplied to the suspension preheater (1) and then to the rotary kiln. The powder containing calcium carbonate (powder produced by the carbonation device) then releases carbon dioxide into the combustion exhaust gas (calciner flue gas and kiln flue gas) through a decarbonation reaction. In the cement firing equipment of this embodiment, approximately 20% of the carbon dioxide generated by the decarbonation reaction from the powder containing calcium carbonate (powder produced by the carbonation device) is released into the kiln flue gas, and the remaining approximately 80% is released into the calciner flue gas. By reducing the carbon dioxide contained in the kiln flue gas in the carbonation device and using it to dry the cement raw material before releasing it into the atmosphere, the amount of carbon dioxide released into the atmosphere can be reduced. Furthermore, by using the powder with carbon dioxide adsorbed in the carbonation device 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 device.

[0067] The powder produced by the carbonation device, which is calcined in the calciner system air duct and releases 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 the carbonation apparatus) can be effectively used as a filler (admixture) contained 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 combustion exhaust gas discharged from the suspension preheater, and a calciner combustion exhaust gas exhaust duct (5) for supplying the calciner combustion exhaust gas discharged from the calciner combustion exhaust gas outlet to the carbon dioxide capture device. That is, in the cement calcination system of this embodiment, the combustion exhaust gas supplied to the carbon dioxide capture device must be at least calciner combustion exhaust gas. As described above, calciner combustion exhaust gas contains more carbon dioxide than kiln combustion exhaust gas. Therefore, capturing carbon dioxide from the calciner combustion exhaust gas improves the carbon dioxide capture efficiency. Furthermore, by using the carbon dioxide contained in the kiln combustion exhaust gas recovered as powder in the carbonation device as a cement raw material, the carbon dioxide content of the calciner combustion exhaust gas can be improved. Therefore, it is effective to supply the calciner combustion exhaust gas to a carbon dioxide capture device and capture carbon dioxide.

[0070] The cement firing 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 pulverizing device] The cement firing facility of this embodiment includes a drying and pulverizing device that dries and pulverizes the cement raw material to produce a powder raw material. As described above, the kiln combustion exhaust gas supplied to the carbonation device is used as a heat source for drying the cement raw material.

[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] [Blending of cement raw materials] The cement firing equipment of this embodiment preferably further includes a powdered raw material mixture sampling device (17) that samples a 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] (Powdered Raw Material Mixture Sampling Device, Chemical Component Measuring Device) In the cement firing equipment of this embodiment, in addition to the above-mentioned cement raw materials, a powdered raw material mixture containing the powdered material produced by the carbonation device (powdered material containing calcium carbonate) transported 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) transported from the carbonation device. By having these devices, when the powdered material containing calcium carbonate transported from the carbonation device is used as the cement raw material, it is possible to quickly measure 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 transported from the carbonation device. Then, by feeding back the chemical components to the cement raw material blending device, it is possible to quickly adjust the chemical components of the powdered raw material supplied to the suspension preheater (1) to target values.

[0077] There are no particular limitations on the type of the sampling device and measuring device. 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 used for adjusting the cement raw materials.

[0078] (Cement Raw Material Blending Device) The cement firing facility of this embodiment preferably includes a cement raw material blending device for adjusting the powdered raw materials to be supplied to the suspension preheater to target chemical compositions based on the chemical compositions of the powdered raw materials to be supplied to the suspension preheater measured by the chemical composition measuring device described above.

[0079] In the cement raw material blending apparatus, 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. This makes it possible to adjust the chemical components of the clinker to 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] Furthermore, the powder supplying devices and conveying devices, namely, 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), described above, 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] (Regarding Other Equipment) The above has described the configuration and various conditions of the suspension preheater, the configuration and various conditions of the carbonation device, the configuration and various conditions of the carbon dioxide capture device, the configuration and various conditions of the drying and pulverizing device, etc. In addition to these devices, the cement calcination facility 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. More specifically, it is a device that completely decarbonates calcium carbonate contained in the powdered raw materials to produce calcium oxide, and then burns the calcium oxide at a high temperature of about 1,450°C to produce cement clinker. The clinker cooler is a device that cools the clinker produced in the rotary kiln. Conventional devices can be used as these rotary kilns and clinker coolers without any restrictions.

[0083] [Method for Producing Cement Clinker] The method for producing cement clinker of this embodiment is a production method using the cement firing equipment of this embodiment described above, and adjusting by any of the following adjustment methods (i) to (iii): (i) Adjusting the amount of powdered raw material supplied to the suspension preheater (ii) Adjusting the amount of fuel supplied to the rotary kiln (iii) Adjusting the amount of water sprayed onto the combustion exhaust gas duct of the rotary kiln

[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 adjustment methods (i) to (iii) above, in the manufacturing method of this embodiment, one of the adjustment methods (i) to (iii) above 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 adjustment methods (i) to (iii) above.

[0086] In the method for producing cement clinker of this embodiment, it is preferable to adjust the temperature of the kiln flue gas to 250°C or higher and 600°C or lower using any of the adjustment methods (i) to (iii) above. Adjusting the temperature of the kiln flue gas discharged from the kiln flue gas outlet to 250°C or higher and 600°C or lower is as explained above in the cement firing equipment of this embodiment. 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, it is also preferable to set the temperature to 300°C or higher and 400°C or lower, as explained above in the cement firing equipment of this embodiment.

[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: Using cement firing equipment having the flow diagram configuration shown in Figure 1, cement raw materials were charged at 200 tons / h 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 the kiln flue gas discharged from the kiln flue gas outlet ((Jg) in Figure 4) was supplied to a carbonation device, and the entire amount of the 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 separation device 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 the powdered material containing calcium carbonate conveyed from the carbonation device ((G) in Figure 4) was used as cement raw material. The entire amount of the calciner combustion exhaust gas (Mg in FIG. 4) discharged from the calciner combustion exhaust gas outlet was supplied to the carbon dioxide recovery unit.

[0089] When the operation of the cement burning equipment 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 (G) containing calcium carbonate transported from the carbonation device, the powdered raw material (C) discharged from the cyclone dust collector at the lowest stage of the kiln system air duct of the suspension preheater, the powdered raw material (D) discharged from the cyclone dust collector at the lowest stage 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 (G) containing calcium carbonate transported from the carbonation device, as well as the contents of calcium carbonate and calcium oxide contained in the powdered materials, were measured. 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] It was confirmed that by using the carbonation device, the amount of carbon dioxide (Lg) contained in the kiln combustion exhaust gas and released into the atmosphere was 4 tons / h, and the amount of carbon dioxide (Mg) recovered in the carbon dioxide recovery device was 111 tons / 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 immediately before merging 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 device, 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) 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 carried out 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 using a carbonation device, the amount of carbon dioxide released into the atmosphere along with the kiln combustion exhaust gas was 37 tons / h, and the amount of carbon dioxide captured in the carbon dioxide capture device was 78 tons / h.

[0094] *, "Non-energy-derived CO ２ " indicates carbon dioxide generated from the powder raw materials, and "energy origin" indicates carbon dioxide generated from the fuel used in the suspension preheater and rotary kiln.

[0095] In the above table, the abbreviations A to Mg are as follows: (A): Powdered raw material at the outlet of the drying and grinding device; (B): Powdered raw material mixture of powdered raw material (A) and 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 in the cyclone dust collector K1 by decarbonation of the powdered raw material supplied to K1; (D) Powdered raw material discharged from the cyclone dust collector at the bottom of the calciner system air duct; (Dg): Carbon dioxide produced in the cyclone dust collector C1 from the calciner by decarbonation of the powdered raw material (C) from the calciner; (E) Powdered raw material separated from the powdered raw material (D) by the separation device and then supplied to the rotary kiln; (F) Powdered raw material separated from the separation device and supplied to the carbonation device; (G) Powdered material containing calcium carbonate transported from the carbonation device. (H): Powder produced by decarbonation of powder raw material (E) in the rotary kiln. (Hg): Carbon dioxide produced by decarbonation of powder raw material (E) in the rotary kiln. (Ig): Kiln flue 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 device. (Lg): Kiln flue gas discharged from the dryer. (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 tons / h to 4 tons / h, the amount of carbon dioxide recovered in the carbon dioxide recovery equipment (Mg) can be increased from 78 tons / h to 111 tons / 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. A drying and grinding device for drying and grinding cement raw materials to produce powdered raw materials, a suspension preheater for preheating and calcining the powdered raw materials, a rotary kiln for burning the preheated and calcined powdered raw materials to produce cement clinker, a cement clinker cooler for cooling the cement clinker, a carbon dioxide recovery device for recovering carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater, and a carbonation device for producing powdered material containing calcium carbonate by reacting the combustion exhaust gas discharged from the suspension preheater with a powdered material containing calcium oxide; the suspension preheater comprises: a calciner for calcining the powdered raw materials, 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 from the suspension preheater, which has preheated and calcined the powdered raw materials by passing through the calciner system air duct, and a kiln flue gas outlet that discharges the kiln flue gas, which has passed through the kiln system air duct to preheat and calcinate the powdered raw material, from the suspension preheater; and further comprising: a calciner flue gas exhaust duct for supplying the calciner flue gas discharged from the calciner flue gas outlet to the carbon dioxide capture device; a kiln flue gas exhaust duct for supplying the kiln flue gas discharged from the kiln flue gas outlet to a drying device included in the drying and pulverizing device; a carbonator air intake duct for supplying the kiln flue gas passing through the kiln flue gas exhaust duct to the carbonator; and a carbonator exhaust duct for supplying the kiln flue gas discharged from the carbonator to the kiln flue gas exhaust 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 a gas 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 materials contained in the kiln combustion exhaust gas extracted by the gas extraction device, and a powder supply device 2 that supplies the powder raw materials separated by the powder raw material separation device to the carbonation device as powdered materials containing calcium oxide.

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. 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 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 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 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 claim 1, wherein the carbonation device is a fluidized bed reactor.

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

7. A method for producing cement clinker as set forth in 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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