Method for producing cement clinker and cement firing equipment

Abstract

The present invention provides a cement firing facility and a method for producing cement clinker in which the amount of carbon dioxide contained in combustion exhaust gas generated by a cement firing facility is adjusted by adjusting the dust collection efficiency of a cyclone dust collector using a prescribed adjustment means included in a specific cyclone dust collector constituting a suspension preheater included in the cement firing facility without having to perform large-scale modification of the cement firing facility.

Description

Cement clinker manufacturing method and cement burning equipment

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

[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 and then directs 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 clinker cooler for cooling exhaust gas generated in the rotary kiln. a kiln exhaust gas discharge conduit for discharging carbon dioxide-containing exhaust gas generated in the calciner after passing through an oxygen-enriched combustion-supporting gas supply device and the combustion-supporting gas supply device; a first recovery means for recovering slaked lime-containing raw materials from the carbon dioxide-containing exhaust gas; and a calciner exhaust gas supply conduit for merging a portion of the carbon dioxide-containing exhaust gas with the combustion-supporting gas downstream of the first recovery means in the calciner exhaust gas supply conduit.

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

[0007] The cement calcination equipment disclosed in Patent Document 1 uses 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 attempting to inexpensively remove carbon dioxide from the exhaust gas by utilizing the thermal energy of the exhaust gas generated in the cement manufacturing equipment. However, because the concentration of carbon dioxide contained in the exhaust gas is low, the equipment for recovering carbon dioxide, i.e., the absorption tower and regeneration tower, must be large, and in this respect there is room for improvement.

[0008] The cement clinker production system disclosed in Patent Document 3 can be an effective system for new construction. However, applying it to an existing cement calcination facility, for example, would require large-scale modifications to the cement calcination facility, such as modifications to the exhaust pipes for discharging the kiln exhaust gas and the calciner exhaust gas, the raw material supply pipes, and other equipment, as well as modifications to the calciner and other equipment.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a method for producing cement clinker and cement firing equipment that adjusts the amount of carbon dioxide contained in combustion exhaust gas generated in cement firing equipment without requiring large-scale modifications to the cement firing equipment.

[0010] In order to solve the above problems, the present invention provides the following method for producing cement clinker: 1. A method for producing cement clinker using cement calcination equipment including a drying and pulverizing device for drying and pulverizing 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, and a cement clinker cooler for cooling the cement clinker, wherein the suspension preheater has a calciner for calcining the powdered raw materials, and two different air ducts: a C-system air duct having three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and through which calciner combustion exhaust gas discharged from the calciner passes, and a K-system air duct having three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and through which kiln combustion exhaust gas discharged from the rotary kiln passes. a raw material conduit K-I connecting the cyclone dust collector of the K system air duct and a gas flow path for supplying the calciner combustion exhaust gas to a cyclone dust collector of the C system air duct that is at the same stage as the cyclone dust collector of the K system air duct; a raw material conduit C-I connecting the cyclone dust collector of the C system air duct and a gas flow path for supplying the kiln combustion exhaust gas to a cyclone dust collector of the K system air duct that is at one stage below the cyclone dust collector of the C system air duct; a raw material conduit K-II connecting the cyclone dust collector at the lowest stage of the K system air duct and the calciner; a raw material conduit C-II connecting the cyclone dust collector at the lowest stage of the C system air duct and the rotary kiln; and a powdered raw material feeder for supplying the powdered raw material to the cyclone dust collector at the highest stage of at least one of the two air ducts, at least one of the cyclone dust collectors at the lowest stage in the two air ducts and at least one of the cyclone dust collectors one stage above the lowest stage have means for adjusting the dust collection efficiency of the powder raw material, and the adjustment means adjusts the dust collection efficiency of the cyclone dust collector.

[0011] The present invention provides the following methods for producing cement clinker as preferred embodiments. 2. A method for producing cement clinker as set forth in 1 above, wherein the dust collection efficiency of the lowest-stage cyclone dust collector is reduced by the adjustment means. 3. A method for producing cement clinker as set forth in 1 or 2 above, wherein the dust collection efficiency of the cyclone dust collector one stage above the lowest stage is increased by the adjustment means. 4. A method for producing cement clinker as set forth in any one of 1 to 3 above, wherein the temperature of the kiln combustion exhaust gas after passing through the cyclone dust collector one stage above the lowest stage in the K-system air duct is 700°C or less. 5. A method for producing cement clinker as set forth in any one of 1 to 4 above, wherein carbon dioxide is recovered from the calciner combustion exhaust gas using carbon dioxide recovery equipment. 6. A method for producing cement clinker as set forth in any one of 1 to 5 above, wherein at least the kiln combustion exhaust gas is used to dry the cement raw materials. 7. 7. The method for producing cement clinker according to any one of 1 to 6, wherein the drying and crushing device has a drying device or a drying and crushing device, and at least the kiln combustion exhaust gas is supplied to the drying device or the drying and crushing device.

[0012] The present invention also provides the following cement calcination equipment: 8. Cement calcination equipment comprising: a drying and pulverizing device for drying and pulverizing cement raw materials to produce powdered raw materials; a suspension preheater for preheating and calcining the powdered raw materials; a rotary kiln for calcining the preheated and calcined powdered raw materials to produce cement clinker; and a cement clinker cooler for cooling the cement clinker, wherein the suspension preheater has a calciner for calcining the powdered raw materials, and two different air ducts: a C-system air duct having three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and through which calciner combustion exhaust gas discharged from the calciner passes; and a K-system air duct having three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and through which kiln combustion exhaust gas discharged from the rotary kiln passes. a raw material conduit K-I connecting the cyclone dust collector of the K system air duct and a gas flow path for supplying the calciner combustion exhaust gas to a cyclone dust collector of the C system air duct that is at the same stage as the cyclone dust collector of the K system air duct; a raw material conduit C-I connecting the cyclone dust collector of the C system air duct and a gas flow path for supplying the kiln combustion exhaust gas to a cyclone dust collector of the K system air duct that is at one stage below the cyclone dust collector of the C system air duct; a raw material conduit K-II connecting the cyclone dust collector at the lowest stage of the K system air duct and the calciner; a raw material conduit C-II connecting the cyclone dust collector at the lowest stage of the C system air duct and the rotary kiln; and a powdered raw material feeder for supplying the powdered raw material to the cyclone dust collector at the highest stage of at least one of the two air ducts, 9. A cement calcination facility, wherein at least one of the cyclone dust collectors in the lowest stage of the two air ducts and at least one of the cyclone dust collectors one stage above the lowest stage have means for adjusting the dust collection efficiency of the powder raw materials. 9. The cement calcination facility according to claim 8, further comprising a carbon dioxide recovery system for recovering carbon dioxide from the calciner combustion exhaust gas.10. The cement firing facility according to claim 8 or 9, wherein the drying and crushing device has a drying device or a drying and crushing device, and has an exhaust gas supply pipe that supplies at least the kiln combustion exhaust gas to the drying device or the drying and crushing device.

[0013] According to the present invention, it is possible to provide a cement clinker manufacturing method and cement calcination equipment that adjust the amount of carbon dioxide contained in combustion exhaust gas generated in cement calcination equipment without large-scale modifications to the cement calcination equipment.

[0014] FIG. 1 is a schematic diagram showing a preferred embodiment of cement firing equipment used in the manufacturing method of this embodiment.

[0015] 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.

[0016] [Method for manufacturing cement clinker] A method for manufacturing cement clinker according to this embodiment is a method for manufacturing cement clinker using cement calcination equipment including: a drying and pulverizing device for drying and pulverizing cement raw materials to form 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 form cement clinker; and a cement clinker cooler for cooling the cement clinker, wherein the suspension preheater has a calciner for calcining the powdered raw materials, and comprises two different air ducts: a C-system air duct having three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and through which calciner combustion exhaust gas discharged from the calciner passes; and a K-system air duct having three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and through which kiln combustion exhaust gas discharged from the rotary kiln passes. a raw material conduit K-I connecting the cyclone dust collector of the K system air duct and a gas flow path for supplying the calciner combustion exhaust gas to a cyclone dust collector of the C system air duct that is at the same stage as the cyclone dust collector of the K system air duct; a raw material conduit C-I connecting the cyclone dust collector of the C system air duct and a gas flow path for supplying the kiln combustion exhaust gas to a cyclone dust collector of the K system air duct that is at one stage below the cyclone dust collector of the C system air duct; a raw material conduit K-II connecting the cyclone dust collector at the lowest stage of the K system air duct and the calciner; a raw material conduit C-II connecting the cyclone dust collector at the lowest stage of the C system air duct and the rotary kiln; and a powdered raw material feeder for supplying the powdered raw material to the cyclone dust collector at the highest stage of at least one of the two air ducts, At least one of the cyclone dust collectors at the lowest stage in the two air passages and at least one of the cyclone dust collectors one stage above the lowest stage have means for adjusting the dust collection efficiency of the powder raw material, and the dust collection efficiency of the cyclone dust collector is adjusted by the adjustment means.

[0017] As described above, the cement firing equipment described in Patent Document 1 introduces flue gas with a low concentration of carbon dioxide discharged from the preheater into a carbon dioxide recovery equipment having a regeneration tower and an absorption tower, which results in an increase in the size of the carbon dioxide recovery equipment.

[0018] Furthermore, in order to put the cement clinker production system described in Patent Document 3 into practice, it is necessary to carry out large-scale modifications to the cement burning equipment.

[0019] Under these circumstances, the present inventors focused on the dust collection efficiency of the multiple cyclone dust collectors included in a suspension preheater. The dust collection efficiency is generally set high to more efficiently produce cement clinker, and is not set to adjust the concentration of carbon dioxide in the flue gas. For this reason, Patent Documents 1 to 3 above make no mention of adjusting the dust collection efficiency of a cyclone dust collector or of the ability to adjust the amount (concentration) of carbon dioxide in the flue gas through such adjustment. Furthermore, they make no mention of the ability to improve the amount of carbon dioxide recovered from the flue gas by adjusting the dust collection efficiency. The present inventors deliberately adjusted the dust collection efficiency in order to adjust the amount (concentration) of carbon dioxide in the flue gas. They found that adjusting the dust collection efficiency of specific cyclone dust collectors included in a suspension preheater, i.e., the lowest cyclone dust collector or the cyclone dust collector one level above the lowest, was effective. As a result, it has become possible to adjust the amount of carbon dioxide contained in the combustion exhaust gas generated in cement calcination equipment without large-scale modifications to the equipment.

[0020] 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 cement calcination equipment used in the method for producing cement clinker of this embodiment. Fig. 1 shows that the cement calcination equipment includes a suspension preheater that preheats and calcines powdered raw materials, a rotary kiln that calcines the powdered raw materials preheated and calcined in the suspension preheater to produce cement clinker, and a clinker cooler that cools the cement clinker.

[0021] (Suspension Preheater) The suspension preheater used in the manufacturing method of this embodiment has three or more 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 three or more stages of cyclone dust collectors. This has two air passages (a C-system flow path and a K-system flow path) through which different exhaust gases pass independently, as shown in FIG. 1. Here, calciner combustion exhaust gas, which is exhaust gas emitted by burning fuel in a calciner, passes through the C-system flow path, and kiln combustion exhaust gas, which is exhaust gas emitted by burning fuel in a rotary kiln, passes through the K-system flow path.

[0022] In addition, in FIG. 1 , calciner combustion exhaust gas and kiln combustion exhaust gas, which are different from each other, pass independently through the C-system air duct and the K-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).

[0023] As described above, the suspension preheater has two air ducts through which different exhaust gases pass independently, a raw material conduit, a powder raw material feeder, a means for adjusting the dust collection efficiency of a predetermined powder raw material, and a calciner. The provision of the calciner allows for more efficient preheating and calcination of the powder raw material.

[0024] The suspension preheater may have three or more stages of cyclone dust collectors, and may have, for example, four or more stages of cyclone dust collectors as shown in Fig. 1. From the viewpoint of more efficiently recovering heat from the exhaust gas, four or more stages are preferable.

[0025] In FIG. 1, raw material conduits include raw material conduit K-I (K2b to K4b in FIG. 1) which connects a cyclone dust collector in a K-line air duct to a gas flow path for supplying calciner combustion exhaust gas to a cyclone dust collector in a C-line air duct at the same stage as the cyclone dust collector in the K-line air duct, and raw material conduit K-II (K1b in FIG. 1) which connects a cyclone dust collector at the lowest stage of the K-line air duct to the calciner; The diagram shows that the C-system raw material conduits of the C-system air duct include raw material conduits C-I (C2b to C4b in FIG. 1 ) that connect the cyclone dust collector in the air duct and a gas flow path that supplies kiln combustion exhaust gas to a cyclone dust collector in the K-system air duct that is one level below the cyclone dust collector in the C-system air duct, and raw material conduits C-II (C1b in FIG. 1 ) that connect the cyclone dust collector in the lowest level of the C-system air duct and the rotary kiln. Here, if the cyclone dust collector in the K-system air duct is designated K3, the cyclone dust collector in the C-system air duct that is in the same level as cyclone dust collector K3 in the K-system air duct is designated C3, and the raw material conduit connected to gas flow path C2a that supplies calciner combustion exhaust gas to this cyclone dust collector C3 is designated K3b. For example, if the cyclone dust collector in the C-system air duct is designated C3, the cyclone dust collector in the K-system air duct, which is one level below the cyclone dust collector C3 in the C-system air duct, is designated K2, and the raw material conduit connected to the gas flow path K1a that supplies kiln combustion exhaust gas to this cyclone dust collector K2 is designated C3b.

[0026] The cement raw material that has passed through the drying and grinding device is supplied from a powder raw material feeder (described later) to a suspension preheater, more specifically, from the powder raw material feeder to the cyclone dust collector at the top of the suspension preheater. In Fig. 1, the powder raw material is supplied from the K-system powder raw material feeder to the cyclone dust collector K4 at the top of the K-system air duct, and from the C-system powder raw material feeder to the cyclone dust collector C4 at the top of the C-system air duct. The powdered raw material supplied from the K-system powdered raw material feeder 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 of the C system is supplied to the cyclone dust collector C4, and together with the powdered raw material supplied from the powdered raw material supply device of the K system, it passes through the raw material conduit C4b and the raw material conduit C1b, where it is preheated and calcined and supplied to the rotary kiln.

[0027] In this way, the powdered raw material supplied to the suspension preheater moves alternately from the upper to the lower cyclone collectors of the C-type and K-type air passages, which are different from each other, 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 passage, i.e., from the bottom cyclone collector to the top cyclone collector, thereby enabling efficient preheating and calcination.

[0028] The powdered raw material feeder is a device that supplies the powdered raw material obtained in the drying and grinding device to the uppermost cyclone dust collector of at least one of the two air ducts, the C-system air duct and the K-system air duct. In Fig. 1, a powdered raw material feeder is provided for each of the two air ducts, the C-system air duct and the K-system air duct. That is, the powdered raw material feeders include a C-system powdered raw material feeder that supplies the powdered raw material to the uppermost cyclone dust collector of the C-system air duct and a K-system powdered raw material feeder that supplies the powdered raw material to the uppermost cyclone dust collector of the K-system air duct.

[0029] More specifically, the powdered raw materials from the powdered raw material feeder are supplied into a gas flow path connected to the cyclone dust collector that is the supply destination. Taking the powdered raw materials in the K system as an example, the powdered raw materials in the K system are supplied to a gas flow path K3a connected to the cyclone dust collector K4 that is the supply destination of the kiln combustion exhaust gas from the cyclone dust collector K3. Also, taking the powdered raw materials in the C system as an example, the powdered raw materials in the C system are supplied to a gas flow path C3a connected to the cyclone dust collector C4 that is the supply destination of the calciner combustion exhaust gas from the cyclone dust collector C3.

[0030] The powdered raw material feeder may be provided so as to supply the powdered raw material to the uppermost cyclone dust collector of at least one of the two air ducts, the C-line air duct and the K-line air duct. In the case of Figure 1, since the powdered raw material can pass through all of the cyclone dust collectors, it is sufficient to provide a powdered raw material feeder that supplies the powdered raw material to at least the uppermost cyclone dust collector K4 of the K-line air duct. Alternatively, as shown in Figure 1, two powdered raw material feeders may be provided, such as a C-line powdered raw material feeder and a K-line powdered raw material feeder, so as to supply the powdered raw material to the uppermost cyclone dust collectors C4 and K4 of the C-line air duct and the K-line air duct, which are both air ducts. In the manufacturing method of this embodiment, it is preferable to provide a powdered raw material feeder for each of the two air ducts, from the viewpoints of more stable powdered raw material supply and more efficient preheating and calcination.

[0031] In a suspension preheater, at least one of the cyclone dust collectors at the lowest stage of the two air ducts, the C-line air duct and the K-line air duct, and at least one of the cyclone dust collectors one stage above the lowest stage, is equipped with a means for adjusting the dust collection efficiency of the powder raw material provided in these cyclone dust collectors to adjust the dust collection efficiency. By effectively utilizing the adjustment means in these cyclone dust collectors to adjust the dust collection efficiency, it is possible to adjust the amount of carbon dioxide in the combustion exhaust gas. Here, the cyclone dust collector at the lowest stage of the C-line air duct corresponds to cyclone dust collector C1 in Figure 1, and the cyclone dust collector at the lowest stage of the C-line air duct corresponds to cyclone dust collector K1. The cyclone dust collector one level above the bottom in the C-system air duct corresponds to the cyclone dust collector C2 in FIG. 1, and the cyclone dust collector one level above the bottom in the K-system air duct corresponds to the cyclone dust collector K2 in FIG. 1.

[0032] The lowest cyclone dust collector whose dust collection efficiency is adjusted using an adjustment means may be at least one of the cyclone dust collectors arranged at the lowest stage of the C system air duct and the K system air duct. Considering the ease of adjusting the amount of carbon dioxide contained in the combustion exhaust gas, it is preferable to adjust the dust collection efficiency using the adjustment means of the lowest cyclone dust collector in the C system air duct, cyclone dust collector C1 in Figure 1, and it is more preferable to adjust the dust collection efficiency using the adjustment means of multiple, or even all, of the lowest cyclone dust collectors (this applies to both cyclone dust collectors C1 and K1 in Figure 1).

[0033] The cyclone dust collector one level above the bottommost level, whose dust collection efficiency is adjusted using an adjustment means, may be at least one cyclone dust collector arranged one level above that cyclone dust collector, and considering the ease of adjusting the amount of carbon dioxide in the combustion exhaust gas, it is preferable to adjust the dust collection efficiency using the adjustment means of the cyclone dust collector in the K system air duct, cyclone dust collector K2 in Figure 1, and it is more preferable to adjust the dust collection efficiency using the adjustment means of the cyclone dust collector one level above the bottommost level in each of the C system air duct and the K system air duct (this applies to both cyclone dust collectors C2 and K2 in Figure 1).

[0034] The above has described a case where the dust collection efficiency is adjusted using the adjustment means in one of the cyclone dust collectors in either the lowest cyclone dust collector in the C system air duct and the K system air duct, or the cyclone dust collector one stage above the lowest cyclone dust collector. However, as already mentioned, it is preferable to adjust the dust collection efficiency using the adjustment means in both of the cyclone dust collectors in the C system air duct and the K system air duct, or in other words, in both cyclone dust collectors.

[0035] It is more preferable to adjust the dust collection efficiencies of the four cyclone dust collectors at the lowest and one level above the lowest in the C-system air duct and the K-system air duct. Furthermore, the dust collection efficiencies of these four cyclone dust collectors only need to achieve a predetermined amount of carbon dioxide in the combustion exhaust gas. Adjusting the dust collection efficiency does not necessarily mean that the dust collection efficiency remains the same before and after the adjustment, nor does it matter if the dust collection efficiency remains unchanged. In other words, the dust collection efficiencies of one to four of these four cyclone dust collectors can be adjusted to achieve a predetermined amount of carbon dioxide in the combustion exhaust gas.

[0036] When adjusting the dust collection efficiency using the adjustment means of both of the cyclone dust collectors (cyclone dust collectors C1 and K1) at the lowest stage of the two air ducts, the C system air duct and the K system air duct, and both of the cyclone dust collectors (cyclone dust collectors C2 and K2) at the stage one level above the lowest stage, how the amount of carbon dioxide in the combustion exhaust gas can be adjusted will be described in more detail below, taking a preferred embodiment as an example.

[0037] (Regarding the powdered raw material in the cyclone dust collector C1: decarbonation reaction) When calcium carbonate contained in the powdered raw material is heated in the calciner at a high temperature of preferably 800 to 900°C, the following decarbonation reaction proceeds, and calcium carbonate is converted into calcium oxide: CaCO ３ →CaO+CO ２The powdered raw material decarbonated in the calciner is entrained in the calciner combustion exhaust gas and supplied to the cyclone dust collector C1, which is the lowest cyclone dust collector in the air duct C. Here, the decarbonation rate of the powdered raw material is about 90%, and the decarbonation rate is a rate expressed by the following formula.

[0038] Decarboxylation rate (%) = (Ca ０ -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 : Amount of calcium carbonate (tons / h) contained in the powder raw material in the cyclone dust collector C1. Here, the powder raw material fed to the suspension preheater corresponds to the powder raw material fed from the C-type powder raw material feeder and the K-type powder raw material feeder in FIG.

[0039] (Regarding the powdered raw material in the cyclone dust collector K2: Carbonation reaction) The powdered raw material containing calcium oxide that has been decarbonated in the cyclone dust collector C1, which is the cyclone dust collector at the lowest stage of the air duct, is supplied to an atmosphere of combustion exhaust gas that is at a lower temperature than the cyclone dust collector C1, preferably to an atmosphere of combustion exhaust gas in the K-system air duct. As a result, the carbon dioxide contained in the combustion exhaust gas reacts with the calcium oxide contained in the powdered raw material, and the following carbonation reaction proceeds to produce calcium carbonate: CaO + CO ２ →CaCO ３

[0040] (Dust Collection Efficiency in Cyclone Dust Collectors) Powdered raw materials entrained in the combustion exhaust gases of the calciner combustion exhaust gas and the kiln combustion exhaust gas and supplied to the cyclone dust collector are collected by inertial force and discharged from the raw material conduit (hereinafter also referred to as "collected raw materials"). On the other hand, powdered raw materials that are not collected (hereinafter also referred to as "scattered raw materials") are entrained in the combustion exhaust gas and discharged from the gas flow path, and are supplied to a higher-stage cyclone dust collector. Here, the dust collection efficiency in a cyclone dust collector is calculated by the following formula: Dust Collection Efficiency (%) = Collected Raw Materials / (Collected Raw Materials + Scratched Raw Materials) × 100

[0041] The dust collection efficiency can be adjusted by the dust collection efficiency adjustment means of the cyclone dust collector, and by adjusting the dust collection efficiency, the amounts of the collected raw material and the scattered raw material can be increased or decreased. Furthermore, as will be described later, by adjusting the dust collection efficiency, the decarbonation and carbonation can be adjusted, and therefore the amount of carbon dioxide contained in the combustion exhaust gas can be adjusted.

[0042] (Regarding the powdered raw material in the cyclone dust collector C1: behavior of the powdered raw material) The powdered raw material containing calcium oxide is supplied from the calciner to the cyclone dust collector C1 at the bottom of the air passage via the gas flow path C0a. The powdered raw material is separated into a collected raw material and an airborne raw material. The collected raw material is supplied to the rotary kiln via the raw material conduit C1b, where it is completely decarbonated and burned to form clinker.

[0043] Meanwhile, the scattered raw material from cyclone dust collector C1, which is the lowest cyclone dust collector in the air duct, is entrained with the calciner combustion exhaust gas and passes through gas flow path C1a, where it meets with the collected raw material in cyclone dust collector K2 in raw material conduit K2b and is supplied to cyclone dust collector C2, which is one stage above the bottom of air duct C. Considering the need to adjust the amount of carbon dioxide contained in the combustion exhaust gas and to increase the amount of carbon dioxide contained in the calciner combustion exhaust gas in air duct C, it is preferable to adjust and reduce the collection efficiency of cyclone dust collector C1 so that the scattered raw material containing a larger amount of calcium oxide is transferred to cyclone dust collector C2.

[0044] The dust collection efficiency of the lowest cyclone dust collector (preferably cyclone dust collector C1) is preferably 50% or more, more preferably 55% or more, with an upper limit of preferably 80% or less, more preferably 70% or less, and even more preferably 65% ​​or less. By setting the dust collection efficiency of cyclone dust collector C1, which serves as the lowest cyclone dust collector, to 50% or more, the collected raw material can be efficiently supplied to the rotary kiln, allowing for efficient production of cement clinker. On the other hand, by setting the dust collection efficiency to 80% or less, the amount of scattered raw material containing calcium oxide can be increased, and carbon dioxide contained in the kiln combustion exhaust gas can be efficiently used for carbonation.

[0045] (Regarding the powdered raw material in the cyclone dust collector C2: behavior of the powdered raw material) The powdered raw material supplied to the cyclone dust collector C2, which is one level above the bottom level in the air duct, is separated into collected raw material and scattered raw material. The collected raw material is supplied to the cyclone dust collector K1, which is the bottom level in the K-system air duct, via the raw material conduit C2b and entrained in the kiln combustion exhaust gas passing through the gas flow path K0a.

[0046] Meanwhile, the raw material scattered from cyclone dust collector C2, the cyclone dust collector one level above the bottom of the air duct, is entrained with the calciner combustion exhaust gas via gas flow path C2a, merges with the collected raw material of cyclone dust collector K3 in raw material conduit K3b, and is then supplied to cyclone dust collector C3, the second level above the bottom of the C air duct. Considering the need to adjust the amount of carbon dioxide contained in the combustion exhaust gas and to increase the amount of carbon dioxide contained in the calciner combustion exhaust gas in the C air duct, it is preferable to adjust and increase the collection efficiency of cyclone dust collector C2. This adjustment allows more collected raw material containing calcium oxide to be supplied to cyclone dust collector K1, the lowest level in the K air duct, thereby more efficiently utilizing the carbon dioxide contained in the kiln combustion exhaust gas for the carbonation of calcium oxide. Furthermore, the raw material scattered to cyclone dust collector C3, the next level above, can be reduced, thereby suppressing carbonation in cyclone dust collector C3.

[0047] The dust collection efficiency of the cyclone dust collector one level above the bottom (preferably cyclone dust collector C2) is preferably 85% or higher, more preferably 90% or higher. By setting the dust collection efficiency of the cyclone dust collector one level above the bottom to 85% or higher, a larger amount of raw material containing calcium oxide can be supplied to the lowest cyclone dust collector K1 in the K-system air duct, and carbon dioxide contained in the kiln combustion exhaust gas can be used more efficiently to carbonate calcium oxide.

[0048] (Regarding the powdered raw material in the cyclone dust collector K1: behavior of the powdered raw material) By adjusting the cyclone dust collectors C1 and C2, the powdered raw material containing calcium oxide supplied to the cyclone dust collector K1, which is the cyclone dust collector at the bottom of the air passage, is separated into a collected raw material and an airborne raw material. The collected raw material is supplied to a calciner via a raw material conduit K1b.

[0049] Meanwhile, the scattered raw material from the cyclone dust collector K1 at the bottom of the air duct is entrained by the kiln combustion exhaust gas and passes through the gas flow path K1a, where it meets with the collected raw material from the cyclone dust collector C3 in the raw material conduit C3b and is then supplied to the cyclone dust collector K2 one level above the bottom of the K air duct. In this embodiment, it is preferable to adjust and reduce the dust collection efficiency of the cyclone dust collector K1. By adjusting the efficiency in this way, a powdered raw material containing a larger amount of calcium oxide can be supplied as scattered raw material to the cyclone dust collector K2 one level above, thereby accelerating the carbonation reaction and enabling adjustments to increase the amount of carbon dioxide contained in the calciner combustion exhaust gas in the C air duct.

[0050] The dust collection efficiency of the lowest cyclone dust collector (preferably cyclone dust collector K1) is preferably 50% or more, more preferably 55% or more, with an upper limit of preferably 80% or less, more preferably 70% or less, and even more preferably 65% ​​or less. By setting the dust collection efficiency of cyclone dust collector K1, which serves as the lowest cyclone dust collector, to 50% or more, the collected raw material can be efficiently supplied to the calciner, thereby promoting decarbonation of the powdered raw material in the calciner. On the other hand, by setting the dust collection efficiency to 80% or less, the amount of scattered raw material containing calcium oxide can be increased, and a larger amount of powdered raw material containing calcium oxide can be supplied to cyclone dust collector K2, which serves as the next cyclone dust collector above the lowest cyclone dust collector, allowing the carbon dioxide contained in the kiln combustion exhaust gas to be efficiently used for carbonation.

[0051] (Regarding the Powdered Raw Material in the Cyclone Dust Collector K2: Behavior of the Powdered Raw Material) By adjusting the cyclone dust collectors at the bottom of the air duct (cyclone dust collectors C1 and K1) and the cyclone dust collector C2 one level above the bottom one, a powdered raw material containing a larger amount of calcium oxide is supplied to the cyclone dust collector K2 one level above the other bottom one, as described above. By supplying a powdered raw material containing a larger amount of calcium oxide from the bottom to the cyclone dust collector K2 one level above the other cyclone dust collector in the K-system air duct, the calcium oxide contained in the powdered raw material is carbonated by the carbon dioxide contained in the kiln combustion exhaust gas, producing calcium carbonate. This allows the amount of carbon dioxide contained in the kiln combustion exhaust gas to be reduced, and the more calcium oxide contained in the powdered raw material is increased, the more the amount of carbon dioxide can be reduced.

[0052] The temperature of the kiln combustion exhaust gas passing through the cyclone dust collector K2 one stage above the bottom stage of the air duct (i.e., the heating temperature of the powdered raw material in the cyclone dust collector K2) is preferably 550°C or higher, more preferably 600°C or higher, and even more preferably 650°C or higher, with the upper limit preferably being 700°C or lower. If the temperature of the kiln combustion exhaust gas passing through the cyclone dust collector K2 is 550°C or higher, the preheating of the powdered raw material can be promoted, and if it is 700°C or lower, the carbonation of calcium oxide can be promoted, making it possible to reduce the amount of carbon dioxide in the kiln combustion exhaust gas.

[0053] To reduce the temperature of the kiln flue gas passing through the cyclone dust collector K2, which is located one level above the lowest level in the air passage, water or a wet waste material may be supplied to the flue gas passing through at least one of the gas passages K0a and K1a, preferably on the rotary kiln side of the cyclone dust collector K2, more preferably to the flue gas passing through the gas passage K0a. Supplying the wet waste material to the gas passage K0a is particularly preferred. Supplying the wet waste material to the gas passage K0a not only adjusts the temperature of the kiln flue gas passing through the cyclone dust collector K2, but also allows the wet waste material to be introduced into the rotary kiln, thereby preventing clogging of the cyclone dust collector. Typical examples of wet waste material include organic sludge such as sewage sludge, and various wastewaters, such as waste acid and waste alkali.

[0054] In order to raise the temperature of the kiln combustion exhaust gas passing through the cyclone dust collector K2, which is one stage above the lowest stage in the air duct, combustible waste may be supplied to the combustion exhaust gas passing through at least one of the gas passages K0a and K1a, preferably on the rotary kiln side of the cyclone dust collector K2, more preferably to the combustion exhaust gas passing through the gas passage K0a. Typical combustible wastes include oil-containing sludge such as waste clay, waste oil, and waste plastics.

[0055] Powdered raw material containing calcium oxide supplied to cyclone dust collector K2, which is the cyclone dust collector one level above the bottom level, becomes powdered raw material containing calcium carbonate through a carbonation reaction of calcium oxide and is separated into collected raw material and scattered raw material. The collected raw material passes through raw material conduit K2b, passes through gas flow path C1a, or is entrained in the furnace combustion exhaust gas, and is supplied to cyclone dust collector C2, which is one level above the bottom level of the C system air duct.

[0056] Meanwhile, the raw material scattered from the cyclone dust collector K2, which is the cyclone dust collector one level above the bottom of the air duct, into the gas flow path K2a joins with the collected raw material from the cyclone dust collector C4, which is supplied to the gas flow path K2a via the raw material conduit C4b, and is then supplied to the cyclone dust collector K3, which is the second level above the bottom of the K-line air duct. In the manufacturing method of this embodiment, it is preferable to adjust and increase the collection efficiency of the cyclone dust collector K2. By adjusting in this way, a powdered raw material containing calcium carbonate can be supplied as the collected raw material to the calciner via the cyclone dust collector C2, which is one level above the bottom of the air duct, making it possible to adjust the amount of carbon dioxide contained in the calciner combustion exhaust gas to be increased.

[0057] The dust collection efficiency of the cyclone dust collector one level above the bottom (preferably cyclone dust collector K2) is preferably 85% or more, more preferably 90% or more. By setting the dust collection efficiency of the cyclone dust collector K2 one level above the bottom to 85% or more, the exhaust gas can be supplied to the calciner via the cyclone dust collector C2 one level above the bottom of the C-system air duct, making it possible to adjust the amount of carbon dioxide contained in the calciner combustion exhaust gas to be large.

[0058] As described above, in order to set a high dust collection efficiency in the cyclone dust collector C2, most of the powder raw material fed to the cyclone dust collector C2 is fed to the cyclone dust collector K1 as collected raw material, and the collected raw material in the cyclone dust collector K1 is fed to the calciner. The raw material scattered in the cyclone dust collector K1 is fed to the calciner while circulating through the gas flow path K1a, raw material conduit C3b, cyclone dust collector K2, raw material conduit K2b, gas flow path C1a, cyclone dust collector C2, raw material conduit C2b, gas flow path K0a, and cyclone dust collector K1.

[0059] Furthermore, the powdered raw material supplied to the calciner contains a large amount of calcium carbonate, which is formed by carbonating calcium oxide. This, together with the calcium carbonate contained in the powdered raw material newly supplied to the suspension preheater, is decarbonated to produce calcium oxide and carbon dioxide. As a result, the carbon dioxide contained in the kiln flue gas is adsorbed by the carbonation of calcium oxide and can be released into the calciner flue gas in the calciner. In this way, the amount of carbon dioxide contained in the kiln flue gas can be increased while reducing the amount of carbon dioxide contained in the kiln flue gas, i.e., the carbon dioxide contained in the kiln flue gas can be transferred to the calciner flue gas.

[0060] (Adjusting the Amount of Carbon Dioxide in the Combustion Exhaust Gas by Adjusting Dust Collection Efficiency) According to the manufacturing method of this embodiment, at least one of the cyclone dust collectors at the lowest stage in the two air passages of the suspension preheater and at least one of the cyclone dust collectors one stage above the lowest stage have a means for adjusting the dust collection efficiency of the powder raw material, and this adjustment means adjusts the dust collection efficiency of the cyclone dust collector. As a result, as described above, it is possible to adjust the amount of carbon dioxide contained in the combustion exhaust gas. Furthermore, depending on the adjustment method, it is also possible, for example, to increase the amount of carbon dioxide in the calciner combustion exhaust gas. Below, regarding the method for adjusting the amount of carbon dioxide in the combustion exhaust gas by adjusting the dust collection efficiency, more specific adjustment of the amount of carbon dioxide contained in the combustion exhaust gas by increasing or decreasing the dust collection efficiency of the lowest cyclone dust collectors C1 and K1 and the cyclone dust collectors C2 and K2 one stage above the lowest cyclone dust collector will be described.

[0061] According to the manufacturing method of this embodiment, the dust collection efficiency of the cyclone dust collector C1, which is the lowest cyclone dust collector in the air passage, can be adjusted to reduce, thereby increasing the amount of scattered raw material in the cyclone dust collector C1. Therefore, the powdered raw material containing a larger amount of calcium oxide can be supplied from the lowest cyclone dust collector to the cyclone dust collector K2, which is one cyclone dust collector above the lowest cyclone dust collector C2, and then to the cyclone dust collector K1, thereby increasing the amount of carbon dioxide contained in the kiln combustion exhaust gas that is adsorbed as calcium oxide through carbonation.

[0062] Conversely, by adjusting the dust collection efficiency of the cyclone dust collector C1 to increase, it is possible to increase the amount of raw material collected in the cyclone dust collector C1. This allows the amount of powdered raw material containing calcium oxide to be reduced to the cyclone dust collector K2, thereby reducing the amount of carbon dioxide contained in the kiln combustion exhaust gas passing through the cyclone dust collector K2 that is adsorbed as calcium carbonate. When adjusting the amount of carbon dioxide contained in the combustion exhaust gas, the dust collection efficiency of the cyclone dust collector can be adjusted to any desired value depending on the target amount of carbon dioxide to be adsorbed. The same applies to the adjustment of the dust collection efficiency described below.

[0063] By adjusting the dust collection efficiency of the cyclone dust collector C2 to increase, the amount of raw material collected in the cyclone dust collector C2 can be increased. This allows a powdered raw material containing a larger amount of calcium oxide to be supplied to the cyclone dust collector K2 via the cyclone dust collector K1 as the raw material to be collected, thereby increasing the amount of carbon dioxide contained in the kiln combustion exhaust gas that is adsorbed as calcium oxide through carbonation. Conversely, by adjusting the dust collection efficiency of the cyclone dust collector C2 to decrease, the amount of raw material to be collected in the cyclone dust collector C2 can be reduced. This reduces the amount of raw material to be collected, which is a powdered raw material containing a larger amount of calcium oxide, and therefore reduces the amount of carbon dioxide contained in the kiln combustion exhaust gas that is adsorbed as calcium oxide that passes through the cyclone dust collector K2.

[0064] By adjusting the cyclone dust collector K1 to reduce its dust collection efficiency, the amount of scattered raw material in the cyclone dust collector K1 can be increased. This allows a powdered raw material containing a larger amount of calcium oxide to be supplied to the cyclone dust collector K2 as scattered raw material, thereby increasing the amount of carbon dioxide contained in the kiln combustion exhaust gas that is adsorbed as calcium oxide through carbonation. Conversely, by adjusting the cyclone dust collector K1 to increase its dust collection efficiency, the amount of scattered raw material in the cyclone dust collector K1 can be reduced. This reduces the amount of collected raw material, which is a powdered raw material containing a larger amount of calcium oxide, and therefore reduces the amount of carbon dioxide contained in the kiln combustion exhaust gas that is adsorbed as calcium oxide that passes through the cyclone dust collector K2.

[0065] By adjusting the dust collection efficiency of the cyclone dust collector K2 to increase, the amount of raw material collected in the cyclone dust collector K2 can be increased. As a result, a powdered raw material containing calcium carbonate obtained by carbonating calcium oxide can be supplied to the calciner via the cyclone dust collectors C2 and K1 as the raw material. In the calciner, calcium carbonate is decarbonated to calcium oxide and carbon dioxide, thereby increasing the amount of carbon dioxide released into the calciner combustion exhaust gas. Conversely, by adjusting the dust collection efficiency of the cyclone dust collector K2 to decrease, the amount of raw material collected in the cyclone dust collector K2 can be reduced. As a result, the amount of raw material collected, which is a powdered raw material containing calcium carbonate, is reduced, and the amount of carbon dioxide released into the calciner combustion exhaust gas can be reduced.

[0066] According to the manufacturing method of this embodiment, the dust collection efficiency of at least one of the cyclone dust collectors in the lowest stage and at least one of the cyclone dust collectors one stage above the lowest stage, each having a means for adjusting the dust collection efficiency of the powder raw material, is adjusted using the adjustment means. By adjusting these cyclone dust collectors, as described above, the amounts of collected raw material and scattered raw material in the cyclone dust collectors can be adjusted, and the amount of carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater, i.e., the kiln flue gas and the calciner flue gas, can be adjusted. Preferably, the amount of carbon dioxide contained in the kiln flue gas can be increased by transferring the carbon dioxide contained in the kiln flue gas to the calciner flue gas.

[0067] (Regarding the impact on the amount of cement clinker produced) The amount of powdered raw material circulating through the suspension preheater changes when the amount of collected raw material and scattered raw material is adjusted by adjusting the dust collection efficiency of the cyclone dust collector, but the powdered raw material supplied from the powdered raw material feeder passes alternately through and / or circulates through the two air ducts of the suspension preheater, is supplied to the calciner, and then introduced into the rotary kiln. Therefore, it is possible to adjust the amount of carbon dioxide contained in the combustion exhaust gas without changing the amount of cement clinker produced.

[0068] In this way, by adjusting the dust collection efficiency of at least one of the cyclone dust collectors at the lowest stage in the two air passages of the suspension preheater and at least one of the cyclone dust collectors one stage above the lowest stage, it is possible to adjust the amount of carbon dioxide contained in the combustion exhaust gas discharged from the suspension preheater without changing the production amount of cement clinker.

[0069] A specific example of a method for adjusting the dust collection efficiency of a cyclone dust collector is adjusting the flow velocity of the exhaust gas supplied to the cyclone dust collector within the gas flow path. One method for adjusting the exhaust gas flow velocity is to adjust the cross-sectional area of ​​the gas flow path; increasing the cross-sectional area can slow the gas flow velocity, while decreasing the cross-sectional area can speed up the gas flow velocity. The exhaust gas flow velocity and the dust collection efficiency are proportional to each other within a certain range, and the faster the exhaust gas flow velocity, the higher the dust collection efficiency. Examples of methods for adjusting the cross-sectional area of ​​the exhaust gas flow velocity include changing the thickness of the refractory material lining the gas flow path and replacing the gas flow path duct. These methods are merely examples, and there are no limitations on the method as long as the exhaust gas flow velocity can be adjusted, and other methods can also be used.

[0070] Another method for adjusting the dust collection efficiency of a cyclone dust collector is to adjust the insertion rate of the inner cylinder of the cyclone dust collector. In this case, within a certain range, the insertion rate of the inner cylinder and the dust collection efficiency are proportional to each other, so that increasing the insertion rate of the inner cylinder can increase the dust collection efficiency, and decreasing the insertion rate of the inner cylinder can decrease the dust collection efficiency. These adjustment methods may be used alone or in combination.

[0071] (Carbon Dioxide Recovery Equipment) In the manufacturing method of this embodiment, when recovering carbon dioxide from the flue gas that has passed through the cyclone dust collector, it is preferable to use a carbon dioxide recovery equipment, and it is more preferable to recover carbon dioxide from the calciner flue gas using a carbon dioxide recovery equipment. The calciner flue gas contains a large amount of carbon dioxide from non-energy sources generated by the decarbonation of calcium carbonate contained in the powder raw material, in addition to carbon dioxide from the energy source generated by the combustion of the fuel. In this case, the calciner flue gas contains more carbon dioxide than the kiln flue gas, resulting in a higher carbon dioxide concentration. Therefore, it is easier to separate and recover carbon dioxide from the calciner flue gas than from the kiln flue gas. Furthermore, as described above, adjusting the dust collection efficiency using the adjustment means of the cyclone dust collector increases the amount of carbon dioxide contained in the calciner flue gas, making carbon dioxide separation and recovery easier. In this way, recovering carbon dioxide from the calciner flue gas discharged from the suspension preheater using a carbon dioxide recovery equipment enables more carbon dioxide to be recovered more efficiently.

[0072] There are no particular limitations on the type of carbon dioxide recovery equipment, as long as it can recover carbon dioxide from 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.

[0073] (Drying of cement raw materials) As described above, the amount of carbon dioxide contained in the kiln flue gas can be reduced, and the kiln flue gas discharged from the suspension preheater can be used to dry the cement raw materials. This allows the thermal energy of the flue gas to be recovered more efficiently, thereby improving the thermal efficiency of the production method of this embodiment. In addition to the kiln flue gas, clinker cooler flue gas discharged from the clinker cooler can also be used as the flue gas used to dry the cement raw materials. In this way, the production method of this embodiment makes it possible to improve thermal efficiency while suppressing the amount of carbon dioxide released into the atmosphere.

[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 perform drying and pulverizing simultaneously.When a drying and pulverizing device that combines a drying device and a pulverizing device is used, the exhaust gas used to dry the cement raw materials can be supplied to the drying device, and when a drying and pulverizing device is used, the exhaust gas can be supplied to the drying and pulverizing device.

[0075] (Regarding Other Equipment) The configuration of the suspension preheater and the method for adjusting the suspension preheater have been described above for the manufacturing method of this embodiment. The cement firing equipment used in the manufacturing method of this embodiment includes, in addition to the suspension preheater, a drying and pulverizing device and a rotary kiln. Conventional devices can be used for these drying and pulverizing devices and rotary kiln.

[0076] [Cement Calcination Equipment] The cement calcination equipment of this embodiment is a cement calcination equipment including: 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; and a cement clinker cooler that cools the cement clinker, wherein the suspension preheater has a calciner that calcines the powdered raw materials, and two different air ducts: a C-system air duct that has three or more stages of cyclone dust collectors that collect the powdered raw materials and a gas flow path that sequentially connects the three or more stages of cyclone dust collectors, and through which calciner combustion exhaust gas discharged from the calciner passes; and a K-system air duct that has three or more stages of cyclone dust collectors that collect the powdered raw materials and a gas flow path that sequentially connects the three or more stages of cyclone dust collectors, and through which kiln combustion exhaust gas discharged from the rotary kiln passes. a raw material conduit K-I connecting the cyclone dust collector of the K system air duct and a gas flow path for supplying the calciner combustion exhaust gas to a cyclone dust collector of the C system air duct that is at the same stage as the cyclone dust collector of the K system air duct; a raw material conduit C-I connecting the cyclone dust collector of the C system air duct and a gas flow path for supplying the kiln combustion exhaust gas to a cyclone dust collector of the K system air duct that is at one stage below the cyclone dust collector of the C system air duct; a raw material conduit K-II connecting the cyclone dust collector at the lowest stage of the K system air duct and the calciner; a raw material conduit C-II connecting the cyclone dust collector at the lowest stage of the C system air duct and the rotary kiln; and a powdered raw material feeder for supplying the powdered raw material to the cyclone dust collector at the highest stage of at least one of the two air ducts, At least one of the cyclone dust collectors at the lowest stage of the two air passages and at least one of the cyclone dust collectors one stage above the lowest stage have means for adjusting the dust collection efficiency of the powder raw material.

[0077] In the cement firing equipment of this embodiment, the drying and crushing device, suspension preheater, and rotary kiln are as described in the cement clinker manufacturing method above. Furthermore, with regard to the suspension preheater, the cyclone dust collector, the two air ducts with gas flow paths, the raw material conduit, and the adjusting means of the cyclone dust collector are also as described in the cement clinker manufacturing method above. Therefore, the cement clinker manufacturing method of this embodiment can be easily performed by using the cement firing equipment of this embodiment.

[0078] 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.

[0079] Comparative Example 1 A cement firing facility having the configuration shown in the flow diagram of Fig. 1 was used. The dust collection efficiencies of cyclone dust collectors C1, K1, C2, and K2 were maintained at 90%, 90%, 80%, and 80%, respectively, which had been set during previous operation of the facility.

[0080] Example 1 A cement firing facility was operated in the same manner as in Comparative Example 1, except that the dust collection efficiencies of cyclone dust collectors C1, K1, C2, and K2 were changed to the efficiencies shown in Table 1. Here, the dust collection efficiency was adjusted by adjusting the cross-sectional area of ​​the gas flow path by increasing or decreasing the thickness of the refractory material lining the gas flow path duct in order to adjust the flow rate of the exhaust gas through the gas flow path, and also by adjusting the insertion rate of the inner cylinder of the cyclone dust collector.

[0081] Comparative Example 2 The cement burning facility was operated in the same manner as in Comparative Example 1, except that the exhaust gas (calciner combustion exhaust gas) from the C-system air duct was supplied to the carbon dioxide recovery facility.

[0082] (Example 2) In Comparative Example 2, the cement burning equipment was operated in the same manner as in Comparative Example 1, except that the dust collection efficiencies in cyclone dust collectors C1, K1, C2, and K2 were changed to the efficiencies shown in Table 1. Here, the dust collection efficiency was adjusted by adjusting the flow rate of the exhaust gas in the gas flow path and the insertion rate of the inner cylinder of the cyclone dust collector in combination.

[0083] Table 1 shows the ratio of the amount of carbon dioxide contained in each exhaust gas to the total amount of carbon dioxide contained in the exhaust gas discharged from the C-line air duct (calciner combustion exhaust gas) and the exhaust gas discharged from the K-line air duct in Examples 1 and 2 and Comparative Examples 1 and 2.

[0084]

[0085] In Comparative Example 1, the proportion of carbon dioxide released from the C-line air duct was 68%, and the proportion of carbon dioxide released from the K-line air duct was 32%. In Example 1, in which the dust collection efficiency of the lowest cyclone dust collectors C1 and K1 was reduced to 60% and the dust collection efficiency of the cyclone dust collectors C2 and K2, one level above the lowest, was increased to 90%, the proportion of carbon dioxide released from the C-line air duct was 81%, and the proportion of carbon dioxide released from the K-line air duct was 19%. Thus, by the extremely simple method of adjusting the dust collection efficiency of specific cyclone dust collectors, namely the lowest cyclone dust collector and the cyclone dust collector one level above the lowest, it was confirmed that the amount of carbon dioxide released from the two air ducts can be adjusted, and that in Example 1, carbon dioxide in the flue gas (kiln combustion flue gas) passing through the K-line air duct can be transferred to the flue gas (calciner combustion flue gas) passing through the C-line air duct.

[0086] Comparative Example 2 is an example in which the exhaust gas (calciner combustion exhaust gas) discharged from the C-line air duct in Comparative Example 1 was supplied to a carbon dioxide recovery system. This confirmed that 68% of the carbon dioxide could be recovered. Example 2 is an example in which the dust collection efficiency of the lowest cyclone dust collectors C1 and K1 in Comparative Example 2 was reduced to 60%, and the dust collection efficiency of the cyclone dust collectors C2 and K2, one level above the lowest, was increased to 90%. According to Example 2, the proportion of carbon dioxide discharged from the C-line air duct was 81%, and it was confirmed that 81% of the carbon dioxide could be recovered by supplying this to the carbon dioxide recovery system. Furthermore, the proportion of carbon dioxide discharged from the K-line air duct was 19%, confirming that the amount of carbon dioxide released into the atmosphere could be reduced while improving the amount of carbon dioxide recovered.

[0087] The production amounts of cement clinker in Comparative Examples 1 and 2 are roughly the same as the production amounts of cement clinker in Examples 1 and 2 in which the dust collection efficiency of the cyclone dust collector was adjusted. It was also confirmed that the production method and firing equipment of this embodiment can adjust the amount of carbon dioxide recovered while maintaining the production amount of cement clinker, and furthermore, can improve the amount of carbon dioxide recovered while suppressing the amount released into the atmosphere.

[0088] Furthermore, in Examples 1 and 2, although the carbon dioxide contained in the exhaust gas (kiln combustion exhaust gas) discharged from the K-system air duct was transferred to the exhaust gas passing through the C-system air duct, the overall flow rate of the exhaust gas was generally maintained at the same level as in Comparative Examples 1 and 2. Therefore, it was confirmed that the required amount of cement raw materials could be dried by supplying the exhaust gas (kiln combustion exhaust gas) discharged from the K-system air duct to the drying and crushing equipment as a heat source for drying the cement raw materials and adjusting the operating time.

[0089] From the above results, it was confirmed that the cement clinker manufacturing method and cement calcination equipment of this embodiment can adjust the amounts of carbon dioxide contained in the two combustion exhaust gases generated in the cement calcination equipment without large-scale modifications to the equipment. Furthermore, it was confirmed that by increasing the amount of carbon dioxide contained in the calciner combustion exhaust gas, it is possible to improve the amount of carbon dioxide recovered and suppress the amount emitted into the atmosphere.

Claims

1. A method for producing cement clinker using cement calcination equipment including a drying and crushing device for drying and crushing cement raw materials to produce powdered raw materials, a suspension preheater for preheating and calcining the powdered raw materials, a rotary kiln for calcining the preheated and calcined powdered raw materials to produce cement clinker, and a cement clinker cooler for cooling the cement clinker, wherein the suspension preheater has a calciner for calcining the powdered raw materials, and has three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and has two different air ducts: a C-system air duct through which calciner combustion exhaust gas discharged from the calciner passes, and a K-system air duct through which kiln combustion exhaust gas discharged from the rotary kiln passes, and has three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, a raw material conduit K-I connecting the cyclone dust collector of the K system air duct and a gas flow path for supplying the calciner combustion exhaust gas to the cyclone dust collector of the C system air duct at the same stage as the cyclone dust collector of the K system air duct; a raw material conduit C-I connecting the cyclone dust collector of the C system air duct and a gas flow path for supplying the kiln combustion exhaust gas to the cyclone dust collector of the K system air duct at one stage below the cyclone dust collector of the C system air duct; a raw material conduit K-II connecting the cyclone dust collector at the lowest stage of the K system air duct and the calciner; a raw material conduit C-II connecting the cyclone dust collector at the lowest stage of the C system air duct and the rotary kiln; and a powdered raw material feeder for supplying the powdered raw material to the cyclone dust collector at the highest stage of at least one of the two air ducts, at least one of the cyclone dust collectors at the lowest stage in the two air ducts and at least one of the cyclone dust collectors one stage above the lowest stage have a means for adjusting the dust collection efficiency of the powdered raw material, and the dust collection efficiency of the cyclone dust collector is adjusted by the adjustment means.

2. The method for producing cement clinker according to claim 1, wherein the dust collection efficiency of the lowest cyclone dust collector is reduced by the adjustment means.

3. A method for producing cement clinker as claimed in claim 1, wherein the dust collection efficiency of the cyclone dust collector one stage above the lowest stage is increased by the adjustment means.

4. A method for producing cement clinker as described in claim 1, wherein the temperature of the kiln combustion exhaust gas after passing through the cyclone dust collector one level above the bottom level in the K system air duct is 700°C or lower.

5. The method for producing cement clinker according to claim 1, wherein carbon dioxide is recovered from the calciner flue gas using a carbon dioxide recovery system.

6. The method for producing cement clinker according to claim 1, wherein at least the kiln combustion exhaust gas is used for drying the cement raw materials.

7. The method for producing cement clinker according to claim 1, wherein the drying and crushing device comprises a drying device or a drying and crushing device, and at least the kiln combustion exhaust gas is supplied to the drying device or the drying and crushing device.

8. A cement calcination facility comprising: 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 calcining the preheated and calcined powdered raw materials to produce cement clinker; and a cement clinker cooler for cooling the cement clinker, wherein the suspension preheater has a calciner for calcining the powdered raw materials, and has three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, and has two different air ducts: a C-system air duct through which calciner combustion exhaust gas discharged from the calciner passes; and a K-system air duct through which kiln combustion exhaust gas discharged from the rotary kiln passes, and has three or more stages of cyclone dust collectors for collecting the powdered raw materials and a gas flow path connecting the three or more stages of cyclone dust collectors in sequence, a raw material conduit K-I connecting the cyclone dust collector of the K system air duct and a gas flow path for supplying the calciner combustion exhaust gas to the cyclone dust collector of the C system air duct at the same stage as the cyclone dust collector of the K system air duct; a raw material conduit C-I connecting the cyclone dust collector of the C system air duct and a gas flow path for supplying the kiln combustion exhaust gas to the cyclone dust collector of the K system air duct at one stage below the cyclone dust collector of the C system air duct; a raw material conduit K-II connecting the cyclone dust collector at the lowest stage of the K system air duct and the calciner; a raw material conduit C-II connecting the cyclone dust collector at the lowest stage of the C system air duct and the rotary kiln; and a powdered raw material feeder for supplying the powdered raw material to the cyclone dust collector at the highest stage of at least one of the two air ducts, at least one of the cyclone dust collectors in the lowest stage of the two air ducts and at least one of the cyclone dust collectors one stage above the lowest stage have a means for adjusting the dust collection efficiency of the powdered raw material.

9. The cement calcination system of claim 8, further comprising a carbon dioxide capture system for capturing carbon dioxide from the calciner flue gas.

10. The cement burning facility according to claim 8, wherein the drying and crushing device has a drying device or a drying and crushing device, and has an exhaust gas supply pipe for supplying at least the kiln combustion exhaust gas to the drying device or the drying and crushing device.

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