Calcination system

Abstract

Provided is a calcination system that allows a decarboxylation reaction of a cement feedstock to proceed while suppressing burning of equipment in a furnace, and that can obtain a gas containing CO2 at a high concentration by using small-scale equipment.　This calcination system comprises: a combustion furnace to which a burner that blows fuel is attached; a feedstock introduction port for introducing the cement feedstock into the combustion furnace; a first inflow port for supplying a first gas containing O2 into the combustion furnace; a duct through which gas fed from the combustion furnace and the heat-treated cement feedstock pass; a second inflow port for supplying a second gas, which has a lower O2 concentration than the first gas, into the duct; and a first discharge port for discharging, to the outside of the duct, the gas and solids that have passed through the duct.

Description

Calcination System

[0001] The present invention relates to a calcination system, and in particular to a calcination system suitable for use in cement manufacturing facilities.

[0002] In recent years, reducing carbon dioxide (CO2) emissions has become an important issue in order to curb global warming. Exhaust gases generated during the cement manufacturing process contain a large amount of CO2. For this reason, technologies for efficiently capturing CO2 are being used in cement manufacturing facilities.

[0003] A widely known CO2 reduction technology that can be applied to exhaust gas from cement manufacturing facilities is the use of absorbents such as amines to absorb and separate the CO2 in the exhaust gas, thereby capturing it as high-concentration CO2. However, the amount of CO2 emitted from cement manufacturing facilities is large, and there are challenges such as the need to introduce large-scale equipment to capture the entire amount, and the large amount of energy required to capture the absorbed CO2.

[0004] If the concentration of CO2 contained in the exhaust gas can be increased, it becomes easier to separate and capture CO2. Furthermore, by reducing the amount of nitrogen and other substances contained in the exhaust gas, the volume of the generated exhaust gas can be relatively reduced, and the equipment required for separating and capturing CO2 can be made smaller.

[0005] One known method for increasing the CO2 concentration in exhaust gas is the technology disclosed in Patent Document 1 below.

[0006] Japanese Patent Application Laid-Open No. 2004-292298

[0007] However, the technology described in Patent Document 1 has a problem in that the equipment becomes large-scale.

[0008] The inventors focused on the fact that a large amount of CO2 is emitted from the calciner in cement production facilities. It is believed that CO2 can be efficiently captured by increasing the CO2 concentration in the gas emitted from the calciner. A specific method is to use a gas with an increased O2 concentration instead of air as the combustion gas supplied to the calciner. This method can increase the CO2 concentration in the combustion exhaust gas during cement production. Furthermore, compared to using air as the combustion gas, it is possible to reduce the scale of the equipment for separating and capturing CO2.

[0009] However, if gas with an increased O2 concentration is used as combustion gas, the combustion temperature will rise too high, exceeding the heat resistance temperature of the furnace walls and causing problems such as burnout of the furnace walls and increased adhesion of molten raw materials (coating). Also, if the CO2 concentration in the calciner becomes high, the decarbonation reaction of the cement raw materials will become more difficult to proceed, and the amount of CO2 generated from the raw materials in the calciner will decrease at the same temperature and residence time as conventional.

[0010] In view of the above problems, an object of the present invention is to provide a calcination system that enables the decarbonation reaction of cement raw materials to proceed while suppressing burnout of equipment inside the furnace, and that can obtain gas containing high concentrations of CO2 using small-scale equipment.

[0011] The calcination system according to the present invention is characterized by comprising: a combustion furnace equipped with a burner for injecting fuel; a raw material inlet through which cement raw materials are charged toward the combustion furnace; a first inlet through which a first gas containing O2 is supplied toward the combustion furnace; a duct connected to the combustion furnace and through which gas sent from the combustion furnace and the heat-treated cement raw materials flow; a second inlet through which a second gas having an O2 concentration lower than that of the first gas is supplied toward the duct; and a first outlet disposed on the top side of the duct and for discharging the gas and solids that have flowed through the duct to the outside of the duct.

[0012] According to the calcination system described above, gases (first gas, second gas) having different O2 concentrations are introduced into the system from different locations.

[0013] More specifically, by supplying the first gas, which has a relatively high O2 concentration, to the combustion furnace, fuel is burned in the combustion furnace in an atmosphere in which this first gas exists, creating a high-temperature environment. When the cement raw materials are charged into the high-temperature combustion furnace through a raw material charging port, the cement raw materials are heated and a decarbonation reaction begins in which the cement raw materials are decomposed into quicklime (CaO) and carbon dioxide (CO2).

[0014] The cement raw materials in which the decarbonation reaction has occurred (or is in progress) are sent to a duct together with the gas in the combustion furnace. Here, a second gas having a relatively lower O2 concentration than the first gas is supplied to the duct. The flow of this second gas causes the cement raw materials after the decarbonation reaction to flow through the duct and be discharged from the first outlet. At this time, CO2 generated by the decarbonation reaction is also discharged from the first outlet.

[0015] For example, by using a gas having a higher CO concentration than the first gas as the second gas, the CO concentration contained in the gas discharged from the first outlet (hereinafter referred to as "calcination exhaust gas") can be maintained at a high concentration. Conversely, by using a gas having a lower CO concentration than the second gas as the first gas, it is possible to prevent inhibition of the progress of the decarbonation reaction of the cement raw materials.

[0016] In this way, with the above configuration, the first gas and the second gas, which have different compositions, are supplied from different locations, so that a concentration gradient of substances such as O2 can be formed within the internal space formed by the combustion furnace and the duct. This allows calcination without increasing the O2 concentration in the entire internal space more than necessary, thereby preventing excessively high temperatures and preventing damage to the equipment.

[0017] The first gas may be blown into the combustion furnace through the first inlet so as to form a swirling flow in the furnace, thereby sufficiently mixing the first gas and the cement raw materials to facilitate the reaction and enhance the function of protecting the furnace wall.

[0018] The O concentration of the first gas is preferably 30% by volume or more, more preferably 40% by volume or more, and particularly preferably 50% by volume or more. The first gas may also be a mixed gas containing O and CO. In this case, the CO concentration of the first gas is preferably 70% by volume or less, more preferably 60% by volume or less, and particularly preferably 50% by volume or less.

[0019] When the first gas is a mixed gas containing O2 and CO2, the composition ratio of the first gas can be adjusted by adjusting the mixing ratio of the third gas whose main component is O2 and the fourth gas whose main component is CO2.

[0020] Specifically, the calcination system includes a first flow rate regulator capable of adjusting the mixing ratio of a third gas whose main component is O2 and a fourth gas whose main component is CO2, and a first pipe connecting the first flow rate regulator and the first inlet, and the gas that has passed through the connecting point between the first flow rate regulator and the first pipe may be led to the first inlet as the first gas after flowing through the first pipe.

[0021] The second gas may be a mixed gas containing O and CO. In this case, similar to the first gas, the composition ratio of the second gas can be adjusted by adjusting the mixing ratio of the third gas whose main component is O and the fourth gas whose main component is CO.

[0022] Specifically, the calcination system may include a second flow regulator capable of adjusting the mixing ratio of the third gas and the fourth gas independently of the first flow regulator, and a second pipe connecting the second flow regulator and the second inlet, and the gas that has passed through the connecting point between the second flow regulator and the second pipe may flow through the second pipe and then be introduced to the second inlet as the second gas.

[0023] According to the above configuration, the compositions of the first gas and the second gas can be appropriately adjusted, thereby making it possible to adjust the temperature of the combustion furnace and the concentration of CO contained in the calcination exhaust gas to desired values ​​by adjusting the compositions of the first gas and the second gas according to the type of cement raw material and fuel.

[0024] More specifically, the calcination system may include: a combustion-supporting gas supply device that supplies the third gas; a third pipe through which the third gas supplied from the combustion-supporting gas supply device flows; and a fourth pipe through which the fourth gas discharged through the first outlet and containing the calcination exhaust gas flows; and the first flow rate regulator and the second flow rate regulator may be configured to be able to adjust the mixing ratio of the third gas flowing through the third pipe and the fourth gas flowing through the fourth pipe, respectively.

[0025] According to the above configuration, by adjusting the mixing ratio of the calcination exhaust gas (fourth gas) having a high CO concentration and the gas (third gas) having a high O concentration supplied from the combustion supporting gas supply device, it is possible to generate the first gas to be blown into the combustion furnace through the first inlet and the second gas to be blown into the duct through the second inlet. In particular, since the calcination exhaust gas has a sufficiently high temperature, by using the gas derived from the calcination exhaust gas as the fourth gas, it is possible to maintain the temperature inside the duct at a temperature environment required for the decarbonation reaction.

[0026] The combustion-supporting gas supplied from the combustion-supporting gas supply device is preferably used as the third gas after being heated by heat exchange with the high-temperature gas supplied from the clinker cooler or the calcination exhaust gas.

[0027] In the above configuration, the calcination system may further include a cyclone connected to the first outlet and configured to separate the solids in the duct supplied from the first outlet from the calcination exhaust gas, and the calcination exhaust gas discharged from the cyclone may be introduced into the fourth pipe.

[0028] In another aspect, the calcination system may further include a third flow regulator connected to the second pipe at a position closer to the second inlet in terms of the flow direction than the connecting point between the second flow regulator and the second pipe, and capable of adjusting the mixing ratio between the gas that has passed through the second flow regulator and a fifth gas whose main component is HO, and the gas that has passed through the connecting point between the third flow regulator and the second pipe may be led to the second inlet as the second gas after flowing through the second pipe.

[0029] The duct may be a cylindrical body whose vertical length is longer than its horizontal length.

[0030] As described above, the decarbonation reaction of the cement raw materials, which has started to proceed, continues to proceed while being transported through the duct. Then, the cement raw materials after the decarbonation reaction are transported through the duct toward the first discharge port by the airflow of the second gas, which has a relatively lower O concentration than the first gas.

[0031] By configuring the duct as a cylindrical body whose vertical length is longer than its horizontal length, it is possible to prevent the installation area of ​​the equipment from increasing while promoting the decarbonation reaction of the cement raw material. Various shapes such as an I-shape or an inverted U-shape can be used for this cylindrical body.

[0032] The calcination system includes a connecting pipe connecting the combustion furnace and the duct, and a second outlet disposed on the bottom side of the combustion furnace for discharging solids and gases in the combustion furnace into the connecting pipe, and the second inlet may be disposed at a position vertically below the connection point between the duct and the connecting pipe.

[0033] According to the above configuration, the combustion furnace and the duct are connected via a connecting pipe, and therefore the combustion furnace and the duct are not directly connected. As a result, the location where the second gas, which has a relatively low O concentration, is injected is distant from the location where the first gas, which has a relatively high O concentration, is injected. This increases the O concentration in the atmosphere in the region where the decarbonation reaction of the cement raw materials occurs, allowing for efficient decarbonation.

[0034] In particular, with the above configuration, the decarbonation reaction of the cement raw materials can be sufficiently promoted while the cement raw materials are being transported through the combustion furnace and the connecting pipe. Therefore, even if the second gas supplied into the duct is a gas with a relatively high CO concentration, it is unlikely to inhibit the decarbonation reaction of the cement raw materials. As a result, a gas with a high CO concentration can be obtained as the calciner exhaust gas discharged to the outside of the duct from the first outlet.

[0035] The raw material inlet and the burner may be disposed on the top side of the combustion furnace.

[0036] According to the above configuration, the cement raw materials are charged into the combustion furnace near the position of the burner flame, which allows the cement raw materials to be heated and decarbonated (endothermic reaction) efficiently, thereby lowering the flame temperature and preventing the furnace from burning out.

[0037] According to the calcination system of the present invention, even with a small-scale facility, it is possible to suppress burnout of the equipment inside the furnace, and to promote the decarbonation reaction of the cement raw material, thereby obtaining gas containing a high concentration of CO2.

[0038] FIG. 1 is a drawing schematically showing a part of a clinker production facility including a calcination system of a first embodiment. FIG. 2 is a plan view schematically showing an example of an arrangement of a first inlet. FIG. 3 is a block diagram schematically showing an example of a method for generating a first gas and a second gas. FIG. 4 is a block diagram schematically showing an example of the configuration of a clinker production facility including the calcination system of the first embodiment. FIG. 5 is a block diagram schematically showing another example of the configuration of a clinker production facility including the calcination system of the first embodiment. FIG. 6 is a drawing schematically showing the configuration of a calcination system of a second embodiment. FIG. 7 is a block diagram schematically showing an example of the configuration of a clinker production facility including the calcination system of the second embodiment.

[0039]

[0023] The calcination system according to the present invention will be described below with reference to the accompanying drawings. Note that the drawings are schematic illustrations, and the dimensional ratios of the drawings do not necessarily correspond to the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily correspond to each other.

[0040] In the following drawings, the flow of gas is schematically indicated by a two-dot chain line with an arrow, and the flow of solids is schematically indicated by a one-dot chain line with an arrow.

[0041] [First embodiment] A first embodiment of the calcination system according to the present invention will be described. Fig. 1 is a diagram schematically illustrating a portion of a cement clinker production facility 90 (hereinafter referred to as "clinker production facility 90") that includes a calcination system 1 according to this embodiment. In Fig. 1, the flow of gas is indicated by a two-dot chain line with an arrow, and the flow of solids is indicated by a one-dot chain line with an arrow.

[0042] 1 also shows an X-Y-Z coordinate system in which the vertical direction is the Z direction and the plane perpendicular to the Z direction is the X-Y plane. In the following description, this X-Y-Z coordinate system will be referenced as appropriate.

[0043] Calcination system 1 is a facility for promoting decarbonation of cement clinker raw material (cement raw material) preheated in a preheater. Fig. 1 shows a configuration in which preheated cement raw material M1 is introduced into calcination system 1 from a cyclone-type preheating device 31, which is part of the preheater, via piping 32.

[0044] 1 , the calcination system 1 includes a combustion furnace 3, a raw material inlet 13 through which cement raw material M1 is introduced toward the combustion furnace 3, a first inlet 11 through which a first gas G1 is supplied toward the combustion furnace 3, a duct 5 connected to the combustion furnace 3, a second inlet 12 through which a second gas G2 is supplied toward the duct 5, and a first outlet 9 through which gas and solids that have flowed through the duct 5 are discharged to the outside of the duct 5. In particular, in the calcination system 1 of this embodiment, a communication pipe 7 is provided between the combustion furnace 3 and the duct 5, and the combustion furnace 3 and the duct 5 are connected via the communication pipe 7.

[0045] In the calcination system 1 of this embodiment shown in Figure 1, the combustion furnace 3 is provided with a second outlet 14 that discharges solids and gases in the combustion furnace 3 into the connecting pipe 7. The burner 10, the first inlet 11, and the raw material inlet 13 are also provided in the combustion furnace 3.

[0046] In the example of FIG. 1 , the raw material inlet 13 is connected to a pipe 32. The raw material inlet 13 is an inlet for introducing the cement raw material M1 supplied through the cyclone preheating device 31 into the combustion furnace 3. The burner 10 injects fuel (not shown) into the combustion furnace 3, burning the fuel therein and creating a high-temperature environment inside the combustion furnace 3. The first inlet 11 is an inlet for introducing a first gas G1 into the combustion furnace 3. The first gas G1 is a gas having a higher O2 concentration than a second gas G2, which will be described later. As a typical example, the first gas G1 has a higher O2 concentration than air and is a mixed gas containing O2 and CO2. As a specific example, the O2 concentration of the first gas G1 is preferably 30 vol% or more, more preferably 40 vol% or more, and particularly preferably 50 vol% or more. The CO2 concentration of the first gas G1 is preferably 70% by volume or less, more preferably 60% by volume or less, and particularly preferably 50% by volume or less.

[0047] Either a mono-fuel burner or a multi-fuel burner can be used as the burner 10. In addition, when the first gas G1 contains pure oxygen or an extremely high concentration of oxygen, a pure oxygen burner can also be used as the burner 10.

[0048] The fuel supplied to the burner 10 is not limited and may be solid, liquid, or gaseous. More specifically, the fuel used in the burner 10 may be a fossil-derived fuel, hydrogen, ammonia, chemical fuels such as hydrocarbons and alcohols, biomass, combustible waste, or a mixture thereof. In particular, it is desirable for this fuel to be carbon-free when produced or discharged. Furthermore, the burner 10 is preferably configured so that the nozzle position can be adjusted according to the temperature inside the combustion furnace 3 and the shape of the flame emitted from the burner 10.

[0049] In the calcination system 1 of this embodiment, as illustrated in Fig. 1, the burner 10, the first inlet 11, and the raw material inlet 13 are all provided on the top side (+Z side) of the combustion furnace 3. Here, the "top side of the combustion furnace 3" may mean a position between the center position in the Z direction of the combustion furnace 3 and the apex position in the Z direction, and closer to the apex position than the center position in the Z direction. More preferably, the "top side of the combustion furnace 3" may mean a region within the upper 1 / 4 of the length (height) of the combustion furnace 3 in the Z direction.

[0050] That is, in the combustion furnace 3, the burner 10 and the first inlet 11 are installed in close proximity. The first gas G1 flowing into the combustion furnace 3 from the first inlet 11 has a higher O2 concentration than air, and therefore, when this first gas G1 is supplied to the burner 10, oxy-combustion is carried out on the fuel supplied from the burner 10 on the top side of the combustion furnace 3. As a result, gas with a high CO2 concentration is produced in the combustion furnace 3. In this specification, the term "oxy-combustion" is a concept that encompasses combustion with pure oxygen, combustion with a mixed gas of oxygen and carbon dioxide, and combustion with a mixed gas containing water vapor in addition to oxygen and carbon dioxide.

[0051] From the viewpoint of increasing the temperature and flow rate of the first gas G1, a heat supply device such as a burner may be installed at the first inlet 11.

[0052] A raw material inlet 13 is provided on the top side of the combustion furnace 3, through which the cement raw material M1 is introduced into the combustion furnace 3. Therefore, the cement raw material M1 is introduced through the raw material inlet 13 toward the region in the combustion furnace 3 where oxy-combustion is occurring, i.e., the high-temperature environment region. This initiates a decarboxylation reaction in the cement raw material M1. Because the decarboxylation reaction is an endothermic reaction, it serves to lower the temperature in the vicinity of the burner 10 where oxy-combustion is occurring, thereby suppressing burn damage to the burner 10 and the bricks on the top side of the combustion furnace 3.

[0053] The cement raw material M1, which has been placed in a high-temperature environment in the combustion furnace 3 and has begun to undergo a decarbonation reaction, moves in the −Z direction through the combustion furnace 3 along the flow of fuel injected from the burner 10 and the flow of other gases (first gas G1, furnace exhaust gas). The combustion furnace 3 has a second exhaust port 14 on the bottom side (−Z side), and is sent out from the second exhaust port 14 to the connecting pipe 7 together with the furnace exhaust gas.

[0054] The first gas G1 injected into the combustion furnace 3 may form a swirling flow within the combustion furnace 3. FIG. 2 is a plan view schematically showing an example of an arrangement of the first inlets 11. According to the example shown in FIG. 2, the first inlets 11 are installed at two different locations in the circumferential direction, and the first gas G1 is injected toward a position shifted from the axial center. In the example shown in FIG. 2, the first gas G1 is injected while generating a counterclockwise swirling flow when viewed from the +Z side to the -Z direction. The cement raw materials M1 travel through the combustion furnace 3 on the first gas G1 forming the swirling flow, which promotes mixing of the cement raw materials M1 and the high-temperature gas within the combustion furnace 3 and facilitates the decarbonation reaction within the combustion furnace 3.

[0055] From the viewpoint of promoting the decarbonation reaction, the cement raw material M1 is heated in the combustion furnace 3 to 830°C or higher, preferably 850°C to 1,100°C, more preferably 880°C to 1,080°C, and particularly preferably 900°C to 1,050°C.

[0056] From this viewpoint, the first gas G1 blown in from the first inlet 11 has a temperature within a range that does not inhibit combustion in the combustion furnace 3. Specifically, the temperature of the first gas G1 is preferably 500°C or higher, more preferably 650°C or higher, and particularly preferably 750°C or higher.

[0057] In the calcination system 1 of this embodiment shown in Fig. 1, the duct 5 is provided with a second inlet 12, a first outlet 9, and a pipe connecting portion 16. The pipe connecting portion 16 is a portion where the connecting pipe 7 is connected to the duct 5. The cement raw material M1 that has moved through the connecting pipe 7 is fed into the duct 5 via the pipe connecting portion 16.

[0058] 1 , the second inlet 12 is disposed on the bottom side (−Z side) of the duct 5 and is an inlet for blowing the second gas G2 into the duct 5. More specifically, the second inlet 12 is located on the −Z side of the pipe connecting portion 16 and blows the second gas G2 into the duct 5 in the +Z direction. However, it is sufficient that the second gas G2 is blown into the duct 5 through the second inlet 12 in a state in which the second gas G2 has at least a velocity vector component related to the +Z direction, and it is not necessary that the second gas G2 be blown in the +Z direction in the strict sense.

[0059] The cement raw material M1 sent into the duct 5 through the pipe connection part 16 is carried upward in the duct 5 by the air current of the second gas G2 blown in through the second inlet 12. The cement raw material M1 has been heated to a high temperature by passing through the combustion furnace 3, and is in a temperature environment in which the decarbonation reaction continues to proceed, so the decarbonation reaction continues to proceed while the cement raw material M1 is being transported through the connecting pipe 7. Furthermore, if the decarbonation reaction of the cement raw material M1 has not been completed when it is sent into the duct 5, the decarbonation reaction continues to proceed in the duct 5. The flow rate of the second gas G2 blown into the duct 5 from the second inlet 12 may be adjusted to adjust the time the cement raw material M1 remains in the high-temperature duct 5.

[0060] From the viewpoint of ensuring time for the decarbonation reaction of the cement raw material M1 to occur while it is moving through the duct 5, it is preferable that the duct 5 be a cylindrical body whose length in the vertical direction (Z direction) is longer than its length in the horizontal direction (X-Y plane direction).

[0061] The second gas G2 has a lower O concentration than the first gas G1, and preferably has a higher CO concentration than the first gas G1. In this case, the duct 5 contains the furnace exhaust gas with a high CO concentration that has flowed in from the combustion furnace 3 through the connecting pipe 7, the second gas G2 with a high CO concentration, and the CO gas generated by the decarbonation reaction.

[0062] The first outlet 9 is provided on the top side (+Z side) of the duct 5. From this first outlet 9, gas with a high CO2 concentration (calcination exhaust gas GH) that has risen inside the duct 5 and the cement raw material M1 in which a decarbonation reaction has occurred (hereinafter referred to as the "decarbonated raw material M1" as appropriate) are discharged. In this specification and drawings, to avoid complexity, the same symbol M1 is used to refer to both the "cement raw material" introduced from the raw material inlet 13 and the "decarbonated raw material" after the decarbonation reaction has occurred by heating in the calcination system 1. The notation "decarbonated raw material M1" is used to clearly indicate that the cement raw material M1 is in a state after the decarbonation reaction has progressed.

[0063] In the calcination system 1 of this embodiment, the second gas G2 is a gas blown into the duct 5, which is a separate facility from the combustion furnace 3, and therefore does not necessarily require oxygen for combustion. Therefore, unlike the first gas G1, the second gas G2 can have a low O2 concentration. On the other hand, if the second gas G2 has a low CO2 concentration, this leads to a decrease in the CO2 concentration of the gas in the duct 5. From this perspective, a gas with a lower O2 concentration than the first gas G1 and a higher CO2 concentration than the first gas G1 is preferably used as the second gas G2. In a typical example, the main component of the second gas G2 is CO2. Here, the term "main component" refers to the component with the highest component ratio.

[0064] As described above, in the calcination system 1 of this embodiment, the heated cement raw material M1 discharged from the combustion furnace 3 is transported through the connecting pipe 7 and then introduced into the duct 5. Therefore, the decarbonation reaction can proceed while the cement raw material M1 is transported through the connecting pipe 7. However, since it is conceivable that the decarbonation reaction may not be complete even when the cement raw material M1 reaches the duct 5, the second gas G2 blown into the duct 5 is preferably at a high temperature within a range that does not inhibit the decarbonation reaction. Specifically, the second gas G2 is preferably at a temperature of 850°C or higher, more preferably at a temperature of 860°C or higher, and particularly preferably at a temperature of 875°C or higher. On the other hand, if the second gas G2 is too hot, the cement raw material M1 may melt and adhere to the wall surface of the duct 5, causing blockage, or the adhered cement raw material M1 may peel off and damage the wall surface of the duct 5. Therefore, from the viewpoints of equipment maintenance and stable operation, the temperature of the second gas is preferably at a temperature of 1,200°C or lower, more preferably at a temperature of 1,100°C or lower.

[0065] The calcination system 1 shown in Fig. 1 includes a cyclone 21 connected to the first discharge port 9. The cyclone 21 separates the decarbonated raw material M1 discharged through the first discharge port 9 from the calcination exhaust gas GH. In detail, the cyclone 21 separates the decarbonated raw material M1 discharged from the calcination system 1 from the calcination exhaust gas GH by centrifugation or the like.

[0066] The separated decarbonated raw material M1 is supplied to at least one of a preheater 30 and a rotary kiln 80 (described later with reference to FIG. 4 ) while maintaining the high temperature after heating. The separated calcination exhaust gas GH is sent to a pipe 71 (described later with reference to FIG. 4 ).

[0067] As shown in FIG. 1 , the duct 5 may be provided with a coating discharge port 18 on the bottom side (−Z side). It is known that when the cement raw material M1 contains sulfur (S) or chlorine (Cl), viscous sulfur compounds and chlorine compounds are generated in a high-temperature environment, causing coating. As described above, a high-temperature environment is created inside the duct 5, so coating is expected to occur inside the duct 5. As the coating grows and its diameter increases, it falls under its own weight. Therefore, by providing the bottom side of the duct 5 with a coating discharge port 18 that can be freely opened and closed, the coating can be discharged to the outside of the duct 5 through the coating discharge port 18.

[0068] 3 is a block diagram showing an example of a method for generating the first gas G1 and the second gas G2. In the example shown in Fig. 3, the first gas G1 and the second gas G2 are both generated by using a third gas G3 whose main component is O2 and a fourth gas G4 whose main component is CO2 and adjusting the mixing ratio between these gases.

[0069] The third gas supply source 23 delivers a third gas G3 to the pair of third pipes (43, 43). The fourth gas supply source 24 delivers a fourth gas G4 to the fourth pipe 44. In the example shown in Fig. 3 , the fourth gas G4 flows in through a pair of branch pipes (44a, 44b) branched from the fourth pipe 44.

[0070] The branch pipe 44a and one of the third pipes 43 are connected to each other, and the mixing ratio between the third gas G3 flowing in through the third pipe 43 and the fourth gas G4 flowing in through the branch pipe 44a is adjusted by a first flow rate regulator 51. The branch pipe 44b and the other third pipe 43 are connected to each other, and the mixing ratio between the third gas G3 flowing in through the third pipe 43 and the fourth gas G4 flowing in through the branch pipe 44b is adjusted by a second flow rate regulator 52.

[0071] The specific configuration and installation manner of the first flow regulator 51 and the second flow regulator 52 are arbitrary as long as they can each independently adjust the mixing ratio of the supplied third gas G3 and fourth gas.

[0072] The gas obtained by mixing the third gas G3 and the fourth gas G4 at the mixing ratio set by the first flow rate regulator 51 flows through the first pipe 41. This first pipe 41 is connected to the first inlet 11. In other words, the gas flowing through the first pipe 41 corresponds to the first gas G1.

[0073] The gas obtained by mixing the third gas G3 and the fourth gas G4 at the mixing ratio set by the second flow rate regulator 52 flows through the second pipe 42. This second pipe 42 is connected to the second inlet 12. In other words, the gas flowing through the second pipe 42 corresponds to the second gas G2.

[0074] 3, the first flow rate regulator 51 and the second flow rate regulator 52 adjust the mixing ratio of the third gas G3 and the fourth gas G4, thereby making it possible to adjust the O2 concentration and the CO2 concentration in each of the first gas G1 injected into the combustion furnace 3 through the first inlet 11 and the second gas G2 injected into the duct 5 through the second inlet 12. For example, it becomes possible to easily adjust the O2 concentration and the CO2 concentration in the first gas G1 and the second gas G2 depending on the type of cement raw material M1 and the raw materials fed from the burner 10. This makes it possible to adjust the compositions of the first gas G1 and the second gas G2 depending on the type of cement raw material M1 and the fuel fed from the burner 10, so that the temperature of the combustion furnace 3 and the concentration of CO2 contained in the calcination exhaust gas GH can be set to desired values.

[0075] In this specification, the term "mixture ratio" is intended to include the case where one gas is 100% and the other gas is 0%. That is, a gas (a mixed gas for convenience) in which the third gas G3 is 100% and the fourth gas G4 is 0% may be used as the first gas G1. Similarly, a gas (a mixed gas for convenience) in which the third gas G3 is 0% and the fourth gas G4 is 100% may be used as the second gas G2. That is, in this specification, a gas in which the mixture ratio of the third gas G3 and the fourth gas G4 is 100% and the other is 0% is also referred to as a "mixture gas."

[0076] The third gas supply source 23 may be any gas supply source that supplies the third gas G3 whose main component is O. For example, the third gas supply source 23 may be a cylinder that stores O gas, or may be a combustion-supporting gas supply device 54 described later with reference to FIG.

[0077] The fourth gas supply source 24 may be any gas supply source capable of supplying a fourth gas G4 whose main component is CO2, and the form thereof is not limited. For example, the fourth gas supply source 24 may be a cylinder storing CO2 gas, or a pipe through which exhaust gas containing a high concentration of CO2 flows. As described above, the exhaust gas (calcination exhaust gas GH) from the calcination system 1 contains a high concentration of CO2. Therefore, the pipe through which this calcination exhaust gas GH flows can be used as the fourth gas supply source 24. This configuration will be described later with reference to FIG. 4.

[0078] FIG. 4 is a diagram schematically illustrating an example of the configuration of a clinker production facility 90 including the calcination system 1 of this embodiment.

[0079] 4 includes a preheater 30 that preheats the cement raw material M1, a rotary kiln 80 that calcines the preheated cement raw material M1 to obtain cement clinker, and the calcination system 1 that promotes decarbonation of the cement raw material M1. The clinker production facility 90 further includes a clinker cooler 83 that is disposed on the kiln front section 82 side of the rotary kiln 80 and that cools the obtained cement clinker.

[0080] The preheater 30 is configured to include a plurality of cyclone-type preheating devices, and the cement raw material M1 charged through the raw material inlet 39 passes through the cyclone-type preheating devices sequentially, thereby being preheated by heat exchange with the high-temperature exhaust gas from the rotary kiln 80. As described above with reference to Fig. 1 , a portion of the preheated cement raw material M1 is introduced into the calcination system 1 from the cyclone-type preheating device 31, which is part of the preheater 30, via the piping 32. Another portion of the preheated cement raw material M1 is sent into the rotary kiln 80 from the kiln end 81 side.

[0081] The clinker production facility 90 shown in Fig. 4 is equipped with a combustion supporting gas supply device 54. As the combustion supporting gas supply device 54, for example, an air separation device that separates oxygen from air GA can be used. This combustion supporting gas supply device 54 corresponds to the third gas supply source 23 described above with reference to Fig. 3. In other words, the combustion supporting gas supply device 54 delivers a third gas G3 whose main component is O2 through the third pipe 43.

[0082] A pipe 71 is connected to the cyclone 21 provided in the calcination system 1, and a calcination exhaust gas GH having a high temperature and a high CO2 concentration flows through this pipe 71. The calcination exhaust gas GH may contain a portion of the cement raw material M1 (more specifically, the decarbonated raw material M1) in the form of extremely fine dust. For this reason, in the example shown in Figure 4, the calcination exhaust gas GH is passed through a dust collector 62. The solid components collected by the dust collector 62 may be returned to the cement raw material M1.

[0083] A portion of the calcination exhaust gas GH is sent to, for example, a CO2 recovery facility (not shown) through a pipe 72, where the CO2 is recovered. Since the calcination exhaust gas GH has an extremely high CO2 concentration, it is possible to recover a large amount of CO2 using a small facility.

[0084] 4, a portion of the calcination exhaust gas GH is fed as the fourth gas G4 through the fourth pipe 44. As described above with reference to FIG. 3, the branch pipe 44a branched from the fourth pipe 44 merges with one of the third pipes 43 via the first flow regulator 51, and the branch pipe 44b branched from the fourth pipe 44 merges with the other of the third pipes 43 via the second flow regulator 52. The third gas G3 and the fourth gas G4 are mixed according to the mixing ratio set by the respective flow regulators (51, 52). That is, in the clinker production facility 90 shown in FIG. 4, the calcination system 1 that generates the calcination exhaust gas GH that can be used as the fourth gas G4, or the pipe 71 through which the calcination exhaust gas GH flows, corresponds to the fourth gas supply source 24 in FIG. 3.

[0085] The gas in which the mixing ratio of the third gas G3 and the fourth gas G4 has been adjusted by the first flow rate regulator 51 is heated through the heat exchanger 63 and the heat exchanger 61, and then blown into the combustion furnace 3 as the first gas G1. Meanwhile, the gas in which the mixing ratio of the third gas G3 and the fourth gas G4 has been adjusted by the second flow rate regulator 52 is heated through the heat exchanger 63 and the heat exchanger 61, and then blown into the duct 5 as the second gas G2.

[0086] The heat exchanger 63 exchanges heat between high-temperature air GA, which has been heated by heat exchange with the cement clinker in the clinker cooler 83 and flows through the pipe 73, and a mixed gas of a third gas G3 and a fourth gas G4 mixed at a mixing ratio set by the flow rate regulators (51, 52). The heat exchanger 61 exchanges heat between the mixed gas and high-temperature calcination exhaust gas GH, which flows through the pipe 71. Note that although the clinker production facility 90 preferably includes the heat exchangers 61 and 63, the embodiment thereof is arbitrary as long as suitable temperatures can be realized for the first gas G1 and the second gas G2.

[0087] For example, if the second gas G2 containing a relatively large amount of the fourth gas G4 has already attained a sufficiently high temperature, it may be introduced into the duct 5 without passing through a heat exchanger. As another example, since the third gas G3 immediately after being sent out from the combustion supporting gas supply device 54 is expected to be at an extremely low temperature compared to the fourth gas G4, it may be heated in advance by heat exchange with the calcination exhaust gas GH or the high-temperature air from the clinker cooler 83 before being mixed with the fourth gas G4.

[0088] Note that water vapor may be mixed with either or both of the first gas G1 and the second gas G2. In this case, a pipe connected to a water vapor supply device may be joined to either or both of the first pipe 41 and the second pipe 42 shown in FIG.

[0089] As an example, as shown in Fig. 5 , water QW may be introduced through a pipe 93 and heated by a heat exchanger 63 and a boiler 91 to generate steam. In the example shown in Fig. 5 , a fifth gas G5 mainly composed of steam generated in the boiler 91 is merged with the gas flowing through the second pipe 42, with the mixture ratio adjusted by a third flow rate regulator 92. The gas that has passed through the joint between the third flow rate regulator 92 and the second pipe 42 flows through the second pipe 42 and is then introduced to the second inlet 12 as the second gas G2. In this case, the second gas G2 is a gas containing at least HO and CO and may further contain O.

[0090] As another example, as shown in Fig. 6 , a clinker production facility 90 includes a condenser 94 for lowering the temperature of the combustion exhaust gas GH flowing through the pipe 72. Water QW is supplied to the condenser 94 as a coolant, and the hot water heated by passing through the condenser 94 is introduced to the boiler 91 via a pipe 95. As in the clinker production facility 90 described above with reference to Fig. 5 , a fifth gas G5 mainly composed of water vapor generated in the boiler 91 is joined to the gas flowing through the second pipe 42 with the mixing ratio adjusted by a third flow rate regulator 92.

[0091] Second Embodiment A second embodiment of the calcination system according to the present invention will be described, focusing on differences from the first embodiment. Fig. 7 is a diagram schematically illustrating the calcination system 1 of this embodiment, following Fig. 1 .

[0092] Similar to the calcination system 1 of the first embodiment, the calcination system 1 of this embodiment includes a combustion furnace 3, a raw material inlet 13 through which cement raw material M1 is introduced toward the combustion furnace 3, a first inlet 11 through which a first gas G1 is supplied toward the combustion furnace 3, a duct 5 connected to the combustion furnace 3, a second inlet 12 through which a second gas G2 is supplied toward the duct 5, and a first outlet 9 through which the gas and solids that have flowed through the duct 5 are discharged to the outside of the duct 5. On the other hand, the calcination system 1 of this embodiment differs from the first embodiment in that the combustion furnace 3 and the duct 5 are directly connected without including a connecting pipe 7.

[0093] In the calcination system 1 of this embodiment shown in Figure 7, the raw material inlet 13 is provided in the duct 5, but this illustration is merely an example. As another example, the raw material inlet 13 may be provided in the combustion furnace 3.

[0094] In the calcination system 1 of this embodiment shown in Fig. 7, a chute 8 for discharging coating is provided on the bottom side of the combustion furnace 3. A first inlet 11 is provided in this chute 8, and a first gas G1 is supplied from the chute 8 side toward the combustion furnace 3. However, the first inlet 11 only needs to be positioned so that the first gas G1 can be supplied toward the combustion furnace 3, and may be provided in the combustion furnace 3, for example.

[0095] In the calcination system 1 of this embodiment shown in Fig. 7, the second inlet 12 is provided in the duct 5. The cement raw material M1 heated in the high-temperature environment created by the combustion furnace 3 is transported to the first outlet 9 by the airflow of the second gas G2 supplied from the second inlet 12.

[0096] In this embodiment, unlike the first embodiment, the connection pipe 7 is not provided, and therefore the decarbonation reaction of the cement raw material M1 is unlikely to be completed by the time the cement raw material M1 is fed into the duct 5. For this reason, the decarbonation reaction of the cement raw material M1 continues to progress even while the cement raw material M1 is being transported through the duct 5. Therefore, the second gas G2 is preferably at a temperature that does not inhibit the progress of the decarbonation reaction of the cement raw material M1, and in detail, as described above in the section on the first embodiment, the second gas G2 is preferably at a temperature of 850°C or higher, more preferably at a temperature of 860°C or higher, and particularly preferably at a temperature of 875°C or higher.

[0097] The configurations of the calcination system 1 of the first embodiment and the clinker production facility 90 including the same, which have been described above with reference to Figures 2 to 6, are also applicable to the calcination system 1 of this embodiment. Figure 8 is a diagram schematically illustrating a clinker production facility 90 including the calcination system 1 of this embodiment, following Figure 4. The aspects shown in Figures 5 to 6 can also be applied to the calcination system 1 of this embodiment.

[0098] In the calcination system 1 of this embodiment, the composition ratio of the first gas G1 and the second gas G2, including the O concentration, may also be appropriately adjusted. This allows the compositions of the first gas G1 and the second gas G2 to be adjusted according to the cement raw material M1 and the type of fuel injected from the burner 10, so that the temperature of the combustion furnace 3 and the concentration of CO contained in the calcination exhaust gas GH can be set to desired values.

[0099] The rest of the system is the same as the calcination system 1 of the first embodiment, so the explanation will be omitted.

[0100] [Other Embodiments] In each of the above embodiments, a heat source supplying device for the purpose of heat insulation may be installed in the duct 5. A known heat source such as an electric heater may be used as the heat source supplying device. In the first embodiment, the heat source supplying device may be installed in the connecting pipe 7.

[0101] DESCRIPTION OF SYMBOLS 1: Calcination system 3: Combustion furnace 5: Duct 7: Connecting pipe 8: Chute 9: First outlet 10: Burner 11: First inlet 12: Second inlet 13: Raw material inlet 14: Second outlet 16: Pipe connection 18: Coating outlet 21: Cyclone 23: Third gas supply source 24: Fourth gas supply source 30: Preheater 31: Cyclone preheating device 32: Pipe 39: Raw material inlet 41: First pipe 42: Second pipe 43: Third pipe 44: Fourth pipe 44a: Branch pipe 44b: Branch pipe 51: First flow regulator 52: Second flow regulator 54: Combustion supporting gas supply device 61: Heat exchanger 62: Dust collector 63: Heat exchanger 71: Piping 72: Piping 73: Piping 80: Rotary kiln 81: Kiln bottom 82: Kiln front 83: Clinker cooler 90: Cement clinker manufacturing equipment 91: Boiler 92: Third flow regulator 93: Piping 94: Condenser 95: Piping G1: First gas G2: Second gas G3: Third gas G4: Fourth gas G5: Fifth gas GA: Air GH: Calcination exhaust gas M1: Cement raw material QW: Water

Claims

1. A calcination system comprising: a combustion furnace equipped with a burner for injecting fuel; a raw material inlet through which cement raw materials are fed toward the combustion furnace; a first inlet for supplying a first gas containing O2 toward the combustion furnace; a duct connected to the combustion furnace and through which gas sent from the combustion furnace and the heat-treated cement raw materials flow; a second inlet for supplying a second gas having a lower O2 concentration than the first gas toward the duct; and a first outlet for discharging the gas and solids that have flowed through the duct to the outside of the duct.

2. The calcination system according to claim 1, comprising: a first flow regulator capable of adjusting the mixing ratio of a third gas whose main component is O2 and a fourth gas whose main component is CO2; and a first pipe connecting said first flow regulator and said first inlet, wherein the gas that has passed through the connecting point between said first flow regulator and said first pipe flows through said first pipe and is then introduced to said first inlet as said first gas.

3. The calcination system according to claim 2, further comprising: a second flow regulator capable of adjusting the mixing ratio of the third gas and the fourth gas independently of the first flow regulator; and a second pipe connecting the second flow regulator and the second inlet, wherein the gas that has passed through the connecting point between the second flow regulator and the second pipe flows through the second pipe and is then introduced to the second inlet as the second gas.

4. A calcination system according to claim 3, comprising: a combustion-supporting gas supply device that supplies the third gas; a third pipe through which the third gas supplied from the combustion-supporting gas supply device flows; and a fourth pipe through which the fourth gas discharged through the first outlet and containing calcination exhaust gas flows, wherein the first flow rate regulator and the second flow rate regulator are configured to be able to adjust the mixing ratio of the third gas flowing through the third pipe and the fourth gas flowing through the fourth pipe, respectively.

5. The calcination system according to claim 4, further comprising a cyclone connected to the first outlet for separating the solids in the duct supplied from the first outlet from the calcination exhaust gas, and the calcination exhaust gas discharged from the cyclone is introduced into the fourth pipe.

6. The calcination system according to claim 3, further comprising a third flow regulator connected to the second pipe at a position closer to the second inlet than the connecting point between the second flow regulator and the second pipe in terms of the flow direction, and capable of adjusting the mixing ratio between the gas that has passed through the second flow regulator and a fifth gas whose main component is H2O, wherein the gas that has passed through the connecting point between the third flow regulator and the second pipe flows through the second pipe and is then introduced to the second inlet as the second gas.

7. A calcination system according to claim 1, characterized in that the duct is a cylindrical body whose vertical length is longer than its horizontal length.

8. A calcination system according to any one of claims 1 to 7, comprising: a connecting pipe connecting the combustion furnace and the duct; and a second outlet disposed on the bottom side of the combustion furnace for discharging solids and gases within the combustion furnace into the connecting pipe, wherein the second inlet is disposed at a position vertically below the point where the duct and the connecting pipe are connected.

9. The calcination system according to claim 8, wherein the raw material inlet and the burner are disposed on the top side of the combustion furnace.

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