Cement firing apparatus

Abstract

The present invention provides a cement firing apparatus that suppresses the suction of cement raw materials by the extraction probe compared to conventional methods. [Solution] The cement firing apparatus comprises a cement kiln for firing cement raw materials, an exhaust passage connected to the tail of the cement kiln through which exhaust gas from the cement kiln flows, an extraction probe connected to the exhaust passage on the cement kiln side of the central axis of the exhaust passage for extracting a portion of the exhaust gas into a chlorine bypass system, and a first raw material chute and a second raw material chute connected to the first side for feeding cement raw materials into the cement kiln. The angles of the first and second raw material chutes with respect to the horizontal plane are 30° to 70°, the angle of the first raw material chute with respect to the first side is 45° to 110°, and the angle of the second raw material chute with respect to the first side is 70° to 135°.

Description

[Technical Field]

[0001] This invention relates to a cement firing apparatus. [Background technology]

[0002] Currently, efforts are underway to utilize waste materials as part of the cement raw materials in order to realize a sustainable society. Specifically, recycled materials made from waste are mixed with the main cement raw material obtained by crushing limestone, etc., and this mixture is fired in a cement kiln as the cement raw material. Examples of waste materials include incinerator ash, and these waste materials contain chlorine compounds.

[0003] In cement firing equipment, cement raw materials and dust can melt and adhere to the walls inside the furnace and ducts, forming clumps (also known as "coating"), which can cause blockage problems. In particular, chlorine compounds tend to become viscous at high temperatures, and if the cement raw materials include recycled materials, the formation of chlorine compounds makes coating more likely to occur.

[0004] In contrast, conventional cement firing equipment is equipped with a chlorine bypass system that extracts chlorine-containing gas and discharges it outside the system. The chlorine bypass system extracts a portion of the exhaust gas via an extraction probe connected to the kiln's tail end, and then cools the extracted exhaust gas (hereinafter referred to as "extracted gas") to recover the chlorine contained in the extracted gas as a solid compound such as potassium chloride (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4434361 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, the raw material chute, which feeds preheated cement raw materials into the cement kiln, is connected to the kiln's tail end, similar to the extraction probe. Therefore, the extracted gas extracted by the extraction probe inevitably contains some of the cement raw materials.

[0007] From the perspective of reusing cement raw materials extracted along with the extracted gas, the chlorine bypass system has a cyclone that classifies dust containing solidified chlorine compounds and cement raw materials into coarse and fine powders. Since the particles of chlorine compounds have a smaller particle size compared to the cement raw materials, the fine powder classified by the cyclone has a higher chlorine content than the coarse powder. On the other hand, the coarse powder has a relatively low chlorine content and is therefore returned to the cement kiln as cement raw material.

[0008] To improve the efficiency of chlorine compound recovery using a chlorine bypass system, it is crucial to suppress the suction of cement raw materials by the extraction probe. If the extracted gas contains a large amount of dust derived from cement raw materials, chlorine compounds are more likely to precipitate on the surface of the dust during the cooling process of the extracted gas. As a result, in the cyclone classification process, the amount of chlorine compounds classified to the coarse powder side along with the dust increases, and the chlorine content in the fine powder side decreases, reducing the efficiency of chlorine compound recovery. Furthermore, if the extracted gas contains a large amount of cement raw materials, the classification efficiency in the cyclone decreases, making it easier for cement raw materials to mix with the fine powder, which could increase the processing cost of the fine powder containing chlorine compounds.

[0009] However, in conventional cement firing apparatuses where both the raw material chute and the extraction probe are connected around the kiln end, the positional relationship between the two has not been studied in detail. Furthermore, in cases where multiple raw material chutes are used, there is room for improvement in reducing the amount of cement raw material sucked in by the extraction probe.

[0010] In view of the above circumstances, the present invention aims to provide a cement firing apparatus in which the suction of cement raw materials by an extraction probe is suppressed compared to conventional methods, when multiple raw material chutes are provided. [Means for solving the problem]

[0011] The cement firing apparatus according to the present invention is A cement kiln for firing cement raw materials, An exhaust passage connected to the tail of the cement kiln, through which exhaust gas from the cement kiln flows, In the exhaust passage, an extraction probe is connected to the cement kiln side of the central axis of the exhaust passage and extracts a portion of the exhaust gas into the chlorine bypass system, The exhaust passage is connected to a first side which is the side opposite to the cement kiln, and includes a first raw material chute and a second raw material chute for feeding the cement raw materials into the cement kiln. The angles of the first raw material chute and the second raw material chute with respect to the horizontal plane are 30° to 70°. The angle of the first raw material chute with respect to the first side surface is 45° to 110°. The angle of the second raw material chute with respect to the first side surface is characterized by being 70° to 135°.

[0012] When the extraction probe extracts exhaust gas from the exhaust passage, a portion of the cement raw material introduced from the raw material chute is extracted along with the exhaust gas. As will be described in detail in the section on "Modes for Carrying Out the Invention," the above configuration allows cement raw material to be introduced into the cement kiln while reducing the influence of the flow of exhaust gas in the exhaust passage and the influence of interference between the inner wall surface of the exhaust passage and the cement raw material. As a result, the above configuration suppresses the suction of cement raw material by the extraction probe.

[0013] In the above cement firing apparatus, The extraction probe may also be connected to the second side of the exhaust passage, which is the side facing the cement kiln.

[0014] The exhaust gas flows from the cement kiln along the exhaust passage towards the preheater side, and an upward flow is generated within the exhaust passage. Therefore, a part of the cement raw material charged from the raw material chute rises in the direction of the upward flow, that is, in the direction from the cement kiln towards the first side surface. On the other hand, according to the above configuration, since the extraction probe is connected to the second side surface located on the opposite side of the first side surface, it becomes difficult for the cement raw material to face the extraction port of the extraction probe, and it becomes easier to suppress the suction of the cement raw material by the extraction probe. Further, according to the above configuration, it is possible to form the extraction port at a position away from the raw material chute connected to the first side surface, which is preferable.

[0015] In the above cement firing apparatus, The extraction probe may be connected to a side surface different from the first side surface and the second side surface.

[0016] [[ID=·12]] At least, by connecting the extraction probe on the cement kiln side of the central axis of the exhaust passage, it is possible to suppress the suction of the cement raw material by the extraction probe. This point will be described later in the section of "Mode for Carrying Out the Invention".

[0017] Also, in the above cement firing apparatus, The angle of the extraction probe with respect to the horizontal plane is 15° to 75°, The angle of the extraction probe with respect to the side surface to which the extraction probe is connected may be 30° to 150°.

[0018] In the above cement firing apparatus, The cement kiln has a cylindrical shape, and when the circular cross section of the end portion on the kiln bottom side is virtually trisected in the circumferential direction starting from the vertex in the vertical direction into fan-shaped regions, the virtual extension lines of the central axes of the first raw material chute and the second raw material chute may intersect in the fan-shaped region located downward with respect to the vertical direction.

[0019] As mentioned above, since the exhaust gas flows from the cement kiln toward the preheater, some of the cement raw materials are carried away by the exhaust gas toward the opposite side of the cement kiln. In contrast, from the viewpoint of smoothly feeding more cement raw materials into the cement kiln, it is preferable that the cement raw materials be fed downwards in the vertical direction. With the above configuration, since the raw material chute is connected toward the downwards of the cement kiln, it becomes easier to feed more cement raw materials downwards into the cement kiln. As a result, the influence of the exhaust gas on the cement raw materials is reduced, and the suction of cement raw materials by the extraction probe can be suppressed.

[0020] In the above cement firing apparatus, The exhaust passage has an inclined section between the tail end of the cement kiln and the first side surface, with an angle of 30° to 60° with respect to the horizontal direction. With respect to the vertical direction, the distance between the upper end of the inclined portion and the lower end of the first supply port to which the first raw material chute is connected on the first side surface, and the distance between the upper end of the inclined portion and the lower end of the second supply port to which the second raw material chute is connected on the first side surface, may both be 3m or less.

[0021] Furthermore, in the cement firing apparatus described above, With respect to the vertical direction, the distance between the center of the extraction port to which the extraction probe is connected and the exhaust flow path, and the distance between the center of the first supply port to which the first raw material chute is connected and the first side surface, and the distance between the center of the extraction port and the center of the second supply port to which the second raw material chute is connected and the first side surface, may both be 3m or less. [Effects of the Invention]

[0022] According to the present invention, a cement firing apparatus is provided in which the suction of cement raw materials by the extraction probe is suppressed compared to conventional methods, when multiple raw material chutes are used. [Brief explanation of the drawing]

[0023] [Figure 1A] This is a diagram showing the configuration of a cement firing apparatus according to the first embodiment. [Figure 1B] This is a diagram showing some of the components of a cement firing apparatus. [Figure 2] This is a schematic cross-sectional view showing the configuration of the exhaust flow path. [Figure 3] This is a schematic cross-sectional view showing the configuration of the exhaust flow path. [Figure 4] This diagram, following Figure 3, shows an alternative configuration example of a cement firing apparatus. [Figure 5] This is a cross-sectional view of the YZ plane at the tail end of a cement kiln. [Figure 6] This diagram, following Figure 3, shows an alternative configuration example of a cement firing apparatus. [Figure 7] This is a diagram showing the configuration of the cement firing apparatus used for verification. [Figure 8] This is a diagram showing the configuration of the cement firing apparatus used for verification. [Figure 9] This is a diagram showing the configuration of the cement firing apparatus used for verification. [Modes for carrying out the invention]

[0024] [First Embodiment] Embodiments of the cement firing apparatus according to the present invention will be described below with reference to the drawings as appropriate. Note that the following drawings are schematic representations, and the dimensional ratios in the drawings do not necessarily correspond to the actual dimensional ratios, nor do the dimensional ratios between the drawings necessarily correspond.

[0025] Figure 1A is a diagram showing the configuration of a cement firing apparatus according to the first embodiment. In Figure 1A, some of the components of the cement firing apparatus 1 are schematically shown in a block diagram. As shown in Figure 1A, the cement firing apparatus 1 comprises a cement kiln 3, an exhaust passage 5 connecting the cement kiln 3 and a preheater 20, an extraction probe 7 for extracting some of the exhaust gas from the exhaust passage 5 to the chlorine bypass system 30, and a raw material chute 9 for feeding cement raw materials toward the cement kiln 3.

[0026] In the following diagrams, the XYZ coordinate system, where the vertical direction is defined as the Z direction and the plane perpendicular to the Z direction is the XY plane, will be referenced and explained as appropriate. Furthermore, in the following explanation, when expressing directions, positive and negative directions will be distinguished by adding a sign, such as "+X direction" and "-X direction". When expressing directions without distinguishing between positive and negative directions, it will simply be written as "X direction". In other words, in this specification, when simply written as "X direction", both "+X direction" and "-X direction" are included. The same applies to the Y direction and Z direction.

[0027] In the cement firing apparatus 1, the cement raw material C1 is supplied to the upper cyclone (not shown) of the preheater 20 and, as it falls to the lower cyclone (not shown), is preheated by the high-temperature exhaust gas G1 flowing from the cement kiln 3. In the following diagram, the flow of solids including the cement raw material C1 is shown by a dashed line with an arrow, and the flow of gases including the exhaust gas G1 from the cement kiln 3 is shown by a dashed line with an arrow. As shown in Figure 1, the cement raw material C1 is fed from the lowest cyclone 25 of the preheater 20 to the kiln end 3a of the cement kiln 3 via the raw material chute 9. The cement firing apparatus 1 produces cement clinker by firing the cement raw material C1 in the rotationally driven cement kiln 3.

[0028] Figure 1B is a diagram showing a part of the configuration of the cement firing apparatus 1. As shown in Figure 1B, the preheater 20 has cyclones 25a and 25b located at the bottom. In other words, although the illustration in Figure 1A is simplified, the cement firing apparatus 1 has a first raw material chute 11 connecting cyclone 25a to the exhaust passage 5, and a second raw material chute 12 connecting cyclone 25b to the exhaust passage 5. This point will be described in detail with reference to Figure 3, etc.

[0029] Cement raw material C1 is obtained by mixing cement main raw materials and recycled raw materials. Examples of cement main raw materials include limestone. Examples of recycled raw materials include incinerated ash from waste incineration plants. The composition of cement raw material C1 is not limited to the above. For example, the supply rate of cement raw material C1 is said to be 80 t / hour to 500 t / hour. More specific examples include the supply rate of 80 t / hour to 100 t / hour, 100 t / hour to 300 t / hour, or 300 t / hour to 500 t / hour. Also, for example, the median particle size of cement raw material C1 is 20 μm to 60 μm, and more specific examples include 30 μm to 45 μm.

[0030] As shown in Figure 1A, the cement kiln 3 has a main burner 41 located on the clinker cooler 40 side and fires the cement raw material C1 that is introduced. The internal space of the cement kiln 3 is heated to, for example, 1000°C to 1600°C. As an example, the cement kiln 3 has a cylindrical shape. The inner diameter of the cement kiln 3 is, for example, about 2m to 6m, and the total length is, for example, about 40m to 120m.

[0031] As shown in Figure 1A, the exhaust passage 5 has a main body 5a connected to the rear end 3a of the cement kiln 3, and a pipe 5b connecting the main body 5a and the preheater 20.

[0032] Figures 2 and 3 are schematic cross-sectional views illustrating the configuration of the exhaust passage 5. Figure 2 corresponds to a cross-sectional view of the exhaust passage 5 in the XZ plane, and Figure 3 corresponds to a cross-sectional view of the main body 5a in the XY plane. In Figure 3, the central axis A1 of the exhaust passage 5 is schematically shown.

[0033] As shown in Figure 2, exhaust gas G1 from the cement kiln 3 is guided to the preheater 20 by the exhaust passage 5 and used to preheat the cement raw material C1 introduced from the upper stage of the preheater 20. From the viewpoint of guiding the exhaust gas G1 to the preheater 20, it is preferable that the main body 5a is connected to the preheater 20 by a pipe 5b whose cross-section in the XY plane is smaller than that of the main body 5a.

[0034] As shown in Figure 2, the main body 5a of the exhaust passage 5 has an inclined portion 6 that is inclined with respect to the horizontal plane. For example, the angle of the inclined portion 6 with respect to the horizontal plane is 30° to 60°, and more preferably 40° to 50°.

[0035] As an example, the width W1 in the X direction of the internal space of the main body 5a is 1m to 6m, and the width W2 in the Y direction is 1m to 6m (see Figure 3). From the viewpoint of guiding the exhaust gas G1 to the preheater 20, the width W1 in the X direction and the width W2 in the Y direction of the internal space are preferably 200% or less of the inner diameter of the cement kiln 3, and more preferably 180% or less.

[0036] As shown in Figures 2 and 3, the raw material chutes (11, 12) are connected to the first side S1, which is the side of the exhaust passage 5 opposite to the cement kiln 3. The first raw material chute 11 feeds the cement raw material C1 into the cement kiln 3 through a supply port 11a formed on the first side S1. The second raw material chute 12 feeds the cement raw material C1 into the cement kiln 3 through a supply port 12a formed on the first side S1. Supply port 11a corresponds to the "first supply port," and supply port 12a corresponds to the "second supply port."

[0037] The raw material chutes (11, 12) may be configured to straddle the central axis A1 with respect to the Y direction (see Figure 3). In other words, in this embodiment, raw material chute 11 is located on the +Y side of the central axis A1, and raw material chute 12 is located on the -Y side of the central axis A1. Preferably, the supply ports (11a, 12a) are formed symmetrically with respect to the central axis A1.

[0038] Figure 2 illustrates the angles (θ1, θ2) of the raw material chutes (11, 12) with respect to the horizontal plane. From the viewpoint of suppressing the influence of the updraft caused by exhaust gas G1 and introducing the cement raw material C1 into the cement kiln 3 along the inclined section 6, an angle (θ1, θ2) of 30° to 70° is preferable.

[0039] More specifically, in the exhaust passage 5, exhaust gas G1 flows from the cement kiln 3 towards the preheater 20. Therefore, for example, if the angle θ1 is 0° and the cement raw material C1 is introduced in a nearly horizontal direction, the updraft caused by the exhaust gas G1 will easily cause dust originating from the cement raw material C1 (hereinafter simply referred to as "dust") to be stirred up, and it is thought that a large amount of the cement raw material C1 will be drawn into the extraction probe 7. On the other hand, if the angle θ1 becomes significantly larger, the angle of the cement raw material C1 with respect to the inclined section 6 when the cement raw material C1 introduced from the supply port 9a reaches the inclined section 6 will become larger. In this case, dust will be more easily stirred up when the cement raw material C1 reaches the inclined section 6, and it is thought that a large amount of the cement raw material C1 will be drawn into the extraction probe 7. In light of the above, an angle θ1 of 30° to 70° is preferable. The same discussion is possible for the angle θ2. This point will be explained in detail in the [Verification 1] section below.

[0040] Figure 2 shows an example where the angle θ1 of the first raw material chute 11 relative to the horizontal plane and the angle θ2 of the second raw material chute 12 relative to the horizontal plane are the same. However, angles θ1 and θ2 may be different from each other.

[0041] Figure 3 schematically shows the angle θ3 of the first raw material chute 11 relative to the first side surface S1 and the angle θ4 of the second raw material chute 12 relative to the first side surface S1 when viewed in the Z direction. In Figure 3, angle θ3 is 60° and angle θ4 is 120°. Figure 4 is a diagram showing another configuration example of the cement firing apparatus 1, following Figure 3. In Figure 4, an example is shown where both angles θ3 and θ4 are 90°.

[0042] When the angle θ3 is small, the cement raw material C1 introduced from the first raw material chute 11 is more likely to collide with the inner wall surface on the -Y side of the exhaust passage 5, and dust is likely to be stirred up within the exhaust passage 5. Conversely, when the angle θ3 is large, the cement raw material C1 is more likely to collide with the inner wall surface on the +Y side of the exhaust passage 5.

[0043] On the other hand, when the angle θ4 becomes small, the cement raw material C1 introduced from the second raw material chute 12 is more likely to collide with the inner wall surface on the -Y side of the exhaust passage 5, and dust is likely to be stirred up within the exhaust passage 5. Also, when the angle θ4 is large, the cement raw material C1 is more likely to collide with the inner wall surface on the +Y side of the exhaust passage 5.

[0044] In light of the above, an angle θ3 is preferably 45° to 110°, and an angle θ4 is preferably 70° to 135°. This point will be explained in detail in the [Verification 3] section below.

[0045] In Figures 2 and 3, the virtual extensions (L1, L2) of the central axes of the raw material chutes (11, 12) are illustrated by dashed lines. As will be described later with reference to Figure 5, it is preferable that the extensions (L1, L2) intersect the area below the cement kiln 3 in the Z direction at the kiln-side end 3a of the cement kiln 3.

[0046] Furthermore, from the viewpoint of facilitating the feeding of cement raw material C1 along the inclined section 6, the height from the upper end of the inclined section 6 to the lower end of the supply ports (11a, 12a) in the Z direction is preferably 3m or less, and more preferably 1.5m or less.

[0047] As an example, the inner diameter of the raw material chute (11,12) is 0.1m to 1.5m. In view of suppressing blockage of the cement raw material C1 within the raw material chute (11,12), the inner diameter of the raw material chute (11,12) is preferably 0.1m or more, and more preferably 0.3m or more. Furthermore, from the viewpoint of making it easier to increase the flow velocity of the cement raw material C1 within the raw material chute (11,12), the inner diameter of the raw material chute (11,12) is preferably 1.5m or less, and more preferably 1.2m or less.

[0048] Figure 5 is a cross-sectional view of the YZ plane of the end 3a on the kiln-bottom side of the cement kiln 3. As shown in Figure 5, the internal space R1 of the cement kiln 3 has a circular cross-section. In Figure 5, the internal space R1 is shown as a fan-shaped region (r1, r2, r3) which is virtually divided into three equal parts starting from the vertex T1 in the Z direction.

[0049] In cement kiln 3, exhaust gas G1 flows in the -X direction (not shown in Figure 5; see Figure 2, etc.). Therefore, from the viewpoint of suppressing the rise of cement raw material C1 introduced from raw material chute 9 by exhaust gas G1, it is preferable that the cement raw material C1 be introduced toward the -Z side of cement kiln 3, i.e., toward region r2. In view of this, it is preferable that the extension lines (L1, L2) (see also Figure 2), which are virtually extensions of the central axis of raw material chute 9, intersect region r2. Figure 5 schematically shows the position where the extension lines (L1, L2) and region r2 intersect.

[0050] The chlorine bypass system 30 recovers chlorine contained in exhaust gas G1 by solidifying it, with the aim of suppressing blockage problems caused by coating in the exhaust passage 5 and the like. The chlorine bypass system 30 has a cooling mechanism (not shown) that cools the gas extracted by the extraction probe 7 (hereinafter referred to as "extracted gas G2" for convenience), and solidifies the chlorine compounds contained in the extracted gas G2.

[0051] As shown in FIG. 2, the extraction probe 7 extracts a part of the exhaust gas G1 flowing through the exhaust passage 5 and feeds it as the extraction gas G2 into the chlorine bypass system 30. In the present embodiment, the extraction probe 7 is connected to an extraction port 7a formed on a second side surface S2 which is a side surface on the cement kiln 3 side of the exhaust passage 5 (see also FIG. 3). As an example, the extraction amount of the exhaust gas G1 by the extraction probe 7 is 50 Nm 3 / h to 40,000 Nm 3 / h. As a more detailed specific example, the extraction amount is 50 Nm 3 / h to 500 Nm 3 / h, 500 Nm 3 / h to 5,000 Nm 3 / h, 5,000 Nm 3 / h to 10,000 Nm 3 / h, 10,000 Nm 3 / h to 40,000 Nm 3 / h.

[0052] From the viewpoint of facilitating suppression of the suction of the cement raw material C1 by the extraction probe 7, it is preferable that the extraction port 7a is formed at a position higher than the supply port 11a to which the raw material chute 11 is connected in the Z direction. As an example, the distance from the center of the supply port 11a tothe center of the extraction port 7a is preferably 0.3 m or more, and more preferably 0.5 m or more. On the other hand, it can be said that when the extraction port 7a is formed at a position close to the preheater 20, coating is likely to occur between the cement kiln 3 and the extraction port 7a. In view of this, the distance from the center of the supply port 11a to the center of the extraction port 7a is preferably 3 m or less, and more preferably 1 m or less. The same applies to the distance between the center of the supply port12a and the center of the extraction port 7a. Although not shown, the supply ports (11a, 12a) may be formed at positions higher than the extraction port 7a in the Z direction.

[0053] Figure 2 illustrates the angle θ5 of the extraction probe 7 with respect to the horizontal plane. The angle θ5 is not limited, but as an example, it is between 15° and 75°. Figure 3 illustrates the angle θ6 of the extraction probe 7 with respect to the second side surface S2 when viewed from the Z direction. The angle θ6 is not limited, but as an example, it is between 30° and 150°.

[0054] Figure 6 is a diagram showing an alternative configuration of the cement firing apparatus 1, following Figure 3. As shown in Figure 6, the extraction probe 7 may be connected to a side other than the first side S1 and the second side S2, i.e., the side on the +Y side of the exhaust passage 5. Although not shown in the diagram, the extraction probe 7 may also be connected to the side on the -Y side. Note that even when the extraction probe 7 is connected to the side on the Y direction of the exhaust passage 5, as shown in Figure 6, the same discussion as described with reference to Figure 3 is possible regarding angles θ5 and θ6. In this case, angle θ6 can be read as "the angle with respect to the side to which the extraction probe 7 is connected."

[0055] Since the extraction probe 7, the first raw material chute 11, and the second raw material chute 12 are connected to the exhaust passage 5, the extraction probe 7 inevitably sucks in a portion of the cement raw material C1. In view of this, the chlorine bypass system 30 has a cyclone (not shown) that classifies the dust, which consists of particles made of solidified chlorine compounds and cement raw material C1, into coarse powder and fine powder. The fine powder has a high proportion of chlorine compounds. On the other hand, the coarse powder has a relatively low chlorine content and is therefore reused as cement raw material.

[0056] As mentioned above, in order to improve the recovery efficiency of chlorine compounds by the chlorine bypass system, it is preferable to suppress the suction of cement raw material C1 by the extraction probe 7.

[0057] Regarding the suppression of the amount of cement raw material C1 absorbed by the extraction probe 7, the inventors conducted the following verifications 1 to 4, which are described below.

[0058] [Verification 1] In the exhaust passage 5, exhaust gas G1 flows from the cement kiln 3 towards the preheater 20. Therefore, for example, if the angle θ1 of the first raw material chute 11 and the angle θ2 of the second raw material chute 12 are set to 0°, and the cement raw material C1 is fed in a nearly horizontal direction, the cement raw material C1 is likely to be stirred up by the exhaust gas G1, and a large amount of the cement raw material C1 is likely to be drawn into the extraction probe 7. In light of this, increasing the angles θ1 and θ2 can be expected to reduce the amount of dust originating from the cement raw material C1 in the extraction gas G2. In view of this, we conducted a verification of increasing the angle θ1 of the first raw material chute 11 and the angle θ2 of the second raw material chute 12 with respect to the horizontal plane, which will be explained below.

[0059] In this verification, Fluent Ver.2024R1 from ANSYS JAPAN was used as the simulation analysis software.

[0060] Figures 7, 8, and 9 are diagrams showing the configuration of the cement firing apparatus used in this verification. Figure 7 corresponds to a view of the area around the exhaust passage 5 in the Y direction, and Figure 8 corresponds to a view of the first side surface S1 in the X direction. In Figure 8, hatching has been applied to the inclined section 6 for ease of understanding. Figure 9 corresponds to a view of the second side surface S2 in the -X direction.

[0061] In Figure 7, the coordinates Px in the X direction of the raw material chute (11,12) and the extraction probe 7 are shown. i (i=7,11,12) is schematically shown. Coordinate Px i The first side S1 is used as the reference (Px i Let = 0) and the second surface S2 be Px i This is shown as =a. Since the first raw material chute 11 and the second raw material chute 12 are connected to the first side surface S1, the coordinate Px 11 and coordinate Px 12This is indicated as 0. Furthermore, for example, if the coordinate Px7 of the extraction probe 7 is indicated as a, it means that the extraction port 7a of the extraction probe 7 is formed on the second side surface S2, and if the coordinate Px7 of the extraction probe 7 is indicated as 0.25a or 0.75a, it means that the extraction port 7a is formed on the +Y side or -Y side of the exhaust passage 5 (see also Figure 6).

[0062] Furthermore, Figure 8 schematically illustrates the height H1 from the upper end of the inclined section 6 to the lower end of the first raw material chute 11, and the height H2 from the upper end of the inclined section 6 to the lower end of the second raw material chute 12.

[0063] In Figures 8 and 9, the coordinates Py of the raw material chute (11,12) and extraction probe 7 in the Y direction are shown. i (i=7,11,12) is schematically shown. Coordinates Py i The end of the first side surface S1 on the +Y side is referenced (Py i Let = 0), and set the position of the end on the -Y side to Py i =b is denoted as such. For example, if the coordinates Py7 of the extraction probe 7 are given as 0.5b, it means that the center of the extraction port 7a to which the extraction probe 7 is connected is located in the center of the second side surface S2 with respect to the Y direction.

[0064] In Figure 9, the positions of the supply ports 11a and 12a on the first side surface S1 are illustrated by dashed lines. Also in Figure 9, the height H3 from the center of the supply port 11a to the center of the extraction port 7a of the extraction probe 7 is schematically illustrated.

[0065] The simulation conditions for this verification are as follows. These simulation conditions are also common to verifications 2-4 described later. Cement raw material supply: 400 tons / hour Particle size of cement raw materials: Median is 37 μm, 32 μm residue 47.2%, 45 μm residue 53.2%, 90 μm residue 66.7%. Exhaust gas flow rate in the exhaust passage: 150,000 Nm 3 / time Exhaust gas temperature in the exhaust passage: 1200℃ Exhaust gas extraction volume using extraction probe: 15,000 Nm³ 3 / time

[0066] Table 1 below shows the verification conditions and results for levels 1 to 5 in Verification 1. [Table 1]

[0067] In this verification, the angles θ1 and θ2 of the raw material chutes (11,12) relative to the horizontal plane were increased. As shown in Table 1, it was found that increasing angles θ1 and θ2 from 25° to 50° reduced dust originating from cement raw material C1 in the extracted gas G2. More specifically, the dust reduction rate at level 2 improved by more than 10% compared to level 1, which is set as the baseline of 0%.

[0068] The amount of dust in the extracted gas at Level 1 was equivalent to the amount of dust in the extracted gas in cement firing equipment conventionally manufactured by the applicant. In other words, when angles θ1 and θ2 are around 25°, the improvement in the amount of dust in the extracted gas is insufficient, and it cannot be said that the suction of cement raw materials by the extraction probe is suppressed more than before. On the other hand, when angles θ1 and θ2 were increased to 50°, an improvement of more than 10% was obtained in the amount of dust in the extracted gas. When a reduction rate of more than 10% is shown compared to Level 1, it can be said that there is less dust in the extracted gas G2, and the suction of cement raw materials C1 by the extraction probe 7 is suppressed more than before.

[0069] In light of this, Table 1 shows evaluation results where a dust reduction rate of 10% or more relative to Level 1 is marked with "Evaluation ○", and a reduction rate below that is marked with "Evaluation ×".

[0070] Furthermore, in Level 3, the case where angle θ1 is 40° and angle θ2 is 60° was verified. Similar to Level 2, a reduction rate of 10% or more was obtained in Level 3 compared to Level 1. Considering Levels 2 and 3, angles θ1 and θ2 are preferably 30° or more, and more preferably 40° or more. Moreover, according to Level 3, angles θ1 and θ2 may be different from each other.

[0071] On the other hand, at level 4, the reduction rate was equivalent to that of level 1, resulting in a "×" rating. This is thought to be because the significantly larger angles θ1 and θ2 made it easier for the cement raw material C1 to collide with the inclined section 6 at a larger angle. In other words, it is thought that when the cement raw material C1 introduced into the exhaust passage 5 collided with the inclined section 6, dust was stirred up, and some of the cement raw material C1 was more easily sucked into the extraction probe 7. In light of this, angles θ1 and θ2 are preferably 70° or less, and more preferably 60° or less.

[0072] Furthermore, it can be seen that if the angle of one of the raw material chutes is smaller than level 5, the suction of dust by the extraction probe 7 cannot be suppressed. In other words, it is preferable that angles θ1 and θ2 are both within the above range.

[0073] Based on the results of Verification 1, angles θ1 and θ2 are preferably between 30° and 70°, and more preferably between 40° and 60°.

[0074] [Verification 2] If an extraction port 7a is formed near the supply ports (11a, 12a), the introduced cement raw material C1 is more easily drawn directly into the extraction probe 7, and it is conceivable that the extraction probe 7 will draw in more cement raw material C1. In view of this, the inventors investigated the effect of the position of the extraction probe 7 relative to the raw material chutes (11, 12) on the extracted gas G2.

[0075] Table 2 below shows the verification conditions and results for levels 6 to 11 in Verification 2. Following Table 1, Table 2 shows evaluations based on level 1. Note that the conditions for the raw material chutes (11, 12) are the same as for level 2 in levels 6 to 11. In light of this, level 2 is also listed in Table 2. [Table 2]

[0076] According to levels 10 and 11, it can be seen that when the extraction port 7a is formed on the second side surface S2 (Px7=a), the extraction probe 7 is less likely to suck in the cement raw material C1. Furthermore, in view of levels 10 and 11, it can be seen that when the extraction port 7a is formed on the second side surface S2, the position of the extraction port 7a in the Y direction is not limited.

[0077] Furthermore, as shown in Table 2, when the coordinate Px7 of the extraction port 7a was set to 0.25a, ​​the extracted gas G2 contained a large amount of dust, resulting in a negative (×) rating. On the other hand, when the coordinate Px7 of the extraction port 7a was set to 0.75a, a good dust reduction rate was obtained, resulting in a positive (○) rating. This is true whether the extraction port 7a is formed on the +Y side or the -Y side.

[0078] In light of the results of Verification 2, it can be seen that when the extraction port 7a is formed near the supply ports (11a, 12a), specifically when the extraction port 7a is formed on the -X side of the central axis A1 of the exhaust flow path 5 (see Figure 3), the distance between the extraction port 7a and the supply ports (11a, 12a) becomes shorter, making it easier for the extraction probe 7 to draw in more cement raw material C1. Therefore, it is preferable that the extraction port 7a be formed on the +X side of the central axis A1 of the exhaust flow path 5. Note that when the extraction port 7a is formed on the +X side of the central axis A1, it means that at least half or more of the area of ​​the extraction port 7a is located on the +X side of the central axis A1.

[0079] Furthermore, from the viewpoint of forming the extraction port 7a as far away as possible from the supply ports (11a, 12a), it is preferable that the extraction port 7a be formed on the second side surface S2.

[0080] [Verification 3] Next, we conducted verification by changing the angle θ3 of the first raw material chute 11 and the angle θ4 of the second raw material chute 12, which will be explained below.

[0081] Table 3 below shows the verification conditions and results for levels 12 to 17 in Verification 3. Following Table 1, Table 3 shows evaluations based on level 1. Note that for levels 12 to 17, the conditions are the same as for level 2, except for angles θ3 and θ4. In light of this, level 2 is also included in Table 3. [Table 3]

[0082] At level 12, the angle θ3 is smaller than at level 2. At level 15, the angle θ4 is larger than at level 2. Both level 12 and level 15 achieved a dust reduction rate equivalent to level 2, resulting in a "○" rating.

[0083] In contrast, at levels 13 and 14, dust increased compared to level 2, resulting in a negative evaluation (×). Level 13 corresponds to a larger angle θ3 than at level 2, and level 14 corresponds to a smaller angle θ4 than at level 2. This is thought to be because when the angle θ3 is large or the angle θ4 is small, the cement raw material C1 introduced from the supply port (11a, 12a) is more likely to collide with the inner wall surface of the exhaust passage 5 in the Y direction. Specifically, at level 13 (θ3=120°), the cement raw material C1 introduced from the first raw material chute 11 collides with the inner wall surface on the +Y side, causing dust to be stirred up in the exhaust passage 5 and more likely to be sucked into the extraction probe 7. Also, at level 14 (θ4=45°), the cement raw material C1 introduced from the second raw material chute 12 collides with the inner wall surface on the -Y side, causing dust to be stirred up and more likely to be sucked into the extraction probe 7.

[0084] Furthermore, at level 16, angles θ3 and θ4 were set to 80°, and a "○" result was obtained. In light of this, it can be seen that with respect to the second raw material chute 12, if angle θ4 is 70° or more, more preferably 80° or more, the cement raw material C1 introduced from the second raw material chute 12 will be less likely to collide with the inner wall surface on the -Y side. Moreover, in light of the symmetry with respect to the X axis, it can be seen that with respect to the first raw material chute 11, if angle θ3 is at least 110° or less, more preferably 100° or less, the cement raw material C1 introduced from the first raw material chute 11 will be less likely to collide with the inner wall surface on the +Y side.

[0085] In Level 17, angles θ3 and θ4 were set to 150°, but a negative evaluation result (×) was obtained. In light of this, it is considered preferable that angle θ4 be at least 140° or less. Referring again to Level 12, it can be seen that θ3 is preferably 45° or greater. Furthermore, considering the symmetry with respect to the X-axis, it can be said that angle θ4 is preferably 135° or less.

[0086] In light of the above, from the viewpoint of suppressing the suction of cement raw material C1 by the extraction probe 7, the angle θ3 of the first raw material chute 11 is preferably 45° to 110°. Also, the angle θ4 of the second raw material chute 12 is preferably 70° to 135°. By setting angles θ3 and θ4 within the above ranges, a good dust reduction rate is obtained, and it can be seen that the suction of cement raw material C1 by the extraction probe 7 is suppressed.

[0087] [Verification 4] Next, we conducted verification by changing the angle (θ5, θ6) of the extraction probe 7, the height H1 of the first raw material chute 11, and the height H2 of the second raw material chute 12, which will be explained below.

[0088] Table 4 below shows the verification conditions and results for levels 18 to 25 in Verification 4. Following Table 1, Table 4 shows evaluations based on level 1. Note that for levels 18 to 25, the conditions other than height (H1, H2) and angle (θ5, θ6) are the same as for level 2. In light of this, level 2 is also included in Table 4. [Table 4]

[0089] The extraction probe 7 draws in a portion of the exhaust gas G1 at a predetermined extraction rate. Therefore, the influence of the angle (θ5, θ6) of the extraction probe 7 on the amount of dust drawn into the extraction probe 7 is considered to be small. This point is consistent with the results for levels 18 to 21. In other words, when only the angle θ5 or θ6 of the extraction probe 7 differs from that of level 2, the same dust reduction rate as level 2 was obtained in both cases, resulting in a good dust reduction rate (evaluation ○). Therefore, the angle (θ5, θ6) of the extraction probe 7 is not limited in the cement firing apparatus.

[0090] Furthermore, it was shown that even when the heights (H1, H2) of the first raw material chute 11 and the second raw material chute 12 were set to 3m, a good dust reduction rate equivalent to that of level 2 could be obtained, as was the case with levels 20 to 25. In light of this, it is preferable that heights H1 and H2 be 3m or less.

[0091] [Summary of Verification] According to verifications 1 to 4 above, it was shown that the cement firing apparatus 1 according to the above embodiment can suppress the suction of cement raw material C1 by the extraction probe 7.

[0092] [Alternative Embodiment] The following describes another embodiment of the cement firing apparatus 1.

[0093] <1> The cement firing apparatus 1 may have a furnace to accelerate the decarboxylation reaction of the cement raw material C1. For example, the cement raw material C1 may be calcined in a calcination furnace and then sent to the cyclone 25 at the bottom of the preheater 20. Alternatively, the raw material chutes (11, 12) may be connected to both the cyclone 25 and the calcination furnace, and the raw material chutes (11, 12) may feed the cement raw material C1 sent from both into the cement kiln 3.

[0094] <2> In the above description, the cement firing apparatus 1 was described as having cyclones 25a and cyclones 25b, but the cement firing apparatus 1 may also be described as having only one cyclone 25. For example, the piping connected to the cyclone 25 may be branched midway and connected to the first side surface S1 of the exhaust passage 5, thereby forming the first raw material chute 11 and the second raw material chute 12.

[0095] <3> In the above description, the exhaust passage 5 was described as having a pipe 5b with a smaller cross-sectional area than the main body 5a. However, the configuration of the exhaust passage 5 is not limited to the above embodiment. The method of connecting the exhaust passage 5 to the preheater 20 is arbitrary, and conventionally known methods can be used.

[0096] <4> The configuration of the cement firing apparatus 1 according to the present invention is not limited to the above embodiment.

[0097] <5> The embodiments and modifications described above can be implemented by combining them as appropriate. [Explanation of Symbols]

[0098] 1: Cement firing apparatus 3: Cement Kiln 5: Exhaust passage 5a: Main body 5b: Piping 6 : Inclined part 7: Extraction probe 7a: Air extraction port 9: Raw material chute 9a: Supply port 20: Preheater 25: Cyclone 30: Chlorine bypass system 40: Clinka Cooler 41: Main Burner C1: Cement raw material G1: Exhaust gas G2: Extracted gas S1: First aspect S2: Second side

Claims

1. A cement kiln for firing cement raw materials, An exhaust passage connected to the tail of the cement kiln, through which exhaust gas from the cement kiln flows, In the exhaust passage, an extraction probe is connected to the cement kiln side of the central axis of the exhaust passage and extracts a portion of the exhaust gas into the chlorine bypass system, The exhaust passage is connected to a first side which is the side opposite to the cement kiln, and includes a first raw material chute and a second raw material chute for feeding the cement raw materials into the cement kiln, The angles of the first raw material chute and the second raw material chute with respect to the horizontal plane are 30° to 70°. The angle of the first raw material chute with respect to the first side surface is 45° to 110°. A cement firing apparatus in which the angle of the second raw material chute with respect to the first side surface is 70° to 135°.

2. The cement firing apparatus according to claim 1, wherein the extraction probe is connected to a second side which is the side of the exhaust passage facing the cement kiln.

3. The angle of the extraction probe with respect to the horizontal plane is 15° to 75°. The cement firing apparatus according to claim 2, wherein the angle of the extraction probe with respect to the second side surface is 30° to 150°.

4. The cement firing apparatus according to claim 1, wherein the extraction probe is connected to a side different from the first side and the second side which is the side of the exhaust passage facing the cement kiln.

5. The angle of the extraction probe with respect to the horizontal plane is 15° to 75°. The cement firing apparatus according to claim 4, wherein the angle of the extraction probe with respect to the side surface to which the extraction probe is connected is 30° to 150°.

6. The cement firing apparatus according to any one of claims 1 to 5, characterized in that the cement kiln is cylindrical, and when the circular cross-section of the end on the kiln-bottom side is virtually divided into three equal parts in the circumferential direction with respect to the vertex in the vertical direction, the virtual extensions of the central axes of the first raw material chute and the second raw material chute intersect the fan-shaped region located below in the vertical direction.

7. The exhaust passage has an inclined portion between the tail end of the cement kiln and the first side surface, with an angle of 30° to 60° with respect to the horizontal direction. With respect to the vertical direction, the distance between the upper end of the inclined portion and the lower end of the first supply port to which the first raw material chute is connected on the first side surface, and the distance between the upper end of the inclined portion and the lower end of the second supply port to which the second raw material chute is connected on the first side surface, are both 3 m or less, as described in any one of claims 1 to 5.

8. With respect to the vertical direction, the distance between the center of the extraction port to which the extraction probe is connected and the exhaust flow path, and the distance between the center of the first supply port to which the first raw material chute is connected and the first side surface, and the distance between the center of the extraction port to the center of the second supply port to which the second raw material chute is connected and the first side surface, are both 3 m or less, as described in any one of claims 1 to 5.

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