Power spreading device for cement kiln and cement kiln using the same

Abstract

The present invention provides a power spreading device for a cement kiln and a cement kiln using the same, which relates to the field of cement kiln equipment and solves the problems of uneven preheating of materials and easy "short circuit" in the prior art. The power spreading device includes a spreading box with an opening on the front side and a discharge port on the upper part. Two groups of spreading discs with power devices are installed inside the spreading box. The two groups of spreading discs are relatively distributed left and right. The spreading discs can rotate around their central axes. The two groups of spreading discs are located below the discharge port of the spreading box to receive materials and can throw the materials toward the opening of the spreading box. The cement kiln adopts a power spreading device, which has a high heat exchange rate between materials and hot gas, and can avoid the problem of "short circuit" of materials, can make the materials very evenly dispersed, well cover the high-temperature gas flow, and achieve full mixing and contact between low-temperature materials and high-temperature gas, thereby greatly improving the heat exchange efficiency of the system.

Description

Technical Field

[0001] The invention relates to the field of cement kiln equipment, in particular to a power material spreading device for a cement kiln and a cement kiln using the power material spreading device. Background Art

[0002] In the new dry-process off-kiln decomposition cement kiln, which is the most common in the world, the material preheating and decomposition system composed of a multi-stage cyclone and a decomposition furnace is widely used for the rapid preheating and decomposition of low-temperature materials. The material flow direction is: low-temperature material feeding point - first-level cyclone - second-level cyclone - third-level cyclone - fourth-level cyclone - decomposition furnace - fifth-level cyclone - rotary kiln, and the high-temperature gas flow direction is: rotary kiln + tertiary air duct - decomposition furnace - fifth-level cyclone - fourth-level cyclone - third-level cyclone - second-level cyclone - first-level cyclone - discharge preheater system.

[0003] The spreading devices used in the new dry process cement kiln preheater and the calciner are all static spreading boxes. Under the action of gravity, the low-temperature material flows down rapidly along the discharge pipe, impacts the bottom of the spreading box, and splashes towards the high-temperature air duct after being impacted. After falling into the high-temperature air duct, it meets the high-temperature gas that rises rapidly in the air duct. The material is lifted up by the high-temperature gas that rises rapidly and changes its direction of movement, and moves in the same direction as the high-temperature gas flow. In this process, the material gradually mixes with the high-temperature gas and contacts each other, realizing the process of transferring the heat carried by the high-temperature gas to the low-temperature material, achieving the purpose of preheating the material and reducing the gas temperature at the same time. However, this type of spreading device has poor material flow control ability and no effective control over the material. The material is completely dispersed by natural flow, falling and splashing. It is difficult to ensure that the material is fully and evenly dispersed and fully contacts with the hot gas flow for heat exchange. The uneven mixing of the low-temperature material and the high-temperature gas leads to low heat exchange efficiency of the system.

[0004] In addition, since the strands of material rush down under the action of gravity at a fast speed and with great force, it is difficult to suspend all the material by the high-temperature gas. As a result, part of the material often collapses directly, causing the so-called material "short circuit", resulting in the entire cement kiln system being unable to produce normally. Summary of the invention

[0005] The purpose of the present invention is to design a power spreading device for a cement kiln and a cement kiln using the power spreading device. The power spreading device can disperse the material very evenly, cover the high-temperature gas flow well, and achieve full mixing and contact between the low-temperature material and the high-temperature gas, thereby greatly improving the heat exchange efficiency of the system.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention provides a power spreading device for a cement kiln, comprising a spreading box with an opening on the front side and a discharge port on the upper part, two groups of spreading discs with a power device are installed on the inner side of the spreading box, the two groups of spreading discs are relatively distributed left and right, the spreading discs can rotate around their central axes, the two groups of spreading discs are located below the discharge port of the spreading box for receiving materials and can scatter the materials toward the opening of the spreading box.

[0008] When the above-mentioned structure is used, two sets of scattering discs are added to the existing scattering box. Both sets of scattering discs have a power device that can drive them to rotate around the rotating axis. When the material rushes out from the discharge port and hits the scattering disc, the rotating scattering disc provides the material with a friction force toward the opening of the scattering box or the side wall of the scattering box. The powdered material in the stream will be driven by the scattering disc and squeezed and collided with each other and will splash more evenly toward the opening of the scattering box. The two sets of scattering discs are relatively distributed left and right in the scattering box to avoid the problem of eccentric scattering of materials in the outlet pipe of the cyclone, which will inevitably be caused by the use of a single set of scattering discs, so as to achieve the purpose of evenly dispersing the material, so that the material can cover the high-temperature gas flow more evenly, and achieve full mixing and contact between the low-temperature material and the high-temperature gas, greatly improving the heat exchange efficiency of the system.

[0009] In order to further better realize the present invention, the following setting structure is particularly adopted: the power device includes a motor and a transmission shaft connected to the motor shaft, and the transmission shaft passes through the material spreading box and is fixedly connected to the material spreading plate.

[0010] In order to better realize the present invention, the following structure is particularly adopted: the material spreading box is connected with a sealing sleeve, the transmission shaft is movably inserted into the sealing sleeve, the two ends of the sealing sleeve are provided with sealing glands which are sleeved on the transmission shaft, and the annular space between the sealing sleeve and the transmission shaft is provided with asbestos.

[0011] When the above-mentioned structure is adopted, the sealing sleeve and the matching sealing gland and asbestos are used to complete the sealing setting of the transmission shaft to ensure that the transmission shaft is not damaged by collision or friction of materials.

[0012] In order to further better realize the present invention, the following setting structure is particularly adopted: the material spreading plate is arranged horizontally, and the angle between the axis of the material spreading plate and the discharge port is 45-70°.

[0013] When the above-mentioned setting structure is adopted, when the angle between the axis of the spreading plate and the discharge port is 45-70°, the material has a better scattering effect after hitting the spreading plate.

[0014] In order to further better realize the present invention, the following setting structure is particularly adopted: the two groups of the spreading discs are relatively distributed up and down, the two groups of the spreading discs have an overlapping area, and the axis of the discharge port intersects with the overlapping area.

[0015] When the above-mentioned arrangement structure is adopted, the material will not completely pass through between the two sets of spreading discs, but will fall into the overlapping area and be thrown by the spreading discs to the opening of the spreading box.

[0016] In order to better realize the present invention, the following setting structure is particularly adopted: at least one spreading strip is fixed to the top surface of each group of the spreading discs, the proximal end of the spreading strip is arranged adjacent to the rotation center of the corresponding spreading disc, and the distal end of the spreading strip is arranged adjacent to the outer edge of the corresponding spreading disc.

[0017] When the above-mentioned setting structure is adopted, the spreading strip is used to forcibly spread the material to improve the spreading effect without causing excessive accumulation of material and the spreading plate.

[0018] In order to further better realize the present invention, the following setting structure is particularly adopted: when there are multiple spreading strips in each group of spreading discs, the spreading strips on the top surface of each group of spreading discs are equidistantly distributed around the circumference of the corresponding spreading disc.

[0019] In order to further better realize the present invention, the following setting structure is particularly adopted: the spreading plate is a flat plate or a concave plate, the concave curvature of the spreading strip is consistent with the concave curvature of the corresponding plate surface of the spreading plate, and the spreading strip is a straight plate-like member whose length direction coincides with the radial direction of the corresponding spreading plate or a curved plate-like member that does not coincide with the radial direction of the corresponding spreading plate.

[0020] In order to better realize the present invention, the following configuration structure is particularly adopted: the height of the spreading strip is less than or equal to 5 cm.

[0021] The present invention also provides a cement kiln, comprising a cyclone outlet pipe, a cyclone main body, a discharge pipe and the above-mentioned powered material spreading device, wherein the cyclone outlet pipe is connected to the air outlet end of the cyclone main body, the material spreading box is fixed to the outer wall of the cyclone outlet pipe, the material spreading box is connected to the interior of the cyclone outlet pipe at its opening, and the discharge pipe is fixedly connected to the discharge port of the material spreading box.

[0022] When the above-mentioned structure is adopted, by adopting a power spreading device, the cement kiln uses a self-powered spreading plate to force and evenly spread the material from the feeding pipe into the cyclone outlet pipe at the material preheating stage, so that the material completely covers the high-temperature gas flow, and achieves full contact and mixed contact between the material and the airflow, which improves the heat exchange between the material and the airflow, and can improve the heat exchange efficiency of the preheater and decomposition furnace system in the cement kiln. In addition, since the material is fully and evenly dispersed, the "short circuit" of the material caused by the downward rush of the stranded material will be avoided, ensuring the normal production of the cement kiln system.

[0023] In order to better realize the present invention, the following setting structure is particularly adopted: the rotation directions of the two groups of spreading discs are opposite, and the linear speed direction of the two groups of spreading discs adjacent to each other points to the opening of the spreading box.

[0024] The present invention has the following advantages and beneficial effects:

[0025] In the present invention, the power spreading device adds two sets of spreading discs in the existing spreading box. Both sets of spreading discs have a power device that can drive them to rotate around the rotating shaft. When the material rushes out from the discharge port and hits the spreading disc, the rotating spreading disc provides the material with a friction force toward the opening of the spreading box or the side wall of the spreading box. The powdered material in the stream will splash more evenly toward the opening of the spreading box through the driving of the spreading disc and the mutual squeezing and collision. The two sets of spreading discs are relatively distributed left and right in the spreading box to avoid the problem of eccentric scattering of materials in the outlet pipe of the cyclone, which will inevitably result from the use of a single set of spreading discs, so as to achieve the purpose of evenly dispersing the material, so that the material can cover the high-temperature gas flow more evenly, and achieve full mixing and contact between the low-temperature material and the high-temperature gas, greatly improving the heat exchange efficiency of the system.

[0026] By adopting a power spreading device, the cement kiln uses a self-powered spreading plate to force and evenly spread the material from the feeding pipe into the cyclone outlet pipe at the material preheating stage, so that the material completely covers the high-temperature gas flow, achieving full contact and mixed contact between the material and the airflow, improving the heat exchange between the material and the airflow, and improving the heat exchange efficiency of the preheater and decomposition furnace system in the cement kiln. In addition, since the material is fully and evenly dispersed, it will also avoid the "short circuit" of the material caused by the downward rush of the stranded material, ensuring the normal production of the cement kiln system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is the front view of the power spreading device for cement kiln;

[0029] Figure 2 yes Figure 1 A-direction cross-sectional structural diagram;

[0030] Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure in the B direction;

[0031] Figure 4It is a schematic diagram of the structure of the part of the cement kiln that uses a powered material spreading device;

[0032] Figure 5 This is a general schematic diagram of the installation position of the power spreading box in the cyclone in the cement kiln;

[0033] Figure 6 This is a schematic diagram of the structure of a spreading disc with a concave conical disc;

[0034] Figure 7 This is a schematic diagram of the structure of a spreading disc that is a concave arc disc;

[0035] Figure 8 This is a schematic diagram of the structure of a spreading strip for a curved plate-like member;

[0036] The markings in the figure are:

[0037] 1-feeding pipe; 2-spreading box; 3-spreading plate; 4-transmission shaft; 5-sealing cover; 6-sealing sleeve; 7-asbestos; 9-bearing seat; 10-coupling; 11-bracket; 12-motor; 13-overlapping area; 14-spreading bar; 15-cyclone outlet pipe; 16-cyclone body; 17-cyclone discharge pipe. DETAILED DESCRIPTION

[0038] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0039] Embodiment 1:

[0040] A power spreading device for cement kiln can make the material dispersed very evenly, cover the high-temperature gas flow well, realize the full mixing and contact of low-temperature material and high-temperature gas, thereby greatly improving the heat exchange efficiency of the system. Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, it is particularly configured as follows:

[0041] It includes a material spreading box 2, the front side of which forms an opening, and the upper part has a discharge port for connecting to the discharge pipe 1 for discharging materials. The opening of the material spreading box 2 is used to be fixed to the side wall of the cyclone outlet pipe 15 and communicate with the interior of the cyclone outlet pipe 15 to pass the material scattered by the material spreading plate 3.

[0042] Two sets of material spreading discs 3 are installed inside the material spreading box 2, and each set of material spreading discs 3 is connected to a power device through a connecting piece, and the power device can drive the material spreading discs 3 to rotate around its central axis. The two sets of material spreading discs 3 are relatively distributed on the left and right sides of the material spreading box 2. The two sets of material spreading discs 3 are located below the material discharge port of the material spreading box 2 for receiving materials. The material spreading discs 3 can rebound the materials during the static process. In addition to rebounding the materials, the material spreading discs 3 can also give the materials friction during the rotation process so that the materials are thrown toward the opening of the material spreading box 2.

[0043] Specifically, the power device includes a motor 12 and a transmission shaft 4. The motor 12 is arranged outside the material spreading box 2, the transmission shaft 4 is arranged vertically, the motor 12 is fixed to the frame 11, the transmission shaft 4 is provided with a bearing and assembled with a bearing seat 9 arranged at the frame 11, the bottom end of the transmission shaft 4 is connected to the motor 12 through a coupling 10, and the top end of the transmission shaft 4 passes through the material spreading box 2 and is fixedly connected to the material spreading plate 3. Among them, the motor 12 is a variable frequency motor with adjustable speed, and the motor 12 must be installed and debugged on site in each factory to determine the optimal speed.

[0044] In order to protect the transmission shaft 4, the material spreading box 2 is plugged with a vertically arranged sealing sleeve 6, the transmission shaft 4 is movably inserted into the sealing sleeve 6, an annulus is formed between the transmission shaft 4 and the sealing sleeve 6, the two ends of the sealing sleeve 6 are fixed with sealing glands 5 by bolts, the sealing glands 5 are sleeved on the transmission shaft 4, and the annulus between the sealing sleeve 6 and the transmission shaft 4 is provided with asbestos 7, and the sealing glands 5 squeeze the asbestos 7 from both ends to achieve sealing. The sealing sleeve 6 and the matching sealing glands 5 and asbestos 7 are used to complete the sealing setting of the transmission shaft to ensure that the transmission shaft is not damaged by collision or friction of materials.

[0045] When the above-mentioned structure is adopted, two groups of scattering discs 3 are added to the existing scattering box 2. Both groups of scattering discs 3 have a power device that can drive them to rotate around the rotating axis. When the material rushes out from the discharge port and hits the scattering disc 3, the rotating scattering disc 2 provides the material with a friction force toward the opening of the scattering box 2 or the side wall of the scattering box 2. The powdered material from the discharge pipe will be driven by the scattering disc 2 and the mutual extrusion and collision will splash more evenly toward the opening of the scattering box 2. The two groups of scattering discs 3 are relatively distributed left and right in the scattering box 2 to avoid the problem of eccentric scattering of materials in the cyclone outlet pipe 15 that will inevitably result from the use of a single group of scattering discs 3, so as to achieve the purpose of evenly dispersing the material, so that the material can more evenly cover the high-temperature gas flow, achieve full mixing and contact between the low-temperature material and the high-temperature gas, and greatly improve the heat exchange efficiency of the system.

[0046] Among them, the scattering plate 3 is preferably set horizontally, and the axial angle between the scattering plate 3 and the discharge port is 45-70°. When the axial angle between the scattering plate 3 and the discharge port is 45-70°, the material has a better scattering effect after hitting the scattering plate 3, but the optimal angle is 60°.

[0047] Embodiment 2:

[0048] This embodiment is further optimized on the basis of the above embodiment, and further adopts the following configuration structure in order to better realize the present invention:

[0049] The two groups of material spreading discs 3 are staggered relative to each other up and down, and the two groups of material spreading discs 3 have an overlapping area 13 in the vertical direction. Figure 3 The closed figure in the dotted line frame is the overlapping area 13, and the axis of the discharge port intersects with the overlapping area 13. In this way, the material will not pass completely between the two sets of scattering discs 3, but will fall into the overlapping area 13 and be thrown to the opening of the scattering box 2 by the scattering discs 3.

[0050] Embodiment 3:

[0051] This embodiment is further optimized on the basis of the above embodiment, and further adopts the following configuration structure in order to better realize the present invention:

[0052] The top surface of each group of scattering discs 3 is provided with at least one scattering strip 14, which is a straight strip plate, the bottom surface of which is connected to the disc surface of the scattering disc 3 and welded and fixed to the top surface of the scattering disc 3, and the length direction of the scattering strip 14 is consistent with the radial direction of the corresponding scattering disc 3. The scattering strip 14 is used to forcibly scatter materials to improve the scattering effect without causing excessive accumulation of materials on the scattering disc 3.

[0053] When there are multiple spreading strips 14 in each group of spreading trays 3, the spreading strips 14 on the top surface of each group of spreading trays 3 are equally spaced around the circumference of the corresponding spreading tray 3. For example, when there are twelve spreading strips 14 welded on the top surface of each group of spreading trays 3, the twelve spreading strips 14 are equally distributed at 30° around the rotating axis of the corresponding spreading tray. The height of the spreading strips 3 is less than or equal to 5 cm, such as 3 cm or 2 cm.

[0054] Regarding the structure of the spreading plate 3, Figure 1 , Figure 6 , Figure 7 As shown, the material spreading disc 3 can be a flat disc or a concave disc, and the concave disc can be an arc-shaped disc with a concave middle portion or a concave cone-shaped disc with a concave middle portion. When the material spreading disc 3 is a concave disc, the concave curvature of the material spreading strip 14 is consistent with the concave curvature of the disc surface of the corresponding material spreading disc 3. For example, when the material spreading disc 3 is a concave concave cone-shaped disc, the material spreading strip 14 is a straight strip-shaped plate member consistent with the inclination of the disc surface. When the material spreading disc 3 is a concave arc-shaped disc, the material spreading strip 14 is a concave arc-shaped straight strip-shaped plate member consistent with the curvature of the disc surface.

[0055] Regarding the structure of the spreading strip 14, Figure 3 , Figure 8As shown, the spreading strip 14 can be a straight plate-like member or a curved plate-like member. For example, the spreading strip 14 can be a straight plate-like member whose length direction coincides with the radial direction of the corresponding spreading disc 3, or it can be a curved plate-like member which does not coincide with the radial direction of the corresponding spreading disc 3. When the spreading strip 14 is a curved plate-like member, the bending direction of the spreading strip 14 matches the rotation direction of the spreading disc 3.

[0056] Embodiment 4:

[0057] This embodiment provides a cement kiln based on the above embodiment, and particularly adopts the following setting structure:

[0058] The cement kiln comprises a cyclone outlet pipe 15, a cyclone body 16, a discharge pipe 1 and the power spreading device in Example 3. The cyclone body 16 has an air outlet at the top and a discharge port at the bottom. The cyclone outlet pipe 15 is vertically arranged and connected to the air outlet of the cyclone body 16. The discharge port at the bottom of the cyclone body 16 is connected to a cyclone discharge pipe 17. A spreading box 2 is welded or fixed to the outer wall of the cyclone outlet pipe 15 by screws. The spreading box 2 is connected to the inside of the cyclone outlet pipe 15 at its opening. The discharge port of the spreading box 2 adopts a flange structure to be fixedly connected to the discharge pipe 1 by screws. The discharge pipe 1 is coaxial with and connected to the discharge port. By adopting a power spreading device, the cement kiln uses a self-powered spreading plate to force and evenly spread the powdered material from the feeding pipe into the cyclone outlet pipe at the material preheating stage, so that the material completely covers the high-temperature gas flow, achieving full contact and mixed contact between the material and the airflow, improving the heat exchange between the material and the airflow, and improving the heat exchange efficiency of the preheater and decomposition furnace system in the cement kiln. In addition, since the material is fully and evenly dispersed, it will also avoid the "short circuit" of the material caused by the downward rush of the stranded material, ensuring the normal production of the cement kiln system.

[0059] When in use, the rotation directions of the two sets of spreading discs 3 should be opposite, and the linear speed directions of the adjacent parts of the two sets of spreading discs 3, i.e., the overlapping areas, should roughly point to the opening of the spreading box 2 so that the materials can be evenly scattered into the cyclone outlet pipe 15. Figure 3 The arrowed line in shows the rotation direction of the spreading plate 3.

[0060] The material enters the spreading box 2 through the discharge pipe 1, and the material falls onto the rotating spreading plate 3 in a stream, and is evenly scattered into the cyclone outlet pipe 15 by the spreading plate 3 and the spreading strips 14, and then mixed with the hot air flow in the cyclone outlet pipe 15 and moves upward with the hot air flow. After completing the heat exchange process in the upward process, the material-gas mixture is discharged from the cyclone outlet pipe 15 of the cyclone of this level.

[0061] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A power spreading device for cement kiln, characterized in that: The invention comprises a material spreading box (2) having an opening on the front side and a discharge port on the top, wherein two groups of material spreading discs (3) having a power device are installed inside the material spreading box (2), the two groups of material spreading discs (3) are relatively distributed left and right, the material spreading discs (3) can rotate around their central axes, the two groups of material spreading discs (3) are located below the discharge port of the material spreading box (2) for receiving materials and throwing the materials toward the opening of the material spreading box (2); the two groups of material spreading discs (3) are relatively distributed up and down, the two groups of material spreading discs (3) have an overlapping area (13), and the axis of the discharge port intersects with the overlapping area (13).

2. A power spreading device for cement kiln according to claim 1, characterized in that: The power device comprises a motor (12) and a transmission shaft (4) axially connected to the motor (12); the transmission shaft (4) passes through the material spreading box (2) and is fixedly connected to the material spreading plate (3).

3. A power spreading device for cement kiln according to claim 2, characterized in that: The material spreading box (2) is plugged with a sealing sleeve (6), the transmission shaft (4) is movably inserted into the sealing sleeve (6), both ends of the sealing sleeve (6) are provided with sealing glands (5) sleeved on the transmission shaft (4), and the annular space between the sealing sleeve (6) and the transmission shaft (4) is provided with asbestos (7).

4. The power spreading device for cement kiln according to claim 1, characterized in that: The material spreading plate (3) is arranged horizontally, and the angle between the axis of the material spreading plate (3) and the material discharge port is 45-70°.

5. A power spreading device for cement kiln according to any one of claims 1 to 4, characterized in that: At least one spreading strip (14) is fixed to the top surface of each group of the spreading discs (3), the proximal end of the spreading strip (14) is arranged adjacent to the rotation center of the corresponding spreading disc (3), and the distal end of the spreading strip (14) is arranged adjacent to the outer edge of the corresponding spreading disc (3).

6. A power spreading device for cement kiln according to claim 5, characterized in that: When there are a plurality of the spreading strips (14) in each group of the spreading discs (3), the spreading strips (14) on the top surface of each group of the spreading discs (3) are equidistantly distributed around the circumference of the corresponding spreading discs (3).

7. A power spreading device for cement kiln according to claim 6, characterized in that: The material spreading plate (3) is a flat plate or a concave plate, the concave curvature of the material spreading strip (14) is consistent with the concave curvature of the corresponding plate surface of the material spreading plate (3), and the material spreading strip (14) is a straight plate-like member whose length direction coincides with the radial direction of the corresponding material spreading plate (3) or a curved plate-like member that does not coincide with the radial direction of the corresponding material spreading plate (3).

8. A cement kiln, characterized in that: It comprises a cyclone outlet pipe (15), a cyclone main body (16), a feed pipe (1) and a powered material spreading device as described in any one of claims 1 to 7, wherein the cyclone outlet pipe (15) is connected to the air outlet end of the cyclone main body (16), the material spreading box (2) is fixed to the outer wall of the cyclone outlet pipe (15), the material spreading box (2) is connected to the interior of the cyclone outlet pipe (15) at its opening, and the feed pipe (1) is fixedly connected to the feed outlet of the material spreading box (2).

9. A cement kiln according to claim 8, characterized in that: The rotation directions of the two groups of material spreading discs (3) are opposite, and the direction of the linear speed of the two groups of material spreading discs (3) adjacent to each other points to the opening of the material spreading box (2).

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