Rotary kiln base plate assembly

Abstract

To provide rotary kiln bottom board assemblies which can suppress the problems of wear and thrust blocking material falling.SOLUTION: Provided are plural bottom board assemblies 10 provided at equal intervals in a circumferential direction in a clearance part between a furnace body 1 and a tire 2 in a rotary kiln. Each comprises: an almost rectangular bottom plate 11; a pair of prismatic thrust blocking materials 12 welded to the surface of the bottom board 11; a pair of almost L-shaped reinforcing materials 13 respectively erected from the longitudinal both end parts of the bottom board 11 to join the longitudinal center parts of the pair of thrust blocking materials 12; four bottom plate stoppers 14 respectively welded to the close positions of the four corner parts of the bottom board 11 in the outer circumferential face of the furnace body 1; and four holding members 15 respectively erected from the four bottom board stoppers 14 and capable of respectively abutting on a face opposite to a facing face of the tire 2 in both end parts of the pair of thrust blocking materials 12.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a lining assembly for a rotary kiln.

Background Art

[0002] A rotary kiln having a structure in which a cylindrical furnace body is horizontally supported rotatably can heat-treat a large amount of powdery or granular workpieces at a relatively low cost. Therefore, it is widely used in various industrial fields such as the non-ferrous metal industry, cement industry, chemical industry, waste treatment industry, etc. For example, a rotary kiln is used in the Waelz kiln method for recovering low-boiling-point metals represented by zinc from iron-based wastes such as electric furnace dust, steel dust, zinc plating sludge, cupola dust, etc.

[0003] In the above Waelz kiln method, iron-based wastes containing zinc charged into a rotary kiln are subjected to reduction roasting treatment in a high-temperature reducing atmosphere of about 1000 to 1500°C. At this time, zinc vapor generated by reduction volatilization from zinc oxides contained in the iron-based wastes is re-oxidized to produce fine powdery zinc oxide. The generated fine powdery zinc oxide is discharged from the rotary kiln together with exhaust gas, and thus can be recovered in a dust collector or the like as crude zinc oxide dust. Incidentally, after impurities such as halogens are removed from the recovered crude zinc oxide dust in a wet refining process, it is calcined in a drying and heating kiln to produce crude zinc oxide sinter ore as a raw material for zinc smelting.

[0004] Like the rotary kiln used in the above Waelz kiln method, a large-scale rotary kiln used on an industrial scale generally has an outer diameter of about several meters and a length of about several tens of meters for the cylindrical furnace body (also referred to as a shell). Therefore, annular bodies called tires are provided coaxially at at least both ends in the axial direction on the outer peripheral portion of the furnace body, and each tire is rotatably supported by two receiving rollers.

[0005] A circular gear called a girth gear is further provided on the outer circumference of the furnace body in a concentric manner. A motor-driven pinion gear meshes with this girth gear, causing the furnace body to rotate at a rotational speed of approximately 0.1 to 2 rpm during operation. Since the axis of the furnace body is slightly tilted from the horizontal, the material to be processed, which is placed into the furnace from one end, is gradually moved toward the other end while being agitated as the furnace body rotates, and is heat-treated by the combustion gas from a burner located at the other end.

[0006] As described above, the heat treatment of the workpiece is performed at high temperatures inside the rotary kiln, so the temperature of the kiln body becomes higher than that of the tires, creating a difference in thermal expansion between the tires and the kiln body. To prevent the rotary kiln from being damaged by thermal stress caused by this difference in thermal expansion, the rotary kiln is manufactured so that the outer diameter of the kiln body is smaller than the inner diameter of the tires, and multiple roughly rectangular plate-shaped base plates (also called liners or washers) are inserted into the gap between the outer surface of the kiln body and the inner surface of the tires at equal intervals in the circumferential direction of the kiln body.

[0007] For example, Patent Document 1 discloses a method for arranging multiple liners at approximately equal intervals around the entire circumference of a rotary kiln in the gap between the outer circumference of the kiln body and the inner circumference of a tire fitted onto the outer circumference. Furthermore, to prevent the tire from moving in the axial direction of the rotary kiln, metal thrust stoppers are provided on the surface of the liners. In addition, a technique is disclosed for connecting these thrust stoppers and the liners with retaining hardware to prevent the thrust stoppers from lifting up or tilting away from the liners. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Official Gazette No. 49-024593 [Overview of the project] [Problems that the invention aims to solve]

[0009] The base plate, which is placed in the gap between the outer surface of the furnace body and the inner surface of the tire of the rotary kiln described above, may be joined to the outer surface of the furnace body by welding or other means. In this case, depending on the heat treatment conditions, thermal stress may occur due to the temperature difference between the furnace body and the base plate, causing the base plate to deform. Therefore, a technique has been adopted in which a roughly rectangular base plate is not joined to the furnace body, but instead base plate stoppers are installed at positions close to each of the four corners of the base plate on the outer surface of the furnace body, defining the sliding area of ​​the base plate along the outer surface of the furnace body. As a result, even if a temperature difference occurs between the furnace body and the base plate, the base plate can slide within a limited range on the outer surface of the furnace body, making it possible to prevent thermal stress from being applied to the base plate.

[0010] Incidentally, in a rotary kiln equipped with the above-mentioned base plate, a small gap is maintained between the inner surface of the tire and the surface of the base plate opposite it, so as not to impose thermal stress on them when a difference in thermal expansion occurs due to the temperature difference between the furnace body and the tire. For this reason, the tire and the furnace body may rotate with a slight misalignment in the circumferential direction. Also, as mentioned above, the furnace body of the rotary kiln is supported so as to be rotatable with its axis slightly tilted from the horizontal, so the furnace body may move slightly relative to the tire in its axial direction (also called the thrust direction) during rotation. Therefore, to prevent the tire from protruding from the longitudinal end of the base plate, for example, a prismatic thrust-blocking member is attached to the surface of the base plate by fillet welding.

[0011] As mentioned above, in a rotary kiln, the furnace body and the tires rotate with a slight offset from each other in the circumferential direction. Therefore, when the tires move relative to the furnace body in the thrust direction and their sides come into contact with the thrust stopper, the sides of the tires and the opposing sides of the thrust stopper rotate while sliding against each other. As a result, problems such as significant wear on one or both of these parts, or the thrust stopper falling off the base plate, can occur. The present invention has been made in view of the above problems of rotary kilns, and aims to provide a base plate assembly that can suppress the above problems of wear and the detachment of the thrust stopper that occur when the tires move relative to the furnace body of a rotary kiln in the thrust direction and their sides come into contact with the sides of the thrust stopper, and these tires and thrust stoppers rotate while sliding against each other. [Means for solving the problem]

[0012] To achieve the above objective, the rotary kiln base plate assembly according to the present invention is a plurality of iron base plate assemblies provided at equal intervals in the circumferential direction of the furnace body in the gap between the outer circumferential surface of the furnace body of the rotary kiln and the inner circumferential surface of tires provided concentrically at at least both ends in the axial direction of the furnace body, wherein each of the plurality of base plate assemblies is a substantially rectangular plate-shaped base plate inserted into the gap with both ends protruding from both sides of the tires, and the surface of the base plate faces each other with the tires in between. The furnace body is characterized by comprising: a pair of welded rectangular prism-shaped thrust-blocking members; a pair of substantially L-shaped reinforcing members erected from both longitudinal ends of the base plate and joined to the longitudinal center of the pair of thrust-blocking members; four base plate stoppers welded to the outer circumferential surface of the furnace body at positions close to the four corners of the base plate; and four pressing members erected from the four base plate stoppers and capable of contacting only the surfaces of the pair of thrust-blocking members opposite to the opposing surfaces of the tires at both ends. [Effects of the Invention]

[0013] According to the present invention, even if the tires move relative to the furnace body of the rotary kiln in the thrust direction and their sides come into contact with the sides of the thrust stoppers of the base plate assembly, it is possible to suppress the rotation of these tires and thrust stoppers while sliding against each other, thereby suppressing problems such as wear of these tires and thrust stoppers or the detachment of the thrust stoppers. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic side view of a rotary kiln in which the base plate assembly of the present invention is preferably provided. [Figure 2] This is a cross-sectional view of the rotary kiln shown in Figure 1, taken from the line II-II. [Figure 3] This is a partial perspective view of the rotary kiln in Figure 1, showing the portion equipped with tires. [Figure 4] Figure 1 is a partial perspective view of a base plate assembly according to an embodiment of the present invention, which is provided in the gap between the outer circumferential surface of the furnace body of the rotary kiln and the inner circumferential surface of the tire. [Figure 5] Figure 4 is a plan view of the base plate assembly. [Figure 6] This is a partial side view of a conventional base plate assembly. [Figure 7] These are a partial plan view and a partial side view of a base plate assembly according to an embodiment of the present invention. [Figure 8] This is a modified example of the rotary kiln base plate assembly of the present invention. [Figure 9] This is a modified example of the retaining member provided in the base plate assembly of an embodiment of the present invention. [Modes for carrying out the invention]

[0015] First, regarding a specific example of a rotary kiln in which the floorboard assembly of the embodiment of the present invention is preferably provided, taking the case of producing crude zinc oxide by treating about 180 to 240 tons of steel dust containing zinc with a melting point of about 1000 to 1100 °C per day by the Waelz kiln method as an example, it will be described while referring to FIG. 1. The rotary kiln shown in FIG. 1 is composed of a furnace body 1 having a structure in which a cylindrical body with an inner wall surface lined with a refractory material such as refractory bricks is placed horizontally. Two tires 2 are provided on the outer peripheral portion thereof at intervals in the axial direction. Each of these two tires 2 is rotatably supported by two receiving rollers 3.

[0016] At positions facing the side surfaces of each of the above two tires 2, frustum-shaped thrust rollers 4 having a rotation axis in a direction orthogonal to the central axis O of the furnace body 1 are provided. By these thrust rollers 4, the position of the furnace body 1 is controlled so as not to deviate from a predetermined range in the direction of its central axis O. Further, between the above two tires 2 on the outer peripheral portion of the above furnace body 1, a substantially annular girth gear 5 is provided concentrically with the furnace body 1, and a motor-driven pinion gear 6 meshes with this girth gear 5.

[0017] With the above configuration, the steel dust of the raw material charged into the furnace body 1 together with a reducing agent such as coke from the charging port 7 of the rotary kiln provided on the charging end side on the left side of the paper surface rotates with the girth gear 4 rotated by the pinion gear 6 and gradually moves toward the discharge end side on the right side of the paper surface while being agitated inside the furnace body 1. At that time, the steel dust is reductively roasted by a high-temperature atmosphere preferably at about 1000 to 1400 °C, more preferably at about 1100 to 1200 °C generated by the combustion of the fuel and the reducing agent in the burner 8 on the discharge end side of the furnace body 1.

[0018] During the reduction roasting of the above-mentioned steel dust, the zinc vapor generated by volatilization is oxidized by oxygen in the gas phase to become fine powder-like crude zinc oxide. This fine powder of crude zinc oxide is discharged from the charging end of the furnace body 1 together with the exhaust gas through the duct 9, and is recovered as crude zinc oxide dust in an electric dust collector (not shown). On the other hand, the residue remaining in the furnace body 1 of the rotary kiln after the reduction roasting of the above-mentioned steel dust is discharged as clinker from the discharge end of the furnace body 1 of the rotary kiln.

[0019] As described above, since heat treatment is performed on the workpiece at a high temperature exceeding 1000°C in the furnace body 1 of the rotary kiln, in order to prevent damage caused by the thermal expansion difference between the furnace body 1 and the tire 2 resulting therefrom, the inner diameter of the tire 2 is made larger than the outer diameter of the furnace body 1. In order to maintain the furnace body 1 and the tire 2 in a coaxial state, a plurality of iron floor plate assemblies 10 are provided at equal intervals in the circumferential direction of the furnace body 1 as shown in FIGS. 2 and 3 in the gap therebetween. Although FIG. 2 shows an example in which 16 floor plate assemblies 10 are provided at equal intervals in the circumferential direction, the number of floor plate assemblies 10 is not limited thereto.

[0020] Each of the above-described base plate assemblies 10 includes, as shown in Figures 4 and 5, a roughly rectangular iron base plate 11, for example, 550-850 mm in length, 200-350 mm in width, and 25-40 mm in thickness, which is inserted into the gap so as to protrude from both sides in the width direction of the tire 2; a pair of parallel iron rectangular prism-shaped thrust prevention members 12, each having a rectangular cross-section, for example, 25-40 mm in length and 25-40 mm in width, and a length approximately 0.7-1.0 times the width direction of the base plate 11, welded to the surface of the base plate 11 so as to face each other with the tire 2 in between; and, to prevent these thrust prevention members 12 from lifting up or falling off the base plate 11, they are erected from both ends in the longitudinal direction of the surface of the base plate 11 and welded to the longitudinal center of the pair of thrust prevention members 12. It consists of a pair of roughly L-shaped iron reinforcing members 13, for example, 100-160 mm in height, 120-180 mm in length, and 25-40 mm in thickness; four roughly L-shaped iron base plate stoppers 14, welded to adjacent positions at each of the four corners of the outer circumferential surface of the furnace body 1 when the base plate 11 is viewed from above, in order to define the sliding area of ​​the base plate 11 along the outer circumferential surface of the furnace body 1; and a roughly L-shaped iron pressing member 15, which is erected from each of the surfaces of these four base plate stoppers 14 and contacts only the non-facing surface 12b opposite to the surface 12a facing the side 2a of the tire 2 at the end of the thrust blocking member 12 that is closest to it, for example, 40-60 mm in vertical length and 15-25 mm in horizontal length, with an overall length of 70-110 mm and a thickness of 15-25 mm.

[0021] With this configuration, when the tire 2 moves relative to the furnace body 1 in the thrust direction and its side surface 2a comes into contact with the opposing surface 12a of the thrust stopper 12, the retaining member 15 is in contact with the non-opposing surface 12b of the thrust stopper 12 opposite to the opposing surface 12a, thus preventing the tire 2 from moving further relative to the thrust direction. As a result, the tire 2 and the base plate 11 can be rotated together, greatly reducing the frequency of sliding between the tire 2 and the thrust stopper 12 during the rotation of the rotary kiln. Consequently, wear on the tire 2 and thrust stopper 12, and the thrust stopper 12 falling off the base plate 11 can be suppressed.

[0022] In other words, in a conventional rotary kiln base plate assembly 110, as shown in Figure 6, the tire 2 moves gradually in the thrust direction from position A, where it is separated from the thrust stopper 112, until it reaches position B, where it contacts the surface 112a of the thrust stopper 112 that is opposite to the side surface 2a of the tire 2. However, since the thrust stopper 112 does not have a retaining member that contacts the non-facing surface 112b opposite to the surface 112a of the tire 2, the tire 2 continues to move further in the thrust direction together with the base plate 111 until it reaches position C, where the end surface of the base plate 111 contacts the base plate stopper 14. During this time, the tire 2 rotates while sliding its side surface 2a against the opposing surface 112a of the thrust stopper 112. As a result, the side of the weld between the thrust-blocking material 112 and the base plate 111 that faces the tire 2 (112a) thinned due to wear, and eventually the thrust-blocking material 112 would lift up or fall off from the base plate 111, as shown by the dashed line.

[0023] In contrast, the base plate assembly 10 of the embodiment of the present invention, as shown in Figures 7(a) and (b), is provided with a pressing member 15 that contacts the non-facing surface 12b of the thrust blocking member 12 when the tire 2 moves little by little in the thrust direction from position A, where it is separated from the thrust blocking member 12, to position B, where it contacts the thrust blocking member 12. Therefore, even if the tire 2 pushes the thrust blocking member 12, the pressing member 15 pushes back against the thrust blocking member 12 in the opposite direction to the pushing direction. This prevents the thrust blocking member 12 from lifting off the base plate 11 even if the welded portion on the tire 2 side of the thrust blocking member 12 thins due to wear.

[0024] Furthermore, since the contact surface area of ​​the tip of the pressing member 15 is smaller than the contact surface area of ​​the end face of the base plate 11 that contacts the base plate stopper 14 mentioned above, the pressing member 15 can be firmly contacted with the non-facing surface 12b of the thrust blocking member 12 with respect to the tire 2 using the contact surface of its tip. As a result, as mentioned above, the tire 2 and the base plate 11 can be rotated together to some extent, so that the frequency of the side surface 2a of the tire 2 sliding against the surface 12a of the thrust blocking member 12 with respect to the tire 2 while rotating is reduced compared to conventional base plate assemblies. When the side surface 2a of the tire 2 contacts the thrust blocking member 12 and the rotary kiln reaches the upper limit position in one axial direction, it contacts the thrust roller 5 which is provided on the underside of the furnace body 1 of the rotary kiln so as to be perpendicular to the rotation axis of the furnace body 1. By rotating this thrust roller, the thrust force on the tire 2 can be mitigated.

[0025] Although embodiments of the base plate assembly 10 of the present invention have been described above, the base plate assembly of the present invention is not limited to the above embodiments, and various modifications and alternatives can be included without departing from the spirit of the present invention. For example, the base plate stopper that restricts the free sliding of the base plate along the outer surface of the furnace body 1 is not limited to the substantially L-shaped one shown in Figure 5, but as shown in Figure 8, a first base plate stopper 24a and a second base plate stopper 24b may be welded to each of the four corners of the outer surface of the furnace body 1 when the base plate 11 is viewed from above, at positions facing the longitudinal end face and the widthwise end face of the base plate 11, respectively, to restrict the movement of the base plate 11 in the longitudinal and widthwise directions. In this case, one push member 15 will be provided for each first base plate stopper 24a.

[0026] Furthermore, in both the roughly L-shaped base plate stopper 14 shown in Figure 5 and the first base plate stopper 24a shown in Figure 8, by providing one pressing member 15 to each stopper, it is possible to attach a pressing member 15 with sufficient thickness to prevent the movement of the tires 2 in the thrust direction of the furnace body 1, while securing working space for inspection and maintenance work on each component of the base plate assembly, even in the installation location of the base plate assembly where space is limited.

[0027] Furthermore, in the base plate assembly 10 of the embodiment of the present invention, as shown in Figure 9, it is preferable to provide a contact member 26, for example, in the columnar or substantially rectangular parallelepiped shape, at the contact portion with the thrust blocking material 12 at the tip of the pressing member 25. This makes it possible to simplify inspection and maintenance work of the base plate assembly by providing a contact member 26 made of, for example, a high-hardness material at the contact portion with the thrust blocking material 12, which is most susceptible to wear due to sliding contact, or by making the contact member 26 detachable from the pressing member 25. [Explanation of Symbols]

[0028] 1. Furnace shell 1a Fireproof material 2 tires 2a Tire side 3. Receiving roller 4 Thrust Rollers 5 Garth Gear 6 pinion gear 7 Charging port 8 burners 9 ducts O center axis 10, 110 base plate assembly 11, 111 Floor plate 12, 112 Thrust blockers 12a, 112a Opposite side 12b, 112b Non-opposing surface 13 Reinforcement 14, 24, 114 Base plate stopper 24a First base plate stopper 24b Second base plate stopper 15, 25 Retaining member 26 Contact Member

Claims

1. A rotary kiln base plate assembly characterized in that, in the gap between the outer surface of the furnace body of a rotary kiln and the inner surface of tires provided concentrically at at least both ends of the furnace body in the axial direction, a plurality of iron base plate assemblies are provided at equal intervals in the circumferential direction of the furnace body, each of the plurality of base plate assemblies comprises a substantially rectangular plate-shaped base plate inserted into the gap with both ends protruding from both sides of the tires, a pair of prismatic thrust-blocking members welded to the surface of the base plate so as to face each other with the tires in between, a pair of substantially L-shaped reinforcing members erected from both longitudinal ends of the base plate and joined to the longitudinal center of the pair of thrust-blocking members, respectively, four base plate stoppers welded to the outer surface of the furnace body at positions close to the four corners of the base plate, and four pressing members erected from the four base plate stoppers so as to contact only the surfaces of the pair of thrust-blocking members opposite to the opposing surfaces of the tires at both ends.

2. The rotary kiln base plate assembly according to claim 1, characterized in that each of the four base plate stoppers has a substantially L-shape in plan view so as to face the longitudinal end face and the widthwise end face of the base plate that constitute the corner closest to it.

3. The rotary kiln base plate assembly according to claim 1 or 2, characterized in that the pressing member has a contact member attached to its contact end.

Images