JP4337272B2 - Hearth structure of rotary hearth furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hearth structure of a rotary hearth furnace, and more particularly to an improvement of the hearth structure of a rotary hearth furnace for reducing steelmaking dust pellets and the like.
[0002]
[Prior art]
In order to reuse steelmaking dust and fine ore, binder and reducing material are mixed into steelmaking dust and kneaded, and then granulated into raw pellets, which are supplied to a rotary hearth furnace for heating and heating. A heat treatment such as reduction is performed. An example is shown in FIG. The rotary hearth furnace 1 has concentric circular inner and outer peripheral walls 11 and 12, and a rectangular closed cross-section in-furnace space S is formed in an annular shape by the peripheral walls 11 and 12 and a bottom wall and a top wall (not shown). . On the bottom wall, a small gap is formed between the inner and outer peripheral walls 11 and 12, and the hearth 2 is positioned. The hearth 2 forms an annular shape along the inner space S and a drive mechanism (not shown). Is rotated in the direction of the arrow. The in-furnace space S of the rotary hearth furnace 1 is divided into a plurality of regions in the circumferential direction by curtain walls 31 to 35 provided at a plurality of positions in the circumferential direction. In the example shown in FIG. Each is divided into a supply / discharge chamber 41, a pre-tropical zone 42, a heating zone 43, an intermediate zone 44, and a reduction zone 45. The heating zone 43, the intermediate zone 44, and the reduction zone 45 are provided with the necessary number of burners 61 to 63 on the inner and outer peripheral walls 11 and 12, respectively.
[0003]
Spherical raw pellets P made of steelmaking dust or the like charged into the furnace from the charging port 51 are dropped onto the hearth 2 and leveled at the lower edge of the curtain wall 31 as the hearth 2 moves. Thus, the stack is placed almost uniformly on the entire upper surface of the hearth 2. The raw pellets P are transported to the pre-tropical zone 42 where they are heated at a low temperature of 600 ° C. or lower, and the internal moisture and gasification components are gradually evaporated and dried without causing explosion or the like. The dried pellet P is heated in the heating zone 43 and its temperature rises sufficiently, reaches the reduction zone 45 through the intermediate zone 44, and the pellet P contains the reducing atmosphere and the reducing material contained in the pellet P. Metal oxide is reduced to metal. The pellet P that has been subjected to the reduction process returns to the supply / discharge chamber 41 and is discharged out of the furnace from the discharge port 52 provided on the outer peripheral wall by the screw conveyor 53.
[0004]
[Problems to be solved by the invention]
By the way, in the rotary hearth furnace, if the inner and outer intermediate parts of the hearth are formed of a fire-resistant castable that can be easily molded, the fire-resistant castable layer may be expanded and deformed due to thermal expansion. As a countermeasure against this, it is conceivable to form a fixed gap for absorbing expansion deformation at an appropriate place in the refractory castable layer. However, if a sufficient gap size is to be secured, a small-diameter pellet penetrates into the gap. There was a possibility that the function of the expansion absorption could be hindered.
[0005]
Accordingly, the present invention solves such problems, and provides a hearth structure of a rotary hearth furnace that can effectively absorb the expansion of the hearth refractory castable layer and prevent its floating without being hindered by pellets. The purpose is to provide.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, the intermediate portion in the inner and outer directions of the annular rotary hearth (2) disposed between the inner peripheral wall (11) and the outer peripheral wall (12) is refractory. A plurality of refractory bricks (73, 74) are arranged in the inner and outer directions on at least one of the inner peripheral side and the outer peripheral side adjacent to the refractory castable layer (45). A gap (57, 58) serving as an expansion allowance for absorbing the expansion in the radial direction of the refractory castable layer (45) is formed between the rows of (73, 74) , and a plurality of refractory castable layers (45) are provided in the circumferential direction. A plurality of rows of refractory bricks (72) that form gaps (56) serving as expansion allowances for absorbing expansion of the refractory castable layer (45) in the circumferential direction are arranged in each divided portion.
[0007]
In the first invention, even if the size of the small-diameter pellets do not penetrate the gap between the rows of the refractory bricks arranged in the inner and outer direction at least one of the inner peripheral side and the outer peripheral side adjacent to the refractory castable layer , A sufficiently large expansion allowance can be ensured in the radial direction of the hearth as the sum of these gaps. As a result, the expansion of the refractory castable layer can be absorbed without being hindered by the pellets, and the lifting thereof can be prevented. In addition, even if the gap between the fire bricks in the divided portion is large enough not to allow small-diameter pellets to enter, a sufficiently large expansion allowance in the circumferential direction can be secured as the sum of these gaps. Therefore, it is possible to absorb the expansion deformation of the castable layer and to avoid the lifting or the like.
[0009]
In the second invention, the fireproof castable layer (45) is divided into a plurality of castable sheets (451), and a gap (55) serving as an expansion allowance for absorbing the expansion of the castable sheets (451) is formed around these layers. Form. In the second aspect of the present invention, the expansion of the castable sheet is absorbed by the surrounding gap that has a size that does not allow the small-diameter pellets to enter, and the refractory castable layer is more effectively prevented from being lifted.
[0010]
In addition, the code | symbol in the said parenthesis shows the correspondence with the specific means as described in embodiment mentioned later.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a vertical section of a hearth 2 of a rotary hearth furnace 1, and FIG. 2 shows a partial perspective view of the hearth 2 viewed from the inner peripheral side. The hearth 2 having a constant width located between the inner peripheral wall 11 and the outer peripheral wall 12 has upper and lower metal frames 21 and 22 in the lower half, and a heat-resistant hearth to be described in detail later on the upper frame 22. The part 23 is placed. In FIG. 1, rail members 31 and 32 extending over the entire circumference are provided at the inner circumferential position and the outer circumferential position of the lower surface of the lower frame 21, respectively, and support rails provided on the floor side are provided on these rail members 31 and 32. The hearth 2 is supported by contacting 33 from below.
[0012]
A guide member 34 extending over the entire circumference protrudes from a lower surface intermediate portion near the inner circumference of the lower frame 21, and a guide roller 35 supported in a horizontal posture is brought into contact with the inner circumference vertical surface to contact the hearth 2. Are positioned in the radial direction. A rack rail 36 extending over the entire circumference is provided at the lower surface intermediate portion near the outer periphery of the lower surface of the lower frame 21, and a pinion gear 37 meshes with a tooth profile formed on the rail surface. The pinion gear 37 is mounted on a rotating shaft 38 that is horizontally inserted and inserted below the outer peripheral wall 12, and the hearth 2 is rotated by rotating the rotating shaft 38 by a driving unit (not shown).
[0013]
The heat-resistant hearth 23 is provided with a heat insulating layer 41 made of heat insulating castable formed on the upper frame 22 with a constant thickness, which covers the entire upper surface of the upper frame 22, and the inner and outer peripheral portions of the heat insulating layer 41 are located below. Is bent to cover the inner and outer peripheral surfaces of the upper frame 22. Insert metal fittings 411 are provided on the upper surface of the inner and outer peripheral edges of the upper frame 22 at intervals in the circumferential direction so as to project upward through the heat insulating layer 41. A fireproof castable is formed in a predetermined cross-sectional shape covering the metal inserts 411. Thus, the frame bodies 42 and 43 are formed. In the annular space between the inner and outer peripheral frame bodies 42 and 43, a brick layer 44 is provided in which a plurality of layers (four layers in this embodiment) of heat insulating bricks are stacked on the heat insulating layer 41. On the brick layer 44, a fire-resistant castable layer 45 having a constant thickness is formed at an intermediate position between the inner and outer peripheries. Layers 46 and 47 are provided. A dolomite layer 48 is formed so as to cover the refractory castable layer 45 and the brick layers 46 and 47 and to be flush with the upper surfaces of the inner and outer peripheral frame bodies 42 and 43. The pellets are supplied and laminated on the dolomite layer 48 and are sequentially conveyed from the supply / discharge chamber 41 (FIG. 4) to the pre-tropical zone 42, the heating zone 43, the intermediate zone 44, and the reduction zone 45 as described in the prior art.
[0014]
As shown in FIG. 3, each of the inner and outer frame bodies 42, 43 is divided into a plurality of frame blocks 421, 431 divided at a constant interval in the circumferential direction, and between adjacent frame blocks 421, 431. A predetermined gap 51, 52 is formed. The gaps 51 and 52 are filled with a ceramic sheet 6 or a ceramic blanket made of ceramic fibers. Here, in the outer peripheral frame 43, both end portions in the circumferential direction of each frame block 431 facing the gap 52 are recessed by a certain amount, and trapezoidal concaves whose left and right sides gradually approach outward in a plan view. A place 432 is formed, and a plurality of refractory bricks 71 are embedded in these recesses 432. Each of the refractory bricks 71 is formed in a sector shape with a gradually decreasing width and is provided in a plurality in the radial direction, and is arranged in a plurality of rows (three rows in the present embodiment) in the circumferential direction. A predetermined gap 53 (FIG. 3) is formed between the rows.
[0015]
In FIG. 2, the upper frame 22 is divided into a plurality of portions in the circumferential direction at the same position as the frame bodies 42, 43. A predetermined gap 54 is formed between the divided frame bodies 221, and the gap 54 A metal seal plate 222 having a constant width is extended in the radial direction so as to cover from the outside. These seal plates 222 are free without welding one side edge. The fire-resistant castable layer 45 formed on the brick layer 44 is divided into a substantially square castable plate 451 in a plan view in the inner and outer directions and the circumferential direction, and a predetermined gap 55 is formed around the castable plate 451. Then, a ceramic sheet (not shown) is filled in the gaps 55. The castable plate 451 is largely separated at regular intervals in the circumferential direction, and a plurality of refractory bricks 72 are arranged in the radial direction in a plurality of rows (two rows in this embodiment) in the circumferential direction. Yes. A predetermined gap 56 is formed around the refractory bricks 72 and between the refractory bricks 72 and the castable plate 451, and the gap 56 is filled with a ceramic sheet (not shown).
[0016]
A large number of refractory bricks 73 of the brick layer 46 on the inner peripheral side are provided in the circumferential direction in two rows inside and outside, as shown in FIG. 3, between each row, between the frame body 42, and the castable plate 451. A predetermined gap 57 is formed between the innermost refractory brick 72 and the innermost refractory brick 72, and a ceramic sheet (not shown) is filled in the gap 57. The refractory bricks 74 of the outer peripheral side brick layer 47 are provided in four rows inside and outside in plan view, between each row, between the frame body 43, between the castable plate 451, and with the outermost refractory brick 72. Predetermined gaps 58 are respectively formed therebetween, and the ceramic sheets (not shown) are filled in the gaps 58. The brick layers 46 and 47 have relatively large gaps 81 and 82 formed at regular intervals in the circumferential direction, and the gaps 81 and 82 are filled with the ceramic sheet 6.
[0017]
In such a hearth structure, brick layers 46 and 47 are provided between the refractory castable layer 45 in the center of the hearth and the inner and outer frames 42 and 43, and the inner brick layer 46 is arranged in two rows. Since the brick layer 47 on the outer peripheral side having a large thermal expansion deformation is constituted by four rows of refractory bricks 74 inside and outside, and the gaps 57 and 58 are formed between the rows. A sufficiently large expansion allowance can be ensured especially in the radial direction of the hearth 2 as the sum of the gaps 57 and 58 having such a size that no pellets can enter. Thereby, the expansion | swelling of the fireproof castable layer 45 can be absorbed and the floating etc. can be prevented.
[0018]
Further, since the fireproof castable layer 45 is divided into substantially rectangular castable sheets 451 and gaps 55 are formed around these, the expansion of the castable sheet 451 is absorbed by the gaps 55, and the fireproof castable layer 45 is lifted. Further effectively prevented. In addition, since a plurality of rows of refractory bricks 72 that form predetermined gaps 56 in the circumferential direction are provided for each of the plurality of rows of castable sheets 451 in the circumferential direction, this also prevents the intrusion of small-diameter pellets. A sufficiently large expansion allowance in the circumferential direction can be secured, the expansion deformation of the castable sheet 451 can be absorbed, and the lifting or the like can be avoided.
[0019]
In the present embodiment, the frame blocks 421 and 431 expand and expand in the circumferential direction in the inner and outer frame bodies 42 and 43 in response to heat in the furnace, but are formed between the frame blocks 421 and 431. The gaps 51 and 52 serve as expansion allowances to absorb expansion deformation. As a result, the frame 43 is prevented from expanding radially outward, and contact with the outer peripheral wall 12 is avoided. Similarly, the frame body 42 is prevented from being lifted, and contact with the inner peripheral wall 11 is also avoided. At this time, the ceramic sheet 6 or the ceramic blanket filled in the gaps 51 and 52 is easily contracted in accordance with the reduction of the gaps 51 and 52 due to the expansion and deformation of the frame blocks 421 and 431 and does not hinder the deformation. In addition, the small diameter pellets are prevented from entering the gaps 51 and 52, and the expansion absorption function by the gaps 51 and 52 is ensured.
[0020]
In the present embodiment, since the upper frame 22 is divided in the circumferential direction at the same position as the frame bodies 42 and 43 to form the predetermined gap 54, the upper frame 22 is integrated with the frame body 42 using the gap 54 as an expansion allowance. This elongates and deforms, thereby preventing the frame body 42 from rising more effectively. Further, since the gap 54 of the upper frame 22 is shielded from above by the seal plate 222, the atmospheric gas in the furnace is not released to the outside air.
[0021]
Further, in the present embodiment, in the outer peripheral side frame body 43, recesses 432 are formed at both ends in the circumferential direction of each frame block 431 facing the gap 52, and refractory bricks 71 are embedded in a plurality of rows in the circumferential direction here. In addition, since the gaps 53 are formed between adjacent rows of the refractory bricks 71, an expansion allowance approximately equal to the size of the gaps 52 may be formed by adding the gaps 53, so that each gap 53 has a small diameter. It can be made small so that the pellets do not enter. Moreover, since the said recessed part 432 is made into the trapezoid shape from which a right-and-left side gradually approaches outward in planar view, the pellet P sent out of a furnace by the screw conveyor 53 (FIG. 4) is radial direction on the firebrick 71 Even if it passes outward, these refractory bricks 71 are not escaped from the recess 432 by the movement of the pellets P. In this embodiment, since the entire upper surface of the upper frame 22 is covered with the heat insulating layer 41 made of a heat insulating castable having a constant thickness, the temperature rise of the upper frame 22 and the accompanying expansion deformation are made as small as possible. be able to.
[0022]
【The invention's effect】
As described above, according to the hearth structure of the rotary hearth furnace of the present invention, it is possible to effectively absorb the expansion of the inner and outer peripheral edges of the hearth and prevent the deformation without being inhibited by the pellets.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view of a hearth of a rotary hearth furnace showing one embodiment of the present invention.
FIG. 2 is a partial perspective view of a hearth of a rotary hearth furnace.
FIG. 3 is a partial plan view of a hearth of a rotary hearth furnace.
FIG. 4 is an overall horizontal sectional view of a rotary hearth furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Rotary hearth furnace, 11 ... Inner peripheral wall, 12 ... Outer peripheral wall, 2 ... Rotary hearth, 22 ... Upper frame, 222 ... Seal plate, 45 ... Refractory castable layer, 451 ... Castable sheet, 55, 56, 57, 58 ... Gap.

Claims (2)

The middle part of the annular rotary hearth disposed between the inner peripheral wall and the outer peripheral wall is configured with a fireproof castable layer, and at least one of the inner peripheral side and the outer peripheral side adjacent to the fireproof castable layer. A plurality of rows of refractory bricks are arranged in the inner and outer directions, a gap serving as an expansion margin is formed between the rows of refractory bricks to absorb the expansion in the radial direction of the refractory castable layer, and the refractory castable layer is circumferentially disposed. A rotary hearth characterized in that a plurality of rows of refractory bricks forming gaps serving as expansion allowances for absorbing expansion of the refractory castable layer in the circumferential direction are disposed in each of the divided portions. The hearth structure of the furnace. The hearth structure of a rotary hearth furnace according to claim 1 , wherein the refractory castable layer is divided into a plurality of castable sheets, and a gap serving as an expansion allowance for absorbing expansion of the castable sheets is formed around them.

Images