JP2002310564A - Hearth structure for rotary hearth type furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the outer peripheral edge of a hearth from being deformed by effectively absorbing the expansion of the outer peripheral edge in the hearth without being disturbed by a pellet. SOLUTION: The inner peripheral edge and the outer peripheral edge of an annular rotary hearth 2 arranged between an inner peripheral wall and an outer peripheral wall are constituted of frames 42 and 43 by castably molding. These frames 42 and 43 are divided at predetermined gaps 51 and 52 at a plurality of positions in circumferential direction, and ceramic sheets 6 are filled in the gaps 51 and 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hearth structure of a rotary hearth furnace, and more particularly to an improvement of a hearth structure of a rotary hearth furnace for reducing steelmaking dust pellets.

[0002]

2. Description of the Related Art In order to reuse steelmaking dust or fine ore, a binder and a reducing agent are mixed into steelmaking dust and the like, kneaded, granulated into raw pellets, and supplied to a rotary hearth furnace. Then, heat treatment such as heating and reduction is performed. An example is shown in FIG. The rotary hearth furnace 1 has concentric inner and outer peripheral walls 11 and 12, and the peripheral walls 11, 12 and a bottom wall and a top wall (not shown) form a furnace space S having a rectangular closed cross section.
Are formed in an annular shape. Inner and outer peripheral walls 1 on the bottom wall
The hearth 2 is located with a small gap formed between the furnace hearth 1 and the furnace hearth 12. The hearth 2 has an annular shape along the furnace space S, and is rotationally moved in the direction of the arrow by a drive mechanism (not shown). ing. The 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. To supply and exhaust chamber 41, pre-tropical zone 42, heating zone 4
3, 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 required number of burners 61 to 63 on the inner and outer peripheral walls 11, 12, respectively.

[0003] The spherical raw pellets P made of steelmaking dust and the like charged into the furnace from the charging port 51 are supplied by falling onto the hearth 2, and the curtain wall 31 is moved with the movement of the hearth 2.
At the lower edge of the furnace hearth 2, and are almost uniformly stacked and mounted on the entire upper surface of the hearth 2. The raw pellets P are transported to the tropical zone 42,
Here, it is heated at a low temperature of 600 ° C. or less, and the moisture and gasified components inside are slowly evaporated and vaporized, and are dried without explosion or the like. The dried pellets P are heated 43
And the temperature rises sufficiently to reach the reduction zone 45 via the intermediate zone 44, where the reducing atmosphere and the pellet P
The metal oxide in the pellet P is reduced to a metal by the reducing agent contained in the metal. The pellets P that have completed the reduction process return to the supply / discharge chamber 41, and are discharged by the screw conveyor 53 from the discharge port 52 provided on the outer peripheral wall to the outside of the furnace.

[0004]

By the way, in the above rotary hearth furnace, if the inner and outer peripheral edges of the hearth are formed by refractory castables which are easy to form, the outer peripheral edge of the hearth expands radially outward due to thermal expansion. In addition, while being in contact with the outer peripheral wall of the furnace, it may also rise up at the inner peripheral edge of the hearth and come into contact with the inner peripheral wall of the furnace, which may hinder smooth rotation of the hearth. As a countermeasure against this, it is conceivable to form a fixed gap at the inner and outer peripheral edges of the hearth to absorb the expansion deformation, however, when trying to secure a sufficient gap size, small-diameter pellets enter the gap. There is a possibility that the function of swelling and absorption may be impaired.

Accordingly, the present invention has been made to solve such a problem, and a hearth structure of a rotary hearth furnace capable of effectively absorbing expansion of an inner peripheral edge of a hearth and preventing deformation thereof without being hindered by pellets. The purpose is to provide.

[0006]

According to a first aspect of the present invention, an inner peripheral wall (11) and an outer peripheral wall (12) are provided.
Frame (42, 4) in which the inner peripheral edge and the outer peripheral edge of the annular rotary hearth (2) disposed between
3), and these frame bodies (42, 43) are each provided with a predetermined gap (51, 52) at a plurality of locations in the circumferential direction.
And the gaps (51, 52) are filled with a ceramic sheet (6) or a ceramic blanket.

In the first aspect of the present invention, the inner and outer peripheral frames expand and expand in the circumferential direction due to the heat in the furnace, but the gaps formed in the divided portions become expansion allowances. The deformation is absorbed. This prevents the outer peripheral frame from expanding radially outward, avoids contact with the outer peripheral wall, and prevents the inner peripheral frame from rising, and also prevents contact with the inner peripheral wall. Be avoided. The ceramic sheets and the like filled in each of the above gaps are easily shrunk in accordance with the reduction of the gaps due to the elongation deformation of the frame, and do not hinder the deformation,
Preventing small-diameter pellets from entering the gap and ensuring the expansion absorption function of the gap.

According to the second aspect of the present invention, the divided frame (43) constituting the outer peripheral edge of the rotary hearth (2) has a concave opening upwardly open at a circumferential end facing the gap (52). Place (4
32), a plurality of rows of refractory bricks (71) are buried in the recess (432) in the circumferential direction, and the refractory bricks (7) are formed.
A predetermined gap (53) is formed between adjacent rows in 1).

In the second aspect of the present invention, the expansion allowance substantially equal to the size of the gap formed in the frame can be formed by the sum of the plurality of gaps formed between the plurality of rows of refractory bricks. Each gap formed between each row of refractory bricks can be made small so that small-diameter pellets do not enter. At this time, if a ceramic sheet or the like is filled in each gap formed between each row of refractory bricks, it is more effective to prevent intrusion of pellets.

In the third invention, the recess (432) is
The trapezoid is such that the left and right sides gradually approach radially outward of the hearth (2) in plan view. In the third invention, the pellets sent out of the furnace by the screw conveyor are:
Even if the refractory bricks buried in the recesses pass radially outward, the refractory bricks do not escape from the recesses due to the movement of the pellets.

In the fourth invention, the frame (42, 43)
The metal frame (22) supporting the frame (42, 4)
It is divided in the circumferential direction at the same position as in 3), and a predetermined gap (54) is formed between them. According to the fourth aspect, the metal frame is extended and deformed integrally with the frame using the gap as an expansion allowance, so that the lifting of the frame is further effectively prevented.

In the fifth aspect of the invention, the metal frame (2) is fixed to one of the divided metal frames (22).
A seal plate (222) that covers the gap (54) formed in 2) from above is provided. In the fifth aspect of the present invention, the furnace atmosphere gas is not released to the outside air through the gap between the metal frames.

The reference numerals in parentheses indicate the correspondence with specific means described in the embodiments described later.

[0014]

FIG. 1 is a vertical sectional view of a hearth 2 of a rotary hearth furnace 1, and FIG. 2 is a partial perspective view of the hearth 2 viewed from an inner peripheral side. The hearth 2 having a fixed width located between the inner peripheral wall 11 and the outer peripheral wall 12 has a lower half formed of two upper and lower metal frames 21 and 22. The part 23 is mounted. In FIG. 1, rail members 31 and 32 extending over the entire circumference are respectively provided at the inner circumferential position and the outer circumferential position on the lower surface of the lower frame 21.
The support rollers 33 provided on the floor side contact the rail members 31 and 32 from below to support the hearth 2.

A guide member 34 extending over the entire periphery protrudes from an intermediate portion of the lower surface near the inner periphery of the lower frame 21, and a guide roller 35 supported in a horizontal posture is brought into contact with a vertical surface of the inner periphery. The hearth 2 is positioned in the radial direction. A rack rail 36 extending over the entire periphery is provided at a lower intermediate portion near the outer periphery of the lower surface of the lower frame 21,
A pinion gear 37 meshes with a tooth profile formed on the rail surface. The pinion gear 37 is mounted on a rotary shaft 38 inserted horizontally below the outer peripheral wall 12, and the hearth 2 is rotationally moved by rotating the rotary shaft 38 by a driving means (not shown).

The heat-resistant hearth 23 has a heat-insulating layer 4 made of a heat-insulating castable formed on the upper frame 22 with a constant thickness.
1 is provided, 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 bent downward to cover the inner and outer peripheral surfaces of the upper frame 22. Insert metal fittings 411 projecting upward through the heat insulating layer 41 are provided on the upper surface of the inner and outer peripheral edges of the upper frame 22 at intervals in the circumferential direction, and a refractory castable is formed in a predetermined sectional shape so as to cover these metal inserts 411. As a result, frame members 42 and 43 are formed. In the annular space between the inner and outer frame bodies 42 and 43, a brick layer 44 in which a plurality of (four in the present embodiment) heat insulating bricks are stacked on the heat insulating layer 41 is provided. On the brick layer 44, a refractory castable layer 45 having a certain thickness is formed at an intermediate position between the inner and outer peripheries, and a refractory brick 73, 74 is laminated in two layers on the inner peripheral side and the outer peripheral side adjacent thereto. 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 so as to be flush with the upper surfaces of the inner and outer frames 42 and 43. Pellets are dolomite layer 4
8, the pre-tropical zone 42, the heating zone 43, and the intermediate zone 4 are supplied from the supply / discharge chamber 41 (FIG. 4) as described in the related art.
4. It is sequentially conveyed to the reduction zone 45.

As shown in FIG. 3, each of the inner and outer frame members 42 and 43 is composed of a plurality of frame blocks 421 and 431 divided at regular intervals in the circumferential direction. Predetermined gaps 51 and 52 are formed between 431. Each of the gaps 51 and 52 is filled with a ceramic sheet 6 or ceramic blanket made of ceramic fiber. Here, in the outer peripheral frame 43, both ends in the circumferential direction of each frame block 431 facing the gap 52 are depressed by a fixed amount, so that the trapezoidal recesses whose left and right sides gradually approach outward in 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 fan shape having a gradually decreasing width outward, 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.

In FIG. 2, the upper frame 22 is divided into a plurality of parts in the circumferential direction at the same position as the frame members 42 and 43. A predetermined gap 54 is formed between the divided frame members 221 and A metal seal plate 222 having a constant width extends in the radial direction so as to cover 54 from above. These seal plates 222 are free without welding on one side edge. In addition, the brick layer 4
The refractory castable layer 45 formed on the upper surface 4 is divided into castable plates 451 having a substantially rectangular shape in a plan view in the inner and outer directions and in the circumferential direction.
Are formed around each other, and these gaps 55 are filled with a ceramic sheet (not shown). The castable plates 451 are largely separated from each other at regular intervals in the circumferential direction, and a large number of refractory bricks 72 are arranged radially in a plurality of rows (two rows in this embodiment) in the circumferential direction. I have. A predetermined gap 56 is formed around the refractory brick 72 or between the refractory brick 72 and the castable plate 451, and the gap 56 is filled with the ceramic sheet 6.

The refractory brick 73 of the brick layer 46 on the inner peripheral side
As shown in FIG. 3 in plan view, a large number are provided in the inner and outer rows in the circumferential direction, between the rows, between the frames 42, between the castable plates 451, and the innermost refractory bricks 72. A predetermined gap 57 is formed between them, and the gap 57 is filled with a ceramic sheet (not shown). The refractory bricks 74 of the brick layer 47 on the outer peripheral side are provided in four rows on the inner and outer sides in plan view, and are provided between the respective rows, between the frame 43, between the castable plates 451, and with the outermost refractory brick 72. A predetermined gap 58 is formed between the gaps, and the gap 58 is filled with a ceramic sheet (not shown). In the brick layers 46 and 47, relatively large gaps 81 and 82 are formed at regular intervals in the circumferential direction, and the gaps 81 and 82 are filled with a ceramic sheet (not shown).

In such a hearth structure, the inner and outer frame members 42 and 43 receive heat in the furnace, and the frame blocks 421 and 431 expand and expand in the circumferential direction. , 431 serve as expansion allowances to absorb expansion deformation. As a result, the frame 43 is prevented from expanding outward in the radial direction, and contact with the outer peripheral wall 12 is avoided. Similarly, the lifting of the frame body 42 is prevented, and the contact with the inner peripheral wall 11 is also avoided. On this occasion,
The ceramic sheets 6 or the ceramic blankets filled in the gaps 51 and 52 are connected to the frame blocks 421 and 431.
The gaps 51 and 52 are easily shrunk in accordance with the contraction of the gaps 51 and 52 due to the elongation and deformation of the gaps, so that the deformation is not hindered. , 52 guarantee the expansion absorption function.

In particular, in the present embodiment, the upper frame 22
Is divided in the circumferential direction at the same position as the frame bodies 42 and 43 to form a predetermined gap 54, so that the upper frame 22 is extended and deformed integrally with the frame body 42 by using the gap 54 as an expansion margin. 42 is prevented 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.

Further, in the present embodiment, recesses 432 are formed at both ends in the circumferential direction of each frame block 431 facing the gap 52 in the outer peripheral side frame body 43, and the fire bricks are formed here in a plurality of rows in the circumferential direction. Since the gaps 53 are formed between adjacent rows of the refractory bricks 71 by burying the gaps 71, the sum of the plurality of gaps 53 may form an expansion allowance substantially equal to the size of the gaps 52. Can be made small so that the small-diameter pellets P do not enter. The recess 432 has a trapezoidal shape in which the left and right sides gradually approach outward in plan view, so that the screw conveyor 53 (FIG. 4) is used.
Pellets sent out of the furnace by the refractory brick 7
1 on the outer side in the radial direction.
Does not escape from the recess 432 as the pellet moves.

Further, in this embodiment, the brick layers 46 and 47 are provided between the refractory castable layer 45 in the middle part of the hearth and the inner and outer frames 42 and 43, and the inner peripheral brick layers 46 are arranged in two rows. And the outer side brick layer 47 having a large thermal expansion deformation is constituted by four rows of inner and outer refractory bricks 74 so as to form gaps 57 and 58 between the rows. A sufficiently large expansion allowance can be secured especially in the radial direction of the hearth 2 as the sum of the gaps 57 and 58 having such a size that small-diameter pellets do not enter.
Thereby, the expansion of the refractory castable layer 45 can be absorbed and the floating thereof can be prevented.

Further, since the refractory castable layer 45 is divided into the substantially square castable sheets 451 and the gaps 55 are formed around these, the expansion of the castable sheets 451 is absorbed by the gaps 55, and the refractory castable layers 45 are formed. Floating and the like are more effectively prevented. In addition, a plurality of castable sheets 45 in the circumferential direction are provided.
Since a plurality of rows of refractory bricks 72 that form a predetermined gap 56 in the circumferential direction are provided for each of them, a sufficiently large expansion allowance in the circumferential direction is secured while preventing intrusion of small-diameter pellets. As a result, the expansion deformation of the castable sheet 451 can be absorbed, and the floating or the like can be avoided.
In the present 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 expansion and deformation accompanying the temperature increase are minimized. be able to.

[0025]

As described above, according to the hearth structure of the rotary hearth furnace of the present invention, the expansion of the inner peripheral edge of the hearth is effectively absorbed without being hindered by the pellets, and the deformation thereof is prevented. be able to.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a hearth of a rotary hearth furnace showing an 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, 42, 43 ... Frame body, 432 ... Concave part, 51, 52, 5
3, 54: gap, 6: ceramic sheet, 71: refractory brick.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K050 AA02 BA00 CA09 CB02 CB08 4K051 AA04 BE00 KA04

Claims (5)

[Claims] An annular rotary hearth disposed between an inner peripheral wall and an outer peripheral wall is formed of a frame formed by refractory castable inner and outer peripheral edges, and these frames are respectively formed in a circumferential direction. A hearth structure for a rotary hearth furnace, wherein the hearth structure is divided at a plurality of locations with predetermined gaps, and the gaps are filled with ceramic sheets or ceramic blankets. 2. A recess that opens upward at a circumferential end of the divided frame that constitutes the outer peripheral edge of the rotary hearth facing the gap, and a peripheral portion is formed in the recess. The hearth structure of a rotary hearth furnace according to claim 1, wherein a plurality of rows of refractory bricks are buried in the direction, and a predetermined gap is formed between adjacent rows of the refractory bricks. 3. The hearth structure of a rotary hearth furnace according to claim 2, wherein the recess has a trapezoidal shape in which the left and right sides gradually approach radially outward of the hearth in plan view. 4. The rotating device according to claim 1, wherein the metal frame supporting the frame is circumferentially divided at the same position as the frame and a predetermined gap is formed therebetween. Hearth structure of hearth furnace. 5. The hearth structure of a rotary hearth furnace according to claim 4, further comprising a seal plate fixed to one of the divided metal frames and covering a gap formed in the metal frame from above.