JP5335488B2 - Hearth structure of rotary hearth furnace - Google Patents

Description

  The present invention relates to a rotary hearth furnace for producing metallic iron by reducing a carbonaceous material-incorporated agglomerate in which iron oxide is incorporated in iron oxide as a reducing agent at a high temperature in an annular rotary furnace. This relates to the hearth structure.

  In a rotary hearth furnace in which a hearth refractory is laid on a hearth trolley having a traveling device, a carbonaceous material agglomerate is charged as a raw material on the hearth refractory and heated from above the raw material. Is supposed to do.

  In consideration of manufacturability, the hearth of this type of rotary hearth furnace is usually formed by combining a plurality of hearth carts in an annular shape, and the structure of the connecting part is the adjacent hearth. There are known a welding structure for welding members of a cart and a bolt fastening structure for fastening members of adjacent hearth carts with a plurality of bolts.

  In the hearth of the rotary hearth furnace having the above-described configuration, the hearth carriage receives heat from the high temperature furnace, and therefore the upper surface side temperature becomes higher than the lower surface side temperature. As a result, if the hearth carts are combined and have an integrated structure, the connected hearth carts may be deformed like a disc spring due to a difference in thermal expansion between the upper surface side and the lower surface side. When the inner peripheral wheel is lifted and an excessive load is concentrated on the outer peripheral wheel, a running failure is caused.

  In addition, if the attitude of the traveling carriage is greatly inclined in the radial direction of the rotary hearth furnace due to the lifting of the inner peripheral wheel, the hearth refractory of the traveling carriage interferes with the furnace wall refractory on the inner wall of the rotary hearth furnace. There is a risk that it will not be possible.

  In order to avoid such a problem, a structure that allows thermal deformation at a joint portion between adjacent hearth carts is required so that the hearth cart can maintain a horizontal posture even after thermal deformation.

  In order to allow thermal deformation in the fastening structure in which the members of adjacent hearth carts are fastened with a plurality of bolts, the nuts are gradually loosened according to the thermal deformation of the hearth carts to the joints between the hearth carts. Can give freedom. However, when the rotary hearth furnace is cooled by maintenance or the like, the bolts are loosened, and rattling occurs between the hearth carts.

  Therefore, in the cold, the hearth cannot maintain a circular shape, which hinders rotation.

  In order to prevent this, it is conceivable to adjust the tightening amount of the nut with respect to the bolt every time a temperature change such as heating or cooling occurs during operation, but it is not realistic.

  Then, the hearth cart combination structure of the rotary hearth furnace which can eliminate the said problem is proposed (for example, refer patent document 1).

  The above-described hearth cart coupling structure has a plurality of hearth carts each having a traveling device, and a predetermined gap is provided by inserting a spacer between adjacent hearth carts. And the adjacent hearth carts are coupled using a plurality of coupling bolts arranged in a row in the horizontal direction.

  Thereby, even if each hearth cart is thermally deformed during operation, it can be freely deformed without being constrained to the curved deformation, so each hearth cart is always held in a stable posture, It is described that the hearth carts that are thermally deformed at the time of operation do not come into contact with each other because the connecting bolts connect adjacent hearth carts through the spacers.

JP 2006-313061 A

  However, in the conventional hearth cart connection structure, although the hearth cart can be deformed, the bending load and the tensile load applied at the time of deformation act directly on the connecting bolt. Therefore, assuming that the size of the rotary hearth furnace is increased, the number of divisions of the hearth cart must be increased in order to reduce the load on the combined bolt by keeping the bending and tensile stresses of the combined bolt within the allowable stress. I must.

  When the number of hearth trolleys is increased, there arises a problem that a great deal of time and labor is spent on the production of the rotary hearth furnace.

  The present invention has been made in view of the problems in the conventional hearth cart combination structure as described above, and the hearth can be freely thermally deformed in response to temperature changes such as heating and cooling during operation. It is possible to provide a hearth structure of a rotary hearth furnace that can reduce the load applied to the hearth joint and can stably operate the rotary hearth furnace.

  The present invention provides a hearth structure of a rotary hearth furnace in which an annular hearth is mounted on an annular rotating frame, and a floor plate is laid on the upper surface of the hearth, the hearth and the floor plate are formed in an arc shape. It is composed of a plurality of formed hearth parts and floor plate parts, and a predetermined gap is provided between the adjacent hearth parts and between the floor plate parts, and the hearth part and the rotating frame are fixed by one part. It is a hearth structure of a rotary hearth furnace provided with a direction regulating component that is connected and regulates the heat expansion direction of the hearth component.

  According to the present invention, the rotary frame and the hearth part are connected at one place, and the unconnected part of the hearth part is not restrained. The stress is not concentrated and damage to the fixed part can be prevented.

  In addition, the direction regulating component regulates the direction of thermal expansion so that the hearth can be thermally expanded in the circumferential direction and the radial direction without rotating around the fixed point by the fixed component.

  In the present invention, it is preferable that a sliding support plate for supporting the hearth part slidably on a horizontal plane is disposed on the rotating frame.

  According to the present invention, since the sliding support plate is arranged on the hearth support portion of the rotating frame, the hearth can be smoothly and smoothly deformed by heat, thereby preventing stress concentration on the fixed parts. be able to.

  Moreover, in this invention, it is preferable to arrange | position the connection part of the said hearth part and the said rotation frame in the position near the inner peripheral side of the said hearth part.

  In the present invention, a bolt / nut for fastening the arc-shaped part and the rotating frame can be provided as the fixing part.

  Further, in the present invention, one end in the circumferential direction of each floor plate component is fixed to the hearth part, and the other end in the circumferential direction is a circumferential end of the hearth part adjacent to the hearth part. A long hole is provided along the circumferential direction at the other end in the circumferential direction, and a long hole is provided in the long hole from the circumferential end of the hearth part adjacent to the hearth part. If the connecting parts to be provided are configured to be loosely inserted, it is possible to prevent the floor board from rising even if thermal elongation occurs.

  Moreover, in this invention, it is preferable to provide the cover which covers the clearance gap between the said adjacent floor board components, and to fill this cover with a heat insulating material.

  According to the present invention provided with the above-mentioned cover, it is possible to prevent foreign matter from entering the gaps between adjacent floor board components, so that stable expansion and contraction can be obtained during heating and cooling of the hearth and the floor board.

  According to the present invention, the hearth can be freely thermally deformed in response to temperature changes such as heating and cooling during operation, and the load applied to the hearth joint is reduced to stabilize the rotary hearth furnace. It becomes possible to drive.

It is the top view which showed the structure of the rotation frame of the rotary hearth furnace which concerns on this invention. (a) is a front view of a sliding support plate provided in the inner peripheral side rotation frame portion, and (b) is a bottom view thereof. It is the top view which showed the structure of the hearth and floor board of the rotary hearth furnace which concerns on this invention. It is a disassembled perspective view of a rotating frame and a hearth. (a) is a principal part perspective view which abbreviate | omits and shows the structure of the floor board of FIG. 4, (b) is a top view which shows the structure of the circumferential direction edge part of floor board components. It is EE arrow sectional drawing of FIG. (a) is explanatory drawing which shows interference of hearth parts, (b) is explanatory drawing which shows operation | movement of direction control components, (c) is explanatory drawing which shows suitable arrangement | positioning of direction control components, (d) is direction control components It is explanatory drawing which shows improper arrangement | positioning.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

  A hearth structure of a rotary hearth furnace according to the present invention includes an annular rotary frame, an annular rotary hearth mounted on the rotary frame, a floor plate that annularly covers the upper surface of the rotary hearth, and a hearth A fixed part that fixes the frame to the rotating frame in one place, and a direction regulating part that regulates the direction of thermal expansion so that the hearth can be thermally expanded in the circumferential direction and the radial direction without rotating around the fixed point by the fixed part And mainly consists of

  In the present embodiment, a hearth structure of a rotary hearth furnace having a diameter of 11.5 m will be described as an example.

1. Rotating frame FIG. 1 is a plan view showing a configuration of a rotating frame.

  The rotating frame 100 is assembled by connecting a plurality of arcuate rotating frame components (hereinafter referred to as rotating frame components) 101 in a circular shape.

  Each rotating frame component 101 includes an inner peripheral side rotating frame portion 102 made of shape steel, and an outer peripheral side rotating frame portion 103 also made of shape steel with a smaller curvature than the curvature of the inner peripheral side rotating frame portion 102. The inner peripheral side rotating frame portion 102 and the outer peripheral side rotating frame portion 103 are mainly composed of a large number of connecting frame portions 104 and 105 that connect in the diametrical direction.

  In the figure, a to f indicate the joint positions of the rotating frame component 101, and g indicates the center position of the rotary hearth furnace.

  In the present embodiment, the rotating frame 100 is exemplified as a structure that can be equally divided into six. However, the number of divisions is appropriately determined in consideration of the thermal expansion amount of the hearth, the ease of manufacture, and the ease of installation. .

  Further, the joint position of the rotating frame 100 is shifted by 2 ° clockwise with respect to the floor plate joint position so as not to coincide with the floor plate joint position described later (refer to the 0 ° position of the rotary hearth furnace in the figure). It has become.

  A mounting base 107 for installing a sliding support plate (described later) is disposed at predetermined intervals on the upper surfaces of the inner peripheral rotating frame portion 102 and the outer peripheral rotating frame portion 103. It is designed to be slidably supported.

  FIG. 2 shows the sliding support plate 108 fixed to the mounting base 107 of the inner peripheral side rotating frame portion 102. FIG. 2 (a) is a front view seen from the center position g of the rotary hearth furnace, FIG. 2B is a plan view thereof.

  As the sliding support plate 108, for example, Pillar Fluoro Gold (PILLAR No. 4801) manufactured by Nippon Pillar Industries Co., Ltd. can be used.

  This type of sliding support plate 108 is formed by firmly joining a resin plate 108a and a metal plate 108b having a low friction coefficient, and can slide on the rotary hearth with low friction, and is self-lubricating. Because it has a maintenance-free, it can be used for a long time.

  The metal plate 108b is fixed to the upper surface of the mounting base 107 by welding.

  Specifically, the mounting base 107 includes a C-shaped steel 107a and a pedestal 107b, and the C-shaped steel 107a is fixed on the inner peripheral rotating frame 102 by welding, and the metal of the sliding support plate 108 is mounted on the pedestal 107b. The plate 108b is fixed by welding.

  The sliding support plate 108 is also provided on the outer peripheral side rotating frame portion 103 via the mounting base 107, and the hearth described later is slidably supported by the resin plate 108a of each sliding support plate 108. It has become.

  FIG. 3 is a plan view showing a hearth 110 provided on the rotary frame 100 and a floor plate 130 covering the hearth 110, and a part of the hearth 110 is shown on the left side of the drawing. A part of the floor board 130 is shown on the right side of the drawing (range shown by arrow C) (in the range shown by arrow B).

2. The hearth 110 is assembled by connecting a plurality of arc-shaped hearth parts (hereinafter referred to as hearth parts) 111 in a circular shape.

  Each hearth part 111 includes an inner peripheral side hearth frame part 112 made of C-shaped steel and an outer peripheral side hearth frame part made of C-shaped steel with a smaller curvature than the curvature of the inner peripheral side hearth frame part 112. 113, the inner peripheral side hearth frame part 112 and the outer peripheral side hearth frame part 113 are arranged concentrically with the numerous connection frame parts 114 connecting the diameter direction and the inner peripheral side hearth frame part 112. It is mainly composed of auxiliary hearth frame portions 115, 116, and 117.

  In the figure, hm indicates the seam position of a floor plate component 131 to be described later, and the seam position of the hearth floor 110 is shifted by 1.5 ° clockwise relative to the floor board seam position (in the figure, the hearth floor 110, 0 ° position).

  D1 to D6 indicate connection positions (fixed points) between the hearth 110 and the rotating frame 100, and are connected to the rotating frame 100 at six locations. The connection structure between the rotating frame 100 and the hearth 110 will be described later.

2.1 Hearth Structure Next, a hearth structure including the rotating frame 100, the hearth 110, and the floor plate 130 will be described.

  FIG. 4 is an exploded perspective view showing the main part of the rotating frame 100 and the main part of the hearth 110.

  In the drawing, a sliding support plate 108 is disposed on an inner peripheral side rotating frame portion 102 and an outer peripheral side rotating frame portion 103 of the rotating frame 100 via a mounting base 107.

  A bolt hole 107d for allowing a bolt to pass through is drilled in the pedestal 107c of the mounting base 107 at positions D1 to D6 (see FIG. 3) on the inner peripheral side rotating frame portion 102 among the many mounting bases 107. ing.

  Also, bolt holes 107f for allowing bolts to pass through are formed in the pedestals 107e on the outer peripheral side rotating frame 103, which are arranged in the radial direction with respect to the pedestals 107c. However, one bolt hole 107f is formed corresponding to one bolt hole 107d.

  A hearth part 111 is placed on the sliding support plate 108, and a plate 119 is provided on the lower surface of the connection frame 114 of the hearth part 111 at a position corresponding to the pedestal 107c, and corresponds to the pedestal 107e. A plate 120 is provided at the position.

  The plate 119 is provided with a bolt hole 119a facing the bolt hole 107d of the base 107c.

2.2 Fixing Parts When a fixing bolt 121 is passed through the bolt hole 107d and the bolt hole 119a and a nut is fitted to the fixing bolt 121, the hearth part 111 is located at a position near the inner peripheral side of the hearth part 111. And the rotating frame component 101 are connected. At this time, the mounting position of the fixing bolt 121 is a fixing point for fixing the rotating frame part 101 and the hearth part 111 at one place.

  The base 107c provided with the bolt hole 107d, the plate 119 provided with the bolt hole 119a, the fixing bolt 121, and the nut function as a fixing part.

2.3 Directional control component With only one fixing with the fixing bolt 121, the hearth part 111 rotates around the fixing point G (see arrow R) as shown in FIG. There is a risk of interference with the component 111.

  Therefore, the direction regulating component is provided so that the hearth component 111 can be thermally expanded in the circumferential direction and the radial direction without rotating around the fixed point G.

  FIG. 7B is an explanatory diagram for explaining the function of the direction regulating component.

  Either one of the rotating frame 100 (see FIG. 4) and the hearth part 111 is provided with a long hole 120a, and the rotating frame 100 and the hearth part 111 are fixed with a pin or bolt through the long hole 120a. However, the direction of the long axis of the long hole 120a needs to be arranged so as to be parallel to a straight line L connecting the fixing point G, which is the mounting position of the fixing bolt 121, and the center H of the long hole 120a. Thereby, the adjacent hearth components 111 can be thermally extended in the circumferential direction and the radial direction without interference.

  For this reason, the fixed point G and the center H are preferably provided side by side on the radial line in the rotating frame 100. However, the present invention is not limited to this, for example, an angle from the radial line as shown in FIG. The long hole 120a may be provided on the inclined line. Also in this case, the long axis of the long hole 120a is arranged so as to be parallel to an inclined line L ′ connecting the fixed point G and the center H of the long hole 120a.

  As shown in FIG. 7D, if the direction of the long hole 120a is not parallel to the inclined line L ′, the hearth part 111 rotates due to thermal elongation, and the adjacent hearth part 111 interferes. It will be.

  In the embodiment of FIG. 4, the plate 120 is provided with a long hole (through hole) 120 a facing the bolt hole 107 f of the base 107 e, and the long axis of the long hole 120 a corresponds to the fixing bolt 121. It arrange | positions so that the line which connects a center (fixed point) and the center of the volt | bolt 122 axially penetrated by the bolt hole 107f may be followed.

  In this manner, the connecting bolt 122 is passed through the bolt hole 107f and the long hole 120a, and the nut is fitted. Thereby, the plate 120 can move along the direction in which the long hole 120a is formed on the sliding support plate 108 of the base 107e.

  The plate 120 provided with the long hole 120a, the pedestal 107e provided with the bolt hole 107f, the bolt 122, and the nut function as a direction regulating component that regulates the heat extension direction of the hearth component 111.

  As described above, the hearth part 111 on each rotary frame part 101 is slidably supported by the twelve sliding support plates 108, and the rotary frame part 101 is arranged on the inner peripheral side of the hearth part 111. The two fixing bolts 121 are connected.

  Therefore, the rotary frame 100 and the hearth 110 rotate in conjunction with each other via a plurality of fixing bolts 121 arranged at positions D1 to D6 on the inner peripheral side of the hearth part 111. Although the side is connected by the connecting bolt 122 but is not restrained in the radial direction, the hearth part 111 can freely heat-extend toward the outer peripheral direction.

  In addition, a gap U is secured between each hearth component 111 so as to allow thermal expansion in the circumferential direction.

2.4 Another Form of Direction Restriction Part Instead of or together with the direction restriction part, a pair of stoppers 109a and 109a is provided on one side in the circumferential direction of the metal plate 108b, and a pair of stoppers 109b is provided on the other side. 109b can also be provided facing each other.

  As shown in FIG. 2, the pair of opposed stoppers 109a and 109b are suspended from the hearth part 111 so as to hold both sides in the circumferential direction of the base 107b like a bowl, and the stopper 109a and the base 107b And clearances S are secured between the stopper 109b and the base 107b. Thereby, the hearth part 111 can be thermally stretched in the circumferential direction, and can be thermally stretched in the direction (radial direction) along the edge of the pedestal 107 b of the mounting base 107.

  Therefore, the pair of stoppers 109a and 109a and the pair of stoppers 109b and 109b can also function as direction restricting parts.

  Note that if the pair of stoppers 109a and 109a and the pair of stoppers 109b and 109b are provided at one place (at the mounting position of the bolt 122) with respect to one hearth part 111, the direction of heat extension of the hearth part 111 However, if it is disposed at both ends (two locations) in the circumferential direction of the hearth part 111, it is possible to cope with the shake of the hearth part 111, which is more preferable.

  If the thermal elongation of the hearth part 111 is not hindered, three or more stoppers can be provided.

3. Floor plate The floor plate 130 is configured by circularly connecting a plurality of floor plate components 131 made of fan-shaped plates, and covers the upper surface of the hearth 110 in an annular shape.

  FIG. 5 is a perspective view of the main part showing the structure of the floor board covering the upper surface of the hearth 110.

  In FIG. 6A, each floor board component 131 constituting the floor board 130 is arranged in a circle with a gap V (30 mm in the present embodiment), and interference between the floor board parts 131 at the time of thermal expansion is caused. You can avoid it.

  Further, a strip plate 132 is attached along one edge of each floor plate component 131 in the circumferential direction, and a strip plate 133 is attached along the same edge to the other end in the circumferential direction. A plurality of bolt holes 134 are formed through the band plate 132 and the floor plate component 131.

  The bolt holes 134 correspond to the bolt holes 123 of the connection frame portion 114 shown in FIG. 4, and the hearth 110 and the floor plate 130 are fastened using the fixing bolts 125 and the nuts 125a.

  On the other hand, a large number of bolt holes 135 formed in the band plate 133 correspond to the bolt holes 124 of the connection frame portion 114 shown in FIG. However, as shown in FIG. 5B, a number of long holes (through holes) 136 are provided along the circumferential direction (arrow A direction) at the other end of the floor plate component 131 provided with the band plate 133. Is formed.

  Each of the long holes 136 is arranged along the edge of the circumferential end 131a of the band plate 133. Bolts 126 are loosely inserted into the long holes 136 and the bolt holes 124 of the connection frame portion 114, and the nuts 126a. Tightened. However, the tightening torque of the nut 126a is set to a value that allows the thermal expansion of the floor plate component 131 in the circumferential direction.

  One end 131 a in the circumferential direction of each floor plate component 131 is fixed to the hearth part 111, and the other end 131 b in the circumferential direction is a hearth part adjacent to the hearth part 111 (referred to as a hearth part 111 ′). A long hole 136 is provided at the other end 131b in the circumferential direction. The long hole 136 is provided upright from the circumferential end of the hearth part 111 '. Bolts 126 as connecting parts are loosely inserted.

  Thus, by providing the long hole 136 at the other end of the floor board component 131, the other end of the floor board component 131 is not restrained, and the floor board component 131 can be thermally stretched in the circumferential direction.

  In addition, a cover 137 having a U-shaped cross section is provided in a gap V portion between the floor board components 131 so that foreign matter does not enter the gap V and hinder thermal expansion of the floor board component 131. The cover 137 is filled with a ceramic fiber blanket 138 that has both flexibility and heat resistance as a heat insulating material. By filling the heat insulating material, the fixing bolt 125 and the bolt 126 are protected, and durability is increased. It has been.

  FIG. 6 shows the hearth structure having the above configuration in a cross-sectional view taken along line EE in FIG.

  In FIG. 6, the inner periphery side rotation frame portion 102 and the outer periphery side rotation frame portion 103 are connected by connection frame portions 104 and 105 (only the connection frame portion 104 is shown in the figure).

  A rail 102a is provided on the lower surface of the inner peripheral side rotating frame portion 102, and this rail 102a is supported by a wheel 140 that is arranged in a circle below the inner peripheral side rotating frame portion 102 and rotates around a horizontal axis. ing.

  Similarly, a rail 103a is provided on the lower surface of the outer peripheral side rotating frame 103, and this rail 103a is supported by a wheel 141 arranged in a circle below the outer peripheral rotating frame 103 and rotating around a horizontal axis. ing.

  Reference numeral 102b denotes a guide rail, which is in contact with the wheel 142 rotating around the vertical axis and prevents eccentricity of the rotating frame 100 during driving.

  The hearth 110 includes a row of sliding support plates 108 provided on the mounting base 107 of the inner peripheral side rotating frame portion 102 and a row of sliding support plates 108 provided on the mounting base 107 of the outer peripheral side rotating frame portion 103. Is supported, and the movement of the hearth 110 in the circumferential direction is restricted by the stopper 109.

  Thus, the rotary frame 100 and the hearth 110 are only fixed by the fixing bolts 121 (see FIG. 4) provided for each hearth part 111. It is possible to freely stretch in any direction of the diameter direction.

  Accordingly, since the hearth 110 can be freely thermally deformed in response to temperature changes such as heating and cooling during operation, stress is not concentrated on the fixing bolt 121 and is mounted on the rotating frame 100. The hearth 110 can be rotated stably.

  Furthermore, although the number of fixing points between the rotating frame 100 and the hearth 110 is small, the outer peripheral side of the hearth 110 is connected to the rotating frame 100 via a connecting bolt 122, so that the hearth 110 rotates. It can operate stably without dropping from the frame 100.

  The technique of the present invention can also be applied to a rotary hearth furnace having a diameter of 50 m or more by appropriately adjusting the number of divisions of the hearth and floor plate.

DESCRIPTION OF SYMBOLS 100 Rotating frame 101 Rotating frame component 102 Inner peripheral side rotating frame part 103 Outer peripheral side rotating frame part 104, 105 Connection frame part 107 Mounting base 108 Sliding support plate 108a Resin plate 108b Metal plate 109 Stopper (Another form of direction regulating component)
110 hearth 111 hearth parts 112 inner periphery side hearth frame part 113 outer periphery side hearth frame part 114 connection frame part 115-117 auxiliary hearth frame part 119 plate 119a bolt hole 120 plate 120a long hole (direction regulating part)
121 Fixing bolt (fixing part)
122 Bolt for connection (direction regulating part)
123, 124 Bolt hole 125 Fixing bolt 126 Bolt 130 Floor board 131 Floor board component 137 Cover

Claims (6)

In the hearth structure of a rotary hearth furnace in which an annular hearth is mounted on an annular rotary frame and a floor plate is laid on the upper surface of the hearth,
The hearth and the floor plate are composed of a plurality of hearth parts and floor plate parts formed in an arc shape, and predetermined gaps are provided between the adjacent hearth parts and the floor plate parts, respectively. A rotary hearth structure of a rotary hearth furnace, wherein the rotary frame is connected at one location by a fixed part, and a direction regulating part for regulating the heat expansion direction of the hearth part is provided.   The hearth structure of a rotary hearth furnace according to claim 1, wherein a sliding support plate is provided on the rotary frame to support the hearth parts slidably on a horizontal plane.   The hearth structure of the rotary hearth furnace according to claim 1 or 2, wherein a connection portion between the hearth part and the rotary frame is disposed at a position close to an inner peripheral side of the hearth part.   The hearth structure of the rotary hearth furnace according to any one of claims 1 to 3, wherein a bolt and a nut for fastening the hearth part and the rotary frame are provided as the fixed part.   One end in the circumferential direction of each floor plate component is fixed to the hearth part, and the other end in the circumferential direction extends to above the circumferential end of the hearth part adjacent to the hearth part, A long hole is provided along the circumferential direction at the other end in the circumferential direction, and a connecting part is erected from the circumferential end of the hearth part adjacent to the hearth part in the long hole. The hearth structure of the rotary hearth furnace according to any one of claims 1 to 4, wherein is inserted loosely.   The hearth structure of the rotary hearth furnace according to any one of claims 1 to 5, further comprising a cover that covers a gap between adjacent floor plate components, and the cover is filled with a heat insulating material.